CN115108956B - Purification method for crude caprolactam prepared by gas phase Beckmann rearrangement - Google Patents
Purification method for crude caprolactam prepared by gas phase Beckmann rearrangement Download PDFInfo
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- CN115108956B CN115108956B CN202110304014.2A CN202110304014A CN115108956B CN 115108956 B CN115108956 B CN 115108956B CN 202110304014 A CN202110304014 A CN 202110304014A CN 115108956 B CN115108956 B CN 115108956B
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- JBKVHLHDHHXQEQ-UHFFFAOYSA-N epsilon-caprolactam Chemical compound O=C1CCCCCN1 JBKVHLHDHHXQEQ-UHFFFAOYSA-N 0.000 title claims abstract description 495
- 238000000034 method Methods 0.000 title claims abstract description 108
- 238000000746 purification Methods 0.000 title claims abstract description 54
- 238000006237 Beckmann rearrangement reaction Methods 0.000 title claims abstract description 28
- 238000002425 crystallisation Methods 0.000 claims abstract description 293
- 230000008025 crystallization Effects 0.000 claims abstract description 289
- 239000002904 solvent Substances 0.000 claims abstract description 97
- 239000012452 mother liquor Substances 0.000 claims abstract description 83
- 238000005984 hydrogenation reaction Methods 0.000 claims abstract description 36
- 239000012535 impurity Substances 0.000 claims abstract description 35
- 238000002156 mixing Methods 0.000 claims abstract description 24
- 230000018044 dehydration Effects 0.000 claims abstract description 11
- 238000006297 dehydration reaction Methods 0.000 claims abstract description 11
- 239000011259 mixed solution Substances 0.000 claims abstract description 4
- 239000000243 solution Substances 0.000 claims description 56
- 239000013078 crystal Substances 0.000 claims description 41
- 239000003054 catalyst Substances 0.000 claims description 33
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 claims description 31
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 29
- 238000001704 evaporation Methods 0.000 claims description 27
- 230000008020 evaporation Effects 0.000 claims description 26
- 239000012071 phase Substances 0.000 claims description 23
- VEZUQRBDRNJBJY-UHFFFAOYSA-N cyclohexanone oxime Chemical class ON=C1CCCCC1 VEZUQRBDRNJBJY-UHFFFAOYSA-N 0.000 claims description 22
- ZAFNJMIOTHYJRJ-UHFFFAOYSA-N Diisopropyl ether Chemical compound CC(C)OC(C)C ZAFNJMIOTHYJRJ-UHFFFAOYSA-N 0.000 claims description 19
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 claims description 18
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 16
- 238000005406 washing Methods 0.000 claims description 15
- 238000004821 distillation Methods 0.000 claims description 13
- 229910052763 palladium Inorganic materials 0.000 claims description 13
- UNAQSRLBVVDYGP-UHFFFAOYSA-N hex-5-enenitrile Chemical class C=CCCCC#N UNAQSRLBVVDYGP-UHFFFAOYSA-N 0.000 claims description 12
- 239000012808 vapor phase Substances 0.000 claims description 11
- PEQSKSXLTLCHTC-UHFFFAOYSA-N 1,3,4,5-tetrahydroazepin-2-one Chemical class O=C1CCCC=CN1 PEQSKSXLTLCHTC-UHFFFAOYSA-N 0.000 claims description 8
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 claims description 8
- IMNFDUFMRHMDMM-UHFFFAOYSA-N N-Heptane Chemical compound CCCCCCC IMNFDUFMRHMDMM-UHFFFAOYSA-N 0.000 claims description 7
- FSHMPNBRNOGDDK-UHFFFAOYSA-N 1,2,3,4,4a,5,5a,6-octahydrophenazine Chemical class C1=CCC2NC(CCCC3)C3=NC2=C1 FSHMPNBRNOGDDK-UHFFFAOYSA-N 0.000 claims description 6
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 claims description 6
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 6
- JYYRTWNCBVRKMN-UHFFFAOYSA-N Octahydrophenazine Chemical class C1CCCC2=C1N=C1CCCCC1=N2 JYYRTWNCBVRKMN-UHFFFAOYSA-N 0.000 claims description 6
- AWSFEOSAIZJXLG-UHFFFAOYSA-N azepan-2-one;hydrate Chemical compound O.O=C1CCCCCN1 AWSFEOSAIZJXLG-UHFFFAOYSA-N 0.000 claims description 6
- 239000001257 hydrogen Substances 0.000 claims description 6
- 229910052739 hydrogen Inorganic materials 0.000 claims description 6
- 229910052759 nickel Inorganic materials 0.000 claims description 6
- OSKXXXKQSBKDLR-UHFFFAOYSA-N 1,2,3,4,4a,5,5a,6,7,8-decahydrophenazine Chemical class C1CCC2NC(CCCC3)C3=NC2=C1 OSKXXXKQSBKDLR-UHFFFAOYSA-N 0.000 claims description 5
- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 claims description 5
- 238000009835 boiling Methods 0.000 claims description 5
- 238000005119 centrifugation Methods 0.000 claims description 5
- FWFSEYBSWVRWGL-UHFFFAOYSA-N cyclohex-2-enone Chemical class O=C1CCCC=C1 FWFSEYBSWVRWGL-UHFFFAOYSA-N 0.000 claims description 5
- 230000000694 effects Effects 0.000 claims description 5
- 239000000203 mixture Substances 0.000 claims description 5
- 238000010992 reflux Methods 0.000 claims description 5
- FYGHSUNMUKGBRK-UHFFFAOYSA-N 1,2,3-trimethylbenzene Chemical compound CC1=CC=CC(C)=C1C FYGHSUNMUKGBRK-UHFFFAOYSA-N 0.000 claims description 4
- PZHIWRCQKBBTOW-UHFFFAOYSA-N 1-ethoxybutane Chemical compound CCCCOCC PZHIWRCQKBBTOW-UHFFFAOYSA-N 0.000 claims description 4
- RGSFGYAAUTVSQA-UHFFFAOYSA-N Cyclopentane Chemical compound C1CCCC1 RGSFGYAAUTVSQA-UHFFFAOYSA-N 0.000 claims description 4
- 150000001335 aliphatic alkanes Chemical class 0.000 claims description 4
- 150000004945 aromatic hydrocarbons Chemical class 0.000 claims description 4
- 125000004432 carbon atom Chemical group C* 0.000 claims description 4
- 150000001924 cycloalkanes Chemical class 0.000 claims description 4
- 150000005826 halohydrocarbons Chemical class 0.000 claims description 4
- UAEPNZWRGJTJPN-UHFFFAOYSA-N methylcyclohexane Chemical compound CC1CCCCC1 UAEPNZWRGJTJPN-UHFFFAOYSA-N 0.000 claims description 4
- GDOPTJXRTPNYNR-UHFFFAOYSA-N methylcyclopentane Chemical compound CC1CCCC1 GDOPTJXRTPNYNR-UHFFFAOYSA-N 0.000 claims description 4
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 4
- SNMVRZFUUCLYTO-UHFFFAOYSA-N n-propyl chloride Chemical compound CCCCl SNMVRZFUUCLYTO-UHFFFAOYSA-N 0.000 claims description 3
- 230000008719 thickening Effects 0.000 claims description 3
- MPPPKRYCTPRNTB-UHFFFAOYSA-N 1-bromobutane Chemical compound CCCCBr MPPPKRYCTPRNTB-UHFFFAOYSA-N 0.000 claims description 2
- DURPTKYDGMDSBL-UHFFFAOYSA-N 1-butoxybutane Chemical compound CCCCOCCCC DURPTKYDGMDSBL-UHFFFAOYSA-N 0.000 claims description 2
- VFWCMGCRMGJXDK-UHFFFAOYSA-N 1-chlorobutane Chemical compound CCCCCl VFWCMGCRMGJXDK-UHFFFAOYSA-N 0.000 claims description 2
- -1 1-n-bromopropane Chemical compound 0.000 claims description 2
- UPSXAPQYNGXVBF-UHFFFAOYSA-N 2-bromobutane Chemical compound CCC(C)Br UPSXAPQYNGXVBF-UHFFFAOYSA-N 0.000 claims description 2
- NAMYKGVDVNBCFQ-UHFFFAOYSA-N 2-bromopropane Chemical compound CC(C)Br NAMYKGVDVNBCFQ-UHFFFAOYSA-N 0.000 claims description 2
- JMTRCXPSDMMAGM-UHFFFAOYSA-N 2-chloro-3-methylbutane Chemical compound CC(C)C(C)Cl JMTRCXPSDMMAGM-UHFFFAOYSA-N 0.000 claims description 2
- BSPCSKHALVHRSR-UHFFFAOYSA-N 2-chlorobutane Chemical compound CCC(C)Cl BSPCSKHALVHRSR-UHFFFAOYSA-N 0.000 claims description 2
- XOBKSJJDNFUZPF-UHFFFAOYSA-N Methoxyethane Chemical compound CCOC XOBKSJJDNFUZPF-UHFFFAOYSA-N 0.000 claims description 2
- BZLVMXJERCGZMT-UHFFFAOYSA-N Methyl tert-butyl ether Chemical compound COC(C)(C)C BZLVMXJERCGZMT-UHFFFAOYSA-N 0.000 claims description 2
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 claims description 2
- 125000001931 aliphatic group Chemical group 0.000 claims description 2
- QQQCWVDPMPFUGF-ZDUSSCGKSA-N alpinetin Chemical compound C1([C@H]2OC=3C=C(O)C=C(C=3C(=O)C2)OC)=CC=CC=C1 QQQCWVDPMPFUGF-ZDUSSCGKSA-N 0.000 claims description 2
- DMEGYFMYUHOHGS-UHFFFAOYSA-N heptamethylene Natural products C1CCCCCC1 DMEGYFMYUHOHGS-UHFFFAOYSA-N 0.000 claims description 2
- ULYZAYCEDJDHCC-UHFFFAOYSA-N isopropyl chloride Chemical compound CC(C)Cl ULYZAYCEDJDHCC-UHFFFAOYSA-N 0.000 claims description 2
- GYNNXHKOJHMOHS-UHFFFAOYSA-N methyl-cycloheptane Natural products CC1CCCCCC1 GYNNXHKOJHMOHS-UHFFFAOYSA-N 0.000 claims description 2
- 229910052697 platinum Inorganic materials 0.000 claims description 2
- CRNIHJHMEQZAAS-UHFFFAOYSA-N tert-amyl chloride Chemical compound CCC(C)(C)Cl CRNIHJHMEQZAAS-UHFFFAOYSA-N 0.000 claims description 2
- NUMQCACRALPSHD-UHFFFAOYSA-N tert-butyl ethyl ether Chemical compound CCOC(C)(C)C NUMQCACRALPSHD-UHFFFAOYSA-N 0.000 claims description 2
- 239000008096 xylene Substances 0.000 claims description 2
- AFABGHUZZDYHJO-UHFFFAOYSA-N dimethyl butane Natural products CCCC(C)C AFABGHUZZDYHJO-UHFFFAOYSA-N 0.000 claims 3
- HNRMPXKDFBEGFZ-UHFFFAOYSA-N 2,2-dimethylbutane Chemical compound CCC(C)(C)C HNRMPXKDFBEGFZ-UHFFFAOYSA-N 0.000 claims 2
- GXDHCNNESPLIKD-UHFFFAOYSA-N 2-methylhexane Natural products CCCCC(C)C GXDHCNNESPLIKD-UHFFFAOYSA-N 0.000 claims 2
- ZUBZATZOEPUUQF-UHFFFAOYSA-N isononane Chemical compound CCCCCCC(C)C ZUBZATZOEPUUQF-UHFFFAOYSA-N 0.000 claims 2
- QWTDNUCVQCZILF-UHFFFAOYSA-N isopentane Chemical compound CCC(C)C QWTDNUCVQCZILF-UHFFFAOYSA-N 0.000 claims 2
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 claims 2
- BKIMMITUMNQMOS-UHFFFAOYSA-N nonane Chemical compound CCCCCCCCC BKIMMITUMNQMOS-UHFFFAOYSA-N 0.000 claims 2
- TVMXDCGIABBOFY-UHFFFAOYSA-N octane Chemical compound CCCCCCCC TVMXDCGIABBOFY-UHFFFAOYSA-N 0.000 claims 2
- NHTMVDHEPJAVLT-UHFFFAOYSA-N Isooctane Chemical compound CC(C)CC(C)(C)C NHTMVDHEPJAVLT-UHFFFAOYSA-N 0.000 claims 1
- 230000006837 decompression Effects 0.000 claims 1
- JVSWJIKNEAIKJW-UHFFFAOYSA-N dimethyl-hexane Natural products CCCCCC(C)C JVSWJIKNEAIKJW-UHFFFAOYSA-N 0.000 claims 1
- 238000004519 manufacturing process Methods 0.000 abstract description 6
- 239000000047 product Substances 0.000 description 97
- 239000002002 slurry Substances 0.000 description 18
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 17
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 12
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 11
- 239000007789 gas Substances 0.000 description 11
- 230000008707 rearrangement Effects 0.000 description 11
- 239000012043 crude product Substances 0.000 description 9
- 238000005265 energy consumption Methods 0.000 description 8
- 239000000523 sample Substances 0.000 description 7
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 6
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 6
- 239000007864 aqueous solution Substances 0.000 description 6
- 230000008033 biological extinction Effects 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 6
- 238000010438 heat treatment Methods 0.000 description 6
- 238000010521 absorption reaction Methods 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 5
- 239000007810 chemical reaction solvent Substances 0.000 description 5
- 239000012286 potassium permanganate Substances 0.000 description 5
- 238000006462 rearrangement reaction Methods 0.000 description 5
- 239000007787 solid Substances 0.000 description 5
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- 239000002585 base Substances 0.000 description 4
- 238000009833 condensation Methods 0.000 description 4
- 230000005494 condensation Effects 0.000 description 4
- 239000012153 distilled water Substances 0.000 description 4
- 239000007791 liquid phase Substances 0.000 description 4
- 239000010413 mother solution Substances 0.000 description 4
- 229910001404 rare earth metal oxide Inorganic materials 0.000 description 4
- 238000011084 recovery Methods 0.000 description 4
- 238000007670 refining Methods 0.000 description 4
- 238000000926 separation method Methods 0.000 description 4
- 239000012086 standard solution Substances 0.000 description 4
- 238000003756 stirring Methods 0.000 description 4
- 235000013162 Cocos nucifera Nutrition 0.000 description 3
- 244000060011 Cocos nucifera Species 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 239000012018 catalyst precursor Substances 0.000 description 3
- 238000010924 continuous production Methods 0.000 description 3
- 230000006866 deterioration Effects 0.000 description 3
- 238000004090 dissolution Methods 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000012074 organic phase Substances 0.000 description 3
- 239000003960 organic solvent Substances 0.000 description 3
- 229910052761 rare earth metal Inorganic materials 0.000 description 3
- 238000004064 recycling Methods 0.000 description 3
- 238000002791 soaking Methods 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- 238000010533 azeotropic distillation Methods 0.000 description 2
- 239000012159 carrier gas Substances 0.000 description 2
- HSJPMRKMPBAUAU-UHFFFAOYSA-N cerium(3+);trinitrate Chemical compound [Ce+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O HSJPMRKMPBAUAU-UHFFFAOYSA-N 0.000 description 2
- 239000007795 chemical reaction product Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
- 239000012467 final product Substances 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- 229910003445 palladium oxide Inorganic materials 0.000 description 2
- 238000006116 polymerization reaction Methods 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 239000011541 reaction mixture Substances 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- 229910002492 Ce(NO3)3·6H2O Inorganic materials 0.000 description 1
- 229910052684 Cerium Inorganic materials 0.000 description 1
- ZWXPDGCFMMFNRW-UHFFFAOYSA-N N-methylcaprolactam Chemical compound CN1CCCCCC1=O ZWXPDGCFMMFNRW-UHFFFAOYSA-N 0.000 description 1
- 229910002676 Pd(NO3)2·2H2O Inorganic materials 0.000 description 1
- 239000007868 Raney catalyst Substances 0.000 description 1
- 229910000564 Raney nickel Inorganic materials 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical compound N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 description 1
- 229910052921 ammonium sulfate Inorganic materials 0.000 description 1
- 235000011130 ammonium sulphate Nutrition 0.000 description 1
- 239000008346 aqueous phase Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000011549 crystallization solution Substances 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000007865 diluting Methods 0.000 description 1
- 229950001902 dimevamide Drugs 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 150000002170 ethers Chemical class 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 238000007701 flash-distillation Methods 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 1
- 239000008258 liquid foam Substances 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000002808 molecular sieve Substances 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- GPNDARIEYHPYAY-UHFFFAOYSA-N palladium(ii) nitrate Chemical compound [Pd+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O GPNDARIEYHPYAY-UHFFFAOYSA-N 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000005191 phase separation Methods 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- KMUONIBRACKNSN-UHFFFAOYSA-N potassium dichromate Chemical compound [K+].[K+].[O-][Cr](=O)(=O)O[Cr]([O-])(=O)=O KMUONIBRACKNSN-UHFFFAOYSA-N 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 239000012264 purified product Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000013557 residual solvent Substances 0.000 description 1
- 238000002390 rotary evaporation Methods 0.000 description 1
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- 239000012047 saturated solution Substances 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 125000003944 tolyl group Chemical group 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
- 238000012795 verification Methods 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
- 230000004580 weight loss Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D201/00—Preparation, separation, purification or stabilisation of unsubstituted lactams
- C07D201/16—Separation or purification
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D223/00—Heterocyclic compounds containing seven-membered rings having one nitrogen atom as the only ring hetero atom
- C07D223/02—Heterocyclic compounds containing seven-membered rings having one nitrogen atom as the only ring hetero atom not condensed with other rings
- C07D223/06—Heterocyclic compounds containing seven-membered rings having one nitrogen atom as the only ring hetero atom not condensed with other rings with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
- C07D223/08—Oxygen atoms
- C07D223/10—Oxygen atoms attached in position 2
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Other In-Based Heterocyclic Compounds (AREA)
Abstract
本发明涉及己内酰胺生产领域，公开了一种经气相贝克曼重排法制取己内酰胺粗品的纯化方法，包括以下步骤：(1)将气相贝克曼重排法制备的含有己内酰胺的混合液经脱溶剂、脱水、脱轻杂质，得到粗己内酰胺；(2)将粗己内酰胺与结晶溶剂混合进行一次结晶，得到一次结晶产品和一次结晶母液；(3)将一次结晶产品与结晶溶剂混合进行二次结晶，得到二次结晶产品和二次结晶母液，将二次结晶母液返至步骤(2)作为至少部分一次结晶溶剂；(4)将二次结晶产品进行加氢反应。该纯化方法不仅省去了脱重的步骤，而且降低了对气相贝克曼重排法制取己内酰胺粗品的质量要求，能够得到高品质的己内酰胺，且并没有明显增加循环溶剂的消耗量。
The present invention relates to the field of caprolactam production, and discloses a purification method for preparing crude caprolactam by gas-phase Beckmann rearrangement, comprising the following steps: (1) removing solvent, dehydration and light impurity removal from a mixed solution containing caprolactam prepared by gas-phase Beckmann rearrangement to obtain crude caprolactam; (2) mixing the crude caprolactam with a crystallization solvent for primary crystallization to obtain a primary crystallization product and a primary crystallization mother liquor; (3) mixing the primary crystallization product with a crystallization solvent for secondary crystallization to obtain a secondary crystallization product and a secondary crystallization mother liquor, and returning the secondary crystallization mother liquor to step (2) as at least part of the primary crystallization solvent; (4) subjecting the secondary crystallization product to hydrogenation reaction. The purification method not only omits the step of removing heavy impurities, but also reduces the quality requirements for crude caprolactam prepared by gas-phase Beckmann rearrangement, and can obtain high-quality caprolactam without significantly increasing the consumption of circulating solvent.
Description
Technical Field
The invention relates to the field of caprolactam production, in particular to a purification method for preparing a caprolactam crude product by a gas-phase Beckmann rearrangement method.
Background
Caprolactam is widely used in the synthesis of plastics, fibers and other materials and is an important organic monomer. Conventional caprolactam is often prepared by a liquid-phase Beckmann rearrangement reaction, but the liquid-phase Beckmann rearrangement product contains sulfuric acid, so that a large amount of ammonia is needed for neutralization, a large amount of low-added-value ammonium sulfate can be generated in the process, and the large amount of sulfuric acid is used, so that the environment-friendly effect of equipment and process flows is greatly improved. In order to not apply sulfuric acid during rearrangement, a variety of new processes have been developed, of which gas phase rearrangement is the most promising one.
In the gas phase rearrangement process, since the composition of the reaction product is different from that of the liquid phase rearrangement process, the conventional purification process of the liquid phase rearrangement process is not suitable for purifying the gas phase rearrangement product, and therefore, for industrialization of the gas phase rearrangement process, development of a caprolactam purification process suitable for the gas phase rearrangement product is highly desired.
The japanese sumitomo company has first proposed a purification scheme for vapor phase rearrangement products, and a step of purifying caprolactam using crystallization was proposed in CN103508954B, CN103420912B, CN103420913B, CN 103420885B. In the patent related to Sumitomo, the gas phase rearrangement product is subjected to desolventizing, dewatering, light removal and heavy removal steps before entering a crystallization unit, and the product entering the crystallization unit is hydrogenated and distilled to obtain the final caprolactam product. However, in these patents caprolactam is repeatedly distilled in this process, losing a large amount of energy, and it is necessary to prevent deterioration of caprolactam at high temperatures.
At present, in the existing patent literature at home and abroad, although various different process flows can obtain good effects, caprolactam basically needs to pass through a heavy removal tower and a final flash evaporation flow, and the repeated distillation process increases the energy consumption of the purification flow. In addition, the quality of the crystalline product is reduced once it is faced with a poor quality of the rearranged product or with more crude caprolactam for recycling.
Therefore, if the caprolactam purification process is provided, the energy consumption is reduced, the problems of crystal purity reduction and the like caused by the problems of fluctuation in the rearrangement reaction process, the repeated use of the reflux crude caprolactam and the like are solved, the purpose of obtaining high-quality caprolactam products more stably is achieved, and the caprolactam purification process has good practical significance and application prospect.
Disclosure of Invention
The invention aims to solve the problems of high weight loss, easy deterioration of caprolactam, high quality requirement on a heavy-duty reaction product, low crystal purity caused by the fact that the refluxing crude caprolactam is used mechanically and the like in the prior art, and provides a purification method for preparing a crude caprolactam product by a gas-phase Beckmann rearrangement method.
In order to solve the above problems, although a secondary crystallization method is attempted in the prior art, that is, a fresh solvent is used for performing a first crystallization to obtain a first crystallization product and a first crystallization mother liquor, and then a fresh solvent is used for performing a second crystallization on the first crystallization product to obtain a second crystallization product and a second crystallization mother liquor, the second crystallization product is transferred to a production stage of a next stage, and the first crystallization mother liquor and the second crystallization mother liquor are transferred to a residual liquid recovery stage. In practice, the inventors of the present invention found that using a large amount of fresh solvent for each crystallization in the existing secondary crystallization manner leads to a large increase in the circulating solvent and requires treatment of the second crystallization mother liquor as a residual liquid, which increases the energy consumption for the subsequent treatment, and that the subsequent treatment after concentrating or crystallizing caprolactam in the second crystallization mother liquor is used for reuse, which leads to a decrease in the quality of the purified product. Based on this, the present invention further overcomes the above technical problems, and the purification method of the present invention also adopts a secondary crystallization method, but the solvent used does not increase the consumption of the circulating solvent significantly, and high quality caprolactam can be obtained after the secondary crystallization mother liquor is applied.
The invention provides a purification method of a caprolactam crude product by a gas-phase Beckmann rearrangement method, which comprises the following steps of (1) subjecting a mixed solution containing caprolactam prepared by the gas-phase Beckmann rearrangement method to solvent removal, dehydration and light impurity removal to obtain crude caprolactam, (2) mixing the crude caprolactam with a crystallization solvent for primary crystallization to obtain a primary crystallization product and a primary crystallization mother liquor, (3) mixing the primary crystallization product with the crystallization solvent for secondary crystallization to obtain a secondary crystallization product and a secondary crystallization mother liquor, returning the secondary crystallization mother liquor to the step (2) as at least part of the primary crystallization solvent, and (4) subjecting the secondary crystallization product to hydrogenation reaction.
According to the technical scheme, the secondary crystallization mother liquor is mechanically used without a heavy removal step, but high-quality caprolactam can still be obtained, and the quality requirement on the crude caprolactam product prepared by the gas-phase Beckmann rearrangement method is reduced by adopting a secondary crystallization mode, so that the high-quality product can be obtained even if the rearrangement reaction quality fluctuates. Although the invention adopts a secondary crystallization mode, the dosage of the crystallization solvent is not obviously increased.
According to the technical scheme, the purification method has the beneficial effects that:
(1) The de-duplication tower is omitted, the energy consumption of equipment is reduced, and the possibility of caprolactam deterioration caused by the de-duplication distillation heating process is reduced;
(2) The problems of reduced crystal purity of the final product and the like caused by the problems of quality fluctuation of the crude product obtained in the rearrangement reaction process, repeated application of the reflux crude caprolactam and the like can be effectively solved;
(3) The crude caprolactam is subjected to a twice crystallization refining process, so that the product purity is higher, the consumption of a circulating solvent is not obviously increased, and the energy consumption for treating secondary crystallization mother liquor is reduced compared with a conventional secondary crystallization mode.
The purification method of the invention is used for refining the crude caprolactam product to obtain a secondary crystallization product, and the secondary crystallization product is subjected to hydrogenation reaction to obtain a superior caprolactam product. The method provided by the invention has the characteristics of high yield, stable long-term operation and the like, and is continuous and efficient. In addition, the absorption value (PM) of the caprolactam obtained by the method is more than 20000s or more, the extinction value (at the wavelength of 290 nm) of the caprolactam is 0.1 or less, the volatile alkali value is 0.3mmol/kg or less, the chromaticity value is 2 or less, and the alkalinity is 0.1mmol/kg or less, thereby completely meeting the requirements of industrial high-grade products.
Drawings
FIG. 1 is a process flow diagram of one embodiment of the present invention;
fig. 2 is a process flow diagram of a preferred embodiment of the present invention.
Detailed Description
The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.
The inventors of the present invention have found during the research that crystallization of caprolactam in the prior art after desolventizing, dewatering, light (light impurity removal) and heavy (heavy impurity removal) is performed, and in particular, the high temperature is required for the heavy removal process, which causes problems, because the heavy removal process is required to be performed under low vacuum and high temperature, long-time high-temperature distillation can lead to polymerization of caprolactam, and further reaction between impurities and caprolactam can also occur, resulting in more impurities. Although the purity of the crude caprolactam obtained after the de-weighting increases, the impurities are not easily removed in the subsequent treatment process due to various impurities and even undefined impurities generated in the de-weighting process, so that the quality of the final product is difficult to improve. Moreover, in the process of application, impurities which are difficult to remove are accumulated continuously, so that the product quality is difficult to be ensured along with the production.
The invention provides a purification method for preparing a caprolactam crude product by a gas-phase Beckmann rearrangement method, which comprises the following steps of (1) subjecting a mixed solution containing caprolactam prepared by the gas-phase Beckmann rearrangement method to solvent removal, dehydration and light impurity removal to obtain crude caprolactam, (2) mixing the crude caprolactam with a crystallization solvent for primary crystallization to obtain a primary crystallization product and a primary crystallization mother solution, (3) mixing the primary crystallization product with the crystallization solvent for secondary crystallization to obtain a secondary crystallization product and a secondary crystallization mother solution, returning the secondary crystallization mother solution to the step (2) as at least part of the primary crystallization solvent, and (4) subjecting the secondary crystallization product to hydrogenation reaction.
According to the technical scheme, the secondary crystallization mother liquor is mechanically used without a heavy removal step, but high-quality caprolactam can still be obtained, and the quality requirement on the crude caprolactam product prepared by the gas-phase Beckmann rearrangement method is reduced by adopting a secondary crystallization mode, so that the high-quality product can be obtained even if the rearrangement reaction quality fluctuates. Although the invention adopts a secondary crystallization mode, the dosage of the crystallization solvent is not obviously increased.
According to the present invention, the crystallization solvent may be selected in various ways, and preferably, the crystallization solvent is azeotropy with water and is not co-soluble with water, and the crystallization solvent selected in this range can achieve the technical effects of the present invention. The caprolactam has a mass percent solubility in said crystallization solvent of less than 20% by weight, preferably at a pressure of 5kPa absolute and at a boiling temperature of said crystallization solvent, the choice of crystallization solvent being verified by routine experimentation by definition of the conditions described above. According to the above conditions, the crystallization solvent has a boiling point of 40 to 180 ℃ at normal pressure, and is preferably one or more selected from the group consisting of ethers, alkanes, cycloalkanes, halohydrocarbons and aromatic hydrocarbons.
According to the present invention, in order to further improve the purity of the crystalline product and further reduce the quality requirement for the crude product, it is preferable that the ether is selected from saturated aliphatic monobasic ether, preferably at least one of isopropyl ether, ethylbutyl ether, methylethyl ether, diethyl ether, n-propyl ether, n-butyl ether, ethylbutyl ether, methyl t-butyl ether and ethyl t-butyl ether, for the crystallization solvent. The cycloalkane contains 5-8 carbon atoms, preferably at least one selected from cyclohexane, cyclopentane, methylcyclopentane and methylcyclohexane, the halohydrocarbon is selected from at least one selected from 1-chloropropane, 2-chloropropane, 1-chloro-n-butane, 2-chlorobutane, 1-chlorodimethylpropane, 2-chlorodimethylpropane, 1-n-bromopropane, 2-bromopropane, 1-bromobutane and 2-bromobutane, and the aromatic hydrocarbon is selected from at least one selected from benzene, toluene, xylene and trimethylbenzene.
According to the invention the conditions for the primary crystallization can be adjusted within wide limits, preferably the conditions for the primary crystallization comprise dissolving the crude caprolactam in the crystallization solvent and then performing the primary crystallization. The caprolactam solution obtained preferably has a caprolactam mass concentration of 15% to 45%. Preferably, the crystallization process in step (2) is generally operated between 10 ℃ and 60 ℃, the specific operating temperature being determined by the solubility of caprolactam in the selected solvent. And more preferably may be between 25 ℃ and 58 ℃.
The primary crystallization process in the step (2) can be cooled and crystallized by preparing a high-temperature saturated solution, can also be used for an adiabatic flash evaporation continuous crystallization process, and can also be used for a reduced pressure evaporation crystallization process. The preferred primary crystallization is evaporative crystallization, which may be performed according to the solubility profile of caprolactam in the solvent. Preferably, adiabatic flash evaporation or reduced pressure evaporative crystallization is employed, and if the solubility varies significantly with temperature, adiabatic flash continuous crystallization is preferred, whereas reduced pressure evaporative crystallization is preferred. In this preferred embodiment, the secondary crystallization mother liquor and impurities in the crude caprolactam can be further removed for application, and finally a higher quality product is obtained.
According to the present invention, the crystallization process used in step (2) may be single-stage or multistage, but preferably does not exceed five stages, more preferably three stages of continuous crystallization. When a multistage continuous crystallization process is used, it is generally preferable that each stage of the crystallizer precipitate the same crystal quality in order to make the particle size of the crystal product large and uniform.
In the process provided by the present invention, preferably, step (2) is carried out by mixing the crude caprolactam upstream with the mother liquor obtained by the secondary crystallization and a part of the organic solvent to a desired concentration and then carrying out the primary crystallization. The crystallization process is preferably a continuous crystallization process.
According to the invention, the concentration of the caprolactam solution entering the primary crystallization unit in step (2) is preferably between 15% and 45% by mass. Different feed concentrations are preferred depending on the crystallization mode. For adiabatic flash crystallization processes, the preferred feed concentration is between 25% and 40%. For the reduced pressure evaporative crystallization process, the preferred feed concentration should be below 20%.
In a preferred embodiment of the invention, the primary crystallization is carried out by adiabatic flash evaporation, the mass concentration of caprolactam in the caprolactam solution is 15% -35% during feeding, and the adiabatic flash evaporation conditions comprise feeding temperature of 40-80 ℃, operating temperature of 15-60 ℃ and operating pressure of 3-100kPa. In this preferred embodiment, the secondary crystallization mother liquor and impurities in the crude caprolactam can be further removed for application, and finally a higher quality product is obtained.
In another preferred embodiment of the invention, the primary crystallization is carried out by evaporation crystallization under reduced pressure, wherein the mass concentration of caprolactam in the caprolactam solution is 15-20%, and the conditions of the evaporation crystallization under reduced pressure comprise an operating temperature of 15-45 ℃ and an operating pressure of 3-100kPa. In this preferred embodiment, the secondary crystallization mother liquor and impurities in the crude caprolactam can be further removed for application, and finally a higher quality product is obtained.
According to the present invention, the yield of the primary crystallization process in the step (2) can be adjusted within a wide range, and it is preferable that the yield of the primary crystallization product is not less than 70% by weight, so that the energy consumption of the overall crystallization process can be further reduced. Preferably, the yield of the primary crystalline product is 75-95 wt%.
According to the invention, the yield of the primary crystallization product is calculated as the mass of caprolactam crystals in the primary crystallization output divided by the mass of caprolactam in the primary crystallization input multiplied by 100%.
According to the invention, the solid content (mass of crystals contained) of the crystal slurry obtained at the end of the crystallization process used in the step (2) should not be higher than 55%, i.e. the content of caprolactam crystals in the mixture obtained at the end of the primary crystallization is not higher than 55% by weight, and if the solid content in the final stage crystallizer is reduced by repeatedly injecting the secondary mother liquor into the final stage crystallizer above that value, the crystallization process can be made more uniform, the entrainment of impurities in the primary crystallization process can be reduced, and the content of impurities in the primary crystallization product can be reduced. According to the invention, the magma discharged from the crystallization in step (2) can be separated from the primary mother liquor by centrifugation, thickening or countercurrent washing. Preferably, countercurrent washing is used, so that caprolactam crystal slurry can be continuously obtained, the scaling problem caused by solvent volatilization during liquid-solid separation is avoided, and the problem of solid conveying is also avoided. The obtained crystal slurry can be directly heated and dissolved in a stirring kettle.
According to the present invention, the crystallizer for the primary crystallization in the step (2) may be selected from a conventional stirred tank type crystallizer, a DTB crystallizer and an OSLO crystallizer, and the present invention is not limited thereto. In order to prevent the problem of wall scaling caused by entrainment of liquid foam on the wall surface of the crystallization kettle in the continuous crystallization process, a heat insulation layer or a jacket heat insulation layer can be preferably added on the wall surface of the crystallizer, and the solvent collected by partial evaporation and condensation can be sprayed on the inner wall surface of the crystallizer to reduce the scaling probability.
According to the present invention, the secondary crystallization process in the step (3) may use the same crystallization method as the primary crystallization process, or may use a different crystallization method. Generally, the secondary crystallization process has a low impurity content, so that a more energy-efficient adiabatic flash crystallization is preferable, and the feed concentration in the secondary crystallization process can be appropriately increased, and the feed concentration in the secondary crystallization process can be preferably 35% to 40%. Thus, the yield can be further improved to further reduce the energy consumption. Still more preferably, the conditions of adiabatic flash distillation include a feed temperature of 40-80 ℃, an operating temperature of 15-60 ℃ and an operating pressure of 3-100kPa.
The output from the secondary crystallization process in step (3) may also optionally be separated from the secondary mother liquor using centrifugation, thickening or countercurrent washing similar to the primary crystallization. Preferably, water is introduced directly into the bottom of the countercurrent scrubber to dissolve the washed crystalline product, which can save a great amount of equipment and avoid the transportation of solids.
According to the invention, the method preferably further comprises the steps of concentrating the primary crystallization mother liquor to obtain concentrated primary crystallization mother liquor and a recovered solvent, recrystallizing the concentrated primary crystallization mother liquor to obtain a crude caprolactam product and mother liquor crystallization residual mother liquor, and returning the crude caprolactam product to the step (2). This can further increase the yield of caprolactam.
According to the present invention, it is preferable to recover the solvent in the mother liquor remaining from the mother liquor crystallization, and the recovered solvent is returned to step (2) or step (3) as the crystallization solvent, thereby further reducing the amount of the recycled solvent to be used.
According to the present invention, the concentration is preferably performed by distillation concentration or multi-effect evaporation, and the concentration is further preferably performed by using a distillation column, and the reflux ratio is still further preferably 0 to 2. Still further preferably, the primary crystallization mother liquor is treated by double distillation using either pre-or post-pressurization. In this preferred embodiment, impurities in the primary mother liquor can be further removed, and a high-quality caprolactam product can be obtained on the basis of further improving the product yield, and the quality stability of the product can be further improved.
According to the invention, the recovery solvent of the crystallization stage of step (2) and/or of the crystallization stage of step (3) is returned to the mixing stage of step (2) and/or of step (3). Thus, the solvent utilization rate can be further improved, and the consumption of the circulating solvent can be further reduced.
The crystallizer used in the crystallization is not limited, and can be a cooling crystallizer, an evaporation crystallizer or a vacuum crystallizer, and can comprise at least one of a forced external circulation type crystallizer, an Oslo type crystallizer, an FC type crystallizer, a DTB type crystallizer, a DP type crystallizer and a Messo turbulent flow crystallizer.
In one embodiment, the process provided according to the present invention further comprises collecting the caprolactam product by evaporation and/or distillation under reduced pressure after the hydrogenation reaction, thereby obtaining a caprolactam product having a higher potassium permanganate absorption value, a lower volatile base value, and a extinction value.
According to the present invention, the hydrogenation means may be conventional hydrogenation means in the art. In a preferred embodiment of the present invention, as shown in FIG. 1, the secondary crystallization product is preferably subjected to hydrogenation reaction in a manner comprising a) mixing the secondary crystallization product with water to obtain an aqueous caprolactam solution, b) distilling the aqueous caprolactam solution to remove residual crystallization solvent to obtain an aqueous caprolactam solution after solvent removal and recovering the solvent, c) contacting the aqueous caprolactam solution after solvent removal with hydrogen in the presence of a hydrogenation catalyst to obtain an aqueous caprolactam solution, and d) dehydrating the aqueous caprolactam solution to obtain a caprolactam product. In this preferred embodiment, the quality of the product can be further improved, the quality requirement on the crude caprolactam can be further reduced, and the stability of the production quality can be improved.
According to the invention, the aqueous caprolactam solution is preferably freed of residual traces of organic solvent before entering the hydrogenation unit to further reduce the possible quality impact of traces of solvent on the hydrogenated product, preferably to below 5 ppm. The removal of the organic solvent from the aqueous caprolactam solution may be carried out azeotropically. The water and caprolactam form an azeotrope, and then the phase is separated by condensation at the top of the column, the aqueous phase is returned to the column, and the organic phase is withdrawn.
According to the invention, the dehydration mode can be a dehydration mode conventional in the art, preferably, the distillation dehydration is preferably carried out under the condition of negative pressure in the step d), so as to further prevent the product quality from being reduced due to the self-polymerization of caprolactam under the condition of high temperature and water, thereby further improving the product quality, and further preferably, the temperature of the caprolactam is controlled below 130 ℃ in the dehydration process.
According to the present invention, it is preferable that the recovered solvent in step b) is dehydrated and then the dehydrated recovered solvent is returned to the mixing stage in step (2) and/or step (3). According to the invention, if step a) is a mixing of the crystal slurry with water to dissolve caprolactam, the organic phase remaining after removal of the aqueous caprolactam solution is required to be azeotropically dehydrated before being returned to the primary crystallization unit. In order to further improve the product quality, further reduce the influence of the moisture content on the solubility of caprolactam, further reduce the adverse effect of the residual trace moisture in the organic phase on the control of the crystallization process, preferably after dehydration, enter a primary crystallization unit, preferably to remove the moisture content in the recovered solvent to below 10 ppm.
The present invention is not particularly limited to the specific embodiment of the hydrogenation reaction, and may be carried out by a means conventionally known in the art. The hydrogenation reaction may be carried out in the presence of water or in a molten state, and is not particularly limited in this regard, and the hydrogenation reaction is preferably carried out in the presence of water. According to the invention, in step a), water is used in an amount of 0.1 to 2.5 parts by weight relative to 1 part by weight of caprolactam in the secondary crystallized product.
According to the invention, the hydrogenation process described in step c) is intended to remove the remaining unsaturated impurities from the crude caprolactam. The hydrogenation catalyst may be selected from those conventional in the art, such as amorphous nickel catalysts, raney nickel catalysts, and the like.
According to a preferred embodiment of the present invention, the hydrogenation reaction is carried out in the presence of a hydrogenation catalyst. Preferably, the hydrogenation catalyst is selected from at least one of nickel-based catalyst, palladium-based catalyst and platinum-based catalyst. The hydrogenation catalyst may be obtained commercially or by self-preparation, and the present invention is not particularly limited. Preferably, the hydrogenation catalyst is a nickel-based catalyst and/or a palladium-based catalyst.
In a preferred embodiment of the present invention, the nickel-based catalyst is an amorphous nickel catalyst. The amorphous nickel catalysts can be found, for example, in CN1272490a and CN1272491a.
According to the present invention, the palladium-based catalyst is widely selected, and preferably, the palladium-based catalyst includes a carrier and palladium and rare earth oxide supported on the carrier. The carrier may be at least one of activated carbon, silica, titania and alumina, and the rare earth oxide may be an oxide of lanthanum and/or cerium. Preferably, the carrier is activated carbon. The content of palladium and rare earth oxide in the palladium-based catalyst of the present invention is selected in a wide range, and preferably the content of palladium is 0.1 to 5 wt% and the content of rare earth oxide is 0.2 to 10 wt% based on the total amount of the palladium-based catalyst. Specifically, the palladium-based catalyst can be prepared, for example, by referring to CN102430406a.
According to the present invention, the hydrogenation conditions may be conventional in the art, and in order to further provide a caprolactam product with a higher potassium permanganate absorption and purity and a smaller extinction, preferably, the hydrogenation reaction conditions include a temperature of 65-180 ℃, a pressure of 0.5-5MPa, and a hydrogen flow rate of 0.1-2L/min.
According to the present invention, the time for the hydrogenation reaction may be adjusted within a wide range, and preferably, when the hydrogenation reaction is a batch operation, the time for the hydrogenation reaction may be 0.5 to 3 hours, more preferably, 1 to 2 hours. When the hydrogenation reaction is a continuous operation (e.g., a fixed bed process), the mass space velocity of caprolactam may be in the range of 0.5 to 30h -1.
The form of the reactor in which the hydrogenation reaction is carried out is not particularly limited in the present invention, and a magnetically stabilized bed reactor, a fixed bed reactor or a slurry bed reactor may be employed, and a fixed bed reactor is preferable.
According to the invention, the crude caprolactam can be obtained by distilling the reaction mixture of the Beckmann rearrangement reaction to recover the reaction solvent, dehydrating and light-removing. The distillation process may be carried out under atmospheric and reduced pressure conditions, which are well known to those skilled in the art and will not be described in detail herein.
According to the present invention, the crude caprolactam after light removal is directly added into a crystallization solvent for crystallization, and the present invention does not include a process of removing heavy impurities. It will be appreciated that the present invention does not exclude small amounts of heavy impurities from being carried over in the process described above.
According to the present invention, the reaction solvent used for the rearrangement reaction of cyclohexanone oxime by Beckmann is an alcohol, preferably an alcohol having 1 to 6 carbon atoms, preferably an alcohol having a boiling point of less than 100 ℃, such as methanol, ethanol, n-propanol, isopropanol, etc., further preferably at least one of methanol, ethanol and isopropanol. In this preferred embodiment, higher quality caprolactam can be obtained with higher yields.
According to the present invention, preferably, the beckmann rearrangement reaction is a gas phase beckmann rearrangement reaction. The vapor phase Beckmann rearrangement reaction according to the present invention may be carried out according to a conventional technique in the art, and the present invention is not particularly limited thereto, for example, the vapor phase Beckmann rearrangement may be carried out by reacting cyclohexanone oxime in a vapor phase in the presence of a carrier gas and a reaction solvent in the presence of a molecular sieve catalyst having an MFI structure. As the conditions for the vapor phase Beckmann rearrangement reaction, the reaction conditions conventional in the art can be employed, and preferably, the amount of the reaction solvent used in the vapor phase Beckmann rearrangement reaction is 40 to 80% by weight, preferably 50 to 70% by weight, based on the total weight of the reaction raw materials and the reaction solvent.
According to the invention, in the vapor-phase Beckmann rearrangement reaction, the reaction raw material refers to a mixture of lower alcohols such as methanol, ethanol or isopropanol and cyclohexanone oxime as a solvent, and the weight ratio of the solvent to the cyclohexanone oxime is 1:1-3:1.
Preferably, the conditions of the vapor phase Beckmann rearrangement reaction may include a temperature of 320-450 ℃, preferably 370-400 ℃, a pressure of 0.05-0.5MPa, preferably 0.1-0.3MPa, and a weight hourly space velocity of 0.1-5h -1 of cyclohexanone oxime. The carrier gas may be various gases that do not react with the cyclohexanone oxime and the solvent under the conditions of the vapor phase Beckmann rearrangement reaction, and may be, for example, nitrogen gas and an inert gas.
The pressure and partial pressure in the present invention are all absolute pressures, unless specifically stated otherwise. The present invention has low purity requirements for crude caprolactam, and can obtain high quality caprolactam product even if the quality fluctuates, preferably the crude caprolactam obtained in the step (1) has a purity of 97 to 99.9 wt%, further preferably the crude caprolactam contains caprolactam, 5-cyano-1-pentene, cyclohexenone, cyclohexanone oxime, octahydrophenazine, decahydro phenazine and isomers of tetrahydroazepin-2-one and/or tetrahydroazepin-2-one, and the caprolactam has a content of 99 to 99.9 wt%, a content of 5-cyano-1-pentene of 0.001 to 0.1 wt%, a content of cyclohexenone of 0.001 to 0.1 wt%, a content of cyclohexanone oxime of 0.001 to 0.3 wt%, a content of octahydrophenazine of 0.001 to 0.1 wt%, and a total content of tetrahydroazepin-2-one and/or tetrahydroazepin-2-one isomers of 0.001 to 0.1 wt%, based on the total weight of the caprolactam crude caprolactam product, and the balance of less than 0.001 to 0.1 wt% of the impurities. Wherein the sum of the mass contents of caprolactam and impurities is 100 percent.
In some of the examples hereinafter, the verification is carried out with crude caprolactam having a purity of 99%. The conventional vapor phase beckmann rearrangement reaction can generally reach the purity after desolventizing, dehydrating and light weight removal. It should be noted that, although the purity of the crude product with 99% purity to the product with excellent grade seems not to be quite different, as mentioned above, crude caprolactam contains not only conventional impurities but also many impurities which are difficult to remove qualitatively, and it is not easy to obtain the product with excellent grade from the crude product with 99% purity, which has been a problem to be studied by those skilled in the art.
The caprolactam crystallization scheme provided by the invention is described below with reference to the accompanying drawings, but the invention is not limited thereto.
In a preferred embodiment of the present invention, as shown in fig. 2, the gas phase rearrangement product is subjected to solvent removal, dehydration and light impurity removal to obtain crude caprolactam, the crude caprolactam is mixed with recycled solvent and secondary mother liquor to prepare a desired concentration, and then the crude caprolactam is subjected to primary crystallization, and the crude crystals obtained in the primary crystallization are mixed with the solvent recovered by condensation of the primary crystallization and the solvent recovered by condensation of the secondary crystallization to prepare a desired concentration, and then the crude caprolactam is subjected to secondary crystallization. The secondary crystallization process obtains a secondary crystallization mother liquor which is returned to the primary crystallization process, and the obtained crystal product is sent to a dissolution unit. The primary mother liquor obtained by primary crystallization is concentrated and distilled to recover the solvent, and concentrated to the temperature required by the crystallization of the mother liquor, then the concentrated mother liquor enters a mother liquor crystallization unit, the crude caprolactam obtained by the mother liquor crystallization unit is returned to the primary crystallization unit, and the mother liquor obtained by the mother liquor crystallization enters a solvent recovery unit to recover the residual solvent, and the residual liquid is discharged. Although secondary crystallization is adopted, the circulating solvent of the whole process is not greatly increased, but the requirement and the dependence on the quality of crude products are reduced, the quality of the products can be obtained, and the quality stability of the products in the production process is improved.
According to the invention, in continuous production, the total yield of crystallization is calculated as the total weight of caprolactam flowing into the hydrogenation stage/total weight of crude caprolactam initially fed in the crystallization stage x 100%.
The quality of the caprolactam product produced was evaluated in the following examples using the following test methods:
(1) Purity of caprolactam
Caprolactam purity and impurity content were analyzed by capillary column Innowax m, gas chromatography 7890GC, with a minimum detection limit of 1 μg/g.
(2) Potassium permanganate absorption value of epsilon-caprolactam
Pouring 3.000 g of caprolactam into a 100ml colorimetric tube, diluting to a scale with distilled water, shaking uniformly, putting into a constant-temperature water bath at 20 ℃, adding 1ml of potassium permanganate solution with the concentration of 0.01N into the colorimetric tube, shaking uniformly immediately, starting a stopwatch at the same time, stopping the stopwatch when the color of the sample solution in the colorimetric tube is the same as that of a standard colorimetric solution (3 g of high-grade pure Co (NO 3). 6H2O and 12 mg of high-grade pure K2Cr2O7 are dissolved in water, diluted to 1 liter and shaking uniformly), and recording the consumed time (calculated in seconds), namely the potassium permanganate absorption value.
(3) Volatile base (V.B)
In alkaline medium, the alkaline low molecular impurities in the sample are distilled out, absorbed by a known amount of hydrochloric acid solution, and excessive hydrochloric acid is dripped back by a sodium hydroxide standard solution. The number of moles of acid consumed per kilogram of sample was used as a measure of volatile base. The calculation formula is as follows:
V.B(mmol/kg)=[(V0-V)×CNaOH/M]×1000
Wherein V 0 is the volume of NaOH standard solution consumed by a blank test, and the unit is ml;
V is the volume of NaOH standard solution consumed by the sample, and the unit is ml;
C NaOH is the accurate concentration of the NaOH standard solution, and the unit is mol/L;
M is the mass of the sample in g.
(4) Extinction value E (at 290nm wavelength)
In a 300ml Erlenmeyer flask, 50 g of the sample was weighed, 50ml of distilled water was added, and the sample was shaken well to dissolve completely and allowed to stand for 10 minutes. The extinction of a sample at a concentration of 50% relative to distilled water was measured using a spectrophotometer at a wavelength of 290 nm.
The present invention will be described in detail by examples.
Example 1
(1) The gas phase rearranged product (containing 45% by weight of methanol, 42% by weight of caprolactam, 1.5% by weight of water and the balance impurities) was desolventized, dehydrated and light, and then a crude caprolactam having a purity of 99% was obtained. The crude caprolactam contains 0.0015% of 5-cyano-1-pentene, 0.2% of N-methylcaprolactam, 0.03% of N-valeramide, 0.04% of octahydrophenazine, 0.06% of decahydrophenazine and the balance of undetermined impurities.
(2) The crude caprolactam is mixed with isopropyl ether to prepare a caprolactam solution with the mass concentration of 30 percent and the temperature of 50.8 ℃ (after the circulation is started, the crude caprolactam is mixed with the crude caprolactam obtained by primary mother liquor crystallization and then is mixed with isopropyl ether and secondary crystallization mother liquor to obtain a target caprolactam solution), then the caprolactam solution is continuously injected into a primary crystallization unit, the primary crystallization unit uses primary adiabatic flash evaporation to continuously crystallize, the operation temperature is set to be 35 ℃, the operation pressure is 27kPa, the residence time is 240 minutes, and the primary crystallization is carried out, wherein the primary crystallization yield is about 85 percent. The condensed solvent collected in the primary crystallization process is recycled.
(3) And (3) centrifuging and washing crystal slurry produced by primary crystallization, mixing with isopropyl ether again for dissolution, preparing a solution with the concentration of 30% and the caprolactam temperature of 50 ℃, then entering a secondary crystallization unit, wherein the operation condition of the secondary crystallization unit is consistent with that of the primary crystallization unit, collecting secondary crystallization crystal slurry after the secondary crystallization unit is stabilized, centrifuging and washing to obtain a caprolactam crystal product, and preparing all secondary crystallization mother liquor for preparing a feed of primary crystallization, namely preparing a caprolactam solution with the mass concentration of 30% for primary crystallization under the condition of isopropyl ether replenishment. The condensed solvent collected in the secondary crystallization process is recycled.
(4) Mixing and dissolving caprolactam crystal product with water with equal mass to obtain caprolactam water solution. The caprolactam aqueous solution is reacted with hydrogen in a stirred tank reactor at 75 ℃ and a pressure of 0.7MPa for a reaction residence time of 1h under the condition that an amorphous nickel catalyst (manufactured by the company of China petrochemical catalyst Chang Ling, trade name: SRNA-4) exists (the mass ratio of the caprolactam aqueous solution to the amorphous nickel catalyst is controlled to be 50-100), the hydrogen flow rate is controlled to be 0.1L/min, and then the caprolactam aqueous solution is obtained. The obtained caprolactam water solution is distilled and dehydrated under the condition of 5kPa, and then heavy impurities are distilled and removed under the condition of 2kPa to obtain a caprolactam product, and the system temperature is controlled below 130 ℃ in the process.
(5) Collecting mother liquor obtained by primary crystallization, recovering solvent in the mother liquor by double-effect evaporation, and concentrating the mother liquor to 45.7%. Introducing the concentrated mother liquor into a mother liquor crystallization kettle, crystallizing by an adiabatic flash evaporation mode, wherein the final temperature is 30 ℃, the crystallization yield of the mother liquor is 94.5%, centrifuging and washing crystals obtained by mother liquor crystallization, and completely returning the obtained crude caprolactam to the primary crystallization step of the step (2). The remaining mother liquor of the primary mother liquor crystallization was recovered from the solvent by distillation at a pressure of 25 kPa. And discharging impurities after recovering the mother solution solvent out of the system. Mother liquor crystallization, double-effect rectification and solvent recycling and recycling of the solvent collected by the solvent recovery unit.
The caprolactam product obtained was analyzed and the results are shown in Table 1, following the procedure described above, for 100 hours.
The overall yield of caprolactam product in the crystallization process, including step (2), step (3) and step (5), is calculated to be above 99 wt%. The total yield is calculated as the total weight of caprolactam flowing into the hydrogenation stage of step (4) per total weight of crude caprolactam initially fed in the crystallization stage of step (2) x 100%.
Comparative example 1
Caprolactam is purified as in example 1, except that step (3) is not performed, otherwise the same as in example 1.
The caprolactam product obtained was analyzed and the results are shown in Table 1, following the procedure described above, for 100 hours.
Comparative example 2
Caprolactam is purified as in example 1, except that in step (3) the secondary crystallization mother liquor is withdrawn without returning to the first crystallization, and the secondary crystallization mother liquor is concentrated, crystallized in the manner of step (5) in example 1, and the secondary mother liquor crystallized crude caprolactam is returned to step (2), otherwise identical to example 1.
The caprolactam product obtained was analyzed and the results are shown in Table 1, following the procedure described above, for 100 hours.
As can be seen from Table 1, although the product quality obtained in comparative example 2 was improved relative to comparative example 1, the parameters of purity, PM value, extinction value, volatile base value and chromaticity value of the caprolactam obtained were significantly inferior to those of example 1.
Furthermore, in the continuous production of comparative example 2, the steps of concentrating and crystallizing the secondary mother liquor were added, and the energy consumption was greatly increased compared to example 1, while in the continuous production of comparative example 2, the step (2) also required to add more fresh solvent due to the need to prepare the target crystallization solution compared to example 1.
Example 2
(1) Treating the gas phase rearranged product as in step (1) of example 1 to obtain the same crude caprolactam;
(2) Mixing the crude caprolactam with isopropyl ether to prepare a caprolactam solution with the mass concentration of 15% and the temperature of 40 ℃ (after the circulation is started, mixing the crude caprolactam with the crude caprolactam obtained by primary mother liquor crystallization, mixing the crude caprolactam with isopropyl ether and secondary crystallization mother liquor to obtain a target caprolactam solution), continuously injecting the caprolactam solution into a primary crystallization unit, continuously evaporating and crystallizing the primary crystallization unit, setting the operation temperature at 40 ℃, the operation pressure at 31kPa, the residence time at 240min, carrying out primary crystallization, controlling the heating rate, and keeping the primary crystallization yield at 85%.
(3) And (3) centrifuging and washing crystal slurry produced by primary crystallization, mixing with isopropyl ether again for dissolution, preparing a solution with the concentration of 30% and the caprolactam temperature of 54 ℃, then entering a secondary crystallization unit, continuously crystallizing the solution by using primary adiabatic flash evaporation in the secondary crystallization unit, setting the operating temperature at 35 ℃, the operating pressure at 27kPa, and the residence time at 240min, and performing secondary crystallization, wherein the secondary crystallization yield is 85%. After the secondary crystallization unit is stabilized, collecting secondary crystallization crystal slurry, and obtaining caprolactam crystal products through centrifugation and washing. The secondary crystallization mother liquor obtained was used entirely for preparing the feed for the primary crystallization, i.e. a caprolactam solution with a mass concentration of 15% was prepared for the primary crystallization with isopropyl ether make-up.
(4) The same as in step (4) of example 1.
(5) The same as in step (5) of example 1.
The caprolactam product obtained was analyzed and the results are shown in Table 1, following the procedure described above, for 100 hours.
Example 3
(1) Crude caprolactam was obtained by the same method as in example 1;
(2) The crude caprolactam product and cyclohexane were prepared as a 29% mass fraction caprolactam solution at 67 ℃ (after the start of the cycle, the crude caprolactam was mixed with crude caprolactam obtained by primary mother liquor crystallization and then with cyclohexane and secondary crystallization mother liquor to obtain the target caprolactam solution). And then continuously injecting the solution into a first-stage caprolactam crystallizer, starting the discharge of the first-stage crystallizer after the material in the first-stage caprolactam crystallizer reaches a set value, continuously injecting the solution into a second-stage caprolactam crystallizer, regulating the vacuum degree of each stage of caprolactam crystallizer after the material in the second-stage caprolactam crystallizer reaches the set value, and regulating the absolute pressure of the first-stage caprolactam crystallizer to 35kPa, wherein the temperature in the caprolactam crystallizer is 52 ℃. The absolute pressure of the second stage crystallizer was adjusted to 18kPa at which the temperature within the crystallizer was 35 ℃. The caprolactam solution is continuously injected, the caprolactam crystal slurry is continuously extracted, and the residence time of each stage of crystallizer is maintained at 2.25h. At this time, the total yield of the whole crystallization process was about 89%. After maintaining the state of continuous crystallization for several tens of hours, a part of the crystal slurry is collected, and the obtained caprolactam crystals are centrifuged and washed.
(3) The crude crystals from the primary crystallization were then re-mixed with cyclohexane to form a 29% caprolactam solution at 67 ℃, and subsequently fed to a secondary crystallization unit operated using a primary adiabatic flash, set at an operating temperature of 35 ℃ and an absolute pressure of 18kPa. After the secondary crystallization unit is stabilized, collecting secondary crystallization crystal slurry, and obtaining caprolactam crystal products through centrifugation and washing. The secondary crystallization mother liquor obtained was used entirely for formulating the feed for the primary crystallization. The secondary crystallization mother liquor is totally returned to the primary crystallization unit.
(4) The same as in step (4) of example 1.
(5) The same as in step (5) of example 1.
The caprolactam product obtained was analyzed and the results are shown in Table 1, following the procedure described above, for 100 hours.
Example 4
Caprolactam is purified according to the method of example 1, except that, prior to hydrogenation, the aqueous caprolactam solution is prepared in the following manner in place of the aqueous caprolactam solution of example 1:
And (3) countercurrent washing is carried out on the crystal slurry obtained by the secondary crystallization and isopropyl ether with equal mass of crystals, so as to obtain the crystal slurry of the caprolactam crystal product. The slurry was directly mixed with 0.22 parts by mass of water to dissolve caprolactam crystals therein, thereby obtaining an aqueous caprolactam solution having a concentration of 80%. The aqueous solution is subjected to azeotropic distillation, normal pressure is used for azeotropic distillation, the temperature of the tower top is 84 ℃, the temperature of the tower bottom is 114 ℃, the water phase after phase separation at the tower top is totally refluxed, and the solvent phase at the tower top is totally extracted.
The caprolactam product obtained was analyzed and the results are shown in Table 1, following the procedure described above, for 100 hours.
Example 5
Caprolactam is purified according to the procedure of example 1, except that the removal conditions in step (1) are adjusted such that the crude caprolactam product contains 98.7% by weight caprolactam, 261. Mu.g/g of 5-cyano-1-pentene, 245. Mu.g/g of cyclohexanone oxime, 1488. Mu.g/g of cyclohexenone, 421. Mu.g/g of octahydrophenazine, 189. Mu.g/g of tetrahydroazepan-2-one and isomers thereof, 1134. Mu.g/g of decahydrophenazine and other undetermined impurities.
The caprolactam product obtained was analyzed and the results are shown in Table 1, following the procedure described above, for 100 hours.
Example 6
Caprolactam is purified according to the procedure of example 1, except that step (2) is replaced by:
(2) And (3) crystallization refining, namely preparing the crude caprolactam obtained in the step (1) and isopropyl ether into a solution according to the mass ratio of 1:1, heating to 54 ℃ to completely dissolve the crude caprolactam product, and then reducing the temperature to 15 ℃ to precipitate caprolactam crystals. And (3) carrying out centrifugal separation on the obtained slurry to obtain primary crystal and primary crystallization mother liquor.
The caprolactam product obtained was analyzed and the results are shown in Table 1, following the procedure described above, for 100 hours.
Example 7
Caprolactam is purified as in example 1, except that the crystallization solvent replaces isopropyl ether with 1-chloropropane.
The caprolactam product obtained was analyzed and the results are shown in Table 1, following the procedure described above, for 100 hours.
Example 8
Caprolactam is purified as in example 1, except that the crystallization solvent is n-heptane instead of isopropyl ether.
The caprolactam product obtained was analyzed and the results are shown in Table 1, following the procedure described above, for 100 hours.
Example 9
Caprolactam is purified as in example 1, except that the crystallization solvent is toluene instead of isopropyl ether.
The caprolactam product obtained was analyzed and the results are shown in Table 1, following the procedure described above, for 100 hours.
Example 10
Caprolactam is purified according to the method of example 1, except that the catalyst is a palladium-based catalyst, the mass ratio of the caprolactam aqueous solution to the palladium-based catalyst is controlled to be 50-100, the hydrogenation reaction temperature is 75 ℃, and the pressure is 0.7Mpa.
The preparation method of the palladium catalyst comprises the steps of taking 104g of 4-10 mesh coconut shell type granular active carbon, placing the activated carbon into a 500mL beaker, a) soaking and stirring for 30min with 300mL of water, washing and filtering, b) then soaking and stirring for 30min with 200mL of water, washing and filtering, and repeating the steps a) and b) once. Then 200mL of 0.5N nitric acid is used, and the mixture is soaked for 60min with gentle stirring, washed and filtered. Washing with distilled water to remove nitric acid until the pH is about 7, and drying at 100-105 ℃ for 6 hours to obtain 100g of treated coconut shell type granular active carbon for later use. An aqueous palladium-rare earth solution was prepared by weighing 1.28g of palladium nitrate Pd (NO 3)2·2H2 O (fw= 266.5) and 6.5 g of cerium nitrate Ce (NO 3)3·6H2 O (fw=434)) and dissolving in 120 g of water, to obtain an aqueous palladium-rare earth solution.
And (3) a catalyst precursor, namely pouring a palladium-rare earth aqueous solution into the treated coconut shell type granular active carbon, keeping the temperature at 50 ℃, soaking for 6 hours (shaking for one time for 30 min), transferring into a rotary evaporator, heating to 70 ℃, and removing water by rotary evaporation to obtain the catalyst precursor.
Reduction treatment the catalyst precursor was dried in a 100 ℃ oven for 10 hours and then calcined at 200 ℃ for 4 hours. The reaction mixture was reduced with H 2 at normal pressure at 90℃for 2H before use, with a flow rate of H 2 of 4mL/min per gram of catalyst. The palladium catalyst was obtained, wherein the content of Pd was 0.5 wt%, the content of CeO 2 was 2.5 wt%, and the carrier was activated carbon.
Example 11
Caprolactam is purified according to the procedure of example 1, except that step (2) and step (3) are replaced by:
(2) And (3) crystallization refining, namely preparing the crude caprolactam obtained in the step (1) and isopropyl ether into a solution according to the mass ratio of 1:1 (after circulation is started, mixing the crude caprolactam with the crude caprolactam obtained by primary mother liquor crystallization, and then mixing the crude caprolactam with isopropyl ether and secondary crystallization mother liquor to obtain a target caprolactam solution), heating to 54 ℃ to completely dissolve the crude caprolactam product, and then reducing the temperature to 15 ℃ to precipitate caprolactam crystals. And (3) carrying out centrifugal separation on the obtained slurry to obtain primary crystal and primary crystallization mother liquor.
(3) Preparing primary crystallization crystals and isopropyl ether into a solution according to the mass ratio of 1:1, heating to 54 ℃ to completely dissolve a crude caprolactam product, and then reducing the temperature to 15 ℃ to precipitate caprolactam crystals. And (3) carrying out centrifugal separation on the obtained slurry to obtain secondary crystallization crystals and secondary crystallization mother liquor. The secondary crystallization mother liquor obtained was used entirely for preparing the feed for the primary crystallization, i.e. a 50% strength by mass caprolactam solution was prepared for the primary crystallization with isopropyl ether make-up.
The caprolactam product obtained was analyzed and the results are shown in Table 1, following the procedure described above, for 100 hours.
TABLE 1
The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.
Claims (37)
1. The purification method for preparing the crude caprolactam product by the vapor phase Beckmann rearrangement method is characterized by comprising the following steps:
(1) Removing solvent, dehydration and light impurities from a mixed solution containing caprolactam prepared by a gas-phase Beckmann rearrangement method to obtain crude caprolactam, wherein the purity of the crude caprolactam is 97-99.9 wt%;
(2) Mixing the crude caprolactam with a crystallization solvent for primary crystallization to obtain a primary crystallization product and a primary crystallization mother liquor, wherein the crystallization solvent can be azeotroped with water and is not co-dissolved with water;
The solubility of caprolactam in the crystallization solvent in mass percent is lower than 20 weight percent under the absolute pressure of 5kPa and the boiling temperature of the crystallization solvent, wherein the boiling point of the crystallization solvent under normal pressure is 40-180 ℃, and the crystallization solvent is one selected from ether, alkane, cycloparaffin, halohydrocarbon and aromatic hydrocarbon;
(3) Mixing the primary crystallization product with a crystallization solvent for secondary crystallization to obtain a secondary crystallization product and secondary crystallization mother liquor, and returning the secondary crystallization mother liquor to the step (2) to serve as at least part of the primary crystallization solvent;
the secondary crystallization mode is adiabatic flash evaporation or decompression evaporation crystallization;
(4) And (3) carrying out hydrogenation reaction on the secondary crystallization product.
2. The purification process according to claim 1, wherein the ether is a saturated aliphatic monobasic ether;
the alkane contains 6 to 12 carbon atoms;
the cycloalkanes contain 5 to 8 carbon atoms;
The halohydrocarbon is selected from at least one of 1-chloropropane, 2-chloropropane, 1-chloro-n-butane, 2-chlorobutane, 1-chlorodimethylpropane, 2-chlorodimethylpropane, 1-n-bromopropane, 2-bromopropane, 1-bromobutane and 2-bromobutane;
the aromatic hydrocarbon is selected from at least one of benzene, toluene, xylene and trimethylbenzene.
3. The purification method according to claim 2, wherein the ether is at least one of isopropyl ether, ethyl butyl ether, methyl ethyl ether, diethyl ether, n-propyl ether, n-butyl ether, ethyl butyl ether, methyl t-butyl ether, and ethyl t-butyl ether;
The alkane is at least one selected from n-heptane, n-hexane, isopentane, n-octane, n-nonane, methylhexane, isohexane, neohexane, isoheptane, isooctane and isononane;
the cycloalkane is selected from at least one of cyclohexane, cyclopentane, methylcyclopentane, and methylcyclohexane.
4. A purification process according to any one of claims 1 to 3, wherein the conditions of primary crystallization include:
the crude caprolactam is dissolved in a crystallization solvent and is crystallized once more.
5. The purification process according to claim 4, wherein the caprolactam solution obtained has a caprolactam mass concentration of 15% to 45%.
6. The purification method according to claim 4, wherein the temperature of the primary crystallization is 10 to 60 ℃.
7. The purification method according to claim 6, wherein the temperature of the primary crystallization is 25 ℃ to 58 ℃.
8. A purification process according to any one of claims 1 to 3 wherein the primary crystallization is by adiabatic flash evaporation or reduced pressure evaporative crystallization.
9. A purification process according to any one of claims 1 to 3, wherein the primary crystallization is carried out in a multistage continuous crystallization.
10. The purification process according to claim 9, wherein the number of stages of the multistage continuous crystallization is not more than 5 stages.
11. The purification process according to claim 10, wherein the primary crystallization is carried out in a 3-stage continuous crystallization.
12. The purification process according to claim 8, wherein the primary crystallization is carried out by adiabatic flash evaporation, and the caprolactam concentration in the fed caprolactam solution is 15-35% by mass.
13. The purification process according to claim 12, wherein the conditions of adiabatic flash evaporation comprise a feed temperature of 40-80 ℃, an operating temperature of 15-60 ℃ and an operating pressure of 3-100kPa.
14. The purification process according to claim 8, wherein the primary crystallization is carried out by evaporation under reduced pressure, and the caprolactam concentration in the fed caprolactam solution is 15-20% by mass.
15. The purification process according to claim 14, wherein the conditions for the evaporation and crystallization under reduced pressure include an operating temperature of 15 to 45℃and an operating pressure of 3 to 100kPa.
16. A purification process according to any one of claims 1-3, wherein the caprolactam crystals content of the mixture obtained at the end of the primary crystallization is not higher than 55% by weight.
17. A purification process according to any one of claims 1 to 3, wherein the yield of the primary crystalline product is not less than 70% by weight.
18. The purification process according to claim 17, wherein the yield of the primary crystallized product is 75 to 95% by weight.
19. A purification process according to any one of claims 1 to 3, wherein the primary crystallization product is separated from the primary crystallization mother liquor by centrifugation, thickening or countercurrent washing.
20. The purification process according to claim 19, wherein the primary crystallization product is separated from the primary crystallization mother liquor by means of countercurrent washing.
21. A purification process according to any one of claims 1 to 3 wherein the secondary crystallization is by adiabatic flash evaporation.
22. The purification process according to claim 21, wherein in the secondary crystallization the mass concentration of caprolactam in the fed caprolactam solution is between 35% and 45%.
23. The purification process according to claim 21, wherein the conditions of adiabatic flash evaporation comprise a feed temperature of 40-80 ℃, an operating temperature of 15-60 ℃ and an operating pressure of 3-100kPa.
24. A purification method according to any one of claims 1 to 3, further comprising:
concentrating the primary crystallization mother liquor to obtain concentrated primary crystallization mother liquor and a recovered solvent;
recrystallizing the concentrated primary crystallization mother liquor to obtain a crude caprolactam product and mother liquor crystallization residual mother liquor;
the crude caprolactam product is returned to step (2).
25. The purification method according to claim 24, further comprising recovering the solvent in the mother liquor remaining from the mother liquor crystallization, and returning the recovered solvent to the step (2) or the step (3) as the crystallization solvent.
26. The purification process according to claim 25, wherein the concentration is by distillation concentration or multiple effect evaporation.
27. The purification method according to claim 26, wherein the concentration is performed using a distillation column.
28. The purification process according to claim 27, wherein the reflux ratio of the distillation column is 0 to 2.
29. A purification process according to any one of claims 1 to 3, wherein the recovered solvent of the crystallization stage of step (2) and/or the crystallization stage of step (3) is returned to the mixing stage of step (2) and/or step (3).
30. A purification process according to any one of claims 1 to 3, wherein the means for carrying out the hydrogenation reaction on the secondary crystalline product comprises:
a) Mixing the secondary crystallization product with water to obtain a caprolactam water solution;
b) Distilling the caprolactam water solution to remove residual crystallization solvent to obtain a caprolactam water solution after solvent removal and a recovered solvent;
c) Contacting the caprolactam water solution after solvent removal with hydrogen in the presence of a hydrogenation catalyst to obtain a caprolactam solution;
d) And dehydrating the caprolactam solution to obtain a caprolactam product.
31. The purification process according to claim 30, wherein in step b) the water content of the caprolactam after removal of the solvent is below 5 ppm.
32. The purification process according to claim 30, wherein in step d) the distillative dehydration is carried out under negative pressure.
33. The purification process according to claim 30, wherein in step d) the temperature of the caprolactam is controlled below 130 ℃ during the dewatering.
34. The purification method according to claim 30, wherein the recovered solvent in step b) is dehydrated and the dehydrated recovered solvent is returned to the mixing stage in step (2) and/or step (3).
35. The purification process according to claim 30, wherein in step a) water is used in an amount of 0.1 to 2.5 parts by weight relative to 1 part by weight of caprolactam in the secondary crystallized product.
36. The purification method according to claim 30, wherein in the step c), the hydrogenation catalyst is at least one selected from the group consisting of a nickel-based catalyst, a palladium-based catalyst and a platinum-based catalyst;
the hydrogenation reaction conditions comprise 65-180 ℃, 0.5-5MPa of pressure and 0.1-2L/min of hydrogen flow.
37. The purification process according to claim 1, wherein the crude caprolactam contains isomers of caprolactam, 5-cyano-1-pentene, cyclohexenone, cyclohexanone oxime, octahydrophenazine, decahydrophenazine and tetrahydroazepin-2-one and/or tetrahydroazepin-2-one, and the caprolactam content is 99 to 99.9% by weight, the 5-cyano-1-pentene content is 0.001 to 0.1% by weight, the cyclohexenone content is 0.001 to 0.1% by weight, the cyclohexanone oxime content is 0.001 to 0.3% by weight, the octahydrophenazine content is 0.001 to 0.1% by weight, the total content of tetrahydroazepin-2-one and/or tetrahydroazepin-2-one isomers is 0.001 to 0.1% by weight, and the decahydrophenazine content is 0.001 to 0.1% by weight, based on the total weight of the crude caprolactam product.
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