CN109603842B - Lanthanum-doped copper-manganese composite oxide catalyst and preparation method thereof - Google Patents
Lanthanum-doped copper-manganese composite oxide catalyst and preparation method thereof Download PDFInfo
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- 239000003054 catalyst Substances 0.000 title claims abstract description 156
- 239000002131 composite material Substances 0.000 title claims abstract description 56
- HPDFFVBPXCTEDN-UHFFFAOYSA-N copper manganese Chemical compound [Mn].[Cu] HPDFFVBPXCTEDN-UHFFFAOYSA-N 0.000 title claims abstract description 56
- 238000002360 preparation method Methods 0.000 title claims abstract description 11
- 239000011572 manganese Substances 0.000 claims abstract description 46
- 239000010949 copper Substances 0.000 claims abstract description 36
- 230000003197 catalytic effect Effects 0.000 claims abstract description 28
- 239000012855 volatile organic compound Substances 0.000 claims abstract description 23
- 238000000034 method Methods 0.000 claims abstract description 17
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 15
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 13
- 238000001228 spectrum Methods 0.000 claims abstract description 12
- 239000011029 spinel Substances 0.000 claims abstract description 10
- 229910052596 spinel Inorganic materials 0.000 claims abstract description 10
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- 238000001035 drying Methods 0.000 claims abstract description 8
- 229910052746 lanthanum Inorganic materials 0.000 claims abstract description 7
- 150000003863 ammonium salts Chemical class 0.000 claims abstract description 6
- 150000001879 copper Chemical class 0.000 claims abstract description 6
- 150000002603 lanthanum Chemical class 0.000 claims abstract description 6
- 150000002696 manganese Chemical class 0.000 claims abstract description 6
- 239000012266 salt solution Substances 0.000 claims abstract description 6
- 239000002244 precipitate Substances 0.000 claims abstract description 5
- 238000003756 stirring Methods 0.000 claims abstract description 4
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 claims description 61
- 238000007254 oxidation reaction Methods 0.000 claims description 21
- 230000003647 oxidation Effects 0.000 claims description 19
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical group [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 15
- 239000011148 porous material Substances 0.000 claims description 12
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical group [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 11
- 125000004430 oxygen atom Chemical group O* 0.000 claims description 10
- 239000013078 crystal Substances 0.000 claims description 9
- 125000004429 atom Chemical group 0.000 claims description 8
- 230000008569 process Effects 0.000 abstract description 6
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- 229910016978 MnOx Inorganic materials 0.000 abstract 1
- 238000003287 bathing Methods 0.000 abstract 1
- 238000004886 process control Methods 0.000 abstract 1
- AMWRITDGCCNYAT-UHFFFAOYSA-L hydroxy(oxo)manganese;manganese Chemical compound [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 description 42
- 229910052760 oxygen Inorganic materials 0.000 description 35
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 33
- 239000001301 oxygen Substances 0.000 description 33
- 230000009467 reduction Effects 0.000 description 26
- 238000006722 reduction reaction Methods 0.000 description 26
- QPLDLSVMHZLSFG-UHFFFAOYSA-N Copper oxide Chemical compound [Cu]=O QPLDLSVMHZLSFG-UHFFFAOYSA-N 0.000 description 14
- 230000000694 effects Effects 0.000 description 13
- 239000007789 gas Substances 0.000 description 11
- 238000012360 testing method Methods 0.000 description 11
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- 230000009286 beneficial effect Effects 0.000 description 7
- GEYXPJBPASPPLI-UHFFFAOYSA-N manganese(III) oxide Inorganic materials O=[Mn]O[Mn]=O GEYXPJBPASPPLI-UHFFFAOYSA-N 0.000 description 7
- 229910052802 copper Inorganic materials 0.000 description 6
- 238000004626 scanning electron microscopy Methods 0.000 description 6
- 230000008901 benefit Effects 0.000 description 5
- 238000007084 catalytic combustion reaction Methods 0.000 description 5
- SYBFKRWZBUQDGU-UHFFFAOYSA-N copper manganese(2+) oxygen(2-) Chemical compound [O--].[O--].[Mn++].[Cu++] SYBFKRWZBUQDGU-UHFFFAOYSA-N 0.000 description 5
- MRELNEQAGSRDBK-UHFFFAOYSA-N lanthanum oxide Inorganic materials [O-2].[O-2].[O-2].[La+3].[La+3] MRELNEQAGSRDBK-UHFFFAOYSA-N 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 230000010718 Oxidation Activity Effects 0.000 description 4
- 238000003795 desorption Methods 0.000 description 4
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- -1 copper cations Chemical class 0.000 description 3
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- 239000001307 helium Substances 0.000 description 3
- 229910052734 helium Inorganic materials 0.000 description 3
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 230000003993 interaction Effects 0.000 description 3
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 3
- VASIZKWUTCETSD-UHFFFAOYSA-N manganese(II) oxide Inorganic materials [Mn]=O VASIZKWUTCETSD-UHFFFAOYSA-N 0.000 description 3
- 230000007420 reactivation Effects 0.000 description 3
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- 238000004364 calculation method Methods 0.000 description 2
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- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- NUJOXMJBOLGQSY-UHFFFAOYSA-N manganese dioxide Chemical compound O=[Mn]=O NUJOXMJBOLGQSY-UHFFFAOYSA-N 0.000 description 2
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 2
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- 229920006395 saturated elastomer Polymers 0.000 description 2
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- 229910000314 transition metal oxide Inorganic materials 0.000 description 2
- RNAMYOYQYRYFQY-UHFFFAOYSA-N 2-(4,4-difluoropiperidin-1-yl)-6-methoxy-n-(1-propan-2-ylpiperidin-4-yl)-7-(3-pyrrolidin-1-ylpropoxy)quinazolin-4-amine Chemical compound N1=C(N2CCC(F)(F)CC2)N=C2C=C(OCCCN3CCCC3)C(OC)=CC2=C1NC1CCN(C(C)C)CC1 RNAMYOYQYRYFQY-UHFFFAOYSA-N 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- 229910002451 CoOx Inorganic materials 0.000 description 1
- 239000005751 Copper oxide Substances 0.000 description 1
- 229910016553 CuOx Inorganic materials 0.000 description 1
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 1
- 239000005977 Ethylene Substances 0.000 description 1
- 229910015189 FeOx Inorganic materials 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910005855 NiOx Inorganic materials 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 238000002159 adsorption--desorption isotherm Methods 0.000 description 1
- 238000003915 air pollution Methods 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000010923 batch production Methods 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
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- 229910000431 copper oxide Inorganic materials 0.000 description 1
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- 125000001967 indiganyl group Chemical group [H][In]([H])[*] 0.000 description 1
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- 239000010453 quartz Substances 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 239000011949 solid catalyst Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/005—Spinels
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
- B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
- B01J23/84—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
- B01J23/889—Manganese, technetium or rhenium
- B01J23/8892—Manganese
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
- F23G7/00—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals
- F23G7/06—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals of waste gases or noxious gases, e.g. exhaust gases
- F23G7/07—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals of waste gases or noxious gases, e.g. exhaust gases in which combustion takes place in the presence of catalytic material
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Abstract
本发明公开了镧掺杂的铜锰复合氧化物催化剂及其制备方法。在该催化剂的XRD衍射图谱中含有Cu1.5Mn1.5O4尖晶石相的衍射峰，无La和Mn2O3的衍射峰；在该催化剂的XPS Cu 2p光谱中有两个分别位于933.3±0.1eV和930.5±0.1eV的峰。Cu1.5Mn1.5O4的存在和MnOx的弱结晶导致更多的活性氧以及更多的活性氧传输通道。本申请通过La进一步提高铜锰复合氧化物催化剂对VOCs的催化性能。该制备方法包括以下步骤：1)将锰盐、铜盐和镧盐溶于水并水浴0.1～1h，水浴温度为50～70℃；2)加入铵盐溶液至pH值为7.5～8.5，并继续搅拌1～3h；3)获取沉淀，然后进行干燥和烧结，即得到镧掺杂的铜锰复合氧化物催化剂。本发明的镧掺杂的铜锰复合氧化物催化剂的制备方法的工艺简单，过程易控制，可以批量化生产。
The invention discloses a lanthanum-doped copper-manganese composite oxide catalyst and a preparation method thereof. In the XRD diffraction pattern of the catalyst, there are diffraction peaks of Cu 1.5 Mn 1.5 O 4 spinel phase, but no diffraction peaks of La and Mn 2 O 3 ; in the XPS Cu 2p spectrum of the catalyst, two are located at 933.3± 0.1 eV and peaks at 930.5 ± 0.1 eV. The presence of Cu 1.5 Mn 1.5 O 4 and weak crystallization of MnOx lead to more reactive oxygen species as well as more reactive oxygen species transport channels. The present application further improves the catalytic performance of the copper-manganese composite oxide catalyst for VOCs through La. The preparation method includes the following steps: 1) dissolving manganese salts, copper salts and lanthanum salts in water and bathing in water for 0.1 to 1 h at a temperature of 50 to 70°C; 2) adding ammonium salt solution to pH 7.5 to 8.5, and Continue to stir for 1-3 hours; 3) obtain a precipitate, and then perform drying and sintering to obtain a lanthanum-doped copper-manganese composite oxide catalyst. The preparation method of the lanthanum-doped copper-manganese composite oxide catalyst of the invention has simple process, easy process control, and can be mass-produced.
Description
Technical Field
The invention relates to the technical field of VOCs catalytic combustion, in particular to a lanthanum-doped copper-manganese composite oxide catalyst and a preparation method thereof.
Background
Most Volatile Organic Compounds (VOCs) are the major cause of air pollution. They are rich in resources, including industrial processes and human activities. Due to the hazards to the atmosphere and human health, it is highly desirable in most countries to control the emissions of VOCs. Among the various technologies, catalytic oxidation is considered to be an effective and economical method for eliminating VOCs. Currently, noble metal catalysts are the most commonly used catalysts because of their good activity in the oxidation of VOCs. However, the widespread use of noble metal catalysts in industry is limited by their high price, susceptibility to poisoning and sintering. Therefore, transition metal oxides are considered as a promising substitute, and have attracted much attention in recent years. Transition metal oxides such as CuOx, MnOx, CoOx, FeOx, NiOx and many complex oxides have been investigated for the removal of VOCs.
Among transition metal composite oxides, manganese-copper composite oxides are considered as inexpensive, environmentally friendly and highly active materials, and have received much attention in catalytic oxidation due to their excellent properties. Meanwhile, the catalyst shows good activity in the combustion of various VOCs, including the oxidation of ethylene and methanol and the combustion reaction of toluene. The performance of the manganese-copper composite oxide catalyst is closely related to the interaction of copper and manganese, and the oxidation-reduction reaction in the system
Resulting in electron transfer between copper cations and manganese cations, and an increased proportion of defective oxygen on the surface due to the interaction between manganese oxide and copper oxide. However, although copper manganese oxide catalysts have been studied and improved, there is still a need to overcome the disadvantages of poor catalytic activity at low temperatures and poor thermal stability.
Disclosure of Invention
The invention aims to provide a lanthanum-doped copper-manganese composite oxide catalyst with good catalytic activity and excellent thermal stability.
In order to achieve the above object, according to one aspect of the present invention, there is provided a lanthanum-doped copper-manganese composite oxide catalyst. The XRD diffraction pattern of the lanthanum-doped copper-manganese composite oxide catalyst contains Cu1.5Mn1.5O4Diffraction peaks of spinel phase, no La and Mn2O3A diffraction peak of (a); there are two peaks in the XPS Cu 2p spectrum of this catalyst located at 933.3 + -0.1 eV and 930.5 + -0.1 eV, respectively.
The lanthanum-doped copper-manganese composite oxide catalyst contains Cu1.5Mn1.5O4Spinel phase, and the crystallinity of manganese oxide (MnOx) is significantly reduced compared to the catalyst not doped with La, Cu1.5Mn1.5O4The mixed structure of spinel phase and MnOx significantly affects the catalytic activity of the copper-manganese composite oxide catalyst in the catalytic combustion of VOCs, because Cu1.5Mn1.5O4The presence of MnOx and the weak crystallization of MnOx result in more active oxygen and more active oxygen transport channels. La is a rich and environment-friendly material, and has a unique electronic structure and excellent oxygen storage property, and the electronic and structural properties of the copper-manganese composite oxide catalyst are changed through La, so that the electron transfer capacity of the copper-manganese composite oxide catalyst is improved, the structure and the function of an electron promoter are played, and the catalytic performance of the copper-manganese composite oxide catalyst on VOCs is further improved. When the lanthanum is not doped, the obtained copper-manganese composite oxide catalyst only contains Cu2+. The XPS Cu 2p spectrum of the lanthanum-doped copper-manganese composite oxide catalyst has two peaks respectively positioned at 933.3 +/-0.1 eV and 930.5 +/-0.1 eV, which shows that the Cu is doped by the lanthanum-doped copper-manganese composite oxide catalyst+And Cu2+Coexistence, easy oxidation and reduction:
the copper-manganese composite oxide catalyst is promoted to have high oxidation activity and reactivation capability. As can be seen from the XPS test, La3d was found for the La-doped catalyst sample5/2The peak of (A) is very close to pure La2O3And thus the valence of La is trivalent.
Further, the specific surface area is 95.9-164.2 m2(ii)/g; the mesoporous volume is 0.353-0.426 mL/g; the total pore volume is 0.37-0.45 mL/g; mn3O4The size of the crystal phase is 13.5-17.7 nm; mn3+56.1-61.3% of the total amount of manganese atoms; the content of O beta is 40.3-44.6% of the total amount of oxygen atoms; the atomic concentration of manganese atoms is 22.35-24.95%, the atomic concentration of copper atoms is 1.79-3.03%, the atomic concentration of La atoms is 2.83-6.40%, and the atomic concentration of oxygen atoms is 68.59-70.60%.
When the doping amount of La is within the above numerical range, the following advantageous effects are produced:
1) the La-doped copper-manganese composite oxide catalyst has a specific surface area, a mesoporous volume and a total pore volume which are obviously higher than those of an undoped copper-manganese composite oxide catalyst, wherein a larger specific surface area can provide more active sites for catalytic reaction, which is beneficial to the adsorption of VOCs and the improvement of the performance of the catalyst; the abundant mesoporous structure can enhance gas diffusion and remarkably improve catalytic efficiency.
2)H2In a TPR spectrogram, the reduction temperature of CuO is 206-235 ℃, and Mn is4+/Mn3+To Mn3+/Mn2+The reduction temperature is 259-315 ℃, Mn3+To Mn2+The reduction temperature is 263-315 ℃; o is2-TPD spectrum with peaks between 160 ℃ and 180 ℃. Compared with the copper-manganese composite oxide catalyst not doped with La, the La-doped copper-manganese composite oxide catalyst has lower initial reduction temperature and can promote H of the copper-manganese composite oxide catalyst2And the overflow effect improves the oxidation reduction capability of the copper-manganese composite oxide catalyst.
3) From O2The TPD test result shows that the La-doped copper-manganese composite oxide catalyst has a larger amount of physically adsorbed and chemically adsorbed oxygen than the La-undoped copper-manganese composite oxide catalyst, which shows that the La doping obviously improves the adsorbed oxygen content of the copper-manganese composite oxide catalyst, is beneficial to oxygen migration and improves the catalytic efficiency.
4) After La doping, the crystallite dimension is obviously reduced by about four times at most, which shows that La doping can prevent crystal growth and play a role of a structure promoter; studies have shown that the weak crystalline structure of MnOx can enhance the presence of oxygen vacancies, which is beneficial for catalytic oxidation.
5) The temperature at which the removal rate of the toluene is 50% is 217-240 ℃; the temperature at which the removal rate of the toluene is 90% is 255-280 ℃; it can be seen that the La doped copper manganese composite oxide catalyst has very high activity for removing toluene.
6) Among the various valence states of manganese, Mn3+Has the best catalytic effect, and the La-doped copper-manganese composite oxide catalyst also has higher content of Mn3+Has higher catalytic activity. Surface chemisorption of oxygen (O β) has been shown to promote full oxidation activity, and surface oxygen can increase reduction and oxygen mobility, which is beneficial for catalytic combustion.
Further, the most preferable specific surface area is 164.2m2(ii)/g; the mesoporous volume is 0.426 mL/g; general holeThe volume was 0.45 mL/g.
Further, Mn is most preferable3O4The size of the crystalline phase was 13.5 nm.
Further, Mn is most preferable3+Accounting for 61.3 percent of the total amount of manganese atoms; most preferably, O β represents 44.6% of the total oxygen atoms.
Further, the atomic concentration of manganese atoms is 22.65% most preferred, the atomic concentration of copper atoms is 3.03% most preferred, the atomic concentration of La atoms is 3.72% most preferred, and the atomic concentration of oxygen atoms is 70.60% most preferred.
In order to achieve the above object, according to another aspect of the present invention, there is also provided a method for preparing a lanthanum-doped copper-manganese composite oxide catalyst, the method comprising the steps of:
1) dissolving manganese salt, copper salt and lanthanum salt in water, and carrying out water bath for 0.1-1 h, wherein the temperature of the water bath is 50-70 ℃;
2) adding an ammonium salt solution until the pH value is 7.5-8.5, and continuously stirring for 1-3 h;
3) and (3) obtaining a precipitate, and then drying and sintering at the sintering temperature of 500-600 ℃ for 1-3 h to obtain the lanthanum-doped copper-manganese composite oxide catalyst.
Therefore, the preparation method of the lanthanum-doped copper-manganese composite oxide catalyst has the advantages of simple process, easily controlled process and batch production.
Further, the manganese salt is Mn (CH)3COO)2·4H2O; the copper salt is Cu (NO)3)2·3H2O; the lanthanum salt is La (NO)3)3·6H2O; the ammonium salt solution is (NH)4)2CO3A solution; the drying temperature is 80-120 ℃, and the drying time is 10-14 h. Therefore, the obtained La-doped copper-manganese composite oxide catalyst is high in quality and less in impurity.
The lanthanum-doped copper-manganese composite oxide catalyst contains Cu1.5Mn1.5O4Catalysis of spinel phases with undoped LaCompared with the catalyst, the crystallinity of MnOx is obviously reduced, and Cu1.5Mn1.5O4The mixed structure of spinel phase and manganese oxide (MnOx) remarkably influences the catalytic activity of the copper-manganese composite oxide catalyst in the catalytic combustion of VOCs (volatile organic compounds) because of Cu1.5Mn1.5O4The presence of MnOx and the weak crystallization of MnOx result in more active oxygen and more active oxygen transport channels. La is a rich and environment-friendly material, and has a unique electronic structure and excellent oxygen storage property, and the electronic and structural properties of the copper-manganese composite oxide catalyst are changed through La, so that the electron transfer capacity of the copper-manganese composite oxide catalyst is improved, the structure and the function of an electron promoter are played, and the catalytic performance of the copper-manganese composite oxide catalyst on VOCs is further improved. When the lanthanum is not doped, the obtained copper-manganese composite oxide catalyst only contains Cu2+. The XPS Cu 2p spectrum of the lanthanum-doped copper-manganese composite oxide catalyst has two peaks respectively positioned at 933.3 +/-0.1 eV and 930.5 +/-0.1 eV, which shows that the Cu is doped by the lanthanum-doped copper-manganese composite oxide catalyst+And Cu2+Coexistence, easy oxidation and reduction:
the copper-manganese composite oxide catalyst is promoted to have high oxidation activity and reactivation capability. As can be seen from the XPS test, La3d was found for the La-doped catalyst sample5/2The peak of (A) is very close to pure La2O3And thus the valence of La is trivalent. The preparation method of the lanthanum-doped copper-manganese composite oxide catalyst has the advantages of simple process, easily controlled process and mass production.
The invention is further described with reference to the following figures and detailed description. Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to assist in understanding the invention, and are included to explain the invention and their equivalents and not limit it unduly. In the drawings:
figure 1 is a nitrogen desorption curve for all catalyst samples.
Figure 2 is a plot of the pore size distribution for all catalyst samples.
FIG. 3 is an SEM of CuMn for a catalyst sample.
FIG. 4 is an SEM photograph of CuMn/La-2% of a catalyst sample.
FIG. 5 is an SEM photograph of CuMn/La-4% of a catalyst sample.
FIG. 6 is an SEM of CuMn/La-6% of a catalyst sample.
Figure 7 is an XRD pattern of all catalyst samples.
Figure 8 is an XPS spectrum (Cu 2p) of all catalyst samples.
FIG. 9 is an XPS spectrum (Mn 2p) of all catalyst samples.
Fig. 10 is XPS spectra (La 3d) of all catalyst samples.
FIG. 11 is an XPS spectrum (O1 s) of all catalyst samples.
FIG. 12 is H for all catalyst samples2-TPR spectrum.
FIG. 13 is O for all catalyst samples2TPD spectrum, wherein curve a is CuMn, curve b is CuMn/La-2%, curve c is CuMn/La-4%, and curve d is CuMn/La-6%.
Figure 14 is a graph of toluene removal efficiency versus all catalyst samples.
Detailed Description
The invention will be described more fully hereinafter with reference to the accompanying drawings. Those skilled in the art will be able to implement the invention based on these teachings. Before the present invention is described in detail with reference to the accompanying drawings, it is to be noted that:
the technical solutions and features provided in the present invention in the respective sections including the following description may be combined with each other without conflict.
Moreover, the embodiments of the present invention described in the following description are generally only some embodiments of the present invention, and not all embodiments. Therefore, all other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without any creative effort shall fall within the protection scope of the present invention.
With respect to terms and units in the present invention. The terms "comprising," "having," and any variations thereof in the description and claims of this invention and the related sections are intended to cover non-exclusive inclusions. The term "H2The "flooding effect" refers to a phenomenon in which active centers (original active centers) on the surface of a solid catalyst are adsorbed to generate an ionic or radical active species, which are transferred to another active center (secondary active center). The term "atomic concentration" means the percentage of a certain number of atoms to the total number of atoms.
The preparation method of the lanthanum-doped copper-manganese composite oxide catalyst of the embodiments 1 to 4 of the present invention includes the following steps:
1) dissolving manganese salt, copper salt and lanthanum salt in water, and carrying out water bath for 0.5h, wherein the temperature of the water bath is 60 ℃;
2) adding an ammonium salt solution until the pH value is 8, and continuously stirring for 2 h;
3) and (3) obtaining a precipitate, and then drying and sintering the precipitate at the sintering temperature of 550 ℃ for 2h to obtain the lanthanum-doped copper-manganese composite oxide catalyst.
Wherein the manganese salt is 0.8mol of Mn (CH)3COO)2·4H2O；
The copper salt is 0.2mol of Cu (NO)3)2·3H2O；
The lanthanum salt is La (NO)3)3·6H2O；
The ammonium salt solution is 1.5mol/L (NH)4)2CO3；
The drying temperature is 105 ℃, and the drying time is 12 h.
La (NO) was calculated in terms of the La contents of 0, 2, 4 and 6% (mol%), respectively3)3·6H2The amount of O used, corresponding four catalyst samples were obtained and are respectively represented as CuMn, CuMn/La-2%, CuMn/La-4% and CuMn/La-6%.
The four catalyst samples of examples 1-4 were characterized using the following characterization methods in sequence:
1) catalyst samples were analyzed for N using the AUTOSORB-IQ adsorption apparatus from Quantachrome Instruments, USA2Adsorption-desorption isotherms. Prior to each analysis, the catalyst samples were degassed at 300 ℃ for 6 hours. The BET (Brunauer Emmett Teller) equation was used to calculate surface area by adsorption isotherm. Based on P/P0Total pore volume was analyzed at a nitrogen adsorption capacity of 0.95. According to N2The desorption branch of the adsorption isotherm was analyzed for micropore volume and pore size distribution using the bjh (barrett Joyner halenda) formula.
2) X-ray diffraction was tested using an X' Pert X-ray diffractometer from the company pananalytical, the netherlands, using copper target radiation (λ ═ 0.15418nm) and operating at 40kV and 30 mA. Intensity data was collected over a 2 theta range of 5 deg. -80 deg..
3) The atomic surface concentration and elemental valence state on the catalyst sample were analyzed by X-ray spectroscopy (XPS) measurements. XPS was tested using an EscaLab model 250Xi photoelectron spectrometer from Thermo Fisher Scientific at 12kV and 15mA in Ultra High Vacuum (UHV) using aluminum target radiation.
4) The surface morphology of the catalyst samples was examined by Scanning Electron Microscopy (SEM) using a JMF-7500F electron microscope equipped with an Oxford INCAEDX detector system, available from JEOL, Japan, operating at 20kV and 80 mA.
5) H is carried out by adopting TP-5076 chemisorption analyzer of Tianjin first industry and trade development company2-TPR(H2temperature programming reduction, hydrogen temperature programmed reduction) test and O2-TPD(O2temperature programming desorption, oxygen temperature programmed desorption). H2Before the TPR test, a 50mg sample of the catalyst was pretreated at 400 ℃ in helium for 1 hour, freed from impurities and water adsorbed on the surface and cooled to 50 ℃.H 25 vol% H in TPR test2/N2The testing temperature is 800 ℃ at the flow rate of 30mL/min, and the heating speed is 10 ℃/min. O is2Before the TPD test, a 100mg sample of the catalyst was pretreated at 400 ℃ in helium for 1 hour, freed from impurities and water adsorbed on the surface and cooled to 50 ℃. O is2For TPD testing, 20 vol% O was used first2/N2Until the catalyst sample is saturated for adsorption, the saturated catalyst sample is then heated in helium from 50 ℃ to 650 ℃ at a rate of 10 ℃/min. Wherein, 5 vol% of H2/N2Is represented by H2And N2Composition of mixed gas H2Is 5% by volume; 20 vol% O2/N2Is represented by O2And N2In the gas mixture of composition O2Is 20% by volume.
6) And (3) testing the catalytic effect: the activity evaluation was carried out in a fixed bed reactor under atmospheric pressure conditions. The fixed-bed reactor was made of a quartz tube having a diameter of 8 mm, the inlet toluene concentration was set to 1000ppm, the total flow rate of toluene and air was set to 550mL/min, and the Gas Hourly Space Velocity (GHSV) was controlled to 30000h-1The temperature is controlled and monitored by a thermocouple. The gas concentration was analyzed by a gas chromatograph model GC-2000III containing FID from Mediterranean force analysis instruments, Inc. available in Shanghai.
The toluene removal rate calculation formula is as follows: wherein the concentration of the inlet toluene is 1000 ppm;
the advantageous effects of the present invention are illustrated by the test results below.
N of all catalyst samples2The physisorption isotherms and the main structural characteristics are shown in figure 1, figure 2 and table 1. From the results, all catalyst samples had hysteresis loops, which could be attributed to the mixing type according to IUPAC classification. For the pure CuMn catalyst sample, the specific surface area is 74.1m2(ii)/g, lower than La doped catalyst sample, and with La doped catalyst sampleThe product had a smaller hysteresis loop than the product, indicating that there were a smaller number of mesopores. Pure CuMn catalyst samples it had minimal and moderate pore volumes. After doping, CuMn/La-4% possesses the largest specific surface area, hollow volume and total pore volume. In general, a larger specific surface area may provide more active sites in the catalyst, which facilitates adsorption of gases and improves the performance of the catalyst. In addition, the abundant mesoporous structure can enhance gas diffusion. As the addition amount of La is increased to 6%, the specific surface area of CuMn/La-6% is obviously smaller than that of CuMn/La-4%, which shows that the addition amount of La is not more and better, and the structure of the catalyst can be improved to the maximum extent only by a proper amount of La.
TABLE 1 specific surface area (S) of catalyst sampleBET) Mesopore volume (V)Mesoporous) And total pore volume (V)Total) And calculations from XRD data.
Wherein D (Mn)3O4) Is a calculated lattice parameter based on Scherrer's equation using (101, 112, 200, 103, 211, 220, 312, 224, and 314) line broadening.
Surface micrographs of all catalyst samples were observed using SEM and the results are shown in figures 3-6.
As can be seen from fig. 3-6, irregular spherulites were observed on the surface of all catalyst samples with no significant difference in shape, indicating that the doping of La does not affect the microscopic shape of the final catalyst.
The phase composition of all catalyst samples was examined by XRD analysis, and the results are shown in FIG. 7, the lattice parameter (D (Mn) calculated from XRD data3O4)，Mn3O4Diameter of crystal phase) is shown in table 1.
The apparent diffraction peaks of the un-doped La CuMn catalyst samples mainly correspond to Mn2O3(23.1 °, 32.9 °, 38.2 °, 45.1 °, 49.3 °, 55.2 ° and 65.8 °, JCPDSNO.41-1442) and Mn3O4The (18.0 °, 28.9 °, 32.4 °, 36.0 °, 44.3 °, 50.9 ° and 60.0 °, jcpdsno.18-0803) phases, indicating good crystallization. For the La-doped catalyst sample, the main phase is obviously changed, and Mn can be continuously observed3O4Diffraction peak of (2), but Mn2O3The peak of (a) disappears. Furthermore, no distinct characteristic peak associated with La was detected for all catalyst samples, indicating that La is present in the amorphous state or enters the MnOx lattice, resulting in more lattice defects. Meanwhile, in the La-doped catalyst sample, spinel phase Cu1.5Mn1.5O4(JCPDSNO.35-1171) has a weak diffraction peak at 36 deg.. A great deal of work has demonstrated that the Cu1.5Mn1.5O4The spinel phase has extensive dispersion or is too small in size to be detected, which results in a weak diffraction peak for this phase. Furthermore, all of the La-doped catalyst samples had weak crystallites with a significant reduction in crystallite size compared to the non-La-doped CuMn catalyst sample, where the D (Mn) of CuMn is3O4) 51.1nm, CuMn/La-4% D (Mn)3O4) 13.5nm, a reduction of about 4 times. It can be seen that the La doping can prevent crystal growth and can act as a structural promoter. In conclusion, XRD (X-ray diffraction) patterns prove that the addition of La changes the phase of the copper-manganese composite oxide catalyst, so that the main phase is formed by Mn2O3And Mn3O4Conversion to Mn3O4And Cu1.5Mn1.5O4And Cu1.5Mn1.5O4The presence of (a) and the weak crystallization of oxides of manganese can result in more active oxygen and more active oxygen transport channels, which are beneficial for catalytic oxidation reactions.
The surface composition and chemical state information of the catalyst samples were investigated by XPS. Figures 8-11 distribution shows XPS spectra of Cu 2p, La3d, O1 s and Mn 2p for all catalyst samples. The corresponding atomic concentrations on the surface of the catalyst samples are listed in table 2.
Table 2 atomic concentrations of all catalyst samples obtained by XPS analysis.
The Cu 2p XPS spectra of the catalyst samples are shown in fig. 8. Studies have shown that the main peak appearing in the range of 933-934eV and the vibration line at 942eV only react with Cu2+The cations are related. Copper in catalyst samples without La doping only appeared Cu2+Characteristic peak of (2). For the La doped catalyst sample, there are two main peaks, located at 933.3 + -0.1 eV and 930.5 + -0.1 eV, respectively. The binding energy at 930.7eV is reported to correspond to Cu0And Cu+However, Cu could not be formed during our preparation due to calcination in air at 550 deg.C0This indicates Cu in the La doped catalyst sample+And Cu2+Coexisting, catalyst sample without La doping only Cu2+. Obviously, after La doping, the valence state of copper changes and decreases. When Cu2+And Cu+In the presence of both, the following redox reactions occur:
this is the decisive reason for the high oxidation activity of the copper manganese oxide catalyst and also the cause of reactivation of the copper manganese oxide catalyst.
The Mn 2p XPS spectra of the catalyst samples are shown in FIG. 9, with the Mn3+The relative proportions of (A) are shown in Table 2. Generally, Mn has several states in oxides, including MnO, Mn2O3，Mn3O4And MnO2. For the La doped catalyst sample, 2p3/2Is deconvolved into three peaks. For the catalyst sample without La doping, the binding energy for each manganese valence state was 640.7, 641.8, and 643.7eV, respectively, Mn2+/Mn2+/3+/4+Is 0.50, and Mn3+Is only 0.38, which means that Mn is present2+Is the main component in the catalyst sample. According to XRD, the predominant phase of CuMn catalyst samples without La doping was Mn2O3And Mn3O4The MnO diffraction peak was not detected, probably due to the good dispersibility of MnO on the catalyst surface. La doped catalystMn of sample3+Content is obviously increased, Mn3+/Mn2+/3+/4+The ratio is respectively: CuMn/La-4% > CuMn/La-2% > CuMn/La-6% > CuMn. The CuMn/La-4% catalyst exhibits better catalytic activity for toluene oxidation due to higher amount of Mn3+And (4) causing.
The La3 dpxs spectra of the catalyst samples are shown in fig. 10. La3d3/2Has a binding energy of 855.3eV and 851.2eV, La3d5/2The binding energies of (A) are 838.5eV and 834.4 eV. For the CuMn catalyst sample without La doping, no characteristic peak of La was detected. For the La doped catalyst sample, La3d3/2Are located at 854.9 + -0.2 eV and 850.9 + -0.1 eV, La3d5/2Are located at 838.1 + -0.2 eV and 834.1 + -0.2 eV, respectively, which are very close to pure La2O3Peaks at 838.0 and 834.4 eV. The results show that lanthanum ions are trivalent in the catalyst sample, and that slight differences in the peaks may be due to changes in the crystal structure or electronic properties.
The O1 s XPS spectra for all catalyst samples are shown in FIG. 11, where the relative proportions of O β are shown in Table 2. For the CuMn catalyst sample without La doping, the O1 s peak consists of two overlapping peaks located near 529.3eV and 531.0eV, corresponding to the lattice oxygen (denoted as O α) and the surface chemisorbed oxygen (denoted as O β), respectively. For the La doped catalyst sample, the spectra were deconvoluted into three peaks centered at 529.1, 530.9, and 533.1eV, corresponding to lattice oxygen, surface chemisorbed oxygen, and adsorbed water and/or surface carbonate (denoted as O γ), respectively. The presence of adsorbed water is related to the lanthanum oxide on the surface, which is prone to moisture absorption in air. Electrophilic oxygen such as O2-And O-Easily participate in over-oxidation and complete oxidation, and O2-Has close relation with selective oxidation. The O beta in CuMn/La-4% has the largest proportion in all oxygen species, and can improve the reducibility and the oxygen mobility, which is beneficial to catalytic combustion.
Carrying out H2TPR to evaluate the reducibility of the catalyst. FIG. 12 shows H for all catalysts2-a TPR map.
From fig. 12, it can be seen that for the CuMn catalyst without La dopingSample, three reduction peaks (226 ℃, 340 ℃, 374 ℃) were observed, the peak at 226 ℃ corresponding to the reduction of the highly dispersed CuO and the peak at 340 ℃ corresponding to Mn4+/Mn3+To Mn3 +/Mn2+At 374 ℃ corresponding to Mn3+To Mn2+The transformation of (3). For the CuMn/La-2% catalyst, the shoulder at 206 ℃ is due to the reduction of CuO, while broad peaks appear at 259 ℃ and 294 ℃ corresponding to Cu, respectively1.5Mn1.5O4And reduction of MnOx. CuMn/La-4% has a peak similar to CuMn/La-2%, and 207 ℃, 246 ℃ and 263 ℃ represent highly dispersed CuO, Cu1.5Mn1.5O4And gradual reduction of MnOx. However, when the La doping amount was 6%, the reduction temperature was significantly increased, and a broad peak appeared at 315 ℃, corresponding to the reduction of MnOx. CuMn/La-4% has the lowest reduction temperature (246 ℃) of CuMn oxide, which is probably due to the stronger interaction between copper and manganese. The initial reduction temperature of the La-doped catalyst sample is obviously lower, which shows that a small amount of La doping can promote H of the copper-manganese oxide catalyst2Overflow effect. It can be seen that the La doping significantly affects the redox capability of the copper manganese oxide catalyst.
In addition, by O2TPD further investigated the oxygen species mobility on all catalyst samples, and the results are shown in fig. 13.
As seen from FIG. 13, peaks between 160 ℃ and 180 ℃ were observed on the curves of CuMn/La-2%, CuMn/La-4% and CuMn/La-6%, indicating that there was a large amount of chemisorbed oxygen, indicating that La doping significantly increased the adsorbed oxygen content of the catalyst. Further confirming the high activity of CuMn/La-4%.
FIG. 14 shows a plot of toluene removal efficiency versus all catalyst samples, wherein the space velocity was 30000h-1The toluene concentration was 1000 ppm.
As can be seen from FIG. 14, the removal rates of CuMn/La-2% at 218 ℃ and 268 ℃ were 50% (T50) and 90% (T90), respectively. The CuMn/La-4% has the best activity, and can reach 50% of conversion rate at 217 ℃ and 90% of conversion rate at 255 ℃. In contrast, the samples of CuMn catalyst without La doping had T50 and T90 as high as 245 ℃ and 274 ℃, respectively. When 6% of La is added, the activity performance becomes poor, T90 is as high as 280 ℃, which shows that the doping amount of La cannot be too high, otherwise the energy consumption at high removal rate is increased. CuMn/La-6% has poor catalytic activity (T90 ═ 280 ℃), probably due to the excess lanthanum covering the reactive sites.
In conclusion, the lanthanum-doped copper-manganese composite oxide catalyst has the following characteristics:
5) containing Cu1.5Mn1.5O4A spinel phase;
6) no La and Mn2O3A diffraction peak of (a);
7)Cu+and Cu2+Coexistence;
8) the valence state of La is trivalent;
by controlling the doping amount of La, the specific surface area of the lanthanum-doped copper-manganese composite oxide catalyst is 95.9-164.2 m2The mesoporous volume is 0.353-0.426 mL/g, the total pore volume is 0.37-0.45 mL/g, and Mn3O4The size of the crystal phase is 13.5-17.7 nm, Mn3+56.1-61.3% of manganese atom, 40.3-44.6% of O beta, 22.35-24.95% of manganese atom, 1.79-3.03% of copper atom, 2.83-6.40% of La atom and 68.59-70.60% of oxygen atom, and has the following advantages obviously superior to the undoped copper-manganese composite oxide catalyst:
1) in an H2-TPR spectrogram, the reduction temperature of CuO is 206-235 ℃, and Mn is4+/Mn3+To Mn3+/Mn2+The reduction temperature is 259-315 ℃, Mn3+To Mn2+The reduction temperature is 263-315 ℃.
2) The O2-TPD spectrum has a peak between 160 ℃ and 180 ℃.
3) The temperature at which the removal rate of the toluene is 50% is 217-240 ℃; the temperature at which the removal rate of the toluene is 90% is 255-280 ℃.
Among them, the most preferable lanthanum-doped copper-manganese composite oxide catalyst is CuMn/La-4%, and the specific surface area thereof is 164.2m2(ii)/g, mesoporous volume of 0.426mL/g, total pore volume of 0.45mL/g, Mn3O4Size of crystal phase 13.5nm, Mn3+The catalyst is characterized by comprising 61.3 percent of total manganese atoms, 44.6 percent of O beta, 22.65 percent of atomic concentration of manganese atoms, 3.03 percent of atomic concentration of copper atoms, 3.72 percent of atomic concentration of La atoms and 70.60 percent of atomic concentration of oxygen atoms, and has the following advantages obviously superior to other La-doped copper-manganese composite oxide catalysts:
4) in H2-TPR spectrogram, the reduction temperature of CuO is 206 ℃, and Mn is4+/Mn3+To Mn3+/Mn2+The reduction temperature was 259 ℃ and Mn3+To Mn2+The temperature of reduction is 263 ℃;
5) the intensity of a peak in an O2-TPD spectrum at 160-180 ℃ is highest;
6) the temperature at which the removal rate of the toluene is 50% is 217-240 ℃; the temperature at which the removal rate of the toluene is 90% is 255-280 ℃.
The CuMn/La-4% has the best catalytic activity, and the energy consumption required for removing the p-toluene is the lowest, specifically:
1) the CuMn/La-4% has the largest specific surface area and abundant mesopores, and is beneficial to the adsorption and diffusion of gas, so that the toluene removal efficiency is improved. The larger specific surface area provides more adsorption sites, while the more mesopores provide channels for gas to enter the inner surface of the catalyst.
2) CuMn/La-4% Mn with the highest concentration3+Ions and active adsorption of oxygen. The oxygen transfer has important significance in the catalytic oxidation process
Relatively high amount of Mn3+Ions and active chemisorption of oxygen can result in high concentrations of oxygen defects and oxygen vacancies, with oxygen in the gas phase being more readily adsorbed and activated as O2-、O-Is used for dynamic equilibrium, and promotes the catalytic oxidation process.
The contents of the present invention have been explained above. Those skilled in the art will be able to implement the invention based on these teachings. All other embodiments, which can be derived by a person skilled in the art from the above description without inventive step, shall fall within the scope of protection of the present invention.
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