CN113754530B - Method for purifying adipic acid - Google Patents
Method for purifying adipic acid Download PDFInfo
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- CN113754530B CN113754530B CN202010486961.3A CN202010486961A CN113754530B CN 113754530 B CN113754530 B CN 113754530B CN 202010486961 A CN202010486961 A CN 202010486961A CN 113754530 B CN113754530 B CN 113754530B
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- WNLRTRBMVRJNCN-UHFFFAOYSA-N adipic acid Chemical compound OC(=O)CCCCC(O)=O WNLRTRBMVRJNCN-UHFFFAOYSA-N 0.000 title claims abstract description 186
- 239000001361 adipic acid Substances 0.000 title claims abstract description 93
- 235000011037 adipic acid Nutrition 0.000 title claims abstract description 93
- 238000000034 method Methods 0.000 title claims abstract description 57
- RTBFRGCFXZNCOE-UHFFFAOYSA-N 1-methylsulfonylpiperidin-4-one Chemical compound CS(=O)(=O)N1CCC(=O)CC1 RTBFRGCFXZNCOE-UHFFFAOYSA-N 0.000 claims abstract description 51
- JFCQEDHGNNZCLN-UHFFFAOYSA-N anhydrous glutaric acid Natural products OC(=O)CCCC(O)=O JFCQEDHGNNZCLN-UHFFFAOYSA-N 0.000 claims abstract description 51
- 239000007788 liquid Substances 0.000 claims abstract description 42
- 238000010438 heat treatment Methods 0.000 claims abstract description 37
- 238000011049 filling Methods 0.000 claims abstract description 16
- 238000000926 separation method Methods 0.000 claims abstract description 14
- 238000007664 blowing Methods 0.000 claims abstract description 7
- 239000012043 crude product Substances 0.000 claims abstract description 4
- 239000012535 impurity Substances 0.000 claims abstract description 4
- 239000007789 gas Substances 0.000 claims description 96
- 239000003570 air Substances 0.000 claims description 64
- 239000000047 product Substances 0.000 claims description 56
- KDYFGRWQOYBRFD-UHFFFAOYSA-N succinic acid Chemical compound OC(=O)CCC(O)=O KDYFGRWQOYBRFD-UHFFFAOYSA-N 0.000 claims description 31
- 239000007787 solid Substances 0.000 claims description 20
- 238000002425 crystallisation Methods 0.000 claims description 16
- 230000008025 crystallization Effects 0.000 claims description 15
- 239000001384 succinic acid Substances 0.000 claims description 15
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 10
- 239000001301 oxygen Substances 0.000 claims description 10
- 229910052760 oxygen Inorganic materials 0.000 claims description 10
- 230000000630 rising effect Effects 0.000 claims description 10
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 8
- 239000000463 material Substances 0.000 claims description 5
- 229910052757 nitrogen Inorganic materials 0.000 claims description 4
- 238000001816 cooling Methods 0.000 claims description 3
- 238000001914 filtration Methods 0.000 claims description 3
- 239000011148 porous material Substances 0.000 claims description 3
- 238000010926 purge Methods 0.000 description 35
- 238000007599 discharging Methods 0.000 description 20
- 239000000155 melt Substances 0.000 description 20
- 230000000052 comparative effect Effects 0.000 description 16
- 239000002904 solvent Substances 0.000 description 8
- 238000002844 melting Methods 0.000 description 7
- 230000008018 melting Effects 0.000 description 7
- 239000000243 solution Substances 0.000 description 7
- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 description 6
- 238000001953 recrystallisation Methods 0.000 description 6
- 230000002950 deficient Effects 0.000 description 5
- 230000003647 oxidation Effects 0.000 description 5
- 238000007254 oxidation reaction Methods 0.000 description 5
- 238000010408 sweeping Methods 0.000 description 5
- 238000009776 industrial production Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 2
- 229910002091 carbon monoxide Inorganic materials 0.000 description 2
- 150000001735 carboxylic acids Chemical class 0.000 description 2
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- 230000035900 sweating Effects 0.000 description 2
- 239000002253 acid Substances 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- -1 and at the same time Chemical compound 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- KDYFGRWQOYBRFD-NUQCWPJISA-N butanedioic acid Chemical compound O[14C](=O)CC[14C](O)=O KDYFGRWQOYBRFD-NUQCWPJISA-N 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 238000004042 decolorization Methods 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 238000000280 densification Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 150000001991 dicarboxylic acids Chemical class 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- KBVZCXJTMMETLB-UHFFFAOYSA-N hexanedioic acid;pentanedioic acid Chemical compound OC(=O)CCCC(O)=O.OC(=O)CCCCC(O)=O KBVZCXJTMMETLB-UHFFFAOYSA-N 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000012452 mother liquor Substances 0.000 description 1
- 239000010413 mother solution Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 210000004243 sweat Anatomy 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/42—Separation; Purification; Stabilisation; Use of additives
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/42—Separation; Purification; Stabilisation; Use of additives
- C07C51/43—Separation; Purification; Stabilisation; Use of additives by change of the physical state, e.g. crystallisation
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Crystallography & Structural Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
A method for purifying adipic acid comprising the steps of using a vertical melt crystallizer comprising: 1) Filling adipic acid crude product containing glutaric acid impurities into a crystallizer to form a fixed bed, and measuring the height of the fixed bed; 2) Heating the crystallizer to an initial working temperature of 90-100 ℃; 3) Maintaining an initial operating temperature; 4) Heating the crystallizer to the end temperature of 120-140 ℃; 5) Maintaining the end point temperature; 6) Solid-liquid separation; in step 3), back-blowing of the gas, i.e. passing the gas through the fixed bed at the initial operating temperature by means of inlet from the bottom of the fixed bed and outlet from the top of the fixed bed; and/or in step 4) the gas is positively blown, i.e. the gas is passed through the fixed bed in such a way that the gas is positively blown in from the top of the fixed bed and out from the bottom of the fixed bed; and/or in step 5) a gas blow-through is carried out, i.e. a gas blow-through is carried out from the top of the fixed bed and from the bottom of the fixed bed.
Description
Technical Field
The invention relates to a method for separating and purifying crude adipic acid in the production of adipic acid by cyclohexane oxidation, belongs to the field of chemical industry, and particularly relates to a method for separating and purifying adipic acid from crude adipic acid obtained by a cyclohexane air oxidation method and preparing glutaric acid products.
Background
The invention relates to a method for efficiently separating and purifying adipic acid, which mainly solves the problems that in the prior art, the purity of adipic acid extracted from a synthesized solution of adipic acid prepared by a cyclohexane oxidation method is not high, a large amount of solvent is needed for recrystallization or repeated melting crystallization is needed for separating adipic acid, the solvent consumption is high, the separation time is long, and the refining is difficult. The scheme well solves the problems, can separate the crude adipic acid product and prepare high-purity adipic acid and glutaric acid products, has high separation efficiency and small equipment investment, has simple separation process, and can be used for industrial production of adipic acid by cyclohexane oxidation.
In industrial production, cyclohexane is oxidized to obtain adipic acid, and at the same time, glutaric acid and succinic acid, which are byproducts, and other impurities, are purified by a solvent recrystallization method, usually using a difference in solubility of dibasic acids, requiring a large amount of solvent to be consumed and multiple recrystallization. There are methods for separating glutaric acid by melt crystallization using the difference of melting points of the dicarboxylic acids, and the same requires repeated melt crystallization for a plurality of times, even by coupling solvent-melt two methods.
For example, patent CN109761793 discloses a method for purifying mixed diacid by solution-melt coupling, which uses water as solvent to recrystallize the mixed diacid to separate the mixture of succinic acid and adipic acid, adds the mother liquor into a melt crystallizer to melt after evaporating, cools and adds glutaric acid seed crystal to crystallize, and then heats and sweat to obtain glutaric acid product. The process consumes a great amount of water, wherein the ratio of raw materials to water is 0.4-2: 1, repeated heating and cooling are needed, even mother solution is evaporated to dryness, a large amount of energy is consumed, on the other hand, the cooling rate is 0.02-0.1K/min in the melting crystallization process, the heating and sweating rate is 0.05-0.2K/min, and the production efficiency is lower for industrial production.
Patent CN106518656 discloses a crystallization method of adipic acid, which utilizes three-stage recrystallization to purify and refine crude adipic acid, and each stage of crystallization needs dissolution, decolorization, densification and dehydration crystallization, so that the energy consumption is high, and the process flow is long.
Patent CN1069632 discloses a method for purifying adipic acid by recrystallization from carboxylic acid, and introducing carbon monoxide to improve the crystal purity, the process has high requirements on equipment, consumes a large amount of carboxylic acid, and is dangerous for carbon monoxide gas.
Disclosure of Invention
The invention mainly solves the problems of low purity of adipic acid extracted from the synthesized solution of adipic acid prepared by cyclohexane oxidation in the prior art, large consumption of solvent, long separation time and difficult refining, and needs a large amount of solvent recrystallization or multiple melting crystallization to separate adipic acid.
In order to solve the technical problems, the technical scheme of the invention is as follows:
a method for purifying adipic acid comprising the steps of using a vertical melt crystallizer comprising:
step 1), filling an adipic acid crude product containing glutaric acid impurities into a crystallizer to form a fixed bed, and measuring the height of the fixed bed;
step 2) heating the crystallizer to an initial working temperature of 90-100 ℃, preferably 94-98 ℃;
step 3) maintaining an initial working temperature;
step 4) heating the crystallizer to a final temperature of 120-140 ℃, preferably 130-138 ℃;
step 5) maintaining the end point temperature;
step 6) solid-liquid separation: the liquid rich in glutaric acid is discharged from the bottom of the fixed bed, and the solid remained in the crystallizer is high-purity adipic acid;
wherein:
in step 3), back-blowing of the gas, i.e. passing the gas through the fixed bed at the initial operating temperature by means of inlet from the bottom of the fixed bed and outlet from the top of the fixed bed; and/or
In step 4), gas is positively blown, namely, gas is positively blown into the fixed bed from the top and discharged from the bottom of the fixed bed and passes through the fixed bed; and/or
In step 5) a gas blow-through is carried out, i.e. a gas blow-through from the top of the fixed bed and from the bottom of the fixed bed is carried out by passing the gas through the fixed bed.
In the prior art, the melt crystallization step 3) and/or the melt crystallization step 4) and/or the melt crystallization step 5) adopt the back blowing or the forward blowing mode to enable gas to pass through a fixed bed, so that the purity of glutaric acid in the liquid obtained by the solid-liquid separation in the step 6) and the purity of adipic acid in the solid obtained by the solid-liquid separation in the step 6) can be simultaneously improved, and the efficiency of obtaining glutaric acid and adipic acid can be improved.
The solid-liquid separation of step 6) leaves the liquid out of the melt crystallizer, while the solid-liquid separated solids generally remain initially in the melt crystallizer. After step 6), the person skilled in the art can reasonably choose various means known in the art to discharge adipic acid from the melt crystallizer, so that the process according to the invention can further comprise the following steps:
step 7) discharging the high purity adipic acid.
Those skilled in the art will know how to handle the high purity adipic acid solids remaining in the crystallizer after step 6) and may employ those commonly used in the art, such as directly discharging as solids, or may employ further heating of the crystallizer until the remaining solids melt and then discharging the pure adipic acid as a liquid.
In the above technical scheme, as a non-limiting example, the initial working temperature in the step 2) may be 90.5 ℃, 91 ℃, 91.5 ℃, 92 ℃, 92.5 ℃, 93 ℃, 93.5 ℃, 94 ℃, 94.5 ℃, 95 ℃, 95.5 ℃, 96 ℃, 96.5 ℃, 97 ℃, 97.5 ℃, 98 ℃, 98.5 ℃, 99 ℃, 99.5 ℃, etc.
In the above-mentioned technical scheme, as a non-limiting example, the end point temperature in the step 4) may be 121 ℃, 122 ℃, 123 ℃, 124 ℃, 125 ℃, 126 ℃, 127 ℃, 128 ℃, 129 ℃, 130 ℃, 131 ℃, 132 ℃, 133 ℃, 134 ℃, 135 ℃, 136 ℃, 137 ℃, 138 ℃, 139 ℃, and the like.
In the above technical scheme, preferably, the crude adipic acid product is a synthetic liquid cooled crystallization product, more preferably, the crude adipic acid product comprises the following components in percentage by mass:
70-95% of adipic acid;
glutaric acid: 5-30%;
succinic acid: 0 to 1 percent.
By way of non-limiting example, the crude adipic acid comprises 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, etc. by mass of adipic acid.
By way of non-limiting example, the weight percent of glutaric acid in the crude adipic acid is 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, etc.
By way of non-limiting example, the mass percent of succinic acid in the crude adipic acid is 0.04%, 0.06%, 0.08%, 0.10%, 0.15%, 0.20%, 0.25%, 0.30%, 0.35%, 0.40%, 0.45%, 0.50%, 0.55%, 0.60%, 0.65%, 0.70%, 0.75%, 0.80%, 0.85%, 0.90%, 0.95%, etc.
In the above technical scheme, the height of the fixed bed in the step 1) is not particularly limited, for example, but not limited to, 0.5 to 1.5m, and more specific examples of the height of the fixed bed may be 0.55m, 0.6m, 0.65m, 0.7m, 0.75m, 0.8m, 0.85m, 0.9m, 0.95m, 1.0m, 1.05m, 1.1m, 1.15m, 1.2m, 1.25m, 1.3m, 1.35m, 1.4m, 1.45m, etc.
In the above technical solution, the duration of the step 3) is preferably 5 to 30min, for example, but not limited to, 6min, 7min, 8min, 9min, 10min, 11min, 12min, 13min, 14min, 15min, 16min, 17min, 18min, 19min, 20min, 21min, 22min, 23min, 24min, 25min, 26min, 27min, 28min, 29min, etc.
In the above technical scheme, the air pressure difference of the gas in the step 3) in and out of the fixed bed is preferably 5 to 50kPa/m in terms of the unit fixed bed height. By way of non-limiting example, the differential gas pressure of the step 3) gas to the fixed bed may be 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, etc. in terms of unit of fixed bed height; but more preferably 20 to 40kPa/m.
In the above technical solution, the temperature rising speed in the step 4) is preferably 0.3-1K/min, such as, but not limited to, 0.35K/min, 0.4K/min, 0.45K/min, 0.5K/min, 0.55K/min, 0.6K/min, 0.65K/min, 0.7K/min, 0.75K/min, 0.8K/min, 0.85K/min, 0.9K/min, 0.95K/min, etc., more preferably 0.3-0.5K/min.
In the above technical scheme, the air pressure difference of the gas in and out of the fixed bed in the step 4) and/or the step 5) is independently preferably 5 to 50kPa/m in terms of the unit fixed bed height. By way of non-limiting example, the gas pressure differential across the fixed bed for step 4) and/or step 5) may be independently selected from 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, etc. in terms of unit of fixed bed height; but independently more preferably 5 to 30kPa/m.
In the above technical solution, the time for maintaining the end point temperature in step 5) is preferably 5-20 min, for example, but not limited to, the time for maintaining the end point temperature in step 5) is 6min, 7min, 8min, 9min, 10min, 11min, 12min, 13min, 14min, 15min, 16min, 17min, 18min, 19min, and so on.
In the above technical solution, the gas in steps 3) to 5) is independently selected from air, nitrogen or oxygen-deficient air. The oxygen-deficient air refers to air having an oxygen content of less than 21% by volume, and the oxygen content of the oxygen-deficient air according to the embodiment of the present invention is 10% by volume, for example only.
In the above technical solution, the solid-liquid separation in step 6) may be, but is not limited to, filtration separation. When filtration separation is employed, the pore size of the filter material is preferably 20 mesh to 100 mesh, such as, but not limited to, the pore size of the filter material is 25 mesh, 30 mesh, 35 mesh, 40 mesh, 45 mesh, 50 mesh, 55 mesh, 60 mesh, 65 mesh, 70 mesh, 75 mesh, 80 mesh, 85 mesh, 90 mesh, 95 mesh, and the like.
Due to the adoption of the technical scheme, compared with the prior art, the invention has the beneficial effects that: the material is not required to be melted at high temperature, cooled, crystallized and heated for sweating, and the reasonable pressure difference of positive and negative air flows is utilized for step by step to promote the surface movement of melt heat exchange and liquid-solid phase, so that the speed and uniformity of the whole melting crystallization process are improved, and experiments prove that the air pressure difference which is too low or too high cannot reach the optimal effect. According to the technology, a third-party solvent is not required to be introduced, repeated multi-stage melting crystallization is not required, adipic acid and glutaric acid can be separated in one heating process, and material consumption and energy consumption are reduced; on the other hand, the heating rate is improved, so that the production efficiency is improved, and finally, adipic acid with purity higher than 99.5% and glutaric acid with purity higher than 95% can be obtained, so that a better technical effect is achieved.
Drawings
FIG. 1 is a schematic diagram of an experimental apparatus used in a specific embodiment of the present invention.
Wherein, 1 is a melting crystallizer, 2 is a heat exchanger, 3 is a discharge valve, 4 is an air flow pressure difference controller, 5 is a filter, and 6 is a feed inlet.
The present invention will be described with reference to specific examples, but the scope of the present invention is not limited to the examples.
Detailed Description
Comparative example 1
1) Closing a discharge valve of the crystallizer, filling a crude adipic acid product into the melt crystallizer, wherein the adipic acid content is 85% (in percentage by weight, the same applies below) and the glutaric acid content is 14.5%, and the succinic acid content is 0.5%, forming a fixed bed, and measuring the height of the fixed bed to be 1m;
2) Starting a heat exchanger, and heating the crystallizer to an initial working temperature of 95 ℃;
3) Maintaining the initial working temperature for 10min;
4) Closing the inlet of the crystallizer, closing the discharge valve, and increasing the temperature of the crystallizer from the initial working temperature to the end temperature of 135 ℃ at a temperature increasing speed of 0.75K/min;
5) Maintaining the crystallization end point temperature at 135 ℃ for 10min;
6) The aperture of the filter plate is 40 meshes, and the emptying liquid of the emptying valve is 86.1% of the purity of the glutaric acid product;
7) And continuously heating until the residual solid in the crystallizer is melted, wherein the discharged liquid is a high-purity adipic acid product, and the purity of the product is 93.2%.
For comparison, the main process parameters and experimental results are listed in table 1.
[ example 1 ]
The main difference from comparative example 1 is that step 3) in example 1 employs a gas purge, specifically:
1) Closing a discharge valve of the crystallizer, filling a crude adipic acid product into the melt crystallizer, wherein the adipic acid content is 85% (in percentage by weight, the same applies below) and the glutaric acid content is 14.5%, and the succinic acid content is 0.5%, forming a fixed bed, and measuring the height of the fixed bed to be 1m;
2) Starting a heat exchanger, and heating the crystallizer to an initial working temperature of 95 ℃;
3) Closing a feed inlet, closing a discharge valve, allowing gas (the gas is air) to pass through the fixed bed in a mode of feeding from the bottom of the fixed bed and discharging from the top of the fixed bed at an initial working temperature, wherein the air flow pressure difference is 25kPa/m in terms of a unit fixed bed height, namely the air pressure difference is 25kPa, and purging for 10 minutes at constant temperature;
4) Stopping gas purging, and increasing the temperature of the crystallizer from the initial working temperature to the end temperature of 135 ℃ at a temperature increasing speed of 0.75K/min;
5) Maintaining the crystallizer at the end temperature for 10min;
6) The aperture of the filter plate is 40 meshes, and the purity of the glutaric acid product is 93.2% when the emptying liquid is discharged through a discharge valve;
7) And continuously heating until the residual solid in the crystallizer is melted, wherein the discharged liquid is a high-purity adipic acid product, and the purity of the product is 96.1%.
For comparison, the main process parameters and experimental results are listed in table 1.
The same ratio as comparative example 1 indicates that: step 3) the gas is led to pass through the fixed bed in the mode of entering from the bottom of the fixed bed and exiting from the top of the fixed bed, so that the purity of glutaric acid and the purity of adipic acid are improved.
[ example 2 ]
The main difference from comparative example 1 is that step 4) in example 2 employs a gas purge, specifically:
1) Closing a discharge valve of the crystallizer, filling a crude adipic acid product into the melt crystallizer, wherein the adipic acid content is 85% (in percentage by weight, the same applies below) and the glutaric acid content is 14.5%, and the succinic acid content is 0.5%, forming a fixed bed, and measuring the height of the fixed bed to be 1m;
2) Starting a heat exchanger, and heating the crystallizer to an initial working temperature of 95 ℃;
3) Closing the feed inlet, closing the discharge valve, and maintaining the initial working temperature for 10min;
4) Raising the temperature of the crystallizer from an initial working temperature to a final temperature of 135 ℃, wherein the temperature raising speed is 0.75K/min, and the total temperature raising process adopts a mode of feeding gas (the gas is air) from the top of the fixed bed and discharging the gas from the bottom of the fixed bed to ensure that the pressure difference of the gas passing through the fixed bed to pass through the fixed bed is 25kPa/m in terms of the height of the fixed bed, namely the pressure difference is 25kPa;
5) Stopping gas purging, and keeping the crystallizer at the end temperature for 10min;
6) The aperture of the filter plate is 40 meshes, and the purity of the liquid emptied by the emptying valve is 94.2% of that of the glutaric acid product;
7) And continuously heating until the residual solid in the crystallizer is melted, wherein the discharged liquid is a high-purity adipic acid product, and the purity of the product is 99.1%.
For comparison, the main process parameters and experimental results are listed in table 1.
The same ratio as comparative example 1 indicates that: step 4) the gas is led to pass through the fixed bed in the mode of entering from the top of the fixed bed and exiting from the bottom of the fixed bed, so that the purity of glutaric acid and the purity of adipic acid are improved.
[ example 3 ]
The main difference from comparative example 1 is that step 5) in example 3 employs a gas purge, specifically:
1) Closing a discharge valve of the crystallizer, filling a crude adipic acid product into the melt crystallizer, wherein the adipic acid content is 85% (in percentage by weight, the same applies below) and the glutaric acid content is 14.5%, and the succinic acid content is 0.5%, forming a fixed bed, and measuring the height of the fixed bed to be 1m;
2) Starting a heat exchanger, and heating the crystallizer to an initial working temperature of 95 ℃;
3) Closing the feed inlet, closing the discharge valve, and maintaining the initial working temperature for 10min;
4) Raising the temperature of the crystallizer from the initial working temperature to the end temperature of 135 ℃ at a temperature raising speed of 0.75K/min;
5) Maintaining the crystallizer at the end temperature for 10min, and enabling the air pressure difference of the air passing through the fixed bed to enter and exit the fixed bed in a mode of entering from the top of the fixed bed and exiting from the bottom of the fixed bed to be 25kPa/m in terms of the height of the fixed bed, namely, the air pressure difference is 25kPa in the whole process of maintaining the crystallizer at the end temperature;
6) The aperture of the filter plate is 40 meshes, and the liquid is emptied by a discharge valve to obtain the purity 93.4.0% of the glutaric acid product;
7) And continuously heating until the residual solid in the crystallizer is melted, wherein the discharged liquid is a high-purity adipic acid product, and the purity of the product is 96.5%.
For comparison, the main process parameters and experimental results are listed in table 1.
The same ratio as comparative example 1 indicates that: step 5) the gas is led to pass through the fixed bed in the mode of entering from the top of the fixed bed and exiting from the bottom of the fixed bed, so that the purity of glutaric acid and the purity of adipic acid are improved.
[ example 4 ]
The main difference between example 4 and comparative example 1 is that in example 4, step 4) and step 5) a gas purge is used, specifically:
1) Closing a discharge valve of the crystallizer, filling a crude adipic acid product into the melt crystallizer, wherein the adipic acid content is 85% (in percentage by weight, the same applies below) and the glutaric acid content is 14.5%, and the succinic acid content is 0.5%, forming a fixed bed, and measuring the height of the fixed bed to be 1m;
2) Starting a heat exchanger, and heating the crystallizer to an initial working temperature of 95 ℃;
3) Closing the feed inlet, closing the discharge valve, and keeping the temperature constant for 10min at the initial working temperature;
4) Raising the temperature of the crystallizer from an initial working temperature to a final temperature of 135 ℃, wherein the temperature raising speed is 0.75K/min, and the air pressure difference of the gas passing through the fixed bed in and out of the fixed bed is 25kPa/m in terms of the unit fixed bed height by adopting the mode that air enters from the top of the fixed bed and exits from the bottom of the fixed bed in the whole temperature raising process, namely the air pressure difference is 25kPa;
5) Stopping gas purging after maintaining the crystallizer at the end temperature for 10min;
6) The aperture of the filter plate is 40 meshes, and the emptying liquid is 94.7% of the purity of the glutaric acid product by a discharge valve;
7) And continuously heating until the residual solid in the crystallizer is melted, wherein the discharged liquid is a high-purity adipic acid product, and the purity of the product is 99.3%.
For comparison, the main process parameters and experimental results are listed in table 1.
As can be seen from the same ratio as example 2 and example 3, the use of the gas purging of step 4) and step 5) simultaneously provides better results than the gas purging of step 4) alone and the gas purging of step 5) alone in terms of improving the purity of glutaric acid and adipic acid.
[ example 5 ]
The main difference from comparative example 1 is that in example 5, steps 3) and 5) are purged with gas, specifically:
1) Closing a discharge valve of the crystallizer, filling a crude adipic acid product into the melt crystallizer, wherein the adipic acid content is 85% (in percentage by weight, the same applies below) and the glutaric acid content is 14.5%, and the succinic acid content is 0.5%, forming a fixed bed, and measuring the height of the fixed bed to be 1m;
2) Starting a heat exchanger, and heating the crystallizer to an initial working temperature of 95 ℃;
3) Closing the feed inlet, closing the discharge valve, and keeping the temperature constant for 10min at the initial working temperature; air is selected from constant temperature, and gas passes through the fixed bed in the same way as entering from the bottom of the fixed bed and exiting from the top of the fixed bed, wherein the air flow pressure difference is 25kPa/m in terms of the height of the fixed bed, namely, the air flow pressure difference is 25kPa, and the purging time is 4min;
4) Stopping gas purging, and increasing the temperature of the crystallizer from the initial working temperature to the end temperature of 135 ℃ at a temperature increasing speed of 0.75K/min;
5) Maintaining the crystallizer at the end temperature for 10min, and simultaneously adopting a mode of feeding gas from the top of the fixed bed and discharging gas from the bottom of the fixed bed to ensure that the gas pressure difference of the gas passing through the fixed bed to enter and exit the fixed bed is 25kPa/m in terms of the height of the fixed bed, namely, the gas pressure difference is 25kPa, and the purging time is 6min;
6) The aperture of the filter plate is 40 meshes, and the purity of the glutaric acid product is 94.6% when the emptying valve empties the liquid;
7) And continuously heating until the residual solid in the crystallizer is melted, wherein the discharged liquid is a high-purity adipic acid product, and the purity of the product is 97.9%.
For comparison, the main process parameters and experimental results are listed in table 1.
Comparing example 5 with example 1 and example 3, it is seen that the use of both step 3) and step 5) gas purges under the same purge time (10 min and 4+6 min) conditions is better than the results of only step 3) gas purges and only step 5) gas purges in terms of improving the purity of glutaric acid and adipic acid, and that the step 3) and step 5) gas purges have a synergistic effect in improving the purity of glutaric acid.
[ example 6 ]
The main difference from comparative example 1 is that in example 6, steps 3) to 5) all use gas purging, specifically:
1) Closing a discharge valve of the crystallizer, filling a crude adipic acid product into the melt crystallizer, wherein the adipic acid content is 85% (in percentage by weight, the same applies below) and the glutaric acid content is 14.5%, and the succinic acid content is 0.5%, forming a fixed bed, and measuring the height of the fixed bed to be 1m;
2) Starting a heat exchanger, and heating the crystallizer to an initial working temperature of 95 ℃;
3) Closing a feed inlet, closing a discharge valve, selecting air at an initial working temperature, enabling the air to pass through the fixed bed in a mode of feeding from the bottom of the fixed bed and discharging from the top of the fixed bed, wherein the air flow pressure difference is 25kPa/m in terms of a unit fixed bed height, namely the air pressure difference is 25kPa, and sweeping for 10 minutes at constant temperature;
4) The temperature of the crystallizer is increased from the initial working temperature to the end temperature of 135 ℃, the temperature rising speed is 0.75K/min, and the air pressure difference of the air passing through the fixed bed in and out of the fixed bed is 25kPa/m in terms of the unit fixed bed height, namely 25kPa in the whole temperature rising process by adopting the modes of feeding the air from the top of the fixed bed and discharging the air from the bottom of the fixed bed;
5) Stopping gas purging after maintaining the crystallizer at the end temperature for 10min;
6) The aperture of the filter plate is 40 meshes, and the emptying liquid is 96.1% of the purity of the glutaric acid product by a discharge valve;
7) And continuously heating until the residual solid in the crystallizer is melted, wherein the discharged liquid is a high-purity adipic acid product, and the purity of the product is 99.9%.
For comparison, the main process parameters and experimental results are listed in table 1.
As is clear from the comparison between examples 1 to 5, the best results were obtained when the gas purging was used in each of steps 3), 4) and 5) in order to increase the purity of glutaric acid and adipic acid.
[ example 7 ]
The main difference from comparative example 1 is that in example 7, steps 3) to 5) all use gas purging, specifically:
1) Closing a discharge valve of the crystallizer, filling a crude adipic acid product into the melt crystallizer, wherein the adipic acid content is 85% (in percentage by weight, the same applies below) and the glutaric acid content is 14.5%, and the succinic acid content is 0.5%, forming a fixed bed, and measuring the height of the fixed bed to be 1m;
2) Starting a heat exchanger, and heating the crystallizer to an initial working temperature of 90 ℃;
3) Closing a feed inlet, closing a discharge valve, selecting oxygen-deficient air with the oxygen volume content of 10% at the initial working temperature, enabling gas to pass through the fixed bed in a mode of feeding from the bottom of the fixed bed and discharging from the top of the fixed bed, wherein the gas flow pressure difference is 25kPa/m in terms of the height of the fixed bed, namely the gas pressure difference is 25kPa, and sweeping for 10min at constant temperature;
4) The temperature of the crystallizer is increased from the initial working temperature to the end temperature of 135 ℃, the temperature rising speed is 0.75K/min, and the air pressure difference of the air passing through the fixed bed in and out of the fixed bed is 25kPa/m in terms of the unit fixed bed height, namely 25kPa in the whole temperature rising process by adopting the modes of feeding the air from the top of the fixed bed and discharging the air from the bottom of the fixed bed;
5) Stopping gas purging after maintaining the crystallizer at the end temperature for 10min;
6) The aperture of the filter plate is 40 meshes, and the emptying liquid is 96.0% of the purity of the glutaric acid product by a discharge valve;
7) And continuously heating until the residual solid in the crystallizer is melted, wherein the discharged liquid is a high-purity adipic acid product, and the purity of the product is 99.6%.
For comparison, the main process parameters and experimental results are listed in table 1.
[ example 8 ]
The main difference from comparative example 1 is that in example 8, steps 3) to 5) all use gas purging, specifically:
1) Closing a discharge valve of the crystallizer, filling a crude adipic acid product into the melt crystallizer, wherein the adipic acid content is 85% (in percentage by weight, the same applies below) and the glutaric acid content is 14.5%, and the succinic acid content is 0.5%, forming a fixed bed, and measuring the height of the fixed bed to be 1m;
2) Starting a heat exchanger, and heating the crystallizer to an initial working temperature of 100 ℃;
3) Closing a feed inlet, closing a discharge valve, selecting nitrogen at an initial working temperature, enabling the gas to pass through the fixed bed in a mode of feeding from the bottom of the fixed bed and discharging from the top of the fixed bed, wherein the gas flow pressure difference is 25kPa/m in terms of a unit fixed bed height, namely, the gas pressure difference is 25kPa, and purging for 30 minutes at constant temperature;
4) The temperature of the crystallizer is increased from the initial working temperature to the end temperature of 135 ℃, the temperature rising speed is 0.75K/min, and the air pressure difference of the air passing through the fixed bed in and out of the fixed bed is 25kPa/m in terms of the unit fixed bed height, namely 25kPa in the whole temperature rising process by adopting the modes of feeding the air from the top of the fixed bed and discharging the air from the bottom of the fixed bed;
5) Stopping gas purging after maintaining the crystallizer at the end temperature for 10min;
6) The aperture of the filter plate is 40 meshes, and the purity of the glutaric acid product is 96.3% when the emptying liquid is discharged from the emptying valve;
7) And continuously heating until the residual solid in the crystallizer is melted, wherein the discharged liquid is a high-purity adipic acid product, and the purity of the product is 99.9%.
For comparison, the main process parameters and experimental results are listed in table 1.
[ example 9 ]
The main difference from comparative example 1 is that in example 9, steps 3) to 5) all use gas purging, specifically:
1) Closing a discharge valve of the crystallizer, filling adipic acid crude product into the melt crystallizer, wherein the adipic acid content is 70% (in percentage by weight, the same applies below) and the glutaric acid content is 29%, and the succinic acid content is 1%, forming a fixed bed, and measuring the height of the fixed bed to be 0.5m;
2) Starting a heat exchanger, and heating the crystallizer to an initial working temperature of 100 ℃;
3) Closing a feed inlet, closing a discharge valve, selecting oxygen-deficient air at an initial working temperature, wherein the oxygen volume content is 10%, enabling gas to pass through a fixed bed in a mode of feeding from the bottom of the fixed bed and discharging from the top of the fixed bed, wherein the gas flow pressure difference is 50kPa/m in terms of the height of the fixed bed, namely the gas pressure difference is 50kPa, and sweeping for 10 minutes at constant temperature;
4) Raising the temperature of the crystallizer from an initial working temperature to a final temperature of 120 ℃, wherein the temperature raising speed is 1K/min, and the air pressure difference of the air passing through the fixed bed in and out of the fixed bed is 50kPa/m in terms of the height of the fixed bed, namely 50kPa in the whole temperature raising process by adopting the mode of feeding the air from the top of the fixed bed and discharging the air from the bottom of the fixed bed;
5) Stopping gas purging after maintaining the temperature of the crystallizer at the end point for 30min;
6) The aperture of the filter plate is 20 meshes, and the emptying liquid is the glutaric acid product purity of 96.0% by a discharge valve;
7) And continuously heating until the residual solid in the crystallizer is melted, wherein the discharged liquid is a high-purity adipic acid product with the purity of 99.8%.
For comparison, the main process parameters and experimental results are listed in table 1.
[ example 10 ]
The main difference from comparative example 1 is that in example 10, steps 3) to 5) all use gas purging, specifically:
1) Closing a discharge valve of the crystallizer, filling a crude adipic acid product into the melt crystallizer, wherein the adipic acid content is 95% (in percentage by weight, the same applies hereinafter) and the glutaric acid content is 5%, forming a fixed bed, and measuring the height of the fixed bed to be 1.5m;
2) Starting a heat exchanger, and heating the crystallizer to an initial working temperature of 100 ℃;
3) Closing a feed inlet, closing a discharge valve, selecting nitrogen at the initial working temperature, enabling the gas to pass through the fixed bed in a mode of feeding from the bottom of the fixed bed and discharging from the top of the fixed bed, wherein the gas flow pressure difference is 10kPa/m in terms of the height of the fixed bed, namely the gas pressure difference is 10kPa, and purging for 20 minutes at constant temperature;
4) The temperature of the crystallizer is increased from the initial working temperature to the end temperature of 125 ℃, the temperature rising speed is 0.3K/min, and the air pressure difference of the air passing through the fixed bed in and out of the fixed bed is 10kPa/m in terms of the unit fixed bed height, namely 10kPa in the whole temperature rising process by adopting the modes of feeding the air from the top of the fixed bed and discharging the air from the bottom of the fixed bed;
5) Stopping gas purging after maintaining the crystallizer at the end temperature for 5min;
6) The aperture of the filter plate is 100 meshes, and the liquid is emptied by a discharge valve to obtain the glutaric acid product with the purity of 95.5%;
7) And continuously heating until the residual solid in the crystallizer is melted, wherein the discharged liquid is a high-purity adipic acid product with the purity of 99.8%.
For comparison, the main process parameters and experimental results are listed in table 1.
[ example 11 ]
The main difference from comparative example 1 is that in example 11, steps 3) to 5) are all purged with gas, specifically:
1) Closing a discharge valve of the crystallizer, filling a crude adipic acid product into the melt crystallizer, wherein the adipic acid content is 95% (in percentage by weight, the same applies hereinafter) and the glutaric acid content is 5%, forming a fixed bed, and measuring the height of the fixed bed to be 1.5m;
2) Starting a heat exchanger, and heating the crystallizer to an initial working temperature of 100 ℃;
3) Closing a feed inlet, closing a discharge valve, selecting air at an initial working temperature, enabling the air to pass through the fixed bed in a mode of feeding from the bottom of the fixed bed and discharging from the top of the fixed bed, wherein the air flow pressure difference is 40kPa/m in terms of a unit fixed bed height, namely the air pressure difference is 40kPa, and sweeping for 20 minutes at constant temperature;
4) Raising the temperature of the crystallizer from an initial working temperature to a final temperature of 125 ℃, wherein the temperature raising speed is 0.3K/min, and the total temperature raising process adopts a mode of feeding gas from the top of the fixed bed and discharging gas from the bottom of the fixed bed to ensure that the gas pressure difference of the gas passing through the fixed bed to enter and exit the fixed bed is 40kPa/m in terms of the height of the fixed bed, namely the gas pressure difference is 40kPa;
5) Stopping gas purging, and then keeping the crystallizer at the end temperature for 5min;
6) The aperture of the filter plate is 80 meshes, and the emptying liquid is 95.6% of the purity of the glutaric acid product by a discharge valve;
7) And continuously heating until the residual solid in the crystallizer is melted, wherein the discharged liquid is a high-purity adipic acid product, and the purity of the product is 99.6%.
For comparison, the main process parameters and experimental results are listed in table 1.
[ example 12 ]
The main difference from comparative example 1 is that in example 12, steps 3) to 5) all use gas purging, specifically:
1) Closing a discharge valve of the crystallizer, filling a crude adipic acid product into the melt crystallizer, wherein the adipic acid content is 85% (in percentage by weight, the same applies below) and the glutaric acid content is 14.5%, and the succinic acid content is 0.5%, forming a fixed bed, and measuring the height of the fixed bed to be 1.2m;
2) Starting a heat exchanger, and heating the crystallizer to the initial working temperature of 94 ℃;
3) Closing a feed inlet, closing a discharge valve, selecting air at an initial working temperature, enabling the air to pass through the fixed bed in a mode of feeding from the bottom of the fixed bed and discharging from the top of the fixed bed, wherein the air flow pressure difference is 15kPa/m in terms of the height of the fixed bed, namely the air pressure difference is 15kPa, and sweeping for 20 minutes at constant temperature;
4) Raising the temperature of the crystallizer from an initial working temperature to a final temperature of 138 ℃, wherein the temperature raising speed is 0.9K/min, and the total temperature raising process adopts a mode of feeding gas from the top of the fixed bed and discharging gas from the bottom of the fixed bed to ensure that the gas pressure difference of the gas passing through the fixed bed to enter and exit the fixed bed is 15kPa/m in terms of the height of the fixed bed, namely the gas pressure difference is 15kPa;
5) Maintaining the crystallizer at the end temperature for 15min and then stopping gas purging;
6) The aperture of the filter plate is 60 meshes, and the liquid is emptied by a discharge valve to obtain the glutaric acid product with purity of 95.8%;
7) And continuously heating until the residual solid in the crystallizer is melted, wherein the discharged liquid is a high-purity adipic acid product with the purity of 99.7 percent.
For comparison, the main process parameters and experimental results are listed in table 1.
The specific method for separating adipic acid glutaric acid from crude adipic acid provided in the present invention has been described by way of preferred embodiments, and it will be apparent to those skilled in the relevant art that modifications and combinations of the structures and methods of preparation described herein can be made to practice the present technology without departing from the spirit, scope and spirit of the invention. It is expressly intended that all such similar substitutes and modifications apparent to those skilled in the art are deemed to be included within the spirit, scope and content of the invention.
Table 1 (waiting)
Note that: in the tables "- -" means no such item.
Table 1 (subsequent)
Note that: in the tables "- -" means no such item.
Claims (11)
1. A method for purifying adipic acid comprising the steps of using a vertical melt crystallizer comprising:
step 1), filling an adipic acid crude product containing glutaric acid impurities into a crystallizer to form a fixed bed, and measuring the height of the fixed bed;
step 2), heating the crystallizer to an initial working temperature, wherein the initial working temperature is 90-100 ℃;
step 3) maintaining an initial working temperature;
step 4), heating the crystallizer to an end temperature of 120-140 ℃;
step 5) maintaining the end point temperature;
step 6) solid-liquid separation: the liquid rich in glutaric acid is discharged from the bottom of the fixed bed, and the solid remained in the crystallizer is high-purity adipic acid;
the method is characterized in that:
in step 3), back-blowing of the gas, i.e. passing the gas through the fixed bed at the initial operating temperature by means of inlet from the bottom of the fixed bed and outlet from the top of the fixed bed; and/or
In step 4), gas is positively blown, namely, gas is positively blown into the fixed bed from the top and discharged from the bottom of the fixed bed and passes through the fixed bed; and/or
In step 5) a gas forward blowing is carried out, i.e. a gas forward blowing is carried out in from the top of the fixed bed and out from the bottom of the fixed bed, so that the gas passes through the fixed bed;
the crude adipic acid is a synthetic liquid cooling crystallization product, and the crude adipic acid comprises the following components in percentage by mass: 70-95% of adipic acid; glutaric acid: 5-30%; succinic acid: 0-1%;
step 3), the air pressure difference of the air entering and exiting the fixed bed is 5-50 kPa/m in terms of the height of the fixed bed;
step 4), the temperature rising speed is 0.3-1K/min;
and (3) independently setting the air pressure difference of the air in and out of the fixed bed in the step 4) and/or the step 5) to be 5-50 kPa/m according to the unit fixed bed height.
2. The method of claim 1, wherein the initial operating temperature of step 2) is 94-98 ℃.
3. The method of claim 1, wherein the end point temperature of step 4) is 130-138 ℃.
4. The method of claim 1, wherein the fixed bed in step 1) has a height of 0.5 to 1.5m.
5. The method of claim 1, wherein the duration of step 3) is 5 to 30 minutes.
6. The method of claim 1, wherein the gas pressure difference of the gas flowing into and out of the fixed bed in step 3) is 20 to 40kpa/m per unit of fixed bed height.
7. The method according to claim 1, wherein the differential gas pressure of the gas flowing into and out of the fixed bed in step 4) and/or step 5) is independently 5 to 30kpa/m per unit of fixed bed height.
8. The method of claim 1, wherein the maintaining of the end point temperature in step 5) is performed for a period of 5 to 20 minutes.
9. The method of claim 1, wherein the gas in steps 3) to 5) is independently selected from air, nitrogen or oxygen-depleted air.
10. The method of claim 1, wherein the solid-liquid separation of step 6) is performed by filtration.
11. The method according to claim 10, wherein the pore size of the filter material in step 6) is 20 mesh to 100 mesh.
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