CN112409210A - Method and device for preparing adiponitrile by ammoniating adipic acid - Google Patents
Method and device for preparing adiponitrile by ammoniating adipic acid Download PDFInfo
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- CN112409210A CN112409210A CN202011087822.XA CN202011087822A CN112409210A CN 112409210 A CN112409210 A CN 112409210A CN 202011087822 A CN202011087822 A CN 202011087822A CN 112409210 A CN112409210 A CN 112409210A
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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 303
- BTGRAWJCKBQKAO-UHFFFAOYSA-N adiponitrile Chemical compound N#CCCCCC#N BTGRAWJCKBQKAO-UHFFFAOYSA-N 0.000 title claims abstract description 203
- 239000001361 adipic acid Substances 0.000 title claims abstract description 146
- 235000011037 adipic acid Nutrition 0.000 title claims abstract description 146
- 238000000034 method Methods 0.000 title claims abstract description 67
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims abstract description 282
- 239000000203 mixture Substances 0.000 claims abstract description 121
- GVNWZKBFMFUVNX-UHFFFAOYSA-N Adipamide Chemical compound NC(=O)CCCCC(N)=O GVNWZKBFMFUVNX-UHFFFAOYSA-N 0.000 claims abstract description 97
- 238000006297 dehydration reaction Methods 0.000 claims abstract description 63
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 55
- 239000003054 catalyst Substances 0.000 claims abstract description 54
- 230000018044 dehydration Effects 0.000 claims abstract description 52
- 238000007112 amidation reaction Methods 0.000 claims abstract description 44
- 238000007333 cyanation reaction Methods 0.000 claims abstract description 43
- 230000009435 amidation Effects 0.000 claims abstract description 36
- 238000007599 discharging Methods 0.000 claims abstract description 12
- 238000000926 separation method Methods 0.000 claims description 146
- 238000006243 chemical reaction Methods 0.000 claims description 134
- 238000003756 stirring Methods 0.000 claims description 117
- 239000011552 falling film Substances 0.000 claims description 107
- 229910021529 ammonia Inorganic materials 0.000 claims description 62
- 239000007788 liquid Substances 0.000 claims description 62
- 238000005235 decoking Methods 0.000 claims description 56
- 239000003085 diluting agent Substances 0.000 claims description 54
- 239000012071 phase Substances 0.000 claims description 51
- OSNDUYDDOHEKEE-UHFFFAOYSA-N azepane-2,7-dione Chemical compound O=C1CCCCC(=O)N1 OSNDUYDDOHEKEE-UHFFFAOYSA-N 0.000 claims description 46
- 238000010438 heat treatment Methods 0.000 claims description 45
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 24
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 23
- 239000012535 impurity Substances 0.000 claims description 22
- 150000002825 nitriles Chemical class 0.000 claims description 20
- 238000009833 condensation Methods 0.000 claims description 6
- 239000007791 liquid phase Substances 0.000 claims description 6
- 239000012074 organic phase Substances 0.000 claims description 6
- 239000008346 aqueous phase Substances 0.000 claims description 5
- 238000007670 refining Methods 0.000 claims description 4
- 230000005494 condensation Effects 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims description 3
- 238000007906 compression Methods 0.000 claims description 2
- 230000006835 compression Effects 0.000 claims description 2
- 238000005261 decarburization Methods 0.000 claims description 2
- 238000004176 ammonification Methods 0.000 claims 4
- 238000006114 decarboxylation reaction Methods 0.000 abstract description 15
- 150000002391 heterocyclic compounds Chemical class 0.000 abstract description 11
- 239000006227 byproduct Substances 0.000 abstract description 8
- 150000003863 ammonium salts Chemical class 0.000 abstract 1
- 239000007789 gas Substances 0.000 description 64
- BGTOWKSIORTVQH-UHFFFAOYSA-N cyclopentanone Chemical compound O=C1CCCC1 BGTOWKSIORTVQH-UHFFFAOYSA-N 0.000 description 45
- 239000000243 solution Substances 0.000 description 45
- 239000000543 intermediate Substances 0.000 description 42
- 239000000463 material Substances 0.000 description 35
- -1 adipoyl imide Chemical class 0.000 description 25
- 239000010408 film Substances 0.000 description 25
- 238000009826 distribution Methods 0.000 description 19
- XZUDGZXKOFPLBC-UHFFFAOYSA-N 5-cyanopentanamide Chemical compound NC(=O)CCCCC#N XZUDGZXKOFPLBC-UHFFFAOYSA-N 0.000 description 18
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 18
- FRMJZJUVLPFLAB-UHFFFAOYSA-N 2-iminocyclopentane-1-carbonitrile Chemical compound N=C1CCCC1C#N FRMJZJUVLPFLAB-UHFFFAOYSA-N 0.000 description 15
- 239000000126 substance Substances 0.000 description 13
- 239000000047 product Substances 0.000 description 12
- KAKZBPTYRLMSJV-UHFFFAOYSA-N Butadiene Chemical compound C=CC=C KAKZBPTYRLMSJV-UHFFFAOYSA-N 0.000 description 10
- 238000002156 mixing Methods 0.000 description 10
- NLHHRLWOUZZQLW-UHFFFAOYSA-N Acrylonitrile Chemical compound C=CC#N NLHHRLWOUZZQLW-UHFFFAOYSA-N 0.000 description 9
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 9
- 238000009835 boiling Methods 0.000 description 9
- 229910002092 carbon dioxide Inorganic materials 0.000 description 9
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 8
- LELOWRISYMNNSU-UHFFFAOYSA-N hydrogen cyanide Chemical compound N#C LELOWRISYMNNSU-UHFFFAOYSA-N 0.000 description 8
- DYSXBURFMWFBSU-UHFFFAOYSA-N azane;5-cyanopentanoic acid Chemical compound [NH4+].[O-]C(=O)CCCCC#N DYSXBURFMWFBSU-UHFFFAOYSA-N 0.000 description 7
- 239000007795 chemical reaction product Substances 0.000 description 7
- 238000005260 corrosion Methods 0.000 description 7
- 230000007797 corrosion Effects 0.000 description 7
- 239000002699 waste material Substances 0.000 description 7
- 230000003197 catalytic effect Effects 0.000 description 6
- 238000000354 decomposition reaction Methods 0.000 description 6
- 238000001514 detection method Methods 0.000 description 6
- 239000011344 liquid material Substances 0.000 description 6
- 229940070710 valerate Drugs 0.000 description 6
- NQPDZGIKBAWPEJ-UHFFFAOYSA-N valeric acid Chemical compound CCCCC(O)=O NQPDZGIKBAWPEJ-UHFFFAOYSA-N 0.000 description 6
- 239000002351 wastewater Substances 0.000 description 6
- 229940039409 ammonium valerate Drugs 0.000 description 5
- 238000001816 cooling Methods 0.000 description 5
- 238000006386 neutralization reaction Methods 0.000 description 5
- 238000011084 recovery Methods 0.000 description 5
- 230000002441 reversible effect Effects 0.000 description 5
- FLDCSPABIQBYKP-UHFFFAOYSA-N 5-chloro-1,2-dimethylbenzimidazole Chemical compound ClC1=CC=C2N(C)C(C)=NC2=C1 FLDCSPABIQBYKP-UHFFFAOYSA-N 0.000 description 4
- 239000001741 Ammonium adipate Substances 0.000 description 4
- 238000009825 accumulation Methods 0.000 description 4
- ZRSKSQHEOZFGLJ-UHFFFAOYSA-N ammonium adipate Chemical compound [NH4+].[NH4+].[O-]C(=O)CCCCC([O-])=O ZRSKSQHEOZFGLJ-UHFFFAOYSA-N 0.000 description 4
- 235000019293 ammonium adipate Nutrition 0.000 description 4
- 239000001569 carbon dioxide Substances 0.000 description 4
- 239000007806 chemical reaction intermediate Substances 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 230000001546 nitrifying effect Effects 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- 238000007086 side reaction Methods 0.000 description 4
- 238000003860 storage Methods 0.000 description 4
- 238000005262 decarbonization Methods 0.000 description 3
- 239000000539 dimer Substances 0.000 description 3
- 238000006471 dimerization reaction Methods 0.000 description 3
- 238000004064 recycling Methods 0.000 description 3
- 239000011269 tar Substances 0.000 description 3
- SKUPALMUTWEAPI-UHFFFAOYSA-N 5-cyanopentanoic acid Chemical compound OC(=O)CCCCC#N SKUPALMUTWEAPI-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 239000000110 cooling liquid Substances 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- ALBYIUDWACNRRB-UHFFFAOYSA-N hexanamide Chemical class CCCCCC(N)=O ALBYIUDWACNRRB-UHFFFAOYSA-N 0.000 description 2
- NAQMVNRVTILPCV-UHFFFAOYSA-N hexane-1,6-diamine Chemical compound NCCCCCCN NAQMVNRVTILPCV-UHFFFAOYSA-N 0.000 description 2
- 125000003651 hexanedioyl group Chemical group C(CCCCC(=O)*)(=O)* 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000012856 packing Methods 0.000 description 2
- 239000000376 reactant Substances 0.000 description 2
- 239000011541 reaction mixture Substances 0.000 description 2
- 230000002194 synthesizing effect Effects 0.000 description 2
- VMJNTFXCTXAXTC-UHFFFAOYSA-N 2,2-difluoro-1,3-benzodioxole-5-carbonitrile Chemical group C1=C(C#N)C=C2OC(F)(F)OC2=C1 VMJNTFXCTXAXTC-UHFFFAOYSA-N 0.000 description 1
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 1
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonium chloride Substances [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-M Bicarbonate Chemical compound OC([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-M 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 239000004952 Polyamide Substances 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 1
- NOIZJQMZRULFFO-UHFFFAOYSA-N adipamic acid Chemical compound NC(=O)CCCCC(O)=O NOIZJQMZRULFFO-UHFFFAOYSA-N 0.000 description 1
- 238000005576 amination reaction Methods 0.000 description 1
- 239000013556 antirust agent Substances 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-N carbonic acid Chemical compound OC(O)=O BVKZGUZCCUSVTD-UHFFFAOYSA-N 0.000 description 1
- 239000012295 chemical reaction liquid Substances 0.000 description 1
- 230000009194 climbing Effects 0.000 description 1
- 238000004939 coking Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 239000000284 extract Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 239000011874 heated mixture Substances 0.000 description 1
- 238000005984 hydrogenation reaction Methods 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 239000003595 mist Substances 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 229920002647 polyamide Polymers 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 238000010992 reflux Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 238000009834 vaporization Methods 0.000 description 1
- 230000008016 vaporization Effects 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C253/00—Preparation of carboxylic acid nitriles
- C07C253/20—Preparation of carboxylic acid nitriles by dehydration of carboxylic acid amides
-
- 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
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/18—Stationary reactors having moving elements inside
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C231/00—Preparation of carboxylic acid amides
- C07C231/02—Preparation of carboxylic acid amides from carboxylic acids or from esters, anhydrides, or halides thereof by reaction with ammonia or amines
Abstract
The invention provides a method and a device for preparing adiponitrile by ammoniating adipic acid, wherein the method for preparing adiponitrile by ammoniating adipic acid comprises the following amidation steps: reacting adipic acid with ammonia gas and partially dehydrating to form a mixture containing adipamide; a cyanation step: the mixture containing adipoamide generates a mixture containing adiponitrile under the action of a dehydration catalyst; and the amidation step further comprises a step of discharging a mixture of water vapor and ammonia gas. Firstly, adipic acid reacts with ammonia gas to generate ammonium salt, then partial dehydration is carried out to generate a mixture containing adipamide, and the generated water is carried by the ammonia gas and discharged out of an amidation system to promote most of adipic acid to be converted into the adipamide; then the adipamide is deeply dehydrated under the action of a dehydration catalyst to generate adiponitrile, the dehydration catalyst is added in the cyanation step, and byproducts heterocyclic compounds and tar generated by decarboxylation of the adipic acid at high temperature can be prevented.
Description
Technical Field
The invention relates to the technical field of chemical industry, in particular to a method and a device for preparing adiponitrile by ammoniating adipic acid.
Background
Adiponitrile is an important chemical intermediate with the molecular formula NC (CH)2)4CN which is mainly used for producing polyamide fiber intermediate hexamethylene diamine, rubber accelerator, antirust agent and the like. With the rapid development of science and technology, the use of adiponitrile in the fields of light industry, electronics and other organic synthesis is more and more extensive.
The prior methods for synthesizing adiponitrile mainly comprise AN Acrylonitrile (AN) hydro-electrolytic dimerization method, a Butadiene (BD) hydrocyanic acid method and AN adipic acid (ADA) catalytic ammoniation method. Among them, the butadiene hydrocyanic acid method is complex in process and also requires a large amount of highly toxic hydrocyanic acid, so that it has high requirements for production equipment, operation, etc. The acrylonitrile hydrogenation electrolytic dimerization method severely limits the industrial development of the raw material acrylonitrile due to the expensive market price and high cost of the raw material acrylonitrile. Adipic acid (ADA) catalytic ammoniation method is lower in cost than Acrylonitrile (AN) hydro-electrolytic dimerization method, and much smaller in environmental safety hidden trouble than Butadiene (BD) hydrocyanic acid method, so that adipic acid (ADA) catalytic ammoniation method is also one of the main methods for industrially synthesizing adiponitrile.
The adipic acid catalytic ammoniation method is that adipic acid and ammonia react at high temperature under the action of a dehydration catalyst to generate adiponitrile. However, under high temperature conditions, the raw material adipic acid is severely corrosive to the reactor; and a plurality of side reactions occur during dehydration, wherein the side reactions mainly comprise decarboxylation of adipic acid and decomposition of adipic acid to generate cyclopentanone, water, carbon dioxide, tar and the like, wherein cyclopentanone can generate heterocyclic compounds, non-heterocyclic compounds and tar which are difficult to rectify and separate by self-condensation, and the decarboxylation of adipic acid can seriously affect the yield of adiponitrile along with the accumulation of tar in a reaction system to block a reactor and a pipeline; with the reaction, the local temperature in the reactor is overhigh or the ammonia gas is unevenly distributed, so that the heavy components and the 1-imino-2-cyanocyclopentane (ICCP) in the product have higher content and the like; at the same time, the amount of tar will continue to increase.
In the prior art methods for producing adiponitrile from adipic acid, the uniformity of ammonia distribution in the reactor is improved by adding a gas distributor to the reactor. Although the contents of heavy components and ICCP in the product are reduced to a certain extent, the problems of corrosion of adipic acid to a reactor, decarboxylation of adipic acid, tar generation and the like under a high-temperature condition are still not solved.
The prior art discloses an adiponitrile production system, which is characterized in that adipic acid, ammonia and a catalyst are mixed and then aminated in a pre-reactor, and then the mixture enters a cyanation reactor to be dehydrated to generate adiponitrile. According to the scheme, the pre-reactor is arranged and the reaction temperature of the pre-reactor is limited, so that the corrosion of adipic acid to the reactor and the probability of adipic acid decarboxylation are reduced to a certain extent, but a large amount of adipic acid is not subjected to neutralization reaction, corrosion, decarboxylation and decomposition phenomena of the adipic acid at high temperature still exist, and a large amount of tar is still contained in a product, so that the yield and the quality of adiponitrile are influenced.
Disclosure of Invention
Therefore, the technical problem to be solved by the invention is to overcome the defects of more byproduct tar, blockage of a reactor and a pipeline and low adiponitrile quality in the process of preparing adiponitrile by using an adipic acid ammoniation method in the prior art, thereby providing the method and the device for preparing the adiponitrile by using the adipic acid ammoniation method.
Therefore, the invention provides the following technical scheme:
a method for preparing adiponitrile by ammoniating adipic acid comprises the following steps,
amidation step: reacting adipic acid with ammonia gas and partially dehydrating to form a mixture containing adipamide;
a cyanation step: dehydrating the adipoamide-containing mixture under the action of a dehydration catalyst to generate an adiponitrile-containing mixture;
and the amidation step further comprises a step of discharging a mixture of water vapor produced by the reaction and excess ammonia gas.
Optionally, the amidation step is carried out in a stirred reactor, and the top of the stirred reactor is provided with a gas discharge port for discharging the mixture of water vapor and ammonia gas generated in the reaction.
Optionally, a guide shell is further disposed in the stirring reactor, and the stirring device in the stirring reactor is disposed in the guide shell.
Alternatively, the difference in reaction temperature between the amidation step and the cyanation step is not less than 30 ℃.
Optionally, the reaction temperature of the amidation step is 160-250 ℃, and the reaction pressure is 140-300 KPa; preferably, the reaction temperature of the amidation step is 180-220 ℃, and the reaction pressure is 150-250 KPa; more preferably, the reaction temperature of the amidation step is 180 ℃ and 200 ℃ and the reaction pressure is 150 ℃ and 250 KPa.
Maximum conversion of adipic acid to adipamide prior to the cyanation step was achieved by controlling the temperature of the amidation step at 180-: on one hand, the decarboxylation of adipic acid and the decomposition of adipic acid can be effectively prevented; on the other hand, the method can promote the reaction of adipic acid and ammonia gas to generate ammonium adipate, and further dehydrate the ammonium adipate to generate adipamide with more stable chemical properties.
Optionally, the mixture containing adipamide is heated to 260-290 ℃ and then enters the cyanation step, and the material temperature of the cyanation step is promoted to be uniform, so that the generation of tar due to the local over-high temperature of the cyanation step is prevented.
The molar ratio of adipic acid to ammonia gas in the amidation step is 1: 3-15; preferably, the molar ratio of adipic acid to ammonia gas is from 1:5 to 8. By controlling the molar ratio of adipic acid to ammonia gas in the amidation step, the adipic acid is converted into the adipamide as much as possible, and the adipic acid is effectively prevented from being decomposed at the high temperature of the cyanation reaction. If the molar ratio of ammonia to adipic acid is less than 3, the chance of generating cyclopentanone is increased; if the molar ratio of the ammonia gas to the adipic acid is more than 15, the circulating amount of the ammonia gas is too large, and energy is wasted.
Optionally, the cyanation step is accomplished using a falling film reactor.
Optionally, the reaction temperature of the cyanation step is 250-310 ℃, and the pressure is normal pressure (101KPa) or slight positive pressure; the micro positive pressure is 105-150 KPa. Preferably, the reaction temperature of the cyanation step is 260-290 ℃, and the pressure of the cyanation step is 120-150 KPa.
The dehydration catalyst is at least one of phosphoric acid, phosphate, silicon oxide, aluminum oxide and titanium oxide;
the mass ratio of adipic acid in the amidation step to the dehydration catalyst in the cyanation step is 100: (0.05-1.0); preferably, the mass ratio of adipic acid in the amidation step to the dehydration catalyst in the cyanation step is 100: (0.1-0.5).
Optionally, the adipoamide-containing mixture is heated to 250-290 ℃ before entering the cyanation step.
Optionally, the method for preparing adiponitrile by ammoniating adipic acid further comprises the steps of separating the mixture containing adiponitrile and converting adipimide, wherein the steps comprise,
a separation step: separating the mixture containing adiponitrile to obtain a diluent, a semi-nitrile solution, a crude nitrile solution containing adipimide and light component impurities;
conversion step of adipimide: reacting the crude nitrile solution containing the adipimide with ammonia water to obtain a gas-phase mixture and a liquid mixture, and converting the adipimide in the crude nitrile solution into the adipimide; the liquid mixture is stood to obtain an ammonia-containing gas phase, an organic phase containing crude adiponitrile, and a water phase containing a small amount of organic matters such as adipoamide and 5-cyanovaleric acid (ammonium).
Optionally, the diluent is recycled to the amidation step and the cyanation step, respectively;
and/or the aqueous phase containing small amounts of organics such as adipamide and 5-cyanovaleric acid (ammonium) is recycled to the separation step.
The diluent mainly contains 5-cyanovaleramide, adiponitrile, small amount of adipamide, ammonium 5-cyanovalerate and the like.
The crude nitrile solution containing adipoyl imide mainly contains adiponitrile, and small amounts of intermediates (5-cyanovaleric acid ammonium, 5-cyanovaleramide and adipoyl imide) and impurity ICCP.
The semi-nitrile solution mainly contains tar, a dehydration catalyst, a small amount of adiponitrile, an intermediate, a dimer of adiponitrile and other high molecular weight substances.
The light component impurities mainly contain ammonia gas, a small amount of water vapor, carbon dioxide, cyclopentanone and light component impurities with low boiling point.
Optionally, the method for preparing adiponitrile by ammoniating adipic acid further comprises a decoking step: reacting the semi-nitrile solution with ammonia gas to obtain a gas phase mixture containing adiponitrile and a liquid phase mixture containing tar and a dehydration catalyst;
the gas-phase mixture comprising adiponitrile is recycled to the cyanation step.
The gas phase mixture containing adiponitrile is mainly ammonia gas, and a small amount of adiponitrile, intermediates (ammonium 5-cyanovalerate, 5-cyanovaleramide, adipoamide) and the like.
Alternatively, the reaction temperature for the decoking step is 220-.
Optionally, a part of condensed liquid obtained by condensing ammonia-containing gas volatilized in the standing process of the light component impurities obtained in the separation step, the gas-phase mixture obtained in the adipimide conversion step and the liquid-phase mixture is recycled to the separation step, and the rest part of condensed liquid is subjected to ammonia recovery; the ammonia gas which is not condensed is sequentially subjected to decarburization, evaporative condensation, dehydration and compression, and then is respectively circulated to the cyanation step, the amidation step and the decoking step to participate in the reaction.
The invention also provides a device for preparing adiponitrile by ammoniating adipic acid, which comprises,
the stirring reactor comprises an ammonia gas inlet, an adipic acid inlet, a diluent inlet and a mixture outlet containing adipamide, the top of the stirring reactor is provided with a gas discharge outlet, the inside of the stirring reactor is provided with a guide shell and a stirring paddle, and the stirring paddle is arranged inside the guide shell and is parallel to the axial direction of the guide shell;
an ammonia distributor is arranged at an ammonia inlet of the stirring reactor;
the falling film reactor comprises an adipoamide-containing mixture inlet, an ammonia gas inlet, a heating medium inlet and a heating medium outlet and an adiponitrile-containing mixture outlet, wherein the adipoamide-containing mixture inlet is communicated with the adipoamide-containing mixture outlet of the stirring reactor, and a catalyst inlet is arranged on a pipeline between the adipoamide-containing mixture inlet and the adipoamide-containing mixture outlet of the stirring reactor.
Under the dual action of the guide shell and the stirring paddle, liquid materials continuously flow in a circulating manner up and down in the stirring reactor, and the liquid is fully mixed and contacted with ammonia in a liquid phase and ammonia in a gas phase in the circulating manner, so that the reaction is promoted. And the circulation frequency of the liquid materials in the stirring reactor per minute can be adjusted by adjusting the rotating speed of the stirring paddle, so that the materials are uniformly mixed and fully contacted for reaction, and the adipic acid is promoted to be converted into the adipamide.
Optionally, a first heating device is arranged on a pipeline between the stirring reactor and the falling film reactor.
Optionally, the falling film reactor is provided with a distributor at the entrance of the adipamide-containing mixture.
Optionally, the device for preparing adiponitrile by ammoniating adipic acid further comprises a separation conversion unit, wherein the inlet of the separation conversion unit is communicated with the outlet of the mixture containing adiponitrile of the falling film type reactor, and the outlet of the separation conversion unit is communicated with the adiponitrile refining device.
Optionally, the separation and conversion unit comprises,
a separation column comprising a lower feed inlet, a gas phase outlet and a side draw outlet; wherein the lower material inlet is communicated with a mixture outlet containing adiponitrile of the falling film reactor;
the adipimide conversion tank comprises an ammonia water inlet, a crude nitrile solution inlet containing adipimide and a side wall outlet; the crude nitrile solution containing adipoyl imide is communicated with the side outlet of the separation tower;
and the separation tank comprises an inlet, a bottom outlet and an overflow outlet, and the inlet is communicated with the side wall outlet of the adipimide conversion tank.
Optionally, the separation column further comprises a diluent outlet;
and a diluent outlet of the separation tower is respectively communicated with an adipoamide-containing mixture inlet of the falling film reactor and a diluent inlet of the stirring reactor.
Optionally, a first cooling device is arranged between the diluent inlet of the stirred reactor and the diluent outlet of the separation tower;
and a second cooling device is arranged between the crude nitrile solution inlet containing the adipimide of the adipimide conversion tank and the side outlet of the separation tower.
Optionally, the separation column further comprises a bottom heminitrile solution outlet;
the device for preparing adiponitrile by ammoniating adipic acid further comprises a decoking reactor, wherein the decoking reactor comprises an ammonia gas inlet, a heminitrile solution inlet, a gas phase outlet, a heating medium inlet, a heating medium outlet and a tar outlet;
a semi-nitrile solution inlet of the decoking reactor is communicated with a semi-nitrile solution outlet at the bottom of the separation tower;
and a gas phase outlet of the decoking reactor is communicated with an ammonia gas inlet of the falling film reactor.
Optionally, the falling film reactor is vertically installed, a film distribution head, an upper tube plate, a tube array and a lower tube plate are sequentially arranged in the falling film reactor from top to bottom, and a liquid distributor is installed on the film distribution head; the liquid material of the falling film reactor flows into the liquid distributor through the adipoamide-containing mixture inlet, flows into the upper tube plate of the reactor tube nest after being uniformly distributed by the liquid distributor, and flows downwards along the inner wall of the tube nest after passing through the liquid film distribution head and the film distribution. The ammonia gas and the reactants in the falling film reactor move in a downstream contact mode, the ammonia gas after dehydration reaction extracts the reaction product adiponitrile and water vapor out of a liquid film layer and enters a gas phase, the liquid and the gas discharged from the bottom of the falling film reactor enter a separation tower together for separation, and light component impurities (ammonia gas, water vapor and CO) are separated2Cyclopentanone and other light components) is discharged from the top of the separation column, a crude nitrile solution containing adipimide is discharged from an outlet at the side of the middle part of the separation column, and a diluent is discharged from the lower part of the separation column; and the semi-nitrile solution obtained at the bottom of the separation tower is sent to a decoking reactor.
The heating temperature of the heating medium adopted by the falling film reactor is only about 5 ℃ higher than the reaction temperature, so that the phenomenon of coking caused by overhigh temperature of the inner surface of the liquid film due to the use of the high-temperature heating medium can be avoided.
Optionally, the adipimide conversion tank is a stirred reactor;
the tops of the adipimide conversion tank and the separation tank are respectively provided with a gas outlet;
and a gas outlet of the adipimide conversion tank, a gas outlet of the separation tank and a gas phase outlet at the top of the separation tower are respectively communicated with ammonia inlets of the falling film reactor, the stirring reactor and the decoking reactor through a third condensing device, the decarbonizing tower, an ammonia evaporator, a dehydrator and a liquid ring compressor in sequence.
Optionally, the separation column further comprises a condensate inlet, and the outlet of the third condensing device is further communicated with the condensate inlet of the separation column;
the separation column further comprises a recycle liquid inlet; and an outlet at the bottom of the separation tank is communicated with a circulating liquid inlet of the separation tower.
The technical scheme of the invention has the following advantages:
1. a large amount of tar and ICCP exist in adiponitrile prepared by the existing method for preparing adiponitrile by ammoniating adipic acid, so that the yield and the quality of the adiponitrile are obviously reduced. The inventors have found, through studies, that the main reason is the low conversion of adipic acid in the amidation step; and the temperature of the cyanation step is not uniform, the local temperature is too high, so that the unconverted adipic acid is decarboxylated to generate a large amount of cyclopentanone, and the cyclopentanone self-condensation generates a large amount of heterocyclic compounds, non-heterocyclic compounds and tar, and also increases the content of heavy components and ICCP.
According to the method for preparing adiponitrile by ammoniating adipic acid, the mixture of water vapor and ammonia gas discharged from the amidation step is limited, namely the water vapor generated by partial dehydration after the reaction of adipic acid and ammonia gas is discharged from the amidation reaction system along with excessive ammonia gas, the balance of reversible reaction of adipic acid and ammonium adipate and the reversible reaction of ammonium adipate and adipamide are broken, the reaction is promoted to be carried out in the direction of generating the adipamide, so that almost all adipic acid in the amidation step is neutralized and converted by the ammonia gas, most of adipic acid is generated into the adipamide, and the situation that unreacted adipic acid enters the cyanation step at high temperature to cause decarboxylation and decomposition of the adipic acid to generate byproducts such as cyclopentanone, heavy components, ICCP, tar and the like is prevented;
the method for preparing adiponitrile by ammoniating adipic acid provided by the invention comprises the steps of firstly, reacting adipic acid with ammonia gas without adding a dehydration catalyst, partially dehydrating to generate a mixture containing adipamide, and carrying water vapor generated in an amidation step by ammonia gas to discharge out of an amidation system, so that most of adipic acid is converted into the adipamide; then the adipamide is deeply dehydrated under the action of a dehydration catalyst to generate adiponitrile, and the dehydration catalyst is added in the cyanation step, so that the amount of adipic acid in a cyanation reaction system is small, and the generation of by-product heterocyclic compounds and tar due to decarboxylation of the adipic acid at high temperature and the corrosion of adipic acid on cyanation equipment can be prevented. The method for preparing adiponitrile by ammoniating adipic acid provided by the invention has the advantages of less tar, high yield of the prepared adiponitrile and high product quality.
The inventor researches and discovers that if the catalyst is mixed with adipic acid and ammonia in the amidation reaction process, the adipic acid still decomposes to generate cyclopentanone, water, carbon dioxide and the like under the catalytic action of the catalyst, wherein the cyclopentanone self-condenses to generate heterocyclic compounds, non-heterocyclic compounds and tar, and the reactor and the pipeline are plugged along with the accumulation of the tar in the reaction system. On the basis of the method, the inventors creatively adjust the adding sequence of the catalyst: the catalyst is added in the cyanation step, the dehydration catalyst is not added in the amidation step, and the amount of the residual adipic acid after the amidation reaction is little, so that the decarboxylation decomposition of the adipic acid in the cyanation step is reduced to the greatest extent fundamentally, the yield and the quality of the adiponitrile are improved, and meanwhile, the corrosion of the adipic acid to equipment at high temperature and the blockage of tar to a pipeline are effectively prevented.
2. According to the method for preparing adiponitrile by ammoniating adipic acid, provided by the invention, the stirred reactor is adopted by limiting the amidation step, so that the flow speed of materials in the reactor can be adjusted, and the full contact reaction of the materials is promoted; through set up the gas outlet at stirred reactor top, on the one hand can adjust the pressure in the stirred reactor, on the other hand can in time discharge with excessive ammonia with the aqueous vapor that generates, promote reversible reaction to generating adipamide direction and go on, make adipic acid almost all by the neutralization conversion, prevent under high temperature that unreacted adipic acid gets into the nitrilation step and causes the corruption to the nitrilation equipment to decarboxylation produces by-products such as cyclopentanone, heavy ends, ICCP and tar.
3. The method for preparing adiponitrile by ammoniating adipic acid provided by the invention has the advantages that the guide shell is arranged in the stirring reactor, liquid materials continuously and circularly flow up and down in the stirring reactor under the double actions of the guide shell and the stirring paddle, and the liquid and ammonia gas in a liquid phase and ammonia gas in a gas phase are fully contacted and mixed in the circulating flow, so that the reaction is promoted. And the circulation frequency of liquid materials in the stirring reactor per minute can be adjusted by adjusting the rotating speed of the stirring reactor, so that the materials are uniformly mixed and fully contacted for reaction, and the adipic acid is promoted to be converted into the adipamide to the maximum extent.
4. According to the method for preparing adiponitrile by ammoniating adipic acid, the falling film type reactor is adopted in the nitrifying step, so that the temperature difference between the reaction temperature of materials in the nitrifying step and a heating medium is controlled to be about 5 ℃, and the generation of tar, heavy components and ICCP caused by overhigh local temperature of the materials in the reaction process is effectively avoided.
5. The method for preparing adiponitrile by ammoniating adipic acid provided by the invention has the advantages that the crude nitrile solution containing adipoimide mainly contains adiponitrile, a small amount of intermediates (5-cyanoammonium valerate, 5-cyanovaleramide and adipoimide) and impurities ICCP. The method for preparing adiponitrile by ammoniating adipic acid provided by the invention has the advantages that the adipoimide in the adipoyl dinitrile can be converted into adipoyl amide by further reacting the adipoyl dinitrile with ammonia water, and the aqueous phase is recycled to the separation step and then to the amidation and cyanation steps, so that intermediates such as the 5-cyanoammonium valerate, the 5-cyanovaleramide and the adipoyl amide can be further converted into adiponitrile, and the yield of the adiponitrile is improved.
6. According to the method for preparing adiponitrile by ammoniating adipic acid, the separated diluent is recycled to the cyanation step and the amidation step, the adiponitrile in the diluent can be recovered, and the intermediates (5-cyanovaleramide, a small amount of adipamide and 5-cyanoammonium valerate) in the diluent are promoted to be further converted into adiponitrile, so that the yield of adiponitrile is improved.
7. According to the method for preparing adiponitrile by ammoniating adipic acid, through the arrangement of the decoking step, unconverted intermediates in the heminitrile solution are further reacted with ammonia gas to be converted into adiponitrile, or further reacted in the atmosphere of ammonia gas to be converted into intermediates such as 5-cyanovaleramide or adipamide and the like, and the adiponitrile and the intermediates are stripped by ammonia gas and recycled to the cyanation step, so that the yield of the adiponitrile can be improved; the mixture of the tar and the dehydration catalyst is discharged out of the system, thereby preventing the tar and the phosphoric acid from accumulating in the system to cause the corrosion and the blockage of equipment or pipelines and influencing the yield of the adiponitrile.
8. The method for preparing adiponitrile by ammoniating adipic acid comprises the following steps of firstly, carrying out neutralization reaction on molten adipic acid and ammonia gas at a temperature lower than the decarboxylation temperature of the adipic acid to generate ammonium adipate salt; partial dehydration reaction of ammonium adipate salt to generate adipamide; the adipoyl amide is deeply dehydrated to generate adiponitrile under the action of higher temperature and catalyst; and the separation of reaction products, the conversion of adipimide, the purification, dehydration and the recycling of ammonia gas. The adipic acid ammoniation method provided by the invention utilizes the flow guide effect of the flow guide cylinder to ensure that molten adipic acid continuously and circularly flows in the stirring reactor and is mixed with excessive ammonia gas for reaction, so that the adipic acid completely reacts; the material is heated uniformly by utilizing a three-stage gradual heating mode of melting and heating adipic acid, heating a mixture containing adipamide and heating a falling film reactor, and the heat load of the falling film reactor is reduced; reducing the temperature difference between a heating medium and a reaction material by utilizing the characteristics of the falling film reactor, and timely leading adiponitrile and hot ammonia water generated by dehydration in the liquid film to leave the liquid film main body when the hot ammonia gas passes through the surface of the liquid film at high speed, so that the dehydration reaction in the liquid film is carried out towards the direction of generating adiponitrile; in the conversion step, freshly prepared ammonia water is adopted to react with adipimide, so that the recovered ammonia water is prevented from bringing impurities such as cyclopentanone and the like into self-condensation in the subsequent steps to generate heterocyclic compounds and tar which are difficult to rectify and remove, and the quality of the adiponitrile product is reduced.
9. The inventor of the device for preparing adiponitrile by ammoniating adipic acid provided by the invention has found that if the catalyst is mixed with adipic acid and ammonia in the process of amidation reaction, the adipic acid can still be dehydrated and decomposed to generate cyclopentanone, water, carbon dioxide and the like under the catalytic action of the catalyst, wherein the cyclopentanone is self-condensed to generate heterocyclic compounds and tar, and the generated adipoyl-amide-containing mixture is black instead of milky. On the basis of the method, the inventors creatively adjust the adding sequence of the catalyst: the catalyst inlet is arranged on the pipeline between the stirring reactor and the falling film reactor, namely, the catalyst is only added into the falling film reactor, so that the amount of adipic acid in the falling film reactor is small, and the materials are uniformly mixed and distributed by using the falling film reactor; the phenomena of decarboxylation and decomposition of adipic acid in a conventional cyanation reactor and generation of heterocyclic compounds and tar are reduced to the greatest extent fundamentally, the yield and quality of adiponitrile are improved, and meanwhile, the phenomena of corrosion of adipic acid on the cyanation reactor at high temperature and blockage of the pipeline by tar are effectively prevented.
Meanwhile, an ammonia gas distributor is arranged at an ammonia gas inlet in the stirring reactor, so that the distribution uniformity of ammonia in the stirring reactor is improved, and the effective conversion of adipic acid is promoted; adipic acid can be converted into adipamide to the maximum extent in the stirred reactor by using the stirred reactor with a gas discharge outlet; by adopting the falling film reactor as the cyanation reactor, the temperature difference between the reaction temperature and the heating medium can be controlled at about 5 ℃, and the generation of tar, heavy components and ICCP caused by uneven material distribution and overhigh local temperature in the reaction process in the cyanation reactor is effectively avoided. Through the mutual cooperation of the stirring type reactor and the falling film type reactor, when the device is used for preparing adiponitrile by ammoniating adipic acid, the produced tar amount is small, the reactor and a pipeline cannot be blocked, and the prepared adiponitrile has high yield and high quality.
10. According to the device for preparing adiponitrile by ammoniating adipic acid, the first heating device is arranged on the pipeline between the stirring reactor and the falling film reactor, namely, a product of the stirring reactor is heated and then enters the falling film reactor to form a stepped heating mode, so that the heat load of the falling film reactor is reduced; on the other hand, the temperature rise of reaction materials can be promoted to be uniform, and the generation of side reactions is reduced; meanwhile, the characteristics of the falling-film reactor are utilized to reduce the temperature difference between the reaction temperature of the heating medium and the material and timely carry adiponitrile and water vapor generated by dehydration in the liquid film away from the main body of the liquid film when hot ammonia gas passes through the surface of the liquid film at high speed, so that the dehydration reaction in the liquid film is carried out towards the direction of generating the adiponitrile, and the problem of the increase of the tar amount caused by the overhigh local temperature due to the uneven temperature in the conventional cyanation reactor is effectively solved.
11. According to the device for preparing adiponitrile by ammoniating adipic acid, provided by the invention, the first cooling device is arranged between the diluent inlet of the stirring reactor and the diluent outlet of the separation tower, so that the diluent can also adjust the temperature in the stirring reactor, and the phenomenon that the temperature is too high and the side reaction is increased is prevented.
12. According to the device for preparing adiponitrile by ammoniating adipic acid, the gas outlets are respectively arranged at the tops of the adipimide conversion tank and the separation tank, ammonia gas in the adipimide conversion tank and the separation tank is discharged from the gas outlets, and then the ammonia gas is condensed by the third condensing device, sequentially enters the decarbonization tower for decarbonization, is condensed by the ammonia gas evaporator, is dehydrated by the dehydrator, and then is respectively circulated to the falling film reactor, the stirring reactor and the decoking reactor for reaction, so that the cyclic utilization of the ammonia gas is realized.
13. The device for preparing adiponitrile by ammoniating adipic acid provided by the invention is provided with the stirring reactor, the falling film reactor, the decoking reactor and the adipimide conversion reaction tank, wherein the four reactors are matched with each other: firstly, carrying out neutralization reaction on adipic acid and ammonia gas in a stirring reactor at the temperature lower than the decarboxylation temperature of the adipic acid to generate ammonium adipate salt; partial dehydration reaction of ammonium adipate salt to generate adipamide; then, carrying out deep dehydration reaction on the adipamide at higher temperature in the falling film reactor under the action of a catalyst to generate adiponitrile; after the tar-containing semi-nitrile solution generated in the falling film reactor is further reacted in the decoking reactor, useful intermediates and adiponitrile are circulated to the falling film reactor; discharging tar and dehydration catalyst from the system to prevent accumulation and blockage of pipelines or equipment; the adipamide generated in the falling film type reactor is further reacted with ammonia in an adipamide conversion tank to generate adipamide, and then the adipamide is circulated to the falling film type reactor for further reaction, so that the yield of adiponitrile can be improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the present technology, the following will briefly introduce the embodiments or drawings used in the technical description, and obviously, the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a schematic view of an apparatus for producing adiponitrile by ammonifying adipic acid in example 1 of the present invention;
reference numerals:
1. an ammonia gas distributor; 2. a draft tube; 3. an adipic acid inlet; 4. a first heater; 5. a first cooler; 6. a deep dehydration condenser; 7. a fourth condenser; 8. an ammonia heater for amidation reaction; 9. a decoking ammonia heater; 10. a decoking reactor; 11. a dehydration catalyst inlet; 12. an ammonia heater for cyanation reaction; 13. a liquid distributor; 14. a falling film reactor; 15. a separation column; 16. a second cooler; 17. an adipimide conversion tank; 18. a separation tank; 19. a crude adiponitrile storage tank; 20. a third condenser; 21. a decarbonizing tower; 22. a liquid ammonia evaporator; 23. a dehydrator; 24. a liquid ring compressor; 25. the reactor was stirred.
Detailed Description
The following examples are provided to further understand the present invention, not to limit the scope of the present invention, but to provide the best mode, not to limit the content and the protection scope of the present invention, and any product similar or similar to the present invention, which is obtained by combining the present invention with other prior art features, falls within the protection scope of the present invention.
The examples do not show the specific experimental steps or conditions, and can be performed according to the conventional experimental steps described in the literature in the field. The reagents or instruments used are not indicated by manufacturers, and are all conventional reagent products which can be obtained commercially.
Example 1
This example provides an apparatus for preparing adiponitrile by ammonifying adipic acid, as shown in FIG. 1, comprising,
the device comprises a stirring reactor 25, wherein an ammonia gas inlet, an adipic acid inlet 3, a diluent inlet, an adipoamide-containing mixture outlet and a gas discharge outlet are formed in the stirring reactor 25; an amidation reaction ammonia heater 8 is arranged on a pipeline of the ammonia inlet; and a gas discharge port of the stirring reactor 25 is communicated with an ammonia inlet of the falling film reactor 14 sequentially through a fourth condenser 7, a deep dehydration condenser 6 and a nitrile reaction ammonia heater 12.
In the embodiment, a guide shell 2 and a stirring paddle are arranged in the stirring reactor 25, and the stirring paddle is arranged in the guide shell 2 and is parallel to the axial direction of the guide shell 2; an ammonia distributor 1 is arranged at an ammonia inlet in the stirring reactor 25; the ammonia gas distributor 1 can be in a ring shape or a grid shape, and a plurality of downward gas distribution small holes are formed in the ammonia gas distributor 1.
Molten adipic acid coming from an adipic acid inlet 3 under the action of a stirrer, diluent coming from a first cooler 5 and amidation reaction products circulating in the stirring reactor are stirred, mixed and move downwards in a guide cylinder 2, the molten adipic acid moves to the bottom of the stirring reactor 25 to be uniformly mixed and reacted with ammonia gas sent from an ammonia gas pipeline, the ammonia gas is heated and distributed by an ammonia gas distributor 1, the mixture flows upwards along an annular gap between the inner wall of the stirring reactor 25 and the outer wall of the guide cylinder 2, the reaction part of the mixture is dehydrated during the movement, when the reaction mixture moves to the surface of a liquid surface in the stirring reactor 25, part of excessive ammonia gas and part of water vapor generated by dehydration pass through the liquid surface to enter the upper gas phase space of the reactor, and enter a fourth condenser 7 along a gas phase outlet at the top of the stirring reactor 25, the water vapor is condensed and then sent to a waste ammonia water storage tank, the ammonia gas which is not condensed is further cooled, condensed and dewatered by a deep dehydration condenser 6, mixed with part of ammonia gas sent by a liquid ring compressor 24, heated by an ammonia gas heater 12 for cyanation reaction and then sent to a falling film reactor 14.
Part of the adipamide-containing mixture is discharged through a reaction product outlet of the stirring reactor 25, heated by the first heater 4 and then enters the falling film reactor 14, but most of the reaction product in the stirring reactor circulates into the guide cylinder 2 to be mixed with the fed molten adipic acid and the diluent circulated from the separation tower 15 in the guide cylinder 2 and moves downwards, and then the diluent is mixed and reacts with the ammonia gas at the bottom, so that the liquid material circulates in the stirring reactor 25, and the added adipic acid can be almost completely reacted by the excessive ammonia gas.
The falling film reactor 14 is provided with an adipoamide-containing mixture inlet, an ammonia gas inlet, a mixture outlet containing adiponitrile at the bottom and a heating medium inlet and outlet, wherein the adipoamide-containing mixture inlet, the ammonia gas inlet, the adiponitrile-containing mixture outlet and the heating medium inlet and outlet are formed in the falling film reactor 14; a liquid distributor 13 is arranged at an entrance of the mixture containing the adipamide in the falling film reactor 14; an adipamide-containing mixture outlet in the stirring reactor 25 is communicated with an adipamide-containing mixture inlet of the falling film reactor 14, a first heater 4 is arranged on a pipeline between the adipamide-containing mixture outlet in the stirring reactor 25 and the adipamide-containing mixture inlet of the falling film reactor 14, and a diluent inlet and a dehydration catalyst inlet 11 are arranged on a pipeline between the outlet of the first heater 4 and the adipamide-containing mixture inlet of the falling film reactor 14. The dehydration catalyst inlet 11 may also be located in the diluent line of the falling film reactor 14. A mixer may also be provided at the dehydration catalyst inlet 11.
The bottom of the stirred reactor 25 is provided with a control valve which is in communication with the adipoamide-containing mixture inlet of the falling film reactor 14 and through which the contents of the stirred reactor 25 can be transferred into the falling film reactor 14 when the plant is not in operation.
The separation tower 15 comprises a gas phase outlet, a side line outlet, a diluent outlet, a semi-nitrile outlet, a lower material inlet, a cooling liquid inlet and a circulating liquid inlet. The lower material inlet is communicated with a mixture outlet containing adiponitrile at the bottom of the falling film reactor 14; the diluent outlet is communicated with the diluent inlet of the stirring reactor 25 through the first cooler 5; the diluent outlet is communicated with the adipoamide-containing mixture inlet in the falling film reactor 14; the distribution ratio of the dilution liquid into the falling film reactor 14 and the stirred reactor 25 is determined according to the reaction conditions and the reaction load of the reactors.
The decoking reactor 10 comprises an ammonia gas inlet, a semi-nitrile solution inlet, a gas phase outlet, a tar outlet and a heating medium inlet and outlet; a decoking ammonia heater 9 is arranged on the pipeline of the ammonia inlet; the semi-nitrile solution inlet is communicated with a semi-nitrile solution outlet at the bottom of the separation tower 15, and the gas phase outlet is communicated with an ammonia gas inlet of the falling film reactor 14; specifically, the decoking reactor 10 in the present embodiment is a wiped film evaporator.
The adipimide conversion tank 17 comprises an ammonia water inlet, a crude nitrile solution inlet, a gas outlet and a side wall outlet; a side outlet of the separation tower 15 is communicated with a crude nitrile solution inlet of an adipimide conversion tank 17 through a second cooler 16;
a separator tank 18 comprising an inlet, a side outlet, a top gas outlet, and a bottom outlet; the side outlet is communicated with a adiponitrile refining device; the outlet of the side wall of the adipimide conversion tank 17 is communicated with the inlet of a separation tank 18; the bottom outlet of the separation tank 18 is communicated with the circulating liquid inlet of the separation tower 15;
the adipimide conversion tank 17 is provided at the bottom with a control valve which is communicated with the inlet of the separation tank 18, and when the device is not in operation, the material in the adipimide conversion tank 17 can be conveyed to the separation tank 18 through the control valve. In the embodiment, a stirrer is arranged in the adipimide conversion tank 17; instead of the stirrer, a rotating tray column with a tray or a packed column may be used.
The gas outlet of the adipimide conversion tank 17, the top gas outlet of the separation tank 18 and the gas phase outlet of the separation tower 15 are all communicated with the inlet of a third condenser 20, and the first outlet of the third condenser 20 is communicated with the condensate inlet of the separation tower 15; a second outlet of the third condenser 20 is communicated with a bottom side wall inlet of the decarbonizing tower 21; a third outlet of the third condenser 20 is communicated with an ammonia recovery device;
the bottom outlet of the decarbonizing tower 21 is communicated with an ammonia recovery device; a desalted water inlet is formed in the side wall of the upper part of the decarbonizing tower 21, and an outlet at the top of the decarbonizing tower 21 is communicated with a side wall inlet of the liquid ammonia evaporator 22; the top of the liquid ammonia evaporator 22 is provided with a fresh liquid ammonia inlet and a gasified ammonia outlet; the side wall outlet of the liquid ammonia evaporator 22 is communicated with the middle inlet of the dehydrator 23; the bottom outlet of the liquid ammonia evaporator 22 is communicated with the outlet of the bottom side wall of the dehydrator 23; the bottom outlet of the dehydrator 23 is communicated with an ammonia recovery device; the outlet of the upper side wall of the dehydrator 23 is respectively communicated with the ammonia gas inlets of the stirring reactor 25, the falling film reactor 14 and the decoking reactor 10 through a liquid ring compressor 24.
Specifically, the dehydrator 23 in this embodiment is a hydrocyclone, and may be configured as the separation tank 18, and the separation tank 18 is provided with separation packing, and the separation packing may be an existing one.
Specifically, the working liquid in the liquid ring compressor 24 is adiponitrile, and water and trace organic impurities in ammonia gas are removed by the circulation of adiponitrile.
The falling film reactor 14 in this embodiment is a vertically installed falling film reactor 14, and includes a liquid distributor 13, a film distribution head, an upper tube plate, a tube array, and a lower tube plate. The upper ends of the tubes are sequentially provided with a film distribution head and an upper tube plate from top to bottom, and a liquid distributor 13 is arranged on the film distribution head; the lower end of the tube array is provided with a lower tube plate; the adipamide-containing mixture delivered from the stirring reactor 25 is heated by the first heater 4, then uniformly mixed with the diluent (adiponitrile is used to replace the diluent when no diluent is generated at the beginning) from the catalyst and separation tower 15, and then enters the liquid distributor 13 (in the embodiment, a distribution disc is used) at the upper part of the falling film reactor 14, is distributed by the liquid distributor 13 and enters the upper tube plate, and is further distributed by the membrane distribution head to enter the tubes of the falling film reactor in a tangential feeding mode to form a liquid membrane; the ammonia gas from the liquid ring compressor 24 is mixed with the ammonia gas from the top of the stirring reactor 25 after being dehydrated by the deep dehydration condenser 6, the ammonia gas is heated by the nitrile reaction ammonia heater 12 and then enters the falling film reactor 14 from the top and is uniformly distributed to enter the reaction tubes, the ammonia gas and the liquid film move from top to bottom together, and the liquid absorbs the heat transferred from the tube wall during the flowing process in the tubes to generate adiponitrile through deep dehydration of adipoyl amide. The reaction intermediates, namely the 5-cyano ammonium valerate, the 5-cyano valeramide, the partially aminated caproamide acid and the like, are further reacted under the protection of ammonia gas to generate adiponitrile. The heat transferred by the 14 tubes of the falling film reactor is provided by the heating medium, the temperature of the heating medium is only about 5 ℃ higher than the temperature of material reaction, namely the temperature difference between the heating medium and the reaction material is small, and the temperature distribution on the tubes is uniform, so that the phenomenon of overhigh local temperature does not exist in the falling film reaction process of the material, the tar and the by-products generated by the reaction are very few, and the yield of adiponitrile is high.
In order to avoid clogging due to the dry tube phenomenon of the tubes, it is necessary to leave a certain amount of liquid at the tube plate outlet of the tubes to carry away the by-products and catalyst generated by the reaction, and to prevent them from accumulating at the lower part and clogging or corroding the tubes. This portion of the liquid is sent out from the bottom of the falling film reactor 14 into a separation column 15 together with the gas under the impetus of gravity and gas.
Reaction products in the falling film reactor 14 enter a separation tower 15 for separation, wherein substances with large molecular weight, such as catalyst phosphoric acid, tar, and dimer of adiponitrile, are sent to a decoking reactor 10 through a half-nitrile outlet at the bottom of the separation tower 15 to remove catalyst, tar, dimer of adiponitrile, and the like, and a small amount of generated adiponitrile and intermediate are entrained by ammonia gas and enter the falling film reactor 14 for recycling;
most of the adiponitrile and the intermediate rise together with ammonia and water vapor into the tray of the separation column 15, where separation takes place; the diluent separated on the first tower plate at the lower part of the separation tower 15 mainly contains 5-cyanovaleramide, adiponitrile, a small amount of adipamide and 5-cyanoammonium valerate, the diluent is recycled to the stirring reactor 25 and the falling film reactor 14 to recover the adiponitrile, and the intermediate is further reacted to generate adiponitrile to be recovered.
Ammonia gasWater vapor, CO2Light component impurities such as cyclopentanone and the like are discharged from a gas phase outlet at the top of the separation tower 15, and are condensed by a third condenser 20 to obtain a part of condensed water vapor, cyclopentanone and light component impurities which are used as reflux at the top of the separation tower 15, and the other part of condensed water vapor, cyclopentanone and light component impurities are sent to an ammonia recovery device to recover ammonia; ammonia and CO not condensed2Sent to a decarbonizing tower 21 to remove CO2And then, the waste water is further dehydrated, compressed and recycled to the falling film reactor 14, the stirring reactor 25 and the decoking reactor 10 for recycling.
Crude nitrile solution obtained by separation at a side outlet in the middle of the separation tower 15 contains adiponitrile, a small amount of adipoyl imide, ICCP, 5-cyano ammonium valerate, 5-cyano valeramide and other organic matters, the cooled crude nitrile solution enters an adipoyl imide conversion tank 17 to react with fresh dilute ammonia water to convert the adipoyl imide into adipoyl amide, the adipoyl amide, 5-cyano ammonium valerate, part of 5-cyano valeramide and the like enter a water phase after being layered by a separation tank 18, and then the adipoyl amide, the 5-cyano ammonium valerate and the 5-cyano valeramide in the crude nitrile solution are recycled to the top of the separation tower 15 to recover the adipoyl amide, the 5-cyano ammonium valerate and the 5-cyano; the organic phase, which contains mainly adiponitrile with small amounts of ICCP and 5-cyanovaleramide and traces of ammonium 5-cyanovalerate, is sent to crude adiponitrile storage tank 19.
The working process is as follows:
molten adipic acid is continuously added into a guide shell 2 of a stirring reactor 25, excessive ammonia gas is heated by an amidation reaction ammonia gas heater 8 and then is sent to the bottom of the stirring reactor 25 through an ammonia gas distributor 1 in the stirring reactor 25, diluent obtained by separation in a separation tower 15 is cooled by a first cooler 5 and then is sent into the guide shell 2 of the stirring reactor 25 to be mixed with the molten adipic acid and reaction liquid circulating inside the stirring reactor 25 in the guide shell 2 uniformly and then is mixed and reacted with the ammonia gas at the bottom, the temperature in the stirring reactor 25 is mainly controlled by the preheating temperature of the ammonia gas, the reaction temperature of the stirring reactor 25 can be adjusted by the diluent, the adipamide generated in the stirring reactor 25 is dissolved and diluted, and adiponitrile is used for replacing the diluent if no diluent is generated at the beginning of the reaction. By adopting the stirring reactor 25 and arranging the guide shell 2 and the ammonia distributor 1, the further neutralization reaction of the adipic acid and the caproamide acid which are not completely aminated and ammonia can be ensured, and the generated adipamide and the intermediate are fully contacted with the ammonia to prevent the reverse hydrolysis reaction.
The mixture containing adipoamide from the stirring reactor 25 is heated by the first heater 4 and then mixed with the diluent separated by the separation tower 15 and the dehydration catalyst input by the dehydration catalyst inlet 11 to enter the falling film reactor 14, and the mixture consisting of the diluent, the dehydration catalyst and the heated mixture containing the adipoamide flows downwards along the inner wall of the tube nest after being distributed by the distributor in the falling film reactor and the membrane-distributing head is distributed; the mixed gas from the gas discharge port at the top of the stirring reactor 25 is condensed and dehydrated by a fourth condenser 7 and a deep dehydration condenser 6 in sequence to be converged with the ammonia gas compressed by a liquid ring compressor 24, and then is heated by a nitrile reaction ammonia heater 12 to be mixed with the gas phase mixture sent from the gas phase outlet of the decoking reactor 10, and then enters a falling film reactor 14, when the hot ammonia gas passes through the surface of the liquid film at high speed, adiponitrile and water vapor generated by dehydrating adipoyl amide and other substances in the liquid film are taken out of the liquid film to enter the gas phase, so that reactants in the liquid film are promoted to continue to proceed towards the direction of generating adiponitrile and water. Because the dehydration reaction of the adipamide is a strong endothermic process, in order to ensure the reaction temperature, the falling film tubes are heated by the heating medium, the heat transfer speed is changed by changing the speed of the heating medium flowing through the outer walls of the tubes, and as long as the temperature of the heating medium is not too high, the liquid in the liquid film cannot be overheated, so that the amount of generated tar is small, and the amount of cyclopentanone generated by decarboxylation of the raw material is also small. In the falling film reactor 14, adipamide and the intermediate produced in the stirred reactor 25 are reacted with ammonia gas in the presence of a dehydration catalyst or under the protection of ammonia gas to produce adiponitrile and intermediates such as 5-cyanovaleramide, ammonium 5-cyanovalerate and adipimide.
The reaction product discharged from the bottom outlet of the falling film reactor 14 is divided into two portions: one part is liquid flowing down from the inner wall of the tube array, mainly contains tar generated by reaction, dehydration catalyst phosphoric acid, adiponitrile dimer, a small amount of reaction intermediate and adiponitrile, and flows into a tower kettle of a separation tower 15 through a bottom pipeline of a falling film reactor under the push of gas; the other part is a gas phase which mainly comprises ammonia gas, water vapor generated by the reaction, adiponitrile generated by the reaction and most of reaction intermediates, and the gas phase and the reaction intermediates also enter the separation tower 15 from a bottom pipeline of the falling film reactor and ascend in the tower, and mist entrained in the gas phase is intercepted when meeting a defoaming net below a first tower plate at the lower part of the separation tower 15 and enters a liquid phase in a tower kettle to form a semi-nitrile solution with liquid sent by the falling film reactor 14. The separation column 15 is not provided with a reboiler and its motive power is derived from the heating power of the falling film reactor 14.
The heminitrile solution separated from the bottom of the separation tower 15 is mixed and reacted with the ammonia gas heated by the decoking ammonia gas heater 9 in the decoking reactor 10, the high boiling point tar and the impurities such as dehydration catalyst are discharged out of the system from the tar outlet of the decoking reactor 10, and the adiponitrile and other intermediates enter the falling film reactor 14 along with the ammonia gas in a circulating way. The decoking reactor 10 incorporates heaters which provide heat for both the reaction and vaporization of adiponitrile and intermediates stripped by ammonia gas.
An intermediate material containing a high boiling point captured from the bottom tower plate in the separation column 15 is called as a diluent (mainly comprising 5-cyanovaleramide, adiponitrile, 5-cyanoammonium valerate, adipamide and the like), and a part of the intermediate material is cooled by a first condenser and then circulated into the stirred reactor 25 for controlling the temperature of the stirred reactor 25; simultaneously, as a diluent of the adipamide crystals, melting and conveying the adipamide crystals to the falling film reactor 14; the other part is mixed with a dehydration catalyst and a mixture containing adipamide from the stirring reactor 25 to enter a falling film reactor, the adiponitrile is recovered, and the intermediate is further dehydrated and converted into adiponitrile.
The crude nitrile solution containing adipoyl imide separated from the upper side outlet of the separation column 15 mainly contains adiponitrile and a small amount of 5-cyanovaleric acid ammonium, 5-cyanovaleramide, adipoyl imide, ICCP and the like, and the organic matters are difficult to separate by adopting a common rectification method (for example, the relative volatility between adiponitrile and 5-cyanovaleric acid is only about 0.4), but the organic matters are mixed with water and then are separated into a water phase after being layered. Therefore, the material separated from the side outlet is cooled by the second cooler 16 and then sent to the adipimide conversion tank 17 to be mixed and stirred with fresh dilute ammonia solution for reaction so as to convert the adipimide in the material into the adipimide, and the reaction mixture enters the separation tank 18 through the side outlet to be separated into an upper organic phase and a lower aqueous phase. Organic matters such as 5-cyanoammonium valerate, adipamide, part of 5-cyanovaleramide and a small amount of adiponitrile enter a water phase, and useful organic matters are recycled by feeding the organic matters into a separation tower 15 from an outlet at the bottom of a separation tank 18 through a circulating liquid inlet of the separation tower 15; the organic phase in the upper layer mainly contains organic impurities such as adiponitrile, water, ammonia, 5-cyanovaleramide, ICCP and the like, overflows through an overflow outlet, enters a crude adiponitrile storage tank 19, and then enters subsequent refining treatment.
The gas phase discharged from the gas phase outlet at the top of the separation tower 15 contains ammonia gas, water vapor and CO2And the gases of low boiling point substances such as cyclopentanone and the like, the gases containing ammonia gas, water vapor and the like discharged from the gas outlet of the adipimide conversion tank 17 and the gas outlet of the separation tank 18 enter a third condenser 20 for condensation, most of the water and the low boiling point organic substances such as cyclopentanone and the like are condensed to form ammonia-containing wastewater, CO2Carbonate (or bicarbonate) which reacts with water and ammonia to form ammonia also enters the wastewater, one part of the ammonia-containing wastewater returns to the top of the separation tower 15 through a cooling liquid inlet of the separation tower 15 for controlling the temperature of the top of the separation tower, and the other part of the ammonia-containing wastewater is sent to a waste ammonia water tank for recovering the ammonia therein. The uncondensed gas mainly contains ammonia gas and a small amount of CO2The low boiling point substances such as water and cyclopentanone enter the bottom of the decarbonizing tower 21, and CO in the low boiling point substances is removed by desalted water, i.e. process water, sprayed from the top of the decarbonizing tower 212Organic impurities such as cyclopentanone and the like are washed into water to form ammonia-containing wastewater which is sent to a waste ammonia water tank to recover ammonia; the washed clean ammonia gas coming out of the top of the decarbonization tower 21 enters a liquid ammonia evaporator 22, is cooled by cold energy brought by liquid ammonia evaporation, enters a dehydrator 23 to separate most of moisture brought by the ammonia gas, then enters a liquid ring compressor 24 to increase pressure, working liquid used by the liquid ring compressor 24 is adiponitrile, can absorb most of moisture and cyclopentanone carried in the ammonia gas in the operation process, so that the ammonia gas becomes drier and cleaner, and the ammonia gas pressurized by the liquid ring compressor 24 is mixed with fresh ammonia gas from the liquid ammonia evaporator 22, heated and then sent into a falling film type reverse evaporatorReactor 14, stirred reactor 25 and decoking reactor 10 to participate in the reaction.
According to the device for preparing adiponitrile by ammoniating adipic acid, the stirring reactor 25, the falling film reactor 14, the decoking reactor 10 and the adipimide conversion tank 17 are arranged and used in combination, so that the generation of byproducts and tar can be reduced, the blockage of equipment or pipelines caused by the accumulation of tar in a system can be effectively avoided, the yield of adiponitrile can be obviously improved, and the quality of adiponitrile can be improved.
Example 2
The embodiment provides a method for preparing adiponitrile by ammoniating adipic acid, which adopts the device for preparing adiponitrile by ammoniating adipic acid shown in fig. 1, and specifically comprises the following steps:
5.8kg/h of ammonia gas is measured by a flowmeter, heated to 185 ℃ by an ammonia gas heater, distributed by an ammonia gas distributor in a stirring reactor and sent to the bottom of the stirring reactor, 10kg/h of 185 ℃ molten adipic acid and 10kg/h of diluent separated from a separation tower are sent to the stirring reactor after being cooled to 185 ℃, the pressure of the stirring reactor is adjusted to 250kPa, and the obtained mixture containing the adipamide is discharged from the stirring reactor after reaction. The conversion rate of adipic acid in the mixture containing adipamide is about 99 percent, wherein about 87 percent of adipic acid is converted into adipamide, and the rest generates intermediates such as adipic acid and the like. The excessive ammonia gas and the generated water vapor in the stirring reactor are condensed by a condenser, and the ammonia gas obtained after deep dehydration can be recycled.
Heating a mixture containing adipoamide discharged from a stirring reactor to about 270 ℃, separating the mixture from a separator to obtain a diluent with the temperature of 265 ℃, adding a phosphoric acid solution with the flow rate of 0.2kg/h and the concentration of 10 percent (wt), uniformly mixing the diluent, adding the mixture into a distribution disc of a falling film reactor, heating ammonia gas with the flow rate of 4.5kg/h and excess ammonia gas 2.8kg/h sent from an amidation step to 270 ℃, mixing the mixture with gas 4.0kg/h sent from a decoking reactor, entering the top of the falling film reactor, carrying out deep dehydration reaction on the materials in the falling film reactor at about 275-285 ℃ and 130kPa to generate a mixture containing adiponitrile (mainly comprising adiponitrile, water, a small amount of intermediate and impurities), and then entering a separation tower for separation.
Discharging 1.45kg/h of tar-containing mixture, namely a semi-nitrile solution, from the bottom of the separation tower, feeding the mixture into a decoking reactor, simultaneously heating 3kg/h of ammonia gas to 270 ℃, feeding the ammonia gas into the decoking reactor, controlling the reaction temperature in the decoking reactor to be about 270 ℃, controlling the reaction pressure to be about 140kPa, reacting part of intermediates with the ammonia gas to obtain adiponitrile and water, wherein the adiponitrile, the rest of intermediates and the ammonia gas circularly enter the falling film reactor; about 0.39kg/h tar was obtained at the bottom of the decoking reactor and was sent to incineration with a dehydration catalyst.
The temperature of the top of the separation tower is controlled to be 80-90 ℃, the pressure of the top of the separation tower is controlled to be 105-110kPa, light component impurities from the top of the separation tower are condensed and then circulated to the top of the separation tower for controlling the temperature of the top of the separation tower, and the residual condensate is sent into a waste ammonia water tank to recover ammonia in the condensate; the ammonia gas which is not condensed is sequentially decarbonized, dehydrated and compressed and then respectively circulated to the falling film reactor, the stirring reactor and the decoking reactor to participate in the reaction. The temperature of the bottom of the separation column was 280 ℃ and 17kg/h of the diluted solution was discharged from the first tray at the lower part of the column. The temperature of the material extracted from the side line of the separation tower is 230-245 ℃, the material is cooled and then sent into an adipimide conversion tank to react with 5 percent of fresh dilute ammonia water, the product after the reaction is separated by a separation tank to obtain 7.63kg/h of crude adiponitrile, the crude adiponitrile contains 6.86kg/h of adiponitrile and the yield of the adiponitrile is 92.7 percent through gas phase detection; the water phase obtained in the separation tank is recycled to the separation tower to recover useful intermediates in the water phase.
Example 3
The embodiment provides a method for preparing adiponitrile by ammoniating adipic acid, which adopts the device for preparing adiponitrile by ammoniating adipic acid shown in fig. 1, and specifically comprises the following steps:
measuring 9.3kg/h ammonia gas by a flowmeter, heating to 220 ℃ by an ammonia gas heater, distributing by an ammonia gas distributor in a stirring reactor, sending into the bottom of the stirring reactor 4, cooling 10kg/h of 200 ℃ molten adipic acid and 8.5kg/h of diluent separated from a separation tower to 232 ℃, sending into the stirring reactor, adjusting the pressure of the stirring reactor to 290kPa, and discharging a mixture containing adipamide out of the stirring reactor after reaction. The conversion rate of adipic acid in the mixture containing adipamide is about 99%, wherein about 86% of adipic acid is converted into adipamide, and the rest generates intermediates such as adipic acid. Excessive ammonia gas and water generated in the reaction in the stirring reactor are dehydrated by a condenser and a deep cooler from a gas phase pipe at the top of the stirring reactor to obtain ammonia gas which is sent to the falling film reactor for utilization.
Heating a mixture containing adipoyl amide discharged from a stirring reactor to about 290 ℃, separating the mixture from a separation tower to obtain a diluent with the temperature of 265 ℃ and the flow rate of 6.5kg/h, adding a phosphoric acid solution with the flow rate of 0.18kg/h and the concentration of 10 percent (wt), uniformly mixing the diluent and the phosphoric acid solution, adding the mixture into a distribution disc of a falling film reactor, heating ammonia gas with the flow rate of 2.0kg/h and excess ammonia gas 6.2kg/h sent from an amidation step to 290 ℃, mixing the mixture with gas 4.0kg/h sent from a decoking reactor, introducing the mixture into the top of the falling film reactor, performing dehydration reaction on the mixture in the falling film reactor at the temperature of about 290 ℃ and 300 ℃ under the pressure of 130kPa to generate a mixture containing adiponitrile, and then introducing the mixture into the separation tower for separation.
Discharging 1.48kg/h of semi-nitrile solution from the separation tower kettle, feeding the semi-nitrile solution into a decoking reactor, simultaneously heating 3.0kg/h of ammonia gas to 270 ℃, feeding the heated semi-nitrile solution into the decoking reactor, controlling the reaction temperature in the decoking reactor to be about 270 ℃, controlling the reaction pressure to be about 140kPa, reacting part of intermediates with the ammonia gas to obtain adiponitrile and water, wherein the adiponitrile, the rest intermediates and the ammonia gas circularly enter the falling film type reactor; about 0.42kg/h tar was obtained at the bottom of the decoking reactor and was sent to incineration with a dehydration catalyst.
The temperature at the top of the separation tower is controlled to be 80-90 ℃, the pressure at the top of the separation tower is controlled to be 105-110kPa, and light component impurities from the top of the separation tower are condensed and then circulated to the top of the separation tower for controlling the temperature at the top of the separation tower; the residual condensate is sent into a waste ammonia water tank to recover ammonia in the condensate; the ammonia gas which is not condensed is sequentially decarbonized, dehydrated and compressed and then respectively circulated to the falling film reactor, the stirring reactor and the decoking reactor to participate in the reaction. The temperature of the bottom of the separation column was 287 ℃ and 15kg/h of the diluted solution was discharged from the first tray at the lower part of the column. The temperature of the material extracted from the side line of the separation tower is 230-245 ℃, the material is cooled and then sent into an adipimide conversion tank to react with 5 percent of fresh dilute ammonia water, the product after the reaction is separated by a separation tank to obtain 7.58kg/h of crude adiponitrile, the crude adiponitrile contains 6.82kg/h of adiponitrile and the yield of the adiponitrile is 92.2 percent through gas phase detection; the water phase obtained in the separation tank is recycled to the separation tower to recover useful intermediates in the water phase.
Example 4
The embodiment provides a method for preparing adiponitrile by ammoniating adipic acid, which adopts the device for preparing adiponitrile by ammoniating adipic acid shown in fig. 1, and specifically comprises the following steps:
measuring 7.6kg/h ammonia gas by a flowmeter, heating to 165 ℃ by an ammonia gas heater, distributing by an ammonia gas distributor in a stirring reactor, sending into the bottom of the stirring reactor 4, cooling 10kg/h of 160 ℃ molten adipic acid and 8.3kg/h of diluent separated from a separation tower to 170 ℃, sending into the stirring reactor, adjusting the pressure of the stirring reactor to 140kPa, and discharging a mixture containing adipamide out of the stirring reactor after reaction. The conversion rate of adipic acid in the mixture containing adipamide is about 97 percent, wherein about 86 percent of adipic acid is converted into adipamide, and the rest generates intermediates such as adipic acid and the like. And part of low boiling point substances such as ammonia water and the like in the stirring reactor are cooled and deeply dehydrated to obtain ammonia gas which can be recycled.
Heating a mixture containing adipoyl amide discharged from a stirring reactor to about 260 ℃, separating the mixture from a separator to obtain a diluent with the temperature of 265 ℃, the flow rate of 6.3kg/h, mixing the diluent with the flow rate of 0.15kg/h and the concentration of 10 percent (wt), adding the mixture into a distribution disc of a falling film reactor after uniform mixing, heating 4kg/h of ammonia gas with the flow rate of 4kg/h and 4.6kg/h of excess ammonia gas sent from an amidation step to 260 ℃, mixing the mixture with 4.0kg/h of gas sent from a decoking reactor, entering the top of the falling film reactor, carrying out dehydration reaction on the materials in the falling film reactor at the temperature of 260-.
Discharging 1.52kg/h of tar-containing mixture (namely, a half-nitrile solution, mainly a small amount of adiponitrile, an intermediate, tar, a dehydration catalyst and the like) from a separation tower kettle, feeding the mixture into a decoking reactor, simultaneously heating 3kg/h of ammonia gas to 270 ℃, feeding the mixture into the decoking reactor, controlling the reaction temperature in the decoking reactor to be about 270 ℃, controlling the reaction pressure to be about 140kPa, reacting part of the intermediate with the ammonia gas to obtain adiponitrile and water, wherein the adiponitrile, the rest of the intermediate and the ammonia gas circularly enter the falling film type reactor; about 0.41kg/h tar was obtained at the bottom of the decoking reactor and was sent to incineration with a dehydration catalyst.
The temperature at the top of the separation tower is controlled to be 80-90 ℃, the pressure at the top of the separation tower is controlled to be 105-110kPa, and light component impurities from the top of the separation tower are condensed and then circulated to the top of the separation tower for controlling the temperature at the top of the separation tower; sending the condensate into a waste ammonia water tank to recover ammonia in the condensate; the ammonia gas which is not condensed is sequentially decarbonized, dehydrated and compressed and then respectively circulated to the falling film reactor, the stirring reactor and the decoking reactor to participate in the reaction. The temperature of the bottom of the separation column was 280 ℃ and 14.6kg/h of the diluted solution was discharged from the first tray at the lower part of the column. The temperature of the material extracted from the side line of the separation tower is 230-245 ℃, the material is cooled and then sent into an adipimide conversion tank to react with 5 percent of fresh dilute ammonia water, the product after the reaction is separated by a separation tank to obtain 7.58kg/h of crude adiponitrile, the crude adiponitrile contains 6.84kg/h of adiponitrile and the yield of the adiponitrile is 92.4 percent through gas phase detection; the water phase obtained in the separation tank is recycled to the separation tower to recover useful intermediates in the water phase.
Example 5
The embodiment provides a method for preparing adiponitrile by ammoniating adipic acid, which adopts the device for preparing adiponitrile by ammoniating adipic acid shown in fig. 1, and specifically comprises the following steps:
16.5kg/h ammonia gas is measured by a flowmeter, heated to 200 ℃ by an ammonia gas heater, distributed by an ammonia gas distributor in a stirring reactor and sent to the bottom of the stirring reactor 4, 10kg/h of 200 ℃ molten adipic acid and 10kg/h of diluent separated from a separation tower are sent into the stirring reactor after being cooled to 200 ℃, the pressure of the stirring reactor is adjusted to 260kPa, and a mixture containing adipamide is obtained after reaction and is discharged out of the stirring reactor. The conversion of adipic acid in the adipamide-containing mixture was determined to be about 99.2%, with about 87.8% of the adipic acid being converted to adipamide and the remainder being adipamic acid and other intermediates. And part of low boiling point substances such as ammonia water and the like in the stirring reactor are cooled and deeply dehydrated to obtain ammonia gas which can be recycled.
Heating a mixture containing adipoamide discharged from a stirring reactor to about 280 ℃, separating the mixture from a separator to obtain a diluent with the temperature of 265 ℃, the flow rate of 8.5kg/h, mixing the diluent with the flow rate of 0.22kg/h and the concentration of 10 percent (wt), adding the mixture into a distribution plate of a falling film reactor after uniformly mixing, heating 13.5kg/h of excessive ammonia gas sent by an amidation step to 280 ℃, mixing the excessive ammonia gas with 4.0kg/h of gas sent by a decoking reactor, entering the top of the falling film reactor, carrying out dehydration reaction on the materials in the falling film reactor at 280-290 ℃ and 120KPa to generate a mixture containing adiponitrile, and then entering a separation tower for separation.
Discharging 1.45kg/h of semi-nitrile solution from the separation tower kettle, feeding the semi-nitrile solution into a decoking reactor, simultaneously heating 3kg/h of ammonia gas to 280 ℃, feeding the ammonia gas into the decoking reactor, controlling the reaction temperature in the decoking reactor to be about 290 ℃, controlling the reaction pressure to be about 130kPa, reacting part of intermediates with the ammonia gas to obtain adiponitrile and water, wherein the adiponitrile, the rest of intermediates and the ammonia gas circularly enter the falling film reactor; about 0.40kg/h of tar and dehydration catalyst were obtained at the bottom of the decoking reactor and sent to incineration.
The temperature of the top of the separation tower is controlled at 80 ℃, the pressure of the top of the separation tower is controlled at 105kPa, and light component impurities from the top of the separation tower are condensed and then circulated to the top of the separation tower for controlling the temperature of the top of the separation tower; sending the condensate into a waste ammonia water tank to recover ammonia in the condensate; the ammonia gas which is not condensed is sequentially decarbonized, dehydrated and compressed and then respectively circulated to the falling film reactor, the stirring reactor and the decoking reactor to participate in the reaction. The temperature of the bottom of the separation column was 280 ℃ and 18.5kg/h of the diluted solution was discharged from the first tray at the lower part of the column. The temperature of the material extracted from the side line of the separation tower is about 240 ℃, the material is cooled and then sent into an adipimide conversion tank to react with 5% of fresh dilute ammonia water, the product after the reaction is separated by a separation tank to obtain 7.56kg/h of crude adiponitrile, the organic phase obtained after the reaction is 7.56kg/h of crude adiponitrile, the adiponitrile content in the crude adiponitrile is 6.85kg/h through gas phase detection, and the adiponitrile yield is 92.6%; the water phase obtained in the separation tank is recycled to the separation tower to recover useful intermediates in the water phase.
Comparative example 1
The comparative example provides a method for preparing adiponitrile by ammonifying adipic acid, which is an original industrial device for preparing adiponitrile by ammonifying adipic acid of Liaoyang petroleum chemical fiber company, wherein the original industrial device is not provided with a pre-reactor and only comprises a nitrifying reactor, the nitrifying reactor is a climbing film reactor, the reaction temperature is 285 ℃, the reaction pressure is about 130kPa, the feed rate of adipic acid is 4840kg/h, the feed rate of ammonia gas is 6000kg/h, and the feed rate of 75 wt% phosphoric acid serving as a dehydration catalyst is 11.6 kg/h; 3450kg/h of crude adiponitrile are produced, wherein the adiponitrile content is 3093.9kg/h, the adiponitrile yield is 86.4 percent, the tar yield obtained at the bottom of the decoking reactor is 304kg/h (the conversion into the adipic acid is 10kg/h, the crude adiponitrile is 7.13kg/h, the adiponitrile content is 6.39kg/h, and the tar yield is 0.628 kg/h).
Comparative example 2
This comparative example provides a process for the amination of adipic acid to adiponitrile similar to example 2, except that the dehydration catalyst (10 wt% phosphoric acid) was added in the stirred reactor.
Detection shows that the conversion rate of adipic acid in the mixture containing adipamide obtained by the reaction in the stirring reactor is about 99.2%, wherein about 85% of adipic acid is converted into the adipamide, and the rest generates intermediates such as adipic acid and the like.
Through gas phase detection, the yield of adiponitrile in the finally prepared crude adiponitrile is 90.2 percent, and the tar amount obtained from the bottom of the decoking reactor is 0.54 kg/h.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of the invention may be made without departing from the spirit or scope of the invention.
Claims (14)
1. A method for preparing adiponitrile by ammoniating adipic acid is characterized by comprising the following steps,
amidation step: adipic acid reacts with ammonia gas and is dehydrated to generate a mixture containing adipamide;
a cyanation step: dehydrating the adipoamide-containing mixture under the action of a dehydration catalyst to generate an adiponitrile-containing mixture;
and the amidation step further comprises a step of discharging a mixture of water vapor and ammonia gas.
2. The method for preparing adiponitrile according to claim 1, wherein the amidation step is performed in a stirred reactor, and a gas discharge port is provided at the top of the stirred reactor for discharging the mixture of water vapor and ammonia gas generated in the reaction.
3. The method for preparing adiponitrile according to claim 2, wherein a guide shell is further arranged in the stirring reactor, and the stirring device in the stirring reactor is arranged in the guide shell.
4. The method for preparing adiponitrile according to any one of claims 1 to 3, wherein the difference between the reaction temperature of the amidation step and the reaction temperature of the cyanation step is not less than 30 ℃.
5. The process for the ammonification of adiponitrile according to any one of claims 1 to 4, wherein the step of cyanation is carried out using a falling film reactor.
6. The method for preparing adiponitrile according to any one of claims 1 to 5, further comprising a step of separately converting a mixture containing adiponitrile, which comprises,
a separation step: separating the mixture containing adiponitrile to obtain a diluent, a semi-nitrile solution, a crude nitrile solution containing adipimide and light component impurities;
conversion step of adipimide: reacting crude nitrile solution containing adipimide with ammonia water to obtain a gas-phase mixture and a liquid mixture; the liquid mixture is allowed to stand to obtain an ammonia-containing gas phase, an organic phase containing crude adiponitrile, and an aqueous phase containing adipoamide.
7. The method for preparing adiponitrile according to claim 6, wherein the diluent is recycled to the amidation step and the cyanation step;
and/or the aqueous phase containing adipamide is recycled to the separation step.
8. The method of manufacturing adiponitrile according to claim 6 or 7, wherein,
and (3) condensing the light component impurities and the gas phase mixture obtained in the step of converting the adipimide to obtain ammonia-containing condensate, partially circulating the ammonia-containing condensate to the separation step, and recovering ammonia from the rest part.
9. The method for preparing adiponitrile by aminating adipic acid according to any one of claims 6 to 8, wherein the method for preparing adiponitrile by aminating adipic acid further comprises a decoking step of: reacting the semi-nitrile solution with ammonia gas to obtain a gas phase mixture containing adiponitrile and a liquid phase mixture containing tar and a dehydration catalyst;
the gas-phase mixture comprising adiponitrile is recycled to the cyanation step.
10. The method for preparing adiponitrile according to claim 8, wherein the ammonia gas which is not condensed is subjected to decarburization, evaporative condensation, dehydration and compression in sequence, and then is recycled to the cyanation step, the amidation step and the decoking step to participate in the reaction.
11. A device for preparing adiponitrile by ammoniating adipic acid is characterized by comprising,
the stirring reactor comprises an ammonia gas inlet, an adipic acid inlet, a diluent inlet and a mixture outlet containing adipamide, the top of the stirring reactor is provided with a gas discharge outlet, the inside of the stirring reactor is provided with a guide shell and a stirring paddle, and the stirring paddle is arranged inside the guide shell and is parallel to the axial direction of the guide shell;
an ammonia distributor is arranged at an ammonia inlet of the stirring reactor;
the falling film reactor comprises an adipoamide-containing mixture inlet, an ammonia gas inlet, a heating medium inlet and a heating medium outlet and an adiponitrile-containing mixture outlet, wherein the adipoamide-containing mixture inlet is communicated with the adipoamide-containing mixture outlet of the stirring reactor, and a catalyst inlet is arranged on a pipeline between the adipoamide-containing mixture inlet and the adipoamide-containing mixture outlet of the stirring reactor.
12. The apparatus of claim 11, wherein a first heating device is disposed on the pipeline between the stirring reactor and the falling film reactor.
13. The apparatus for the ammonification of adiponitrile according to claim 11 or 12, wherein the falling film reactor is provided with a distributor at the entrance of the adipamide-containing mixture.
14. The apparatus for the ammonification of adiponitrile according to any one of claims 11 to 13, wherein the apparatus for the ammonification of adiponitrile further comprises a separation and conversion unit, an inlet of which is connected to an outlet of the adiponitrile-containing mixture of the falling film reactor, and an outlet of which is connected to a adiponitrile refining apparatus.
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