CN115246773B - System for separating MMA from aldol condensation product - Google Patents
System for separating MMA from aldol condensation product Download PDFInfo
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- CN115246773B CN115246773B CN202110454622.1A CN202110454622A CN115246773B CN 115246773 B CN115246773 B CN 115246773B CN 202110454622 A CN202110454622 A CN 202110454622A CN 115246773 B CN115246773 B CN 115246773B
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- 238000005882 aldol condensation reaction Methods 0.000 title claims abstract description 43
- 239000007859 condensation product Substances 0.000 title claims abstract description 43
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims abstract description 314
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 claims abstract description 184
- 238000011084 recovery Methods 0.000 claims abstract description 113
- 238000005886 esterification reaction Methods 0.000 claims abstract description 32
- 239000000047 product Substances 0.000 claims abstract description 20
- 239000002351 wastewater Substances 0.000 claims abstract description 13
- XBDQKXXYIPTUBI-UHFFFAOYSA-N dimethylselenoniopropionate Natural products CCC(O)=O XBDQKXXYIPTUBI-UHFFFAOYSA-N 0.000 claims description 86
- RJUFJBKOKNCXHH-UHFFFAOYSA-N Methyl propionate Chemical compound CCC(=O)OC RJUFJBKOKNCXHH-UHFFFAOYSA-N 0.000 claims description 49
- 229940017219 methyl propionate Drugs 0.000 claims description 49
- 235000019260 propionic acid Nutrition 0.000 claims description 43
- IUVKMZGDUIUOCP-BTNSXGMBSA-N quinbolone Chemical compound O([C@H]1CC[C@H]2[C@H]3[C@@H]([C@]4(C=CC(=O)C=C4CC3)C)CC[C@@]21C)C1=CCCC1 IUVKMZGDUIUOCP-BTNSXGMBSA-N 0.000 claims description 43
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 38
- 238000000605 extraction Methods 0.000 claims description 36
- 230000018044 dehydration Effects 0.000 claims description 33
- 238000006297 dehydration reaction Methods 0.000 claims description 33
- 238000007670 refining Methods 0.000 claims description 22
- 230000032050 esterification Effects 0.000 claims description 16
- CERQOIWHTDAKMF-UHFFFAOYSA-N Methacrylic acid Chemical compound CC(=C)C(O)=O CERQOIWHTDAKMF-UHFFFAOYSA-N 0.000 claims description 15
- 239000012071 phase Substances 0.000 claims description 13
- 238000000926 separation method Methods 0.000 claims description 13
- 238000013461 design Methods 0.000 claims description 11
- 239000000284 extract Substances 0.000 claims description 10
- 239000000463 material Substances 0.000 claims description 10
- 239000000203 mixture Substances 0.000 claims description 10
- 238000010992 reflux Methods 0.000 claims description 9
- 238000009833 condensation Methods 0.000 claims description 8
- 230000005494 condensation Effects 0.000 claims description 8
- 230000010354 integration Effects 0.000 claims description 8
- WSFSSNUMVMOOMR-NJFSPNSNSA-N methanone Chemical compound O=[14CH2] WSFSSNUMVMOOMR-NJFSPNSNSA-N 0.000 claims description 7
- 238000000746 purification Methods 0.000 claims description 6
- 239000007791 liquid phase Substances 0.000 claims description 4
- 239000012074 organic phase Substances 0.000 claims description 4
- 238000005191 phase separation Methods 0.000 claims description 4
- 239000002699 waste material Substances 0.000 claims description 4
- 238000011144 upstream manufacturing Methods 0.000 claims description 3
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- 238000004064 recycling Methods 0.000 abstract description 7
- 230000008901 benefit Effects 0.000 abstract description 5
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- VVQNEPGJFQJSBK-UHFFFAOYSA-N Methyl methacrylate Chemical compound COC(=O)C(C)=C VVQNEPGJFQJSBK-UHFFFAOYSA-N 0.000 description 78
- 238000000034 method Methods 0.000 description 21
- 230000008569 process Effects 0.000 description 15
- 239000008098 formaldehyde solution Substances 0.000 description 10
- 239000007789 gas Substances 0.000 description 9
- 238000006243 chemical reaction Methods 0.000 description 7
- 239000006227 byproduct Substances 0.000 description 6
- BHIWKHZACMWKOJ-UHFFFAOYSA-N methyl isobutyrate Chemical compound COC(=O)C(C)C BHIWKHZACMWKOJ-UHFFFAOYSA-N 0.000 description 6
- 238000009835 boiling Methods 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
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- WDAXFOBOLVPGLV-UHFFFAOYSA-N isobutyric acid ethyl ester Natural products CCOC(=O)C(C)C WDAXFOBOLVPGLV-UHFFFAOYSA-N 0.000 description 3
- 239000011347 resin Substances 0.000 description 3
- 229920005989 resin Polymers 0.000 description 3
- BAPJBEWLBFYGME-UHFFFAOYSA-N Methyl acrylate Chemical compound COC(=O)C=C BAPJBEWLBFYGME-UHFFFAOYSA-N 0.000 description 2
- DKGAVHZHDRPRBM-UHFFFAOYSA-N Tert-Butanol Chemical compound CC(C)(C)O DKGAVHZHDRPRBM-UHFFFAOYSA-N 0.000 description 2
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- 239000003054 catalyst Substances 0.000 description 2
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- 238000004043 dyeing Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 239000000178 monomer Substances 0.000 description 2
- 229920003023 plastic Polymers 0.000 description 2
- 229920003229 poly(methyl methacrylate) Polymers 0.000 description 2
- 239000004926 polymethyl methacrylate Substances 0.000 description 2
- 238000007639 printing Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 230000001502 supplementing effect Effects 0.000 description 2
- NWUYHJFMYQTDRP-UHFFFAOYSA-N 1,2-bis(ethenyl)benzene;1-ethenyl-2-ethylbenzene;styrene Chemical compound C=CC1=CC=CC=C1.CCC1=CC=CC=C1C=C.C=CC1=CC=CC=C1C=C NWUYHJFMYQTDRP-UHFFFAOYSA-N 0.000 description 1
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 description 1
- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 1
- MWFMGBPGAXYFAR-UHFFFAOYSA-N 2-hydroxy-2-methylpropanenitrile Chemical compound CC(C)(O)C#N MWFMGBPGAXYFAR-UHFFFAOYSA-N 0.000 description 1
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 1
- 239000005977 Ethylene Substances 0.000 description 1
- VQTUBCCKSQIDNK-UHFFFAOYSA-N Isobutene Chemical group CC(C)=C VQTUBCCKSQIDNK-UHFFFAOYSA-N 0.000 description 1
- XBDQKXXYIPTUBI-UHFFFAOYSA-M Propionate Chemical compound CCC([O-])=O XBDQKXXYIPTUBI-UHFFFAOYSA-M 0.000 description 1
- KXKVLQRXCPHEJC-UHFFFAOYSA-N acetic acid trimethyl ester Natural products COC(C)=O KXKVLQRXCPHEJC-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000006315 carbonylation Effects 0.000 description 1
- 238000005810 carbonylation reaction Methods 0.000 description 1
- 239000013064 chemical raw material Substances 0.000 description 1
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- 238000010908 decantation Methods 0.000 description 1
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- 239000010985 leather Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000010687 lubricating oil Substances 0.000 description 1
- -1 methyl acrylic ester Chemical class 0.000 description 1
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
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- 230000002194 synthesizing effect Effects 0.000 description 1
- 239000004753 textile Substances 0.000 description 1
- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 description 1
- 229920002554 vinyl polymer Polymers 0.000 description 1
- 239000002023 wood Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C67/00—Preparation of carboxylic acid esters
- C07C67/48—Separation; Purification; Stabilisation; Use of additives
- C07C67/58—Separation; Purification; Stabilisation; Use of additives by liquid-liquid treatment
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention relates to a system for separating MMA from an aldol condensation product, which is arranged downstream of an aldol condensation reactor for producing MMA, separates an initial aldol condensation product discharged from the aldol condensation reactor, and comprises a methanol recovery unit for separating a light component containing methanol in the initial aldol condensation product and purifying and recovering methanol in the light component, an MMA recovery unit coupled with the methanol recovery unit, and an esterification reaction unit. The invention solves the recycling problem of methanol and the environmental protection treatment problem of formaldehyde-containing wastewater, and further improves the yield of MMA product and economic benefit.
Description
Technical Field
The invention relates to the technical field of chemical separation, in particular to a system for separating MMA from aldol condensation products.
Background
Methyl Methacrylate (MMA) is an organic compound, is an important chemical raw material, is a monomer for producing transparent plastic polymethyl methacrylate (PMMA), and can be copolymerized with other vinyl monomers to obtain products with different properties for manufacturing organic glass, paint, lubricating oil additive, plastic, adhesive, resin, wood impregnating compound, motor coil impregnating compound, ion exchange resin, paper polishing agent, textile printing and dyeing auxiliary agent, leather treating agent, printing and dyeing auxiliary agent, insulating pouring material and the like.
The main processes for producing MMA are acetone cyanohydrin method, tert-butanol/isobutylene direct oxidation method, ethylene carbonylation method, methyl propionate aldol condensation method, etc. Among them, methyl propionate aldol condensation is a recent research hotspot, and its subsequent MMA product refining process is also a research hotspot.
For example, patent CN111517953a discloses a production process method for synthesizing methyl methacrylate from methyl acetate and formaldehyde, a gradual reaction and gradual separation mode is adopted, two-stage aldol condensation reactions are respectively carried out in two independent reactors, a multistage efficient rectification separation and purification method is adopted in combination with the two-stage aldol condensation reactions, separation of various intermediate products and products is realized, meanwhile, the product yield is very high, the purity of rectification separation circulating materials is high, the amount of bringing impurities into a reaction system is reduced, and the occurrence of side reactions is effectively reduced.
The aldol condensation product comprises a plurality of components such as MMA, methanol, formaldehyde, methyl propionate, methyl isobutyrate and the like, and various components are difficult to effectively separate and treat in the prior art, such as methanol with high concentration is difficult to obtain, the recycling problem of the methanol is difficult to solve, the environmental protection problem of formaldehyde-containing wastewater is also difficult to solve, and the yield of the product MMA still needs to be further improved.
Disclosure of Invention
The invention aims to solve the problems and provide a system for separating MMA from aldol condensation products, which solves the problems of recycling of methanol and environmental protection treatment of formaldehyde-containing wastewater, further improves the yield of MMA and improves the economic benefit.
The aim of the invention is achieved by the following technical scheme:
A system for separating MMA from an aldol condensation product, the system being provided downstream of an aldol condensation reactor for producing MMA, separating and purifying an initial aldol condensation product discharged from the aldol condensation reactor to obtain high-purity MMA, the system comprising a methanol recovery unit for separating a light component containing methanol in the initial aldol condensation product and purifying and recovering methanol in the light component, an MMA recovery unit coupled to the methanol recovery unit, and an esterification reaction unit;
And introducing a high-purity methanol part obtained by the methanol recovery unit into the esterification reaction unit, carrying out esterification reaction with propionic acid and methacrylic acid from the MMA recovery unit, returning the obtained product to a feed inlet of the methanol recovery unit, mixing with the initial aldol condensation product, and then carrying out separation and purification again.
Further, the system also comprises a formaldehyde recovery unit coupled with the methanol recovery unit, wherein after the heavy components containing MMA and formaldehyde, which are separated by the methanol recovery unit, are separated, the obtained light phase containing MMA enters the MMA recovery unit for separation and purification to obtain high-purity MMA, and the obtained heavy phase containing formaldehyde enters the formaldehyde recovery unit for separation and purification to obtain formaldehyde.
Further, the methanol recovery unit comprises a methanol recovery tower, a high-pressure tower and an atmospheric tower, wherein the methanol recovery tower is used for separating light components containing methanol in condensation product feed, the light components containing methanol are extracted from the top of the methanol recovery tower and enter the high-pressure tower, high-purity methyl propionate is extracted from the tower bottom of the high-pressure tower, the light components extracted from the top of the high-pressure tower enter the atmospheric tower, the overhead extract of the atmospheric tower returns to the high-pressure tower, and high-concentration methanol is extracted from the tower bottom of the atmospheric tower.
Further, the MMA recovery unit comprises an extraction tower, a dehydration tower, a methyl propionate recovery tower, an MMA crude tower and an MMA refining tower, wherein heavy components containing MMA and formaldehyde, which are extracted from the tower bottom of the methanol recovery tower, enter the extraction tower, the light phase of the extraction tower enters the dehydration tower for dehydration, materials with water removed are extracted from the tower bottom of the dehydration tower, enter the methyl propionate recovery tower for separating methyl propionate, methyl propionate is extracted from the tower top of the methyl propionate recovery tower, and the extract from the tower bottom of the methyl propionate recovery tower sequentially passes through the MMA crude tower and the MMA refining tower for separation to obtain high-purity MMA.
Further, the formaldehyde recovery unit comprises a stripping tower and a formaldehyde tower, wherein the heavy phase of the extraction tower enters the stripping tower, the tower top extract of the stripping tower returns to the methanol recovery tower, the tower bottom extract of the stripping tower enters the formaldehyde tower for dehydration and concentration, the tower top of the formaldehyde tower extracts formaldehyde concentrated solution, and the wastewater of the tower bottom is sent to the extraction tower.
Further, the esterification reaction unit comprises a propionic acid recovery tower and an esterification reactor, wherein the tower bottom extract of the MMA crude tower is sent to the propionic acid recovery tower, the tower top of the propionic acid recovery tower is used for extracting a propionic acid and methacrylic acid mixture, and the propionic acid and methacrylic acid mixture is subjected to esterification reaction with high-concentration methanol from the tower bottom of the normal pressure tower; in the esterification reaction, the propionic acid and methacrylic acid mixture and the high-purity methanol react according to the acid-alcohol molar ratio of 0.5-5:1.
Further, the methanol recovery tower is operated under normal pressure, a preheater is arranged at the upstream of the methanol recovery tower, and the initial aldol condensation product feed and heavy components containing MMA and formaldehyde extracted from the tower kettle of the methanol recovery tower exchange heat through the preheater, and the initial aldol condensation product feed is heated to 50-70 ℃ and then enters the methanol recovery tower.
The methanol recovery tower separates most of methanol in the condensation product to reduce the consumption of the downstream extractant, the content of the methanol extracted from the tower bottom of the methanol recovery tower is reduced to below 1.5 percent, and the methanol is firstly subjected to heat recovery, cooled by a water cooler and then sent to the extraction tower.
Further, the extraction tower adopts a turntable tower, and the extractant of the extraction tower is water, including the decantation water from the top of the dehydration tower, the reuse water from the tower kettle of the formaldehyde tower and the water supplementing outside the boundary, so that the formaldehyde content is reduced to below 0.3%.
Further, the dehydration tower is operated under negative pressure, the steam at the top of the dehydration tower is condensed to 35-45 ℃ by a condenser and then is sent to a reflux tank to realize liquid-liquid phase separation, wherein the organic phase is refluxed to the dehydration tower, the decanted water extracted by the reflux tank returns to the top of the extraction tower to be used as an extractant, and the water content of the tower kettle of the dehydration tower is controlled to be below 0.1-1%, so as to avoid the aggravation of hydrolysis side reaction brought into an aldol condensation section.
Further, the methyl propionate recovery tower is operated by negative pressure, and the methyl propionate content of the discharged material of the tower kettle is reduced to below 0.1 percent.
Further, the system is also provided with an esterification reaction unit which comprises a propionic acid recovery tower and an esterification reactor, wherein the effluent from the kettle of the MMA crude tower is sent to the propionic acid recovery tower, and the top of the propionic acid recovery tower is used for extracting a propionic acid/methacrylic acid mixture and methanol according to the mole ratio of 0.8-1.2: 1, and then sending the mixture into the esterification reactor for esterification reaction, and returning the reaction product to the methanol recovery tower.
The esterification reactor can be of isothermal or adiabatic design, and resin catalyst is arranged in the esterification reactor to accelerate the reaction of propionic acid/methyl acrylic ester, and the conversion rate of methanol is about 85-95%.
Further, the MMA crude tower is operated by negative pressure, the propionic acid content is lower than 0.01%, and the MMA refining tower is operated by negative pressure, and the MMA concentration reaches 99.9%.
Further, the pressure of the high-pressure tower is 1-6 barg, the high-pressure tower and the normal pressure tower adopt a heat integration design, and the steam at the top of the high-pressure tower is condensed and released in a condensation reboiler of the normal pressure tower to provide heat required by rectification for the normal pressure tower.
Further, the formaldehyde tower has a pressure of 2-5 barg to destroy the association and state of formaldehyde/water, the formaldehyde tower adopts a heat integration design, the tower top steam is divided into two parts, one part is condensed by a stripping tower condensation reboiler to provide heat for the stripping tower, and the other part is condensed in a low-pressure waste boiler to generate low-pressure steam of 1-4 barg for heating other equipment in the device.
Further, the tops of the methanol recovery tower, the dehydration tower, the methyl propionate recovery tower, the MMA crude tower and the MMA refining tower are respectively provided with an aftercooler before the noncondensable gas is sent out of the boundary region.
Compared with the prior art, the invention has the following beneficial effects:
1. The methanol recovery unit comprises a pressure swing rectifying device (a high-pressure tower and an atmospheric tower), can separate and obtain high-concentration methanol from condensation products, and solves the recycling problem of the methanol.
2. According to the invention, the purpose of extracting formaldehyde from the extracted wastewater is realized by arranging the formaldehyde tower operated under pressure, 37% -50% formaldehyde solution can be prepared, and wastewater discharged after rectification of the formaldehyde tower is returned to the extraction tower to be reused as an extractant, so that the economic benefit is improved, and the problem of environmental protection treatment of formaldehyde-containing wastewater is solved.
3. The invention sets up esterification reactor, has solved the problem of the hydrolysis by-product propionic acid and methacrylic acid recycling, can raise the MMA yield of the product.
4. The tail gas aftercooler is arranged behind the condenser at the top of the methanol recovery tower, so that the loss of methanol and methyl propionate is reduced.
5. The invention can obviously reduce the consumption of heating steam by carrying out thermal coupling design on the high-pressure tower and the normal-pressure tower.
6. The formaldehyde tower adopts a heat integration design, part of the steam at the top of the tower supplies heat for a reboiler of the stripping tower, and part of byproduct low-pressure steam is recycled, so that the steam consumption can be reduced in total.
Drawings
FIG. 1 is a process flow diagram of a system for separating MMA product from aldol condensation products according to the invention;
FIG. 2 is a process flow diagram of the system of comparative example 1;
In the figure: a methanol recovery column 1, an extraction column 2, a dehydration column 3, a methyl propionate recovery column 4, an MMA crude column 5, an MMA refining column 6, an atmospheric column 7, a higher pressure column 8, a stripping column 9, a formaldehyde column 10, a propionic acid recovery column 11, an esterification reactor 12, a preheater 13, a condenser 14, a aftercooler 15, a water cooler 16, an atmospheric column condensation reboiler 17, a stripping column condensation reboiler 19, a low pressure waste pan 20, a condenser 22, an aftercooler 23, an aftercooler 24, an aftercooler 25, an aftercooler 26, an aftercooler 27, and a water cooler 29.
Detailed Description
The invention will now be described in detail with reference to the drawings and specific examples.
As shown in figure 1, the invention provides a system for separating MMA from aldol condensation products, the condensation products firstly enter a preheater 13 to exchange heat with the discharged material of the tower bottom of a methanol recovery tower 1 to recover heat, then rise the temperature to 50-70 ℃, and enter the methanol recovery tower 1 to separate most of methanol in the condensation products so as to reduce the consumption of a downstream extractant. The methanol recovery tower 1 is operated at normal pressure, the noncondensable gas at the top of the tower is sent to an external torch or used as fuel gas, and an aftercooler 15 is arranged to reduce the loss of methanol and methyl propionate. Most of the methanol in the feed is withdrawn overhead in the form of an azeotrope and sent to higher pressure column 8 for further separation. The condensation product after removing most of the methanol is extracted from the tower kettle of the methanol recovery tower 1, the methanol content is reduced to below 1.5 percent, and the condensation product is sent to the extraction tower 2 to remove unreacted formaldehyde and residual small amount of methanol after heat recovery and cooling by the water cooler 16.
The extraction tower 2 adopts a turntable tower to improve the separation efficiency, and water is selected as an extractant to reduce the formaldehyde content to below 0.3 percent. The extractant consists of three parts: decanted water from the top of the dehydration column 3; reuse water from the bottom of the formaldehyde tower 10; the water is supplemented by extraction input outside the boundary. The extraction water supplementing adopts boiler water without oxygen. The light phase after formaldehyde removal is extracted from the top of the extraction tower 2 and sent to a dehydration tower 3 for further drying; the heavy phase containing formaldehyde is extracted from the bottom of the extraction 2 tower and then sent to a stripping tower 9 for further treatment, and the heavy phase contains formaldehyde, a small amount of propionic acid and a large amount of water.
The dehydration column 3 mainly has the function of removing the dissolved water in the light phase of the extraction column 2. The dehydration column 3 is operated with a negative pressure to lower the column temperature and reduce the polymerization of MMA. Condensing the steam at the top of the dehydration tower 3 to 35-45 ℃ through a condenser 22, then sending the condensed steam to a reflux tank to realize liquid-liquid phase separation, and obtaining an organic phase and decanted water after the liquid-liquid phase separation, wherein the organic phase returns to the top of the dehydration tower 3 for reflux; decanted water is returned to the top of extraction column 2 as extractant to reduce the amount of extraction make-up water. The aftercooler 23 is arranged before the noncondensable gas at the top of the dehydration tower 3 is sent out of the boundary region so as to reduce the loss of effective components. The discharged material of the dehydration tower 3 is pumped to a methyl propionate recovery tower 4 for further treatment, and the water content in the discharged material of the tower is required to be controlled below 0.1-1 percent (mass percent) so as to avoid that water is brought into a subsequent working section to exacerbate hydrolysis side reaction.
The methyl propionate recovery column 4 mainly has the function of recovering methyl propionate and returning it to the upstream aldol condensation section for further reaction to improve the yield. The methyl propionate recovery tower 4 adopts negative pressure operation, and methyl propionate is extracted from the top of the methyl propionate recovery tower 4. An aftercooler 24 is arranged before the noncondensable gas at the top of the methyl propionate recovery tower 4 is sent out of the boundary region so as to reduce the loss of methyl propionate. And the discharged material of the tower bottom of the methyl propionate recovery tower 4 is sent to an MMA crude tower 5 for further refining, and the discharged material of the tower bottom is required to reduce the content of methyl propionate to below 0.1 percent.
The MMA crude column 5 mainly has a function of removing heavy components including propionic acid, methacrylic acid and high boiling substances. The MMA-crude column 5 is operated under negative pressure, and a light component containing MMA is withdrawn from the top of the MMA-crude column 5 and then fed into the MMA-refining column 6, the light component containing MMA requiring a propionic acid content of less than 0.01%. An after cooler 25 is provided before the overhead noncondensable gas of MMA crude column 5 is sent out of the boundary region to reduce loss of MMA. Polymerization inhibitor was added to reduce polymerization before entering MMA refining column 6. The heavy fraction recovered from the bottom of MMA crude column 5 contains a large amount of propionic acid and acrylic acid, and is further processed in propionic acid recovery column 11.
MMA-refining column 6 is mainly used for removing methyl isobutyrate close to the boiling point of MMA product. The MMA-refining column 6 is operated under negative pressure, and methyl isobutyrate as an impurity is taken out from the top of the column and then sent to an impurity buffer tank. An after cooler 26 is provided before the noncondensable gas at the top of the MMA refining tower 6 is sent out of the boundary region to reduce loss of MMA. MMA product is extracted from the tower kettle of the MMA refining tower 6, is cooled by a water cooler 28 and is sent to an intermediate tank area, and the concentration of the extracted MMA product is up to 99.9%.
The azeotrope extracted from the top of the methanol recovery tower 1 enters the middle part of the high-pressure tower 8 after being preheated, and the high-pressure tower 8 mainly has the function of removing methyl propionate from the azeotrope. The higher pressure column 8 is operated at 1 to 6barg, and the top of the higher pressure column 8 is taken to contain an azeotrope with a methanol concentration of 50 to 70% and then sent to the atmospheric column 7 for further treatment. Methyl propionate extracted from the tower kettle of the high-pressure tower 8 is returned to the aldol condensation section, and the concentration of methyl propionate is up to 98%.
The normal pressure tower 7 mainly has the function of separating high-concentration methanol from an azeotrope with 50-70% concentration of methanol extracted from the top of the high pressure tower 8. The normal pressure azeotrope extracted from the top of the normal pressure tower 7 is mixed with the azeotrope extracted from the top of the methanol recovery tower 1 and then returned to the middle part of the high pressure tower 8 to be used as feed. The methanol with the concentration of more than 95% is extracted from the tower kettle of the atmospheric tower 7 and is divided into two parts: a part of the liquid is sent to a methanol buffer tank; another portion is fed as feed to the inlet of esterification reactor 12.
The high-pressure tower 8 and the normal-pressure tower 7 adopt a heat integration design, the steam at the top of the high-pressure tower 8 condenses in the condensation reboiler 17 of the normal-pressure tower to release heat, and the released heat provides the heat required by rectification for the normal-pressure tower 7, so that the consumption of device steam and cooling water is reduced.
The dilute formaldehyde solution with the mass concentration of 2-3% extracted from the tower bottom of the extraction tower 2 is sent to a stripping tower 9 for removing light components. The stripping tower 9 is operated under normal pressure, and light components including methyl propionate and methanol are extracted from the top of the stripping tower and returned to the methanol recovery tower 1. The aqueous solution containing dilute formaldehyde is extracted from the bottom of the stripping tower 9 and sent to a formaldehyde tower 10 for dehydration and concentration.
The formaldehyde column 10 is operated at a pressure of 2 to 5barg to disrupt the formaldehyde/water association. The 37% -50% formaldehyde concentrated solution extracted from the top of the formaldehyde tower 10 is cooled and then is sold as a byproduct, the tower kettle wastewater is cooled and then sent to the top of the extraction tower 2 to be reused as an extractant, so that the water consumption of extraction and water supplement is reduced, and the device has no wastewater discharge during normal operation.
The formaldehyde tower 10 adopts a heat integration design, and overhead steam is divided into two parts: a portion is condensed by stripper condenser reboiler 19 to provide heat to stripper 9; another portion is condensed in the low pressure reject boiler 20 to produce low pressure steam of 1 to 4barg for heating by other equipment in the plant, such as a reboiler.
The reformed fraction from the bottom of MMA crude column 5 is fed to propionic acid recovery column 11, and propionic acid recovery column 11 functions mainly to remove high boiling impurities and recover propionic acid and methacrylic acid. The propionic acid recovery tower 11 is operated under negative pressure, the mixture of propionic acid and methacrylic acid is taken out from the tower top and sent to the esterification reactor 12, and an aftercooler 27 is arranged before the noncondensable gas at the tower top is sent out of the boundary zone so as to reduce propionic acid loss. The high-boiling-point substances in the tower bottom of the propionic acid recovery tower 11 are cooled by a water cooler 29 and then sent out of the boundary region.
The propionic acid/methacrylic acid mixture from the top of the propionic acid recovery column 11 is mixed with methanol in an acid-alcohol molar ratio (molar ratio of H + to OH -) of 0.8 to 1.2:1 and then fed into the esterification reactor 12. Esterification reactor 12 may be of isothermal or adiabatic design with a resin catalyst incorporated to accelerate the propionic acid/methylacrylate reaction, with methanol conversion of about 85-95%. The esterification reaction product is extracted from the tower bottom of the propionic acid recovery tower 11, and then returned to the inlet of the methanol recovery tower 1 for separation.
Considering that most of the equipment of the system operates under negative pressure, the tower internals all adopt structured packing to reduce the pressure difference and reduce the occurrence of polymerization side reaction. And aftercoolers are arranged before the tower top gas phase enters the vacuum pump so as to reduce loss of effective components and reduce power consumption of the vacuum pump.
The invention separates and obtains the methanol with the concentration of more than 95% from the condensation product, thereby solving the recycling problem of the methanol; the formaldehyde solution with the concentration of more than 37 percent can be sold as a byproduct, and the rectified wastewater is returned to the extraction tower to be reused as an extractant, so that the economic benefit is improved, and the problem of environmental protection treatment of formaldehyde-containing wastewater is solved.
The esterification reactor is arranged, so that the recycling problem of hydrolysis byproducts of propionic acid and methacrylic acid is solved, the product MMA with the purity of 99.9% is obtained, and the yield of the product MMA is improved by about 2%; by thermally coupling the higher pressure column and the atmospheric column, the consumption of heating steam is significantly reduced by at least 14%. In addition, the formaldehyde tower adopts a heat integration design, part of the steam at the top of the tower supplies heat for a reboiler of the stripping tower, and part of byproduct low-pressure steam is recycled, so that the steam consumption is reduced by at least 33% in total, and the formaldehyde tower has remarkable economic advantages. The system adjusts the process conditions of each column, including temperature, pressure, reflux ratio, etc., as appropriate according to the content of each component of the aldol condensation product specifically treated, see specifically table 1.
Table 1 process conditions for the column in the system
Example 1
The system is specifically applied to an MMA production device for producing 10 ten thousand tons of MMA in a certain year, a condensation product with 5-10% of MMA concentration of 160ton/h enters the system, and after the condensation product is processed by the system, 12.5ton/h of MMA is obtained from the tower bottom of the MMA refining tower 6. A formaldehyde solution of 14.7ton/h was obtained from the top of the formaldehyde column 10, methyl propionate of 125ton/h was obtained from the bottom of the high-pressure column 8 and the top of the methyl propionate recovery column 4, methanol of 12.7ton/h was obtained from the bottom of the atmospheric column 7, a light fraction of 0.23ton/h was obtained from the top of the MMA refining column 6, a high-boiling substance of 1.7ton/h was obtained from the bottom of the propionic acid recovery column 11, and the extraction water was consumed by 6ton/h. The steam consumption of the device is 223ton/h, the circulating cooling water is 16268ton/h, and the normal operation device has no waste water discharge.
Wherein, the MMA concentration of the product obtained above is 99.99%, the methanol concentration is 96.98%, the formaldehyde solution concentration is 37%, and the methyl propionate concentration is 99.50%.
The process conditions for each column in the system are shown in Table 2.
TABLE 2 Process conditions for each column
Example 2
The process conditions for each column in the system differ from example 1, see in particular table 3.
TABLE 3 Process conditions for each column
| Tower device | Temperature (DEG C) | Pressure barg | Reflux ratio |
| Methanol recovery tower 1 | 90 | 0.6 | 4 |
| Extraction column 2 | 40 | 6 | 1.5 |
| Dehydration tower 3 | 72 | -0.8 | 4 |
| Methyl propionate recovery column 4 | 100 | -0.6 | 3 |
| MMA crude column 5 | 120 | -0.9 | 3 |
| MMA refining tower 6 | 75 | -0.8 | 150 |
| Atmospheric tower 7 | 130 | 0.6 | 2.5 |
| High-pressure tower 8 | 71 | 6 | 3 |
| Stripping column 9 | 115 | 0.5 | 8 |
| Formaldehyde column 10 | 150 | 5 | 20 |
| Propionic acid recovery tower 11 | 140 | -0.9 | 2 |
| Esterification reactor 12 | 100 | 6 | -- |
The obtained product had an MMA concentration of 99.90%, a methanol concentration of 97.85%, a formaldehyde solution concentration of 40% and a methyl propionate concentration of 98.05%.
Example 3
The process conditions for each column in the system differ from example 1, see in particular table 4.
TABLE 4 Process conditions for each column
| Tower device | Temperature (DEG C) | Pressure barg | Reflux ratio |
| Methanol recovery tower 1 | 40 | 0.1 | 2 |
| Extraction column 2 | 38 | 3 | 0.5 |
| Dehydration tower 3 | 48 | -0.5 | 3 |
| Methyl propionate recovery column 4 | 55 | -0.4 | 2 |
| MMA crude column 5 | 38 | -0.7 | 0.5 |
| MMA refining tower 6 | 55 | -0.6 | 50 |
| Atmospheric tower 7 | 95 | 0.3 | 1 |
| High-pressure tower 8 | 42 | 1 | 1.8 |
| Stripping column 9 | 75 | 0.1 | 3 |
| Formaldehyde column 10 | 135 | 3 | 13 |
| Propionic acid recovery tower 11 | 80 | -0.6 | 0.5 |
| Esterification reactor 12 | 75 | 3 | -- |
The obtained product had an MMA concentration of 99.95%, a methanol concentration of 95.00%, a formaldehyde solution concentration of 55% and a methyl propionate concentration of 99.00%.
Example 4
The process conditions for each column in the system differ from example 1, see in particular table 5.
TABLE 5 Process conditions for each column
The obtained product had an MMA concentration of 99.96%, a methanol concentration of 97.89%, a formaldehyde solution concentration of 37% and a methyl propionate concentration of 99.55%.
Comparative example 1
Comparative example 1 compared to example 1, there was no aftercooler; there are no propionic acid recovery column 11 and no esterification reactor 12; the formaldehyde recovery system is simplified (the pipeline for removing the reuse of the overhead steam of the formaldehyde column 10 and the low-pressure waste boiler 20), and the process flow chart of the system is shown in fig. 2.
The system is specifically applied to an MMA production device for producing 10 ten thousand tons of MMA in a certain year, a condensation product with 5-10% of MMA concentration of 160ton/h enters the system, and after the condensation product is processed by the system, 12.2ton/h of MMA is obtained from the tower bottom of the MMA refining tower 6. A formaldehyde solution of 14.0ton/h was obtained from the top of the formaldehyde column 10, methyl propionate of 124ton/h was obtained from the bottom of the high-pressure column 8 and the top of the methyl propionate-recovering column 4, methanol of 12.1ton/h was obtained from the bottom of the atmospheric column 7, a light fraction of 0.26ton/h was obtained from the top of the MMA-refining column 6, a heavy fraction of 17.4ton/h was obtained from the crude MMA column, and the extraction water charge was consumed by 20ton/h. The steam consumption of the device is 296.6ton/h, and the cooling water is 16268ton/h.
Wherein, the MMA concentration of the product obtained above is 99.50%, the methanol concentration is 92.12%, the formaldehyde solution concentration is 32%, and the methyl propionate concentration is 90.85%.
The previous description of the embodiments is provided to facilitate a person of ordinary skill in the art in order to make and use the present invention. It will be apparent to those skilled in the art that various modifications can be readily made to these embodiments and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above-described embodiments, and those skilled in the art, based on the present disclosure, should make improvements and modifications without departing from the scope of the present invention.
Claims (8)
1. A system for separating MMA from an aldol condensation product, the system being arranged downstream of an aldol condensation reactor for producing MMA, separating an initial aldol condensation product discharged from the aldol condensation reactor, characterized in that the system comprises a methanol recovery unit for separating a light fraction containing methanol from the initial aldol condensation product and purifying and recovering methanol in the light fraction, an MMA recovery unit coupled to the methanol recovery unit, an esterification reaction unit, and a formaldehyde recovery unit coupled to the methanol recovery unit;
Introducing a high-purity methanol part obtained by the methanol recovery unit into the esterification reaction unit, carrying out esterification reaction with propionic acid and methacrylic acid from the MMA recovery unit, returning the obtained product to a feed inlet of the methanol recovery unit, mixing with the initial aldol condensation product, and then carrying out separation and purification again;
Separating the heavy component containing MMA and formaldehyde, which is separated by the methanol recovery unit, and then separating and purifying the obtained light phase containing MMA in the MMA recovery unit to obtain high-purity MMA, and separating and purifying the obtained heavy phase containing formaldehyde in the formaldehyde recovery unit to obtain formaldehyde;
The methanol recovery unit comprises a methanol recovery tower (1), a high-pressure tower (8) and an atmospheric tower (7), wherein the methanol recovery tower (1) is used for separating light components containing methanol in condensation product feed, the light components containing the methanol are extracted from the tower top of the methanol recovery tower (1) and enter the high-pressure tower (8), high-purity methyl propionate is extracted from the tower bottom of the high-pressure tower (8), the light components extracted from the tower top of the high-pressure tower (8) enter the atmospheric tower (7), the tower top extract of the atmospheric tower (7) returns to the high-pressure tower (8), and high-concentration methanol is extracted from the tower bottom of the atmospheric tower (7);
The formaldehyde recovery unit comprises a stripping tower (9) and a formaldehyde tower (10), wherein the heavy phase of the extraction tower (2) enters the stripping tower (9), the tower top extract of the stripping tower (9) returns to the methanol recovery tower (1), the tower bottom extract of the stripping tower (9) enters the formaldehyde tower (10) for dehydration concentration, the tower top of the formaldehyde tower (10) is used for extracting formaldehyde concentration solution, and the wastewater at the tower bottom is sent to the extraction tower (2);
the pressure of the high-pressure tower (8) is 1-6 barg, the high-pressure tower (8) and the normal-pressure tower (7) are in heat integration design, and the heat generated by condensation of the steam at the top of the high-pressure tower (8) through a condensation reboiler (17) of the normal-pressure tower provides heat required by rectification for the normal-pressure tower (7);
The pressure of the formaldehyde tower (10) is 2-5 barg, the formaldehyde tower (10) adopts a heat integration design, the top steam is divided into two parts, one part is condensed by a stripping tower condensation reboiler (19) to provide heat for the stripping tower (9), and the other part is condensed in a low-pressure waste boiler (20).
2. The system for separating MMA from aldol condensation product according to claim 1, wherein the MMA recovery unit comprises an extraction tower (2), a dehydration tower (3), a methyl propionate recovery tower (4), an MMA crude tower (5) and an MMA refining tower (6), wherein heavy components containing MMA and formaldehyde, which are extracted from the tower bottom of the methanol recovery tower (1), enter the extraction tower (2), the light phase of the extraction tower (2) enter the dehydration tower (3) for dehydration, the materials with water removed are extracted from the tower bottom of the dehydration tower (3) and enter the methyl propionate recovery tower (4) for separating methyl propionate, methyl propionate is extracted from the tower top of the methyl propionate recovery tower (4), and the tower bottom extract of the methyl propionate recovery tower (4) is sequentially separated by the MMA crude tower (5) and the MMA refining tower (6) for obtaining high-purity MMA.
3. A system for separating MMA from aldol condensation product according to claim 2, wherein the esterification reaction unit comprises a propionic acid recovery column (11) and an esterification reactor (12), the MMA crude column (5) bottom effluent being sent to the propionic acid recovery column (11), the propionic acid recovery column (11) top being provided with a propionic acid and methacrylic acid mixture, the propionic acid and methacrylic acid mixture being subjected to esterification reaction with high concentration methanol from the atmospheric column (7) bottom;
In the esterification reaction, the propionic acid and methacrylic acid mixture and the high-purity methanol react according to the acid-alcohol molar ratio of 0.5-5:1.
4. The system for separating MMA from aldol condensation product according to claim 1, wherein the methanol recovery tower (1) is operated at normal pressure, a preheater (13) is arranged at the upstream of the methanol recovery tower (1), and the initial aldol condensation product feed and heavy components containing MMA and formaldehyde extracted from the tower bottom of the methanol recovery tower (1) exchange heat through the preheater (13), and after the initial aldol condensation product feed is heated to 50-70 ℃, the heavy components enter the methanol recovery tower (1).
5. A system for separating MMA from aldol condensation product according to claim 1 or 2, wherein the extraction column (2) is a rotating disc column, and the extractant of the extraction column (2) is water, including decanted water from the top of the dehydration column (3), recycled water from the bottom of the formaldehyde column (10) and make-up water for external input.
6. The system for separating MMA from aldol condensation product according to claim 1, wherein the dehydration column (3) is operated under negative pressure, the vapor at the top of the dehydration column (3) is condensed to 35-45 ℃ by a condenser (22) and then sent to a reflux tank to realize liquid-liquid phase separation, wherein the organic phase is refluxed to the dehydration column (3), and the decanted water extracted from the reflux tank is returned to the top of the extraction column (2) as an extractant.
7. A system for separating MMA from aldol condensation product according to claim 1, wherein the methyl propionate recovery column (4) is operated with negative pressure;
the MMA crude tower (5) is operated by negative pressure, and the MMA refining tower (6) is operated by negative pressure.
8. A system for separating MMA from aldol condensation product according to claim 1, wherein the tops of the methanol recovery column (1), the dehydration column (3), the methyl propionate recovery column (4), the MMA crude column (5) and the MMA purification column (6) are each provided with an aftercooler before noncondensable gas is sent out of the boundary zone.
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| CN111574371A (en) * | 2020-06-22 | 2020-08-25 | 北京旭阳科技有限公司 | Method and device for joint production of anhydrous gas-phase formaldehyde and methyl methacrylate |
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| WO2021037660A1 (en) * | 2019-08-28 | 2021-03-04 | Röhm Gmbh | Simplified workup of the reactor discharge of an oxidative esterification |
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| CN106699560A (en) * | 2015-11-18 | 2017-05-24 | 上海浦景化工技术股份有限公司 | Separation device and separation method of material flow containing methyl methacrylate |
| WO2021037660A1 (en) * | 2019-08-28 | 2021-03-04 | Röhm Gmbh | Simplified workup of the reactor discharge of an oxidative esterification |
| CN111574371A (en) * | 2020-06-22 | 2020-08-25 | 北京旭阳科技有限公司 | Method and device for joint production of anhydrous gas-phase formaldehyde and methyl methacrylate |
| CN111574374A (en) * | 2020-06-22 | 2020-08-25 | 北京旭阳科技有限公司 | Separation method and separation equipment for methyl methacrylate crude product |
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