CN101348252A - Phosgene recovery method for toluene diisocyanate production process - Google Patents
Phosgene recovery method for toluene diisocyanate production process Download PDFInfo
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- CN101348252A CN101348252A CNA2008100181213A CN200810018121A CN101348252A CN 101348252 A CN101348252 A CN 101348252A CN A2008100181213 A CNA2008100181213 A CN A2008100181213A CN 200810018121 A CN200810018121 A CN 200810018121A CN 101348252 A CN101348252 A CN 101348252A
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- phosgene
- monochloroethane
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Abstract
The invention provides a method for recovering phosgene in toluene diisocynate preparation process. In the method, materials containing HCl, ethyl chloride and phosgene are firstly absorbed by solvents containing benzene, cooled by toluene absorption system and has HCl fixed gases absorbed by alkaline liquors, toluene absorption liquids absorbing ethyl chloride and phosgene are subjected to separation, and the toluene obtained after separation is recovered; the phosgene materials containing ethyl chloride obtained after separation are subjected to phosgene destruction, ethyl chloride separated is neutralized by alkaline liquors, and the phosgene separated is recovered and returned back to a phosgene room.
Description
Technical field
The invention relates to the recovery method of phosgene in tolylene diisocyanate (TDI) production technique.
Background technology
TDI (tolylene diisocyanate) product is one of isocyanic ester series products of consumption maximum in the world, is one of main raw material of urethane.The TDI production technique mainly is that the chlorine reaction that the carbon monoxide that provided by gas sweetening and electrolysis of hydrochloric acid provide generates phosgene (COCl
2), again by TDA and COCl
2The anti-TDI (tolylene diisocyanate) that generates, master operation has unit such as phosgene is synthetic, phosgenation, TDI rectifying, phosgene recovery, solvent recuperation, waste gas destruction.
The major company of a few family that at present produces TDI in the world all uses the proprietary technology of oneself, and all uses traditional phosgenation without exception.These companies are Bayer (BAYER), BASF (BASF), Dow Chemical (DOWSCHEM), rhone-poulenc (RHONE POULENE), ENI chemistry (ENI CHEM), Olympic (OLIN) and Mitsui East Asia.Traditional phosgenation is even with phosgene and toluene two ammonia reacts in inert solvent, generate TDI and also emit HCl gas.Phosgenation reaction carries out in tower or in the reactor mostly.
In traditional phosgene recovery system, material enters the toluene absorption tower, and phosgene is absorbed by toluene, and non-condensable gases such as HCl are discharged from cat head.The toluene desorption tower desorbs phosgene from absorb toluene, and delivers to other unit, and the gas that cat head contains HCl is got back to the toluene absorption tower.Part discharging was made with extra care at the bottom of the toluene treating tower absorbed Tata with toluene, and the toluene after making with extra care is from tower middle part extraction, and the difference extraction absorbs the weight component in the toluene at the bottom of cat head, the tower.Toluene absorption tower cat head comes out contains HCl gas, one phosgene that contains monochloroethane of toluene desorption tower extraction enters phosgene and destroys tower, with in the alkali lye and destroy.The problem that this system exists in producing at present has:
(1) toluene absorption tower fluctuation of service, because the vacuum system that the charging major part is produced from TDI, its phosgene content fluctuation is bigger, causes cat head phosgene content excessive easily, the amount fluctuation that therefore absorbs toluene is very big, brings difficulty to control.Absorb the factor of assurance that the toluene amount increases the phosgene absorption if only strengthen, HCl content also increases greatly in the absorption toluene of discharging at the bottom of the tower, can cause the instability of tower toluene desorption tower and toluene treating tower operation.
(2) byproduct of reaction monochloroethane in the how discharge system is avoided the monochloroethane enrichment.Chloroethane concentration is crossed conference and is caused phosgene concentration to reduce, and monochloroethane itself has explosivity.
(3) owing to there is minor amount of water to exist in the system, HCl and water generate hydrochloric acid in the material, and equipment corrosion is serious, and is bigger to toluene desorption tower and the harm of toluene treating tower especially.Toluene desorption tower and toluene treating tower upper part, overhead condenser all adopt expensive Hastelloy manufacturing in the actual production, will find out the higher place of quality mark in system, and hydromining is gone out, and reduce the corrosion to device.
(4) the cat head gas HCl flow that comes out in toluene absorption tower is very high, directly enters phosgene and destroys the consumption that tower has increased alkali lye.
Summary of the invention
The purpose of this invention is to provide the phosgene recovery method in a kind of toluene diisocyanate production process.The recovery method of phosgene in the toluene diisocyanate production process, it is characterized in that, the material that contains HCl, monochloroethane photoreactive gas adopts toluene to absorb earlier, then the toluene absorption system is cooled off, absorb the HCl non-condensable gas with alkali lye again, to absorb the toluene absorption liquid of monochloroethane photoreactive gas again, separate, toluene after the separation is recycled, the phosgene material that contains monochloroethane after separating is carried out the phosgene destructive process, monochloroethane and alkali lye neutralization with removing out are recovered to the phosgene chamber with the phosgene of separating.
Adopt method of the present invention, can stablize the toluene absorption tower operation, improved the salt acid recovering rate, reduce monochloroethane massfraction in the TDI device, reduce the corrosion of tower, and reduce the discharging of alkali lye to the corrosion failure and the waste lye of tower, help the recovery of carrying out phosgene of safety and environmental protection.
Description of drawings
Fig. 1 is the phosgene of the present invention process flow sheet of waving.V1 is an alkali liquid tank among the figure, and S1 contains the HCl logistics for what other unit came; S2 is a toluene desorption tower cat head non-condensable gas; S3-S7 does not contain the HCl logistics for what other unit came.
Embodiment
The present invention is the recovery method of phosgene in a kind of toluene diisocyanate production process, the material that contains HCl, monochloroethane photoreactive gas adopts toluene to absorb earlier, then the toluene absorption system is cooled off, absorb the HCl non-condensable gas with alkali lye again, to absorb the toluene absorption liquid of monochloroethane photoreactive gas again, separate, toluene after the separation is recycled, the phosgene material that contains monochloroethane after separating is carried out the phosgene destructive process, monochloroethane and alkali lye neutralization with removing out are recovered to the phosgene chamber with the phosgene of separating.
As shown in Figure 1, the material that contains HCl, monochloroethane photoreactive gas enters toluene absorption tower T1, and phosgene is absorbed by toluene, and the T1 charging of toluene absorption tower divides two portions, and a part enters at the bottom of tower, and a part enters from the 12nd block of plate, and the non-condensable gas that contains HCl is discharged from cat head; A side cooler E1 is installed at place, mid-way at toluene absorption tower T1; Toluene desorption tower T2 desorbs phosgene from absorb toluene, and delivers to other unit, and the gas that cat head contains HCl is got back to toluene absorption tower T1; The 9th block of a certain amount of monochloroethane of plate side line extraction on toluene desorption tower T2 top; Toluene treating tower T3 with the tower of toluene absorption tower T1 at the bottom of part discharging make with extra care, the toluene after refining is from tower middle part extraction, extraction absorbs weight component the toluene respectively at the bottom of the cat head of toluene treating tower T3, the tower; The gas that contains HCl that the cat head of toluene absorption tower T1 comes out absorbs by salt acid tower T6, enters first phosgene again and destroys tower T4, and the phosgene that contains monochloroethane of toluene desorption tower T2 extraction enters first phosgene and destroys tower T4, with in the alkali lye and destroy; First phosgene destruction tower T4 cat head expellant gas enters second phosgene destruction tower T5 and handles.
As shown in Figure 1, a side cooler E1 is installed at the place in T1 mid-way, toluene absorption tower, and side cooler E1 extracts whole liquid out from toluene absorption tower T1 piece plate, is cooled to-10 ℃, returns next column plate.The installation site of side cooler E1 is at the 9th block of plate.
As shown in Figure 1, at the 8th or the 9th block of column plate side line extraction monochloroethane on toluene desorption tower T2 top.
As shown in Figure 1, destroy at toluene treating tower T3 and first phosgene salt acid tower T6 is installed between the tower T4, the overhead gas of salt acid tower T6 enters first phosgene and destroys tower T4 and remove wherein phosgene.Salt acid tower T6 is a packing tower, and wherein 30% hydrochloric acid extraction at the bottom of the tower is cooled to 40 ℃ through interchanger, takes away after HCl absorbs liberated heat in the tower, and a part is returned tower middle part, a part of extraction.
As shown in Figure 1, the column plate position of the charging S1 of toluene absorption tower T1 and charging S2 is located at the 12nd block of plate.The HCl flow reduces the consumption that cat head absorbs toluene well below 30kg/h at the bottom of can making tower like this.
As shown in Figure 1, toluene absorption tower T1 installs a side cooler E1, can produce a large amount of heats because the HCl photoreactive gas absorbs, and the tower upper temp is raise, and is unfavorable for that phosgene separates with HCl, and therefore, the side cooler E1 of installation can address this problem.Side cooler E1 extracts whole liquid out from toluene absorption tower T1 piece plate, is cooled to-10 ℃, returns next column plate.Best results when the position of middle water cooler E1 is the 9th block of plate, needed toluene flux also significantly reduces.Side cooler has not only improved the separating effect of HCl photoreactive gas, and has strengthened the anti-fluctuation ability of toluene absorption tower T1.
As shown in Figure 1, at a certain amount of monochloroethane of toluene desorption tower T2 top piece plate side line extraction, with monochloroethane accumulation in the elimination system with alleviate corrosion to toluene absorption tower T2 and toluene treating tower T3.Mainly in phosgenation side reaction generation during the stage, because the monochloroethane photoreactive gas is difficult to separate, if there is not the monochloroethane extraction in the system, the monochloroethane massfraction can be more and more higher in the phosgene, influences the effect of photochmeical reaction for monochloroethane.And monochloroethane itself has explosivity, and massfraction is too high unfavorable to keeping the safety in production.In addition, because toluene desorption tower T2 and toluene treating tower T3 service temperature are higher, the minor amount of water and the HCl that exist in the tower can produce more serious corrosion to toluene absorption tower T2 and toluene treating tower T3.Water than low 1 to the 2 block of column plate of monochloroethane enrichment column plate, therefore, reduces the extraction that 1 block of plate helps water in the system with toluene desorption tower T2 extraction position at toluene desorption tower T2 rectifying column Board position when from the 8th plate side line extraction of toluene desorption tower T2 80kg/h.Because the monochloroethane that advances the phosgene recovery system is about 7kg/h, thereby can meet the demands at the 8th plate extraction 80kg/h.
As shown in Figure 1, toluene treating tower T3 photoreactive gas destroys salt acid tower T6 of increase between the tower IT4 in technical process.This be since the gas that comes out of toluene absorption tower T1 cat head to contain HCl dense, directly absorb with alkali lye, can cause HCl waste and alkali lye to consume excessive.Therefore, increase a salt acid tower T6 in the flow process, this strand gas can absorb with process water makes hydrochloric acid.The hydrochloric acid tower adopts packing tower, and the extraction at the bottom of the tower of 30% hydrochloric acid is cooled to 40 ℃ through interchanger, takes away after HCl absorbs liberated heat in the tower, and a part is returned tower middle part, a part of extraction.Owing to contain a spot of toluene in the HCl gas that comes out of toluene absorption tower T1, this toluene in HCl absorbs with tower at the bottom of discharging enter in the hydrochloric acid, therefore can not make product hydrochloric acid, in TDI produces can in and salkali waste use and the boiler rinsing pipeline.
Claims (9)
1, the recovery method of phosgene in the toluene diisocyanate production process, it is characterized in that, the material that contains HCl, monochloroethane photoreactive gas adopts the solvent absorbing that contains benzene earlier, then the toluene absorption system is cooled off, absorb the HCl non-condensable gas with alkali lye again, to absorb the toluene absorption liquid of monochloroethane photoreactive gas again, separate, toluene after the separation is recycled, the phosgene material that contains monochloroethane after separating is carried out the phosgene destructive process, monochloroethane and alkali lye neutralization with removing out are recovered to the phosgene chamber with the phosgene of separating.
2, the recovery method of phosgene in the toluene diisocyanate production process according to claim 1, the solvent that it is characterized in that containing benzene is a toluene, perhaps chlorobenzene, perhaps dichlorobenzene.
3, the recovery method of phosgene in the production of toluene diisocyanate according to claim 1, it is characterized in that, the material that contains HCl, monochloroethane photoreactive gas enters toluene absorption tower (T1), phosgene is absorbed by toluene, toluene absorption tower (T1) charging divides two portions, a part enters at the bottom of tower, and a part enters from the 12nd block of plate, and the non-condensable gas that contains HCl is discharged from cat head; A side cooler (E1) is installed at place, mid-way at toluene absorption tower (T1); Toluene desorption tower (T2) desorbs phosgene from absorb toluene, and delivers to other unit, and the gas that cat head contains HCl is got back to toluene absorption tower (T1); The 9th block of a certain amount of monochloroethane of plate side line extraction on toluene desorption tower (T2) top; Toluene treating tower (T3) with the tower of toluene absorption tower (T1) at the bottom of part discharging make with extra care, the toluene after refining is from tower middle part extraction, extraction absorbs weight component the toluene respectively at the bottom of the cat head of toluene treating tower (T3), the tower; The gas that contains HCl that the cat head on toluene absorption tower (T1) comes out absorbs by salt acid tower (T6), enters first phosgene again and destroys tower (T4), and the phosgene that contains monochloroethane of toluene desorption tower (T2) extraction enters first phosgene and destroys tower (T4), with in the alkali lye and destroy; First phosgene destruction tower (T4) cat head expellant gas enters second phosgene destruction tower (T5) and handles.
4, according to claim 1, the recovery method of phosgene in the 2 described production of toluene diisocyanate is characterized in that toluene absorption tower (T1) charging divides two portions, and a part enters at the bottom of tower, and a part enters from the 12nd block of plate.
5, according to claim 1, the recovery method of phosgene in the 2 described production of toluene diisocyanate, it is characterized in that one side cooler (E1) being installed at place, mid-way, toluene absorption tower (T1), side cooler (E1) is extracted whole liquid out from toluene absorption tower (T1) certain piece plate, be cooled to-10 ℃, return next column plate.
6, according to claim 1, the recovery method of phosgene in 2, the 4 described production of toluene diisocyanate, the installation site that it is characterized in that side cooler (E1) is at the 9th block of plate.
7, according to claim 1, the recovery method of phosgene in the 2 described production of toluene diisocyanate is characterized in that the 8th or the 9th block of column plate side line extraction monochloroethane on toluene desorption tower (T2) top.
8, according to claim 1, the recovery method of phosgene in the 2 described production of toluene diisocyanate, it is characterized in that destroying at toluene treating tower (T3) and first phosgene salt acid tower (T6) is installed between the tower (T4), the overhead gas of salt acid tower (T6) enters first phosgene and destroys tower (T4) and remove wherein phosgene.
9, according to claim 1,2, the recovery method of phosgene in the 7 described production of toluene diisocyanate, it is characterized in that salt acid tower (T6) is a packing tower, wherein 30% hydrochloric acid extraction at the bottom of the tower is cooled to 40 ℃ through interchanger, takes away after HCl absorbs liberated heat in the tower, a part is returned tower middle part, a part of extraction.
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| Application Number | Priority Date | Filing Date | Title |
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| CNA2008100181213A CN101348252A (en) | 2008-04-25 | 2008-04-25 | Phosgene recovery method for toluene diisocyanate production process |
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| CNA2008100181213A CN101348252A (en) | 2008-04-25 | 2008-04-25 | Phosgene recovery method for toluene diisocyanate production process |
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Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102001658A (en) * | 2010-11-16 | 2011-04-06 | 湖南国发精细化工科技有限公司 | Novel method for purifying gaseous phosgene |
| CN101671274B (en) * | 2009-09-18 | 2011-10-26 | 天津大学 | Method for recycling phosgene in continuous production process of toluene di-isocyanate |
| CN101671276B (en) * | 2009-09-18 | 2011-10-26 | 赛鼎工程有限公司 | Method for recovering phosgene in continuous production process of toluene di-isocyanate |
| CN101671273B (en) * | 2009-09-18 | 2011-11-09 | 天津大学 | Method for recycling phosgene in continuous production process of toluene di-isocyanate |
| CN102258935A (en) * | 2011-04-22 | 2011-11-30 | 顾伟文 | Recovery and utilization method of phosgene in phosgenation reaction tail gas |
| CN102498093A (en) * | 2009-07-09 | 2012-06-13 | 拜尔材料科学股份公司 | Method for producing isocyanates |
| CN103638688A (en) * | 2013-12-24 | 2014-03-19 | 湖南国发精细化工科技有限公司 | Recycling method for phosgene in tail gas generated in calorescence reaction for synthesizing normal-butyl isocyanate |
| CN103787920A (en) * | 2014-02-18 | 2014-05-14 | 青岛科技大学 | Method for urgently decomposing phosgene in toluene diisocynate production |
| CN111359401A (en) * | 2020-03-18 | 2020-07-03 | 江西汇和化工有限公司 | Method for co-producing amine salt by utilizing prochloraz acylated acidic tail gas |
| WO2022047681A1 (en) * | 2020-09-03 | 2022-03-10 | 万华化学集团股份有限公司 | Method for preparing mdi and method for preparing phosgene |
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2008
- 2008-04-25 CN CNA2008100181213A patent/CN101348252A/en active Pending
Cited By (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102498093A (en) * | 2009-07-09 | 2012-06-13 | 拜尔材料科学股份公司 | Method for producing isocyanates |
| CN102498093B (en) * | 2009-07-09 | 2015-03-04 | 拜耳材料科技股份有限公司 | Method for producing isocyanates |
| CN101671273B (en) * | 2009-09-18 | 2011-11-09 | 天津大学 | Method for recycling phosgene in continuous production process of toluene di-isocyanate |
| CN101671276B (en) * | 2009-09-18 | 2011-10-26 | 赛鼎工程有限公司 | Method for recovering phosgene in continuous production process of toluene di-isocyanate |
| CN101671274B (en) * | 2009-09-18 | 2011-10-26 | 天津大学 | Method for recycling phosgene in continuous production process of toluene di-isocyanate |
| CN102001658A (en) * | 2010-11-16 | 2011-04-06 | 湖南国发精细化工科技有限公司 | Novel method for purifying gaseous phosgene |
| CN102001658B (en) * | 2010-11-16 | 2012-07-11 | 湖南国发精细化工科技有限公司 | Novel method for purifying gaseous phosgene |
| CN102258935A (en) * | 2011-04-22 | 2011-11-30 | 顾伟文 | Recovery and utilization method of phosgene in phosgenation reaction tail gas |
| CN103638688A (en) * | 2013-12-24 | 2014-03-19 | 湖南国发精细化工科技有限公司 | Recycling method for phosgene in tail gas generated in calorescence reaction for synthesizing normal-butyl isocyanate |
| CN103638688B (en) * | 2013-12-24 | 2015-09-02 | 湖南国发精细化工科技有限公司 | A kind of recoverying and utilizing method synthesizing phosgene in n-butyl isocyanate thermo-optical reaction end gas |
| CN103787920A (en) * | 2014-02-18 | 2014-05-14 | 青岛科技大学 | Method for urgently decomposing phosgene in toluene diisocynate production |
| CN103787920B (en) * | 2014-02-18 | 2016-05-11 | 青岛科技大学 | Urgent method of decomposing phosgene in production of toluene diisocyanate |
| CN111359401A (en) * | 2020-03-18 | 2020-07-03 | 江西汇和化工有限公司 | Method for co-producing amine salt by utilizing prochloraz acylated acidic tail gas |
| WO2022047681A1 (en) * | 2020-09-03 | 2022-03-10 | 万华化学集团股份有限公司 | Method for preparing mdi and method for preparing phosgene |
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Open date: 20090121 |