Unit and process for purification of crude methyl methacrylate

Patent metadata

Field	Value
Publication number	US-2016251297-A1
Application number	US-201415029300-A
Country	US
Kind code	A1
Filing date	Oct 17, 2014
Priority date	Oct 18, 2013
Publication date	Sep 1, 2016
Grant date	—

Abstract

The invention relates to a purification unit ( 200 ) which is able to separate crude MMA from light and heavy impurities in order to obtain high quality of MMA, suitable to produce optimal grade polymethylmethacrylate (PMMA). The unit ( 200 ) comprises two distillation columns ( 210, 250 ) in series, fed with mixture to be distilled in their median part, in order to separate each column in two upper ( 213, 253 ) and lower ( 212, 252 ) parts, the first distillation column ( 210 ) being fed with crude prewashed MMA, and the second distillation column ( 250 ) being fed with distilled liquid stream containing MMA, separated from light impurities, issued from bottom of first distillation column ( 210 ). The upper part ( 213 ) of first distillation column ( 210 ) is connected to a lateral extraction system ( 220 ), able to minimize MMA content in light impurities flowing upward said first column ( 210 ).

First claim

1 . A methyl methacrylate purification unit ( 200 ) able to separate methyl methacrylate (MMA) from light and heavy impurities, said unit being characterized in that it comprises two distillation columns ( 210 , 250 ) in series, fed with the mixture to be distilled in their median part, in order to separate each column in two upper ( 213 , 253 ) and lower ( 212 , 252 ) parts, the first distillation column ( 210 ) being fed with crude prewashed methyl methacrylate (MMA), and the second distillation column ( 250 ) being fed with distilled liquid stream containing methyl methacrylate (MMA), separated from light impurities, issued from the bottom of first distillation column ( 210 ), and the upper part ( 213 ) of the first distillation column ( 210 ) is connected to a lateral extraction system ( 220 ), able to minimize methyl methacrylate (MMA) content in a gas phase of light impurities flowing upward said first column ( 210 ).

2 . The unit according to claim 1 , wherein the lateral extraction system ( 220 ) comprises a feeding pipe ( 221 ) for adding water to the light impurities containing a MMA-water azeotropic mixture extracted from an extraction liquid outlet ( 216 ) located in the upper part ( 213 ) of first distillation column ( 210 ), a cooling device ( 222 ) for cooling the obtained mixture, at a temperature between 20° C. and 34° C., and a settler ( 223 ) for recovering the liquid phase and for obtaining a phase separation between an aqueous phase containing water and methanol, and an organic phase containing methyl methacrylate (MMA), said settler ( 223 ) being connected to an inlet ( 217 ) of the first distillation column ( 210 ) located below said extraction liquid outlet ( 216 ), in order to re-inject organic phase containing methyl methacrylate (MMA) inside upper part ( 213 ) of said first distillation column ( 210 ).

3 . A The unit according to claim 2 , wherein the settler ( 223 ) further comprises an outlet ( 224 ) at its bottom through which the aqueous phase flows to be recycled towards a washing unit of crude methyl methacrylate (MMA).

4 . A The unit according to claim 1 , wherein both columns ( 210 , 250 ) are respectively connected to a vacuum system ( 236 , 266 ) in order to have a pressure at the bottom of said columns being comprised between 66.66 mbar and 666.6 mbar.

5 . A The unit according to claim 4 , wherein said pressure inside second distillation column ( 250 ) is lower than pressure inside first distillation column ( 210 ).

6 . A The unit according to claim 1 , wherein the temperature inside each column is lower than 90° C.

7 . The unit according to claim 1 , wherein the bottom of each distillation column ( 210 , 250 ) is connected to a reboiler system ( 241 ; 271 ) able to re-inject a vaporized part of distilled liquid stream into the respective lower part ( 212 , 252 ) of each column, while the liquid part of said distilled liquid stream flows towards a pump ( 242 , 272 ).

8 . The unit according to claim 1 , wherein the top of each column ( 210 , 250 ) is respectively connected to a condenser system ( 230 , 260 ) for liquefying gas phase, a reflux drum ( 234 ; 264 ) which recovers the obtained liquid phase and a pump ( 239 , 269 ) which recycles part of said obtained liquid phase into the respective upper part ( 213 , 253 ) of said column.

9 . The unit according to claim 8 , wherein each condenser system ( 230 . 260 ) comprises at least one condenser ( 231 , 261 ).

10 . The unit according to claim 8 , wherein each condenser system ( 230 , 260 ) comprises a first condenser ( 231 ; 261 ) being fed with cooling water at a temperature between 20° C. and 34° C. and a second condenser placed downstream the first and fed with chilling water at a temperature between 4° C. and 15° C.

11 . The unit according to claim 8 , wherein each condenser system ( 230 , 260 ) further comprises another condenser ( 235 ; 265 ) fed with liquid brine or glycol water at a temperature comprised between −20° C. and −5° C. to trap vents.

12 . The unit according to claim 1 , wherein said upper part ( 213 , 253 ) of each column ( 210 , 250 ) comprises an inlet (I 1 , I 2 ) for feeding an inhibitor (INHIB) able to prevent polymerization of MMA.

13 . The unit according to claim 1 , wherein said settler ( 223 ) and a condenser ( 231 ) of first condenser system ( 230 ) comprise an inlet (I 3 , I 4 ) for feeding an inhibitor (INHIB) able to prevent polymerization of MMA.

14 . The unit according to claim 12 , wherein the inhibitor may be the same or different for each column and is selected from the group consisting of: hydroquinone; 4-alcoxyphenol; hydroquinone monobenzylether; 1.2-dihydroxybenzene, 2-methoxyphenol; 2,5-dichlorohydroquinone; 2,5-di-terbutylhydroquinone, 2-acethylhydroquinone; hydroquinone monobenzoate; 1,4-dimercaptobenzene, 1,2-dimercaptobenzene; 2,3,5-trimethylhydroquinone; 4-aminophenol, 2-aminophenol; 2-N,N-dimethylaminophenol; 2-mercaptophenol; 4-mercaptophenol; catechol; monobutylether; 4-ethylaminophenol; 2,3-dihydroxyaminophenone; pyrogallol; 1,2-dimethylether; 2-methylthiophenol; t-butyl catechol; di-ter-butylnitroxide; di-ter-amylnitroxide; 2,2,6,6-tetramethyl-piperidinyloxy; 4-hydroxy-2,2,6,6-tetramethyl-piperidinyloxy; 4-oxo-2,2,6,6-tetramethyl-piperidinyloxy; 4-ethanoyloxy-2,2,6,6-tetramethyl-piperidinyloxy; 2,2,5,5-tetramethyl-pyrrolidinyloxy; 3-amino-2,2,5,5-tetramethyl-pyrrolidinyloxy; 2,2,5,5-tetramethyl-1-oxa-3-azacyclopentyl-3-oxy; 2,2,5,5-tetramethyl-3-pirrolinyl-1-oxy-3carboxylic acid; 2,2,3,3,5,5,6,6,-octamethyl-1,4-diazacyclohexyl-1,4dioxy; sodium nirosophenolate; copper compounds such as copper dimethyldithiocarbamate; copperdiethyldithiocabamate; copper dibutyldithiocarbamate; copper salicylate; methylene blue; iron; phenothiazine; 1,4-benzenediamine, N-(1,4-dimethylpentyl)-N′-phenyl; 1,4-benzenediamine,N-(1,3-dimethylbutyl)-N′-phenyl; isomers thereof; and a mixture of two or more thereof.

15 . The unit according to claim 1 , wherein each upper ( 213 ; 253 ) and lower ( 212 ; 252 ) part of each distillation column ( 210 ; 250 ) comprises between 4 and 30 trays or plates ( 214 , 215 , 290 ; 254 , 255 ).

16 . The unit according to claim 1 , wherein said unit h comprises downstream the condenser system ( 260 ) of second distillation column ( 250 ), a heat exchanger ( 267 ), fed with liquid brine or glycol water at a temperature comprised between −20° C. and −5° C., able to chill the obtained pure MMA at a temperature of 0° C.

17 . The unit according to claim 1 , wherein the top of each distillation column ( 210 ; 250 ) comprises a safety valve ( 205 ; 206 ) connected either to a vent network or to atmosphere.

18 . A The unit according to claim 1 , wherein all parts of the unit ( 200 ) are made in stainless steel.

19 . A The unit according to claim 1 , wherein said unit it comprises a plurality of temperature sensors (T 1 to T 6 ) placed at least at the bottom and at the top of each distillation column ( 210 , 250 ), on the lateral extraction system ( 220 ) and on the exit ( 268 ) of pure MMA, and a plurality of pressure sensors (P 1 to P 6 ) placed at least on the suction part of each vacuum system ( 236 ; 266 ) and at the bottom and at the top of each distillation column ( 210 , 250 ).

20 . Process fir purifying crude methyl methacrylate (MMA), said crude methyl methacrylate (MMA) being prewashed with water before the purification said process comprises the following steps:
introducing pre-washed crude methyl methacrylate (MMA) in a median part of a

Assignees

• Arkema France

Inventors

• Bernardin Yves
• Billon Romain
• Marcarian Xavier
• WALLET Florent

Classifications

• C07C67/58

  by liquid-liquid treatment · CPC title

• C07C51/44 Primary

  by distillation · CPC title

• B01D3/36

  Azeotropic distillation · CPC title

• C07C67/54 Primary

  by distillation · CPC title

• B01D3/143 Primary

  by two or more of a fractionation, separation or rectification step · CPC title