Process for manufacturing high purity methacrylic acid

Abstract

A process is provided herein for the high yield production of high purity glacial methacrylic acid (“HPMAA”) that is substantially pure, specifically 99% pure or greater, with water content of 0.05% or less and low levels of other impurities, including HIBA, acrylic acid, MOMPA, methacrolein and others. This improved process comprises providing a crude MAA stream and purifying the crude methacrylic acid stream in a series of successive distillation steps involving two distillation columns. The inventive process is capable producing high purity methacrylic acid product that is especially suitable for the production of specialty MAA polymers.

What is claimed is:  
     
         1 . A process for the preparation of high purity methacrylic acid, said process comprising: 
 (i) providing a first distillation column and a second distillation column;    (ii) feeding a crude methacrylic acid stream to said first distillation column, said crude methacrylic acid stream comprising methacrylic acid, light ends and heavy ends;    (iii) distilling said crude methacrylic acid stream in said first distillation column to form a first overhead vapor stream and a first bottom liquid stream;    (iv) feeding said first bottom liquid stream to said second distillation column;    (v) distilling said first bottom liquid stream in said second distillation column to form a second overhead vapor stream and a second bottom liquid stream; and    (vi) drawing a product stream from a middle section of said second distillation column.    
     
     
         2 . The process for the preparation of high purity methacrylic acid according to  claim 1 , wherein said first overhead vapor stream comprises substantially acetone, water, and other light ends and wherein said first bottom liquid stream substantially comprises methacrylic acid, HIBA, and other heavy ends.  
     
     
         3 . The process for the preparation of high purity methacrylic acid according to  claim 1 , wherein said second overhead vapor stream comprises substantially acetone, water, and methacrylic acid and wherein said second bottom liquid stream comprises substantially HIBA.  
     
     
         4 . A process for the preparation of high purity methacrylic acid, said process comprising: 
 (i) providing a first distillation column and a second distillation column;    (ii) feeding a crude methacrylic acid to said first distillation column, said crude methacrylic acid stream comprising methacrylic acid, light ends and heavy ends;    (iii) distilling said crude methacrylic acid stream in said first distillation column to form a first overhead vapor stream and a first bottom liquid stream;    (iv) condensing said first overhead vapor stream to produce a reflux stream and a feed stream;    (v) directing said feed stream to said second distillation column;    (vi) distilling said feed stream in said second distillation column to form a second overhead vapor stream and a second bottom liquid stream; and    (vii) drawing a product stream from a middle section of said second distillation column.    
     
     
         5 . The process for the preparation of high purity methacrylic acid according to  claim 4 , wherein said first overhead vapor stream comprises substantially methacrylic acid, acetone, water, and other light ends and wherein said first bottom liquid stream substantially comprises HIBA and other heavy ends.  
     
     
         6 . The process for the preparation of high purity methacrylic acid according to  claim 4 , wherein said second overhead vapor stream comprises substantially acetone, and water and wherein said second bottom liquid stream comprises substantially heavy ends.  
     
     
         7 . A high purity methacrylic acid comprising: 
 at least 99% by weight of methacrylic acid;    water, present at up to 0.05% by weight;    up to 0.1% by weight methacrolein; and    up to 0.9% by weight of HIBA;    
     
     
         8 . The high purity methacrylic acid of  claim 7  further comprising: 
 up to 0.1% by weight of 3-methacryloxy-2-methylpropionic acid and methyl methacrylate; and  
 and up to 0.075% by weight methacrylamide.  
 
     
     
         9 . The high purity methacrylic acid of  claim 7  further comprising: 
 up to 0.1% by weight of acetic acid;  
 up to 0.08% by weight of acetone;  
 up to 0.04% by weight of acrylic acid; and  
 up to 0.02% by weight of propionic acid.  
 
     
     
         10 . A method of preventing HIBA decomposition within a stream containing methacrylic acid and an acid-catalyst comprising: 
 adding a stabilizing agent to said methacrylic acid containing stream, said stabilizing agent being capable of neutralizing the acid-catalyst.    
     
     
         11 . The method of  claim 10  further comprising removing the neutralized acid-catalyst from said methacrylic acid containing stream by filtration or distillation.  
     
     
         12 . The method of  claim 10 , wherein said stabilizing agents are selected from the group consisting of ammonia, caustic, magnesium hydroxide, and magnesium oxide.  
     
     
         13 . A method of removing HIBA from a methacrylic acid containing stream comprising: 
 adding a Lewis acid component to said methacrylic acid containing stream to create a mixture;    heating said mixture such that the HIBA within said methacrylic acid containing stream is decomposed into decomposition products; and    distilling said decomposition products from said methacrylic acid containing stream.    
     
     
         14 . The method of  claim 13  wherein said Lewis acid component is selected from the group consisting of sulfuric acid, phosphoric acid, a superacid, and an ion exchange resin having acidic functionality.  
     
     
         15 . A method of preventing HIBA decomposition within a stream containing methacrylic acid and an acid-catalyst comprising: 
 contacting said methacrylic acid containing stream with an ion exchange resin.    
     
     
         16 . A method of purifying a HIBA-containing MAA stream in a purification process which utilizes a distillation column, comprising: 
 maintaining residence time of said MAA stream at a bottom section of the distillation column up to 48 hours, whereby HIBA decomposition is minimized.    
     
     
         17 . A method of purifying a HIBA-containing MAA stream in a purification process which utilizes a distillation column, comprising: 
 maintaining temperature of said MAA stream at a bottom section of the distillation column at up to 145° C., whereby HIBA decomposition is minimized.    
     
     
         18 . A method of purifying a HIBA-containing MAA stream in a purification process which utilizes a distillation column, comprising: 
 maintaining total acid-catalyst concentration of said MAA stream at a bottom section of the distillation column at up to 2.5 percent by weight, whereby HIBA decomposition is minimized.    
     
     
         19 . The method of  claim 18 , wherein said acid-catalyst is selected from the group consisting of sulfuric acid and compounds capable of providing sulfate ions.