Separation of Propylene Oxide from a Mixture Comprising Propylene Oxide and Methanol

Abstract

A method of separating propylene oxide from a mixture (M) comprising 5 to 50 percent by weight propylene oxide and 50 to 85 percent by weight methanol, said method comprising (i) introducing said mixture (M) into an extractive distillation column; (ii) additionally introducing a polar solvent into said extractive distillation column; (iii) distilling propylene oxide overhead from said extractive distillation column at a bottoms temperature of from 40 to 70° C. and at a pressure of from 300 to 750 mbar.

1 . A method of separating propylene oxide from a mixture (M) comprising 5 to 50 percent by weight propylene oxide and 50 to 85 percent by weight methanol, said method comprising 
 (i) introducing said mixture (M) into an extractive distillation column;    (ii) additionally introducing a polar solvent into said extractive distillation column;    (iii) distilling propylene oxide overhead from said extractive distillation column at a bottoms temperature of from 40 to 70° C. and at a pressure of from 300 to 750 mbar.    
     
     
         2 . The method as claimed in  claim 1 , said mixture (M) comprising 5 to 15 percent by weight propylene oxide and additionally comprising 10 to 25 percent by weight water.  
     
     
         3 . The method as claimed in  claim 1 , wherein the polar solvent is introduced in an amount of 2 percent by weight of the mixture (M) or less.  
     
     
         4 . The method as claimed in  claim 1 , wherein said extractive distillation column has up to 80 theoretical plates.  
     
     
         5 . The method as claimed in  claim 1 , wherein water is used as polar solvent.  
     
     
         6 . The method as claimed in  claim 5 , wherein the water is introduced as vapor at a pressure of not more than 2 bar.  
     
     
         7 . The method as claimed in  claim 1 , wherein the distillate obtained overhead from (iii) is partially refluxed into said extractive distillation column and wherein the ratio of reflux to distillate is smaller than or equal to 4.  
     
     
         8 . The method as claimed in  claim 1 , wherein the top stream distilled overhead comprises 100 ppm methanol or less.  
     
     
         9 . The method as claimed in  claim 1 , wherein the bottoms stream withdrawn from said extractive distillation column has a propylene oxide content of 100 ppm or less.  
     
     
         10 . The method as claimed in  claim 1 , wherein the mixture (M) is formed by reacting propene with hydrogen peroxide in methanol as solvent and in the presence of a titanium zeolite fixed-bed catalyst.  
     
     
         11 . A method of separating propylene oxide from a mixture (M) comprising 5 to 15 percent by weight propylene oxide, 50 to 85 percent by weight of methanol, and 10 to 25 percent by weight water, said method comprising 
 (i) introducing said mixture (M) into an extractive distillation column having up to 80 theoretical plates;    (ii) additionally introducing water into said extractive distillation column in an amount of 2 percent by weight of the mixture (M) or less;    (iii) distilling propylene oxide overhead from said extractive distillation column at a bottoms temperature of from 40 to 70° C. and at a pressure of from 300 to 750 mbar,    wherein the distillate obtained overhead from (iii) is partially refluxed into said extractive distillation column and wherein the ratio of reflux to distillate is smaller than or equal to 4, wherein the top stream distilled overhead comprises 100 ppm methanol or less, and wherein the bottoms stream withdrawn from said extractive distillation column has a propylene oxide content of 100 ppm or less.    
     
     
         12 . The method as claimed in  claim 11 , wherein the mixture (M) is formed by reacting propene with hydrogen peroxide in methanol as solvent and in the presence of a titanium zeolite fixed-bed catalyst.  
     
     
         13 . The method as claimed in  claim 11 , wherein the water is introduced as vapor at a pressure of not more than 2 bar.