Apparatus for preparing a dialkyl carbonate

Abstract

Unexpected corrosion of downstream sections of a dialkyl carbonate manufacturing apparatus has been traced to alkyl chloroformate impurities, which slowly decompose to yield hydrochloric acid. An improved process and apparatus for dialkyl carbonate synthesis reduce corrosion by physically removing or chemically decomposing the alkyl chloroformate impurities within the corrosion-resistant upstream sections of the apparatus. The alkyl chloroformate may be decomposed by passing it through a passageway at a temperature of about 30° C. to about 130° C. for a time of about 0.5 hour to about 10 hours. The passageway may include one or more holding vessels or a tubular section that promotes plug flow.

1 . An apparatus for preparing a dialkyl carbonate, comprising: 
 means for reacting an alkanol, oxygen, carbon monoxide, and a catalyst to form a mixture comprising a dialkyl carbonate, an alkyl chloroformate, hydrochloric acid, water, carbon dioxide, and carbon monoxide; and    means for removing alkyl chloroformate from said mixture.    
     
     
         2 . An apparatus for preparing a dialkyl carbonate, comprising: 
 a reactor for reacting an alkanol, oxygen, carbon monoxide, and a catalyst to a produce a mixture comprising a dialkyl carbonate, an alkyl chloroformate, hydrochloric acid, water, and carbon dioxide; and    a fluid passageway for removing alkyl chloroformate.    
     
     
         3 . The apparatus of  claim 2 , wherein said fluid passageway comprises a heat exchanger.  
     
     
         4 . The apparatus of  claim 2 , wherein said fluid passageway comprises a holding vessel.  
     
     
         5 . The apparatus of  claim 2 , wherein said fluid passageway comprises a plurality of holding vessels.  
     
     
         6 . The apparatus of  claim 2 , wherein said fluid passageway comprises a section having a length to volume ratio of at least about 5.  
     
     
         7 . The apparatus of  claim 2 , wherein said fluid passageway comprises a section having a length to volume ratio of at least about 10.  
     
     
         8 . The apparatus of  claim 2 , further comprising a condenser in fluid communication with said reactor and said fluid passageway.  
     
     
         9 . The apparatus of  claim 8 , further comprising a gas-liquid separator in fluid communication with said condenser and said fluid passageway.  
     
     
         10 . The apparatus of  claim 2 , further comprising an acid removal column in fluid communication with said fluid passageway.  
     
     
         11 . The apparatus of  claim 2 , further comprising an azeotrope column in fluid communication with said fluid passageway.  
     
     
         12 . An apparatus for preparing a dialkyl carbonate, comprising: 
 a reactor for reacting an alkanol, oxygen, carbon monoxide, and a catalyst to produce a mixture comprising a dialkyl carbonate, an alkyl chloroformate, hydrochloric acid, water, carbon dioxide, and carbon monoxide;    a gas-liquid separator; and    a fluid passageway for removing alkyl chloroformate, wherein said fluid passageway has a length to diameter ratio of at least about 0.2.    
     
     
         13 . The apparatus of  claim 12 , wherein said fluid passageway comprises a holding vessel having a length to diameter ratio less than 5.  
     
     
         14 . The apparatus of  claim 12 , wherein said fluid passageway comprises a plurality of holding vessels having a length to diameter ratio less than 5.  
     
     
         15 . The apparatus of  claim 12 , wherein said fluid passageway comprises a section having a length to diameter ratio of at least about 10.