Processes and systems for the production of propylene glycol from glycerol

Abstract

Processes and systems for converting glycerol to propylene glycol are disclosed. The glycerol feed is diluted with propylene glycol as the primary solvent, rather than water which is typically used. The diluted glycerol feed is sent to a reactor where the glycerol is converted to propylene glycol (as well as other byproducts) in the presence of a catalyst. The propylene glycol-containing product from the reactor is recycled as a solvent for the glycerol feed.

1 - 11 . (canceled) 
     
     
         12 . A process for producing propylene glycol, comprising:
 providing a feed comprising glycerol;   providing a catalyst for converting the glycerol to propylene glycol;   reacting the glycerol feed with the catalyst in the presence of a soluble base, thereby producing a product comprising propylene glycol;   recycling at least a part of the product back to further provide for a diluted glycerol feed; and   
       wherein at least a portion of the soluble base is also recycled back along with at least a part of the product. 
     
     
         13 . The process of  claim 12  further comprising reacting the diluted feed with the catalyst after recycling back the product and soluble base. 
     
     
         14 . The process of  claim 12  wherein up to about 60% of the product is recycled back into the feed. 
     
     
         15 . The process of  claim 12  wherein the feed was derived from a biodiesel process. 
     
     
         16 . The process of  claim 12  wherein the diluted glycerol feed comprises from about 40% to 60% by weight glycerol. 
     
     
         17 . The process of  claim 12  wherein the diluted glycerol feed comprises from about 40% to 60% by weight propylene glycol. 
     
     
         18 . The process of  claim 12  wherein the reaction is carried out at a temperature from about 160° C. to about 240° C. 
     
     
         19 . The process of  claim 12  wherein the reaction is carried out at a pressure from about 400 to about 1600 psi. 
     
     
         20 . The process of  claim 12  wherein the recycled product comprises less than about 20% water by weight. 
     
     
         21 . The process of  claim 13  wherein further reacting the diluted feed with the catalyst after recycling the product and soluble base results in about 70% or greater selectivity to propylene glycol. 
     
     
         22 . The process of  claim 12  wherein the feed comprises less than about 12% water by weight. 
     
     
         23 - 40 . (canceled)