Dual Catalyst Esterification

Abstract

Methods, processes, apparatus, equipment and systems are disclosed for converting carboxylic acids into esters by esterification with alcohol and a dual catalyst. The method combines a homogenous and heterogeneous catalyst in one or more reactors to increase the conversion of carboxylic acids compared to using a homogenous and/or heterogeneous catalyst independently. The invention converts free fatty acids into esters by esterification with alcohol and a dual catalyst such that the reaction mixture contains sufficiently low free fatty acids and the amount of free fatty acids in the product stream leaving the process remains stable over time.

What is claimed is: 
     
         1 . A method for producing esters, comprising:
 providing at least one alcohol from an alcohol source;   providing carboxylic acids from a carboxylic acid source; and   reacting the alcohol and the carboxylic acids in the presence of a homogenous catalyst and a heterogeneous catalyst to form a reaction mixture comprising esters, alcohol, water, and homogenous catalyst.   
     
     
         2 . The method of  claim 1 , wherein the alcohol comprises methanol. 
     
     
         3 . The method of  claim 1 , wherein said carboxylic acids are free fatty acids. 
     
     
         4 . The method of  claim 1 , wherein the carboxylic acid source comprises at least one of corn oil, animal fat, waste cooking oil, palm oil, algae oil, brown grease, and fatty acid distillate. 
     
     
         5 . The method of  claim 1 , wherein said heterogeneous catalyst is regenerated with at least one of hydrochloric acid, sulfuric acid, and methane sulfonic acid. 
     
     
         6 . The method of  claim 1 , further comprising the step of separating said reaction mixture into an alcohol and water phase and an oil phase. 
     
     
         7 . The method of  claim 6 , further comprising the step of reacting the oil phase in at least one of a transesterification process and a hydrogenation process. 
     
     
         8 . The method of  claim 1 , wherein said reaction mixture is formed in a first reactor. 
     
     
         9 . The method of  claim 8 , wherein a second reactor is used with the first reactor. 
     
     
         10 . The method of  claim 9 , wherein the first reactor and the second reactor are used in parallel. 
     
     
         11 . The method of  claim 9 , wherein the reaction mixture is formed in the second reactor before entering the first reactor. 
     
     
         12 . The method of  claim 9  further comprising the step of taking at least one of the first reactor and the second reactor offline to regenerate the heterogeneous catalyst while leaving the other of the first reactor and the second reactor online. 
     
     
         13 . The method of  claim 8 , wherein at least two different heterogeneous catalysts are contained in said first reactor. 
     
     
         14 . The method of  claim 8 , wherein said first reactor includes both a homogenous catalysis stage and a heterogeneous catalysis stage. 
     
     
         15 . The method of  claim 8 , further comprising the step of adding heterogeneous catalyst into the first reactor using a fluid. 
     
     
         16 . The method of  claim 8 , further comprising the step of removing heterogeneous catalyst from the first reactor using a fluid. 
     
     
         17 . A method for prolonging heterogeneous catalyst activity, comprising:
 providing a feedstock from a feedstock source, wherein feedstock contains contaminants;   providing a homogenous catalyst from a homogenous catalyst source;   mixing homogenous catalyst with feedstock to create a mixture;   introducing said mixture to a heterogeneous catalyst wherein said homogenous catalyst in said mixture prevents contaminants from binding to said heterogeneous catalyst thereby reducing deactivation of said heterogeneous catalyst.   
     
     
         18 . The method of  claim 17 , wherein sufficient homogenous catalyst is included in said mixture to increase overall conversion of said feedstock relative to a reaction mixture produced in the absence of said homogeneous catalyst. 
     
     
         19 . A method for stabilizing the carboxylic acid content of a reaction mixture leaving a continuous flow heterogeneous catalyst esterification reactor, comprising:
 providing an alcohol from an alcohol source;   providing a feedstock from a feedstock source, wherein the feedstock has a carboxylic acid content;   providing a homogenous catalyst from a homogenous catalyst source;   reacting the alcohol and the feedstock in the presence of a heterogeneous catalyst; and   introducing said homogenous catalyst to the continuous flow heterogeneous catalyst esterification reactor to produce a reaction mixture with a carboxylic acid content that remains more stable over time relative to a reaction mixture produced in the absence of said homogeneous catalyst.