Methods and systems for reducing the level of one or more impurities that are present in a pretreated cellulosic material and/or distillate

Abstract

The present invention relates to methods and systems for remediating one or more impurities (e.g., diacetyl) that are present in manufacturing an alcohol (e.g., ethanol) from cellulosic biomass. The methods and systems include reacting the one or more impurities with at least one treatment compound (e.g., an oxidizing agent, an alkali compound, or a mixture thereof) to form a reaction product that can be separated from the alcohol.

What is claimed is: 
     
         1 . A system for reducing the concentration of diacetyl that is present in a pretreated cellulosic material comprising:
 a source of a fermentation product comprising:
 an alcohol; and 
 diacetyl; 
   a distillation system in fluid communication with the source of a fermentation product, wherein the distillation system can distill the fermentation product to form a distillate comprising the alcohol and the diacetyl;   a source of at least one treatment compound, wherein the at least one treatment compound is chosen from an oxidizing agent, an alkali compound, and mixtures thereof; and   a treatment system in fluid communication with the distillation system and the source of at least one treatment compound, wherein the treatment system causes the least one treatment compound to contact the distillate so that the at least one treatment compound reacts with the diacetyl to form a reaction product thereby reducing the concentration of the diacetyl and forming a treated distillate.   
     
     
         2 . The system of  claim 1 , further comprising a vaporizing system in fluid communication with the treatment system, wherein the vaporizing system can subject the treated distillate to a vaporization process to vaporize at least a portion of the treated distillate to form a liquid fraction and a vapor fraction, wherein the vapor fraction comprises at least a portion of the alcohol and the concentration of the alcohol in the vapor fraction is higher as compared to the concentration of the alcohol in the treated distillate. 
     
     
         3 . The system of  claim 2  wherein the liquid fraction from the vaporization process comprises at least a portion of the reaction product and the concentration of the reaction product in the liquid fraction is higher as compared to the concentration of the reaction product in the treated distillate. 
     
     
         4 . The system of  claim 1 , wherein the treatment system further comprises an ultraviolet light system that can expose the distillate to ultraviolet light to reduce the concentration of the diacetyl. 
     
     
         5 . The system of  claim 1 , wherein the at least one treatment compound is chosen from an hydrogen peroxide, sodium hydroxide, and mixtures thereof. 
     
     
         6 . A method of reducing the concentration of at least one impurity that is present in a distilled alcohol comprising:
 providing a feedstock;   subjecting the feedstock to a fermentation process to form a fermentation product comprising:
 an alcohol; and 
 an impurity; 
   distilling the fermentation product to form a liquid distillate comprising the alcohol and the impurity, the impurity being present in the liquid distillate in a first concentration; and   contacting the liquid distillate with at least one treatment compound so that the at least one treatment compound reacts with the impurity to form a reaction product thereby forming a treated liquid distillate, the reaction product having a higher boiling point than the alcohol, wherein the at least one treatment compound is chosen from an oxidizing agent, an alkali compound, and mixtures thereof; and   subjecting the treated liquid distillate to a vaporization process to form a liquid fraction and a vapor fraction, wherein the vapor fraction comprises at least a portion of the alcohol, the vapor fraction containing a concentration of the impurity that is lower than the first concentration.   
     
     
         7 . The method of  claim 6 , wherein the at least one treatment compound comprises hydrogen peroxide. 
     
     
         8 . The method of  claim 6 , wherein the impurity comprises diacetyl. 
     
     
         9 . The method of  claim 6 , wherein the reaction product comprises acetic acid. 
     
     
         10 . The method of  claim 6 , wherein the alcohol comprises ethanol. 
     
     
         11 . The method of  claim 6 , wherein the vapor fraction is at least 150 proof ethanol. 
     
     
         12 . The method of  claim 11 , wherein the vapor fraction is condensed to a post treatment liquid that is at least 150 proof ethanol, the post treatment liquid having a concentration of the impurity that is lower than the first concentration. 
     
     
         13 . The method of  claim 6 , wherein the at least one treatment compound comprises sodium hydroxide. 
     
     
         14 . The method of  claim 13 , wherein the distillate is contacted with an amount of sodium hydroxide so that the pH of the distillate is at least 10. 
     
     
         15 . The method of  claim 13 , wherein the distillate is contacted with an amount of sodium hydroxide so that the pH of the distillate is at least 12. 
     
     
         16 . The method of  claim 6 , wherein the distillate comprises alcohol, wherein the impurity is present in the distillate at a concentration of at least 50 parts per million, and the distillate is contacted with the at least one treatment compound so that the concentration of the impurity is reduced to 20 parts per million or less in a time period of twenty minutes or less. 
     
     
         17 . The method of  claim 6 , further comprising exposing the distillate to ultraviolet light to reduce the concentration of the impurity. 
     
     
         18 . The method of  claim 17 , wherein the exposing the distillate to ultraviolet light can occur before, during, or after contacting the distillate with at least one treatment compound. 
     
     
         19 . The method of  claim 6 , wherein the providing a feedstock comprises providing cellulosic material. 
     
     
         20 . The method of  claim 19 , wherein the cellulosic material comprises at least corn stover.