Biomass conversion systems providing integrated stabilization of a hydrolysate using a slurry catalyst and methods for use thereof

Abstract

Digestion of cellulosic biomass solids to form a hydrolysate may be conducted with integrated catalytic reduction during digestion to transform soluble carbohydrates in the hydrolysate into a more stable reaction product. Such integrated catalytic reduction may be conducted using a slurry catalyst. Biomass conversion systems for performing integrated catalytic reduction can comprise: a hydrothermal digestion unit that contains a slurry catalyst capable of activating molecular hydrogen; an optional hydrogen feed line that is operatively connected to the hydrothermal digestion unit; and a fluid circulation loop comprising the hydrothermal digestion unit and a catalytic reduction reactor unit, the catalytic reduction reactor unit also containing the slurry catalyst.

We claim: 
     
         1 . A biomass conversion system comprising:
 a hydrothermal digestion unit that contains a slurry catalyst capable of activating molecular hydrogen;   an optional hydrogen feed line that is operatively connected to the hydrothermal digestion unit; and   a fluid circulation loop comprising the hydrothermal digestion unit and a catalytic reduction reactor unit, the catalytic reduction reactor unit also containing the slurry catalyst.   
     
     
         2 . The biomass conversion system of  claim 1 , wherein the fluid circulation loop is configured to establish upward fluid flow in the hydrothermal digestion unit. 
     
     
         3 . The biomass conversion system of  claim 1 , further comprising:
 a retention mechanism within the hydrothermal digestion unit that is operable to retain cellulosic biomass solids having a particle size of about 3 mm or above.   
     
     
         4 . The biomass conversion system of  claim 1 , further comprising:
 a reaction product takeoff line in fluid communication with the fluid circulation loop, the reaction product takeoff line being located between the hydrothermal digestion unit and an outlet of the catalytic reduction reactor unit.   
     
     
         5 . The biomass conversion system of  claim 4 , further comprising:
 a solids separation mechanism that is operatively connected to the reaction product takeoff line.   
     
     
         6 . The biomass conversion system of  claim 1 , wherein the slurry catalyst comprises a poison-tolerant catalyst. 
     
     
         7 . The biomass conversion system of  claim 1 , wherein the slurry catalyst is regenerable through exposure to water having a temperature of at least about 200° C. 
     
     
         8 . The biomass conversion system of  claim 1 , wherein the slurry catalyst is operable to generate molecular hydrogen. 
     
     
         9 . The biomass conversion system of  claim 1 , further comprising:
 a solids introduction mechanism that is operatively connected to the hydrothermal digestion unit, the solids introduction mechanism comprising an atmospheric pressure zone and a pressure transition zone that cycles between atmospheric pressure and a higher pressure state.   
     
     
         10 . The biomass conversion system of  claim 1 , wherein the fluid circulation loop is configured to establish upward fluid flow in the catalytic reduction reactor unit. 
     
     
         11 . A method comprising:
 providing cellulosic biomass solids in a hydrothermal digestion unit that contains a slurry catalyst capable of activating molecular hydrogen;   heating the cellulosic biomass solids in the hydrothermal digestion unit in the presence of molecular hydrogen while circulating the slurry catalyst therethrough, thereby forming a hydrolysate comprising soluble carbohydrates within a liquor phase;   at least partially transforming the soluble carbohydrates into a reaction product while the soluble carbohydrates are within the hydrothermal digestion unit; and   transferring at least a portion of the liquor phase to a catalytic reduction reactor unit that also contains the slurry catalyst, so as to further transform the soluble carbohydrates into the reaction product.   
     
     
         12 . The method of  claim 11 , further comprising:
 recirculating at least a portion of the liquor phase from the catalytic reduction reactor unit to the hydrothermal digestion unit.   
     
     
         13 . The method of  claim 11 , further comprising:
 after further transforming the soluble carbohydrates into the reaction product, withdrawing a portion of the reaction product from the catalytic reduction reactor unit; and   converting the reaction product into a biofuel.   
     
     
         14 . The method of  claim 13 , further comprising:
 separating solids from the reaction product after withdrawing.   
     
     
         15 . The method of  claim 11 , further comprising:
 further forming the reaction product in the catalytic reduction reactor unit.