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 method comprising:
 providing cellulosic biomass solids to 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;   transferring at least a portion of the liquor phase to a catalytic reduction reactor unit that also contains a slurry catalyst capable of activating molecular hydrogen; wherein the slurry catalyst in the hydrothermal digestion unit and the catalytic reduction reactor unit comprises a particulate size of about 250 microns or less;   heating at least the liquor phase in the catalytic reduction reactor unit in the presence of molecular hydrogen and the slurry catalyst to further transform the soluble carbohydrates into the reaction product; and   recirculating at least a portion of the liquor phase from the catalytic reduction reactor unit to the hydrothermal digestion unit via a fluid circulation loop comprising the hydrothermal digestion unit and the catalytic reduction reactor unit, wherein the liquor phase is recirculated to the hydrothermal digestion unit at a recycle ratio in a range of about 0.2 and about 10.   
     
     
         2 . The method according to  claim 1  wherein the hydrothermal digestion unit comprises an upward fluid flow. 
     
     
         3 . The method of  claim 1  further comprising:
 retaining in the hydrothermal digestion unit cellulosic biomass solids having a particle size of about 3 mm or above; and 
 allowing cellulosic biomass solids having a particle size of less than about 3 mm to exit the hydrothermal digestion unit. 
 
     
     
         4 . The method of  claim 1 , 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, wherein the withdrawing is achieved at least via 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; and   converting the reaction product into a biofuel.   
     
     
         5 . The method of  claim 4 , further comprising:
 separating solids from the reaction product after withdrawing, wherein said separating is achieved with a solids separation mechanism that is operatively connected to the reaction product takeoff line.   
     
     
         6 . The method of  claim 1 , further comprising:
 further forming the reaction product in the catalytic reduction reactor unit.   
     
     
         7 . The method of  claim 1  wherein the slurry catalyst comprises a poison-tolerant catalyst. 
     
     
         8 . The method of  claim 1  wherein the slurry catalyst is regenerable through exposure to water having a temperature of at least about 200 degrees C. 
     
     
         9 . The method of  claim 1  wherein the slurry catalyst is operable to generate molecular hydrogen. 
     
     
         10 . The method of  claim 1  wherein the providing cellulosic biomass solids to the hydrothermal digestion unit comprises using 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. 
     
     
         11 . The biomass conversion system of  claim 1 , wherein the catalytic reduction reactor unit comprises an upward fluid flow.