Biomass conversion systems having a single-vessel hydrothermal digestion unit/catalytic reduction reactor unit for integrated stabilization of a hydrolysate and methods for use thereof

Abstract

Digestion of cellulosic biomass solids may be conducted in a pressure vessel that contains both a hydrothermal digestion unit and a catalytic reduction reactor unit. Biomass conversion systems incorporating such a feature may comprise: a pressure vessel that comprises a first section comprising a hydrothermal digestion unit and a second section comprising a first catalytic reduction reactor unit that contains a first catalyst capable of activating molecular hydrogen; wherein the hydrothermal digestion unit and the first catalytic reduction reactor unit are in fluid communication with one another; a biomass feed mechanism that is operatively connected to the pressure vessel, the biomass feed mechanism being capable of introducing cellulosic biomass solids to the pressure vessel and also capable of withdrawing a reaction product from the first catalytic reduction reactor unit; and a hydrogen feed line that is operatively connected to the first catalytic reduction reactor unit.

We claim: 
     
         1 . A biomass conversion system comprising:
 a pressure vessel comprising a first section and a second section, the first section comprising a hydrothermal digestion unit and the second section comprising a first catalytic reduction reactor unit that contains a first catalyst capable of activating molecular hydrogen;
 wherein the hydrothermal digestion unit and the first catalytic reduction reactor unit are in fluid communication with one another; 
   a biomass feed mechanism that is operatively connected to the pressure vessel, the biomass feed mechanism being capable of introducing cellulosic biomass solids to the pressure vessel and also capable of withdrawing a reaction product from the first catalytic reduction reactor unit; and   a hydrogen feed line that is operatively connected to the first catalytic reduction reactor unit.   
     
     
         2 . The biomass conversion system of claim  0 , wherein the pressure vessel comprises an annular structure, with the first section comprising an outer portion of the annular structure and the second section comprising an inner portion of the annular structure. 
     
     
         3 . The biomass conversion system of claim  0 , wherein the first section and the second section are located alongside one another in the pressure vessel. 
     
     
         4 . The biomass conversion system of claim  0 , wherein the first catalyst comprises a poison-tolerant catalyst. 
     
     
         5 . The biomass conversion system of claim  0 , wherein the first catalyst comprises a slurry catalyst. 
     
     
         6 . The biomass conversion system of  claim 5 , wherein the slurry catalyst is regenerable through exposure to water having a temperature of at least about 200° C. 
     
     
         7 . The biomass conversion system of claim  0 , further comprising:
 a fluid circulation loop establishing fluid communication between a fluid inlet of the pressure vessel and a fluid outlet of the biomass feed mechanism.   
     
     
         8 . The biomass conversion system of  claim 7 , wherein the fluid circulation loop further comprises a second catalytic reduction reactor unit that contains a second catalyst capable of activating molecular hydrogen. 
     
     
         9 . The biomass conversion system of  claim 8 , wherein the first catalyst and the second catalyst are the same. 
     
     
         10 . The biomass conversion system of  claim 8 , further comprising:
 a solids separation mechanism located within the fluid circulation loop between the fluid outlet of the biomass feed mechanism and a fluid inlet of the second catalytic reduction reactor unit.   
     
     
         11 . The biomass conversion system of  claim 8 , further comprising:
 a reaction product takeoff line in fluid communication with the fluid circulation loop, the reaction product takeoff line being located between the fluid inlet of the pressure vessel and a fluid outlet of the second catalytic reduction reactor unit.   
     
     
         12 . A biomass conversion system comprising:
 a pressure vessel comprising a first section and a second section, the first section comprising a hydrothermal digestion unit and the second section comprising a first catalytic reduction reactor unit that contains a first catalyst capable of activating molecular hydrogen;
 wherein the hydrothermal digestion unit and the first catalytic reduction reactor unit are in fluid communication with one another; 
   a biomass feed mechanism that is operatively connected to the pressure vessel, the biomass feed mechanism being capable of introducing cellulosic biomass solids to the pressure vessel while the pressure vessel maintains a pressurized state;   a hydrogen feed line that is operatively connected to the first catalytic reduction reactor unit; and   a fluid circulation loop comprising the pressure vessel and a second catalytic reduction reactor unit that contains a second catalyst capable of activating molecular hydrogen.   
     
     
         13 . The biomass conversion system of  claim 12 , wherein the pressure vessel comprises an annular structure, with the first section comprising an outer portion of the annular structure and the second section comprising an inner portion of the annular structure. 
     
     
         14 . The biomass conversion system of  claim 12 , wherein the first section and the second section are located alongside one another in the pressure vessel. 
     
     
         15 . The biomass conversion system of  claim 12 , wherein the first catalyst comprises a poison-tolerant catalyst. 
     
     
         16 . The biomass conversion system of  claim 12 , wherein the first catalyst comprises a slurry catalyst. 
     
     
         17 . The biomass conversion system of  claim 16 , wherein the slurry catalyst is regenerable through exposure to water having a temperature of at least about 200° C. 
     
     
         18 . The biomass conversion system of  claim 12 , wherein the first catalyst and the second catalyst are the same. 
     
     
         19 . The biomass conversion system of  claim 12 , wherein the fluid circulation loop further comprises the biomass feed mechanism, the fluid circulation loop establishing fluid communication between a fluid inlet of the pressure vessel and a fluid outlet of the biomass feed mechanism. 
     
     
         20 . The biomass conversion system of  claim 12 , further comprising:
 a solids separation mechanism located within the fluid circulation loop between a fluid outlet of the pressure vessel and a fluid inlet of the second catalytic reduction reactor unit.   
     
     
         21 . The biomass conversion system of  claim 12 , further comprising:
 a reaction product takeoff line in fluid communication with the fluid circulation loop, the reaction product takeoff line being located between a fluid inlet of the pressure vessel and a fluid outlet of the second catalytic reduction reactor unit.   
     
     
         22 . A method comprising:
 providing a pressure vessel comprising a first section and a second section, the first section comprising a hydrothermal digestion unit and the second section comprising a first catalytic reduction reactor unit that contains a first catalyst capable of activating molecular hydrogen;
 wherein the hydrothermal digestion unit and the first catalytic reduction reactor unit are in fluid communication with one another; 
   adding cellulosic biomass solids to the pressure vessel;   heating the cellulosic biomass solids in the hydrothermal digestion unit of the pressure vessel, thereby forming a hydrolysate comprising soluble carbohydrates within a liquor phase;   conveying the liquor phase through the first catalytic reduction reactor unit in the presence of molecular hydrogen so as to at least partially transform the soluble carbohydrates into a reaction product; and   conveying at least a portion of the liquor phase from the pressure vessel to a second catalytic reduction reactor unit that contains a second catalyst capable of activating molecular hydrogen, so as to further transform the soluble carbohydrates into the reaction product.   
     
     
         23 . The method of  claim 22 , further comprising:
 recirculating at least a portion of the liquor phase from the second catalytic reduction reactor unit to the pressure vessel.   
     
     
         24 . The method of  claim 23 , wherein the liquor phase is recirculated to the pressure vessel at a recycle ratio of about 2 or less. 
     
     
         25 . The method of  claim 22 , wherein at least about 90% of the cellulosic biomass solids, on a dry basis, are digested to produce hydrolysate. 
     
     
         26 . The method of  claim 22 , further comprising:
 after further transforming the soluble carbohydrates into the reaction product, withdrawing a portion of the reaction product from an outlet of the second catalytic reduction reactor unit; and   converting the reaction product into a biofuel.   
     
     
         27 . The method of  claim 22 , wherein the first catalyst, the second catalyst, or both comprises a poison-tolerant catalyst. 
     
     
         28 . The method of  claim 22 , wherein the first catalyst comprises a slurry catalyst. 
     
     
         29 . The method of  claim 28 , further comprising:
 regenerating the slurry catalyst through exposure to water having a temperature of at least about 200° C.   
     
     
         30 . The method of  claim 22 , wherein the first section and the second section are located alongside one another in the pressure vessel. 
     
     
         31 . The method of  claim 22 , wherein the first section and the second section comprise an annular structure within the pressure vessel, with the first section comprising an outer portion of the annular structure and the second section comprising an inner portion of the annular structure. 
     
     
         32 . The method of  claim 22 , wherein the cellulosic biomass solids are added to the pressure vessel from a biomass feed mechanism, the biomass feed mechanism being capable of introducing cellulosic biomass solids to the pressure vessel while the pressure vessel maintains a pressurized state. 
     
     
         33 . The method of  claim 32 , wherein the cellulosic biomass solids are added to the pressure vessel while the pressure vessel is at a pressure of at least about 30 bar. 
     
     
         34 . The method of  claim 32 , wherein the liquor phase is conveyed to the second catalytic reduction reactor unit through the biomass feed mechanism. 
     
     
         35 . The method of  claim 34 , wherein the biomass feed mechanism contains cellulosic biomass solids while the liquor phase is being conveyed therethrough.