Process for the production of furfural from pentoses

Abstract

The invention is directed to a process for the production of furfural from pentoses and/or water soluble pentosans, said process comprising converting the said pentoses and/or water soluble pentosans in aqueous solution in a first step to furfural and in a second step feeding the aqueous solution containing furfural obtained in the first step to the top of a distillation column to produce an aqueous, liquid downflow, which column is heated at the bottom to produce an upflow water vapour flow, recovering a gaseous water and furfural containing product stream from the top of the said column, compressing the said vapour flow and condensing it on the hot side of a reboiler at the bottom of the said column.

1 . Process for the production of furfural from pentoses and/or water soluble pentosans, said process comprising converting the said pentoses and/or water soluble pentosans in aqueous solution in a first step to furfural and in a second step feeding the aqueous solution containing furfural obtained in the first step to the top of a distillation column to produce an aqueous, liquid downflow, which column is heated at the bottom to produce an upflow water vapour flow, recovering a gaseous water and furfural containing product stream from the top of the said column, compressing the said vapour flow and condensing it on the hot side of a reboiler at the bottom of the said column. 
     
     
         2 . Process according to  claim 1 , which process comprises feeding an aqueous solution of one or more pentoses or soluble pentosans to the top of a distillation column to produce an aqueous, liquid downflow, which column is heated at the bottom to produce an upflow water vapour flow, recovering a gaseous water and furfural containing product stream from the top of the said column after recompression and condensation. 
     
     
         3 . Process according to  claim 1 , wherein the first step and the second step are carried out consecutively. 
     
     
         4 . Process according to  claim 3 , wherein the reaction is partly carried out before and partly inside the distillation column. 
     
     
         5 . Process according to  claim 1 , wherein the said gaseous product stream is recompressed and led through a heat exchanger which is in contact with the contents of the said column, preferably at a location near the bottom thereof. 
     
     
         6 . Process according to  claim 1 , wherein the said aqueous solution of pentoses is obtained from biomass, more in particular from a biomass residue. 
     
     
         7 . Process according to  claim 1 , wherein the said product stream is condensed to produce a concentrated aqueous furfural product stream. 
     
     
         8 . Process according to  claim 7 , wherein furfural is recovered from the said concentrated aqueous furfural product stream by distillation with vapour recompression. 
     
     
         9 . Process according to  claim 1 , wherein the pressure in the said distillation column is between 1 and 50 bar(abs). 
     
     
         10 . Process according to  claim 1 , wherein the temperature in the said distillation column is between 100 and 300° C., or between 150 and 250° C. 
     
     
         11 . Process according to  claim 1 , wherein the concentration of pentoses during the reactive steps is lower than 10 wt. %, or between 1 and 4 wt %. 
     
     
         12 . Process according to  claim 1 , wherein the production of furfural occurs under acidic conditions. 
     
     
         13 . Process according to  claim 12 , wherein at least one acidic material is present in the said liquid downflow. 
     
     
         14 . Process according to  claim 13  wherein the acidic material is sulphuric acid, phosphoric acid or hydrochloric acid. 
     
     
         15 . Process according to  claim 12 , wherein the distillation column contains a solid acid, optionally on packing material, or trays in the distillation column. 
     
     
         16 . Process according to  claim 12 , wherein the liquid additionally contains at least one salt. 
     
     
         17 . Process according to  claim 16 , wherein the salt is an alkali, earth alkaline or ammonium halide.