Multi-ligand metal complexes and methods of using same to perform oxidative catalytic pretreatment of lignocellulosic biomass

Abstract

A homogeneous catalyst is provided comprising one or more metals; and at least two metal coordinating ligands wherein the homogeneous catalyst is a multi-ligand metal complex_adapted for use with an oxidant in an oxidation reaction to catalytically pretreat lignocellulosic biomass. In one embodiment, the homogenous catalyst is copper (II) 2,2′ bipyridine ethylenediamine (Cu(bpy)en). Related methods are also disclosed.

What is claimed is: 
     
         1 . A homogeneous catalyst comprising:
 one or more metals; and   at least two metal coordinating ligands, wherein the homogeneous catalyst is a multi-ligand metal complex adapted for use with an oxidant in an oxidation reaction to catalytically pretreat lignocellulosic biomass.   
     
     
         2 . The homogeneous catalyst of  claim 1  wherein the multi-ligand metal complex is a multi-ligand copper complex. 
     
     
         3 . The homogeneous catalyst of  claim 2  wherein said metals capable of interacting with the multi-ligand metal complex are selected from aluminum, zinc, nickel, magnesium and combinations thereof. 
     
     
         4 . The homogenous catalyst of  claim 3  wherein said metals are selected from Fe(II), Fe(III)), Cu(I), Cu(II), Co(III), Co(VI)), V(II), V(III), V(IV), V(V) and combinations thereof. 
     
     
         5 . The homogeneous catalyst of  claim 1  wherein the metal coordinating ligand is selected from pyridine, 1,10-phenanthroline, ethylenediamene, histidine, glycine and combinations thereof. 
     
     
         6 . The homogeneous catalyst of  claim 1  comprising copper (II) 2,2′ bipyridine ethylenediamine (Cu(bpy)en). 
     
     
         7 . The homogeneous catalyst of  claim 1  wherein the oxidant is selected from air, oxygen, hydrogen peroxide, persulfate, percarbonate and sodium peroxide and/or ozone. 
     
     
         8 . The homogenous catalyst of  claim 1  wherein the lignocellulosic biomass contains more than trace amounts of at least one transition metal. 
     
     
         9 . The homogenous catalyst of  claim 8  wherein the transition metal is selected from iron, cupper and/or manganese. 
     
     
         10 . The homogenous catalyst of  claim 1  wherein said metals and said metal coordinating ligands are in a state of interaction with each other. 
     
     
         11 . A method of pretreating plant biomass comprising catalytically pretreating the plant biomass with a multi-ligand metal complex and oxidant in an alkaline oxidative pretreatment to produce a catalytically pretreated plant biomass. 
     
     
         12 . The method of  claim 11  wherein the plant biomass, the multi-ligand metal complex and the oxidant form a solution having a pH of at least 11.5. 
     
     
         13 . The method of  claim 12  wherein the oxidant is hydrogen peroxide and the multi-ligand metal complex is a multi-ligand copper complex. 
     
     
         14 . The method of  claim 13  wherein the copper complex is a copper(II) 2,2′-bipyridine complex (Cu(bpy)) modified to contain at least one additional metal-coordinating ligand. 
     
     
         15 . The method of  claim 14  wherein said additional metal coordinating ligand is ethylenediamine. 
     
     
         16 . The method of  claim 11  wherein the oxidant is added at a gradual rate. 
     
     
         17 . The method of  claim 16  wherein the gradual rate is equal to or less than a rate of consumption of the oxidant by the plant biomass and the multi-ligand metal complex. 
     
     
         18 . The method of  claim 11  wherein the method further comprises extracting the lignocellulosic biomass prior to produce a solids fraction and a liquid fraction, wherein the solids fraction is catalytically pretreated. 
     
     
         19 . The method of  claim 11  wherein the method further comprises recovering and reusing the multi ligand metal complex. 
     
     
         20 . The method of  claim 11  wherein the catalytic pretreating step also produces a liquid phase and the method further comprises:
 separating the catalytically pretreated biomass from the liquid phase to produce separated catalytically pretreated biomass; and 
 hydrolyzing the separated catalytically pretreated biomass to produce hydrolyzed catalytically pretreated biomass.