Methods of using multi-ligand metal complexes to perform oxidative catalytic pretreatment of lignocellulosic biomass

A method comprising:

• catalytically delignifying alkaline-pretreated lignocellulosic biomass having a lignin glass transition temperature by combining the biomass with a homogeneous multi-ligand metal complex catalyst and hydrogen peroxide in an oxidation reaction performed at atmospheric pressure and at a temperature below the lignin glass transition temperature, wherein the hydrogen peroxide is added at a rate equal to or less than a rate of consumption of the hydrogen peroxide by said biomass and the complex catalyst, further wherein a weight ratio of the hydrogen peroxide to biomass loading is less than 15% and said metal complex catalyst comprises a combination of a metal-ligand complex and at least one metal coordinating ligand selected from pyridine, 1,10-phenanthroline, ethylenediamene, histidine, glycine and combinations thereof, wherein said biomass, the multi-ligand complex catalyst and the hydrogen peroxide form a solution having a pH of at least 11, and radicals formed during the oxidation reaction react with lignin present in the alkaline-pretreated lignocellulosic biomass to solubilize the lignin to produce catalytically delignified lignocellulosic biomass, wherein the multi-ligand metal complex catalyst is a multi-ligand copper complex catalyst.