Catalysts for Depolymerization of Biomass
Solid acid catalysts with their advantages such as easy separation, reusability, and high activity have great potentialities in the efficient depolymerization of lignocellulose to valuable chemicals. This Chapter is an overview of the main types of solid acid catalysts for biomass depolymerization. Under consideration are ion-exchange resins, carbons, zeolites, oxides, and heteropoly acids. The main focus is on transformations of polysaccharides (cellulose and hemicelluloses). The carbon catalysts and ion-exchange resins seem to be the most promising catalysts for the depolymerization. They provide the highest yields of monomer products from plant polymers. On the other hand, zeolites and some oxides are extremely stable and applicable under very severe conditions. Some aspects of the mechanism of interaction between the solid lignocellulose substrate and solid acid catalysts are discussed. Efficient transformation of lignocellulose components is shown to need some preactivation procedures. The main types of auxiliary physical and chemical methods for pretreatment of lignocellulose to partly destroy the structure and separate the components of lignocellulose are considered.