Lignin depolymerization over porous copper-based mixed-oxide catalysts in supercritical ethanol

This Chapter explains the roles of the catalyst and solvent. In lignin depolymerization by CuMgAl mixed-oxide catalysts, the use of supercritical ethanol as a solvent was found to be significantly more effective in producing monomers and avoiding heavy lignin residue and char formation than using methanol. The effect of reaction temperature and time are evaluated during depolymerization of lignin. Without catalyst and with increasing the reaction temperature, both the yield of lignin monomers and char are increased, the yield of light lignin residue decreased. However, without catalyst the reaction is dominated by char-forming reactions. The chapter describes the effect of catalyst composition in the depolymerization of soda lignin in supercritical ethanol. The higher the basicity of the catalyst, the higher the amount of alcohols and esters formed via Guerbet-type and esterification reactions, and the less repolymerized products are formed.