Hydrothermal depolymerization of alkali lignin to high-yield monomers over nickel nitrate modified commercial hydrotalcites catalyst

Abstract The depolymerization of alkali lignin was investigated over several nitrate modified commercially hydrotalcites catalysts via hydrothermal depolymerization strategy in this study. The obtained results demonstrated that nickel nitrate modified hydrotalcites (HTCs) exhibits excellent catalytic performance to dissociation of C–C and C–O bonds linkage of alkali lignin to yield aromatics. The bio-oil yield increased to 87.9% with 5%Ni-rhHTCs as catalysts from 65.3% with rhHTCs as catalysts, and guaiacol and guaiacol derivatives were found to be the main composition and the highest monomers yield of 35.2 wt% was achieved. It was also found that the characteristic structure of HTCs was restored during rehydration and the structure of rhHTCs was not changed during the preparation of catalyst, but the basic site tensity and distribution are evidently influenced by the loaded metal nitrate and thus promised the excellent catalytic performance of the modified catalyst.