Reductive Catalytic Fractionation of Lignocellulose over Ni/Al2O3 Catalyst Prepared by an EDTA-Assisted Impregnation Method

A new type of Ni-EDTA/Al2O3 catalyst was prepared by effectively anchoring Ni(EDTA)2– complex anions to the surface of the positively charged mesoporous alumina support. The crystal structure and texture properties of the catalysts were characterized by TGA, XRD, XPS, TPR, and BET techniques. In the lignocellulose reductive catalytic fractionation process using poplar wood as feedstock, the highest total monomer yield of 34.5% was achieved on the Ni-EDTA/Al2O3 catalyst, while it was only 25.9% on the Ni/Al2O3 catalyst prepared by the conventional impregnation method. The promotion effect of EDTA chelate over Ni-EDTA/Al2O3 catalyst in valorizing lignin components into low-molecular-weight phenolic products can be attributed to two aspects. First, the chelation of metal ions with EDTA ligand can facilitate the high dispersion of nickel metal nanoparticles on the support surface. Second, under the protection of the carbon layer surrounding the surface, the agglomeration of the nickel particles can be effectively inhibited.