Efficient Utilization of Biomass Hydrolysis Residues in Preparing a Metal/Acid Bifunctional Catalyst for Butyl Levulinate Hydrogenation to γ-Valerolactone

Abstract

The comprehensive utilization of whole components of biomass is an important strategy for improving the economics of biomass energy. In this work, three kinds of acid hydrolysis residues (AHRs) derived from different lignocellulosic biomass, including sugarcane bagasse (SB), cornstalk (CS), and wheat straw (WS), were used to prepare carbon-based solid acid (CBSA) through pyrolysis and further sulfonation. Results showed that AHR-SB, which has high carbon content, is the best choice to graft −SO 3 H groups for preparing CBSA with the highest yield. Then, the 20Sn1RuB/CBSA-SB bifunctional catalyst was synthesized through the progressive impregnation and chemical reduction method and applied to synthesize γ-valerolactone (GVL) from butyl levulinate (BL) hydrogenation. Under optimal reaction conditions (180 °C, 3 MPa H 2 , 3 h), the fresh catalyst showed a BL conversion of 99.6% and a GVL yield of 87.7%. According to the characterization results of CBSA and 20Sn1RuB/CBSA-SB by NH 3 -TPD, pyridine adsorption Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), the SnRuB hydrogenation active site was partially reduced into Sn 0 species, and the number of surface acidic sites of the catalyst was decreased relative to that of the CBSA-SB support, whereas a stronger synergetic effect was present for BL hydrogenation to GVL. The catalyst also showed outstanding recyclability, on which the BL conversion loss was only 3.5%, and the GVL yield remained almost unchanged after six cycles. The increased oxygen vacancies and the synergistic effect between the SnRuB active site with a suitable atomic fraction and more Brønsted acid sites promoted activity recovery. In summary, the biomass hydrolysis residue is a promising feedstock for realizing its high value-added application in converting biomass-derived platform molecules into fuel or chemicals.