Hf-SBA-15 supported heteropolyacid: An efficient catalyst for one-pot production of γ-valerolactone from furfural

Developing conversion routes from lignocellulosic platform compounds to high-value chemicals is fundamental to advancing sustainable resource utilization in the bioeconomy. In this study, we designed a series of SBA-15-supported bifunctional catalysts with precisely tunable Lewis acid sites (LAS), Brønsted acid sites (BAS), and basic sites through strategic incorporation of hafnium species and heteropolyacids (HPAs), demonstrating their exceptional performance in the multi-step tandem conversion of furfural (FUR) to γ-valerolactone (GVL). HfO 2 was used LAS and basic sites to catalyze the transfer hydrogenation reaction of FUR and levulinate ester using 2-propanol as the H-donor. Complementary to this, HPA could catalyze the hydrolytic ring-opening of furans. The amount of LAS, BAS, and basic sites was adjusted by changing the ratio of HPA to HfO 2 and the types of HPA (phosphotungstic acid (HPW), phosphomolybdic acid (HPMo), silicotungstic acid (HSiW) and silicomolybdic acid (HSiMo)). The ratio of HPA to HfO 2 and types of HPA have a great influence on the catalytic performance, among which HPW/Hf-SBA-15_0.37 (W/Hf = 0.37) was identified as the best catalyst and presented the highest GVL selectivity (73.5 %) under optimized reaction conditions. The poison experiment (addition of benzoic acid, pyridine, or 2,6-lutidine to the reaction) indicated that both acidic and basic sites play important role in the FUR to GVL reaction. Moreover, by correlating the catalyst performance with the BAS/LAS ratio of catalysts, it can be found that the balance between the BAS and LAS is also the key to higher GVL selectivity.