Impact of hafnium dioxide morphology on catalytic transfer hydrogenation of methyl levulinate to γ-valerolactone: A comparative study

Abstract

Background

The catalytic transfer hydrogenation (CTH) of methyl levulinate (ML) to γ-valerolactone (GVL) is a promising method for producing renewable fuels and chemicals. The efficiency of this process depends heavily on the choice of catalysts, with morphology playing a critical role in their performance.

Methods

This study synthesized and characterized rice-like (r-HfO₂) and ball-like (b-HfO₂) hafnium oxide nanostructures. r-HfO₂ was prepared using a microwave system, while b-HfO₂ was synthesized via a solvothermal method. The catalysts were characterized using SEM, TEM, XRD, TPD-NH₃ analysis, and nitrogen sorption isotherms to determine their morphological, structural, and acidic properties. The catalytic performance of these nanostructures was tested under optimal conditions of 160 °C and 2 h in a batch-type solvothermal reactor.

Significant Findings

The results showed that b-HfO₂ exhibited a conversion efficiency of 90 % and a GVL yield of 90 %, outperforming r-HfO₂, which achieved 94.8 % conversion and 75.2 % yield. Recyclability tests confirmed the durability of both catalysts, with b-HfO₂ maintaining better activity. Detailed analyses revealed that b-HfO₂ exhibits superior catalytic activity and energy efficiency, achieving higher GVL yield and better energy efficiency. The conversion rates reached up to 100 % for both catalysts at 200 °C, with b-HfO₂ achieving a higher GVL yield and better energy efficiency. These findings demonstrate the potential of HfO₂-based catalysts, especially b-HfO₂, in efficiently converting biomass-derived feedstocks to valuable chemicals.