Crude levulinic acid conversion to valeric acid over La–TiO2 supported Ni catalysts: an environmentally friendly route to fuel additive synthesis

Abstract

Transformation of biomass into energy or other valuable products is a sustainable route. This study encompasses the single step synthesis of valeric acid by hydrodeoxygenation of biomass derived crude levulinic acid using formic acid as a hydrogen source over different loadings of lanthanum modified TiO₂-supported Ni catalysts. Modification with La resulted in a comparatively low ratio of acid sites on the catalyst surface. Formic acid adsorbed IR studies revealed that 10 wt%Ni/3 wt%La–TiO₂ displayed a high proportion of surface basic sites, which were responsible for the high rate of valeric acid (∼56 × 10⁻⁸ mol g_cat⁻¹ s⁻¹) with a stable activity up to 48 h. Pyridine and acetone adsorbed IR results indicated an increase in the La loading from 1 to 5 wt% on TiO₂ and a decrease in the Lewis and Brønsted acidic sites and carbonyl interactions with the catalyst, respectively. Considering the probe (HCOOH, acetone, pyridine) adsorbed IR spectroscopic results, levulinic acid conversion and the product distribution, a plausible surface reaction mechanism has been proposed.