Catalytic hydrogenation of stearic acid over reduced NiMo catalysts: Structure–activity relationship and effect of the hydrogen-donor

Abstract

Reduced NiMo catalysts were prepared by loading NiMo elements on a γ-Al2O3-β-zeolite composite support, followed by reduction with hydrogen at temperatures in the range of 400–600°C. The hydrogenation activities were investigated through treatment of stearic acid (SA), and were compared with those obtained with the composite support and the oxidized NiMo catalyst (Cox). In the tested reduction temperature range, the catalyst reduced at 450°C (T450) achieved the highest conversion (close to 100%) and C18 hydrocarbon selectivity (58.0%), which were much higher than the results obtained over the composite support and Cox. Reduction treatment contributed to production of more reducible metal species and improvement of the dispersity of metal active sites, consequently leading to high hydrodeoxygenation activity. Furthermore, the effects of H2 pressure and the hydrogen-donor (tetralin) on the catalytic activity of T450 were investigated. Higher H2 pressures promoted SA conversion and C18 selectivity. In contrast with dodecane as a solvent, tetralin significantly promoted the formation of C18 in a H2 atmosphere, but improved the production of C17 and suppressed the formation of lighter hydrocarbons (≤C16) in a N2 atmosphere. This is associated with the hydrogen-donating activity of tetralin.