Catalyst structure-based hydroxymethylfurfural (HMF) hydrogenation mechanisms, activity and selectivity over Ni

Catalytic hydrodeoxygenation of hydroxymethylfurfural was investigated in a three-phase batch reactor over a range of reaction temperatures (170?230 ?C), under 5 MPa of hydrogen, and tetrahydrofuran solvent. Nickelbased carbon-supported catalysts were also promoted by lanthanum and niobium, despite promoters alone demonstrated no activity. Based on experimentally-obtained liquid products, a reaction pathway was proposed and a microkinetic model was established, by considering adsorption, desorption and surface reaction kinetics, mass transfer and thermodynamics. An unpromoted Ni/C resulted in primarily unsaturated furan diol, a highly desirable intermediate in the polymer industry. As reaction temperatures increased > 200 ?C, dehydration yielded deoxygenated products suitable for solvents and biofuel. In spite of enhancements to reducibility, Lapromotion significantly decreased both hydrogenation (8-times) and deoxygenation (25-times) rate constants. Alternatively, Nb-incorporation offered additional acidity, while lower activation energies resulted in 200% higher deoxygenation rates via dehydration reactions and humin formation at lower temperatures. It exhibited the highest deoxygenation activity.

Automated summary

The catalytic hydrodeoxygenation of hydroxymethylfurfural was studied over a range of temperatures with nickel-based carbon-supported catalysts, promoted by lanthanum and niobium. The presence of promoters significantly altered both the reaction products and rate constants, showing the importance of catalyst composition in determining reaction outcomes. Lanthanum promotion decreased hydrogenation and deoxygenation rates, while niobium incorporation led to higher deoxygenation rates and the formation of humins at lower temperatures.