Modelling of transport, adsorption and surface reaction kinetics on Ni, Pd and Ru metallic/acidic catalyst sites during hydrodeoxygenation of furfural

The furfural hydro-treatment process over Ni/Al2O3, Ni/SiO2, Pd/Al2O3, Pd/SiO2, Ru/Al2O3 and Ru/SiO2 was investigated in a three-phase batch reactor operation at 150 °C, 175 °C and 200 °C, 60 barg hydrogen and tetrahydrofuran as solvent. The strength and rate of adsorption and desorption to/from acidic, metallic and interface site structures were determined, using H2 temperature-programmed reduction (H2-TPR), CO (CO-TPD) and NH3 (NH3-TPD) desorption experiments, and subsequent regression analysis of the results by numerical modelling and optimisation. To quantify the contribution of transport, active metal materials and support effect relationship, a generalized micro-kinetic model was postulated, which has been shown to describe experimental result outcomes well. Mechanistic description and regression analysis were applied to evaluate the role of the support (Al2O3 or SiO2) on the catalytic element (Ni, Pd or Ru) atoms, their energy impact on the individual steps and selectivity. Evaluation of morphological and structural characteristics, and sorption or intrinsic reaction kinetics has indicated that the coverage of acidic sites (on alumina or silica) facilitated yielding ring hydrogenation, inhibited deoxygenation, decarbonylation and cyclic compound opening, and supressed etherification. The rates for aromatics or aldehyde functional groups were, nonetheless, affected in a different order. Understanding the chemistry of bio-based furanic derivatives mechanistically is vital and can improve the process of their conversion into of mono- or di-alcohols.