Kinetic models for hydroconversion of furfural over the ecofriendly Cu-MgO catalyst: An experimental and theoretical study

Abstract

For the first time, the Eley–Rideal mechanism and different forms of Langmuir–Hinshelwood mechanism were modeled by including the contributions of the reactants and product in a wide range of furfural concentrations to present kinetic models of furfural hydrogenation over the co-precipitated chromium-free copper-magnesia catalyst. Among the appropriate models, the ones which explained a dissociative reaction of hydrogen either in one step or two steps on the same sites as that of furfural proved the best goodness of fit to the experimental data. The dependencies of the reaction rate on transport limitations were examined by the relevant criteria. The results also correlated well with a power-law kinetic model in which the reaction order with respect to furfural was almost zero. An activation energy of 6.1kcal/mol was obtained, pointing to relatively facile reaction events over this catalyst. A Sips (Langmuir–Freundlich) model satisfactorily described the effect of space velocity on the fractional conversion. The density functional theory (DFT) calculations at B3LYP/6-31+G* revealed a doubly favorable adsorption of furfural relative to furfuryl alcohol. The theoretical results favored the formation of an alkoxide intermediate in the dominant mechanisms rather than of a hydroxyalkyl counterpart.