Vanillin hydrodeoxygenation kinetics on takovite derived NiAlOx mixed oxides

Abstract

Vanillin, a representative moiety of lignin, having three different oxygenated groups, was used as a model molecule on catalytic hydrodeoxygenation (HDO). The transformation of vanillin was carried out at in a batch reactor at 413–573 K, 1.2 MPa of H2 and using a takovite-derived, reduced NiAlOx mixed oxide. The concentration of the reaction products, as well as vanillin conversion, was measured by gas-chromatography. After identifying the products, a reaction network scheme was proposed in order to calculate the reaction rates by assuming a pseudo-first order. Then, from an ordinary differential equations system for each species of each reaction network, the concentration value evolution was calculated using Runge Kutta- Butcher 5th order method. For each concentration experimental data in the reaction mixture a minimum-square adjustment with Levenberg-Marquardt minimization was used. The experimental data were fitted by a FORTRAN (“mIKC”) code, which numerically solved the differential equations system until obtaining the ones in this work. A very good fitting between experimental data and the calculated ones using the proposed reaction rate equations validated the reaction scheme. Reaction temperature plays a crucial role when aiming to obtain fully deoxygenated products, e.g. hydrocarbons like cyclohexane and methyl cyclohexane, 553 K being the ideal one.