Hydrodeoxygenation and hydrodenitrogenation of n-hexadecanamide over Pt catalysts: effect of the support

Abstract

Efficient catalysts for simultaneous hydrodeoxygenation (HDO) and hydrodenitrogenation (HDN) are needed for the production of renewable fuels. In this study, Pt catalysts supported on SiO₂, γ-Al₂O₃, SiO₂–Al₂O₃, ZrO₂, CeO₂–ZrO₂, Nb₂O₅, and TiO₂ were studied for the hydrotreatment of n-hexadecanamide (C16 amide) to n-paraffins at 300 °C and 80 bar H₂. The catalysts favored HDO over HDN, and the initial differences in the nitrogen removal level were smaller than the differences in the oxygen removal level. The Lewis acid properties of the support influenced the initial C16 amide conversion route and HDO activity, which was reflected in the reaction network and condensation reaction selectivity of the catalysts. Pt/Nb₂O₅ and Pt/TiO₂, with intermediate strength Lewis acid sites, initially favored the HDO of C16 amide to nitrogen-containing compounds. In contrast, the other catalysts converted C16 amide to oxygen- and nitrogen-containing compounds with similar selectivity. The HDO of the oxygen-containing compounds proceeded more efficiently on the Pt catalysts supported on oxides with weak Lewis acid sites (Pt/ZrO₂, Pt/CeO₂–ZrO₂) than on the irreducible oxides with strong or no Lewis acid sites (Pt/γ-Al₂O₃, Pt/SiO₂–Al₂O₃, Pt/SiO₂). As the presence of oxygen-containing compounds suppressed HDN activity, the catalysts with the highest HDO activity eventually gave the highest paraffin yield, regardless of which oxygen removal pathway was favored.