Comparison of alumina supports and catalytic activity of CoMoP/γ-Al2O3 hydrotreating catalysts obtained using flash calcination of gibbsite and precipitation method

Abstract

Abstract The influence of alumina precursors on catalytic activity CoMoP/Al2O3 hydrotreating catalysts has been studied. Alumina precursors were prepared by eco-friendly technology including hydrothermal treatment at different stabilization time of a flash calcined gibbsite. One sample was synthesized with the addition of boric acid. A reference sample of pseudoboehmite was obtained by precipitation from aluminum nitrate with aqueous ammonia. Alumina precursors, supports and catalysts were studied by XRD, nitrogen adsorption/desorption, XPS, HRTEM. CoMoP/Al2O3 catalysts were tested in hydrotreating of model feed and fuel mixture. It is shown that the samples obtained from the product of flash calcination of gibbsite, besides pseudoboehmite, also include the amorphous phase, while the reference sample, synthesized by precipitation, is a pure pseudoboehmite. The introduction of boron prevents the crystallization of pseudoboehmite. Textural properties of the catalysts depend of initial support: alumina samples prepared by hydrothermal treatment have a bimodal pore distribution with peaks at 60–70 A and 150–200 A, the support synthesized through reprecipitation has a unimodal distribution with a maximum at 80 A. The initial alumina used as a catalyst support has a significant impact on the share of CoMoS phase of type II. The highest activities in the hydrotreating of model feed (dibenzothiophene, quinoline and naphthalene in undecane) and fuel mixture shown catalyst prepared using hydrothermal treatment of flash calcined gibbsite without addition boric acid and with short stabilization time.