Influence of Cobalt Content on the Hydrotreatment Catalytic Activity of CoMo 6 / -Al 2 O 3 Heteropolyoxomolybdate-Based Catalyst

Abstract

The influence of Co content in the catalytic activity in hydrotreatment reactions (hydrodesulfurization (HDS) of thiophene and hydrogenation (HYD) of cyclohexene) using CoMo6/γ-Al2O3-type catalysts, where the precursor is Co(III) heteropolymolybdate of (NH4)3[CoMo6O24H6⋅7H2O formula and Anderson-type planar structure, (hereafter CoMo6) was investigated. The preparation of catalysts was carried out by the coimpregnation of γ-alumina with CoMo6 and (NH4)6[TeMo6O24]⋅]7H2O (TeMo6) in order to obtain catalysts with variable amounts of Co(III) keeping about the same Mo amount. The Anderson phase of Te(VI), (TeMo6) was chosen because of its good solubility and because no promoting effect of the Te was observed in hydrotreatment. Five catalysts were prepared by coimpregnation of γ-Al2O3 by using aqueous solutions of both phases in different proportions. Catalysts with a ratio [Co]/([Co] + [Mo]) between 0 and ∼0.14 and a Mo loading (wt% Mo) between 8 and 10 were obtained. The Raman and diffuse reflectance (DR) spectroscopies were used for the characterization of bulk and supported CoMo6 phase. By analyzing the respective adsorption isotherms and parameters and according to the catalytic tests, it could be established that HDS as well as HYD activities of the catalysts increase as a function of the added Co.