No abstract

No abstract

No abstract

J o s i M. P~z o s and PAULINO ANDREU. Can. J. Chem. 58.479 (1980). The hydrodesulphurization mechanism of thiophene and tetrahydrothiophene has been developed at high pressures and over a broad range of temperature and contact time on a commercial CoMo-A1203 catalyst. The influence of the pretreatment on the catalyst activity and stability was also studied. The pretreatment with a mixture of H, and H2S was found to be the most convenient. It was found that the sulphur uptake of the fresh catalyst increases with temperature and that an excess of sulphur in the catalyst leads to an initial higher activity.The thiophene reaction seems to occur simultaneously by two pathways: one consists of ring opening, and the second is yielding tetrahydrothiophene. The latter is the slowest step. The tetrahydrothiophene reacts faster than the thiophene and its reaction mechanism involves mainly the rupture of the C-S bond. However, thiophene was detected in small concentrations, showing the contribution of a second route for the tetrahydrothiophene hydrodesulphurization. Experiments carried out with benzene seem to indicate the existence of three different kinds of active sites in the catalyst: desulphurization, aromatics hydrogenation, and olefin saturation sites.J o s i M. PAZOS et PAULINO AKDREU. Can. J. Chem. 58,479(1980). On a elabore le mecanisme d'hydrodesulfurisation du thiophene et du tetrahydrothiophkne a haute pression et sur une large echelle de temperature et de temps de contact avec une catalyseur commercial mixte: CoMo-Al,03. On a egalement etudie la stabilite ainsi que I'influence d'un traiternent prealable sur l'activite du catalyseur. On a trouve que le traitement prealable, par un melange de H, et de H2S, est celui qui convient le mieux. On a constate que la fixation de soufre sur le catalyseurfrais augmente avec la temperature et que l'exces de soufre sur le catalyseur conduit a une activite initiale plus forte.La reaction du thiophene semble se produire suivant deux voies: l'une consiste en une ouverture du cycle. et l'autre conduit au tetrahydrothiophene. La derniere voie est l'etape la plus lente. Le tetrahydrothiophene reagit plus vite que ie thiophene et le mecanisme de sareaction implique principalement la rupture de la liaison C-S. Cependant on adecele de faibles concentrations de thiophene indiq~rant parlal'existence d'une deuxieme fagon d'hydrodesulfuriser le tetrahydrothiophene. Les experiences conduites dans le benzene semblent indiquer l'existence de trois differentes sortes de sites actifs sur le catalyseur: un site de desulfurisation un d'hydrogenation aromatique et un de saturation des olefines.[Traduit par le journal] Introduction other hand, the mechanisms proposed are generally Numerous sulphur compounds have been used valid only at conditions far from those used industo study different aspects of the hydrodesul-trially. Therefore, in this work we studied the phurization of crude oil distillates. As the greater mechanism of thio~hene h~drOdesul~hurization part of the sulphur in the crude is...