Experimental proof of thiophene hydrodesulfurization reaction steps by isotope (14C) labeled thiophene

Hydrodesulfurization of thiophene has been studied over alumina supported sulfided molybdena, nickel-promoted molybdena and over nickel (Mo, NiMo and Ni) catalysts. The experiments were carried out with a mixture of thiophene, labeled with radioactive carbon (thiophene-[G-]-14C) and of non-radioactive tetrahydrothiophene (1:1 mol ratio) in a micro catalytic system. It was established, that the main products were tetrahydrothiophene-14C, 1-butene-14C, 2-butene-14C, butane-14C. Tetrahydrothiophene-14C was a major intermediate in the conversion of thiophene—14C in the experimental condition applied. The amounts of converted tetrahydrothiophene on the catalysts were substantially higher than those of thiophene under the same conditions. Hydrothiophene and dihydrothiophene—14C were intermediate products in the hydrodesulfurization of thiophene and tetrahydrothiophene. The hydrodesulphurization of tetrahydrothiophene was paired with dehydrogenation, producing small amounts of thiophene. The experimental results have been considered in the discussion of the mechanism of thiophene and tetrahydrothiophene desulfurization reaction pathway.

Sulfur uptake determination on Ni containing molybdena-alumina samples by radioisotope tracer technique

Five solid oxides, used as hydrodesulfurization catalysts (Al(2)O(3) supported Ni, MoO(x), Ni-MoO(x)-s of different Ni:Mo ratio) were sulfided by [(35)S]H(2)S. Amounts of the total, reversible and irreversible sulfur uptakes were determined measuring the change of gas phase radioactivity during exposure [(35)S]H(2)S to the oxides, and compared with the amounts determined measuring radioactivity of the sulfided samples. The S/(Ni+Mo) values determined by X-ray photoelectron spectroscopy (XPS) were in satisfactory agreement with the results obtained by radiosulfur. Significantly different sulfur uptakes were observed for the different samples.