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

Abstract

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.

Hydrodesulfurization of Thiophene in n-Heptane Stream Using CoMo/SBA-15 and CoMo/AlSBA-15 Mesoporous Catalysts

“…In hydrodesulfurization reactions, MoO 3 and CoMoO 4 species can, during the HDS and sulfidation steps, transform into the MoS 2 and "CoMoS" phases, which are active and stable for the reaction. The presence of Co 3 O 4 can give rise to Co 9 S 8 , a phase that is very inactive for HDS catalysts but can also be reduced to metallic cobalt, which, properly accommodated at the ends of MoS 2 crystals, gives rise to active phases, known as "CoMoS" [67][68][69]. Before starting the catalytic tests for hydrodesulfurization of thiophene, some preliminary tests were carried out with the aim of verifying the occurrence of thermal cracking reactions under the operating conditions of the tests.…”