Comparative study of hydrogenolysis of a C-X bond in three homologous heterocyclic compounds of chemical formula C_5H_(10)X with X = S, O and NH

摘要

A theoretical study of hydrogenolysis of a C-X bond of 2-methyltetrahydrothiophene (2-MTHT), 2-methyltetrahydrofuran (2-MTHF) and 2-methylpyrrolidine (2-MP) molecules, over molybdenum disulfide (MoS_2) and tungsten disulfide (WS_2) has been performed by MP2 calculations in the Lanl2DZ basis set. Both catalysts were modeled by catalytic sites with three anionic vacancies MoS_3H_3~+ and WS_3H_3~+ respectively. The temperature and pressure conditions respected in the study are respectively 573 K and 70 atm. The obtained results shown that, the Hydrogenolysis of a C-X bond of methyled carbon of 2-MTHT and 2-MTHF molecules led to the formation of 1-pentanethiol and 1-pentanol adsorbed over the each catalyst. On the other hand, in the case of the 2-MP molecule, the catalytic site was implicated in the reaction with formation of hydrogen sulfide (H_2S). The Hydrogenolysis activation energies of various transformations were variable from MoS_2 to WS_2 catalysts except for 2-MTHT. In presence of a same kind of catalyst, the activation energies of Hydrogenolysis of the C-X bond (methyled carbon atom) of 2-MTHF and 2-MTHT increase in the order X = O, S.