Poisoning of the HDS of dibenzothiophene and 4,6-dimethyldibenzothiophene by N-containing molecules

摘要

We studied the influence of 2-methylpyridine (2-MPy) and 2-methylpiperidine (2-MPiper) on the hydrodesulfurisation (HDS) of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) over a sulfided NiMo/Al_2O_3 catalyst at 5 MPa total pressure and 340°C. DBT and its substituted molecules undergo HDS via two different pathways: direct desulfurization (DDS) leading to the formation of biphenyl and hydrogenation (HYD) to tetrahydrodibenzothiophene followed by desulfurizaion to cyclohexylbenzene. N-containing molecules have an inhibitory influence on the active sites responsible for the DDS of the S-compound and on the active sites promoting the HYD pathway. The HYD route of the transformation of S-containing molecules is affected much stronger by the presence of 2-MPy and 2-Mpiper, whereas the DDS is inhibited by N-containing molecules to a smaller extent. DBT and 4,6-DMDBT, in turn, have an inhibitory influence on (de)hydrogenation reactions taking part in the HDN of 2-Mpy, but no effect on the C-N bond cleavage.