Catalytic desulphurization of benzothiophene in an emulsion via in situ generated H2 Original Research Article

Catalytic desulphurization of benzothiophene (BTH) in a water/toluene emulsion, a model system for heavy oil emulsions, was achieved at 340°C using a water-soluble phosphomolybdic acid (PMA), a precursor for dispersed Mo catalyst. This process is based on the activation of H2O to generate H2 in situ via the water gas shift reaction (WGSR) for hydrodesulphurization (HDS). At 340°C with an initial CO loading of 4.14 MPa, essentially complete sulphur removal was obtained. Kinetic expressions for the WGSR and HDS of BTH with in situ generated H2 and externally supplied H2 were developed and verified experimentally. The kinetic analysis indicates that WGSR is rate-determining and desulphurization with in situ generated H2 is a relatively fast step. Apparently, in situ H2 is about seven times more active than externally supplied H2 for the hydrogenation of BTH. A mechanism for desulphurization involving initial hydrogenation of BTH to dihydrobenzothiophene (DHBTH) followed by hydrogenolysis to give ethylbenzene (EB) and H2S is proposed.