Inhibiting effects of nitrogen compounds on deep hydrodesulfurization of straight-run gas oil over a NiW/Al2O3 catalyst

- Quinoline had stronger inhibiting effects on the HDS of the straight run gas oil than that of indole.
- HDS of simple structure sulfur compounds have not or slightly been inhibited by the increment of N/S ratios.
- Nitrogen inhibition effects on the HDS of thiophene series sulfur compounds decreased as: 4,6-DMDBT > 4-MDBT > C1DBT > DBT > C2-C3DBT.

The inhibiting effects of nitrogen compounds on the hydrodesulfurization (HDS) of thiophene-series sulfur compounds in straight-run gas oil over a NiW/Al2O3 catalyst were studied. The nitrogen compounds investigated here were quinoline and indole; nitrogen to sulfur mass ratios (N/S) varying from 0.9 to 1.2 were comparably studied. The results showed that quinoline was much easier to be converted but harder to be denitrogenated as compared with indole. Quinoline displayed stronger inhibiting effects on the HDS of individual sulfur compounds in the gas oil than that of indole. Langmuir-Hinshelwood type rate equations were used to compare the nitrogen inhibiting effects. The nitrogen inhibiting effects on these thiophene series sulfur compounds decreased in the order 4,6-DMDBT(4,6-dimethyl-dibenzothiophene) > 4-MDBT > C1DBT > DBT > C2-C3DBT. The HDS of C2-C3DBT group with relative substituents at different 4 and 6 positions got the lowest nitrogen inhibiting effects due to their better approach abilities to the catalyst.

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