Hydrodesulfurization of catalytic cracked gasoline -: Selective catalytic cracked gasoline hydrodesulfurization using Co-Mo/γ-Al2O3 catalyst modified by pyridine

The effects of pyridine modification on the catalyst activity and selectivity of Co-Mo/gamma -Al2O3 were investigated in thiophene hydrodesulfurization (HDS) and olefin hydrogenation (PIG). Pyridine injection into the reactant flow caused strong inhibition of thiophene HDS, diisobutylene HG and 1-octene HG reactions on Co-Mo/gamma Al2O3 at 150 degreesC. Inhibition of thiophene HDS was totally recovered after the temperature was raised to 300 degreesC for a while. However, inhibition of diisobutylene and 1-octene HG persisted after the same temperature rise. The possibility of improving the HDS selectivity (higher activity for HDS and lower activity for olefin HG) by pyridine modification (i.e. pyridine injection at 150 degreesC and partial pyridine desorption at 300 degreesC) was investigated for HDS reactions of model gasolines and catalytic cracked gasoline (CCG). Thiophene HDS was little affected, but benzothiophene HDS was slightly inhibited. Olefin HG and thiol production reaction were strongly inhibited. Improvement of HDS selectivity was observed in the reactions of model gasolines and CCG after pyridine modification. The fall in octane value became smaller. Improvement of HDS selectivity by pyridine modification was considered to result from the selective deactivation of the active sites for olefin reactions (HG and thiol production).