Catalytic activities and product selectivities of noble metal-supported ZSM-5 hydrodesulfurization catalysts

Hydrodesulfurization (HDS) of thiophene was performed over noble metals (Pt , Ph, Pd, Ru)-supported HZSM-5 and NaZSM-5. Among the tested catalysts, Pt/ HZSM-5 exhibited the highest HDS activity. Butane was the dominant product in HDS of thiophene over Pt/HZSM-5. Selectivity of aromatics was high on Rh /HZSM-5, Pd/HZSM-5 and Ru/HZSM-5, and remarkable deactivation was observed on these catalysts. Products of consecutive reaction, mainly aromatics, wer e thought to be the sources of carbon deposit. Because deactivation was rem arkable in HDS over the catalysts which produced aromatics. The IR spectra of acidic hydroxy groups and adsorbed pyridine, and the NH3- TPD spectra show that the amount of acid site of HZSM-5 impregnated with no ble metals were almost the same as that of original HZSM-5. The dispersion of Pt determined by XRD was lower than those of Rh and Pd. However, Pt was stable against hydrogen sulfide. It was indicated that HDS activity depende d on the hydrogen activation ability of metals in the presence of hydrogen sulfide. Moreover, HDS activity depended on the dispersion of Pt, and the acidity of zeolite affected on dispersion of Pt. These results indicate that a highly active catalyst for HDS can be prepare d by the use of zeolite which has a large amount of acid sites and Pt which shows anti-sulfur ability.