Preparation Of Ni-Mo Catalyst Supported On A Mixture Of MCM-41 And Y Zeolite For Deep Hydrodesulfurization

In recent years, much attention has been paid to deep hydrodesulfurization (HDS) of diesel fuel because air pollution by exhaust gas from diesel engine has become a serious problem. Moreover, worldwide environmental legislation places increasingly severe restrictions on transportation fuels. Hence, deep HDS processes will become more and more important for providing environmentally friendly fuel. The deep HDS catalysts were prepared by depositing Ni-Mo species on mixture of HY zeolite and MCM-41. The HDS activities of the prepared catalysts were investigated using a representative polyaromatic sulfur-containing model compound, such as dibenzothiophene (DBT), 4,6-dimethydibenzothiophene (4,6-DMDBT). The supports and catalysts were characterized by XRD, N₂ adsorption, TPR, UV-Vis, SEM, TEM, ICP-AES and IR. The effects of sodium content and acidity of the supports on the HDS performance of the catalysts were studied. The effects of pore structures and distribution of acid sites of the support on the performance of catalysts were also investigated. The main contents are as follows:A series of HDS catalysts were prepared by depositing Ni-Mo species on a mechanical mixture of HY zeolite and MCM-41 with different Ni/Mo molar ratios and a different content of HY in the supports. It is indicated that the introduction of HY zeolite into the matrix of MCM-41 enhanced the HDS performance of the catalyst. A maximum HDS activity was observed at a content of 25wt% HY in the support. Moreover, the catalyst with a Ni/Mo molar ratio of 0.75 exhibited the highest HDS activity. The conversions of DBT and 4,6-DMDBT reach 98% and 75% catalyzed by NiMo(0.75)/M-Y(25) at 280℃, respectively.In order to investigate the effect of support acidity and the sodium content on the performance of catalysts, a series of HDS catalysts were prepared by depositing Ni-Mo species on MCM-41, NaMCM-41 and the mechanical mixtures of MCM-41 and HY, MCM-41 and NaY, NaMCM-41 and HY, and NaMCM-41 and NaY. It is shown that the HDS activity of the catalysts are related to their Br(?)nsted acidity and sodium contents of the supports. It is suggested that Br(?)nsted acidity has a positive effect on the HDS activity of the supported Ni-Mo catalysts while Na⁺ has a negative effects on the HDS activity of the supported Ni-Mo catalysts. Both TPR and HDS investigations of the catalysts suggest that migration of spillover hydrogen may be a rate-limited step in the hydrogenation reaction on...