Preparation, Characterization Of Ni₂P/Ti-MCM-41Catalyst And The Hydrodesulfurization Performance Of Dibenzothiophene

Ni2P/Ti-MCM-41catalysts were successfully prepared based on ammoniumhypophosphite and nickel chloride by temperature programmed reduction method at a lowreduction temperature，as well as the Ni2P/MCM-41and Ni2P/Al-MCM-41catalysts. Theobtained catalysts were characterized by XRD, BET, FT-IR, Py-FT-IR, XPS, TEM and COuptake. The hydrodesulfurization performance of catalysts were investigated on a fixed bedby applying the dibenzothiophene as model compound.The results of Ni2P/Ti-MCM-41catalysts indicated that comparatively low initial Ni/Pmolar ratio might favor the formation and dispersion of Ni2P phase. The incorporation of Tican modify the acidic nature of supports and catalysts, and the incorporation of Ti enhancedthe Lewis acidity as well as the Br nsted acid intensity of supports. For the catalysts withdifferent reduction temperature, initial Ni/P molar ratio and Ti content, biphenyl (BP) wereformed in greater proportions than that of cyclohexylbenzene (CHB), and thehydrodesulfurization(HDS) of dibenzothiophene(DBT) preferentially occurred via the directdesulfurization(DDS) route. The incorporation of Ti is beneficial to the formation of Ni2Pbecause of the electronic properties of Ti. Moreover, the value of Ti content had a largeinfluence on the dispersion of Ni2P, and catalyst with appropriate amount of Ti incorporation(y=1.5) showed the best Ni2P dispersion. At the conditions of340°C,3.0MPa, weight hourlyspace velocity (WHSV) of3.5h-1and H2/oil ratio of650(v/v), the catalyst with an initial Ni/Pmolar ratio of1/2and a Ti/Si molar ratio of1.5%showed the highest DBT conversion of99.4%,17.5%higher than that of the Ni2P/MCM-41(1/2) catalyst. The electronic effect of Ti(through the direct desulfurization route) and the moderate surface Lewis acidity (through thehydrogenation route) may explain the improved HDS catalytic activity of the Ti-dopedsamples.For Ni2P/Al-MCM-41catalysts, results showed that a moderate amount of Alincorporation can promote the formation of the Ni2P phase and induce a better Ni2P dispersion,as well as modify the crystallite sizes of Ni2P phase, which can be ascribed to electronicatmosphere changes due to the incorporation of Al and the interaction between supports andactive phases. Proper amount of Al addition is beneficial to the increase of DBT conversion,kHDSand TOF values, however, excessive Al addition might result in a decrease in catalyticperformance because of the Strong Metal-Support Interaction(SMSI) effect. At the conditionsof340°C,3.0MPa, weight hourly space velocity (WHSV) of3.5h-1and H2/oil ratio of650 (v/v), the catalyst with Al/Si molar ratio of2%exhibited the best HDS performance of97.6%,and its catalytic performance remained at approximately of97.0%within120h withoutactivity loss.