Preparation Of Supported M_xNi₂P Catalysts And Its Catalytic Performance Of Hydrodesulfurization Pathway Selectivity

The complete removal of sulfur compounds from petroleum feedstock is important for the production of clean transportation fuels and is an area of active research.As crude oils get heavier,the hydrodesulfurization technology has been put forward higher requirements.Compared with the conventional Co Mo and Ni Mo sulfide catalysts,the transition metal phosphide catalyst,especially Ni₂P,has been introduced as a new class of highly active hydrotreating catalysts and has attracted attention as a potential substitute for conventional catalysts.It is thus a major goal of this study to investigate the effect of different modified metal on the crystal structure,morphology and surface properties of supported Ni²P catalysts and on the catalytic activity,path selectivity in the hydrodesulfurization（HDS）of 4,6-dimethyldibenzothiophene（4,6-DMDBT）,and the mechanism of modified metal in hydrodesulfurization performance.In this work,Al₂O₃,SiO₂ and amorphous silicon aluminum（ASA）were adopted as supports to prepare the Ni₂P catalysts with temperature programmed reduction（TPR）of oxidic precursors（metal phosphates）at moderately high temperatures.A series of physicochemical properties were characterized,and the hydrodesulfurization performance of these catalysts on 4,6-dimethyldibenzothiophene（4,6-DMDBT）was investigated.The results show that SiO₂ has the most superior performance in supporting of Ni₂P and Ni₂P/SiO₂ catalyst has the most excellent catalytic performance.In particular,Ni₂P/SiO₂ gave a highest HDS conversion of 61.81%,the HYD route is primary and the selectivity of DDS route is low,about 10%.On the basis of the above findings,the addition of a third component to Ni₂P/SiO₂catalyst has been researched for improving the hydrodesulfurization performance of Ni₂P/SiO₂ catalyst.The catalyst was modified by impregnating Co and Fe ion to modify the properties of the catalyst for hydrodesulfurization,and the as prepared catalysts were characterized by various characterization methods to investigated effect of Co and Fe modification on the physical and chemical properties of Ni₂P/SiO₂ catalyst.The catalytic activity of hydrodesulfurization（HDS）was measured using a model liquid feed containing 4,6-dimethyldibenzothiophene（4,6-DMDBT）,and the effects of different modified metal,the concentration of modified metal,reaction temperature and liquid hourly space velocity on the conversion of 4,6-DMDBT and the HDS pathway selectivity were investigated.Finally,preparation the bimetallic phosphide Fe Ni P/SiO₂catalyst and investigated the effect of bimetallic phosphide with different Fe/Ni molar ratio on the conversion of 4,6-DMDBT and HDS pathway selectivity on the Fe Ni P/SiO₂catalystThe results show that the synthesized M_xNi₂P/SiO₂ samples prepared by introducing Co and Fe into Ni₂P/SiO₂ catalyst can significantly improve the conversion of 4,6-DMDBT,and the maximum conversion of 4,6-DMDBT was increased to 81.22%and 80.06%respectively.However,their HDS pathway selectivity of is quite different,the catalyst which modified with Co improved the DDS pathway selectivity significantly,the maximum selectivity of DDS pathway can be increased to 22.61%,and the catalyst which modified with Fe is beneficial to the progress of HYD pathway,the DDS pathway selectivity decreased,and the minimum selectivity of DDS pathway can be decreased to 5.25%.The conversion of 4,6-DMDBT of the bimetallic phosphides Fe Ni P/SiO₂ catalyst is lower compared with Ni₂P/SiO₂ catalyst,but the pathway selectivity of DDS is much higher than that of conventional Co Mo and Ni Mo sulfide catalysts with the maximum selectivity of DDS pathway can be increased to 45.02%.