Study On The Effect Of Complexing Agent On The Structure And Performance Of CoMo Hydrodesulfurization Catalyst

Petroleum products are the main energy sources used in China at this stage,but sulfur products in petroleum products will cause a series of adverse effects during the use of oil products.How to efficiently remove sulfur compounds in oil products has become a major concern for researchers.In industrial refineries,oil is desulfurized by hydrodesulfurization?HDS?.However,there is a large demand for catalysts in the industry,and it is difficult to improve catalyst performance through the perspective of materials.Industrial HDS catalysts are prepared using an equal volume impregnation method.Researchers have found that adding complexing agents such as citric acid?CA?to the impregnating solution can significantly improve the performance of the catalyst.Therefore,the study of the effect of complexing agents on the HDS catalyst has certain feasibility and industrial value.In HDS reaction,sulfide can be moved along two paths of direct desulfurization?DDS?and pre-hydrogenation?HYD?.The DDS path has low hydrogen consumption and is an ideal desulfurization path.Therefore,an ideal catalyst should have high desulfurization rate and DDS selectivity.In summary,we research the role of complexing agents to explore the preparation of a catalyst with high selectivity for DDS.The specific work is as follows:Part 1:a series of Co Mo P/?-Al₂O₃ HDS catalysts were prepared by using different complexing agents,and their effects were systematically studied by XRD,XPS,Py-FTIR,HRTEM and H₂-TPR.Results have shown that thiourea?Th?causes the active phase MoS₂ to form a high number of stacked layers and small size morphology,making it easier to form Co MoS active phases at the edges of the active phase.Compared with traditional catalysts,the addition of thiourea helps to improve the DDS selectivity.The H₂-TPR results confirmed that reducing the Mo-S bond strength by adding thiourea would result in more SH groups and generate coordination unsaturated site?CUS?.The above-mentioned reasons lead to the reaction tending to proceed through the DDS path,and this result is expected to reduce the hydrogen consumption in production in industrial production.Part 2:The research shows that although the selectivity of HDS catalyst is improved,but the desulfurization rate of thiourea has decreased.We attribute it to the increase of the viscosity of the impregnating solution,which leads to an increase in the difficulty of vulcanization and a decrease in the number of active phases.In the part 2 of the experiment,we prepared a double complexing agent catalyst through the combined use of the traditional complexing agent citric acid and thiourea.The catalyst showed a high conversion rate and maintained a high DDS selectivity.Therefore,we believe that this method has prepared a catalyst showing excellent comprehensive performance.Through characterization,it was found that citric acid and thiourea each had their original lifting effect when using the double complexing agent.When the amount of citric acid was fixed,the addition of a small amount of thiourea had little effect on the catalyst conversion rate,but it could significantly improve desulfurization selectivity.