Density Functional Theory Study On Pd-based Catalyst Catalytic Hydrogenation Of Acetylene

Ethylene is one of the most basic raw materials in the petrochemical industry.The size of ethylene production measures the development level of the national petrochemical industry.For most regions in China,ethylene is mainly produced by the pyrolysis process of petroleum hydrocarbon,which always exists small amount of acetylene in the production process,poison the catalyst and result in deactivation.Therefore,removing the impurity acetylene and reducing its concentration to the qualified standard has become a crucial step in the ethylene production.For XinJiang,a special region rich in acetylene,ethylene can be prepared by direct hydrogenation of high concentration of acetylene into ethylene.So no matter in the reaction process is in addition to vinyl acetylene refined or high concentration of acetylene hydrogenation to ethylene,acetylene hydrogenation reaction has important research significance,according to the study found that the Pd catalysts are widely used,so in order to further improve the catalyst activity and selectivity,explore new hydrogenation catalyst is imminent.Based on the density functional theory,the reaction mechanism of acetylene hydrogenation was explored from the aspects of active component and carrier of Pd-based catalyst.The active component mainly improves the performance of the catalyst through non-metallic Si doped Pd₇ metal clusters,while for the carrier,we use g-C₃N₄supported by Pd single atom and S-doped g-C₃N₄ to study.The results showed that the structure of Pd₇ clusters changed a lot and the electron distribution also accumulated after the doping of Si atoms.Pd7 and Pd6Si clusters catalyzed the hydrogenation of acetylene to produce ethylene with activation energies of 22.59 kcal/mol and 11.25 kcal/mol,respectively,and selectivity of 8.46kcal/mol and 15.19 kcal/mol,respectively.The results showed that the activity and selectivity of Si atom doped were improved,which indicated that the non-metal doped metal clusters had great influence on the catalyst.However,by comparing g-C₃N₄ loaded with single-atom Pd with S-doped g-C₃N₄,we found that Pd atom is the only active site.Through the study of the whole reaction all paths,and the optimal reaction path for Co-adsorption R1 started a single continuous hydrogenation reaction path,through contrast activation energy and selectivity between not doping S atoms and S dope C,N site,we found that S doped C site can improve the activity of the reaction,but with low selectivity;There was no increase in the activity of S atom doped N site,but there was a slight increase in the selectivity.