Pd Migration. 1. A Possible Reason for the Deactivation of Pyrolysis Gasoline Partial Hydrogenation Catalysts

The catalyst deactivation of the selective hydrogenation of pyrolysis gasoline of a commercial plant was investigated. Both the fresh and the regenerated catalysts, sampled from the commercial plant, were characterized by the palladium wt %, BET surface area, pore volume, the dispersion of Pd/Al[sub 2]O[sub 3], XRD (X-ray diffraction), and EPMA (electron probe microanalyzer). The results indicated that the major factors affecting the catalyst deactivation of the selective hydrogenation of pyrolysis gasoline of a commercial plant are palladium migration and coke deposition, 53.2%, poor palladium dispersion, 37%, and palladium metal loss, 9.8%. However, the pore mouth plugging, loss of surface area, and phase change of support were the minor factors for catalytic deactivation. The first findings of the effect of palladium migration on the catalyst deactivation of the eggshell palladium profile catalyst are meaningful and important for improving the performance of the catalyst with nonuniform active site distribution.