SINTERING REDISPERSION OF PT-RE/AL2O3 DURING REGENERATION

The influence was studied of temperature and gas flow rate on total metallic dispersion and specific surface area of Pt-Re/Al2O3 reforming catalyst during the burning of coke deposited on its surface. A laboratory catalyst coked to different coke concentrations and a commercial catalyst coked in a commercial plant were used. The chloride level during oxychlorination and its influence on total metallic dispersion were also studied. The actual temperature inside the catalyst during coke burning is the main parameter affecting the total metallic dispersion; other parameters affect this temperature. During catalyst oxychlorination the metallic phase is redispersed and the total dispersion at values of 0.9-1% chloride on the catalyst is the same, independent of the initial dispersion. The total metal dispersion of Pt-Re/Al2O3 is fixed by the platinum complexes in either sintering or redispersion. This is because, on reduction of platinum complexes, metallic platinum forms crystallites where rhenium is reduced producing the platinum-rhenium clusters. © 1990.