TEMPERATURE-PROGRAMMED GASIFICATION OF THE COKE ON SPENT HYDROTREATING CATALYSTS WITH OXYGEN AND HYDROGEN

Spent hydrotreating catalysts are characterized by temperature-programmed gasification with oxygen and hydrogen. This technique yields production/consumption patterns as a function of temperature, which are characteristic for the type of carbon or sulfur "source". The reactivity of the carbonaceous material is a function of the intrinsic reactivity of the coke and the catalytic effect of the metals on the gasification of the carbon. Apart from inorganic sulfur (metal sulfides), the spent catalysts contain organic sulfur, which causes an additional maximum in the consumption patterns of both oxygen and hydrogen. Gasification of the carbonaceous material in hydrogen shows that at low temperature the functional groups are hydropyrolyzed, whereas at high temperature uncatalyzed gasification of the remains of the coke takes place, indicating that this part of the carbonaceous material is not located in the vicinity of the active sites.