Abstract:
There is disclosed a method for reactivating a fixed bed of used platinum group metal-alumina catalyst of the type in which the alumina is derived from hydrous alumina predominating in alumina trihydrate. Such catalysts are employed in, for instance, the catalytic reforming of gasoline boiling range hydrocarbons to obtain fuels of high-octane ratings or aromatics. The method for reactivating the catalyst which has declined in activity during use and contains carbonaceous deposits, involves treating the deactivated catalyst at elevated temperatures with an oxygencontaining gas to burn the carbonaceous deposits therefrom. The relatively carbon-free catalyst is contacted under controlled conditions with a gaseous stream containing small amounts of chlorine, in combined or elemental form, oxygen and often water vapor to deposit chloride in a first portion of the catalyst bed. After the chlorine component is added to the catalyst, preferably in a relatively short period of time, the catalyst is then contacted with a gaseous stream containing oxygen and water vapor. This treatment may continue for a longer time than the chlorine treating period and until the chloride deposited on the catalyst is distributed through a major portion of the catalyst bed. Distribution of the chloride is a function of the time, temperature and water vapor partial pressure observed during the treatment and thus the distribution is controlled essentially by kinetics. The extent of water contact with the catalyst is limited by controlling the amount of water in the gaseous streams and the length of the overall treatment.