Hydrogenation of hydrocarbon residuum

Claim 1

In the process for the hydrocracking of a residuum oil in an ebullated bed reactor to convert at least 50 weight percent of the hydrocarbons boiling above 975°F in a reaction zone at a pressure between about 300 and 1000 psi of hydrogen when a temperature between about 750° and 850°F is used and at a pressure between about 1000-3000 psi when a temperature between about 900° and 950° is used by contacting said oil with a hydrocracking catalyst wherein coke deposits on the catalyst to reduce its activity and fresh catalyst is added to maintain a desired average catalyst activity at a rate such that between 5 and 20 barrels of oil are processed per pound of fresh catalyst and wherein the oil and hydrogen pass upwardly through the reaction zone under conditions to maintain the catalyst in random motion with substantial carryover of catalyst with liquid effluent from the reaction zone, the improvement comprising: a. continuously removing said catalyst from said reaction zone at a rate at least twice as great as the rate of addition of fresh catalyst; b. regenerating said catalyst to remove deposited carbon; and c. recycling an appropriate portion of the regenerated catalyst to said reactor at a rate supplementing the rate of addition of fresh catalyst so as to maintain the desired inventory of total catalyst in the reactor and processing between 0.5 and 3.0 bbl/lb of carbon-free catalyst, both fresh and regenerated added to the reactor.