Regeneration of reduced supported chromium oxide catalyst for alpha-olefin oligomerization

In a process for the preparation of liquid hydrocarbons suitable as lubricant basestocks from alpha olefin feedstock containing 6 to 20 carbon atoms, or mixtures of such olefins, comprising contacting said olefins under oligomerization conditions, at reaction temperature between 90.degree. to 250.degree. C. to vary product viscosity, and with a chromium catalyst on a porous support, which catalyst has been treated by oxidation at a temperature of 200.degree. C. to 900.degree. C. in the presence of an oxidizing gas and then by treatment with a reducing agent at a temperature and for a time sufficient to reduce said catalyst to a lower valence state to obtain an oligomeric liquid lubricant composition comprising C.sub.30 -C.sub.1300 hydrocarbons, said composition having a branch ratio of less than 0.19, weight average molecular weight between 420 and 45,000, number average molecular weight between 420 and 18,000, molecular weight distribution between 1 and 5 and pour point below -15.degree. C., the improvement comprising;

• regenerating deactivated chromium catalyst under regenerating conditions in a process comprising the steps of:
• (a) purging said deactivated catalyst with inert gas at elevated temperature and time sufficient to strip unreacted olefin and lubricant product;
• (b) contacting said deactivated and purged catalyst with a stream of oxidizing gas while heating to elevated temperature at a rate and for a time sufficient to oxidize said catalyst and remove carbonaceous deposits;
• (c) cooling said oxidized catalyst and contacting with a stream of reducing gas in an amount sufficient and at a temperature and for a time sufficient to reduce said oxidized catalyst to essentially lower valent chromium.