Lube oil hydrotreating process

Claim 1

A process for the production of lubricating oils in order to obtain comparatively low viscosity lubricating oil base stocks of enhanced viscosity index from a crude lubricating oil which process comprises fractionating a crude lubricating oil containing from about 10% to about 90% by volume of a distillate fraction boiling below 950° F. and from 90% to 10% of a residual fraction boiling above 950° F. into a residual and a distillate fraction, subjecting the residual fraction to hydrotreating wherein the operating conditions employed comprise a temperature in the range from about 650° F. to about 850° F., a pressure in the range from about 2,000 to about 10,000 psig, a liquid hourly space velocity in the range from about 0.1 to about 10 volumes of residual charge stock per volume of catalyst per hour and a hydrogen feed rate in the range from about 2,000 to about 10,000 standard cubic feet per barrel of residual charge stock, said operating conditions being selected so as to maintain a yield of at least 50% by volume based upon the residual fraction of hydrotreated material boiling above about 625° F., separately subjecting the distillate fraction to hydrotreating under more severe conditions than employed in hydrotreating the residual fraction wherein the operating conditions employed comprise a temperature in the range from about 700° to about 900° F. and at least 15° F. greater than the temperature employed in hydrotreating the residual fraction when the remaining hydrotreating process parameters are substantially the same as like hydrotreating process parameters for the residual fraction, a pressure in the range from about 2,000 to about 10,000 psig, a liquid hourly space velocity in the range from about 0.1 to about 10 volumes of distillate charge stock per volume of catalyst per hour and a hydrogen feed rate in the range from about 2,000 to about 10,000 standard cubic feet per barrel of distillate charge stock, said operating conditions being selected so as to maintain a yield of at least 50% by volume based upon the distillate fraction of hydrotreated material boiling above about 625° F., and recovering hydrotreated crude lubricating oil boiling above about 625° F. as lubricating oil base stock product from each hydrotreating process.