PRODUCTION OF LUBRICANT BASE STOCKS WITH CONTROLLED AROMATIC CONTENTS

摘要

Methods are provided for producing Group II and Group III base stocks with a controlled or consistent aromatics content. An aromatics-rich base stock, such as a Group I base stock or an alkylated aromatic base stock, can be added to the catalytically treated base stock in a minimal amount after the final catalytic treatment step but prior to fractionation. At the beginning of a processing run for forming lubricant base stock products, about 0.25 wt % to about 1.25 wt % of the Group I base stock can be added to a catalytically processed feed after the final catalytic processing stage but prior to fractionation to form the Group II and/or Group III base stock. During the course of the processing run, the amount of Group I base stock added can be reduced roughly in correspondence with the increase in aromatics caused by catalyst deactivation. This can allow a catalytically processed lubricant base stock product to be generated that contains at least about a threshold (minimum) aromatics content during the course of a processing run. Alternatively, this can allow a catalytically processed lubricant base stock product to be generated that has consistent aromatics content during the course of the processing run.

主权项

1. A method for forming a lubricant base stock having at least a threshold aromatics content during the course of a processing run, the method comprising:
hydroprocessing a feedstock under effective hydroprocessing conditions to form a hydroprocessed effluent; separating the hydroprocessed effluent to form at least a gas phase effluent and a liquid phase effluent; dewaxing at least a portion of the liquid phase effluent in the presence of a dewaxing catalyst under effective dewaxing conditions to form a dewaxed effluent; blending at least a portion of the dewaxed effluent with an aromatics-rich base stock to form an aromatics-enriched effluent, the aromatics-rich base stock comprising a Group I base stock, an alkylated aromatic base stock, or a combination thereof, the aromatics-enriched effluent containing about 0.25 wt % to about 1.25 wt % of the aromatics-rich base stock at a first time during the processing run; decreasing the amount of aromatics-rich base stock blended with the at least a portion of the dewaxed effluent at one or more times during the processing run subsequent to the first time; and fractionating at least a portion of the aromatics-enriched effluent to form at least a lubricant base stock product having a viscosity index of at least about 80 and a sulfur content of 300 wppm or less, wherein the lubricant base stock product at the first time during the processing run contains an amount of aromatics corresponding to at least an aromatics threshold amount, and wherein the lubricant base stock product at the one or more times during the processing run subsequent to the first time contains an amount of aromatics corresponding to at least the aromatics threshold amount.