Method for producing an american petroleum institute standards group iii base stock from vacuum gas oil

A method for producing an American Petroleum Institute Standards Group III base stock from vacuum gas oil derived from used oil, comprising:

• a. combining a petroleum derived product having a viscosity index greater than 120 into a vacuum gas oil derived from used oil forming a vacuum gas oil mixture with a combined boiling point range from 450 degrees F. to 1050 degree F. as defined by ASTM D-86;
• b. increasing temperature of the vacuum gas oil mixture to a temperature from 450 degrees Fahrenheit to 600 degrees Fahrenheit, forming a heated vacuum gas oil mixture while simultaneously increasing pressure on the heated vacuum gas oil mixture from 50 psig to a pressure from 1000 psig and 1500 psig by injection of hydrogen;
• c. saturating the heated vacuum gas oil mixture forming a first partially saturated heated base oil then a fully saturated heated base with hydrogen through a plurality of hydrogen reactors connected in series, having a liquid hourly space velocity (LHSV)−1 through the hydrogen reactors from 0.5 to 2.5;
• d. separating a saturated heated base oil from a recycle overhead at a high pressure from 1000 psig to 1500 psig;
• e. removing contaminants from the saturated heated base oil producing contaminant free saturated heated base oil;
• and
• f. fractionating the contaminant free saturated heated base oil using steam to remove a light oil fraction with an initial boiling point less than 600 degrees F. while simultaneously refluxing, forming an API Standards Group III Base Stock 113 with less than 0.03 percent sulfur, greater than 90 percent saturates and a viscosity index greater than 120 as defined by ASTM D-2270 and a viscosity range from 2 to 10 centistokes as defined by ASTM D-445 with a boiling range from 600 degrees F. to 1050 degrees F. as defined by ASTM D-86, and a cold crank viscosity (CCS) between 1200 and 5000 centipoise at minus 25 degrees C. and as defined by ASTM D-5293.