A method for re-refining used oils comprises contacting feedstock comprising purified used oil with extraction solvent to perform continuous liquid-liquid solvent extraction, to produce an extract stream comprising the extraction solvent and an extract dissolved in the extraction solvent. The feedstock and the extraction solvent are agitated by a variable speed agitator during the solvent extraction at a selected agitation speed. The extract is separated from the extraction solvent and subjected to a continuous flow liquid phase hydrogenation treatment to produce an oil product. A system for performing the method includes a purification unit for purifying the used oil; an extraction column for extracting the extract from the feedstock; and a continuous flow liquid phase hydrogenation unit. The extraction column comprises an agitator configured to agitate the feedstock and the extraction solvent flowing through the extraction column at a variable agitation speed.

Disclosed are solvency enhancer compositions, for example, as additives to lubricating oils and as formulated in lubricating oil compositions and associated methods of preparation and use thereof. The compositions and methods can dissolve at least one of oxidation products and other organic polar compounds, due to lubricant degradation, formed and suspended in oil compositions including adding an effective amount of a solvency enhancer to the oils, wherein the solvency enhancer includes Guerbet alcohols. Further described are methods for dissolving organic deposits in an oil system including adding an effective amount of a solvency enhancer to the oil system, wherein the solvency enhancer includes Guerbet alcohols. Also provided are methods for preventing sludge and varnish formation in in-service oils including adding an effective amount of a solvency enhancer to the oils, wherein the solvency enhancer includes Guerbet alcohols.

A system for producing an American Petroleum Institute Standards Group III Base Stock from vacuum gas oil, by injecting hydrogen, heating, saturating the mixture through hydrogen reactors connected in series with a liquid hourly space velocity (LHSV).sup.1 of from 0.5 to 2.5, forming a saturated heated base oil, and coproduct. The system fractionates the saturated heated base oil to while simultaneously refluxing a cooled fuel oil fraction forming an American Petroleum Institute Standards Group III Base Stock with less than 0.03% sulfur, with greater than 90% saturates and a viscosity index greater than 120 as defined by ASTM D-2270, a viscosity from 2 to 10 centistokes as defined by ASTM D-445 a boiling range from 600 degrees F. to 1050 degrees F., and a cold crank viscosity (CCS) between 1200 and 5000 centipoise at 25 degrees C. and as defined by ASTM D-5293.

A culture medium protective liquid material of the present invention covers a culture medium when a living cell is cultured. The culture medium protective liquid material contains liquid paraffin which is liquid at room temperature as a main component thereof and an antioxidative substance for restraining the liquid paraffin from being oxidized.

A system for producing an American Petroleum Institute Standards Group III Base Stock from vacuum gas oil, by injecting hydrogen, heating, saturating the mixture through hydrogen reactors connected in series with a liquid hourly space velocity (LHSV).sup.1 of from 0.5 to 2.5, forming a saturated heated base oil, and coproduct. The system fractionates the saturated heated base oil to while simultaneously refluxing a cooled fuel oil fraction forming an American Petroleum Institute Standards Group III Base Stock with less than 0.03% sulfur, with greater than 90% saturates and a viscosity index greater than 120 as defined by ASTM D-2270, a viscosity from 2 to 10 centistokes as defined by ASTM D-445 a boiling range from 600 degrees F. to 1050 degrees F., and a cold crank viscosity (CCS) between 1200 and 5000 centipoise at 25 degrees C. and as defined by ASTM D-5293.

A method for producing an American Petroleum Institute Standards Group III Base Stock from vacuum gas oil, by injecting hydrogen, heating, saturating the mixture through hydrogen reactors connected in series with a liquid hourly space velocity (LHSV).sup.1 from 0.5 to 2.5, forming a saturated heated base oil, and coproduct. The method fractionates the saturated heated base oil while simultaneously refluxing a cooled light oil fraction forming an American Petroleum Institute Standards Group III Base Stock with less than 0.03% sulfur, with greater than 90% saturates and a viscosity index greater than 120 as defined by ASTM D-2270, a viscosity from 2 to 10 centistokes as defined by ASTM D-445 a boiling point 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.

A method for producing an American Petroleum Institute Standards Group III Base Stock from vacuum gas oil, by injecting hydrogen, heating, saturating the mixture through hydrogen reactors connected in series with a liquid hourly space velocity (LHSV).sup.1 from 0.5 to 2.5, forming a saturated heated base oil, and coproduct. The method fractionates the saturated heated base oil while simultaneously refluxing a cooled light oil fraction forming an American Petroleum Institute Standards Group III Base Stock with less than 0.03% sulfur, with greater than 90% saturates and a viscosity index greater than 120 as defined by ASTM D-2270, a viscosity from 2 to 10 centistokes as defined by ASTM D-445 a boiling point 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.

A method for the regeneration of used lubricating oils to produce lubricant base oils includes the steps of (a) removing resin and impurities by distillation, (b) catalytic oxidation treatment and (c) adsorption process. The method can efficiently reduce the color, metal ions, and sulfur content under mild reaction conditions at low cost and obtain high yield of regenerated oil above 85 wt. %.

Disclosed is a method of treating a used hydrocarbon lubricant of ISO Viscosity Grade 46 or higher comprising oxidation products that adversely affect lubricant performance. The hydrocarbon lubricant has a Group II hydrocarbon oil or Group III hydrocarbon oil, optionally one or more lubricant additives, and an amount of varnish. The hydrocarbon lubricant is free of zinc-containing additives. The method comprises adding to the used hydrocarbon lubricant from about 2 percent by weight to about 20 percent by weight of a polyhydroxy polypropylene oxide homopolymer that has a hydroxyl number of from about 12 mg KOH/g to about 58 mg KOH/g as measured according to ASTM D4274.

Disclosed is a method of treating a used hydrocarbon lubricant of ISO Viscosity Grade 46 or higher comprising oxidation products that adversely affect lubricant performance. The hydrocarbon lubricant has a Group II hydrocarbon oil or Group III hydrocarbon oil, optionally one or more lubricant additives, and an amount of varnish. The hydrocarbon lubricant is free of zinc-containing additives. The method comprises adding to the used hydrocarbon lubricant from about 2 percent by weight to about 20 percent by weight of a polyhydroxy polypropylene oxide homopolymer that has a hydroxyl number of from about 12 mg KOH/g to about 58 mg KOH/g as measured according to ASTM D4274.