Exxon Research and Engineering Company

Theodore H West

Ian A Cody

William A Wachter

David J Martella

Biddanda U Achia

John A Thompson

David A Gudelis

James David Bell

John F Eagen

Slack waxes and synthetic wax are isomerized and processed into high viscosity index and very low pour point lube base stock oils and blending stocks by the process comprising the steps of hydrotreating the wax, if necessary, to remove heteroatom and polynuclear aromatic compounds and/or deoiling the wax, if necessary, to an oil content between about 5-20% oil, isomerizing the wax over a Group VI-Group VIII on halogenated refractory metal oxide support catalyst, said isomerization being conducted to a level of conversion such that .about.40% and less unconverted wax remains in the 330.degree. C..sup.+, preferably the 370.degree. C..sup.+ fraction sent to the dewaxer. The total isomerate from the isomerization unit is fractionated into a lube oil fraction boiling at 330.degree. C..sup.+, preferably 370.degree.p9 C..sup.+. This oil fraction is solvent dewaxed preferably using MEK/MIBK at 20/80 ratio and unconverted wax is recycled to the isomerization unit. Operating in this manner permits one to obtain isomerate oil of very high VI (in excess of 130) possessing low pours (-21.degree. C., preferably -24.degree. C., most preferably -27.degree. C.).

Method for isomerizing wax to lube base oils

Solvent dewaxing of waxy hydrocarbon oils is improved by using a poly (n-C.sub.24) alkyl methacrylate polymer dewaxing aid in combination with lower melting point weight poly (C.sub.8 -C.sub.20) alkyl methacrylate polymer dewaxing aids. The solvent dewaxing processes improved using this combination dewaxing aid are the incremental and total predilution solvent type processes employing either surface chilled indirect heat exchanger means or direct chilling using cold solvent. The solvent dewaxing processes are those employing normally liquid dewaxing solvents, as exemplified by C.sub.3 -C.sub.6 ketones, such as methyl ethyl ketone, methyl isobutyl ketone and mixtures thereof, mixtures of ketones with aromatic such as MEK/toluene, halogenated C.sub.2 -C.sub.4 hydrocarbons such as tetrachloraethane, trichloro ethylene, etc. Autorefrigerative solvent dewaxing processes employing low boiling point, normally gaseous hydrocarbons, such as propane, propylene, butane, butene and mixtures of such solvents, with the aforesaid ketones, e.g., propane/MEK, are also benefited by use of the present dewaxing aid combination. Use of the combination dewaxing aid results in an improvement in feed filter rate and liquids/solids. ratio in the dewaxing process.

Solvent dewaxing using combination poly (n-C.sub.24)

Wax crystals of improved morphology are produced by employing a dewaxing aid in an agitated solvent dewaxing environment, preferably an agitated indirect chilling solvent dewaxing environment, such as an agitated chiller, such as a scraped surface chiller which has been modified so that the scraper is not in contact with the internal wall of the chiller wherein a high degree of agitation is maintained by rotating the paddles to achieve a paddle tip speed of 25 to 400 ft./min. and the gap between the agitator tip and the inner wall of the vessel is about 0.5 to 40% of the internal diameter of the chiller. Agitation in agitated indirect chiller appratus has been shown to produce significantly improved feed filter rates and liquids/solids ratios when employed in conjunction with dewaxing aids in solvent dewaxing processes.

Wax crystal modification using dewaxing aids under agitated conditions

Refined waxes and dewaxed lubricating oil basestocks are simultaneously produced in a reversed deoiling-dewaxing process employing conventional dewaxing solvents and existing process equipment. Improved yields, lower solvent useage, and higher throughputs are achieved using dewaxing aids in the final stage. Waxy hydrocarbon oils are solvent dewaxed to a temperature which produces a low oil content refined high melting point hard wax product which is recovered, e.g. by filtration. The hard wax product can be deoiled. The filtrate from the initial dewaxing operation is then injected with dewaxing aid and further chilled in secondary chiller means such as scraped surface chillers to a lower temperature to produce more deeply dewaxed oil and a low melting point soft wax product which are separated e.g. by filtration. The low melting point wax is desolvated and the dewaxing aid may be recovered for example by passing the wax through a membrane or by distillation. Any recovered dewaxing aid may be recycled to the process.

Modified deoiling-dewaxing process

An improved method for separating a slack wax into a wax fraction and a lube oil fraction is disclosed. The method comprises passing the slack wax into a first mixing zone and subsequently into a second mixing zone. Solvent selectively miscible with the lube oil fraction is added to the zones. The temperature of the solvent added to the second mixing zone is substantially higher than the temperature of the solvent added to the first mixing zone. This process produces a wax fraction having a relatively low lube oil content.

Slack wax de-oiling process

A process is disclosed for the solvent dewaxing of wax containing hydrocarbon oils, preferably waxy petroleum oils most preferably waxy lubricating or transformer oils. The process employs methyl tertiary butyl ether as the dewaxing solvent, either alone or in combination with other dewaxing solvents such as ketones, halogenated hydrocarbon anti-solvents, and mixtures thereof. The use of methyl tertiary butyl ether as a dewaxing solvent, or in combination with conventional dewaxing anti-solvents permits lower volumes of solvent to be employed in the dewaxing process while simultaneously producing an oil of lower wax content and lower dewaxed oil pour point at the same filter temperature as that commonly employed using conventional dewaxing solvents. Dewaxed oil yields for equivalent pour point are 3 to 4% higher with the MTBE system.

Solvent dewaxing with methyl tertiary butyl ether

A method for separating a mixture into a first fraction and a second fraction is disclosed. The method comprises passing the mixture into a decantation zone where the solution is separated into a first fraction relatively rich in a first compound and a second fraction relatively deficient in the first compound. One of the separated fractions subsequently is passed to a membrane separation zone for further purification. The subject invention is of particular utility in petroleum processing, where the solution passed to the decantation zone may be a petroleum processing fraction, such as filtrate from a dewaxing zone or an extract or raffinate from an extraction separation zone.

Membrane separation process

An improvement in a dilution chilling dewaxing process wherein waxy lubricating oil stocks are solvent dewaxed by contacting them with successive increments of cold dewaxing solvent at a plurality of points along the height of a vertical tower divided into a plurality of stages while agitating the oil-solvent mixture in each stage to provide substantially instantaneous mixing of the waxy oil and solvent thereby precipitating wax from the oil while avoiding the well known shock chilling effect. The improvement resides in using as the dewaxing solvent, a mixture selected from the group consisting of (a) methylene chloride and (b) acetone, methylethyl ketone, methanol and mixtures thereof, and wherein the methylene chloride comprises at least about 20 LV% of the dewaxing solvent. This invention results in substantial energy savings, requires less solvent per volume of waxy oil feed and gives significant improvements in the filtration rate of the dewaxed oil over conventional autorefrigerant and/or ketone dewaxing solvents.

Dilution chilling dewaxing solvent

Waxy oils are solvent refined in a relatively low temperature, combination extraction-dewaxing process wherein the waxy oil is simultaneously extracted and at least partially dewaxed in a dilution chilling zone, sequentially followed by a second extraction and a second dewaxing to produce wax and useful lube oils, and wherein solvent does not have to be removed from the oil as it passes from step to step of the process. Further, if the second dewaxing is performed in a dilution chilling zone, then scraped-surface chillers are not required prior to filtering the wax from the oil.

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Sarnia, Canada

Theodore H West