Biodegradable high performance hydrocarbon base oils

Details Biodegradable high performance hydrocarbon base oils Biodegradable high performance hydrocarbon base oils

2000-04-11

2003-01-14

Dang, Thuan D. (Department: 1764)

Mineral oils: processes and products

Products and compositions

Lubricating oils

C208S019000

Reexamination Certificate

active

06506297

ABSTRACT:

1. FIELD OF THE INVENTION
This invention relates to biodegradable high performance hydrocarbon base oils, suitable as engine oil and industrial oil compositions. In particular, it relates to lubricant base oil compositions, and process for making such compositions by the hydroisomerization/hydrocracking of paraffinic waxes, suitably Fischer-Tropsch waxes.
2. BACKGROUND
It is well known that very large amounts of lubricating oils, e.g., engine oils, transmission oils, gear box oils, etc., find their way into the natural environment, accidentally and even deliberately. These oils are capable of causing much environmental harm unless they are acceptably biodegradable. For this reason there is increasing emphasis in this country, and abroad, to develop and employ high performance lubricant base oils which are environmentally friendly, or substantially biodegradable on escape or release into the environment.
Few hydrocarbon base oils are environmentally friendly though their qualities as lubricants may be unchallenged. The literature stresses the superior biodegradability of ester based lubricants, natural and synthetic, over hydrocarbon based products. However there is little or no emphasis on performance. Few references are found relating to the biodegradability of hydrocarbon lubricants. Ethyl Petroleum Additives's EP 468 109A however does disclose the biodegradability of lubricating oils containing at least 10 volume percent of a “biodegradable liquid hydrocarbon of lubricating viscosity formed by oligomerization of a 1-alkene hydrocarbon having 6 to 20 carbon atoms in the molecule and hydrogenation of the resultant oligomer.” Apparently hydrogenated oligomers of this type have unexpectedly high biodegradability, particularly those having at least 50 volume percent dimer, trimer and/or tetramer. Ethyl Petroleum Additive's EP 558 835 A1 discloses lubricating oils having similar polyalphaolefin, PAO, components. However, both references point out performance debits for the synthetic and natural ester oils, such as low oxidative stability at high temperatures and poor hydrolytic stability. British Petroleum's FR 2675812 discloses the production of biodegradable PAO hydrocarbons base oils by dewaxing a hydrocracked base oil at low temperatures.
There is a clear need for biodegradable high performance hydrocarbon base oils useful as engine oil and industrial oil, or lubricant compositions which are at least equivalent to the polyalphaolefins in quality, but have the distinct advantage of being more biodegradable.
3. SUMMARY OF THE INVENTION
This invention, which supplies these and other needs, accordingly relates to biodegradable high performance paraffinic lubricant base oils, and process for the production of such compositions by the hydrocracking and hydroisomerization of paraffinic, or waxy hydrocarbon feeds, especially Fischer-Tropsch waxes or reaction products, all or at least a portion of which boils above 700° F., i.e., 700° F.+. The waxy feed is first contacted, with hydrogen, over a dual functional catalyst to produce hydroisomerization and hydrocracking reactions sufficient to convert at least about 20 percent to about 50 percent, preferably from about 20 percent to about 40 percent, on a once through basis based on the weight of the 700° F.+ feed, or 700° F.+ feed component, to 700° F.− materials, and produce 700° F.+ materials rich in methyl-paraffins. This resultant crude product, which contains both 700° F.− and 700° F.+ materials, characterized generally as a C
5
-1050° F.+ crude fraction, is first topped via atmospheric distillation to produce a lower boiling fraction the upper end of which boils between about 650° F. and 750° F., e.g., 700° F., and a higher boiling, or bottoms fraction having an initial boiling point ranging between about 650° F. and 750° F., e.g., 700° F., and an upper end or final boiling point of about 1050° F.+, e.g., a 700° F.+ fraction. The lower boiling fraction, e.g., the 700° F.− fraction, from the distillation is a non-lube, or fuel fraction.
At these conversion levels, the hydroisomerization/hydrocracking reactions convert a significant amount of the waxy, or paraffinic feed to 700° F.+ methyl-paraffins, i.e., isoparaffins containing one or more methyl groups in the molecule, with minimal formation of branches of carbon number greater than 1; i.e., ethyl, propyl, butyl or the like. The 700° F.+ bottoms fractions so-treated contain 700° F.+ isoparaffins that have less than about 7.5 methyl branches per 100 carbon atoms or 6.0 to 7.5 methyl branches, preferably less than about 7.0 methyl branches or 6.0 to 7.0 methyl branches, more preferably from about 6.5 to about 7.0 methyl branches per 100 carbon atoms, in the molecule. These isoparaffins, contained in a mixture with other materials, provide a product from which high performance, highly biodegradable lube oils can be obtained. The degree of branching, particularly methyl branching, is indicative of the biodegradability of the oil. That is, higher degrees of branching are less biodegradable or not biodegradable at all, while lower degrees of branching, e.g., <7.8 methyls, are indicative of biodegradability.
The higher boiling bottoms fractions, e.g., the 700° F.+ bottoms fraction containing the methyl-paraffins, or crude fraction, is dewaxed in a conventional solvent dewaxing step to remove n-paraffins, and the recovered dewaxed product, or dewaxed oil, is fractionated under vacuum to produce paraffinic lubricating oil fractions of different viscosity grades, including hydrocarbon oil fractions suitable as high performance engine oils and engine lubricants which, unlike most hydrocarbon base oils, are biodegradable on release or escape into the environment. In terms of their performance they are unsurpassed by the PAO lubricants, and are superior thereto in terms of their biodegradability.
4. DETAILED DESCRIPTION
The feed materials that are isomerized to produce the lube base stocks, and lubricants with the catalyst of this invention are waxy feeds, i.e., C
5
+, preferably having an initial boiling point above about 350° F. (117° C.), more preferably above about 550° F. (288° C.), and contain a major amount of components boiling above 700° F. (370° C.). The feed may be obtained either from a Fischer-Tropsch process which produces substantially normal paraffins, or from petroleum derived slack waxes.
Slack waxes are the by-products of dewaxing operations where a diluent such as propane or a ketone (e.g., methylethyl ketone, methyl isobutyl ketone) or other diluent is employed to promote wax crystal growth, the wax being removed from the base oil by filtration or other suitable means. The slack waxes are generally paraffinic in nature, boil above about 600° F. (316° C.), preferably in the range of 600° F. (316° C.) to about 1050° F. (566° C.), and may contain from about 1 to about 35 wt. % oil. Waxes with low oil contents, e.g., 5-20 wt. % are preferred; however, waxy distillates or raffinates containing 5-45% wax may also be used as feeds. Slack waxes are usually freed of polynuclear aromatics and hetero-atom compounds by techniques known in the art; e.g., mild hydrotreating as described in U.S. Pat. No. 4,900,707, which also reduces sulfur and nitrogen levels preferably to less than 5 ppm and less than 2 ppm, respectively. Fischer-Tropsch waxes are preferred feed materials, having negligible amounts of aromatics, sulfur and nitrogen compounds. The Fischer-Tropsch liquid, or wax, is characterized as the product of a Fischer-Tropsch process wherein a synthetic gas, or mixture of hydrogen and carbon monoxide, is processed at elevated temperature over a supported catalyst comprised of a Group VIII metal, or metals, of the Periodic Table of The Elements (Sargent-Welch Scientific Company, Copyright 1968), e.g., cobalt, ruthenium, iron, etc. The Fischer-Tropsch wax contains C
5
+, preferably C
10
+, more preferably C
20
+ paraffins. A distillation showing the fractional make up

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