Fuel and related compositions – Liquid fuels – Containing organic -c
Patent
1992-12-09
1995-06-13
Ivy, C. Warren
Fuel and related compositions
Liquid fuels
Containing organic -c
44443, C10L 114, C10L 118
Patent
active
054238900
DESCRIPTION:
BRIEF SUMMARY
This invention relates to fuel oil compositions, and more especially to fuel oil compositions susceptible to wax formation at low temperatures, and to additive compositions for such fuel oil compositions.
Heating oils and other distillate petroleum fuels, for example, diesel fuels, contain alkanes that at low temperature tend to precipitate as large crystals of wax in such a way as to form a gel structure which causes the fuel to lose its ability to flow. The lowest temperature at which the fuel will still flow is known as the pour point.
As the temperature of the fuel falls and approaches the pour point, difficulties arise in transporting the fuel through lines and pumps. Further, the wax crystals tend to plug fuel lines, screens, and filters at temperatures above the pour point. These problems are well recognized in the art, and various additives have been proposed, many of which are in commercial use, for depressing the pour point of fuel oils. Similarly, other additives have been proposed and are in commercial use for reducing the size and changing the shape of the wax crystals that do form. Smaller size crystals are naturally desirable since they are less likely to clog a filter; certain additives inhibit the wax from crystallizing as platelets and cause it to adopt an acicular habit, the resulting needles being more likely to pass through a filter than are platelets. The additives may also have the effect of retaining in suspension in the fuel the crystals that have formed, the resulting reduced settling also assisting in prevention of blockages.
Effective wax crystal modification (as measured by CFPP and other operability tests, as well as simulated and field performance) may be achieved by flow improvers, mostly ethylene-vinyl acetate copolymer (EVA)-based, in distillates containing up to 4 wt %-n-alkanes at 10.degree. C. below cloud point (wax appearance temperature), as determined by gravimetric or DSC methods.
Problems still remain, however, especially with high wax content distillates like those encountered in the Far East and Australia which although featuring similar distillation characteristics have much higher wax contents (between 5 and 10% at 10.degree. C. below the cloud point as measured by DSC or gravimetric analysis) and different carbon number distribution. Particularly difficult to treat fuels are those with a high wax content and a relatively low final boiling point, i.e., no higher than 370.degree. C., sometimes below 360.degree. C., which have high wax contents over a narrow carbon number distribution. The most difficult to treat are those fuels obtained from high wax crudes such as those from the crudes in Australia and the Far East where the total n-alkane content of the distillate can be greater than 20%, the total content being C.sub.9 and higher n-alkanes as measured by GLC.
The present invention is concerned to provide a fuel additive effective both to improve low temperature flow of the fuel and also to inhibit wax settling.
In one aspect, the present invention is directed to a fuel oil additive composition comprising: weight of at least 30,000 and an ethylene content of from 50 to 85 molar per cent, copolymer having an ester content of at least 10 molar per cent or an ethylene-.alpha.-olefin copolymer having a number average molecular weight of at most 7500, and
The invention also provides a fuel oil containing the additive composition, and an additive concentrate comprising the additive composition in admixture with a fuel oil or a solvent miscible with the fuel oil. The invention further provides the use of the additive composition to improve the low temperature properties of a fuel oil.
The ethylene-.alpha.-olefin copolymer that forms component (a) of the additive composition of the invention is a copolymer of ethylene and at least one .alpha.-olefin, preferably one having at most 20 carbon atoms. Examples of such olefins are propylene, 1-butene, isobutene, n-octene-1, isooctene-1, n-decene-1, and n-dodecene-1. The copolymer may also comprise small amounts, e.g., up to
REFERENCES:
patent: 4211534 (1980-07-01), Feldman
patent: 4375973 (1983-03-01), Rossi et al.
patent: 4546137 (1985-10-01), Rossi et al.
patent: 5045088 (1991-09-01), More et al.
Camarco Wayne M.
More Iain
Smith Darryl R. T.
Covington Raymond
Exxon Chemical Patents Inc.
Ivy C. Warren
White Vivienne T.
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