No-Sulfur Fuel Lubricity Additive (Baker Hughes)

CATEGORY: LUBRICANTS
PATENT
No-Sulfur Fuel Lubricity Additive (Baker Hughes)
United States Patent Application 20120317876
Inventors:
Hoang, Viet Q. (Houston, TX, US)
Leung, Philip L. (Houston, TX, US)
Rivers, Gordon T. (Houston, TX, US)
Application Number:
13/597367
Publication Date:
12/20/2012
Assignee:
Baker Hughes Incorporated (Houston, TX, US)
Abstract:
Reacting an alkylene carbonate, such as ethylene carbonate, with dimer acid in the presence of a catalyst, such as a tertiary amine catalyst, gives a dimer acid diester having essentially no sulfur, and thus may be added to ultra-low sulfur diesel fuel downstream of a refinery. The diester enhances the lubricity properties of hydrocarbon fuels, increases their service life and fuel efficiency. The manufacturing process time may be decreased significantly compared with a process using ethylene glycol instead of ethylene carbonate, and much less ethylene glycol by-product results.
TECHNICAL FIELD
The present invention relates to methods and compositions for improving lubricity in hydrocarbon fuels, and more particularly relates, in one non-limiting embodiment, to methods and compositions for hydrocarbon fuel lubricity additives having essentially no sulfur.
BACKGROUND
It is well known that in many engines the fuel is also the lubricant for the fuel system components, such as fuel pumps and injectors. Many studies of fuels with poor lubricity have been conducted in an effort to understand fuel compositions that have poor lubricity and to correlate lab test methods with actual field use. The problem is general to diesel fuels, kerosene and gasolines, however, most of the studies have concentrated on the first two hydrocarbons.
Previous work has shown that saturated, monomeric and dimeric, fatty acids of from 12 to 54 carbon atoms used individually give excellent performance as fuel lubricity aids in diesel fuels. Fatty acids are for the most part unbranched. A number of other kinds of lubricity additives are also known. Since the advent of low sulfur diesel fuels in the early 1990s, relatively large amounts of these lubricity additives have been used to provide a fuel that does not cause excessive wear of engine parts.
Unfortunately, many commercially available fatty acids and fatty acid blends tend to freeze or form crystals at temperatures common during winter weather. The freezing or formation of crystals makes handling of the additives, and particularly injection into fuel, difficult. Blending the fatty acid with a solvent can lower the freezing point and reduce the crystal formation temperature, or cloud point. However, addition of a solvent may increase cost and preparation complexity.
Some of the fatty acids, fatty acid ammonium salts and fatty acid amides presently used may have the disadvantage of solidifying on storage at low temperatures. Often even at room temperature, crystalline fractions may separate and cause handling problems. Diluting the additives with organic solvents only partly solves the problem, since fractions may still crystallize out from solutions or the solution may gel and solidify. Thus, for use as lubricity additives, the fatty acids, fatty acid ammonium salts and fatty acid amides either have to be greatly diluted or kept in heated storage vessels and added via heated pipework.
It is also known to make fuel lubricity additives by reacting alkylene glycols with monomeric and dimeric carboxylic acids using sulfur-containing catalysts such as toluene sulfonic acid. However, this method takes considerable time, on the order of 40 to 60 hours, produces significant amounts of alkylene glycol and water as by-products and leaves certain amounts of sulfur in the additive which undesirably wind up in the hydrocarbon fuel. Further, as environmental regulations have become more stringent, low sulfur fuels are mandated to have increasingly lower amounts of sulfur present and even the small amounts present in these additives become problematic.
Thus, it would be desirable if a way could be discovered to enhance the lubricity of distillate fuels, but that involved essentially no sulfur. Further, it would be helpful if a no-sulfur fuel additive could be made by a process relatively quickly without large amounts of by-products.
SUMMARY
There is provided, in one non-limiting form, a dimer acid diester fuel lubricity additive having the formula (I):
where: R and R′ are the same or different, saturated, unsaturated or polyunsaturated, straight or branched alkyl groups having from 1 to 30 carbon atoms;
• ◦n, m, n′ and m′ are the same or different, ranging from 0 to 20; and
◦there may be more than one C—C crosslink between the monofunctional carboxylic acid moieties.
Alternatively there is provided in one non-restrictive embodiment a fuel lubricity additive produced by reacting a first reactant, such as an alkylene carbonate, an alkylene sulfite, an alkylene thionocarbonate and mixtures thereof, with dimer acid in the presence of a catalyst. The catalyst may be a tertiary amine or a weakly basic metal oxide or metal hydroxide, where the metal is chosen from the alkaline earth metals, the transition metals and/or the lanthanide metals. “Weakly basic” is defined as having a pK-b greater than 1. Strongly basic alkali metal hydroxides have also been tried with some success, where a strongly basic catalyst is defined herein as having a pK-b less than 1, such as NaOH.
In another non-limiting version there is provided a method for producing a fuel lubricity additive comprising reacting ethylene carbonate with dimer acid in the presence of a catalyst as described above.
Further there is provided in one non-restrictive embodiment a hydrocarbon fuel containing a fuel lubricity additive, where the fuel lubricity additive in turn is a dimer acid diester having the formula (I):
where R and R′ are the same or different, saturated, unsaturated or polyunsaturated, straight or branched alkyl groups having from 1 to 30 carbon atoms, and n, m, n′ and m′ are the same or different, ranging from 0 to 20, and there may be more than one C—C crosslink between the monofunctional carboxylic acid moieties. The amount of the fuel lubricity additive is effective to improve the lubricity of the hydrocarbon fuel as compared to an otherwise identical fuel absent the fuel lubricity additive.
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