It has long been desired to maximize fuel economy, power and driveability in diesel fuel powered vehicles while enhancing acceleration, reducing emissions, and preventing hesitation. While it is known to enhance gasoline powered engine performance by employing dispersants to keep valves and fuel injectors clean in port fuel injection engines, such gasoline dispersants are not necessarily effective direct fuel injected diesel engines. In addition, dispersants for indirect fuel injected diesel engines may not be effective for direct fuel injected diesel engines. The reasons for this unpredictability lie in the many differences between the direct and indirect fuel injected diesel engines and the fuels suitable for such engines.
For example, there is a dramatic difference between indirect fuel injected diesel engines, and more modern high pressure common rail (HPCR), direct fuel injected diesel engines. Also, low sulfur diesel fuels and ultra low sulfur diesel fuels are now common in the marketplace for such engines. A “low sulfur” diesel fuel means a fuel having a sulfur content of 50 ppm by weight or less based on a total weight of the fuel. An “ultra low sulfur” diesel fuel (ULSD) means a fuel having a sulfur content of 15 ppm by weight or less based on a total weight of the fuel. Fuel injectors in an HPCR engine perform at much higher pressures and temperatures compared to older style engines and fuel injection systems. The combination of low sulfur or ULSD and HPCR engines have resulted in a change to the type of injector deposits and frequency of formation of injector deposits now being found in the marketplace.
Over the years, dispersant compositions for diesel fuels have been developed. Dispersant compositions known in the art for use in fuels include compositions that may include polyalkylene succinimides, polyamines and polyalkyl substituted Mannich compounds. Dispersants are suitable for keeping soot and sludge suspended in a fluid, however the foregoing dispersants are not particularly effective for cleaning surfaces once deposits have formed on the surfaces.
Hence, fuel compositions for direct fuel injected diesel engines often produce undesirable deposits in the internal engine surfaces and fuel filters. Accordingly, improved compositions that can prevent deposit build up, maintaining “as new” cleanliness for the vehicle life are desired. Ideally, the same composition that can clean up dirty fuel injectors restoring performance to the previous “as new” condition would be equally desirable and valuable in the attempt to reduce air borne exhaust emissions and to improve the power performance of the engines.
In accordance with the disclosure, exemplary embodiments provide a fuel soluble additive for a diesel engine, a diesel fuel containing the additive, a method for improving performance of fuel injectors and a method for cleaning fuel injectors for a diesel engine. The fuel soluble additive includes a quaternary ammonium salt derived from an amido amine containing at least one tertiary amino group and an epoxide, in the presence of a proton donor. The amido amine is made in a reaction medium that is substantially devoid of an acylating agent.
Another embodiment of the disclosure provides a method of improving the injector performance of a direct fuel injected diesel engine. The method includes operating the engine on a diesel fuel composition containing a major amount of diesel fuel and from about 5 to about 100 ppm by weight based on a total weight of the fuel composition of a quaternary ammonium salt derived from an amido amine containing at least one tertiary amino group and an epoxide, in the presence of a proton donor selected from a carboxylic acid and an alkyl phenol. The amido amine is made in a reaction medium that is substantially devoid of an acylating agent.
A further embodiment of the disclosure provides a method of operating a direct fuel injected diesel engine. The method includes combusting in the engine a fuel composition containing a major amount of fuel and from about 5 to about 100 ppm by weight based on a total weight of the fuel composition of a quaternary ammonium salt derived from an amido amine containing at least one tertiary amino group and an epoxide, in the presence of a proton donor selected from a carboxylic acid and an alkyl phenol. The amido amine is made in a reaction medium that is substantially devoid of an acylating agent.
In another embodiment of the fuel additive, an amido amine is derived from a fatty acid.
An advantage of the fuel additive described herein is that the additive may not only reduce the amount of deposits forming on fuel injectors, but the additive may also be effective to clean up dirty fuel injectors sufficient to provide improved power recovery to the engine.
Another advantage of the fuel additive described herein is that it may be used at a much lower concentration than a quaternary ammonium salt derived made from an amine that is derived from an acylating agent, yet provide better injector cleanliness performance than conventional quaternary ammonium salts made from amines derived from acylating agents.
Additional embodiments and advantages of the disclosure will be set forth in part in the detailed description which follows, and/or can be learned by practice of the disclosure. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure, as claimed.