Normally liquid hydrocarbon fuels often require additives to improve their performance characteristics. Thus, in fuels such as gasoline, diesel fuel and jet fuel, various additives are employed to assist in maintaining cleanliness in the carburetor and fuel intake system and to prevent carburetor icing as well as to inhibit rust. The additives vary in effectiveness, and it is often necessary to use a number of additives in a single composition.
Many additives for hydrocarbon fuels are only marginally soluble in hydrocarbons. Furthermore, they are often employed in concentrations that approach their limits of solubility. As a result, hydrocarbon compositions containing such additives often exhibit poor stability and, as a result, on standing the additive may precipitate.
In addition, many additives for hydrocarbon fuels have poor water tolerance. When fuel compositions containing such additives come in contact with water as, for example, in storage tanks, water enters the hydrocarbon phase. This is particularly deleterious in jet fuels. The temperatures at high altitudes where jet aircraft operate are well below freezing. Hence, water in the fuel crystallizes and plugs fuel filters, thereby cutting off the flow of fuel to the engines. To combat this, fuel tank heaters and additives to prevent ice formation are employed.
A serious problem relating to internal combustion engines is environmental pollution as, for example, air pollution by exhaust emissions from internal combustion engines. A component of the exhaust from internal combustion engines is unburned hydrocarbons. Various methods have been used to reduce the hydrocarbons in engine exhausts, for example, catalytic mufflers and positive crank case ventilation systems.