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Three monoalkyl fatty acid esters derived from tallow and grease were prepared by lipase-catalyzed transesterification and evaluated as prospective diesel engine fuels. The lowtemperature properties of the esters, both neat and as 20% blends in No. 2 diesel fuel, were evaluated. Those properties included cloud point, pour point, cold filter plugging point, low-temperature flow test, and crystallization onset temperature. Other properties of the esters, such as kinematic viscosity, heating value, and calculated cetane number, also were determined. All three esters had acceptable physical and low-temperature properties, as well as acceptable fuel properties at the 20% level in diesel blends. Engine performance and emissions for the ester blends were determined in a direct-injection, matched two-cylinder diesel engine. Among the monoalkyl esters studied, ethyl greasate had better properties and engine performance characteristics than the two tallow esters. For the latter esters, isopropyl tallowate had better properties than ethyl tallowate.

A hybrid fuel and No. 2 diesel fuel were burned in direct-injection diesel engines to compare the effects of the fuels on engine durability. The hybrid fuel was a microemulsion of soybean oil, diesel fuel, 190-proof ethanol and 1-butanol. The engines were run for 200 hr on each fuel with loads and speeds controIled by computer according to a cycle suggested by the EMA (Engine Manufacturer's Association). Engines were disassembled before and after the runs to determine the difference in wear and carbon deposits. The engine running on the hybrid fuel completed the 200-hr EMA test without difficulty. The hybrid produced less engine wear than diesel fuel, but produced greater deposits of carbon and lacquer on the injector tips, intake valves and tops of the cylinder liners. Also, engine performance was degraded ca. 5% at the end of the 200-hr test.

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