Evaluation of catalyst and alcohol fuel emissions control for a small four cycle utility engine

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Virginia Tech


This research investigated emissions of formaldehyde, acetaldehyde, carbon monoxide, and hydrocarbons from a small utility engine fueled with mixtures of gasoline, ethanol, and methanol. Measurements made for each fuel mixture, with and without a catalyst, allowed a qualitative evaluation of the catalyst effect on the aforementioned pollutants. California Air Resources Board small utility engine regulations motivated this research.

The engine was loaded by an electrical generator with output of approximately 1000 watts to simulate actual operating conditions. Operation occurred at steady state conditions with a fixed air/fuel ratio.

Alcohol addition reduced emissions of carbon monoxide (CO) and total hydrocarbons (THC) from gasoline only levels. Adding a 50% volume of ethanol to the fuel, CO and THC emissions decreased 75% and 50% respectively. Adding 50% methanol reduced CO and THC 95% and 60% respectively.

Qualitatively, no catalytic control of CO or THC was demonstrated with any of the fuels used. However, a lack of replicates prevented quantification of catalyst results.

Both formaldehyde and acetaldehyde emissions increased with the addition of ethanol. Addition of 50% ethanol resulted in an increase of at least 600% in acetaldehyde emissions. Methanol addition increased formaldehyde emissions, but correlation of emissions with alcohol content was not possible. Acetaldehyde emissions appeared to decrease with increasing methanol content after an initial increase from the gasoline only values.

No catalytic oxidation of formaldehyde was demonstrated, but acetaldehyde emissions may have been decreased by the catalyst when employing 50% ethanol fuel.