Investigation of Emission Performance of Green Diesel and Naphtha Blends in a Passenger Vehicle

The effects of using a blend of hydroprocessed vegetable oil (also known as green diesel) and heavier naphtha obtained from catalytic processing of non-edible oils in a small displacement passenger car were evaluated in this paper. Prior to the vehicle tests, the blend was optimized to meet the cetane number and flashpoint specifications of commercial diesel. A blend of neat naphtha (10%) and the green diesel (90%) fuel met the specification of cetane number, but could not meet the flashpoint specifications. To improve the flash point, naphtha was distilled to extract the heavier fractions to produce the heavier naphtha blendstock with an initial boiling point (IBP) of 120°C that was used for blending with green diesel. Vehicle tests were conducted with a blend of 90% green diesel and 10% heavier naphtha (GD90N10) and were compared with a fossil-based diesel fuel (DF). The emission results indicated that GD90N10 fuel emits lower carbon monoxide (CO), carbon dioxide (CO₂), and particulate matter (PM) emissions as compared to DF. A slight improvement in fuel economy was observed with the GD90N10 fuel. Initial studies indicated a promising way to use naphtha blended with green diesel, and further research is required to explore the full potential of similar blends as vehicle fuels.