Submitted to: Fuel Processing Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/1/2009
Publication Date: 5/28/2009
Citation: Moser, B.R., Williams, A., Haas, M.J., Mccormick, R.L. 2009. Exhaust Emissions and Fuel Properties of Partially Hydrogenated Soybean Oil Methyl Esters Blended with Ultra Low Sulfur Diesel Fuel. Fuel Processing Technology. 90:1122-1128. Interpretive Summary: Biodiesel has many advantages over conventional petroleum-derived diesel fuel (petrodiesel), such as derivation from a renewable and domestic feedstock, displacement of imported petroleum, inherently good lubricating properties, essentially no sulfur content, superior flash point and biodegradability, as well as a reduction in most exhaust emissions. However, exhaust emissions of nitrogen oxide species (NOx) are unfortunately increased during biodiesel combustion in comparison to petrodiesel. Nitrogen oxide emissions are regulated by the U.S. Code of Federal Regulations because they are implicated in deterioration of air quality through promotion of unhealthy smog formation. Smog is of course a serious threat to air quality in large urban centers and environmentally sensitive areas such as national parks. For universal acceptance of biodiesel, it is desirable to reduce smog-forming NOx exhaust emissions to levels equal to or lower than those observed for petrodiesel. In the current study, the chemical composition of biodiesel prepared from soybean oil was modified in an effort to reduce NOx emissions through catalytic partial hydrogenation. Exhaust emissions analysis performed using a compression-ignition (diesel) engine demonstrated that hydrocarbon, carbon monoxide and particulate matter emissions were reduced significantly in comparison to petrodiesel. The increase in NOx during combustion of the chemically modified soybean-derived biodiesel was not as great as that observed for normal soybean-based biodiesel. In conclusion, this work is expected to further support American agriculture by demonstrating that chemical modification of domestically produced soybean oil is an effective tool to reduce problematic NOx exhaust emissions.
Technical Abstract: Important fuel properties and emissions characteristics of blends (20 vol%) of soybean oil methyl esters (SME) and partially hydrogenated SME (PHSME) in ultra low sulfur diesel fuel (ULSD) were determined and compared with neat ULSD. The following changes in physical properties were noticed for B20 blends of SME and PHSME in comparison to neat ULSD: improved lubricity, higher kinematic viscosity, lower oxidative stability, and inferior low temperature performance. With respect to exhaust emissions, B20 blends of PHSME and SME exhibited lower PM and CO emissions in comparison to neat ULSD. Furthermore, the PHSME blend also resulted in a significant reduction in THC emissions. Both SME and PHSME B20 blends yielded a small increase in NOx emissions. The reduction in double bond content of PHSME did not result in a statistically significant difference in NOx emissions in comparison to SME at the B20 blend level. As typically seen, both the SME and PHSME blends resulted in a greater amount of fuel consumption than neat ULSD, which was due to the lower energy content of biodiesel. However, the increase in fuel consumption was less for the PHSME blend, indicating that it possessed more energy content than the SME blend. The results indicate that a small degree of hydrogenation, sufficient to render SME compliant with existing European specifications regarding iodine value, does not results in an increase in NOx exhaust emissions.