Submitted to: Fuel Processing Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2007
Publication Date: 7/1/2007
Citation: Hess, M.A., Haas, M.J., Foglia, T.A. 2007. Attempts to Reduce NOx Exhaust Emissions by Using Reformulated Biodiesel. Fuel Processing Technology. 88(7):693-699. Interpretive Summary: Biodiesel is a renewable and biodegradable diesel fuel made from vegetable oils and animal fats that runs in any conventional, unmodified diesel engine. Additional advantages to using biodiesel are that it improves engine lubricity and reduces engine emissions such as carbon monoxide and particulates. Unfortunately, soy oil-based biodiesel, the most widely available form of this fuel in the U.S., when used directly or as a blend in petroleum diesel, causes an increase in nitrogen oxides emissions. To further advance the use of this renewable fuel, there is a need to address the elevated levels of this primary pollutant. To address this need, we examined two reformulated soy-based biodiesels and determined their nitrogen oxide (NOx) emissions in a simple test engine. Results indicated that decreased saturation of this fuel in combination with increased oxygenation has the potential for decreasing its nitrogen oxide emissions. The results should advance the use of this readily available and renewable biodiesel fuel.
Technical Abstract: Two routes were investigated for reformulating soy-based biodiesel in an effort to reduce its nitrogen oxide emissions. In the first approach, methyl soyate was modified by converting a proportion of the cis-bonds in the fatty acid chains of its methyl esters to their trans isomers. In the second approach, polyol derivatives of soybean oil were transesterified to form soy polyol fatty acid methyl esters. The NOx emissions of these modified biodiesels were then measured using a Yanmar L100 single cylinder, four stroke, naturally aspirated, air cooled, direct injection diesel engine. Using either isomerized methyl oleate or isomerized methyl soyate, at a 20% blend level in petroleum diesel (B20), nitrogen oxide emissions were elevated by between 1.5 and 3 percentage points relative to the combustion of a B20 blend of commercial soy-based biodiesel. On the other hand, NOx emissions were reduced in proportion to blend level during the combustion of polyol biodiesel, with a 20% blend in petrodiesel resulting in a reduction of about 4.5 percentage points relative to the emissions of a comparable blend of commercial soy-based biodiesel.