Isopropyl esters as solutions to biodiesel challenges

Soy methyl esters when used as biodiesel fuel has problems that are not associated with diesel fuel use such as increased oxides of nitrogen (NOx) emissions; a pollutant, cold flow issues, and limited shelf life. On the production side, there is a limited feedstock supply, and many production facilities are performing under capacity. The work described here will address these two issues through the continued improvement of biodiesel and by the identification of raw material prices when isopropyl esters of animal fat are economically viable. The effects of the fatty acid profile, degree of unsaturation, and alkyl groups on NOx emissions, cold flow, and oxidative stability were studied. The economic feasibility of using isopropyl esters in blends with different alkyl esters was evaluated through the use of a predictive cloud point model as a constraint. The predictive cloud point model was built from experimental data using methyl and isopropyl esters of soybean oil and tallow. Cost minimization was then performed for blends with a cloud point constraint. Through the characterization studies, isopropyl esters showed improvement on the cold flow properties. Steady state NOx emissions from isopropyl esters were NOx neutral or lower than methyl esters from the same feedstock depending on the engine load. Oxidative stability for isopropyl esters was low due to the production process, which removed its vitamin E content. Generally, the minimum cost blend for a specified cloud point is a binary blend. Isopropyl esters from animal fat are economically viable as a blend component if the price difference between methanol and isopropanol is less than {dollar}0.30/1b, where isopropanol is more expensive than methanol, and the price difference between soybean oil and tallow/lard is greater than {dollar}0.10/1b, where soybean oil is more expensive. These findings showed that isopropyl esters are potential solutions to the problems faced by soy methyl esters as a biodiesel fuel.