Date of Graduation


Document Type


Degree Name

Master of Science in Chemical Engineering (MSChE)

Degree Level



Chemical Engineering


Jamie A. Hestekin

Committee Member

William R. Penney

Second Committee Member

Wen Zhang


Biodiesel, One-step, Soybean Oil, Subcritical Conditions


Due to the environmental and economic impacts of diesel fuel based on petroleum, several studies have been done to find an alternative source of energy. Biodiesel is considered one of these alternative sources. It is a renewable source of energy produced from vegetable oils and animal fats. There are two main reaction routes used to produce biodiesel (fatty acid methyl esters). Transesterification reaction is the first route used to convert triglycerides to fatty acid methyl esters (FAMEs), while hydrolysis followed by esterification reactions are the second route employed to convert triglycerides to free fatty acids (FFA) and then further converted to FAMEs. The traditional method used to produce FAMEs is the catalytic method, such as acid and alkali-catalyzed. However, a common drawback of these two methods is they are very sensitive to the presence of water. The free-catalytic method (supercritical methanol method) was, also, developed to generate FAMEs. The major drawback in this method is the severe conditions, of temperature and pressure used to produce FAMEs.

The objective of this study was to evaluate the one-step catalytic free method at subcritical conditions using soybean oil (SBO), methanol (MeOH), and water (H2O) as reactants. Two system configurations were investigated, continuous and batch systems. A variety of conditions were tested, such as reaction time, temperature, and molar ratio (SBO:MeOH:H2O). Furthermore, a kinetic model described by four reactions (transesterification, hydrolysis, esterification, and degradation) was developed depending on current and previous studies done to produce FAMEs. Theoretical results of this model showed a sufficient agreement with experimental results due to obtaining an accepted standard error of estimate (3.86 and 6), which can indicate how much experimental and theoretical results are different, in both batch and continuous systems, respectively. This model showed that the optimum biodiesel yield values are ((83% and 55%) in batch and continuous systems, respectively, which occurred under sub-critical conditions and 1:39:22 molar ratio of SBO:MeOH:H2O. Also, the effects of degradation reactions were explained in this work. In general, the results in this study establish a strong understanding about all the reactions which happened in a one-step sub-critical method.