Date of Award

6-2008

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Biosystems Engineering

Advisor

Walker, Terry H

Committee Member

Drapcho , Caye M

Committee Member

Toler , Joe E

Abstract

Transesterification of cottonseed oil and canola oil was carried out using low molecular weight alcohols and potassium hydroxide. For cottonseed oil, a central composite design with eight factorial, six center and six axial points was used to study the effect of catalyst concentration, molar ratio of ethanol to cottonseed oil and reaction temperature on percentage yield and percentage initial absorbance (%A385nm) of the biodiesel. Catalyst concentration and molar ratio of ethanol to cottonseed oil were the most influential variables affecting percentage conversion and percentage initial absorbance. Maximum percentage yield of 98 % is predicted at a catalyst concentration of 1.07 % (wt/wt) and ethanol to cottonseed oil molar ratio of 20:1 at reaction temperature of 25¡C. Maximum %A385nm of more than 80 % is predicted at 0.5 % (wt/wt) catalyst concentration and molar ratio of 3:1 at 25¡C. The response surfaces that described percentage yield and %A385nm were inversely related. Gossypol concentration (% wt), oxidative stability and %A385nm of biodiesel were found to be highly correlated with each other. Hence, color (%A385nm) is a measure of the amount of pigments present in biodiesel fuels not yet subjected to autoxidation. High gossypol concentration also corresponds to a fuel with high oxidative stability. The FAEE produced from cottonseed oil had superior oxidative stability to FAME produced from cottonseed oil.
Canola oil was transesterified using a 1:1 mole mixture of methanol and ethanol (M/E) with potassium hydroxide (KOH) catalyst. Effect of catalyst concentration (0.5 to 1.5 % wt/wt), mole ratio of M/E to canola oil (3:1 to 12:1) and reaction temperature (25 to 75 ¡C) on the percentage yield measured after 2.5 and 5.0 minutes were optimized using a central composite design with eight factorial, six center and six axial points. Maximum percentage yield of 98 % was predicted for catalyst concentration of 1.1 % (wt/wt) and M/E to canola oil mole ratio of 20:1 at a reaction temperature of 25 ¡C at 2.5 minutes. Maximum percentage yield of 99 % was predicted for a catalyst concentration of 1.15 % (wt/wt) and any mole ratio at reaction temperature of 25 ¡C at 5 minutes. Statistical analysis revealed that, increasing catalyst concentration and mole ratio resulted in curvilinear and linear trends in percentage yield, both at 2.5 minutes and 5 minutes. However, reaction temperature, which affected percentage yield at 2.5 minutes linearly, was insignificant at 5 minutes. The resultant mixed methyl/ethyl canola esters exhibited enhanced low temperature performance and lubricity properties in comparison to neat canola oil methyl esters and also satisfied ASTM D 6751 and EN 14214 standards with respect to oxidation stability, kinematic viscosity, and acid value.

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