Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Biosystems Engineering


Walker, Terry

Committee Member

Chen , Feng

Committee Member

Chow , Alex

Committee Member

Toler , Joe


Biodiesel production was carried out from soybean, canola and cottonseed oils along with poultry fat using catalytic potassium hydroxide. Further, the physical properties of biodiesel were studied with addition of ethyl levulinate (ethyl 4-oxopentanoate), short-chain alcohols (ethanol, isopropanol and butanol), and commercial cold flow improver (CFI) additives. The effects of adding ethyl levulinate, short-chain alcohols, and commercial additives were determined by studying their influence on the acid value (AV), cloud point (CP), pour point (PP), cold filter plugging point (CFPP), induction period (IP), kinematic viscosity (KV) and the flash point (FP). The results showed improved low temperature properties of the methyl esters compared to unblended samples of biodiesel. In addition, KV and FP decreased with increasing content of ethyl levulinate and short-chain alcohol added to the biodiesel fuels. Parameters such as AV and IP were essentially unchanged upon addition of ethyl levulinate, short-chain alcohols, and CFI additives. In summary, it was demonstrated that specific fuel properties such as low temperature operability could be improved through blending (ethyl levulinate and short-chain alcohols) and additive (CFI) strategies.
In another study, transesterification of refined cottonseed oil was carried out with methanol, ethanol, 1-butanol and various mixtures of these alcohols at constant volume ratio of alcohol to oil (1:2) using KOH (1 wt %) as catalyst to produce biodiesel. In the mixed alcohol transesterifications, the formation of methyl esters was faster than ethyl and butyl esters. Cottonseed oil-based biodiesel prepared from methanol to ethanol and methanol to butanol volume ratios of 1:1 or greater with respect to higher alcohol exhibited enhanced cold flow properties versus neat methyl esters. Furthermore, these alkyl esters exhibited KVs and AVs within the limits prescribed in the ASTM D6751 and EN 14214 biodiesel fuel standards. Also examined was the influence of blending alkyl esters with ultra-low sulfur (<15 ppm S) diesel (ULSD) fuel. All blends exhibited improved cold flow properties (CP, PP, and CFPP) versus unblended alkyl esters and significantly enhanced lubricities versus unblended petrodiesel. In summary, mixed alkyl esters prepared from cottonseed oil displayed improved fuel properties versus methyl esters alone.
Lastly, transesterification of refined cottonseed oil was carried out using methanol and Novozym-435 (N-435;' Candida antarctica ' lipase B). The effect of N-435 concentration (0.9 to 2.5 % wt/wt), volume ratio of methanol to cottonseed oil (8:1 to 42:1) and reaction temperature (25 to 75 °C) on the percentage conversion measured after 24 hours was optimized using a central composite design with six center, eight factorial and six axial points. N-435 concentration was the only variable that significantly affected percentage conversion. Maximum observed percentage conversion of 98.5 % was obtained at an N-435 concentration of 1.7 % (wt/wt) and a methanol to cottonseed oil volume ratio of 42:1 at a reaction temperature of 50 °C. In summary, N-435 proved to be successful for synthesis of methyl esters from refined cottonseed oil, and exhibited excellent reusability, as it retained 81 % of its initial activity after 10 reuses at the reaction conditions where maximum conversion was obtained.