Date of Award

12-2008

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Food Technology

Advisor

Chen, Feng

Committee Member

Wang , Xi

Committee Member

Walker , Terry H

Committee Member

Toler , Joe E

Abstract

Biodiesel, derived from the transesterification of vegetable oils or animal fats with simple alcohols, has attracted more and more attention recently. As a cleaner burning diesel alternative, biodiesel has many attractive features including: biodegradability, nontoxicity, renewability and low emission profiles.
Although cottonseed oil was the first commercial cooking oil in the U.S, it has progressively lost its market share to some vegetable oils that have larger production and less cost. However, regarding the active researches on biodiesel production from vegetable oils, there is a promising prospective for the cottonseed oil as a feedstock for biodiesel production, which may enhance the viability of the cottonseed industry.
The focus of this research is to optimize the biodiesel production from crude cottonseed oil. The effect of variables including methanol/oil molar ratio, catalyst concentration, reaction time, reaction temperature, and rate of mixing on the biodiesel yield was examined and optimized by response surface methodology (RSM). Besides, a second-order model was deduced to predict the biodiesel yield. Confirmation experiment was further conducted, validating the efficacy of the model.
In addition to conventional transesterificaiton method, low frequency ultrasonic irradiation was also investigated for biodiesel production. This study demonstrated that the ultrasound treatment was more efficient in biodiesel production than the conventional method. This was attributed to the ultrasound effect, which can make methanol to cavitate so as to disperse the oil phase into nano-droplets and form a fine emulsion ofmethanol in oil. As a result, contact surface between the reagents is dramatically increased resulting in a significant increase of the reaction speed.
Moreover, engine performance test of the cottonseed oil biodiesel (cottonseed oil methyl esters, COME) was examined. The results showed that CO, CO2 and NOx emissions of the COME were lower than those of the No. 2 diesel fuel, although there was no significant difference at the statistical level of p<0.05. The engine test also demonstrated a slightly higher amount of consumption and less tendency of coke formation from the COME than those from the No. 2 diesel fuel. In general, the cottonseed oil biodiesel exhibited friendly environmental benefits and acceptable stability, demonstrating its feasibility as an alternative fuel.

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