Abstract
Transesterification of waste vegetable oil is one of the promising partial substitutes for fossil fuels. The degradation characteristics of waste vegetable oil using supercritical alcohols (ethanol and methanol) have been studied in this research. The elementary target was to conduct comparative analysis of the effect of supercritical methanol and supercritical ethanol as solvents on the transesterification along with the analysis of product obtained in terms of carbon number. The experiments were carried out at transesterification temperatures of 250, 270 and 290 °C, retention time of 0 to 60 min at an interval of 15 min and oil to alcohol molar ratios of 1:6, 1:12 and 1:18 for both alcohols. The conversion increased with increase in transesterification temperature and retention time. At 290 °C, almost 99% conversion was achieved for 60-min holding time for both alcohols. Increase in conversion of waste vegetable oil was observed as the molar ratio increased. Supercritical transesterification resulted into ester yield higher than 95% with non-ester composition and glycerol collectively less than 5%.
Highlights
Diminishing fuel resources along with the urgency to reduce greenhouse gas emissions have been a dominant aspiration for the development of alternative fossil fuels
Temperature plays a critical part in supercritical alcohol transesterification reaction for biodiesel production
In consonance with the results acquired in this work, the work by Madras at al. [33] features conversion in supercritical ethanol is higher compared to supercritical methanol during transesterification of sunflower oil
Summary
Diminishing fuel resources along with the urgency to reduce greenhouse gas emissions have been a dominant aspiration for the development of alternative fossil fuels. Fossil fuels, such as petroleum, coal and natural gas are consumed continually to meet the energy requirement of the human race and are correlated with the adverse environmental impacts including global warming [1,2]. Fossil fuels, formed over series of geological activities, are exhausted at a rate more than million times faster than they were formed leaving us in a perilous position for petroleum products [3]. In developing countries, the price invested in petrol, its products and diesel dominates overall expenditures forming a major part of those countries’ import invoice [3]
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