EFFECT OF USING DIFFERENT ALCOHOLS ON THE FUEL QUALITY OF BIODIESEL

Abstract

Due to rapid industrialisation and use of advanced technologies there has been increase in the consumption of fossil fuels, especially petroleum. Increasing needs are reciprocally proportionate to diminishing reserves of coal and petroleum. So, the exaggerated need of energy has to be fulfilled and to curb the problem of increasing fuel prices; researchers are putting their efforts to produce an alternative fuels on large scale from resources which can be replenished. Liquid Biofuel is one of the potential alternatives to petroleum diesel because of their renewable and environmentally safe nature as these are principally derived from bio-based resources. Among different biofuels, Biodiesel is one of the promising alternative to petroleum diesel as it is proving to be a reliable and competent competitor to non-renewable petroleum diesel. Biodiesel is typically a mono-alkyl ester of fatty acids, which is being produced from commonly accustomed plants like Rapeseed, Soybean, Sunflower and Palm etc. But, over exploitation of these edible resources for fuel production led to socio-economic complications because of the over burden on land that is used for food crops. Thus, non-edible raw materials oils such as Karanja (Pongamia), Jatropha, Mahua, Moringa seed oil etc. have been promoted to raise the standards of these oils and being produced to complete the level of petroleum and be proven as the best resources for biodiesel production in all approaches both technically and economically. Though, literature study has revealed a number of techniques to produce biodiesel but trans-esterification reaction is most commonly adopted because of its simplicity. For trans-esterification, mainly methanol has been used as alcohol which is extracted from fossil resources. But as methanol is derived from fossil resources, biodiesel produced (methyl ester) cannot be said completely renewable. To make biodiesel renewable completely, alcohols used must be derived from bio-based degradable resources. Ethanol, Butanol and Pentanol are the alcohols which are derived from renewable sources. This primary goal of this dissertation is to focus on biodiesel production from Karanja oil, a 2nd largest non-edible oil found in India after Jatropha, using different higher alcohols and then investigate the effect of alcohols on fuel quality of biodiesel. The important reaction parameters that govern the trans-esterification reaction are molar ratio of alcohol to oil, catalyst type and its concentration and reaction time and temperature. Firstly, biodiesel production was optimised experimentally for methanol and ethanol and kinetics of trans-esterification reaction were studied to understand the impact of iv alcohol on biodiesel production. Optimised reaction parameters for both alcohols were as: 9:1 molar ratio, 60 °C temperature, 1.25 wt. % catalyst (KOH) and 120 minutes reaction time. It was observed that reaction was slower for ethanol trans-esterification and more energy was required to achieve equilibrium. Further, process variables were optimised with Response Surface Methodology by using Design Expert software for methanol, ethanol, 2-propanol, 1-butanol and 1-pentanol. Most notable point was that biodiesel yield dropped down with use of higher alcohols that can be attributed to decreasing alcohol reactivity. Moreover, biodiesel yield obtained with 2-propanol was least which can also owed to the lower reactivity of branched chain alcohol due to the steric hindrance. Fuel properties of different biodiesel fuels were checked in order to investigate the effect of different alcohols on biodiesel. It was noted that there is improvement in Cold Flow Properties, Calorific Value, Flash Point and Cetane Number. In addition, engine operation was done to analyse the performance characteristics of for different biodiesel fuels. Performance evaluation of diesel engine showed that Brake Specific Fuel Consumption for B20 blends was comparable to neat diesel whereas for pure biodiesel fuels, results obtained were inferior compared to pure diesel. However, among different biodiesel fuels, Brake Specific Fuel Consumption improved for higher alkyl esters. Similar observations were found in case of Brake Thermal Efficiency of most of biodiesel fuels in comparison to neat diesel. Thus, bio-based higher alcohols can be utilised for biodiesel production, even though there is drop is yield in comparison to methanol, but significant improvement in fuel properties and comparable engine performance is found for higher alkyl esters.