International Research Journal of Engineering and Technology (IRJET) Volume: 04 Issue: 03 | Mar -2017
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e-ISSN: 2395 -0056 p-ISSN: 2395-0072
Compensation Effect in Transesterification Kinetics of Croton Megalocarpus Oil using Heterogeneous Alkaline Earth Catalysts Anil Kumar, Saul S. Namango Department of Chemical & Process Engineering Moi University, Eldoret, Kenya ----------------------------------------------------------------------------------***--------------------------------------------------------------------------biofuels. Production in 2014 was 126 billion litres, expected to rise to 144.5 billion litres in medium terms to year 2020 [1]. In spite of the recent discoveries of new crude sources, especially in Africa; petroleum reserves are finite, and would deplete or exhaust. It is estimated that the world is consuming 2.7% of petroleum reserve annually, and the stocks would last about 50 years [2]. Another advantage of biofuels is their superior environmental footprint. Biofuels consist of mainly carbon, hydrogen and oxygen. Upon combustion, these fuels are carbon neutral, do not produce nitrogen and sulphur oxides, unlike petroleum derived fuels. Biodiesel fuel produces far lower emissions of unburned-hydrocarbons, carbon dioxide, carbon monoxide, sulphates, polycyclic aromatic hydrocarbons, nitrated polycyclic aromatic hydrocarbons, ozone forming hydrocarbons and particulate matters [3]. Greenhouse gas emissions from biodiesel are between 22 and 59% of the emissions from petro-diesel. [4]. Biodiesel is produced by reacting vegetable oils or animal fats with an alcohol in presence of a catalyst. The reaction is a transesterification reaction producing alkyl ester (biodiesel) and glycerol.
Abstract - Reaction kinetics of transesterification of croton megalocarpus oil with methanol to produce fatty acid methyl ester was studied at 70 oC, using homogeneous and heterogeneous catalysts through conventional heating and microwave irradiation. NaOH was used as a homogenous catalyst, and alkaline earth metal oxides, BaO, SrO, CaO, MgO and BeO, were the heterogeneous catalysts. Reaction rate constant k; and Arrhenius equation parameters, pre-exponential factor A and activation energy E were estimated from kinetic data, using the overall reaction. By considering the magnitudes of k, NaOH was the most active catalyst, followed by BaO, SrO, CaO, MgO and BeO. However, no specific order was observed in the estimated values of A and E. Activation energy was not found to be a direct measure of catalyst activity for heterogeneous catalysts. This was explained by the complex nature of the three-phase reaction system where twenty one reactions were likely to be taking place simultaneously, and the observed kinetic parameters were the overall apparent values. Cremer Constable scatter plot showed the data points roughly following a straight line. It was concluded that the discrepancies in A and E values were due to oversimplification of kinetic model, rather than being a physical phenomena.
1.1 Transesterification reaction In a transesterification reaction of a triglyceride (oils and fats) alcohol is displaced from the triglyceride ester by another alkyl alcohol to produce an alkyl ester (biodiesel) and glycerol. The overall reaction can be represented as follows:
Key Words: Transesterification, Croton megalocarpus, Alkaline earth oxides, Kinetics, Conventional heating, Microwave irradiation, Compensation effect, Cremer Constable plot.
Triglyceride + 3 ROH ↔Glycerol + 3 alkyl ester
When methanol is used as alkyl alcohol, the corresponding alkyl ester is fatty acid methyl ester (FAME). The above reaction is a reversible reaction, and is usually carried out in presence of a catalyst. Reaction (i) is the overall reaction, supposed to take place in three steps. In the first step, triglyceride reacts with alcohol to produce diglyceride and ester. Further reaction with alcohol produces nonoglyceride and ester (second step), followed by reaction of monoglyceride with alcohol to produce
1. INTRODUCTION Biodiesel is a biofuel obtained from renewable sources and is recognized as an alternative to petro-diesel. In 2014 biofuels provided 4% of the fuel for transport sector, which is to rise to 4.3% in 2020. Reduction in petroleum crude prices in 2014 affected the production and use of
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