Sulphonated carbon catalyst for biodiesel synthesis.
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Date
2021
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Abstract
The uncertainty surrounding the sustainability of petroleum and petroleum derived products along with efficient waste management methods and the increasing energy demands are of great concern in modern society. As a result, the development of innovative industries capable of converting waste products into high value products has garnered interest from researchers and industrialists worldwide. Biodiesel is a promising candidate to replace or blend with petro-diesel since it is synthesised using renewable sources and its application requires no modification to the existing engine. The fuel has many superior properties compared to petroleum-based diesel such as, increased lubricity, non-toxicity, biodegradability, ease of handling, transport, storage, and that production can be decentralized to improve rural economies. The Fatty Acid Methyl Esters (FAME) constituting biodiesel is manufactured commercially using two methods, which is the transesterification of triglycerides (TGs) and the esterification of free fatty acids (FFAs). Both these processes occur in the presence of a catalyst hence there is urgency for an efficient and cost-effective catalyst capable of promoting both reactions without the process challenges encountered when heterogeneous base or homogenous acid and base catalysts are used. The main aim of the study was to synthesize a sulphonated catalyst based on tyre pyrolysis char, and to determine the performance of this catalyst for biodiesel production using the model esterification reaction between oleic acid and methanol. The sulphonation was carried out using concentrated sulphuric acid and under high temperature, and the final catalyst was subjected to Fourier transform infrared spectroscopy and surface area analysis. The characterization confirmed that the catalyst had been successfully prepared. The process was examined using a Box-Behnken experimental design. The process factors which were investigated were temperature, catalyst loading and alcohol to oil ratio. The experimental data were fitted to a quadratic response model with a satisfactory R2 value of 0.938. Temperature was found to have the most significant effect on product yield and that it may be possible to recover some of the energy used in heating the reaction mixture by condensing the exit vapour stream. The highest yield of methyl oleate obtained was 95.32% at a temperature of 65 °C, alcohol to oil ratio of 6:1, and catalyst loading of 1.5%. The lowest yield obtained was 75.44% at a temperature of 25℃, alcohol to oil molar ratio of 5.35 and catalyst ratio of 0.5%. The catalyst was recovered and reused and produced a methyl oleate yield of 75.58% which was 18.89% lower than the fresh catalyst so a regeneration may be required in the form of mild sulphonation. The sulphonated char catalyst was able to perform as a solid acid catalyst for the esterification of oleic acid and methanol and hence is a viable catalyst for biodiesel production.
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Masters Degree. University of KwaZulu- Natal, Durban.