Synthesis, Characterization, and Evaluation of Solid Acid Catalysts Derived from Waste Avocado Seeds for Biodiesel Production via Transesterification

Chan, Ivory Yun Xuan (2026) Synthesis, Characterization, and Evaluation of Solid Acid Catalysts Derived from Waste Avocado Seeds for Biodiesel Production via Transesterification. Final Year Project (Bachelor), Tunku Abdul Rahman of Management and Technology.

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Abstract

The present work synthesis and characterizes sulfonated solid acid catalysts from wasted avocado seeds for the transformation of oleic acid towards its transesterification to produce the biodiesel. Due to their abundance and economic viability, by-products like avocado seeds offer a promising route towards catalyst creation while promoting valorisation and a circular economy approach. The biochar from avocado seeds was first subjected to varieties of temperatures such as 200 °C, 400 °C, and 600 °C through carbonization and later to concentrated sulfuric acid to introduce functional groups like -SO3H. FTIR and TGA analyses were carried out to verify the functionality of the sulfonic acid groups and to determine functional group stability and thermal behaviour, respectively. The catalytic performance of the resultant catalysts was evaluated through oleic acid esterification and transesterification reactions. Saponification value (SV) determined average molecular weight of the fatty acids or ester bonds present in oleic acid whereas biodiesel quality was evaluated by yield, acid value (AV) determination as well as percentage of free fatty acid (FFA) content. Results showed that a catalyst resulting from carbonization at 400 °C exhibited better performance with resulting biodiesel having acid value of 0.3995 mg KOH/g and FFA content of 0.998%, which had met ASTM D6751 and EN 14214. On the contrary, catalysts resulting from 200 °C as well as 600 °C showed low activity, probably due to incomplete carbonization or structure collapse and loss of -SO3H group, respectively. Therefore, the results of this work demonstrate the potential of the waste avocado seeds as precursor for solid acid catalysts, being a low cost and environment friendly for a sustainable biodiesel production.