A comprehensive study of the upcycling of litchi chinensis waste into a sustainable transesterification catalyst

Biodiesel has gained popularity in the past decade and now serves in the forefront as a renewable fuel substitute to fossil fuel in the transportation sector. The current investigation aims at producing a low-cost transesterification catalyst from litchi residue, generated as a waste from the food processing industries. The catalyst was utilized for biodiesel formation from jatropha curcas oil. Advanced analytical tools were used to thoroughly characterize both the catalyst and the final product. The catalyst characterization results established the presence of Ca and K as active metal components. Utilizing one-factor-at-a-time approach, the influence of reaction parameters on the catalytic transesterification process was rigorously investigated. An impressive biodiesel yield of 99.4% along with a fatty acid methyl ester (FAME) conversion rate of 99.5% was attained under optimal reaction conditions characterized by a methanol to oil ratio of 1:7.5, a catalyst loading of 5 wt%, a reaction duration of 150 min, and a temperature of 65 °C. Furthermore, the kinetics and thermodynamics of the reaction was evaluated and the activation energy of the process was calculated to be 37.01 KJmol^-1. The fuel properties of the product were in correspondence to the ASTM standards. The catalyst was successfully recycled for over five successive runs with recorded 95.8% yield from last cycle. The Life cycle cost analysis (LCCA) was performed and the production cost per kg of catalyst was determined to be $0.217.