Biodiesel Synthesis from Refined Palm Oil Using a Calcium Oxide Impregnated Ash-Based Catalyst: Parametric, Kinetics, and Product Characterization Studies

Abstract

Heterogeneous catalyzed transesterification has been proposed as a promising technology to mitigate the limitations of homogeneous transesterification such as wastewater generation, low free fatty acids, low water tolerance, and inability to recycle the catalyst. This work aims to evaluate a refined palm biodiesel synthesis process through heterogeneous catalyzed transesterification. Three major process variables were studied over a reaction duration of 3–6 h, including the reaction temperature (45–65 °C), percentage of catalyst loading (4–6 wt.%), and methanol to oil molar ratio (6:1–12:1). The highest biodiesel yield of 88.58% was recorded under the conditions of temperature 55 °C, catalyst loading 4 wt.% and methanol to oil molar ratio 9:1 at 5 h. A pseudo-first order reaction mechanism was applied in the kinetic analysis of the fatty acid methyl esters (FAME) concentrations. In addition, the activation energy and pre-exponential factors, as determined through the kinetic analysis, were 31.2 kJ/mol and 680.21 min−1, respectively. The key fuel properties of the produced palm biodiesel were determined to be acceptable according to the ASTM D 6751 and EN 14214 standards. The developed catalyst could feasibly be reused for the palm biodiesel synthesis up to the third cycle with lower reaction performance in the fourth cycle.