Kinetics of African pear seed oil (APO) methanolysis catalyzed by phosphoric acid-activated kaolin clay

Abstract

Kinetics and mechanism of heterogeneous transesterification reaction of African pear seed oil (APO) catalyzed by phosphoric acid-activated kaolin clay to produce biodiesel were investigated. Heterogeneous catalyst synthesized by activating clay with phosphoric acid was used to examine the effect of time, temperature, methanol/oil molar ratio, catalyst concentration and agitation speed on the production of biodiesel. The kinetics was studied using two elementary reaction mechanisms: Eley–Rideal (ER) and Langmuir–Hinshelwood–Hougen–Watson (LHHW). The results obtained showed that the clay belongs to kaolinite group and acid-activated clay catalyst, AAC was able to convert APO to standard biodiesel with the variation of catalyst concentration, temperature methanol, speed and reaction time having significant effect in the production. About 78–80% biodiesel production was obtained with 10:1 methanol/oil molar ratio, 3?wt% AAC catalyst concentration, time 3?h, speed 300?rpm and at 60?°C temperature. The kinetics result revealed that the LHHW is the most reliable representation of the experimental data using acid-activated clay catalyst with surface reaction between adsorbed triglyceride and adsorbed methanol as rate determining step (RDS). The activation energy for the forward reaction was determined to be 10.08?kJ/mol. Hence, the production of biodiesel from non edible oil APO with cheap and available heterogeneous catalyst (AAC) is achievable.