SOURCE:

Faculty: Engineering
Department: Chemical Engineering

CONTRIBUTORS:

Ude, C. N.
Onukwuli, D. O.

ABSTRACT:

The kinetics and engine performance of biodiesel from African pear seed oil (APO) and Gmelina seed oil (GSO) by modified clay catalysts were carried out. The catalyst was synthesized by activating it with heat, phosphoric acid and sodium hydroxide. They were characterized using American Society for Testing Materials (ASTM) D4067 (1986) standard methods to determine their phsico-chemical properties.The parameters investigated for transesterification of the oils were the reaction time 1, 2, 3, 4 and 5hours, catalysts concentration 1, 2, 3, 4 and 5 % wt,methanol/oil molar ratio 6:1, 8:1, 10:1, 12:1 and 14:1, reaction temperature 45, 50, 55, 60 and 65oC and agitation speed 100, 200, 300, 400 and 500rpm. The oil were extracted by solvent extraction using two solvents: n-hexane and petroleum ether and the process parameters were optimized using response surface methodology (RSM). The physical and chemical properties of the oil and biodiesel were determinedusing (ASTM) 6751(1973) standard methods in order to investigate the effects of the properties of the triglyceride and the reaction parameters on the product characteristics and yields. The biodiesel process parameters were optimized using response surface methodology (RSM) in combination with central composite design, CCD. The heterogeneous catalysis kinetics was studied using two elementary reaction mechanisms: Eley-Rideal (ER) and Langmuir–Hinshelwood–Hougen–Watson (LHHW).The engine performance was carried out with a steady-state diesel engine test bed. Some of the experimental data were used to train and develop Artificial Neural Network (ANN) model based on optimization algorithm for the engine performance and biodiesel production. The results obtained proved that the modification of the clay improved its catalytic properties thereby facilitating the production of biodiesel. The results obtained show that n-hexane and petroleum ether are good solvents for extracting APO and GSO. The properties of the APO and GSO determined showed that they require pretretment but the use of the modified clay catalyst circumvented the process. The reaction conditions did not significantly affect the properties of the biodiesel but affected the yield. The yield increased as the process parameters increased and decreased when the reaction time, catalyst concentration, reaction temperature, methanol/oil molar ratio and agitation speed were above 3h, 3wt%, 60oC, 10:1 and 350rpm respectively. The biodiesel produced generally met the criteria required for commercial biodiesel. The optimum reaction conditions were; reaction time of 3h, catalyst concentration of 3 wt%, reaction temperature of 60oC, methanol/oil molar ratio 10:1 and agitation speed of 350rpm. The optimal yield rangingfrom 77-80% was obtained for activated clay catalysts. The heterogeneous kinetics result revealed that the LHHW is the most reliable representation of the experimental data using activated clay catalysts with surface reaction between adsorbed triglyceride and adsorbed methanol as rate determining step (RDS). The effective rate constantfor the reaction increased as temperature increased showing that the reactions are endothermic and proceed at temperature below the boiling point of methanol.The thermodynamic parameters showed that the reactions were feasible and spontaneous.The thermal efficiency and brake power of biodiesel blends especially B20 were almost similar to conventional diesel fuel with negligible emission of gaseous pollutants. It was observed that the ANN model can predict the engine performance and biodiesel production quite well with good correlation coefficients (0.9 ≤ R ≤ 1) and very low mean square error. The results exhibited the potential of activated clay in catalysis of transesterification of APO and GSO to methyl ester.