Optimum Biodiesel Production from Palm Kernel Oil Using Heterogeneous Catalyst from Carbide Slag and Termite Hill Clay

Abstract

This study is aimed at optimizing biodiesel production from palm kernel oil (PKO), using heterogeneous catalyst made from carbide slag and termite hill clay. The precursors (carbide slag and termite hill clay) were prepared and characterized. The composite catalyst was doped with Zn(NO3)2 by wet impregnation method. The PKO was characterized to obtain its different properties. Design of Experiments (DOE) was systematically used to study the effects of different variables on biodiesel yield and to ascertain the ideal conditions for optimum yield. The modelling was limited to RSM, using Box-Behnken design. The PKO’s acid value, saponification value, average molecular weight, density, viscosity, moisture content, iodine value and peroxide value were obtained as 7.34 mgKOH/g oil, 234.18 mgKOH/g oil, 741.93 g/mol, 0.901 g/cm3, 4.7 mPa.s, 1.09%, 18.7 mg I2/100g oil and 16.2 mEq/kg respectively. The XRF results showed that the carbide slag contained 89.763% CaO, 4.036 % SiO2, 3.880 % Al2O3, etc., while the THC contained 46.924% SiO2, 24.144% Al2O3, 20.619 % Fe2O3, etc. The composite contained the required oxides for carrying out esterification and transesterification process simultaneously. The yield was observed to be significantly impacted by all the factors. RSM numerical optimization gave an optimum yield of 98.22% at 66.95 oC, 94.04 minutes, 11.98:1 alcohol/oil ratio, and 2.39 wt% catalyst loading. There was an overall reduction of 28.4% in yield between the first and sixth reactions, for the catalyst reusability studies, which catalysed six different reactions. The produced biodiesel was characterized and the properties were found to be in agreement with the ASTM D6571 and EN 14214 standards.