Production of Biodiesel Using Phosphate Rock as a Heterogeneous Catalyst. An Optimized Process Using Surface Response Methodology

In the present study, calcined phosphate rock was used as a heterogeneous catalyst for biodiesel production from waste cooking oil (WCO). Response surface methodology was used to optimize and determine the significant process variables that affected the experiment. A 5-level-4 factor Central composite design consisting of 30 experiments was used to develop a quadratic polynomial model. The following parameters were optimized, namely, reaction temperature (40–90 °C), catalyst to oil weight ratio (1–5 %), reaction time (40–120 min), and methanol to oil ratio (10:1–18:1). Maximum biodiesel yield of 96.07 % was obtained through numerical optimization at reaction temperature 62.63 °C, catalyst to oil weight ratio of 3.32 %, reaction time 79.07 min, and alcohol to oil ratio 14.79:1. Fourier transform Infrared Spectra (FTIR) analysis was used to characterize the phosphate rock in its raw form, after calcination at 1000 °C and after the first and the fourth reuse cycle. According to the American society for testing and material (ASTM D6751), the fuel properties such as kinematic viscosity, pour point, cloud point, and density were measured and were found to be within the stipulated range.