Phosphomolybdic acid/chitosan as acid solid catalyst using for biodiesel production from pomegranate seed oil via microwave heating system: RSM optimization and kinetic study

Abstract

In this research, a green solid catalyst of phosphomolybdic acid (HPA) prated on Chitosan was synthesized to produce biodiesel. The prepared catalyst was characterized using Fourier Transform Infrared spectroscopy (FTIR), Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive X-Ray (EDX), X-ray diffraction (XRD), and XRF analyses. The catalyst was applied in microwave-assisted trans-esterification of Pomegranate oil, and the biodiesel production process was optimized by response surface methodology based on central composite design (RSM-CCD). The effect of influential reaction parameters, including time (33–142 min), catalyst weight (0.15–5.6 wt%), and methanol to oil molar ratio (3.3:1–17:1), were investigated. The maximum biodiesel yield of 95% was obtained in a short time (74 min) using the catalyst weight of 1.25 wt% and methanol to oil molar ratio of 6:1 at the temperature of 65 °C. The catalyst was reused six times without any significant reduction in catalyst activity. The H NMR spectroscopy was employed to compare Pomegranate oil and biodiesel. The kinetic results of transesterification via microwave-assistant have good agreement with first-order kinetics as well as the activation energy and Arrhenius constant are 50 kJ/min and 16.47 × 107 min−1, respectively. As a result, Pomegranate biodiesel has high quality. The physicochemical properties of Pomegranate biodiesel under the optimal condition agreed with the ASTM standard. In conclusion, phosphomolybdic acid/Chitosan as a catalyst has a high potential for biodiesel production on a large scale.