Cotton/Fe3O4@SiO2@H3PW12O40 a magnetic heterogeneous catalyst for biodiesel production: Process optimization through response surface methodology

Abstract

Use of green alternative sources for energy like biofuels is one of the most important requirements of sustainable development. This research aims to design and prepare a new magnetically recoverable catalyst based on agro-wastes. For this purpose, cotton waste was selected and its application in the preparation of magnetic catalysts (Cotton/Fe3O4@SiO2@ H3PW12O40) used for the production of biodiesel, which is based on heteropoly acid (HPA), was investigated. Magnetic cotton powder with high dispersibility, porosity, and magnetism were prepared by the co-precipitation method and covered by silica using tetraethyl orthosilicate (TEOS) to form Cotton/Fe3O4 @SiO2. Finally, the nanostructured catalyst was prepared by impregnation of phosphotungstic acid (HPW). The proposed catalyst was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Field emission scanning electron microscopy (FESEM) equipped with Dispersive Energy X-ray spectroscopy (EDS), Thermo gravimetric analysis (TGA), The Brunauer-Emmett-Teller (BET) surface area analysis, Barrett-Joyner-Halenda (BJH) pore size and volume analysis and vibrating sample magnetometer (VSM). The performance of the proposed core-shell nanocomposite to catalyze transesterification reaction was evaluated and optimized by response surface methodology (RSM). The optimum conditions were found as 3 wt%, 3.5 h, 12:1, and 70 °C, for catalyst dosage, reaction time, the molar ratio of methanol to oil, and reaction temperature, respectively. The production yield was higher than 90% for three runs. On the fourth attempt, the catalyst performance was decreased slightly to 85.5%. The used catalyst was characterized by FT-IR, XRD, EDS, and FESEM for leaching studies. The quality of the biodiesel product was tested according to the standard procedures defined by the American Society for Testing and Materials (ASTM) and European Union (EU).