Synthesis of sodium zincsilicate (Na2ZnSiO4) and heterogeneous catalysis towards biodiesel production via Box-Behnken design

•Synthesis of Na2ZnSiO4 via a facile and low-cost solid-state method.•Na2ZnSiO4 evaluated as heterogeneous catalysts in soybean oil transesterification.•Transesterification reaction parameters optimized using Box-Behnken design.•99% FAMEs conversion achieved under optimized conditions at 65 °C after 45 min.•Optimized conditions using 5.3 wt% catalyst, 500 RPM and 1:14 MeOH:oil ratio. This study synthesizes a Na2ZnSiO4 phase as efficient and low-cost heterogeneous catalyst for biodiesel production. X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) along with Energy Dispersive X-Ray Spectroscopy (EDS), Brunauer–Emmett–Teller (BET) surface area analysis isotherms are herein conducted to characterize the structure, texture, composition and surface area of the catalyst, respectively. A Box-Behnken design (BBD) is performed to screen out: the methanol: oil ratio (6:1 to 14:1), catalyst load (0.5 to 5.5 wt%) and stirring rate (500 to 800 RPM), affecting the transesterification reaction using commercial soybean oil as a triglyceride source while fixing the temperature reaction at 65 °C. The oil and its fatty acid methyl esters (FAME) are characterized using Fourier Transform Infrared Spectroscopy with an Attenuated Total Reflectance modulus (FT-IR-ATR). XRD and SEM confirm the successful synthesis of the monoclinic Na2ZnSiO4 phase with low traces of ZnO ( methanol: oil ratio > stirring rate. The FAME conversions drop to 48.4 and 62.42% after 5 cycles of continuous catalyst reuse, according to FT-IR-ATR and proton nuclear magnetic resonance (1H NMR) measurements, respectively.