Synthesis and characterization of new bifunctional SnZrSi oxide catalysts for biodiesel production

Abstract

A set of unprecedented (mesoporous SnO2/ZrSiO4) solids has been synthesized via the ultrasound-assisted co-precipitation path. The impact of silica dopant content (ranged between 0.05 and 0.4 mol%) on the characterization evolution of the sonicated ZrSnO4 interface and their biodiesel production efficiency were examined. Physio-chemical characteristics of the synthesized catalysts were analyzed by XRD, SEM-EDS, TEM, TGA-DTG, N2 adsorption–desorption analysis, NH3-TPD, UV–Visible/ DR, and FT-IR before and after pyridine adsorption. The obtained results revealed the formation of reconstructed rutile-SnO2 and zircon as new active phases by calcination at 500 °C, good morphology with mesoporous structure, and significant increase in the SBET, pore volume, interesting optical behavior, and exhibited different acidic properties. The impacts of reaction temperature, silica dopant content, fatty acid type and calcination temperature on the biodiesel % were examined. The tertiary oxide catalysts were gainful for the biodiesel production. The optimum catalyst (0.2 % SiO2/ZrSnO4) had the biggest number of both strong Brönsted and Lewis acid sites compared to the doped and undoped catalysts, so, its maximum yield at optimum conditions for esterification of palmitic acid reaction was 90.2 % and can be reused until the fifth run with giving excellent yield for biodiesel production. But, for the transesterification of soybean oil reaction with methanol was maxima at 88% for (0.4 % SiO2/ZrSnO4) sample. The kinetic, mechanism studies and thermodynamic parameters were estimated. The important role of the doped silica molecules in the mechanism of the esterification process was emphasized by the computational chemistry study.