Preparation of ethane-bridged organosilica group and keggin type heteropoly acid co-functionalized ZrO2 hybrid catalyst for biodiesel synthesis from eruca sativa gars oil

Abstract

A series of mesostructured ZrO₂-based hybrid catalysts, functionalized by both an ethane-bridged organosilica group and the Keggin type heteropoly acid, H₃PW₁₂O₄₀–ZrO₂–Si(Et)Si, were prepared by one-step sol-gel-hydrothermal method in the presence of a triblock copolymer surfactant (F127). The materials were well characterized by spectroscopy methods such as FT-IR and MAS NMR, transmission electron microscopy, and nitrogen gas physisorption measurements to confirm the structural integrity of the Keggin units and ethane-bridged organosilica groups in the hybrid materials, and to test the mesostructure, morphology, and porosity of the materials. The materials were subsequently utilized as environmentally-friendly solid acid catalysts in the transesterification of low-cost Eruca Sativa Gars oil with methanol to produce fatty acid methyl esters under atmosphere refluxing. Compared with alkyl-free H₃PW₁₂O₄₀–ZrO₂, the prepared H₃PW₁₂O₄₀–ZrO₂–Si(Et)Si exhibited higher catalytic activity toward the target reaction. This enhanced acid-catalytic activity after the introduction of both acidic and hydrophobic functionalities within the ZrO₂ matrix was explained in terms of strong Brϕnsted acidity, excellent porosity, and enhanced hydrophobicity of the hybrid materials.