Highly active alumina-supported Cs–Zr mixed oxide catalysts for low-temperature transesterification of waste cooking oil

•Developed a novel aluminum supported Cs–Zr mixed oxide catalyst.•The prepared catalyst was characterized for its chemical and physical properties.•FAMEs were produced from cheap feed stock of waste cooking oil.

An impregnation method was used to develop a reusable and highly active heterogeneous catalyst (CsxZry/Al2O3) with different Cs/Zr molar ratio (0.3 ≤ x, y ≤ 0.7). The catalyst activity was evaluated in the transesterification of waste cooking oil (WCO) with methanol for the synthesis of fatty acid methyl esters (FAMEs). A typical Cs0.6Zr0.4/Al2O3 catalyst was characterized for physical and chemical properties in terms of the amount of FAME produced. Brunauer–Emmett–Teller method, X-ray diffraction, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, basic strength analysis, scanning electron microscopy, and high-resolution transmission electron microscopy were utilized in the characterization of the catalysts. The effects of different process variables of transesterification reaction, such as methanol-to-WCO ratio (10:1–30:1), catalyst amount (1 w/w–5 w/w oil), and reaction time (1–5 h), on the catalyst performance were investigated. During 3 h reaction time 90%FAME content was produced at 65 °C with 20:1 methanol-to-WCO molar ratio and 3 wt.% catalyst loading. Results of the reusability tests indicated that the solid catalyst can be re-used for four batch cycles. Also, the catalyst exhibited good tolerance toward 0.8 w.% water, without significant changes in the FAME content.

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