Diethyl carbonate synthesis by ethanolysis of urea using Ce-Zn oxide catalysts

- Cerium-zinc catalysts in various Ce:Zn ratio prepared using sol-gel method.
- Catalyst characterization XRD, CO2- and NH3-TPD, N2 adsorption/desorption, FTIR and SEM-EDX techniques.
- Conversion of urea with ethanol to produce diethyl carbonate.
- Optimization of reaction conditions.

Diethyl carbonate (DEC) is a linear organic carbonate which has applications as a fuel additive, in production of polycarbonates, and as a solvent in lithium ion batteries. Ethanolysis of urea, as compared to other methods of DEC synthesis, has an edge having requirements of cheap and abundant raw materials. However, only few studies have been reported due to low acidity of ethanol. In the present study, cerium-zinc based oxides in various molar ratios were used for DEC synthesis from ethanol and urea. These catalysts were prepared by auto combustion technique and characterized by thermogravimetric analysis (TGA), Raman spectroscopy, X-ray diffraction (XRD), N2 adsorption-desorption, field emission scanning electron microscope (FE-SEM), energy dispersive X-ray (EDX), Fourier transform infra-red (FTIR), and NH3- and CO2-temperature programmed desorption (TPD) methods. No additional phases except pure Ce and Zn oxide were observed in the catalyst from XRD analysis. Effects of pore surface area and surface acidity/basicity were found to be profound in the synthesis of DEC. DEC yield of 28.8% was obtained at 190 °C and 5 h using Ce0.1-Zn0.9 mixed oxide. Effect of operating parameters such as ethanol/urea molar ratio, temperature, time and catalyst concentration were also studied.

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