Efficient ceria-zirconium oxide catalyst for carbon dioxide conversions: Characterization, catalytic activity and thermodynamic study

In this study, ceria-zirconia based catalysts (CeO 2 , ZrO 2 and Ce 0.5 Zr 0.5 O 2 ) were synthesized by hydrothermal method and characterized by N 2 -sorption, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Acidity and basicity of synthesized catalysts were investigated by NH 3 and CO 2 temperature-programmed desorption (TPD). Brunauer-Emmett-Teller (BET) surface area of CeO 2 , Ce 0.5 Zr 0.5 O 2 and ZrO 2 were found to be 88, 117 and 70 m 2 g −1 and average crystallite sizes was 9.48, 7.09 and 9.45 nm, respectively. These catalysts were further used for direct conversion of CO 2 with methanol for the synthesis of dimethyl carbonate (DMC). DMC yield was found to be highly dependent upon the both basicity and acidity of catalysts. Ce 0.5 Zr 0.5 O 2 catalysts showed better activity as compared to CeO 2 and ZrO 2 catalysts. Effect of reaction conditions (such as catalyst dose, reaction temperature and reaction time) and catalyst reusability was studied with Ce 0.5 Zr 0.5 O 2 catalyst. The optimum operating condition for direct conversion of CO 2 into DMC at constant pressure of 150 bar were found to be reaction time = 24 h, catalyst dose = 1.25 g and temperature = 120 °C. Moreover, chemical equilibrium modeling was performed using Peng–Robinson–Stryjek–Vera equation of state (PRSV-EoS) along with the van der Waals one-fluid (1PVDW) mixing rule to calculate the heat of reaction and Gibbs free energy change.