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

Abstract

In this study, ceria-zirconia based catalysts (CeO2, ZrO2and Ce0.5Zr0.5O2) were synthesized by hydrothermal method and characterized by N2-sorption, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Acidity and basicity of synthesized catalysts were investigated by NH3[sbnd] and CO2[sbnd] temperature-programmed desorption (TPD). Brunauer-Emmett-Teller (BET) surface area of CeO2, Ce0.5Zr0.5O2and ZrO2were found to be 88, 117 and 70 m2 g?1and average crystallite sizes was 9.48, 7.09 and 9.45 nm, respectively. These catalysts were further used for direct conversion of CO2with methanol for the synthesis of dimethyl carbonate (DMC). DMC yield was found to be highly dependent upon the both basicity and acidity of catalysts. Ce0.5Zr0.5O2catalysts showed better activity as compared to CeO2and ZrO2catalysts. Effect of reaction conditions (such as catalyst dose, reaction temperature and reaction time) and catalyst reusability was studied with Ce0.5Zr0.5O2catalyst. The optimum operating condition for direct conversion of CO2into 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. © 2016 Elsevier B.V.