Surface Properties and Catalytic Activity of TiO2–ZrO2 Mixed Oxides in Dehydration of Methanol to Dimethyl Ether

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A series of TiO2–ZrO2 mixed oxides with varying molar ratio of TiO2 to ZrO2 were prepared by the co-precipitation method. The crystalline phases of the oxides were characterized by XRD and their acid–base properties by TPD of NH3 and CO2 and IR of adsorbed pyridine. The catalytic activities were investigated for the vapor phase dehydration of methanol to dimethyl ether (DME) in a fixed-bed reactor under atmospheric pressure. The mixed oxides are highly amorphous in nature. The acid–base properties and CH3OH conversion activity are increasing with TiO2 content and an optimum value is achieved for a molar ratio of Ti/Zr in the vicinity of 1/1. At lower reaction temperature (<300 °C), the selectivity for DME is nearly 100%. A good correlation is observed between dehydration activity and the acid–base properties of the TiO2–ZrO2 catalysts. It is significant to note that TiO2–ZrO2 catalysts show high stability against water during dehydration reaction. Based on our results, a surface mechanism involving both acid–base sites has been proposed for DME formation.

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