Zr- and La-containing Catalysts in Synthesis of Methanol and Dimethyl Ether

Resumo

Zirconium oxide samples synthesized and modified with Al, Si, W oxides were studied as dehydrating components of bifunctional catalysts for synthesis of dimethyl ether. ZrO₂ modified with Al and Si oxides is inactive in the dehydration of methanol, but its dehydrating activity becomes comparable with the activity of γ-Al₂O₃ upon introduction of WO₃. According to the data on methanol adsorption at 46°C, the adsorption capacity of ZrO₂ modified with SiO₂ is comparable with the capacity of γ-Al₂O₃, and that of ZrO₂ modified with WO₃ is four times lower. The difference in the catalytic and adsorption behavior of the samples is accounted for by the data of in situ high-temperature diffuse reflection IR spectroscopy. A high content of weak Brønsted acid centers is observed on the ZrO₂ surface, with the interaction of these with methanol resulting in the methoxylation of the catalyst surface. When W oxide is deposited onto zirconium oxide, the surface has strong Brønsted centers involved in the reaction of methanol dehydration. A coprecipitation from solution of nitrate salts of Cu, Zn, La with Na carbonate, followed by the procedures of filtration, washing, and thermal treatment, yielded a catalyst for synthesis of methanol, the activity of which is close to that of the industrial catalyst.