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在CO常压气相催化偶联合成草酸酯反应体系中 ,考察了原料气CO中不同氧杂质含量和不同反应温度对钯系催化剂活性的影响 .结果表明 ,随着氧含量的增加和反应温度的升高 ,CO的转化率和草酸二乙酯 (DEO)的空时收率升高 ,但DEO的选择性下降 ,且有副产物乙酸乙酯生成 ;氧杂质的存在同时加快了CO偶联主副反应速率 .根据实验现象及XPS表征结果探讨了催化剂活性变化规律的机理 ,并考察了在反应温度下无CO偶联反应时氧对钯系催化剂中活性组分钯及助剂铁的氧化作用 .实验结果表明 ,氧引起的钯系催化剂活性的改变具有可逆性
The effect of different oxygen impurities and different reaction temperatures on the catalytic activity of palladium-based catalysts was investigated in the CO gas-phase catalytic synthesis of oxalate reaction system. The results showed that with the increase of oxygen content and the reaction temperature , The conversion of CO and the space time yield of diethyl oxalate (DEO) increased, but the selectivity of DEO decreased with the formation of by-product ethyl acetate. The presence of oxygen impurity accelerated the CO coupling The main and minor reaction rate.According to the experimental phenomena and the XPS characterization results, the mechanism of the change of the catalyst activity was discussed, and the oxidation of the active component palladium and the additive iron in the palladium-based catalyst was investigated when there was no CO coupling reaction at the reaction temperature The experimental results show that the oxygen-induced changes in the activity of palladium-based catalysts are reversible