负载型Pd-Cu催化剂的制备及富氢气氛下CO优先氧化性能

分别以Al₂O₃, SiO₂和C₃N₄为载体, 通过简单浸渍法制备了3种负载型Pd-Cu催化剂(PC-Al₂O₃, PC-SiO₂, PC-C₃N₄), 考察了其在室温下富氢气氛中CO优先氧化反应性能. 采用X射线衍射(XRD)、 傅里叶变换红外光谱(FTIR)、 氮气物理吸附仪(N₂-physisorption)、 氢气程序升温还原(H₂-TPR)、 二氧化碳程序升温脱附(CO₂-TPD)、 X射线光电子能谱(XPS)和原位漫反射傅里叶变换红外光谱(In situ DRIFTS)等手段对其进行了表征. 结果表明, 与PC-SiO₂和PC-C₃N₄相比, PC-Al₂O₃具有更高的CO优先氧化性能. 这是由于PC-Al₂O₃上形成了大量与Pd物种具有强相互作用的Cu₂Cl(OH)₃物种; 而PC-SiO₂中仅有少量的Cu₂Cl(OH)₃, 且与Pd物种相互作用较弱; PC-C₃N₄中Cu物种则更易与C₃N₄基质配位, 由此削弱了Pd, Cu之间的相互作用. 在反应气氛下PC-Al₂O₃表面还易形成具有更强CO活化能力的Pd⁺物种, 通过与大量Cu⁺物种紧密相互作用, 在一定程度上抑制Pd⁺被过度还原为Pd⁰, 从而维持了其催化活性. 与SiO₂和C₃N₄相比, Al₂O₃更适合负载Pd-Cu用于富氢气氛下CO优先氧化反应.

Preparation of Supported Pd-Cu Catalyst and Its Preferential Oxidation of CO Under Hydrogen-rich Atmosphere

Three supported Pd-Cu catalysts（PC-Al₂O₃， PC-SiO₂， PC-C₃N₄） were prepared by a simple impregnation method using Al₂O₃， SiO₂， and C₃N₄ as supports. And their catalytic performance toward CO preferential oxidation at room temperature were investigated. XRD， FTIR， N₂-physisorption， H₂-TPR， CO₂-TPD， XPS and in situ DRIFTS were used for analysis and characterization. The results show that compared with PC-SiO₂ and PC-C₃N₄， PC-Al₂O₃ shows better CO preferential oxidation performance， which is due to the formation of a large number of Cu₂Cl（OH）₃ species with strong interaction with Pd species on PC-Al₂O₃. However， PC-SiO₂ exists only a small amount of Cu₂Cl（OH）₃ and its weaker interaction with Pd species. In addition， Cu species in PC-C₃N₄ is more likely to coordinate with C₃N₄ matrix， which weakens the interaction between Pd and Cu. Above all， Pd⁺ species with stronger CO activation ability readily emerge on the surface of PC-Al₂O₃ in the reaction atmosphere， which possess the close interaction with a large number of Cu⁺ species. And this can inhibit the complete reduction of Pd⁺ to Pd⁰ to a certain extent， so as to maintain its catalytic activity. Hence， compared with SiO₂ and C₃N₄， Al₂O₃ is more suitable for supporting Pd-Cu for CO preferential oxidation in hydrogen.