CO在Pd系双金属及其单金属催化剂上的吸脱附红外光谱

红外光谱表明吸附在担载于Al_2O_3上的Pd-Cu、Pd-Ag、Pd-Co和Pd-Pt 双组分催化剂上的CO仍保持其在单金属上的主要吸附物种,但其部分CO吸收带发生位移,吸附的CO易于脱附.CO在还原态Pd-Cu和Pd-Ag双金属催化剂上以吸附于Pd上者为主,其吸收带明显变弱而更易脱附.在Pd- Pt和Pd-Co氧化和还原态催化剂上CO桥式和线式吸收带强度比发生显著变化.似乎在这二类双金属催化剂上的几何结构效应比电子配位效应更为明显.

Studies of the Adsorption-Desorption of CO on Alumina-Supported Pd-Series Bimetallic Catalysts

The adsorption-desorption of CO on alumina- supported Pd- Cu, Pd- Ag, Pd- Pt and Pd- Co bimetallic and their monometallic catalysts have been studied by "in situ" IR spectroscopy. When CO are adsorbed on the oxidized and reduced bimetallic catalysts, the absorption bands of the CO corresponding to main species of adsorbed CO on the monometallic catalysts are observed. Most bands of CO in the bimetallic systems are obviously shifted. With the increase of temperature, the adsorbed CO are easily removed in vacuum. The intensities of the bands of CO adsorbed on the reduced Pd-Cu and Pd-Ag catalysts are rather weak. When CO are adsorbed on the reduced and the oxidized Pd-Pt catalysts, the bands of bridged Pt-CO become stronger and the bands of linear Pd-CO evanesce. The influences of geometric and ligand factors on the adsorption-desorption behaviours of CO on the supported Pd-series bimetallic catalysts are discussed. It appears that for these systems the geometric effect are more pronounced than the ligand effect.