Pt/TiO2催化剂上CO氧化反应动力学研究

利用沉积沉淀法制备了Pt/TiO₂催化剂, 将其在不同温度下焙烧, 以得到不同颗粒尺寸的Pt. 并将这些样品用于CO催化氧化反应以及反应动力学研究. 结果表明: 焙烧温度对催化剂有明显影响, Pt 颗粒尺寸随着焙烧温度的升高而增加; 与此同时, CO催化活性随焙烧温度的升高呈先增加后降低的趋势, 其中, 400℃焙烧的样品表现出最高的催化活性. 反应动力学结果表明, 催化剂上CO氧化反应表观速率方程为r=5.4×10^-7p_CO^0.17p_O2^0.36,说明在该催化剂上CO氧化遵循Langmuir-Hinshelwood机理. 同时, 对催化剂进行了CO化学吸附红外光谱和O₂化学吸附表征. 结果表明, 随着焙烧温度的升高, 催化剂上CO和O₂吸附量均呈现先升高后降低的趋势, 这与反应结果和反应动力学方程一致, 说明反应受到催化剂表面上CO和O₂吸附浓度的影响. 而在400℃焙烧的催化剂上, CO和O₂吸附量均最高, 因此其反应活性也最好. 这可能是焙烧过程影响了Pt 和TiO₂之间的相互作用引起的.

Kinetics Study of CO Oxidation Reaction over Pt/TiO2 Catalysts

A series of Pt/TiO₂ catalysts were prepared using a deposition-precipitation method and calcined at different temperatures to obtain various Pt particle sizes. The catalysts were tested for catalytic CO oxidation and the kinetics of the reaction was studied. The results showed that the Pt particle size increased with calcination temperature, and that their reactivity for CO oxidation first increased and then decreased with increasing calcination temperature, with the catalyst calcined at 400℃ possessing the highest reactivity. The kinetic investigation revealed that the reaction rate could be described by r=5.4×10^-7p _CO^0.17p_O2^0.36, suggesting that the reaction followed a Langmuir-Hinshelwood mechanism. Meanwhile, O₂ chemisorption and infrared (IR) spectroscopy of CO chemisorption on the catalysts were conducted to reveal the relationship between the catalyst structure and its catalytic behavior. It was found that the amount of O₂ chemisorption and the intensity of CO chemisorption by IR on the catalysts first increased and then decreased with increasing calcination temperature, which was consistent with the catalytic results and the kinetic equation. This could explain the catalytic behaviors of the catalysts. For example, the highest amounts of chemisorbed O₂ and CO were obtained over the Pt/TiO₂ calcined at 400℃, which resulted in the highest reactivity. Such an enhancement in reactivity was probably due to the strong interaction between Pt and TiO₂ induced by the calcination process.