Abstract:

Pd/α-Al₂O₃ with different particle sizes were prepared by the incipient wetness method and characterized by BET, XRD, ICP-AES, CO chemisorption and TEM. The kinetic characteristics over these catalysts were explored following a fractional factorial designs of experiment and the experiment results were analyzed by microkinetic method. The size of three catalysts obtained was 1.6 nm, 3.4 nm and 5.5 nm, respectively, as verified by TEM and CO chemisorption results. After stable performance of the catalyst, the exposed surface Pd number of catalysts measured from CO chemisorption agreed well with that of Pd(111) surface calculated from Hardeveld's model. The microkinetic analysis results showed that the microkinetic model can fit the kinetic experiment results quite well on all catalysts. C₂H₄^* and C₂H₃^* were the most abundant surface species independent of the reaction conditions. The rate determining step was the hydrogenation of vinyl group to form ethylene according to the relationship between microkinetic information and macrokinetic characteristics.

Key words: multiphase reaction, acetylene hydrogenation, microkinetic model, particle size effects, catalyst

摘要：

采用等量浸渍法制备了α-Al₂O₃负载的系列Pd催化剂，运用BET、XRD、ICP-AES、CO化学吸附、TEM等手段对催化剂进行了表征；根据部分析因实验设计方案进行动力学实验，采用微观反应动力学方法模拟和分析了所获稳定期本征动力学实验结果。结果发现，制备所得催化剂Pd颗粒的平均粒径分别为1.6、3.4、5.5 nm，CO化学吸附所测定达到活性稳定期后的催化剂表面Pd原子数与Hardeveld模型计算的Pd（111）表面原子数一致；模拟结果表明该微观动力学模型可以很好地模拟不同粒径催化剂上的动力学结果，在所研究范围内表面最丰物种为C₂H₄^*和C₂H₃^*，通过微观与宏观动力学的特征判断3种催化剂上乙炔加氢的速率控制步骤为乙烯基加氢生成乙烯。

关键词: 多相反应, 乙炔加氢, 微观动力学模型, 粒径效应, 催化剂