CIESC Journal ›› 2018, Vol. 69 ›› Issue (2): 674-681.DOI: 10.11949/j.issn.0438-1157.20171007

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Microkinetic analysis of acetylene hydrogenation over Pd-Ag/Al2O3 catalyst with different Pd/Ag ratios

ZHANG Jian, HUANG Bangyin, SUI Zhijun, ZHOU Xinggui, YUAN Weikang   

  1. State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China
  • Received:2017-07-31 Revised:2017-11-17 Online:2018-02-05 Published:2018-02-05
  • Supported by:

    supported by the National Natural Science Foundation of China (21376076).

不同Pd/Ag配比Pd-Ag/Al2O3催化乙炔加氢微观反应动力学分析

张健, 黄邦印, 隋志军, 周兴贵, 袁渭康   

  1. 化学工程联合国家重点实验室, 华东理工大学, 上海 200237
  • 通讯作者: 隋志军
  • 基金资助:

    国家自然科学基金项目(21376076)。

Abstract:

Selective acetylene hydrogenation is an important purifying reaction in ethylene industry. Pd-Ag/α-Al2O3 catalysts with different Pd/Ag ratios were prepared by stepwise incipient wetness impregnation method and characterized for structure and composition by N2-physisorption,XRD,ICP,XPS,TEM and CO chemisorption. A microkinetic model of acetylene hydrogenation over these catalysts was established from a fractional factorial design of experiment and effects of Ag amount on the hydrogenation kinetics were analyzed through microkinetic simulation and parameter value change. After values for basic parameters used DFT calculation results of C2 hydrogenation over Pt-Ag catalysts and activation energies optimized by adsorption-desorption steps, the microkinetic model could fit kinetic experiment results quite well on acetylene hydrogenation over all catalysts of various Pt-Ag ratios. The study showed that C2H4* was the most abundant surface species and vinyl hydrogenation was rate control step, which did not change with increase of Ag content. However, the increase of Ag greatly reduced activation energy of hydrogen desorption and improved ethylene selectivity. This phenomenon might be correlated to enhancement of electron transfer from Ag to Pd on the catalyst surface upon increase of Ag content.

Key words: acetylene hydrogenation, Pd-Ag catalyst, microkinetic modeling, Ag effect

摘要:

乙炔加氢是乙烯工业中的重要精制反应。以α-Al2O3作为载体,采用分步等量浸渍法制备了不同Pd/Ag配比的加氢催化剂,使用N2物理吸附、XRD、ICP、XPS、TEM和CO化学吸附等手段表征催化剂的结构和组成,根据正交实验设计方案进行动力学实验,建立了微观反应动力学模型,并根据动力学模拟结果和动力学参数值的变化分析了Ag助剂含量对乙炔加氢反应动力学的影响。研究结果表明,以Pd-Ag催化剂上碳二加氢的DFT计算结果为基础参数来源,经过吸脱附步骤活化能的优化,微观反应动力学模型可以很好地模拟不同Pd/Ag配比催化剂上的乙炔加氢反应动力学结果;在所研究范围内,各催化剂上加氢反应的表面最丰物种皆为C2H4*,速率控制步骤为乙烯基加氢,不会随着Ag含量的不同发生变化;但是Ag含量的增加显著降低了氢气脱附活化能,提高了乙烯的选择性,这可能与Ag含量的提高增加了催化剂表面Ag和Pd之间的电子转移现象有关。

关键词: 乙炔加氢, Pd-Ag催化剂, 微观反应动力学, Ag助剂影响

CLC Number: