Acta Phys. -Chim. Sin. ›› 2011, Vol. 27 ›› Issue (04): 793-800.doi: 10.3866/PKU.WHXB20110332

• THEORETICAL AND COMPUTATIONAL CHEMISTRY • Previous Articles     Next Articles

Reaction Mechanism of Acetylene Hydrogenation Catalyzed by Pd8 Cluster

LI Jun-Nan, PU Min, HE Shu-Heng, HE Jing, EVANS David G.   

  1. State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, P. R. China
  • Received:2010-10-19 Revised:2010-12-02 Published:2011-03-29
  • Contact: PU Min E-mail:pumin@mail.buct.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (20531010, 20773009) and National Key Basic Research Program of China (973) (2009CB939802).

Abstract:

The mechanism of acetylene hydrogenation catalyzed by Pd8 cluster was investigated by density functional theory (DFT) method at B3PW91/GEN level. The calculation results showed that H2 dissociated into H atoms wherever it adsorbed and the H atoms then adsorbed onto the surface of the Pd8 cluster. The dissociation of H2 is necessary for the hydrogenation of acetylene to ethane catalyzed by the Pd8 cluster. The mechanism of acetylene hydrogenation is dependent on two isomers: acetylene and vinylidene on the Pd8 cluster (Pd8(2H)-CH=CH and Pd8(2H)-C=CH2). The two pathways follow a multistep and successive process to complete the hydrogenation of acetylene. However, a difference exists between Pd8(2H)-CH=CH and Pd8(2H)-C=CH2. For the Pd8(2H)-CH=CH pathway, dissociated H atoms add to the C atom of acetylene on the Pd8 cluster in different steps until they produce ethane. The Pd8(2H)-CH=CH2 pathway is complex and proceeds by two different transition states to create ethylidyne, and then H atoms add to the C atom until hydrogenation ceases. Many valuable C2 organic intermediate compounds are produced during the process and some of them transform by proton translocation, which connects the Pd8(2H)-CH=CH and Pd8(2H)-C=CH2 pathways.

Key words: Density functional theory, Pd8 cluster, Acetylene hydrogenation, Ethylene, Reaction mechanism

MSC2000: 

  • O641