Acta Phys. -Chim. Sin. ›› 2012, Vol. 28 ›› Issue (07): 1630-1636.doi: 10.3866/PKU.WHXB201204171

• THEORETICAL AND COMPUTATIONAL CHEMISTRY • Previous Articles     Next Articles

Theoretical Study on the Synthesis of Ethyl Tertiary Butyl Ether over HZSM-5 Zeolite

LI Jun-Nan, PU Min, SU Yong, HE Jing, EVANS David G.   

  1. State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, P. R. China
  • Received:2011-12-01 Revised:2012-03-26 Published:2012-06-07
  • Contact: PU Min E-mail:pumin@mail.buct.edu.cn

Abstract:

The formation mechanism of ethyl tertiary butyl ether (ETBE) from ethanol and isobutene catalyzed by HZSM-5 has been investigated using the ONIOM (B3LYP/6-31G(d,p):UFF) method. The calculation results of the reactants adsorbability reveal that the interaction between ethanol and the acidic sites on HZSM-5 leads to the formation of hydrogen bonds. The interaction between isobutene and Brönsted acidic sites leads to the formation of a π-complex. It is subsequently found that the mechanism of the ETBE formation from ethanol and isobutene catalyzed by HZSM-5 is a concerted reaction, and that the order of reactant adsorption onto HZSM-5 affected the reaction. The favorable pathway is based on the complex formed by the simultaneous adsorption of ethanol and isobutene, in which the H atom of the π-complex is transferred to the C atom of the C=C in isobutene, and the O atom of the adsorbed ethanol is transferred to the other C atom of the C=C to form the C-O bond. In this process, the proton of the acidic sites adds to the C=C bond forming the C-H bond, and the H atom of the ethanol hydroxyl interacts with acidic sites, generating a new proton. The corresponding lowest energy barrier was 25.14 kJ·mol-1.

Key words: Ethanol, Isobutene, HZSM-5 zeolite, ONIOM, Ethyl tertiary butyl ether

MSC2000: 

  • O641