Mechanism of Decomposition of Surface Ethoxy Species to Ethene and Acidic OH Groups on H-ZSM-5

Junko N Kondo; Hiroshi Yamazaki; Ryota Osuga; Toshiyuki Yokoi; Takashi Tatsumi

doi:10.1021/acs.jpclett.5b00846

Mechanism of Decomposition of Surface Ethoxy Species to Ethene and Acidic OH Groups on H-ZSM-5

J Phys Chem Lett. 2015 Jun 18;6(12):2243-6. doi: 10.1021/acs.jpclett.5b00846. Epub 2015 Jun 3.

Authors

Junko N Kondo¹, Hiroshi Yamazaki¹, Ryota Osuga¹, Toshiyuki Yokoi¹, Takashi Tatsumi¹

Affiliation

¹ Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.

PMID: 26266598
DOI: 10.1021/acs.jpclett.5b00846

Abstract

The reaction mechanism of the decomposition of ethoxy species to ethene and acidic OH groups on H-ZSM-5 was studied by IR spectroscopy using isotope-labeled ethanol. The concerted mechanism occurring on both the ethoxy (acid) site and the counterpart lattice oxygen was suggested by GC-MS analysis of evolved d2-ethene and IR observation of the recovery of OH s groups on acid sites from the decomposition of CH3CD2O- ethoxy species. The concerted mechanism was further confirmed by the estimation of activation energy for decomposition of CH3CH2O-, CH3CD2O-, and CD3CD2O- ethoxy species, 122 ± 3, 125 ± 3, and 140 ± 5 kJ mol(-1), respectively, where the kinetic isotope effect was observed for the cleavage of the CH or CD bond of the methyl group of the ethoxy species.

Keywords: IR spectroscopy; catalysis; ethanol; ethoxy species; mechanism; zeolite.