Premium
A DFT Study of Tungsten–Methylidene Formation on a W/ZSM‐5 Zeolite: The Metathesis Active Site
Author(s) -
Maihom Thana,
Probst Michael,
Limtrakul Jumras
Publication year - 2015
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201500427
Subject(s) - active site , zeolite , chemistry , metathesis , tungsten , salt metathesis reaction , catalysis , cycloaddition , reaction mechanism , photochemistry , inorganic chemistry , organic chemistry , polymerization , polymer
Tungsten–methylidene formation from ethene on either the W IV , W V , or W VI active sites of a W/ZSM‐5 zeolite is investigated by using the M06‐L functional. The reaction is assumed to proceed in two steps; the first step is the [2+2] cycloaddition between ethene and the W−O active site to form an oxametallacycle intermediate. The intermediate is then decomposed to produce the W–methylidene active site from the metathesis reaction. The overall activation barrier of the reaction on W VI (27.3 kcal mol −1 ) is considerably lower than the ones for W IV and W V (69.4 and 37.1 kcal mol −1 , respectively). Moreover, the reaction involving the W VI site also stabilizes intermediates and products to a larger extent than the ones on the W IV and W V sites. As a result, we have demonstrated that the reaction of the W–methylidene metathesis active site is both kinetically and thermodynamically favored to occur on the W VI active site of the zeolite.