A DFT Study of Tungsten–Methylidene Formation on a W/ZSM‐5 Zeolite: The Metathesis Active Site. Issue 15 (25th August 2015)

• Record Type: Journal Article
• Authors: Maihom, Thana; Probst, Michael; Limtrakul, Jumras
• Is Part Of: Chemphyschem. Volume 16:Issue 15(2015)
• Page Start: 3334
• Page End: 3339
• Publication Date: 2015-08-25
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.05
• DOI: 10.1002/cphc.201500427
• Languages: English
• ISSNs: 1439-4235

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>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.</p> </abstract>