Adsorption and desulfurization of thiophene on nickel(111)

Abstract

The adsorption and desulfurization of thiophene on clean and sulfided Ni(lll) surfaces were studied with LEED, AES, TPR, and RAIS. The RAIS data indicate that thiophene adsorbs with its ring parallel or nearly parallel to the surface below room temperature. On clean Ni(lll), thiophene polymerizes slightly above room temperature, as evidenced by paraffinic and aromatic C-H stretches in the reflection infrared spectrum and TPR product yields. Decomposition of the polymer aggregates produces a wide variety of hydrocarbons including C6 fragments at 470 K. On a more acidic sulfided Ni(lll) surface (0S = 0.19), thiophene appears to undergo electrophilic attack at an -carbon as evidenced by TPR products and by methane evolution from the reaction of 2,5-dimethylthiophene. An electrophilic attack by a surface metal atom at an -carbon of thiophene is discussed in terms of molecular orbital theory.

An Organometallic Guide to the Chemistry of Hydrocarbon Moieties on Transition Metal Surfaces

“…It is worth mentioning that this thiophene decomposition pathway is not universal: on other surfaces the first step has been suggested to be the removal of an a hydrogen with retention of the sulfur atom. 275,276 This latter mechanism has some support in the organometallic 1iteratu1-e.~~~…”

Infrared Spectroscopy and Temperature-Programmed Desorption Study of Adsorbed Thiophene on γ-Al2O3

“…Thiophene (C 4 H 4 S) has been used for many years as a model compound for the investigation of the hydrodesulfurization (HDS) process over single-crystal − and supported catalysts. , In addition to these catalytic studies, numerous surface science studies have been carried out in which spectroscopic techniques have been employed to characterize both the adsorption and reactions of thiophene on metal − and semiconductor − single-crystal surfaces. The surface chemistry of thiophene has also been examined on amorphous and single-crystalline molybdenum sulfide (MoS 2 ). , As might be expected, these substrates exhibit greatly different reactivities toward thiophene with early transition metal surfaces (e.g.…”

Two-dimensional tin-119 NMR exchange spectroscopy as a tool for the elucidation of the dynamic stereochemistry of tin compounds

“…3! (4) reduces to the identity and no cross peak at all will appear in the 2D spectrum. For a suitably choosen value of rm, the operator K is approximated by I + Lrm and the cross peaks of the 2D spectrum are in one-to-one correspondence to the desired nondiagonal elements of L that establish the nature of chemical exchange.…”