Interaction of hydrogen sulphide with nickel, tungsten and silver films

Abstract

The interaction of hydrogen sulphide with films of nickel and tungsten has been studied over the temperature range -80" to 100°C. Rapid dissociative adsorption, followed by desorption of hydrogen occurred on both metals. The average composition of the surface phase was expressed as H,S and n decreased with increase of both surface coverage and temperature. Adsorption of hydrogen sulphide on silver films at -80°C caused sintering to occur ; a substantial fraction of the adsorption was reversible but some dissociation also took place.The completion of the surface layer on nickel at 0°C was followed by the formation of bulk sulphide. Activation energies for the incorporation process were determined as the thickness of the sulphide layer increased over the temperature range 0" to 90°C. No clear evidence for incorporation on tungsten was obtained at temperatures below 100°C but a slow process was observed on silver films between 150" and 260°C.Evidence for two kinds of adsorbed hydrogen atoms was found by exchange experiments with deuterium on films of nickel and tungsten partially covered with hydrogen sulphide.

Mechanism and Site Requirements of Thiophene Hydrodesulfurization Catalyzed by Supported Pt Clusters

“…[1,7] The relative values of these equilibrium constants show that S* species are much more abundant than HS*H species at the conditions of these experiments, in agreement with the proposal that dissociation of H 2 S on metals mainly forms S* via SH surface species as intermediates. [32] As a results, inhibition by H 2 S reflects the occupancy of vacancies by S* and depends on H 2 S/H 2 ratios [S* in Equation (5)] and is independent of H 2 [H*H in Equation (5) ] for thiophene desulfurization and hydrogenation, respectively, consistent with the isotopic data reported in the next section. The mechanistic findings and catalytic consequences reported here for Pt are similar to those reported on Ru-based catalysts [17] and indicate that similar site requirements and elementary steps are likely to mediate desulfurization and hydrogenation on other metals similar in metal-sulfur bonds and surface reactivity to Ru and Pt.…”

“…[32] As a results, inhibition by H 2 S reflects the occupancy of vacancies by S* and depends on H 2 S/H 2 ratios [S* in Equation (5)] and is independent of H 2 [H*H in Equation (5)] or H 2 S [HS*H in Equation (5)] pressures. [32] As a results, inhibition by H 2 S reflects the occupancy of vacancies by S* and depends on H 2 S/H 2 ratios [S* in Equation (5)] and is independent of H 2 [H*H in Equation (5)] or H 2 S [HS*H in Equation (5)] pressures.…”

Effects of alumina phases as nickel supports on deep reactive adsorption of (4,6-dimethyl) dibenzothiophene: Comparison between γ, δ, and θ-alumina

“…Thus, a combination of three phenomena may cause two-zone behavior observed for the nickel-based adsorbent: (1) rapid adsorption of sulfur compound on nickel active sites (2) formation of Ni x S y surface layer which may be followed by a slower bulk transformation into Ni 3 S 2 [49], (3) coke formation on nickel active sites, and (4) pore blockage by coke. Saleh et al [50] studied sulfidation of nickel by H 2 S and observed that the activation energy for sulfidation process progressively increased as the thickness of Ni x S y layer increased. Due to high densities of both the reduced nickel and sulfide layer [51], it is plausible to assume that diffusion of the Ni 2+ or S 2− ions through these structures is the rate-determining step [50,51].…”

“…Saleh et al [50] studied sulfidation of nickel by H 2 S and observed that the activation energy for sulfidation process progressively increased as the thickness of Ni x S y layer increased. Due to high densities of both the reduced nickel and sulfide layer [51], it is plausible to assume that diffusion of the Ni 2+ or S 2− ions through these structures is the rate-determining step [50,51]. FTIR analysis (not shown for the sake of brevity) of the effluent of batch reactor demonstrated that there was no H 2 S resulting from Ni x S y reduction.…”

The catalytic activity and structure of evaporated silver films used for the oxidation of carbon monoxide

“…When a coherent layer of crystallites of any metal is in existence on the substrate, further deposition will give rise to growth of these crystallites normal to the surface and fresh nucleation of new crystallites. The greater mobility of the atoms in metals of low melting-point, e.g., copper or silver deposited at about room temperature, should generally favour growth of the existing crystallites and the real surface area will remain nearly constant and approximately equal to the apparent surface area?, 28 High-melting point metals and low substrate temperatures favour fresh nucleation, and a porous f i l m , with a much larger true surface area, may be formed. If the crystallites do not sinter together appreciably, the amount of porous film built up, and hence its area, will depend directly on the weight of metal, once the initial crystallite layer is established.…”