Search

Methyl mercaptan, CH 3 SH, is an industrial waste as well as the reactive product of several H 2 and H 2 S induced catalytic hydrogenation processes of COS and CS 2 . Its coupling into value added products is of great importance in monetizing sour natural gas. In the present work, the full theoretical cycle of catalytic CH 3 SH coupling to form ethene was investigated by means of density functional theory (DFT) using chabazite as a model catalyst with emphasis on the first C C bond formation. Calculated thermodynamics were compared with those of analogous and well established CH 3 OH processes to identify the similarities and differences in the reactive pathways. With few exceptions, CH 3 SH catalytic transformations are of higher free energy when compared to those of CH 3 OH. The trimethylsulfonium ion, TMS, isostructural with that of the trimethyloxonium ion, TMO, is shown to be a key reactive intermediate and a thermodynamically stable species leading to ethene formation. [ABSTRACT FROM AUTHOR]

Highlights: [•] Diamond-like carbon (DLC) films were deposited using a closed drift ion beam source. [•] Surface morphological, chemical, adhesive and structural properties were studied. [•] Wear mechanisms of DLC films were investigated. [•] DLC nanocomposite films showed better mechanical strength. [•] Terminal oxygenated carbon bonds were absent for nitrogen-doped SiO x containing DLC films. [ABSTRACT FROM AUTHOR]

Abstract: In this study SiOx containing amorphous hydrogenated carbon (a-C:H/SiOx) and nitrogen-doped a-C:H/SiOx (a-C:H:N/SiOx) films were deposited on polyvinylpyrrolidone (PVP) templates of variable thickness using a Hall-type closed drift ion beam source with constant irradiation parameters. A detailed surface characterization was followed using atomic force microscopy (AFM) topography images, surface morphology parameters, height distribution histograms and bearing ratio curves with hybrid parameters. The AFM analysis directly showed that the a-C:H/SiOx/PVP and a-C:H:N/SiOx/PVP composite films represent different morphologies with characteristic surface textures. Surface adhesive properties were evaluated by measuring the force required to separate the AFM tip from the surface by means of AFM force-distance curves. The variance in adhesion force detected was lower for a-C:H/SiOx/PVP composite films due to lower structural homogeneity of the surfaces. Fourier transform infrared spectroscopy analysis was performed to study the blend behavior of PVP upon a-C:H/SiOx and a-C:H:N/SiOx direct ion beam deposition. It was determined that interfacial interactions of PVP with the direct ion beam induced changes in the carbonyl group of the PVP and are dependent on the carrier gas used for the synthesis of the amorphous hydrogenated carbon films. [Copyright &y& Elsevier]