Influence Of Coadsorbates Research Articles

Influence of Co-adsorbates on CO2 induced phase transition in functionalized pillared-layered metal–organic frameworks

Co-adsorption measurements reveal the flexible and gas separation behavior of functionalized pillared-layered MOFs when exposed to gas mixtures.

Fischer-Tropsch Synthesis on Multicomponent Catalysts: What Can We Learn from Computer Simulations?

In this concise review paper, we will address recent studies based on the generalized-gradient approximation (GGA) of the density functional theory (DFT) and on the periodic slab approach devoted to the understanding of the Fischer-Tropsch synthesis process on transition metal catalysts. As it will be seen, this computational combination arises as a very adequate strategy for the study of the reaction mechanisms on transition metal surfaces under well-controlled conditions and allows separating the influence of different parameters, e.g., catalyst surface morphology and coverage, influence of co-adsorbates, among others, in the global catalytic processes. In fact, the computational studies can now compete with research employing modern experimental techniques since very efficient parallel computer codes and powerful computers enable the investigation of more realistic molecular systems in terms of size and composition and to explore the complexity of the potential energy surfaces connecting reactants, to intermediates, to products of reaction. In the case of the Fischer-Tropsch process, the calculations were used to complement experimental work and to clarify the reaction mechanisms on different catalyst models, as well as the influence of additional components and co-adsorbate species in catalyst activity and selectivity.

Intermolecular distances of carboxylated TEMPO derivatives on TiO2 evaluated by spin-probe ESR

Nearest-neighbor intermolecular distances of molecules adsorbed on the surface of nanocrystalline TiO(2) particles were evaluated by the electron spin resonance (ESR) technique with molecules having a nitroxide radical and a carboxyl group as a spin probe to clarify their aggregation behaviors on TiO(2) and the influence of coadsorbates.

Influence of Coadsorbates on the NO Dissociation on a Rhodium(311) Surface

Density functional theory (DFT) studies were performed to investigate the influence of coadsorbates on the nitrogen oxide dissociation on the vicinal rhodium(311) surface. This study amplifies prior studies on the dissociation of oxygen and nitrogen oxide on the (111) facet of rhodium. The influence of coadsorbates on the kinetic parameters and thermochemistry of the NO dissociation on Rh311 was studied. In addition, the activation energy and thermochemistry of this reaction were determined as a function of oxygen preoccupation/initial coverage. Steric and electronic effects and their influence on the dissociation reaction were examined. The results are discussed in the face of an NOx dissociation catalyst system proposed by Nakatsuji.

Influence of co-adsorbates on the methylene coupling reaction on Ag(1 1 1)

The influence of co-adsorbates on the methylene coupling reaction on Ag(1 1 1) was investigated by means of reflection–absorption infrared spectroscopy (RAIRS) and temperature-programmed reaction spectroscopy (TPRS). Generated by thermal decomposition of adsorbed CH 2I 2, CH 2(a) selectively self-couples to form ethylene. The desorption of ethylene resulted from methylene coupling reaction shows an interesting coverage-dependent, which on basis of the RAIRS and TPD results, is attributed to both the existence of co-adsorbates on the surface and the coverage-dependent C–I rupture of CH 2I 2(a). The reaction kinetics of methylene coupling reaction is also affected by the co-existence of CF 3I(a) on the surface. It is the migration and/or assembly of methylene on the surface, not the actual methylene coupling reaction, which is influenced by the co-adsorbates.

The influence of coadsorbates on the overlayer structure of PF 3 on Pt(111)

We have used measurements of the infrared lineshape of the symmetric P-F stretch fundamental of PF 3 chemisorbed on Pt(111) in the presence of coadsorbed Xe, CO and NH 3 to probe the PF 3 overlayer structure on Pt(111). In the absence of coadsorbates, PF 3 forms two distinct phases on the surface at intermediate coverages as indicated by a splitting of the P-F stretch band into two components. The higher frequency component is attributed to molecules in dense two-dimensional islands and the lower frequency component to molecules in a lower density disordered phase. Coadsorbed Xe induces red shifts in the P-F stretch which depend on the number of Xe atoms adsorbed at sites adjacent to the PF 3 molecules. This enhances the sensitivity of the P-F stretch to the molecular environment and allows additional components of the P-F stretch to be resolved. Coadsorbed CO causes the higher frequency components of the P-F stretch to shift to higher frequencies and the lower frequency components to shift to lower frequencies. This is attributed to the coalescence of small PF 3 islands into larger islands. Coadsorbed NH 3 decreases the P-F stretch by as much as 27 cm −1 and affects the PF 3 through a short-range interaction. Unlike Xe and CO, NH 3 appears to break apart small islands of PF 3 molecules.

Elimination de micropolluants par adsorption sur charbon actif dans l'eau: cas d'un tensioactif non ionique; influence de co-adsorbats removal of non ionic surfactant from water onto activated carbon, influence of organic compounds

Adsorption of organic micropollutants on activated carbon is nowadays an integral part of most advanced water and wastewater purification systems. Equilibria and capacity relationships for monocomponent systems are well established and quantitatively expressed by the Langmuir or Freundlich isotherms. The results of the adsorption of a nonionic surfactant: CH 3(CH 2) 8C 6H 4O (CH 2CH 2O) 7CH 2CH 2OH (NP8) have been determined for micromolar concentration range. Using Langmuir and Derylo-Jaroniec equations, the ultimate capacity, the equilibrium constant and energetic parameters can be deduced. Influence of co-adsorbates are tested: linear and ramified alcohols (C 2 to C 5) anionic surfactant CH 3(CH 2) 11 SO 14Na (DSS); the experimental results of adsorption are compared with those obtained by using two bi-solute systems ( Jain and Snoeyink, 1973; Derylo-Jaroniec, 1982) and discussed in terms of competition, inhibition or promotion of the adsorption of co-adsorbates on the carbon sites.