Topic
Elementary reaction
About: Elementary reaction is a research topic. Over the lifetime, 2972 publications have been published within this topic receiving 76110 citations.
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TL;DR: In this article, density functional theory calculations have been carried out to investigate the adsorption of reaction intermediates appearing during water-gas-shift reaction at the sulfur covered MoS2 (1.0.0) surfaces, Mo-termination with 37.5% S coverage and Stermination with 50%S coverage using periodic slabs.
Abstract: Density functional theory calculations have been carried out to investigate the adsorption of reaction intermediates appearing during water–gas-shift reaction at the sulfur covered MoS2 (1 0 0) surfaces, Mo-termination with 37.5% S coverage and S-termination with 50% S coverage using periodic slabs. The pathway for water–gas-shift reaction on both terminations has been carefully studied where the most favorable reaction path precedes the redox mechanism, namely the reaction takes place as follows: CO + H2O → CO + OH + H → CO + O + 2H → CO2 + H2. The most likely reaction candidates for the formate species HCOO formation is the surface CO2 reaction with H as a side reaction of CO2 desorption on S-termination with 50% S coverage. The formed HCOO species will react further with adsorbed hydrogen yielding H2COO followed by breaking its C–O bond to form the surface CH2O and O species.
50 citations
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TL;DR: In this article, the effect of Ca on NO heterogeneous reduction by char was investigated using density functional theory calculations with correction of London dispersion interaction, and the activation energy of each elementary reaction in the two reaction pathways indicated that Ca showed catalytic activity in the formation of N-N bond and the desorption of N2 molecule.
50 citations
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TL;DR: Results show that H2 addition increases the laminar burning velocity, while it shortens the ignition delay time of H2/CH4/air mixture, which may effectively reduce the explosion hazards.
50 citations
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TL;DR: In this paper, three approaches to the technical application of hot compressed water are presented to show and discuss the technology, potential, technical hurdles and future research demand in this area of research and development.
Abstract: Hot compressed water in the sub-?and supercritical state exhibits exciting physical and chemical properties, which can be varied continuously from gas-like to liquid-like behaviour. Correspondingly, the solvent properties can change from non-polar behaviour as present, for example, in organic solvents to highly ionic characteristics like in salt melts. This opens up several promising opportunities for separation processes and chemical reactions. Under supercritical conditions, substantial amounts of gases and organic substances can homogeneously be mixed with water, which then can be separated by adjusting the subcritical conditions by forming additional phases. This can beneficially be combined with chemical reactions occurring in the homogeneous state leading to integrated processes, which are more effective and competitive. Three approaches to the technical application of hot compressed water are presented to show and discuss the technology, potential, technical hurdles and future research demand in this area of research and development. In supercritical water oxidation (SCWO) water is used as a medium in which organic pollutants are completely degraded under the addition of oxygen, which is completely miscible with water under the process conditions of up to 650??C and pressures around 25?MPa. Thus, high space?time yields in compact reactor designs can be realized. Hydrogen is produced from biomass by hydrothermal gasification. Here, in an excess of water, the reaction at temperatures up to 700??C and pressures around 30?MPa directly leads to valuable hydrogen instead of synthetic gas, as in conventional gasification processes, or methane at subcritical conditions in water. After reaction, pressurized hydrogen is obtained and can easily be enriched due to the different partition coefficients of hydrogen and carbon dioxide between the aqueous and gas phase. Even homogeneous catalysis is possible in supercritical water. This has been demonstrated with the cobalt-catalysed cyclotrimerization of acetylenes to form benzene derivatives or hydroformylation to produce aldehydes from olefins. There, only the addition of CO is necessary, the H2 required being formed by the equilibrium of the water?gas-shift reaction. After a homogeneous reaction in the supercritical state, the reaction mixture can be separated at subcritical conditions. In support of the chemical and technical developments and to principally understand the experimental findings fundamental aspects have to be investigated as well. Intensive studies have been devoted to chemical kinetics including the modelling with elementary reaction steps, e.g.?to separate ionic and radical reaction pathways. Depending on the reaction conditions, ionic or radical reaction pathways can be favoured or suppressed, allowing for control selectivity. Furthermore, corrosion of relevant reactor materials has been investigated.
50 citations
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TL;DR: The rate of chemical-initiated bulk polymerization is studied theoretically and experimentally over the complete course of reaction taking into consideration the effects of the decrease of jump frequency of a polymer segment during polymerization on the rate of each elementary reaction.
Abstract: The rate of chemical-initiated bulk polymerization is studied theoretically and experimentally over the complete course of reaction Taking into consideration the effects of the decrease of jump frequency of a polymer segment during polymerization on the rate of each elementary reaction, a new kinetic model is proposed This model is applied to the bulk polymerization of methyl methacrylate and styrene for several initiator concentrations and temperatures Though the polymerization of these monomers shows very different auto-acceleration effects, experimental data of conversion and number-average and weight-average chain length can be successfully correlated to limiting conversion by this model
50 citations