Kinetics Of Carbon Deposition Research Articles

Kinetics of monticular carbon growth on polycrystalline iron

The kinetics of carbon deposition on polycrystalline iron surfaces from methane at 750 Torr pressure and at temperatures between 1013 and 1133 K have been studied using the change in power dissipation of an electrically heated filament caused by the increased emissivity as the surface is blackened by deposit. The carbon formed has a monticular-type structure. The growth kinetics follow a direct logarithmic rate law which is explained in terms of the availability of active sites at the surface. The total carbon uptake at maximum coverage of the monticular layer, i.e. at maximum emissivity, depends on the filament temperature and can be correlated with the amount of carbon taken up into solution during the prior induction period in accordance with the phase diagram. The activation energy has a value of 66 ± 8 kJ mol–1. The rate-determining step for monticular growth cannot be established, but certain possibilities, such as carbon dissolution, bulk diffusion of carbon in the metal, and surface and bulk self-diffusion of iron, can be eliminated. Various aspects of the mechanism of formation of the monticular growths are discussed.

Kinetics of carbon deposition during methanation of carbon monoxide

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTKinetics of carbon deposition during methanation of carbon monoxideDavid C. Gardner and Calvin H. BartholomewCite this: Ind. Eng. Chem. Prod. Res. Dev. 1981, 20, 1, 80–87Publication Date (Print):March 1, 1981Publication History Published online1 May 2002Published inissue 1 March 1981https://doi.org/10.1021/i300001a007RIGHTS & PERMISSIONSArticle Views862Altmetric-Citations69LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts

Summary Abstract: Kinetics of carbon deposition from Co on Ru(110) and Ni(100)

Summary Abstract: Kinetics of carbon deposition from Co on Ru(110) and Ni(100)

Carbon Formation on Unsupported and Supported Nickel Catalysts

AbstractStudies have been made of the kinetics of carbon deposition on supported nickel catalysts used for steam reforming. Comparison with results obtained with nickel foils show that the support has little effect on the rate of deposition, except that hydrogen did not affect the kinetics of the process on supported catalysts. This is explained in terms of the initial production of nickel crystallites, which are then carried with the growing carbon by a process of diffusion of carbon through the nickel. Calculations show that this diffusion process may well involve the formation of an intermediate carbide.

Kinetics of carbon deposition on diamond powder

The rate of carbon deposition on 0–1-μm diamond seed crystals was investigated in the temperature range 1140–1475 °C, methane partial pressures form 10−3 to 44.4 Torr and hydrogen partial pressures from 0 to 16.4 Torr. Two distinct kinetic regimes were found. A relatively rapid initial rate of diamond growth decayed exponentially to a final slow constant rate as graphitic carbon was codeposited and covered the surface. A maximum initial diamond growth rate of 1.06×10−7 g cm−2 min−1, which corresponded to a nominal linear growth rate of only 0.45 μm per day, was observed. Dilution of methane with hydrogen decreased the nucleation rate of graphitic carbon relative to that of diamond resulting in a increase in the diamond yield. The activation energy for diamond deposition from pure methane was 55 kcal mole−1. The dependence of the initial rate data on methane partial pressure could be described by a Langmuir-type equation. The deposits were identified by chemical etching, chemical analysis, density measurements, x-ray and electron diffraction, transmission electron microscopy, and optical measurements. The crystalline quality of the diamond was not determined and could be highly defective.

Carbon films from carbon suboxide decomposition. Inhibition by carbon monoxide and the heat of formation of C 2O

A theoretical analysis of carbon-deposition kinetics has been developed to take into account a back-reaction in a simple kinetic case and has been applied to experimental data for deposition from C 3O 2 in the presence of CO. The analysis may serve as a prototype for the treatment of more complex systems. In the case of C 3O 2, experimental data on CO-inhibited deposition provide an approximate figure for the rate constant of the reaction, C 2 O+ CO→ C 3 O 2, and this in turn has permitted the equilibrium constant at 1060°K to be determined for the reaction, C 3 O 2( g) C 2 O+ CO. An estimate of ΔS° for the reaction permits calculation of its ΔH° (+55 kcal) and the ΔH° f of C 2O (+58 kcal), with uncertainties of 2 or 3 kcal. The most interesting result of the work is its strong support for a 3∑ state as the ground state of C 2O together with the conclusion that the thermal decomposition of C 3O 2 provides a further example to add to the short list of elementary reactions known to involve a change of spin. The transmission coefficient is found to be approximately 10 −4.

An analysis of carbon deposition kinetics in isothermal flow systems

An analysis is presented of the steady-state deposition of carbon from a pyrolyzing gas in an isothermal flow system. It is assumed that the parent material is decomposing in the gas phase by first-order kinetics. Three system geometries are examined : an infinite slit, an annulus, and a cylindrical tube. A convenient kinetic criterion for each case is found to be the ratio of a characteristic diffusion time to the first-order rate constant. When this ratio is much less than unity, when carbon deposition from the parent molecules is much less efficient than deposition from decomposition products, and when deposition from products occurs at moderate-to-large efficiencies, it is predicted that the deposition rate will be approximately equal to the rate of gas-phase decomposition of the parent species times some geometric factors.

Kinetics of carbon deposition in a fluidized bed

AbstractRate data have been obtained for the deposition of carbon films from methane and acetylene in fluidized beds of alumina, uranium dioxide, uranium monocarbide, uranium dicarbide, and a solid solution of uranium‐thorium dicarbide powders. These carbon films have been shown to provide excellent protection for the powdered fertile material against attack by hot concentrated nitric‐acid solutions. The coated uranium‐thorium dicarbide particles were also shown to be stable in humid air.