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Relevant bibliographies by topics / Langmuir-Hinshelwood mechanism

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Academic literature on the topic 'Langmuir-Hinshelwood mechanism'

Author: Grafiati

Published: 4 June 2021

Last updated: 17 February 2022

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Journal articles on the topic "Langmuir-Hinshelwood mechanism"

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Xiang, Jinyao, Xuesen Du, Yuyi Wan, Yanrong Chen, Jingyu Ran, and Li Zhang. "Alkali-driven active site shift of fast SCR with NH3 on V2O5–WO3/TiO2 catalyst via a novel Eley–Rideal mechanism." Catalysis Science & Technology 9, no. 21 (2019): 6085–91. http://dx.doi.org/10.1039/c9cy01565e.

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The heterogeneous SCR reaction obeys the well-known Eley–Rideal mechanism or Langmuir–Hinshelwood mechanism, while fast SCR over alkali-doping catalysts follows the another “E–R” mechanism with adsorbed NO<sub>2</sub>.

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Baxter, R. J., and P. Hu. "Insight into why the Langmuir–Hinshelwood mechanism is generally preferred." Journal of Chemical Physics 116, no. 11 (2002): 4379–81. http://dx.doi.org/10.1063/1.1458938.

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Singh, Archana, Veerabhadraiah Palakollu, Aman Pandey, Sriram Kanvah, and Sudhanshu Sharma. "Green synthesis of 1,4-benzodiazepines over La2O3 and La(OH)3 catalysts: possibility of Langmuir–Hinshelwood adsorption." RSC Advances 6, no. 105 (2016): 103455–62. http://dx.doi.org/10.1039/c6ra22719h.

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Borovinskaya, Ekaterina. "Redundancy-Free Models for Mathematical Descriptions of Three-Phase Catalytic Hydrogenation of Cinnamaldehyde." Catalysts 11, no. 2 (2021): 207. http://dx.doi.org/10.3390/catal11020207.

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A new approach on how to formulate redundancy-free models for mathematical descriptions of three-phase catalytic hydrogenation of cinnamaldehyde is presented. An automatically created redundant (generalized) model is formulated according to the complete reaction network. Models based on formal kinetics and kinetics concerning the Langmuir-Hinshelwood theory for three-phase catalytic hydrogenation of cinnamaldehyde were investigated. Redundancy-free models were obtained as a result of a step-by-step elimination of model parameters using sensitivity and interval analysis. Starting with 24 parameters in the redundant model, the redundancy-free model based on the Langmuir-Hinshelwood mechanism contains 6 parameters, while the model based on formal kinetics includes only 4 parameters. Due to less degrees of freedom of molecular rotation in the adsorbed state, the probability of a direct conversion of cinnamaldehyde to 3-phenylpropanol according to the redundancy-free model based on Langmuir-Hinshelwood approach is practically negligible compared to the model based on formal kinetics.

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Atitar, M. Faycal, Asmae Bouziani, Ralf Dillert, Mohamed El Azzouzi, and Detlef W. Bahnemann. "Photocatalytic degradation of the herbicide imazapyr: do the initial degradation rates correlate with the adsorption kinetics and isotherms?" Catalysis Science & Technology 8, no. 4 (2018): 985–95. http://dx.doi.org/10.1039/c7cy01903c.

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The Langmuir–Hinshelwood mechanism applies to the photocatalytic degradation of imazapyr only when assuming the occurence of light-induced changes of the photocatalyst surface affecting the adsorption of the probe molecule.

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Gao, Xiaoyan, Yunhong Zhang, and Yong Liu. "A kinetics study of the heterogeneous reaction ofn-butylamine with succinic acid using an ATR-FTIR flow reactor." Physical Chemistry Chemical Physics 20, no. 22 (2018): 15464–72. http://dx.doi.org/10.1039/c8cp01914b.

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Heterogeneous reaction between succinic acid thin film and gas phasen-butylamine was studied, and results show that the reaction follows Langmuir–Hinshelwood mechanism and overall kinetics is dominated by surface reaction.

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Rai, Sandhya, Masahiro Ehara, and U. Deva Priyakumar. "Nucleobases tagged to gold nanoclusters cause a mechanistic crossover in the oxidation of CO." Physical Chemistry Chemical Physics 17, no. 37 (2015): 24275–81. http://dx.doi.org/10.1039/c5cp04273a.

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A mechanistic crossover is observed upon using nucleobase tagged gold clusters as catalysts favoring the Eley–Rideal mechanism, over the conventional Langmuir–Hinshelwood pathway followed using pristine gold clusters during CO oxidation.

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Mehrvar, Mehrab, William A. Anderson, and Murray Moo-Young. "Photocatalytic degradation of aqueous tetrahydrofuran, 1,4-dioxane, and their mixture with TiO2." International Journal of Photoenergy 2, no. 2 (2000): 67–80. http://dx.doi.org/10.1155/s1110662x00000106.

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Photocatalytic degradation of tetrahydrofuran, 1,4-dioxane, and their mixture in a slurry photoreactor was studied. Using both GC/MS and ion chromatography (IC) methods, possible intermediates were detected and the reaction mechanism pathways for both compounds were proposed. Kinetic models were developed and the kinetic parameters were estimated using a statistical method of non-linear parameter estimation in which all experimental data were utilized. It was shown that tetrahydrofuran was disappeared via direct oxidation as well as hydroxyl radical attack. A modified Langmuir-Hinshelwood described the degradation behavior of tetrahydrofuran and the binary system. 1,4-Dioxane obeyed a simple Langmuir-Hinshelwood kinetic form in the single compound system.

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Camu, Esteban, Cesar Pazo, Daniel Becerra, et al. "A new approach to the mechanism for the acetalization of benzaldehyde over MOF catalysts." New Journal of Chemistry 44, no. 35 (2020): 14865–71. http://dx.doi.org/10.1039/d0nj02416c.

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The benzaldehyde acetalization catalyzed by UiO-66 and UiO-66F, was carried out in a batch-type reactor at room temperature and atmospheric pressure, and the full kinetic study was performed using the Langmuir–Hinshelwood and Eley–Rideal models.

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Zhao, Bo, Jun Han, Linbo Qin, Wangsheng Chen, Zijian Zhou, and Futang Xing. "Impact of individual flue gas components on mercury oxidation over a V2O5–MoO3/TiO2 catalyst." New Journal of Chemistry 42, no. 24 (2018): 20190–96. http://dx.doi.org/10.1039/c8nj05084h.

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Dissertations / Theses on the topic "Langmuir-Hinshelwood mechanism"

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Farias, Manuel de Jesus Santiago. "Eletrooxidações de acetaldeído comum e etanol isotopicamente marcado (H3 13C-12CH2OH) em superfície de platina policristalina acompanhadas por FTIRS in situ." Universidade Federal do Maranhão, 2006. http://tedebc.ufma.br:8080/jspui/handle/tede/1561.

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Submitted by Rosivalda Pereira (mrs.pereira@ufma.br) on 2017-06-02T18:48:59Z No. of bitstreams: 1 ManuelFarias.pdf: 1389622 bytes, checksum: 6e4849f2b44871723791cde342c7bf04 (MD5)<br>Made available in DSpace on 2017-06-02T18:48:59Z (GMT). No. of bitstreams: 1 ManuelFarias.pdf: 1389622 bytes, checksum: 6e4849f2b44871723791cde342c7bf04 (MD5) Previous issue date: 2006-06-19<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)<br>This is work treat of the acetaldehyde and labeled ethanol oxidations, both kinds in percloric acidic medium, 0,1 Mol L-1 HClO4 on the Pt polycrystalline surface with used conventional electrochemical and spectroscopy techniques (FTIRS in situ). From acetaldehyde, wanted to find the mean concentration that better favor the reaction to evolve for CO2 in the potential smaller from production of the kind. The concentration 0,01 Mol L-1 was better suitable, but the increase of the concentration in solution, this is pathway was whole inhibited. However, in the high potential the form to acetic acidic is favorable. For main cronoamperometry, acetaldehyde in the concentration 0,02 Mol L-1, were able proof results in situ FTIRS. According to potential, this is results was interpreted second pattern to consider: the pear adsorbed kinds (Langmuir-Hinshelwood) and other where consider only one adsorbed kinds between adsorbed (pattern Eley-Rideal mechanism). In the case of ethanol labeled oxidation (H3 13CO 12CH2OH), it is search to look into the path delineated from way severous of the reaction from to form CO2. The results showed that is product would to be results of the intermediates oxidations contained carbon from alcohol group and intermediates contained carbon from group methyl; however, the intermediates contained carbon alcohol group is mores able reactive in the zone potential searched in the work, is this mores, confronted with able reactive metil group. The path double that yield CO2 in the zone potential below 1,0 V, are yielded coupling bands 12COL and 13COL which coexist in below potential. In the presence kind 13COL in 0,4 V potential proof that of the efficiency of the platinum electrode for the oxygenation group metil in the zone below potential. In the potential largest that 1,0 V, where exist the formation continuous of carbon dioxide, the difference in the greatness bands associated from 12CO2 e 13CO2 (double path product contained carbon), was interpreted in the sense of the electrochemical conditions infortunable for remover hydrogen group metil; additional this is kind was to promote for yield from molecules, which not is able identify for whole technique.<br>Este trabalho trata das reações de eletrooxidações de acetaldeído comum e etanol isotopicamente marcado, ambas reações em superfície de platina policristalina em meio de ácido perclórico, HClO4, 0,1 Mol L-1, com a utilização de técnicas eletroquímicas convencionais e espectroscopia (FTIRS in situ). Para o acetaldeído, essa reação foi estuda com a dependência do potencial aplicado e a concentração do aldeído em solução, que melhor resultaram na transformação desta molécula a CO2. Assim, para o potencial 0,6 V, a concentração de aldeído 0,01 Mol L-1 foi a mais apropriada deduzida a partir de FTIRS in situ e, a concentração 0,02 Mol L-1 permitiu a geração de maior densidade de corrente e foi inferida a partir de cronoamperometria. Essa discrepância foi discutida em termos das reações específicas que resultam no sinal analítico para cada técnica. Dependendo da concentração do acetaldeído, a via de formação de CO2 foi completamente inibida e, em altos potenciais, prevalecia sempre a formação de ácido acético. Paralelamente, dependendo do potencial, estes resultados foram interpretados com base em modelos de mecanismos de reações que considera: um par de reagentes adsorvidos (mecanismo Langmuir-Hinshelwood) e apenas uma espécie adsorvida do par fundamental de reagentes (mecanismo Eley-Rideal). Para o etanol isotopicamente marcado (H3 13C 12CH2OH), foram investigados passos delineados pelas diferentes vias de reação de formação de CO2. Os resultados mostraram que este produto pode ser resultante da eletrooxidação de intermediários contendo o carbono do grupo álcool e do grupo metil, sendo que o intermediário contendo o carbono do grupo álcool, para toda a faixa de potenciais investigados, é bem mais reativo que o intermediário contendo o carbono do grupo metil. As vias duplas que geram CO2 em potenciais abaixo de 1,0 V são resultantes de bandas acopladas de 12COL e 13COL que coexistem em baixos potenciais. A presença de 13COL em 0,35 V foi encarada como uma evidência da eficiência da Pt para oxigenação do grupo metil em baixos potenciais. Em potenciais acima de 1,0 V, onde há produção contínua de dióxido de carbono, a diferença na magnitude das intensidades de bandas relativa ao 13CO2 e 12CO2 (das vias de origem de carbono), foi interpretada como sendo as referidas condições eletroquímicas desfavoráveis para desprotonação do metil.

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Wunder, Stefanie. "Synthesis, characterization and catalytic activity of immobilized metallic nanoparticles." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2013. http://dx.doi.org/10.18452/16752.

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In dieser Arbeit wurden Gold- und PlatinNanopartikel in sphärischen Polyelektolyt-Bürsten (SPB) synthetisiert. Diese wurden zu mechanistischen Untersuchungen der p-Nitrophenol-Reduktion mittels Natriumborhydrid herangezogen. Dabei konnte der Mechanismus der Reaktion auf der Oberfläche der Nanopartikel aufgeklärt werden. Die Reaktion folgt einem Langmuir Hinshelwood (LH) Mechanismus. Hierbei adsorbieren beide Edukte auf die Oberfläche, bevor sie im zu p-Aminophenol umgesetzt werden. Nach der Reaktion desorbiert das Reaktionsprodukt. Mittels des LH Modells konnten für verschiedene Temperaturen die intrinsische Geschwindigkeitskonstante, sowie die Adsorptionskonstanten der Edukte bestimmt werden. Mit diesen Daten konnten dann die Enthalpie und Entropie der Adsorption der Edukte und die Aktivierungsenergie berechnet werden. Neben dem Reaktionsmechanismus wurde die Induktionszeit der p-Nitrophenol Reduktion untersucht. Hierbei konnte gezeigt werden, dass diese Totzeit der Reaktion wahrscheinlich auf eine Restrukturierung der Nanopartikeloberfläche zurückzuführen ist. Sie ist unabhängig von den eingesetzten Konzentrationen des Borhydrids, hingegen abhängig von der Konzentration an p-Nitrophenol auf der Oberfläche der Nanopartikel, was auf Restrukturierung der Nanopartikel durch p-Nitrophenol hindeutet. Zudem wurden Hinweise auf eine spontane Rekonstruktion der Nanopartikel gefunden, die unabhängig von der Konzentration des p-Nitrophenols ist. Des Weiteren wurde die katalytische Oxidation von Morin mit Manganoxid Nanopartikeln untersucht. Diese sind in der Polyelektrolytschale der SPB immobilisiert. Analysen der Reaktionskinetik der Morin Oxidation ergaben, dass auch in diesem Fall der LH Mechanismus vorliegt. Hierbei konnten die Adsorptionskonstanten und Geschwindigkeitskonstanten für verschiedene Temperaturen ermittelt werden und somit die Aktivierungsenergie der Oxidation sowie die Adsorptionsenthalpie und Entropie der Edukte.<br>In this work, gold and platinum nanoparticles were synthesized into spherical polyelectrolyte brushes (SPB) in order to apply them as catalysts for kinetic studies of the reduction of p-nitrophenol by sodium borohydride. It was found that the reaction follows the Langmuir-Hinshelwood (LH) mechanism where both educts must adsorb onto the surface of the catalyst in order to react. Thereby, the rate determining step is the surface reaction of both educts. After the reaction, the product desorbs from the surface and a free active site is formed. With this model the intrinsic reaction rate and the adsorption constants for both educts could be determined. The measurements at different temperatures allowed the calculation of the activation energy and the adsorption enthalpy and entropy of the educts. Besides the reaction mechanism, the induction time of the reaction was analyzed. Here, it was shown that the reason of this delay time is a restructuring of the nanoparticle surface. The induction time is solely dependent on the concentration of p-nitrophenol on the surface of the nanoparticles and independent of the applied concentrations of borohydride. Moreover, hints for a spontaneous reconstruction of the nanoparticles without p-nitrophenol were found. In the second part, the catalytic oxidation of morin by manganese oxide has been studied. These nanoparticles were embedded inside the polyelectrolyte layer of the SPB. These nanoparticles were used for systematic studies of the oxidation of morin with hydrogen peroxide. It was shown that in this case the reaction followed a LH kinetics as well. Here, the intrinsic rate constants and the adsorption constants could be obtained for different temperatures. The activation energy and the adsorption enthalpy and entropy could be determined accordingly. The adsorption enthalpy is exothermic in both cases.

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Andrieux, Jérome. "Stockage de l'hydrogène dans les borohydrures alcalins : hydrolyse du borohydrure de sodium." Phd thesis, Université Claude Bernard - Lyon I, 2009. http://tel.archives-ouvertes.fr/tel-00654299.

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Le contexte environnemental (réchauffement climatique) et économique (épuisement des ressources en énergies fossiles) entraîne une nécessaire mutation du paysage énergétique mondial. L'hydrogène est présenté comme un vecteur d'énergie propre pouvant, par l'intermédiaire d'une pile à combustible, fournir de l'électricité pour diverses applications (nomade, portable, automobile et stationnaire). Cependant, son développement reste tributaire de son mode de stockage. Parmi les composés présentant de bonnes capacités de stockage, le borohydrure de sodium NaBH4 se distingue puisqu'il permet aussi un dégagement contrôlé de l'hydrogène d'après la réaction d'hydrolyse suivante : ( ) (2 ) ( ) ( ) 4 ( ) 4 2 2 2 2 NaBH ++ x H O l→NaBO . xH O + H g Il constitue ainsi une solution sûre et facile d'utilisation, et est donc envisageable pour des applications grand public. La thèse avait pour objectif l'approfondissement des connaissances relatives à la réaction catalysée d'hydrolyse du borohydrure de sodium selon deux axes principaux: la catalyse de la réaction et l'étude des produits d'hydrolyse. Concernant le premier axe, notre objectif était de mieux comprendre et d'améliorer la cinétique de la réaction d'hydrolyse, les catalyseurs étudiés étant à base de cobalt. Un catalyseur " modèle " a été utilisé et comparé à des nanoparticules métalliques synthétisées et d'autres espèces chimiques à base de cobalt (oxyde, hydroxyle et carbonate). Le modèle cinétique de Langmuir-Hinshelwood a permis de décrire la cinétique de l'hydrolyse. Un mécanisme réactionnel basé sur les adsorptions en surface du catalyseur de BH4 - et de H2O a été proposé. Enfin, la nature des sites actifs en surface a été discutée. En ce qui concerne le second axe de la thèse, nous avions deux objectifs : identifier les phases formées en fonction des conditions expérimentales et approfondir les connaissances thermodynamiques du système binaire NaBO2-H2O pour définir les différents équilibres se formant à l'issu de la réaction d'hydrolyse. Pour ce faire, les borates ont d'abord été synthétisés, puis caractérisés en termes de structure cristallographique et de stabilité en température. C'est ainsi qu'un nouveau borate de sodium, Na3[B3O4(OH)4] ou NaBO2*2/3H2O, a été obtenu. D'autre part, l'étude des équilibres liquide+solide, solide+solide et liquide+vapeur nous a permis d'établir le diagramme binaire NaBO2-H2O à pression atmosphérique.

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Critchfield, Brian L. "Statistical Methods For Kinetic Modeling Of Fischer Tropsch Synthesis On A Supported Iron Catalyst." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1670.pdf.

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Book chapters on the topic "Langmuir-Hinshelwood mechanism"

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Irvine, William M. "Langmuir-Hinshelwood Mechanism." In Encyclopedia of Astrobiology. Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-662-44185-5_863.

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Irvine, William M. "Langmuir-Hinshelwood Mechanism." In Encyclopedia of Astrobiology. Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-27833-4_863-3.

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Irvine, William M. "Langmuir-Hinshelwood Mechanism." In Encyclopedia of Astrobiology. Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-11274-4_863.

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Caycedo Villalobos, Luis Alejandro. "Langmuir–Hinshelwood Mechanism Implemented in FPGA." In Communications in Computer and Information Science. Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-030-00350-0_27.

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Shahbazi, Fatemeh, Masoud Jabbari, Mohammad Nasr Esfahani, and Amir Keshmiri. "Numerical Simulation of Langmuir-Hinshelwood Mechanism for Heterogeneous Biosensors in Microfluidic Channel." In 8th European Medical and Biological Engineering Conference. Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-64610-3_101.

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Conference papers on the topic "Langmuir-Hinshelwood mechanism"

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Gokon, Nobuyuki, Yusuke Osawa, Daisuke Nakazawa, Tsuyoshi Hatamachi, and Tatsuya Kodama. "Kinetics of CO2 Reforming of Methane by Catalytically Activated Metallic Foam Absorber for Solar Receiver-Reactors." In ASME 2008 2nd International Conference on Energy Sustainability collocated with the Heat Transfer, Fluids Engineering, and 3rd Energy Nanotechnology Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/es2008-54156.

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Ni-Cr-Al alloy foam absorber with high porosity was catalytically activated using a Ru/γ-Al2O3 catalyst, and was subsequently tested with respect to CO2 reforming of methane in a small-scale volumetric receiver-reactor by using a sun simulator. A chemical storage efficiency of about 40% was obtained for a mean light flux of 325 kWm−2. Furthermore, the activity and the stability of the metallic foam absorber were compared with those of a SiC foam absorber activated with the same Ru/γ-Al2O3 catalyst for 50 h of light irradiation, and it was found that the metallic foam absorber has superior catalytic stability in comparison to the SiC form absorber. In addition, unlike ceramic foams such as SiC, metallic foams feature superior plasticity, which prevents the emergence of cracks caused by mechanical or thermal shock. The kinetics of CO2 reforming of methane over metallic foam absorbers were also examined for temperatures of 600–750°C using a quartz tube reactor and an electric furnace. The experiments were performed by varying the methane/CO2 ratios of 0.5–2.3. Moreover, the kinetic data were fitted to four different types of kinetic models, namely the Langmuir-Hinshelwood, Basic, Eley-Rideal, and Stepwise mechanisms. The kinetic model which provided the best prediction of the experimental reforming rates was the Langmuir-Hinshelwood mechanism.

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Gellman, Andrew J., and Yang Yun. "Issues in Vapor Phase Lubrication of Magnetic Data Storage Media." In World Tribology Congress III. ASMEDC, 2005. http://dx.doi.org/10.1115/wtc2005-63165.

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Vapor phase lubrication (VPL) integrates media lubrication with the vacuum processing steps used throughout most of the hard disk media fabrication process. This avoids exposure of the unlubricated a-CHx overcoat surface to the ambient air and airborne contamination. In vapor lubrication the a-CHx surface can be oxidized under controlled conditions immediately prior to lubricant adsorption. The kinetics of a-CHx oxidation have been studied using x-ray photoemission spectroscopy in an apparatus that allows oxidation of freshly deposited a-CHx films. The dissociative sticking coefficient of oxygen is ∼10−6 and the initial oxidation kinetics can be described by a Langmuir-Hinshelwood mechanism.

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Stamatiou, Anastasia, Peter G. Loutzenhiser, and Aldo Steinfeld. "Solar Syngas Production From H2O and CO2 via Two Step Thermochemical Cycles Based on FeO/Fe3O4 Redox Reactions: Kinetic Analysis." In ASME 2010 4th International Conference on Energy Sustainability. ASMEDC, 2010. http://dx.doi.org/10.1115/es2010-90009.

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Syngas production via a two-step H2O/CO2-splitting thermochemical cycle based on FeO/Fe3O4 redox reactions is considered using highly concentrated solar process heat. The closed cycle consists of: 1) the solar-driven endothermic dissociation of Fe3O4 to FeO; 2) the non-solar exothermic simultaneous reduction of CO2 and H2O with FeO to CO and H2 and the initial metal oxide; the latter is recycled to the first step. The second step was experimentally investigated by thermogravimetry for reactions with FeO in the range 973–1273 K and CO2/H2O concentrations of 15–75%. The reaction mechanism was characterized by an initial fast interface-controlled regime followed by a slower diffusion-controlled regime. A rate law of Langmuir-Hinshelwood type was formulated to describe the competitiveness of the reaction based on atomic oxygen exchange on active sites, and the corresponding Arrhenius kinetic parameters were determined by applying a shrinking core model.

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De La Pena-Cortes, Ernesto, Francisco Elizalde-Blancas, Abel Hernandez-Guerrero, Armando Gallegos-Munoz, and Juan M. Belman-Flores. "Numerical Analysis of the Internal Fuel Processing in Solid Oxide Fuel Cells." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-65273.

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The high operating temperature of a SOFC (solid oxide fuel cell) has several consequences, from which the most important one is the possibility to feed the cell directly with unprocessed fuels. This eliminates the need for expensive external fuel reformers that hinder the cell from achieving a greater overall efficiency when coupled into a power generation system. Direct internal reforming (DIR) takes place directly on the anode of a SOFC by harnessing the available Nickel catalyst on its surface to process the incoming fuel. In this study a three dimensional steady state computational fluid dynamics model is implemented in a planar DIR SOFC to compare the overall cell performance operating on biogas, and coal syngas. Since chemical kinetics plays a significant role in the model accuracy, the present work also focuses on comparing three different chemical reaction mechanisms for the internal reforming process. These include a detailed heterogeneous mechanism consisting of 42 elementary reactions, a global homogeneous catalyzed mechanism, and a Langmuir-Hinshelwood based mechanism. The former includes autothermal reforming, steam reforming and water gas shift reaction effects, the latter two include steam reforming, and water gas shift reaction effects. The analysis yields detailed information about the cell, including polarization curves that help to assess the cell performance for each fuel. Meanwhile the chemical kinetics comparison amongst the analyzed mechanisms helps in establishing the best compromise between the accuracy of the model, and the computational resources devoted for the calculation.

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Gharebaghi, M., B. Goh, J. M. Jones, L. Ma, M. Pourkashanian, and A. Williams. "Numerical Investigation of Char Reactivity in Oxy-Coal Combustion in Carbon Capture and Sequestration Technologies." In ASME Turbo Expo 2009: Power for Land, Sea, and Air. ASMEDC, 2009. http://dx.doi.org/10.1115/gt2009-59887.

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Oxy-coal combustion with CO2 capture from flue gas is an emerging technology that can be adapted to both new and existing coal-fired power stations leading to substantial reduction in carbon emission from the power generation industry. However, switching to oxy-coal brings a number of uncertainties to the combustion process and there is a significant knowledge gap in this new technology. Computational Fluid Dynamic (CFD) studies can be used as one of the tool to identify the extent of the modifications required due to changes in the process. One of the possible challenges is related to the the changes in char combustion and char reactivity which may have an impact on unburned carbon in the furnace. In this study, two approaches have been undertaken to investigate the impact of oxy-coal combustion on char reactivity: simple equilibrium calculations and numerical 3-D simulations. As the focus of this study, the influence of CO2-O2 combustion environment on char reactivity and particularly carbon in ash has been investigated. It has been found that the effect of C-CO2 and C-H2O reactions on overall char reactivity cannot be disregarded. In addition, in this study, it is suggested that using the Langmuir-Hinshelwood mechanism can provide a more accurate prediction for the effect of gasification reactions on unburnt carbon and char reactivity. The accuracy of the CFD modeling has been investigated using experimental data from a one MWth combustion test facility. In order to improve the validity of the CFD code for design purposes, further modeling improvements for accurate predictions are addressed.

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Toema, Mohamed, and Kirby S. Chapman. "Interpreting the Lambda Sensor Output Signal to Control Emissions From Natural Gas Fueled Engines." In ASME 2010 Internal Combustion Engine Division Fall Technical Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/icef2010-35164.

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This paper presents the work done to date on a modeling study of the Non-Selective Catalytic Reduction (NSCR) system. Several recent experimental studies indicate that the voltage signal from the heated exhaust gas oxygen sensor commonly used to control these emission reduction systems may not be interpreted correctly because of the physical nature in the way the sensor senses the exhaust gas concentration. While the current signal interpretation may be satisfactory for modest NOX and CO reduction, an improved understanding of the signal is necessary to achieve consistently low NOX and CO emission levels. The increasingly strict emission regulations may require implementing NSCR as a promising emission control technology for stationary spark ignition engines. Many recent experimental investigations that used NSCR systems for stationary natural gas fueled engines showed that NSCR systems were unable to consistently control the emissions level below the compliance limits. Modeling of NSCR components to better understand, and then exploit, the underlying physical processes that occur in the lambda sensor and the catalyst media is now considered an essential step toward improving NSCR system performance. This paper focuses only on the lambda sensor that provides feedback to the air-to-fuel ratio controller. The goals of this modeling study are: • Improve the understanding of the transport phenomena and electrochemical processes that occur within the sensor. • Investigate the cross-sensitivity of exhaust gases from natural gas fueled engines on the sensor performance. • Serve as a tool for improving NSCR control strategies. This model simulates the output from a planar switch type lambda sensor. The model consists of three modules. The first module models the multi-component mass transport through the sensor protective layer. A one dimensional mass conservation equation is used for each exhaust gas species. Diffusion fluxes are calculated using the Maxwell-Stefan equation. The second module includes all the surface catalytic reactions that take place on the sensor platinum electrodes. All kinetic reactions are modeled based on the Langmuir-Hinshelwood kinetic mechanism. The third module is responsible for simulating the reactions that occur on the electrolyte material and determining the sensor output voltage. The details of these three modules as well as a parametric study that investigates the sensitivity of the output voltage signal to various exhaust gas parameters is provided in the paper.

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Toema, Mohamed, and Kirby S. Chapman. "Modeling of Lambda Sensor Output With Exhaust Gas Mixtures From Natural Gas-Fueled Engines." In ASME 2011 Internal Combustion Engine Division Fall Technical Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/icef2011-60188.

Full text

Abstract:

The increasingly strict emission regulations may require implementing Non-Selective Catalytic Reduction (NSCR) system as a promising emission control technology for stationary rich burn spark ignition engines. Many recent investigations used NSCR systems for stationary natural gas fueled engines showed that NSCR systems were unable to consistently control the emissions level below the compliance limits. Modeling of NSCR components to better understand, and then exploit, the underlying physical processes that occur in the lambda sensor and the catalyst media is now considered an essential step toward the required NSCR system performance. This paper presents the work done to date on a modeling of lambda sensor that provides feedback to the air-to-fuel controller. Several recent experimental studies indicate that the voltage signal from the lambda sensor may not be interpreted correctly because of the physical nature in the way the sensor senses the exhaust gas concentration. Correct interpretation of the sensor output signal is necessary to achieve consistently low emissions level. The goal of this modeling study is to improve the understanding of the physical processes that occur within the sensor, investigate the cross-sensitivity of various exhaust gas species on the sensor performance, and finally this model serves as a tool to improve NSCR control strategies. This model simulates the output from a planar switch type lambda sensor. The model consists of three modules. The first module models the multi-component mass transport through the sensor protective layer. Diffusion fluxes are calculated using the Maxwell-Stefan equation. The second module includes all the surface catalytic reactions that take place on the sensor platinum electrodes. All kinetic reactions are modeled based on the Langmuir-Hinshelwood kinetic mechanism. The model incorporates for the first time methane catalytic reactions on the sensor platinum electrode. The third module is responsible for simulating the reactions that occur on the electrolyte material and determine the sensor output voltage. The model results are validated using field test data obtained from a mapping study of a natural gas-fueled engine equipped with NSCR system. The data showed that the lambda sensor output voltage is influenced by the reducing species concentration, such as carbon monoxide (CO) and hydrogen (H2). The results from the developed model and the experimental data showed strong correlations between CO and H2 with the sensor output voltage within the lambda operating range between 0.994 to 1.007 (catalytic converter operating window). This model also showed that methane does not significantly influence the lambda sensor performance compared to the effect of CO and H2.

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