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Ledoux, Marc J.; Pham‐Huu, Cuong

doi:10.1023/a:1014092930183

Cited by 229 publications

(151 citation statements)

References 43 publications

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“…This synthesis was developed few years ago by Ledoux et al 14 and overcome the disadvantages cited above. Since its discovery, SiC prepared according to the SMS method was efficiently used for several reactions such as hydrodesulfurization, automotive exhaust-pipe reactions, isomerization of linear saturated hydrocarbons, n-butane dehydrogenation-isomerization reactions, reported in detailed reviews published by Ledoux et al 11,15 Due to its interesting physico-chemical properties, SiC seems to be a promising substitute to traditional oxidic supports for the selective oxidation of H 2 S by oxygen into elemental sulfur.…”

Section: (Equation 1)mentioning

confidence: 99%

“…It had a mesoand macroporosity, with no microporous network. 15 Figures 2A and 2B show respectively the macroporosity of the β-SiC support and the presence of a 1-3 nm thick amorphous oxygen containing surface layer. Previous characterizations by XPS/mapping-Auger coupled to TEM analyses evidenced that the surface of SiC prepared according to the gas-solid SMS was heterogeneous in nature: 15,18,19 a fraction of the surface is composed of this amorphous surface phase, made of a mixture of silicon oxycarbide and silica phases, expected to present a hydrophilic character due to the presence of oxygen atoms on the surface, whereas the remaining surface is pure SiC, oxygen-free, expected to be hydrophobic in nature, due to the absence of any oxygen bonds.…”

Section: Medium Surface Area β-Silicon Carbidementioning

confidence: 99%

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New catalysts based on silicon carbide support for improvements in the sulfur recovery. Silicon carbide as support for the selective H2S oxidation

Keller¹,

Vieira²,

Nhut³

et al. 2005

J. Braz. Chem. Soc.

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As fases ativas NiS 2 e Fe 2 O 3 suportadas em β-carbeto de silício (SiC) com média área específica mostraram alta atividade, seletividade e estabilidade na oxidação direta do H 2 S a enxofre elementar. Os catalisadores foram testados a temperaturas que variaram da temperatura ambiente, no caso do Ni em reator de leito gotejante, até temperaturas superiores à do ponto de orvalho do enxofre, no caso do Fe em reator de leito fixo. Para ambos os casos, foi proposta a formação de uma fase bastante ativa de oxisulfeto de Ni ou de Fe, formada pela oxidação do NiS 2 e pela sulfuração do Fe 2 O 3 . A ausência de microporosidade no suporte contribuiu à alta seletividade do catalisador. A grande estabilidade ao carregamento de enxofre sólido, apresentada pelos catalisadores suportados em SiC em temperaturas inferiores a 100 °C, foi explicada pela maneira especial da deposição do enxofre, a qual depende do papel da água presente na reação e do caráter heterogêneo (hidrofílico e hidrofóbico) da superfície do suporte.The NiS 2 and Fe 2 O 3 active phases supported on medium surface area β-silicon carbide (SiC) showed high activity, selectivity and stability in the direct oxidation of H 2 S into elemental sulfur. The catalysts were tested under a large range of temperatures, from room temperature using Ni (tricklebed reactor) to over-dewpoint temperatures using Fe (fixed bed reactor). For both cases, the formation on stream of a Ni and Fe oxysulfide high active phase was proposed by oxidation of NiS 2 and sulfidation of Fe 2 O 3 , respectively. The absence of microporosity in the support contributed to the high selectivity into sulfur. At low temperatures (below 100 °C), the high stability of β-SiC supported catalysts towards the solid sulfur loading was explained by a specific mode of sulfur deposition, involving the role of water in the feed and the heterogeneous nature of the SiC surface, being partly hydrophilic and hydrophobic.Keywords: silicon carbide, catalyst support, sulfur recovery, H 2 S oxidation, hydrophilicity, hydrophobicity IntroductionThe removal of hydrogen sulfide (H 2 S) from the acid gases generated by oil refineries or natural gas plants is a crucial aspect of air pollution control, due to ever increasing standards of efficiency required by the environmental protection pressure. The general trend is to selectively transform H 2 S into elemental sulfur and steam, by the wellknown modified Claus process.1 (equation 1) 2 H 2 S + SO 2 ↔ 3/n S n + 2 H 2 OAccording to the different running processes, typical sulfur efficiencies are only 90-96 % for a two stage reactor unit and 95-98 % for a three stage process, due to the thermodynamic limitations of the Claus reaction.2 This means that for a conventional sulfur plant, the SO 2 emissions may amount to many thousand tons per year released into the atmosphere, and a large amount of sulfur compounds remains in the tail gas, i.e., SO 2 (≈ 6000 ppm), H 2 S (≈ 12000 ppm), COS and CS 2 (≈ 700 ppm). New catalysts and processes for the tail-gas treatment of the industri...

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Section: (Equation 1)mentioning

confidence: 99%

Section: Medium Surface Area β-Silicon Carbidementioning

confidence: 99%

New catalysts based on silicon carbide support for improvements in the sulfur recovery. Silicon carbide as support for the selective H2S oxidation

Keller¹,

Vieira²,

Nhut³

et al. 2005

J. Braz. Chem. Soc.

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“…The role of condensed water, acting as a conveyor belt on the catalyst surface when using SiC grains has already been reported and discussed in details. 3,13,17 A liquid water film allowed the sulfur formed to be removed from the NiS 2 active sites before the subsequent storage on hydrophobic SiC surfaces, outside the pores, which are free of active phase.…”

Section: Oxidation Of H 2 S In a Trickle-bed Modementioning

confidence: 99%

“…8 The aim of this article is to report the synthesis of SiC nanotubes via a gas-solid reaction. [9][10][11][12][13] and their use as catalyst support for the trickle-bed oxidation of H 2 S into elemental sulfur at 60 °C.…”

Section: Introductionmentioning

confidence: 99%

New catalysts based on silicon carbide support for improvements in the sulfur recovery: new silicon carbide nanotubes as catalyst support for the trickle-bed H2S oxidation

Keller¹,

Vieira²,

Nhut³

et al. 2005

J. Braz. Chem. Soc.

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Nanotubos de carbeto de silício (SiC) foram preparados a partir da reação gás-sólido entre vapor de SiO e nanotubos de carbono. A fase ativa NiS 2 suportada em nanotubos de SiC apresentou maior atividade catalítica e maior capacidade de armazenamento de enxofre na reação de oxidação seletiva do H 2 S a enxofre elementar, em reator do tipo trickle-bed, que a mesma fase ativa suportada em grãos de SiC. O melhor desempenho deste catalisador foi explicado pela ocorrência do efeito de confinamento no interior dos nanotubos de SiC; ou seja, pelo aumento artificial da pressão parcial de H 2 S no interior dos nanotubos em relação à mesma pressão fora dos nanotubos, resultando assim em um aumento na taxa da oxidação, uma vez que a velocidade de reação do H 2 S é de primeira ordem. O catalisador suportado em nanotubos de SiC apresentou elevada resistência ao carregamento de enxofre devido a uma peculiar evacuação do enxofre pelo vapor de água condensado, permitindo assim uma limpeza contínua dos sítios ativos. A maior capacidade de armazenamento do enxofre sólido no suporte a base de nanotubos de SiC foi atribuído ao seu maior volume específico disponível para o armazenamento do enxofre do que o do suporte a base de grãos de SiC.Silicon carbide nanotubes were prepared via a gas-solid reaction between SiO vapor and carbon nanotubes. The NiS 2 active phase on this support displayed both a high catalytic activity and high solid sulfur storage capacity in the trickle-bed selective oxidation of H 2 S into elemental sulfur as compared to the grain-based SiC catalyst. The hypothesis of a confinement effect inside the SiC nanotubes has been put forward to explain the catalytic results. An artificial increase in the H 2 S partial pressure inside the tubes when compared to the H 2 S partial pressure outside the tubes would lead to an increase in the oxidation rate, due to the first order reaction rate toward H 2 S. The SiC nanotube supported catalyst displayed very high resistance to the sulfur loading, due to a peculiar mode of sulfur evacuation by condensed steam which allows the continuous cleaning of the active site. The high solid sulfur storage capacity was due to a much larger void volume between each SiC nanotube available for the sulfur storage, than the void volume of SiC support with a grain size morphology.

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“…The obtained highly pure CNTs arrays can be further functionalized, e.g., by doping with nitrogen or boron. Considering that SiC materials have superior mechanical, thermal, and electric properties as well as high chemical stability [16,17], the metal-free and functionalized CNT arrays immobilized on SiC supports may be used as novel catalytic systems for many reactions. 5.0 Â 10.0 Â 0.3 mm 3 ) were cleaned in a 20% hydrofluoric acid (HF) solution, deionized water, and organic solutions, respectively [18].…”

Section: Introductionmentioning

confidence: 99%

Controlled growth of metal-free vertically aligned CNT arrays on SiC surfaces

Wang

et al. 2011

Chemical Physics Letters

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Cited by 229 publications

References 43 publications

New catalysts based on silicon carbide support for improvements in the sulfur recovery. Silicon carbide as support for the selective H2S oxidation

New catalysts based on silicon carbide support for improvements in the sulfur recovery. Silicon carbide as support for the selective H2S oxidation

New catalysts based on silicon carbide support for improvements in the sulfur recovery: new silicon carbide nanotubes as catalyst support for the trickle-bed H2S oxidation

Controlled growth of metal-free vertically aligned CNT arrays on SiC surfaces

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