The effect of water in the low-temperature catalytic oxidation of hydrogen sulfide to sulfur over activated carbon

Primavera, Alessandra; Trovarelli, Alessandro; Andreussi, Paolo; Dolcetti, Giuliano

doi:10.1016/s0926-860x(98)00178-1

Cited by 129 publications

(77 citation statements)

References 14 publications

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“…It is seen that water presence enhanced the adsorption of H 2 S. Previous results stated that water is very important in H 2 S removal (Primavera et al, 1998;Bandosz et al, 2000;Yang et al, 1998;Yan et al, 2004;Flytzani-Stephanopoulos et al, 2006;Li et al, 2008;Klein and Henning, 1984;Mikhalovsky and Zaitsev, 1997). According to Primavera et al (1998), water presence may affect the removal reaction path in two ways: (a) H 2 S dissolution to HS -ions occurs in the water film inside the adsorbent pores; thus, the removal reaction proceeds faster in water than on the catalyst surface; (b) water continuously removes sulfur from the active sites and promotes sulfur adsorption on different carbon sections (Xiao et al, 2008, Primavera et al, 1998, Klein and Henning, 1984). Hydrophilicity of activated carbon is believed to increase in the presence of oxygencontaining functional groups on the carbon surface (Choi et al, 2008).…”

Section: Resultsmentioning

confidence: 62%

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Investigation of Impregnated Activated Carbon Properties Used in Hydrogen Sulfide Fine Removal

Isik-Gulsac

2016

Braz. J. Chem. Eng.

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-The effects of relative humidity (RH), carbon dioxide (CO 2 ), methane (CH 4 ), oxygen (O 2 ) presence and gas hourly space velocity (GHSV) on H 2 S adsorption dynamics of KOH/CaO impregnated activated carbon are investigated in this study. X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray detector (SEM-EDX), thermogravimetric analysis (TGA), and Fourier Transform Infrared Spectroscopy (FTIR) techniques are applied and nitrogen adsorption characteristics are determined for characterization. The presence of water, O 2 and lower GHSV has beneficial effects on the activated carbon performance. CO 2 decreases the adsorption capacity due to its acidic characteristics. Best adsorption capacity is obtained as 13 wt % in KOH/CaO impregnated activated carbon, in a CH 4 (60%)/CO 2 (38%)/O 2 (2%) gas atmosphere, at ambient temperature, RH 90 and 5000 h -1 GHSV. Sulphur species formation was verified with the help of SEM-EDX, XRD, TGA, FTIR and nitrogen adsorption analysis on the exhausted samples.

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Section: Resultsmentioning

confidence: 62%

“…Especially for higher relative humidites, water may be adsorbed when these functional groups are present, thus, direct contact of HS -with the carbon surface may be restricted. It was found that an increasing trend in sulfur deposition occurred until 60% relative humidity for activated carbons (Primavera et al, 1998;Le Lauch et al 2003).…”

Section: Resultsmentioning

confidence: 99%

Investigation of Impregnated Activated Carbon Properties Used in Hydrogen Sulfide Fine Removal

Isik-Gulsac

2016

Braz. J. Chem. Eng.

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“…temperature has also been extensively studied [7][8][9]. Given the combination of their unique surface features (high specific surface and pore volume) and surface chemistry (improved by the addition of functional groups or by its metallic content), activated carbon-based materials have been proved to work efficiently as adsorbents of sulphurcontaining species such as H 2 S, SO 2 or methyl mercaptans from the gas phase.…”

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confidence: 99%

Use of sewage sludge combustion ash and gasification ash for high-temperature desulphurization of different gas streams

Gil-Lalaguna

Sánchez

Murillo

et al. 2015

Fuel

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Due to its metal content, sewage sludge ash appears as a potential sorbent material for H 2 S removal at high temperature. The desulphurization ability of the solid by-products of combustion and gasification of sewage sludge has been evaluated in this work. Ash characterization results revealed that metal fraction in sewage sludge did not remained completely inert during the combustion and gasification processes. Iron content was lower in the gasification ash and X-ray patterns showed different crystalline phases in the solids: Fe 2 O 3 in the combustion ash and Fe 3 O 4 in the gasification ash. These differences resulted in a lower sulphur capture capacity of the gasification ash.Desulphurization tests were carried out in a lab-scale fixed bed reactor operating at 600-800 ºC. Different gases containing 5000 ppmv H 2 S (H 2 S/N 2 mixture and synthetic gasification gas) were used. The H 2 S breakthrough curves were negatively affected by the reducing atmosphere created by the gasification gas and by the presence of steam in the reaction medium. However, H 2 S breakthrough curves alone do not provide enough information to evaluate the sulphur capture capacity of the sorbent materials. Ultimate analyses of the spent solid samples showed that the total amount of H 2 S removed from the gas was only partially captured in the ash. Thermodynamic data pointed to a significant fraction of sulphur forming part of other gases, such as SO 2 . In the best 2 operating conditions, an outlet gas with less than 100 ppmv of H 2 S was obtained during 300 min, thus resulting in a sulphur loading of 63 mg S·g -1 ash . This experimental sulphur content was 39% lower than the maximum theoretical value predicted by equilibrium simulations.

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“…The solid sulfur formed by reaction between H 2 S and oxygen on the NiS 2 active particles should very rapidly block the access of the reactants to the active phase, i.e., for low solid sulfur amounts on the catalyst, as usually reported over traditional catalysts. 21,22 A peculiar sulfur deposition mode on the catalyst surface has been advanced, in order to explain why the catalyst could maintain high performances, even when the sulfur loading on the catalyst surface reached 80 wt. %.…”

Section: Selective Oxidation Of H 2 Smentioning

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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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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The effect of water in the low-temperature catalytic oxidation of hydrogen sulfide to sulfur over activated carbon

Cited by 129 publications

References 14 publications

Investigation of Impregnated Activated Carbon Properties Used in Hydrogen Sulfide Fine Removal

Investigation of Impregnated Activated Carbon Properties Used in Hydrogen Sulfide Fine Removal

Use of sewage sludge combustion ash and gasification ash for high-temperature desulphurization of different gas streams

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

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