The role of reactant and product bond energies in determining limitations to selective catalytic oxidations

Batiot, C.; Hodnett, B.K.

doi:10.1016/0926-860x(95)00322-3

Cited by 117 publications

(103 citation statements)

References 73 publications

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“…Considering all catalyst compositions tested for destruction of these three OVs, activity' for complete OV combustion generally decreased in the order of l-butanol>MEK> toluene. A similar trend also Was observed in the literature, and correlated with dissociation energies of the weakest C-H bond and surface adsorption affinity (Batiot and Hodnett 1996;O'Malley and Hodnett i 997, 1999). However, the compositions with the best performance for 1-butanol destruction were different than those with the best performance for toluene destruction.…”

Section: /Journal Of Environmental Engineering ©Asce / March 2004supporting

confidence: 64%

“…However, the mechanism for oxidation of OVs is different than for CO. The advantages gained by small Au and Pt clusters for CO oxidation are attributed to enhanced dissociation of 0 2 (Haruta et al 1993;Haruta 1997;Valden et al 1998;Heiz et al 1999), which does not appear to be the limiting process for OV oxidation (Batiot and Hodnett 1996;Hodnett 1997, 1999). Whether simply increasing the number of active sites or creating electronic interactions, the challenge for synthesizing these catalysts will be attaining high dispersions of active metals using practical preparation methods.…”

Section: Supported Platinum Catalystsmentioning

confidence: 99%

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Catalytic Oxidation of Volatile Organic Liquids

et al. 2004

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The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, «lathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information including suggestions for reducing the burden, PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)Air Force Research Laboratory Airbase Technologies Division 139 Barnes Drive, Suite 2 Tyndall AFB FL 32403-5323 SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) PERFORMING ORGANIZATION REPORT NUMBER AFRL-ML-TY-TP-2003-4539 SPONSOR/MONITOR'S ACRONYM(S) SPONSOR/MONITOR'S REPORT NUMBER(S) DISTRIBUTION/AVAILABILITY STATEMENTDistribution Statement "A". Distribution Unlimited SUPPLEMENTARY NOTES Published in the Journal of Environmental Engineering 130(3) 2004 pp 329-337 ABSTRACTMetal oxide and supported-Pt catalysts were developed for complete oxidation of volatile organic compounds (VOCs) and other solvent-derived organic vapors (OVs) in air at relatively low temperatures. The goal for this work is to produce a simple, costeffective technology for reducing the concentration of organic contaminants in air to acceptable levels before the air is released into the atmosphere or recirculated. Specific applications include ventilated work spaces for spray painting and engine maintenance, indoor air decontamination, dry cleaning, food processing, fume hoods, residential use, and solvent-intensive industrial processes. Catalyst powders and monolith-supported catalysts were screened for conversion of 1-butanol, toluene, and methyl ethyl ketone to carbon dioxide and water.... However, the catalysts quickly deactivated in the presence of sulfur and phosphorus. Abstract: Metal oxide and supported-Pt catalysts were developed for complete oxidation of volatile organic compounds (VOCs) and other solvent-derived organic vapors (OVs) in air at relatively low temperatures. The goal for this work is to produce a simple, cost-effective technology for reducing the concentration of organic contf iiinants in air to acceptable levels before the air is released into the atmosphere or recirculated. Specific applications include ventilated work spaces for spray painting and engine maintenance, indoor air decontamination, dry cleaning, food processing, fume hoods, residential use, and solvent-intensive industrial processes. Catalyst powders and monolith-supported catalysts were screened for conversion of 1-butanol, toluene, and methyl ethyl ketone to carbon dioxide and water. The concentration of OVs in the feedstream was maintained at approximately 100 ppmv, and the space velocity was between 6,000 and 18,000 h -1 . Metal oxide catalysts without Pt generated complete conversion of 1-butanol to C0 2 at 150°C, 69% conversion at 100°C, and 15% conversion at 80°C. For toluene, complete conversion was achieved at 200°C, and greater than 75% conversion at 150°C. Addit...

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Section: /Journal Of Environmental Engineering ©Asce / March 2004supporting

confidence: 64%

Section: Supported Platinum Catalystsmentioning

confidence: 99%

Catalytic Oxidation of Volatile Organic Liquids

et al. 2004

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“…It is worth remembering that our target of ~30 % OCM yield approximately corresponds to a kB-to-kA ratio of unity. Figure 6 shows selectivity-conversion plots for the catalytic results found in the literature for the Mn/Na2WO4/SiO2 catalyst (open circles) 52) and for other reported catalysts, such as Li/MgO, Mo-based oxides, Sm2O3 and La2O3 (closed circles 50) , and closed diamond 53) ). The dotted lines in Fig.…”

Section: Selective Oxidation Of Hydrocarbons and Thementioning

confidence: 99%

Catalytic Conversion of Methane: Carbon Dioxide Reforming and Oxidative Coupling

Takanabe

2012

J. Jpn. Petrol. Inst.

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Natural gas conversion remains one of the essential technologies for current energy needs. This review focuses on the mechanistic aspects of the development of efficient and durable catalysts for two reactions, carbon dioxide reforming and the oxidative coupling of methane. These two reactions have tremendous technological significance for practical application in industry. An understanding of the fundamental aspects and reaction mechanisms of the catalytic reactions reviewed in this study would support the design of industrial catalysts. CO2 reforming of methane utilizes CO2, which is often stored in large quantities, to convert as a reactant. Strategies to eliminate carbon deposition, which is the major problem associated with this reaction, are discussed. The oxidative coupling of methane directly produces ethylene in one reactor through a slightly exothermic reaction, potentially minimizing the capital cost of the natural gas conversion process. The focus of discussion in this review will be on the attainable yield of C2 products by rigorous kinetic analyses.

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“…9,11 As a result, the relative rates of these reactions and the concomitant attainable maximum C 2 yields are essentially dictated by the relative C-H bond energies among the hydrocarbons involved in OCM. 17 We report here rigorous kinetic and isotopic assessments of primary and secondary OCM pathways and their elementary steps. We also provide evidence for previously unrecognized effects of H 2 O on the relative rates of these steps and confirm the kinetic irrelevance of the other OCM products (C 2 H 6 , C 2 H 4 , CO x ) in C-H bond activation of CH 4 reactants.…”

Section: Introductionmentioning

confidence: 99%

Mechanistic Aspects and Reaction Pathways for Oxidative Coupling of Methane on Mn/Na₂WO₄/SiO₂ Catalysts

2009

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Kinetic and isotopic methods were used to determine the identity, rate constants, and reversibility of elementary steps for primary and secondary reactions involved in the oxidative coupling of methane (OCM) on Mn/ Na 2 WO 4 /SiO 2 . We provide evidence in this study for parallel C-H bond activation pathways, in which H-abstraction is mediated by either oxygen species on surfaces or by OH radicals formed via H 2 O/O 2 equilibration on catalyst surfaces. OCM rates and C 2+ yields are higher when H 2 O is present and OH-mediated pathways prevail, because of the high reactivity of OH radicals and of their lesser sensitivity to the energy of the C-H bond containing the hydrogen abstracted. These coupled homogeneous-catalytic sequences account for all observed kinetic effects of O 2 , CH 4 , and H 2 O on rates and selectivities for both CH 4 conversion and for subsequent reactions of C 2 H 6 , C 2 H 4 and C 3 products; they are also consistent with measured kinetic and thermodynamic isotope effects for C-H bond activation mediated by surface and OH radicals. C 3 H 6 with and without added H 2 O show that H-abstraction from hydrocarbons is much less sensitive to C-H bond strength when OH radicals are used to abstract hydrogen instead of oxide surfaces. Maximum C 2+ yields require conditions that favor OH-mediated pathways while maintaining equilibrium oxygen surface coverages and OH radical concentrations. OH-mediated pathways are more sensitive to O 2 pressure than surface-mediated pathways; thus, low O 2 pressures and staging strategies that maintain stoichiometric O 2 requirements and low local O 2 pressures can improve C 2+ selectivities but only when OH radicals are maintained at equilibrium concentrations via catalytic H 2 O-O 2 reactions. These findings and interpretations indicate that intermediate O 2 pressures give maximum C 2+ yields, but that their optimal value depends sensitively on prevalent H 2 O concentrations as they vary with conversion along the reactor. These predictions about the consequences of various operating strategies have become feasible because of the detailed and quantitative nature of the mechanism-based kinetic networks reported here for the first time.

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The role of reactant and product bond energies in determining limitations to selective catalytic oxidations

Cited by 117 publications

References 73 publications

Catalytic Oxidation of Volatile Organic Liquids

Catalytic Oxidation of Volatile Organic Liquids

Catalytic Conversion of Methane: Carbon Dioxide Reforming and Oxidative Coupling

Mechanistic Aspects and Reaction Pathways for Oxidative Coupling of Methane on Mn/Na₂WO₄/SiO₂ Catalysts

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The role of reactant and product bond energies in determining limitations to selective catalytic oxidations

Cited by 117 publications

References 73 publications

Catalytic Oxidation of Volatile Organic Liquids

Catalytic Oxidation of Volatile Organic Liquids

Catalytic Conversion of Methane: Carbon Dioxide Reforming and Oxidative Coupling

Mechanistic Aspects and Reaction Pathways for Oxidative Coupling of Methane on Mn/Na2WO4/SiO2 Catalysts

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Product

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Mechanistic Aspects and Reaction Pathways for Oxidative Coupling of Methane on Mn/Na₂WO₄/SiO₂ Catalysts