The Influence of Hydrogen-Permeable Membranes and Pressure on Methane Dehydroaromatization in Packed-Bed Catalytic Reactors

Kee, Benjamin L.; Karakaya, Canan; Zhu, Huayang; DeCaluwe, Steven C.; Kee, Robert J.

doi:10.1021/acs.iecr.6b04960

Cited by 15 publications

(12 citation statements)

References 18 publications

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“…The results of a recent computational modelling study performed by Kee et al. demonstrated that increasing pressure should result in a higher benzene selectivity over naphthalene, the latter being generally considered a coke precursor …”

Section: Figurementioning

confidence: 72%

Reversible Nature of Coke Formation on Mo/ZSM‐5 Methane Dehydroaromatization Catalysts

et al. 2019

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Non‐oxidative dehydroaromatization of methane over Mo/ZSM‐5 zeolite catalysts is a promising reaction for the direct conversion of abundant natural gas into liquid aromatics. Rapid coking deactivation hinders the practical implementation of this technology. Herein, we show that catalyst productivity can be improved by nearly an order of magnitude by raising the reaction pressure to 15 bar. The beneficial effect of pressure was found for different Mo/ZSM‐5 catalysts and a wide range of reaction temperatures and space velocities. High‐pressure operando X‐ray absorption spectroscopy demonstrated that the structure of the active Mo‐phase was not affected by operation at elevated pressure. Isotope labeling experiments, supported by mass‐spectrometry and 13 C nuclear magnetic resonance spectroscopy, indicated the reversible nature of coke formation. The improved performance can be attributed to faster coke hydrogenation at increased pressure, overall resulting in a lower coke selectivity and better utilization of the zeolite micropore space.

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Section: Figurementioning

confidence: 72%

Reversible Nature of Coke Formation on Mo/ZSM‐5 Methane Dehydroaromatization Catalysts

et al. 2019

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“…The reactions leading to the formation of hydrogen‐poor coke species, in accordance with the Le Chatelier’s principle, are more sensitive to the hydrogen concentration than the aromatization itself. [ 93 ]

6 {CH}_{4} \leftrightarrow 1 C_{6} H_{6} + 9 H_{2} Aromatization

{6CH}_{4} \leftrightarrow {CH}_{x} {(solid)}_{x \to 0} + 12 H_{2} Coke formation

…”

Section: Process Intensificationmentioning

confidence: 99%

Reactivity, Selectivity, and Stability of Zeolite‐Based Catalysts for Methane Dehydroaromatization

2020

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strong C-H bonds complicates the selective conversion of methane to higher hydrocarbons and oxygenates. Currently, the main industrial method to use methane as a material feedstock involves the transformation to syngas by steam reforming, followed by processes such as methanol synthesis and Fischer-Tropsch synthesis to obtain liquid fuels and other useful chemicals. A disadvantage of this indirect technology is the high capital cost of reforming plants, making it only economically attractive at a very large scale. An efficient direct process for the conversion of methane to higher hydrocarbons or oxygenates remains one of the "holy grails" of chemistry. [6,7] The approaches to directly convert methane can be categorized into oxidative and non-oxidative methods. Oxidative processes are often met with low product selectivity because of the higher reactivity of targeted products as compared to methane itself, resulting in overoxidation to CO 2. Non-oxidative methods are generally more atom-efficient, because, in addition to valuable hydrocarbon products, pure CO xfree hydrogen gas (H 2) is obtained, which can be used for instance in fuel cells. [8] Among several alternatives, including non-oxidative coupling of methane to ethylene and deep methane dehydrogenation to solid carbon and hydrogen, [9-12] methane dehydroaromatization (MDA) remains one of the most promising non-oxidative reactions for the direct valorization of natural gas. MDA involves the selective conversion of methane to a mixture of easily transportable aromatics, that is, benzene (predominantly), naphthalene, and toluene. As all other non-oxidative methane conversion reactions, MDA is a highly endothermic process: 6CH C H 9H 532 kJ mol Non-oxidative dehydroaromatization is arguably the most promising process for the direct upgrading of cheap and abundant methane to liquid hydrocarbons. This reaction has not been commercialized yet because of the suboptimal activity and swift deactivation of benchmark Mo-zeolite catalysts. This progress report represents an elaboration on the recent developments in understanding of zeolite-based catalytic materials for high-temperature non-oxidative dehydroaromatization of methane. It is specifically focused on recent studies, relevant to the materials chemistry and elucidating i) the structure of active species in working catalysts; ii) the complex molecular pathways underlying the mechanism of selective conversion of methane to benzene; iii) structure, evolution and role of coke species; and iv) process intensification strategies to improve the deactivation resistance and overall performance of the catalysts. Finally, unsolved challenges in this field of research are outlined and an outlook is provided on promising directions toward improving the activity, stability, and selectivity of methane dehydroaromatization catalysts.

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“…To improve the conversion to an acceptable level for industrial application without increasing the operating temperatures,t hese catalysts could be incorporated into membranes that can selectivity remove hydrogen to drive the reactioni n the forward direction.S everal studies in the literature have successfully demonstrated the use of such membranes on systems with either catalysts that are significantly more expensiveo r not as active as the catalyst in this study or for non-oxidative methane aromatization at high temperatures (700-800 8C). [27,65]…”

Section: Strategy For Improved Performancementioning

confidence: 99%

Coupling of Methane to Ethane, Ethylene, and Aromatics over Nickel on Ceria–Zirconia at Low Temperatures

et al. 2018

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Methane is converted over nickel on ceria zirconia (Ni/CZ) into ethane, aromatics, and hydrogen at steady state up to the thermodynamic limit at temperatures of 350 to 500 °C. At 450 and 500 °C, traces of ethylene are also produced. Ni/NiO particles activate methane and couple the resulting surface species to hydrocarbon products. Large Ni particles are responsible for the formation of carbonaceous deposits. Furthermore, aromatics are formed on these sites. Smaller Ni/NiO particles are responsible for the formation of ethane and ethylene and appear to provide sustained activity. It is suggested that these Ni sites are too small to assemble aromatic deposits, and hence they remain active throughout the reaction.

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The Influence of Hydrogen-Permeable Membranes and Pressure on Methane Dehydroaromatization in Packed-Bed Catalytic Reactors

Cited by 15 publications

References 18 publications

Reversible Nature of Coke Formation on Mo/ZSM‐5 Methane Dehydroaromatization Catalysts

Reversible Nature of Coke Formation on Mo/ZSM‐5 Methane Dehydroaromatization Catalysts

Reactivity, Selectivity, and Stability of Zeolite‐Based Catalysts for Methane Dehydroaromatization

Coupling of Methane to Ethane, Ethylene, and Aromatics over Nickel on Ceria–Zirconia at Low Temperatures

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