Methane dehydroaromatization over molybdenum supported on sulfated zirconia catalysts

Kanitkar, Swarom; Abedin, Ashraful; Bhattar, Srikar; Spivey, James J.

doi:10.1016/j.apcata.2019.01.013

Cited by 34 publications

(10 citation statements)

References 63 publications

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“…Although the oxidative activation pathway can well explain the formation of carbenium ions in alkane isomerization over SZ catalyst, there are several questions still under debate. One is that expect for the n ‐alkane isomerization, the SZ also has high activity in many other types of acid‐catalyzed reactions, such as cracking of cumene, esterification of long‐chain–free fatty acids, arylation of oleic acid with aromatics, dehydration of fructose, transesterification, synthesis of ethyl levulinate from furfuryl alcohol, alkylation, oligomerization of hydrocarbons, and so on . Most of reactants for these reactions must be activated by protonation route on superacid sites.…”

Section: Activation Of Alkane Over Sulfated Zirconiamentioning

confidence: 99%

Alkane isomerization over sulfated zirconia solid acid system

et al. 2020

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Summary Sulfated zirconia (SZ) and its modified versions attract great interest in recent years, because of their promising potential in n‐alkane isomerization. The oxidative and protonation routes are active and interactional in n‐alkane activation over SZ catalysts. The bimolecular reaction becomes dominant with increasing the density of active sites on SZ surface and decreasing the carbon chain of feed. Pentane and hexane are mainly isomerized by protonated cyclopropane mechanism, while which is thermodynamically unflavored for n‐butane isomerization. The deactivation of SZ catalysts is primarily caused by the loss of superacidity and oxidizing ability, resulted from the structure changes of sulfate species. Several strategies for improving the activity of SZ are reviewed. The intrinsic structure‐reactivity relationship of SZ catalysts in alkane isomerization is updated to illuminate the prerequisite for the highly active catalysts and the mechanism of active sites formation. The applications of Pt/SZ in fixed‐bed and unmodified SZ in circulating fluidizing bed in light alkanes isomerization are compared with the conventional technologies based on the chlorinated alumina catalysts. Finally, the future study of SZ catalysts is outlooked from the academic investigations to the industrial applications.

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Section: Activation Of Alkane Over Sulfated Zirconiamentioning

confidence: 99%

Alkane isomerization over sulfated zirconia solid acid system

et al. 2020

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“…Benzene was a major product observed at 650-700 °C, due to the enhanced acidity provided by SZ [15] (Fig. 7).…”

Section: Activation Of Methanementioning

confidence: 98%

“…A similar mechanism can also be proposed for direct activation of methane to C 2 hydrocarbons. Progress has been made toward understanding how methane can be directly activated by forming methyl radicals [15], without the involvement of coreactants, which may further react to produce higher hydrocarbons. This route of methane activation to ethane and ethylene requires the presence of a solid acid catalyst [16].…”

Section: Introductionmentioning

confidence: 99%

“…It has been reported that the metal carbide species produced from Mo/W oxides activate methane by forming CH x species, which is dimerized into C 2 H y species [13,26]. Previously, this group demonstrated high activity and strong aromatic selectivity for methane dehydroaromatization (MDHA) using Mo oxide doped on sulfated zirconia (SZ) solid acid catalysts [15]. During these studies, it was observed that the addition of W as promoter to Mo/SZ shifted the MDHA product selectivity toward ethylene and ethane [24].…”

Section: Introductionmentioning

confidence: 99%

“…It has been reported that the sulfurized form of ZrO 2 known as sulfated zirconia (SZ), actively helps the active metal sites to stabilize on the oxide support at a greater degree [29,33]. SZ is a well-known solid acid possessing surface H + ions [29,34], which can react with some of the excess methyl radicals and remove these in the form of benzene and heavier hydrocarbons as valuable side products [15,35].…”

Section: Introductionmentioning

confidence: 99%

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Direct conversion of methane to C2 hydrocarbons using W supported on sulfated zirconia solid acid catalyst

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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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Methane dehydroaromatization over molybdenum supported on sulfated zirconia catalysts

Cited by 34 publications

References 63 publications

Alkane isomerization over sulfated zirconia solid acid system

Alkane isomerization over sulfated zirconia solid acid system

Direct conversion of methane to C2 hydrocarbons using W supported on sulfated zirconia solid acid catalyst

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

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