Carbon and oxygen atom mobility during activation of Mo2C catalysts

Leary, Kevin J.; Michaels, James N.; Stacy, Angelica M.

doi:10.1016/0021-9517(86)90257-5

Cited by 83 publications

(18 citation statements)

References 9 publications

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“…The slow continued weight increase implies that full passivation requires long exposure times. It has been reported that oxygen is very mobile in Mo 2 C and that oxygen will diffuse into Mo 2 C if it is exposed for several weeks at room temperature [41]. Consistent with these reports, the additional oxygen uptake of an already passivated Mo 2 C sample during storage in the laboratory for 11 months was significant.…”

Section: Passivation Procedures and Their Effectivenesssupporting

confidence: 74%

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Passivation agents and conditions for Mo2C and W2C: Effect on catalytic activity for toluene hydrogenation

Mehdad

Jentoft

2017

Journal of Catalysis

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The passivation and reactivation of Mo 2 C and W 2 C was investigated by thermogravimetry with effluent gas analysis, and by comparison of the toluene hydrogenation activity of fresh carbides with that of passivated and reactivated carbides (20 bar, H 2 : toluene = 33, 150 or 200 °C, WHSV = 10 or 20 g g cat-1 min-1). Contrary to the literature, CO 2 and H 2 O were unsuitable passivation agents for Mo 2 C. Mo 2 C and W 2 C reacted readily with O 2 at 40 °C. The mass gained during oxidation could be quantitatively removed through reduction in 1 bar H 2 at 300 °C (Mo 2 C) or 400 °C (W 2 C). The rate of toluene conversion was fully recovered only for Mo 2 C that had been passivated with an initial O 2 concentration of 0.1 vol.% and not for other passivation conditions or for W 2 C. Intervening operation of toluene hydrogenation at 300 or 400 °C enhanced the activity of samples that were previously oxidized and reduced or harshly reduced. This enhancement suggests that carbide formation is possible at milder temperatures than typically employed.

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Section: Passivation Procedures and Their Effectivenesssupporting

confidence: 74%

“…Oxygen can be removed either by temperature-programmed desorption (TPD) or TPR using H 2 . With TPD, the oxygen will react with carbon in the carbide structure and leave as CO or CO 2 [41,[48][49][50]. TPR with H 2 removes the oxygen as water.…”

Section: Reactivation Of Passivated Carbidesmentioning

confidence: 99%

Passivation agents and conditions for Mo2C and W2C: Effect on catalytic activity for toluene hydrogenation

Mehdad

Jentoft

2017

Journal of Catalysis

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“…For fresh catalysts (Figure c), the distinct peaks at 350–400 °C correspond to the reduction of Mo 6+ to Mo 4+ and the second peak at 500–720 °C is consistent with the reduction of pyrolytic carbon from thermal cracking of hydrocarbons. − Moreover, higher temperatures are needed for further reduction of Mo 4+ to Mo 0 . As proved by XPS and XRD, the fact is that less-existed Mo 6+ species and more gradually generated MoC 1– x for all spent catalysts can be well reflected by the decreased peak intensity for the reduction of Mo 6+ to Mo 4+ (Figure d).…”

Section: Results and Discussionmentioning

confidence: 54%

Hybrid Mo–C_T Nanowires as Highly Efficient Catalysts for Direct Dehydrogenation of Isobutane

Shi

et al. 2018

ACS Appl. Mater. Interfaces

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Direct dehydrogenation of isobutane to isobutene has drawn extensive attention for synthesizing various chemicals. The Mo-based catalysts hold promise as an alternative to the toxic CrO - and scarce Pt-based catalysts. However, the low activity and rapid deactivation of the Mo-based catalysts greatly hinder their practical applications. Herein, we demonstrate a feasible approach toward the development of efficient and non-noble metal dehydrogenation catalysts based on Mo-C hybrid nanowires calcined at different temperatures. In particular, the optimal Mo-C catalyst exhibits isobutane consumption rate of 3.9 mmol g h and isobutene selectivity of 73% with production rate of 2.8 mmol g h. The catalyst maintained 90% of its initial activity after 50 h of reaction. Extensive characterizations reveal that such prominent performance is well correlated with the adsorption abilities of isobutane and isobutene and the formation of η-MoC species. In contrast, the generation of β-MoC crystalline phase during long-term reaction causes minor decline in activity. Compared to MoO and β-MoC, η-MoC plays a role more likely in suppressing the cracking reaction. This work demonstrates a feasible approach toward the development of efficient and non-noble metal dehydrogenation catalysts.

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“…The calculated Auger parameters confirm these assignments. Table 4 summarizes To remove the oxide layer that forms on the catalyst surface during passivation and eliminate the remaining oxide traces and/or any oxygen incorporated in the Mo 2 C structure due to air exposure [44], it is necessary to pretreat the catalysts in hydrogen prior to the reaction. Temperatureprogrammed reduction was thus performed to determine an appropriate pretreatment temperature.…”

Section: Cumentioning

confidence: 99%

CO₂ conversion over Cu–Mo₂C catalysts: effect of the Cu promoter and preparation method

Heracleous

Koidi

Lappas

2021

Catal. Sci. Technol.

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Carbon and oxygen atom mobility during activation of Mo2C catalysts

Cited by 83 publications

References 9 publications

Passivation agents and conditions for Mo2C and W2C: Effect on catalytic activity for toluene hydrogenation

Passivation agents and conditions for Mo2C and W2C: Effect on catalytic activity for toluene hydrogenation

Hybrid Mo–C_T Nanowires as Highly Efficient Catalysts for Direct Dehydrogenation of Isobutane

CO₂ conversion over Cu–Mo₂C catalysts: effect of the Cu promoter and preparation method

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Carbon and oxygen atom mobility during activation of Mo2C catalysts

Cited by 83 publications

References 9 publications

Passivation agents and conditions for Mo2C and W2C: Effect on catalytic activity for toluene hydrogenation

Passivation agents and conditions for Mo2C and W2C: Effect on catalytic activity for toluene hydrogenation

Hybrid Mo–CT Nanowires as Highly Efficient Catalysts for Direct Dehydrogenation of Isobutane

CO2 conversion over Cu–Mo2C catalysts: effect of the Cu promoter and preparation method

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Hybrid Mo–C_T Nanowires as Highly Efficient Catalysts for Direct Dehydrogenation of Isobutane

CO₂ conversion over Cu–Mo₂C catalysts: effect of the Cu promoter and preparation method