Steady-state isotopic transient-kinetic analysis of iron-catalyzed ammonia synthesis

Nwalor, J.

doi:10.1016/0021-9517(89)90225-x

Cited by 35 publications

(8 citation statements)

References 17 publications

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“…John and co-workers found that NH x species are the primary surface intermediates in the temperature range from 623 K to 673 K (204 kPa) and adsorbate N is the most abundant intermediate from 623 K to 773 K using SSITKA. 42 To date, a systematic and detailed comparison of the exact mechanism and microkinetic model for NH 3 decomposition on Ru and Ir supported nanoparticles is scarce in the literature, especially including the model describing the Ru fcc surface, which is observed in the Ru nanoparticle size range of 2.0–5.5 nm. 44 …”

Section: Introductionmentioning

confidence: 99%

Kinetic and mechanistic analysis of NH₃decomposition on Ru(0001), Ru(111) and Ir(111) surfaces

Zhang

Chen

et al. 2021

Nanoscale Adv.

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Section: Introductionmentioning

confidence: 99%

Kinetic and mechanistic analysis of NH₃decomposition on Ru(0001), Ru(111) and Ir(111) surfaces

Zhang

Chen

et al. 2021

Nanoscale Adv.

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“…In operando steady-state kinetic methods provide a useful technique for the investigation of catalytic mechanisms on catalysts under reaction conditions . The collection of both infrared spectroscopic data and reaction rates (typically using mass spectrometry, noted MS) under steady-state isotopic transient kinetic analysis (SSITKA , ) conditions can allow us to directly relate the formation of a given reaction product to a particular surface intermediate. This technique has only been performed by a limited number of research groups over the past fifteen years or so.…”

Section: Introductionmentioning

confidence: 99%

Spectrokinetic Investigation of Reverse Water-Gas-Shift Reaction Intermediates over a Pt/CeO₂ Catalyst

Goguet¹,

Meunier²,

Tibiletti³

et al. 2004

J. Phys. Chem. B

337

230

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The reactivity of the surface species present over a 2%Pt/CeO 2 catalyst during the reverse water-gas-shift (RWGS) reaction was investigated by a detailed operando spectrokinetic analysis. A single reactor common for the kinetic and the spectroscopic measurements was used. The reactor employed was a modified hightemperature diffuse reflectance FT-IR (DRIFT) cell from SpectraTech. The reactivity of the surface species was monitored by DRIFT spectroscopy (DRIFTS) and mass spectrometry (MS) using steady-state isotopic transient kinetic analysis (SSITKA) techniques, i.e., switching between 1% CO 2 + 4% H 2 reaction mixtures containing either 13 CO 2 or 12 CO 2 . The combination of these techniques allowed time-resolved simultaneous monitoring of the variation of the coverage of 12 C and 13 C-containing surface intermediates and the concentration of the gas-phase products 12 CO(g) and 13 CO(g) due to the isotope exchange. These results clearly indicated that surface formates observed by DRIFTS were not the main reaction intermediates for the formation of CO(g) over the present catalyst under these experimental conditions, although the formation of CO(g) from formates was likely to occur to a limited extent. A quantitative analysis of the number of reactive surface species also showed that Pt-bound carbonyls could not be the only reaction intermediate. Surface carbonates are shown as being a main surface intermediate in the formation of CO(g). A reaction scheme involving a direct reoxidation of the ceria support by the CO 2 via surface carbonates is suggested. A parallel between these results and mechanisms previously proposed for CO 2 hydrogenation and CO 2 -reforming (i.e., dryreforming) of methane on redox oxide-supported noble metal is made. In a more general perspective, the present data underlines the feasibility and appropriateness of the DRIFT-MS-SSITKA technique based on a single reactor in providing critical information about the nature of surface species (e.g., kinetic intermediate as opposed to spectator) on catalysts when the surface species are observable by DRIFT spectroscopy.

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“…By applying quasi-steady-state approximation and integrating the concept of most abundant reactive intermediate (MARI) [6,[23][24][25], a range of rate expressions were derived for those mechanisms laid out earlier which are summarized in Table 2 (where P CH 4 partial pressure of methane,P H 2 O partial pressure of steam, K CH 4 : methane adsorption constant, K H 2 O : steam adsorption constant,: k rxn methane steam reforming constant). Illustrations of rate expression derivations are shown in Appendix A.…”

Section: Eley-rideal Mechanismmentioning

confidence: 99%

“…Further, in this study, we have used the methane consumption data from experiments carried out in our previous study [22] and evaluated in terms of the formal LH and ER models to determine MSR mechanism over 1 wt.% Ce/10 wt.% Ni/ SBA-15. In this investigation, the mechanistic models were proposed using reaction pathways that are defined by the most abundant reactive intermediates (MARI) which are converted into products through surface reaction over the one or more catalyst active sites [6,[23][24][25]. Nevertheless, mechanistic model based on single-site dissociative adsorption of methane and steam adequately captured the rate behaviour on the Ce/Ni/SBA-15 catalyst.…”

Section: Introductionmentioning

confidence: 97%

Mechanistic investigation of methane steam reforming over Ce-promoted Ni/SBA-15 catalyst

et al. 2015

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Methane steam reforming experiments were carried out at atmospheric pressure for temperatures between 873 and 1073 K and by varying the partial pressure of methane and steam to achieve S:C between 0.5 and 2.5. Mechanistic considerations for Methane steam reforming (MSR) were derived on the basis of Langmuir-Hinshelwood and Eley-Rideal reaction mechanisms based on single-and dual-site associative and dissociative adsorption of one or both reactants. However, discrimination of these models on statistical and thermodynamic grounds revealed that the model representing a single-site dissociative adsorption of methane and steam most adequately explained the data. However, the product formation rates from these experiments were reasonably captured by power-law model. The parameter estimates from the power-law model revealed an order of 0.94 with respect to methane and -0.16 for steam with activation energy of 49.8 kJ mol -1 for MSR. The negative order with respect to steam for methane consumption was likely due to steam inhibition.

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Steady-state isotopic transient-kinetic analysis of iron-catalyzed ammonia synthesis

Cited by 35 publications

References 17 publications

Kinetic and mechanistic analysis of NH₃decomposition on Ru(0001), Ru(111) and Ir(111) surfaces

Kinetic and mechanistic analysis of NH₃decomposition on Ru(0001), Ru(111) and Ir(111) surfaces

Spectrokinetic Investigation of Reverse Water-Gas-Shift Reaction Intermediates over a Pt/CeO₂ Catalyst

Mechanistic investigation of methane steam reforming over Ce-promoted Ni/SBA-15 catalyst

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Steady-state isotopic transient-kinetic analysis of iron-catalyzed ammonia synthesis

Cited by 35 publications

References 17 publications

Kinetic and mechanistic analysis of NH3decomposition on Ru(0001), Ru(111) and Ir(111) surfaces

Kinetic and mechanistic analysis of NH3decomposition on Ru(0001), Ru(111) and Ir(111) surfaces

Spectrokinetic Investigation of Reverse Water-Gas-Shift Reaction Intermediates over a Pt/CeO2 Catalyst

Mechanistic investigation of methane steam reforming over Ce-promoted Ni/SBA-15 catalyst

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Product

Resources

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Kinetic and mechanistic analysis of NH₃decomposition on Ru(0001), Ru(111) and Ir(111) surfaces

Kinetic and mechanistic analysis of NH₃decomposition on Ru(0001), Ru(111) and Ir(111) surfaces

Spectrokinetic Investigation of Reverse Water-Gas-Shift Reaction Intermediates over a Pt/CeO₂ Catalyst