Dependence of the kinetics of the low-temperature water-gas shift reaction on the catalyst oxygen activity as investigated by wavefront analysis

Fiolitakis, E.

doi:10.1016/0021-9517(83)90258-0

Cited by 39 publications

(9 citation statements)

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“…CO 2 + 3H 2 [1,2]. During these transformations, the WGS reaction can occur simultaneously, affecting the hydrogen selectivity in these reactions [1,3,4]. Thus, the behavior of intermediates formed on transition metal surfaces upon H 2 /CO 2 exposure and under reaction conditions is of high interest.…”

Section: Introductionmentioning

confidence: 98%

Isotope Effects in Methanol Synthesis and the Reactivity of Copper Formates on a Cu/SiO2 Catalyst

et al. 2008

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Here we investigate isotope effects on the catalytic methanol synthesis reaction and the reactivity of copper-bound formate species in CO 2 -H 2 atmospheres on Cu/SiO 2 catalysts by simultaneous IR and MS measurements, both steady-state and transient. Studies of isotopic variants (H/D, 12 C/ 13 C) reveal that bidentate formate dominates the copper surface at steady state. The steadystate formate coverages of HCOO (in 6 bar 3:1 H 2 :CO 2 ) and DCOO (in D 2 :CO 2 ) are similar and the steady-state formate coverages in both systems decrease by *80% from 350 K to 550 K. Over the temperature range 413 K-553 K, the steady-state methanol synthesis rate shows a weak H/D isotope effect (1.05 ± 0.05) with somewhat higher activation energies in H 2 :CO 2 (79 kJ/mole) than D 2 :CO 2 (71 kJ/mole) over the range 473 K-553 K. The reverse water gas shift (RWGS) rates are higher than methanol synthesis and also shows a weak positive H/D isotope effect with higher activation energy for H 2 /CO 2 than D 2 /CO 2 (108 vs. and 102 kJ/mole) The reactivity of the resulting formate species in 6 bar H 2 , 6 bar D 2 and 6 bar Ar is strongly dominated by decomposition back to CO 2 and H 2 . H 2 and D 2 exposure compared to Ar do not enhance the formate decomposition rate. The decomposition profiles on the supported catalyst deviate from first order decay, indicating distributed surface reactivity. The average decomposition rates are similar to values previously reported on single crystals. The average activation energies for formate decomposition are 90 ± 17 kJ/mole for HCOO and 119 ± 11 kJ/mole for DCOO. By contrast to the catalytic reaction rates, the formate decomposition rate shows a strong H/D kinetic isotope effect (H/D *8 at 413 K), similar to previously observed values on Cu(110).

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Section: Introductionmentioning

confidence: 98%

Isotope Effects in Methanol Synthesis and the Reactivity of Copper Formates on a Cu/SiO2 Catalyst

et al. 2008

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“…The effect of water concentration on surface chemistry is complex. For industrial Cu/ZnO catalysts, nonempirical rate laws are available , for low water/carbon monoxide ratios, but these elementary rate laws did not fit behavior at higher water/CO ratios, and empirical power-law equations are needed for accurate rate prediction . One reason for the large concentration effect is likely due to the site competition between water and WGS intermediates .…”

Section: Introductionmentioning

confidence: 99%

Density Functional Theory Investigation of the Role of Cocatalytic Water in the Water Gas Shift Reaction over Anatase TiO₂ (101)

Hook

Celik

2018

Ind. Eng. Chem. Res.

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The water gas shift reaction (WGS) mechanism on the anatase TiO2 (101) surface has been investigated using periodic density functional theory. Reaction energies and activation energy barriers for direct CO oxidation and associative pathways with carboxyl and formate intermediates were calculated and compared. Unassisted by water, the formation of formate was infeasible due to the difficulty in transferring hydrogen from the anatase surface to hydrogenate CO, while the carboxyl mechanism had the lowest apparent activation energy barrier among the three. Coadsorbed water species were found to be effective hydrogen transfer cocatalysts, with molecularly physisorbed water acting as a hydrogen donor and dissociatively chemisorbed water acting as a hydrogen acceptor. Using water as the hydrogen donor, CO hydrogenation became competitive with the carboxyl mechanism, indicating that the reactivity of water could change the relative competitiveness of different WGS pathways. These results suggest that adsorbed water concentration plays an important role in determining adsorbate speciation and concentration on the anatase surface during WGS.

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“…A number of different kinetic rate expressions have been reported and tested to evaluate the WGS reaction rate [2][3][4][5][6][7][8][9][10]. According to Fott et al [2], over 20 different kinetic equations have been proposed and there is still a lack of consensus over the nature and role of active sites and the reaction mechanism.…”

Section: Introductionmentioning

confidence: 99%

Kinetics of high-temperature water-gas shift reaction over two iron-based commercial catalysts using simulated coal-derived syngases

Hla¹,

Park²,

Duffy³

et al. 2009

Chemical Engineering Journal

144

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Dependence of the kinetics of the low-temperature water-gas shift reaction on the catalyst oxygen activity as investigated by wavefront analysis

Cited by 39 publications

References 5 publications

Isotope Effects in Methanol Synthesis and the Reactivity of Copper Formates on a Cu/SiO2 Catalyst

Isotope Effects in Methanol Synthesis and the Reactivity of Copper Formates on a Cu/SiO2 Catalyst

Density Functional Theory Investigation of the Role of Cocatalytic Water in the Water Gas Shift Reaction over Anatase TiO₂ (101)

Kinetics of high-temperature water-gas shift reaction over two iron-based commercial catalysts using simulated coal-derived syngases

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Dependence of the kinetics of the low-temperature water-gas shift reaction on the catalyst oxygen activity as investigated by wavefront analysis

Cited by 39 publications

References 5 publications

Isotope Effects in Methanol Synthesis and the Reactivity of Copper Formates on a Cu/SiO2 Catalyst

Isotope Effects in Methanol Synthesis and the Reactivity of Copper Formates on a Cu/SiO2 Catalyst

Density Functional Theory Investigation of the Role of Cocatalytic Water in the Water Gas Shift Reaction over Anatase TiO2 (101)

Kinetics of high-temperature water-gas shift reaction over two iron-based commercial catalysts using simulated coal-derived syngases

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Density Functional Theory Investigation of the Role of Cocatalytic Water in the Water Gas Shift Reaction over Anatase TiO₂ (101)