The dehydrogenation of methanol to methyl formatePart II. The effect of chromia on deactivation kinetics for copper-based catalysts

Huang, Xiaojing; Cant, Noel W.; Wainwright, Mark; Ma, Long

doi:10.1016/s0255-2701(04)00144-8

Cited by 4 publications

(6 citation statements)

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“…During 1000 h of continuous catalytic reactions, no noticeable deactivation was observed, and the overall deactivation corresponded to only 4% of the initial SO 3 conversion. The deactivation kinetics of the SO 3 decomposition over Pt/TiO 2 -A was studied using a simple power law equation, which is given in eq ; − this equation assumes that the concentration of the active sites is a time-dependent power function of the remaining active sites, and the rate of deactivation is independent of the involved chemical species where r d and k d are the rate of deactivation and the rate constant for deactivation, respectively, and d is the order of deactivation. The relative catalyst activity ( a ) is expressed as the rate of reaction on the deactivated catalyst with time ( r t ) divided by that on the fresh catalyst ( r 0 ).…”

Section: Resultsmentioning

confidence: 99%

Catalytic SO₃ Decomposition Activity and Stability of Pt Supported on Anatase TiO₂ for Solar Thermochemical Water-Splitting Cycles

et al. 2017

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Pt-loaded anatase TiO 2 (Pt/TiO 2 -A) was found to be a highly active and stable catalyst for SO 3 decomposition at moderate temperatures (∼600 °C), which will prove to be the key for solar thermochemical water-splitting processes used to produce H 2 . The catalytic activity of Pt/TiO 2 -A was found to be markedly superior to that of a Pt catalyst supported on rutile TiO 2 (Pt/TiO 2 -R), which has been extensively studied at a higher reaction temperature range (≥800 °C); this superior activity was found despite the two being tested with similar surface areas and metal dispersions after the catalytic reactions. The higher activity of Pt on anatase is in accordance with the abundance of metallic Pt (Pt 0 ) found for this catalyst, which favors the dissociative adsorption of SO 3 and the fast removal of the products (SO 2 and O 2 ) from the surface. Conversely, Pt was easily oxidized to the much less active PtO 2 (Pt 4+ ), with the strong interactions between the oxide and rutile TiO 2 forming a fully coherent interface that limited the active sites. A long-term stability test of Pt/TiO 2 -A conducted for 1000 h at 600 °C demonstrated that there was no indication of noticeable deactivation (activity loss ≤ 4%) over the time period; this was because the phase transformation from anatase to rutile was completely prevented. The small amount of deactivation that occurred was due to the sintering of Pt and TiO 2 and the loss of Pt under the harsh reaction atmosphere.

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Section: Resultsmentioning

confidence: 99%

Catalytic SO₃ Decomposition Activity and Stability of Pt Supported on Anatase TiO₂ for Solar Thermochemical Water-Splitting Cycles

et al. 2017

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“…The additional steps involved in the formation of MF from CH 3 OH oxidation are also shown in Figure 4 and labeled as [9] to [12] in blue. These steps are [9] 3.1.5. Alternative Active Sites.…”

Section: Resultsmentioning

confidence: 99%

“…Effect on the MF Selectivity. From the reaction network shown in Figure 4 for CH 3 OH oxidation on the V 2 O 5 / TiO 2 catalyst, we can attribute the selectivities of CH 2 O and MF to the differences in the maximum energy barriers (ΔE a ) for steps [2] to [3] and steps [9] to [12], although steps [4] to [5] also lead to the formation of CH 2 O, and other products such as DMM and DME can also be formed under certain conditions, which will be investigated in our future work. With the cluster model, the energy barrier of step [2] of 1.29 eV is the highest for the formation of CH 2 O, whereas that of step [11] of 1.19 eV is the highest for the formation of MF.…”

Section: The Journal Of Physical Chemistry Cmentioning

confidence: 99%

“…Due to the poor efficiency of the above process, ,− there is significant interest in developing greener catalytic processes for MF synthesis. During the past decade, a number of different routes have been explored, and MF can be synthesized at varying efficiency by CH 3 OH dehydrogenation, − CH 3 OH oxidation, ,,,,− dimethyl ether (CH 3 OCH 3 , DME) oxidation, CO 2 hydrogenation or reduction in CH 3 OH, ,− CH 3 OH carbonylation, , as well as directly from synthesis gas. − …”

Section: Introductionmentioning

confidence: 99%

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Catalytic Mechanisms of Methanol Oxidation to Methyl Formate on Vanadia–Titania and Vanadia–Titania–Sulfate Catalysts

Wang

Ren

et al. 2016

J. Phys. Chem. C

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Density functional theory calculations were carried out using both cluster and slab models to investigate the catalytic reaction network and the effect of sulfate promoter on methanol selective oxidation using the V2O5/TiO2 catalyst. The hemiacetal mechanism was reaffirmed to be the most favorable reaction pathway for the formation of methyl formate (MF) by the prediction of another reaction pathway involving formic acid. Molecular oxygen was found to assist the desorption of the reaction products from the reduced catalyst active site, both formaldehyde and methyl formate (MF). The mechanism of catalyst regeneration was elucidated based solely on first-principles calculations, which involve the conversion of another methanol molecule to formaldehyde over a peroxo species. This leads to our formulation of a complete catalytic reaction network for methanol selective oxidation to formaldehyde and MF on the V2O5/TiO2 catalyst. In addition, the detailed mechanism for the formation of formaldehyde and MF was also predicted on the sulfate-promoted V2O5/TiO2 catalyst. Based on the calculated reaction networks, the preferred formation of MF on the V2O5/TiO2-based catalysts was attributed to the lower energy barrier of the oxidative dehydrogenation (ODH) of the CH3OCH2O* intermediate than that of CH3O*. Furthermore, our calculated energy barriers also suggest that the sulfate-promoted V2O5/TiO2 catalyst has not only higher catalytic activity for methanol conversion but also higher selectivity of MF over CH2O, consistent with previous experimental observations. The sulfate promoter was found to increase the positive charge at the V site, leading to a lower energy barrier for the ODH of CH3O* than the unpromoted catalyst.

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“…The deactivation behavior is very similar at both temperatures. The dashed lines in these figures are calculated deactivation curves, which are estimated using a simple power-law equation: − where r d is the rate of deactivation, k d is the rate constant for deactivation, and d is the order of deactivation. The relative catalytic activity ( a ) is obtained from the rate of reaction over the deactivated catalyst with time ( r t ) divided by that over the as-prepared catalyst ( r 0 ).…”

Section: Resultsmentioning

confidence: 99%

Stability of Molten-Phase Cs–V–O Catalysts for SO₃ Decomposition in Solar Thermochemical Water Splitting

Nur

Matsukawa

Ikematsu

et al. 2018

ACS Appl. Energy Mater.

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Supported molten cesium vanadate catalysts (Cs–V–O/SiO2) showed activities comparable to that of a reference Pt catalyst (1 wt % Pt/TiO2) for SO3 decomposition at moderate temperatures (∼600 °C), which is essential as an O2 evolution reaction in solar thermochemical water splitting cycles. Stability testing of the catalyst over a 1000 h continuous reaction at 600 °C resulted in deactivation by ∼20% of the initial activity. Kinetic analysis of the activity versus time-on-stream indicated that the observed deactivation behavior can be divided into an induction period (≤100 h) and an acceleration period (>100 h). The deactivation is mainly caused by the vaporization loss of active components (Cs and V) from the molten phase. At the earliest stage, most vapor is generated in the upstream section of the catalyst bed and then redeposits therebelow. Upon repeating these vaporization and deposition cycles, Cs and V move gradually downstream. During this induction period, the deactivation is not obvious because the total Cs and V content of the catalyst bed remains almost unchanged. After this period, however, detachment of Cs and V from the downstream end of the catalyst bed induces accelerated deactivation. The vaporization loss was found to be significantly suppressed by inverting the catalyst bed every 100 h during the stability test. Consequently, this operation reduced the extent of catalyst deactivation from 20% to less than 10% of the initial activity.

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The dehydrogenation of methanol to methyl formatePart II. The effect of chromia on deactivation kinetics for copper-based catalysts

Cited by 4 publications

References 0 publications

Catalytic SO₃ Decomposition Activity and Stability of Pt Supported on Anatase TiO₂ for Solar Thermochemical Water-Splitting Cycles

Catalytic SO₃ Decomposition Activity and Stability of Pt Supported on Anatase TiO₂ for Solar Thermochemical Water-Splitting Cycles

Catalytic Mechanisms of Methanol Oxidation to Methyl Formate on Vanadia–Titania and Vanadia–Titania–Sulfate Catalysts

Stability of Molten-Phase Cs–V–O Catalysts for SO₃ Decomposition in Solar Thermochemical Water Splitting

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The dehydrogenation of methanol to methyl formatePart II. The effect of chromia on deactivation kinetics for copper-based catalysts

Cited by 4 publications

References 0 publications

Catalytic SO3 Decomposition Activity and Stability of Pt Supported on Anatase TiO2 for Solar Thermochemical Water-Splitting Cycles

Catalytic SO3 Decomposition Activity and Stability of Pt Supported on Anatase TiO2 for Solar Thermochemical Water-Splitting Cycles

Catalytic Mechanisms of Methanol Oxidation to Methyl Formate on Vanadia–Titania and Vanadia–Titania–Sulfate Catalysts

Stability of Molten-Phase Cs–V–O Catalysts for SO3 Decomposition in Solar Thermochemical Water Splitting

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Catalytic SO₃ Decomposition Activity and Stability of Pt Supported on Anatase TiO₂ for Solar Thermochemical Water-Splitting Cycles

Catalytic SO₃ Decomposition Activity and Stability of Pt Supported on Anatase TiO₂ for Solar Thermochemical Water-Splitting Cycles

Stability of Molten-Phase Cs–V–O Catalysts for SO₃ Decomposition in Solar Thermochemical Water Splitting