Kinetic investigations on methanol steam reforming on PdZn catalysts in microchannel reactors and model transfer into the pressure gap region

Pfeifer, Peter; Kölbl, A.; Schubert, K. R.

doi:10.1016/j.cattod.2005.09.014

Cited by 35 publications

(32 citation statements)

References 30 publications

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“… Refs. : [a] 105; [b] 35; [c] 24; [d] 83; [e] 3–6, 48, 49; [f] 17, 102; [g] 92; [h] 3–5, 12, 24, 36, 37, 50–52, 54–65, 85–88, 118, 122, 124, 130, 131–135, 139, 141, 145, 147, 148, 150, 152, 153; [i] 79; [j] 3–6; [k] 12; [l] 50, 51, 58, 59, 74, 75; [m] 58, 59; [n] 3, 6; [o] 12; [p] 11; [q] 7; [r] 8; [s] 154; [t] 9; [u] 10; [v] 138. …”

Section: Structural and Catalytic Aspects In Selected Examplesmentioning

confidence: 99%

Formation of Intermetallic Compounds by Reactive Metal–Support Interaction: A Frequently Encountered Phenomenon in Catalysis

2014

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This Review discusses the structural and catalytic aspects of the recently introduced reactive metal-support interaction. This special term was coined to account for the inability of the original concept of the strong metal-support interaction to accurately describe the structural, compositional, and electronic changes frequently occurring in oxide-supported metal particle catalysts at very high temperatures upon reduction in hydrogen, in many cases leading to intermetallic compound or substitutional alloy formation. This inaccuracy predominantly refers to the requirement of full reversibility upon oxidation and mild reduction for a strong metal-support interaction. A close look at the formation of oxide-supported intermetallic compounds upon high-temperature reduction reveals that these compounds are very common in catalysis and the situation is much more complex compared to unsupported intermetallic compounds due to the presence of the intermetallic compound-oxide interface

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Section: Structural and Catalytic Aspects In Selected Examplesmentioning

confidence: 99%

Formation of Intermetallic Compounds by Reactive Metal–Support Interaction: A Frequently Encountered Phenomenon in Catalysis

2014

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“…On the basis of kinetic studies in micro-channel reactors Pfeifer et al [45] have shown that methyl formate is unlikely the main sequential intermediate toward CO 2 . It rather represents a by-product resulting from the reaction of formate species with a sufficient amount of coadsorbed methanol, i.e.…”

Section: Surface Chemistry On Pdzn During Msrmentioning

confidence: 99%

Steam reforming of methanol on PdZn near-surface alloys on Pd(1 1 1) and Pd foil studied by in-situ XPS, LEIS and PM-IRAS

Rameshan

Weilach

Stadlmayr

et al. 2010

Journal of Catalysis

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The CO2-selectivity in methanol steam reforming was investigated for a "multilayer" PdZn 1:1 surface alloy (thickness of ~1.3 nm) and for a subsurface-Zn diluted "monolayer" PdZn surface alloy, both exhibiting a 1:1 composition in the surface layer. Despite having almost the same surface layer stoichiometry, these two types of near-surface alloys exhibit different corrugations and electronic structures. The CO2-selective multilayer alloy features a lowered density of states close to the Fermi edge and surface ensembles of PdZn exhibiting a "Zn-up/Pd-down" corrugation, acting as bifunctional active sites both for reversible water activation as ZnOH and for reaction of methanol (via formaldehyde + ZnOH) toward CO2. The thermochemical stability limit of the multilayer alloy at around 573 K was determined in-situ at elevated pressures of water, methanol and CO, applying in-situ XPS, PM-IRAS spectroscopy, LEIS and AES. Above 573 K, the coordination of the surface 1:1 PdZn layer with subsurfaceZn gradually decreased by bulk diffusion of Zn "escaping" from the second and deeper layers, resulting in a transition from the CO2-selective PdZn "multilayer" state to the unselective "monolayer" state, which only catalyses methanol dehydrogenation to CO.

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“…[15] This assumption is also indirectly justified by the good agreement between the calculated activation energies of methoxide on the PdZn-A C H T U N G T R E N N U N G (111) surface and the reported apparent activation energies on the PdZn catalysts. [25] In the following sections, we describe the computational methods and models including the theoretical background of atomistic thermodynamics. The adsorption complexes of various H 2 O-related species on two regular surfaces, CuA C H T U N G T R E N N U N G (111) and PdZnA C H T U N G T R E N N U N G (111), followed by a discussion of possible model surface reactions occurring on the catalysts are then addressed.…”

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confidence: 99%

Surface Composition of Materials Used as Catalysts for Methanol Steam Reforming: A Theoretical Study

2006

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PdZn (1:1) alloy is assumed to be the active component of a promising catalyst for methanol steam reforming. Using density functional calculations on periodic supercell slab models, followed by atomistic thermodynamics modeling, we study the chemical composition of the surfaces PdZn(111) and, as a reference, Cu(111) in contact with water and hydrogen at conditions relevant to methanol steam reforming. For the two surfaces, we determine similar maximum adsorption energies for the dissociative adsorption of H(2), O(2), and the molecular adsorption of H(2)O. These reactions are calculated to be exothermic by about -40, -320, and -20 kJ mol(-1), respectively. Using a thermodynamic analysis based on theoretically predicted adsorption energies and vibrational frequencies, we determine the most favorable surface compositions for given pressure windows. However, surface energy plots alone cannot provide quantitative information on individual coverages in a system of coupled adsorption reactions. To overcome this limitation, we employ a kinetic model, from which equilibrium surface coverages of H, O, OH, and H(2)O are derived. We also discuss the sensitivity of our results and the ensuing conclusions with regard to the model surfaces employed and the inaccuracies of our computational method. Our kinetic model predicts surfaces of both materials, PdZn and Cu, to be essentially adsorbate-free already from very low values of the partial pressure of H(2). The model surfaces PdZn(111) and Cu(111) are predicted to be free of water-related adsorbates for a partial H(2) pressure greater than 10(-8) and 10(-5) atm, respectively.

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Kinetic investigations on methanol steam reforming on PdZn catalysts in microchannel reactors and model transfer into the pressure gap region

Cited by 35 publications

References 30 publications

Formation of Intermetallic Compounds by Reactive Metal–Support Interaction: A Frequently Encountered Phenomenon in Catalysis

Formation of Intermetallic Compounds by Reactive Metal–Support Interaction: A Frequently Encountered Phenomenon in Catalysis

Steam reforming of methanol on PdZn near-surface alloys on Pd(1 1 1) and Pd foil studied by in-situ XPS, LEIS and PM-IRAS

Surface Composition of Materials Used as Catalysts for Methanol Steam Reforming: A Theoretical Study

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