Steam reforming of methanol over Pd/ZnO: Effect of the formation of PdZn alloys upon the reaction

Iwasa, Nobuhiro; Masuda, Satoshi; Ogawa, Noriaki; Takezawa, Nobutsune

doi:10.1016/0926-860x(95)00004-6

Cited by 336 publications

(268 citation statements)

References 20 publications

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“…In line with previous studies on PdZn formation 8,[12][13][14] , the present electron microscopy study unambiguously reveals the onset of the formation of a tetragonal PdZn phase upon reduction at T ≥ 473 K. The formation of the alloy phase proceeds most likely via topotactic formation of PdZn on top of the Pd particles. This growth mechanism is probably favoured by the relatively small mismatch of the lattice constants of fcc Pd (0.388 nm) and tetragonal PdZn (0.410 nm).…”

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confidence: 74%

Growth and structural stability of well-ordered PdZn alloy nanoparticles

Penner

Jenewein

Gabasch

et al. 2006

Journal of Catalysis

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Despite many recent attempts to unravel the structure of novel PdZn alloys, promising catalysts in methanol steam reforming, a detailed study on the formation of Pd-Zn alloy particles and of their structural and thermal stability is still missing. We take advantage of the unique properties of epitaxially grown Pd particles embedded in layers of amorphous ZnO and mechanically stabilized by SiO 2 , and present an electron microscopy study of the preparation of well-ordered PdZn alloy nanoparticles at surprisingly low reduction temperatures. They are formed by topotactic growth on the surface of the Pd nanoparticles and are structurally and thermally stable in a broad temperature regime (473 -873 K). At and above 873K, partial decomposition of PdZn and beginning interaction with the SiO 2 support has been observed. Keywords:Thin film model catalyst, hydrogen reduction, alloy formation, electron microscopy, selected area electron diffraction ManuscriptMuch recent effort has been invested in the development of suitable catalysts for methanol steam reforming 1-15 as this is one of the most promising processes for hydrogen production with a high hydrogen-to-carbon ratio 16 . Cu/ZnO catalysts have been commercially used to produce hydrogen with high selectivity and activity 2-6 , but they suffer from deactivation at reaction temperatures above 573 K 17 . Recently, novel Pd/ZnO systems 3-15 (as well as Pd/Ga 2 O 3 and Pd/In 2 O 3 18,19 ) have attracted more attention because of their enhanced long-term and thermal stability 20,21 . As unsupported pure Pd exhibits only a poor selectivity 22 , the observed high activity and selectivity for CO 2 formation was ascribed to the formation of distinct PdZn, PdIn and PdGa alloys upon reductive activation at elevated temperatures 18 . Best characterized is the Pd/ZnO system, where alloy formation has been studied and confirmed by X-ray diffraction (XRD) 18,23 , temperature-programmed reduction (TPR) 18,23 and X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS) [24][25][26] . Iwasa et al. 23 observed PdZn alloy formation upon reduction at very low T (≥ 473 K). Density functional studies revealed the close relationship between the electronic structure of PdZn and Cu-based catalysts giving rise to a similar catalytic performance in methanol steam reforming 27,28 . Comparatively few studies have been carried out on the structural characterization of the PdZn alloys by electron microscopy, and these were limited to overview imaging of powder catalysts in the as-prepared state and after hydrogen reduction, thereby mainly supporting XRD measurements 29,30 . The Pd-Zn system is known to form several stable bulk alloy phases 31 . The most important and thermally most stable is the PdZn (β1) phase, which crystallizes in a tetragonal (AuCu-type) L1 0 structure 32 . A key point for understanding the catalytic pecularities of the above-mentioned Pd-Zn alloy particles is also to determine their surface composition. Recent experiments in our laboratory 33 show that a well-orde...

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confidence: 74%

Growth and structural stability of well-ordered PdZn alloy nanoparticles

Penner

Jenewein

Gabasch

et al. 2006

Journal of Catalysis

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“…Preparation methods for the development of efficient bimetallic Pd-Fe catalysts were focused, in addition to the fundamental properties (activity, selectivity and stability) and practical applications (reuse, reproducibility and easy separation from the reaction mixture), on the optimization of metal-metal or metal/support interactions [116][117][118][119][120][121][122][123][124][125]190]. …”

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confidence: 99%

Upgrading Lignocellulosic Biomasses: Hydrogenolysis of Platform Derived Molecules Promoted by Heterogeneous Pd-Fe Catalysts

et al. 2017

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Abstract:This review provides an overview of heterogeneous bimetallic Pd-Fe catalysts in the C-C and C-O cleavage of platform molecules such as C2-C6 polyols, furfural, phenol derivatives and aromatic ethers that are all easily obtainable from renewable cellulose, hemicellulose and lignin (the major components of lignocellulosic biomasses). The interaction between palladium and iron affords bimetallic Pd-Fe sites (ensemble or alloy) that were found to be very active in several sustainable reactions including hydrogenolysis, catalytic transfer hydrogenolysis (CTH) and aqueous phase reforming (APR) that will be highlighted. This contribution concentrates also on the different synthetic strategies (incipient wetness impregnation, deposition-precipitaion, co-precipitaion) adopted for the preparation of heterogeneous Pd-Fe systems as well as on the main characterization techniques used (XRD, TEM, H 2 -TPR, XPS and EXAFS) in order to elucidate the key factors that influence the unique catalytic performances observed.

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“…Iwasa et al [46] proposed that the Pd-Zn alloy formed in hydrogen treatment has positive effects on the selectivity of methanol steam reforming. Formaldehyde species formed in the reaction were able to be effectively transformed into H 2 and CO 2 over the catalyst containing Pd-Zn alloys.…”

Section: Palladium Based Catalystsmentioning

confidence: 99%

Review on Copper and Palladium Based Catalysts for Methanol Steam Reforming to Produce Hydrogen

Shuai

2017

Catalysts

101

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Abstract:Methanol steam reforming is a promising technology for producing hydrogen for onboard fuel cell applications. The methanol conversion rate and the contents of hydrogen, carbon monoxide and carbon dioxide in the reformate, significantly depend on the reforming catalyst. Copper-based catalysts and palladium-based catalysts can effectively convert methanol into hydrogen and carbon dioxide. Copper and palladium-based catalysts with different formulations and compositions have been thoroughly investigated in the literature. This work summarized the development of the two groups of catalysts for methanol steam reforming. Interactions between the activity components and the supports as well as the effects of different promoters were discussed. Compositional and morphological characteristics, along with the methanol steam reforming performances of different Cu/ZnO and Pd/ZnO catalysts promoted by Al 2 O 3 , CeO 2 , ZrO 2 or other metal oxides, were reviewed and compared. Moreover, the reaction mechanism of methanol steam reforming over the copper based and palladium based catalysts were discussed.

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Steam reforming of methanol over Pd/ZnO: Effect of the formation of PdZn alloys upon the reaction

Cited by 336 publications

References 20 publications

Growth and structural stability of well-ordered PdZn alloy nanoparticles

Growth and structural stability of well-ordered PdZn alloy nanoparticles

Upgrading Lignocellulosic Biomasses: Hydrogenolysis of Platform Derived Molecules Promoted by Heterogeneous Pd-Fe Catalysts

Review on Copper and Palladium Based Catalysts for Methanol Steam Reforming to Produce Hydrogen

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