Hydrogen Production by Steam Reforming of Methanol

Iwasa, Nobuhiro; Nomura, Wataru; Mayanagi, Tomoyuki; Fujita, Shin‐ichiro; Arai, Masahiko; Takezawa, Nobutsune

doi:10.1252/jcej.37.286

Cited by 28 publications

(24 citation statements)

References 16 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).…”

supporting

confidence: 91%

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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supporting

confidence: 91%

Growth and structural stability of well-ordered PdZn alloy nanoparticles

Penner

Jenewein

Gabasch

et al. 2006

Journal of Catalysis

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“…The TOF was estimated to be 0.39 s -1 , which is comparable to the value of 0.8 s -1 reported in the literature for Pd/ZnO catalysts [25]. As a comparison, the TOF for Cu/ZnO/Al 2 O 3 catalysts reported in the literature has been reported to range from 0.0152 s -1 [26] to 0.11 s -1 [27]. After Table 2: Reactivity comparison of two catalysts exposed to different pretreatments prior to steam reforming conditions The TOF was estimated to be 0.39 s -1 , which is comparable to the value of 0.8 s -1 reported in the literature for Pd/ZnO catalysts [25].…”

Section: Ftir Of Absorbed Cosupporting

confidence: 79%

“…After Table 2: Reactivity comparison of two catalysts exposed to different pretreatments prior to steam reforming conditions The TOF was estimated to be 0.39 s -1 , which is comparable to the value of 0.8 s -1 reported in the literature for Pd/ZnO catalysts [25]. As a comparison, the TOF for Cu/ZnO/Al 2 O 3 catalysts reported in the literature has been reported to range from 0.0152 s -1 [26] to 0.11 s -1 [27]. After 4 hours of exposure to steam reforming conditions, both these catalysts were analyzed via FTIR of adsorbed CO. Figure 8 shows that the surfaces of the two catalysts give nearly identical IR spectra after reaction.…”

Section: Ftir Of Absorbed Cosupporting

confidence: 64%

Stability of bimetallic Pd–Zn catalysts for the steam reforming of methanol

Conant

Karim

Lebarbier

et al. 2008

Journal of Catalysis

184

126

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ZnO-supported palladium-based catalysts have been shown in recent years to be both active and selective towards the steam reforming of methanol, although they are still considered to be less active than traditional copper-based catalysts. The activity of PdZn catalysts can be significantly improved by supporting them on alumina. Here we show that the Pd/ZnO/Al 2 O 3 catalysts have better long-term stability when compared with commercial Cu/ZnO/Al 2 O 3 catalysts, and that they are also stable under redox cycling. The Pd/ZnO/Al 2 O 3 catalysts can be easily regenerated by oxidation in air at 420 ºC followed by re-exposure to reaction conditions at 250 ºC, while the Cu/ZnO based catalysts do not recover their activity after oxidation. Reduction at high temperatures (>420 ºC) leads to Zn loss from the alloy nanoparticle surface resulting in a reduced catalyst activity. However, even after such extreme treatment, the catalyst activity is regained with time on stream under reaction conditions alone, leading to highly stable catalysts. These findings illustrate that the nanoparticle surface is dynamic and changes drastically depending on the environment, and that elevated reduction temperatures are not necessary to achieve high CO 2 selectivity.

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“…The need for only a preferential oxidation of CO (PROX) process for gas purification prior to supply to a fuel cell makes this system suitable for the realization of small reformer requiring a simple system. Cu/ZnO catalysts have been studied for use in methanol synthesis, water gas shift reaction, and methanol steam reforming 5) 13) . However, there were few reports on the development of the catalyst for low-temperature hydrogen production as required for miniaturized methanol reformers, and the applicability as a power source for portable electronic devices had yet to be discussed in the early 2000's when the authors started the research.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen Production by Methanol Steam Reforming Using Microreactor

Kawamura¹,

Ogura²,

Igarashi³

2013

J. Jpn. Petrol. Inst.

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A microreactor technology, in which a microchannel is used as a catalytic reaction field in order to supply hydrogen to a small polymer electrolyte fuel cell (PEFC) for portable electronic devices, was described. The reduction of heat loss in the microreactor is the primary requirement for improving system efficiency, since heat release in microreactors is higher than in conventional reactors due to the increased specific surface area. Therefore, the methanol steam reforming, operated below 300 , is an appropriate process for the hydrogen production using the microreactor. First, the high-performance Cu/ZnO/Al2O3 catalyst for methanol reforming at low temperature was developed under the optimized preparation condition. The miniaturized methanol reformer was then developed to utilize this Cu/ZnO/Al2O3 catalyst. The length of the microchannel was determined based on one-dimensional mass and heat balance analyses. The microreactor was fabricated from silicon and glass substrates using a number of microfabrication techniques. Methanol reforming using this reactor has been demonstrated to reach the levels necessary to power a 1 W-class small PEFC system. The multilayered integrating the miniature methanol reformer with a CO remover, a catalytic combustor as a heat source for methanol reforming, vaporizers, and several necessary functional elements for hydrogen production has also been successfully fabricated. Finally, the microreactor system has been demonstrated to produce hydrogen at a rate sufficient to generate electrical power of 2.5 W.

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Hydrogen Production by Steam Reforming of Methanol

Cited by 28 publications

References 16 publications

Growth and structural stability of well-ordered PdZn alloy nanoparticles

Growth and structural stability of well-ordered PdZn alloy nanoparticles

Stability of bimetallic Pd–Zn catalysts for the steam reforming of methanol

Hydrogen Production by Methanol Steam Reforming Using Microreactor

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