Microstructured reactors for catalytic reactions

Kiwi‐Minsker, Lioubov; Renken, Albert

doi:10.1016/j.cattod.2005.09.011

Cited by 436 publications

(189 citation statements)

References 86 publications

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“…46 These E B 's are almost identical to those in Mo 2 C (227.8 eV) and significantly lower than Mo metal (228.5 eV). 49 The fact that the measured Mo binding energies in both Mo 2 TiAlC 2 and Mo 2 Ti 2 AlC 3 are almost identical is fully consistent with the fact that the Molayers are on the outside and the Ti layers are on the inside, i.e., ordered.…”

Section: Alcsupporting

confidence: 61%

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Experimental and theoretical characterization of ordered MAX phases Mo2TiAlC2 and Mo2Ti2AlC3

Anasori

Dahlqvist

Halim

et al. 2015

Journal of Applied Physics

262

180

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Herein, we report on the phase stabilities and crystal structures of two newly discovered ordered, quaternary MAX phases-Mo 2 TiAlC 2 and Mo 2 Ti 2 AlC 3 -synthesized by mixing and heating different elemental powder mixtures of mMo:(3-m)Ti:1.1Al:2C with 1.5 m 2.2 and 2Mo: 2Ti:1.1Al:2.7C to 1600 C for 4 h under Ar flow. In general, for m ! 2 an ordered 312 phase, (Mo 2 Ti)AlC 2 , was the majority phase; for m < 2, an ordered 413 phase (Mo 2 Ti 2 )AlC 3 , was the major product. The actual chemistries determined from X-ray photoelectron spectroscopy (XPS) are Mo 2 TiAlC 1.7 and Mo 2 Ti 1.9 Al 0.9 C 2.5 , respectively. High resolution scanning transmission microscopy, XPS and Rietveld analysis of powder X-ray diffraction confirmed the general ordered stacking sequence to be Mo-Ti-Mo-Al-Mo-Ti-Mo for Mo 2 TiAlC 2 and Mo-Ti-Ti-Mo-Al-Mo-Ti-TiMo for Mo 2 Ti 2 AlC 3 , with the carbon atoms occupying the octahedral sites between the transition metal layers. Consistent with the experimental results, the theoretical calculations clearly show that M layer ordering is mostly driven by the high penalty paid in energy by having the Mo atoms surrounded by C in a face-centered configuration, i.e., in the center of the M nþ1 X n blocks. At 331 GPa and 367 GPa, respectively, the Young's moduli of the ordered Mo 2 TiAlC 2 and Mo 2 Ti 2 AlC 3 are predicted to be higher than those calculated for their ternary end members. Like most other MAX phases, because of the high density of states at the Fermi level, the resistivity measurement over 300 to 10 K for both phases showed metallic behavior. V C 2015 AIP Publishing LLC.

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Section: Alcsupporting

confidence: 61%

“…This binding energy is higher than the corresponding energies in TiC (281.7 to 281.9 eV), Ti 3 AlC 2 (281.5 eV), [50][51][52]54 or Mo 2 C (282.7 eV). 49 The other two peaks correspond to C-C and CH x species that are due to adventitious C and contamination from the atmosphere.…”

Section: Alcmentioning

confidence: 99%

Experimental and theoretical characterization of ordered MAX phases Mo2TiAlC2 and Mo2Ti2AlC3

Anasori

Dahlqvist

Halim

et al. 2015

Journal of Applied Physics

262

180

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“…Recently, structured matrices that contain micrometer-scale open paths for fluids have attracted much attention as promising catalyst supports, since they allow for the effective diffusion of heat and reactants during catalytic reactions [15]. In this context, various types of structured supports, such as foams [16], strings [17] and honeycombs [18,19], have been developed.…”

Section: Structured Catalystsmentioning

confidence: 99%

On-paper Synthesis of Metal Nanoparticles for Catalytic Applications

Koga

Kitaoka²

2011

Sen-i Gakkaishi

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Metal catalysts have played essential roles in a wide range of chemical industrial processes [1][2][3]. For example, the copper/zinc oxide (Cu/ZnO) catalyst has been especially important for methanol synthesis [4] and alcohol reforming to produce hydrogen for fuel cell applications [5]. Energy, environmental and resource problems have escalated in recent times. Therefore, the development of high-performance catalytic materials that can effectively and selectively promote desired reactions is required for sustainability. Metal nanocatalystsNanosized metal particles have received an increasing amount of attention in various fields, such as in electronic [6], optical [7] and biomedical [8] applications, because of their unique and specific properties. In particular, the extremely large specific surface areas of metal nanoparticles (NPs) are very advantageous for effective catalytic reactions [9]. This has led to the active use of metal NPs as heterogeneous catalysts for a variety of industrial processes [9] including energy conversion, fine chemical synthesis and environmental cleanup. For example, gold (Au) nanocatalysts have received considerable interest for use in various reactions, including the reduction of 4-nitrophenol (4-NP) in the liquid phase [10] and low-temperature carbon monoxide (CO) oxidation [11] in the gas phase, even though bulk Au is typically regarded as an ineffective catalyst. However, the practical implementation of metal NPs is difficult, because they are difficult to handle and they aggregate easily, which minimizes their surface area. The aggregation of metal NPs results in the formation of ordinary bulk metals, and this consequently deteriorates their excellent functionalities. Therefore, catalytic metal NPs are generally attached to various support materials, such as polymers [9,12] and metal oxide powders [9,13]. Since these supported catalysts are fine and are handled with difficulty in practice, they are generally fashioned as beads or pellets. This eventually decreases their catalytic reactivity, because of the poor contact efficiency between the reactants and the catalytically active sites [14]. In addition, filling a reactor with solid catalysts can cause a high pressure drop, local reactant flow and an uneven thermal environment inside the catalyst layer, leading to an inefficient overall process, particularly for flow-type reactions. Therefore, establishing an efficient and practical immobilization technique that enables highly active metal NPs to be attached to and exposed on easyto-handle porous matrices is a challenge. On-paper Synthesis of Metal Nanoparticles for Catalytic ApplicationsDepartment of Agro-environmental Sciences, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan ( † Present address : Department of Biomaterials Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan)Abstract: We discuss the successful in ...

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“…In recent years, microchannel devices such as microreactors [1][2][3][4][5][6][7][8][9][10][11][12][13] and microchannel heat sinks [14][15][16][17][18] have actively been investigated with attention on the excellent heat exchange capability coming from the high surface to volume ratio of the microchannel structure. The heat exchange capability is one of the essential properties in the microreactor systems for precise control of reaction temperatures and effective use of heat from external sources.…”

Section: Introductionmentioning

confidence: 99%

Formation of Al-Ni Intermetallic Layers Lining Microchannels Produced by Powder-Metallurgical Process Using Aluminum Sacrificial Cores

Ohmi

Hayashi

2016

Mater. Trans.

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The mechanism of in-situ formation of Al-Ni intermetallic lining layers during microchannel formation in nickel bodies by a powder-metallurgical process has been investigated. Aluminum wire was used as a sacri cial core that gives the shape of the microchannel and supplies the alloying element for the lining layer. Nickel powder compacts with 29(±1)% porosity containing aluminum wires were heated from room temperature and then quenched at various temperatures between 873 K and 1473 K. Porous intermetallic lining layers were clearly recognized at temperatures above 1073 K. Each lining layer was built up from an outward-growing layer and an inward-growing layer. Change in the voidage in the outward-growing layer during heat treatment and the formation of a high-voidage zone around the lining layer were accounted for in terms of phase equilibria and unequal diffusion rates of the alloy elements in the Al-Ni intermetallic compounds and nickel solid solution.

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Microstructured reactors for catalytic reactions

Cited by 436 publications

References 86 publications

Experimental and theoretical characterization of ordered MAX phases Mo2TiAlC2 and Mo2Ti2AlC3

Experimental and theoretical characterization of ordered MAX phases Mo2TiAlC2 and Mo2Ti2AlC3

On-paper Synthesis of Metal Nanoparticles for Catalytic Applications

Formation of Al-Ni Intermetallic Layers Lining Microchannels Produced by Powder-Metallurgical Process Using Aluminum Sacrificial Cores

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