Local structures and TWC activity of Pd supported on Ni-substituted aluminium oxide borates

Nagao, Yuki; Hamada, Takafumi; Imamura, Ayaka; Hinokuma, Satoshi; Nakahara, Yujiro; Machida, Masato

doi:10.1039/c5cy02274f

Cited by 6 publications

(7 citation statements)

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“…: 1950 °C); its crystal structure is described as mullite analogues comprising AlO 6 octahedra, irregular AlO 5 polyhedra, AlO 4 tetrahedra, and planar BO 3 triangles (Supporting Information). − The catalytic application of this material was first reported for catalytic CH 4 combustion over Pd/10A2B, and we have studied this for automotive three-way catalysts. , Figure shows the XRD patterns of CuO x /10A2B and CuO x /Al 2 O 3 (Al 2 O 3 : JRC-ALO-8, supplied by Catalysis Society of Japan) as a reference before and after thermal aging at 900 °C for 100 h in air. For as-prepared catalysts, the diffraction peaks of CuO x /10A2B could be assigned to 10A2B and CuO; however, those of CuO x /Al 2 O 3 could be assigned to only γ-Al 2 O 3 .…”

Section: Results and Discussionmentioning

confidence: 99%

“…A wide variety of commercially available metal oxides (Table ) were used as support materials for CuO x . As a support with high performance for NH 3 combustion, aluminum oxide borate (Al 20 B 4 O 36 , 10Al 2 O 3 ·2B 2 O 3 : 10A2B) was prepared by a reverse coprecipitation method. , An aqueous solution containing Al(NO 3 ) 3 and H 3 BO 3 (Wako Pure Chemicals) with a molar ratio of Al/B = 10:2 was added dropwise to a 3 mol·L –1 solution of (NH 4 ) 2 CO 3 (Wako Pure Chemicals) under vigorous stirring until the pH reached 7.0. The precipitate thus formed was calcined at 500 °C for 3 h and finally at 1000 °C for 5 h in air.…”

Section: Methodsmentioning

confidence: 99%

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Copper Oxides Supported on Aluminum Oxide Borates for Catalytic Ammonia Combustion

et al. 2016

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The catalytic NH 3 combustion properties and local structures of copper oxides (CuO x ) supported on aluminum oxide borates (Al 20 B 4 O 36 , 10Al 2 O 3 •2B 2 O 3 : 10A2B) were studied by means of high-angle annular dark-field scanning transmission electron microscopy, energy dispersive X-ray mapping, X-ray absorption fine structure, X-ray photoelectron spectroscopy, gas adsorption techniques, etc. Among the CuO x supported on various metal oxide materials, CuO x / 10A2B exhibited high catalytic NH 3 combustion activity, highest N 2 (lowest N 2 O•NO) selectivity, and high thermal stability. Because the combustion activity is closely associated with the reducibility and dispersion of CuO x , highly dispersed CuO x nanoparticles on supports are considered to play a key role in the low temperature light-off of NH 3 . For NO and N 2 O selectivities, the oxidation state of CuO x and the dissociative species of adsorbed NH 3 are suggested to be important catalytic combustion properties, respectively. On the basis of these discussions, the reaction mechanism of catalytic NH 3 combustion over CuO x /10A2B is described.

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Section: Results and Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Copper Oxides Supported on Aluminum Oxide Borates for Catalytic Ammonia Combustion

et al. 2016

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“…The decrease in CO conversion with the increase in NO conversion indicates that the Ni loading caused the selectivity to change from the CO–O 2 reaction to the CO–NO reaction. It has been reported that the partially oxidized Ni species promote NO adsorption, ,− indicating that the Ni loading on Cu/Al 2 O 3 promoted NO adsorption when a stream of the stoichiometric NO–CO–C 3 H 6 –O 2 gas mixture was used and accelerated the CO–NO reaction with the decrease in the CO–O 2 reaction. The influence of Ni on the structure of the Cu active sites and catalysis will be discussed later.…”

Section: Results and Discussionmentioning

confidence: 99%

“…Three-way catalysts (TWCs) are employed in state-of-the-art technologies for automotive emission control. − The use of platinum group metals (PGMs) deposited on conventional TWCs should be limited owing to their scarcity. Therefore, the development of alternative catalytic materials comprising inexpensive and abundant base metals has attracted extensive attention. − Nitrogen oxides (NO x ), carbon monoxide (CO), and unburned hydrocarbons such as C 3 H 6 are the primary constituents of exhaust gas.…”

Section: Introductionmentioning

confidence: 99%

Enhanced Catalytic NO Reduction in NO–CO–C₃H₆–O₂ Reaction Using Pseudo-Spinel (NiCu)Al₂O₄ Supported on γ-Al₂O₃

et al. 2021

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This study aims to clarify the effect of Ni addition on the enhancement of the NO reduction activity of Cu/Al2O3, which possesses high thermal durability, and to elucidate the associated structure–catalysis relationship. Thermal aging of Ni and Cu supported on γ-Al2O3 at a high temperature (900 °C) induced the formation of a pseudo-spinel (NiCu)Al2O4 solid solution on the γ-Al2O3 surface, which was observed using X-ray diffraction and high-angle annular dark-field scanning transmission electron microscopy techniques. Owing to the co-presence of Ni, the preferential occupation of octahedral sites by Ni increased the number of tetrahedrally coordinated Cu2+ ions, which played a key role in the reduction of NO in a stoichiometric NO–CO–C3H6–O2 reaction. XPS analysis revealed that Cu active sites with electron-rich states were formed in pseudo-spinel (NiCu)Al2O4 owing to electron donation from Ni to Cu, which promoted NO adsorption on Cu+ and accelerated NO reduction. The tetrahedrally coordinated Cu formed on the pseudo-spinel oxide was structurally robust, and its local structure remained unchanged even after the redox cycle occurred at a high temperature; this indicated that the formation of pseudo-spinel (NiCu)Al2O4 was effective for the enhancement of NO reduction activity and thermal durability.

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“…Поскольку бор имеет особенность интенсивно выгорать в процессе СВС, то было добавлено его избыточное количество с целью компенсировать выгоревшие потери. Также в системе Al-B-O характерно образование боратов алюминия при высоких температурах, начиная с 900 -950°С [24,25]. При СВС образование боратов происходит за счет взаимодействия оксида алюминия с борсодержащими соединениями.…”

Section: результаты и обсуждениеunclassified

Features of the structure and phase composition of materials based on aluminum oxide and chromium borides obtained under conditions of SHS and free SHS compression

2020

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In the present work, ceramic materials based on aluminum oxide and chromium borides in the Cr 2 O 3 -Al-B system with different ratios of the starting components, from stoichiometric to excess free boron, are obtained by self-propagating high-temperature synthesis (SHS) method. Excess boron was introduced into the system in order to compensate for its loss due to burnout during SHS. It was shown that, as a result of SHS, a ceramic composite material with an Al 2 O 3 matrix filled with various chromium borides: CrB, CrB 2 , and Cr 3 B 4 is formed in the studied system. It was also shown that in the 2Cr 2 O 3 -2Al-7B system, the formation of metastable phase of aluminum borate AlBO 3 is possible as a result of SHS. Since AlBO 3 is a promising material for use in refractories, this system was chosen as the starting material for producing plates by the free SHS compression method. The free SHS compression method combines the synthesis of material in SHS mode with subsequent shear high-temperature deformation. The specified method allowed obtaining ceramic plates with dimensions of 50 × 40 × 7 mm. According to the results of XRD and SEM, the obtained plates consisted of two phases: Al 2 O 3 , CrB 2 , as well as free boron. Due to changes in the conditions of heat removal under free SHS compression and a decrease in the residence time of the synthesized material at elevated temperatures, the formation of chromium monoboride and aluminum borate does not occur. Since the formation of aluminum borates begins in the temperature range 900 -950°С, an additional heat treatment of the obtained samples was carried out at a temperature of 950°С for 20 hours. It was found that as a result of heat treatment due to the interaction of free boron and aluminum oxide, the formation of aluminum borate Al 4 B 2 O 9 occurs, as well as the formation of chromium monoboride takes place as a result of thermal decomposition of CrB 2 . By this method, ceramic plates with dimensions of 50 × 40 × 7 mm were obtained. The maximum density of the obtained plates was 3.98 g/cm 3 , while the porosity was about 15%.

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Local structures and TWC activity of Pd supported on Ni-substituted aluminium oxide borates

Abstract: The Pd catalyst supported on Ni-substituted aluminum oxide borate (Ni–10A2B) achieved the highest catalytic activity under three-way catalysis conditions, where NO adsorption onto the Ni site promoted the reaction with hydrogen spilt over from Pd under rich conditions.

Cited by 6 publications

References 46 publications

Copper Oxides Supported on Aluminum Oxide Borates for Catalytic Ammonia Combustion

Copper Oxides Supported on Aluminum Oxide Borates for Catalytic Ammonia Combustion

Enhanced Catalytic NO Reduction in NO–CO–C₃H₆–O₂ Reaction Using Pseudo-Spinel (NiCu)Al₂O₄ Supported on γ-Al₂O₃

Features of the structure and phase composition of materials based on aluminum oxide and chromium borides obtained under conditions of SHS and free SHS compression

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Local structures and TWC activity of Pd supported on Ni-substituted aluminium oxide borates

Abstract: The Pd catalyst supported on Ni-substituted aluminum oxide borate (Ni–10A2B) achieved the highest catalytic activity under three-way catalysis conditions, where NO adsorption onto the Ni site promoted the reaction with hydrogen spilt over from Pd under rich conditions.

Cited by 6 publications

References 46 publications

Copper Oxides Supported on Aluminum Oxide Borates for Catalytic Ammonia Combustion

Copper Oxides Supported on Aluminum Oxide Borates for Catalytic Ammonia Combustion

Enhanced Catalytic NO Reduction in NO–CO–C3H6–O2 Reaction Using Pseudo-Spinel (NiCu)Al2O4 Supported on γ-Al2O3

Features of the structure and phase composition of materials based on aluminum oxide and chromium borides obtained under conditions of SHS and free SHS compression

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Resources

About

Enhanced Catalytic NO Reduction in NO–CO–C₃H₆–O₂ Reaction Using Pseudo-Spinel (NiCu)Al₂O₄ Supported on γ-Al₂O₃