In situ FTIR and XANES studies of thiophene hydrodesulfurization on Ni2P/MCM-41

Oyama, S. Ted; Gott, Travis; Asakura, Kiyotaka; Takakusagi, Satoru; Miyazaki, Kei; Koike, Yuichiro; Bando, Kyoko K.

doi:10.1016/j.jcat.2009.09.018

Cited by 72 publications

(47 citation statements)

References 65 publications

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“…DFT study of HDO revealed that 3-fold hollow Ni and P sites are active for 14 adsorption of H and OH species [43]. Different from the above mentioned studies based 15 on Ni3P2-terminated surface, which is more stable than Ni3P-terminated surface, 16 dissociative adsorption of hydrogen was found on Ni3P-terminated surface [25]. In Fig.…”

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confidence: 82%

“…In addition Oyama et al found that the NiPS phase are active for 6 hydrodesulfurization reaction and they suggested the Ni(2) provides active site. [16][17][18][19][20][21] Despite these current insights, a thorough understanding of the high activity of Ni2P 8 at the atomic level requires us to investigate the structures and properties of Ni2P single 9 crystals. Many efforts have been made to date to elucidate the surface properties of Ni2P 10 single crystal surfaces, using X-ray photoelectron spectroscopy (XPS) [22,23], scanning 11 tunneling microscopy (STM) [24][25][26][27][28], low-energy electron diffraction (LEED) [24][25][26][27][28][29][30], 12 photoemission electron microscopy (PEEM) [25], photoelectron diffraction [31] and 13 photoemission spectroscopy (PES) [30,[32][33][34][35].…”

Section: Introductionmentioning

confidence: 99%

“…Theoretical calculations using density 14 functional theory (DFT) [11,14,15,[36][37][38] have also played an important role in 15 understanding the catalytic properties of the surface. These studies have indicated that 16 the Ni2P single crystal surface is stabilized by reordering of the P atoms. In this review 17 paper, we survey the available literature concerning the surface structure and electronic 2.…”

Section: Introductionmentioning

confidence: 99%

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An Investigation of Ni2P Single Crystal Surfaces: Structure, Electronic State and Reactivity

2015

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8Ni2P has demonstrated high catalytic activity for hydrodesulfurization and has 9 recently been employed as a catalyst in a variety of other reactions. We have thoroughly 10 reviewed the literature concerning Ni2P single crystal surfaces, with the aim of 11 determining the relationship between surface structure and catalytic properties. 12Published results to date indicate that Ni2P single crystal surfaces exhibit reconstructed 13 structures, and so the bulk terminated structure may not be stable. We have also 14 reviewed the surface structures and electronic states of (1×1) and reconstructed Ni2P

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confidence: 82%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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An Investigation of Ni2P Single Crystal Surfaces: Structure, Electronic State and Reactivity

2015

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“…6 This would indicate that tetrahedral Ni on the surface preferentially reacts with sulfur. Figure 2c shows the EXAFS difference spectrum for the sample before the H 2 S treatment and the same sample with the H 2 S treatment during the HDS reaction.…”

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confidence: 99%

“…6,8 Briefly, the support was impregnated with a solution of nickel nitrate and ammonium phosphate, dried, calcined, and reduced (See Supporting Information (SI)). 23 For the measurements in this study, 30.0 mg of reduced and then passivated samples was pressed into a disk with a diameter of 15 mm and was re-reduced in a XAFS cell under H 2 flow (100 mL min ¹1 ) at 803 K for 2 h (H 2 activated sample).…”

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Operando Observation of Ni2P Structural Changes during Catalytic Reaction: Effect of H2S Pretreatment

et al. 2012

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In situ X-ray absorption spectroscopy was used to study the effect of H 2 S pretreatment on the activation of Ni 2 P catalysts for the thiophene hydrodesulfurization (HDS) reaction. It was found that H 2 S treatment produced NiS bonds that were slightly longer and that had higher coordination numbers than those formed during reaction. The longer NiS bonds formed by H 2 S treatment were changed to the shorter NiS bonds by the catalytic reaction, and these shorter bonds were associated with high activity. The work provides evidence that a NiPS phase is active in the HDS reaction.Removal of sulfur compounds from petroleum feedstocks is important for satisfying environmental regulations. Nickel phosphide (Ni 2 P) catalysts have shown higher catalytic activity in hydrodesulfurization (HDS) reactions than commercially available NiMoS or CoMoS catalysts have.14 Previous work with time-resolved simultaneous measurements of quick X-ray absorption fine-structure (QXAFS) and Fourier transform infrared (FTIR) spectra of Ni 2 P catalysts during thiophene HDS indicated that a nickel phosphosulfide (NiPS) phase was responsible for the catalytic activity. 59 Recently, it was reported that pretreatment of Ni 2 P by H 2 S had a positive effect on the catalytic activity probably because of the formation of a surface NiPS phase.10,11 However, no information has been presented about the structure of the active catalyst formed by the H 2 S treatment. This paper reports results of in situ XAFS analysis of the Ni 2 P during the H 2 S pretreatment and the Ni 2 P after the HDS reaction with and without H 2 S treatment. The results indicate the formation of a catalytically active NiPS phase.The MCM-41-supported Ni 2 P catalysts of loading 1.15 mmol Ni g support ¹1 (12.2 wt % Ni 2 P/support) were prepared as described in previous reports. 6,8 Briefly, the support was impregnated with a solution of nickel nitrate and ammonium phosphate, dried, calcined, and reduced (See Supporting Information (SI)). 23 For the measurements in this study, 30.0 mg of reduced and then passivated samples was pressed into a disk with a diameter of 15 mm and was re-reduced in a XAFS cell under H 2 flow (100 mL min ¹1 ) at 803 K for 2 h (H 2 activated sample). The thus-reduced sample was first cooled to a set temperature (529, 559, and 583 K) to measure the in situ EXAFS and was then treated in 5.0 vol % H 2 S/H 2 at 559 K for 0.3 h until in situ XAFS monitoring of a NiS bond showed no changes. The sample was then cooled or heated again to the HDS reaction temperatures under He flow. The sample was not moved during these steps, which allowed the measurement of accurate difference spectra. The mixed reactant gas composed of thiophene (0.1 vol %), He (1.9 vol %), and H 2 (98 vol %) was introduced at a rate of 100 mL min 12 The ring energy and current were 2.5 GeV and 430 mA, respectively. The monochromator was rotated by a stepping motor at a speed at 10 s per spectrum in the Ni K-edge region from 8080 to 8900 eV. It took another 10 s to rewind the motor and save t...

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Layered Double Hydroxide‐Based Catalysts: Recent Advances in Preparation, Structure, and Applications

Wei

2018

Adv Funct Materials

361

163

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Layered double hydroxides (LDHs) are a class of functional anionic clays, which consist of positively charged host layers (brucite-like M(OH) 6 octahedra) and interlayer anions. By virtue of their unique combination of structural features (including the tunability of both host layers and interlayer guest anion, exfoliation property, structure topological transformation, confinement effect), LDHs have many potential applications in heterogeneous catalysisas catalysts themselves, catalyst supports, or catalyst precursors. In addition, the properties of LDH-based catalysts can be tailored for specific purposes by facile modulation of their surface/interface defect structure (e.g., oxygen vacancy defects or metal defects), controlling the concentration/strength of surface acid/base sites, tuning the geometric/electronic structure of active sites, or by taking advantage of the confinement effect intrinsic to 2D materials. In addition, by utilizing the topological structural transformation of LDH precursors, supported metal catalysts can be obtained (as single metals, bimetallic alloys or heterostructures, and intermetallic compounds) with tunable particle size/morphology and intriguing electronic properties. The main focus of this review is on recent advances in structure design, preparation, and catalytic applications of LDH-based heterogeneous catalysts. In addition, future challenges and development strategies are discussed from the viewpoints of modulation of intrinsic active sites and establishment of scalable fabrication processes. activity, selectivity, and stability. [8,11,12] Therefore, by virtue of their unique combination of structural features (layered structure, compositional flexibility, tunable interlayer anions, and exfoliation properties) and their topological transformation, LDH materials have been widely studied as catalysts, catalyst precursors, and catalyst supports.This Review highlights recent developments in the design and preparation of LDH-based nanocatalysts (Figure 1) and their potential applications in heterogeneous catalysis. New synthetic approaches and exfoliation techniques for the preparation of LDH-based catalysts are first reviewed, with a strong emphasis on the ways in which the structure of the active sites (e.g., surface defect structure, interface structure, geometric/electronic structure, and preferential exposure of highly active facets) of LDHbased nanocatalysts can be precisely tailored. The identification and characterization of active sites as well as structure-property correlations are discussed in detail, since these provide helpful guidelines for the rational design and preparation of future highperformance heterogeneous catalysts. In the final section, future opportunities and challenges in the fabrication of LDH-derived catalysts are discussed in terms of structural design and control over intrinsic active sites, and some strategies to resolve these critical issues are proposed. It is hoped that this review will focus attention on new LDH-based catalysts and encourage...

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In situ FTIR and XANES studies of thiophene hydrodesulfurization on Ni2P/MCM-41

Cited by 72 publications

References 65 publications

An Investigation of Ni2P Single Crystal Surfaces: Structure, Electronic State and Reactivity

An Investigation of Ni2P Single Crystal Surfaces: Structure, Electronic State and Reactivity

Operando Observation of Ni2P Structural Changes during Catalytic Reaction: Effect of H2S Pretreatment

Layered Double Hydroxide‐Based Catalysts: Recent Advances in Preparation, Structure, and Applications

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