Characterization of Solid Catalysts: Sections 3.2.3 – 3.2.4

Hall, W. Keith; Spiewak, B. E.; Cortright, Randy D.; Dumesic, J.A.; Knözinger, H.; Pfeifer, H.; Kazansky, V.B.; Bond, G. C.

doi:10.1002/9783527619474.ch3c

Cited by 4 publications

(5 citation statements)

References 547 publications

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“…While BAS are the primary active sites for zeolite-catalyzed dehydration of alcohols, 24 the turnover frequencies (TOFs) of intramolecular dehydration of 1-octadecanol varied quite remarkably on the three catalysts, when normalized to BAS or strong BAS (see Figure 3b and Table 2). Since the acid− base properties of the three zeolites do not indicate a difference in the strength of BAS and LAS (and it would also not be expected from the chemical compositions 25 ), the differences suggest that only a (varying) fraction of the acid sites is involved in catalysis. Indeed, estimating the effectiveness factor (η) (Table 2; see the detailed calculation in the SI and in Table S3 in the SI) points to a varying fraction of sites being active.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Dehydration of 1-Octadecanol over H-BEA: A Combined Experimental and Computational Study

et al. 2016

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Liquid-phase dehydration of 1-octadecanol, which is intermediately formed during the hydrodeoxygenation of microalgae oil on zeolite H-BEA, has been studied, combining experiment and theory. Both the OH group and the alkyl chain of 1-octadecanol interact with zeolite Brønsted acid sites, inducing inefficient utilization in the presence of high acid-site concentrations. The parallel intramolecular and intermolecular dehydration pathways, leading to octadecene and dioctadecyl ether, have different activation energies and pass through different reaction intermediates. The formation of surface alkoxides is the rate-limiting step in the intramolecular dehydration, whereas the intermolecular dehydration proceeds via a bulky dimer intermediate, occurring preferentially at the pore mouth or outer surface of zeolite crystallites. Despite the main contribution of Brønsted acid sites toward both dehydration pathways, Lewis acid sites are also active to form dioctadecyl ether.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Dehydration of 1-Octadecanol over H-BEA: A Combined Experimental and Computational Study

et al. 2016

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“…The Co dispersion ( D ) was then calculated by the following equation The mean particle size ( d particles , Å) was calculated based on the following equation where a m is the area occupied by a surface Co atom and v m is the volume occupied by a Co atom in bulk metal. For face-centered cubic (fcc) Co, a m = 6.59 Å 2 and v m = 11.00 Å 3 …”

Section: Experimental Sectionmentioning

confidence: 99%

Ru₁Co_n Single-Atom Alloy for Enhancing Fischer–Tropsch Synthesis

et al. 2021

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Fischer−Tropsch synthesis (FTS) is a significant catalytic process for the production of liquid fuel and fine chemicals from natural gas-, coal-, and biomass-derived syngas. However, exploring high-performance catalysts and understanding the catalytic mechanism remain challenging. Herein, we design a Ru 1 Co n single-atom alloy (SAA) catalyst with isolated Ru atoms anchored onto a Co nanoparticle surface through a twodimensional confinement strategy to achieve greatly improved FTS activity (2.6 mol CO mol M −1 h −1 ) and long-chain hydrocarbon selectivity (C 5 + : 86.0%) at a low reaction temperature of 150 °C. A series of in situ experiments, catalytic tests, and density functional theory (DFT) calculations reveal that the Ru single-atom sites in Ru 1 Co n SAA are more active for the FTS reaction than pure Ru and Co surfaces. This is because single-atom Ru with a much higher electronic density near the Fermi level could effectively and simultaneously decrease the rate-limiting barriers of both C−O splitting and chain growth processes. This work demonstrates the possibility of designing Ru single-atom sites to improve FTS performance and provides a deeper understanding of the strategy for developing other high-performance industrial catalysts.

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“… 10 , 11 While structural properties and the interconnection of micro- and mesopores can be studied with high-resolution scanning electron microscopy (HR-SEM) and transmission electron microscopy (TEM), 12 , 13 the acidic properties of zeolites are mainly assessed via bulk measurements, such as solid-state NMR, 14 X-ray absorption spectroscopy, 15 , 16 temperature-programmed desorption (TPD), and infra-red (IR) spectroscopy, of numerous probe molecules. 17 Very recent advances in scanning transmission X-ray microscopy (STXM) enabled mapping of Al coordination in 3D with ∼30 nm resolution. 18 , 19 Microspectroscopic methods that utilize probe molecules such as UV–Vis microscopy, 20 confocal fluorescence microscopy, 21 , 22 IR microscopy, 23 and coherent Raman spectroscopy, 24 − 26 provide essential chemical information about reactive acid sites; however, they do so with the limited, micrometer, resolution.…”

Section: Introductionmentioning

confidence: 99%

“…However, molecular transport, and therefore the reactivity, in purely microporous zeolite crystals is tremendously hindered by slow diffusion . Steaming of zeolites is the most preferred, simple, and cost-efficient industrial post-treatment method to shorten the effective diffusion pathways and enhance the accessibility of acid sites via the creation of mesopores. , During this process, dealumination of the zeolite takes place, which inevitably leads to a partial or a complete loss of Brønsted acidity. , While structural properties and the interconnection of micro- and mesopores can be studied with high-resolution scanning electron microscopy (HR-SEM) and transmission electron microscopy (TEM), , the acidic properties of zeolites are mainly assessed via bulk measurements, such as solid-state NMR, X-ray absorption spectroscopy, , temperature-programmed desorption (TPD), and infra-red (IR) spectroscopy, of numerous probe molecules . Very recent advances in scanning transmission X-ray microscopy (STXM) enabled mapping of Al coordination in 3D with ∼30 nm resolution. , Microspectroscopic methods that utilize probe molecules such as UV–Vis microscopy, confocal fluorescence microscopy, , IR microscopy, and coherent Raman spectroscopy, − provide essential chemical information about reactive acid sites; however, they do so with the limited, micrometer, resolution.…”

Section: Introductionmentioning

confidence: 99%

Quantitative 3D Fluorescence Imaging of Single Catalytic Turnovers Reveals Spatiotemporal Gradients in Reactivity of Zeolite H-ZSM-5 Crystals upon Steaming

et al. 2015

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Optimizing the number, distribution, and accessibility of Brønsted acid sites in zeolite-based catalysts is of a paramount importance to further improve their catalytic performance. However, it remains challenging to measure real-time changes in reactivity of single zeolite catalyst particles by ensemble-averaging characterization methods. In this work, a detailed 3D single molecule, single turnover sensitive fluorescence microscopy study is presented to quantify the reactivity of Brønsted acid sites in zeolite H-ZSM-5 crystals upon steaming. This approach, in combination with the oligomerization of furfuryl alcohol as a probe reaction, allowed the stochastic behavior of single catalytic turnovers and temporally resolved turnover frequencies of zeolite domains smaller than the diffraction limited resolution to be investigated with great precision. It was found that the single turnover kinetics of the parent zeolite crystal proceeds with significant spatial differences in turnover frequencies on the nanoscale and noncorrelated temporal fluctuations. Mild steaming of zeolite H-ZSM-5 crystals at 500 °C led to an enhanced surface reactivity, with up to 4 times higher local turnover rates than those of the parent H-ZSM-5 crystals, and revealed remarkable heterogeneities in surface reactivity. In strong contrast, severe steaming at 700 °C significantly dealuminated the zeolite H-ZSM-5 material, leading to a 460 times lower turnover rate. The differences in measured turnover activities are explained by changes in the 3D aluminum distribution due to migration of extraframework Al-species and their subsequent effect on pore accessibility, as corroborated by time-of-flight secondary ion mass spectrometry (TOF-SIMS) sputter depth profiling data.

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Characterization of Solid Catalysts: Sections 3.2.3 – 3.2.4

Cited by 4 publications

References 547 publications

Dehydration of 1-Octadecanol over H-BEA: A Combined Experimental and Computational Study

Dehydration of 1-Octadecanol over H-BEA: A Combined Experimental and Computational Study

Ru₁Co_n Single-Atom Alloy for Enhancing Fischer–Tropsch Synthesis

Quantitative 3D Fluorescence Imaging of Single Catalytic Turnovers Reveals Spatiotemporal Gradients in Reactivity of Zeolite H-ZSM-5 Crystals upon Steaming

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Characterization of Solid Catalysts: Sections 3.2.3 – 3.2.4

Cited by 4 publications

References 547 publications

Dehydration of 1-Octadecanol over H-BEA: A Combined Experimental and Computational Study

Dehydration of 1-Octadecanol over H-BEA: A Combined Experimental and Computational Study

Ru1Con Single-Atom Alloy for Enhancing Fischer–Tropsch Synthesis

Quantitative 3D Fluorescence Imaging of Single Catalytic Turnovers Reveals Spatiotemporal Gradients in Reactivity of Zeolite H-ZSM-5 Crystals upon Steaming

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Ru₁Co_n Single-Atom Alloy for Enhancing Fischer–Tropsch Synthesis