Catalysis by crystalline aluminosilicates II. Molecular-shape selective reactions

Weisz, Paul B.; Frilette, V. J.; Maatman, Russell W.; Mower, E.B.

doi:10.1016/0021-9517(62)90058-1

Cited by 182 publications

(27 citation statements)

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“…Therefore, attention should also be focused towards the shape and dimensions of catalyst network, and also, the relative steric hindrance of the There have been a number of studies to understand the mechanism of shape selectivity of catalysts in hydroconversion of alkanes. The early findings by Weisz et al (359,360) and Csicsery (361,362) have intensified the studies of this phenomenon. Different assumptions used in developing the models have led to different interpretations of shape selectivity in the porous materials.…”

Section: Recent Advances and Future Aspects In N-alkanesmentioning

confidence: 92%

Recent Advances and Future Aspects in the Selective Isomerization of High n‐Alkanes

2007

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Section: Recent Advances and Future Aspects In N-alkanesmentioning

confidence: 92%

Recent Advances and Future Aspects in the Selective Isomerization of High n‐Alkanes

2007

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“…Mesoporous silica (MS, surface area 800 m 2 /g) was firstly functionalized by organosilane phenylaminopropyl-trimethoxysilane (PHAPTMS, Sigma-Aldrich, Saint Louis, MI, USA) at the molar ratio: SiO 2 :60H 2 O:x (x = 0, 0.065, 0.12, or 0.20) PHAPTMS:6CH 3 OH to obtain organo-functionalized mesoporous silica with a different silanization degree. In a typical organic-functionalization process, 10 g fumed silica was added into 350 mL of distilled water.…”

Section: Synthesismentioning

confidence: 99%

“…Besides, the catalytic properties of zeolite A were also paid attention. Selective dehydration of n-butanol in the presence of i-butanol and selective cracking of n-alkanes in the presence of branched alkanes over the CaA were early examples for the applications of zeolite LTA in catalytic reaction [3,4]. The high selectivity over CaA is attributed to the fact that only n-butanol and n-alkanes can penetrate into the pore system of the zeolite, while branched reactants cannot.…”

Section: Introductionmentioning

confidence: 99%

A Hierarchically Micro-Meso-Macroporous Zeolite CaA for Methanol Conversion to Dimethyl Ether

et al. 2016

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Abstract:A hierarchical zeolite CaA with microporous, mesoporous and macroporous structure was hydrothermally synthesized by a "Bond-Blocking" method using organo-functionalized mesoporous silica (MS) as a silica source. The characterization by XRD, SEM/TEM and N 2 adsorption/desorption techniques showed that the prepared material had well-crystalline zeolite Linde Type A (LTA) topological structure, microspherical particle morphologies, and hierarchically intracrystalline micro-meso-macropores structure. With the Bond-Blocking principle, the external surface area and macro-mesoporosity of the hierarchical zeolite CaA can be adjusted by varying the organo-functionalized degree of the mesoporous silica surface. Similarly, the distribution of the micro-meso-macroporous structure in the zeolite CaA can be controlled purposely. Compared with the conventional microporous zeolite CaA, the hierarchical zeolite CaA as a catalyst in the conversion of methanol to dimethyl ether (DME), exhibited complete DME selectivity and stable catalytic activity with high methanol conversion. The catalytic performances of the hierarchical zeolite CaA results clearly from the micro-meso-macroporous structure, improving diffusion properties, favoring the access to the active surface and avoiding secondary reactions (no hydrocarbon products were detected after 3 h of reaction).

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“…While the conventional ion exchange method works only for inserting metal ion precursors into larger pore zeolite such as zeolite Y, it is difficult to add metal precursors into the cavity of zeolite A due to the small pore size of NaA. So far, much effort has been devoted to introducing Pt into zeolite A by adding a platinum precursor to the synthesis mixture containing both Al and Si source [1,2]. Although preliminary results of chemisorption and shape-selective catalytic test have indicated that the platinum clusters located inside the larger cavity (α cage) of zeolite A [1,[3][4][5], the direct information on the location and distribution of Pt particles, and the microstructure of zeolite support after loading is still in shortage.…”

mentioning

confidence: 99%

TEM Study of Pt Cluster Incorporated Zeolite A

Shi¹,

Wang

Qian

et al. 2009

Microsc Microanal

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Zeolite supported noble metal catalysts provide simultaneously both hydrogenation active sites and acid sites for hydrocracking reaction, which have been widely used in petroleum hydroprocessing processes. The size, location and distribution of the metal particles, as well as the pore structure and crystallinity of the zeolite support are the key factors affecting the activity and selectivity of the catalyst. To enhance the activity and durability of the catalyst, it is of great importance to obtain highly dispersed noble metal clusters within zeolite support. It is of particular importance to introduce small metal particles into the confines of the zeolite micropores. While the conventional ion exchange method works only for inserting metal ion precursors into larger pore zeolite such as zeolite Y, it is difficult to add metal precursors into the cavity of zeolite A due to the small pore size of NaA. So far, much effort has been devoted to introducing Pt into zeolite A by adding a platinum precursor to the synthesis mixture containing both Al and Si source [1,2]. Although preliminary results of chemisorption and shape-selective catalytic test have indicated that the platinum clusters located inside the larger cavity (α cage) of zeolite A [1,3-5], the direct information on the location and distribution of Pt particles, and the microstructure of zeolite support after loading is still in shortage. Transmission electron microscopy (TEM) can provide insight into the structure (atomic/nanoscopic) , crystallography and chemical composition of solid catalysts. Our SEM and Xray diffraction (XRD) study has shown that both morphology and crystallinity of the synthesized zeolite changed when a platinum precursor was incorporated into the initial synthesis mixture (see Fig. 1) [5]. Here, we present the experimental results of the Pt nanoparticles and the microstructure of the aforementioned samples in TEM (JEOL 2200FS). To obtain ultrathin sections (~40 nm) of the zeolite catalysts, samples were first embedded in epoxy resin, and then microtomed and collected onto a carbon coated Cu-grid. Figure 2 presents the high angle annular dark field (HAADF) STEM image for the high Pt loaded sample, showing that very small (less than 2 nm) Pt particles are evenly distributed within the support. The diffraction rings can be attributed to Face Centered Cubic (FCC) platinum, and no obvious reflections from zeolite were observed. Figure 3 shows the STEM image taken from 0.69 wt% Pt loaded sample. Selected area electron diffraction (SAED) patterns recorded from different particles indicate that the large particles (μm scale in Fig. 1) are crystalline while the smaller ones with rough surfaces (see inset of Fig. 1b) are amorphous. The sharp diffraction rings originate from Pt. Electron Energy Loss Spectra (EELS) were also taken for local structural and chemical analysis. Figure 4 shows a comparison of EELS spectra of O-K edge between NaA and high Pt loaded sample after background subtraction and Fourier-ratio deconvolution [6]. The dramatic...

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Catalysis by crystalline aluminosilicates II. Molecular-shape selective reactions

Cited by 182 publications

References 1 publication

Recent Advances and Future Aspects in the Selective Isomerization of High n‐Alkanes

Recent Advances and Future Aspects in the Selective Isomerization of High n‐Alkanes

A Hierarchically Micro-Meso-Macroporous Zeolite CaA for Methanol Conversion to Dimethyl Ether

TEM Study of Pt Cluster Incorporated Zeolite A

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