Hydrocarbon Adsorption Characterization of Some High Silica Zeolites

Wu, E.; Landolt, G.R.; Chester, Arthur W.

doi:10.1016/s0167-2991(09)60918-6

Cited by 26 publications

(12 citation statements)

References 7 publications

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“…Unfortunately, data could not be recorded for ⁄ MRE (5.3 Â 5.6 Å), which has relatively large 10-ring channels. However, in a similar and more extensive study, Wu et al [78] investigated the uptake of several hydrocarbons in a range of zeolites. It was seen that ⁄ MRE behaved very similarly to TON (4.6 Â 5.7 Å).…”

Section: Of the Supplementarymentioning

confidence: 99%

Morphology-induced shape selectivity in zeolite catalysis

Teketel

Lundegaard

Skistad

et al. 2015

Journal of Catalysis

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a b s t r a c tZeolites are crystalline aluminosilicates that are widely used as shape-selective catalysts in the refinery and petrochemical industries. By synthesizing a series of structurally related zeolite catalyst and applying them in the industrially relevant conversion of methanol to hydrocarbons, new and extended understanding of the concept of shape selectivity has been reached. We have analyzed the relationship between particle morphology and pore system for catalysts having both small-and medium-sized pores using microscopy and diffraction, as well as performing extensive standard characterization. Two instances of preferential exposure of certain crystal facets, favoring access to one pore system over the other, have been found. Zeolites ZSM-57 (MFS) and SUZ-4 (SZR) both have both 8-and 10-ring channels. MFS prefers a plate-like or nanosheet-type morphology, where the 10-ring channels are perpendicular to the plates/sheets. This leads to favorable diffusion properties and a pronounced deactivation resistance. For SZR, needle-like crystals with high aspect ratio are preferred. In this instance, the sides of the needles are covered by the 8-ring pore openings, whereas the 10-ring pore openings are only exposed at the ends of the needles. This leads to unexpected product selectivity, as the material behaves essentially as an 8-ring catalyst. We argue that it should be possible to tune the shape selectivity of zeolite catalysts having pore systems of different dimensions by controlling the crystal morphology.

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Section: Of the Supplementarymentioning

confidence: 99%

Morphology-induced shape selectivity in zeolite catalysis

Teketel

Lundegaard

Skistad

et al. 2015

Journal of Catalysis

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“…However, it was found by several groups that ZIF-8 could accommodate larger molecules than it would be expected, based on the pore size calculated from crystallographic data; [23] a phenomenon that was already known from zeolites. [24] On the other hand, it was demonstrated that only the surface of ZIF-8 operated in the transesterification of large molecules.…”

Section: Oa C H T U N G T R E N N U N G (Ohfh 2 O) 3 -A C H T U N Gmentioning

confidence: 99%

Pyrazolate‐Based Cobalt(II)‐Containing Metal–Organic Frameworks in Heterogeneous Catalytic Oxidation Reactions: Elucidating the Role of Entatic States for Biomimetic Oxidation Processes

Tonigold

Mavrandonakis

et al. 2011

Chemistry A European J

141

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Crystal structures of two metal-organic frameworks (MFU-1 and MFU-2) are presented, both of which contain redox-active Co(II) centres coordinated by linear 1,4-bis[(3,5-dimethyl)pyrazol-4-yl] ligands. In contrast to many MOFs reported previously, these compounds show excellent stability against hydrolytic decomposition. Catalytic turnover is achieved in oxidation reactions by employing tert-butyl hydroperoxide and the solid catalysts are easily recovered from the reaction mixture. Whereas heterogeneous catalysis is unambiguously demonstrated for MFU-1, MFU-2 shows catalytic activity due to slow metal leaching, emphasising the need for a deeper understanding of structure-reactivity relationships in the future design of redox-active metal-organic frameworks. Mechanistic details for oxidation reactions employing tert-butyl hydroperoxide are studied by UV/Vis and IR spectroscopy and XRPD measurements. The catalytic process accompanying changes of redox states and structural changes were investigated by means of cobalt K-edge X-ray absorption spectroscopy. To probe the putative binding modes of molecular oxygen, the isosteric heats of adsorption of O(2) were determined and compared with models from DFT calculations. The stabilities of the frameworks in an oxygen atmosphere as a reactive gas were examined by temperature-programmed oxidation (TPO). Solution impregnation of MFU-1 with a co-catalyst (N-hydroxyphthalimide) led to NHPI@MFU-1, which oxidised a range of organic substrates under ambient conditions by employing molecular oxygen from air. The catalytic reaction involved a biomimetic reaction cascade based on free radicals. The concept of an entatic state of the cobalt centres is proposed and its relevance for sustained catalytic activity is briefly discussed.

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“…The solution of a dozen or more new zeolite structure types within the last several years has added to our knowledge base for looking at unknowns (for examples, see references [25][26][27][28][29][30][31], and has made us better able to characterize catalyst materials and to correlate synthesis, sorptive, catalytic, and process parameters to their structures (32,33).…”

Section: Xrd -Present and Futurementioning

confidence: 99%

Factors Affecting X-ray Diffraction Characteristics of Catalyst Materials

Rohrbaugh

1989

ACS Symposium Series

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X-ray diffraction (XRD) is a major tool employed to identify and characterize catalytic materials. A brief review of the diffraction phenomenon and the effect of crystallite size is presented.Appli cations of XRD to catalyst characterization are illustrated, including correlation of XRD powder patterns to molecular structural features, deter mination of Pt crystallite size and others. Factors that affect the appearance of XRD powder patterns, such as framework structure perturbations, extra framework material, crystal morphology, impurities, sample preparation, instrument configurations, and x-ray sources, are discussed.X-ray diffraction (XRD), in particular x-ray powder diffraction, has been used extensively to identify and characterize materials used as catalysts in the petroleum refining and petrochemical industries. This is not surprising, since many of the materials are crystalline; i.e., the atoms can be arranged in threedimensional periodic arrays. Every atom in a crystalline solid contributes to the observed XRD pattern, thus making the pattern characteristic of the material-a virtual fingerprint. The diffraction data obtained for catalytic materials can tell us many things about these materials, ranging from the structural nature of the crystalline components to the average Pt crystallite size on a supported-metal catalyst. It can be used to monitor and correlate molecular structural features to catalytic process and reaction variables, or to specify composition for patent definition. In short, XRD is an invaluable technique in catalyst research and development. This discussion will illustrate some of the applications of XRD to catalyst characterization and point out some of the factors that affect the appearance of x-ray powder diffraction patterns of these materials.

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Hydrocarbon Adsorption Characterization of Some High Silica Zeolites

Cited by 26 publications

References 7 publications

Morphology-induced shape selectivity in zeolite catalysis

Morphology-induced shape selectivity in zeolite catalysis

Pyrazolate‐Based Cobalt(II)‐Containing Metal–Organic Frameworks in Heterogeneous Catalytic Oxidation Reactions: Elucidating the Role of Entatic States for Biomimetic Oxidation Processes

Factors Affecting X-ray Diffraction Characteristics of Catalyst Materials

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