IR spectroscopic reinvestigation of the generation of acid sites in Pt-containing faujasite zeolites

Bakó, Imre; Hannus, I.; Kiricsi, Imre

doi:10.1016/s0022-2860(02)00654-3

Cited by 16 publications

(13 citation statements)

References 5 publications

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“…2a), peaking at 8 nm and ranging from 2 to 20 nm. As expected for the impregnation method, many particles should be located outside the zeolite crystal in agreement with a previous report [39].…”

Section: à3supporting

confidence: 92%

“…± 0.55 nm. Similar results have been observed earlier via EXAFS [38,39] and also have been assigned to intracrystalline Pt clusters at locally destroyed lattice spots.…”

Section: à3supporting

confidence: 90%

“…According to the authors, this observation is related to the presence of additional potassium species in the pores of the impregnated zeolite, which would hinder the migration of platinum to form larger particles. However, in Pt/Na-Y catalysts, ion-exchange has been reported to lead to smaller Pt clusters, located in the pores of the zeolite, while impregnation gave large Pt clusters agglomerated on the outer surface [39]. The ZSM-5 sample loaded via CIE (entry 3, Table 5) shows the highest Pt dispersion and hence the smallest Pt particles.…”

Section: Ie and Cie)mentioning

confidence: 99%

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Selectivity in sorption and hydrogenation of methyl oleate and elaidate on MFI zeolites

Philippaerts

Paulussen

Turner

et al. 2010

Journal of Catalysis

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a b s t r a c tDifferent zeolites were tested for selective removal of methyl elaidate (trans isomer) from an equimolar mixture with methyl oleate (cis isomer). Sorption experiments of the geometric isomers show that only ZSM-5 samples with reduced Al content in the framework are able to discriminate among the bent cis and the linear trans fatty acid methyl esters. Hydrogenation experiments of equimolar methyl oleate and elaidate mixtures at low temperature (65°C) and high hydrogen pressure (6.0 MPa), using Pt catalysts, confirm this result. Only with a Pt/Na-ZSM-5 catalyst outspoken selectivity for the hydrogenation of the trans isomer is obtained. In order to prepare a selective Pt/ZSM-5 catalyst, the influence of Pt addition (impregnation, ion-exchange and competitive ion-exchange) and Pt activation (different calcination and reduction temperatures) on the Pt-distribution and Pt particle size was investigated using SEM, bright-field and HR TEM, EDX, electron tomography, CO-chemisorption, XPS, XRD, and UV-vis measurements. The best result in terms of hydrogenation activity and selectivity is obtained with a Pt/ZSM-5 catalyst, which is prepared via competitive ion-exchange, followed by slow calcination up to 350°C under high O 2 flow and a reduction up to 500°C under H 2 . This preparation method leads to a Pt/ZSM-5 catalyst with the best Pt distribution and the smallest Pt clusters occluded in the zeolite structure. Finally, the influence of zeolite crystal size, morphology, and elemental composition of ZSM-5 on hydrogenation activity and selectivity was investigated in detail.

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Section: à3supporting

confidence: 92%

“…± 0.55 nm. Similar results have been observed earlier via EXAFS [38,39] and also have been assigned to intracrystalline Pt clusters at locally destroyed lattice spots.…”

Section: à3supporting

confidence: 90%

Section: Ie and Cie)mentioning

confidence: 99%

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Selectivity in sorption and hydrogenation of methyl oleate and elaidate on MFI zeolites

Philippaerts

Paulussen

Turner

et al. 2010

Journal of Catalysis

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“…The Pt and Co peaks were not distinguishable in the low-load membrane with 15 min of ion exchange time (denoted as M15) due to the minimal quantity and highly dispersed state of metals. In the high-load membrane (24 h of ion exchange time), the diffraction peaks of Y zeolite disappeared as also observed in the literature [15]. There were broad peaks of Pt but no well-defined diffraction peaks of cobalt found for the high-load membrane (figure 2).…”

Section: Catalytic Membrane Synthesis and Characterizationsupporting

confidence: 79%

A platinum–cobalt-loaded NaY zeolite membrane for nonoxidative conversion of methane to higher hydrocarbons and hydrogen

Zhang

Dong

et al. 2005

Catal Lett

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Platinum-Cobalt-loaded NaY zeolite (Pt-Co/NaY) membranes were synthesized for continuous, single-step nonoxidative conversion of methane to higher hydrocarbons (C 2+ ) and hydrogen. During isothermal operation at 300°C, CH 4 flowed on the feed side of the membrane whilst H 2 flowed through the sweep side of the membrane. The C 2+ products formed continuously on the H 2 sweep side. The results indicate that the Pt-Co/NaY catalytic membrane can overcome the two-step limitation for nonoxidative CH 4 conversion.

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“…NaY-FAU (Union Carbide product) was used as the parent zeolite of the faujasite catalysts with Na58Al58Si134O384 unit cell composition (Si/Al = 2.3). NaY zeolite was impregnated with [Pt(NH3)4]Cl2 solution and conventional ion exchange was carried out in [Pd(NH3)4]Cl2 and [Pt(NH3)4]Cl2 solutions, respectively 12) . IR spectroscopic self-supporting wafer technique was used for acidity, adsorption and catalytic measurements.…”

Section: Methodsmentioning

confidence: 99%

Hydrodechlorination over Zeolite Supported Catalysts—Clarification of Reaction Mechanism—

Hannus

Halász

2006

J. Jpn. Petrol. Inst.

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Chlorinated compounds emitted into the atmosphere are responsible for the current thinning and shrinking of the ozone layer in the stratosphere. Two main potential methods have been suggested for their transformation: oxidative destruction to form environmentally safe products or hydrodechlorination to form potentially valuable chemical compounds. In this review, performances of halogenated compounds over the zeolites and the noble metal-containing zeolite catalysts are characterized by different spectroscopic methods (IR, NMR, etc.) to clarify the reaction mechanism of hydrodechlorination over the catalysts. NMR studies provided evidence that chlorofl uorocarbon reacts more aggressively with zeolites at elevated temperatures. The extent and nature of reaction depended on the zeolite type and the exchanged cation. Infrared spectra of the gas phase showed that HCl, CO2 and COCl2 were detected as the reaction products in the hydrodechlorination reaction of CCl2F2 over HY. The phosgene intermediate is believed to be the key to the structural damage of the zeolite. Pt-containing zeolite catalyst was more active in the hydrodechlorination of carbon tetrachloride than the Pd-containing catalyst, and beside the main products (methane and HCl) chloroform as intermediate product was formed. On Pd-containing zeolite no chloroform, but high amounts of ethane as fi nal products together with methane were formed. The activity and selectivity of the hydrodechlorination reaction of various chlorine-containing compounds (C1, C2, with and without fl uorine content) on different metal-containing zeolites of various types is summarized.

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IR spectroscopic reinvestigation of the generation of acid sites in Pt-containing faujasite zeolites

Cited by 16 publications

References 5 publications

Selectivity in sorption and hydrogenation of methyl oleate and elaidate on MFI zeolites

Selectivity in sorption and hydrogenation of methyl oleate and elaidate on MFI zeolites

A platinum–cobalt-loaded NaY zeolite membrane for nonoxidative conversion of methane to higher hydrocarbons and hydrogen

Hydrodechlorination over Zeolite Supported Catalysts—Clarification of Reaction Mechanism—

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