Interaction of CO with platinum species in zeolites. Evidence for platinum carbonyls in partially reduced zeolite PtNaX

Bischoff, H.; Jaeger, N. I.; Schulz‐Ekloff, G.; Kubelková, Ludmila

doi:10.1016/0304-5102(93)87112-l

Cited by 62 publications

(33 citation statements)

References 27 publications

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“…In the carbonyl domain, the band of the linear CO increased in intensity and shifted from 2,021 cm -1 to 2,037 cm -1 , indicating a higher coverage, with a possible trend to polycarbonyl formation. The same trend was observed in the multi-bonding range with bands frequency shifting to 1,906 and 1,830 cm -1 [43][44][45]. Bands attributed to ethoxy species declined indicating their progressive conversion.…”

Section: Drift Surface Analysis On Rh 5 _alsupporting

confidence: 72%

Oxidative Steam Reforming of Ethanol over Ni–Cu/SiO2, Rh/Al2O3 and Ir/CeO2: Effect of Metal and Support on Reaction Mechanism

et al. 2008

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The effect of metal and support on ethanol oxidative steam reforming (OSR) has been investigated over a series of stable and active catalytic systems with noble (Rh or Ir) and non noble metal (Ni-Cu) supported over neutral (SiO 2 ), amphoteric (Al 2 O 3 ) or redox (CeO 2 ) supports. Ethanol decomposition and oxidative steam reforming was investigated by in situ diffuse reflectance infrared spectroscopy under temperature-programmed desorption and surface reaction conditions. Different mechanisms were established for these systems, from the initial steps of ethanol activation to the final equilibration of the decomposition products CO, CO 2 , H 2 and H 2 O. Various intermediates such as formates, acetates and/or carbonates were found to play different roles depending on the catalyst composition. The stability and activity of the investigated systems were finally assigned to specific features of these mechanisms.

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Section: Drift Surface Analysis On Rh 5 _alsupporting

confidence: 72%

Oxidative Steam Reforming of Ethanol over Ni–Cu/SiO2, Rh/Al2O3 and Ir/CeO2: Effect of Metal and Support on Reaction Mechanism

et al. 2008

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“…The corresponding bands were obtained from the adsorption of CO on the O 2 -treated Pt/HM catalysts ( Figures 5A, a, and 6A, a). Earlier studies 75,76 assigned similar bands to carbonyls of Pt 2+ ions. According to Chakarova et al, 73,74 the CO bands stem from two different Pt 3+ (CO) 2 species.…”

Section: Pt Oxidation Statementioning

confidence: 70%

Activation of Hydrogen and Hexane over Pt,H-Mordenite Hydroisomerization Catalysts

et al. 2009

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Various Pt species were shown to be present in Pt/H-mordenite catalyst preparations containing 1.5 and 2.6 wt % Pt. Air calcination of the catalyst precursor generated large Pt 0x metal particles (average size of >10 nm) by autoreduction, whereas a fraction of the platinum was converted to cations and oxycations, such as Pt 2+ and Pt 2 O 2+ , balancing negative charges on the zeolite framework. The results of temperature-programmed H 2 reduction (H 2 sTPR) suggested that Pt 2 O 2+ was reduced to Pt + below 550 K. The Pt n+ cations (n ) 1 or 2) became reduced to Pt 0 and Pt 0x above 550 K. Reduction was introduced by heterolytic H 2 dissociation, generating neutral platinum hydride and zeolite Brønsted acid sites, [PtsnH] 0 and H + . A similar platinum species, x[Pt 0 snH], was obtained from homolytic H 2 dissociation on Pt 0x . When H 2 was removed from the system, electrons were transferred from Pt 0 atoms or Pt 0x nanoparticles to the zeolite protons. When H 2 was released, acid sites were annihilated, and the highly dispersed metal again became the zeolite cation Pt n+ . The oxidation state and the chemical environment of the platinum were characterized by the vibrational spectra of chemisorbed CO. The spectral feature in the 2090-2100 cm -1 range, present in the spectrum of each H 2 -reduced catalyst, was shown to stem from two overlapping component bands. These bands were assigned to CO bound to Pt + and Pt 0 . The results confirm that the active surface intermediates of alkane hydroisomerization are platinum hydride/carbenium ion and platinum hydride/zeolite proton pair sites, such as [Pt 0 sH]/ZO -C n H 2n+1 + (species 1) and [Pt 0 sH]/ZO -H + (species 2) sites, in dynamic equilibrium with gas-phase alkane and H 2 . Hydrogen promotes release of the alkane from species 1 by generating species 2 (hydride transfer). If the rate of isomer formation is governed by the transformation rate of the carbenium ion, this suggested mechanism corresponds to kinetics that is first-order in hexane and negative-order in hydrogen. The large Pt 0x clusters were shown to catalyze the saturation of the eventually formed alkenes and, thereby, to suppress coke formation and catalyst deactivation.

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“…The band at 2126 cm −1 can be attributed to the valence vibrations of C≡O bonds in carbon monoxide molecules adsorbed linearly on Pt 2+ cations; the band at 2090 cm −1 , to ones adsorbed on platinum metal particles. The band at 1851 cm -1 can be attributed to a bridging adsorption form of CO on Pt 0 [18][19][20][21][22][23].…”

Section: Resultsmentioning

confidence: 99%

“…The band at 2364 cm −1 can be attributed to valence vibrations of C=O bonds in CO 2 molecules that form during the oxidation of CO on Ni 2+ cations [15,16]. The band at 2199 cm −1 was probably due to linear complexes of CO with the LASes of the carrier [15,16], [Pt 4+ (CO)Cl 5 ]ionic carbonyl remaining after the decomposition of platinum chloride [17], and linear carbonyl on Pt 4+ cations [16,[18][19][20][21][22][23]. The band at 2150 cm −1 can be attributed to the valence vibrations of C≡O bonds in carbon monoxide molecules adsorbed linearly on Pt 2+ cations; the band at 2098 cm −1 , to ones adsorbed on Pt + cations and/or large clusters of metallic platinum [15][16][17][18][19][20][21][22][23].…”

Section: Resultsmentioning

confidence: 99%

Studying the Stability of Supported Heteropoly Compounds Using Data from Diffuse Reflectance Infrared Spectroscopy

Ткаченко

Gazarov

Кustov

2021

Russ. J. Phys. Chem.

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Interaction of CO with platinum species in zeolites. Evidence for platinum carbonyls in partially reduced zeolite PtNaX

Cited by 62 publications

References 27 publications

Oxidative Steam Reforming of Ethanol over Ni–Cu/SiO2, Rh/Al2O3 and Ir/CeO2: Effect of Metal and Support on Reaction Mechanism

Oxidative Steam Reforming of Ethanol over Ni–Cu/SiO2, Rh/Al2O3 and Ir/CeO2: Effect of Metal and Support on Reaction Mechanism

Activation of Hydrogen and Hexane over Pt,H-Mordenite Hydroisomerization Catalysts

Studying the Stability of Supported Heteropoly Compounds Using Data from Diffuse Reflectance Infrared Spectroscopy

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