Topotactic Kinetics in Zeolite Nanoreaction Chambers

Ozin, Geoffrey A.; Özkâr, Saim; Pastore, Heloise O.; Poë, Anthony J.; Vichi, Eduardo J. S.

doi:10.1021/bk-1992-0499.ch022

Cited by 10 publications

(17 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Pooling the variances from all 61 rate constants leads to a value of 24%. Similar values were found when all the individual rate constants were used in Eyring analyses (Table 2), and previous studies [2][3][4]8 led to comparable values. This relatively low reproducibility is evidently a function of the nature of the zeolitic environment and should not be surprising.…”

Section: Discussionsupporting

confidence: 86%

“…This, and the direct formation of the subcarbonyl [Mo(CO) 3 ], coordinated by three neighboring oxide ions in the cavity walls, was taken to indicate that the rate determining step involved a concerted attack by those oxide ions on the carbon atoms of three fac CO ligands (Scheme 1). This conclusion differed from that previously reached [2][3][4] where interaction between the Na + ions and the oxygen atoms of the CO ligands was considered the source of activation. However, the same rate determining step, to form a common intermediate, was implied for the reactions of the undissociated [Mo(CO) 6 ] in which it became "anchored" within a "12-ring window" between two alpha cages in the zeolite by as many as six sodium ions.…”

Section: Introductioncontrasting

confidence: 85%

“…xH 2 O was donated to Professor Geoffrey Ozin (of the Chemistry Department at the University of Toronto -U. of T.) by Dr. Edith Flanigen, then at UOP, Tarrytown, NY, some years ago, and kindly passed on to us. [Mo(CO) 6 ] (Strem), carbon monoxide (BOC, grade 2.3) and the adduct (trimethylphosphine)silver iodide {(PMe 3 .AgI) 4 (Aldrich)} were used as received. The IR spectra were recorded with a Nicolet Magna 550 FTIR spectrophotometer.…”

Section: Chemicals and Instrumentsmentioning

confidence: 99%

“…The sample was then briefly heated under static vacuum to remove any residual [Mo(CO) 6 ] that had not become fully encapsulated within the zeolite. The (PMe 3 .AgI) 4 was then loaded into a side arm of the reaction cell in amounts that would lead eventually to complete saturation of the zeolite with chemisorbed PMe 3 , and with some physisorbed PMe 3 as well. The side arm was evacuated and opened up to the reaction cell so that PMe 3 could be loaded into the zeolite wafer by gentle heating of the adduct for ca.10 min.…”

Section: Kinetic Studiesmentioning

confidence: 99%

“…Preliminary studies of the reactions in other M 56 Y zeolites were also reported. 4 Apart from the detection 3 of what were essentially bimolecular substitution reactions with physisorbed PMe 3 , a very striking observation was the very low activation enthalpy of the CO exchange reaction which was offset, but not overcome, by a substantially unfavorable activation entropy. The combined effect was to accelerate the reactions by a factor of ~1000 at 66 C, compared with those in homogeneous solution or in the gas phase.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Zeolite activation of organometallics: revisiting substitution kinetics of [Mo(CO)6] with chemisorbed PMe3 in dehydrated Na56Y zeolite

Fernandez

Parkes

Poë

et al. 2008

J. Braz. Chem. Soc.

Self Cite

View full text Add to dashboard Cite

2 ] são produzidas sob CO. Reações sob vácuo exibem fatores entálpicos baixos e fatores entrópicos muito negativos ( H ‡ = 71,4 ± 3,5 kJ mol -1 and S ‡ = -102 ± 11 J K -1 mol -1 ), comparados com fatores entálpicos muito mais altos e fatores entrópicos positivos para reações de substituição dissociativa de CO por P(n-Bu) 3 em xileno observadas em outros trabalhos. A reação a 66 C sob vácuo é cerca de 10 3 vezes mais rápida do que reações dissociativas 'espontâneas'de CO em solução. Conclui-se que a substituição intrazeólito ocorre por um mecanismo "assistido por zeólito" em que dois íons óxidos nas paredes da cavidade deslocam simultaneamente dois ligantes CO vizinhos do [Mo(CO) 6 ]. Isso contrasta com valores de entalpia ainda menores e de entropia mais negativos para o deslocamento simultâneo de três ligantes CO vizinhos em reações de descarbonilação térmica. As cavidades comportam-se como ligantes "zeolato" aniônicos multidentados, com números variáveis de íons O 2-participando da criação de estados de transição altamente ordenados. Os resultados enfatizam o alto grau com que estes estudos cinéticos podem revelar detalhes íntimos da natureza dos efeitos ativadores. Reactions under vacuum exhibit low enthalpic and very negative entropic factors ( H ‡ = 71.4 ± 3.5 kJ mol -1 and S ‡ = -102 ± 11 J K -1 mol -1 ) compared with much higher enthalpic and positive entropic factors for CO dissociative reactions with P(n-Bu) 3 in xylene observed elsewhere. Reaction at 66 C under vacuum is ca.10 3 times faster than "spontaneous" CO dissociative reactions in solution. Intrazeolite substitution is concluded to occur by a "zeolite assisted" mechanism in which two oxide ions in the cavity walls simultaneously displace two neighbouring CO ligands from the [Mo (CO) 6 ]. This contrasts with even lower enthalpy, and more negative entropy values, for simultaneous displacement of three neighbouring CO ligands in thermal decarbonylation reactions. The -cages behave as multidentate anionic "zeolate" ligands with varying numbers of O 2-ions participating to create highly ordered transition states. These results emphasize the high degree to which such kinetic studies can reveal intimate details of the nature of these activating effects.Keywords: hexacarbonylmolybdenum(0), Na 56 Y zeolite, intrazeolite kinetics, PMe 3 substitution IntroductionThe catalytic effect of zeolite cavities on many chemical reactions has been well known for over 60 years. 1 However, it was not until much later 2-4 that the intrazeolite kinetics Fernandez et al. 863 Vol. 19, No. 5, 2008 of some simple stoichiometric reactions were reported, reactions that had previously been thoroughly studied in homogeneous solution and the gas phase. 5 136 ). Preliminary studies of the reactions in other M 56 Y zeolites were also reported. 4 Apart from the detection 3 of what were essentially bimolecular substitution reactions with physisorbed PMe 3 , a very striking observation was the very low activation enthalpy of the CO exchange reaction which was offset, b...

show abstract

Section: Discussionsupporting

confidence: 86%

Section: Introductioncontrasting

confidence: 85%

Section: Chemicals and Instrumentsmentioning

confidence: 99%

Section: Kinetic Studiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Zeolite activation of organometallics: revisiting substitution kinetics of [Mo(CO)6] with chemisorbed PMe3 in dehydrated Na56Y zeolite

Fernandez

Parkes

Poë

et al. 2008

J. Braz. Chem. Soc.

Self Cite

View full text Add to dashboard Cite

show abstract

Mesoporous inorganic solids

Behrens

1993

Advanced Materials

144

View full text Add to dashboard Cite

With pore sizes in the range of 20–500 Å mesoporous materials are of use for extending zeolite‐type chemistry, which is based on materials with a pore size of around 7 Å, to larger molecules. The pores can be produced by pillaring (the propping of layered materials) or by extending the template method used to produce zeolites. The new, ultra‐large‐pore materials recently presented by researchers from Mobil Oil Research are described and their production and application discussed

show abstract

Water‐soluble/dispersible cationic pressure‐sensitive adhesives. II. Adhesives from emulsion polymerization

Yan¹,

Luo

Deng³

et al. 2003

J of Applied Polymer Sci

View full text Add to dashboard Cite

ABSTRACT:In our previous work, we reported that cationic water-soluble pressure-sensitive adhesives (PSAs) could be synthesized in ethanol or methanol. These cationic water-soluble adhesives would not cause a stickies problem during paper recycling and can be easily removed from the papermaking system by adsorbing on wood fibers. In this study we report the synthesis and application of waterbased cationic PSAs using miniemulsion polymerization. A redox initiator system of cumene hydroperoxide/tetraethylenepentamine was used to force interfacial polymerization. The end-use properties of the PSAs were evaluated, and the repulpability of the PSAs in paper recycling was studied. It was found that the cationic PSA from miniemulsion polymerization itself was insoluble and nondispersible in water during the paper recycling process. However, if this waterinsoluble cationic PSA from miniemulsion was formulated with a water-soluble cationic PSA made from ethanol, the solubility or dispensability of the former PSA in water was improved. The molecular weight and degree of crosslinking of the PSA polymer have significant effects on the properties and dispersability of PSA.

show abstract

Topotactic Kinetics in Zeolite Nanoreaction Chambers

Cited by 10 publications

References 0 publications

Zeolite activation of organometallics: revisiting substitution kinetics of [Mo(CO)6] with chemisorbed PMe3 in dehydrated Na56Y zeolite

Zeolite activation of organometallics: revisiting substitution kinetics of [Mo(CO)6] with chemisorbed PMe3 in dehydrated Na56Y zeolite

Mesoporous inorganic solids

Water‐soluble/dispersible cationic pressure‐sensitive adhesives. II. Adhesives from emulsion polymerization

Contact Info

Product

Resources

About