Zeolite CoNaY

Transmission geometry has been exclusively applied to the investigation of zeolites. Sendoda et al. (1975) compared transmission and reflection spectra and reported good agreement, except that the transmission mode gave "more intense bands". Forster et al. (1983) compared their transmission spectra of CoNaY to reflection spectra in the literature and claimed that the former are of at least equal quality. 

A 129-Xe NMR study of the - Xe interactions in partially exchanged CoNaY zeolites influence of the hydration level. 

Flexible ligand method. 0.9 g of 1,2-phenylenediamine were slowly added with stirring to 2 g of salicylaldehyde. After 10 minutes stirring, the mixture was allowed to cool down and the product was transferred to 40 mL of ethanol. The solids were filtered off, recrystallized from ethanol and dried in vacuo overnight. 1 g of CoNaY was mixed with 2 g salophen and heated in an open tube to 450 K with continuous stirring for 12 hours. The molten slurry was allowed to cool, and the zeolite was soxhiet extracted with methylene chloride. The solid material was dried in vacuo overnight. 

Catalysts. Co(N03)2-6H20 was of pure grade. CoNaY zeolite and tetra-n-butylammonium salts of PWiiCo and CoW 12 heteropolyanions were obtained as described in [19] and [25], respectively. The content of cobalt in the CoNaY zeolite was 3.29 % wt. The formation of the Keggin structure and the purity of C0W12 and PWuCo were confirmed by 0 and P NMR, respectively. 

We have studied efficiency of MNaY and MNaZSM-5 type zeolites with M= Co(II), Cu(II), Ni(n) and Fe(III) in aerobic epoxidation using /roras-stilbene as model substrate and isobutyraldehyde (IBA) as reductant. The results are summarized in Table 1. Trons-stilbene epoxide was found to be the main oxidation product, isobutyric add being the main product of transformation of IBA. Order of the catalytic activity of the metal ions introduced into NaY zeolites (Co > Cu Ni, Fe, NaY) is similar to that obtained previously for M-substituted heteropolytungstates [13]. Pronounced catalytic activity of CoNaY and NiNaY zeolites was earlier observed for co-oxidation of linear alkenes with acetaldehyde at 70°C [15]. The extents of ion exchange that can be attained for NaZSM-5 catalysts are less than those for NaY... 

As one can see from Table 1, catalytic activity of MNaY and MNaZSM-5 zeolites is not the same despite the same content of the transition metal. Activity of CoNaY is higher than that of CoNaZSM-5 at the same content of cobalt (respectively 100 and 42% stilbene conversion for... 

The zeolite catalysts were prepared by ion-exchange of NaY (Aldrich, Si/Al 2.7) with measured amounts of the relevent metal compounds (chromium acetate and cobalt nitrate). In a typical procedure 10 g of the zeolite was dispersed in 500 ml of dionized water. The metal salt solution was added dropwise to this vigorously stirred mixture, after which the mixture was stirred overnight, followed by filtering and drying of the material at 1(K) C. Chemical analysis of the samples (XRF) indicated the presence of 10 wt% Co in CoNaY-1 and 4 wt Cr in CrY. 

Uncatalyzed, this reaction has a induction period of approximately 24 h. The reaction can be catalyzed by CoNaY-zeolite, while adding certain Co and Mn complexes increase the decomposition of the peroxide to A-methylsuccinimide. The u.se of the CoNaY zeolite results in increased yield without any observed induction period. As will be discussed later, NMP appears to play a more important role than just as an initiator in the reaction with CrY. 

Cr-exchanged zeolite NaY is found to convert cyclohexene selectively to cyclohexen-1-one by oxidation with molecular oxygen, in contrast to an equivalent CoNaY system. The initiator, NMP, is found to play an important role in the transformation, both components being necessary to achieve the high selectivities observed. A reaction mechanism consistent with the experimental data is proposed. 

Early IR and UV-VIS spectroscopic studies on the formation of carbonium ions from triphenyl methyl compounds on zeolites, titania and alumina were carried out by Karge [111]. In 1979, upon interaction of olefins Hke ethene and propene with zeoHtes CoNaY, NiCaNaY, PdNaY and HY, the appearance of electronic bands between 230 and 700 nm was observed by Garbowski and PraHaud and attributed to an allylic carbenium ion which upon thermal treatment transforms into polyenyl carbenium ions and/or aromatic compounds [112]. These findings were corroborated and extended by studies of the interaction of propene, cyclopropane and frans-butene on zeoHtes NaCoY and HM [30]. In spite of the obscuration of the spectrum in the range between 450 and 700 nm by the threefold spHt d-d band of tetrahedraUy coordinated Co(II) ions in the case of zeoHte NaCoY,the development of bands near 330,385 and 415 nm was assigned to unsaturated carbocations. 

An example of xenon s ability to probe cation sites is the recent work on the charaeterization of CuHZSM-5 zeolites and CuSAPO-34moleeular sieves. Laser-indueed fluorescence indicated that there were at least two different sites in both of these zeolites, while Xe NMR showed that the copper ions were diamagnetie Cu, and not paramagnetic Cu ". This was evidenced by the monotonie inerease of the xenon chemical shift as a function of xenon pressure (see Curve 2 in Fig. 3). In constrast, paramagnetie ions typically cause a large inerease in the xenon ehemical shift at low pressure, sueh as in the case of CoNaY zeolite or Ni cations. ... 

The sulfidation of CoNaY was extensively studied by Vissenberg et al. [267-269]. In zeolites prepared by ion exchange an interaction exists between... 

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