Zeolite TON

Nature of active sites in the Fe-TON Zeolites Mossbauer and IR studies... 

XL30). Mossbauer spectroscopy (KFKIj was applied to follow the state of Fe species in the zeolites. Carbon monoxide and ammonia adsorption (monitored with FTIR) (EQUINOX 55) was used to determine the nature, concentration and acid strength of the active sites in the Fe-TON zeolites. 

Low temperature CO sorption experiments monitored with the IR spectroscopy were used to determine the nature of active (acid) sites present in the Fe-TON zeolites. It is well known that CO is a useful probe molecule for Lewis acid sites. Narrow and well resolved bands appear in the region 2135 - 2150 cm"1. The IR spectra of CO sorbed in amount sufficient to cover all Lewis sites in the Fe-TON of different Si/Fe ratios are presented in Figure 2A. The samples of a high iron content (Si/Fe=27, 36) showed a significantly lower thermal stability. The activation of the NFL form of these Fe-TON... 

Figure 2. (A) IR spectra of CO adsorbed on the Fe-TON zeolites of different Si/Fe ratio at very low CO coverage required for the detection of the Lewis sites., (B) Difference spectra of CO adsorbed on Fe-TON of different Si/Fe ratio recorded upon the saturation of all Bronsted sites.

Aromatization activity of gallium containing MEl and TON zeolite catalysts in n-butane conversion effects of gallium and reaction conditions. Appl. Catal. A, 316, 61-67. 

In the last years a great interest was paid to the catalytic properties of iron-containing zeolites that show interesting activities in different industrial reactions. The Fe-BEA zeolite is reported to be a good catalyst in the vapour phase alkylation processes [1], the Fe-TON zeolite shows very high activity and selectivity in the olefin isomerization [2, 3]. Finally, new applications of zeolitic catalysts in the partial oxidation catalysis, such as the Solatia Inc. processes for benzene hydroxylation to phenol using Fe-MFI, open a novel route for the use of zeolites in oxidation processes [4, 5]. On the other hand, the catalytic properties of the metal-modified MOR type zeolite in the isomerization process are well known. 

More recently (428), the bands responsible for dimeric structures were identified for a sample of TON zeolite, as labeled in Figure 2.34. 

Fe-TON (Fe-ZSM-22) zeolites of different Si/Fe ratios (27, 36, 50, and 150) were synthesized hydrothermally using 1-ethylpirydinium bromide (EtPBr) as template. The syntheses were carried out following the procedure reported in Ref [7]. The molar composition of gels used for the syntheses was ... 

Irrespectively of the iron content, the applied synthesis procedure yielded highly crystalline microporous products i.e. the Fe-ZSM-22 zeolite. No contamination with other microporous phases or unreacted amorphous material was detected. The SEM analysis revealed that size and morphology of the crystals depended on the Si/Fe ratio. The ZSM-22 samples poor in Fe (Si/Fe=150) consisted of rice-like isolated crystals up to 5 p. On the other hand the preparation with a high iron content (Fe=27, 36) consisted of agglomerates of very small (<0.5 p) poorly defined crystals. The incorporation of Fe3+ into the framework positions was confirmed by XRD - an increase of the unit cell parameters with the increase in the number of the Fe atoms introduced into the framework was observed, and by IR - the Si-OH-Fe band at 3620 cm 1 appeared in the spectra of activated Fe-TON samples. 

High-resolution EM also showed that the synthetic zeolitic catalyst ZSM-23 (MTT) is a recurrently twinned version of the synthetic zeolite theta-1 (TON) (51). It is noteworthy that the elucidation of the structures of zeolite beta, for a long time an enigma and problematic for X-ray crystallographers, came only through the application of HRTEM (50). 

Often the ratio of Henry coefficients, related to adsorption at zero loading, is used for predicting the selectivity of adsorption for mixtures. The ratio of Henry coefficients for linear and mono-branched alkanes with carbon number n = 5-8 are summarized for various zeolites in Figure 13.10 [15]. The Henry coefficient ratios were 1 for FAU, 2 for BEA, MOR and MFI, 6-9 for TON and 10-14 for MTT. Interestingly, CBMC simulations suggest that the ratio of Henry coefficients, actu-... 

Octadecane hydroprocessing behavior of Pt-containing bifunctional catalysts with TON and MTT framework types was compared, as illustrated in Figure 13.31 [28]. While the two zeolitic catalysts showed similar activities, the selectivity vs conversion performances were different. At any given conversion, the selectivity to dibranched isomers was lower and the selectivity to mono-branched isomers... 

BEA (Si/Al2 = 30), FAU (Si/Al2 = 8.6) and EMT (Si/Afi = 8.6) framework types were compared for i-butane/2-butylene alkylation. During the lifetime of the catalyst the butylene turnover number (TON) was approximately the same for each of the three zeolites and the acid sites were equivalent from the standpoint of stability in each case. With EMT the lowered selectivity to consecutive reaction products 2,2,4-TMP -I- 2,3,4-TMP relative to 2,2,3-TMP -i- 2,3,3-TMP and the lowered selectivity to heavies relative to BEA was interpreted as higher hydride transfer activity. 

Pieterse, J.A.Z., Veefkind-Reyes, S., Seshan, K and Lercher, J.A. (2000) Sorption and ordering of dibranched alkanes on medium-pore zeolites ferrierite and TON. /. Phys. Chem. B, 104 (24), 5715-5723. 

The distribution of isomers formed as a result of this reaction tends to be higher in OX at the expense of PX, so catalysis through this route is less desirable from an industrial perspective. Comparisons of the monomolecular versus bimolecular reaction have been made, providing insight into the properties of zeolitic catalysts that favor one route over the other [64, 65]. Mechanistic aspects in MOR and TON structure zeolites have been evaluated using ah initio calculations, which suggest that the initiation step involves a defect site rather than an acidic proton [66]. It is... 

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