TON framework

For propane, n-pentane and n-hexane the differential heats of adsorption over FER dropped more rapidly, right after 1 molecule was adsorbed per Bronsted acid site. Similar results were obtained with TON. In contrast, with MOR and FAU the drop in the differential heats of adsorption for n-alkanes occurred at lower coverages, indicating that only a certain fraction of the Bronsted acid sites were accessible to the adsorbing alkane probe molecules. With MFI the drop did not occur until 2 molecules of n-alkane were adsorbed per Bronsted acid site, suggesting perhaps a higher stoichiometry of about two n-alkanes per Bronsted acid site. In the cases of i-butane and i-pentane the drop occurred around one alkane per Bronsted acid site. Finally, n-butane adsorption isotherms measured over TON framework type catalysts having three different A1 contents (Si/Al2 = 90, 104, 128) showed Henry coefficients to increase with increase in the A1 content [5], Based... 

Figure 13.17 Optimized adsorption structure of 2,2-dimethylhexane over TON framework type, (a) methyl group penetrating the pore mouth (18kJ/mol). (b) longer hydrocarbon chain penetrating the pore mouth (65k)/mol) [42].

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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. 

For various alkanes over TON, MFI, MOR and FAU framework types the entropy of adsorption was calculated based on the measured values for the adsorption equilibrium constant and for the heat of adsorption. Figure 13.13 indicates that each time a linear relation is found between the entropy and the heat of adsorp-... 

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... 

Figure 13.31 Hydroprocessing octadecane 2% feed diluted with heptane) over biflinctional catalysts (contains Pt) with TON and MTT framework types at230°C, 450kPa, H2 HCBN = 13 and varying flow rates [28],...

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. 

Among other factors, the strength of the protons in zeolite depends on the framework A1 content, and should go toward a maximum around Si/Al = 10 (ref.20). Indeed, a volcano-shaped dependency between the rate and m = Al/(A1+Si) was reported for odCB isomerisation on HMOR, HBETA and HOFF (ref.7). Moreover, the nature of the zeolite influences the proton strength too. Table 3 reports the reaction rates and intrinsic activities, expressed as turnover number (TON), on various zeolites at a Si/Al content close to the optimum. The TON was calculated by dividing the rate by the proton concentration in the zeolite. 

Besides charge transfer interactions, dipolar coupling between ttk transitions of bases may lead to delocalization of the excited states. In order to obtain some guidelines for our experimental studies, we have undertaken the calculation of excited Frank-Condon states within the framework of the exci-ton theory [26]. These studies were enriched by combining data from quantum chemistry and molecular dynamics calculations in collaboration with Krystyna Zakrzewska and Richard Lavery [26,27,27-29]. The general formalism is described in the Chapter by E. Bittner and A. Czader in the present volume. 

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