Cumene cracking activity

Kerr, Plank, and Rosinski reported the preparation and catalytic properties of aluminum-deficient zeolite Y materials 35). Topchieva and co-workers studied the catalytic properties of cationic forms of aluminum-deficient Y zeolites, the aluminum deficiency being effected by the H4EDTA method 36-40). They found that up to 50% aluminum removal increased both stability and cumene cracking activity maximum activity was observed at the 50% removal level. Increased catalytic cracking activity was observed by Eberly and Kimberlin for mordenites from which about 80% aluminum had been removed (. 1). Weiss et al. removed over 99% of the aluminum from a hydrogen mordenite and found the zeolite retained catalytic activity of the type induced by Bronsted acids 42). Although the initial activity of this material was lower than that of more aluminum-rich mordenites, the aging rate was markedly reduced, and in a relatively short time the aluminum-deficient catalyst was the most active. 

Fluoride addition promotes the cracking (108-110) and isomerization (108, 111) activity of alumina, presumably, because of the formation of Brdnsted acid sites. In a comprehensive study of fluorided aluminas, Antipina et al. (110) demonstrated that there is a close parallelism between generation of cumene cracking activity at 430°C and surface acidity when fluoride content is increased from 0 to 7% wt (see Fig. 15). Acidity was measured by n-butylamine titration endpoints were determined by means of an arylcarbinol indicator that detected Br0nsted acids stronger than those corresponding to a pKa of — 13.3. In a separate article (112), Anti-... 

Fig. 15. Dependence of cumene cracking activity and Br0nsted acidity on fluorine content in samples of fluorided alumina U10).

In order to distinguish clearly between the contributions of Lewis and Br0nsted acid sites to the cumene cracking activity of H—Y zeolite, a method of selective poisoning was applied by Jacobs and Heylen (44). As was shown previously (54), 2,6-dimethylpyridine (DMPy) selectively ad-... 

Fig. 23. Relation between cumene cracking activity and acidic hydroxyl concentration (169).

Initial Cumene Cracking Activity per Active Site of H—Y Zeolite (169) (% Conversion per... 

Topchieva and T Huoang (204) reported a similar dependence of cumene cracking activity on the framework aluminum content. They observed a maximum in catalytic activity in dealuminated samples with Si02 Al203 molar ratio of 8, which corresponds to about 33 aluminum atoms per unit cell. Further removal of aluminum resulted in a decrease in activity. 

Brpnsted Acidity and Cumene Cracking Activity of Y Zeolite"... 

Cumene Cracking Activity. Portions of each of the first five separated fractions were regenerated and subjected to cumene cracking investigations in order to determine relative acidity and coke selectivity trends. The catalyst within the... 

Nevertheless, Hambleton and Hockey21 were still able to conclude that the hydrolyzed AlMej catalyst exhibited a cumene cracking activity that was comparable to industrial cracking catalysts. Moreover, these new catalysts showed a much less tendency for carbonization during the cumene cracking process. 

The cumene cracking activities over zeolites with different amounts of pyridine, quinoline and aniline adsorption were studied. The reaction rate data of cumene cracking were treated by linearization of eq. (11) as follows ... 

On the basis of the poisoning studies, the number of active sites of the catalyst were 1.63 x 10 per gram obtained from pyridine poisoning and cumene cracking reaction at 300°C. This number is close to the number reported by Jacobs and Heylen (13) in the study of poisoning with 2,6-methylpyridine of cumene cracking activity of the HY zeolites. 

Figure 5. Effect of temperature on cumene cracking activity of Sm faujasites (0.43 W/hr/W)...

The various rare earth faujasites were calcined at 538°C and then tested for cumene cracking activity. Conversion levels are plotted in Figure 6. HY is superior to the rare earth forms. With the exception of La, Eu, and Yb, the rare earths generally give conversions in the 15-25% range. 

Figure 7. Cumene cracking activity vs. irreversible Bronsted acidity...

Although for a different reaction, the cracking of cumene, a similar difference in behavior was found by Traynard and Orsini (94) for two silica-aluminas of different purities. After bombardment to about 2 X IQi nvt (fast) the purer of the two was less active after irradiation than before (ratio = ca. 0.3) while the less pure was more active (ratio = ca. 2). When the principal impurities of the second (Zn and V) were added to the first, the irradiated sample was then more active (ratio = ca. 1.7). A very pure silica, irradiated to 8 x lO nvt, showed no measurable cumene cracking activity, although there was evidence (discoloration) of some reaction of cumene with the catalyst (10). 

Ri and R2 could be alkyl groups. The electron-deficient carbon atom of a C—H bond so polarized could then serve as the active center for reactions of the carbonium ion type complete cleavage of the C—H bond is not required. The Linde workers were unable to correlate zeolite hydrogen content with hexane isomerization activity (40) nor did they attribute the great rise in cumene cracking activity (48) obtained by replacing univalent cations with bivalent cations in zeolite Y as arising... 

Figure 4 Cumene cracking activity (mmol.h Vm ) and dispersion capacity of M0O3 as determined by XRD (iimol.m ) as a fimction of sample type.

The studies of Mills, Boedeker, and Oblad (2) on the chemisorption of the inhibition quinoline on similar catalysts can be used to place an upper limit on the value of Bo. Their data show that 1.27 X quinoline mole-cules/sq. m. are required to reduce the cumene cracking activity to essentially zero. 

The influence of pH value in the solution on the realumination process of BEA zeolite was investigated by mean of nitrogen adsorption, XRD, A1 MAS NMR and FT-IR. It was found that non-framework aluminum species (octahedrally coordinated aluminums) in the solution are easily reinserted into the framework of dealuminated BEA zeolite by controlling the pH value of the solution below 7. The cumene cracking activity of the realuminated BEA zeolite at pH 5.1 was comparable to that of the parent BEA zeolite. The influence of aluminum species in the solution on the realumination process was also investigated using various aluminum compounds. 

Since Ca belongs to Group 5 cations like La, but is less susceptible to hydrolysis than is La the cumene cracking activities of Ca -PTSM catalysts were measured and are shown in Figure 14-3 as a function of the calc. 1 temperature. When the catalyst is dried at 60 C as calc. 1, the cumene... 

Figure 14-3. Effect of the temperature of calc. 1 on cumene cracking activity of Ca -PTSM. Reaction temp.= 300 C, W/F= 33 g-cat. h/mol, flow rate of carrier gas= 600 ml/h.

TABLE 14-2 Cumene Cracking Activity of Ca -modified Pillared Clays... 

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