E zeolite

Figure 5. Top Adsorption isotherms of C02 for 1-en at the indicated temperatures. Bottom Adsorption-desorption cycling of C02 for 1-en showing reversible uptake from (a) simulated air (0.39 mbar C02 and 21% 02 balanced with N2) and from (b) simulated flue gas (0.15 bar C02 balanced with N2). (c) time-dependent C02 adsorption for porous materials (A = 1-en, B = mmen-Mg2(dobpdc), C = 1, D = Mg-MOF-74, E = Zeolite 13X, F = MOF-5). (d) C02 adsorption ratio of 1-en in flue gas (after 6 min exposure to 100% RH at 21 °C) to 1-en in flue gas (Adapted from [192]).

FIGURE 6.7. Catalytic conversion of 1-butene in the alkylation of isobutane with 1-butene (at a mol ratio of 12 1) versus reaction time over various catalysts (1 g each) JML-I50 (A) JML-I50 regenerated five times by calcination and sulphation (B) SZ(C) SZ/Si02 (Zr/Si = 50/100, mol/mol) (D) zeolite Beta (Si02/Al203 = 40) (E) zeolite ZSM-5 (Si02/Al203 = 40) (F). 

Senderov, E. E., Khitarov, N. E., Zeolites, Their Synthesis and Conditions of Formation in Nature, Nauka Publishing House, Moscow, 1970. 

From a mechanistic viewpoint it is worth noting that the TS-1 catalyst contains the same chemical elements in roughly the same proportions as the Shell amorphous TiIV/Si02 catalyst referred to earlier. However, the former displays a much broader range of activities than the latter. A possible explanation may be that the TS-1 catalyst contains more (or more active) isolated titanyl centres than the amorphous Ti1v/Si02. Based on the quite remarkable results obtained with TS-1 we expect many more examples of redox zeolites, i.e. zeolites, alpos, etc. modified by isomorphous substitution with redox metal ions in the crystal lattice, as selective oxidation catalysts.66... 

Figure 3. Binary phase masks of equilibrium VGO catalyst images. a) particle location mask b) Si/Al intensity ratio c) high Si/Al ratio mask d) high lanthanum mask e) zeolite mask (logical AND of c d)...

From Table V, the zeolite anion is more electronegative than F. Also shown in Table V are the electron occupancies in the 5s orbital of the Ag+ that is bonded to the anion. For a perfect anion, the Ag+ to which it is bonded should have an empty 5s orbital. Again, it is seen that Ag+ in AgZ has the lowest occupancy in its 5s orbital, indicating that the Z (i.e., zeolite framework anion) is the most electronegative anion. 

The metastable form which preferentially crystallizes could then transform to a more stable phase (i.e. zeolite Y - zeolite X or zeolite A - hydroxysodalite). Nucleation and growth rates would then become the limiting factors in determining how long this would take. For example, when synthesis conditions are chosen to produce zeolite A, the rate of hydroxysodalite formation is dependent on five variables. These variables and their effect on the conversion of zeolite A to hydroxysodalite are as follows ... 

One of the most significant stages in the development of zeolite catalysts was the synthesis by Mobil scientists (U.S. Patent 3,702, 866) of the zeolite now universally known as ZSM-5 (i.e. Zeolite Socony Mobil-5). This was the first - and most important - member of a new class of shape selective catalysts, which have made viable the production of synthetic gasoline . In this process, high-octane gasoline is produced by the catalytic conversion of methanol to a mixture of aromatic and aliphatic hydrocarbons (Derouane, 1980). Because of its unique combination of chemical nature and pore structure, ZSM-5 is a highly effective dehydration, isomerization and polymerization catalyst. 

Aluminum. Previous Al NMR studies have demonstrated four possible local environments for Al in SAPO materials (3,4). These environments are illustrated in Figure 3, and may be classified as either phosphorous rich (i.e., ALPO -like) with a chemical shift ranging from 30 to 40 ppm, or silicon rich (i.e., zeolite-like) with a chemical shift greater than 48 ppm. Both types of environments are characteristic of a substitution mechanism involving silicon substitution for phosphorus. A fifth possibility for an Al environment involves two Si and two P second nearest neighbors. However, no such environment has yet been identified by NMR, either because the Al chemical shift is similar to that for the silicon- or phosporous-rich environments, or because materials with an appropriate level of Si to give rise to... 

However this is compensated by the temperature increase. At the second stage T — 633 K) the two systems with the lowest zeolite amounts, i.e. zeolite-to-polymer ratio of 1 3 and 1 4, form the highest liquid fraction amount. At the third stage T = 673 K) the degradation had been already completed for all systems. Minimal liquid amounts were formed. 

During the last decade, there have been several published accounts on using adsorption for liquid fuel desulfurization. Commercially available sorbents (i.e., zeolites, activated carbon and activated alumina) were used in all of these studies. Weitkamp et al. 

Figure t. Framework structures of the most commonly studied zeolitic structures (a) zeolite A (b) zeolite X/Y (c) mordenite (d) Z5M-5 (e) zeolite L. 

Our experiments on the blocking of adsorption centers (i.e., zeolite cations) by preadsorbed water molecules serve to substantiate the physical meaning of Equation 9. For the adsorption of carbon dioxide on dehydrated crystals of zeolite NaX, 0 = 3470 cal/mole, n = 3, Goh = 2.90 mmole/gram, and 3 = 5200 cal/mole, the second term of Equation 9 expressing adsorption on active centers, which amount to 2.90 mmole/ gram. Water is adsorbed energetically on active centers (n = 4, 4 = 9150 cal/mole), and as a result of preadsorption of 3.5 mmole/gram of... 

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