Of sodium mordenite

Molecular sieve zeolites have become established as an area of scientific research and as commercial materials for use as sorbents and catalysts. Continuing studies on their synthesis, structure, and sorption properties will, undoubtedly, lead to broader application. In addition, crystalline zeolites offer one of the best vehicles for studying the fundamentals of heterogeneous catalysis. Several discoveries reported at this conference point toward new fields of investigation and potential commercial utility. These include phosphorus substitution into the silicon-aluminum framework, the structural modifications leading to ultrastable faujasite, and the catalytic properties of sodium mordenite. 

The high activity of sodium mordenite for catalyzing benzene hydrogenation as reported by Minachev et al. This result is so unique that additional investigation is warranted. 

T his paper reports the first syntheses of lithium mordenite, lithium A analeime, and lithium phillipsite. A systematic study of the system lithia—alumina-silica—water has been in progress for several years and has proven so far to be a unusually challenging system in which to determine phase relationships of the zeolite phases. In this preliminary note, the authors will present only the reactant conditions to synthesize lithium mordenites and lithium, sodium mordenites, and compare these syntheses with that of sodium mordenites previously reported in the literature. 

Ca.ta.lysts, A small amount of quinoline promotes the formation of rigid foams (qv) from diols and unsaturated dicarboxyhc acids (100). Acrolein and methacrolein 1,4-addition polymerisation is catalysed by lithium complexes of quinoline (101). Organic bases, including quinoline, promote the dehydrogenation of unbranched alkanes to unbranched alkenes using platinum on sodium mordenite (102). The peracetic acid epoxidation of a wide range of alkenes is catalysed by 8-hydroxyquinoline (103). Hydroformylation catalysts have been improved using 2-quinolone [59-31-4] (104) (see Catalysis). 

T1he zeolite minerals mordenite (1), ptilolite (2), arduinite (3), flokite (4), and ashtonite (5) have been considered identical on the basis of x-ray diffraction studies and are now named mordenite (6, 7, 8,9,10). Meier (11) determined the structure on a sample of sodium-exchanged ptilolite (Challis Valley, Idaho). The symmetry was orthorhombic with space group either Cmcm or Cmc2i. 

The reactants used for mordenite synthesis were an amorphous substrate of near-mordenite composition (Zeolex S-6-10, 0.91 Na -AkOa-10.6 Si02-7.4 H20, J. M. Huber Co.) and two different types of sodium sili-... 

It has been claimed that noble metal dual function catalysts based on H-mordenite are more active for paraffin isomerization than their counterparts based on H-zeolite Y (25). For both zeolites the isomerization activity depends strongly on the degree of sodium removal and comparison of low sodium Pd-H-mordenite and low sodium Pd-H-zeolite Y for isomerization of n-hexane at 250° C shows that both materials have about the same activity (Table IV), the Y sieve based material being slightly more active. 

For optimal performance of dual function isomerization catalysts based on zeolite Y or mordenite, extensive removal of sodium is necessary. The finished catalyst must be highly crystalline, and the finely dispersed metallic hydrogenation function should be well distributed throughout the catalyst particles. The proposed mechanism explains the stabilizing influence on conversion and the suppression of cracking reactions by addition of the metallic hydrogenation function to the active acidic catalyst base. 

The nitrogen-15 nmr spectra (Figure 3) of sodium exchanged Alaskan and HB33 mordenites were analyzed for the chemical shift anisotropy tensors. The chemical shift anisotropy tensors have been measured for solid nitrogen at 4.2K(23) and calculated to be 603 28 ppm for the static molecule. The observed chemical shift tensors can be used to calculate an orientational parameter , where... 

The emission spectra for uranyl-exchanged zeolites Y, mordenite and X all have differences but do show some fine structure and therefore resemble the solid state spectrum of uranyl acetate dihydrate. In fact, the spectrum of uranyl ions exchanged into sodium mordenite is very similar to that of the uranyl acetate dihydrate solid spectrum shown in Figure 1. Further support for our belief that some zeolites have a solution like environment and others have a solid like environment comes from the correlation between the crystallinity of these uranyl-exchanged zeolites and the appearance of some fine structure in the emission spectrum. We find no apparent correlation between this fine structure and the concentration of the uranyl ion in the zeolites even with a ten-fold change in the concentration of the uranyl ion. 

Diffusion of permanent gases in zeolites is an activated process, activation energy increasing with gas molecular weight to, for example, 15 kcal/mole for SFe in sodium-mordenite (18). Kr diffuses less rapidly in mordenites than in either 5A or Y-zeolites (18) but n-octane diffuses slightly more rapidly in mordenite than 5A-zeolite (4, 19). 

Many more stories can be told in this regard. The chaimel structure of natural mordenite was not foreseen on the basis of sorption experiments because a relatively small number of blockages or dislocations quite adequately blocked the large charmels. In an experiment in my laboratory, sodium LTA failed completely to sorb tetrachloroethylene (both fully anhydrous) because of its size (The crystal structure of a single crystal in an atmosphere of ca 100 torr of C2CI4 for more than a week was exactly that of fully dehydrated LTA.) we should have honored a simple mechanical calculation of size apparently no alternative mechanism existed. In contrast, statements that Cs ions should not be able to enter sodalite cavities in LTA or FAU, have repeatedly been shown crystallographically to be incorrect such entry of Cs" " appears to occur both in the presence and absence of water. 

Since the work of Lee et al. [37], zeolite mordenite continues to play an extraordinary role as a shape selective catalyst for the isopropylation of biphenyl. A high degree of dealumination [37, 38] and high pressure of propylene [39] seem to be advantageous to achieve high selectivities for 4,4 -diisopropylbiphenyl. Also, selective poisoning of the external sites with tributylphosphite [40] and the use of cerium exchanged sodium mordenites [41] are reported to suppress an undesired consecutive isomerization of 4,4 -diisopropylbiphenyl once formed in the pores. 

Molecular Nitrogen, Azido- and Related Groups. - DRIFT data for N2 adsorbed on sodium mordenites gave evidence for both end-on and perpendicular coordination of the N2 to Na+.164 Ultrafast polarisation IR spectra were reported for v3 (vas) for azide in NaN3, MgN3+ and CaN3+ ion-pairs in dmso solutions.165... 

Sugi, Y., T. Matsuzaki, T. Hanaoka, Y. Kubota, J.-H. Kim, X. Tu and M. Matsumoto. Shape-Selective Alkylation of Biphenyl over Mordenite Cerium Exchanged Sodium Mordenite and Unmodified H-Mordenite with Low Si02/Al203 Ratio. Catal. Lett., 1994c, 27, 315-322. 

The procedure for alkylation of polynuclear aromatics with mordenite catalysts developed at Dow Chemical [15,16] requires sodium mordenite with an SI from 0.6 to 1.0. The crystalline aggregates of mordenite range in size from 1-20 pm and are formed from crystallites ranging in size from 500-5000 A. The selected sodium mordenite is treated with inorganic acids to make hydrogen mordenite (HM). HM is calcined at 400-700 °C and further treated with strong acid to produce catalyst precursors. The severity of the thermal and acid treatments, the number and sequence of the treatments, and the type of binder defines the properties of the 3-DDM catalysts. 

No lithium-containing mordenites have been found in natural occurrences these are calcium, sodium mordenites with varying but small contents of potassium. The first probable synthesis of mordenite in 1927 by Leonard (10) was the autoclaved product of reacting sodium carbonate solution with spodumene. Although the product, identified tentatively as mordenite( ) was not analyzed, the results of our studies suggest that he synthesized a Na,Li-mordenite. 

Charanjit Rai (Cities Service Research, Cranbury, N. J. 08512) How do the properties of various lithium and lithium,sodium mordenites reported in your paper change as a function of the temperature at which the synthesis has been carried out ... 

Fig. 45. IR bands of pyridine (nigt, mode, [679]) adsorbed on Bronsted acid sites (B-sites), true Lewis sites (L-sites) and cations (C-sites) in hydrogen faujasite-type zeolite H-Y (H-FAU), hydrogen mordenite (H-MOR) and sodium mordenite (Na-MOR) see text...

In a sodium mordenite of unit cell composition Nag[Al8Si4o096]24 H2O the ideal ou assed hydrogen form should have 1.61 x 10 Brcinsted acid sites per gram of dry zeolite. The maximum reaction rate correspcmds with 1.7 xlO molecules of water added to the zeolite. This quantity of water is just suffident to convert the hydrogen mordenite to hydronium mordenite. However, for general validity of the water co-catalysis mechanism it is necessary to prove that maximum reaction rates should appear in other hydrogen zeolite catalysts when the water added is equal to the number of Bronsted add sites. 

In case of Rb-mordenite [0711], the positions of extra-framework atoms with no distinction between alkali cations and water molecules were similar to those in Na-mordenite [89S1]. The atomic positions of Rbl, Rb2, and Rb3 in Rb-mordenite were shown to correspond to OWl, OW3, and OW2 in Na-mordenite, respectively. The location of the site OW3 in Rb-mordenite corresponded to that of the sodium ion in Na-mordenite. 

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