Thallium zeolite

Thallium zeolites, 4A and 13X. The catalyst is prepared from a mixture of T12C03 and the crushed molecular sieves in water at 45°, and then washed with acetone and dried at 190°. Co or Cd zeolites are prepared similarly with C0CO3 or CdC03.1... 

O-Glycosylation. Traditional glycosylation catalysts are silver or mercury salts. Recently silver zeolite2 has been recommended as the catalyst for preparation of 1,2-cw-glycosides. The thallium zeolite is useful when the glycosyl bromide is unstable in the presence of silver catalysts.1 Example ... 

Glycosidation Allyl chloroformate, 9 Boron trifluoride etherate, 43 Silver(I) tetrafluoroborate, 273 Silver (I) trifluoromethanesulfonate, 274 Thallium zeolites, 296 Tin(II) trifluoromethanesulfonate, 301 Trichloroacetonitrile, 321 Grignard reactions and reactions of... 

Thallittm z oIile , 4A and 13X, The catalyst is prepared from a mixture of TliCOj and the crushed molecular sieves in water at 45, and then washed with acetone and dried at 190. Co or Cd zeolites arc prepared similarly with CoCO or CdCO). 0 Glyto lation. 1 raditional glycosylation catalysts ate silver or mercury salts. Recently silver zeolite has been recommended as the catalyst for preparation of 1.2-ciS glyooside. The thallium zeolite is useful when the glycosyl hromide is unstable in the presence of silver catalysts. ... 

Garegg s silver zeolite [87] is also a powerful promoter [82, 88-90] and has been reported to afford increased yields and P-selectivity over silver silicate [82, 91]. Other activators, including silver imidazolate [92], silver salicylate [93], and thallium zeolite [88] have also been investigated. 

McMurray L, Holmes AJ, Kuperman A, Ozin GA, Ozkar S (1991) IntrazeoUte semiconductors sodium-23 MAS NMR, thallium(l+) luminescence quenching and far-IR studies of acid-base precursor chemistry in zeolite Y. J Phys Chem 95 9448-9456... 

ST1 is a very favorable nucleus for solid-state NMR studies it has f = 2, high natural abundance and high sensitivity. Its large chemical shift range makes it possible to observe individual environments of the nucleus. Thallium can be easily introduced into zeolites by cation exchange. 

Silver zeolites, 296 Zinc-Silver-Graphite, 348 Thallium Compounds... 

The photolyses of conformationally fixed 3,y-unsaturated ketones can also be performed in constrained media. This was described for the ODPM rearrangement of bicyclo[2.2.1]heptenone and bicyclo[2.2.2]octenone in MY zeolites [47]. It is remarkable that direct irradiation of the guest-incorporated thallium-Y (TIY) zeolites at 254 nm resulted in higher yields of ODPM products than the triplet-sensitized solution photolyses (Sch. 19). This indicates that the triplet carbonyl species are generated more efficiently in the supercages of the zeolites presumably because of the presence of heavy... 

Thallium and Silver Zeolite-A The zeolite-A structure is constructed from simple aluminosilicate cubeoctahedra, connected to form a three-dimensional, cubic network by so-called double-4 rings (Figure 1). This arrangement leads to the formation of large a-cages whose internal diameter is approximately 11 A. 

Almost linear decrease of adsorption capacity has been observed with thallium—sodium zeolites of type A (n = 1.98) for water vapor with an increase of the degree of exchange (Figure 1). This is a result of a decrease of the cation electric field which causes a decrease of the adsorption layer density. 

Using thallium—sodium zeolites of type X (n = 2.30), we observed an increase of adsorption capacity for water vapor and benzene at 38% replacement of sodium ions by thallium ions, and then its decrease with an increase in the degree of exchange. As thallium ions replace sodium ions in the position Sm (25) we may assume redistribution of cations at dehydration under the conditions of high vacuum and thermal treatment at 350°C, and stronger chemical bonds of thallium atoms in screened positions in comparison with sodium atoms. 

The presence of thallium atoms at the K3 and K4 sites in the larger cavities of the zeolite framework is considered to be an artifact of heavy liquid separation. 

Aromatic molecules such as naphthalene will emit phosphorescence when adsorbed in zeolites exchanged with heavy ions such as thallium. This was exploited in a convenient, zeolite TlY-coated optical fiber format in order to detect naphthalene.[131]... 

G. V. Tsitsishvili (Academy of Sciences of the Georgian SSR, Tbilisi, USSR) Interesting results are presented in the paper about sodium ion replacement by thallium ions. You observed that total replacement of Na+ by Tl+ in NaY proceeds at 100 °C. Did you study the temperature dependence of this ion exchange process If the 6-membered rings in zeolite Y are only about 0.01A smaller in diameter than those of zeolite X, can one expect the strong temperature dependence of the sodium—thallium exchange process ... 

Heravi et al. have used zeolite-supported thallium(III) nitrate to convert oximes into the parent carbonyl compounds in high yields (Scheme 8.15) [57]. Silica-supported ceric ammonium nitrate has also been used under the action of MW... 

The presence of thallium(0) led to an increase in activity and selectivity of metallic palladium catalysts supported on silica in aldose oxidation reactions. However, silica-supported thallium(0) had no activity by itself (entry 3). ° Similarly, the bimetallic catalyst platinum-thallium/ZSM-5, prepared by impregnation of thallium sulfate and chloroplatinic acid on Zeolite Socony Mobil-5 (ZSM-5), showed greater selectivity in propane aromatisation and almost the same catalytic activity as monometallic thallium/ZSM-5 (entry 4). Similar comparison of vanadium-caesium-copper and vanadium-caesium-copper-thallium catalysts supported on TiOa.SiC demonstrated that addition of thallium improved the catalytic activity in partial oxidation of p-tert-butyltoluene to p-tert-butyl-benzaldehyde (entry The application of solid-supported thallium-based catalysts in different processes includes (a) iron-thallium catalysts in carbon monoxide hydrogenations to form hydrocarbons and alcohols, and catalytic reforming of... 

The natural phosphorescence rate constants suggest again that the Tj transitions are about 10 to 100 times more allowed for ketones than for cis-azoalkanes. It should be noted that the phosphorescence rate of azoalkanes is not accelerated by heavy atoms such as in 1,2-dibromoethane as solvent [50] or thallium in zeolites [147]. This is expected since phosphorescence from a (n,7i) state to the 71 ground state is an El-Sayed rule allowed process [143], which is inherently fast (in comparison to phosphorescence from (7r,7r) states) and is less likely to be much assisted by heavy atoms [153]. 

Until recent work by Zhen et al. [ 149,150], there has been little evidence for the formation of mixed metal clusters in zeolites. Through single crystal XRD, they studied the reaction of zinc vapour with Cd-X and Tl-X (FAU) and identified a unique range of possible cadmium-zinc and thallium-zinc clusters. Some evidence has also been presented that the reaction of various alkali metals with zeolites containing the cations of a different metal may result in the formation of mixed metal clusters [68, 71, 151], but, for the most part, these products remain poorly characterized. 

---