Titanium silicate molecular sieves

TS-1 (titanium silicate molecular sieve), H2O2, MeOH, reflux, 4-18 h, 60-64% yield. ... 

After the submission of this contribution, a remarkable review authored by Ratnasamy, Srinivas and Knozinger has appeared on the investigation, by means of both experimental and theoretical methods, of the active sites and reactive intermediates in titanium silicate molecular sieves [126]. 

Active Sites and Reactive Intermediates in Titanium Silicate Molecular Sieves... 

Appendix C. Synthesis of Titanium Silicate Molecular Sieves. 143... 

TS-1 and TS-2 microporous titanium silicate molecular sieves with MFI... 

ETS-4 and ETS-10 Engelhard Corporation titanium silicate molecular sieves... 

The main objective of this review is to summarize and critically analyze recent advances made in the characterization and catalytic properties of titanium silicate molecular sieves after the reviews of Notari (33) and Vayssilov (34) in 1996 and 1997, respectively. Of special interest are... 

V.C. Epoxidation on Titanium Silicate Molecular Sieves V.C.l. General Features of Epoxidations... 

Titanium silicate molecular sieves not only catalyze the oxidation of C=C double bonds but can be successfully employed for the oxidative cleavage of carbon-nitrogen double bonds as well. Tosylhydrazones and imines are oxidized to their corresponding carbonyl compounds (243) (Scheme 19). Similarly, oximes can be cleaved to their corresponding carbonyl compounds (165). The conversion of cyclic dienes into hydroxyl ketones or lactones is a novel reaction reported by Kumar et al. (165) (Scheme 20). Thus, when cyclopentadienes, 1,3-cyclohexadiene, or furan is treated with aqueous H202 in acetone at reflux temperatures for 6 h in the presence of TS-1, the corresponding hydroxyl ketone or lactone is obtained in moderate to good yields (208). 

Acid catalysis by titanium silicate molecular sieves another area characterized by recent major progress. Whereas only two categories of acid-catalyzed reactions (the Beckmann rearrangement and MTBE synthesis) were included in the review by Notari in 1996 (33), the list has grown significantly since then. In view of the presence of weak Lewis acid sites on the surfaces of these catalysts, they can be used for reactions that require such weak acidity. 

The review of Notari (33) covers the synthesis methodologies of titanium silicate molecular sieves available up to 1996. The reviews of Corma (279) and subsequently of Biz and Occelli (280) describe the synthesis of mesoporous molecular sieves. An informative article on the preparation of TS-1 was reported recently by Perego et al. (68). In this section we list some of the recent developments in the synthesis of micro and mesoporous titanosilicate molecular sieves. 

Kuznicki, S.M., Trush, K.A., Allen, F.M., Levine, S.M., Hamil, M.M., Hayhurst, D.T., and Mansom, M. (1992) Synthesis and adsorptive properties of titanium silicate molecular sieves, in Synthesis of Microporous Materials, Molecular Sieves, vol. 1 (eds M.L. Ocelli, and H.E. Robson), Van Nostrand Reinhold, New York,... 

Highly regioselective cyclizations of 3,4-, 4,5- and 5,6-unsaturated alcohols to yield tetrahydrofuranols and tetrahydropyranols have been carried out with the TS-I-H2O2 system (this is a titanium silicate molecular sieve-H202 complex.) The reactions involve the intermediate formation of epoxides and their Ni ring opening. 

The Ti02 used here was made by hydrolyzing TNBT in distillated H2O with subsequent calcination at 500 °C. ETS-10, which is a titanium silicate molecular sieve with titanium in octahedral coordination, was provided by Engelhard, Co. For comparison, pure-silica ZSM-5 was also synthesized in the absence of alkali metal cations. Its synthesis involves the use of tetrapropylammonium bromide (TPABr) and piperazine. 

Bhaumik A., Mukherjee P. and Kumar R., Triphase catalysis over titanium-silicate molecular sieves under solvent-free conditions -1. Direct hydroxylation of benzene, J. Catal. (1998) 178 pp. 101-107. 

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