SYNTHESIS AND MOLECULAR SIEVES

Recently synthesis and molecular-sieve properties of other kinds of polymers have been described. Cross-linked polyacrylamide, polyvinyl pyridine, and polyvinyl carbitol may turn out to be very useful (Lea and Sehon, 1962 Hjert n and Mosbach, 1962). 

In contrast to TPS with its branched alkyl chain, n-dodecylbenzene sulfonate exhibits an extremely fast rate of biodegradability. The change-over from a branched to a straight-chain structure is easily achieved, and thus by the use of Ziegler synthesis and molecular-sieve extraction techniques, industrial processes for the production of linear olefines and -alkanes soon became readily available. These are the basic starting materials for the synthesis of linear alkylbenzene derivatives. 

ZEOLITES AND MOLECULAR SIEVES SYNTHESIS AND MOLECULAR SIEVING PROPERTIES... 

Szostak R 1998 Synthesis of molecular sieve phosphates Molecular Sieves Science and Technology vol 1, ed H G Karge and J Weitkamp (Berlin Springer) pp 157-85... 

Nadimi S, Oliver S, Kuperman A, Lough A, Ozin G A, Garces J M, Olken M M and Rudolf P 1994 Nonaqueous synthesis of large zeolite and molecular sieve crystals Stud. Surf. Sol. Catal. 84 93-100... 

A wide range and a number of purification steps are required to make available hydrogen/synthesis gas having the desired purity that depends on use. Technology is available in many forms and combinations for specific hydrogen purification requirements. Methods include physical and chemical treatments (solvent scmbbing) low temperature (cryogenic) systems adsorption on soHds, such as active carbon, metal oxides, and molecular sieves, and various membrane systems. Composition of the raw gas and the amount of impurities that can be tolerated in the product determine the selection of the most suitable process. 

A similar series of reactions was performed by Paulsen and Hdlck141 for the preparation of the T-antigenic, unprotected, amino acid-disaccha-rides 200 and 201, starting from the 4,6-0-benzylidene-N-(benzyloxy-carbonyl) benzyl esters 198 and 199, respectively, by condensation with 110 in the presence of mercury dicyanide-mercury dichloride and molecular sieves 4A, and deprotection of the product. Sinay and co-workers148 also reported the synthesis of hexa-O-acetyl derivatives of 200 and 201 by application of the sequence of azido-nitration-bromination. 

Scheme 5.17 Kong and coworkers approach to oligosaccharide synthesis. Reaction conditions (i) 2,4-1 utidine, AgOTf and molecular sieves (ii) TMSOTf, 0°C.

Synthesis of Large Pore Zeolites and Molecular Sieves... 

SYNTHESIS OF LARGE PORE ZEOLITES AND MOLECULAR SIEVES... 

Balkus, Kenneth J., Jr., Synthesis of Large Pore Zeolites and Molecular Sieves 50 217... 

Barter, R.M. (1948) Synthesis of a zeolitic mineral with chabazite-like sorptive properties. /. Chem. Soc., 127 Barter, R.M. and Riley, D.W. (1948) Sorptive and molecular sieve properties of a new zeolitic mineral. /. Chem. Soc., 133. 

Microwave Synthesis of Zeolites and Molecular Sieves The use of microwaves holds promise for efficiency improvements in zeolite synthesis due to the rapid heating possible when using microwave radiation [166], The first report of microwave synthesis of zeolites was by Mobil Oil in 1988, which broadly claimed the synthesis of zeolite materials in the presence of a microwave-sympathetic material, such as water or other pro tic component [167]. A number of reports have appeared since, including synthesis of zeolites Y, ZSM-5 [168] and metaUoaluminophosphate-type materials, such as MAPO-5 [169], There have also been extensive investigations in using microwaves for zeoHte membrane synthesis. Recent reviews discuss the progress in microwave zeoHte synthesis [170, 171]. 

In the synthesis of the glycolipid asialo GMI described by Ogawa and co-workers [107] the trisaccharide derivative (215) (used in the synthesis of asialo GM2) was converted into the 4,6-O-benzylidene derivative (233) and this was condensed with aceto-bromogalactose in the presence of mercury(II) cyanide and molecular sieves to give the P-linked acetylated galactose derivative in 97 % yield. The product was deprotected and acetylated to give the peracetyl derivative (234) of the tetrasaccharide which was converted into the free sugar (235) with hydrazine hydrate. Compound (235) was converted into asialo GMI via the imidate as described above for the synthesis of asialo GM2 from the imidate (219). 

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