Sieves and sieving

FIGURE 12.26 Performance profiles of representative crossflow trays. The upper plot is of efficiency vs. F-factor (= C/j The lower plot is of pressure drop per theoretical stage. Profiles for both sieve and sieve-valve hybrid devices are shown. (R. Billet et ah, 1969. IChemE Symp. Ser. il 5, 111.)... 

Set of standard sieves and sieve shaker as well as analytical balance. 

The mechanism of ultrafiltration is not simply a sieve effect, but depends also upon the electrical conditions of both the membrane and the colloid. 

This type of analysis requires several chromatographic columns and detectors. Hydrocarbons are measured with the aid of a flame ionization detector FID, while the other gases are analyzed using a katharometer. A large number of combinations of columns is possible considering the commutations between columns and, potentially, backflushing of the carrier gas. As an example, the hydrocarbons can be separated by a column packed with silicone or alumina while O2, N2 and CO will require a molecular sieve column. H2S is a special case because this gas is fixed irreversibly on a number of chromatographic supports. Its separation can be achieved on certain kinds of supports such as Porapak which are styrene-divinylbenzene copolymers. This type of phase is also used to analyze CO2 and water. 

Feedstocks are natural gas, refinery fuel gas, LPG and paraffinic naphthas. After elimination of CO2, the last traces of contaminants are converted to methane (methanation) or eliminated by adsorption on molecular sieves (PSA process). 

Products of the described type have very high quality requirements as the consumers are typically families with children or restaurants catering to same, where even the smallest bones are unacceptable. Previously, sample tests were conducted on selected blocks. The blocks were thawed and sieved. This was a very slow way of inspection where the production line had to wait for the raw material. 

Electron Spin Resonance Spectroscopy. Several ESR studies have been reported for adsorption systems [85-90]. ESR signals are strong enough to allow the detection of quite small amounts of unpaired electrons, and the shape of the signal can, in the case of adsorbed transition metal ions, give an indication of the geometry of the adsorption site. Ref. 91 provides a contemporary example of the use of ESR and of electron spin echo modulation (ESEM) to locate the environment of Cu(II) relative to in a microporous aluminophosphate molecular sieve. 

W. H. Flank and T. Whyte, Perspective in Molecular Sieve Science, ACS Symposium Series, No. 135, American Chemical Society, Washington, DC, 1980. 

Horvath G and Kawazoe K 1983 Method for oaloulation of effeotive pore size distribution in moleoular sieve oarbon J. Chem. Eng. Japan 16 470-5... 

Zeolites (section C2.13) are unique because they have regular pores as part of their crystalline stmctures. The pores are so small (about 1 nm in diameter) that zeolites are molecular sieves, allowing small molecules to enter the pores, whereas larger ones are sieved out. The stmctures are built up of linked SiO and AlO tetrahedra that share O ions. The faujasites (zeolite X and zeolite Y) and ZSM-5 are important industrial catalysts. The stmcture of faujasite is represented in figure C2.7.11 and that of ZSM-5 in figure C2.7.12. The points of intersection of the lines represent Si or A1 ions oxygen is present at the centre of each line. This depiction emphasizes the zeolite framework stmcture and shows the presence of the intracrystalline pore stmcture. In the centre of the faujasite stmcture is an open space (supercage) with a diameter of about 1.2 nm. The pore stmcture is three dimensional. 

Sumelius I G 1992 Attempted translation of the original old-Swedish paper by Cronstedt Molecular Sieves ed M L Ocelli and H E Robson (New York Van Nostrand Reinhold) pp 1-5... 

Casci J L 1994 The preparation and potential applications of ultra-large pore molecular sieves a review Stud. Surf. Sc/. Catai. 85 329-56... 

Kresge C T, Leonowicz M E, Roth W J, Vartuli J C and Beck J S 1992 Ordered mesoporous molecular sieves synthesized by a liquid-crystal template mechanism Nature 359 710-12... 

Vartuli J C, Roth W J, Beck J S, McCullen S B and Kresge C T 1998 The synthesis and properties of M41S and related mesoporous materials Moiecuiar Sieves Science and Technoiogy vol 1, ed FI G Karge and J Weitkamp (Berlin Springer) pp 97-119... 

Flanigen E M, Bennet J M, Grose R W, Cohen J P, Patton R L, Kirchner R M and Smith J V 1978 Silicalite a new hydrophobic crystalline silica molecular sieve Nature 271 512-16... 

Schunk S A and Schuth F 1998 Synthesis of zeolite-like inorganic compounds Molecular Sieves Science and Technology vo 1, ed H G Karge and J Weitkamp (Berlin Springer) pp 229-63... 

Martens J A and Jacobs P A 1999 Phosphate-based zeolites and molecular sieves Catalysis and Zeolites, Fundamentals and Applications ed J Weitkamp and L Puppe (Berlin Springer) pp 53-80... 

McDaniel C V and Maher P K 1968 New ultra-stable form of fau]asite Molecular Sieves (London Society of Chemical Industry) pp 186-95... 

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... 

Breck D W 1974 Zeoiite Moiecuiar Sieves Structure, Chemistry, and Use (New York Wiley)... 

This book concentrates on synthesis and identification methods for molecular sieves including nonaluminosilicate molecular sieves and gives a good overview of structures and patented materials. 

Karge H G and Weitkamp J 1998 Moleoular Sieves - Soienoe and Teohnology voi 1 Synthesis (Beriin Springer)... 

The chief disadvantages of a Buchner funnel for filtration are (i) it is impossible to see whether the underside of the perforated plate is perfectly clean, and (ii) the larger sizes are top heavy. The first drawback is absent in the Jena slit-sieve funnel (Fig. 11,1, 7,/) this is an all-glass funnel provided with a sealed-in transparent plate, perforated by a series of angular slots, upon which the filter paper rests. The sintered glass... 

The reaction of a halide with 2-butene-1,4-diol (104) affords the aldehyde 105, which is converted into the 4-substituted 2-hydroxytetrahydrofuran 106, and oxidized to the 3-aryl-7-butyrolactone 107[94], Asymmetric arylation of the cyclic acetal 108 with phenyl triflate[95] using Pd-BINAP afforded 109, which was converted into the 3-phenyllactone 110 in 72% ee[96]. Addition of a molecular sieve (MS3A) shows a favorable effect on this arylation. The reaction of the 3-siloxycyclopentene 111 with an alkenyl iodide affords the. silyl... 

Grateful acknowledgment is hereby made of an indebtedness to those who have contributed to previous editions and whose compilations continue in use in this edition. In particular, acknowledgment is made of the contribution of L. P. Buseth, who prepared the conversion tables for the thirteenth edition and who prepared the table on the U.S. Standard Sieve Series. 

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