Natural cascades

FIG. 11-114 Three- and nine-level cascade cycle cooling curve for natural gas. 

The mixed refrigerant cwcle was developed to meet the need for hq-uefying large quantities of natural gas to minimize transportation costs of this fuel. This cycle resembles the classic cascade cycle in principle and may best be understood by referring to that cycle. In the latter, the natural gas stream after purification is cooled successively by vaporization of propane, ethylene, and methane. Each refrigerant may be vaporized at two or three pressure levels to increase the natural gas coohng efficiency, but at a cost of considerable increased process complexity. 

Cascade coating The cascade coating technique is used extensively for the external coating of metal pipes with polyethylene to convey natural gas throughout Europe. There are several ways of using this technique but in all cases the pipe is evenly heated to a surface temperature of 250-350°C. Powder is then poured from above, cascaded , onto the rotating pipe. A second heating operation may be necessary to completely fuse the powder. 

M. Berggren, A. Dodabalapur, R.E. Slusher, Z. Bao, Light amplification in organic thin films using cascade energy transfer. Nature 1997, 389, 466. 

Although the biosynthetic cascade hypothesis predicts the co-occurrence of endiandric acids D (4) and A (1) in nature, the former compound was not isolated until after its total synthesis was completed in the laboratory (see Scheme 6). Our journey to endiandric acid D (4) commences with the desilylation of key intermediate 22 to give alcohol 31 in 95% yield. The endo side chain is then converted to a methyl ester by hydrolysis of the nitrile to the corresponding acid with basic hydrogen peroxide, followed by esterification with diazomethane to afford intermediate 32 in 92% overall yield. The exo side chain is then constructed by sequential bromination, cyanide displacement, ester hydrolysis (33), reduction, and olefination (4) in a straight-... 

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