Spinning mass transfer characteristics

Excellent heat and mass transfer characteristics of the SDR have been confirmed by the study of a phase-transfer-catalyzed Darzens reaction for preparing a drug intermediate. The SDR allowed for a 99.9% reduction in reaction time, 99% reduction of inventory and 93% reduction in the level of impurities [106]. Other possible applications of the SDR include polymerizations and polycondensations (in both cases considerable time savings and more uniform product) as well as precipitation/crystallization (smaller crystals with much narrower size distribution). Two large chemical companies have patented processes based on spinning-disc technology. SmithKline Beecham has claimed a method to epoxidize substituted... 

For a spinning disk, the standard model for falling film flow is complicated by the changing thickness and shear as the liquid flows over the disk. An approximation of this to conditions on a spinning disk surface can, however, be made by substitution of Eq. (9) for average liquid-solid surface shear into the above equation for mass transfer. If it is also assumed that the characteristic distance L traveled by the liquid is equal to that of the disk radius then an equation for the liquid-solid mass transfer coefficient ls can be written for an SDR as... 

Spin polarization transfer via SPINOE requires effective adsorption of laser-polarized 2 Xe on the sample under study. Figure 63 shows the - Xe MAS NMR spectra of laser-polarized - Xe adsorbed on fullerenes at 150 K. The spectra exhibit narrow signals at ca 0 ppm due to gaseous xenon and broad signals centered at 100-120 ppm (50-80 ppm wide), characteristic of adsorbed xenon. The intensity of the latter signals is 4-5 times higher for C70 than for Ceo, because the specific surface of the C70 sample was approximately twice the specific surface of Ceo and the mass of the C70 sample was 2.5 times the... 

Bornside et al. [138] have developed a model for spin coating in which evaporation has been analyzed in terms of the mass flux (or mass transfer) from the liquid phase into the adjacent gas phase. Such a mass flux is controlled by a convection-diffusion process that depends on the solution concentration that increases as the solvent leaves the liquid phase. The characteristics of the gas phase in the close vicinity may also have a speciflc effect on the evaporation process. A modifled model based on the equations of Meyerhofer and Bornside was used by Chang et al. [123] to predict the fllm thickness of spin-coated polymers. In their model, two equations were used one to predict the wet fllm thickness, h, after spin coating but before drying and another to determine the final fllm thickness (hf). The film thicknesses that they have theoretically predicted agree well with those experimentally determined, especially in solutions of low polymer concentration. 

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