Diffusional separation processes

Olivet, E. D., Diffusional Separation Processes Theory, Design and Evaluation. Wiley, New York, 1966. Reid, R. C., Prausnitz, J. M., and Sherwood, T. K., The Properties of Gases and Liquids. McGraw-Hill, New York, 1977. 

Kirk Othmer, 2nd edit 7 (1965), pp 79-175 (E. VonHalle, R.L. Huglund 8c J. Shacter, Diffusion and Diffusion Sepaiation Methods ) 28) E.D. Oliver, Diffusional Separation processes Theory, Design, and Evaluation , Wiley, NY(1966), 444 pp... 

Oliver, E. D., Diffusional Separation Processes Theory, Design and Evalu-... 

Using Fig. 1.17 with data from Appendix I, plot logo (relative volatility) of C5 to C12 normal paraffins as referred to n-Cs against the carbon number (5 to 12) at a reasonable temperature and pressure. On the same plot show log a for Cs to Cio aromatics (benzene, toluene, ethylbenzene, etc.), also with reference to n-Cs. What separations are possible by ordinary distillation, assuming a mixture of normal paraffins and aromatic compounds (E. D. Oliver, Diffusional Separation Processes Theory, Design Evaluation, J. Wiley Sons, New York, 1966, Chapter 13. 

Adapted from E. D. Oliver, Diffusional Separation Processes-. Theory, Design, and Evaiuatlon, John Wiley Sons, New York, 1966. 

Ordinary diffusion involves molecular mixing caused by the random motion of molecules. It is much more pronounced in gases and Hquids than in soHds. The effects of diffusion in fluids are also greatly affected by convection or turbulence. These phenomena are involved in mass-transfer processes, and therefore in separation processes (see Mass transfer Separation systems synthesis). In chemical engineering, the term diffusional unit operations normally refers to the separation processes in which mass is transferred from one phase to another, often across a fluid interface, and in which diffusion is considered to be the rate-controlling mechanism. Thus, the standard unit operations such as distillation (qv), drying (qv), and the sorption processes, as well as the less conventional separation processes, are usually classified under this heading (see Absorption Adsorption Adsorption, gas separation Adsorption, liquid separation). 

The fates of the radical ion pairs produced upon electron transfer depends on the nature of their production. As already mentioned, the Bp DMA" com formed from irradiation of the ground-state CT complex. Bp - DMA, is suggested by Mataga and co-workers [24] to decay only by febet, on a timescale of 85 ps. Diffusional separation to solvent separated radical ion pairs or proton transfer within Bp -DMA com are not kinetically competitive. The triplet CRIP Bp -I- DMA" ip has two decay pathways that occur on the picosecond timescale. The first process is proton transfer, fept, to generate a triplet radical pair, BpH-l- DMA ] (Scheme 2.3). In acetonitrile, this occurs with a rate constant of fept of 1.3 x 10 s [43]. The second process leading to the decay of the CRIP is diffusional separation to the SSRIP, kips, which occurs with a rate constant of 5 x 10 s (Scheme 2.3) [43]. Thus the efficiency of the... 

In the following, the principles of mass-transfer separation processes will be outlined first. Details of mass-transfer calculations will be introduced next and examples will be given of both equilibrium-stage processes and diffusional rate processes. The chapter will then conclude with a detailed discussion of the two single most applied mass-transfer processes in the chemical industries, namely distillation and absorption. 

Mass-transfer calculations, such as the analysis or design of separation units, can be solved by two distinctly different methods, based on either the concept of (1) Equilibrium stage processes or (2) Diffusional rate processes. 

From a kinetic standpoint (4), mass transfer per unit volume in distillation is limited only by the diffusional resistances on either side of the vapor-liquid interface in turbulent phases, with no inerts present, In almost every other separation process, there are inert solvents or... 

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