Acetone desorption

The concept according to which elastomer is bonded by a spectrum of energies receives support from the excellent photographs by Ban and Hess1 and by Ban, Hess and Papazian2, in which extraction by benzene appears to have removed rubber from parts of the surface of the black, leaving a non-uniform layer on other parts. This would appear to be confirmed by Rivin s analysis of the acetone desorption curves from ISAF black, in which several activation energies were determined. 

Figures 8.39 and 8.40 display the velocity distributions perpendicular to the interface of the liquid at different time, and Rcq of the acetone desorption process. As shown in figures at t = 5 s, two-cell symmetrical convection is clearly formed near the interface (Fig. 8.39a). Following att — 15 s, the convection cells are developed and merged into the bulk liquid. At f = 25 s, the large convection cells are dissipated, and new smaller convection cells are generated.

The mean mass transfer coefficient during 30s interval can be obtained for the acetone desorption from acetone-ethyl acetate solution. The measured average mass transfer coefficient i L.exp can be calculated by the following equation ... 

In the actual mass transfer process, the liquid mass transfer coefficient is enhanced by the interfacial convection, usually represented by the enhancement factor F as described in Sect. 8.8.2. The F factor calculated by Chen [32] for acetone desorption at different Ra and Rcq as given in Fig. 8.44. As shown in figure, the F factor increases with increasing Ra and Rea. The corresponding critical Ra Ra at F = 1) is seen around 10 at Reo = 13.78. 

Fig. 8.50 Experimental observation of interfacial solute concentration gradient for aqueous acetone desorption at different time, a 0 s, b 30 s, c 60 s, d 90 s, e 120 s, f 150 s (reprinted from Ref. [34], Copyright 2008, with permission from Elsevier)...

When acetylene is recovered, absorption—desorption towers are used. In the first tower, acetylene is absorbed in acetone, dimethylformarnide, or methylpyroUidinone (66,67). In the second tower, absorbed ethylene and ethane are rejected. In the third tower, acetylene is desorbed. Since acetylene decomposition can result at certain conditions of temperature, pressure, and composition, for safety reasons, the design of this unit is critical. The handling of pure acetylene streams requires specific design considerations such as the use of flame arrestors. 

Experiments have been carried out on the mass transfer of acetone between air and a laminar water jet. Assuming that desorption produces random surface renewal with a constant fractional rate of surface renewal, v, but an upper limit on surface age equal to the life of the jet, r, show that the surface age frequency distribution function, 4>(t), for this case is given by ... 

Fig.3.1.9 (a) The adsorption-desorption isotherm (circles, right axis) and the self-diffusion coefficients D (triangles, left axis) for cyclohexane in porous silicon with 3.6-nm pore diameter as a function of the relative vapor pressure z = P/PS1 where Ps is the saturated vapor pressure, (b) The self-diffusion coefficients D for acetone (squares) and cyclohexane (triangles) as a function of the concentration 0 of molecules in pores measured on the adsorption (open symbols) and the desorption (filled symbols) branches. 

Figure 6.21 Field desorption mass spectrum of the rubber compound (acetone extract analysis) of Table 6.36. After Lattimer et al. [229]. Reprinted with permission from Rubber Chemistry and Technology. Copyright (1990), Rubber Division, American Chemical Society, Inc.

Fig. 20. Peak optical density of the perturbed OH band produced by the adsorption of acetone at 20, 75, and 135° C. and methyl chloride at 20° C. Peak optical densities of the 2,970-cm. CH stretching band of adsorbed methyl chloride are also given. Value obtained on adsorption 0> after desorption X.

Host Acetone/host (imbibed) V(C=0) (cm- ) Desorption temperature (°C) Acetone/host (crystallized)... 

Figure 6 DRIFT desorption spectra of acetone on Pd/AbOs during heating from 25°C to 250°C at 25°C increments. The catalyst was first reduced in Fl2 at 120°C for 1.5 h and purged in He for Ih at 25°C...

DCP in 15% (v/v) acetone in cyclohexane. In other tests, desorption efficiency was determined prior to capacity tests. 

PCB DESORPTION. PCBs are very soluble in a number of organic solvents. Because acetone is very effective in displacing the water from the pores of the polymer, it will be used in this example of desorption. A fairly strong interaction of acetone with the styrene-divinylbenzene surface can be predicted because acetone and benzene are miscible solvents. Consequently, a small amount of acetone will desorb the PCBs because strong solvent-solute and solvent-polymer interactions override the strong solute-polymer interaction. This desorption, commonly called elution, does not occur during the adsorption process because the matrix water is a poor eluent dictated by its weak interaction with hydrophobic polymers. 

The solubility of NHDC in hot water, alcohol, aqueous alkali, acetonitrile, dimethyl sulfoxide, and alcohol/water mixture facilitates its selective extraction from food samples (20,91,94). It is extracted from jams, fruit juices, and dairy products with methanol (66,93) or acetone (95) and filtered or centrifuged. Chewing gum samples are dissolved in chloroform and extracted with water. The extract is centrifuged, and the clear supernatant is injected into the HPLC (95). If necessary, sample cleanup and concentration may be achieved by selective adsorption or desorption (20) on Sep-Pak Cl8 (96). Tomas-Barberan et al. (93) used Amberlite XAD-2 resin for purification of jam extract. Sugars, pectin, and other polar compounds were eluted with water, and NHDC was eluted with methanol. After concentration, the extract was further purified on a Sephadex LH-20 column prior to HPLC analysis. 

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