Isobutylene, effective diffusivity

Equilibrium Uptake (mg gas/g sample) CO] Propylene Isobutylene Effective Diffusivity (cmVsec) Propylene Isobutylene I nop sobttt... 

The ion exchange particles may be regarded as isothermal, and the effective diffusivity of isobutylene within the particles may be taken as 2.0 x 10 5 cm2/sec. The resin particles may be considered as spheres with radii equal to 0.0213 cm. The density of the swollen resin is assumed to be equal to 1.0 g/cm3. 

Many computational studies of the permeation of small gas molecules through polymers have appeared, which were designed to analyze, on an atomic scale, diffusion mechanisms or to calculate the diffusion coefficient and the solubility parameters. Most of these studies have dealt with flexible polymer chains of relatively simple structure such as polyethylene, polypropylene, and poly-(isobutylene) [49,50,51,52,53], There are, however, a few reports on polymers consisting of stiff chains. For example, Mooney and MacElroy [54] studied the diffusion of small molecules in semicrystalline aromatic polymers and Cuthbert et al. [55] have calculated the Henry s law constant for a number of small molecules in polystyrene and studied the effect of box size on the calculated Henry s law constants. Most of these reports are limited to the calculation of solubility coefficients at a single temperature and in the zero-pressure limit. However, there are few reports on the calculation of solubilities at higher pressures, for example the reports by de Pablo et al. [56] on the calculation of solubilities of alkanes in polyethylene, by Abu-Shargh [53] on the calculation of solubility of propene in polypropylene, and by Lim et al. [47] on the sorption of methane and carbon dioxide in amorphous polyetherimide. In the former two cases, the authors have used Gibbs ensemble Monte Carlo method [41,57] to do the calculations, and in the latter case, the authors have used an equation-of-state method to describe the gas phase. 

The analysis of fast polymerisation reactions has shown that the effects, revealed during the mathematical simulation (diffusion model), are identical to the experimental effects of the cationic polymerisation of isobutylene (as an example). The important consequence of process nonisothermicity is its adverse effect on polymer quality, while the external thermostating is not effective enough in this case [52],... 

Using Equations (4) and (S), and the effective diffiisivity measurements from Table 16-3, the toms in Equation (3) can be calculated to provide an estimate of the conversion ratio for each of the CMS supported catalysts. There is (Mie additional complication. The McBain-Bakr balance utilized for the molecular probe studies was limited to measurments at ambient temperature. Thus, the effective diffiisivities of prqpylene and isobutylene were determined at 21X. Howevo, beonise the reactor stupes were perfcmned at 12S C, the diffiisivity ratio in Equadai (3) should also be at 12S C, for comparsicxt to the experimental d. Chihara et al. (1978) showed that the diffusion in ca n molecular sieve matoials is an activated diffusion process, and thus has an exprmential dependence on temperature,... 

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