Micropore diffusion coefficients for propane, n-butane, and isobutane in three samples of silicalite crystals were measured by using the zero-length column method. Experiments were analyzed (table 35) by using the traditional long-time approach and also by using a short-term method. For isobutane, micropore diffusion coefficients obtained from all three samples by both methods of analysis agreed well with previously reported chromatographic and membrane measurements. For the linear alkanes, the rate of micropore diffusion, even in the largest crystals (350 x 100pm), was too fast for reliable measurement and the form of the zero-length column response curves was consistent with equilibrium control. Taken as a lower limit, the apparent diffusion coefficients obtained for propane and n-butane were consistent with the results of microscopic experiments and recent chromatographic and frequency response studies. Diffusion of Light Alkanes in Silicalite Studied by the Zero Length Column Method. J.R.Hufton, D.M.Ruthven: Industrial and Engineering Chemistry Research, 1993, 32[10], 2379–86

Table 35

Diffusion of Butane and Propane in Silicalite