DIFFUSION OF LIGHT ALKANES IN SILICALITE STUDIED BY THE ZERO LENGTH COLUMN METHOD

Micropore diffusion coefficients for propane, n-butane, and isobutane in three samples of silicalite crystals were measured by the zero leng th column (ZLC) method. Experiments were analyzed by the traditional l ong-time approach and by a new short-time method. For isobutane, micro pore diffusion coefficients obtained from all three samples by both an alysis methods agreed well with previously reported chromatographic an d membrane measurements. For the linear alkanes, the rate of micropore diffusion, even in the largest crystals (350 x 100 mum), was too fast for reliable measurement and the form of the ZLC response curves was consistent with equilibrium control. Taken as a lower limit, the appar ent diffusion coefficients obtained for propane and n-butane are consi stent with the results of microscopic experiments and recent chromatog raphic and frequency response studies.