Synthesis, Characterization and Vapor Permeation Performance of B-ZSM-5 Membranes

In the present work, B-ZSM-5 zeolite membranes were synthesized on porous tubular α-alumina supports by several subsequence in situ crystallization hydrothermal treatments. The TiO2- Bohmite and ɣ- alumina intermediate layers were applied to improve the lattice matching between zeolite layer and the support. The uniform membrane intermediate layers with low permeation resistance were prepared on the alumina support surface. The N2 permeance of the intermediate layers and support showed that after the modification of the support surface with ɣ-alumina the Knudsen diffusion can be the dominant mechanism. Selectivity of binary mixture of normal pentane (n-C5) and iso-pentane (i-C5) through B-ZSM-5 zeolite membrane was investigated as a function of feed pressure, temperature and sweep gas flowrate in vapor permeation membrane process using the concentration gradient method. The selectivity results depend strongly on the measurement conditions. The obtained results showed that rising sweep gas flowrate from 5ml/min to 15 ml/min, feed pressure from 1.05 bar to 1.3 bar and decreasing temperature from 200°C to 150°C increased the driving force for n-C5 transfer across the membrane. The selectivity of n-C5/i-C5 8.2 was obtained at 150°C for sweep gas flow of 5 ml/min and 10.4 for sweep gas flow of 10ml/min.