Scalable synthesis and modular properties of tubular silicalite-1 membranes for industrial butane isomer separation

We have reported scale-up synthesis of 50-cm-long tubular sililcalite-1 membranes and separation of industrial n-butane/i-butane mixtures using the membrane modules for the first time. The membranes had 6-μm-thick, well-intergrown and [h0h]-oriented silicalite-1 layers. Twenty silicalite-1 membranes of the total twenty-one ones exhibited an average n-butane permeance, n-butane flux and separation factor of (6.5 ± 1.1) × 10^-8 mol/(m² s Pa), (35 ± 5.1) × 10^-4 mol/(m² s) and 25 ± 3.7, respectively, for the industrial n-butane/i-butane (∼30/70 mol%) mixture at 363 K. It suggests that membrane fabrication had good reproducibility. The separation performance of membrane modules with different membrane elements was studied. A practical separation test was performed for the industrial n-/i-butane mixture using membrane setup assembled by seven 3-tube membrane modules with a total membrane area of 0.38 m². The separation system displayed excellent separation performance and stability during continuous test for 48 h. Isobutane concentration in the retentate side was enriched to > 98 mol% from 70 mol% in the feed with recovery of 83 % for the one-stage separation system at 363 K when the flow rate was 3.0 standard L/min (4.32 m³/d). The results show that silicalite-1 membranes are promising candidates for industrial separation of n-/i-butane mixtures.