Synthesis of ZSM-5 and SAPO-34 membranes in a high temperature-pressure recirculating-flow system

- MFI and SAPO-34 membranes were synthesized in a recirculating flow system.
- The highest system pressures were ∼20 and 30 bar for MFI and SAPO-34, respectively.
- This technique allows to prepare thinner zeolite membranes with better quality.

MFI and SAPO-34 type zeolite membranes were prepared on tubular alumina supports in a recirculating flow system at elevated temperatures and reported for the first time in the literature. During membrane synthesis, the synthesis mixture flowed between the reservoir and the membrane module, which includes the membrane support. The highest synthesis temperatures were 180 °C and 220 °C, and the corresponding system pressures were approximately 20 and 30 bar for MFI and SAPO-34, respectively. The best performing MFI membrane had a CH4 single gas permeance of 2.8 × 10−7 mol/m2 s Pa and CH4/n-C4H10 ideal selectivity of 24 at 25 °C. The n-C4H10/CH4 separation selectivity was 43.6 with n-C4H10 permeance of 8 × 10−7 mol/m2 s Pa at 25 °C. The ideal selectivities of CO2/CH4 of SAPO-34 membranes synthesized at 220 and 200 °C in an autoclave without flow were 227 and >1000, respectively. However, the membranes synthesized by flow-induced crystallization exhibit CO2/CH4 ideal selectivities of less than 10.

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