Understanding and improving the modular properties of high-performance SSZ-13 membranes for effective flue gas treatment

High-performance tube-supported standard oil synthetic zeolite-13 (SSZ-13) membranes were prepared using low-temperature ozone calcination and modularized in different-sized permeation cells. The hydrophobic SSZ-13 membrane exhibited robust, marked CO₂/N₂ separation performances at a H₂O vapor partial pressure of 10 kPa at 50 °C (CO₂ permeance of 1.3 × 10⁻⁷ mol∙m⁻² s⁻¹∙Pa⁻¹ and CO₂/N₂ separation factor (SF) of ca. 31.5). However, these intrinsic values were obtained at high feed flow rates, where the optimal recovery of CO₂ molecules cannot be obtained. Thus, we correlated membrane (permeance and SF) and feed stream (Reynolds number) properties, finding that convective mass transfer from feed to outer membrane surface (Sherwood number) was described by the Reynolds number and cell dimensions. This further accounted for the CO₂ molar flux and CO₂/N₂ SF. Based on this, we proposed critical parameters (comprising total feed flow rate and pressure, and characteristic module dimension) to describe the representative module properties of the recovery, purity, and process efficiency (PE) for CO₂. Finally, the PE of the membrane unit was improved in double-stage configuration, yielding noticeable improvements in CO₂ purity and PE at the slight expense of CO₂ recovery. Crucially, the process-based module properties were well understood and predicted using the feed stream properties.