Novel Gradient Porous ZSM-5 Zeolite Membrane/PSSF Composite for Enhancing Mass Transfer of Isopropanol Adsorption in a Structured Fixed Bed

A novel gradient porous ZSM-5 membrane/PSSF (paperlike sintered stainless steel fiber) composite was prepared by the wet layup papermaking/sintering technique and a secondary growth process. The effects of crystallization time on the morphology, thickness, and Si/Al ratio of the ZSM-5 membranes were studied. The composites were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and N2 adsorption. Adsorption behaviors of isopropanol in structured fixed beds filled with granular activated carbon (GAC) or ZSM-5 particles in the inlet of the bed and ZSM-5/PSSF composites in the outlet of the bed were investigated. Adsorption breakthrough behaviors of isopropanol in fixed beds containing only GAC or ZSM-5 particles were also studied. Theoretical breakthrough curves were predicted using the Yoon–Nelson model and compared with the experimental results. Satisfactory agreement between the theoretical breakthrough curves and the experimental data was obtained. The parameter κ′ (rate constant) of the Yoon–Nelson model was used to reflect the mass-transfer rate of isopropanol in structured fixed beds. All of the results indicate that the mass transfer was obviously enhanced by including ZSM-5/PSSF composites in the outlet of the structured fixed bed. The concept of the length of unused bed (LUB) was also used to analyze the experimental breakthrough curves. The results showed that the utilization of the bed was obviously increased by including ZSM-5/PSSF composites in the outlet of the structured fixed bed.