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A novel concept of multilayer polymer/zeolite Y composite membrane structure was developed and investigated for CO2 capture from flue gas. Zeolite Y nanoparticles with an average particle size of 40 nm were successfully deposited onto flexible polymer supports with uniform coverage by the vacuum-assisted dip deposition approach. The zeolite Y dispersion concentration was varied for different commercial polymer supports to obtain a crack-free zeolite Y layer. Scanning electron microscopy (SEM) analysis indicated that a uniform zeolite Y layer could be formed either on Biomax polyethersulfone (PES) membrane or on TM10 polyvinylidene fluoride (PVDF) membrane with appropriate vacuum-assisted dip deposition conditions. Atomic force microscopy (AFM) analysis showed that the zeolite Y/Biomax PES substrate was smoother than the zeolite Y/TM10 PVDF substrate. The Pebax®/PEG-200 membrane prepared on the zeolite Y/Biomax PES substrate exhibited higher CO2 permeance than that prepared on the bare Biomax PES support since the penetration of the polymer membrane was minimized by the smaller interparticle pore size on the zeolite Y layer. The membrane of the multilayer composite structure showed a CO2 permeance of 745 GPU and a CO2/N2 selectivity of 25.4 under flue gas operating conditions at 57 °C and ~1 atm. This concept has provided the basis for high performance membranes with the selective polymer cover layer containing amino groups and for grown zeolite Y membranes with continuous polycrystalline structure supported by the flexible polymer substrate.

In recent years, integrated gasification combined cycle (IGCC) technology has gained significant attention for large-scale power generation with carbon capture. In an IGCC power plant, the syngas is typically directed to the gas turbine (for power generation) after CO2 and H2S removal. This work describes the transport properties of the CO2-selective polymeric facilitated transport membranes for syngas purification at different pressures (2–15 bar) and 107 °C. These membranes contain amines as CO2-carriers that are dispersed in a crosslinked polyvinylalcohol (PVA) matrix. Furthermore, a two-stage membrane process is proposed for CO2 removal from syngas in an IGCC plant. A process modeling and cost-sensitivity analysis of the proposed two-stage membrane process was performed. The effects of feed pressure, temperature, membrane permeance, and selectivity on the overall increase in the cost of electricity (COE) were analyzed. An increase in the COE of 14–18% was estimated for 90% CO2 removal and >99% H2 recovery using the two-stage membrane process in an IGCC power plant.

Zeolites are microporous, crystalline aluminosilicates with the framework made up of T-O-T (T = Si, Al) bonds and enclosed cages and channels of molecular dimensions. Influencing and manipulating the nucleation and growth characteristics of zeolites can lead to novel frameworks and morphologies, as well as decreased crystallization time. In this study, we show that manipulating the supersaturation during synthesis of zeolite X/Y (FAU) via dehydration led to extensive nucleation. Controlled addition of water to this nucleated state promotes the transport of nutrients, with a 4-fold increase in the rate of crystal growth, as compared to conventional hydrothermal process. Structural signature of the nucleated state was obtained by electron microscopy, NMR, and Raman spectroscopy. This extensively intermediate nucleated state was isolated and used as the starting material for zeolite membrane synthesis on porous polymer supports, with membrane formation occurring within an hour. With this time frame for growth, it becomes practical to fabricate zeolite/polymer membranes using roll-to-roll technology, thus making possible new commercial applications.

In the present work, high-performance mixed matrix membranes containing amines have been developed for effective CO2 removal at high pressures (15–28 bar) and high temperatures (103–121 °C). The membrane was synthesized by compatibly embedding amino-functionalized multi-walled carbon nanotubes (AF-MWNTs) as mechanical reinforcing fillers in the crosslinked polyvinylalcohol–polysiloxane/amine blend. The surface functionalization of MWNTs allows strong coupling with the hydrophilic membrane matrix to form a nano-reinforced facilitated transport membrane, which achieved exceptional CO2 selectivity and permeability via the facilitated transport mechanism as well as attractive membrane stability via the incorporation of MWNTs. The synthesized membranes exhibited an average CO2 permeability of 957 Barrers coupled with high selectivities vs. H2 (56), CH4 (264), and N2 (384) at 107 °C and 15 bar. The effects of AF-MWNT loading, high molecular weight species content, selective layer thickness, feed pressure, relative humidity, and temperature on membrane performance were thoroughly studied for a fundamental understanding of membrane properties. Furthermore, a mathematical model has been used to describe and explain the thickness-dependent CO2 transport behavior in the membrane. The combination of high CO2 permeability and good selectivities vs. CH4, H2, and N2, along with enhanced mechanical stability, makes the membrane a promising candidate for the gas separation applications at high pressures.