Development of poly(amidoamine) dendrimer/poly(vinyl alcohol) hybrid membranes for CO₂ separation

A novel hybrid membrane of poly(amidoamine) (PAMAM) dendrimer/cross-linked poly(vinyl alcohol) (PVA) was developed for the selective separation of CO₂ from a mixture of CO₂ and H₂. PAMAM dendrimers were incorporated into a cross-linked PVA matrix to improve CO₂ separation performance at elevated pressures. An organic metal compound di-isopropoxy-bis(triethanol aminato) titanium (Ti cross-linker) was selected as the PVA cross-linker. The characterization of PAMAM/cross-linked PVA hybrid membranes was conducted using Fourier transform infrared spectrometry/attenuated total reflectance (FTIR/ATR), wide-angle X-ray diffraction (WAXD), and small-angle X-ray scattering (SAXS) spectra. Cross-linking of PVA with Ti cross-linker was confirmed by FTIR/ATR spectra. WAXD spectra showed that the relative crystallinity of PAMAM/PVA hybrid membrane decreased greatly when compared with PVA film. SAXS results indicated that PAMAM and PVA are compatible in the PAMAM/PVA hybrid membrane. To improve the CO₂ separation performance, the addition of amino acids such as glycine, proline, and 2,3-diaminopropionic acid was investigated. Separation performance was improved by addition of amino acids, such as proline. The resulting PAMAM/cross-linked PVA membrane with 5 wt.% proline addition demonstrated an high CO₂/H₂ selectivity of 38 with CO₂ permeance of 1.9 × 10^-12 (m³(STP)/(m² s Pa)) at CO₂ partial pressure of 560 kPa at 60 °C. The PAMAM dendrimer/cross-linked PVA membrane shows great potential for CO₂ separation from H₂ at elevated pressures that are typically found in IGCC processes.