Development of poly(amidoamine) dendrimer/polyvinyl alcohol hybrid membranes for CO₂ capture at elevated pressures

A novel hybrid membrane of poly(amidoamine) (PAMAM) dendrimer/cross-linked poly(vinyl alcohol) (PVA) was developed for the selective separation of CO ₂ from a mixture of CO₂ and H₂. PAMAM dendrimers were incorporated into a cross-linked PVA matrix to improve CO ₂ 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 effects of cross-linker concentration and membrane thickness on separation performance were discussed. The optimum concentration of Ti cross-linker was from 10 to 25 wt%. CO₂ permeance increased with decreasing thickness, but the CO₂/H₂ selectivity decreased with decreasing thickness. The effect of operating temperature on CO₂ separation properties using of the thinnest membrane was discussed. Both QCO₂ and CO₂/H₂ selectivity increased with increasing temperature. The CO₂/H ₂ selectivity reached a maximum of 32 with CO₂ permeance of 3.0 × 10^-11 m³(STP)/(m² s Pa) at 60 °C under CO₂ partial pressure of 560 kPa. SEM observation and XPS spectra showed that the selective layer of thickness 6 m of PAMAM/cross-linked PVA hybrid composite membrane onto a PVDF substrate was formed. The PAMAM dendrimer/cross-linked PVA membrane shows great potential for CO₂ separation from H₂ in high pressure applications, such as IGCC process.