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Crosslinked polyvinylalcohol–polysiloxane/fumed silica mixed matrix membranes containing amines for CO₂/H₂ separation

Xing, Rong, Ho, W.S. Winston
Journal of membrane science 2011 v.367 no.1-2 pp. 91-102
amines, artificial membranes, carbon dioxide, crosslinking, hydrogen, permeability, polyvinyl alcohol, pressure, separation, silica, temperature
CO₂-selective membranes containing both amine carriers and fumed silica (FS) in crosslinked poly(vinyl alcohol)–poly(siloxane) (PVA–POS) (FS loading<22wt%) and crosslinked PVA (FS loading>22wt%) were synthesized for CO₂/H₂ separation. The effects of temperature, feed pressure, gas relative humidities (or water contents) on the feed and sweep sides, crosslinking degree of PVA, and FS loading on transport properties including CO₂ permeability, CO₂/H₂ selectivity, and H₂ permeability, were investigated using a mixed gas containing 20% CO₂ and 80% H₂. The optimal temperature identified was 107°C. The CO₂ permeability and CO₂/H₂ selectivity typically increased with the relative humidities on the feed and sweep sides. Increasing the crosslinking degree of PVA slightly decreased the CO₂ permeability. The CO₂ permeability and CO₂/H₂ selectivity decreased with increasing feed pressure due to the carrier saturation phenomenon. The CO₂/H₂ selectivity increased by 33.8% from 65 to 87 as FS loading increased from 12wt% to 22.3wt% while CO₂ permeability remained nearly constant at about 1130Barrers. Further increase of FS loading decreased both CO₂/H₂ selectivity and CO₂ permeability. At 107°C and 220psia, the membrane with 22.3wt% FS loading showed the best performance with a CO₂ permeability of 1296Barrers (1Barrer=3.35×10⁻¹⁶molm/(m²sPa)) and a CO₂/H₂ selectivity of 87.