(11f) Facilitated Transport Membranes for Hydrogen Purification from Coal-Derived Syngas

Han, Y., The Ohio State University
Ho, W. S. W., The Ohio State University
Facilitated Transport Membranes for Hydrogen Purification from Coal-derived Syngas

Yang Han and W.S. Winston Ho

William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH

In this presentation, three amine-containing facilitated transport membranes were tailored for a single-stage membrane process to decarbonize coal-derived syngas. In these membranes, water-swellable crosslinked polyvinyl alcohol was used as polymer matrix, along with high MW polyvinylamine as fixed-site carrier. For Membrane 1, an amino acid salt of 2-(1-piperazinyl)ethylamine and sarcosine was used as the mobile carrier; sarcosine has a mild degree of steric hindrance. In Membrane 2, the 2-(1-piperazinyl)ethylamine salt of 2-aminoisobutyric acid (PZEA-AIBA) was used as the mobile carrier; AIBA is a sterically hindered amine. Membrane 3 utilized 1-(2-hydroxyethyl)piperazine as the mobile carrier, which contains 2 amino groups and a CO2-phile hydroxyl group. In addition, poly(ethylene glycol) dimethyl ether was incorporated in Membrane 3 as a CO2-phile moiety. Nanoporous graphene oxide was dispersed in all three membranes to avoid membrane compaction upon high feed pressure. The membranes were tested at 107 °C and 31.7 bar feed pressure with a CO2 partial pressure of 12.5 to 0.5 bar, which corresponded to the feed CO2 partial pressures before and after the bulk CO2 removal, respectively. The separation performances of Membranes 1 and 2 depended strongly on the CO2 partial pressure, yielding a CO2 permeance of 72 – 435 GPU (1 GPU = 10-6 cm3 (STP)·cm-2·s-1·cmHg-1) with a CO2/H2 selectivity of 93 – 558. The CO2 permeance reduced significantly with increasing CO2 partial pressure due to the carrier saturation phenomenon. On the other hand, the presence of amino groups and the abundant CO2-phile moieties in Membrane 3 enhanced the CO2 solubility at high CO2 partial pressure, thereby a CO2 permeance of 206 – 246 GPU and a decent CO2/H2 selectivity of 103 – 123 were obtained for a CO2 partial pressure of 12.5 – 3.5 bar. The different degrees of dependence on the feed CO2 partial pressure provide a design opportunity for a single-stage membrane process. The more permeable but less selective Membrane 3 can be implemented to the proximity of feed inlet, where the CO2 partial pressure is high but the H2 partial pressure is low. Upon CO2 removal, the feed CO2 partial pressure sharply reduces whereas the H2 transmembrane driving force increases. In this case, Membrane 1 or 2 can be used to elevate the CO2 permeance and CO2/H2 selectivity. Initial techno-economic analysis shows that the single-stage membrane process can achieve 90% CO2 removal with >99% H2 recovery. A 15.7% increase in cost of electricity is estimated, which is much cost-efficient then Selexol.