| About 95% of the H2 synthesized in the United States is produced by steam reforming of hydrocarbons followed by the water gas shift reaction. However, this process gives ∼25 mol% CO2 as a byproduct, and the energy and capital-intensive pressure swing adsorption (PSA) procedures for CO2 removal exhibit some unavoidable H2 loss. Membrane separations, especially those with reverse-selective membranes that selectively permeate CO2 from H2 streams, are a promising alternative to pressure swing adsorption. The purified H2 on the high-pressure feed side of the membrane could directly go to storage and transportation without re-pressurizing.;This research aims to develop reverse-selective membranes containing thin poly(ethylene oxide) (PEO)-based polymer films grown from porous substrates via surface-initiated atom transfer radical polymerization (ATRP). PEO has an excellent CO2 solubility, but crystallization of PEO chains leads to low CO2 permeability and minimal CO2/H 2 selectivity. To prevent crystallization, we copolymerized poly(ethylene glycol)methyl ether methacrylate (PEGMEMA) monomers containing PEO side chains with 23-24 (PEGMEMA-1100) and 8-9 (PEGMEMA-475) PEO unites. The shorter PEO chains prevent crystallization, and the copolymer membranes still exhibit a CO2/H2 selectivity of 12 with a CO2 permeability of about 20 Barrers.;Cross-linking of poly(PEGMEMA) films may slightly decrease CO2 permeability and CO2/H2 selectivity, but it should also enhance the membrane's chemical and physical durability. Cross-linked copolymer films prepared by polymerization of PEGMEMA-1100, PEGMEMA-475 and poly(ethylene glycol)diacrylate (PEGDA-700) on RC membranes showed CO2/H 2 selectivities ranging from 6.5 to 19.9, but a CO2 permeability of 5-15 Barrer. Efforts to increase permeability included embedding SiO 2 nanoparticles into the cross-linked poly(PEGMEMA-1100-co-PEGMEMA-475- co-PEGDA-700) film to increase fractional free volume (FFV). Unfortunately, nanoparticles didn't enhance the CO2 permeability, perhaps because the non-rigid chains.;During the course of membrane preparation, growth of poly(PEGMEMA-1100- co-PEGMEMA-475) films in water resulted in an exceptionally rapid polymerization (200 mum-thick films in just 30 min of polymerization). The remarkable thickness does not stem from precipitation, but seems to arise from a unique increase in catalyst activity in the presence of water and PEO side chains.;Future work should include further examination of the kinetics of the very rapid polymerization as well as studies of nanoparticle-containing membranes made with glassy, reverse-selective polymers. The nanoparticles embedded in glassy polymer should give more FFV, and finally increase the permeability and selectivity of the membrane. |
