Scott presents his paper entitled, "Interactions of basic nanoparticles with polyacetylenes and their influence upon gas transport and aging properties" at the 2004 North American Membrane Society (NAMS) meeting. Co-authors Scott Metteucci, Roy Raharjo, Scott Kelman, and Benny D. Freeman.
Abstract
Due to increasing use of H2 in refining and as an expected fuel for fuel cells, there is growing interest in finding economically and industrially feasible methods of producing and purifying H2. Currently H2 is produced from steam reforming of hydrocarbons, which produces byproducts such as CO2, H2O, and CO.
Relative to current separation technologies for purifying H2, membranes offer advantages of compact size, modularity, low capital costs, and low environmental impact [1]. However most membranes separate gases based on molecular size, which causes smaller gases (e.g. H2) to permeate preferentially into the low pressure stream. Since H2 is the major component of the feed stream and since H2 is typically required at or above the feed pressures which would be available for membrane separators, there is significant interest in membranes that could remove the minor components (e.g. CO2) and maintain H2 at high pressure. High free volume glassy polymers such as poly(1-trimethylsilyl-1-propyne) [PTMSP] can selectively remove larger, more condensable gases from mixtures with smaller, less condensable species. Additionally the permeability of high free volume glassy polymers can be greatly increased by dispersing nanosized inorganic nonporous particles, such as fumed silicia [FS], in the polymer matrix [2].
Our goal has been to use nanoparticles to selectively improve the solubility of CO2 in nanocomposite membranes, thereby increasing the CO2 / H2 selectivity. We have found that PTMSP membranes containing 0 to 25 % by volume of basic nanoparticles (3-100 nm diameter) exhibit higher permeabilities for CO2 (up to 106,000 Barrers at 35oC) and permanent gases relative to the previously reported pure polymer or PTMSP/FS composites [2]. However, the nanocomposite selectivity is similar to that of the pure polymer. Physical aging properties are also reported for nanocomposites. While nanocomposite samples do age, their long-term permeation properties are substantially above those of PTMSP alone. Both polymer-particle and gas-particle interactions are believed to contribute to the altered transport properties. These interactions have been observed using FTIR, XPS, and AFM and will be discussed herein. These results will also be extended to other high free volume glassy polymers to study the generality of the observed changes in permeation and aging properties.
[1] A. Kohl and R. Nielsen, Gas Purification, 5th ed., Gulf Publishing Company, Houston, 1997, pp. 1238-1295.
[2] T. C. Merkel, B. D. Freeman, R. J. Spontak, Z. He, I. Pinnau, P. Meakin and A. J. Hill, Ultrapermeable, Reverse-Selective Nanocomposite Membranes, Science, 296 (2002) 519-522.