Carbon Membranes: A Viable Technology for the Recovery and Purification of Hydrogen Gas
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0971-Z06-09
Carbon Membranes: A Viable Technology for the Recovery and Purification of Hydrogen Gas Anna Merritt1, Ramakrishnan Rajagopalan2, and Henry C. Foley1 1 Chemical Engineering, The Pennsylvania State University, University Park, PA, 16802 2 Materials Research Institute, The Pennsylvania State University, University Park, PA, 16802
ABSTRACT High throughput, asymmetric carbon membranes derived from the pyrolysis of polyfurfuryl alcohol (PFA) have been fabricated on a novel support composed of porous stainless steel filled with nanoparticles. Variation of PFA molecular weight was found to have a significant impact on the single gas permeances of resultant carbon membranes. High molecular weight precursor materials yielded the best results; oxygen permeance values for membranes synthesized from high molecular weight resins were on the order of ~1x10-8 mol m-2s-1Pa-1 with oxygen over nitrogen ideal selectivities of greater than 7. Binary separations of hydrogen from nitrogen and hydrogen from carbon monoxide were carried out using a nanoporous carbon (NPC) membrane synthesized from high molecular weight precursor material. For both separations, hydrogen purities of better than 99% by volume were obtained in the permeate stream. INTRODUCTION The successful development of new and more effective materials separation processes is a vital step in the progression towards a hydrogen based economy. Processing syngas from methane reforming and separation of nitrogen from ammonia purge gases are some significant separations for the procurement of hydrogen. Membrane systems, which are more efficient than conventional separation methods, because they employ a mechanical rather than thermal driving force for separation, can offer a substantial energy savings in upstream gas processing. Nanoporous carbons (NPCs) are an especially promising membrane material for these separations, as the molecular sieving property of these carbons allows the separation of gases with sufficiently dissimilar features by introduction of a pressure differential. Recent work has demonstrated that the permeance characteristics of supported NPC membranes can be dramatically influenced by the support properties. In the case of NPC membranes supported on porous metal, the incorporation of nanofillers before membrane fabrication has been shown to increase permeance through NPC membranes by as much as two orders of magnitude as compared to membranes fabricated on unmodified porous metal supports [1]. The effect of the nanofiller variable on the pore structure of the support and as a result, the properties of the resultant carbon membranes have been examined in detail [2]. Carbon membrane performance is optimized when the nanofiller saturates the porous metal support. Given this novel support structure, current work focuses on the variation of the carbon layer itself via variation of the polymeric precursor properties. The permselectivity of NPC membranes on nanofiller modified porous stainless steel supports as a function of the polymer
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