Application of Inorganic Membrane Technology to Hydrogen-hydrocarbon Separations

Trowbridge, L.D.

Oak Ridge National Laboratory

关键词: Hydrocarbons;    Diffusion;    Membranes;    08 Hydrogen;    Gases;   

DOI  :  10.2172/885739
RP-ID  :  ORNL/TM-2003/139
RP-ID  :  DE-AC05-00OR22725
RP-ID  :  885739

美国|英语

来源: UNT Digital Library

【 摘 要 】

Separation efficiency for hydrogen/light hydrocarbon mixtures was examined for three inorganic membranes. Five binary gas mixtures were used in this study: H{sub 2}/CH{sub 4} , H{sub 2}/C{sub 2}H{sub 6}, H{sub 2}/C{sub 3}H{sub 8}, He/CO{sub 2}, and He/Ar. The membranes examined were produced during a development program at the Inorganic Membrane Technology Laboratory in Oak Ridge and provided to us for this testing. One membrane was a (relatively) large-pore-diameter Knudsen membrane, and the other two had much smaller pore sizes. Observed separation efficiencies were generally lower than Knudsen separation but, for the small-pore membranes, were strongly dependent on temperature, pressure, and gas mixture, with the most condensable gases showing the strongest effect. This finding suggests that the separation is strongly influenced by surface effects (i.e., adsorption and diffusion), which enhance the transport of the heavier and more adsorption-prone component and may also physically impede flow of the other component. In one series of experiments, separation reversal was observed (the heavier component preferentially separating to the low-pressure side of the membrane). Trends showing increased separation factors at higher temperatures as well as observations of some separation efficiencies in excess of that expected for Knudsen flow suggest that at higher temperatures, molecular screening effects were observed. For most of the experiments, surface effects were stronger and thus apparently overshadow molecular sieving effects.