SELECTIVITY OF TOXIC AND ACID GASES OVER METHANE AND NITROGEN IN LANGMUIR-BLODGETT-FILMS

Composite membranes for gas separation were fabricated by depositing polymeric Langmuir-Blodgett (LB) films on porous support membranes. By bridging over the pores of the porous support, the polymeric LB film acted as a selective barrier to gas diffusion. The gas selectivity of the LB films was demonstrated by measuring pure-component permeabilities as a function of temperature. LB composite membranes were selective for hydrogen sulfide (a toxic and acid gas) and carbon dioxide (an acid gas) over methane and nitrogen. Carbon dioxide selectivities were reduced by a slow reaction of H2S with the LB film. Grazing angle infrared reflection-absorption spectra (IRRAS) of separate films on aluminized glass slides showed irreversible disordering of the hydrocarbon side groups of the polymer at 35-degrees-C. Disordering improved the selectivities of H2S and CO2 relative to CH4 and N2.