| This Ph.D. dissertation presents a sol-gel based approach to develop gas separation membranes that find a place in a wide range of industrial separations. The primary application driving this work was the upgrading of sub-quality natural gas to bring it to pipeline standards by removal of CO{dollar}sb2{dollar} and N{dollar}sb2{dollar} from CH{dollar}sb4{dollar}.; A single step deposition of oligomeric fractal silica clusters on commercial alumina supports was used to prepare membranes with truly molecular sieving properties. Membrane deposition on a porous support involves a combination of both slip-casting and dip-coating mechanisms. Membrane deposition conditions were optimized to deposit a thin ({dollar}400, alphasb{lcub}N2/CH4{rcub}>100,{dollar} and {dollar}rmalphasb{lcub}He/CH4{rcub}>2000{dollar} {dollar}220spcirc{dollar}C and {dollar}rmalphasb{lcub}He/CO2{rcub}>200{dollar} {dollar}40spcirc{dollar}C with the He permeance at {dollar}220spcirc{dollar}C being {dollar}rm 1.4times10sp{lcub}-4{rcub} cmsp3/cmsp2{dollar}-s-cm Hg.; Titania derivatization of lower quality silica membranes resulted in improved selectivities and re-appearance of the thermal cut-off behavior along with superior stability under storage at {dollar}150spcirc{dollar}C. The improved selectivity was attributed to the blockage of larger pores (defects) by the titania precursor.; The thermal cut-off behavior of the membranes could not be fully explained, but molecular dynamics simulations of fully condensed siloxane rings showed an increase in the resumed transport-limiting pore aperture with increasing temperatures. |
PDF Full Text Request