Predicting second gas-solid virial coefficients using calculated molecular properties on various carbon surfaces.
Gas-solid chromatography was used to obtain values of the second gas-solid virial coefficient, B2s, in the temperature range from 343 to 493 K for seven adsorbate gases: methane, ethane, propane, chloromethane, chlorodifluoromethane, dimethyl ether, and sulfur hexafluoride. Carboxen-1000, a 1200 m2/g carbon molecular sieve (Supelco Inc.), was used as the adsorbent. These data were combined with earlier work to make a combined data set of 36 different adsorbate gases variously interacting with from one to four different carbon surfaces. All B2s values were extrapolated to 403 K to create a set of 65 different gas-solid B2s values at a fixed temperature. The B2s value for a given gas-solid system can be converted to a chromatographic retention time at any desired flow rate and can be converted to the amount of gas adsorbed at any pressure in the low-coverage, Henry's law region. Beginning with a theoretical equation for the second gas-solid virial coefficient, various quantitative structure retention relations (QSRR) were developed and used to correlate the B2s values for different gas adsorbates with different carbon surfaces. Two calculated adsorbate molecular parameters (molar refractivity and connectivity index), when combined with two adsorbent parameters (surface area and a surface energy contribution to the gas-solid interaction), provided an effective correlation (r2 = 0.952) of the 65 different B2s values. The two surface parameters provided a simple yet useful representation of the structure and energy of the carbon surfaces and thus our correlations considered variation in both the adsorbate gas and the adsorbent solid.
Department of Chemistry, University of Tennessee at Chattanooga, Chattanooga, TN 37403, USA. tom-rybolt@utc.edu
Thomas R
TR
Rybolt
Vanessa E
VE
Janeksela
Dana N
DN
Hooper
Howard E
HE
Thomas
Nathan A
NA
Carrington
Eric J
EJ
Williamson
D000327:Adsorption; D012275:Oryza / Q000187:drug effects / Q000502:physiology*; D012822:Silicon Dioxide / Q000494:pharmacology*; D013501:Surface-Active Agents / Q000494:pharmacology*
C481639:FSM 16; D013501:Surface-Active Agents; D012822:Silicon Dioxide