Enthalpy of fuel gas odorants on surrogate soil surfaces by gas chromatography

Heats of adsorption and heats of interaction for natural gas odorants on clay and organo-clay, respectively, were determined by means of wall-coated open-tubular (WCOT) column gas chromatography. The odorants studied are organic thiol and sulfide compounds. Clay stationary phases were created from the synthetic clay Laponite-RD. Subsequent coatings with octadecane created an organo-clay stationary phase. Experimental results show that, as a class, sulfide odorants have larger enthalpies on clay and organo-clay surfaces than thiol odorants. Therefore, we conclude that thiols are less likely to be sequestered on soil surfaces. The effect of hydrated clay surfaces on odorant enthalpies is also presented. Further, we demonstrate that Lewis acid-base chemistry on clay surfaces explains the significant difference in enthalpy magnitudes between the sulfide and thiol classes.