Gas chromatographic investigation of adsorption of normal alkenes C6−C10 on graphitized thermal carbon black

Abstract

The retention volumes, differential heats of adsorption, the standard change in the chemical potential of adsorbate and entropies of adsorption at low surface coverages of graphitized thermal carbon black (GTCB) for n-alkenes C6−C10 have been determined. Differences in retention of n-alkenes on the highly homogeneous non-specific surface of GTCB is determined principally by their cis-trans isomerism but is dependent on the position of the double bond, too. At equal molecular mass cis-isomers are eluted first. Their retention times increase with shifting of the double bond from the centre towards the end of the molecule. Cis-isomers are followed by trans-isomers in the same order. Resolution of cis-trans-isomers increases in order: 3-alkenes<2-alkenes<4- and 5-alkenes. Differences in the isosteric heats of adsorption of geometric isomers have been found to be about 0.2–0.5 kcal mole−1. GTCB can be recommended for separating cis-trans isomers of n-alkenes by gas solid chromatography.