Single and Competitive Adsorption of Linear and Branched Paraffins over Silicalite: Thermodynamic and Kinetic Study

A thermodynamic and kinetic study was realized by competitive and non-competitive adsorption for the separation of n-hexane isomers. Two mixtures of n-C6/3MP and 3MP/23DMB were studied. For the single component adsorption the maximal adsorption capacity were close for the different isomers while the diffusivity for the 23DMB isomer was outstandingly low due to steric hindrance. For the competitive adsorption we had from an initial proportion of 50% for each sorbate an adsorption of 34% and 66% respectively for 3MP and n-C6. For the 3MP/23DMB mixture we had an adsorption of 62% and 38% for 3MP and 23DMB respectively. For the two mixtures the selectivity of the zeolite increased with the adsorption capacity and decreased after the values of 0.63 mmol/g and 1.65 mmol/g respectively for the 3MP/23DMB and n-C6/3MP mixtures. The adsorption rates were lower in the case of competitive adsorption and a kinetic separation could be envisaged for the improvement of the octane number.