Removal of Linear and Monobranched Alkane from Aviation Gasoline by 5A Zeolite Adsorption for Octane Number Enhancement

Due to continued concern about effects of tetraethyl lead (TEL) emission on the environment and human health, the complete removal of TEL from aviation gasoline (avgas) is a desirable pursuit. In order to maintain high antiknock performance of avgas, an advanced adsorption method was developed using 5A zeolite to remove linear and monobranched alkane from avgas for octane number enhancement. An experimental study of single, binary, and quaternary adsorption of octane isomers on a fixed bed reactor was performed in this work. The effects of partial pressure, operating temperature, and initial mixture composition on breakthrough curves and sorption selectivity were thoroughly studied. At fixed partial pressure, normal octane was the strongest-adsorbed component, followed by 2-methylheptane, 2, 5-dimethylhexane, and 2, 2, 4-trimethylpentane. Adsorption capacity of all components increased with increased partial pressure and decreased with increased operating temperature. However, for all binary mixtures studied in this work, the sorption selectivity decreased as total pressure increased. At equimolar concentrations the normal and monobranched isomers were preferentially adsorbed, while when the volume percentages of the isomers were different, the adsorption of the isomer with the higher volume ratio was favoured. The quaternary breakthrough curves for octane isomers at 473 K with each component having partial pressure of 0.15 kPa also indicated the feasibility of simultaneous removal of normal and monobranched isomers from a multiple-component mixture by this 5A zeolite.