Pure Component and Binary Mixture Adsorption of Light Alkanes and Alkenes on Zeolite NaX at Low Temperatures: Influence of Chain Length

In this study, the separation of short-chain alkane/alkene pairs by fixed-bed adsorption on zeolite NaX at low temperatures is investigated. Experiments are carried out with pure components and mixtures of ethane/ethene, propane/propene, and <i>n</i>-butane/1-butene in the temperature range between -75 and +40 °C and partial pressures up to 450 Pa. For a short chain length, much stronger adsorption of the alkene is observed. In contrast, with an increase in chain length, the isotherms of alkanes and alkenes of the same chain length become more similar. In addition, a greater influence of temperature on capacity is seen, the shorter the chain length is. In binary mixtures, a strong competition occurs at high total loadings with the alkene displacing the alkane. A characteristic curve is formed for the selectivity in the mixture, which shifts to higher temperatures with an increase in the chain length.