Efficient separation of linear and mono-branched hexane isomers using large-area silicalite-1 membranes

Membrane-based hydrocarbon isomer separation is a promising and energy-saving alternative to distillation. For the first time, tubular silicalite-1 membranes with large areas of 180 cm² were employed in this study to separate linear and mono-branched hexane isomers. The membrane had a thickness of around 8 μm and showed highly (h0h) orientation. In binary and ternary mixtures of n-hexane (n-C₆), 2-methylpentane (2MP), and 3-methylpentane (3MP), the effects of temperature and partial pressure on the separation performance of silicalite-1 membrane were examined. Moreover, the long-term stability of the membrane in binary and ternary mixture separation was also investigated. The large-area membrane showed a n-C₆ permeance of 2.4 × 10^-8 mol/(m² s Pa) and n-C₆/2MP and n-C₆/3MP separation factors of 36 and 74 in the ternary n-C₆/2MP/3MP (2.8 kPa/2.9 kPa/2.8 kPa) mixture with N₂ as the balanced gas at 100 kPa absolute and 303 K, respectively. The scaling-up membranes demonstrated good and stable separation performance during the long-term test, highlighting the effectiveness and potential application of using large-area silicalite-1 membranes for the separation of hexane isomer mixtures.