Confined growth of UiO-66 into ultrahigh-loading membranes for efficient hexane isomer separation

Abstract

The efficient separation of hexane isomers is a crucial process in the petrochemical industry. Mixed-matrix membranes (MMMs) hold tremendous potential for hexane isomer separation. However, maintaining their continuity at high filler loading remains a substantial challenge. Here, UiO-66/PP mixed-matrix membranes are fabricated via an in situ confined growth synthesis strategy that achieves an exceptional filler loading of 72.9 wt%. The resulting UiO-66/PP-(96) membrane maintains structural continuity while effectively discriminating linear and mono-branched hexane isomers from their di-branched counterparts, exhibiting a flux of 473.5 g m⁻² h⁻¹ and a separation factor of 4.53 for n-hexane/2,2-dimethylbutane mixtures. Remarkably, this membrane enriches n-hexane content from 50.0 wt% in the feed to 81.9 wt% in the permeate through a single processing stage, while retaining robust performance across various hexane isomer combinations. These characteristics highlight its potential for extracting linear alkanes to enhance the gasoline research octane number (RON). Molecular dynamics (MD) simulations corroborate these findings, revealing faster transport kinetics for n-hexane compared to branched isomers. This straightforward synthesis approach presented herein significantly broadens the avenues for the advancement of MOF-based mixed-matrix membranes in petrochemical separation applications.