Separation of alkane isomers in a hierarchically structured 3D-printed porous carbon monolith.

[Display omitted] • 3D-printed carbon-based monoliths were studied in adsorptive alkane isomer separation. • Fixed bed breakthrough experiments were conducted for C5/C6 isomer feed mixtures. • The pristine monolith shows a near molecular sieving effect for the branched alkanes. • The CO 2 -activated monoliths significantly adsorbed all the alkane isomers. • A dynamic fixed bed adsorption model is developed to simulate the experimental data. Hierarchically structured 3D printed porous carbons monoliths, exhibiting cylinder structures composed of tetragonal cubic centered unit cells, were studied for their applicability in adsorptive pentane (C5) and hexane (C6) alkane isomers separation (linear/branched). Three materials of the same macroscopic shape were employed in the study, which varied in the micro- and mesoporosity by changing the final CO 2 activation step: non-activated and activated at 1133 K for 6 and 12 h, respectively. Fixed bed breakthrough experiments were conducted for C5/C6 isomer feed mixtures, covering 373, 423, and 473 K temperatures and total alkane partial pressure up to 50.0 kPa. Results demonstrated that the initial porosity for the non-activated monolith enables the complete separation of linear from their respective branched isomers (slightly adsorbed) via a near molecular sieving effect, showing the following sorption hierarchy order (nC6 > nC5) ≫>≫ (2MP > 3MP > 23DMB ≈ iC5 > 22DMB). Regarding the CO 2 -activated monoliths, both showed a completely different picture, being all the alkane isomers adsorbed (much higher loadings) following the sorption hierarchy order: nC6 > 3MP > 2MP > 23DMB > 22DMB > nC5 > iC5. These results indicate that besides enhancing the microporosity and available specific surface area, the pore sieving effect of branched alkanes is lost due to the pore widening during the CO 2 activation. The breakthrough data for the non-activated monolith is also numerically fitted with a convenient, dynamic adsorption model. [ABSTRACT FROM AUTHOR]