3D-Printed ZIF-8 Monoliths for Biobutanol Recovery

We report the use of 3D-printed ZIF-8 adsorbent monoliths for the recovery of biobutanol from model fermentation mixtures. Two ZIF-8 monoliths, obtained by layer-by-layer printing, with different fiber thickness (250 and 600 μm), front channel size (350 μm × 350 μm and 760 μm × 760 μm), and side channel size (<60 and 260 μm) were studied. Equilibrium isotherms of acetone-butanol-ethanol (ABE) fermentation products showed that both monoliths retained a high saturation capacity (0.2 g/g) for n-butanol and a low saturation capacity for water (0.04 g/g). Mixture breakthrough experiments demonstrate that a high amount of butanol is adsorbed (0.2 g/g) in dynamic conditions, close to the pure component capacity. When increasing the carrier gas flow rate, broadening of the n-butanol breakthrough profile was observed for the 250 μm fiber monolith, while no broadening of the profile was observed for the 600 μm fiber monolith. Computational fluid dynamics (CFD) simulations show that the small side channels of the 250 μm monolith (<60 μm) leads to maldistribution of the flow at the inlet. Finally, the thermal regeneration of the monoliths was investigated, showing the capacity of the ZIF-8 monoliths could be fully restored for different adsorption-desorption cycles.