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 mu m), front channel size (350 mu m x 350 mu m and 760 mu m x 760 mu m), and side channel size (<60 and 260 mu m) 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 mu m fiber monolith, while no broadening of the profile was observed for the 600 mu m fiber monolith. Computational fluid dynamics (CFD) simulations show that the small side channels of the 250 mu m monolith (<60 mu m) 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.