Size-Controllable MOF Composite Particles for Adsorptive Separations: Formulation, Characterization and Study of Mass Transfer Resistances

Recovery of useful chemicals produced in fermentation processes is complicated by the low concentration of those products in the fermentation broth. The excess of water results in large energy costs if distillation is used. Adsorption has been identified as an efficient alternative for the traditional energy-intensive
distillation technique. Among various porous materials, including zeolites, active carbons and metalorganic frameworks (MOFs), we found that that hydrophobic MOFs such as ZIF-8 show interesting properties, giving perspectives for an economical and low energy-intensive production of biofuels and
beochemicals such as biobutanol [1].

The formulation of the ZIF-8 MOF material into a resistant structure is a key aspect towards its implementation into an actual separation process. Therefore, resistant MOF composite beads were produced by combining polymers with ZIF-8 crystals under different conditions. The formulation method, which easily allows varying the particle size, will be presented. In addition, the adsorptive properties, studied under dynamic and static conditions in liquid and vapor phase, as well as the stability of the composite particles under chemical and mechanical stress will be discussed. Mass transfer resistances related to the
formulation will be highlighted. Additional results obtained by various characterization techniques, such as argon and mercury porosimetry will also be presented. The results of these different experiments demonstrated that the formulation method allows to produce resistant ZIF-8 MOF composite particles with controllable size and with limited change in properties of the original material, which are important for the efficient adsorptive recovery of bio-butanol. The formulation method is, moreover, expected to be applicable to any other nanoporous material.