Macroporous polymer mixers

Abstract

Macroporous polymers produced by polymerising the continuous phase of high (or medium) internal phase emulsions (H/MIPEs), commonly known as poly(merised)HIPEs (or polyMIPEs), have been intensively researched over the past two decades. The have been investigated for use in many diverse applications including chromatography, membranes, sorbtion, electrodes, bioengineering and filters amongst others. However this work investigates the use of their intricate internal pore structure for the mixing of fluids passing through polyHIPEs. When producing polyHIPEs (also polyMIPEs) by polymerisation of HIPE and MIPE templates it was found that the pore size could be controlled effectively by varying the energy used to agitate the emulsion template. The gas permeability of polyM/HIPEs increased linearly with increasing mean pore throat diameter for a given porosity. Through both residence time distribution experiments and examination of homogenous micromixing it was shown that the mixing in single-phase liquids increased when passed through a polyHIPE as the mean pore throat diameter decreases. There was no difference in mixing performance observed between polyHIPEs produced from Pickering emulsions compared to those produced from surfactant stabilised emulsions. By performing the liquid-liquid extraction of caffeine from aqueous solution with ethyl acetate within a polyHIPE flow cell it was shown that the overall mass transfer coefficient decreased with smaller mean pore throat diameters suggesting more effective mixing. The porosity of the polyHIPE monolith was not found to affect the overall mass transfer coefficient. It was possible to produce interfacial areas, up to 17,600 m2m-3, between the two immiscible liquid phases within polyHIPEs, comparable to industrial extraction methods such as mixer settlers. Impregnating the polyHIPE flow cells with palladium allowed examining whether it is possible to use them as three phase catalytic reactor for nitroreduction. The gas-liquid mixing within the reactor was found to be insufficient to prevent the reduction being mass transfer limited even in the reactors containing the smallest mean pore throat diameters. Less than 0.2% of the palladium catalyst within the reactor was lost from the polyHIPE pore structure during the nitroreductions reactions for all the polyHIPE reactors tested.