Abstract
Pickering emulsions (PEs) have received increasing interest for their application in catalytic multiphase reactions. Organic solvent nanofiltration of PEs was shown to be a promising procedure for efficient and effective catalyst recycling. In this work, a systematic parameter study to identify the main influencing parameters on PE filtration was conducted for a large variety of PE compositions for the first time. In addition to temperature, only the type of organic solvent significantly influenced the filtration performance, which could be mathematically modeled via a combination of the solution–diffusion and the resistance in the series model. Particle type and concentration, dispersed phase fraction and the presence of reaction (by-)products did not show any significant impact on the permeability. The stirrer speed only became important when emulsions stabilized by particles without the tendency to form 3D network structures were filtered in long-term filtration experiments. These results pave the way towards the application of PE membrane filtration for catalyst recovery in continuous liquid/liquid multiphase reactions and enable broad operation windows. As the mechanical separation of PEs was shown to be a very robust process, the emulsion composition can now be tuned to meet the needs of the reaction without any (significant) loss in filtration performance.
Highlights
Consistent with results published in the literature [5,26,28], more hydrophobic silica particles led to larger drop sizes and Pickering emulsions (PEs) stabilized by fumed silica particles showed smaller Sauter mean diameters than those stabilized by spherical ones
Experimental data concerning the rheological behavior of PEs stabilized by particle types H15, H20, H30 and H2000 were already published in [14] with emulsions stabilized by particle types H15, H20 and H30 showing shear-thinning rheological behavior while emulsions stabilized by particle type H2000 showed a Newtonian flow behavior
The impact of PE composition as well as operating conditions on the filtration behavior of w/o PEs using the organic solvent nanofiltration membrane oNF-3 was systematically investigated for the first time
Summary
The ultrafiltration membranes used in these studies (molecular weight cut-off (MWCO) ranging from 1 to 10 kDa) were originally designed for aqueous applications and showed—in some cases—an unexpected disproportionate increase of flux with pressure and strong fluctuations in pure organic solvent flux [10,11,13,14]. An organic solvent nanofiltration membrane with a relatively high MWCO of 900 Da was tested for w/o PE filtration for the first time in [13,15]. Despite the low applied pressures (1–4 bar, based on the first investigations using ultrafiltration membranes), in [13,15], feasible and very reproducible fluxes could be achieved using the organic liquid 1-dodecene (pure organic solvent flux: J (p = 4 bar) = 14.34 ± 2.38 Lm−2h−1). An increase in temperature led to an increase in flux and could be modeled via a combination of the solution–diffusion and the resistance in series model including an Arrhenius-type relationship to describe the temperature dependency of the diffusion coefficient [15]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
