Characteristics of Stable Pickering Emulsions under Process Conditions

Abstract

Emulsions stabilized by solid particles are so called Pickering emulsions which are characterized by their high stability against coalescence. This type of emulsion can be used for a lot of applications. Very little is known about how reaction conditions affect their properties. In this study the influence of important reaction conditions like shear stress, pressure, temperature, and the influence of synthesis gas on Pickering emulsions is investigated. It is shown that the emulsions remain stable in terms of coalescence in a broad range of the reaction conditions and are suitable as reaction media for industrial processes and for a reaction optimization with a subsequent separation step.

Influence of Nanoparticles and Drop Size Distributions on the Rheology of w/o Pickering Emulsions

“…As reported by Stehl et al [35] for identical material systems, shaking does not affect the drop size distribution of the Pickering emulsions. To avoid sedimentation of the particles or droplets, suspensions and emulsions were shaken before transferring them to the plate using a spoon.…”

Mass Transfer and Drop Size Distributions in Reactive Nanoparticle‐Stabilized Multiphase Systems

“…Fumed partly hydrophobized silica nanoparticles HDK H20® (Wacker) synthesized from silicon tetrachloride at high temperatures by a flame hydrolysis‐oxidation were applied. These pyrogenic particles form non‐spherical, chemically bonded aggregates , . The properties of the investigated nanoparticles are depicted in Tab.…”

“…The particles act as an emulsifying agent and can substitute surfactants in various processes, which is especially advantageous, e.g., in applications of cosmetics, biomedicine, or food industry . Another promising application is the use of particle‐stabilized emulsions, i.e., Pickering emulsions, as reaction media since they enable efficient catalytic reactions such as the hydroformylation of long‐chained olefins , , . Using specific ligands, the catalyst can be solubilized within particle‐stabilized droplets of an aqueous phase which are surrounded by an ambient organic phase .…”

“…Another promising application is the use of particle‐stabilized emulsions, i.e., Pickering emulsions, as reaction media since they enable efficient catalytic reactions such as the hydroformylation of long‐chained olefins , , . Using specific ligands, the catalyst can be solubilized within particle‐stabilized droplets of an aqueous phase which are surrounded by an ambient organic phase . Knowledge of the effect of solid particles on interfacial phenomena and on mass transfer processes during reaction is crucial for the choice of particle type, the definition of relevant process parameters, and process optimization.…”

Description of Disperse Multiphase Processes: Quo Vadis?

“…Within the different solvent systems, the requirements vary significantly, e.g., coalescence in a decanter is intended in a phase separation step in micellar and thermomorphic solvent systems whereas it should be prevented in nanoparticle‐stabilized emulsions where droplets are separated from the bulk phase by ultrafiltration. The measurement techniques used to monitor the swarm behavior, reaction performance and system characteristics range from (cryogenic) scanning electron microscopy (SEM) , and endoscopes and phase contrast magnetic resonance imaging (PC‐NMR) to inductively coupled plasma optical emission spectroscopy (ICP‐OES) , .…”