Pickering‐Emulsion Inversion Strategy for Separating and Recycling Nanoparticle Catalysts

Abstract

With the recent advances in nanoscience and nanotechnology, more and more nanoparticle catalysts featuring high accessibility of active sites and high surface area have been explored for their use in various chemical transformations, and their rise in popularity among the catalysis community has been unprecedented. The industrial applications of these newly discovered catalysts, however, are hampered because the existing methods for separation and recycling, such as filtration and centrifugation, are generally unsuccessful. These limitations have prompted development of new methods that facilitate separation and recycling of nanoparticle catalysts, so as to meet the burgeoning demands of green and sustainable chemistry. Recently, we have found that Pickering-emulsion inversion is an appealing strategy with which to realize in situ separation and recycling of nanoparticle catalysts and thereby to establish sustainable catalytic processes. We feel that at such an early stage, this strategy, as an alternative to conventional methods, is conceptually new for readers but that it has potential to become a popular method for green catalysis. This Concept article aims to provide a timely link between previous efforts and both current and future research on nanoparticle catalysts, and is expected to facilitate further investigation into this strategy.

Pickering Interfacial Catalysis for Biphasic Systems: From Emulsion Design to Green Reactions

“…Possible strategies for boosting catalyst recovery include a careful control of adsorption energy by tuning the particle size and contact angle, as well as the formulation of smart systems allowing emulsion inversion on demand with external controllable stimuli using thermo-, pH-, light-, or electromagnetic-responsive catalytic nanoparticles (see for instance Ref. [87]).…”

An Overview of Pickering Emulsions: Solid-Particle Materials, Classification, Morphology, and Applications

“…One promising method is to collect products by simple phase-inversion of Pickering emulsions from O/W type to W/O type and directly separating the product-containing oil phase, without the need of demulsification and filtration. This goal could be realized by adding acid or base to tune the hydrophilicity of solid particles locating at oil–water interface, and in turn bringing about inversion of Pickering emulsions, which was confirmed to be able to recycle for at least 36 times (Yang et al, 2013; Yu et al, 2014). …”

Grenzflächenkatalyse in Pickering‐Zweiphasensystemen: vom Emulsionsdesign zu grünen Reaktionen

“…Eine solche Inversion kann durch äußere Reize auf die katalytischen Nanopartikel ausgelöst werden, wenn diese auf Wärme, pH‐Wert, Licht oder elektromagnetische Felder ansprechen (Beispiele hierfür finden sich in Lit. 87).…”