Abstract

Supported (nano)Catalysis within Microreactors

Willem Verboom, Professor, University of Twente

The development and activity of different organic and nanometallic catalysts supported in different ways on the inner walls of glass microreactors will be presented. Functionalization of the inner surface of microreactors was achieved by using a single layer of an organic acid catalyst, by catalyst-bearing polymer brushes, and by dendrimer-encapsulated nanoparticles. Functionalization of the inner walls via single-step anchoring of a ß-sulton gives a catalytic monolayer containing perfluorosulfonic acid groups. This system turned out to be highly active in acid-catalyzed reactions. Sulfonic-acid bearing polymer brushes (poly-3-sulfopropyl methacrylate; PSPM) in continuous flow microreactors are very effective as was demonstrated for the hydrolysis of benzaldehyde dimethyl acetal as a model reaction. The activity and stability could be considerably increased using a 1:1 mixed PSPM-PHEMA (poly-2-hydroxyethyl methacrylate) brush system. This behavior can be ascribed to the cooperative effect of the OH groups in stabilizing the sulfonic acid moieties, due to the environment created within the brush architecture. Generation 3 PAMAM dendrimer-encapsulated nanoparticles, covalently attached to the inner surface of a microreactor, exhibit a high activity and stability for model Suzuki-Miyaura, copper-free Sonogashira, and Mizoroki-Heck cross-coupling reactions.