A Gold‐Immobilized Microchannel Flow Reactor for Oxidation of Alcohols with Molecular Oxygen

Abstract

Goldene Kapillaren: Mit einem goldimmobilisierten Kapillarsäulenreaktor gelingt die Oxidation von Alkoholen mit molekularem Sauerstoff zu Carbonylverbindungen. Diese Kapillarsäulen (siehe Bild) können mindestens vier Tage ohne Aktivitätsverlust verwendet werden.magnified image

A Brush‐Gel/Metal‐Nanoparticle Hybrid Film as an Efficient Supported Catalyst in Glass Microreactors

“…However, packed‐bed microreactors may cause pressure drops along the channel,7 and it is difficult to control the exact residence time. To overcome these disadvantages metal catalysts have been immobilized in microchannel walls by anchoring microencapsulated Pd8 and Au,9 polysilane with metal oxide,10 Pd 2+ bound to organic polymer monoliths11 or embedded in a catalytic membrane,12 batchwise synthesized metal nanoparticles,13 and metal films 14. One example of in‐situ synthesis of gold nanoparticles in a poly(dimethylsiloxane) (PDMS) microfluidic chip was very recently published 15.…”

A Microchemical System with Continuous Recovery and Recirculation of Catalyst‐Immobilized Magnetic Particles

“…More importantly, it is also possible to replace the catalyst with fresh catalyst in this case, which is impossible with heterogeneous catalytic system. [3] To test the robustness and stability of the catalyst activity and the separation efficiency of the magnetic particles over an extended period of time, two reactions ( Table 1, entries 1 and 2) were carried out continuously for up to 10 h. It is satisfying that little deviation of the product yield was observed (Figure 4), indicating the excellent durability of catalyst. In addition, the product solution did not contain any black dots during the 10 h reaction, and no palladium was detected in the solution by ICP-AES.…”

“…[2] For heterogeneous catalytic reactions, efforts have been made to take advantage of accelerated kinetics resulting from the shortened diffusion path of the reagents, little or no product contamination, and full resource utilization. Immobilizing catalysts on channel surfaces [3] and packing solid catalysts including mesoporous structures [4] have been attempted. However, the catalyst immobilization on the channel surface is hampered by many difficulties such as tricky immobilizing processes, the need for precise quantitative control of immobilized catalysts, and an inability to replace deactivated or poisoned catalysts.…”

Wirtschaft

“…A polysiloxane (PSiO)‐coated capillary column containing primary amine groups on its interior was functionalized with microencapsulated gold 211b , and was used to test the oxidation of alcohols 118. The catalytic device gave quantitative conversions for the oxidation of a variety of alcohols (aliphatic and allylic) using molecular oxygen as an oxidant.…”