Development of a Continuous‐Flow System for Catalysis with Palladium(0) Particles

Abstract

Heterogeneous catalysis for organic synthesis under continuous‐flow conditions becomes possible by a new reactor‐based approach. Continuous‐flow reactors with a monolithic glass/polymer composite interior are loaded with palladium particles by ion exchange followed by reduction. When incorporated into a continuous‐flow setup (PASSflow) this reactor allows the transfer‐hydrogenation of alkenes, alkynes, nitro‐substituted aromatic compounds and benzyl ethers in the flow‐through mode. In addition, the activity of the catalysts is well suited to achieve Suzuki, Sonogashira and Heck cross‐coupling reactions in the absence of phosphanes or any other ligands, resulting in a greatly simplified purification. As an extension to this concept a bifunctional support was prepared inside the reactor consisting of Pd particles and an ion‐exchange group (hydroxide form). In the Suzuki− Miyaura reaction the reactor serves as a base for immobilisation and activation of the boronic acid as boronate and as a catalyst for promoting the C−C coupling reaction under continuous‐flow conditions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Chemical reaction engineering, process design and scale-up issues at the frontier of synthesis: Flow chemistry

“…Additionally, nanoconfinement of asymmetric catalysts in multiwalled carbon nanotubes was also accomplished [72,73]. Pd supported over 8 monoliths has been considered for continuous flow reactions [50,68,[74][75][76][77]. The comparison of homogeneous and heterogeneous paths for the ligandless Mizoroki-Heck reactions are also overviewed [78].…”

“…A continuous flow microreactor was obtained from a monolithic glasspolymer composite [77]. An oxime-based palladacycle was immobilised onto polyvinylpyridine resin and it was loaded in a microreactor containing a monolithic composite material.…”

Palladium(0) Nanoparticles on Glass‐Polymer Composite Materials as Recyclable Catalysts: A Comparison Study on their Use in Batch and Continuous Flow Processes

“…[28] By taking advantage of ionic stabilization of palladium(0) particles [29] we demonstrated that these particles can be generated after reduction of palladate anions loaded on anion exchange resins [obtained by precipitation polymerization inside the void volume of megaporous glass [30] using chlormethylvinylbenzene (VBC) and divinylbenzene (DVB) as cross-linker]. [31] Beneficially, the deposition of palladium was carried out on the surface of this monolithic glass/polymer composite material inside a PASSflow reactor, a continuous flow system which was developed in our laboratories ( Figure 1). This reactor concept has the unique feature that it can be operated at a wide range of volumetric flow rates thereby reducing mass transfer phenomena.…”

A Palladium Wall Coated Microcapillary Reactor for Use in Continuous Flow Transfer Hydrogenation

“…The general procedure was modified from previous protocols for immobilising Pd within monolithic structures or on beads. [11,15,[18][19][20] The reactor system presented herein contrasts traditional polystyrene or silica solid sup-ports, which have a granular, bead or gel form, [7,[20][21][22][23][24] as it consists of multiple capillaries manufactured from ethylene-vinyl alcohol (EVOH). The capillary geometry provides a known flow profile, which can be easily characterised and modelled, and does not suffer from channelling problems that are typically observed in packed bed systems.…”