Inductive Heating with Magnetic Materials inside Flow Reactors

Abstract

Superparamagnetic nanoparticles coated with silica gel or alternatively steel beads are new fixed-bed materials for flow reactors that efficiently heat reaction mixtures in an inductive field under flow conditions. The scope and limitations of these novel heating materials are investigated in comparison with conventional and microwave heating. The results suggest that inductive heating can be compared to microwave heating with respect to rate acceleration. It is also demonstrated that a very large diversity of different reactions can be performed under flow conditions by using inductively heated flow reactors. These include transfer hydrogenations, heterocyclic condensations, pericyclic reactions, organometallic reactions, multicomponent reactions, reductive cyclizations, homogeneous and heterogeneous transition-metal catalysis. Silica-coated iron oxide nanoparticles are stable under many chemical conditions and the silica shell could be utilized for further functionalization with Pd nanoparticles, rendering catalytically active heatable iron oxide particles.

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

“…Examples of magnetic cores surrounded by silica shells were used for flow microreactors heating. Surface Pd functionalization was additionally proposed [47].…”

Ten key issues in modern flow chemistry

“…The corresponding batch reaction employing the same reaction conditions afforded 43 only after an extended reaction time of 3 h in 70 % yield. 18 Furthermore, Kirschning and co-workers reported on the Petasis multicomponent reaction. 18 In their tailor-made glass reactor loaded with steel beads as heating source aldehyde 44, morpholine 11 and aryl boronic acid 45 were reacted to afford the Petasis product 46 in higher yield compared to the corresponding batch experiment (Scheme 12).…”

Application of alternative energy forms in catalytic reactor engineering

“…Heating of the particles is achieved by subjecting the catalyst bed to an RF fi eld, achieving reactor performance comparable to microwave heating. The heat is generated over an iron oxide packed bed in a number of organic reactions [77,78] . However, the stoichiometric synthetic routes have several drawbacks, such as generation of waste products, consisting of inorganic salts, and use of toxic and corrosive reagents or raw materials with signifi cant safety issues.…”