Continuous multitubular millireactor with a Cu thin film for microwave-assisted fine-chemical synthesis

The productivity of microwave-assisted continuous specialty chemical synthesis has been brought to a commercially interesting scale of 1 kg/day. To that end, a counter-current multitubular millireactor/heat exchanger (MTMR) assembly has been developed with the reactant flow through millitubular reactors, while the coolant flows in the shell side. The efficiency of microwave absorption under continuous operation in a single mode microwave cavity has been improved with the deposition of a thin (350 ± 40 nm) Cu film on the inner walls of the reactor tubes. This design ultimately resulted in an enhanced product (1,3-diphenyl-2-propynyl piperidine) yield of a multicomponent reaction (of piperidine, benzaldehyde, and phenylacetylene). The Cu film also improved the uniformity of microwave energy absorption in the reactor tubes along the radial direction. A near-isothermal operation was achieved by cooling with a counter-current flow of a microwave transparent coolant in the outer shell of the MTMR. A production ...