Microwave-Mediated Site-Selective Heating of Spherical-Carbon-Bead-Supported Platinum for the Continuous, Efficient Catalytic Dehydrogenative Aromatization of Saturated Cyclic Hydrocarbons

Abstract

A microwave (MW)-assisted method for the continuous production of hydrogen from methylcyclohexane using platinum on spherical carbon beads has been developed, and its application to the efficient dehydrogenative aromatization of fully saturated cyclic alkanes, including piperidines as representative heterocycles, has been studied. Effective dehydrogenation was achieved by the construction of a highly intense energy field, which acted as a reactive site, on the irradiation of the carbon beads (CB) support. The reaction could be carried out with only 10-W single-frequency MWs. The catalyst system could be used continuously for at least 12 h without any loss of catalyst activity. Dehydrogenative aromatization could also be catalyzed and simple cyclohexane derivatives, as well as piperidine derivatives as representative N-heterocyclic alkanes, were tested.

Microwave-Mediated Continuous Hydrogen Abstraction Reaction from 2-PrOH Catalyzed by Platinum on Carbon Bead

“…The reaction system is shown in Figure 3. When the catalyst-packed cartridge equipped with a thermocouple was set in the microwave cavity, the catalyst was located on the horizontal center line in the microwave cavity [39]. This device uses a solid-state oscillator and can change the frequency of the irradiated microwave based on the shift in the resonant frequency in 1-W increments between 1-50 W, and the resonant frequency was always monitored during microwave irradiation.…”

“…Straight cartridge. The 5% Pt/CB (80 mg, Pt: 20.5 μmol)-packed cartridge was prepared according to the procedure demonstrated in our recently reported literature [39]. Glass beads (0.991-1.397-mm diameter, 2.01 g) were packed on the glass filter, which reached the narrow part over the partially bulging part of the straight glass tube, and then a small amount of glass wool was packed on the glass beads.…”

“…Since microwave directly heats up reaction systems without heat medium, energetic efficiency during the reaction process is superior to the conventional heating device, such as an oil bath, a heating block, and an air-mediated heater. We recently reported on an activated carbon-supported platinum (Pt) metal-catalyzed effective dehydrogenation method of primary and secondary alcohols in basic aqueous media [37,38], and a method of microwave-enhanced continuous hydrogen production from MCH using a carbon-bead-supported Pt catalyst (Pt/CB) [39]. We also found that the combination of microwave irradiation and a flow system enabled the sufficient progress of the dehydrogenation of MCH.…”

High Efficiency Microwave Flow Chemistry Towards Synthesis of Functional Materials and Pharmaceutical Cores

“…1). 8 When methylcyclohexane (MCH, 220 mL) was passed through a straight-tube reactor filled with Pt catalyst mounted on carbon beads and heated by AFT MW (10 W applied power) at 0.5 mL/min for 12 h of recirculation, 34 L of pure H2 gas was collected. This represented an energy-efficient method for H2 production, because the reflected MW power was only 1 W (90% heating efficiency) with a catalyst TON of ca.…”

“…1000 mol Lcat -1 h -1 , far superior to the rivalling organic chemical hydride (K-Pt/Al2O3-catalyzed) technology at 46 mol Lcat -1 h -1 . 8 This process has great promises for H2 storage and transfer hydrogenation applications, because hydrogenation of aromatic rings (the reverse reaction) can be readily achieved under Pd catalysis. Therefore, it is an example of a functional material synthesis.…”