Continuous Flow Microreactor System Research Articles

ChemInform Abstract: Direct Oxidative Amidation of Aromatic Aldehydes Using Aqueous Hydrogen Peroxide in Continuous Flow Microreactor Systems.

A practical and economical protocol has been developed for the direct oxidative amidation of aromatic aldehydes with secondary amines to synthesize amides in a single operation under mild conditions within 15–40 min. The utilization of aqueous hydrogen peroxide affords a clean synthetic route. No catalysts or promoting reagents are required.

Direct oxidative amidation of aromatic aldehydes using aqueous hydrogen peroxide in continuous flow microreactor systems

A practical and economical protocol has been developed for the direct oxidative amidation of aromatic aldehydes with secondary amines to synthesize amides in a single operation under mild conditions within 15–40 min. The utilization of aqueous hydrogen peroxide affords a clean synthetic route. No catalysts or promoting reagents are required.

Efficient Synthesis of Imidazoles from Aldehydes and 1,2-Diketones under Superheating Conditions by Using a Continuous Flow Microreactor System under Pressure

A simple and efficient method for the synthesis of 2,4,5-trisubstituted imidazoles has been developed by using a continuous flow microreactor system under pressure; aryl-, alkyl-, and heteroaryl-substituted imidazoles were obtained in high yields within 2 min under superheating conditions.

Investigation of the Moffatt−Swern Oxidation in a Continuous Flow Microreactor System

The Moffatt−Swern oxidation of different alcohols is performed in a continuous flow microreactor system. The microreactor process offers significant advantages over the batch process. First, because of the small reactor volume, accumulation of the labile trifluoroacetoxydimethylsulfonium salt (3) and alkoxydimethylsulfonium salt (5) is minimized. Second, because of the short residence times, which can be applied in the microreactor, the exothermic Pummerer rearrangement of the unstable intermediate 3 is limited. Because of this, the process can be operated at remarkably high temperatures in comparison with a batch reaction, viz. 0−20 °C instead of −70 °C. In the present study, a continuous flow microreactor system was optimized using reactors of different volumes allowing modulation of the residence times of labile intermediates. The efficiency of mixing was studied using different mixing devices. It has been shown that the continuous flow microreactor is an ideal tool for rapid optimization of reaction p...

Understanding the role of nitridation in butan-1-ol and butan-2-ol dehydration mechanisms over oxynitrides

Conversions and selectivities of butan-2-ol and butan-1-ol dehydration were studied over a series of five AlGaPO(N) samples with increasing nitrogen contents (0, 5.3, 11.0, 15.9 and 23.3 wt.%) in a conventional continuous flow micro-reactor system at 200 and 275 °C for butan-2-ol and butan-1-ol dehydration, respectively. Those reactions were chosen as test reactions of the changes induced by nitridation on the acid, base and bifunctional acid–base properties of AlGaPON under catalytic conditions. The catalytic properties of the AlGaPO phosphate precursor are compared to those of the four nitrided phosphates and the influence of nitridation on the initial activities, selectivities and on the stability of the catalysts are discussed in relation to the changes induced by nitridation on their acid–base properties. Cis- and trans-2-butene are the main reaction products from butan-2-ol dehydration, indicating an E2 elimination mechanism, with a strong E1 character. The number of active sites for butan-2-ol dehydration decreases with nitrogen enrichment, in parallel with the number of acid sites evaluated by ammonia chemisorption experiments. Dibutylether is the main reaction product from butan-1-ol dehydration, indicating that two alcohol molecules can be activated simultaneously on adjacent acid and base sites. The number of acid–base conjugated sites catalysing the intermolecular dehydration of butan-1-ol is increased at the beginning of nitridation, but an optimum density of sites is attained for intermediate nitrogen contents. To determine the nature of the surface species interacting with the reactants, we compare the FT-IR spectra recorded before and after methanol and butan-1-ol adsorption.

Isobutane Dehydrogenation over Supported Platinum Acid–Base AlGaPON Catalysts

Isobutane dehydrogenation was studied on platinum impregnated galloaluminophosphate AlGaPO and nitrided galloaluminophosphates AlGaPON, in a conventional continuous flow microreactor system at 500°C. By comparison with AlPO(N), it is shown that gallium plays an important role in the catalytic process by increasing the selectivity of the transformation for isobutene. An isobutene yield of 62% was obtained for a platinum impregnated AlGaPON sample containing 11.8 wt%N, whereas the platinum impregnated precursor AlGaPO only converts isobutane to isobutene with a yield of 49% under similar reaction conditions. This indicates the participation of the basic sites, created by nitridation, to the catalytic conversion of isobutane on Pt/AlGaPON. Both catalysts deactivate with time on stream, due to the deposition of carbonaceous species on the surface, but the activity decay is delayed on the less acid nitrided samples.