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A safe, straightforward, and atom economic approach for the oxidation of aliphatic aldehydes to the corresponding carboxylic acids within a continuous flow reactor is reported. Typically, the reaction is performed at room temperature using 5 bar of oxygen in PFA tubing and does require neither additional catalysts nor radical initiators except for those already contained in the starting materials. In some cases, a catalytic amount of a Mn(II) catalyst is added. Such a flow process may prove to be a valuable alternative to traditionally catalyzed aerobic processes.

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Analysis of the literature on α-methylstyrene (AMS) hydrogenation reveals very large variations in the reported reaction rates. The presence of traces of water and mass-transfer limitations make reproducible intrinsic kinetic determination difficult. Under anhydrous conditions, the intrinsic kinetic law was, nevertheless, determined under a wide range of operating conditions: 0.5−100 wt % AMS, 0.1−0.6 MPa, 273−320 K, with an activation energy of 38.7 ± 1.5 kJ·mol-1.

The hydroformylation of olefins (oxo synthesis) is the most important process for the production of higher aldehydes (.C 4 ). The liquid phase oxidation of the latter to carboxylic acids by molecular oxygen or air has been known for more than 150 years and is an industrially important process. However, in the recent literature, several different oxidizing reagents and catalytic processes have been reported for this oxidation but most of them have limitations as they use environmentally unacceptable reagents or unnecessarily sophisticated conditions. Herein, we re-evaluated the air oxidation of aldehydes. We show that under mild conditions (air or oxygen and non-optimized stirring), reactions are transfer limited and thus catalyst has no effect on reaction rate. Using efficient stirring (self-suction turbine), uncatalysed air oxidation of 0.8 M aldehyde is possible in 50 min at room temperature whereas less than 10 min was necessary with 10 ppm Mn(II). Thus, recommendations for avoiding common pitfalls that may rise during the evaluation of new catalysts are made.

The gas-liquid oxidation of cyclohexane is performed at high temperature (>200 degrees C) and pressure (up to 25 bar) using pure oxygen in a Pyrex capped silicon etched microreactor which allows convenient screen reaction conditions well above the flammability limit.

A high throughput test which is based on a micromachined mixer for molecular gas-liquid reactions was evaluated for the kinetic investigation of the asymmetric hydrogenation of methyl Z-(a)-acetamidocinamate with a rhodium/(S,S-BDPPTS) catalyst in an aqueous phase. Up to 214 tests were performed in a short time and with an average inventory of Rh/test as low as 14 mg. Comparisons with traditional batch experiments are provided.

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