With the development of microreaction technology and the key issues of liquid-liquid batch bromination process for the synthesis of 4-bromo-3-methylanisole, a modular microreaction system was constructed by taking microreactor and microbead-packed bed as the major functional microdevice units to intensify the bromination of methylanisole. And in this modular microreaction system, the liquid-liquid heterogeneous continuous bromination of 4-bromo-3-methylanisole was studied. The following optimized conditions were obtained, concentration of Br2 (xBr2): 17.5 wt%, molar ratio of Br2 to methylanisole (nBr2/nM): 1.01, initial reaction temperature (T): 0℃, residence time (τ): 0.78 min, with yield of 4-bromo-3-methylanisole more than 98%, and percentage of polybrominated side product less than 1%. Comparing with the conventional batch process, the continuous microreaction technology has obvious advantages. For example, it can change the traditional batch process to a continuous one with a significant increase of productivity (space time yield: 6.5×104 kg/(m3·h)). Besides, since this process is mainly controlled by mass transfer, the modular microreaction system with excellent mass transfer could reduce 50% of polybrominated side product. The study might provide a good foundation for the continuously controllable synthesis of 4-bromo-3-methylanisole in safety. 相似文献
We present a 3D metal printing showerhead mixer to blend effectively two reagent streams into a confined mixing volume. Each stream is predistributed to multiple channels to increase the contact area in the mixing zone, which enables high mixing performance with smaller pressure drop. The showerhead mixer shows excellent mixing performance owing to its ability to intersperse rapidly the two streams as characterized by the diazo coupling reactions and computational fluid dynamics (CFD) simulations. Experimental results demonstrate superior performance of the showerhead mixer compared to two common commercial micro T-mixers, especially in low Reynolds number regime. CFD results are employed to (a) help understand the mixing mechanism, (b) reproduce the experimental observations, and (c) inform the design specifications for optimal performance. Good agreement between experiments and simulations is achieved. The final design includes multiple side-fed inlets for improved mixing performance of the showerhead mixer, as suggested by the validated CFD models. 相似文献
Polyarylacetylene resins have received great attention due to their outstanding heat resistance, while the absence of an efficient method to produce their monomer, p-diethynylbenzene (p-DEB), has discouraged their commercial development. Industrial production of p-DEB consists of bromination and dehydrobromination in a semi-batch reactor, state of the art yield from which is only 70%–75%. Herein, a combined effort of byproduct characterization and density functional theory calculations revealed that side reactions mainly consisted of aromatic substitution which would be promoted by thermal runaway derived from exothermic bromination due to higher activation energy of side reactions. From these considerations, we developed a microreactor system to enhance heat transfer thereby mitigating byproduct formation, from which a p-DEB yield of 99.2% could be achieved. Moreover, the high heat removal efficiency avoided the use of slow feeding and reactant dilution required in semi-batch operation, thereby shortening the reaction time to 14 s while generating more concentrated product. 相似文献
A copper(I)/N‐heterocyclic carbene complex‐catalyzed addition of terminal alkynes to trifluoromethyl ketones at low loading is described. The developed process functions well using a range of terminal alkynes but functions best when an aryl trifluoromethyl ketone is used. This substrate scope is well‐suited for the production of active pharmaceutical ingredients (APIs) such as efavirenz. In this vein, we demonstrate that the described method can be translated into a flow process laying the framework for a completely continuous synthesis of efavirenz in the future.
