Nucleating agent intermediate 2,2′-methylene-bis(4,6-di-tert-butylphenol) phosphate chloride was synthesized successfully in a continuous flow by the phosphorylation reaction for the first time. After evaluating several different continuous flow reactors, the continuous Coflore agitated cell reactor (ACR) designed based on the continuous stirred-tank reactor (CSTR) principle was proved capable of overcoming the severe channel clogging caused by the precipitation product triethylamine hydrochloride. This can be attributed to the violent agitation and particle size control by the moving agitators. The yield in continuous flow after optimization reached nearly 98% at 100 °C within the residence time of only 4 min and the optimal equivalents of triethylamine and POCl3 are 2.8 and 1.1, respectively. In contrast to the batch operation, the yield has been increased through continuous operation. This is an effective method for the synthesis of the desired product and exhibits the merits of short residence time, easy operation, and straightforward scale-up.
A novel method for the synthesis of triphenyl phosphite and its derivatives has been developed in continuous flow. With a total residence time of 20 s, the target product was prepared in a microreactor, and the reaction time was significantly shortened compared with standard single batch reaction conditions. In addition, the reaction of various substrates gave the corresponding products in good to excellent yields under optimized conditions. The reactants could be employed in a stoichiometric ratio, making the reaction more efficient, economical, and environmentally friendly. In addition, scale-up apparatus was designed and assembled, and the kilogram-scale production (up to 18.4 kg/h) of tris(2,4-di-tert-butylphenyl) phosphite was achieved in 88% yield.
A practical approach to the synthesis of antioxidant 4,4′-dicumyldiphenylamine (DCDPA) and its derivatives by Friedel−Crafts alkylation of aromatic amines was developed under continuous flow conditions. Because of the enhanced mass and heat transfer features of the microreactor, the reaction time was significantly reduced in contrast to a batch mode. The reaction was carried out using a 1:6 v/v ethanol/Cl(CH 2 ) 2 Cl cosolvent system with ZnCl 2 as the catalyst to achieve satisfactory yields. This is an effective method for the synthesis of DCDPA and its derivatives with excellent para selectivity that has the merits of shorter reaction time, easy operation, and straightforward scale-up.
From the safety point of view, thermal risk analysis in the process industry is generally of significant importance and often requires calorimetric and kinetic modeling. These techniques were applied for the first time in the study of a highly exothermic condensation reaction, which is used to prepare 2,2′-methylene-bis(4,6-di-tert-butylphenol) phosphate chloride, a quite important intermediate in the fine chemical industry. The thermodynamics properties such as reaction heat, adiabatic temperature rise, and specific heat capacity of the synthesis reaction were experimentally investigated under isothermal conditions using a robust process analytical technology-based in-line reaction calorimeter EasyMax. A kinetic correlation model was developed based on the calorimetry and subsequently verified. This exhibited a much more efficient and convenient way to study the reaction kinetics compared with the conventional off-line determination of molar concentration or conversion. An accelerating rate calorimeter was used to reveal the thermal controllability of the reaction system as well as some potential hazards. The thermal and kinetic parameters lay a solid foundation for the design and safe operation of reactors. The related methods are also anticipated to be extended to a wide range of similar highly exothermic reactions.
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