Synthesis of Cyclobutane-1, 2, 3, 4-tetracarboxylic Dianhydride in Continuous Flow Photoreactor

Cyclobutane-1, 2, 3, 4-tetracarboxylic dianhydride (CBDA) was continuously and efficiently synthesized by photodimerization of maleic anhydride (MA) using ethyl acetate as solvent in a continuous flow photoreactorunder UV irradiation. The influences of residence time of solution in reactor tube, tube size, reaction temperature and mass concentration of reactants on the product yield and the unit time output of product were studied. In addition, the effects of continuous flow photoreactor and batch photoreactor on the product yield were compared. The results showed that longer residence time, smaller inner diameter of the tube and lower reactant concentration were benefit to improve the yield of product. The yield and the unit time output of product reached as high as 51.57% and 4.64 g/h under the conditions of residence time 80 min, inner diameter of reactor tube 2.00 mm, reaction temperature 5℃ and mass concentration of reactants 0.15 g/mL. The continuous flow photoreactor has the advantages of high photon utilization efficiency, small photon loss in the light propagation process, high quantum flux density, more adequate and uniform irradiation area, large specific surface area, high mixing efficiency and heat transfer. Compared with the batch photoreactor, the product yield was increased by more than 33%. © 2019, Editorial Office of FINE CHEMICALS. All right reserved.