Comparative study of continuous flow catalytic systems for the transformation of CO2 into propylene carbonate

This work presents a comparative study of two continuous flow reaction systems for the synthesis of propylene carbonate (PC) from CO2 and propylene oxide (PO). The reaction systems in continuous flow consist of a flow tubular reactor and a Robinson-Mahoney (RM) isothermal packed bed reactor in homogeneous regime. The formulation of the synthesized catalyst had KI as the active phase on a support of aluminum oxy-hydroxide, activated carbon, sodium dihydrogen sulfate, nitric acid and poly (vinyl alcohol); the mixture of materials was spheronized to improve its mechanical and workability properties. The results revealed that the reaction followed a catalyst deactivation pattern, since the yield under heterogeneous regime dropped for both reaction systems after the first 4 h of operation; however, the overall performance of the RM reactor, determined by Total Dynamic Performance (TDP) measurements, turned out to be 5 times higher than that of the tubular reactor. The RM reactor was then used in a mixed heterogeneous/homogeneous operation, thus keeping a sustained yield and selectivity of about 90 and 84%, respectively, for the total evaluation time (50 h) after adjusting to homogeneous regime. The mixed operation proposal using the RM reactor ensured the correct distribution of reagents and catalyst, along with the additional benefits of using a three-phase reactor system. In addition, the continuous flow operation allowed to maintain high performance and selectivity rates, enabling to continue the next stages of the scaling-up process.