Design and fabrication of a monolith catalyst for continuous flow epoxidation of styrene in polypropylene printed flow reactor

The relationship between 3-D printing, catalysis and flow chemistry has produced encouraging results which have opened up a large and unexploited avenue of possibilities in heterogeneous catalysis. In this study, 3-D printing technology was employed to develop a flow system consisting of syringe pumps, palladium immobilized alumina monolith and a polypropylene-based flow reactor. The alumina monolith was fabricated from a 3D printed template followed by immobilization of palladium nanoparticles via deposition-precipitation method. The prepared monolith catalyst was extensively characterized with pXRD, N₂-sorption, TGA, SEM, TEM and the presence of PdNps is confirmed. The catalytic performance of the monolith catalyst was studied in the continuous flow epoxidation of styrene using tert-butyl hydroperoxide (TBHP) as the oxidant in the fabricated flow reactor. Physical conditions such as the effect of reactor configuration, flow direction and reaction conditions were studied in order to investigate the catalytic activity of the flow system. The results show a good conversion and excellent selectivity towards styrene oxide in 50 min residence time. In addition, our 3D printed flow system demonstrates superior advantage such as low cost, convenient catalyst separation and recyclability of more than 7 cycles without a significant loss in catalytic activity.