Synchronously synthesizing and immobilizing porphyrins on crosslinked polystyrene microspheres and preliminary study on catalytic activity of supported metalloporphyrins

摘要

A novel method for immobilizing porphyrins as well as metalloporphyrins (MPs) on polymeric supports was found, and it is the way to synchronously synthesize and immobilize porphyrins on polymeric microspheres. By using 4-hydroxybenzaldehyde (HBA)-bound crosslinked polystyrene (CPS) microspheres, pyrrole, and benzaldehyde in a solution as co-reactants and through the Adler's reaction between solid-liquid phases, it was successfully realized to simultaneously synthesize and immobilize phenyl porphyrin (PP) on CPS microspheres, resulting in PP-supported microspheres PP-CPS. With the same method, substituted PPs, 4-chlorophenyl porphyrin (CPP) and 4-nitrophenyl porphyrin (NPP), were also successfully immobilized on CPS microspheres by using substituted benzaldehydes, 4-chlorobenzaldehyde and 4-nitrobenzaldehyde, as one reactant in the solution, respectively, and other two porphyrin-supported microspheres, CPP-CPS and NPP-CPS, were obtained. The effects of various factors on the process of synchronously synthesizing and immobilizing porphyrins on CPS microspheres were mainly studied. Further, the coordination reaction of cobalt salt with PP-CPS as well as CPP-CPS and NPP-CPS was conducted, forming three solid catalysts, CoPP-CPS, CoCPP-CPS, and CoNPP-CPS. The catalytic properties of these catalysts in the catalytic oxidation of ethylbenzene to acetophenone by dioxygen were preliminarily examined. The experimental results indicate that the Adler's reaction between solid-liquid phases, namely the reaction between HBA-bound CPS microspheres and pyrrole as well as free benzaldehyde or analogs in the solution can favorably be carried out. For this process, the fitting protonic acid catalyst is p-nitrobenzoic acid and appropriate solvent is dimethyl sulfoxide (DMSO). By comparison, the process of preparing CPP-CPS microspheres is easier to be carried out. The obtained three solid catalysts can effectively catalyze the oxidation of ethylbenzene to acetophenone by dioxygen. In comparison, the catalytic activity of CoNPP-CPS is the highest.