Selective oxidation of pyridine to pyridine-N-oxide with hydrogen peroxide over Ti-MWW catalyst

The oxidation of pyridine to pyridine-N-oxide (PNO) with hydrogen peroxide has been investigated on various titanosilicate catalysts. Superior to other titanosilicates like TS-1, Ti-Beta and Ti-MOR, Ti-MWW showed a higher catalytic activity and product selectivity. The reaction parameters such as solvent, temperature, hydrogen peroxide/substrate ratio, the amount of catalyst and Ti content were optimized to maximize the PNO yield. Ti-MWW was capable of giving pyridine conversion and PNO selectivity both over 99% under optimum reaction conditions. Ti-MWW was a highly active, selective, and reusable catalyst for the synthesis of PNO. The mechanism for the oxidation of pyridine over titanosilicates has also been considered. Ti-MWW was further structurally modified to posses open reaction spaces by interlayer expansion, which reduced the diffusion limitations in the oxidation of pyridine derivatives with bulkier molecular dimensions.