N and P co-doped graphene-like carbon nanosheet as metal-free catalyst for selective oxidation of methacrolein to methacrylic acid: High methacrylic acid selectivity

Methacrylic acid (MAA) is an important chemical intermediate. In this study, a kind of nitrogen-phosphorus co-doped graphene-like carbon nanosheet catalysts have been prepared by co-pyrolysis of starch and (NH4)2HPO4, which have high specific surface area (1057.55 m2g−1) and excellent catalytic performance (35% of MAL conversion and 90% of MAA selectivity) for the selective oxidation of methacrolein to methacrylic acid. The graphite nitrogen provides new active sites for adsorption and activation of O2 which can accelerate the reaction. P in carbon skeleton can enrich the electron on the surface of carbon catalyst and turn the electrophilic groups to nucleophilic groups which can increase the MAA selectivity. This study provides a convenient and fast method to prepare efficient nitrogen and phosphorus co-doped carbon catalysts for the selective oxidation of methacrolein to methacrylic acid.