N-hydroxyphthalimide anchored on hexagonal boron nitride as a metal-free heterogeneous catalyst for deep oxidative desulfurization

Abstract

A metal-free N-hydroxyphthalimide/hexagonal boron nitride (NHPI/h-BN) catalytic system was developed for deep oxidative desulfurization (ODS) of fuel oils. Detailed experiments find that the heterogenization process of loading NHPI on h-BN not only benefits to the dispersion and utilization of NHPI, but also can significantly promote the catalytic performance. By employing NHPI/h-BN as the catalyst, azodiisobutyronitrile (AIBN) as the metal-free initiator, a 95% conversion of dibenzothiophene (DBT) can be acquired under the reaction conditions of 120 °C and atmospheric pressure with molecular oxygen (O2) as oxidant. Moreover, the heterogenization is convenient for the regeneration of the catalyst with >94% DBT conversion after being recycled seven times. Characterizations illustrate that the promoted catalytic activity along with the regenerability originate from the interactions between NHPI and h-BN. The catalytic mechanism study shows that molecular oxygen is readily activated by the NHPI/h-BN to form a superoxide radical (O2•−), which oxidize DBT to DBTO2 for desulfurization.