Oxidative denitrogenation of liquid fuel over W2N@carbon catalyst derived from a phosphotungstinic acid encapsulated metal-azolate framework

Tungsten nitride-incorporated carbon (W2N(x)@C) was firstly prepared via pyrolysis of a newly developed phosphotungstic acid-loaded metal-azolate framework-6, PTA(x)@MAF-6 s. The obtained (without ammonia feeding) W2N(x)@C materials, were utilized as catalysts for oxidative denitrogenation (ODN) of fuels. The W2N (x)@C materials, especially W2N(15)@C, under ultrasound (US) irradiation was found to be a very efficient catalyst for oxidative removal of various organo-nitrogen compounds (ONCs). Importantly, the W2N(15)@C showed around 80-147 times turnover frequency those of reported catalysts for stubborn carbazole oxidation. Electron density on the N-atom of the ONCs has a dominant role in the oxidation. The oxidation mechanism was suggested mainly based on the calculated electron density of the reactants and analysis of major intermediates/ products. Moreover, the US-assisted ODN was progressed by both non-radical and radical paths, as supported by the electron spin resonance and radical scavenger experiments. The recyclability of the catalyst in the US irradiative ODN was also confirmed.

Automated summary

Tungsten nitride-incorporated carbon was successfully prepared and utilized for oxidative denitrogenation of fuels, demonstrating high efficiency in removing organo-nitrogen compounds. The oxidation mechanism of this material may be determined by the electron density on the N-atom of ONCs, and the ultrasonic-assisted oxidative denitrogenation reaction pathway was supported by peroxide crystallinity and radical experiments.