Oxidative upgrade of furfural to succinic acid using SO3H-carbocatalysts with nitrogen functionalities based on polybenzoxazine

Abstract

SO3H-carbocatalysts with nitrogen functionalities were prepared using the carbonization of polybenzoxazine derived from four different amines (aniline, ethylenediamine, triethylenetetramine, and tetraethylenepentamine) and then sulfonation. The obtained SO3H-carbocatalysts underwent catalytic testing for furfural oxidation with H2O2 to produce succinic acid. The effects of nitrogen functionalities were reported for the first time. The results showed that all carbon samples exhibited a microporous characteristic with comparable textural properties and contained various nitrogen functionalities (N-6, N-5, N-Q, and N-X). After sulfonation, the SO3H-carbocatalyst prepared from tetraethylenepentamine-based polybenzoxazine had the highest amount of sulfonic acid groups (1.45 mmol g−1) and a high nitrogen content (4.23%), providing a maximum succinic acid yield of 93.0% within a rapid reaction time of 60 min under the optimized conditions. This was higher than from Amberlyst-type catalysts and SO3H-carbocatalyst without nitrogen functionalities and was ascribed to the synergistic activity of the sulfonic acid groups and nitrogen functionalities. The XPS spectra and computational study confirmed that such nitrogen functionalities, especially N-5, are capable of forming hydrogen bonding with furfural, facilitating the formation of an intermediate compound and thereby enhancing the catalytic efficiency. However, after four cycles, the succinic acid yield decreased to 40% due to leaching of the sulfonic acid groups.