An environmentally friendly approach for the reduction of nitrobenzene to aniline promoted by carbonaceous bio-based materials was successfully achieved under subcritical water conditions. The proposed methodology features a metal-free process, no-hydrogen input as reductor, the use of commercial bio-based carbon materials having low cost and availability, and water as green solvent under subcritical conditions. Using optimized conditions, reduction of nitrobenzene in the presence of commercial NORIT GAC 12-40 or DACARB PC1000 was accomplished at 310 °C for 6 h and quantitatively furnished the target aniline. Treatment of NORIT GAC 12-40 with KOH allowed to decrease charcoal loading (6 g vs 40 g) and increase aniline yields (80% vs 66%).

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A green reduction of nitrobenzene to aniline was carried out using lignocellulosic biomass as a hydrogen source in a subcritical polar protic solvent, such as water and alcohol. The method is simple to implement, inexpensive, and easily applicable on a larger scale. The present method does not demand elaborated experimental conditions nor any metal catalyst. Optimal conditions provided aniline with a 90% yield by reduction of nitrobenzene in the presence of sawdust impregnated by KOH in subcritical methanol at 240 °C for 6 h.

A green and sustainable approach for the production of 3-aminobenzoic acid (3-ABA) from 3-nitrobenzaldehyde promoted by NORIT GAC 12-40 as carbonaceous bio-based material was successfully achieved in subcritical water. The process involves two successive reactions: reduction of the nitro group and oxidation of the formyl group. At 300 °C under 90 bar for 6 h, the yield of 3-ABA is 59%.