A critical review on the role of carbon supports of metal catalysts for selective catalytic hydrogenation of chloronitrobenzenes

Hydrogenation of chloronitrobenzenes (CNB) emerges as a prominent topic of interest in catalysis research owing to its enormous industrial importance. However, hydrogenation of CNB is difficult due to the undesired side reaction of hydrodechlorination. As a result, selective nitro group hydrogenation in the presence of other reducing groups (C-Cl) continues to be challenging. Recent research has focused on the development of more selective catalysts. A huge variety of metal-based nanocatalysts and significant research outcomes have been reported in recent years. However, nanoparticle agglomeration and the cost-effectiveness of the catalyst are considered the critical controlling parameter for hydrogenation reactions. Carbon materials have become particularly promising carriers for such hydrogenation processes to overcome this challenge due to their unique chemical and structural properties. More recently, the widespread usage of novel carbons such as carbon nanotubes and graphene, as well as the fine-tuning of surface chemistry with heteroatom doping, have recently opened up new avenues for their applications in catalysis, particularly in CNB hydrogenation. Hence, this review aims at the selective hydrogenation of CNB on carbon-supported metal-based catalysts and summarizes the latest improvements in the use of different carbonaceous materials in this regard, and investigates the role of carbon support through the mechanistic pathway.