Biochar-Based Catalysts for Reduction Reactions

Metal catalyzed reduction reactions find an important place in organic chemistry. However, the use of metal catalysts for reductions has their own set of disadvantages like the toxicity of metals ions, cost, need for non-commercial ligands, high catalyst loading, and harsh reaction conditions. Consequently, the metal-free reactions are often more practical, rather the use of biodegradable catalyst offers a better solution. Biochar is a carbon-rich alternative, high porosity, and green catalyst that can be used for various other applications beyond soil remediation and includes synthetic preparations, production of biodiesel from biomass, and degradation of contaminants in the environment. Biochar-based catalyst are favored over conventional carbon-based, silica or resin-based catalysts owing to the intricate structure of biochar which offers distinctive active sites for carrying out different types of reactions. This review focuses on the different types of biochar catalysts used for reduction reactions. Biochar has been used extensively as a catalyst, however, the studies regarding its reduction reactions are scarce. This chapter highlights some of the important reduction reactions catalyzed by biochar and biochar-based metal composites. Selective catalytic reductions, reduction of heavy metal ions, hydrotreating processes, reduction of alcohols to arenes, aldehydes to alcohol, and degradation of dyes and drugs, viz., tetracyclines are some important types of reactions catalyzed by biochar. This book chapter also focuses on the better catalytic performance of the biochar–metal composites as compared to the conventional directing the tailor-made production of application-oriented biochar-based catalyst in the future.