SYNTHESIS, CHARACTERIZATION, AND CATALYTIC APPLICATIONS OF NANOCRYSTALLINE TRANSITION METAL OXIDES

Abstract

Nanocrystalline metal oxides of late transition metals such as iron, cobalt, and zinc offer a wide range of applications due to their tremendously promising surface chemistry, varying morphology, and high surface area. Different techniques can prepare these metal oxides including sol-gel, solvothermal, ceramic, and single source precursor methods. In this research, the single source precursor method involved the pyrolysis of metal pyruvic acid oxime (PAO) and metal oxalate complexes at relatively lower temperatures. These complexes produce nanocrystalline ceramic materials because thermal decomposition produces volatile compounds such as acetonitrile, water, and carbon dioxide as byproducts. Nanocrystalline metal oxides are frequently used in several fields due to their diverse surface characteristics. One method of determining their surface acidity and basicity is to utilize them as catalysts in organic reactions. The products formed on acidic catalyst sites differ from those created on basic catalyst sites. This can reveal whether the surface is acidic, basic, or both, and the relative contributions of these sites. Morphology is another property affected by the process used to produce nanometric metal oxides and has a significant impact on their attributes. Herein, metal oxides have excellent reactivity, with basic sites being the most reactive. Trans-chalcone (benzylideneacetophenone) is an essential intermediate for synthesizing other organic compounds and has practical medical applications. Previously, a one-pot solventless method was developed to prepare trans-chalcone. The condensation of benzaldehyde and acetophenone with a nanocrystalline zinc oxide catalyst produces this compound. Exploration is now utilized by other binary and ternary nanocrystalline metal oxides to act as catalysts for synthesizing this valuable chemical. Benzaldehyde spontaneously undergoes autoxidation when exposed to air at an ambient temperature, yielding benzoic acid. Although aldehydes are oxidizable, converting aldehydes to carboxylic acids in a highly efficient and clean approach under milder and more eco-friendly conditions is still lacking. Copper(I) complex is an interesting reducing agent in aqueous media. It is applied for different reactions, and decarboxylation of p-nitrophenyl acetic acid to p-nitrotoluene was successful. This approach is a greener process, using a copper(I) reducing agent.