Modified ceria as a substitute for sulfuric acid in the liquid phase nitration of toluene

Abstract

Ceria, sulfated ceria, ceria–zirconia and sulfated ceria–zirconia catalysts were prepared via the co-precipitation method and calcined at 823 K. The catalysts were characterized by XRD, BET surface area, FTIR, TGA and EDAX. The acidity of the catalysts was studied by pyridine adsorbed FTIR. All the peaks in XRD correspond to the cubic fluorite structure of ceria. The crystallite size of the catalysts was found to be 4–8 nm. Incorporation of zirconia stabilizes the surface sulfate species and thus increases the sulfate content. Sulfation decreases the surface area, but increases the acidity, leading to enhanced catalytic activity. All the catalysts were found to be stable up to 923 K. Catalytic activities were tested towards the liquid phase nitration of toluene. A maximum conversion of about 34 % is achievable for the nitration of toluene to dinitrotoluene. Solid acids effectively play the role of sulfuric acid in the reaction, assisting the formation of nitronium species.