Solid-solid reactions, although of considerable industrial importance, have not received significant attention in the chemical engineering literature. In conventional method of manufacturing products using reactants in solid phase, the rate of heat transfer and rate of diffusion are very slow. In order to overcome these problems, an attempt is made to investigate these reactions employing a stirred fluidized bed. The addition reaction of phthalic anhydride and p-nitro aniline system that takes place between 80 and 120• C, forming phthaloyl derivative of p-nitro aniline is selected for the investigations. The reaction is conducted in a stainless steel column of 0.1 m diameter and 1-m height. The variables considered are reaction temperature, stirrer speed, flow rate of fluidizing medium, and static bed height. Experiments are performed using statistically designed factorial experiments. Data are used to find the model suitable to the mechanism of the reaction. Mathematical equations relating reaction parameters viz., steady state conversion, time for steady state conversion, reaction rate constant, and activation energy with operating variables are developed and activation energy is reduced from 14 kcal/mol reported in literature to less than 5.3 kcal/mol depending on operating conditions. The concept could be adopted for the manufacture of cement, and other materials with required modifications of experimental setup. 