Azolation in a rotating packed bed reactor: Kinetics and process studies

As the most common type of synthetic dyes, azo dyes are widely used for coloring fibers, paints, plastics, rubber, etc. However, due to the high local concentration in azolation, the decomposition and hydrolysis of diazo salts lead to the decline in the quality of azo dyes. In this work, the azolation of p -aminobenzene diazo sulfate ( p -ADS) and N -cyanoethyl- N -benzyl aniline ( N -CBA) as the model reaction to analyze the potential of rotating packed bed (RPB) reactor in improving the quality of azo dyes. Firstly, the intrinsic kinetic models of main reaction and side reactions were proposed and verified, revealing that the high local concentrations could accelerate the side reactions. After that, the DFT calculation indicates that the azolation process needs to be completed in two steps, and the process of generating the complex has a higher reaction energy barrier (19.88 kcal/mol). Under optimal process conditions, the purity and yield of product were 92.80 % and 98.37 % in the RPB reactor, while 89.90 % and 96.09 % in the stirred tank reactor (STR). Moreover, the strength and average particle size of DO-288 synthesized in the RPB reactor were 728 and 0.6 μm respectively, which were significantly better than 715 and 0.78 μm in STR. These results indicate that the RPB reactor has obvious advantages in the synthesis of high-quality, highly dispersed and highly strength azo dyes.