No abstract

The present work establishes in depth study of ultrasound assisted preparation of performic acid (PFA) in a continuous flow microstructured reactor. The influence of various parameters viz. formic acid: hydrogen peroxide molar ratio, flow rate, temperature and catalyst loading on the PFA formation were studied in a continuous flow microstructured reactor. In a continuous microstructured reactor in the presence of ultrasonic irradiation, the formation of PFA was found to be dependent on the molar ratio of formic acid: hydrogen peroxide, flow rate of reactants, temperature and catalyst loading (Amberlite IR-120H). The optimized parameter values are 1:1M ratio, 50mL/h, 40°C and 471mg/cm respectively. Further, the performance of Amberlite IR-120H catalyst was evaluated for three successive cycles in continuous microstructured reactor. The performance of catalyst was found to be decreased with the usage of the catalyst and is attributed to neutralization of the sulfonic acid groups, catalyst shrinkage, or loss in pore sites. The experimental results revealed that, for an ultrasound assisted synthesis of PFA in continuous microstructured reactor the observed reaction time was even less than 10min. The observed intensification in the PFA synthesis process can be attributed to the intense collapse of the cavities formed at low temperature during ultrasonic irradiations, which further improved the heat and mass transfer rates with the formation of HO during the reaction. The combined use of ultrasound and a continuous flow microstructured reactor has proved beneficial process of performic acid synthesis.

Ultrasonic cavitation induced degradation of Congo red in aqueous solution was investigated for a variety of operating conditions. It is found that the degradation of Congo red in aqueous solution follows pseudo-first-order reaction kinetics and the degradation rate is dependent on the initial concentration of Congo red, the temperature and pH of the aqueous medium. The effects of Fe 2+ and Fenton reagent addition on the sonochemical degradation of Congo red were also investigated. The results obtained here indicate that the degradation rate of Congo red in aqueous solution was substantially accelerated by Fe 2+ , NaCl or Fenton reagent addition.