Sonochemical reaction of formic acid-water solution - Effects of dissolved gases, formic acid concentration and reaction temperature on the rate of production and the distribution of sonochemical products

The sonochemical reaction of argon-dissolved formic acid-water solution was carried out. The main gaseous products were CO, CO2 and H-2. It was interesting that CO was obtained by sonolysis of formic acid. In the cases of degassed or CO2-dissolved sample, only a little product was detected. The reactivity depended on the dissolved gases. For example, the amounts of CO and H-2 decreased for the air-saturated sample. Thus, dissolved gases play an important role in the sonolysis. Effects of formic acid concentration and temperature on the reactivity were also examined. Not only the amounts of gaseous products for 1h but also the ratio of CO to the other products reached the maximum value at 1 : 1 solution. Temperature dependence of the gas evolution rate was observed in the rage of 5-45 degrees C. It was found that the temperature dependence was affected by formic acid concentration. In the case of low concentration (5 %), temperature dependence was clear; i.e. the rate of CO production decreased with increase of temperature.