Abstract
Water sonolysis generates hydrogen through acoustic cavitation. In this work, based on a model for a reactive acoustic bubble, correlations between the sonochemical production of hydrogen and the maximum temperature and pressure reached in the bubble at the violent collapse have been made. The computational analysis has been performed for more than 800 points obtained by combining various cavitation parameters, i.e., frequency, acoustic intensity, liquid temperature, and ambient bubble radius. The simulation results showed that hydrogen production rate progressed linearly with the bubble temperature and pressure rise up to plateaus, which begin at 3500 +/- 200 K and 100 +/- 10 atm. Analyzing the progress of H-center dot and (OH)-O-center dot (H-2 precursors) as function of bubble temperature and pressure showed very similar evolutions as those obtained for H-2 with the same optimums at 3500 +/- 200K and 100 +/- 10 atm. Consequently, in addition to the quench of hydrogen formation at very high bubble temperatures through the reaction H-2 + (OH)-O-center dot -> H2O + H-center dot, the existing optimum temperature and pressure for H2 production may also be due the hard consumption of their precursors ((OH)-O-center dot and H-center dot) above 3500 K and 100 atm.