Decomposition reaction of H2O2 over Pd/C catalyst in an aqueous medium at high pressure: Detailed kinetic study and modelling

Decomposition of H2O2 is an undesired side reaction that occurs during the direct synthesis of H2O2 over Pd/C catalysts. Experiments have been carried out to understand the influence of pressure (0.2–7.5 MPag), temperature (23–50 °C), pH, halide concentration, catalyst and inert gas in decomposition. A model considering these effects is proposed, achieving average deviations lower than 5%. It has been found that a pH lower than 1.8 and halide to Pd ratios over 2.2 are enough to reduce the decomposition more than 90%. Activation energies between 15.0 and 83.8 kJ/mol, with and without promoters, have been found. The influence of pressure is limited for the case of decomposition above 2.5 MPag. Decomposition increases almost linearly with the amount of the active metal catalyst. Specific decomposition rates between 6.65 and 23,295 min−1 molPd−1 with and without promoters have been observed in this study.

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► Kinetics of decomposition of H2O2 in water at high pressures with N2 and CO2.
► Model explaining the effect of acid, halide, pretreatment, temperature and catalyst.
► CO2 produces an acidic protection without the need of mineral acid added.
► Improvement of the direct synthesis of H2O2 using supercritical CO2 in water.