A trickle bed reactor (TBR) was used to study different process parameters upon hydrogen peroxide direct synthesis. The catalysts used were commercial palladium on active carbon. The influence of pressure (1.75–25 barg), temperature (5–60°C), liquid flow rate (2–13.8 ml·min-1), gas flow rate (3.4–58.5 ml·min-1), catalyst amount (90–540 mg), Pd percentage on the support (5% wt., 10% wt. and 30% wt. Pd/C) as well as promoter concentrations (0.0005–0.001 m) were all varied as process parameters to better understand the behaviour of the system. By contrast, the gas phase molar composition of the feed (4:20:76=H2:O2:CO2) was kept constant. The strong influence between liquid flow rate, gas flow rate and catalyst amount were identified as the key parameters to tune the reaction, and related to the activity of the catalyst. In essence, these parameters must be carefully tuned to control the hydrogen consumption. The maximum productivity (289 μmol H2O2·min-1) and yield (83.8%) were obtained when a diluted bed of 30% Pd/C was applied. The H2O2 hydrogenation was studied in order to understand its role in the H2O2 direct synthesis reaction network. The hydrogenation reaction mechanism and the role of NaBr were identified thanks to the experiment proposed in the present work. Consequently, understanding the whole reaction mechanism from the process conditions studied led to a deeper understanding of all of the phenomena involved in the H2O2 direct synthesis.
Walter de Gruyter, 2016.
direct synthesis; heterogeneous catalysis; hydrogen peroxide; palladium on carbon; trickle bed reactor