Modeling of Direct Synthesis of Hydrogen Peroxide in a Packed-Bed Reactor

Direct synthesis of hydrogen peroxide from oxygen and hydrogen continues to be a research topic of high interest. It would be most desirable if this synthesis could be carried out in a continuous fixed-bed reactor in a safe way, with a catalyst providing both high selectivity and high productivity. This could significantly simplify the hydrogen peroxide production process and reduce both operating and investment costs. In the conventional anthraquinone-based production process, the hydrogenation and oxidation steps are carried out in separate reactors, and extraction is finally used for hydrogen peroxide recovery. Recirculation of large quantities of the multicomponent organic working solution takes place, and expensive filtration of the hydrogenation catalyst from this vast stream is required when a slurry reactor is used. The main benefit of the conventional process is that it is a well-proven and reliably operating technology. The most straightforward approach for the direct synthesis is to carry out the reaction between H-2 and O-2 on a heterogeneous catalyst, preferably Pd or Pd/Au catalyst, in a suitable solvent. Methanol is one of the most popular choices for the solvent because the solubilities of H-2 and O-2 in methanol are much larger than those in water. This article presents a modeling study for the direct synthesis of hydrogen peroxide with methanol as the solvent in a continuous three-phase reactor. The modeling study used data from an experimental study performed with a Pd/CeS catalyst in our laboratory reactor. The aim of the modeling was to provide insight into the physical and chemical phenomena occurring during the process. The reaction system was a challenging one, because both side reaction and decomposition reactions took place simultaneously with the highly desirable synthesis. The model was found to describe the experimental data from the fixed-bed reactor rather well. Particle diffusion was found to be most severe for the synthesis and oxidation reactions.