Direct synthesis of hydrogen peroxide in methanol and water using scCO2 and N2 as diluents

Abstract

Direct synthesis of hydrogen peroxide is of high importance nowadays due to its improvement over the traditional anthraquinone hydrogenation-oxidation process. In this work we show how H₂O₂ can be obtained from H₂ and O₂ in water pressurised with CO₂ under supercritical conditions or with N₂ at similar conditions without using organic solvents. Pressures up to 16.7 MPa and mild temperatures from 10 to 45 °C using a commercial 5 wt.% Pd/C catalyst lead to yields from 10.8% to 82.6%, concentrations from 0.22 to 4.01 wt.% of H₂O₂ and Turn Over Frequency at 30 minutes values, TOF₃₀, from 6.0 to 1538 mol·h⁻¹·kg_cat⁻¹. The effect of several variables on H₂O₂ yield has been examined: amount of catalyst, promoters/Pd ratio, amount and nature of solvent and inert gas, reaction temperature, and O₂/H₂ ratio. Results for methanol and water are compared.