Direct Synthesis Of Hydrogen Peroxide From H₂/O₂ Plasma Under High Concentration Of O₂

Hydrogen peroxide is an important green oxidizing agent. The direct synthesis of H2O2 via H2/O2 non-equilibrium plasma, which is characterized by simple operation process, high concentration and ultra high purity of the product, provides a promising alternative route for H2O2 production. Based on our previous works, the synthesis feasibility of H2O2 in the explosion limit of H2/O2 mixture using the self-cooling double dielectric-barrier discharge (DDBD) reactor have been carried out in this study. The following main results were obtained:1. When the atmospheric pressure is 1 atm, using the self-cooling double dielectric-barrier discharge (DDBD) reactor can get safety discharge when the concentration of O2 is below 30%; when the concentration of O2 is between 30%-50%,the explosion happens occasionally due to the voltage fluctuations; when the concentration of O2 is more than 50%, the explosion will happen as soon as the discharge starts. The use of liquid in the high-voltage electrode and grounding electrode can improve synthesis results of H2O2 when the concentration of O2 is below 30%.2. When the concentration of O2 is below 30%, the concentration of O2, cooling water temperature and discharge frequency all have significant effects on H2O2 synthesis. The selectivity of H2O2 can be enhanced by using high concentration of O2 under the premise of ensuring safety. The increase of discharge frequency and decrease of cooling-water temperature at a certain extent also favored the improvement of O2 conversion, H2O2 yield and energy efficiency. The direct synthesis of H2O2 has achieved 17%O2 conversion,83% H2O2 selectivity and 50 gH2O2/kWh energy efficiency under the conditions of saturated sodium chloride solution high-voltage electrode, cooling water grounding electrode, the cooling-water temperature 15℃,the discharge frequency 12 kHz, the H2/O2 mixture flow rate 80 ml/min, the O2 concentration in the H2/O2 mixture 20% and. the reactor input power 4 W.3. The synthesis of H2O2 from H2/O2 under high concentration of O2 via dielectric barrier discharge at ambient conditions by increasing DDBD reactors was studied. Varying the number of reactors had no significant effect on discharge mode, the H2O2 selectivity is the same as that of the single reactor. By increasing DDBD reactors higher H2O2 productivity and higher energy efficiency can be obtained.