Yanhui Yi

A review on research progress in the direct synthesis of hydrogen peroxide from hydrogen and oxygen: noble-metal catalytic method, fuel-cell method and plasma method

Hydrogen peroxide (H2O2) as a highly efficient and green oxidant has become one of the 100 most important chemicals in the world. Some current research progress in the direct synthesis of H2O2 from H2 and O2 by noble-metal catalyst, fuel cell and plasma methods has been reviewed systematically in this paper. Perspectives about the development direction and application prospect of the above-mentioned three methods have also been discussed.

Safe Direct Synthesis of High Purity H2O2 through a H2/O2 Plasma Reaction

Extensive studies have been done on direct H2O2 synthesis from a H2/O2 mixture. To achieve high efficiency, direct H2O2 synthesis is generally performed in acidified solvent over supported noble-metal catalysts (Au, Pd, Au–Pd, and Pd– Pt). However, the direct synthesis of H2O2 from a H2/O2 mixture catalyzed by metals is quite hazardous, and it is very difficult to directly obtain high-purity and high-concentration H2O2. Research 13] published in the 1960s has demonstrated that H2O2 can be generated in H2/O2 non-equilibrium plasma through free-radical reactions in the absence of any catalyst or chemical. However, this plasma method has not yet drawn much attention, owing to low H2O2 yield (less than ca. 5%) and safety concerns about the discharge-triggered H2/O2 reaction. The content of O2 must be strictly controlled below 4 mol % in order to prevent explosion and ignition. Our previous research showed that the structure of the plasma reactor played an important role in the direct synthesis of H2O2. A H2/O2 mixture containing 3 mol% of O2 reaches 100% O2 conversion, but the H2O2 selectivity is only 3.5% (based on O2) in a single dielectric barrier discharge (SDBD) plasma reactor with a naked metal highvoltage (HV) electrode and an aqueous grounding electrode. On the other hand, 57.8% O2 conversion and 56.3 % H2O2 selectivity (based on O2) can be obtained by using a double dielectric barrier discharge (DDBD) plasma reactor with a pyrex-covered metal HV electrode (the pyrex cover acts as an additional dielectric barrier) and an aqueous grounding electrode. Although the selectivity has been greatly improved, the safety concerns and low efficiency, owing to low O2 content, are still big challenges. Herein, we report an experimental realization of controllable H2/O2 combustion processes by an optimized plasma reactor. High purity (Grade 1 electronic grade H2O2 according to the SEMI standard) and highly concentrated H2O2 solution (ca. 60 wt %) can be directly produced from a H2/O2 mixture without explosion. These results suggest a different mechanism from conventional H2/O2 combustion processes in the H2/O2 plasma reaction. As shown in Scheme 1, the electron activation of H2 into H is responsible for H2O2

Plasma-Triggered CH4/NH3 Coupling Reaction for Direct Synthesis of Liquid Nitrogen-Containing Organic Chemicals

Nitrogen-containing organic chemicals such as amines, amides, nitriles, and hydrazones are crucial in chemical and medical industries. This paper reports a direct synthesis of N,N-dimethyl cyanamide [(CH3)2NCN] and amino acetonitrile (NH2CH2CN) through a methane/ammonia (CH4/NH3) coupling reaction triggered by dielectric barrier discharge plasma, with by-products of hydrazine, amines, and hydrazones. The influence of CH4/NH3 molar ratio, feedstock residence time, and specific energy input on the CH4/NH3 plasma coupling reaction has been investigated and discussed. Under the optimized conditions, the productivities of (CH3)2NCN and NH2CH2CN reached 0.46 and 0.82 g·L–1·h–1, respectively, with 8.83% CH4 conversion. In addition, through combining the optical emission spectra diagnosis and the reaction results, a possible CH4/NH3 plasma coupling reaction mechanism has been proposed. This paper provides a potential fine application of CH4 and NH3 in green synthesis of liquid nitrogen-containing organic chemicals, such as nitriles, amines, amides, and hydrazones.