Weimin Gong

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

In Situ FT-IR Studies on Catalytic Nature of Iron Nitride: Identification of the N Active Site

Iron nitride has been widely used and played an important role in many catalytic processes, such as Haber–Bosch process (key intermediates), biological ammonia synthesis (nitrogen fixation), ammonia and hydrazine decomposition, NO removal, hydrodenitrogenation (HDN), and hydrodesulfurization (HDS), etc. The modification of properties of the Fe hosts upon N atom insertion into the closely packed metal lattice has been intensively studied by various techniques (Mçssbauer spectroscopy, XPS, LEED, XRD, and TEM) in terms of the structure change, electronic and steric effects, magnetic properties, mechanical hardness, electrical conductivity, and corrosion resistance. In comparison with metallic Fe, the increasing density of state at the Fermi level for Fe in the form of iron nitride originates from the d-band contraction of the metal with elongated M M bonds caused by the introduction of N atoms. 22] This renders the excellent catalytic behavior of iron nitrides comparable to noble metals. However, the essence of the iron nitride in catalysis has remained ambiguous so far, and especially challenging is the precise understanding of the surface-active sites, such as the Fe site, the N site, or the joint Fe N sites on the surface of iron nitride. Thus, more insights are needed to clearly identify the active sites on iron nitride surface. Infrared spectroscopy (IR), with the ability to probe surface process at the molecular level, is a powerful technique to identify the surface active sites of heterogeneous catalysts. Q. Xin. et al. first reported IR spectroscopic investigation on the nature of the surface sites of fresh Mo2N/Al2O3 by using CO as the probe molecule. Herein we report, for the first time, the identification of the N site as a chemically active center coexisting with the Fe site on the surface of iron nitride by using in situ FTIR coupled with CO, NH3, and H2-probe molecules. Moreover, the direct synthesis of amines from ethylene and ammonia were first achieved over iron nitride. Analysis of the adsorption of CO

Direct and continuous synthesis of concentrated hydrogen peroxide by the gaseous reaction of H2/O2 non-equilibrium plasma

Under ambient conditions, H2O2 has been synthesized with 32.51% yield and 56.25% selectivity via the gas-phase reaction of H2/O2 non-equilibrium plasma.

Study on the hydrogenation coupling of methane

At atmospheric pressure and ambient temperature, the hydrogenation coupling of methane was studied by using pulse corona plasma and its synergism with catalyst. The results showed that (i) under pulse corona plasma, the coupling of methane could be fulfilled by the addition of hydrogen, and with the increase of the amount of hydrogen, the conversion of methane and the yield of C2 hydrocarbon increased, and the deposit of carbon decreased; (ii) the conversion of methane was affected by pulse voltage and repeated frequency; (iii) in the system, the addition of Ni/γ-Al2O3 could improve the distribution of C2 hydrocarbon; (iv) the activity of Ni/γ-Al2O3 prepared by cold plasma was better than that by chemical methods. The experiment opened up a new technical route of the coupling of methane.