Hydrogen production by radio frequency plasma stimulation in methane hydrate at atmospheric pressure

Methane hydrate, formed by injecting methane into 100 g of shaved ice at a pressure of 7 MPa and reactor temperature of 0 °C, was decomposed by applying 27.12 MHz radio frequency plasma in order to produce hydrogen. The process involved the stimulation of plasma in the methane hydrate with a variable input power at atmospheric pressure. It was observed that production of CH₄ is optimal at a slow rate of CH₄ release from the methane hydrate, as analyzed by in light of the steam methane reforming (SMR) and the methane cracking reaction (MCR) processes in accordance with the content of gas production. In comparison with the steam methane reforming (SMR), it was found that methane-cracking reaction (MCR) was dominant in conversion of CH₄ into hydrogen. An H₂ content of 55% in gas production was obtained from conversion of 40% of CH₄ at an input power of 150 W. The results clearly show that hydrogen can be directly produced from methane hydrate by the in-liquid plasma method.     

The effect of different atmosphere treatments on the performance of Ni/Nb–Al2O3 catalysts for methane steam reforming

Methane steam reforming is currently the most widely used hydrogen production reaction in industry today. Ni/Nb–Al₂O₃ catalysts were prepared by treatment under H₂, N_2, and air atmosphere prior to reduction and applied for methane steam reforming reaction at low temperature (400–600 °C). The hydrogen-treated catalysts increased catalytic activity, with 55.74% methane conversion at S/C = 2, GSVH of 14400 mL g^?1 h^?1 and 550 °C. The H₂ atmosphere treatment enhanced the Ni–Nb interaction and the formation of stable, tiny, homogeneous Ni particles (6 nm), contributing to good activity and stability. In contrast, the catalysts treated with nitrogen and air showed weaker interactions between Ni and Nb species, whereas the added Nb covered the active sites, which caused the decrease in activity. Meanwhile, carbon accumulation was also observed. This work is informative for preserving small nano-sized nickel particles to enhance catalytic performance.     

On the comparison of energy sources: Feasibility of radio frequency and ambient light harvesting

With growing interest in multi source energy harvesting including integrated microchips we propose a comparison of radio frequency (RF) and solar energy sources in a typical city. Harvesting devices for RF and solar energy will be competing for space of a compact micro or nano device as well as for orientation with respect to the energy source. This is why it is essential to investigate importance of every source of energy and make a decision whether it will be worthwhile to include such harvesters. We considered theoretically possible irradiance by RF signal in different situations, typical for the modern urban environment and compared it with ambient solar energy sources available through the night, including moonlight.Our estimations show that solar light energy dominates by far margin practically all the time, even during the night, if there is a full moon in the absence of clouds. At the same time, in the closed compartments or at the new moon RF harvesting can be beneficial as a source of “free” energy.     

射频识别技术在物流工程中的应用

结合汽车制造业、超市的实例提出了如何识别物件信息的问题,简要介绍了射频识别技术的基本原理,对所面临的技术障碍作了比较全面客观的分析,并对其应用前景作了合理的预测。     

过滤器微波再生系统的射频测控技术

根据微粒过滤器微波再生的需要,提出了过滤体微粒沉积及再生的射频测控方法。叙述了射频测控技术的基本原理。通过理论推导给出了检测天线的设计方法,并从功率容量的要求出发对检测天线进行了设计。利用设计的测试系统在柴油机上进行了大量的试验测定,对实际测量结果进行了分析,并对各种影响因素进行了研究。试验结果验证了过滤体微粒沉积量射频测试方法的可行性。文中提出的射频测控技术为柴油机微粒后处理系统的实际应用奠定了基础     

Experimental and numerical investigations of coke descending behavior in a coke dry quenching cooling shaft

A viscous flow model based on the Navier–Stokes equation is developed to describe coke descending behavior in the 1/7-scaled-down experimental setup of an actual 75 t/h cooling shaft. It is found that the internal friction due to cokes viscosity significantly influences the descending behavior of cokes in the lower part of the shaft, while the external wall friction dominates the sluggish flow of the cokes in the shaft. An asymptotic friction coefficient expression is proposed for granular mixtures flowing along the shaft wall modified from normal wall tress, and the concept of bulk solid viscosity is introduced to describe the internal friction between coke particles. The results simulated by the present model are compared with those by the potential flow and the kinematic model without friction. The viscous flow model is quite good to simulate the bulk coke flow as the physically important frictions are engaged.     

Carbon dioxide reforming of methane over Ni/Mg0.4Al0.4-La0.1Zr0.1(O) catalyst prepared by recombination sol–gel method

Based on several catalysts preparation methods, we developed a new sol–gel method and produce a series of quaternary catalysts Ni/Mg_xAl_x-La_0.5-xZr_0.5-x(O) (x = 0, 0.13, 0.25, 0.33, 0.4, 0.43, 0.5) using different ratios of binary metallic oxide (MgAl(O) to LaZr(O)). The synthesized samples were employed in the dry reforming of methane (DRM) and mixed reforming of hydrocarbons (CH₄ & C₂H₆) (MRH) to evaluate their performances at 800 °C under atmospheric pressure. The experimental result indicates that the catalytic activity was mainly dependent on the interaction between active component (NiO particle) and support, and Ni/Mg_0.4Al_0.4-La_0.1Zr_0.1(O) exhibited the highest activity (CH₄ 96.1% & CO₂ 95.9%) during DRM. The physicochemical properties of these catalysts were analyzed by N₂ adsorption–desorption, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), H₂ temperature-programmed reduction (H₂-TPR) and thermogravimetric analysis (TGA). The TPR analysis result illustrated that strong interaction between Ni active species and support was observed on catalysis Ni/Mg_0.4Al_0.4-La_0.1Zr_0.1(O), increasing the stability of Ni and thus enhanced both abilities of anti-sintering and anti-coking during the reaction. The XRD characterization of fresh and used Mg_0.4Al_0.4-La_0.1Zr_0.1(O) witnessed that the active component Ni was well dispersed on the support, and the minimal carbon deposition was detected on the used Ni/Mg_0.4Al_0.4-La_0.1Zr_0.1(O) by TGA and SEM compared with other catalysts. The 80 h activity test confirmed that the Mg_0.4Al_0.4-La_0.1Zr_0.1(O) can still perform high conversions (both CH₄ & CO₂ > 95% after 80 h) and stability after a long time DRM reaction. Moreover, the quaternary Ni/Mg_0.4Al_0.4-La_0.1Zr_0.1(O) is also suitable for mixed hydrocarbons reforming to produce syngas, which showed its excellent performance (CH₄ 94%, CO₂ 96% and C₂H₆ 100%) during the reaction and may be widely used in the future.     

Plasma reforming for hydrogen production: Pathways,reactors and storage

Hydrogen is an energy carrier with a very high energy density (>119 MJ/kg). Pure hydrogen is barely available; thus, it requires extraction from its compounds. Steam reforming and water electrolysis are commercially viable technologies for hydrogen production from water, alcohols, methane, and other hydrocarbons; however, both processes are energy-intensive. Current study aims at understanding the methane and ethanol-water mixture pathway to generate hydrogen molecules. The various intermediate species (like CH_X, CH₂O, CH₃CHO) are generated before decomposing methane/ethanol into hydrogen radicals, which later combine to form hydrogen molecules. The study further discusses the various operating parameters involved in plasma reforming reactors. All the reactors work on the same principle, generating plasma to excite electrons for collision. The dielectric barrier discharge reactor can be operated with or without a catalyst; however, feed flow rate and discharge power are the most influencing parameters. In a pulsed plasma reactor, feed flow rate, electrode velocity, and gap are the main factors that can raise methane conversion (40–60%). While the gliding arc plasma reactor can generate up to 50% hydrogen yield at optimized values of oxygen/carbon ratio and residence time, the hydrogen yield in the microwave plasma reactor is affected by flow rate and feed concentration. Therefore, all the reactors have the potential to generate hydrogen at lower energy demand.     

Effect of Ar plasma treatment on the photo-electrical properties of nanocrystal TiO2 films

Nanocrystal TiO₂ films were prepared by radio frequency (RF) sputtering technique and coating method, respectively. The samples were treated by Ar RF plasma. The crystal structure, absorption spectra and morphology of the TiO₂ films were investigated by X-ray diffraction (XRD), UV–VIS spectrophotometry and atomic force microscopy (AFM). The voltages and photo-currents of the TiO₂ electrodes were also measured. By Ar plasma treatment, the photo-currents of the sputtered and coated TiO₂ electrodes increased by 80% and 60%, respectively.     

介质特性对介质阻挡放电脱除NO影响试验研究

在介质阻挡气体放电等离子体条件下,研究阻挡介质特性对NO脱除的影响规律。首先建立了介质阻挡放电等离子体脱硝试验系统,实验研究了Al2O3、CaO、MgO和玻璃等不同介质阻挡下NO的脱除效果,并对此影响规律进行了理论分析。实验结果及理论分析表明,不同阻挡介质所形成的气体放电的电场强度不同,提供给活性粒子的能量也不同,从而对NO的脱除效果具有不同的影响。     

Coke resistance of Ni-based catalysts enhanced by cold plasma treatment for CH4–CO2 reforming: Review

Carbon dioxide reforming of methane can reduce emissions of greenhouse gases, and has been extensively studied. The conventional Ni-based catalysts easily coke, sinter, and deactivate in the CRM reaction. The studies suggested that the cold plasma treatment can improve the structure of Ni-based catalysts, and so enhance coke resistance of the catalysts. The review summarized the effect of cold plasma treatment on the coke resistance of Ni-based catalysts for the CRM reaction. The main goal of the paper was to illuminate: the structure change of catalysts treated by cold plasma, such as crystal planes of Ni particles, the particles size of Ni, the Ni dispersion, the metal-support interaction, and CO₂ absorption capacity; the correlation between plasma treatment conditions (treatment way and parameters) and coke resistance of the catalyst treated by cold plasma; and the mechanism of plasma treatment to improve the coke resistance of the catalysts.     

A highly effective and stable nano-sized Ni/MgO–Al2O3 catalyst for gas to liquids (GTL) process

Highly active and stable nano-sized Ni catalysts supported on MgO–Al₂O₃ prepared from hydrotalcite-like materials have been designed for the combined steam and carbon dioxide reforming of methane (CSCRM), which is a useful process to adjust the H₂/CO ratio for Fischer–Tropsch process. Ni/MgO–Al₂O₃ exhibits remarkable coke resistance, while commercial Ni/MgAl₂O₄ catalyst shows considerable coke deposition during the target reaction. A strong metal to support interaction (SMSI) of Ni/MgO–Al₂O₃ enhances coke resistance. The change of the surface area and NiO crystallite size with varying the pre-calcination temperature of support was investigated in relation to the coke resistance. It has been concluded that highly dispersed Ni metal pre-calcined at 800 °C shows good coke resistance and high activity. As a consequence, Ni/MgO–Al₂O₃ catalyst will be a promising catalyst in CSCRM for the GTL process.     

Coke-resistance over Rh–Ni bimetallic catalyst for low temperature dry reforming of methane

Methane and carbon dioxide can be converted into syngas using the prospective dry reforming of methane technology. Carbon deposition is a major cause of catalyst deactivation in this reaction, especially at low temperature. The superior stability of bimetallic catalysts has made their development more and more appealing. Herein, a series of bimetallic RhNi supported on MgAl₂O₄ catalysts were synthesized and used for low temperature biogas dry reforming. The results demonstrate that the bimetallic RhNi catalyst can convert CH₄ and CO₂ by up to 43% and 52% over at low reaction temperature (600 °C). Moreover, the reaction rate of CH₄ and CO₂ of RhNi–MgAl₂O₄ remains stable during the 20 h long time stability test, most importantly, there was no obviously carbon deposition observed over the spent catalyst. The enhanced coking resistance should be attributed to the addition of a little amount of noble metal Rh can efficiently suppress dissociation of CH_X1 species into carbon, and the high surface areas of MgAl₂O₄ support can also promote the adsorption and activation of carbon dioxide to generate more O1 species. Balancing the rate of methane dissociation and carbon dioxide activation to inhibit the development of carbon deposition is a good strategy, which provides a guidance for design other high performance dry reforming of methane catalysts.     

Production of synthesis gas from propane using thermal water vapor plasma

In this work, an experimental plasma-chemical reactor equipped with a water vapor plasma torch was used for catalyst-free thermal plasma reforming of propane to produce a synthesis gas. Thermal arc discharge plasma (a mixture of water vapor and argon) was generated at atmospheric pressure.