盐酸克伦特罗在乙炔黑电极上的电化学行为及其分析测定研究

研究了盐酸克伦特罗(CLB)在乙炔黑电极上的电化学行为,发现阴离子表面活性剂十二烷基苯磺酸钠(SDBS)能显著提高CLB的氧化峰电流并降低其氧化过电位。优化了实验参数,建立了一种直接测定CLB的新电分析方法,其线性范围为1.0×10-7~7.5×10-5mol/L,开路富集1 min后的检出限为2.5×10-8mol/L。平行10次测定1.0×10-5mol/L盐酸克伦特的RSD为3.1%。方法用于猪尿中盐酸克伦特罗含量的测定。     

A kinetic study of methane conversion by a dinitrogen microwave plasma

Conversion of CH₄ with a N₂ microwave plasma (2.45 GHz) is studied. The experiments cover the absorbed microwave power range 300–700 W with 17–62% of methane in the gas mixture, with pressures of 10–40 mbar and flow rates of 140–650 ml· min^–1. The yields of C₂ hydrocarbons and dihydrogen are analyzed by gas chromatography. The distance of methane addition downstream of the plasma plays an important role on the composition and the concentration of the products obtained. This distance mainly determines the energy concentrated in the active species of the plasma when they react with methane. Different behaviors for acetylene formation, on the one hand, and for ethane and ethene formation, on the other hand, have been observed, and this finding allows us to propose a kinetic mechanism for the decay of methane and for the formation of C₂ hydrocarbons.     

CARS diagnostics of acetylene formation in a plasma test reactor for hydrocarbon synthesis

Measurements of acetylene concentrations in an arc plasma test reactor using coherent anti-Stokes Raman scattering (CARS) are described. The method is based on the measurement of relative spectral shapes in the presence of a substantial nonresonant background. Calculations of CARS spectra, necessary for the concentration analysis, are described. The quality of calculated spectra is examined with the aid of reference spectra taken in a graphite oven operated under variable, known temperatures and concentrations. The measurements with the plasma test reactor yield spatially resolved concentration distributions of a few percent. Comparison with 1R absorption measurements shows satisfactory agreement.     

A High-Efficiency Reactor for the Pulsed Plasma Conversion of Methane

The authors recently developed a high-frequency pulsed plasma process for methane conversion to acetylene and hydrogen using a co-axial cylindrical (CAC) type of reactor. The energy efficiency represented by methane conversion rate per unit input energy has been improved so that such a pulsed plasma has potential for commercial acetylene production. A pulsed plasma consists of a pulsed corona discharge and a pulsed spark discharge. Most of energy is injected over the duration of the pulsed spark discharge. Methane conversion using this kind of pulsed plasma is a kind of pyrolysis enhanced by the pulsed spark discharge. In this study, a point-to-point (PTP) type of reactor that can produce a discharge channel over the duration of a pulse discharge was used for the pulsed plasma conversion of methane. The energy efficiency and carbon formation on electrodes have been improved. The influences of pulse frequency and pulse voltage on methane conversion rate and product selectivity were investigated. The features of methane conversion using PTP and CAC reactors were discussed.     

滑动弧电极放电等离子体作用甲烷制C2烃的工艺

采用刀片式不锈钢电极放电反应器,以Ar气为稀释气,研究了等离子体作用下甲烷转化制C2烃的工艺条件。考察了CH4流量、高频电源输入电压和电极间距等参数对甲烷转化率、C2烃选择性、收率和反应表观能耗的影响。结果表明,增加CH4流量,表观能耗随之降低;当输入电压和电极间距较小时,甲烷转化率随输入电压和电极间距的增大而增大,但输入电压和电极间距过大时,C2烃收率明显下降,积碳严重。在CH4流量14 mL/min、Ar气流量60 mL/min、高频电源输入电压22 V、电流0.44 A、电极间距4 mm的优化条件下,甲烷最高转化率为43.1%,C2烃收率、选择性和表观能耗分别为40.1%、93.2%和2.41 MJ/mol。C2烃中不饱和烃的体积分数可达95%以上。     

Beyond-thermal-equilibrium" conversion of methane to acetylene and hydrogen under pulsed corona discharge

At ambient temperature and pressure, C2H2 and H2 are the dominating products from pure methane conversion under pulsed corona discharge (PCD). When the energy density of 194-1788 kJ/mol was applied, 7%-30% of C2H2 yield and 6%-35% of H2 yield per pass have been obtained. These results are higher than the maximum thermodynamic yield of C2H2 (5.1%) and H2 (3.8%) at 100 kPa and 1100 K, respectively. Thereby, pulsed corona discharge is a very effective tool for "beyond-thermal-equilibrium" conversion of methane to C2H2 and H2 at ambient temperature and pressure. In the PCD energy density range of 339-822 kJ/mol, the carbon distribution of the methane conversion products is found to be: C2H2 86%-89%, C2H6 4%-6%, C2H4 4%-6%, C3 -2%, C4 -1%. Through comparison of the product from pure methane, ethane and ethylene conversion at the same discharge conditions, it can be concluded that three pathways may be responsible for the C2H2 formation via CHx radicals produced from the collisions of CH4 molecules with energi     

Energochemical technologies: energy and bulk/basic chemicals in a single process

The exoergic reactions, which underlie the production of large-scale basic chemicals for organic industry, can be used for one-pot generation of energy and chemical products. Typical examples include methane oxidative conversion to produce synthesis gas and methane oxidative dimerization to give ethylene and ethane.     

基于火花放电等离子体部分氧化重整二甲醚制氢研究

应用自制的多级式等离子体富氢气体制备装置，进行了二甲醚部分氧化重整制氢实验。实验结果表明，常温常压下二甲醚的转化率和氢产率随占空比的增大先增大后减小，当占空比为80%时最大值分别为87.6%和39.4%。随着电源电压的增加，放电能量和持续时间逐渐增加，转化率和氢产率逐渐增加。当反应器采用保温措施或对反应物进行加湿时，转化率和氢产率均有明显提高，同时制氢能耗下降，热效率有一定提高。实验过程中附着在电极上的积炭主要是由于氧气不足造成，随空醚比的增大，积炭明显减少。     

W－Mn／SiO_2催化剂甲烷氧化偶联制乙烯流化床工艺条件考察

本文报导了浸渍法制备的Ｗ－Ｍｎ／ＳｉＯ_２催化剂分别在Φ２８和Φ３８毫米反吹式流化床上进行的条件试验和３００ｈ稳定性试验结果。并用ＸＲＤ、ＦＴ－ＩＲ、ＢＥＴ等方法对催化剂进行了表征。结果表明，该催化剂可适用于流化床，并具有较好的ＣＨ４氧化偶联制Ｃ２烃的催化活性和稳定性。催化剂的结构研究表明，经３００ｈ反应后，该催化剂中结晶形式的Ｎａ_２ＷＯ_４和Ｍｎ_２Ｏ_３均已消失；α－方石英结构已完全转变为α－磷石英和α－ＳｉＯ_２石英，但催化剂的这种结构变化尚未对生成Ｃ２烃的收率和选择性产生明显影响。     

Platinum- and CuOx-Decorated TiO2 Photocatalyst for Oxidative Coupling of Methane to C2 Hydrocarbons in a Flow Reactor

Oxidative coupling of methane (OCM) is considered one of the most promising catalytic technologies to upgrade methane. However, C₂ products (C₂H₆/C₂H₄) from conventional methane conversion have not been produced commercially owing to competition from overoxidation and carbon accumulation at high temperatures. Herein, we report the codeposition of Pt nanoparticles and CuO_x clusters on TiO₂ (PC-50) and use of the resulting photocatalyst for OCM in a flow reactor operated at room temperature under atmospheric pressure for the first time. The optimized Cu_0.1Pt_0.5/PC-50 sample showed a highest yield of C₂ product of 6.8 μmol h⁻¹ at a space velocity of 2400 h⁻¹, more than twice the sum of the activity of Pt/PC-50 (1.07 μmol h⁻¹) and Cu/PC-50 (1.9 μmol h⁻¹), it might also be the highest among photocatalytic methane conversions reported so far under atmospheric pressure. A high C₂ selectivity of 60 % is also comparable to that attainable by conventional high-temperature (>943 K) thermal catalysis. It is proposed that Pt functions as an electron acceptor to facilitate charge separation, while holes could transfer to CuO_x to avoid deep dehydrogenation and the overoxidation of C₂ products.     

The Design Optimization of a Plasma Reactor for Chemical Waste Destruction

The heat flux and destruction and removal efficiency (DRE) measurements have been made on 100, 150 and 200 mm diameter plasma reactors to optimize the performance. The DRE was measured for pressure and gas atomization techniques of waste injection using both argon and CO₂ gases. As a result, the design of the reactor was optimized and the waste throughput was increased by ~17% with improved destruction performance. The 150 mm diameter reactor was found to perform better using gas atomization of feed injection using carbon dioxide at the given power and waste feed rate.     

By-Products NOx Control and Performance Improvement of a Packed-Bed Nonthermal Plasma Reactor

NO_x are main toxic by-products in the effluent gas whendecomposing volatile organic compounds in air by a packed-bed plasmareactor. Several types of materials such as 13X zeolite, BaTiO₃and Pd/Pt catalysts have been selected to be packed in the reactor, andmethane decomposition and NOx by-products in discharged gases areinvestigated at different range of reaction temperature and dischargeenergy density at atmospheric pressure. The ratios of methane decompositionpercentage/NO_x concentration are used to assess these packed bedmaterials and reaction conditions. The results show that usingPd/-Al₂O₃ with lower percentage Pd as packedbed, and discharging with lower discharge density at higher reactiontemperature can reduce NO_x output effectively and greatly improveperformance of the reactor.     

氧泵型催化膜反应器中甲烷氧化偶联反应—SEM和XPS研究

氧泵型催化膜反应器中甲烷氧化偶联反应—ＳＥＭ和ＸＰＳ研究国秀梅，陈洪钫（天津大学化工系，天津３０００７２）关键词甲烷氧化偶联，氧泵型催化膜反应器，ＳＥＭ，ＸＰＳ由于氧泵型催化膜反应器具有可简化分离过程，改变催化剂性质，控制传递氧量，避免副反应发生等优...     

Study of a transferred-arc plasma reactor with a converging wall and flow through a hollow cathode

In this paper the behavior of an arc in a transferred-arc plasma reactor with a converging wall geornetrr and flow through a hollow cathode is investigated numerically with emphasis on the fluid dynamics. The general conservation equations and auxiliary relations for the calculation domain are established based on reasonable assumptions Then, the coupled nonlinear differential equations are solved with suitable boundary conditions and temperature-dependent argon plasma properties at atmospheric pressure, by employing an efficient finite-difference method. The results, for a hollow cathode geornetrr with low injection flow rates, clear/y demonstrate the existence of the Maecker elect which is responsible Joy the formation of two recirculation zones. As the plasma gas flow rate is increased, the downstream recirculation zoner is swept away leaving only an upstream recirculation zone.     

Parametric study of the decomposition of NH3 for an induction plasma reactor design

The present paper reports a study of the gas mixing and chemical transformation in an induction plasma reactor under atmospheric pressure, and its dependence on the plasma operating conditions. For this purpose, the thermal dissociation of ammonia into nitrogen and hydrogen was chosen because of the relative simplicity of the reactions involved and its use in a number of studies on plasma synthesis of ultrafine nitride ceramic powders using ammonia as nitriding agent. A hot-wall reactor configuration is investigated in which ammonia is injected radially through multiple orifices into the gases at the exit nozzle of an induction plasma torch. Concentration mapping in the mixing zone was carried out, using a VG-Micromass-PC 300 D quadrupole mass spectrometer, for different plasma power levels, in the range 13–24 kW. A 3-point injection mode is used with the injection ports oriented upstream at 45° to the torch axis. This allows uniform mixing of the injected gas in the plasma jet. A systematic study of the effects of plate power and ammonia and plasma gas flow rates on the mixing and dissociation of NH₃ in the reactor is reported. The results are analyzed and discussed from the viewpoint of their use for optimizing the design of induction plasma reactors, to he applied to the vapor-phase synthesis of ultrafine silicon nitride powders.     

Comparison between Gibbs free energy minimization and mass action law for a multitemperature plasma with application to nitrogen

This paper gives all the necessary physical equations to determine the composition and the thermodynamic properties in a multitemperature plasma utilizing two different methods: the first method is based on Gibbs free energy minimization and the second is based on the resolution of the mass action law. The lowering terms of the ionization potential and thermodynamic properties are given for a multitemperature plasma using the Debye-Hückel approximation. Numerical application is made to a nitrogen plasma.     

Design and Operating Characteristics of a Simple and Reliable DBD Reactor for Use with Atmospheric Air

The paper reports on the construction and operating characteristics of a planar dielectric barrier discharge (DBD) plasma generator. The generator was powered from a commercial frequency inverter at 400 Hz through a high voltage transformer. It could be operated up to a specific energy density (power per gas flow) of 20 Wh/m³. The corresponding power density was about 0.5 W per cubic centimeter of discharge volume. Special emphasis was given to a simple and reliable construction, which was easy to assemble and is based on a new, nonexpensive barrier material with excellent electrical, mechanical, and thermal properties. The modular reactor design allows simple plasma power scale-up. The reactor works with undried ambient air without additional cooling. In the range up to 10 Wh/m³ the ozone generation from ambient air was directly proportional to the energy density at a rate of 60 g O₃ per kWh or 30 ppm/Wh/m³. Thus the generator can serve as an effective source for chemically active radicals in plasma gas cleaning applications.     

Design and Implementation of a Novel Quench Flow Reactor for the Study of Nascent Olefin Polymerisation

A novel stopped flow reactor system is described in the current work, along with the underlying design philosophy. While the concept of stopped flow technology is not recent, this system is the first to be designed with the objective of studying particle morphology, and to work at extremely short (40 ms) residence times. It is shown that traditional chemical engineering principles are required to properly design and operate this type of reactor, and that when correctly design, it is a very flexible tool for the study of nascent polymerisation of olefins.

     

The effect of a carbon-carbon double bond on electron beam-generated plasma decomposition of trichloroethylene and 1,1,1-trichloroethane

The effect of a carbon-carbon double bond on the energy required for decomposition in an electron beam-generated plasma reactor is studied by comparing the decomposition of trichloroethylene and 1,1,1-trichloroethane. A reaction mechanism for TCE decomposition based on a chlorine radical chain reaction is presented which accounts for the formation of all of the experimentally observed reaction products. TCE decomposition is autocatalyzed by reaction products, whereas TCA decomposition is inhibited. The rate expression for the decomposition of TCE in the reactor is determined to be r=−[T](15.07[T₀]^−0.40+0.006{[T₀]−[T]}), where [T] and [T₀] are both in ppm, and r is in ppm Mrad⁻¹. The energy expense ɛ for TCE decomposition is determined as a function of inlet concentration. For 99% decomposition of 100 ppm TCE in air, ɛ=28 eV/molecule, and ɛ=2.5 eV/molecule at 3000 ppm. This is only 2.5–5% of the amount of energy required to decompose a similar amount of TCA as reported by the authors in a previous study. By comparing the energy requirements for TCE decomposition to those for TCA decomposition, the TCE reaction chain length is determined to increase from approximately 20 at 100 ppm initial TCE concentration, to 40 at 3000 ppm. This work was supported by the Contaminant Plume Containment and Remediation Focus Area, Office of Environmental Management, U.S. Department of Energy.     

Mechanical and rheological properties of poly(ethylene-co-ethyl acrylate) as a function of carbon black content

Carbon black (CB) filled poly(ethylene-co-ethyl acrylate) (EEA-CB) is used as conductive phase in conductive polymer composites (CPC). Electrical conductivity of CPC obtained from blends of immiscible polymers results from CB particles localization within the material, which depends on composition and processing conditions. It is particularly important to control viscosity of such systems as this parameter determines both the phase morphology and conductive pathway structure. The small scale, at which CB particle aggregation/dispersion phenomena occur within CPC, makes direct observations difficult. But the effect of carbon black particles/polymers interactions is clearly visible by means of rheological measurements. A strong reinforcing effect of CB on CPC in both solid and liquid states has been noticed. This phenomenon has been analyzed using classical models as a function of temperature and CB content. The results confirm the necessity of CPC rheology control especially during the process to achieve good reproducibility of electrical properties.