Rh/γ-Al2O3催化剂上甲烷-氘化氢间的氢氘交换性能

采用Rh/γ-Al₂O₃催化剂,在固定床微型反应器上实验考察进料组成、反应温度和反应物总流量对甲烷氢氘交换的催化性能的影响。结果表明：在进料组成不变的条件下,当温度低于642K时,甲烷的转化率随温度的升高而快速增加,当温度高于642K时,甲烷的转化率不随温度的升高而变化;在反应温度为524～792K、进料组成不变的条件下,当温度低于642K时,甲烷的转化率随反应物流量的增加而明显减小,当温度高于642K时,甲烷的转化率基本不随温度的升高而变化;在反应温度为524～792K、反应物总流量不变的条件下,当HD/CH₄流量比在1.1～2.5间变化时,甲烷的转化率随HD/CH₄流量比的增加而减小。     

NH4HF2氟化制备UF4工艺及热力学研究

采用自制氟化反应器,以NH₄HF₂为氟化剂,开展了不同反应温度、氟化剂过量比条件下NH₄HF₂氟化制备UF₄工艺研究,实验获得了反应温度、NH₄HF₂过量比对氟化效率的影响规律,采用化学分析结合X射线粉晶衍射法对反应产物进行鉴定。研究结果表明：温度为573、673、823 K时,氟化产物中UF₄含量随NH₄HF₂过量比的增加而逐渐增大,当温度为723、773 K时,氟化率随NH₄HF₂过量比的增加呈先增大后减小的趋势。温度为723 K、NH₄HF₂过量比为300%时,该反应氟化率最大,为92.53%。反应温度为573～823 K时,该氟化反应氟化产物中包括4NH₄F·UF₄、NH₄F·3UF₄、3...     

载钯硅藻土吸氕/氘动力学同位素效应

恒温等容条件下,通过p-t曲线测量,研究在223~393K范围内载钯硅藻土(Pd/K)吸氕、氘动力学特性。应用反应速率分析方法计算了反应速率常数,得到了Pd/K吸氕、氘反应活化能。动力学计算结果显示:在整个温度范围内,载钯硅藻土与氕、氘反应明显分为两个温度段。低温段(223~313K),载钯硅藻土吸氕、氘反应速率常数随温度升高而增大且吸氕反应速率大于吸氘反应速率,吸氕、氘反应活化能分别为19.5、19.2kJ/mol;高温段(313~393K),载钯硅藻土吸氕、氘反应速率则随温度升高而减小,氕、氘反应活化能分别为:-18.6、-12.1kJ/mol。测试结果表明,载钯硅藻土吸氕、氘反应存在显著的动力学同位素效应且同位素效应依赖于温度的变化。     

低温精馏氢同位素分离影响因素研究

本文系统研究了低温精馏氢同位素分离中总板数、进料位置、回流比、采出率等操作条件对系统分离性能的影响,获得了精馏柱上的浓度和温度分布.随着进液位置向底端移动,再沸器和冷凝器中HD浓度均减小;随着回流比的增大,再沸器和冷凝器中HD浓度均减小;顶端采出率增大,再沸器中HD浓度明显增大;在相同的总板数下,H2/HD和D2/DT两个体系的分离特性明显有差别.     

负载型Ru/γ-Al2O3催化剂上甲烷与氘化氢之间的氢氘交换性能

实验研究了以浸渍法制备的负载型Ru/γ-Al2O3催化剂体系上甲烷与氘化氢之间的氢氘交换性能,考察了各反应工艺条件包括反应温度、反应原料气流量、反应原料气中HD/CH4的比等因素对Ru/γ-Al2O3催化剂上甲烷与氘化氢之间的氢氘交换性能的影响,采用程序升温还原（H2-TPR）和X射线粉末衍射（XRD）手段对催化剂进行了检测。实验结果表明,Ru和载体γ-Al2O3发生了强相互作用;在对甲烷与氘化氢间的氢氘交换反应中,Ru/γ-Al2O3催化剂显示出较好的催化活性和稳定性。     

H_2/HD和D_2/DT低温精馏分离影响因素研究

系统研究了低温精馏氢同位素分离中总板数、进料位置、回流比、采出量等对系统分离性能的影响,获得了蒸馏柱上的浓度和温度分布。随着进液位置向底端移动,再沸器和冷凝器中HD(或DT)浓度均减小;随着回流比的增大,再沸器和冷凝器中HD(或DT)浓度均减小;顶端采出量增大,再沸器中HD浓度明显增大;在相同的总板数下,H2/HD,D2/DT两个体系的分离特性明显有差别。     

碘硫循环中Bunsen反应液-液相分离影响因素的实验研究

Bunsen反应液-液相分离是整个碘硫循环的枢纽,H₂SO₄相与HI_x相分离效果直接影响整个循环系统的热效率。为提高两相分离效果和循环效率,对Bunsen反应平衡时液 液相分离特性进行研究。配制H₂SO₄、HI、I₂、H₂O混合溶液,研究实验条件对溶液分离效果的影响。研究结果表明,当n(H₂O)/n(H₂SO₄)小于18时,分层所需碘量随温度变化不大,之后随着溶液温度升高和水量增大,分层所需碘量明显增加;在提升温度和增加碘量的同时减小水量可有效提高溶液分离效果;增大水量可减小副反应进行程度,随着温度升高,抑制作用越明显。通过实验研究最终得到较好的分离条件。     

BCC-Fe中螺位错与［010］间隙位错环相互作用分子动力学模拟

本文利用分子动力学方法对BCC-Fe中螺位错与［010］间隙位错环的相互作用机制进行了模拟,研究结果表明,螺位错在不同温度下滑移靠近不同尺寸位错环时,它们之间的相互作用机制不同。当位错环尺寸为1.5 nm时,位错环在2 K下稳定存在,螺位错在剪切应力作用下滑移通过它,并与之位错反应生成1/2［11^-1^- ］位错环,临界剪切应力明显增加;随温度升高到300 K和600 K,［010］位错环因稳定性降低会转变为1/2［11^-1^- ］位错环,该位错环与螺位错反应可生成［010］位错片段,对螺位错阻碍作用逐渐变弱,临界剪切应力增量逐渐降低;随温度进一步升高到823 K,螺位错易交滑移,其与位错环始终无接触,因此无阻碍作用。当位错环尺寸增大到4 nm时,［010］位错环稳定性增加,300~823 K下位错环对螺位错滑移阻碍作用也明显增加。     

氕氘比CH/CD的四极质谱计测量

研究采用ELITE SXP-50型低分辨率四极质谱计(QMS)在不制备HD标样的条件下精确测量并计算混合气体中的氕氘分压比CH/CD的方法.标定结果表明:QMS对H2及D2的响应与氕、氘气体压力呈良好线性,且有直线斜率K(H2)=2K(D2)的关系,并据此推断K(HD)=1.5K(D2).对已知氕氘摩尔比为1.01～4.02的混合气体试样进行了测定,计算得到混合气体中的CH/CD比与给定值间的相对偏差小于4.0%.用CD/CH=1.05的标准混合气体进行了方法验证,4次测定的CD/CH平均值为1.07,与标准值的相对偏差为1.9%.验证实验证实:所推断出的K(HD)=1.5K(D2)关系是可靠的,利用此型号四极质谱计可较精确地测定氕、氘混合气体中的氕氘比CH/CD.     

钯钇合金膜分离器的氕氘分离系数测定

文章设计钯钇合金膜氢同位素分离器，并系统研究分离系数与温度、分流比、气体流速等因素间的关系。研究结果表明：分离系数随温度的增加而下降，在573～723K范围内，对于66.2%H2-33.8%D₂气体，当进料流速为5L/min、分流比为0.1时，分离系数由2.09下降至1.85；而当分流比为0.2时，分离系数由1.74下降至1.52。随着分流比的增大，分离系数逐渐降低。在573K下，进料流量为5L/min时，对于15.0%H2-85.0%D₂，当分流比由0.050增大至0.534时，分离系数由2.43降低至1.35；对于66.2%H2-33.8%D₂，当分流比由0.050上升至0.688时，分离系数由2.87下降至1.30。对于一定的分离过程，原料气体流速存在最佳值，达到该值时，分离系数最大。     

Effect of methane content and the oscillating electric field between electrodes on atmospheric Ar/methane plasma jet and DLC coating deposition

In this work, the effects of the methane gas flow and the internal oscillating electric field between electrodes on radio-frequency(RF) atmospheric pressure argon/methane plasma jet and process of diamond-like carbon(DLC) film deposition have been investigated. Properties of RF atmospheric Ar/methane plasma jet such as active species density, length, electron temperature,appearance and ionization process of argon/methane plasma jet are changed due to the changing of methane flow content and electric field vector and its gradient. With increasing methane flow,the formation of C2 hydrocarbon and CH band content is decreased because injected electrical energy to a mixture of Ar/methane gases is insufficient to stabilize the ionization process of methane gas and the electrical-chemical reaction rate is decreased. With shortening the gas gap between two electrodes, electric field strength and its gradient are increased leading to more energy injection to the electron. Electrical-chemical reactions are strengthened leading to increasing the CH band content. These phenomena introduce the Ar/methane plasma jet in different modes causing to deposit the DLC film with different structures and properties. With using quartz glass and alumina ceramic as dielectric barriers tubes, RF atmospheric pressure Ar/methane plasma jet has been used to deposit DLC coating in different modes. Increasing methane content and shortening the gas gap leads to decreasing sp3 bonded content and the quality of the deposited film.     

Incorporation of Nitrogen into Amorphous Carbon Films Produced by Surface-Wave Plasma Chemical Vapor Deposition

In order to study the influence of nitrogen incorporated into amorphous carbon films, nitrogenated amorphous carbon films have been deposited by using surface wave plasma chemical vapor deposition under various ratios of N2/CH4 gas flow. Optical emission spectroscopy has been used to monitor plasma features near the deposition zone. After deposition, the samples are checked by Raman spectroscopy and x-ray photo spectroscopy (XPS). Optical emission intensities of CH and N atom in the plasma are found to be enhanced with the increase in the N2/CH4 gas flow ratio, and then reach their maximums when the N2/CH4 gas flow ratio is 5%. A contrary variation is found in Raman spectra of deposited films. The intensity ratio of the D band to the G band (ID/IG) and the peak positions of the G and D bands all reach their minimums when the N2/CH4 gas flow ratio is 5%. These show that the structure of amorphous carbon films has been significantly modified by introduction of nitrogen。     

应用于等离子体排灰气处理的甲烷水汽重整反应的热力学分析

Tokamak装置中的等离子体反应一段时间后,需对产生的排灰气进行净化处理,以回收其中的氘氚。目前拟采用甲烷水汽重整反应将化合态的氘氚转化为单质并回收。本文运用Gibbs自由能最小化方法,对应用于等离子体排灰气处理的水汽重整反应进行热力学分析,考查反应温度、原料比例、反应压力、O₂、CO₂、H₂、CO等因素对反应平衡的影响,确定了适宜的反应条件,即反应温度范围650～700 ℃,压力1×105 Pa,水碳比1.5～2.0。此外,原料气中O₂或CO₂的存在有利于减少积碳的生成量,并获得较高的氢同位素平衡转化率;H₂的存在对重整反应的热力学平衡无明显影响;CO的存在会使积碳量增加,对反应产生不利影响,在进入重整反应器前应将其去除。     

Methane Conversion to C2 Hydrocarbons by Abnormal Glow Discharge at Atmospheric Pressure

Methane conversion to C2 hydrocarbons has been investigated with the addition of hydrogen in a plasma reactor of abnormal glow discharge at atmospheric pressure. The aim of this experiment is to minimize coke formation and improve discharge stability. The typical conditions in the experiment are 300 ml of total feed flux and 400 W of discharge power. The experimental results show that methane conversion is from 91.6% to 35.2% in mol, acetylene selectivity is from 90.2% to 57.6%, and ethylene selectivity is approximately from 7.8% to 3.6%, where the coke increases gradually along with the increase of CH4/H2 from 2 ： 8 to 9 ： 1. A stable discharge for a considerable running time can be obtained only at a lower ratio of CH4/H2 = 2：8 or 3： 7. These phenomena indicate that the coke deposition during methane conversion is obviously reduced by adding a large amount of hydrogen during an abnormal glow discharge. A qualitative interpretation is presented, namely, with abundant hydrogen, the possibility that hydrogen molecules are activated to hydrogen radicals is increased with the help of the abnormal glow discharge. These hydrogen radicals react with carbon radicals to form C2 hydrocarbon products. Therefore, the deposition of coke is restrained.     

OES diagnostic of radicals in 33MHz radio-frequency Ar/C_2H_5OH atmospheric pressure plasma jet

Ar/C_2H_5OH plasma jet is generated at atmospheric pressure by 33 MHz radio-frequency power source. This RF excitation frequencies which are higher than 13.56 MHz had rarely been used in atmospheric pressure plasma. The plasma characteristics of ethanol are investigated. The introduction of ethanol leads to the generation of four excited carbonaceous species C, CN, CH and C_2 in plasma, respectively. Optical emission intensities of four carbonaceous species were strengthened with ethanol content increasing in the range of 0-4600 ppm. The ethanol content increase results in all the Ar spectra lines decrease. The reason is that the electron temperature decreases when ethanol content is high. The emission intensity ratios of C/C_2, CN/C_2 and CH/C_2 decrease with the increase of ethanol content, showing that the relative amount of C_2 is increasing by increasing the ethanol flow. The emission intensity ratios of excited species did not change much with the increase of RF power in stable discharge mode.     

Plasma-chemical Synthesis and Regeneration of Catalysts for CH4 Steam Conversion

We carried out experimental studies concerning the plasma-chemical synthesis(PCS) of a catalyst for CH4 steam conversion and designed and built the equipment for PCS and/or regeneration of spent catalyst for CH4 steam conversion .Under the conditions of an electric-arc low-temperature plasma(LTP),we studied the Ni-O-Al system and performed a comprehensive physicochemical analysis of the ultradispersed product obtatined .It‘s the first time worldwide when the conditions of plasma-chemical synthesis and /or regeneration of CH4 steam coversion catalysts under the conditions of electric-are LTP are investigated depending on the plasma-chemical process (PCP) paracmeters and the plasma-chemical reactor (PCP) TYPE (with CW-“cold walls“ TW=500K or WW-“warm walls“ TW=1500K),samples with a specific surface of 120 m^2/g are obtained.Plasma-chemically synthesized and/ or regenerated samples have a homogenous chemical composition similar to that the Girdller (USA) convertional industrial catalyst.It is empirically established that the optimal temperature range in PCR for synthesis of samples with maximum dispersity is (2000-3000)k.Results from inverstigation on dynamics and kindetics of plasma-chemically synthesized and /or regenerated catalysts for CH4 steam conversion slow that under LTP conditions premises for the formation of catalyst compositions are established.They are reduced 3 to 4 times faster than their industrial analogues.High specific surface of the samples ,homogenous composition,high rate of active chemical surface formed by reduction, faulty craystal lattice of catalytically active phases and mostly high catalytic activity make them a potential competitor tiwh their industrial analogues for their probable production in catalyst shops.     

A numerical simulation study on active species production in dense methane-air plasma discharge

Recently, low-temperature atmospheric pressure plasmas have been proposed as a potential type of ‘reaction carrier' for the conversion of methane into value-added chemicals. In this paper, the multi-physics field coupling software of COMSOL is used to simulate the detailed discharge characteristics of atmospheric pressure methane-air plasma. A two-dimensional axisymmetric fluid model is constructed, in which 77 plasma chemical reactions and 32 different species are taken into account. The spatial density distributions of dominant charged ions and reactive radical species, such as CH_4~+CH_3~+N_2~+O_2~+H, O, CH_3, and CH_2, are presented, which is due to plasma chemical reactions of methane/air dissociation(or ionization) and reforming of small fragment radical species. The physicochemical mechanisms of methane dissociation and radical species recombination are also discussed and analyzed.