Coupling of methane under pulse corona plasma (Ⅰ)——In the absence of oxygen

At normal temperature and pressure, pulse corona plasma was used as a new method for the dehydrogenative coupling of methane in the absence of oxygen. The effects of voltage polarity and input energy on the dehydrogenative coupling of methane were investigated. The parameter "energy efficiency" was introduced to examine the coupling of the input energy and the dehydrogenative coupling of methane. The experimental results show that positive corona gives higher energy efficiency than negative corona. When the positive corona was chosen, C2. yield per pass was 31.6% and acetylene yield per pass was 30.1% with 44.6% methane conversion at an input energy density of 1788kJ/mol and a pulse repetition frequency of 66Hz. The function of input energy density towards methane conversion may be expressed as a formula of -ln(1-X) = k (P/F). In the range of input energy employed, C2 yield is proportional to input energy density, but energy efficiency drops off with increasing input energy density.     

Methane Coupling Using Hydrogen Plasma and Pt／γ—Al2O3 Catalyst

In this paper,methane coupling at ambient temperature, under atmospheric pressure and in the presence of hydrogen was firstly investigated by using pulse corona plasma and Pt/γ-Al2O3 catalyst. Experimental results showed that Pt/γ-Al2O3 catalyst has catalytic activity for methane couplin to C2H4. Over sixty percent o outcomes of C2 hydrocarbons were detected to be ethylene.     

脉冲电晕等离子体作用下CH4/H2反应的机理

本文利用发射光谱技术,对脉冲电晕等离子体作用CH4/H2反应进行了原位诊断,根据等离子体作用下CH4、H2和CH4/H2体系中部分激发态物种的光谱检测数据和有关实验的结果,结合等离子体特性及小分子光化学反应规律,对等离子体作用CH4/H2转化制备C2烃反应的机理进行了讨论。     

Coupling of methane under pulse corona plasma (I)

At normal temperature and pressure, pulse corona plasma was used as a new method for the dehydrogenative coupling of methane in the absence of oxygen. The effects of voltage polarity and input energy on the dehydrogenative coupling of methane were investigated. The parameter “energy efficiency” was introduced to examine the coupling of the input energy and the dehydrogenative coupling of methane. The experimental results show that positive corona gives higher energy efficiency than negative corona. When the positive corona was chosen, C₂ yield per pass was 31.6% and acetylene yield per pass was 30.1% with 44.6% methane conversion at an input energy density of 1788kJ/mol and a pulse repetition frequency of 66Hz. The function of input energy density towards methane conversion may be expressed as a formula of-In(1-X) =k (PIF). In the range of input energy employed, C₂ yield is proportional to input energy density, but energy efficiency drops off with increasing input energy density.     

等离子体条件下甲烷在CO_2存在下的脱氢偶联(英文)

在常温常压下,利用脉冲电晕等离子体研究了甲烷和二氧化碳的转化。在等离子体一催化反应装置上,测试了Ｐｄ／γ－Ａｌ２Ｏ３对甲烷偶联的催化活性。实验发现,在脉冲电晕等离子体作用下,甲烷和二氧化碳被转化为Ｃ２烃、ＣＯ、Ｈ２、Ｏ２、少量积碳和高碳烃;在等离子体条件下引入Ｐｄ／γ－Ａｌ２Ｏ３催化剂,能够有效地改善甲烷偶联产物Ｃ２烃的分布,有利于生成更高附加值的乙烯。     

DEHYDROGENATIVE COUPLING OF METHANE UNDER PULSE CORONA PLASMA OVER A MnO|?/|?-A12O3 CATALYST

Pulse corona plasma was used as an activation method fordehydrogenative coupling of methane at the normal temperature and under' the normal pressure. The exprimental results showed that a great enhancement in the selectivity to C2 was achieved by the combination of pulse corona plasma with a y-Mn2OO3/Y-A12O3 catalyst. The distribution of C2 hydrocarbons was mainly affected by the power input and the nature of the catalyst. In addition, the gas stream direction exerted an influence upon the C2 yield, especially at higher power input.     

CeO2和Pd在Ni/γ-Al2O3催化剂中的助剂作用

采用脉冲微反技术研究了添加n型半导体氧化物CeO2及贵金属Pd对Ni/γ Al2O3催化剂上CH4积炭/CO2消炭反应性能的影响,并运用BET、TPR、CO2 TPSR及氢吸附等技术对催化剂进行了表征.结果表明, n型半导体氧化物CeO2的添加可以降低Ni/γ Al2O3催化剂上CH4裂解积炭活性,提高CO2消炭活性,添加少量贵金属Pd可以进一步改变载体Al2O3、助剂CeO2和活性组分Ni之间的相互作用,从而改善Ni/γ Al2O3催化剂的抗积炭性能.通过Ni Ce Pd/γ Al2O3催化剂上CH4积炭/CO2消炭模型对上述作用机制作出了新的解释.     

有氧气氛下等离子体甲烷偶联反应的研究

近年来,非平衡等离子体应用于甲烷直接转化的研究备受关注,但多数研究工作采用的是低气压下微波或高频放电产生的非平衡等离子体[1－9].在常压下获得非平衡等离子体一般是通过脉冲电晕放电或介质阻挡放电产生的[10,11].Liu等[12]采用电晕放电（非脉冲）研究了CH4＋O2＋He(pCH4=2.03×104Pa,pO2=5.07×103Pa,He平衡)体系的甲烷偶联反应.　　如前文[13]所述,脉冲电晕等离子体是一种新型常压非平衡等离子体,其电子通过上升沿陡峭的窄脉冲电场加速而获得能量（1～20eV）.将其应用于甲烷偶联反应,不仅具有反应条件温和（常温常压）…     

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.     

脉冲电晕等离子体下甲烷偶联反应研究(Ⅲ)──金属氧化物的多相催化作用

考察了常温常压脉冲电晕等离子体作用下金属氧化物对甲烷脱氢偶联反应的催化作用,观察到不同催化剂在脉冲电晕等离子体作用下的催化活性差别很大,且对C₂产物的分布具有一定的调变作用.γ-MN₂O₃/γ-Al₂O₃催化剂的C₂烃收率较空白载体提高了近2倍,C₂烃选择性提高30%以上,该催化剂与脉冲电晕等离子体的结合可使其能量效率提高2倍以上.提出了一种等离子体催化作用促进甲烷脱氢偶联反应的初步模型.     

脉冲电晕等离子体作用下甲烷偶联反应的研究 Ⅱ.反应添加气的影响

脱氢偶联;脉冲电晕等离子体作用下甲烷偶联反应的研究 Ⅱ.反应添加气的影响     

Effect of ceria loading on the carbon formation during low temperature methane steam reforming over a Ni/CeO2/ZrO2 catalyst

The characterization and catalytic activity of a Ni/CeO₂/ZrO₂ catalyst for methane steam reforming at 600°C were investigated. The addition of ceria increased the surface area and basicity of the catalysts. The redox reaction capability of the ceria increased the hydrogen yield and carbon monoxide selectivity, and inhibited carbon formation.     

甲烷在Ni/TiO2催化剂表面的活化

考察了Ni/TiO2催化剂甲烷部分氧化和二氧化碳重整制合成气的反应活性,实验表明,以TiO2为载体的镍系催化剂对于甲烷部分氧化制合成气反应具有较好的活性,尤其对H2的选择性较高,对二氧化碳重整制合成气反应具有较好的低温反应活性.采用脉冲-质谱在线分析等技术,在无气相氧条件下向Ni/TiO2催化剂脉冲CH4,发现甲烷在催化剂表面的活化（转化）及其氧化产物的选择性与金属催化剂表面氧的浓度密切相关.CH4与Ni/TiO2催化剂作用过程中存在明显的氢溢流和氧溢流现象,可能是这种溢流效应使得Ni/TiO2催化剂具有良好的反应活性和抗积碳性能.     

Catalytic Activity and Morphological Properties of Ni/MgO Catalysts for the Oxidative Coupling of Methane

The catalytic activity of Ni/MgO catalysts was studied for the oxidative coupling of methane (OCM). The catalysts were characterized using transmission electron microscope (TEM) and XRD. The increase in C2+ selectivity of Ni/MgO was attributed to the presence of bulk dislocations and MgNiO₂ phase. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effect of decomposition of catalyst precursor on Ni/CeO2 activity for CO methanation

CO methanation on Ni/CeO₂ has recently received increasing attention. However, the low-temperature activity and carbon resistance of Ni/CeO₂ still need to be improved. In this study, plasma decomposition of nickel nitrate was performed at ca. 150°C and atmospheric pressure. This was followed by hydrogen reduction at 500 °C in the absence of plasma, and a highly dispersed Ni/CeO₂ catalyst was obtained with improved CO adsorption and enhanced metal-support interaction. The plasma-decomposed catalyst showed significantly improved low-temperature activity with high methane selectivity (up to 100%) and enhanced carbon resistance for CO methanation. For example, at 250°C, the plasma-decomposed catalyst showed a CO conversion of 96.8% with high methane selectivity (almost 100%), whereas the CO conversion was only 14.7% for a thermally decomposed catalyst.     

Carbon Dioxide Reforming of Methane over Ni Catalysts Supported on Al2O3 Modified with La2O3, MgO, and CaO

The preparation of synthesis gas from carbon dioxide reforming of methane (CDR) has attracted increasing attention. The present review mainly focuses on CDR to produce synthesis gas over Ni/MO_x/Al₂O₃ (X = La, Mg, Ca) catalysts. From the examination of various supported nickel catalysts, the promotional effects of La₂O₃, MgO, and CaO have been found. The addition of promoters to Al₂O₃-supported nickel catalysts enhances the catalytic activity as well as stability. The catalytic performance is strongly dependent on the loading amount of promoters. For example, the highest CH₄ and CO₂ conversion were obtained when the ratios of metal M to Al were in the range of 0.04–0.06. In the case of Ni/La₂O₃/Al₂O₃ catalyst, the highest CH₄ conversion (96%) and CO₂ conversion (97%) was achieved with the catalyst (La/Al = 0.05 (atom/atom)). For Ni/CaO/Al₂O₃ catalyst, the catalyst with Ca/Al = 0.04 (atom/atom) exhibited the highest CH₄ conversion (91%) and CO₂ conversion (92%) among the catalysts with various CaO content. Also, Ni/MgO/Al₂O₃ catalyst with Mg/Al = 0.06 (atom/atom) showed the highest CH₄ conversion (89%) and CO₂ conversion (90%) among the catalysts with various Mg/Al ratios. Thus it is most likely that the optimal ratios of M to Al for the highest activities of the catalysts are related to the highly dispersed metal species. In addition, the improved catalytic performance of Al₂O₃-supported nickel catalysts promoted with metal oxides is due to the strong interaction between Ni and metal oxide, the stabilization of metal oxide on Al₂O₃ and the basic property of metal oxide to prevent carbon formation.     

微波等离子体下甲烷偶联制乙炔的研究

通过优化设计矩形波导谐振腔微波化学反应器,可以大幅提高微波等离子体下甲烷转化率（最高为93．7％）、C2烃收率（最高为91．0％）和乙炔收率（最高为88．6％）．且优化后,在实验的压强范围内,甲烷转化率和C2烃收率较为稳定,C2烃主要是乙炔,其选择性都在90％以上．生成乙炔的能量产率和时空产率也都比较高．利用发射光谱法对微波等离子体下甲烷偶联制乙炔的反应进行了诊断研究,在300nm～750nm波长范围内激发态物种有：CH,C2,H2,Hα-根据反应产物和激发态物种从化学反应热力学和动力学上对反应机理进行了初步探索．     

正压、低温脉冲微波等离子体裂解天然气直接转化 制C2烃的研究

利用脉冲微波强化、扩展丝光等离子体反应装置,在常压和正压条件下,对低温脉冲微波等离子体裂解甲烷和氢气混合气制C2烃的反应进行了研究。考察了压力、微波功率、脉冲通/断时间以及氢气/甲烷比例、流量等参数对反应的影响。结果表明,在脉冲微波的作用下,常规高压放电形成的在空间呈非连续分布的丝状等离子体被强化和扩展成为连续分布的伞状等离子体,等离子体利用率和活性均得以大幅度提高;利用这种低温等离子体可以获得高的甲烷转化率,而且产物纯净,只有乙烯和乙炔;通过改变压力,还可能调节产物中C2H2/C2H4的物质的量比值,当气体总流量为300mL/min、物质的量比n(H2)/n(CH4)=2:1、压力为0.13MPa、微波峰值功率为120W、脉冲通/断比=400/400ms时,甲烷转化率可达59.2%,C2烃单程收率可达52%,其中乙炔单程收率达42.7%。     

MnOχ/γ-A1_2O_3对等离子体甲烷脱氢偶联反应的催化作用(英文)

在常温常压下，研究了脉冲电晕等离子体作用下的甲烷脱氢偶联反应。结果表明，脉冲电晕等离子体与y-Mn2O_3／y-A12O_3催化剂的共同作用显著提高了C_2选择性；C_2产物分布主要决定于等离子体功率和催化剂性能。另外，在较高功率下，气流方向对C_2收率影响较大。初步揭示了在等离子体作用下CH_4在气相形成CH_x自由基，而后CH_x自由基在催化剂表面进行定向复合形成C_2产物。     

SiO2气凝胶负载的Ni催化剂在甲烷部分氧化制合成气反应中的催化性能及稳定性

以常压有机溶剂置换(A)和溶剂置换-表面改性(B)方式制备的两种SiO₂气凝胶(SiO₂-A(或B)型气凝胶,记为SiO₂-A(or B)G)为载体, 采用常规浸渍法和聚乙烯吡咯烷酮(PVP)添加浸渍法合成不同SiO₂气凝胶负载的Ni/SiO₂催化剂, 并考察其催化的甲烷部分氧化(POM)制合成气的反应性能. 结果表明, 各催化剂的初始反应性能相近, 但Ni/SiO₂-BG的POM稳定性明显较Ni/SiO₂-AG的差, 而PVP添加制备的催化剂稳定性则获明显改善, Ni/SiO₂-AG-PVP、Ni/SiO₂-BG-PVP上POM稳定性相近. 结合X射线衍射(XRD)、程序升温还原反应(H₂-TPR)、高分辨透射电镜(TEM)和Brunauer-Emmett-Teller (BET)等表征结果的分析发现: (1) SiO₂-AG表面上存在一定量的羟基, 可促进亲水性金属物种与其的相互作用, 而SiO₂-BG表面上基本为有机基团, 与亲水性金属物种几乎无作用; (2) PVP的存在可使金属物种进入亲/疏水载体孔道深处, 抑制焙烧中载体骨架的收缩和金属颗粒的生长, 进而促进金属-载体的相互作用. 这二者均能有效地提高催化剂的POM反应稳定性.