Methane Conversion Using Dielectric Barrier Discharge: Comparison with Thermal Process and Catalyst Effects

The direct conversion of methane using a dielectric barrier discharge has been experimentally studied. Experiments with different values of flow rates and discharge voltages have been performed to investigate the effects on the conversion and reaction products both qualitatively and quantitatively. Experimental results indicate that the maximum conversion of methane has been 80% at an input flow rate of 5 ml/min and a discharge voltage of 4 kV. Experimental results also show that the optimum condition has occurred at a high discharge voltage and higher input flow rate. In terms of product distribution, a higher flow rate or shorter residence time can increase the selectivity for higher hydrocarbons. No hydrocarbon product was detected using the thermal method, except hydrogen and carbon. Increasing selectivity for ethane was found when Pt and Ru catalysts presented in the plasma reaction. Hydrogenation of acetylene in the catalyst surface could have been the reason for this phenomenon as the selectivity for acetylene in the products was decreasing.

Development of Cu foam-based Ni catalyst for solar thermal reforming of methane with carbon dioxide

Using solar energy to produce syngas via the endothermic reforming of methane has been extensively inves- tigated at the laboratory- and pilot plant-scales as a promising method of storing solar energy. One of the challenges to scaling up this process in a tubular reformer is to improve the reactor＇s performance, which is limited by mass and heat transfer issues. High thermal conductivity Cu foam was therefore used as a sub-strate to improve the catalyst＇s thermal conductivity during solar reforming. We also developed a method to coat the foam with the catalytically active component NiMg3AlOx. The Cu foam-based NiMg3AlOx performs better than catalysts supported on SiSiC foam, which is currently used as a substrate for solar-reforming cat- alysts, at high gas hourly space velocity （≥400,000 mL/（g.h）） or at low reaction temperatures （≤ 720 ℃）. The presence of a γ-Al2O3 intermediate layer improves the adhesion between the catalyst and substrate as well as the catalytic activity.

First-principles study of the relationship between the formation of single atom catalysts and lattice thermal conductivity

Single atom catalysts(SACs)have been in the forefront of catalysts research because of their high efficiency and low cost and provide new ideas for development of renewable energy conversion and storage technologies.However,the relationship between the intrinsic properties of materials such as lattice thermal conductivity and catalysis remains to be explored.In this work,the lattice thermal conductivity of BN and graphene was calculated by Sheng BTE.In addition,the adsorption properties of 3d-TM(TM=V,Cr,Mn,Fe,Co,Ni)on BN and graphene were investigated using first-principles methods,and it was found that Ni atom can form relatively stable SACs compared to other TMs.The molecular dynamics(MD)simulation and migration barrier of Ni loaded on BN and graphene were calculated.Our study found that graphene has higher thermal conductivity and is easier to form SACs than BN,but the SACs formed on BN surface have higher thermodynamic stability.

Synthesis Gas Production from Natural Gas on Supported Pt Catalysts

Auto-thermal reforming of methane, combining partial oxidation and reforming of methane with CO2 or steam, was carried out with Pt/Al2O3, Pt/ZrO2 and Pt/CeO2 catalysts, in a temperature range of 300-900℃. The auto-thermal reforming occurs in two simultaneous stages, namely, total combustion of methane and reforming of the unconverted methane with steam and CO2, with the O2 conversion of 100% starting from 450℃. For combination with CO2 reforming, the Pt/CeO2 catalyst showed the lowest initial activity at 800℃, and the highest stability over 40 h on-stream. This catalyst also presented the best performance for the reaction with steam at 800℃. The higher resistance to coke formation of the catalyst supported on ceria is due to the metal-support interactions and the higher mobility of oxygen in the oxide lattice.

Thermally stable Ir/Ce0.9La0.1O2 catalyst for high temperature methane dry reforming reaction

In this study, the use of a thermally stable Ir/Ce0.9La0.1O2 catalyst was investigated for the dry reforming of methane. The doping of La203 into the CeO2 lattice enhanced the chemical and physical properties of the Ir/Ce0.9La0.1O2 catalyst, such as redox properties, Ir dispersion, oxygen storage capacity, and thermal stability, with respect to the Ir/CeO2 catalyst. Hence, the Ir/Ce0.9La0.1O2 catalyst exhibits higher activity and stabler performance for the dry reforming of methane than the Ir/CeO2 catalyst. This observation can be mainly attributed to the stronger interaction between the metal and support in the Ir/Ce0.9La0.1O2 catalyst stabilizing the catalyst structure and improving the oxygen storage capacity, leading to negligible aggregation of Ir nanoparticles and the Ce0.9La0.1O2 support at high temperatures, as well as the rapid removal of carbon deposits at the boundaries between the Ir metal and the Ce0.9La0.1O2 support.

Estimation of ultra-stability of methane hydrate at 1 atm by thermal conductivity measurement

Thermal conductivity of methane hydrate was measured in hydrate dissociation self-preservation zone by means of the transient plane source（TPS） technique developed by Gustafsson.The sample was formed from 99.9%（volume ratio） methane gas with 280 ppm sodium dodecyl sulfate（SDS） solution under 6.6 MPa and 273.15 K.The methane hydrate sample was taken out of the cell and moved into a low temperature chamber when the conversion ratio of water was more than 90%.In order to measure the thermal conductivity,the sample was compacted into two columnar parts by compact tool at 268.15 K.The measurements are carried out in the temperature ranging from 263.15 K to 271.15 K at atmospheric pressure.Additionally,the relationship between thermal conductivity and time is also investigated at 263.15 K and 268.15 K,respectively.In 24 h,thermal conductivity increases only 5.45% at 268.15 K,but thermal conductivity increases 196.29% at 263.15 K.Methane hydrates exhibit only minimal decomposition at 1 atm and the temperature ranging from 263.15 K to 271.15 K.At 1 atm and 268.15 K,the total gas that evolved after 24 h was amounted to less than 0.71% of the originally stored gas,and this ultra-stability was maintained if the test was lasted for more than two hundreds hours before terminating.

Molecular dynamics simulation of decomposition and thermal conductivity of methane hydrate in porous media

The hydrate has characteristics of low thermal conductivity and temperature sensitivity. To further analysis the mechanism of thermal conductivity and provide method for the exploitation, transportation and utilization of hydrate, the effect of decomposition and thermal conductivity of methane hydrate in porous media has been studied by using the molecular dynamics simulation. In this study, the simulation is carried out under the condition of temperature 253.15 K-273.15 K and pressure 1 MPa. The results show that the thermal conductivity of methane hydrate increases with the increase of temperature and has a faster growth near freezing. With the addition of porous media, the thermal conductivity of the methane hydrate improves significantly. The methane hydrate-porous media system also has the characteristics of vitreous body.With the decrease of the pore size of the porous media, thermal conductivity of the system increases gradually at the same temperature. It can be ascertained that the porous media of different pore sizes have strengthened the role of the thermal conductivity of hydrates.

介质阻挡放电辅助催化CO_(2)甲烷化的研究

重点介绍了近10年来用于介质阻挡放电(DBD)辅助催化CO_(2)甲烷化的镍基催化剂的研究成果,包括不同等离子体工艺参数下的催化剂活性,同时涉及催化剂的活化方式、载体、助剂等实验条件对催化效果的影响,揭示了介质阻挡放电辅助催化CO_(2)甲烷化中等离子体与催化剂的协同效应和反应机理。最后针对DBD等离子体辅助催化体系目前所面临的挑战,提出了新的展望。

热催化还原二氧化碳制甲烷催化剂研究进展

二氧化碳(CO_(2))作为一种生产高价值燃料和化学品的可再生碳源,将其催化转化为工业相关的化学品是减少温室气体排放的一项战略。近年来的研究表明,热催化CO_(2)加氢制备甲烷技术因副产物少、转化率高、成本较低等优点,成为最具有吸引力的选择。催化剂的研究是这项技术的关键。结合近年来热催化技术催化CO_(2)甲烷化常见的催化材料的发展现状,从催化剂的研究视角出发,从载体、负载金属等方面分析其对催化剂的活性和选择性的影响;系统介绍粒径、比表面积、负载量、碱性位点、氧空位、分散度等对CO_(2)甲烷化的影响;简述甲烷化反应路径及反应过程中产生的中间体。最终提出未来CO_(2)甲烷化的主要研究方向,以期为热催化技术的研究提供参考和借鉴。

沁水盆地大地热流与地温场特征

分析了20口井的温度数据和39个岩石样品的热导率数据，计算了20个大地热流值．结果表明：沁水盆地具有偏高的大地热流背景，现今热流变化于44．8—101．8mW／m^2之间，平均62．7±15．2mW／m^2，现今地温梯度介于20．9—47．6℃／km之间，平均地温梯度28．2±10．3℃／km．热流的分布与本区上、下主煤层含气量的分布特征相似，在一定程度上反映了现代热流继承了煤层气生气期的古地热背景．

动态法测定耐硫甲烷化催化剂的有效导热系数

本文采用动态法原理，用单丝直径为０．２ｍｍ的铜－康铜热偶作为测温元件，在３１３～５３３Ｋ温度区间，测定了耐硫甲烷化催化剂的有效导热系数。用石蜡和锡作为参比物，对所用仪器及实验方法进行了可靠性检验。实验表明，动态法是测定多孔硫化物催化剂导热系数的有效方法，其精度符合工程要求，亦能用于其它材料导热系数的测定。对所测数据用单纯形方法优化拟合，得到大于３５３Ｋ范围内的有效导热系数的经验公式Ｋｅ＝０．２５５１＋８．

客体分子数对甲烷水合物导热性能影响的分子动力学模拟

采用EMD方法 Green-Kubo理论计算263.15K晶穴占有率0～100%sI甲烷水合物的热导率,研究客体分子数对甲烷水合物导热性能的影响。模拟结果显示,甲烷水合物的低导热性能由主体分子构建的笼形结构决定。而在相同温压条件下,随着客体分子甲烷进入晶胞数目增多,晶穴占有率增大后,密度增大,同时客体分子对声子的散射也增强,二者均导致导热性能增强。

环柱状催化剂内强放热复合反应──传质──传热耦合过程研究(Ⅰ)催化剂曲折因子、有效导热系数的测定

采用经典定态法和改进的单颗粒线反应器法（SPSRM)测定了环柱状环氧乙烷银催化剂的曲折因子，两种方法测定结果十分吻合。提出一种测定固体催化剂颗粒有效导热系数的新方法。该方法简单、方便且不改变催化剂原有的形状及物理结构，可以在催化剂允许使用的任何温度下进行测定，准确度较高。用本方法测定了环氧乙烷合成银催化剂颗粒的有效导热系数，并用于催化剂内部浓度、温度、选择性计算，计算与实验结果吻合良好。

甲烷催化部分氧化制合成气固定床反应器的热波研究

研究了 甲烷部 分氧化（ Ｐ Ｏ Ｍ） 反 应 在 固定 床 反应 器 中 轴向 的 温度 场 分 布（ 或 热波 分 布） ．催化剂 床层的 热波呈不 对称分布 ，入口段 温度高 于出口温 度，热波 峰值位于 入口偏下 处． 考察了空速、ｎ（ Ｃ Ｈ４ ）／ ｎ（ Ｏ２ ） 比值、高 径比 等对 热波 分 布的 影响 ，结 果表 明： 相 同外 温 下，增 加 空速 导 致 热波峰温升 高； 随 着 ｎ（ Ｃ Ｈ４）／ ｎ（ Ｏ２） 值 的降低，目 标产物 Ｈ２ 和 Ｃ Ｏ 的深度 氧化（ 强放 热） 加强， 故热 波峰温升高 ； 适当 降低催 化剂床层 的高径 比有利于 降低热波 峰温和 提高反应 性能． 催化 剂用 载体 稀释后，由于 Ｈ２ 和 Ｃ Ｏ 深度氧 化反应 的加强，导 致热波 峰温 升 高． 不同 高 度催 化剂 床 层的 热波 特 征揭示， Ｐ Ｏ Ｍ 反应 主要在入 口段一 薄层区域 内进行 ，此区域近 似呈等 温分布，说 明 Ｐ Ｏ Ｍ 反应遵 循直接氧化机

有机硅灌封材料的研究进展

本文主要综述了国内外用于电子元器件、大规模集成电路等高科技领域的有机硅灌封材料在流动、耐高温、阻燃和绝缘导热等方面的性能以及催化剂对灌封材料的影响的研究应用进展。

甲烷氧化偶联Na_2WO_4-Mn/SiO_2催化剂用于乙烷脱氢

研究了高效甲烷氧化偶联制乙烯Na2WO4-Mn/SiO2催化剂对C2H6热裂解脱氢及C2H6与CO2、O2氧化脱氢反应的催化性能。实验结果表明,Na2WO4-Mn/SiO2催化剂在800℃以上可有效促进C2H6的高温热裂解脱氢反应,同时在CO2存在时C2H6与CO2发生明显的氧化脱氢反应;O2存在时,C2H6与O2发生氧化脱氢反应,在660℃时,C2H6转化率可达63.3%,乙烯选择性可达68.2%。考察了反应条件对C2H6与O2氧化脱氢反应的影响,实验结果表明,C2H6与O2的体积比大时,可有效提高目的产物乙烯的选择性,提高空速可抑制CO2的生成,稀释气(水蒸气)的引入仅能部分抑制CO2的生成,对CO选择性和C2H6转化率的影响不大。

耐硫甲烷化催化剂的有效导热系数研究

在常压空气气氛下采用稳态法测试了KD306型耐硫甲烷化催化剂的有效导热系数,运用Woodside随机模型,建立了反应状态下有效导热系数的计算模型。研究表明,该催化剂有效导热系数较大,温度、压力影响明显,组成影响较小。

KD306甲烷化催化剂有效导热系数的简便快速测定

根据动态法原理，采用单丝直径为０．２ｍｍ的铜－康铜热偶作为测温元件，简便快速地测试了ＫＤ３０６耐硫甲烷化催化剂的有效导热系数并得到经验计算公式。以石蜡和锡作为参比物，对所用方法及测试仪器进行了检验，证明该方法是测定硫化物催化剂导热系数的一种有效方法，其测量精度符合工程要求。

BaCO_3/La_2O_3催化剂低温甲烷氧化偶联及床层热点效应

以BaCO3和不同的镧化合物作为催化剂组分,分别采用干混法和湿混法制备了BaCO3质量含量为2.5%～15%的BaCO3/La2O3催化剂,在微型固定床反应器上评价了催化剂的甲烷氧化偶联反应性能,考察了反应条件对催化剂性能的影响,以及催化剂床层中的热点效应,采用XRD和TPR对催化剂的结构和性能进行了表征。结果表明,不同方法制备的BaCO3/La2O3催化剂在较低炉温的条件下都具有好的甲烷氧化偶联反应性能,其中湿混法制备的10%BaCO3/La2O3催化剂性能最好,在烷氧比为2,反应气体空速为36000 mL.g-1.h-1的条件下,反应炉温在125℃时甲烷氧化偶联反应仍能平稳进行。存在于催化剂床层的热点是维持甲烷氧化偶联反应的关键。不同方法制备的BaCO3/La2O3催化剂其物相和氧化还原性能也有一定的差别。

Ni/Al_2O_3催化剂上CH_4三重整反应-催化剂床层温度分布

在连续流动的固定床反应装置上，考察了Ni／Al2O3催化剂上CH4三重整反应中催化剂床层的温度分布。实验在常压、750℃～950℃、2000h^-1～20000h^-1下进行，研究了外控炉温、空速和进料组成对催化剂床层温度分布的影响。结果表明，催化剂床层中的温度梯度较甲烷部分氧化反应平缓，在CH4／CO2／H2O／O2=50／12．5／12．5／25（摩尔比）、20000h^-1下，催化剂床层中入口处温度比炉温高约80℃，出口处温度与器壁温度相当。空速越低，催化剂床层入口处温度（tmax）与炉温之差△tmax越小（20000h^-1时，Δtmax=80℃；2000h^-1时，Δtmax=30℃）。当原料气中不含O2时，催化剂床层入口处没有观测到温度骤升的现象。催化剂床层温度分布出现“低谷”现象，温度最低点（tmin）比炉温低30℃～40℃。根据温度分布曲线，大体可将催化剂床层分为三个区域：富氧区、贫氧区和无氧区。富氧区内只发生燃烧反应，贫氧区内发生重整反应和部分氧化反应，无氧区内只发生重整反应。