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。     

Ni-La/CexZr1-xO2对甲烷部分氧化/CH4-CO2重整耦合制合成气的催化剂制备及反应性能

通过共沉淀法制备铈锆固溶体作为载体,采用等体积、分步浸渍的方法制备了一系列10% Ni-3% La/CexZr1-xO2（X=0、0.16、0.5、0.75、1）催化剂,并将其应用到甲烷部分氧化和甲烷二氧化碳重整耦合制合成气的反应中。对不同Ce/Zr比的催化剂性能展开研究,采用XRD、H2-TPR、SEM手段对载体及催化剂进行了表征。结果表明,铈锆固溶体的形成不仅提高了催化剂表面活性组分的分散度,使催化剂表面NiO晶粒尺寸从26.5 nm减到13.7 nm;而且能够加强活性组分与载体之间的相互作用,提高催化剂的热稳定性能;随着Ce/Zr比的增加,催化剂的转化率、选择性及稳定性随之增强,其关系为：Ni-La/Ce0.75Zr0.25O2 > Ni-La/Ce0.5Zr0.5O2 > Ni-La/Ce0.16Zr0.84O2。     

桥头碳上氮杂芳基功能化的双吡唑甲烷与羰基钨反应

研究了(氮甲基咪唑-2-基)双(3,5-二甲基吡唑)甲烷(L¹),2-吡啶基双(3,5-二甲基吡唑)甲烷(L²)及4-吡啶基双(3,5-二甲基吡唑)甲烷(L³)与羰基钨的反应,合成了一系列以单齿,双齿及三齿氮配位的羰基金属衍生物LW(CO)₅ (L=L¹或L³),LW(CO)₄ (L=L¹,L²或L³)和LW(CO)₃ (L=L¹或L²).核磁,红外及X-射线单晶衍射分析表明这3种配体表现出了可变的配位方式.在LW(CO)₅中,当配体为L¹时,其倾向于通过咪唑氮与金属配位,而为L³则倾向于利用吡啶氮与金属作用;在LW(CO)₄中,配体L¹表现为通过咪唑氮和吡唑氮原子配位的[N,N']双齿配体,而L²和L³表现为通过吡唑氮原子配位的[N,N]双齿配体;在LW(CO)₃中,L¹和L²起着[N,N,N']三齿螯合配体的作用.     

羟基磷灰石负载Ni催化剂中Ni含量对催化甲烷二氧化碳重整制合成气性能的影响

以低温沉淀方法制备的羟基磷灰石(HAp)为载体,采用浸渍法制备了一系列不同Ni含量的Ni/HAp催化剂,并采用BET、H2-TPR、XRD、SEM、FT-IR、TEM和TG-DTA技术对催化剂进行了表征。结果表明,NiO含量为13%的催化剂表现出最好的催化甲烷二氧化碳重整制合成气活性,在850℃、空速3.6×104mL/(h·gcat)的反应条件下,甲烷和二氧化碳的转化率在10 h内分别稳定在72%和83%。这主要归因于催化剂中金属和载体之间的强相互作用。虽然反应后的催化剂表面有少量的积炭,但这些积炭多以丝状炭存在,并不会影响催化剂的活性和稳定性。     

Solar Driven Gas Phase Advanced Oxidation Processes for Methane Removal - Challenges and Perspectives

Methane (CH₄) is a potent greenhouse gas and the second highest contributor to global warming. CH₄ emissions are still growing at an alarmingly high pace. To limit global warming to 1.5 °C, one of the most effective strategies is to reduce rapidly the CH₄ emissions by developing large-scale methane removal methods. The purpose of this perspective paper is threefold. (1) To highlight the technology gap dealing with low concentration CH₄ (at many emission sources and in the atmosphere). (2) To analyze the challenges and prospects of solar-driven gas phase advanced oxidation processes for CH₄ removal. And (3) to propose some ideas, which may help to develop solar-driven gas phase advanced oxidation processes and make them deployable at a climate significant scale.     

Rational Development of a Metal-Free Bifunctional System for the C−H Activation of Methane: A Density Functional Theory Investigation

The activation or heterolytic splitting of methane, a challenging substrate usually restricted to transition metals, has so far proven elusive in experimental frustrated Lewis pair (FLP) chemistry. In this article, we demonstrate, using density functional theory (DFT), that 1-aza-9-boratriptycene is a conceptually simple intramolecular FLP for the activation of methane. Systematic comparison with other FLP systems allows to gain insight into their reactivity with methane. The thermodynamics and kinetics of methane activation are interpreted by referring to the analysis of the natural charges and by employing the distortion-interaction/activation strain (DIAS) model. These showed that the nature of the Lewis base influences the selectivity over the reaction pathway, with N Lewis bases favoring the deprotonation mechanism and P bases the hydride abstraction one. The lower barrier of activation for 1-aza-9-boratriptycene and the higher products stability are due to a better interaction energy than its counterparts, itself due to electrostatic interactions with the methane moiety, favorable orbital overlaps allowed by the side-attack, and space proximity between the B and N atoms.     

甲烷与氯气取代反应实验的创新设计*

基于甲烷氯代反应的机理,对物质体系、反应容器、光照条件、实验表征等进行分析,创新设计甲烷氯代反应实验,利用数字化实验的压强和温度传感器采集的实验数据为支持,更直观地多重表征甲烷与氯气发生的“取代”过程,对于成功实现甲烷氯代反应实验具有指导意义。     

Water‐Stable Zirconium‐Based Metal–Organic Framework Material with High‐Surface Area and Gas‐Storage Capacities

We designed, synthesized, and characterized a new Zr‐based metal–organic framework material, NU‐1100 , with a pore volume of 1.53 ccg^?1 and Brunauer–Emmett–Teller (BET) surface area of 4020 m²g^?1; to our knowledge, currently the highest published for Zr‐based MOFs. CH₄/CO₂/H₂ adsorption isotherms were obtained over a broad range of pressures and temperatures and are in excellent agreement with the computational predictions. The total hydrogen adsorption at 65 bar and 77 K is 0.092 g g^?1, which corresponds to 43 g L^?1. The volumetric and gravimetric methane‐storage capacities at 65 bar and 298 K are approximately 180 v_STP/v and 0.27 g g^?1, respectively.     

Methane Activation by Diatomic Molybdenum Carbide Cations

Metal carbide species have been proposed as a new type of chemical entity to activate methane in both gas‐phase and condensed‐phase studies. Herein, methane activation by the diatomic cation MoC⁺ is presented. MoC⁺ ions have been prepared and mass‐selected by a quadrupole mass filter and then allowed to interact with methane in a hexapole reaction cell. The reactant and product ions have been detected by a reflectron time‐of‐flight mass spectrometer. Bare metal Mo⁺ and MoC₂H₂⁺ ions have been observed as products, suggesting the occurrence of ethylene elimination and dehydrogenation reactions. The branching ratio of the C₂H₄ elimination channel is much larger than that of the dehydrogenation channel. Density functional theory calculations have been performed to explore in detail the mechanism of the reaction of MoC⁺ with CH₄. The computed results indicate that the ethylene elimination process involves the occurrence of spin conversions in the C?C coupling (doublet→quartet) and hydrogen atom transfer (quartet→sextet) steps. The carbon atom in MoC⁺ plays a key role in methane activation because it becomes sp³ hybridized in the initial stages of the ethylene elimination reaction, which leads to much lower energy barriers and more stable intermediates. This study provides insights into the C?H bond activation and C?C coupling involved in methane transformation over molybdenum carbide‐based catalysts.