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排序方式: 共有792条查询结果,搜索用时 15 毫秒
771.
[Co2(bdc)2(ted)]·2DMF·3H2O ( 2 ), (DMF = N,N′‐dimethylformamide, bdc = 1,4‐benzenedicarboxylate dianion, ted = triethylenediamine) was prepared and characterized by IR, elemental analysis, TGA, powder X‐ray analysis and single‐crystal X‐ray determination. At ambient temperature the material [Co2(bdc)2(ted)] ( 1 ) was found to be high adsorbent of methane but poor adsorbent of hydrogen. 相似文献
772.
Wei Gao Prof. Dr. Qiang Wang Dr. Guodong Qi Jiawei Liang Dr. Chao Wang Prof. Dr. Jun Xu Prof. Dr. Feng Deng 《Angewandte Chemie (International ed. in English)》2023,62(31):e202306133
Methane dehydroaromatization (MDA) over Mo-modified zeolite is a potential catalytic route for converting natural gas into valuable aromatics. However, the active species in this reaction are highly complex, involving diverse Mo species, acidic sites of zeolite, and organic molecules. Herein, we apply 1D 95Mo NMR and 2D 1H-95Mo heteronuclear correlation solid-state NMR spectroscopy to directly observe the active ensembles in the confined channels of Mo/ZSM-5 zeolite during the MDA reaction. We monitor the evolution of the spatial correlations of Mo species with the Brønsted acid sites and organic products (olefins and aromatics) in the zeolite channels. We identified two kinds of MoOxCy species, with the more carbidic one (MoOxCy-II) exhibiting higher activity for methane activation and benzene formation. The strong spatial interactions between the active Mo species and the organic species in the Mo/ZSM-5 pores are related to the MDA activity. 相似文献
773.
Hui Song Hengming Huang Xianguang Meng Qi Wang Huilin Hu Shengyao Wang Hongwei Zhang Wipakorn Jewasuwan Naoki Fukata Ningdong Feng Jinhua Ye 《Angewandte Chemie (International ed. in English)》2023,62(4):e202215057
Direct photocatalytic oxidation of methane to liquid oxygenated products is a sustainable strategy for methane valorization at room temperature. However, in this reaction, noble metals are generally needed to function as cocatalysts for obtaining adequate activity and selectivity. Here, we report atomically dispersed nickel anchored on a nitrogen-doped carbon/TiO2 composite (Ni−NC/TiO2) as a highly active and selective catalyst for photooxidation of CH4 to C1 oxygenates with O2 as the only oxidant. Ni−NC/TiO2 exhibits a yield of C1 oxygenates of 198 μmol for 4 h with a selectivity of 93 %, exceeding that of most reported high-performance photocatalysts. Experimental and theoretical investigations suggest that the single-atom Ni−NC sites not only enhance the transfer of photogenerated electrons from TiO2 to isolated Ni atoms but also dominantly facilitate the activation of O2 to form the key intermediate ⋅OOH radicals, which synergistically lead to a substantial enhancement in both activity and selectivity. 相似文献
774.
Dr. Yuehan Cao Wang Yu Chunqiu Han Yuantao Yang Zhiqiang Rao Rui Guo Prof. Fan Dong Dr. Ruiyang Zhang Prof. Ying Zhou 《Angewandte Chemie (International ed. in English)》2023,62(18):e202302196
Restrained by uncontrollable dehydrogenation process, the target products of methane direct conversion would suffer from an inevitable overoxidation, which is deemed as one of the most challenging issues in catalysis. Herein, based on the concept of a hydrogen bonding trap, we proposed a novel concept to modulate the methane conversion pathway to hinder the overoxidation of target products. Taking boron nitride as a proof-of-concept model, for the first time it is found that the designed N−H bonds can work as a hydrogen bonding trap to attract electrons. Benefitting from this property, the N−H bonds on the BN surface rather than C−H bonds in formaldehyde prefer to cleave, greatly suppressing the continuous dehydrogenation process. More importantly, formaldehyde will combine with the released protons, which leads to a proton rebound process to regenerate methanol. As a result, BN shows a high methane conversion rate (8.5 %) and nearly 100 % product selectivity to oxygenates under atmospheric pressure. 相似文献
775.
Yuxiong Wang Guang Hong Yaoyu Zhang Prof. Yue Liu Dr. Wanglai Cen Prof. Lianzhou Wang Prof. Zhongbiao Wu 《Angewandte Chemie (International ed. in English)》2023,62(42):e202310525
C−H dissociation and C−C coupling are two key steps in converting CH4 into multi-carbon compounds. Here we report a synergy of Au and Ag to greatly promote C2H6 formation over Au1Ag single-atom alloy nanoparticles (Au1Ag NPs)-modified ZnO catalyst via photocatalytic oxidative coupling of methane (POCM) with O2 and H2O. Atomically dispersed Au in Au1Ag NPs effectively promotes the dissociation of O2 and H2O into *OOH, promoting C−H activation of CH4 on the photogenerated O− to form *CH3. Electron-deficient Au single atoms, as hopping ladders, also facilitate the migration of electron donor *CH3 from ZnO to Au1Ag NPs. Finally, *CH3 coupling can readily occur on Ag atoms of Au1Ag NPs. An excellent C2H6 yield of 14.0 mmol g−1 h−1 with a selectivity of 79 % and an apparent quantum yield of 14.6 % at 350 nm is obtained via POCM with O2 and H2O, which is at least two times that of the photocatalytic system. The bimetallic synergistic strategy offers guidance for future catalyst design for POCM with O2 and H2O. 相似文献
776.
Anton Purnomo Susan Gallardo Leonila Abella Chris Salim Hirofumi Hinode 《Reaction Kinetics and Catalysis Letters》2008,95(2):213-220
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. 相似文献
777.
B. Fidalgo Y. Fernndez A. Domínguez J.J. Pis J.A. Menndez 《Journal of Analytical and Applied Pyrolysis》2008,82(1):158-162
The aim of this work was to study the microwave-assisted pyrolysis of CH4 over an activated carbon, which acted as both microwave receptor and catalyst, and the influence of using different CH4/N2 ratios on the conversion of CH4 to H2. In order to compare the results obtained in the microwave oven, the pyrolysis was also carried out under conventional heating (electric furnace, EF). The effects of N2, which enhanced significantly CH4 conversion, differed depending on the heating device used. Under EF heating, N2 seemed to have an effect similar to distribute the CH4 molecules within the activated carbon bed. Under microwave heating (MW), the N2, as well as distributing the CH4 molecules, favoured the generation of energetic microplasmas, leading to higher conversions. The prevalence of one role over the other depended on the CH4/N2 ratio, the appearance of energetic microplasmas being favoured with high percentages of N2. Consequently, CH4 conversion was higher at low CH4/N2 ratios. Additionally, the formation of carbon nanofibres in experiments where a combination of N2 and MW heating was used is also reported. 相似文献
778.
气体分子对甲烷水合物稳定性的影响 总被引:1,自引:0,他引:1
通过B3LYP方法, 在6-31G(d,p)水平下, 分别优化了结构I型甲烷水合物十二面体和十四面体晶穴结构. 结果表明, CH4分子使晶穴的相互作用能降低, 增强了晶穴的稳定性. 计算了晶穴中甲烷分子C—H键的对称伸缩振动频率, 计算结果与实验值相符合. 研究发现CH4分子影响晶穴中氧原子的电荷分布, 从而增强了氢键的稳定性. 通过分子动力学方法研究水合物晶胞中气体分子的占有率对水合物稳定性的影响, 进一步说明气体分子对水合物晶穴稳定性的重要作用. 相似文献
779.
金属-有机骨架材料MOF-5的改进与吸附甲烷的巨正则蒙特卡罗模拟 总被引:1,自引:0,他引:1
根据金属-有机骨架材料(MOFs)的设计思想, 在MOF-5(对苯二甲酸为桥联配体, Zn4O金属簇为中心的配位化合物)的基础上设计了10 种以Zn4O 金属簇为中心(Corner), 以不同基团单取代的对苯二甲酸(BDC)衍生物为桥联配体(Linker)的多孔材料. 用巨正则蒙特卡罗(GCMC)模拟方法, 计算了这些材料在298 K、1-10 MPa条件下对甲烷的吸附量, 讨论了不同取代基与甲烷吸附量的关系.结果发现, 在298 K、3.5 MPa 时甲烷的吸附量主要取决于吸附热, 并且以硝基取代的配体构成的MOF分子吸附甲烷效果最好. 在此基础上, 进一步设计了以四硝基取代对苯二甲酸为桥联配体的MOF-4NO2, 该结构在相同条件下对甲烷的超额吸附量为209 cm3·cm-3, 总吸附量达到228 cm3·cm-3, 比美国能源部(DOE)提出的甲烷吸附材料应用要求标准高26%. 相似文献
780.
La0.8Sr0.2Fe1-xScxO3-δ催化剂的制备、表征及甲烷催化燃烧性能 总被引:1,自引:0,他引:1
采用甘氨酸-硝酸盐溶液燃烧法制备了钙钛矿型氧化物催化剂La0.8Sr0.2Fe1-xScxO3-δ (LSFS, x=0, 0.3,0.4, 0.5, 0.6, 0.8, 1), 利用X射线衍射(XRD)、H2程序升温还原(H2-TPR)、扫描电子显微镜(SEM)和比表面积测试等手段对催化剂进行了系统表征, 并在常压微型固定床反应器上考察了催化剂对甲烷燃烧的催化性能. 结果表明, 经空气气氛下900 °C煅烧5 h制备的LSFS均具有单一的钙钛矿结构, 在La0.8Sr0.2FeO3-δ (LSF)中掺杂Sc有助于改善催化剂的抗烧结性能, 提高催化剂的比表面积. 当LSF 中的Sc 掺杂量为0.4-0.6 时, 所形成的LSFS表现出良好的甲烷催化燃烧活性, 其中Sc 掺杂量为0.5 时, 其起燃温度(T10)和完全转化温度(T90)分别为406和563 °C, 与La0.8Sr0.2FeO3-δ和La0.8Sr0.2ScO3-δ相比, T10分别降低了14和87 °C; T90分别降低了59和95 °C. 相似文献