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121.
利用溶胶-凝胶法,采用三种酸性金属氧化物(氧化铌、氧化钨和氧化钼)对锰铈复合氧化物催化剂进行了改性. 测试了催化剂的氮氧化物选择性催化还原(SCR)活性,以筛选对应不同温度窗口的合适酸性氧化物改性剂. 同时评价了催化剂的NO氧化和NH3氧化活性. 利用X射线衍射、BET比表面积测试、H2程序升温还原、NH3/NOx程序升温脱附和NH3/NOx吸附红外光谱等手段对催化剂进行了表征. MnOx-CeO2催化剂表现出良好的低温(100-150 ℃)活性. 酸性金属氧化物的添加削弱了催化剂的氧化还原特性,从而抑制了NH3的活化和NO2辅助的快速SCR反应. 与此同时,相对高温(250-350 ℃)区NH3的氧化也受到了抑制,B酸和L酸上的NH3吸附得以增强. 因此,催化剂的SCR脱硝温度窗口向高温移动,改性效果Nb2O5 < WO3 < MoO3. 相似文献
122.
Meng-Yue Jiang Li Yu Yi-Cheng Zhou Jing Jia Xue-Jian Si Wen-Wen Dong Zheng-Fang Tian Jun Zhao Dong-Sheng Li 《无机化学与普通化学杂志》2020,646(5):268-274
A novel three-dimensional (3D) d-f heterometallic metal-organic framework (MOF) formulated as [EuCd1.5L2(H2O)3] · 2H2O ( 1 ) [H3L = 5-(4-(tetrazol-5-yl)phenyl)isophthalic acid] was successfully synthesized and characterized. Structural analysis displays that 1 features a 3D (3, 12)-connected framework constructed by [Eu2Cd3(tetrazole)4(COO)8] units. The powder X-ray diffraction measurement of 1 immersed in different solvents reveals that 1 possess good solvent stability. It is worth noting that 1 displays highly selective detection for ronidazole (RDZ) and 4-nitrophenol (4-NP) through luminescence quenching. The possible mechanism of luminescent sensing is also well discussed. 相似文献
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124.
以3-异丙基苯乙酮(1)为原料,经3步反应合成了花青醛[3-(3-异丙基苯基)丁醛(4)],并优化了反应条件。确定合成3-(3-异丙基苯基)-2-丁烯酸乙酯(2)的最优条件为:n(1)/n(磷酰基乙酸三乙酯)/n(氢化钠)=5/6/6,于室温反应12 h,收率84.5%;合成3-(3-异丙基苯基)-1-丁醇(3)的最佳条件为:n(2)/n(硼氢化钠)/n(六水合二氯化钴)/n(二异丙基胺)=10/20/1/2,于55 ℃反应24 h,收率87.8%;合成4的最优条件为: n(3)/n(乙酸酐)/n(亚硝酸钠)=5/4/15,投料顺序为:乙酸酐、3、亚硝酸钠,反应时间为2 min,收率91.0%。产物结构经1H NMR, 13C NMR和MS(ESI)确证。 相似文献
125.
Yuxiang Chen Ke Gong Feng Jiao Xiulian Pan Guangjin Hou Rui Si Xinhe Bao 《Angewandte Chemie (International ed. in English)》2020,59(16):6529-6534
Despite significant progress achieved in Fischer–Tropsch synthesis (FTS) technology, control of product selectivity remains a challenge in syngas conversion. Herein, we demonstrate that Zn2+‐ion exchanged ZSM‐5 zeolite steers syngas conversion selectively to ethane with its selectivity reaching as high as 86 % among hydrocarbons (excluding CO2) at 20 % CO conversion. NMR spectroscopy, X‐ray absorption spectroscopy, and X‐ray fluorescence indicate that this is likely attributed to the highly dispersed Zn sites grafted on ZSM‐5. Quasi‐in‐situ solid‐state NMR, obtained by quenching the reaction in liquid N2, detects C2 species such as acetyl (‐COCH3) bonding with an oxygen, ethyl (‐CH2CH3) bonding with a Zn site, and epoxyethane molecules adsorbing on a Zn site and a Brønsted acid site of the catalyst, respectively. These species could provide insight into C?C bond formation during ethane formation. Interestingly, this selective reaction pathway toward ethane appears to be general because a series of other Zn2+‐ion exchanged aluminosilicate zeolites with different topologies (for example, SSZ‐13, MCM‐22, and ZSM‐12) all give ethane predominantly. By contrast, a physical mixture of ZnO‐ZSM‐5 favors formation of hydrocarbons beyond C3+. These results provide an important guide for tuning the product selectivity in syngas conversion. 相似文献
126.
Kai Wu Kang Li Sha Chen Ya‐Jun Hou Yu‐Lin Lu Jing‐Si Wang Mei‐Juan Wei Mei Pan Cheng‐Yong Su 《Angewandte Chemie (International ed. in English)》2020,59(7):2639-2643
A nanocage coupling effect from a redox RuII‐PdII metal–organic cage (MOC‐16) is demonstrated for efficient photochemical H2 production by virtue of redox–guest modulation of the photo‐induced electron transfer (PET) process. Through coupling with photoredox cycle of MOC‐16, tetrathiafulvalene (TTF) guests act as electron relay mediator to improve the overall electron transfer efficiency in the host–guest system in a long‐time scale, leading to significant promotion of visible‐light driven H2 evolution. By contrast, the presence of larger TTF‐derivatives in bulk solution without host–guest interactions results in interference with PET process of MOC‐16, leading to inefficient H2 evolution. Such interaction provides an example to understand the interplay between the redox‐active nanocage and guest for optimization of redox events and photocatalytic activities in a confined chemical nanoenvironment. 相似文献
127.
Si‐Hua Hou Adriana Y. Prichina Mengxi Zhang Guangbin Dong 《Angewandte Chemie (International ed. in English)》2020,59(20):7848-7856
To show the synthetic utility of the catalytic C?C activation of less strained substrates, described here are the collective and concise syntheses of the natural products (?)‐microthecaline A, (?)‐leubehanol, (+)‐pseudopteroxazole, (+)‐seco‐pseudopteroxazole, pseudopterosin A–F and G—J aglycones, and (+)‐heritonin. The key step in these syntheses involve a Rh‐catalyzed C?C/C?H activation cascade of 3‐arylcyclopentanones, which provides a rapid and enantioselective route to access the polysubstituted tetrahydronaphthalene cores presented in these natural products. Other important features include 1) the direct C?H amination of the tetralone substrate in the synthesis of (?)‐microthecaline A, 2) the use of phosphoric acid to enhance efficiency and regioselectivity for problematic cyclopentanone substrates in the C?C activation reactions, and 3) the direct conversion of serrulatane into amphilectane diterpenes by an allylic cyclodehydrogenation coupling. 相似文献
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129.
Deping Hu Yuandong Li Hui Zhao Yang Zhao Si Huang Juan Li Zhenjie Li Yuanxing Duan Yingzhuang Chen Jianjun Xia 《Journal of separation science》2020,43(8):1423-1430
An online high‐pH reversed‐phase liquid chromatography× low‐pH reversed‐phase liquid chromatography tandem electrospray ionization mass spectrometry combined with pulse elution gradient in the first dimension was constructed to separate and identify alkaloids from Macleaya cordata (willd.) R. Br. The modulation was performed by using a dual second dimensional columns interface combined with a make‐up dilution pump, which is responsible for dilution and neutralization of the first dimensional effluent, and the dual second dimensional columns integrated the trapping and the separation function to reduce the second dimension system dead volume. Taking advantage of the dissociable characteristics of alkaloids, mobile phases with different pH values were applied in the first dimension (pH 9.0) and the second dimension (pH 2.6) to improve the orthogonality of two‐dimension separation. Besides, the pulse elution gradient in first dimension and second dimensional gradient were carefully optimized and much better separation was achieved compared to the separation with the traditional two‐dimensional liquid chromatography approach. Finally, mass measurement was performed for alkaloids in M. cordata (willd.) R. Br. by coupling proposed two‐dimensional liquid chromatography system with triple quadrupole mass spectrometry, and 39 alkaloids were successfully identified by comparing the obtained result with the former reported results. 相似文献
130.
Nonlinear Dynamics - Intelligent fault diagnosis provides great convenience for the prognostic and health management of the rotating machinery. Recently, the multiscale diversity entropy has been... 相似文献