The Effects of CO2 Additional on Flame Characteristics in the CH4/N2/O2 Counterflow Diffusion Flame

The effects (chemical, thermal, transport, and radiative) of CO₂ added to the fuel side and oxidizer side on the flame temperature and the position of the flame front in a one-dimensional laminar counterflow diffusion flame of methane/N₂/O₂ were studied. Overall CO₂ resulted in a decrease in flame temperature whether on the fuel side or on the oxidizer side, with the negative effect being more obvious on the latter side. The prominent effects of CO₂ on the flame temperature were derived from its thermal properties on the fuel side and its radiative properties on the oxidizer side. The results also highlighted the differences in the four effects of CO₂ on the position of the flame front on different sides. In addition, an analysis of OH and H radicals and the heat release rate of the main reactions illustrated how CO₂ affects the flame temperature.     

Selective sensing of CrVI and FeIII ions in aqueous solution by an exceptionally stable TbIII-organic framework with an AIE-active ligand

We herein report a new lanthanide metal-organic framework (MOF) that exhibits excellent chemical stability, especially in the aqueous solution over a wide pH range from 1 to 14. In contrast to many reported lanthanide MOFs, this Tb-based MOF emits cyan fluorescence inherited from the integrated AIE-active ligand, rather than Ln³⁺ ions. More remarkably, its fluorescence signal features a highly selective and sensitive “turn-off” response toward CrO₄²⁻, Cr₂O₇²⁻ and Fe³⁺ ions, highlighted with the low detection limits down to 68.18, 69.85 and 138.8 ppm, respectively. Thus, the exceptional structural stability and sensing performance render this material able to be a superior luminescent sensor for heavy metal ions in wastewater.     

Biselective refocusing pulses and the SERF experiment

The SERF experiment is a variant of the homonuclear J-resolved experiment, in which a single coupling constant is measured. It consists of a single chemical shift selective excitation that is followed by a biselective spin echo. Recent articles mention the existence of artefacts in SERF spectra that are supposedly related to pulse imperfections. This article presents a detailed study of the biselective refocusing pulses. It also reports a method for predicting the position and amplitude of the expected and unexpected 2D spectral peaks in SERF spectra. Artefacts can be partially eliminated by phase cycling or by the introduction of static field gradient pulses in the acquisition sequence. A procedure to obtain of pure absorption peaks in SERF spectra is proposed.     

Selective adsorption behaviors of guest molecules COR in the hexamer host networks at liquid/solid interface

Here,the selective adsorption behaviors of guest molecule COR in two hexamer host grids were investigated by means of scanning tunnelling microscope(STM).The assembled structures of small functional organic molecules TTBTA and TATBA were thermodynamically stable.Interestingly,the introduction of the guest molecule COR destroyed the original hexamer structure of TTBTA and combined with it to form a new triangular host-guest system.Different from TTBTA,the introduction of the guest molecule COR did not affect the six-membered ring structure of TATBA.Furthermore,the co-assembly structure of TTBTA/TATBA/COR was established and the guest molecule COR showed preferential adsorption to the TATBA host grid.Density functional theory(DFT) calculations had been performed to disclose the mechanism of the involved assemblies.     

无碱条件下Au/ZnO选择性催化氧化1,3-丙二醇合成3-羟基丙酸甲酯

采用溶胶-沉积法合成了高选择性的Au/ZnO催化剂,用于1,3-丙二醇选择性氧化酯化为3-羟基丙酸甲酯的反应.研究了保护剂PVA用量、金溶胶合成温度、金负载量及催化剂循环利用对反应的影响,且优化了反应温度和反应压力,并对催化剂进行了XRD和TEM表征.结果表明,PVA∶Au(m/m)=1∶4、金溶胶合成温度25℃、金负载量1%的Au/ZnO对目标反应的催化活性最好,在100℃和Po2=2MPa的条件下1,3-丙二醇的转化率达82.8%,产物3-羟基丙酸甲酯的选择性达95.4%.Au纳米粒子的粒径影响催化性能,在Au平均粒径为2.8~6.1nm的范围内,产物选择性随Au纳米粒子的粒径的减小而增大,平均粒径在2.8~4.8nm的范围内时,催化剂具有较好的产物选择性(大于90%);Au/ZnO催化剂循环利用4次后催化性能(转化率和选择性)无明显下降;并推测了无碱条件下Au/ZnO选择性催化氧化1,3-丙二醇合成3-羟基丙酸甲酯的反应机制.     

NH3选择性还原NOx技术在重型柴油车尾气净化中的应用

基于实验室对柴油车用V₂O₅-WO₃/TiO₂催化剂配方以及涂覆成型技术的大量研究,设计了一条产量为6000只/月的NH₃选择性催化还原NO_x （NH₃-SCR）催化剂中试生产线,并对生产的催化剂产品进行了发动机台架测试. 结果表明,实验室制备的V₂O₅-WO₃/TiO₂粉体催化剂和生产线产品,在空速为50000 h^-1和200-450 ℃条件下NO_x转化率均可达80%以上;采用大尺寸堇青石载体涂覆后制备的V₂O₅-WO₃/TiO₂整体催化剂经实验室小样测试,在空速为10000-30000 h^-1和250-450 ℃条件下NO_x转化率也为80%以上. 发动机台架测试结果表明,该催化剂产品可使重型柴油机NO_x排放达到国IV标准中欧洲稳态循环（ESC）和欧洲瞬态循环（ETC）排放限值的要求. 该生产线经适当调整后也可用于生产非钒基NH₃-SCR整体催化剂,以满足未来钒基NH₃-SCR催化剂更新换代的需求.     

酸性金属氧化物对锰铈氧化物催化剂脱硝温度窗口的调控作用

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/NO_x程序升温脱附和NH₃/NO_x吸附红外光谱等手段对催化剂进行了表征. MnO_x-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.     

非晶Ce-Ti氧化物用于NH3选择性催化还原NO的原位红外研究

采用原位红外光谱研究了在具有短程有序Ce-O-Ti结构的非晶Ce-Ti氧化物上NH₃选择性催化还原（SCR） NO_x反应. 在反应条件下,催化剂表面主要被NH₃吸附物种覆盖,而检测不到NO_x吸附物种. 经测定,NO的反应级数为0.5-0.6,表明Langmuir-Hinshelwood机理和Eley-Rideal机理同时存在. 可能的机理是NH₃吸附物种和弱吸附的NO_x反应,生成NH_yNO₃ （y = 0-4）活性中间物种,并通过GAUSSIAN计算和原位红外结果证实了它们的存在. Ce-O-Ti结构中Ce与Ti之间表现出原子尺度的相互作用,所以在SCR反应的活性温度窗口下,催化剂的氧化还原活性提高.     

磷酸铜锆催化剂上醇选择性氧化（英文）

The catalytic activity of copper zirconium phosphate(ZPCu) in the selective oxidation of alcohols to their corresponding ketones or aldehydes, using H2O2 as an oxidizing agent, was studied. The oxida‐tion reaction was performed without any organic solvent, phase‐transfer catalyst, or additive. Steric factors associated with the substrates influenced the reaction. The catalyst was characterized using X‐ray diffraction, inductively coupled plasma atomic emission spectroscopy, energy‐dispersive X‐ray spectroscopy, and scanning electron microscopy. It was shown that the interlayer distance increased from 0.74 to 0.80 nm and the crystallinity was reduced after Cu2+ intercalation into the layers. This catalyst can be recovered and reused three times without significant loss of activity and selectivity.