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991.
Yuemin Lin Yuanyuan Zhang Renfeng Nie Kai Zhou Yao Ma Mingjie Liu Dan Lu Zongbi Bao Qiwei Yang Yiwen Yang Qilong Ren Zhiguo Zhang 《Frontiers of Chemical Science and Engineering》2022,16(12):1782
Ultra-dispersed Ni nanoparticles (7.5 nm) on nitrogen-doped carbon nanoneedles (Ni@NCNs) were prepared by simple pyrolysis of Ni-based metal–organic-framework for selective hydrogenation of halogenated nitrobenzenes to corresponding anilines. Two different crystallization methods (stirring and static) were compared and the optimal pyrolysis temperature was explored. Ni@NCNs were systematically characterized by wide analytical techniques. In the hydrogenation of p-chloronitrobenzene, Ni@NCNs-600 (pyrolyzed at 600 °C) exhibited extraordinarily high performance with 77.9 h–1 catalytic productivity and > 99% p-chloroaniline selectivity at full p-chloronitrobenzene conversion under mild conditions (90 °C, 1.5 MPa H2), showing obvious superiority compared with reported Ni-based catalysts. Notably, the reaction smoothly proceeded at room temperature with full conversion and > 99% selectivity. Moreover, Ni@NCNs-600 afforded good tolerance to various nitroarenes substituted by sensitive groups (halogen, nitrile, keto, carboxylic, etc.), and could be easily recycled by magnetic separation and reused for 5 times without deactivation. The adsorption tests showed that the preferential adsorption of –NO2 on the catalyst can restrain the dehalogenation of p-chloronitrobenzene, thus achieving high p-chloroaniline selectivity. While the high activity can be attributed to high Ni dispersion, special morphology, and rich pore structure of the catalyst. 相似文献
992.
Xuxin Zhao Kunling Yang Zhou Liu Ho Cheung Shum Tiantian Kong 《Frontiers of Chemical Science and Engineering》2022,16(11):1681
Bubbles and foams are ubiquitous in daily life and industrial processes. Studying their dynamic behaviors is of key importance for foam manufacturing processes in food packaging, cosmetics and pharmaceuticals. Bare bubbles are inherently fragile and transient; enhancing their robustness and shelf lives is an ongoing challenge. Their rupture can be attributed to liquid evaporation, thin film drainage and the nuclei of environmental dust. Inspired by particle-stabilized interfaces in Pickering emulsions, armored bubbles and liquid marble, bubbles are protected by an enclosed particle-entrapping liquid thin film, and the resultant soft object is termed gas marble. The gas marble exhibits mechanical strength orders of magnitude higher than that of soap bubbles when subjected to overpressure and underpressure, owing to the compact particle monolayer straddling the surface liquid film. By using a water-absorbent glycerol solution, the resulting gas marble can persist for 465 d in normal atmospheric settings. This particle-stabilizing approach not only has practical implications for foam manufacturing processes but also can inspire the new design and fabrication of functional biomaterials and biomedicines. 相似文献
993.
Yang Zhang Guowu Zhan Yibo Song Yiping Liu Jiale Huang Shu-Feng Zhou Kok Bing Tan Qingbiao Li 《Frontiers of Chemical Science and Engineering》2022,16(12):1793
Recycling industrial solid waste not only saves resources but also eliminates environmental concerns of toxic threats. Herein, we proposed a new strategy for the utilization of petrochemical-derived carbon black waste, a waste vanadium-bearing resource (V > 30000 ppm (10 −6)). Chemical leaching was employed to extract metallic vanadium from the waste and the leachate containing V was used as an alternative raw material for the fabrication of vanadate nanomaterials. Through the screening of various metal cations, it was found that the contaminated Na+ during the leaching process showed strong competitive coordination with the vanadium ions. However, by adding foreign Ce3+ and Y3+ cations, two rare-earth vanadates, viz., flower-like CeVO4 and spherical YVO4 nanomaterials, were successfully synthesized. Characterization techniques such as scanning electron microscopy, transmission electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, Fourier-transform infrared, and N2 physisorption were applied to analyze the physicochemical properties of the waste-derived nanomaterials. Importantly, we found that rare-earth vanadate catalysts exhibited good activities toward the semi-hydrogenation of α,β-unsaturated aldehydes. The conversion of cinnamaldehyde and cinnamic alcohol selectivity were even higher than those of the common CeVO4 prepared using pure chemicals (67.2% vs. 27.7% and 88.4% vs. 53.5%). Our work provides a valuable new reference for preparing vanadate catalysts by the use of abundant vanadium-bearing waste resources. 相似文献
994.
为实现30 MHz~1 GHz频率范围内的机箱机柜电磁屏蔽效能测量,研制了直径为100 mm的信号源内置式球形偶极子天线.该天线采用具有陡峭上升沿与下降沿的30 MHz方波信号作为信号源,信号源和电源部分均置于天线内部.对天线幅值动态范围的测试结果表明:在与接收天线相距1 m的条件下,该天线在30 MHz~1 GHz频率范围内的动态范围都在50dB以上,大多数谱线的动态范围达到60dB.所研制天线体积小、可连续工作5小时以上,解决了体积较小机箱机柜的电磁屏蔽效能测试难题. 相似文献
995.
996.
997.
旧城商业街开发的模式探讨 总被引:2,自引:0,他引:2
旧城商业街改造是都市复兴计划的一个重要部分,针对旧城商业街的发展及其面临问题,从区域背景与自身特点和影响、改造模式、改造效果等方面比较国内旧城商业街不同的开发模式.在此基础上,提出了旧城商业街开发相结合的复合开发模式,并阐述了复合开发模式的主要内容. 相似文献
998.
重点论述了当前施工现场签证工作中存在的主要问题,并就此提出了加强施工现场签证管理工作的对策和办法,以供研讨. 相似文献
999.
低温热水地板辐射采暖的发展优势及尚存问题 总被引:2,自引:0,他引:2
低温热水地板辐射采暖系统具有节约能源、减少环境污染、热舒适性好、卫生保健、初投资不高、维修费用低等优点,但在应用中尚存在一些问题,本文指出了其在设计和施工中存在的一些问题及相应的解决方法,同时通过对共约2000m^2实铺面积的统计,得出了不同管间距时单位面积大约所需的管长,根据经验提出了一种设计穹孽謦方孽虿母可哆使设计者节省设计时间,还可以避免管材浪费现象,节省工程成本。 相似文献
1000.
消防队灭火行为涉及的几个法律问题 总被引:1,自引:0,他引:1
用法学理论对消防队实施的灭火行为可能涉及的法律问题进行了探讨,重点论述了消防队灭火行为的法律性质、灭火行为与紧急避险的关系、消防队员在履行职责过程中的紧急避险以及对不作为如何处理等方面的问题。 相似文献