共查询到19条相似文献,搜索用时 171 毫秒
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以硝酸镁和硝酸铝为原料,用氨水溶液作为pH调节剂,采用共沉淀法制备了镁铝复合氧化物载体,研究了制备过程中镁铝比、pH调节剂种类、水解过程pH值的大小、反应温度、焙烧温度及回流晶化温度对复合氧化物载体理化性质的影响。并以RFCC汽油加氢脱硫为探针反应,考察了以镁铝复合氧化物为载体的催化剂选择性加氢脱硫性能。实验结果表明,在镁铝分子比为10、反应温度为80℃、pH值为9.5条件下制备的镁铝复合氧化物载体具有适宜的比表面积和均匀的孔分布,且晶型较完整,结晶度高。以该复合氧化物为载体制备的催化剂具有良好的RFCC汽油选择性加氢脱硫反应性能。 相似文献
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在制备高硬度、高热导、耐磨、耐腐蚀、耐高温的新兴陶瓷材料氧化硼、氮化硅的固相反应中,氮化镁是不可缺少的烧结助剂[‘,’j.同时,氮化镁还可用于制备发泡合金和回收核废料等领域.目前氮化镁的制备方法有:镁粉直接与氮气反应法[‘,‘1、镁在氮等离子流中与氮反应法*‘、在氮气气氛下镁线圈爆炸法‘’‘和低压化学气相沉积法[’j.在上述方法中,有些方法需要复杂和昂贵的设备.有些方法得到氮化镁的产率较低.镁粉直接与氮气反应是具有工业生产价值的方法一然而,这种方法需要SOO”C到gOO”C的高温.我们曾经报道过利用温和… 相似文献
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研究了通过萘锂还原法制得的活性镁与环戊二烯原位合成环戊二烯基镁(Cp~2Mg)的方法。Cp~2Mg的存在是由它与醛酮反应生成富烯得到证实。此法产率高, 方法简单, 条件温和。 相似文献
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共沉淀法制备的镁铝氧化物催化剂上丙酮气相缩合反应 总被引:1,自引:0,他引:1
采用共沉淀法, 以氨水为沉淀剂制备了一系列具有不同Mg/Al摩尔比的镁铝氧化物催化剂, 考察了它们在丙酮气相缩合反应中的催化性能, 并通过XRD, XPS, ICP, TG-DTA和TPD等手段对催化剂的结构和性质进行了表征. 实验结果表明, 以反滴沉淀方式制备的Mg1.0AlO催化剂具有较高的反应活性和稳定性, 在反应温度为573 K条件下, 反应85 h后丙酮的转化率仍可以达到65%. 镁铝氧化物表面存在一定量强度和密度相互匹配的弱碱和强碱中心对提高催化剂的活性和稳定性有利. 相似文献
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Yao X Wu C Du A Zou J Zhu Z Wang P Cheng H Smith S Lu G 《Journal of the American Chemical Society》2007,129(50):15650-15654
Synergistic effect of metallic couple and carbon nanotubes on Mg results in an ultrafast kinetics of hydrogenation that overcome a critical barrier of practical use of Mg as hydrogen storage materials. The ultrafast kinetics is attributed to the metal-H atomic interaction at the Mg surface and in the bulk (energy for bonding and releasing) and atomic hydrogen diffusion along the grain boundaries (aggregation of carbon nanotubes) and inside the grains. Hence, a hydrogenation mechanism is presented. 相似文献
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Hydrogen spillover mechanism on a Pd-doped Mg surface as revealed by ab initio density functional calculation 总被引:2,自引:0,他引:2
The hydrogenation kinetics of Mg is slow, impeding its application for mobile hydrogen storage. We demonstrate by ab initio density functional theory (DFT) calculations that the reaction path can be greatly modified by adding transition metal catalysts. Contrasting with Ti doping, a Pd dopant will result in a very small activation barrier for both dissociation of molecular hydrogen and diffusion of atomic H on the Mg surface. This new computational finding supports-for the first time by ab initio simulation-the proposed hydrogen spillover mechanism for rationalizing experimentally observed fast hydrogenation kinetics for Pd-capped Mg materials. 相似文献
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A model to explain the increasing rates associated with hydrogen evolution (HE) originating at the dissolving regions of Mg under anodic polarization is presented. The actively dissolving anodes have been shown experimentally to be the primary source of anomalous evolution of hydrogen. In this model, standard electrochemical laws are used to account for this phenomenon. The fractional coverage of active Mg sites is introduced to localize the cathodic contribution of HE during anodic polarization. A kinetic equation is derived showing that the rate of HE will increase with increasing potential if the charge transfer coefficient associated with the Mg oxidation reaction is greater than the charge transfer coefficient for the HE reaction. Experimental data obtained on high purity Mg galvanodynamically polarized at potentials above and below its Ecorr in 0.1 M NaCl solution are presented to validate the model. 相似文献
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采用乙炔等离子体蒸发Mg的方法成功制备了40 nm左右的超细Mg纳米颗粒. 通过透射电子显微镜(TEM)、X射线衍射(XRD)、比表面积测试(BET)和吸放氢测试等方法对其微观结构和吸放氢循环性质进行了研究. 超细Mg纳米颗粒具有比普通Mg颗粒更大的比表面积, 氢扩散至颗粒内部所需距离更短, 因而大大提高了其吸放氢动力学性质. Mg纳米颗粒表面的C既减少了Mg的氧化, 又阻碍了吸放氢过程中Mg颗粒的长大. 这种超细结构的Mg纳米颗粒具有良好的循环性质, 30次循环后容量仍没有衰减. 相似文献
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Carsten Schröder Philipp A. Haugg Ann-Katrin Baumann Marvin C. Schmidt Jan Smyczek Prof. Dr. Swetlana Schauermann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(68):17240-17254
We present a mechanistic study on the formation of an active ligand layer over Pd(111), turning the catalytic surface highly active and selective in partial hydrogenation of an α,β-unsaturated aldehyde acrolein. Specifically, we investigate the chemical composition of a ligand layer consisting of allyl cyanide deposited on Pd(111) and its dynamic changes under the hydrogenation conditions. On pristine surface, allyl cyanide largely retains its chemical structure and forms a layer of molecular species with the CN bond oriented nearly parallel to the underlying metal. In the presence of hydrogen, the chemical composition of allyl cyanide strongly changes. At 100 K, allyl cyanide transforms to unsaturated imine species, containing the C=C and C=N double bonds. At increasing temperatures, these species undergo two competing reaction pathways. First, the C=C bond become hydrogenated and the stable N-butylimine species are produced. In the competing pathway, the unsaturated imine reacts with hydrogen to fully hydrogenate the imine group and produce butylamine. The latter species are unstable under the hydrogenation reaction conditions and desorb from the surface, while the N-butylimine adsorbates formed in the first reaction pathway remain adsorbed and act as an active ligand layer in selective hydrogenation of acrolein. 相似文献
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A magnesium oxide-supported polyalumazane–platinum complex was synthesized and characterized by X-ray photoelectron spectroscopy (XPS) and its performance toward the hydrogenation of norbornene. XPS data indicated that a large amount of platinum existed in a zero-valent state. The catalyst showed high performance for the hydrogenation of norbornene. Its performance depended on the type of the support, the platinum loading and the reaction temperature. With 0.1544 mmol/g platinum loading at 25°C, the hydrogenation of norbornene to norbornane was completed within 2 min. Also, the turnover number of the catalyst reached 11,000 within 280 min. 相似文献
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Ni2P/TiO2的制备及其对苯加氢反应的催化性能 总被引:2,自引:1,他引:2
采用程序升温还原方法制备了TiO2负载的晶态Ni2P催化剂。用X射线衍射(XRD)及低温N2吸附(BET)等技术对样品的物相、比表面积等性质进行了表征。以苯气相加氢为模型反应考察了Ni2P/TiO2催化剂加氢性能,并对Ni2P负载量、前驱体中P的质量分数对催化剂的物相及性能的影响进行了研究。实验结果表明, TiO2负载的晶态磷化镍催化剂上,Ni2P是主要物相。Ni2P/TiO2催化剂对苯加氢反应具有较高的活性、选择性以及良好的稳定性能。Ni2P/TiO2制备对催化剂的性能有影响。Ni2P负载量增加,催化剂的活性先升高后降低,Ni2P负载量为12%时催化剂活性较高。催化剂前驱体中P的质量分数越高,制备出的催化剂对苯加氢反应的稳定性越好,但随前驱体中P的质量分数增加,催化反应的活性先升高,后降低。与Ni2P/SiO2比较,Ni2P/TiO2催化剂具有较高的活性和稳定性。 相似文献
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Pei Jing Tao Gan Hui Qi Bin Zheng Xuefeng Chu Guiyang Yu Wenfu Yan Yongcun Zou Wenxiang Zhang Gang Liu 《催化学报》2019,40(2):214-222
An efficient and low-cost supported Pt catalyst for hydrogenation of niroarenes was prepared with colloid Pt precursors and α-Fe2O3 as a support. The catalyst with Pt content as low as 0.2 wt% exhibits high activities, chemoselectivities and stability in the hydrogenation of nitrobenzene and a variety of niroarenes. The conversion of nitrobenzene can reach 3170 molconv h?1 molPt?1 under mild conditions (30 °C, 5 bar), which is much higher than that of commercial Pt/C catalyst and many reported catalysts under similar reaction conditions. The spatial separation of the active sites for H2 dissociation and hydrogenation should be responsible for the high chemoselectivity, which decreases the contact possibility between the reducible groups of nitroarenes and Pt nanoparticles. The unique surface properties of α-Fe2O3 play an important role in the reaction process. It provides active sites for hydrogen spillover and reactant adsorption, and ultimately completes the hydrogenation of the nitro group on the catalyst surface. 相似文献