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纳米级Pd/Fe双金属体系对水中2,4-二氯苯酚脱氯的催化作用 总被引:15,自引:0,他引:15
利用化学沉淀法制备了纳米级Fe和纳米级Pd/Fe双金属催化剂,研究了它们对2,4-二氯苯酚(2,4-DCP)还原脱氯的催化性能. 结果表明,纳米级颗粒具有较高的比表面积和表面反应活性,其BET比表面积可达12.4 m2/g,当Pd/Fe用量为6 g/L时,2,4-DCP脱氯率达到90%以上. 脱氯效率与pH值、温度、钯含量和Pd/Fe投加量等因素有关. 2,4-DCP在脱氯过程中先生成2-氯苯酚和4-氯苯酚,最终生成苯酚,而少量的2,4-DCP可直接降解成苯酚. 相似文献
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卢烨 Yoshinori Yamamoto Abdulrahman I. Almansour Natarajan Arumugam Raju Suresh Kumar 包明 《催化学报》2018,39(11):1746-1752
纳米多孔金属是近十年发展起来的一类具有三维通孔结构的新型功能材料,其由纳米尺度的细孔和韧带构成,具有极大的比表面积;它还是一种无毒无载体的宏观材料,并且易制备、易回收和重复利用,因此作为高效的非均相催化剂已逐渐引起人们的重视.1,2,3,4-四氢喹啉是许多医药、农药、染料和天然产物的重要骨架.通过喹啉及其衍生物的选择性加氢反应制备1,2,3,4-四氢喹啉,具有原子利用率高和原料易得等优点.在过去,已经开发了许多类型的均相和非均相催化体系,并成功地用于催化喹啉及其衍生物的选择性加氢反应.尽管非均相催化体系具有诸多优点,但仍存在H_2压力(10–50 atm)和反应温度(60–150℃)相对较高的缺点.因此,开发更加温和条件下的喹啉及其衍生物的选择性加氢反应具有重要意义.此外,在喹啉及其衍生物的加氢反应过程中,H_2分子在非均相催化剂表面的裂解模式,即均裂还是异裂尚不清楚.因此,本文采用新型非均相催化剂纳米多孔钯,研究了喹啉及其衍生物的选择性加氢反应,在相对较低的H_2压力(2–5 atm)和温度(室温–50℃)下实现了目标反应,高收率、高选择性地得到1,2,3,4-四氢喹啉化合物.在最佳反应条件下,对底物的适用范围进行了考察.结果表明,各种含喹啉结构单元的化合物均能顺利发生反应,产物收率在62%–95%.而且该反应对甲基、甲氧基、羟基、酯基、醛基、酰胺基、卤素(F,Cl和Br)等官能团具有较好的兼容性.苯环上取代基的电子效应对反应有一定的影响,吸电子基有利于目标反应的进行.反应完成后,纳米多孔钯催化剂很容易回收,且循环使用多次后,仍未见催化活性降低.扫描电镜和透射电镜结果发现,循环使用后的纳米多孔钯催化剂结构没有发生明显改变,表明其结构稳定.浸出实验结果证明,没有钯原子浸出到反应液中,表明该纳米多孔钯催化反应属于多相催化过程.喹啉的选择性氢化反应被放大到克级的规模时,目标产物的收率仅略有降低,说明该方法具有很好的实用性.通过动力学实验发现,随着反应的进行,反应速率不断加快,表明反应过程中生成的乙胺和1,2,3,4-四氢喹啉同样扮演着路易斯碱性添加剂的角色,促进了反应的进行.通过反应机理研究,揭示了H–H键在纳米多孔钯表面发生了异裂,原位形成的Pd–H物种作为弱亲核试剂,对目标反应的选择性控制起到了至关重要的作用. 相似文献
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作为一类重要的含氮杂环化合物, 3-氨基-2-二氢喹啉酮结构存在于一些药物和生物活性分子中.目前还没有手性催化的方法直接合成无保护基的此类结构.在过渡金属的催化作用下,乙烯基苯并噁嗪酮脱除一分子二氧化碳,生成的两性离子中间体可以参与多种反应合成含氮杂环化合物.我们设想乙烯基苯并噁嗪酮和2-氨基丙二酸酯直接发生不对称烯丙基化反应/去对称化反应,则可直接实现无保护基2-喹啉酮骨架环状氨基酸的手性合成.然而2-氨基丙二酸酯作为亲核试剂时,如何实现碳选择性进攻而不是固有的氮选择性进攻将成为此反应中一个重要挑战.本文通过钯催化的不对称烯丙基化/去对称化反应合成具有2-喹啉酮骨架的环状氨基酸.采用手性膦配体与钯作为催化剂,成功实现了乙烯基苯并噁嗪酮与2-氨基丙二酸酯的不对称α-烯丙基取代反应.随后无需提纯,烯丙基取代产物直接在三氟乙酸的作用下,发生分子内的去对称化内酰胺化反应,最终生成具有无保护基的2-喹啉酮骨架环状氨基酸产物.该催化方法反应条件温和,催化体系简单高效(钯催化剂负载量可降低至1 mol%,非对映选择性可高达15/1,对映选择性高达96%ee),并且具有良好的官能团兼容性.经盐酸处理... 相似文献
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设计开发可用于电催化氧还原反应(ORR)的高效催化剂对于推进可持续能源技术(如燃料电池和金属空气电池等)的进一步发展至关重要.然而,由于ORR涉及多电子转移过程,并且动力学迟缓,电位高,从而限制了相关技术的实际应用.到目前为止,铂族金属被认为是ORR的基准电催化剂.然而,由于铂族金属资源稀缺、价格高、催化剂稳定性不足阻碍了其在不同能源装置中的进一步应用.因此,亟需开发出高活性、低成本、耐用的ORR电催化剂,从而推进可再生能源技术的进一步发展.双金属纳米合金因具有良好的导电性、可调整的电子态且金属间存在协同效应而被认为是一种有较大应用前景的ORR催化材料.本文采用自我牺牲模板法,将均匀的Co Ni合金纳米颗粒原位封装在N掺杂碳纳米管/纳米线耦合的分层结构中,构建了莫特-肖特基电催化剂(CoNi@N-CNT/NWs),并应用于金属空气电池.采用X射线衍射、拉曼光谱、热重、BET比表面积测试、X射线光电子能谱、扫描电子显微镜和透射电镜等方法对催化剂进行了表征.扫描电子显微镜和透射电镜结果表明,复合材料呈现一维多级结构的纳米管分支/纳米线主干的层次结构.实验结果和理论计算表明, CoNi纳米合... 相似文献
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Song Shu Peng Wang Wendong Zhang Weilu Wang Jianjun Li Yinghao Chu Fusheng Wei Xianming Zhang Guangming Jiang 《中国化学快报》2020,31(10):2762-2768
Here we report a facile defect-engineering strategy on the support to optimize the metal-support interaction and enhance the metal’s electrocatalytic hydrodechlo rination perfo rmance in converting 2,4-dichlorophenol(2,4-DCP) to phenol.The specific activity of the Pd nanoparticles(Pd NPs) on defective polymer carbon nitride(Pd/PCN-x) reaches 0.09 min-1 m-2Pd,which is 1.5 times that of the Pd NPs supported on the perfect PCN(Pd/PCN-0).The combined experimental and... 相似文献
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Gold nanoparticles (AuNPs) of different sizes were synthesized by the citrate reduction method. It was found that AuNPs could enhance the chemiluminescence (CL) of the luminal-NaOH system and 2,4-dichlorophenol (2,4-DCP) could inhibit AuNPs-luminal-NaOH CL signals in alkaline solution. CL spectra, UV-visible spectra, and transmission electron microscopy (TEM) were used to investigate the CL mechanism. On the basis of the inhibition, a flow-injection CL method has been established for determination of 2,4-DCP in water samples. Under the optimized conditions, the linear range for determination of the 2,4-DCP was 0.1 × 10(-6) to 20 × 10(-6) g mL(-1), LOD (limit of detection, S/N = 3) was 1.36 × 10(-8) g mL(-1), with RSD of 1.8% (n = 11). This method has been successfully used for analysis of 2,4-DCP in environmental water samples. 相似文献
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《Journal of Saudi Chemical Society》2020,24(9):663-672
Nanoscaled palladium particles supported on graphitic carbon nitride (Pd0/g-C3N4) is prepared to improve the oxygen transfer in Wacker oxidation via chemical reduction method. From the analysis of FT-IR, XRD, SEM, TEM, XPS and ICP, Pd0 particles are firmly combined with g-C3N4 layers, and sub-surface ones occupy most of the components. It is worth mentioning that graphene oxide (GO), which is completely recyclable without further pollution, can be used as a ‘solid weak acid’ taking the place of H2SO4 and CF3COOH. Under the optimization conditions, as many as 46 kinds of olefins are transferred into corresponding products with satisfactory yields, and o-methyl styrene gets the highest yield of 94%. After five times of recycling experiment, the yield of acetophenone only decreases by about 7.0% in the uniform reaction process. In virtue of former research results and molecular electrostatic potential, a possible mechanism is put forward to explain the catalytic process. 相似文献
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Titanium nitride nanorods have been successfully synthesized by low temperature solid-state metathesis of titanium (III) chloride and sodium azide without using any organic solvent. The conditions required for the synthesis of these nanorods have been optimized. It was found that the temperature and time of reaction had a significant effect on the product morphology. Thermal treatment at 360 °C, for 3 days gave the nanorods of the aspect ratio ∼10 (i.e. diameter ∼50 nm and length ∼ 500 nm), whereas the thermal treatment at 400 °C for 3 days gave the nanorods of the aspect ratio ∼50 (i.e. diameter ∼50 nm and length ∼2-3 μm). Scanning and transmission electron microscopies clearly showed the rod-type morphology. Further evidence for the phase purity and crystallinity of titanium nitride nanorods was given by X-ray diffraction, field emission high-resolution electron microscopy and X-ray photoelectron spectroscopy analyses. 相似文献
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Enhancement of the catalytic hydrodechlorination of tetrachloroethylene in methanol at mild conditions by water addition 总被引:1,自引:0,他引:1
The dechlorination of tetrachloroethylene (PCE) over carbon-supported palladium catalyst (Pd/C) in methanol (MeOH) at mild conditions was enhanced through the addition of water to the reaction mixture. The dechlorination of PCE was accelerated by increasing the amount of water in the mixture from 0% to 50%, and beyond which the reaction slowed down, however. The presence of water in the mixture enhanced the adsorption of PCE onto the Pd/C but compromised the solubility of H2 gas in the mixture. It was also noted that the selectivity of the HDC reaction was improved with the increase in the amount of water in the mixture as the formation of trichloroethylene (TCE) was completely eliminated when the HDC was carried out in mixtures with 50% water or more. Other chlorinated intermediates were not detected in all the reactions. 相似文献
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《Arabian Journal of Chemistry》2022,15(9):104084
As of late, graphene-like boron nitride (g-BN), has been created another schedule as aerobic catalysis, and have a profound effect on the key performance of the catalyst. In this paper, C-nanodots with low resistivity, were bounded through g-BN (C-dots/g-BN) to help electron versatility by a straight forward one-pot pathway. C-dots were bounded in graphene-analogous boron nitride (g-BN) via a one-step, in situ process at increased temperature, which could upgrade the interactions of C-dots and control the dimensions of C-dots in the scope of nearly 4–5 nm. The results demonstrated that C-dots/g-BN has a superior execution in high-impact oxidation of dibenzothiophene (DBT) in fuel oil with a reactant movement of 93.5%. Estimation showed that hydroxyl radicals produced from H2O2 as a result of the interaction with C-dots ended up a proficient catalyst in the framework. The C-dots had a synergetic impact to enhance the proficiency of H2O2 in the catalyst. The portrayal results showed that piece of the DBT was oxidized to its comparing sulfoxide which requires less oxidant than sulfone. Both of the oxidation items could be extracted in the oil phase on the catalyst. 相似文献
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Ziyu Gan Chaofeng Huang Yanfei Shen Qing Zhou Dan Han Jin Ma Songqin Liu Yuanjian Zhang 《中国化学快报》2020,31(2):513-516
As an emerging 2D conjugated material,graphitic carbon nitride(CN) has attracted great research attention as important catalytic medium for transforming solar energy.Nanostructure modulation of CN is an effective way to improve catalytic activities and has been extensively investigated,but remains challenging due to complex processes,time consuming or low yield.Here,taking advantage of recent discovered good solvents for CN,a nanoprecipitation approach using poor solvents is proposed for preparation of CN nanoparticles(CN NPs).With simple processes of CN dissolution and precipitation,we can quickly synthesize CN NPs(^40 nm) with a yield of up to 50%,the highest one to the best of our knowledge.As an example of potential applications,the as-prepared CN NPs were applied to photocatalytic degradation of dyes with an evident boosted performance up to 2.5 times.This work would open a new way for batch preparation of nanostructured CN and pave its large-scale industrial applications. 相似文献
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A new palladium incorporated carbonaceous catalyst Pd@CCSO3HNH2 was synthesized by introducing palladium on glucose derived carbocatalyst. The catalyst was well characterized and was used for the Suzuki coupling of phenyl boronic acid with different aryl halides under aqueous conditions. This green methodology represents a ligand free, cost-effective and operationally convenient method for the synthesis of a variety of biaryl’s under the conditions that are tolerant for a broad range of functional groups with good to excellent yields. Moreover, the catalyst could be easily recycled and reused at least five times without any significant loss of its catalytic activity. 相似文献