共查询到20条相似文献,搜索用时 62 毫秒
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制备、表征了混合铝/铬金属氧化物柱撑α-磷酸锆(Al/Cr-ZrP),并对胶体化使用有机胺的种类、柱化液金属离子浓度以及金属离子用量等因素进行了研究。研究表明以乙醇胺为胶体化有机胺比使用正丙胺为胶体化有机胺所得到的产物的层间距更大;采用较低金属离子浓度、较高金属离子用量有利于Al/Cr-ZrP的合成。在Al/Cr比为1、以正丙胺为胶体化有机胺、金属离子浓度为0.067mol·L-1、金属离子用量为6.67CEC的条件下,制备出了混合金属氧化物柱撑α-磷酸锆,其层间距可达3.60nm, 相似文献
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本文采用单分子层技术将聚合羟基铝簇离子嵌入到二硫化钼板层间,得到层间距为1.481至1.519 nm的柱撑二硫化钼复合材料。XRD、DSC等研究表明,柱化液的滴加浓度越稀、柱撑反应体系中Al∶MoS2物质的量之比越小越有利于获得层间距较大的柱撑材料。与原料2H-MoS2相比,柱撑材料的层间距增大,颗粒度变小,比表面积增加。在氧气条件下,对Na2S的催化氧化实验表明,柱撑材料较原料2H-MoS2的催化氧化活性提高3~4倍,且光催化活性大于催化活性。这与柱撑材料的比表面积增加所导致催化活性部位的增多,以及光致电子-空穴对的产生有关。 相似文献
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以十六胺插层磷酸锆为原料,利用十二烷基二甲基苄基氯化铵为导向模板剂,通过正硅酸乙酯和巯丙基三甲氧基硅烷的层间共水解缩聚,并结合双氧水对巯丙基的熏蒸氧化,制备了磺酸基修饰的硅柱磷酸锆材料。通过XRD、SEM、N2吸附-脱附和FT-IR等方法对柱撑材料进行了结构表征。结果表明,通过调变预撑剂和模板剂中的碳链长度可以优化材料的柱撑结构和孔结构,磺酸基修饰的材料孔径分布在2.17 nm左右,比表面积可达163 m2·g-1,且保留有规整有序的柱撑磷酸锆层板结构。磺酸基的修饰则成功调变了材料的酸位性质,Br觟nsted酸量最高可达2.71 mmol·g-1,总酸量可达5.20 mmol·g-1。利用柠檬酸与正丁醇的酯化反应为探针反应,由于磺酸基修饰的硅柱磷酸锆材料具有独特的空间反应效应和较为丰富的Br觟nsted酸位,酯化反应转化率最高可达95.74%。 相似文献
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层状磷酸盐在有机胺溶液中的胶体化和稳定性研究 总被引:4,自引:0,他引:4
系统地研究了层状磷酸锆(α-ZrP)、磷酸锡(α-SnP)和磷酸钛(α-TiP)在有机胺水溶液中的胶体化(即层板剥离)和水解状况。发现磷酸盐在有机胺嵌入而胶体化的同时,层板表面的HPO4^2-和金属离子发生水解而脱离,HPO4^2-的脱离先于金属离子,HPO4^2-水解度超过40%则磷酸盐层状结构破坏严重。在相同的有机胺溶液中,不同磷酸盐的水解和胶体化状况不同,其中磷酸钛的水解最严重层板最信打开, 相似文献
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采用单分子层技术将羟基铬聚合离子[Cr4(OH)6(H2O)10]6+嵌入到二硫化钼板层间,得到层间距为1.319~1.341 nm的柱撑复合材料. X射线粉末衍射表明,羟基铬聚合物溶液经70 ℃恒温下陈化4 d即可作为稳定的柱撑液使用; 在柱撑反应体系中,较小的n(Cr)/n(Mo)比和较低的Cr3+浓度有利于获得结晶度较好的柱撑材料. 与原料2H-MoS2相比,柱撑材料的层间距增大,晶粒变小,比表面积增加并且热稳定性提高. 对催化苯饱和加氢反应表明,柱撑材料Cr-MoS2的催化活性明显优于未柱撑的2H-MoS2和Raney Ni催化剂,且结晶度较好的柱撑材料更具有较高的催化活性和较好的可重复性. 相似文献
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In this report, we try to show the importance of incorporation of name reactions in the sequential cascade reaction in which significantly decreasing the number of steps towards an ideal and practical multi-step synthesis of natural products as well showing virtually all the advantages already mentioned for “Click Chemistry”. In addition, since the chiral inductions are desired for most of these sequential name reactions, their asymmetric catalyzed reactions were also described. 相似文献
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《Green Chemistry Letters and Reviews》2013,6(4):311-320
Abstract In the second part of our paper, further recent developments of ionic liquids in selected name reactions of carbonyl chemistry such as Mannich, Reformatsky, Cannizaro, Streacker, Barbier, Pechmann, etc. are described. 相似文献
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Thermal reaction of 2-[N-(alk-2-enyl)benzylamino]-3-(2-substituted and 2,2-disubstituted)vinylpyrido[1,2-a]pyrimidin-4(4H)-ones gave azepine, the desired ene products, and/or pyran derivatives. The formation of the latter was responsible for the [4+2] cycloaddition reaction between the α,β-unsaturated ester carbonyl moiety as a diene part and the alkenylamino moiety as an ene one. The reaction features depended upon the kinds of substituents both on the vinyl and alkenyl counterparts; strongly electron-withdrawing substituents on the vinyl moiety or an electron-donating substituent on the alkenyl one changed the reaction feature from the ene reaction to the hetero Diels-Alder reaction. 相似文献
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Palladium bis(2,2,6,6-tetramethyl-3,5-heptanedionate) catalyzed Suzuki, Heck, Sonogashira, and cyanation reactions 总被引:1,自引:0,他引:1
Nitin S. Nandurkar 《Tetrahedron》2008,64(17):3655-3660
Palladium bis(2,2,6,6-tetramethyl-3,5-heptanedionate): a structurally well-defined O-containing transition metal complex is reported as an efficient catalyst for Suzuki, Heck, and Sonogashira cross-coupling reactions. The protocol was also applied successfully for cyanation of aryl halides under milder operating conditions. The system tolerated the coupling of various aryl halides with alkenes, alkynes, and organoboronic acid along with the cyanation of aryl halides providing good to excellent yields of desired products. 相似文献
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Arash Ghorbani‐Choghamarani Masoud Mohammadi Robert H.E. Hudson Taiebeh Tamoradi 《应用有机金属化学》2019,33(8)
A boehmite@tryptophan‐Pd nanoparticulate catalyst was prepared by a simple, fast and convenient route. The nanomaterial was characterized using various techniques and employed as a thermally stable catalyst for Heck, Stille and Suzuki cross‐coupling reactions. Optimized conditions for these reactions are described. The catalyst could be isolated, post‐reaction, by simple filtration and recycled for several consecutive cycles without a notable change in its activity. 相似文献
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Thomas A. Klein 《Tetrahedron letters》2005,46(27):4535-4538
Dimethylnitro alcohols are constructed in a one-pot process from benzylic halides and 2-nitropropane. The use of tetrabutylammonium fluoride (TBAF) as the promoter is essential for this tandem Hass-Bender/Henry reaction to proceed. 相似文献
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温度和时间对有机合成反应影响的探讨 总被引:1,自引:0,他引:1
根据物理化学和有机合成原理,从动力学、热力学、反应机理及溶解度等各方面详细分析了反应温度和反应时间对有机合成反应的影响。通过这些分析,可以让同学们更好地在合成反应课程的学习中掌握和分析反应温度和反应时间对反应的影响。 相似文献
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钯催化的交叉偶联反应是非常实用的合成新方法.文章给出了Heck反应、Negishi反应和Suzuki反应的概念,对其反应机理作了详细的说明,并对其在复杂化合物和天然产物全合成中的应用作了评价. 相似文献
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Yoshishige Okuno 《International journal of quantum chemistry》2000,77(4):791-796
A microscopic method to examine a nonequilibrium solvation effect is reported. The solution reaction is simplified as a barrier‐crossing reaction within a solution reaction surface that corresponds to a two‐dimensional space determined by solute and solvent reactive coordinates. For this simplification, the motions within the space spanned by nonreactive coordinates are frozen. We derive three rate constant expressions: (1) in the nonadiabatic solvation limit, (2) in the equilibrium solvation limit, and (3) of the transition‐state theory. This method was applied to the examination of the contact‐ion‐pair formation of t‐BuCl in four waters. We found that the nonadiabatic solvation picture overestimates the nonequilibrium solvation effect. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 77: 791–796, 2000 相似文献