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The basicities of aluminated zeolites βhave been investigated by FTIR spectra of chemisorbed pyrrole. The NH-stretching frequency of pyrrole adsorbed on the samples shifts towards lower wavenumber as the St/Al ratio is decreased and correlates well with the negative charge on the framework oxygen calculated from the Sanderson electronegativity equalization principle, revealing zeolite β to possess a stronger overall basicity after alumination and, therefore, the alumination to be an effective method to improve the basicity. It is also found that the heterogeneity of basic strength occurs and some stronger basic sites appear after alumination. 相似文献
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Koji Nemoto 《Tetrahedron letters》2009,50(31):4512-7862
The Lewis acid-mediated carboxylation of arenes with CO2 has been successfully applied to 1-substituted indoles and pyrroles by using dialkylaluminum chlorides instead of aluminum trihalides. Thus, the carboxylation of 1-methylindoles, 1-benzyl-, and 1-phenylpyrroles proceeds regioselectively with the aid of an equimolar amount of Me2AlCl under CO2 pressure (3.0 MPa) at room temperature to afford the corresponding indole-3-carboxylic acids and pyrrole-2-carboxylic acids in 61-85% yields, while the same treatment of 1,2,5-trimethylpyrrole affords the 3-carboxylic acid in 52% yield. 相似文献
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We report a one‐step convenient chemical coating method of high alumina content onto mesoporous silicas. Aluminia‐coated mesoporous silica with high surface area (?900 m2/g), tuneable pore size (2.0–3.0 nm) and high hydrothermal stability (> 60 h) is obtained. The method may also be generalized for grafting other metal oxides onto mesoporous silica in future work. 相似文献
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用高温气-固相置换法对ZK-4、NaA和NaHS3种沸石进行铝化。组成分析、尾气分析、X射线衍射、晶体形貌分析、红外光谱和29Si高分辨魔角固体核磁结果表明,3种低硅铝比沸石铝化后骨架可能存在Al-O-Al键。 相似文献
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β-沸石骨架铝化改性的红外光谱 总被引:1,自引:0,他引:1
β沸石是以有机胺为模板剂合成的高硅沸石.为在孔道中进行吸附和催化反应,通常是在空气中 (550℃ )进行焙烧,将有机胺脱除并使质子酸中心形成.但这种脱模板剂方法,会造成骨架脱铝[1 -4],使质子酸中心显著减少.β沸石固有结构中存在着孔道位错和结构空穴,空气中焙烧脱有机胺可能会进一步损伤沸石的骨架结构[4,5].沸石骨架改性已发展了多种铝化方法[6 -8].有的研究工作表明,通常用红外光谱和MASNMR表征的非骨架铝,在温和的条件下,例如回馏温度下的离子交换或者在较低温度下 (100℃或室温 )与碱反应就可… 相似文献
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