| Hydrotalcite (HT) compounds referred to as layered double hydroxides (LDHs) are a class of anion intercalated materials with layered structure. Because of their special layered structure, they have shown a good performance in catalysis, adsorption, separation, ion exchange as well as effluent disposal and so on, and have found important applications in the production and living of society. Thanks to the particularity of layered structure and exchangeability of intercalated anion possessed by hydrotalcite compounds, modification on hydrotalcite materials and using hydrotalcites as the supports of supported catalysts have also received extensive research.In this paper, Mg-Al LDH samples were synthesized in the presence of different amount of glucose by coprecipitation, being modified by carbon product obtained from the carbonization of glucose as mesoporous template, and the catalytic performance of their derivative products was investigated in detail. In addition, highly dispersed Pd catalyst loaded on hydrotalcite was prepared, taking advantage of the homodisperse effect of hydrotalcite compounds, by introducing a small amount of noble metal Pd into ZnAl-LDH support with subsequent reduction treatment, and the catalytic performance of hydrotalcite-supported palladium catalysts was investigated. With the view of providing the foundation for design and preparation of catalyst materials using hydrotalcite compounds as precursors or catalyst supports through this research, so that hydrotalcite compounds may be applied in the field of catalysis more extensively.1) Effect of glucose introduced into synthesis system of Mg-Al hydrotalcites on physical and chemical properties and catalytic performance of the as-synthesized Mg-Al LDHs as well as their derived Mg-Al mixed oxides and calcinated-rehydrated products.A series of Mg-Al hydrotalcites (HTs) was synthesized in the presence of different amount of glucose by coprecipitation method. It was found that the introduction of glucose into preparation process of Mg-Al hydrotalcites has great effect on the structures along with physical and chemical properties of as-synthesized HTs, simultaneously influencing the structures, basicity and catalytic properties of their derived Mg-Al mixed oxides. Upon calcination at550℃, Mg-Al LDHs synthesized in the presence of glucose were transformed into Mg(Al)O structure mixed oxides (marked as LDH-x-C) accompanied by the disappearance of their layered structure. Mg-Al mixed oxide derived from HT synthesized in the presence of glucose, possessing more accessible base sites in water, demonstrated higher catalytic activity in citral-acetone condensation. While in transesterification reaction of glyceryl tributyrate, Mg-Al mixed oxide derived from HT synthesized in the presence of glucose exhibited higher catalytic activity mainly due to its much stronger basic sites and uniform mesoporous pore, moreover uniform mesoporous pore makes the basic sites more accessible.2) Preparation and the catalytic performance of zinc-aluminium hydrotalcite-supported palladium catalystsHydrotalcite, as a kind of anionic clay, was used as supports loading metal palladium widely due to its layered structure and exchangeability of intercalated anion. Through the approach of ion exchange of metal complexing anion with intercalated anion of hydrotalcite, hydrotalcite sample ZnAl-LDH-PdCl42-with PdCl42-as intercalated anion was prepared by introducing PdCl42anion into the interlayer of zinc-aluminium hydrotalcite on certain pH condition. Hydrotalcite-supported palladium catalyst Pd/ZnAl-LDH was obtained after subsequent reduction treatment. XRD and UV-vis measurements preliminarily proved that metal palladium could be effectively loaded on hydrotalcite by this method. And then, the catalytic effect of Pd/ZnAl-LDH was investigated via benzyl alcohol oxidation. It turned out that sample Pd/ZnAl-LDH had an excellent catalytic activity to this reaction. Moreover, its catalytic stability was good. |
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