Synthesis and Applications of Semiconducting Microporous Crystals

柱状粘土是一种新型的微孔固体，它开辟了除沸石外微孔晶体的新领域。在这个项目中，一种半导体层状钛酸盐用二氧化硅作为支柱。研究了其吸附和催化性能及其应用。用二氧化硅柱撑RbxMnxTi2-XO4 （x=0.75）结构的钛酸锰a层的合成及吸附性能。首先将Rb离子与n-烷基铵离子（CnH2n+1NH3, n=6-18）交换以分离钛酸盐层间空间，然后在层间水解四乙氧基硅烷。燃烧掉有机部分产生二氧化硅柱状微孔固体，其表面积高达500-800m2/g。在高达600℃的温度下，多孔结构稳定。测定了对水、甲醇、甲苯和三甲基甲苯等不同气体的吸附解吸等温线，表明层间形成的孔隙结构与沸石非常相似，且均匀。孔隙具有疏水性。它们的大小估计在三聚氰胺的数量级。二氧化硅柱钛酸盐微孔结构的控制为了控制微孔结构，将RbxMnxTi2-xO4 （x=0.75）通过KMnO4氧化降低离子交换容量，然后再用二氧化硅柱化。原以为离子交换容量降低的钛酸盐的孔径会变小，但实验结果表明，钛酸盐的孔径会变大。这一发现具有重要意义，并应与矿柱形成机理进行进一步研究。二氧化硅柱状钛酸锰在催化剂中的应用二氧化硅柱状钛酸锰负载多种离子。负载Cu离子的样品对co的氧化表现出极高的催化活性，这可以用柱状结构的高表面积和微孔的重盒特性来解释。

Pillared clay is a new type of microporous solids which have opened a new field of microporous crystals other than zeolies. In this project, a semiconducting layred titanate has been pillared with silica. The adsorption and catalytic properties and their applications are studied.1. Synthesis and adsorption properties of silica pillared manganese titanateA layr structured RbxMnxTi2-XO4 (x=0.75) was pillared with silica. The Rb ions were first exchanged with n-alkylammonium ions (CnH2n+1NH3, n=6-18) to separate the interlayr space of the titanate, and then tetraethoxysilane was hydrolyzed between the layrs. Burning off the organic parts resulted in silica pillared microporous solids with a surface area as large as 500-800m2/g. The porous structure was stable up to 600ﾟC.Adsorption desorption isotherms for various vapors, water, methanol, toluene and mesitylene, were measured, which suggested that the porous structure formed between the layrs was very similar to those of zeolites, and uniform. The pores showed hydrophobic properties. Their size was estimated to be in the order of mesitylene.2. Control of micropore structures in silica pillared titanatesIn an attempt to control the pore structure, the ion exchange capacity of RbxMnxTi2-xO4 (x=0.75) was reduced by the oxidation with KMnO4, and then pillared with silica similarly. It had been expected that the titanate with a reduced ion exchange capacity could give a smaller pore size, however, the experimental results suggested that a larger pore size was obtained. This finding is important and should be further studied in relation with the mechanism of pillar formation.3. Application of silica pillared titanate to catalystsSilica pillared manganese titanates were loaded with various kinds of ions. The sample loaded with Cu ions showed an extremely high catalytic activity to oxidation of CO.This can be explained in terms of the high surface area of the pillared structure and the rebox properties of the micropores.