Development of Novel Methods for Synthesizing Hydrophobic Metallosilicates

疏水性金属硅酸盐合成新方法的开发

基本信息

批准号：
11555212
负责人：
TATSUMI Takashi
金额：
$ 7.94万
依托单位：
Yokohama National University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

By increasing hydrophobicity, zeolite catalysts showing high activity and selectivity for the oxidation of organic compounds with aqueous hydrogen peroxide were synthesized. The relationship between catalytic performance and either hydrophobicity or acidity was investigated for TS-1, Ti-β and Ti-MWW.Ti-β, which has 3D-12 MR channel, was able to epoxidize bulky cyclic compounds ; however, epoxides were cleaved by water to give diols, which should be due to the acidity of Ti-β. By ion-exchanging calcined Ti-β with quaternary ammonium ions, Ti-β showing high activity and selectivity for epoxidation was successfully prepared. Ammonium ion-exchanged catalyst was not selective for epoxidation because of the oxidation of ammonium ion during the reaction while ion-exchange with alkali metal ions resulted in suppression of oxidation activity. With the coexistence of boric acid, Ti-MWW was successfully crystallized to show pure phase by using either piperidine or hexamethyleneimine as a structure directing agent. Ti-MWW always contained a part of octahedral Ti species which aggregated upon the calcination to form anatase. Nevertheless, these extraframework Ti species together with a part of framework boron was removed readily by treating the as-synthesized samples with acid solutions. Ti-MWW thus pretreated was characterized as containing mainly tetrahedral Ti species in the framework sites by various spectroscopic techniques. Ti-MWW was more active for the epoxidation reactions with hydrogen peroxide than TS-1. Piperidine-directed Ti-MWW was more active than hexamethyleneimine-directed Ti-MWW.The former was hexagonal plate with small crystallite size in shape and the latter consisted of a coagulation of needle-like particles. Thus we have developed a method of obtaining titanosilicate catalysts having small crystallite size, high hydrophobicity and low acidity, which show high activity in liquid-phase oxidations.

通过增加疏水性，合成了对过氧化氢水氧化有机化合物具有高活性和选择性的沸石催化剂。研究了 TS-1、Ti-β 和 Ti-MWW.Ti 的催化性能与疏水性或酸性之间的关系。 -β具有3D-12 MR通道，能够环氧化大体积的环状化合物；然而，环氧化物会被水裂解得到这应该是由于Ti-β的酸性所致，通过将煅烧的Ti-β与季铵离子进行离子交换，成功制备了具有高环氧化活性和选择性的铵离子交换催化剂。由于反应过程中铵离子被氧化而发生环氧化，而与碱金属离子的离子交换导致氧化活性受到抑制。在硼酸共存的情况下，通过使用哌啶或六亚甲基亚胺作为结构导向剂，Ti-MWW 成功结晶出纯相，但 Ti-MWW 始终含有部分八面体 Ti 物质，这些物质在煅烧时聚集形成锐钛矿。通过用酸溶液处理合成的样品，可以很容易地去除骨架外的钛物质和部分骨架硼，由此预处理的特征在于主要含有。通过各种光谱技术，Ti-MWW 的骨架位点中的四面体 Ti 物种对于与过氧化氢的环氧化反应比 TS-1 比六亚甲基亚胺引导的 Ti-MWW 更活跃。具有小晶粒尺寸的六角板，后者开始于针状颗粒的凝聚，因此我们开发了一种获得具有小晶粒尺寸的钛硅酸盐催化剂的方法。微晶尺寸、高疏水性和低酸性，在液相氧化中表现出高活性。