催化学报 ›› 2020, Vol. 41 ›› Issue (7): 1109-1117.DOI: 10.1016/S1872-2067(20)63546-X

• 论文 • 上一篇    下一篇

TS-2微球的形成机理、后处理修饰和催化应用

徐浩, 田文文, 徐丽萍, 金鑫, 薛腾, 陈丽, 何鸣元, 吴鹏   

  1. 华东师范大学化学与分子工程学院, 上海市绿色化学与化工过程绿色化重点实验室, 上海 200062
  • 收稿日期:2019-09-21 出版日期:2020-07-18 发布日期:2020-04-18
  • 通讯作者: 吴鹏
  • 基金资助:
    国家自然科学基金(21533002,21603075,21872052);科技部重大项目(2016YFA0202804).

Crossed intergrowth triggered TS-2 microsphere: Formation mechanism, modification and catalytic performance

Hao Xu, Wenwen Tian, Liping Xu, Xin Jin, Teng Xue, Li Chen, Mingyuan He, Peng Wu   

  1. Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China
  • Received:2019-09-21 Online:2020-07-18 Published:2020-04-18
  • Supported by:
    This work was supported by the National Natural Science Foundation of China (21533002, 21603075, 21872052) and the China Ministry of Science and Technology (2016YFA0202804).

摘要: 钛硅分子筛材料是一种优异的选择性氧化反应催化剂,能在温和的条件下活化双氧水,并且只副产水,构建了一系列绿色高效的催化反应体系,已成功地应用于环己酮氨肟化、丙烯环氧化等工业过程.但是,工业上使用的钛硅分子筛通常需要经过成型,这避不可免地引入惰性的粘结剂甚至会造成堵孔,导致催化剂的活性降低.因此,直接合成具有微米尺度的钛硅分子筛材料有望解决上述问题.本文通过控制晶化条件直接水热合成了一种由初级粒子经晶间交叉生长堆积成的TS-2微球,详细考察反应条件,包括季铵盐模板剂的用量、H2O/Si比、醇的存在与否和晶化温度等的影响,发现反应体系保持高的碱度、静态晶化以及体系无醇是TS-2微球形成的关键因素.进一步地对TS-2晶化过程进行详细跟踪考察,发现常规TS-2纳米颗粒与TS-2微球在晶化初期均会形成无定形微球.随着晶化的进行,无定形相晶化成为TS-2纳米晶粒,是一级粒子,相互堆积形成次级粒子.较高的碱度使得TS-2微球的一级粒子以交叉生长的方式堆积,从而保证微球形貌在整个晶化过程中得以保持;而TS-2纳米颗粒中初级粒子以平行的方式堆积,无法保持初始的微球形貌,最终形成纳米尺度的聚集体.扫描电镜和透射电镜照片均证实了TS-2微球中初级粒子成交叉生长的方式堆积.TS-2微球催化剂经模板剂、氯化铵和哌啶组成的混合溶液水热处理,发生了溶解-再晶化过程,外比表面积从148增至176 m2 g-1,介孔孔容从0.16 cm3 g-1升至0.24cm3 g-1;成功引入介孔的同时,仍能保持TS-2微球形貌以及Ti活性中心的四配位状态.经哌啶混合溶液处理后得到的MS-TS-2-PI在环己酮肟化反应中表现出优于MS-TS-2微球的催化性能,环己酮转化率从18.6%升至91.4%,环己酮肟选择性从86.6%升至97%.再经Na+离子交换可以消除骨架中的Si-OH,增强了骨架的疏水性,进一步地提高了其在环己酮肟化反应中的催化性能;环己酮转化率和环己酮肟选择性均>99%.在环己酮肟化连续反应中,TS-2微球表现出稳定的催化性能,使用寿命达到90 h,与工业TS-1催化剂相当,是一种具有工业前景的催化剂.

关键词: 钛硅分子筛, TS-2 微球, 交叉生长, 肟化反应, 后处理

Abstract: TS-2 microspheres, consisting of intergrown primary nanocrystals, was prepared by controlling the synthetic parameters. The effects of the amount of quaternary ammonium cations as structure-directing agent, H2O/Si ratio, the presence of alcohol and the temperature were carefully investigated on the crystallization process. The high alkalinity was proved to be highly important for the preservation of the microsphere morphology initially formed, due to the unique intergrown stacking style. An alkali treatment with the aqueous solution of structure-directing agent, organic amine and ammonium salt and subsequent Na+ ion-exchange were performed to enhance the catalytic activity of TS-2 microsphere in the cyclohexanone ammoximation reactions, with both the conversion and selectivity higher than 99%. In the continuous reaction, the TS-2 microspheres exhibited to be durable catalyst with potential application in industrial ammoximation processes.

Key words: Titanosilicate, TS-2 microsphere, Crossed intergrowth, Ammoximation reaction, Post-treatment