Titanium-Catalyzed Heterogeneous Oxidations of Silanes, Chiral Allylic Alcohols, 3-Alkylcyclohexanes, and Thianthrene 5-Oxide: A Comparison of the Reactivities and Selectivities for the Large-Pore Zeolite Ti-β, the Mesoporous Ti-MCM-41, and the Layered Alumosilicate Ti-ITQ-2
作者:Waldemar Adam、Avelino Corma、Hermenegildo García、Oliver Weichold
DOI:10.1006/jcat.2000.3043
日期:2000.12
A comparative study of silane oxidation, olefin epoxidation, and thianthrene 5-oxide sulfoxidation with the oxidants Ti-β/H2O2, Ti-MCM-41/t-BuOOH, and Ti-ITQ-2/t-BuOOH provides the catalytic reactivity order Ti-β>Ti-MCM-41>Ti-ITQ-2. The steric constraints of the narrow channels make the Ti-β zeolite the most selective. For the more open structures of the Ti-MCM-41 and Ti-ITQ-2 hosts, such steric constraints
用氧化剂Ti-β/ H 2 O 2,Ti-MCM-41 / t -BuOOH和Ti-ITQ-2 / t -BuOOH对硅烷氧化,烯烃环氧化和噻吨5氧化物硫氧化的比较研究提供了催化反应顺序为Ti-β> Ti-MCM-41> Ti-ITQ-2。狭窄通道的空间限制使Ti-β沸石具有最高的选择性。对于Ti-MCM-41和Ti-ITQ-2主体的更开放的结构,这种空间约束不太明显,因此,这些多相催化剂显示出较低的选择性。两者均通过类似于均相Ti(O i -Pr)4 / t的过渡结构激活t -BuOOH进行氧转移-BuOOH氧化剂。