Improved template – ion exchange synthesis of Cu-nanostructured molecular sieves

Abstract

A series of M41S type mesoporous molecular sieves modified with copper were synthesized through Template-Ion Exchange (TIE). The influence of hydrothermal treatment and mixing time at room temperature over the solids structural and chemical properties was evaluated in detail for a single Cu content. Characterization of the materials was carried out through various techniques: XRD, N2 adsorption-desorption, SEM, XPS, atomic absorption, UV–vis DR and TPR. It was found that different stirring times at room temperature had no significant influence over the physical and chemical characteristics of the final solid. However, hydrothermal treatment had a slight effect over the materials structure and metallic species distribution. In order to assess copper content influence, two other non-treated solids with different metallic contents were synthesized, characterized, and compared with hydrothermally treated samples. The catalytic performance of the hydrothermally treated and non-treated materials was tested in the liquid phase oxidation of limonene employing hydrogen peroxide (H2O2) as oxygen donor, an important fine chemical reaction. Only one of the evaluated Cu contents exhibited a minor difference in catalytic activity according to the applied synthesis conditions. Hence, a simple TIE procedure without hydrothermal treatment can be employed for the synthesis of Cu-MCM materials. By suppressing hydrothermal treatment, it is possible to save around 10% of the total energy requirement for the complete synthesis process.