Abstract
Acid–base bifunctional catalysts were prepared by immobilization of basic amines on acidic silica–alumina (SA) surfaces. Silane-coupling reagents with various amino-functional groups, such as primary, secondary, and tertiary alkylamines, alkyldiamine, and dialkylaminopyridine, were examined as anchoring reagents for the amines in the preparation of catalysts. The obtained immobilized catalysts (SA–NR′R′′) were characterized by solid-state 13C and 29Si MAS NMR and elemental analysis. The catalytic activity of tertiary alkylamines for Michael reactions increased dramatically by the immobilization on silica–alumina, whereas a homogeneous tertiary amine scarcely promoted the reaction. Regarding the kind of amines, the dialkylaminopyridine immobilized silica–alumina with low Al content (SAL) showed the highest catalytic performance among the amine immobilized catalysts. The solid-state 13C NMR analysis revealed the interaction between the nitrogen atom on pyridine ring and a surface strong acid site of the silica–alumina support.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.