Impact of Brønsted acid sites in MWW zeolites modified with cesium and amine species on Knoevenagel condensation
| Autor: | Aneta Grzesinska, Maria Ziolek, Anna Wojtaszek-Gurdak, Rosa M. Martín-Aranda, Vanesa Calvino-Casilda |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
02 engineering and technology
General Chemistry 010402 general chemistry 021001 nanoscience & nanotechnology Condensed Matter Physics 01 natural sciences 0104 chemical sciences Catalysis Benzaldehyde chemistry.chemical_compound Adsorption chemistry Mechanics of Materials Ethyl acetoacetate Pyridine Polymer chemistry General Materials Science Knoevenagel condensation 0210 nano-technology Zeolite Brønsted–Lowry acid–base theory |
| Zdroj: | Microporous and Mesoporous Materials. 280:288-296 |
| ISSN: | 1387-1811 |
| Popis: | Layered zeolites of MWW family, MCM-22 and pillared MCM-36, were used as supports for base modifiers: cesium species (introduced via cation exchange or impregnation) and 3-aminopropyl trimethoxysilane (AP). The obtained materials were characterized by different methods (ICP-OES, N2 adsorption, XRD, XPS, TG/DTA, FTIR combined with pyridine adsorption, 2-propanol decomposition) for evaluation of chemical, structural and surface properties. All materials obtained were subjected to the Knoevenagel condensation of benzaldehyde with ethyl cyanoacetate and ethyl acetoacetate. The effect of the zeolite structure, the stability of the catalysts as well as acid-base properties of zeolites on the activity in Knoevenagel condensation were considered. Of particular interest was the role of Bronsted acid sites (BAS). The nature of basic sites and BAS played different roles depending on the methylene compound used in the Knoevenagel condensation. AP-modified zeolites were the most active in the condensation between benzaldehyde and ethyl cyanoacetate, in which, in the first step of the reaction AP abstracted hydrogen from methylene carbon in ethyl cyanoacetate. A different reaction pathway was postulated for the condensation with ethyl acetoacetate on the basis of the highest activity of unmodified zeolites and the relationship between benzaldehyde conversion and the number of BAS. For this reaction protonation of benzaldehyde was postulated as the initial step of the reaction. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Full Text from ScienceDirect