Zeolites are aluminosilicates that can show Brønsted acidity when in protonic form. As the microporous structure of the zeolite is formed, its total acidity becomes greater. However, in parallel, there is a confinement of acidic sites inside the zeolite structure, reducing its accessibility. In this sense, less crystallized materials can present, in various reactions, greater catalytic activity. This class of partially formed aluminosilicates has received particular attention in recent years as a promising class of catalysts for reactions involving bulky molecules. These zeolitic precursors also have many surface silanols, which can be used for anchoring functional groups, such as amines derived from silanes, adding basic properties to protonic aluminosilicates. In this proposal, we intend to evaluate the use of partially crystallized acidic aluminosilicates to the functionalization with amino silanes, producing acid-base catalysts, focusing on reducing diffusion limitation for applications in reactions with bulky molecules. H-ZSM-5 zeolites and their precursors with different crystallinities and Si/Al ratios will be prepared and functionalized with (3-Aminopropyl)-trimethoxy silane (APTMS), Trimethoxy[3-(methylamino)propyl] silane (MAPTMS), or (N,N-Dimethylaminopropyl)trimethoxy silane (DMAPTS). These solids will be used as catalysts in acid deacetalization of benzaldehyde dimethyl acetal, followed by Knoevenagel condensation with ethyl cyanoacetate, a model reaction for evaluating acid-base catalysts. This proposal for international collaboration will allow the evaluation of the physicochemical properties of zeolite precursors with advanced characterization techniques, mainly aimed at the study of acidic and basic sites with probe molecules, allowing the development of new materials for series reactions with bulky molecules.
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