What is the main focus of the research described?

The article focuses on the creation of custom catalysts, specifically, amine-functionalized SAPO-37 materials. These materials are microporous silicoaluminophosphates used to improve chemical reactions, offering enhanced performance and stability for various industrial applications. The goal is to tailor the catalyst's properties for specific chemical processes.

What is the significance of SAPO-37 in this research?

SAPO-37 is a type of microporous material, similar to zeolites, which are crucial in catalytic processes. While the article discusses the challenges associated with SAPO-37's instability in moisture-rich environments, the functionalization with organosilanes enhances the material's properties by creating a hydrophobic environment. This improvement is significant because it allows SAPO-37 to be used more effectively in chemical reactions, particularly in the petroleum and petrochemical industries.

What are organosilanes, and how are they used in this process?

Organosilanes are compounds used to modify the surface of materials like SAPO-37. In this context, the researchers used (3-aminopropyl)triethoxysilane, N-[3-(triethoxysilyl)propyl]ethylenediamine, and N-[3-(trimethoxysilyl)propyl]aniline to functionalize SAPO-37. This functionalization enhances the material's catalytic properties by improving its ability to interact with reactants and improving its stability. The direct co-condensation method ensures uniform organosilane distribution within the SAPO-37 framework, leading to better performance.

How is the direct co-condensation method used in the synthesis of these materials?

The direct co-condensation method involves incorporating organosilanes during the synthesis of the SAPO-37 material. This method is advantageous because it allows for a more uniform distribution of the organosilanes throughout the material's structure compared to post-synthesis grafting. The process includes mixing pseudoboehmite, fumed silica, orthophosphoric acid, tetramethyl-ammonium hydroxide (TMAOH), and tetrapropylammonium hydroxide (TPAOH). Then, organosilanes are added to the precursor and crystallized. This method ensures that the functional groups are integrated into the SAPO-37 framework.

Why is the solvent extraction method important in this process?

The solvent extraction method is used to remove templates from the synthesized SAPO-37 materials without damaging the material's structure. In this study, the samples were refluxed in ethanol containing sodium nitrate. This technique avoids the dealumination that can occur with mineral acids like HCl, preserving the structural integrity of SAPO-37. The preservation of the framework is essential because it maintains the catalyst's activity and selectivity in chemical reactions. The resulting extracted SAPO-37 samples were then tested for β-amino alcohol preparation through propylene oxide ring opening with aniline.

Custom designed catalyst with amines

Custom Catalysts: How Tailored Materials Boost Chemical Reactions

Reese Marlowe in Science & Nature December 2025 • 4 min read.

"Unlocking the potential of amine-functionalized SAPO-37 microporous materials for efficient and selective chemical processes."

Zeolites and similar materials are critical in various catalytic and adsorption processes, particularly in the petroleum and petrochemical industries. Faujasite-type zeolites, such as zeolite-Y, are well-known catalysts in fluid catalytic cracking (FCC) and crude oil processing. However, SAPO-37, a microporous silicoaluminophosphate, is less explored due to its instability in moisture-rich environments.

Surface functionalization with organosilanes can enhance these materials by creating a hydrophobic environment, improving their catalytic and adsorbent properties. While introducing organosilanes into mesoporous silica-based molecular sieves is common, surface functionalization of microporous molecular sieve materials is less developed. This can be achieved through post-synthesis grafting or direct co-condensation, with the latter ensuring uniform organosilane distribution within the framework surfaces.

This article explores the preparation of amine-functionalized SAPO-37 molecular sieves using a direct co-condensation method. The process involves introducing organosilanes—(3-aminopropyl)triethoxysilane, N-[3-(triethoxysilyl)propyl]ethylenediamine, and N-[3-(trimethoxysilyl)propyl]aniline—during hydrothermal synthesis. A novel solvent extraction method, employing ethanolic sodium nitrate solution, efficiently removes templates without dealumination, preserving the material’s structural integrity.

Customizing SAPO-37: A Step-by-Step Guide

The researchers prepared a series of monoamine, diamine, and aniline-functionalized SAPO-37 materials using a direct co-condensation method. This involved creating a SAPO-37 precursor with a specific molar gel composition. Pseudoboehmite was dissolved in orthophosphoric acid, and fumed silica was added to a mixture containing tetramethyl-ammonium hydroxide (TMAOH) and tetrapropylammonium hydroxide (TPAOH).

The two solutions were combined and stirred overnight. A known amount of organosilane was then added to the SAPO-37 precursor, and the resulting gel was crystallized for 16 hours at 200 °C. The materials were then filtered, washed, and dried.

Materials: Pseudoboehmite, fumed silica, (3-aminopropyl)triethoxysilane, N-[3-(triethoxysilyl)propyl]ethylenediamine, N-[3-(trimethoxysilyl)propyl]aniline, orthophosphoric acid, tetramethyl-ammonium hydroxide, tetrapropylammonium hydroxide, Aniline, Propylene oxide.
Precursor Preparation: Mix pseudoboehmite with orthophosphoric acid. Separately, combine fumed silica with TMAOH and TPAOH. Combine both mixtures.
Organosilane Addition: Add a specific organosilane to the SAPO-37 precursor.
Crystallization: Crystallize the mixture at 200°C for 16 hours.
Extraction: Reflux the sample in ethanol with sodium nitrate to remove templates.

To remove the templates, the synthesized materials were refluxed in ethanol containing sodium nitrate at 80 °C for 6 hours. This extraction method avoids the framework dealumination that can occur with mineral acids like HCl, preserving the material's structure. The resulting extracted SAPO-37 samples were then tested for β-amino alcohol preparation through propylene oxide ring opening with aniline under solvent-free conditions.

The Future of Customized Catalysts

The study successfully demonstrated a method for incorporating monoamine, diamine, and aniline organo-functional groups into the SAPO-37 framework using a co-condensation technique. The presence of -NH and -NH2 functionality was confirmed through FT-IR and 13C-MAS NMR studies, while 29Si-MAS NMR showed covalent grafting of the organo-functional group.

The resulting materials exhibited retained faujasite-type SAPO-37 structure and enhanced surface area due to hierarchical pore formation, particularly with aniline silane. These functionalized materials proved to be effective catalysts for epoxide ring opening under ambient conditions.

This research paves the way for designing more efficient and stable catalysts for a range of chemical reactions, potentially impacting industries from petrochemicals to pharmaceuticals. By tailoring the surface properties of microporous materials, scientists can optimize catalytic performance and address specific industrial needs.