ZEolite synthesis in Unusual Reactors for Enhanced CAtalysts

Informations projet

Z-EURECA

N° de convention de subvention: 948449

DOI

10.3030/948449

Projet clôturé

Date de signature de la CE 18 Novembre 2020

Date de début 1 Janvier 2021

Date de fin 31 Decembre 2025

Financé au titre de

• EXCELLENT SCIENCE - European Research Council (ERC)

Coût total

€ 1 498 500,00

Contribution de l’UE

€ 1 498 500,00

Coordonné par

KATHOLIEKE UNIVERSITEIT LEUVEN
Belgium

Periodic Reporting for period 3 - Z-EURECA (ZEolite synthesis in Unusual Reactors for Enhanced CAtalysts)

Période du rapport: 2024-01-01 au 2025-06-30

Résumé du contexte et des objectifs généraux du projet

Zeolites are minerals, which occur in nature or can be synthesized artificially. These microporous crystalline materials have a wide everyday use: due to low cost, natural zeolites mostly find their application as ion exchangers in washing powders, wastewater treatment technologies and adsorbents. However, their phase purity, porosity and composition are far from the ones required for application on a level of industrial chemical processes, such as catalysis and gas separation. Therefore, synthetic zeolites are more suitable for such applications. Yet, for certain applications, their properties are not apt. A modern approach to their manufacturing would be a mechanism for tuning materials’ properties and/or overall diversity.
Z-EURECA aims to overcome current challenges in the zeolite synthesis field through reactor-based solutions. In contrary to the classic closed batch system, which is limited by starting ingredients composition and concentration profiles, we implement two different modes of reactor-based control: by electric field and by fed-batch driven modes.
Roughly, control over zeolite synthesis by electric field can be presented in two very different by its nature ways: electro-kinetic control (EKC) and electro-assisted synthesis (EAS). The first one is presented as an influence of external electric field on a crystallization mixture; with this influence, we expect to change various equilibria existing in a synthesis solution, for instance, by altering Coulomb interactions between charged particles, a heteroatom distribution might be affected. The second mode is of electrochemical nature, thus by a real transfer of electrons through the system. Having a current caused by an external power source, we perform a precise dissolution of an electrode material to feed the zeolite synthesis mixture during key events of crystallization.
On the other hand, the basic idea of “Fed-batch” reactors is to directly impact concentration profiles by a timed and gradual ingredient feeding during synthesis (in situ). In addition, by the “Fed-batch” sampling feature, samples could be extracted at operational temperature and pressure along a synthesis, providing an accurate picture of zeolite crystallization and growth process. With these kinetic profiles in hand, one can avoid initially-present side reactions.

Travail effectué depuis le début du projet jusqu’à la fin de la période considérée dans le rapport et principaux résultats atteints jusqu’à présent

A large set of experiments have been done to investigate the effects of electro-kinetic control (EKC) during the synthesis of several zeolite systems using low-voltage non-uniform (rod electrodes) and uniform (planar electrodes) external electric fields. Our initial results reveal the extreme complexity of the electro-kinetic approach for harsh synthesis mixtures (pH is high, Temperature), however, the achieved data indicate the possible existence of the possibility to manipulate the charge interactions and local saturations for controlling phase selectivity during zeolite synthesis. How this is happening and how to control it, is still a question.
Also, trials have been performed to study the effects of electrochemically releasing OH- on zeolite formation in bulk. It has been seen that the pH of the synthesis mixture can be increased from 4 to 12, which results in gelation, by water electrolysis without inserting any alkali precursor from the beginning.
The largest part of the research has put its attention on the Electro-Assisted Synthesis (EAS) of zeolites. For the first time, we implemented an electrochemical dissolution of an electrode material during a zeolite crystallization process successfully. This novel feature allows a very efficient incorporation of heteroatoms into a zeolitic framework, the recovered crystalline materials have higher metal loading and insertion on a metal into a lattice, these properties assure higher activity of our materials in catalytic reactions. The proof of concept was studied on tin-containing MFI (structure code by IZA) zeolite.
Furthermore, we were able to create other isostructural materials with different elements incorporated into the framework, and expanded our approach to other zeolite frameworks (4) and metals (5).
We explored an efficient way for building S-curves (growth profile of crystals) in a new Fed-batch reactor with increased capacity (180ml) from one synthesis run only by sampling and yield extrapolation. Moreover, a new lid was designed to measure pH along with other parameters and this will improve kinetic mapping of zeolite synthesis. Therefore, having a more precise picture of zeolite formation made by Fed-batch, we explored a more efficient way (than conventional batch systems) for incorporating heteroatoms. Similar to EAS, the proof of concept was studied on tin-containing MFI zeolite.

Progrès au-delà de l’état des connaissances et impact potentiel prévu (y compris l’impact socio-économique et les conséquences sociétales plus larges du projet jusqu’à présent)

The EAS dataset and patents and papers are hugely beyond the state of the art, as recognized by the reviewers of the first paper. EAS proof of concepts and first milestones are published (and filed IP) and furthermore, translating the concept to Sn-BEA has been done (submitted).
It is truly beyond the art that now by having in mind a final heteroatom property of a zeolite, we can create the desired material by EAS by simply varying parameters of the electric supply, and, therefore, have a control over metal release from the electrode. For instance, the speed of dissolution, which is, in our experience, in charge of the heteroatom concentration profile inside the EAS reactor, can be alternated by voltage, current, signal waveform and/or timing of the release. This novel approach led to 3 patent applications and 1 published high-impact paper (Ivanushkin, Dusselier: Chemistry of Materials, 2023) and is now the basis for explorations in Sn-BEA, Ti and Zn (ongoing) and all beyond the art.
Two of these are industrially/application relevant topics: Sn-BEA is a catalyst for various bio-mass valorization reactions (e.g. sugar isomerization) and we have already demonstrated successful synthesis attempts, reaching record Si/Sn 14. The next phase beyond the art will be Ti by EAS, as Ti also has an applicational aspect since the materials are utilized in oxidation reactions using peroxides (e.g. Ti-MFI). The incorporation of titanium in the framework creates active sites, which mimic the activity of certain oxidation enzymes. Zeolites are perfectly suitable for working as heterogeneous catalysts in more harsh environments, which bring added value to these materials. From our side, we expect to have a better distribution and incorporation of the metal managed by EAS, and, therefore, increase efficiency and control over the zeolite’s manufacturing process and test their catalytic productivity.
The EKC part of the project will be continued with an upgrade of the existing set-up since we discovered that much higher voltages are required for the investigation of bulk effects on a zeolite synthesis. With this in mind, we are currently upgrading our synthesis cell and voltage generator, so the new system will be able to handle 20 kV of direct voltage (maximum current 0.6 mA) likely enabling the creation of uniform electric fields up to mega-V/m.
In the Fed-Batch part, mode 6 will be continued to look for new topologies or ways to steer between existing topologies via charge density approaches with two types of organic templates. ‘Competition or cooperation?’ of these organics will be the research question at the heart. Another part of the research will be on mode 5 that targets topologies for Si/Al optimization.

Chemistry of Materials Front Cover featuring our publication on Electro-Assisted Synthesis