Microporous materials: green syntheses for green applications – MICROGREEN

Le dénominateur commun des recherches proposées dans ce projet est que la synthèse de zéolithes (équipe Française) et PAFs (équipe Chinoise) se déroulera à température ambiante. Cette approche permet de ralentir suffisamment les vitesses de cristallisation afin d’étudier les intermédiaires réactionnels en conditions quasi in-situ. Des informations détaillées sur les phases présentes, les inhomogénéités présentes à différents stades de leur formation et des transformations de gels réactionnels seront ainsi obtenues. Cette approche permettra également un contrôle fin des cinétiques de cristallisation et donc d’isoler des phases qui ne le sont pas par des techniques plus conventionnelles. Ces basses températures permettent également de synthétiser directement des zéolithes sur des supports sensibles à la température. Les zéolithes, PAFs et leurs composites seront ensuite utilisés pour éliminer des gaz à effet de serre et purifier des eaux polluées.

The first stage of the project included development and optimization of synthesis techniques and their application to the synthesis of zeolites and PAFs crystals including conducting time-series synthesis experiments under variable conditions and starting materials in order to reveal the dynamics and kinetics as well as the spatial aspects of the process of transformation of the amorphous gels (suspensions) into crystalline solids;

The french team ha studied the zeolite formation in the system Me2O-Al2O3-SiO2-H2O where Me is Na has been studied.
Systematic study of the system comprising a single alkali cation and monomeric silicon and aluminmium precursors allowed to reach a high uniformity of the initial gel. The other gel characteristics that will be subjected to investigation are Si/Al ratio and water content in the systems. The reaction kinetics through time-series synthesis experiments with different duration, was performed. At ambient temperature due to the slow kinetics of the process finer details of the transformation process have been observed. Experiments up to several weeks in duration has been conducted providing detail informtaion of the consequence of crystallization events.
Following experiments will be conducted:
Variation pH and temperature in the range from RT to 100°C to test the reaction rates and gel structure transformations.
Variation of SiO2/H2O ratio from 1:10 to 1:300 to test the influence of water activity and viscosity of the reactive gels on the crystallization process
Variation of Al2O3/SiO2 ratio in the range 0.1 to 0.5 to test the rates of polymerization reactions and their influence on the processes during different stages of reaction.
Variation of Me2O/SiO2 ratios in the ranges 1 to 5.
The envisaged framework types are: FAU-, EMT-, LTA- and LTL-type.

Following experiments will be conducted:
Variation pH and temperature in the range from RT to 100°C to test the reaction rates and gel structure transformations.
Variation of SiO2/H2O ratio from 1:10 to 1:300 to test the influence of water activity and viscosity of the reactive gels on the crystallization process
Variation of Al2O3/SiO2 ratio in the range 0.1 to 0.5 to test the rates of polymerization reactions and their influence on the processes during different stages of reaction.
Variation of Me2O/SiO2 ratios in the ranges 1 to 5.
The envisaged framework types are: FAU-, EMT-, LTA- and LTL-type.

Poster presentation at 5th Advanced Micro- & Mesoporous materials Symposium (September 6-9, 2013; Golden sands, Bulgaria)
Title: Rheological properties of zeolite precursor gels having different aluminium content
Authors: A. Palcic, J. Bronic, V. Valtchev

Oral presentation at 5th Advanced Micro- & Mesoporous materials Symposium (September 6-9, 2013; Golden sands, Bulgaria)
Title: Synthesis of copolymerized porous aromatic frameworks (PAFs) with high CO2 storage properties
Authors: T. Ben, S. Qiu

The present project deals with synthesis of microporous zeolite type materials with the ultimate goal to reach a deeper understanding of their mechanism of formation. Zeolites and zeolite-like materials are studied today and applied in many different ways and fields including but not limited to ion exchange, catalytic processes, adsorption applications, electronic and sensing applications as well as in medicine and nanotechnology. Zeolites are ecologically friendly and expanding the scope and range of their applications would improve and transform many technological and industrial processes towards more environmentally beneficial operations. Understanding the process of zeolite nucleation and crystal growth and the factors controlling it is of importance because it provides a basis for rational design and prediction of zeolite structures with desired properties, which include not only their crystal structure but also their physical and chemical properties such as size, shape stability, reactivity, and composition. Together with zeolites, metal-organic-frameworks (MOFs) and lately the porous aromatic frameworks (PAFs) attracted the attention of academic and applied scientist with their extremely high sorption capacity in respect to greenhouse gases.
A specific feature of proposed research is that the synthesis of zeolites (French team) and PAF-type materials (Chinese team) will be performed at ambient temperature. This approach will be used in order to slow down the crystallization kinetics and to study the intermediates under quasi in situ conditions. Thus detail information on the intermediates, type of structures, phases and inhomogeneities present at different stages of microporous materials formation and gel transformation will be obtained. This approach will also provide a fine control of crystal growth kinetics and thus synthesis of microporous phases that cannot be obtained under conventional conditions. Low temperature conditions will be further employed for synthesis of zeolites on supports that cannot withstand conventional hydrothermal treatment. Synthesized series of zeolites, PAFs and composites materials will be further used for greenhouse gases and water pollutants elimination.
The project includes:
(i) development and optimization of synthesis techniques and their application to the synthesis of zeolites and PAFs crystals including conducting time-series synthesis experiments under variable conditions and starting materials in order to reveal the dynamics and kinetics as well as the spatial aspects of the process of transformation of the amorphous gels (suspensions) into crystalline solids;
(ii) structural and compositional characterization of the synthesis products and their intermediates;
(iii) iterative analysis of the results and modification of the experimental condition in order to achieve the set goals;
(iv) synthesis of zeolite-type materials under “green conditions” that includes minimum use of energy and full recycling of the reactants;
(v) employment of these materials for gases (PAFs) and liquid (zéolithes) separations addressing important environmental problems of modern society.
The project involves two groups that possess all critical and complementary expertise to address the tasks of the project in a rational and comprehensive way. The French team will concentrate its efforts on the preparation of classical zeolites, while the Chinese partner will work on recently discovered polymer aromatic framework molecular sieves. The parallel study of these two important groups of crystalline microporous materials will allow making parallels and distinguishing differences in the nucleation and crystal growth mechanism.