Projects / Programmes
January 1, 2004
- December 31, 2008
| Code |
Science |
Field |
Subfield |
| 1.04.00 |
Natural sciences and mathematics |
Chemistry |
|
| Code |
Science |
Field |
| P360 |
Natural sciences and mathematics |
Inorganic chemistry |
Micro- and mesoporous molecular sieves; zeolite materials, catalysts, aluminosilicates, aluminophosphates, modified molecular sieves, organic-inorganic hybrids, bimodal pore size distribution, X-ray diffraction, solid state spectroscopy, catalytic reactions, polymer-modified concretes.
Researchers (15)
Organisations (2)
Abstract
Nanoporous materials are inorganic or organic substances having a regular array of pores with diameters of up to 50 nm that are comparable to kinetic diameters of molecules taking part in chemical reactions. These materials (zeolites and zeolite- and oxide materials) can separate reactants or products on the basis of their dimension and shape. They act as catalysts in the petroleum industry and for the preparation of specialty chemicals; they also enable the clustering of atoms or smaller molecules. Basic periodical 3-D structures are built of corner-connected tetrahedra and contain channels and cavities that can be modified by choosing an appropriate organic molecule acting like a structure-directing agent. The fractional substitution of transition metals for basic tetrahedral atoms results in the formation of acid and redox centers that exhibit catalytic properties. The nature and quantity of substituted metal atoms influence the strength and concentration of active sites.
Microporous molecular sieves with pore dimensions ranging from 0.3 to 2 nm are crystalline materials capable of separating molecules with an accuracy of 0.01 nm. The consequences of their ordered frameworks are high thermal stability and adsorption capacity and large surface area.
Zeolite-like silicate-, aluminosilicate- and aluminophosphate-based mesoporous materials are less crystalline solids with pore diameters in the range from 2 to 50 nm. Thermal- and active sites stabilities are lower due to less ordered frameworks. Though their preparation is very demanding, they nevertheless generate a lot of research efforts because of their potential use in processes where larger molecules are present. The latest area of research deals with inorganic-organic hybrids where organic molecules form a part of the framework. The length of organic chain influences the dimensions of cavities and channels.
Our research will focus on the preparation of new nanoporous materials for the use in hydrocarbon conversions. Materials will be thoroughly characterised, particularly their microscopic structures, framework topologies and catalytically active sites. Metal-modified aluminosilicate- and aluminophosphate-based zeolite-like materials exhibiting acid and redox sites will form the basis of our research. Microporous (pore diameters from 0.6 to 2 nm) and mesoporous (pore diameters up to 10 nm) materials will be prepared. The advantageous properties of micro- and mesoporous zeolite materials will be combined with the preparation of composites with bimodal pore size distributions. New phosphate-based hybrid materials will be prepared for the potential use in catalytic and adsorption processes.
Research will also be carried out in the area of structural investigations of polycrystalline pharmaceutical solids by means of X-ray diffraction and MAS NMR.
Polymer-modified cement with mineral admixtures represents an important nanocomposite material. In order to understand its improved physical, chemical and mechanical properties it is necessary not only to monitor its bulk properties but also to gain an insight into its microscopic- and nanostructure.
Significance for science
The purpose of the programme Nanoporous materials was the development of stable catalysts with larger pores (with diameters of 2 nm and more). Such catalysts should, for example, enable environment friendly catalytic cracking of higher hydrocarbons or synthesis of pharmaceutical substances. We prepared several transition-metal-modified materials on the silicate and phosphate basis. Although the transition-metal ions were predominantly stable within the framework and their leaching was not detected, the materials themselves were still not as hydrothermally stable as are microporous zeolitic materials. Therefore we also synthesised several composite microporous/mesoporous materials and indeed succeeded to increase the stability of these potential catalysts. We compared two different ways of preparation of composites. In one way we first prepared colloidal solution of zeolitic nanoparticles and then added surfactants, which got arranged into micelles and directed the formation of mesoporous material with microporous domains included. In another way we used already prepared mesoporous material with thicker walls and larger pores and we simply deposited zeolitic nanoparticles into the pores of the mesoporous material. We pointed out that the second way of preparation was simpler and should be favourable. Irrespectively of the way of preparation of composites, knowledge of the formation of zeolitic particles is very important for the successful synthesis. The hydrothermal process leading to microporous zeolites namely has to be stopped as soon as grains with typical zeolitic framework are formed, so that these grains are still small enough. This requirement induced studies of zeolite formation and crystal growth. Pores of mesoporous aluminophosphate materials were up to now arranged mostly in a hexagonal stack. Such pores are all parallel and because they all point into the same direction, the interior of the material is in practice poorly accessible to molecules. In our programme group we managed to prepare two cubic aluminophosphate materials with pores running along three mutually orthogonal axes. Because of different pore arrangement and because of their 10 nm large diameters, the materials are very promising. The materials were prepared as powders and as thin films with a thickness of about 500 nm. Such films open many new application opportunities. Within our group we already continue investigation with the aim to functionalize or to modify thin films. We also presented some new developments in the field of solid-state nuclear magnetic resonance spectroscopy. For example, we introduced a method for studying proximities between dipolar-coupled quadrupolar nuclei, e.g. between aluminium nuclei within aluminophosphate and aluminosilicate zeolitic materials. The method is based on the resonance between the strength of the radiofrequency magnetic field and the spinning speed of the sample. Performance of the method was demonstrated on aluminophosphate molecular sieve AlPO4-14, in which aluminium nuclei have diverse quadrupolar coupling constants and isotropic shifts, and different distances to nearest neighbours. We have shown that the method was robust and that it allowed quantitative analysis of distances among quadrupolar constituents. The method was recently used for studying aluminium-generated enhanced acid sites in industrially important zeolite Y. Of course, the method can be employed also for investigations of other solids that contain quadrupolar nuclei. Based on the method presented by our group, several European research groups followed up with research in the field of homonuclear couplings among quadrupolar nuclei.
Significance for the country
The science of nanoporous materials is nowadays in its full swing although many advantages have not yet been adequately exploited and successfully transformed into practice. Our programme group has been active for nine years. Over this period it became one of the leading groups in the field of preparation of metal-modified nanoporous materials in Europe. Since 2004 we were included into the FP6 European Network of Excellence INSIDE PORES and into an ERDF centre of excellence Nanoscience and nanotechnologies. We transferred our knowledge on preparation and characterisation of nanoporous materials to several fields of application. With the University of Zagreb and Slovenian company SILKEM from Kidričevo we explored the possibilities for the removal of zinc from wastewaters of galvanic industry using natural and synthetic zeolites as adsorbents. Together with SILKEM we also developed a technological process for the compaction of silicate products. The expansion of the production significantly improved the competitiveness of the company in the European markets. With SALONIT Anhovo we defined the influences of soluble carbonates on the overall hydration, final phase development and composition of Portland cement. Further long-term cooperation will be focused on the study of the kinetics of the ternary system Portland cement-limestone-fly ash to formulate an optimal composition with the highest resistance against sulphate corrosion. Our research group got included into Slovenian Technology Platform NaMaT, a member of European EuMaT, and Slovenian Thermosolar Technology Platform STTP, a member of European ESTTP. Another mission of the group was education and training of young researchers in the field of inorganic synthesis and characterization of materials. Within the postgraduate course on Heterogeneous catalysts at the Faculty of Chemistry and Chemical Technology of University of Ljubljana professor Venčeslav Kaučič has transferred knowledge and experiences from scientific research to educational process. Another three researchers from the group have delivered courses in the field of material science at the undergraduate and postgraduate level at University of Nova Gorica. Several young researchers and undergraduate students have been included in the frame of the programme Nanoporous materials. The programme group is tightly bound to research environment of Slovenia. We cooperate with other programme groups at the National Institute of Chemistry, especially with the ones that are active in the materials area (Laboratory for electrochemistry of materials, Laboratory for infrared spectroscopy of materials, Laboratory for catalysis and NMR centre). We also cooperate with programme groups located at the Jožef Stefan Institute (Laboratory for microscopy of materials), Faculty of Chemistry and Chemical Technology, University of Ljubljana (Department of inorganic chemistry) and School of Environmental Sciences, University of Nova Gorica (Laboratory for environmental applications).
Most important scientific results
Final report,
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Most important socioeconomically and culturally relevant results
Final report,
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