Centre for Surface Chemistry and Catalysis - Research

Development of highly dispersed materials and the study of their genesis

The synthesis and chemistry of highly dispersed materials is studied in the frame of the development of new materials or in the frame of the modification of existing materials by the incorporation of new functions. The systematic study of the genesis of the solids via intermediate nano-structures is considered essential in this research field.

The final aim is to develop tailor-made materials for application as catalyst and adsorbent. This requires the control over:

• The number and nature of the active sites (acidity, basicity, redox)
• Shape selectivity of the catalyst (shape and connectivity of the micro/mesopores)
• Mass transport and heat transport characteristics
• Enantioselectivity in chiral catalysis

Surface chemistry of highly dispersed materials

To understand and improve the catalytic and sorptive properties of the highly dispersed materials, the COK studies both the chemical surface composition of these materials and the interaction of these surface atoms with molecules. This is approached in a combined scheme where both experiments and theoretical calculations are applied.

Special emphasis is put on the:

• Acidity/basicity of surfaces in relationship with the structure and chemical composition of the catalyst
• Redox properties of catalysts
• Organisation of molecules on surfaces to generate supramolecular entities
• Hydrophobicity/hydrophilicity and their balance on surfaces and membranes
• The development and study of active sites in solids and membranes for enantioselective discrimination

Heterogeneous, bio-organic and bio-inorganic catalysis

Today's key factors in the development of chemical processes are the concepts of "zero-waste" and "100 % selectivity". In the field of catalysis, the chemistry at interphases, referred to as heterogeneous catalysis, is promising to achieve both goals. The interphases of different aggregation states are applied for the discrimination of chemical compounds and for the directed reaction of reagents, resulting finally in a hyperselectivity towards the desired products. Recent interest is focused on the enantioselective preparation of fine chemicals.

The research group has gained expertise in many different fields of the heterogeneously catalysed reactions. Without being exhausting, examples are found in:

• isomerisation and cracking of paraffins catalysed by bifunctional zeolites
• alkylation and acylation by solid Brönsted acids
• immobilised metallo-porphyrines, -phthalocyanines, Jacobsen's complex and transition metal ion containing molecular sieves as solid (chiral) redox catalyst
• oligomerisation of olefins by metallocenes on alumoxane anchored hosts

Environmental chemistry

Since nature is essentially constituted of interphases, the knowledge of interphase chemistry can be considered as the crucial basis for each of the environmental chemical phenomena. Two fundamental approaches are followed in this field. Heterogeneous catalysis is applied for the development of "zero-waste" processes, this both from the point of view of 100 % selectivity as from the immobilisation of transition metals / acids to lower the emission levels. On the other hand, adsorption and catalysis are used for the treatment and prevention of air pollution.

Membrane separation and catalysis

The membrane research performed in our centre can be divided into two routes, namely separation and catalysis.

In the field of the membrane separations one can not overlook the importance of organomineral membranes. The inclusion of nano-materials in polymers can significantly improve both flux and selectivity of the membrane.

In separation of racemates over solid membranes, the research is currently focused on the relation between the membrane structure and the separative capacity of the membrane.

In the field of catalysis, we apply membranes mainly as the host for the heterogenisation of catalytically active compounds, and to recover homogeneous catalysts from reaction mixtures. The emphasis of this research is on

• the modification of the membrane polymers by the introduction of functional groups
• control of the membrane polarity and the retention of the heterogenized catalyst
• the development of membrane reactors.