Design and development of catalysts for heterogeneous catalysis

In the last century, the heterogeneous catalysis became one of the key principles in chemistry, revolutionized both, academia and industry. The heterogeneous catalyst is usually a solid material, whereas the reactions are gaseous or liquids. This makes the separation of products and recycling of the catalyst very easy and allows efficient processes on a large scale. Heterogeneous catalyst usually consists from active sites homogeneously distributed at the high surface area of the solid material (e.g. 10 – 1000 m2/g) as a catalysts support. Since the heterogeneous catalysis is a surface controlled process, physical transport process of substrates (and products) to (and from) the active centres of the catalyst can significantly influences the overall reaction rate as well as the selectivity. Designing a catalyst to suppress transport limitation on one hand and enhance activity and stability of the catalyst on the other hand is a big challenge. In this lecture we aim to contribute in spreading the understanding of some of the fundamental principles of the art of design and development of heterogeneous catalysts. Furthermore, we will present a case study on the design and development of bimetal catalyst for catalytic oxidation of volatile organic compounds (VOCs).
VOCs are the main class of air pollutants, emitted from various industrial processes. Catalytic oxidation is one of the most efficient processes for the removal of VOC from polluted air. The advanced VOC removal process is composed of adsorption unit followed by catalytic incinerator. Recently, many efforts have been made to design combined adsorption-catalytic unit with optimal activity and selectivity. Transition metal oxides immobilised on a suitable support are a low-cost alternative to currently used noble metal-containing catalysts. The nature of the support and the method of immobilisation are critical as the surface area and functionality determine the nature and dispersion of the metal oxide nanoparticles and thence their catalytic activity. Mesoporous silica supports have been of particular interest because of their high specific surface areas. We have recently demonstrated the nature and reducing properties of copper oxide nanoparticles and found that these are influenced by the peculiarity of silica with interparticle mesoporosity and the presence of a second metal (iron) in the silica matrix. An overview of the design and development of nanostructured catalyst with superior activity for removal of VOCs from polluted air will be presented.