Heterogenized Homogeneous Catalysts for Fine Chemicals Production Ma
Table 1 E factors (tonnes of waste generated per tonne of product manufactured [7] Industry segment Annual product tonnage E factor 6 8 Oil refining 10 –10 Approx. 0. 1 4 6 Bulk chemicals 10 –10
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Fine Chemicals Synthesis Through Heterogenized Catalysts: Scopes, Challenges and Needs Duncan Macquarrie
Abstract The development of new, highly efficient heterogenized catalysts is an active and important area in fine chemicals production. Many opportunities present themselves in terms of the significant developments in the tailoring of solid supports, which allow a rich variety of surface functionalities and properties, along with unprecedented control of physical features such as porosity, pore connectivity and high surface area. Key challenges include making full use of this palette of materials in the drive towards sustainable manufacturing. The knowledge base in materials chemistry and catalysis, coupled with ever-improving techniques to analyse catalytic materials and the reactions they promote will provide a sound foundation for future research and applications in this area.
1.1 Introductory Remarks The synthesis of fine chemicals through the use of heterogenized catalysts has been an active research field for several decades Over about the same period, the chemical industry has been enormously reliant on the use of solid catalysts, in particular the zeolites (3D crystalline solids with pore sizes below 1 nm) for the conversion of crude oil into a range of small molecules. These high temperature, gas phase processes run continuously and are amongst the largest volume chemical processes in existence. The enormous thermal stability, robustness and high acidity of the zeolite catalysts employed, combined with their very well defined crystalline nature means that they are extremely effective and highly selective catalysts. Part of this selectivity comes from the fact that, in a crystalline material, active sites are always situated in the same environment and therefore always have the same activity and selectivity (although transport processes taking substrate to, and product from, the D. Macquarrie (*) Green Chemistry Centre of Excellence, Department of Chemistry, University of York, Heslington, York YO10 5DD, UK e-mail: [email protected] P. Barbaro and F. Liguori (eds.), Heterogenized Homogeneous Catalysts for Fine Chemicals Production, Catalysis by Metal Complexes 33, DOI 10.1007/978-90-481-3696-4_1, © Springer Science+Business Media B.V. 2010
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active sites may restrict the frequency of their utilisation). A second major contributor to their selectivity comes from the fact that their pore dimensions are often more or less the same size as the substrates/products that are involved in the reaction, leading to the notion of shape selectivity, crucial in the formation of p-xylene with a sufficiently high purity (>99.9%) for use in terephthalic acid production. Such selectivity is well beyond normal chemoselectivity. The crystalline nature of the zeolites also means that they can be very well characterised and therefore a thorough understanding of their behaviour is possible. In stark contrast, there is a distinct lack of solid catalysts or continuous processes in the predominantly soluti
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