Dr J. Thompson
BSc (Queen’s University of Belfast), 1996
PhD (Queen’s University of Belfast), 1999
Tel: + 44 (0) 28 9097 4420
Fax: + 44 (0) 28 9097 6524
Chemistry is concerned with the production of a wide variety of materials by the safest, most environmentally friendly and cheapest route available which often involves the use of catalysts. However, understanding how catalysts facilitate reactions, particularly in the liquid phase, is often very limited. We use a number of reactor designs and analytical techniques to investigate the behaviour of catalysts, in-situ, as the reaction occurs giving improved mechanistic insights and ultimately cleaner, more environmentally friendly catalysts and catalytic processes.
Liquid phase catalysis is involved in almost every aspect of everyday life from enzymes in biological sciences, through to drug development in pharmacological sciences as well as the fine and bulk chemical industries and with increasing legislation necessitating processes to be run under milder conditions and minimal waste production, the importance of this field continues to grow. An ability to understand the catalytic mechanism, allowing intelligent changes to be made to improve catalytic performance has become a necessary skill; however, for multiphase solid, liquid, gas reactions, the mass transfer phase boundaries and the presence of solvent complicates any kinetic analysis with the result that relatively little information on the nature of the catalyst during a reaction can be obtained using existing techniques. The main aim of our research is to develop techniques so that liquid phase catalytic reactions can be monitored closer to the catalyst particle rather than the bulk liquid phase where the reaction is conventionally observed.
We have developed; along with Avalon Instruments a Raman spectroscopy technique to monitor the concentration of species in the liquid phase, as the reaction is taking place. Raman spectra can be obtained over very short timescales and by applying a calibration set, the concentration of each species in the reactor can be displayed in real time, giving rapid and improved kinetic analysis compared to off line techniques.
However, to further improve our understanding of the catalytic mechanism, it is necessary to monitor the reaction closer to the catalyst surface and see what the catalyst sees. To achieve this we are currently developing an Attenuated Total Reflectance Infrared spectroscopy (ATR/IR) technique that not only measures the concentration of reagents within catalyst pores but the rate of diffusion of species to and from the catalyst surface providing valuable mass transfer information, difficult to obtain by other methods. IR spectra are taken over a very short timescale and integration under each spectrum gives a measure of the decrease in concentration of each species as it is removed from the catalyst bed.
Ionic liquids are salts that are liquid at or near room temperature. They have a number of interesting properties that make them a unique environment in which to carry out chemistry. For example, they are capable of dissolving both metal salt complexes, normally insoluble in organic solvents, and organic reagents, improving contact between homogeneous catalysts and reagents in what may otherwise be biphasic reactions. Their negligible vapour pressure allows product isolation from reaction mixtures by distillation, improving process design. Until recently very little information has been available on the effect these liquids have on catalytic reactions and part of our research is to use the reactors and analytical techniques developed for molecular solvents on these new reaction media.