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Details of Grant 

EPSRC Reference: EP/R04483X/1
Title: Development of a Dual-Mode Microwave-EPR Reactor-Resonator for Studies of Paramagnetic Catalytic Reactions
Principal Investigator: Murphy, Professor DM
Other Investigators:
Porch, Professor A Slocombe, Dr DR Richards, Dr E
Researcher Co-Investigators:
Project Partners:
Department: Chemistry
Organisation: Cardiff University
Scheme: Standard Research
Starts: 01 September 2018 Ends: 31 May 2022 Value (£): 720,434
EPSRC Research Topic Classifications:
Analytical Science Catalysis & Applied Catalysis
EPSRC Industrial Sector Classifications:
No relevance to Underpinning Sectors
Related Grants:
Panel History:
Panel DatePanel NameOutcome
25 Apr 2018 EPSRC Physical Sciences - April 2018 Announced
Summary on Grant Application Form
Microwave (MW) heating continues to grow as an important enabling technology, primarily owing to the proven capability of MWs to speed up the rate of chemical reactions. Most of us associate MWs with cooking using the domestic MW-oven, in which the food is quickly heated as the MWs interact with the (water) molecules. However, it is surprising that the precise molecular explanation of how MWs heat liquids and solids remains poorly understood. It is known for example that MW heating is in many cases better than conventional heating (which relies on comparatively slow and inefficient conductive and convective heat transfer principles) but it is not clear if the beneficial heating effects are specific to the MW radiation. Understating this is vitally important owing to the growing use of microwave reactors for enhancing the rates of chemical reactions (i.e., the MW-specific reaction rate enhancement effect). This is particularly relevant in catalysis, where a rate enhancement in some reactions of at least one order of magnitude can be achieved using MW-heating. Another key advantage of MW-heating for catalysis is the almost instantaneous and rapid heating (and subsequent rapid cooling) of the sample. One immediate benefit of this rapid heating, is that the outcome of the chemical reaction (the products formed) can be altered through the kinetic and thermodynamic selectivity of competitive reactions; rapid heating can result in the formation of significant proportions of thermodynamically unfavoured products. Therefore, whilst MW-heating is very important in reaction rate enhancement, particularly in catalysis, our understanding of the MW-specific enhancement or heating effects are poorly understood.

At the same time, the ability to rapidly heat a chemical system can also be exploited for the study of reaction mechanisms. Most chemical reactions involve an equilibrium process, with the rate of the forward and reverse reactions controlling the overall concentration of reactants and products at any given point in time. The chemical or conformational equilibrium can be easily perturbed and shifted in either direction, when a stress is applied. This stress may involve a change in concentration, pressure or temperature. The rate of change from the old to the new equilibrium will depend on the rate constant for the forward and reverse reactions or the conformational change, so that analysis of this rate is extremely informative in chemical kinetics and dynamics. It is important that the perturbation is applied more rapidly than the relaxation time, and usually on a time scale that is faster than the mixing times involved. TJ is one such type of relaxation method used to study chemical kinetics and reaction mechanisms. Rapid heating by microwaves (creating a TJ) using a suitable resonator, could therefore be used as a novel means of studying reaction kinetics and dynamics.

Therefore, in this project we will develop a unique dual-mode Electron Paramagnetic Resonance (EPR) based reactor-resonator. EPR is a spectroscopic technique that employs microwaves to detect paramagnetic species. Two separate MWs frequencies will be introduced into the reactor-resonator in resonant mode, such that one frequency will be used to detect the paramagnetic species by EPR, while the second frequency will be used to heat the sample. We will build the device specifically to demonstrate its utility for investigating the fundamental nature of how MW heating can influence the rate and product distribution in a series of homogeneous and heterogeneous catalytic reactions (involving paramagnetic species), to potentially follow how the reaction pathways are altered by a rapid rise in temperature (T-jump heating), to fundamentally understand how MW-specific effects lead to enhancement of photogenerated radical lifetimes in magnetic fields, and to indirectly understand how MWs heating of liquids and solids occurs.
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