Tunable High Frequency Microwave Assisted Chemistry

1. Tunable High Frequency Microwave Assisted Chemistry Presented by Gareth Lewis

2. Project Overview • Using high frequency microwaves to increase the yield and reaction rate of organic reactions • Intelligent monitoring and control system to continually optimise microwave parameters • Design of microwave reaction cavity

3. Project Overview • Investigate mechanics of microwave assisted reactions • Implementation of more energy efficient reactions • Green chemistry

4. Microwave Region

5. Current Systems • Pharmaceutical manufacturers have only been using non-automated 2.45GHz • Traditional heating systems use 2.45GHz • This project investigates the use of higher frequencies (8 – 18 GHz)

6. Typical Organic Products

7. Dielectric Heating • A number of mechanisms contribute to the heating process • Most heating occurs due to rotation of dipoles

8. Dielectric Heating

9. Dielectric Heating

10. Dielectric Heating

11. Dielectric Constant • Homogenous materials have their dielectric properties described by the complex dielectric constante • It is a complex term consisting of both real and imaginary parts

12. Dielectric Constant • The real part (e’) represents the ability of a material to be polarised by external electric fields • Complete representation in the real part at d.c. and low frequencies • This is because the dipole will follow the field change near perfectly

13. Dielectric Constant • As the frequency is increased a phase difference is introduced between the field and dipole • The imaginary part (e’’) of the complex term represents this lag • Collisions occur and energy is lost as heat

14. Dielectric Constant Variation of the real and complex parts of the dielectric constant against frequency for water

15. Dielectric Constant • At very high frequency the alternation of the field is very rapid • Movement of the dipoles is very limited due to their inability to adjust in time • This situation, like low frequencies affords very little heating

16. Dielectric Constant

17. Temperature Effect • To increase heating, it has been established that intelligent frequency selection is important • During heating, temperature changes the values of e’ and e’’

18. Temperature Effect • The time constant tis given by the following equation: • As can be seen, temperature must also be considered

19. HFSS Simulation Side View – Thermal Overlay Freq= 8-12 GHz 100 mm 10 mm (Internal) 150 mm

20. Specific Absorption Rate High absorption

21. HFSS and Experimental Comparison (cont.)

22. Water Heating

23. Ethanol Heating

24. Experimental System Setup Condenser Condenser Reaction Cavity Reaction Cavity Sensors Sensors Microwave Test Set Microwave Test Set

25. P Set Point I Power Source Microwave Cavity - + D Sensor (Temperature/Power) Monitoring and Control Software - PID • PID (Proportional Integral Derivative) controller for Temperature/Power

26. Monitoring and Control Software Frequency Set Power Readouts Power or Temperature Hold Start/Stop System Power and Temperature Charts

27. Thank You Any Questions?