A novel, photocatalytic, atmospheric-pressure plasma reactor for air pollution remediation

This project aims to develop a novel plasma catalysis process for decomposing volatile organic compounds (VOCs) from industrial emissions. This comprehensive investigation involves the use of physical vapour deposition to produce photocatalytic materials to maximise decomposition of VOCs within the plasma catalysis process.

The aim of this project is to develop a novel plasma catalysis process to decompose volatile organic compounds (VOCs) in atmospheric-pressure, air plasma.
Introduction:
Volatile organic compounds are air pollutants that are associated with the formation of smog, acid rain and global warming. There are several traditional methods to remove VOCs from a gas stream such as thermal oxidation, catalytic oxidation and adsorption. However, these techniques suffer from a variety of problems, such as the generation of harmful by-products, high-energy costs and the disposal of contaminated adsorbents. Non-thermal plasmas generated at atmospheric pressure and room temperature provide several advantages for pollutant abatement. In non-thermal plasma, the feed gas is ionised to create highly energetic electrons and reactive species for the initiation of plasma-assisted chemical reactions. These highly energetic electrons can easily break most chemical bonds without the need of high temperatures required by conventional thermal processes. The energy input into the plasma process can be rapidly varied and controlled depending upon load, leading to significant increase of energy efficiency and, therefore, offers a promising alternative method for VOCs removal from industrial emissions. Currently, approaches to adding catalysts to non-thermal plasma processes tend to be limited to using catalysts developed for thermal processes, rather than ones more suited to plasma conditions.

This work proposes the novel approach of using magnetron sputtering to coat photocatalytic material on key plasma reactor components. Photocatalysts are semiconductors that produce reactive radicals upon the action of light of specific wavelengths. These catalysts do not require high temperatures to be active, and are activated by light with wavelengths below 400 nm, which non-thermal atmospheric pressure plasmas generate. The world class surface analysis facilities available to the Surface Engineering and Advanced Materials research group at Manchester Metropolitan University will be utilized to characterize the photocatalytic coatings on the surface of dielectric beads commonly used in plasma reactors.

Objectives:
1- Design and build a dielectric barrier plasma reactor (DBD):
A comprehensive investigation into the properties of existing plasma reactors will be carried out. This will inform the design of a suitable plasma reactor with sampling points, optical, and electrical access for measurements of the key plasma parameters.

2- Produce and characterise dielectric and catalytic coatings on dielectric particles:
A novel magnetron sputtering technique will be used to produce photocatalytic coatings on dielectric particulates. This technique allows for close control of the chemistry of the coatings produced. The coated particulate surfaces will be characterised using several advanced analytical techniques comprising characterisation of the surface chemistry of the coatings using EDX and Raman spectroscopy; morphology of the coatings by X-Ray diffraction; surface topography by scanning electron microscopy, white light profilometry and atomic force microscopy.

3- Investigate the effect of coated dielectric particulates on plasma chemistry:
The effect of photocatalytic coatings on plasma parameters and the decomposition of VOCs will be investigated through both in situ and in-line testing. In situ optical emission spectroscopic measurements of metastable molecules and atomic species generated in the plasma will be carried out in combination with in-line FTIR spectroscopic measurements of by-products generated and remaining VOCs.

4- Optimise the plasma process to maximise decomposition of VOCs.
Results obtained from the surface analysis of the coatings, together with in situ and in-line measurements will provide a better understanding of the parameters governing breakdown of VOCs and as a result allow us to modify the process, maximizing decomposition of VOCs. In addition, the power consumption of the plasma process will also be measured, to assess optimum processing conditions.