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A Career in Catalysis: Exceptions That Prove Dowden’s Rule

Gary Bond is Professor of Materials Chemistry in the School of Forensic & Investigative Sciences at UCLan. Gary joined the academic staff at the University of Central Lancashire in 1995 after having spent a brief period at Leeds Metropolitan University.

He is the Academic Lead & Principal Lecturer in Inorganic and Analytical Chemistry.

Following Gary’s Inaugural Professorial Lecture which was based around “Dowden’s rule” – Dennis Dowden is commonly regarded as being one of the most eminent catalytic chemists of the 20th Century, his observation led him to suggest that the greater the activity that a catalyst displays then the lower will be its selectivity towards the desired product. Professor Bond’s work has centred on a range of catalytic reactions that do not obey Dowden’s rule; the exceptions that prove the rule. Mike Holmes joined Gary in his office in JB Firth Building to find out more.

Gary Bond

Can I start by asking you what your research is about? I know it is about catalysis, but can you tell me in a bit more detail.

Since the start of my research career, I have been interested in catalysis, which is the acceleration of a chemical reaction or enabling a chemical reaction to take place at a lower temperature. Catalysis is of huge commercial and environmental importance, not only providing financial savings to the chemical industry but also enabling the clean-up of environmental pollutants in, for example, vehicle exhaust emissions. Initially I worked with ICI Polymers Division on the hydrogenation of nitriles (a nitrile is a compound that contains the chemical group -CN), which is important industrially in the production of nylon and a variety of other common chemical products.

Can I interrupt and clarify what happens in catalysis? For catalysis to occur you need a material, such as platinum to be present, to enable the reaction to go faster or take place at a lower temperature?

That is right. The active catalyst, we are talking generally about metal catalysts such as platinum, needs to be present but you don’t have a big solid piece of platinum. It is just not effective. The catalyst is produced by dispersing the metal in atomic or very small ensembles of atoms on the surface of an inert substrate, such as silica or alumina.

By dispersing them, you increase the surface area and the effectiveness of the catalyst.

How did your interest in microwave catalysis develop?

It was through our work with ICI that I developed an interest in microwave catalysis. There was a lot of early work, and early reports in the literature, of microwaves being used to give rapid reactions and vastly enhanced rates. There appeared to be this wonderful microwave effect! Therefore, we set about a programme of work involving ICI and EPSRC to look at the possible advantageous effects of microwaves on catalysts. Since those initial studies, I have had a number of EPSRC awards in the area of microwaves. I have developed the technique of microwave thermal analysis in conjunction with Professor Phil Barnes from the University of Huddersfield, and have worked with groups throughout the UK.

I have had visiting professorship at the University of Technology of Compiègne where we have developed specialised reactors for studying catalysts under microwave conditions. Currently I am a member of the AMPERE Committee – the Association for Microwave Power in Education and Research in Europe.

I know a few years ago you were working with companies like Jaguar on microwave catalysis of exhaust fumes. Can you tell me about that?

We have a strong track record of working with industry. With Jaguar we had an extensive research and development programme. What we were looking at were systems for the removal of diesel particulate matter from vehicle exhaust streams. This material is mainly made up of carbon, which is deposited in the exhaust filter leading to the filter eventually becoming ineffective. The idea was to design a system, which used microwaves to oxidise the carbon particles to carbon dioxide and water so the filter had a much longer life. Whilst allowing combustion, it could not produce any back pressure in the exhaust system, and had to have a very minimum size in terms of the effect on the floor pan of the vehicle. We started developing a microwave induced plasma to perform the oxidation reaction. While we took this to vehicle trials, it was apparent at a relatively early stage that the exhaust velocities required and the available power on board the vehicle were incompatible. We therefore changed tactic slightly, and started to look at systems for the re-generation of diesel particulate filters. We developed two patents on a prototype system, which Jaguar currently holds. These have been vehicle tested but given the current legislation, it is not cost effective for them to change the system they have.

Microwaves give a clean and efficient alternative, but it is a case of whether or not the consumer will pay the extra cost that is required. Currently manufacturers can stay within current EU legislation for emissions using existing technologies. It is all based on finance, and not always using the best technology that is available.

What is currently engaging you in your research?

Currently I am looking at microwave induced plasma. I am part of a European partnership, which is looking at its beneficial effects in the production, and regeneration of heterogeneous catalysts. A microwave induced plasma is what is known as a “cold” plasma; it has a high energy but low thermal temperature. You can produce very reactive species in that plasma, so in terms of preparing catalysts, we can de-compose catalyst pre-cursors at very low thermal temperatures. This means that effects such as the sintering of catalytic particles into larger clumps is reduced. Usually you want to keep your active particles as far apart as possible giving the maximum catalytic surface area. We already have companies interested in this process.

For efficient catalysis to occur, you want the catalytic surfaces to be separated from each other?

The very small particles of catalytic material such as platinum are active and can migrate across the surface of the substrate, the support, very easily. Therefore, you want to expose your catalyst to the lowest possible temperature during preparation to reduce sintering or clumping. A cold plasma allows you to do that.

Can I ask you about a cold plasma, because it won’t be a concept that many people are familiar with.

What is a cold plasma?

Most people describe plasma as probably the fourth state of matter. In a plasma, generated from a gas, the atoms have been ionised into their component charges i.e. electrons and atoms carrying an electric charge. Argon is an easily ionised gas so it is a good base, but then we also need a reactive component, so we would put some oxygen in there, to make oxygen radicals. These will effectively oxidise the organic component at a very low temperature leaving us our single atom of metal on the support.

What other projects do you have active at the moment?

I am working with Professor Harry Eccles in the John Tyndall centre. We have projects looking at irradiated graphite, both in terms of the radioactive C14 content, and its selective removal from the radioactive graphite. If we succeed, then we can probably have that graphite changed from being an intermediate level waste, which needs deep repository disposal, into a low level waste which could be in a shallow deposit. We are also interested in developing some technology for the separation of metals, metal ions, and particularly radio nuclides which has potential applications for nuclear clean up, and de-commissioning.