Gold catalysts could let homeowners produce hydrogen peroxide on a small-scale in order to safely treat grey water.
This is one of the anticipated outcomes of research being conducted at Cardiff University’s School of Chemistry, where researchers including Dr Philip Davies, a senior lecturer in physical chemistry, are looking at new ways to exploit the properties of the noble metal at the nanoscale.
Their work stems from research carried out by Prof Graham Hutchings, FRS and director of the Cardiff Catalysis Institute (CCI) at the University, who predicted that gold would be the best catalyst for hydrochlorination of ethyne to make vinyl chloride, which is the precursor to poly-vinyl chloride (PVC).
Dr Davies said: ‘The present catalyst that’s used is mercury-based, which obviously is very environmentally bad. It’s also relatively short lived as a catalyst.
‘Hutchings was looking for an alternative and he predicted, based on thermodynamics, that gold would be the best. He subsequently proved that.
‘Afterwards, he started looking at gold as a catalyst for all sorts of processes. For example, it’s a selective catalyst for the hydrogenation of crotonaldehyde. It’s also a very good selective oxidation catalyst.’
Dr Davies explained that hydrogen peroxide (H2O2) is used extensively in industry as it is very reactive and an effective cleaning agent. It is, however, only economical to produce in bulk quantities, which requires large processing plants and subsequent transportation to customers.
He added that CCI is looking to create H2O2 from hydrogen-oxygen at low pressure using a gold-palladium mixture as a catalyst.
‘You need to make the gold and palladium into nanoparticles,’ said Dr Davies. ‘Then you can make a very active catalyst that makes H2O2 on a low scale. You’re dealing with low pressures of hydrogen and oxygen in a non-explosive…regime.
‘It’s perfectly safe and you can make small amounts of H2O2 that might be used there and then, instead of making large amounts and transporting it.’
By producing H2O2 in such quantities, said Dr Davies, homeowners could make better use of so-called grey water, which is the wastewater from activities such as washing.
‘This is water that could be recycled for use again in flushing toilets or in dishwashers if you could just clean it up a bit,’ he said. ‘What you may do is have a catalyst that’s creating H2O2 up in your loft, which could then be used to clean up the water instead of just getting rid of it down the sink.’
More generally, the quantities of gold required in such catalysts are small enough to be cost competitive and the metal has a long lifespan, making it reusable.
‘It’s highly selective and productive…a cheaper catalyst won’t last as long, will give you more waste that you then have to dispose of because it’s not as precise, [and] it’s not as efficient. So, overall costs are better with gold.’
According to the University, research being conducted at CCI could lead to devices that convert carbon monoxide into carbon dioxide, and “cold start” catalysts in car exhaust systems to reduce carbon emissions.
Dr Davies said tangible technology from CCI is close to market, which will be licensed through CCI’s supporting companies.