Catalysts speed up the rate of a chemical reaction without being itself consumed. Gold catalysts are used in many types of chemical reactions to produce products and are involved in several chemical processes. Some of the notable products that gold catalysts are used to make include vinyl acetate monomer (VAM) for the production of wood glues, emulsion-based paints, and wallpaper pastes. VAM capacity is currently at 5 million metric tonnes per year and rising, and VAM consumption is several hundred tonnes per year.
Other products that rely on gold catalysts semi-conductors, cosmetics, and cleaner for broilers and metals. Gold is used as a catalyst in the liquid-phase air oxidation process for the one step process to produce methyl glycolate from ethyl glycol and methanol. Methyl glycolate is used asa solvent for semiconductor manufacturing, as a cleaner for broilers and metals, and is used as a building block for cosmetics.
The conversion of glucose to gluconic acid requires gold as a catalyst. Gluconic acid is important in the food and beverage industry as an additive. It is also used as a cleansing agent and is produced at a magnitude of around 60000 tonnes per year.
The PVC manufacturing industry may be switching to gold as a catalyst in the production of Vinyl chloride monomer (VCM), an intermediate chemical for PVC manufacturing. The majority of the industry currently uses a mercury-based catalyst for PVC production. The Chinese PVC industry alone is the world's largest consumer of mercury and is responsible for around a quarter of global consumption. In the PVC process, a significant amount of mercury is lost through evaporation and can result in emissions into both air and water.
Mercury contamination has historically devastated areas or the world such as Minamata, Japan, which destroyed thousands of lives and took over 20 years to clean up, costing the Japanese government over $350 million dollars. The ongoing mercury emissions from the PVC industry is believed to cause health issues in China and elsewhere in the world since volatile mercury compounds can travel significant distances. The US West Coast has seen continually rising mercury levels in freshwater fish since the rapid industrialization of China began in the 1980s. Johnson Matthey is one of several companies that intend to resolve the mercury issue in the Chinese PVC industry by replacing mercury-based catalysts with gold. Commercialization of PVC using gold as a catalyst has been held back by the relatively high cost of gold, but Johnson Matthey has developed and commercialized an efficient catalyst with a reduced amount of gold suitable for large-scale manufacturing. They have developed a technically and economically viable alternative to a mercury-based catalyst that will allow the gold to be recyclable too. However, due to the large scale of the industry, significant quantities of gold would be required to see a full conversion of the reactors in China to mercury-free ones-this could be a great opportunity for gold investors.
Gold is also used in catalytic converters to breakdown pollutants and to purify the air. Catalytic converters are required by fossil fuel powered vehicles on the road to help remove harmful pollutants that would otherwise contaminate the atmosphere. Platinum, palladium, and rhodium are commonly used in catalytic converters, but gold can also be used. Gold, when combined with palladium and platinum has shown to be an effective formulation to convert Carbon monoxide, nitrogen oxide, and unburned hydrocarbons into less harmful molecules such as carbon dioxide and water. The catalytic converter is arranged with a honeycomb structure that contains gold, platinum and palladium nanoparticles on the structure’s grid which in turn acts to remove pollutants.
Scientists discovered that gold nanoparticles react with oxygen to convert carbon monoxide to carbon dioxide. A team of scientists from Switzerland, UK, and the USA proposed an explanation for this process. Using high- energy X-ray absorption spectroscopy, they found that oxygen becomes chemically active when bound to gold nanoparticles. They found that oxygen bound to gold ‘nanoparticles reacted with carbon monoxide to form carbon dioxide. Before this discovery, the scientific community knew that small gold particles were reactive, they just didn’t know how they were reacting.