New vinyl catalyst curbs mercury pollution

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Gold (pictured here in turquoise) on carbon catalysts can replace toxic mercury containing catalysts (photo: Johnson Matthey).

A discovery made by a scientist 30 years ago is now being commercialized to prevent mercury (Hg) pollution in the polyvinyl chloride (PVC) industry in China.

Production of PVC is estimated to be the largest industrial use of Hg in China, the nation which produces most of the world’s PVC. Countless Chinese workers are exposed to toxic Hg during the manufacture of these plastics, and the emissions from these plants contribute to the global Hg problem as Hg is emitted into the atmosphere.

Starting in the mid-1980s, Professor Graham Hutchings discovered that a gold catalyst was the best way to replace the toxic Hg used in making vinyl chloride monomer (VCM), a precursor to PVC. The Hg salt used to produce VCM is toxic and volatile, so it escapes to the environment and is inefficient. The gold catalyst would reduce the problem of Hg pollution, but gold is also more expensive and Hutchings original process would have involved another type of corrosive chemical reaction, so it wasn’t adopted.

However, after being approached by a sustainable technologies company, Johnson Matthey, Hutchings undertook more research beginning again in the late 2000s. Now, Hutchings and colleagues published their results that reduces the amount of gold needed to make the process much more affordable. The production of this new low-level gold catalyst has been tested at one of the largest PVC facilities in China, and there is hope that a lot of other Chinese manufacturers will adopt this new technology.

The Minamata Convention on Mercury, a binding international treaty, states that VCM plants should go Hg-free by 2022. This research helps make that goal a reality.

Read a more detailed summary of Hutchings and colleagues 2015 paper here.

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