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Gold nanoparticles used to turn biofuel waste into useful products

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A stable gold catalyst has been developed for obtaining useful chemical products based on glycerol, a major by-product of biofuel production.

As pressure mounts to reduce dependency on non-renewable fuel sources such as coal and natural gas, biofuel production has become a steadily growing industry. Biofuels are produced through biological processes and can include plants and animal waste.

“[Biofuels] can be obtained from a great variety of biomasses,” said Professor Alexey Pestryakov, head of the department of physical and analytical chemistry at Tomsk Polytechnic University, Russia. “In Latin America it is orange and tangerine peel as well as banana skin. In the [US] biofuels are produced from corn, in the central part of Russia and Europe, from rape.”

As these plants are processed into biofuels, an enormous amount of glycerol is formed. Glycerol, a colourless liquid, has many uses, including as a sugar substitute, a laxative and a key component in e-liquid.

While glycerol is a versatile by-product, many thousands of tonnes are produced every year and much of this goes to waste.

As a result, many researchers have been trying to solve the problem of how to efficiently transform this waste glycerol into useful chemicals. The Tomsk Polytechnic University researchers have been working on using gold-based catalysts to provoke this transformation.

Gold catalysts – which have only been utilised since the early 1990s – are very active, entering into chemical reactions with other substances even at room temperature. Gold is only useful as a catalyst, however, at the nanolevel, when the size of the particle is below two nanometres.

“Only then it gets its amazing properties,” said Professor Pestryakov.

According to the researchers, catalytic oxidation using gold nanoparticles is among the most effective techniques for harvesting aldehydes, esters, carboxylic acids and other useful substances from glycerol. These are valuable in the cosmetic, pharmaceutical and agricultural industries.

These gold nanoparticle catalysts are not the only gold-based catalysts available, but they stand out among others for their stability; they retain their activity for far longer than alternative catalysts.

“A great challenge in this area is that gold catalysts are very rapidly deactivated, not only during work, but even during storage. Our objective is to ensure their longer shelf life,” said Professor Pestryakov.

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