Producing environmentally friendly nylon from scrap wood
A major breakthrough in sustainability: nylon can be made out of scrap wood, without creating waste. This discovery was made by Professor of Inorganic Chemistry Lies Bouwman and PhD student Saeed Raoufmoghaddam
Nylon is found in things like fabric, toothbrushes and Velcro and is produced on a massive scale. Caprolactam, the base material used to produce nylon, is made using our ever-dwindling supply of fossil fuels. The process also produces a large quantity of salt as a by-product: four or five kilograms of it for every kilo of caprolactam. While that salt can be used as a fertiliser, it would obviously be much better if nylon could be made using a production method that was completely clean. And this is what the Leiden researchers have discovered.
Bouwman and Raoufmoghaddam have developed a path for synthesising caprolactam out of scrap wood, without producing any harmful by-products. ‘Waste wood contains cellulose, and that can be worked up into levuline acid,’ Bouwman explains. ‘This acid is quite similar to the caprolactam molecule. What we have succeeded in is making caprolactam from levuline in just a few steps.’ Levuline acid can also be made from cellulose found in materials like waste products from maize. A patent for this method has now been applied for.
To produce caprolactam for nylon in a sustainable fashion it is important to use a catalyst. Bouwman explains, ‘That is, a substance that can speed up the chemical reaction. That catalyst needs to be able to carry out the reaction at least 100,000 times. Only then does it become economically interesting for a business to consider this production method. The catalyst that we have now developed can carry out the reaction about 100 times. We still need to improve that. It will still take some time before we have found the right catalyst.’ Nevertheless, Bouwman’s research team is already in contact with the industry through the CatchBio consortium, that aims to convert biomass into fuels and into raw materials for chemical and pharmaceutical products.
Besides finding a catalyst for producing caprolactam from biomass, in the coming years Bouwman also wants to concentrate on cleaning up other chemical processes, such as that for the base material used to produce polyurethane. This polymer can be found in things like PUR foam, wetsuits, roller skates and mattresses. The current method for producing the base material for polyurethane uses phosgene, a highly toxic substance that was used as a poison gas during World War I.
(3 December 2014)
Molecular Science and Technology