UK scientists have converted crude biodiesel waste into useful amines with no need for difficult separation techniques.  

Glycerol is produced in significant quantities as a by-product in biodiesel production, making it a cheap renewable feedstock for the chemical industry. For example, using microbial processes to ferment glycerol is an attractive route to 1,3-propanediol, which can be used as a precursor to high value polymers and platform chemicals. However, the fermentation products are produced in dilute solutions along with cell material and other metabolic products, making purification and separation difficult.

Now a team of scientists, led by Andrew Marr at Queen's University Belfast and Gillian Stephens at the University of Manchester, has combined microbial and transition metal catalysed processes to produce secondary amines without having to isolate and purify the diol intermediate.

Marr and Stephens treated glycerol with the bacterium Clostridium butyricum, then centrifuged the mixture of bacteria, 1,3-propanediol and by-products to remove the cells. The team then added a solution of an iridium catalyst, base and aniline in toluene to the solution, creating a biphasic mixture. After 24 hours at 115°C, 20 per cent of the 1,3-propanediol had been converted to secondary amine.

'As fossil fuels become less accessible, chemists need to start developing new methods to convert renewable feedstocks into the chemical products and materials that society demands,' says Marr. 'Our key advance is to integrate biocatalytic and chemocatalytic processes to avoid the need to separate the fermentation products.'
  
'This is an important example of adding value to renewable resources,' says Mark Harmer, a research fellow at DuPont, Delaware, US. 'The ability to use all of the components from renewable feedstocks will be key to developing a biorefinery to replace the current oil-based refinery.'

Stephens agrees: 'The new approach will allow a myriad chemical products to be derived from a single fermentation mixture. To our knowledge, this is the first time that a one-pot approach has been applied using products from whole microbial cells. This approach should be general, since the chemistry can be changed by replacing the non-aqueous phase with an alternative reactant and catalyst mixture. The microbiology can also be changed, allowing conversion of a wide range of feedstocks to diverse fermentation products.' 

Vikki Chapman

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