A research team at Japan's Nagoya University has developed a series of new catalysts can hydrogenate ‘difficult substrates', such as amide bonds under much milder conditions than was previously possible. The scientists recently published a study suggesting that the neworganometallic ruthenium catalysts could play an important role in developing a more effective recycling process for amide-based plastics.
As the researchers point out, amide bonds can give great strength to plastics, but at the end of life, the difficulty of breaking these bonds usually prevents the recovery of useful products.
Catalysts are widely used in chemistry to help speed up reactions, but breaking the kinds of amide bonds in plastics, such as nylon, and other materials requires harsh conditions and large amounts of energy.
"Our previous catalysts could hydrogenate most amide bonds, but the reactions needed a long time at high temperature and high pressure. This new ruthenium catalyst can hydrogenate difficult substrates under much milder conditions," said lead author Takashi Miura.
Hydrogenation is the key step leading to breakdown of amide bonds. The new catalyst features a ruthenium atom that can adsorb hydrogen and deliver it to the amide bond to initiate the breakdown. By making sure that the hydrogen molecule was is the best possible position for interaction with amide bonds, the team achieved much more effective hydrogenation.
"The changes we made to the catalyst allowed some tricky amide bonds to be selectively cleaved for the first time,” explained group leader Susumu Saito.
“This catalyst has great potential for making designer peptides for pharmaceutics and could also be used to recover materials from waste plastics to help realise an anthropogenic chemical carbon cycle."
"Multifaceted catalytic hydrogenation of amides via diverse activation of a sterically confined bipyridine-ruthenium framework" was published in Scientific Reports at DOI: 10.1038/s41598-017-01645-z