Chemical Upcycling of Nitrile Butadiene Rubbers to Polyamines and Polyols by Chemoselective Catalytic Hydrogenation

We report here two new approaches for the chemical recycling/upcycling of nitrile butadiene rubber (NBR) to make either polyamines or polyols. Both processes are achieved through ruthenium-catalysed hydrogenation reactions, where the chemoselective reduction of nitriles leads to the formation of either amines or alcohols. The hydrogenation of NBR to polyamines could be achieved at temperatures as low as 35 °C, whereas a higher temperature (150 °C) was required for the formation of polyols with catalytic turnover numbers reaching up to 2000. Additionally, polyamines were demonstrated for their potential application in CO2 capture, absorbing 1.34 mmol of CO2/g of absorbents. This was significantly higher in comparison to that obtained in the case of NBR, which adsorbed only 0.015 mmol of CO2/g of absorbent. The synthesised polyol exhibited a markedly greater ductility than the commercial NBR, reaching an elongation at break of ≈ 550 % versus ≈ 420 % for NBR, suggestive of potential use in stretch-demanding applications.