Ammonolytic transfer dehydrogenation of amines and amides: a versatile method to valorize nitrogen compounds to nitriles

Abstract

The dehydrogenation of amines has been identified as an efficient method for nitrile synthesis. At present, this approach is restricted to (oxidative) dehydrogenations of primary amines, most often with specialized...

Effective and sustainable depolymerization of Nylon 66 – a transamidation for the complete recycling of polyamides

“…Such sulfur-containing molecules typically poison metal-based catalysts almost immediately. 8,10 In addition, we succeeded in breaking down Nylon 6 as well (entry 10). Therefore, our innovative depolymerization system has the potential to be a valuable approach for carpet recycling, where Nylon 66/Nylon 6/PP are commonly mixed and/or copolymerized.…”

“…via alcoholysis, ammonolysis, hydrolysis etc . 3,4,6,8–10 In particular, the steam-assisted depolymerization of PAs proved to be very effective for lactam-based PAs such as Nylon 6. In supercritical liquid or with overheated steam molten Nylon 6 is depolymerized at temperatures of up to 420 °C.…”

“…To deal with this drawback, Coeck et al coupled the ammonolysis to an irreversible reaction. 10 This approach worked excellently for long-chain polyamides (LCPA) to generate α,ω-diamines, α,ω-dinitriles or amidonitriles. However, these new recycling methods have not yet been proven effective for Nylon 66.…”

“…This comes to no surprise; we previously reported the ability of Nb 2 O 5 to activate secondary amide bonds. 10 Ammonia (NH 3 ) was also introduced into the system, to assist in breaking down the polymer by ammonolysis. Under the applied conditions, virtually no amine products were detected.…”

“…15 This side reaction is caused by the Nb 2 O 5 catalyst, which is known for its ability to (partially) dehydrate primary amides to nitriles. 10,16 In order to maximize the solvent's reusability, we did not further increase the reaction temperature.…”