H2-free Plastic Conversion: Converting PET back to BTX by Unlocking Hidden Hydrogen

Graphical Hidden hydrogen : Polyethylene terephthalate (PET) is the most widely used synthetic polyester, and its degradation is increasingly recognized as essential to develop the future provision of energy and reduce environmental pollution. Reported herein is a salient example of H 2 -free conversion of PET back to BTX stream with alkyl aromatics as the main products by unlocking hidden hydrogen in the structural ethylene glycol part in a selective manner. The strong desire for a circular economy makes obtaining fuels and chemicals via plastic degradation an important research topic in the 21st century. Here, the first example of the H 2 -free polyethylene terephthalate (PET) conversion to BTX (benzene, toluene and xylene) was achieved by unlocking hidden hydrogen in the ethylene glycol part over Ru/Nb 2 O 5 catalyst. Among the whole process (hydrolysis, reforming and hydrogenolysis/decarboxylation), the parallel hydrogenolysis and decarboxylation were competing and the rate-determining step. Ru/Nb 2 O 5 exhibited superior hydrogenolysis and poorer decarboxylation performance in direct comparison with Ru/NiAl 2 O 4 , accordingly contributing to the distinct selectivity to alkyl aromatics among BTX. Ru species on Nb 2 O 5 , unlike those on NiAl 2 O 4 , showed more Ru δ + species owing to the strong interaction between Ru and Nb 2 O 5 , restricting the undesired decarboxylation. Along with NbO x species for C−O bond activation, excellent reactivity towards the H 2 -free conversion of PET back to BTX with alkyl aromatics as dominant species was achieved. This H 2 -free system was also capable of converting common real PET plastics back to BTX, adding new options in the circular economy of PET.