Catalytic fast pyrolysis of polyethylene terephthalate plastic for the selective production of terephthalonitrile under ammonia atmosphere.

Terephthalonitrile (TPN) was directly produced from polyethylene terephthalate (PET) plastic via catalytic fast pyrolysis with ammonia. The optimal condition for producing TPN was over 1 g γ-Al2O3-2 wt% catalyst at 500 °C under carrier gas (50% NH3 and 50% N2) with yield of nitriles and TPN of 58.1 and 52.3 C%, respectively. The selectivity of TPN in the nitriles was around 90%. Meanwhile, a bit of aromatics, benzonitrile, acetonitrile were also produced as by-products with the total yields of less than 3 C%. The catalyst deactivated slightly after 5 cycles. Possible reaction routes were proposed and it was found that terephthalic acid, benzoic acid, related esters and amides were the major intermediates from PET to nitriles. Acetonitrile could be produced from acetaldehyde and its corresponding imines. In addition, 32.1 C% TPN with high purity (>95%) was obtained via freezing recrystallization. Catalytic pyrolysis with ammonia process was a promising technology for converting waste PET plastics to TPN. This study provided a new method for producing N-containing chemicals from polyester plastics.