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Catalytic Pyrolysis of Poly(ethylene terephthalate) in the Presence of Metal Oxides for Aromatic Hydrocarbon Recovery Using Tandem μ‑Reactor-GC/MS
journal contribution
posted on 2020-01-15, 19:37 authored by Shogo Kumagai, Ryota Yamasaki, Tomohito Kameda, Yuko Saito, Atsushi Watanabe, Chuichi Watanabe, Norio Teramae, Toshiaki YoshiokaPoly(ethylene terephthalate)
(PET) pyrolysis products and those
produced from their subsequent catalytic reactions under various metal
oxides (ZnO, MgO, TiO2, and ZrO2) were evaluated
qualitatively and semiquantitatively using a tandem μ-reactor
gas chromatography–mass spectrometry (TR-GC/MS) system. The
catalytic reaction products were analyzed in situ to determine the
duration and temperature dependence of their production. In the TR-GC/MS,
a reactor with two-tier, independent heat sources was linked directly
to a GC/MS device. PET pyrolysis was carried out at 450 °C, whereas
the pyrolysis products were reacted in the presence of metal oxides
at 700 °C. ZnO, which has a high base strength, promoted decarboxylation
of the principal pyrolysis products of benzoic acid and terephthalic
acid (TPA) selectively and at a low temperature. The proportion of
oil components made up by benzene was up to 88.8 area%. On the other
hand, MgO, TiO2, and ZrO2 have lower base strengths
than ZnO. Hence, their capabilities for benzoic acid and TPA decarboxylation
were low, and carboxylation using these oxides required temperatures
50–70 °C higher than that using ZnO. In summary, the present
study found that benzene-rich aromatic hydrocarbons can be obtained
by the catalytic pyrolysis of PET using various metal oxides and that
the product composition depends on the acid–base properties
of the metal oxides. These findings will help promote feedstock recycling
to convert PET waste materials or mixed plastics that contain PET
into raw chemical materials by pyrolysis.