UiO-66(Zr/Ti) for catalytic PET polycondensation

PET (poly(ethylene terephthalate)) is one of the most important type of thermoplastic polyesters and widely used in various fields. Titanium-based catalysts are environmentally friendly and have higher catalytic activity than antimony-based catalysts when used in industry. However, titanium-based catalysts are prone to hydrolysis and result in discolored products. UiO-66 (Zr/Ti) with different Ti4+ contents were successfully synthesized via one-step method. The material was characterized by XRD, SEM, FT-IR, XPS, BET and TG techniques. The results demonstrates that Ti4+ was integrated into the UiO-66 framework. NH3-in situ DRIFTS, pyridine-IR, and NH3-TPD were used to explore the acidic properties of the samples, which proved that stable Lewis acidic sites are present in the samples even at 300 degrees C. The catalytic performance of UiO-66 (Zr/Ti) containing different Ti4+ was explored under different conditions. At the same time, the scale-up experiment was carried out in a 5 L reactor, and the PET chips obtained had a lower b value. The catalytic reaction mechanism of UiO-66(Zr/Ti) was demonstrated by DFT calculations and the catalytic performance was close to Sb-based catalysts.