Construction of Interface-Bonded SiO2/TiO2 Catalyst for PET Synthesis

Traditional titanium-based catalysts for polyethylene terephthalate (PET) synthesis suffer from serious TiO 2 aggregation, poor dispersion, and an inability to balance catalytic activity and anti-yellowing performance, limiting their practical application. To address these issues and promote the green substitution of antimony-based catalysts, a SiO 2 /TiO 2 composite catalyst was prepared via a sol–gel method using tetraethyl orthosilicate and tetrapropoxysilane as dual silicon sources and titanium isopropoxide as the titanium source. The dual-silicon strategy enabled the formation of stable Ti–O–Si interfacial bonds, which suppressed TiO 2 agglomeration, improved catalyst dispersion, and modulated the Lewis acidity of Ti 4+ sites. The catalyst exhibited a high specific surface area (443.8 m 2 g −1 ) and uniform Ti 4+ distribution. At a low dosage (0.005 wt%), it afforded PET with an intrinsic viscosity of 0.706 dL g −1 , a viscosity-average molecular weight of 19,985 g mol −1 , and the Hunter b coordinate is 3.69, outperforming pure TiO 2 . Notably, the catalyst required no high-temperature calcination and was obtained by room-temperature stirring and low-temperature vacuum drying. With low cost and good structural stability, it shows promising potential for industrial PET production.