Highly Efficient Synthesis and Property Characterization of PETG Using Titanium-Based Bimetallic Catalysts

A series of titanium-based bimetallic catalysts (Ti–M, where M = Mg, Mn, Ca, Co, Al) were synthesized via the sol–gel method for the preparation of polyethylene terephthalate-1,4-cyclohexanedimethanol ester (PETG). Their catalytic performance was compared to that of conventional catalysts, specifically tetrabutyl titanate (TBT) and germanium dioxide (GeO2). Results showed that Ti–M catalysts exhibited excellent catalytic activity at a 6 ppm loading. Among them, the Ti–Co catalyst demonstrated a rate constant of 7.53 × 10–3 min–1 during esterification, surpassing both TBT and GeO2. The Ti–Mg catalyst achieved the highest reaction rate in the polycondensation stage, producing PETG with a number-average molecular weight of 2.87 × 104 g/mol and a relatively narrow polymer dispersity index (Đ = 2.08). Analyses revealed that PETG synthesized with the Ti–Mg catalyst had a higher thermal decomposition activation energy, indicative of improved thermal stability. These titanium-based bimetallic catalysts demonstrate high efficiency and superior performance in PETG synthesis, making them promising alternatives to traditional catalysts.