The synthesis of polyethylene terephthalate PET from terephthalic acid and ethylene glycol typically involves two main steps: esterification and polycondensation. The optimal temperature and concentration of catalyst for this process depend on the specific catalyst being used, as well as the desired properties of the final product.For the esterification step, the reaction is usually carried out at temperatures between 220-260C. The catalysts commonly used for this step are strong acids, such as sulfuric acid or p-toluenesulfonic acid. The concentration of the catalyst can vary, but a typical range is 0.01-0.1 mol% based on the moles of terephthalic acid.For the polycondensation step, the reaction is typically carried out at temperatures between 270-290C under vacuum to remove the byproduct, ethylene glycol. The catalysts commonly used for this step are metal-based catalysts, such as antimony trioxide Sb2O3 , titanium-based catalysts e.g., titanium isopropoxide , or germanium-based catalysts e.g., germanium dioxide . The concentration of the catalyst can vary, but a typical range is 0.01-0.05 mol% based on the moles of terephthalic acid.It is important to note that the optimal temperature and concentration of catalyst may need to be adjusted depending on the specific reaction conditions, the desired molecular weight and properties of the PET, and the presence of any additives or comonomers. Additionally, the choice of catalyst can have a significant impact on the reaction rate, yield, and properties of the final product, so it is essential to carefully select and optimize the catalyst system for a given application.