Study of various catalysts in the synthesis of poly(propylene terephthalate) and mathematical modeling of the esterification reaction

Pure terephthalic acid (TPA) was esterified with 1,3-propanediol (1,3-PDO) in the presence of various catalysts, in order to find the most effective one for this esterification reaction. The prepared oligomers were polycondensated in a second step under high vacuum and using the same catalyst (Sb(OCOCH3)3, Ti(OC4H9)4, GeO2) as before, or the well known catalyst for poly(ethylene terephthalate) (PET) production technology Sb2O3. The esterification reaction was monitored by measuring the distilled water as a function of time and from these data the modeling of this process was carried out. The received poly(propylene terephthalate) (PPT) samples were characterized by viscometry, carboxyl end-group content and color measurement. From this study, tetrabutoxytitanium was proved to be the most effective catalyst for the esterification reaction. When this catalyst was used in the second step a PPT polymer with the highest molecular weight was received.