Effect of diantimony trioxide on direct esterification between terephthalic acid and ethylene glycol

Abstract

SynopsisExperiments a t various SbO, concentrations were made in a pilot plant and the effect of Sb03 on continuous esterification between terephthalic acid (TPA) and ethylene glycol (EG) was obtained. Reaction rate constants of the previously reported reaction scheme were determined to fit with the experimental data obtained. It was found that the effect of Sb03 on reaction rate constant (k,) can be expressed as follows.k, = (3.50 x 10-4Sb + 1.0) x 7.7069 X exp(-2810/RT) k , = (1.75 X 10-4Sb + 1.0) X 6.2595 X 106exp( -14,960/RT) k , = (3.75 x 10-4Sb + 1.0) x 2.0583 X 10'5exp(-42,520/RT) Simulation of esterification with these reaction rate constants at various S!+03 concentrations was made and the following results were obtained.1. Sb03 accelerates the esterification reaction between TPA and EG. 2. SbO, accelerates the main reaction and its effects on side reactions are minor. The higher the addition rate of SbO,, the lower the carboxyl end-group concentration (AV) and diethylene glycol content (DEG). 3. The comparison between simulation with potassium titanium oxyoxalate (PTO) in the previous report and with SbO, in the present report shows that the acceleration of polycondensation reaction by Sb03 is higher. DEG formation rate is lower with PTO than S!+O,.

Reasons for the Discoloration of Postconsumer Poly(ethylene terephthalate) during Reprocessing

“…Sb 2 O 3 is a catalyst which can be used for both steps in the PET synthesis and is known to minimize side reactions. [7] The activation energy of BHET with antimony trioxide as catalyst is lower than without addition of any catalyst. [8] Duh proposed a mechanism for the effect of the antimony catalyst on the solid-state polycondensation of PET.…”

Poly(Ethylene Terephthalate) Polymerization – Mechanism, Catalysis, Kinetics, Mass Transfer and Reactor Design

“…In Figure 2.4, data for the equilibrium constants of esterification/hydrolysis and transesterification/glycolysis from different publications [21][22][23][24] are compared. In addition, the equilibrium constant data for the reaction TPA + 2EG BHET + 2W, as calculated by a Gibbs reactor model included in the commercial process simulator Chemcad, are also shown.…”

“…38.1 kJ mol −1 Equilibrium constants of esterification and polycondensation as a function of temperature. The data have been published by Yamada and co-workers[23,24], Reimschuessel[21] and Challa[22], or have been calculated by using the commercial process simulator Chemcad(Chemstations) catalyst, whereas zinc acetate or diantimony trioxide are not. For the esterifications of aromatic carboxylic acids with glycols it has been concluded[25] that the formation of complexes of the metal compound with the acid or of the acid with the metal glycolate having high ligand exchange rates is a prerequisite for a high catalytic activity.Kinetic measurements have been performed by different working groups for the esterification of TPA with EG and for model systems.…”

A mathematical model for a continuous esterification process with recycle between terephthalic acid and ethylene glycol

“…The concentration of DEG is given by the sum of C6, C7, and Cs. 6. The pressure in the reactor is given only by the sum of partial pressures of EG and water existing in it.…”