| Abstract: | The products of the ester exchange of DMT with EG in the presence of two catalysts (calcium acetate and a mixture of manganese and sodium acetate) obtained under manufacturing conditions have been investigated. The ester exchange product and the distillate obtained during different reaction times were analysed. On the base of the obtained results of the effect of the duration and temperature the reaction was established as well as of the type of catalyst on the progress of the fundamental and by-reactions. It was found that the trans-esterification proceeds through a mixed ester of terephthalic acid, namely methylethylolterephthalate. After the trans-esterification of the methylester groups of methylethylolterephthalate and DMT the reaction does not stop, but continues with the oligomerization of the diethylterephthalate. At the end of the process about 82% of oligomers are obtained when the catalyst is calcium acetate and 93% with the mixed catalyst. The experimental results show that part of the initial monomers participate in undesired side-reactions (by-processes): hydrolysis of DMT to terephthalic acid and breaking down of EG to acetaldehyde. The results obtained indicate the greater effectiveness of the mixed catalyst. |
