The isolation and purification of these products are outlined in Scheme 3. The DMT, ethylene glycol and excess methanol exit from the methanolysis reactor as a vapor and the methanol is isolated in a methanol removal column. The recovered methanol is then recycled back into the methanolysis reactor. DMT and ethylene glycol are difficult to separate because they form a low-boiling azeotrope (the combination of two substances that boil at a lower temperature than either pure substance). This problem is remedied by adding methyl p-toluate (MPT) to the reaction mixture. This creates a low-boiling azeotrope between MPT and ethylene glycol, which boils at a lower temperature than the DMT/ethylene glycol azeotrope. This difference in the boiling points allows the MPT/ethylene glycol azeotrope to distill, leaving DMT behind. DMT is then further purified by fractional distillation. The MPT/ethylene glycol distillate spontaneously separates into two phases, one rich in ethylene glycol and one rich in MPT. The MP-rich phase is decanted and reused to separate additional mixtures of DMT/ethylene glycol. The ethylene glycol and purified DMT can then be used to form first-quality PET.