page_title: Dimethyl terephthalate
section_title: Dimethyl terephthalate (DMT) (Witten Process)
hierarchical_section_title: Dimethyl terephthalate / Production / Dimethyl terephthalate (DMT) (Witten Process)
caption_attribution_description: English: structure of monomethyl terephthalate
context_page_description: Dimethyl terephthalate is an organic compound with the formula C₆H₄(COOCH₃)₂. It is the diester formed from terephthalic acid and methanol. It is a white solid that melts to give a distillable colourless liquid.
context_section_description: The common method for the production of DMT from p-xylene (PX) and methanol consists of a multistep process involving both oxidation and esterification.  A mixture of p-xylene (PX) and methyl p-toluate is oxidized with air in the presence of a cobalt and manganese catalysts.
  The acid mixture resulting from the oxidation is esterified with methanol to produce a mixture of esters.  The crude ester mixture is distilled to remove all the heavy boilers and residue produced; the lighter esters are recycled to the oxidation section.  The raw DMT is then sent to the crystallization section to remove DMT isomers, residual acids and aromatic aldehydes.
  Oxidation of methyl p-toluate followed by esterification also yields dimethyl terephthalate (DMT) as shown in the below reaction:
  Dimethyl terephthalate (DMT) production through direct esterification
  If highly impure terephthalic acid is available, DMT can be made in a separate process by esterification with methanol to dimethyl terephthalate, which is then purified by distillation:
  C₈H₆O₄ + 2CH₃OH   →  C₁₀H₁₀O₄ + 2 H₂O
  at presence of o-xylene at 250–300 °C.
caption: Structure of monomethyl terephthalate.
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