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Dimethyl Terephthalate: Terephthalic Acid and Methanol Sprayed through a Hot Tube
Dimethyl terephthalate (DMT) is the methyl ester of terephthalic acid, a raw material for polyesters. Terephthalic acid does not melt, so Lotz and Gerlach (US 2,876,252, 1959) spray it as a suspension in methanol, with a little phosphoric acid, into a tube heated to 280–300 °C. The ester condenses as long needles that melt at 141 °C; the patent's yield was 97 %.
The picture: our diagram.
Ilọsíwájú
Continuous
Ìlànà
1
1
Make the suspension
Make the suspension
Stir 1000 g of finely powdered terephthalic acid and 60 cc of 85 % phosphoric acid into 1000 cc of methanol.
Àwọn ohun èlò fún ìgbésẹ̀ yìí:
Ásídì Tẹrẹfitálíìkì1000 g
Methanol1000 mlÀwọn irinṣẹ́ tí a nílò:
Acid phosphoric (ìpín 85)
Òǹwọ̀n ìdọ́gba
Silinda òǹwọ̀n
Gílásì Ààbò Fún Ìfọ́n Kẹ́míkà
Ìbọ̀wọ́ rọ́bà2
2
Heat the reaction tube
Heat the reaction tube
Heat a long cylindrical reaction tube electrically to 280–300 °C (the patent's was 300 cm long and 40 cm wide). A cooled condenser follows it.
Àwọn irinṣẹ́ tí a nílò:
Ọ̀pọ̀n ìhùwàpọ̀ tí a gbóná
Thermocouple pẹ̀lú ìkà
Ìyípo ẹ̀rọ ìtutù3
3
Spray it in with nitrogen
Spray it in with nitrogen
Spray the suspension with nitrogen through a nozzle into the tube, so the fine spray travels in a spiral along the tube wall. The acid and methanol react on the way.
Àwọn irinṣẹ́ tí a nílò:
Ihò ìfọ́n tí ń sọ di ìrì kékeré
Sílíńdà Gáàsì NàìtírójìnỌ̀pọ̀n ìhùwàpọ̀ tí a gbóná
Ìbọ̀wọ́ Tí Ń Fara Da Ooru4
4
Collect the needles
Collect the needles
The dimethyl terephthalate collects in the cooled condenser as long prismatic needles, melting point 141 °C. The patent's yield was 97 %.
Àwọn irinṣẹ́ tí a nílò:
Ìyípo ẹ̀rọ ìtutùÌbọ̀wọ́ rọ́bà5
5
Recycle nitrogen and methanol
Recycle nitrogen and methanol
Draw the nitrogen and the excess methanol out with a membrane (diaphragm) pump and send them round again.
Àwọn irinṣẹ́ tí a nílò:
Ẹ̀rọ ìfúnpá aláwọ̀ araSílíńdà Gáàsì NàìtírójìnÀwọn irinṣẹ́ tó nílò
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