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Dimethyl Terephthalate: Terephthalic Acid and Methanol Sprayed through a Hot Tube
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Charlie

19. uMfumfu 2026DE
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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.
Osezingeni eliphezulu
Continuous

Imiyalelo

1

Make the suspension

Stir 1000 g of finely powdered terephthalic acid and 60 cc of 85 % phosphoric acid into 1000 cc of methanol.

Izinto zokwakha zalesi sinyathelo:

I-Terephthalic AcidI-Terephthalic Acid1000 g
I-methanolI-methanol1000 ml

Amathuluzi adingekayo:

I-asidi ye-phosphoric (85 %)I-asidi ye-phosphoric (85 %)
Isikali sesilinganisoIsikali sesilinganiso
Isilinda esinezilinganisoIsilinda esinezilinganiso
Izibuko Zokuchitheka KwamakhemikhaliIzibuko Zokuchitheka Kwamakhemikhali
Amagilavu erabhaAmagilavu erabha
2

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.

Amathuluzi adingekayo:

Ipayipi lokusabela eliqhumisiweIpayipi lokusabela eliqhumisiwe
I-thermocouple enesibonisiI-thermocouple enesibonisi
Ugoqo lwe-condenserUgoqo lwe-condenser
3

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.

Amathuluzi adingekayo:

Umlomo wokufutha wokwenza inkunguUmlomo wokufutha wokwenza inkungu
Isilinda Segesi Ye-NitrogenIsilinda Segesi Ye-Nitrogen
Ipayipi lokusabela eliqhumisiweIpayipi lokusabela eliqhumisiwe
Amagilavu Amelana NokushisaAmagilavu Amelana Nokushisa
4

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 %.

Amathuluzi adingekayo:

Ugoqo lwe-condenserUgoqo lwe-condenser
Amagilavu erabhaAmagilavu erabha
5

Recycle nitrogen and methanol

Draw the nitrogen and the excess methanol out with a membrane (diaphragm) pump and send them round again.

Amathuluzi adingekayo:

Iphampu ye-diaphragmIphampu ye-diaphragm
Isilinda Segesi Ye-NitrogenIsilinda Segesi Ye-Nitrogen

Izinto

2

Amathuluzi Adingekayo

12

Le blueprint yenza

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I-dimethyl terephthalate

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