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Terephthalic Acid: Para-Xylene Oxidised by Air with Manganese and Bromide
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Charlie

19. uMfumfu 2026DE
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Terephthalic Acid: Para-Xylene Oxidised by Air with Manganese and Bromide

Terephthalic acid is the acid half of PET. Both methyl groups of para-xylene are burnt to acid groups by air under pressure in hot acetic acid, with a little manganese salt and bromide as catalyst: the Mid-Century process of Saffer and Barker (US 2,833,816, 1958). The acid does not dissolve, so it is simply filtered off. Example 24 of the patent, all parts by weight. The picture: our diagram of the reactor.
Osezingeni eliphezulu
1 day

Imiyalelo

1

Charge the reactor

Into a corrosion-resistant pressure reactor with a water-cooled condenser on top, put 75 parts para-xylene, 150 parts acetic acid, 1 part manganese acetate (tetrahydrate) and 0.75 part ammonium bromide.

Izinto zokwakha zalesi sinyathelo:

I-Para-XyleneI-Para-Xylene75 parts

Amathuluzi adingekayo:

I-acetic acid (i-glacial)I-acetic acid (i-glacial)
I-Manganese AcetateI-Manganese Acetate
I-Ammonium BromideI-Ammonium Bromide
Isikali sesilinganisoIsikali sesilinganiso
I-reactor yengcindeziI-reactor yengcindezi
Ugoqo lwe-condenserUgoqo lwe-condenser
Izibuko Zokuchitheka KwamakhemikhaliIzibuko Zokuchitheka Kwamakhemikhali
Amagilavu Amelana NamakhemikhaliAmagilavu Amelana Namakhemikhali
2

Pressurise with air and heat to 385 °F

Raise the pressure to 400 psig with air, blown in near the bottom. Set the vent so gas leaves at 3,000 volumes per hour per volume of liquid. Heat to 385 °F (196 °C), then switch the heat off: the reaction heats itself.

Amathuluzi adingekayo:

I-reactor yengcindeziI-reactor yengcindezi
Umcindezeli womoya wezimboniUmcindezeli womoya wezimboni
Ugoqo lwe-condenserUgoqo lwe-condenser
Ithemomitha YaselabhorethriIthemomitha Yaselabhorethri
3

Hold at 385–400 °F

Once the first rush is over, heat as needed to hold 385–400 °F (196–204 °C), 1.5 hours in all. It is finished when the exit gas is back to 20–21 % oxygen (Orsat analysis).

Amathuluzi adingekayo:

I-reactor yengcindeziI-reactor yengcindezi
Ithemomitha YaselabhorethriIthemomitha Yaselabhorethri
Isihlaziyi Segesi Se-OrsatIsihlaziyi Segesi Se-Orsat
4

Cool, empty and filter

Cool to 185 °F (85 °C) and let the pressure off. Push the liquid out at 150–200 °F with nitrogen pressure, scrape out the solid, and filter everything together.

Amathuluzi adingekayo:

Isilinda Segesi Ye-NitrogenIsilinda Segesi Ye-Nitrogen
Ifanela Lengilazi ElinomlomoIfanela Lengilazi Elinomlomo
Iphepha LokuhluzaIphepha Lokuhluza
Amagilavu Amelana NamakhemikhaliAmagilavu Amelana Namakhemikhali
5

Wash and dry

Wash the terephthalic acid twice with hot acetic acid (75 ml each in the example) and dry it. The patent got 115 parts by weight from 100 of para-xylene.

Amathuluzi adingekayo:

I-acetic acid (i-glacial)I-acetic acid (i-glacial)
Ifanela Lengilazi ElinomlomoIfanela Lengilazi Elinomlomo
Iphepha LokuhluzaIphepha Lokuhluza
Ihhavini yokomisaIhhavini yokomisa

Izinto

1

Amathuluzi Adingekayo

15

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Para-Xylene by Three-Stage Crystallisation from Xylene

Para-Xylene by Three-Stage Crystallisation from Xylene

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