Dmt and Terephathalic Acid, Polyester, Pet Resin, Pbt Resin
Global polyester production in all forms is currently around 56 million tones and may cross 100 million in the next decade. Higher capacity addition is estimated in polyester filament and chips segment compared to staple fibres in the next 2-3 years. Indian textile industry has the potential to grow to US $ 220 billion by 2020 from current size of around 80 billion. Besides, the lower per capita consumption of around 5 kg as against global average of 11 kg indicates huge potential for expansion of fibre . Table M-VIII 6.1 gives the details of fibre per capita consumption.
Table M-VIII 6.1: Per capita Fibre Consumption
Kg/per capita | 2000 | 2011 |
North America | 35 | 35 |
Latin America | 7 | 8 |
West Erope | 22 | 24 |
East Europe | 6 | 12 |
Africa/M. east | 3 | 4 |
China | 10 | 20 |
India | 4 | 5 |
Name of the synthetic fiber | Monomer | Basic chemicals | Properties of the synthetic fiber | Characteristics | ||
Dens ity | Mois ture regain | Melting point | ||||
Polyester | Dimethyl Terephthalate and Purified Terephthalic acid (PTA) | p-Xylene, methanol, ethylene glycol | 1.38 | 0.4-0.5 | 250 oC, Sticking point= 240oC | Disintegrate in conc. H2SO4, resistant to alkali, disintegrate in boiling strong alkalies, biological resistance is good, resistance to weak acid and alkali is good. Ironing temperature 135 0C. Tenacity 4.0-7.0 gm/denier, elongations at break 18-22%. |
There are two major steps
Catalytic Oxidation of PX to Make Crude Terephthalic Acid (CTA): This involves oxidation, crystallisation, solvent recovery, filtering, drying etc.
Purification of CTA to make PTA: Involves hydrogenation, crystallization [Amco process], centrifuging, drying, conveying, storage, bagging etc., or by leaching and sublimation [Mobil process]
PTA Manufacturing Process Technology
AMCO Process: Manufacture of terephthalic acid by AMCO process consists of two steps– oxidation of p-xylene to crude terephthalic acid and purification of crude terephthalic acid by crystallisation.
Crude Terephthalic Acid
Pure Terephthalic Acid
Oxidation of P-XYLENE: P-Xylene is oxidised with air at 20 atm pressure and 200-210 oC temperature in presence of catalyst cobalt acetate, manganese acetate and hydrobromic acid as promoter. Reaction involve in manufacturing process is shown in Figure M-VIII 6.1. Figure M-VIII 6.2 illustrates the process technology for PTA.
Figure M-VIII 6.1: Reaction Involve in PTA Manufacturing from P-xylene
Figure M-VIII 6.2: Process Technology for Purified Terephthalic Acid
Henkel has described a process for manufacturing of PTA which is shown in Figure M-VIII 6.3
Henkel I Process
HenKel II Process
Disproportionation
Benzoic acid → Potassium Benzo ate → Di-potassium benzoate
Di-potassium benzoate+ H2SO4 → Purified terepht halic acid
Potassium recovery
Figure M-VIII 6.3: Purified Terephthalic Acid by Henkel Process
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1. What is DMT and how is it used in chemical engineering? |
2. What is the significance of terephthalic acid in the production of polyester? |
3. What is the difference between PET resin and PBT resin? |
4. What are the main applications of polyester? |
5. How is polyester manufactured on an industrial scale? |
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