Higher Institute of Engineering and Technology in Tanta

Chemical engineering Department

Petrochemical Industries (CHE361)
Lecture (10)

Lecture (10)

Continued conversion processes for selected petrochemicals

Terephthalic Acid:

Terephthalic Acid (TPA) is an organic compound widely used as a precursor in the production of
polymers, especially polyethylene terephthalate (PET). It is a white, crystalline solid with the
chemical formula C₆H₄(COOH)₂.

Applications

1. Polyester Production:
o Primary use is as a monomer in the production of PET (polyethylene
terephthalate).
o PET is used in fibers for textiles, bottles, and food packaging.
2. Engineering Plastics:
o Terephthalic acid is used in manufacturing polybutylene terephthalate (PBT) and
other polyester resins.
3. Coatings and Films:
o As a component in the production of coatings, films, and high-performance
adhesives.
4. Pharmaceuticals and Dyes:
o Used in some chemical syntheses for pharmaceuticals and organic dyes.

Advantages of Terephthalic Acid

• High chemical purity (especially in PTA form) leads to superior polymer performance.
• Stable and versatile, suitable for a wide range of polyester applications.
• Recyclable: PET-based products can be recycled into TPA for reuse.

Environmental and Safety Considerations

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 Higher Institute of Engineering and Technology in Tanta
Chemical engineering Department
Petrochemical Industries (CHE361)
Lecture (10)

• Toxicity: Generally low, but excessive exposure to dust can cause respiratory irritation.
• Sustainability: Increasing interest in bio-based production of TPA from renewable
resources like biomass or sugars.
• Recycling: PET recycling loops help reduce reliance on virgin terephthalic acid.

Production Methods

Oxidation of p-Xylene (most common industrial process):

1. Feedstock: p-Xylene is oxidized with air in the presence of a catalyst (e.g., cobalt and
manganese salts combined with bromides) in acetic acid as a solvent.
2. Conditions: The reaction is carried out at elevated temperatures (~180–220°C) The
reaction temperature varies with the source of oxygen, i.e., whether from air or pure
oxygen.Usually, air is used as the cheapest source of oxygen .and pressures (20–30 atm).
3. Intermediate Formation: p-Toluic acid is initially formed, which further oxidizes to
terephthalic acid.
4. Purification: The crude terephthalic acid (CTA) is purified by hydrogenation to remove
impurities like 4-carboxybenzaldehyde, yielding purified terephthalic acid (PTA).

Steps :

➢ In this process, p xylene is used as the feed , which is oxidized in the presence of a cobalt
sulfate catalyst supplied as a solution of acetic acid to a reactor where air or pure oxygen
is blown through a sparger .
➢ The product mixture is then passed to a vapour liquid separator. Liquid containing
terephthalic acid and catalyst slurry is then separated by a centrifugal separator.
➢ After drying, dimethyl terephthalate (DMT) ester is drawn as the final product, which can
be converted to acid form in the presence of water in the PET plant.

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 Higher Institute of Engineering and Technology in Tanta
Chemical engineering Department
Petrochemical Industries (CHE361)
Lecture (10)

Terephthalic acid from p-xylene

Ethylene Glycol:

Ethylene Glycol (EG) is a simple organic compound widely used as a raw material in the
production of polyesters and as an antifreeze agent in cooling systems. Its chemical formula is
C₂H₆O₂.

Applications:

1. Polyester Manufacturing:
o A primary raw material in producing polyethylene terephthalate (PET), used for
fibers, textiles, and bottles.
2. Antifreeze and Coolants:
o Used in automotive and industrial cooling systems due to its ability to lower the
freezing point and raise the boiling point of water.

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 Higher Institute of Engineering and Technology in Tanta
Chemical engineering Department
Petrochemical Industries (CHE361)
Lecture (10)

3. De-icing Agent:
o Applied to aircraft and runways to prevent ice formation.
4. Hydraulic and Brake Fluids:
o Utilized in formulating industrial fluids due to its low volatility and high boiling
point.
5. Industrial Solvent:
o Employed in various chemical formulations as a solvent for paints, inks, and
plastics.
6. Heat Transfer Agent:
o Used in geothermal and solar power systems for heat exchange.

Advantages

• Thermal Properties: Effective in heat transfer applications.

• Chemical Reactivity: Versatile in producing polymers and other derivatives.
• Availability: Economically viable due to established production methods.

Environmental and Safety Considerations:

1. Toxicity:
o Toxic if ingested; ingestion can lead to metabolic acidosis and kidney damage.
o Sweet taste increases the risk of accidental poisoning, especially in animals and
children.
2. Biodegradability:
o Ethylene glycol is readily biodegradable in the environment, breaking down into
carbon dioxide and water.
3. Recycling:
o Antifreeze containing ethylene glycol can be recycled for reuse, reducing
environmental waste.

Production Methods:

Ethylene glycol is manufactured by catalytic oxidation of ethylene followed by hydration to

glycol .
✓ High purity ethylene is converted to ethylene oxide in the presence of silver oxide as the
catalyst in a tubular reactor .
✓ Air or pure oxygen may be used for the reaction. Ethylene dichloride is dosed in the
reactor in very small amounts to avoid ethylene combustion.

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 Higher Institute of Engineering and Technology in Tanta
Chemical engineering Department
Petrochemical Industries (CHE361)
Lecture (10)

✓ Ethylene oxide and unconverted ethylene are scrubbed with water and unconverted
ethylene is recycled.
✓ Operating temperature 250°C−300°C
✓ Operating pressure of 1 atm.
Chemical reaction :

Figure (6) Ethylene Glycol production flow sheet

Polystyrene:
Polystyrene is a versatile synthetic polymer made from the monomer styrene.
a liquid hydrocarbon derived from petroleum or natural gas.
It is widely used in various industries due to its lightweight, rigid, and easily moldable properties.
Polystyrene exists in both solid and foam forms, each with distinct applications.

Types of Polystyrene:

1. General-Purpose Polystyrene (GPPS):

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 Higher Institute of Engineering and Technology in Tanta
Chemical engineering Department
Petrochemical Industries (CHE361)
Lecture (10)

oClear, rigid, and brittle

oCommonly used in disposable utensils, CD cases, and laboratory equipment.
2. High-Impact Polystyrene (HIPS):
o Modified with polybutadiene rubber for better impact resistance
o Used in products requiring durability, such as toys and refrigerator liners.
3. Expanded Polystyrene (EPS):
o Foam form created by expanding polystyrene beads
o Lightweight, excellent insulator, widely used in packaging and building
insulation.
4. Extruded Polystyrene (XPS):
o Denser foam form
o Often used in structural insulation.

Applications:

• Packaging: For food containers, protective packaging for electronics, and other goods.
• Construction: Insulation panels, lightweight concrete, and under-slab void formers.
• Consumer Products: Disposable cups, plates, and cutlery.
• Industrial Use: Molded parts, casings, and model prototypes.

Environmental Concerns:

Polystyrene is not biodegradable and can persist in the environment for centuries. Its disposal
contributes to pollution, particularly in marine ecosystems.

Recycling efforts are limited due to economic and logistical challenges, but initiatives for reuse
and alternative materials are being explored.

the mass polymerization method:

Polymerization of styrene can be done by mass, solution, emulsion, or suspension

polymerization methods .

➢ In the mass polymerization method , styrene is heated at 80°C− 85°C in a batch reactor
under nitrogen pressure.
➢ The conversion is 30%−40% in a long residence time , ranging from 40 to 50 h. This is
suitable for small production units.
➢ Since no catalyst or initiator is used, this polymer is suitable for electrical insulation.
➢ In the emulsion polymerization method, a stirred tank autoclave is employed, in which
styrene and water are emulsified with an initiator. The product is then separated from
unreacted monomers, which are then recycled.

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 Higher Institute of Engineering and Technology in Tanta
Chemical engineering Department
Petrochemical Industries (CHE361)
Lecture (10)

solution polymerization method :

In the solution polymerization method , styrene and a solvent are mixed in a stirred tank blender
followed by pumping through a series of reactors with heating facilities.
batch suspension polymerization process :
In a batch suspension polymerization process , drops of styrene are dispersed in water in the
presence of a benzoyl peroxide initiator.
Polytetrafluoroethylene:
Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene, widely
recognized for its exceptional chemical resistance, low friction, and non-stick properties.
It is commonly known by the brand name Teflon, which was introduced by DuPont.

Applications:

1. Cookware:
o Non-stick coatings on pans, bakeware, and other kitchen utensils.
2. Industrial Use:

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 Higher Institute of Engineering and Technology in Tanta
Chemical engineering Department
Petrochemical Industries (CHE361)
Lecture (10)

o Gaskets, seals, and linings in chemical processing industries due to its chemical
inertness.
o Bearings, bushings, and gears in applications requiring low friction.
3. Electronics:
o Insulation for wires and cables, particularly in high-temperature environments.
4. Medical Devices:
o Used in implants and catheters due to its biocompatibility.
5. Aerospace and Automotive:
o Used in seals, bearings, and components exposed to harsh conditions.
6. Other Uses:
o Coatings in textiles for stain resistance, and in pipes or tubes to prevent corrosion.

Advantages of PTFE (Polytetrafluoroethylene) in Brief:

1. Chemical Resistance: Inert to most chemicals.

2. Non-Stick: Prevents adhesion of materials.
3. Low Friction: Excellent for reducing wear in moving parts.
4. High-Temperature Resistance: Operates from -200°C to +260°C.
5. Electrical Insulation: Superior insulator, even at high frequencies.
6. Water and Oil Repellence: Hydrophobic and oleophobic.
7. UV and Weather Resistant: Durable in harsh environments.
8. Biocompatibility: Safe for medical applications.
9. Non-Flammable: Enhances safety.
10. Long Service Life: Durable and low-maintenance.

Limitations:

1. Mechanical Weakness: PTFE is relatively soft and can deform under high pressure or
load.
2. Processing Difficulty: It is not easy to mold or fabricate due to its high melting point and
stability.
3. Environmental Concerns: Decomposition of PTFE at extremely high temperatures
(>400°C) can release toxic fluorinated gases.

PTFE remains a material of choice in demanding applications where durability, chemical

resistance, and non-reactivity are critical.

Production of the tetrafluoroethylene (C2F4 ) monomers :

➢ This monomer is prepared from methanol chlorination followed by fluorination .

➢ The reactions are carried out in three reactors.
➢ Trichloromethane produced in the chlorinator is reacted with hydrofluoric acid in the first
reactor at about 65°C in the presence of SbCl5 as the catalyst and is converted to produce

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 Higher Institute of Engineering and Technology in Tanta
Chemical engineering Department
Petrochemical Industries (CHE361)
Lecture (10)

mono chloro difluoromethane (CHF2Cl) in the presence of AlCl3 as the catalyst in the
second reactor.

Production of polymer :

➢ In the third reactor, CHF2Cl is then converted to C2F4 by catalytic pyrolysis at a temperature
of 650°C−800°C in the presence of platinum (Pt) as the catalyst.
➢ Polymerization of C2 F4 is then carried out in a batch reactor preferably by the suspension
polymerization method at a temperature of 200°C and at a pressure of 1000 psi. The
reaction time is about 1 h.
Questions on lecture (10)
Answer the following questions:
1. write short notes on the Applications of Terephthalic Acid.
2. Write the steps of Production Method for Terephthalic Acid.
3. Draw the flow sheet of Terephthalic acid from p-xylene
4. write short notes on the advantages and disadvantages of Ethylene Glycol.
5. write the Chemical reaction of Ethylene Glycol production .
6. Draw the flow sheet of Ethylene Glycol production .
7. write short notes on the advantages and disadvantages of Teflon
Best wishes
Asso.Prof :Wafaa Ahmed