Higher Institute of Engineering and Technology in Tanta

Chemical engineering Department

Petrochemical Industries (CHE361)
Lecture (2)

Lecture (2)

Raw materials used in petrochemical industries

Raw materials used in petrochemical industries

synthesis gas Olefines BTX

coal and
vegetable oils

Synthesis gas (syn gas) :

Is a mixture of CO and H2 obtained either by steam reforming of Natural gas orby partial oxidation
of Natural gas , Naphtha or heavy oil fuel .

The steam reforming process:

CH 4 + H 2O → CO + 3H 2
Uses of Synthesis gas (syn gas) :

✓ It is mainly used in manufacture of Ammonia which is used in fertilizers production .

✓ It is mainly used also in methanol production .

Olefines :

They are un saturated hydrocarbon obtained by steam cracking, hydrolysis ,pyrolysis of ethane ,
naphtha ,heavy oil , crude oil , paraffine hydrocarbons of petroleum thermal cracking and
dehydrogenation

𝑻𝒉𝒆𝒓𝒎𝒂𝒍 𝒄𝒓𝒂𝒄𝒌𝒊𝒏𝒈
𝑪𝟐 𝑯𝟔 → 𝑪𝟐 𝑯𝟒 + 𝑯𝟐
Olefines are considered a link between un reactive Paraffinic hydrocarbons (ethane , naphtha
,heavy oil) of petroleum and petrochemical industries .
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 Higher Institute of Engineering and Technology in Tanta
Chemical engineering Department
Petrochemical Industries (CHE361)
Lecture (2)

Olefines are main block of petrochemical industry .

petroleum
productes

Olefines :

petrochemical
industry

Olefines have double bond un saturated reactive compounds so that they want to achieve
saturation .

BTX(Aromatic BTX)

BTX

Bezene(C6) Toluene (C7) Xylene (C8)

(Benzene , toluene and Xylene ) the most important aromatic hydrocarbon used to produce
aromatic petrochemicals . although they are present in petroleum but the main source is catalytic
reforming streams.

catalytic reforming is partial conversion of paraffins to produce aromatic compounds of naphtha

to aromatic (6,7,8)(BTX)

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 Higher Institute of Engineering and Technology in Tanta
Chemical engineering Department
Petrochemical Industries (CHE361)
Lecture (2)

catalytic reforming:
is a process at which conversion of paraffinic compounds specially (Naphtha fractions ) to
aromatics with higher octane number using (PT) catalyst .

✓ catalytic reforming is also mean to obtain higher octan number of gasoline .

Acetylene (C₂H₂):
✓ Acetylene (C₂H₂) is the simplest and best-known member of the hydrocarbon series
containing one or more pairs of carbon atoms linked by triple bonds, called the acetylenic
series, or alkynes.
✓ It is an organic compound a colorless, highly flammable gas with a distinct odor.
✓ It is the simplest alkyne, characterized by a triple bond between two carbon atoms.
✓ Acetylene is commonly used as a fuel and chemical building block, especially in welding
and cutting due to its high combustion temperature when mixed with oxygen.

Figure 1: Acetylene

physical properties of acetylene (C₂H₂) listed in points:

✓ Molecular formula: C₂H₂

✓ Molecular weight: 26.04 g/mol
✓ Appearance: Colorless gas
✓ Odor: Distinct, garlic-like odor when impure
✓ Melting point: −80.8°C (liquid state)
✓ Boiling point: −84°C at 1 atm
✓ Density: 1.097 g/L at 0°C (slightly lighter than air)
✓ Solubility: Sparingly soluble in water; more soluble in organic solvents like acetone or
ethanol
✓ Flammability: Highly flammable; forms explosive mixtures with air

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 Higher Institute of Engineering and Technology in Tanta
Chemical engineering Department
Petrochemical Industries (CHE361)
Lecture (2)

✓ Autoignition temperature: 305°C (ignition occurs without a flame or spark)

✓ Explosive limits in air: 2.5% – 82% by volume
✓ Critical temperature: 35.18°C
✓ Critical pressure: 61.4 atm
✓ Triple bond: Contains a carbon-carbon triple bond, making it highly reactive
✓ Heat of combustion: Very high (around 1300°C in oxygen combustion)

These properties make acetylene useful but also require careful handling due to its flammability
and explosiveness.

chemical properties of acetylene (C₂H₂) listed in points:

✓ Unsaturated hydrocarbon:

Acetylene is an alkyne, characterized by a carbon-carbon triple bond, making it highly reactive.

✓ Combustion:

✓ Burns with a smoky, luminous flame in air.

✓ Produces a very high flame temperature (around 3300°C) in oxygen, useful for welding.
✓ Combustion reaction:

𝑪𝟐 𝑯𝟐 + 𝟓𝑶𝟐 → 𝟒𝑪𝑶𝟐 + 𝟐𝑯𝟐 𝑶 + 𝑯𝑬𝑨𝑻

✓ Polymerization:

Under certain conditions, acetylene can polymerize to form larger molecules such as benzene or
polyacetylene.

✓ Hydrogenation:

Acetylene reacts with hydrogen (H₂) in the presence of a catalyst (such as palladium or nickel) to
form ethylene (C₂H₄) or ethane (C₂H₆), depending on the reaction conditions.

✓ Partial hydrogenation:

𝑪𝟐 𝑯𝟐 + 𝑯𝟐 → 𝑪𝟐 𝑯𝟒

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 Higher Institute of Engineering and Technology in Tanta
Chemical engineering Department
Petrochemical Industries (CHE361)
Lecture (2)

✓ Complete hydrogenation:

𝑪𝟐 𝑯𝟐 + 𝟐𝑯𝟐 → 𝑪𝟐 𝑯𝟔

✓ Addition reactions:

The triple bond in acetylene makes it reactive towards addition reactions with halogens, hydrogen
halides, and other electrophiles.

✓ Halogenation:

Acetylene reacts with chlorine or bromine to form di-haloalkenes or tetra-haloalkanes.

✓ Hydrohalogenation:

Acetylene reacts with hydrogen halides (HCl, HBr) to form vinyl halides.

𝑪𝟐 𝑯𝟐 + 𝑯𝑪𝒍 → 𝑪𝟐 𝑯𝟐 𝑪𝑯𝑪𝒍

✓ Acidic nature:

The hydrogen atoms in acetylene are slightly acidic (pKa ≈ 25), allowing it to react with strong
bases (like sodium amide, NaNH₂) to form acetylide anions (C₂²⁻).

𝑪𝟐 𝑯𝟐 + 𝑵𝒂𝑵𝑯𝟐 → 𝑵𝒂𝑪𝟐 𝑯 + 𝑵𝑯𝟑

✓ Explosiveness:

Acetylene can decompose explosively, especially under high pressure or in the presence of certain
metal catalysts (e.g., copper), releasing large amounts of energy.

✓ Reactivity with metals:

Forms acetylides when reacted with metals such as copper, silver, or gold, which are often highly
sensitive and explosive.

These properties make acetylene highly versatile in chemical synthesis, but also require careful
handling due to its reactivity and explosiveness.

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 Higher Institute of Engineering and Technology in Tanta
Chemical engineering Department
Petrochemical Industries (CHE361)
Lecture (2)

Applications of Acetylene :

✓ Oxy-acetylene welding and cutting:

Acetylene is widely used in combination with oxygen to produce a flame with a high temperature
(around 3300°C), ideal for welding, cutting, and brazing metals.

✓ Chemical synthesis:

✓ Acetylene is a key raw material in the production of various chemicals, such as

vinyl chloride (for PVC), acetaldehyde, and acrylonitrile.
✓ Used to produce ethylene and ethylene derivatives via hydrogenation.

✓ Plastic and polymer production:

Acetylene is used to synthesize polymers such as polyvinyl chloride (PVC) and other plastics and
resins.

✓ Synthesis of vinyl compounds:

Acetylene reacts with hydrogen chloride to produce vinyl chloride, a precursor for PVC.

𝑪𝟐 𝑯𝟐 + 𝑯𝑪𝒍 → 𝑪𝟐 𝑯𝟐 𝑪𝑯𝑪𝒍

✓ Lighting (historical use):

Acetylene was once used in carbide lamps, particularly in mining, caving, and marine buoys, due
to its bright, white flame when burned.

✓ Synthesis of acetylenic compounds:

Used in the production of acetylenic chemicals, which are important intermediates in

pharmaceuticals, agrochemicals, and specialty chemicals.

✓ Polymerization reactions:

Acetylene is used in producing butadiene, a key ingredient in synthetic rubber, and can be
polymerized to produce polyacetylene, a conducting polymer.

✓ Rocket propulsion:

Acetylene has been considered as a fuel for rockets due to its high energy content.

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 Higher Institute of Engineering and Technology in Tanta
Chemical engineering Department
Petrochemical Industries (CHE361)
Lecture (2)

✓ Metal production:

Acetylene is used to manufacture acetylides, compounds where acetylene reacts with metals such
as copper, silver, or gold.

These applications highlight the versatility of acetylene in industries such as manufacturing,

chemicals, and materials science.

Safety of Acetylene :

Acetylene can form explosive mixtures with air, so its handling requires strict safety measures. It
is typically stored in special cylinders containing a porous material and a solvent (like acetone) to
stabilize it.

1. Flammability:

Acetylene is highly flammable and can form explosive mixtures with air (flammability range:
2.5% to 100% by volume). Avoid open flames, sparks, and heat sources.

2. Storage:

Store acetylene cylinders upright in well-ventilated areas, away from heat sources and oxidizing
agents. Use proper storage racks and secure cylinders to prevent tipping.

3. Leak Detection:

Acetylene is colorless and has a distinctive garlic-like odor. Implement leak detection systems and
regularly inspect equipment for leaks.

4. Inhalation Hazards:

High concentrations of acetylene can cause dizziness, headache, and respiratory distress. Ensure
adequate ventilation and use respiratory protection in confined spaces.

5. Personal Protective Equipment (PPE):

Wear appropriate PPE, including safety goggles, gloves, and flame-resistant clothing, when
handling acetylene.

6. Emergency Procedures:

Establish and communicate emergency procedures for leaks, spills, or fires. Train personnel to
respond effectively to such incidents.

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 Higher Institute of Engineering and Technology in Tanta
Chemical engineering Department
Petrochemical Industries (CHE361)
Lecture (2)

7. Transport Regulations:

Comply with regulations for transporting acetylene as a flammable gas. Ensure proper labeling,
packaging, and handling during transportation.

8. Environmental Concerns:

Acetylene can contribute to air pollution. Implement measures to minimize emissions and releases
into the environment.

9. First Aid Measures:

In case of exposure, move affected individuals to fresh air immediately and seek medical attention
if symptoms persist. For skin contact, wash with soap and water.

10. Training and Awareness:

Ensure all personnel who work with or around acetylene are properly trained in its hazards and
safe handling practices.

By adhering to these safety considerations, the risks associated with handling acetylene can be
minimized.

Production of Acetylene :

Acetylene is typically produced by the reaction of calcium carbide (CaC₂) with water or through
the cracking of hydrocarbons.

production of acetylene using the cracking of hydrocarbons :

The production of acetylene through the cracking of hydrocarbons is a process where high-
temperature pyrolysis (thermal cracking) breaks down hydrocarbons, such as methane or other
light hydrocarbons, to produce acetylene.

steps:

1. Feedstock:

Light hydrocarbons like methane (CH₄) or ethane are used as raw materials.

2. High-Temperature Pyrolysis:

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 Higher Institute of Engineering and Technology in Tanta
Chemical engineering Department
Petrochemical Industries (CHE361)
Lecture (2)

The feedstock is subjected to extremely high temperatures (around 1500°C) in the absence of
oxygen, causing the hydrocarbons to break down into smaller molecules.

3. Formation of Acetylene:

Under these conditions, hydrocarbons decompose, and acetylene (C₂H₂) is formed as a major
product along with other byproducts like ethylene and hydrogen.

4. Quenching:

The hot gas mixture is rapidly cooled (quenched) to stop further reactions and prevent the
decomposition of acetylene.

This method is often employed in large-scale industrial production due to its efficiency in
generating acetylene from hydrocarbons.

production of hydrocarbons from acetylene :

The production of hydrocarbons from acetylene is typically achieved through catalytic

hydrogenation or polymerization processes. Acetylene, being a highly reactive compound with a
triple bond, can easily be converted into various hydrocarbons. Here are two common methods:

1. Hydrogenation of Acetylene:

In the hydrogenation process, acetylene (C₂H₂) reacts with hydrogen (H₂) in the presence of a
metal catalyst (usually palladium, nickel, or platinum) to form saturated hydrocarbons.

✓ Partial Hydrogenation:

✓ Acetylene can be partially hydrogenated to form ethylene (C₂H₄):

𝑪𝟐 𝑯𝟐 + 𝑯𝟐 → 𝑪𝟐 𝑯𝟒

✓ Complete Hydrogenation:

✓ Further hydrogenation of acetylene or ethylene produces ethane (C₂H₆):

𝑪𝟐 𝑯𝟐 + 𝟐𝑯𝟐 → 𝑪𝟐 𝑯𝟔

This process is widely used in the petrochemical industry to produce ethylene and ethane, which
are precursors for plastics and other chemicals.

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 Higher Institute of Engineering and Technology in Tanta
Chemical engineering Department
Petrochemical Industries (CHE361)
Lecture (2)

2. Polymerization of Acetylene:

Acetylene can undergo polymerization to form larger hydrocarbons, such as butadiene, benzene,
or more complex hydrocarbon compounds. In this process, acetylene molecules combine through
controlled reactions, often using metal catalysts.

✓ Example: Two acetylene molecules can dimerize to form vinylacetylene (C₄H₄), which can
be further processed into other hydrocarbons like butadiene, a key material for producing
synthetic rubber.

𝑪𝒂𝒕𝒂𝒍𝒚𝒔𝒕
𝟐 𝑪𝟐 𝑯𝟐 → 𝑪𝟒 𝑯𝟒

These processes make acetylene an important starting material for a wide range of hydrocarbons
used in the chemical industry.

Questions on lecture (2)

Answer the following questions:
1. Defined the following:
✓ Raw materials used in petrochemical industries
✓ Synthesis gas.
✓ BTX.
✓ catalytic reforming
2. write short notes on the chemical properties of Acetylene .
3. what are the applications of Acetylene ?
4. what are the common methods for hydrocarbons production from Acetylene ?

Best wishes
Asso.Prof :Wafaa Ahmed

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