benzene manufacturing

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PONNALA SWATHI-B130896CH RAHUL CR-B130746CH REGHURAM V-B130245CH

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Page 1: Benzene manufacturing

PONNALA SWATHI-B130896CH

RAHUL CR-B130746CH

REGHURAM V-B130245CH

Page 2: Benzene manufacturing

CONTENTS

Raw Materials

Chemical Reactions

Properties

Flow Chart

Process descriptions

Engineering Problems

Alternate Process for Productions

Page 3: Benzene manufacturing

RAW MATERIALS (HYDRODEALKYLATION )

Hydrodealkylation is the named process for the conversion of

toluene to benzene through reaction with hydrogen gas .

The principal raw materials for the process are obviously:

TOLUENE

HYDROGEN

Note: The above process can be used for preparing naphtha from

alkyl naphthalenes.

Page 4: Benzene manufacturing

CHEMICAL REACTIONS

Toluene adds hydrogen gas to produce benzene

and methane.

2C6H5CH3 + H2 --------------> C6H6 + CH4

Dimethyl benzenes undergo similar reactions with

2 moles of hydrogen.

C6H4(CH3)2 + 2H2-------------> C6H6+2CH4

Page 5: Benzene manufacturing

Properties of benzene

Molar mass : 78.11g/mole

Appearance: It is a colourless liquid with an odour

similar to that of most gasoline compounds.

Density: 0.8765 g/ cu.cm

Melting point: 278.68K

Boiling point:353.2K

Solubility: Soluble in chloroform, alcohols and

organic solvents.

Page 6: Benzene manufacturing

Flow chart:

Page 7: Benzene manufacturing

PROCESS DESCRIPTION:

Hydrodealkylation of toluene can be operated under

catalytic or thermal conditions. Catalytic process requires

milder conditions of 600-650oC and lower pressures

whereas the thermal process requires temperatures above

800oC.

Toluene is mixed with heavier aromatics or paraffins from

the benzene fractionation column.

The make up gas rich in hydrogen is compressed with

recycle gas and mixed with the liquid toluene stream.

The combined feed is then preheated using heat

exchange and then into a fired preheater before being

charged into the reactor.

Page 8: Benzene manufacturing

The reactor effluents are cooled by heat exchange

and then by water before being sent to a separator.

The liquid and gas components are separated here.

The gas containing methane and remaining hydrogen

is either used directly as fuel or as a source of

methane.

The liquid is then sent to a stripping column where

residual gases are also removed.

The gas free liquid is then sent into the fractionator

where benzene is separated out.

Page 9: Benzene manufacturing

Engineering Problems:

Reactor design: Catalytic processes were first utilised first

,operating at 600-650oC and pressure 35-40 atms.

Economic balances in yield include residence

time,temperature and reaction rates.Comparitive yields

were obtained at higher temperatures and pressures.

Hydrogen problems: The use of hydrogen requires

explosion-proof plant construction and its use at high

reaction conditions need use of chrome steel to avoid

embrittlement.

Page 10: Benzene manufacturing

Other processes

Catalytic Reforming: Catalytic reforming involves the dehydrogenation of naphthenes to aromatics, or the isomerization of alkyl naphthenes and the dehydrogenation of them.

Toluene disproportionation: Alkylated aromatics are trans alkylated to produce benzene and alkylated benzenes.

Pyrolysis gasoline distillation to remove benzene and diolefins.

Page 11: Benzene manufacturing

USES OF BENZENE

Benzene is mainly used as intermediate to make

their chemicals, most important of which include

cumene, ethyl benzene and cyclohexane.

It finds extensive use in producing precursors for

plastics, resins, rubber, pesticides, explosive

lubricant, detergents and fibres.

Page 12: Benzene manufacturing

EXPOSURE AND HEALTH HAZARDS

• Benzene increases the risk of cancer and other illnesses, also

causing bone marrow failure ,aplastic anaemia, acute leukaemia

and related diseases in substantial amounts.

• It targets liver, kidney,lung,heart and the brain and can cause

DNA strand breaks.

Page 13: Benzene manufacturing

Vapours from products that contain benzene such as

glues,paints,furniture,detergents etc. can also be a source of

exposure.

Exposure of the general population to benzene occurs while

breathing ,the major sources being tobacco smoke and

automobile service stations .

Certain batches of soft drinks manufactured across various

parts of the world have been found to contain benzene levels

above the limits prescribed by the world health organisation.

Page 14: Benzene manufacturing

THANK

YOU