CPI201T 12 PetroChemical Industry

7/29/2019 CPI201T 12 PetroChemical Industry

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CHEMICAL PROCESS INDUSTRIES

CPI 201T-11

Petrochemical Industry2012

By

Dr Alex SofianosBsc Chem Eng, Msc, PhD Ind Chem (GERMANY), MBL

(UNISA)


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Course Contents

1. Introduction

2. Inorganic Bulk Commodity Chemicals

3. Synthesis Gas Processes

4. Petroleum Refining5. Polymerisation and Petrochemicals

6. Organic Chemical Process Industries

7. Cement, Glass, Dyes Manufacturing

8. Hydrometallurgical Processes

9. Environmental Issues and Green Chemistry

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Inorganic Bulk Chemicals

Sulphuric Acid Contact Process

Phosphoric Acid Lurgi- Fisons Process

Ammonia Haber-Bosch Process

Nitric Acid Ostwald Process

Urea and Fertilizers

Sodium Hydroxide Chloralkali Process

Chlorine Chloralkali Process

Soda Ash Solvay Process

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Synthesis Gas Processes

Synthesis Gas Production

Coal Gasification

Steam Reforming of Methane

Water Gas Shift Reaction

Fischer-Tropsch Process

Methanol Synthesis Methanol Conversion to Chemicals

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Petroleum Refining

Petroleum refining processes are those chemicalengineering processes and other facilities used in

petroleum refineries (also referred to as oil refineries).

The purpose is to transform crude oilinto useful

products such as liquefied petroleum gas (LPG),

gasoline orpetrol,

kerosene,

jet fuel,

diesel oiland

fuel oils.

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Petrochemistry

Petrochemistry is a science that can readily be applied tofundamental human needs, such as health, hygiene,

housing and food.

Inventive business sector, constantly adapting to new

environments and meeting new challenges. Chemicals derived from petroleum or natural gas -

petrochemicals - are an essential part of the chemical

industry today.

Petrochemistry is a fairly young industry; it only started togrow in the 1940s, more than 80 years after the drilling of

the first commercial oil well in 1859.

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Petrochemistry (2)

During World War II, the demand for synthetic materials toreplace costly and sometimes less efficient products

caused the petrochemical industry to develop into a major

player in today's economy and society

Before then, it used to be a tentative, experimental sector,starting with basic materials: synthetic rubbers in the

1900s,

Bakelite, the first petrochemical-derived plastic in 1907,

the first petrochemical solvents in the 1920s,

polystyrene in the 1930s...

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Petrochemistry (3) Petrochemistry then moved to an incredible variety of

areas - from household goods (kitchen appliances, textile,furniture) to medicine (heart pacemakers, transfusion

bags), from leisure (running shoes, computers...) to highly

specialised fields like archaeology or crime detection.

Petrochemicals do not reach the final consumer - the manin the street; they are first sold to customer industries,

undergo several transformations, and finally go into

products that seem to bear no relation whatsoever to the

initial raw material.

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Petrochemistry (4) The result is: few make the connection between the

petrochemical industry and their GP's equipment,

their CDs,

food packaging or computers;

few realise the amount of scientific efforts that went into

these commonplace objects. Although benefiting daily

from end products that have been made thanks to theinput of the petrochemical industry,

Mostly no obvious connection between these everyday

commodities and petrochemistry.

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Petrochemical Industry

Petrochemicals are chemicals made from raw

materials with origin mainly crude oil and gasOnly about five percent of the oil and gas consumed

each year is needed to make all the petrochemical

products.

The rest Petrol, Diesel, lubricants etc.

Petrochemicals have had a dramatic impact on our

food, clothing, shelter and leisure.

Some synthetics, tailored for particular uses, actuallyperform better than products made by nature because

of their unique properties,

example: natural rubbervs synthetic rubber10


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Gallons per barrel (bbl) of petroleum or related products = 42

Barrels of Crude Oil per Metric Ton = 7.33; 1 bbl = 159 litres

U.S. Gallons to litres = 3.785


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Overview of the Petrochemicals Industry Petrochemicals are chemicals made from raw

materials with origin

Petroleum (crude oil) and/or

Natural gas

Petroleum and natural gas are made up of

hydrocarbon molecules,These consist of one or more carbon atoms, to which

hydrogen atoms are attached: (C H) n

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Overview of the Petrochemicals Industry Currently, oil and gas are the main sources of the raw

materials:

because they are the least expensive,

most readily available, and

can be processed most easily into the primary

petrochemicals

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Raw Materials & Feedstocks

Primary Petrochemicals

Petrochemical Intermediates

Derivatives

End Product - Petrochemicals


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Petrochemical Plant Feedstocks

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Major hydrocarbon sources used in

producing petrochemicals are:1. Methane, ethane, propane and butanes:

Obtained primarily from natural gas processing

plants.

2. Naphtha obtained from petroleum refineries.3. Benzene, toluene and xylenes, referred to as BTX

aromatics obtained from petroleum refineries by

extraction from the reformate produced in

catalytic reformers.4. Gas oil obtained from petroleum refineries.


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Petrochemical plant

feedstock sources

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Petrochemical Plant Feedstocks

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Methane and BTX aromatics are used directly as

feedstocks for producing petrochemicals. Ethane, propane, butanes, naphtha and gas oil

serve as optional feedstocks for steam-assisted

thermal cracking plants referred to as steam

crackers that produce these intermediatepetrochemical feedstocks:

ethylene

propylene

n-butenes and butadiene (C4 fraction) Benzene

In 2007, the amounts of ethylene and propylene

produced in steam crackers were about 115 Mt

(megatonnes) and 70 Mt, respectively.


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Primary Petrochemicals

"Primary Petrochemicals" include: olefins (ethylene, propylene and butadiene)

aromatics (benzene, toluene, and xylenes); and

methanol.

Olefins are unsaturated molecules of carbon (C) and

hydrogen (H) that appear as short chains, of two, three or

four carbons in length.

Aromatics contain a six carbon ring structure. The oxygen/hydrogen (OH) group in methanoldenotes that

it is an alcohol.

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Petrochemical Intermediates &

Derivatives

Petrochemical intermediates: generally produced by chemical conversion of primary

petrochemicals to form more complicated derivative

products

Petrochemical derivative products can be made in a varietyof ways:

directly from primary petrochemicals;

through intermediate products which still contain only

carbon and hydrogen;

through intermediates which incorporate chlorine, nitrogen

or oxygen in the finished derivative.

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Derivatives

Petrochemical intermediates: In some cases, they are finished products; in others,

more steps are needed to arrive at the desired

composition.

Of all the processes used, one of the most important is

Polymerization.

It is used in the production ofplastics, fibers and

synthetic rubber; the main finishedpetrochemicalderivatives.

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Derivatives

Typical Petrochemical intermediates:vinyl acetate for paint (PVA), paper and textile coatings

vinyl chloride for polyvinyl chloride (PVC) - plastics

resin manufacture

ethylene glycol for polyester textile fibers

styrene which is important in rubber and plastic

manufacturing

Formaldehyde (from methanol); Phenol-formaldehydepolymers (resins) for glue

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Petrochemicals Produced from

Ethylene


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Propylene


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Benzene


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Toluene


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Xylenes


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Benzene


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Example 1


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Introduction to Polymerization

Polymers are a large class of materials consisting of manysmall molecules (called monomers) that can be linked

together to form long chains, thus they are known as

macromolecules.

The picture below is a short section of such a chain. A

typical polymer may include tens of thousands of

monomers. Because of their large size, polymers are

classified as macromolecules.

Humans have used polymers for centuries in a variety of

applications, in the form of oils, tars, resins, and gums.


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During the industrial revolution modern polymer industrybegan to develop.

In the late 1830s, Charles Goodyear succeeded in

producing a useful form of natural rubber through a

process known as "vulcanization."

Some 40 years later, Celluloid (a hard plastic formed from

nitrocellulose) was successfully commercialized.

In the 1930s, new materials such as vinyl, neoprene,

polystyrene, and nylon were developed.

The introduction of these revolutionary materials began anexplosion in polymer research that is still going on today.


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Unmatched in the diversity of their properties, polymerssuch as cotton, wool, rubber, Teflon(tm), and all plastics

are used in nearly every industry.

Natural and synthetic polymers can be produced with a

wide range of stiffness, strength, heat resistance, density,

and even price.

With continued research into the science and applications

of polymers, they are playing an ever increasing role in

society.

The following sections provide an introduction to thescience of macromolecules.


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Chain-Growth Polymerization

Chain-growth (or Addition) polymerization is apolymerization technique where unsaturated

monomer molecules add on to a growing polymer

chain one at a time

It can be represented with the chemical equation:

n.M (monomer) (-M-)n (polymer)

where n is the degree of polymerization.

Example: n CH2 = CH2 - (CH2 - CH2 )n -


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Chain-Growth Polymerization

The most common type of addition polymerization is freeradical polymerization.

Afree radicalis simply a molecule with an unpaired

electron.

The tendency for this free radical to gain an additional

electron in order to form a pair makes it highly reactive so

that it breaks the bond on another molecule by stealing an

electron, leaving that molecule with an unpaired election

(which is another free radical).

Free radicals are often created by the division of a molecule(known as an initiator) into two fragments along a single

bond. The following diagram shows the formation of a

radical from its initiator, in this case benzoyl peroxide.


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Polymerization

A polymerization process takes place in three distinct steps:1. chain initiation, usually by means of an initiator which

starts the chemical process. Typical initiators include any

organic compound with a labile group: e.g. azo (-N=N-),

disulfide (-S-S-), or peroxide (-O-O-). Two examples arebenzoyl peroxide and AIBN.

2. Chain propagation

3. Chain termination, which occurs either by combination

or disproportionation.

Termination, in radical polymerization, is when the free

radicals combine and is the end of the polymerization

process.40

P l i ti I iti ti


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Polymerization - Initiation

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benzoyl peroxide

Benzoyl peroxide is usually prepared by treating

hydrogen peroxide with benzoyl chloride.

The oxygen-oxygen bond in peroxides is weak. Thus benzoyl peroxide readily undergoes homolysis

(symmetrical scission), forming free radicals:

*C6H5C(O)+2O2 2 C6H5CO2

P l i ti I iti ti


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*C6H5C(O)+2O2 2 C6H5CO2

The symbol indicates that the products are radicals;

i.e., they contain at least one unpaired electron.

Such species are highly reactive. The homolysis is usually

induced by heating.

The half-life of benzoyl peroxide is one hour at 920C. At 131 C, the half-life is one minute.

The stability of a radical refers to the molecule's

tendency to react with other compounds.

An unstable radical will readily combine with manydifferent molecules. However a stable radical will not

easily interact with other chemical substances.

Polymerization Initiation


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The stability of free radicals can vary widely depending

on the properties of the molecule. The active center is the location of the unpaired

electron on the radical because this is where the

reaction takes place.

In free radical polymerization, the radical attacks onemonomer, and the electron migrates to another part of

the molecule.

This newly formed radical attacks another monomer and

the process is repeated. Thus the active center moves down the chain as the

polymerization occurs.

Propagation Reaction


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After a synthesis reaction has been initiated, thepropagation reaction takes over.

In the propagation stage, the process of electron

transfer and consequent motion of the active center

down the chain proceeds. In this diagram, (chain) refers to a chain of connected

monomers, and X refers to a substituent group (a

molecular fragment) specific to the monomer.



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For example, if X were a methyl group, the monomer

would be propylene and the polymer, polypropylene.

In free radical polymerization, the entire propagation

reaction usually takes place within a fraction of asecond.

Thousands of monomers are added to the chain within

this time.

The entire process stops when the termination reactionoccurs.

Termination Reaction


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In theory, the propagation reaction could continue until

the supply of monomers is exhausted! However, this outcome is very unlikely. Most often the

growth of a polymer chain is halted by the termination

reaction.

Termination typically occurs in two ways: combination and

disproportionation.

Combination occurs when the polymer's growth isstopped by free electrons from two growing chains that

join and form a single chain.



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The following diagram depicts combination, with the

symbol (R) representing the rest of the chain. For example, if X were a methyl group, the monomer

would be propylene and the polymer, polypropylene.

Disproportionation halts the propagation reaction when

a free radical strips a hydrogen atom from an activechain.

A carbon-carbon double bond takes the place of the

missing hydrogen. Termination by disproportionation is

shown in the diagram.



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Termination by disproportionation is shown in the

diagram above. Disproportionation can also occur when the radical

reacts with an impurity.

This is why it is so important that polymerization be

carried out under very clean conditions.


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Other types of Polymerization

The new monomer adds on the growing polymer chainvia the reactive active centre which can be a:

free radical in radical polymerization

carbocation in cationic polymerization

carbanion in anionic polymerization

organometallic complexin coordination

polymerization.

the monomer molecule can be a: unsaturated compoundlike ethylene or acetylene, see

vinyl polymer

Alicyclic compound, see ring-opening polymerization49


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Cationic Polymerization

In carbo-cationic polymerization the active site is acarbocation with a counter-ion in close proximity.

1. Initiation

A+B- + H2C=CHR A-CH2-RHC+ -B-

2. Chain propagation:

A-CH2-RHC+-B- + H2C=CHR A-(CH2-RHC)n-CH2-RHC

+-B-

3. Chain termination:

A-(CH2-RHC)n-CH2-RHC+-B- A-(CH2-RHC)n-CH2-RHC-B

4. Chain transfer:

A-(CH2-RHC)n-CH2-RHC+-B- A-(CH2-RHC)n-CH2=CR H

+-B-

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Statistical Analysis of Polymers


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When dealing with millions of molecules in a tiny

droplet, statistical methods must be employed to makegeneralizations about the characteristics of the polymer.

It can be assumed in polymer synthesis that each chain

reacts independently.

Therefore, the bulk polymer is characterized by a widedistribution of molecular weights and chain lengths.

The degree of polymerization (DP) refers to the number

of repeat units in the chain, and gives a measure of

molecular weight.

Many important properties of the final result are

determined primarily from the distribution of lengths

and the degree of polymerization.



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In order to characterize the distribution of polymerlengths in a sample, two parameters are defined:

number average andweight average molecular weight.

The number average is just the sum of individual

molecular weights divided by the number of polymers.The weight average is proportional to the square of the

molecular weight.



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Therefore, the weight average is always larger than the

number average. The graph in previous slide shows a typical distribution

of polymers including the weight and number average

molecular weights.

The molecular weight of a polymer can also berepresented by the viscosity average molecular weight.

This form of the molecular weight is found as a function

of the viscosity of the polymer in solution (viscosity

determines the rate at which the solution flows - the

slower a solution moves, the more viscous it is said to

be - and the polymer molecular weight influences the

viscosity).



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It is possible by measuring the viscosity of a polymersolution to use the data you find to produce the

viscosity average molecular weight.

The degree of polymerization has a dramatic effect on

the mechanical properties of a polymer. As chain length increases, mechanical properties such as

ductility, tensile strength, and hardness rise sharply and

eventually level off.

This is schematically illustrated by the blue curve in thefigure below.



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However, in polymer melts, for example, the flow

viscosity at a given temperature rises rapidly with

increasing DP for all polymers, as shown by the red

curve in the diagram.

A fundamental property of bulk polymers is the degree

of polymerization,

Thephysical structure of the chain is also an important

factor that determines the macroscopic properties

Physical Structure of Polymers


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Physical Structure of Polymers

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Thephysical structure of the chain is also an important

factor that determines the macroscopic properties

Termsconfigurationand conformationare used to

describe the geometric structure of a polymer and are

often confused:

Configuration: The geometrical arrangement in

polymers arising from the order of atoms determined by

chemical bonds.

Conformation: The geometrical arrangement in

polymers arising from rotation about adjacent carbon-

carbon single bonds.


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Polymer Configuration

Two types of polymer configurations are cis and trans.These structures can not be changed by physical means

(e.g. rotation).

The cis configuration arises when substituent groups areon the same side of a carbon-carbon double bond.

Trans refers to the substituents on opposite sides of the

double bond.

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Polymer Configuration

Stereoregularityis the term used to describe the

configuration of polymer chains; Three distinct

structures:

Isotacticis an arrangement where all substituents are on

the same side of the polymer chain. A syndiotacticpolymer chain is composed of alternating groups and

atacticis a random combination of the groups. The

following diagram shows two of the three stereoisomers

of polymer chain.

.

58Isotactic Syndiotactic


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Other Definitions in Polymers

Conformation: The geometrical arrangement in polymers

arising from rotation about adjacent carbon-carbon single

bonds.Anti (Trans), Eclipsed (Cis), and Gauche (+ or -).

Branched polymers: when there are "side chains" attached

to a main chain.

.

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Other Definitions in Polymers

Conformation: The geometrical arrangement in polymers

arising from rotation about adjacent carbon-carbon single

bonds.Anti (Trans), Eclipsed (Cis), and Gauche (+ or -).

Branched polymers: when there are "side chains" attached

to a main chain.

.

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Co-Polymers

A separate kind of chain structure arises when more that

one type of monomer is involved in the synthesis reaction.

These polymers that incorporate more than one kind of

monomer into their chain are calledcopolymers.

There are three important types of copolymers.A random copolymercontains a random arrangement of

the multiple monomers.

A block copolymercontains blocks of monomers of the

same type.

A graft copolymercontains a main chain polymer

consisting of one type of monomer with branches made up

of other monomers.61


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Co-Polymers

There are three important types of copolymers.

A random copolymercontains a random arrangement of

the multiple monomers.

A block copolymercontains blocks of monomers of the

same type.A graft copolymercontains a main chain polymer

consisting of one type of monomer with branches made up

of other monomers.

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BlockCopolymer

GraftCopolymer

RandomCopolymer

Co-Polymers

Nylon is an alternating copolymer with 2 monomers, a 6

carbon diacid and a 6 carbon diamine;One monomer of

the diacid combined with one monomer of the diamine


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PetroChemical Industry

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