Process. Chem Harith

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Topic Page

Introduction

Acknowledgements

Contact Process

Haber Process

Alloy

Polymer

Glass

Reference



Contact process

y trioxide into concentrated sulphuric acid.

y The contact process is the current method of producing sulfuric acid in

the high concentrations needed makes sulphur dioxide;

y convers the sulphur dioxide into sulphur trioxide (the reversible reaction

at the heart of the process);

converts the sulphur for industrial processes. Platinum was formerly employed

as a catalyst for the reaction, but as it is susceptible to poisoning by arsenic

impurities in the sulfur feedstock, vanadium(V) oxide (V2O5) is now preferred[1]

.

This process was patented in 1831 by the British vinegar merchant Peregrine

Phillips. In addition to being a far more economical process for producing

concentrated sulfuric acid than the previous lead chamber process, the contact

process also produces sulfur trioxide and oleum Making the sulphur dioxide

This can either be made by burning sulphur in an excess of air:

. . . or by heating sulphide ores like pyrite in an excess of air:



In either case, an excess of air is used so that the sulphur dioxide produced is

already mixed with oxygen for the next stage.

C onverting the sulphur dioxide into sulphur trioxide

This is a reversible reaction, and the formation of the sulphur trioxide is

exothermic.

A flow scheme for this part of the process looks like this: (next page)

C onverting the sulphur trioxide into sulphuric acid



T his can't be done by simply adding water to the sulphur trioxide - the reaction is so

uncontrollable that it creates a fog of sulphuric acid. Instead, the sulphur trioxide is first

dissolved in concentrated sulphuric acid:

T he product is known as fuming sulphuric acid or oleum.

T his can then be reacted safely with water to produce concentrated sulphuric acid - twice as

much as you originally used to make the fuming sulphuric acid.

The process can be divided into three stages :

1. Preparation and purification of sulfur dioxide

2. Catalytic oxidation (using vanadium pentoxide catalyst) of sulfur dioxide

to sulfur trioxide

3. Conversion of sulfur trioxide to sulfuric acid



DCDA

The next step to the Contact Process is DCDA or Double Contact

Double Absorption. In this process the product gases (SO2) and (SO3)

are passed through absorption towers twice to achieve further

absorption and conversion of SO2 to SO3 and production of higher

grade sulfuric acid.

SO2 rich gases enter the catalytic converter, usually a tower with

multiple catalyst beds, and get converted to SO3, achieving the first

stage of conversion. The exit gases from this stage contain both SO2

and SO3 which are passed through intermediate absorption towers

where sulfuric acid is trickled down packed columns and SO3 reacts

with water increasing the sulfuric acid concentration. Though SO2 too

passes through the tower it is unreactive and comes out of the

absorption tower.

This stream of gas containing SO2, after necessary cooling is passed

through the catalytic converter bed column again achieving up to 99.8%

conversion of SO2 to SO3 and the gases are again passed through the

final absorption column thus resulting not only achieving high

conversion efficiency for SO2 but also enabling production of higher

concentration of sulfuric acid.

The industrial production of sulfuric acid involves proper control of

temperatures and flow rates of the gases as both the conversion

efficiency and absorption are dependent on these.



Haber Process

Sometimes called the most important technological advance of this century, the

Haber -Bosch process allows the economical mass synthesis of ammonia (NH3)

from nitrogen and hydrogen. It was developed immediately prior to World War

I by Fritz Haber and Carl Bosch, German chemists. Haber won the Nobel Prize

for Chemistry in 1918 for his discoveries, while Bosch shared a Nobel Prize

with Friedrich Bergius in 1931 for his work on high-pressure chemical reactions.

At first a German national secret, the chemistry and techniques behind the

effective synthesis of ammonia spread to the rest of the world in the 20s and 30s.

Ammonia is important because it is the primary ingredient in artificial fertilizers,

without which modern-day agricultural yields would be impossible. Sometimes

called the "Haber Ammonia process," the Haber-Bosch process was the first

industrial chemical process to make use of extremely high pressures (200 to 400

atmospheres). In addition to high pressures, high temperatures (75 0 to 1200

degrees Fahrenheit or 400 to 650 degrees Celsius) are used. The efficiency of

the reaction is a function of pressure and temperature - greater yields are

produced at higher pressures and lower temperatures.

In the first decade of the 20th century, the artificial synthesis of nitrates was

being researched because of fears that the world's supply of fixed nitrogen was

declining rapidly relative to the demand. While nitrogen in its inactive,



atmospheric gas form is very plentiful, agriculturally useful "fixed" nitrogen

compounds were harder to come by at that time in history. Agricultural

operations require liberal amounts of fixed nitrogen to produce good yields. At

the turn of the century, all the world's developed countries were required to

mass import nitrates from the largest available source - Chilean saltpeter

(NaNO3). Many scientists started worrying about the declining supply of

nitrogen compounds.

The Haber-Bosch process provided a solution to the shortage of fixed nitrogen.

Using extremely high pressures and a catalyst composed mostly of iron, critical

chemicals used in both the production of fertilizers and explosives, we re made

highly accessible to German industry, making it possible for them to continue

fighting WWI effectively. As the Haber-Bosch process branched out in global

use, it became the primary procedure responsible for the production of chemical

fertilizers. Today, the Haber-Bosch process is used to produce more than 500

million tons (453 billion kilograms) of artificial fertilizer per year; roughly 1%

of the world's energy is used for it, and it sustains about 40% of our planetary

population.The Haber Process combines nitrogen from the air with hydrogen

derived mainly from natural gas (methane) into ammonia.

The reaction is reversible and the production of ammonia is exothermic.



A flow scheme for the Haber Process looks like this:

The proportions of nitrogen and hydrogen

The mixture of nitrogen and hydrogen going into the reactor is in the ratio of 1

volume of nitrogen to 3 volumes of hydrogen.

Avogadro's Law says that equal volumes of gases at the same temperature and

pressure contain equal numbers of molecules. That means that the gases are

going into the reactor in the ratio of 1 molecule of nitrogen to 3 of hydrogen.

That is the proportion demanded by the equation.

In some reactions you might choose to use an excess of one of the rea ctants.

You would do this if it is particularly important to use up as much as possible of



the other reactant - if, for example, it was much more expensive. That doesn't

apply in this case.

There is always a down-side to using anything other than the equat ion

proportions. If you have an excess of one reactant there will be molecules

passing through the reactor which can't possibly react because there isn't

anything for them to react with. This wastes reactor space - particularly space

on the surface of the catalyst

When the gases leave the reactor they are hot and at a very high

pressure. Ammonia is easily liquefied under pressure as long as it isn't

too hot, and so the temperature of the mixture is lowered enough for

the ammonia to turn to a liquid. The nitrogen and hydrogen remain as

gases even under these high pressures, and can be recycled.



The Properties of Ammonia :

-colourless and pungent gas

-alkaline gas

-soluble in water

-reacts with Hydrogen chloride to form white fumes of ammonia chloride

NH3+HCL=>NH4CL

-reacts with dilute acid to produce salt.

The Uses of Ammonia :

-manufacture of nitric acid

-manufacture of explosives

- as a cooling agentin refrigerators

-as an alkali to prevent coagulation of latex



Alloys

An alloy is a partial or complete solid solution of one or more elements in a

metallic matrix. Complete solid solution alloys give single solid phase

microstructure, while partial solutions give two or more phase s that may be

homogeneous in distribution depending on thermal (heat treatment) history.

Alloys usually have different properties from those of the component el ements.

Alloys' constituents are usually measured by mass.

A pure metal(alloy) has the following characteristics:

p Ductile- can be drawn to wires

p Malleable- can be made into sheets

p High melting and boiling points

p High density

p High electric conductivity





Properties

The malleability and acoustic properties of brass have made it the metal of

choice for brass musical instruments such as the trombone, tuba, trumpet, cornet,

euphonium, tenor horn, and the French horn. ven though the saxophone is

classified as a woodwind instrument and the harmonica is a free reed aerophone,

both are also often made from brass. In organ pipes of the reed family, brass

strips (called tongues) are used as the reeds, which beat against the shallot (or

beat "through" the shallot in the case of a "free" reed).

Brass has higher malleability than copper or zinc. The relatively low melting

point of brass (900 to 940°C, depending on composition) and its flow

characteristics make it a relatively easy material to cast. By varying the

proportions of copper and zinc, the properties of the brass can be changed,

allowing hard and soft brasses. The density of brass is approximately 8400 to

8730 kilograms per cubic metre[11]

(equivalent to 8.4 to 8.73 grams per cubic

centimetre).

Today almost 90% of all brass alloys are recycled.[12]

Because brass is not

ferromagnetic, it can be separated from ferrous scrap by passing the scrap near a

powerful magnet. Brass scrap is collected and transported to the foundry where

it is melted and recast into billets. Billets are heated and extruded into the

desired form and size.



Aluminium makes brass stronger and more corrosion resistant. Aluminium also

causes a highly beneficial hard layer of aluminium oxide (Al2O3) to be formed

on the surface that is thin, transparent and self healing. Tin has a similar effect

and finds its use especially in sea water applications (naval brasses).

Combinations of iron, aluminium, silicon and manganese make brass wear and

tear resistant

Alloy(bronze)

Alloy traditionally composed of copper and tin. Bronze was first made before

3000 BC ( see Bronze Age) and is still widely used, though iron often replaced

bronze in tools and weapons after about 1000 BC because of iron's abundance

compared to copper and tin. Bronze is harder than copper, more readily melted,

and easier to cast. It is also harder than iron and far more resistant to corrosion.

Bell metal (which produces pleasing sounds when struck) is bronze with 20

25% tin content. Statuary bronze, with less than 10% tin and an admixture of

zinc and lead, is technically a brass. The addition of less than 1% phosphorus

improves the hardness and strength of bronze; that formulation is used for pump

plungers, valves, and bushings. Also useful in mechanical engineering are

manganese bronzes, with little or no tin but considerable amounts of zinc and up

to 4.5% manganese. Aluminum bronzes, containing up to 16% aluminum and

small amounts of other metals such as iron or nickel, are especially strong and



corrosion-resistant; they are cast or wrought into pi pe f ittings, pumps, gears,

shi p propellers, and turbine blades. Most "copper " coins are actually bronze,

typically with about 4% tin and 1% zinc, or copper plating over base metal

Ass

¡

ted ancient bronze castings

Proper ties

Bronze is considerably less br ittle than iron. Typically bronze only oxidizes

superf icially; once a copper oxide (eventually becoming copper carbonate) layer

is formed, the under lying metal is protected from fur ther corrosion. However, if

copper chlor ides are formed, a corrosion-mode called " bronze disease" will

eventually completely destroy it.[10]

Copper-based alloys have lower melting

points than steel or iron, and are more readily produced from their constituent

metals. They are generally about 10 percent heavier than steel, although alloys



using aluminium or silicon may be slightly less dense. Bronzes are softer and

weaker than steel²bronze springs, for example, are less stiff (and so store less

energy) for the same bulk. Bronze resists corrosion (especially seawater

corrosion) and metal fatigue more than steel and is also a better conductor of

heat and electricity than most steels. The cost of copper -base alloys is generally

higher than that of steels but lower than that of nickel-base alloys.

Copper and its alloys have a huge variety of uses that reflect their versatile

physical, mechanical, and chemical properties. Some common examples are the

high electrical conductivity of pure copper, the excellent deep drawing qualities

of cartridge case brass, the low-friction properties of bearing bronze, the

resonant qualities of bell bronze, and the resistance to corrosion by sea water of

several bronze alloys.

The melting point of Bronze varies depending on the actual ratio of the alloy

components and is about 950 °C.



Alloys(Duralumin)

(also called duraluminum, duraluminium or dural) is the trade name of one of

the earliest types of age-hardenable alloys. The main alloying constituents are

copper , manganese, and magnesium. A commonly used modern equivalent of

this alloy type is AA2024, which contains 4.4% copper, 1. 5% magnesium, 0.6%

manganese and 93.5% aluminium by weight. Typical yield strength is 450 MPa,

with variations depending on the composition and temper .[1]

Duralumin was developed by the German metallurgist Alfred Wilm at Dürener

Metallwerke Aktien Gesellschaft. In 1903, Wilm discovered that after

quenching, an aluminium alloy containing 4% copper would slowly harden

when left at room temperature for several days. Further improvements led to the

introduction of duralumin in 1909.[2]

The name is obsolete today, and mainly

used in popular science to describe the Al-Cu alloy system, or 2000 series as

designated by the International Alloy Designation System (IADS) originally

created in 1970 by the Aluminum Association.



Its f irst use was r igid airshi p frames. Its composition and heat treatment were a

war time secret. With this new r i p-resistant mixture, duralumin quick ly spread

throughout the aircraf t industry in the ear ly 1930s, where it was well suited to

the new monocoque construction techniques that were being introduced at the

same time. Duralumin also is popular for use in precision tools such as levels

because of its light weight and strength.

Although the addition of copper improves strength, it also makes these alloys

suscepti ble to corrosion. For sheet products, corrosion resistance can be greatly

enhanced by metallurgical bonding of a high-pur ity aluminium surface layer.

These sheets are referred to as alclad, and are commonly used by the aircraf t

industry.[3]



Alloys(stainless steel)

Stainless steel is an iron-containing alloy²a substance made up of two or more

chemical elements²used in a wide range of applications. It has excellent

resistance to stain or rust due to its chromium content, usually from 12 to 20

percent of the alloy. There are more than 57 stainless steels recognized as

standard alloys, in addition to many proprietary alloys produced by different

stainless steel producers. These many types of steels are used in an almost

endless number of applications and industries: bulk materials handling

equipment, building exteriors and roofing, automobile components (exhaust,

trim/decorative, engine, chassis, fasteners, tubing for fuel lines), chemical

processing plants (scrubbers and heat exchangers), pulp and paper

manufacturing, petroleum refining, water supply piping, consumer products,

marine and shipbuilding, pollution control, sporting goods (snow skis), and

transportation (rail cars), to name just a few.

About 200,000 tons of nickel-containing stainless steel is used each year by the

food processing industry in North America. It is used in a variety of food

handling, storing, cooking, and serving equipment ²from the beginning of the

food collection process through to the end. Beverages such as milk, wine, beer,

soft drinks and fruit juice are processed in stainless steel equipment. Stainless



steel is also used in commercial cookers, pasteurizers, transfer bins, and other

specialized equipment. Advantages include easy cleaning, good corrosion

resistance, durability, economy, food flavor protection, a nd sanitary design.

According to the U.S. Department of Commerce, 1992 shipments of all stainless

steel totaled 1,514,222 tons.

Stainless steels come in several types depending on their microstructure.

Austenitic stainless steels contain at least 6 percent nickel and austenite ²

carbon-containing iron with a face-centered cubic structure²and have good

corrosion resistance and high ductility (the ability of the material to bend

without breaking). Ferritic stainless steels (ferrite has a body -centered cubic

structure) have better resistance to stress corrosion than austenitic, but they are

difficult to weld. Martensitic stainless steels contain iron having a needle-like

structure.

Duplex stainless steels, which generally contain equal amounts of ferrite and

austenite, provide better resistance to pitting and crevice corrosion in most

environments. They also have superior resistance to cracking due to chloride

stress corrosion, and they are about twice as strong as the common austenitics.

Therefore, duplex stainless steels are widely used in the chemical industry in

refineries, gas-processing plants, pulp and paper plants, and sea water piping

installations.



Stainless steels are made of some of the basic elements found in the earth: iron

ore, chromium, silicon, nickel, carbon, nitrogen, and manganese. Properties of

the final alloy are tailored by varying the amounts of these elements. Nitrogen,

for instance, improves tensile properties like ductility. It also improves

corrosion resistance, which makes it valuable for use in duplex stainless steels.]



Polymer

a chemical compound of high molecular weight (from several thousand up to

many millions), whose molecules (macromolecules) consist of a large number

of repeating groups, or monomeric units. The atoms composing the

macromolecules are bound on one another by regular and/or coordinate bonds.

Polymers are classified according to origin as natural polymers, or biopolymers

(for example, proteins, nucleic acids, and natur al resins), and synthetic polymers

(polyethylene, polypropylene, and phenol -formaldehyde resins). The atoms or

atomic groups may be arranged in an open chain or a sequence of consecutive

rings (linear polymers, such as natural rubber), a branched chain (am ylopectin),

or a three-dimensional network (crosslinked polymers, such as solid epoxy

resins). Polymers consisting of identical monomer units²for example,

polyvinyl chloride, polycaproamide, and cellulose ²are called homopo-lymers.

Properties and most important characteristics. Linear polymers have a

specific set of physicochemical and mechanical properties. The most important

properties are the ability to form high-strength anisotropic, highly oriented

fibers and films; the capacity for large, slowly devel oping reversible

deformations; the ability to swell in the hyperelastic state before dissolving; and

the high viscosity of solutions. This set of properties results from the high

molecular weight, the chain structure, and the flexibility of the macromolecu les.



In the transition from linear to branched, sparse three-dimensional networks,

and finally to dense cross-linked structures, these properties become

decreasingly pronounced. Strongly crosslinked polymers are insoluble, infusible,

and incapable of hyperelastic deformations.

Polymers may exist in the crystalline and amorphous states. A necessary

condition for crystallization is regularity of sufficiently long segments of the

macromolecule. Various textures, such as fibrils, spheroidal aggregates, and

single crystals, may arise in crystalline polymers, depending largely on the

properties of the polymer material. Textures are less pronounced in amorphous

polymers than in crystalline polymers.

Synthetic polymers are often referred to as " plastics", such as the well-known

polyethylene and nylon. However, most of them can be classified in at least

three main categories: thermoplastics, thermosets and elastomers.

Man-made polymers are used in a wide array of applications: food packaging,

films, fibers, tubing, pipes, etc. The personal care industry also uses polymers to

aid in texture of products, binding, and moisture retention (e.g. in hair gel and

conditioners).



Polyethylene-Polyethylene is a polymer consisting of long chains of the

monomer ethylene (IUPAC name ethene). The recommended scientific name

polyethene is systematically derived from the scientific name of the

monomer.[1][2]

In certain circumstances it is useful to use a structure based

nomenclature. In such cases IUPAC recommends poly(methylene).[2]

The

difference is due to the opening u p of the monomer's double bond upon

polymerisation.

In the polymer industry the name is sometimes shortened to PE in a manner

similar to that by which other polymers like polypropylene and polystyrene are

shortened to PP and PS respectively. In the United Kingdom the polymer is

commonly called polythene, although this is not recognised scientifically.

The ethene molecule (known almost universally by its common



Glass

(non-crystalline) solid material. Glasses are typically brittle, and often optically

transparent. Glass is commonly used for windows, bottles, and eyewear ;

examples of glassy materials include soda-lime glass, borosilicate glass, acrylic

glass, sugar glass, Muscovy-glass, and aluminium oxynitride. The term g la ss

developed in the late Roman mpire. It was in the Roman glassmaking center at

Trier , now in modern Germany, that the late-Latin term g l esum originated,

probably from a Germanic word for a transparent, lustrous substance.[1]

Strictly speaking, a glass is defined as an inorganic product of fusion which has

been cooled through its glass transition to the solid state without

crystallising.[2][3][4][5][6]

Many glasses contain silica as their main component and

g la ss f or mer .

[7]

The term "glass" is, however, often extended to all amorphous

solids (and melts that easily form amorphous solids), including plastics, resins,

or other silica-free amorphous solids. In addition, besides traditional melting

techniques, any other means of preparatio n are considered, such as ion

implantation, and the sol-gel method.[7]

Commonly, g la ss science and physics

deal only with inorganic amorphous solids, while plastics and similar organics

are covered by polymer science, biology and further scientific disciplines.

Glass plays an essential role in science and industry. The optical and physical

properties of glass make it suitable for applications such as flat glass, container



glass, optics and optoelectronics material, laboratory equipment, thermal

insulator (glass wool), reinforcement fiber (glass-reinforced plastic, glass fiber

reinforced concrete), and art.

Glass(soda lime)

Soda-lime glass, also called soda-lime-silica glass, is the most prevalent type

of glass, used for windowpanes, and glass containers (bottles and jars) for

beverages, food, and some commodity items. Glass bakeware is often made of

tempered soda-lime glass.[1]

Soda-lime glass is prepared by melting the raw materials, such as sodium

carbonate (soda), lime, dolomite, silicon dioxide (silica), aluminium oxide

(alumina), and small quantities of fining agents (e.g., sodium sulfate, sodium

chloride) in a glass furnace at temperatures locally up to 1675 °C.

[2]

The

temperature is only limited by the quality of the furnace superstructure material

and by the glass composition. Green and brown bottles are obtained from raw

materials containing iron oxide. Relatively inexpensive minerals such as trona,

sand, and feldspar are used instead of pure chemicals. The mix of raw materials

is termedbatch.

Soda-lime glass is divided technically into glass used for windows, called f loat

g la ss or f lat g la ss, and glass for containers, called cont ainer g la ss. Both types

differ in the application, production method ( float process for windows, blowing



and pressing for containers), and chemical composition (see table below). Float

glass has a higher magnesium oxide and sodium oxide content as compared to

container glass, and a lower silica, calcium oxide, and aluminium oxide

content.[3]

From this follows a slightly higher quality of container glass

concerning the chemical durability against water (see table), which is required

especially for storage of beverages and food.

Glass(borosilicate)

is a type of glass with the main glass-forming constituents silica and boron

oxide. Borosilicate glasses are known for having very low coefficients of

thermal expansion (~5 × 10í6

/°C at 20°C), making them resistant to thermal

shock , more so than any other common glass. Borosilicate glass has a very low

thermal expansion coefficient, about one-third that of ordinary glass. This

reduces material stresses caused by temperature gradients, thus making it more

resistant to breaking. This makes it a popular material for objects like telescope

mirrors, where it is essential to have very little deviation in shape. It is also used

in the processing of high-level radioactive waste, where the waste is

immobilised in the glass through a process known as vitrification (contrast with

Synroc).



The softening point (temperature at which viscosity is approximately 107.6

poise)

of type 7740 Pyrex is 820 °C (1,510 °F).[4]

Borosilicate glass is less dense than ordinary glass.

While more resistant to thermal shock than other types of glass, borosilicate

glass can still crack or shatter when subject to rapid or uneven temperature

variations. When broken, borosilicate glass tends to crack into large pieces

rather than shattering (it will snap rather than splinter).

Optically, borosilicate glasses are crown glasses with low dispersion (Abbe

numbers around 65) and relatively low refractive indices (1.51 1.54 across the

visible range).

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Process. Chem Harith