Petroleum naphthaPetroleum naphtha is an intermediate hydrocarbon liquid stream derived from the refining of crude oil.[1][2][3] It is most usually desulfurized and then catalytically reformed, which re-arranges or re-structures the hydrocarbon molecules in the naphtha as well as breaking some of the molecules into smaller molecules to produce a high-octane component of gasoline (or petrol).

There are quite literally hundreds of different petroleum crude oil sources worldwide and each

crude oil has its own unique composition or assay. There are also hundreds of petroleum

refineries worldwide and each of them is designed to process either a specific crude oil or

specific types of crude oils. That means that it is virtually impossible to provide a definitive,

single definition of the word naphtha since each refinery produces its own naphthas with their

own unique initial and final boiling points and other physical and compositional characteristics.

In other words, naphtha is a generic term rather than a specific term.

In addition, naphthas may also be produced from coal tar, shale deposits, tar sands such as in

Canada, the destructive distillation of wood and coal gasification or biomass gasification to

produce a syngas[4][5] followed by the Fischer-Tropsch process to convert the syngas into liquid

hydrocarbon products. For that reason, this article is entitled Petroleum naphtha and deals

only with naphthas produced by the processing of crude oil in petroleum refineries.

Contents

[hide]

1 The major source of petroleum naphtha in a petroleum refinery

2 Types of virgin naphthas

3 Cracked naphthas

4 Removal of sulfur compounds from naphthas

5 Other uses

6 References

The major source of petroleum naphtha in a petroleum refinery

The first unit process in a petroleum refinery is the crude oil distillation unit. The overhead liquid

distillate from that unit is called virgin or straight-run naphtha and that distillate is the largest

source of naphtha in most petroleum refineries. The naphtha is a mixture of very many different

hydrocarbon compounds. It has an initial boiling point (IFP) of about 35 °C and a final boiling

point (FBP) of about 200 °C, and it contains paraffin, naphthene (cyclic paraffins) and aromatic

hydrocarbons ranging from those containing 4 carbon atoms to those containing about 10 or 11

carbon atoms.

The virgin naphtha is often further distilled into two streams:[6]

a virgin light naphtha with an IFP of about 30 °C and a FBP of

about 145 °C containing most (but not all) of the hydrocarbons

with 6 or less carbon atoms

a virgin heavy naphtha containing most (but not all) of the

hydrocarbons with more than 6 carbon atoms. The heavy

naphtha has an IFP of about 140 °C and a FBP of about 205

°C.

It is the virgin heavy naphtha that is usually processed in a catalytic reformer because the light

naphtha has molecules with 6 or less carbon atoms which, when reformed, tend to crack into

butane and lower molecular weight hydrocarbons which are not useful as high-octane gasoline

blending components. Also, the molecules with 6 carbon atoms tend to form aromatics which is

undesirable because governmental environmental regulations in a number of countries limit the

amount of aromatics (most particularly benzene) that gasoline may contain.[7][8][9]

Types of virgin naphthas

The table just below lists some fairly typical virgin heavy naphthas, available for catalytic

reforming, derived from various crude oils. It can be seen that they differ significantly in their

content of paraffins, naphthenes and aromatics:

Typical Heavy Naphthas

Crude oil name Location

Barrow IslandAustralia[10]

Mutineer-ExeterAustralia[11]

CPC BlendKazakhstan[12]

DraugenNorth Sea[13]

Initial boiling point, °C 149 140 149 150

Final boiling point, °C 204 190 204 180

Paraffins, liquid volume % 46 62 57 38

Naphthenes, liquid volume %

42 32 27 45

Aromatics, liquid volume % 12 6 16 17

Cracked naphthas

Some refinery naphthas also contain some olefinic hydrocarbons, such as naphthas derived

from the fluid catalytic cracking, visbreakers and coking processes used in many refineries.

Those olefin-containing naphthas are often referred to as cracked naphthas.

In some (but not all) petroleum refineries, the cracked naphthas are desulfurized and

catalytically reformed (as are the virgin naphthas) to produce additional high-octane gasoline

components.

Removal of sulfur compounds from naphthas

For more information, see: Hydrodesulfurization, Amine gas treating, and Merox

Most uses of petroleum refinery naphtha require the removal of sulfur compounds down to very

low levels (a few parts per million or less). That is usually accomplished in a catalytic chemical

process called hydrodesulfurization which converts the sulfur compounds into hydrogen sulfide

gas that is removed from the naphtha by distillation.

The hydrogen sulfide gas is then captured in amine gas treating units and subsequently

converted into byproduct elemental sulfur. In fact, the vast majority of the 64,000,000 metric

tons of sulfur produced worldwide in 2005 was byproduct sulfur from petroleum refining and

natural gas processing plants (which also use amine gas treating units to remove hydrogen

sulfide from the raw natural gas).[14][15]

In lieu of hydrodesulfurization, light naphthas may be treated in a Merox unit to remove any

hydrogen sulfide and, more particularly, to remove mercaptans.

Other uses

Some petroleum refineries also produce small amounts of specialty naphthas for use as

solvents, cleaning fluids, paint and varnish diluents, asphalt diluents, rubber industry solvents,

dry-cleaning, cigarette lighters, and portable camping stove and lantern fuels. Those specialty

naphthas are subjected to various purification processes.

Sometimes the specialty naphthas are called petroleum ether, petroleum spirits, mineral spirits,

paraffin, benzine, hexanes, ligroin, white oil or white gas, painters naphtha, refined solvent

naphtha and Varnish makers' & painters' naphtha (VM&P) . The best way to determine the

boiling range and other compositional characteristics of any of the specialty naphthas is to read

the Material Safety Data Sheet (MSDS) for the specific naphtha of interest.

On a much larger scale, petroleum naphtha is also used in the petrochemicals industry as

feedstock to steam reformers and steam crackers for the production of hydrogen (which may be

and is converted into ammonia for fertilizers), ethylene and other olefins. Natural gas is also

used as feedstock to steam reformers and steam crackers.

Petroleum refining processesPetroleum refining processes are those chemical engineering processes and other facilities used in petroleum refineries (also referred to as oil refineries) to transform crude oil into useful products such as liquefied petroleum gas (LPG), gasoline or petrol, kerosene, jet fuel, diesel oil and fuel oils.[1][2][3]

Petroleum refineries are very large industrial complexes that involve a great many different

processing units and auxiliary facilities such as utility units and storage tanks. Each refinery has

its own unique arrangement and combination of refining processes largely determined by the

refinery location, desired products and economic considerations. There are most probably no

two refineries that are identical in every respect.

Some modern petroleum refineries process as much as 800,000 to 900,000 barrels (127,000 to

143,000 cubic meters) per day of crude oil.

Brief history of the petroleum industry and petroleum refining

Prior to the 19th century, petroleum was known and utilized in various fashions in Babylon,

Egypt, China, Persia, Rome and Azerbaijan. However, the modern history of the petroleum

industry is said to have begun in 1846 when Abraham Gessner of Nova Scotia, Canada

discovered how to produce kerosene from coal. Shortly thereafter, in 1854, Ignacy Lukasiewicz

began producing kerosene from hand-dug oil wells near the town of Krosno, now in Poland. The

first large petroleum refinery was built in Ploesti, Romania in 1856 using the abundant oil

available in Romania.[4][5]

In North America, the first oil well was drilled in 1858 by James Miller Williams in Ontario,

Canada. In the United States, the petroleum industry began in 1859 when Edwin Drake found

oil near Titusville, Pennsylvania. The industry grew slowly in the 1800s, primarily producing

kerosene for oil lamps. In the early 1900's, the introduction of the internal combustion engine

and its use in automobiles created a market for gasoline that was the impetus for fairly rapid

growth of the petroleum industry. The early finds of petroleum like those in Ontario and

Pennsylvania were soon outstripped by large oil "booms" in Oklahoma, Texas and California.[6]

Prior to World War II in the early 1940s, most petroleum refineries in the United States

consisted simply of crude oil distillation units (often referred to as atmospheric crude oil

distillation units). Some refineries also had vacuum distillation units as well as thermal cracking

units such as visbreakers (viscosity breakers, units to lower the viscosity of the oil). All of the

many other refining processes discussed below were developed during the war or within a few

years after the war. They became commercially available within 5 to 10 years after the war

ended and the worldwide petroleum industry experienced very rapid growth. The driving force

for that growth in technology and in the number and size of refineries worldwide was the

growing demand for automotive gasoline and aircraft fuel.

In the United States, for various complex economic reasons, the construction of new refineries

came to a virtual stop in about the 1980's. However, many of the existing refineries in the United

States have revamped many of their units and/or constructed add-on units in order to: increase

their crude oil processing capacity, increase the octane rating of their product gasoline, lower

the sulfur content of their diesel fuel and home heating fuels to comply with environmental

regulations and comply with environmental air pollution and water pollution requirements.

Processing units used in refineries

Crude Oil Distillation unit: Distills the incoming crude oil into

various fractions for further processing in other units.

Vacuum Distillation unit: Further distills the residue oil from the

bottom of the crude oil distillation unit. The vacuum distillation

is performed at a pressure well below atmospheric pressure.

Naphtha Hydrotreater unit: Uses hydrogen to desulfurize the

naphtha fraction from the crude oil distillation or other units

within the refinery.

Catalytic Reforming unit: Converts the desulfurized naphtha

molecules into higher-octane molecules to produce reformate,

which is a component of the end-product gasoline or petrol.

Alkylation unit: Converts isobutane and butylenes into

alkylate, which is a very high-octane component of the end-

product gasoline or petrol.

Isomerization unit: Converts linear molecules such as normal

pentane into higher-octane branched molecules for blending

into the end-product gasoline. Also used to convert linear

normal butane into isobutane for use in the alkylation unit.

Distillate Hydrotreater unit: Uses hydrogen to desulfurize

some of the other distilled fractions from the crude oil

distillation unit (such as diesel oil).

Merox (mercaptan oxidizer) or similar units: Desulfurize LPG,

kerosene or jet fuel by oxidizing undesired mercaptans to

organic disulfides.

Amine gas treater, Claus unit, and tail gas treatment for

converting hydrogen sulfide gas from the hydrotreaters into

end-product elemental sulfur. The large majority of the

64,000,000 metric tons of sulfur produced worldwide in 2005

was byproduct sulfur from petroleum refining and natural gas

processing plants.[7][8]

Fluid Catalytic Cracking (FCC) unit: Upgrades the heavier,

higher-boiling fractions from the the crude oil distillation by

converting them into lighter and lower boiling, more valuable

products.

Hydrocracker unit: Uses hydrogen to upgrade heavier

fractions from the crude oil distillation and the vacuum

distillation units into lighter, more valuable products.

Visbreaker unit upgrades heavy residual oils from the vacuum

distillation unit by thermally cracking them into lighter, more

valuable reduced viscosity products.

Delayed coking and Fluid coker units: Convert very heavy

residual oils into end-product petroleum coke as well as

naphtha and diesel oil by-products.

Auxiliary facilities required in refineries

Steam reformer unit: Converts natural gas into hydrogen for

the hydrotreaters and/or the hydrocracker.

Sour water stripper unit: Uses steam to remove hydrogen

sulfide gas from various wastewater streams for subsequent

conversion into end-product sulfur in the Claus unit.[9]

Utility units such as cooling towers for furnishing circulating

cooling water, steam generators, instrument air systems for

pneumatically operated control valves and an electrical

substation.

Wastewater collection and treating systems consisting of API

separators, dissolved air flotation (DAF) units and some type

of further treatment (such as an activated sludge biotreater) to

make the wastewaters suitable for reuse or for disposal.[9]

Liquified gas (LPG) storage vessels for propane and similar

gaseous fuels at a pressure sufficient to maintain them in

liquid form. These are usually spherical vessels or bullets

(horizontal vessels with rounded ends).

Storage tanks for crude oil and finished products, usually

vertical, cylindrical vessels with some sort of vapor emission

control and surrounded by an earthen berm to contain liquid

spills.

The crude oil distillation unit

The crude oil distillation unit (CDU) is the first processing unit in virtually all petroleum refineries.

The CDU distills the incoming crude oil into various fractions of different boiling ranges, each of

which are then processed further in the other refinery processing units. The CDU is often

referred to as the atmospheric distillation unit because it operates at slightly above atmospheric

pressure.[1][2][10]

Below is a schematic flow diagram of a typical crude oil distillation unit. The incoming crude oil

is preheated by exchanging heat with some of the hot, distilled fractions and other streams. It is

then desalted to remove inorganic salts (primarily sodium chloride).

Following the desalter, the crude oil is further heated by exchanging heat with some of the hot,

distilled fractions and other streams. It is then heated in a fuel-fired furnace (fired heater) to a

temperature of about 398 °C and routed into the bottom of the distillation unit.

The cooling and condensing of the distillation tower overhead is provided partially by

exchanging heat with the incoming crude oil and partially by either an air-cooled or water-cooled

condenser. Additional heat is removed from the distillation column by a pumparound system as

shown in the diagram below.

As shown in the flow diagram, the overhead distillate fraction from the distillation column is

naphtha. The fractions removed from the side of the distillation column at various points

between the column top and bottom are called sidecuts. Each of the sidecuts (i.e., the

kerosene, light gas oil and heavy gas oil) is cooled by exchanging heat with the incoming crude

oil. All of the fractions (i.e., the overhead naphtha, the sidecuts and the bottom residue) are sent

to intermediate storage tanks before being processed further.

(PD) Drawing: Milton BeychokSchematic flow diagram of a typical crude oil distillation unit.

Flow diagram of a typical petroleum refinery

The image below is a schematic flow diagram of a typical petroleum refinery that depicts the

various refining processes and the flow of intermediate product streams that occurs between the

inlet crude oil feedstock and the final end-products.

The diagram depicts only one of the literally hundreds of different oil refinery configurations. The

diagram also does not include any of the usual refinery facilities providing utilities such as

steam, cooling water, and electric power as well as storage tanks for crude oil feedstock and for

intermediate products and end products.[1][2][11]

(GNU) Image: Milton BeychokA schematic flow diagram of a typical petroleum refinery.

Refining end-products

The primary end-products produced in petroleum refining may be grouped into four categories:

light distillates, middle distillates, heavy distillates and others.

Light distillates

Liquid petroleum gas (LPG)

Gasoline (also known as petrol)

Kerosene

Jet fuel and other aircraft fuel

Middle distillates

Automotive and railroad diesel fuels

Residential heating fuel

Other light fuel oils

Heavy distillates

Heavy fuel oils

Bunker fuel oil and other residual fuel oils

Others

Many of these are not produced in all petroleum refineries.

Specialty petroleum naphthas

Specialty solvents

Elemental sulfur (and sometimes sulfuric acid)

Petrochemical feedstocks

Asphalt and tar

Petroleum coke

Lubricating oils

Waxes and greases

Transformer and cable oils

Carbon black

Sulfuric acid

sulfuric acidIUPAC name: sulfuric acid

Synonyms:sulphuric acid and others

Formula: H2SO4

 Uses:acid, dehydration, reduction

 Properties: strong acid

 Hazards:Toxic, Corrosive

Mass (g/mol): CAS #:98.08 7664-93-9

Sulfuric acid, also spelled sulphuric acid, is a strong, corrosive acid and

oxidizing agent having the chemical formula H2SO4. It is the diprotic acid of the

sulfate anion SO4-2. At room temperature and pressure, it is a clear, colorless,

rather viscous liquid. Sulfuric acid is one of the most important chemicals in the

chemical industry. Personal protective gear should be worn when using

sulfuric acid.

Contents

[hide]

1 Synonyms

2 Properties and uses of sulfuric acid

3 Synthesis of sulfuric acid

4 Soluble and insoluble sulfate salts

Synonyms

Sulfuric acid is also called oil of vitriol, mattling acid, vitriol, battery acid, dipping

acid, electrolyte acid, vitriol brown oil, sulphuric acid, Babcock acid and sulphuric

acid.

Properties and uses of sulfuric acid

Sulfuric acid is a strong acid, an oxidizing agent and a dehydrating agent. Two

hydrogen ions can dissociate from H2SO4. In an aqueous (water) solution, the first

hydrogen dissociates completely (100%) to form the bisulfate anion HSO4-. Since

this dissociation is complete, sulfuric acid is considered a strong acid. HSO4- is a

medium strength acid from which the second hydrogen dissociates to form the

sulfate anion SO4-2.

H2SO4 + H2O → H3O+ + HSO4−    K1 = 2.4 x 106   (strong acid)

HSO4− + H20 → H3O+ + SO4

2−     K2 = 1.0 x 10-2   [1]

K1 and K2 are the acid dissociation constants.

Sulfuric acid is used to make many soluble phophates for fertilizers, ammonium

sulfate and many other chemicals, including drugs. Newly made steel is cleaned

with sulfuric acid to remove rust before the steel is coated with a protective layer of

zinc, tin or enamel. It is also used in lead sulfate batteries. Many explosives are

manufactured using sulfuric acid.

Because it has a high boiling point (33°C), it can be used to make other more

volatile acids using the appropriate acid salt. Nitric acid can be made by reacting

sulfuric acid with sodium nitrate, NaNO3. Distilling the resultant nitric acid

(BP=86°C) drives the reaction towards completion.

NaNO3 + H2SO4 → HNO3 + NaHSO4

Contact of water and sulfuric acid is exothermic. When handling them, always add

acid to water, not the reverse or the resulting boiling can spray hot acid.

The explosive nitroglycerin (glyceryl trinitrate), is made by reacting glycerine and

nitric acid in the presence of sulfuric acid. This reaction is very dangerous, do

not attempt.

C3H5(OH)3 + 3HNO3 + (H2SO4 catalyst)→ C3H5(NO3)3 + 3H2O.

Sulfuric acid can be used as a drying agent for gases that do not react with sulfuric

acid by bubbling the gas through sulfuric acid.

Synthesis of sulfuric acid

Sulfuric acid is made be reacting sulfur trioxide with water in an exothermic

reaction.

SO3(g) + H2O(l) → H2SO4(l) + 130 kJ mole-1

In the commercial production of sulfuric acid, the contact process or the lead-

chamber process is used. In the contact method, sulfur dioxide is catalytically

converted to sulfur trioxide by surface chemistry with fine platinum powder or,

more recently, vanadium pentoxide (V2O5). The resulting sulfur trioxide gas is

bubbled through sulfuric acid and the addition of water at the correct rate yields

98% acid pulled out.

The lead-chamber process uses sulfur dioxide, oxygen, nitric acid and water vapor

are introduced into a lead-lined chamber. White crystals of nitrosulfuric acid

(nitronium sulfate), NOHSO4, are formed. The introduction of steam then converts

the nitrosulfuric acid to sulfuric acid liberates nitrogen oxides, which can be reused

in the first step of the reaction.

1) 2SO2 + NO + NO2 + O2 + H2O → 2NOHSO4

2) 2NOHSO4 + H2O → 2H2SO4 + NO + NO2

Soluble and insoluble sulfate salts

The soluble salts of sulfate include sodium sulfate (Na2SO4)•10H2O, ammonium

sulfate (NH4)2SO4, magnesium sulfate (Epsom salt, MgSO4•7H2O, copper sulfate

(blue vitriol, CuSO4•5H2O), iron sulfate (FeSO4•7H2O), zinc sulfate (ZnSO4•7H2O),

potassium aluminum sulfate (alum, KAl(SO4)2•12H2O), ammonium aluminum

sulfate (ammonium alum, NH4Al(SO4)2•12H2O), and chrome alum

(KCr(SO4)2•12H2O).

Barium sulfate (barite) is the least soluble sulfate salt and its white precitate is

used as a test for sulfate anions. Other sulfates with diminished solubility include

lead sulfate (PbSO4), strontium sulfate (SrSO4) and calcium sulfate (gypsum,

CaSO4•2H2O.

PetrochemicalsPetrochemicals are chemical products made from the hydrocarbons present in

raw natural gas and petroleum crude oil. The largest petrochemical manufacturing

industries are to be found in the United States, Western Europe, Asia and the

Middle East.

A relatively small number of hydrocarbon feedstocks form the basis of the

petrochemical industries, namely methane, ethylene, propylene, butanes,

butadiene, benzene, toluene and xylenes.[1][2]

As of 2007, there were 2,980 operating petrochemical plants in 4,320 locations

worldwide.[3] The petrochemical end products from those plants include plastics,

soaps, detergents, solvents, paints, drugs, fertilizer, pesticides, explosives,

synthetic textile fibers and rubbers, flooring and insulating materials and much

more.

Petrochemicals are found in such common consumer products as aspirin, cars,

clothing, compact discs, video tapes, electronic equipment, furniture, and a great

many others.[4]

Feedstocks sources

(PD) Image: Milton Beychok Figure 2: Petrochemical feedstock sources.

Figure 2 schematically depicts the major hydrocarbon sources used in producing

petrochemicals are:[1][2][5][6]

Methane, ethane, propane and butanes:

Obtained primarily from natural gas

processing plants.

Naphtha obtained from petroleum

refineries.

Benzene, toluene and xylenes, as a

whole referred to as BTX and primarily

obtained from petroleum refineries by

extraction from the reformate produced in

catalytic reformers.

Gas oil obtained from petroleum

refineries.

Methane and BTX are used directly as feedstocks for producing petrochemicals.

However, the 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 intermediate petrochemical feedstocks:

Ethylene

Propylene

Butenes and butadiene

Benzene

In 2007, the amounts of ethylene and propylene produced in steam crackers were

about 115 Mt (megatonnes) and 70 Mt, respectively.[7] The output ethylene capacity

of large steam crackers ranged up to as much as 1.0 – 1.5 Mt per year.[8][9]

Steam crackers are not to be confused with steam reforming plants used to

produce hydrogen and ammonia.

Worldwide usage of optional steam cracking feedstock sources

As of 2004, the percentage of the worldwide steam cracking plants using each of

the optional steam cracking feed sources was:[10]

Ethane: 35%

Propane: 9%

Butanes: 3%

Naphtha: 45%

Gas oil: 5%

Other: 3 %

The effect of feedstock on the steam cracking yields of intermediate petrochemical products

The effect of feedstock selection upon the yields of steam cracking products is

summarized in the table below:

Steam cracking feedstocks versus yields of intermediate petrochemical products

Product Yields

Feedstocksource

Ethyleneweight %

Propyleneweight %

Butadieneweight %

Aromatics (a)

weight%

Ethane 84.0 1.4 1.4 0.4

Propane 45.0 14.0 2.0 3.5

Butane 44.0 17.3 3.0 3.4

Naphtha (c) 34.4 14.4 4.9 14.0

Gas oil (d) 25.5 13.5 4.9 12.8

(a) Includes benzene, toluene, xylenes and any other aromatics.

(b) Includes hydrogen, methane, butenes, non-aromatic portion of pyrolysis gasoline

oil.

(c) Full-range naphtha (as differentiated from light or heavy naphtha).

(d) The portion of petroleum crude oil that has a boiling range of about 250 to 550 °C (480 to

1020 °F).

That encompasses the boiling range of atmospheric gas oil (AGO) produced by the

distillation

of petroleum crude oil and the boiling range of vacuum gas oil (VGO) produced by the

distillation

of petroleum crude oil.

Feedstocks and example petrochemical products

The table below includes some representative examples of the petrochemical end

products produced from the eight hydrocarbon feedstocks – methane, ethylene,

propylene, butenes, butadiene, benzene, toluene and xylenes:

Feedstocks and example petrochemical products

methane ethylene propylenebutenes

and Bhutanese

benzene toluene xylenes

hydrogen polyethylenepolypropyle

ne

styrene-butadiene

rubber (SBR)

styrenebenzoic

acidphthalic

anhydride

ammonia ethanol isopropanolmethyl tert-butyl ether

(MTBE)

polystyrene

toluene diisocyanat

epolyesters

methanol ethylene glycolpropylene

glycolpolybutadie

nephenol

polyurethanes

dimethyl terephthal

ate

methyl chloride

vinyl acetate allyl chloride

acrylonitrile-butadiene-

styrene

cumene caprolactam

terephthalate acid

(ABS)

carbon black

perchloroethylene

acrylonitrilepolybutene

saniline nylons

polyethylene

terephthalate

acetylenepolyvinyl acetate

acrylic acid

methyl ethyl

ketone (MEK)

adipic acid

polyureasdioctyl

phthalate

formaldehyde

glycol ethersepoxy resins

tert-butanol nylons