chemical Engineering

Petroleum products and

test methods
Shayma Hamza

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 Crude petroleum products
• Petroleum products are materials derived from crude oil (petroleum) as it is processed
in oil refineries.
• Complex mixtures, in which their composition vary depending on the type of crude oil

• Petroleum products are separated by distillation based on the difference in their boiling
point

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•
• American Standard for Testing
Materials ASTM provides methods
to test the quality of these products
Crude petroleum
products
Methane and Ethane are separated
spontaneously at atmospheric
pressures.
• Propane and butane are liquids at
pressures slightly above the
atmospheric pressures. They are
separated as LPG from the crude
oil
• The rest of hydrocarbons are
separated based on their boiling
point range.

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•
Crude petroleum analysis-atmospheric distillation
Initial boiling point test IBP: Is defined as the temperature of vapour at which the
first drop of condensate in a batch distillation apparatus is collected.

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•
• This temperature is low, below 0 C, if the concentration of the lowest boiling point
components are high. It increases with increasing the heavier components
concentration.
• The temperature is usually recorded after 5-10 min of heating
• It gives a qualitative estimation of the crude composition.
Crude petroleum analysis-atmospheric distillation
Batch distillation is continued and more and more of hydrocarbons are separated until
no evaporation occurs.
• The vapour temperature and volume of condensate liquid (boiling fractions) are
measured and reported as distillation analysis of crude oil.
• During distillation at atmospheric pressures, the rate of vaporisation decreases after
40-45% of crude is distilled until it ceases. At this point higher temperatures are
needed to induce evaporation. However there is a risk for decomposition of the
fractions at higher temperatures.

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•

Crude petroleum analysis-vacuum distillation

Vacuum distillation is conducted for separation of the heavier fractions of crude oil
which cannot be separated by atmospheric distillation.
• Lower pressures in the distillation setup offers restoration of vaporisation of heavier
fractions.
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•

Crude petroleum analysis-True Boiling Point TBP

Distillation of crude oil in which the vapours and its condensates are in intimate contact
for increased amount of time improves the separation process. Such a method of
distillation is known as True Boiling Point distillation or TBP.

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 •
• TBP offers a separation of 1 vol% at very close
temperature differences.
• The increased contact time between vapour and its
condensates are provided by a reflux ratio of 5:1
• A TBP distillation has to be carried out for each crude
oil sending on the wells they are produced from.
• TBP analysis indicates the maximum possible yield of
raw cuts that can be obtained by distillation
• TBP analysis are necessary in designing the
distillation column of refineries.
• Large variation of TBP means that same distillation
column cannot be for these crude oil types, unless the
maximum yield is sacrificed.

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Crude petroleum analysis-True Boiling Point TBP

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 Crude petroleum analysis
• API gravity is usually used for pricing of the crude oil.
• Characterisation Factor CF in addition to API is used to judge the quality of
crude oil and its products
• Bottom Sediment and Water BSW is a measure of the quantity of the
settable residual sediment and water in crude oil
• BSW may contain heavy asphaltic hydrocarbons or non-hydrocarbons such
as inorganic salts
• Amounts of BSW are routinely tested for every batch of crude oil

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 Crude petroleum analysis-ASTM methods
• Throughout the world the petroleum products are tested according to
methods and equipments specified by the American Standard for Testing
Materials ASTM.

• ASTM methods provide a common

platform in which the test results of
diverse samples could be compared
and evaluated.

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 ASTM HQ in West Conshohocken, PA, as seen
from a nearby bridge

Domestic fuels- Liquid Petroleum Gas LPG

• LPG is a mixture of propane and butane in liquified form at pressures
of 10-15 atm.
• LPG is the first product of distillation from crude oil.

Usage :
• Energy carrier, for cooking and heating
• As fuel for gas driven vehicles
• As refrigerator gas

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 Liquid Petroleum Gas LPG-Weathering test
Weathering test also known as boilaway test is a simple test to determine the
heavy components of LPG by evaporating the volatile components.
Test moments :
• 100 ml of the LPG in an open ended test-tube with
immersed thermometer.
• Evaporation at atmospheric pressure until only 5 ml is
left

Temperature interpretation
• If T < 0 C then the Propane portion of LPG is higher
• If T > 2 C then the Butane portion of LPG is higher

For domestic use the maximum T should not exceed 2 C

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 • Reason: incomplete evaporation that might occur at lower ambient
temperature for example during winter.

Liquid Petroleum Gas LPG-

RVP-test
Reid Vapor pressure test RVP-test: Is
conducted to check the volatility of the
petroleum products by measuring the
absolute vapour pressure of a liquid exerted
at 37.8 C or 100 F according to ASTM -D-323.

Test moments :
• Conducted in high pressure vessel
• Temperature is kept constant by an oil bath
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• The pressure is measured as RVP

Domestic LPG should have a RVP of 8 kg/cm2

• RVP test is important in not exceeding the carrying capacity of gas cylinders,
specially during summers.

Liquid Petroleum Gas LPG- Determining impurities

LPG is usually not a uniform mixture of propane and butane. There are some
other volatile trace gases such as olefinic gases, mercaptan
and hydrogen sulphide.
Copper stripp corrosion test:
• The extent of corrosion on a copper strip determines the amount of
mercaptans and hydrogen sulphide in LPG.

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• Test is conducted by immersing a well polished copper strip in a closed vessel called
a bomb, containing LPG held at constant temperature for 1 hour.
• The discolouration on copper strip is compared to a set of standardised copper strips,
ASTM1.

Doctor’s test
• Determining the trace amount of hydrogen sulphide and mercaptans by a chemical
reaction in which lead sulphide is precipitated

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Domestic fuels- Kerosene
• Kerosene, also known as paraffin, lamp oil and coal oil is a combustible
hydrocarbon liquid which is derived from petroleum, widely used as a fuel
in industry as well as households.

Properties:
• A heavier petroleum product with boiling point in the range of
140 C - 280 C
• Heavier than naphtha or gasoline but lighter than diesel

Usage:
• As heating and lighting fuel
• For cooking
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 • As transportation fuel (mid 20’s century for tractors)
Kerosene- Smoke point test
Smoke point is referred to the height of the flame produced
by kerosene in the wick of a stove or lamp without forming
any smoke.

Smoke point
• The test is carried out in lamp with a wick of specified mass and
dimensions
• A mirror is provided to position the flame in the centre in a way
that the straight height of the flame can be measured in a
graduated scale.
• Domestic kerosene should have a smoke point of 20 mm

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• Lower smoke point indicates presence of heavier fractions of hydrocarbon

Kerosene- Flash point

Flash point is the lowest temperature at which vapours of a volatile material
will ignite, when given an ignition source.

Flash point
• The test is carried out using a standard cup, standard
flame and under atmospheric conditions.
• The fuel is heated at a rate of 5-6 C/min and the temperature is measured.
• A flame is introduced every 30 s.
• The temperature at which a momentary flash occurs is noted as
flash point.

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 Flash point is usually used to distinguish flammable liquids from combustable
liquids. Flash points higher than 37.8 C or 60.5 C are called combustable.

Kerosene- Char point and bloom

Char point is defined as coke and ash left on the wick after complete burning
of the kerosene.

For domestic kerosene this value should not exceed 20 mg/kg of kerosene.
Higher amounts indicate higher concentrations of aromatics.

Bloom is the darkness produced by flame of the fuel while burning in a

standard glass.

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 For domestic kerosene the bloom should not be darker than a standard
brightness desired in a lamp.

Kerosene- Distillation
ASTM distillation of kerosene is carried out at
atmospheric conditions

• Finished kerosene must be at least 20 % distilled at 200

C
• Final boiling point should not exceed 300 C

• Lighter kerosene ( boiling point less than 140 C) is too dangerous for domestic use.
• Heavier kerosene ( boiling point higher than 300 C) is inappropriate burning fuel for
domestic use

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 Kerosene- Sulphur content and corrosion
Sulphur in kerosene produces hazardous sulphur dioxide and may cause
corrosion. The sulphur content should not exceed 0.25 % by mass.

• Copper strip corrosion test is carried out to determine the sulphur content.
• The test is carried out in a bomb for 3.5 hours at 50 C.

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 Important parameters in determining the quality of kerosene

Automotive fuels- gasoline

• Gasoline, Gasoline known as petrol is a transparent, petroleum-derived
liquid that is used primarily as a fuel in internal combustion engines. It

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 consists mostly of organic compounds obtained by the fractional distillation of
petroleum, enhanced with a variety of additives.

Usage:
• Mainly as transportation fuel in internal combustion engines
Gasoline- ASTM Distillation
• ASTM, distillation is carried out at atmospheric
conditions to estimate the quality of gasoline
Procedure
• Distillation of a 100 mL sample and collection of the
condensate in a graduated cylinder.
• The temperature at which the first drop of condensate is
collected is the Initial Boiling Point IBP
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• The final temperature at which the condensate collection is negligible is the Final Boiling
Point FBP

Evaluation
• A low IBP indicates presence of higher volatile compounds- This value may vary
• A high FBP indicated presence of heavier compounds this value should not exceed 215
C.
• The required ASTM distillation is that 10%, 50% and 90% vaporisation should occur at
temperatures of 70 C, 125 C and 180 C

Gasoline- Octane number

• Octane number, is a standard measure of the performance of an engine fuel.
The higher the octane number, the more compression the fuel can withstand
before detonating (igniting).

• Octane number of a fuel is highly dependent on its composition.

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• Presence of more propane, butane, aromatics, xylene, benzene and toluene in the
boiling range of the gasoline will increase the octane number.
• Octane number is therefore defined as the content of iso-octane in the gasoline

100 % iso-octane octane number is 100 Knock-free engine

power rate = 100%

Knocking engine
100 % n-octane octane number is 0 power rate = 0 %
Gasoline- Octane number

• Octane number is measured in a so called CFR engine co-operative Fuel Research

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Depending on the conditions two measurements are
carried out and two values can be given for Octane
number

Research Octane Number RON Motor Octane Number MON

• Measured at 600 rpm • Measured at 900 rpm
• Best for city driving conditions • Best for highway driving conditions
Octane number decreases with increasing speed, consequently MON is always less than
RON.

Tetra-ethyl lead TEL was used to enhance octane number ( hazard for environment and
health). Now MTBE and ETBE are used instead.

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Gasoline- Additional quality tests
• Corrosion test: Copper strip corrosion test is carried out to find the
content of sulphur compounds.

• RVP : Reid vapour pressure is measured same as LPG. The RVP value
should not exceed 0.7 kg/cm2. Higher values than this mean vapour
leaking in the engine and vapour loss during storage. Very low vapour
pressure means problems with startup of the engine.

• Oxidation stability: Presence of unsaturated hydrocarbons from variety of

sources can cause polymerisation of these compounds in presence of
oxygen.

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• To test this the gasoline is contacted with oxygen at pressurised vessels at
constant temperature and any reduction of pressure is measured. This
reduction is correlated to the gum formation.

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Gasoline- summary of important parameters

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Automotive fuels- High speed diesel
• Diesel fuel: in general is any liquid fuel used in diesel engines, whose fuel
ignition takes place, without any spark, as a result of compression of the inlet
air mixture and then injection of fuel.

Properties and usage:

• A mixture of hydrocarbons with a boiling
point in the range 250-360 C
• Used in diesel engine of cars, tractors,
lorries, irrigation pumps and generators

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• Diesel engines work without a spark, the combustion occurs as a result of
compression of the atomised vapour of the diesel in presence of preheated
air.
Diesel- Cetane Number CN
• Cetane number CN is an indicator of the combustion speed of diesel fuel and
compression needed for ignition. It is an inverse of the similar octane rating for
gasoline.

• The paraffinic portion of diesel auto-ignites much easier than the aromatic counterpart
under compression therefore CN is an indication of the paraffinic content in diesel.

• Cetane is a saturated paraffin with chemical formula n-C16H34. Cetane ignites very
easily under compression, so it was assigned a cetane number of 100.
• alpha-methyl naphthalene is an aromatic compound and was assigned a cetane number
of 0.

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• The knocking quality of an diesel oil is measured by CN which is the percentage of
ncetane in a mixture of n-cetane and alpha methyl naphthalene.
• Normal values of CN is in the range 40-55.
• Higher speed diesel engines operate more effectively with higher CN
• CN is measured using the diesel engine of Cooperative Fuel Research CFR
Diesel- Diesel Index DI
• DI is defined as:

• In which the aniline point of an oil is defined as the minimum temperature at which equal
volumes of aniline (C6H5NH2) and the oil are miscible, i.e. form a single phase upon
mixing
• Aniline is an aromatic compound and therefore dissolves/mixes easier with aromatic
compounds

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• Therefore the lower aniline point the higher is the aromatic content in diesel oil.
• DI is directly proportional to CN
• The minimum value of DI is 45
Diesel- Standard Qualities
• Sulphur: The sulphur is removed by catalytic desulphurisation and its content should
not exceed 0.25% by weight.
• Corrosion: Copper strip method at 100 C for 3 h.
• Flash point: Minimum value is 33 C. During summer higher flash point and during winter
lower flash point is preferred
• Flame length: Maximum 18 mm for diesel. A higher flame length can damage the
engine.

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• Pour point: defined as the temperature at which oil cease to flow due to formation of
wax crystals. depending on the climatic condition a pour point of 6 C or lower is required
for diesel.
• Viscosity: lower viscosities are preferred for diesel oil. A range of 2.5 - 7 centi Stoke cSt
at 38 C is recommended.

Aviation fuels.
Aviation fuel is a specialized type of petroleum-based fuel used
to power aircraft. It is generally of a higher quality than fuels used
in less critical applications, such as heating or road transport, and
often contains additives to reduce the risk of icing or explosion due
to high temperature, among other properties.

Aviation fuels

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• Kerosene based, Aviation turbine fuel
ATF • Gasoline based,

• Used in passenger airplanes • Used in jet engines

• alkylated gasoline
• Polymer gasoline
• octane number > 100
Aviation fuels. ATF Aviation Turbine Fuel
Important properties of kerosene bases aviation fuel

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 Lubricating Oils
Lubricant is a solid, semi-solid or liquid material that is used to reduce friction
between two solid surfaces.

Example
• Graphite
• Soap
• Wax
• Sulphur
• Mineral oil

Lubricating oils are liquid lubricants mainly made from petroleum oils (obtained
by vacuum distillation) blended with soaps of fatty acids and other additives.
Function:
• Reduction of the friction between two moving surfaces in contact
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 • Cooling down the heat of friction
Lubricating Oils- Viscosity
Viscosity of a fluid is a measure of its resistance to gradual deformation by
shear stress or tensile stress. It gives a measure of resistance to flowability.

duUnits
F=µA dy• centipoise cP (g.cm/s)
• Pascal.Sec
dynamic Viscosityµ
• centistoke ( kinematic viscosity) ν=

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Measurement methods
Depending on the range:
• Capillary
• Orefice
• Rotatory
• Float
• Falling sphere Rotatory viscometer Falling ball viscometer
• Vibrational

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 Lubricating Oils- viscosity measurement methods

Saybolt method is a capillary method for light and

non sticky hydrocarbons.

The Saybolt method is used where time (t) of efflux a a

definite quantity (60 mL) of liquid through a typically
designed capillary tube, kept at constant temperature
bath is measured.

Viscosity (centistoke) is related to Saybolt time t

by:

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 Lubricating Oils- viscosity measurement methods

Redwood method is an orifice or jet method.

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The Redwood method is used where time (t) taken by definite volume of liquid through an
orifice with specified dimensions is measured. Viscosity is
given as Redwood seconds.

A conversion table is used to convert the

Redweeod seconds to kinematic viscosity

Brookfield method
This method uses a rotatory type viscometer consisting of
two disks containing the liquid under test.
The shear force experienced by rotating disk is measured
against the liquid over the static one.
Lubricating Oils- Viscosity Index VI

Viscosity Index VI is a parameter that indicates

the rate of change of the viscosity of the oil due to a variation in temperature.

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L, H and U refer to viscosities of:
• L: Petroleum (aromatic) oil with VI = 0
• U: The lubricating oil sample
• H: Paraffinic oil with VI = 100

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 Lubricating Oils-

Cloud point is the temperature at which oil becomes hazy or cloudy due to
onset of wax crystallisation or solidification.

Pour point is the temperature at which liquid hydrocarbon ceases to flow or

pour.
Hydrocarbon groups and properties of corresponding lube oil. Paraffinic P, Naphtenic
N and Aromatic A

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In addition to the above three properties, there are other important parameters that
influence the performance and quality of lube oil. These are flash point, carbon
residue, saponification value, acidity, foaming characteristic, sulphur content
and corrosiveness.
Petroleum Products
Jute Batching Oil JBO is straight run product obtained from atmospheric
distillation of crude oil at slightly different temperature of diesel cut and it is 340-
360 C. It is mainly used in jute industry for bailing jute fibres that can later be
used in food packaging. It has two types JBO(c) and JBO(p).

Mineral Turpentine oil (MTO) Has a boiling fraction as kerosene in the range
of 125-240 C. Used mainly in paint industry as solvent or thinner.

Carbon Black Feed Stock (CBSF) A by product from lube extraction plant and
rich in aromatic compounds. Often used for yielding carbon particles for battery
and metallurgical industries.

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 Petroleum Products
Bitumen or Asphalt is a very sticky, semi solid and viscous petroleum,
containing various heteroatomic compounds of hydrocarbons enriched with
metallic, sulfurous, nitrogenous, and oxygenated compounds.

• Used mainly as paving material, paint and water-proofing agent.

• It flows like a liquid at 90 C and solidifies at room temperature.

• Penetration index is defined a the depth of submergence or penetration of

a standard weight through a needle penetrator.

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