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Composition of crude oil, processing of crude oil, Refining,
Reforming & Cracking, Synthetic Oil. Diesel: Diesel engine
ignition temperature, Flash point, Fire point, Smoke point, Cetane
no. Petrol: Spark ignition IC engine, Gasoline fuel, Grading
gasoline, Knocking, Additives & Dopants, Octane No. Alternative
fuels: Propane, Methanol, Ethanol Q.1.
a)WhatisPetroleum?b)DiscusstheaveragecompositionofPetroleum.c)BrieflydiscussaboutthemajorconstitutensofPetroleum.
Ans: a)
Petroleumisoneoftheimportantliquidfuelswhichhaveextensiveuseinindustriesaswellasforthedomesticpurposes.ThetermPetroleumiscomingfromtheLatinwordsPetrameansrockandOleummeansoil.Hencepetroleumisalsoknownasrockoilwhichisfounddeepinthesolideearthscrust.Miningofpetroleumiscarriedoutbydrilingholesandsinkingpipesuptotheoilbearingzonesintheearthcrust.b)
AverageComposition:PetroleumisamixtureofdifferenthydrocarbonswithsmallfractionsoforganiccompoundscontaiingOxygen,Nitrogen,Sulphuretc.Thehydrocarbonspresent
inthepetroleumaremainlystraightchainparaffins,olefinsandaromaticcompounds.Theaveragecompositionofcrudepetroleumisasfollows:Carbon:
8085%, Hydrogen: 1015%, Nitrogent: 0.31.0%Sulphur: 0.1%3.5%
andOxygen: 0.1%1%.c)
ConstituentsofPetroleumThemajorconstituentsarefollowings:i)Hydrocarbons:
Approx70%Normal,BranchedandCycloalkanes.LowerBoiling
fractionsalsocontainalkylbenzenes.HigherBoilingfractionscontainpolynucleararomaticslikenaphthalenes.Terpenesarealsopresenttosmallextent.
ii)Sulphur: H2S,Thiols,Thiopene,Thioalkanesetc.iii)Oxygen:
C4C9carboxylicacidsoccurinlowboilingfractions
Naphthenicacidoccurinhighboilingfractions.
Traceamountsofphenolsandcresolsalsopresent
iv)Nitrogen: Pyrrole,Indole,Pyridine,Quinolineetc.v)Inorganic:
Organomettalic:CU,Fe,NianVareverylittleextent
Q.2.
WritedownthenameofmostpopoularandverstileliquidfuelobtainedfromPetroleum.
Ans: Petrol(Gasoline),Diesel,andKerosenQ.3.
WritedownfewnamesofimportantchemicalsobtaineddirectlyorindirectlyfromPetroleum
Ans: alkane,alkenes,benzene,ethanol,aceticacid,styreneetc.Q.4.
Writedownthemajorsteps,whichinvolveinrefiningofcrudeoil.
Ans:Theprocessofpetroleum(crudeoil)refiningincludesthesequenceofsteps:Step1:
RemovalofWater(CottrellsMethod)Thecrudepetroleumisextremelystableemulsionofoilandsaltwaterasitisderivedfromearthcrust.Thesaltcanbeseparated(demulsification)fromwaterbyallowingthecrudeoilto
flow through
twohighlychargedparallelplaceelectrodes.Thecolloidalwaterparticlescoalescetoformlargesizedropletsandareeasilyseparatedfromoil.
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Step2: RemovalofharmfulsulphurcompoundsSulphur atom has the
addiction twoards CuO (Cupric oxide). Thus to remove
sulphurcompounds fromoil, it is treatedwithCuO.The resultant
solution
containsprecipitateofsolidcoppersulphide(CuS),whichiseasilyseparatedbyfiltration.Step3:
FractionalDistillationThecrudepetroleumistakeninanironretortanditisheateduptot400Ctemperaturesothatallvolatilematterareevaporated.Thehotpetroleumvapouristhenpassedthroughacylindrical
column (fractionation column)which contains a number of
horizontally
placedtraysatshortgap.Eachtrayisconnectedtoasmallchimney.Asthevapourmovesupward,fractionalcondensationtakesplaceatdifferentheightsofthecolumn.Highboilingfractionsarecondensedfirstfollowedbylowboilingfractions.
Figure1 FractionalDistillationofcrudepetroleum
S.No. Constituent BoilingRange #CarbonandUses
1 UncondensedGas 30C C1C4;DomesticFuel(LPG)
2 PetroleumEther 30C70C C5C7;EssentialOil,SolventforFats
3 Petrol(Gasoline) 40C120C C5C9;AsmotorfuelforI.Cengine
4 NaphthaorSolventSpirit 120C180C
C9C10;Solventforpaintandvarnishes.
5 KeroseneOil 180C250C
C10C16;JetEngineFuel,IlluminatingStoveFuel
6 DieselOil 250C320C C10C18;DieselEngineFuel
7 HeavyOil 320C400C C17C30;ShipFuel,MetallurgicalFurnaces
8 Residue(AsphaltandPetroleumCoke)
>400C C30andabove;Waterproofingroofs,moulding,electrode
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Q.5.
Drawalinediagramtodescribefractionaldistillationprocessofcrudepetroleum
Ans. ExplaintheearlierdiscussedFigureandTableQ.6.
Brieflydiscussaboutthemostimportantliquidfuele.g.gasoline,keroseneanddieseloil.
Ans.
i. Petrol or Gasoline: Gasoline is most important fraction of
petroleum (40120), Theapproximate composition of Gasoline is C:
84%, H: 15%, and N,O, S: Low. The mainconstituentofpetrol
isthemixtureofpentane(C5H12)andOctane(C8H18).Petrol
isvolatileinflammableandhasextensiveusesasfuelsforICengines,automobilesandairplanes.TheCalorificValueofpetrolisabout11250Kcal/kg.ii.KeroseneOil(180250):Mainuseindomesticfuelinstoves.ItalsouseinJetenginefueland
for producing oil gas. The main constituent of kerosene oil is
decane (C10H22)
andhexadecane(C16H34).iii.DieselOil:(250320).Themixtureofhigherhydrocarbons
likepentadecane(C15H32)andOctadecane(C18H38).Itisusedmainlyasafuelindieselengine.ThecalorificvalueofDieseloilis10000Kcal/kg.
Q7. WhatismeantbyStraightRunPetrol.?
Ans.
ThemostimportantfractionofpetroleumobtainedbyfractionaldistillationispetrolorgasolineasithasextensiveuseinICengineofmotorvehicles.Unfortunately,only20%ofthetotalpetroleumispetrolorgasoline.ThequalityofthesocalledStraightRungasolineisnotgoodenoughand
it isusedonlyafterproperblending. It contains
surplusamountofheavierpetroleum fractions. To avoid
suchdifficulties, theheavy andmiddle fractionsofhydrocarbon are
cracked to get more useful and volatile petrol. The quality of
petrolobtainedbycrackingismuchbetterthanStraightRunPetrol.
Q.8.
whatismeantbycrackingofpetroleum?Brieflydiscussaboutthemethodofcracking.
Ans.Cracking is
thedecompositionofhighmolecularweighthydrocarbonsofhighboilingpoint
into simpler such as light hydrocarbons, by the breaking of
carboncarbon bonds in theprecursors.Thus,thecracking
isthebreakdownofa largealkane
intosmaller,moreusefulalkanesandanalkene.
LongChainAlkaneSmallerAlkanes+Alkenes+H2
ThemethodsofCrackingaremainlyofthetwotypes:ThermalcrackingandCatalyticcracking.
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ThermalCracking: The thermal cracking is performed by heating
the heavy oils (heavy ormiddle fractions of petroleum) under high
pressure in absence of Catalyst. In thermal cracking,heavier and
larger hydrocarbon molecules break down and produce smaller
molecules of lowmolecularweightparaffins,olefinandsomeH2.
Thermalcrackingisoftwotypes,liquidphaseandvapourphasethermalcracking.LiquidPhaseCracking:
OctaneRating6570,MoretimerequiredVapourPhaseCracking:OctaneRating>70,Lesstimerequired.HoweverOilshouldbevapourizable.CatalyticCracking:
To obtain the better quality petrol in higher quantity, the
cracking ofpetroleum is done in presence of some suitable catalysts
like Aluminum Silicate [Al2(SiO3)3]
orAluminumoxide(Al2O3).Forcatalyticcrackingthetemperatureandpressurerequiredismuchlowerthanthermalcracking.CatalyticCrackingcanbedonebytwodifferentways:i)FixedBedCatalyticCracking
ii)MovingBedCatalyticCracking
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Q.9. Explainschematicallyi)FixedBedCatalyticCracking
ii)MovingBedCatalyticCrackingmethodsofobtaininggasoline.i)FixedBedCatalyticCracking
TEMPERATURE: 425450CPRESSURE 1.5kg/cm2YIELD:
Conversion40%intogasoline,with24%Carbonformation.Carbonadsorptiononcatalyticbedcausingcatalystquenchingandrequiresreactivation.Thustheburningoffmethodneedstousetoremovethedepositedcarbonfromcatalyst.Duringthereactivation,thevapoursaredivertedthroughanothercatalystchamber.ii)MovingBedCatalyticCracking
Cycloneallowsonlythecrackedoillvapourstopassonthefractionaingcolumn,butretainsallthecatalysitpowderinthereactor.TheCarbonadsorbedcatalyst(heavier)setllestothebottom,fromwhereitforcedbyairblowertotheregeneratorchamber(600C)forburningofftheadsorbedcarbon.Regeneratedcatalystwillmixedwithfreshbatchofheavyoilvapourforfurthercracking.
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Q.10. Discuss the advantages associated with Catalytic Cracking
over Thermal Cracking
I. Quality of Petrol obtained by Catalytic Cracking is better
than thermal cracking II. The quantity of petrol obtained is higher
in catalytic cracking.
III. In catalytic cracking no external fuel is required. IV. A
much lower pressure is sufficient for catalytic cracking V. The
product obtained by catalytic cracking contains higher amount of
aromatic
compounds and hence it has better anti-knock properties. VI. The
cost involved in production of low molecular weight hydrocarbons by
catalytic
cracking is much lower as high temperature and pressure is not
needed in the process.
Q.11. Discuss the gasoline production by catalytic cracking with
an example.
Catalytic cracking increases the proportion of gasoline and also
produces alkenes and branched-chain hydrocarbons by isomerization.
Thus the product is high quality motor fuel, its octane number
being greatly improved. Q.12.
Illustratethemechanismfora)Thermalandb)CatalyticCracking.a)Itisbelievedthatthermalcrackinggothroughwithfreeradicalmechanism.GenerallyfreeradicalreactionprocessthroughwelldefinedpathwaysvizInitiation,PropagationandTermination.Illustrationwithanexampleofthermalcrackingofnnonane:
b) Catalytic Cracking: The catalytic cracking process involves
the presence of acid catalyst (silica or alumina based), which
promote a heterolytic breakage of bonds yielding pairs of
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ions, usually a carbocation and unstable hydride anion. The
chain of reactions is eventually terminated by radical or ion
recombination.
Duetothermalcracking,firstasmallamountofAlkenesisformedwhichgetsprotonatedattheacidicsitesofthecatalyst.
Thechainofreactionsiseventuallyterminatedbyradicalorionrecombination.
Q. 13 What is knocking? In the internal combustion engine, the
mixture of petrol vapour and air is ignited. The efficiency of I.C.
engine depends on compression ratio which in turn depends on the
quality of the nature of components present in the petrol used. In
presence of some specific components, the petrol burns with a high
rate and the remaining portion of the fuel-air mixture burns
instantaneously and produces an explosive violence or metallic
rattling known as knocking. Due to knocking the efficiency of
engine decreases. It is observed that the components like
straight-chain alkanes produce greater amount of knocking compared
to the branched chain alkanes. Q.14. Define the term Octane number
or Octane rating The anti-knocking efficiency of a fuel is measure
by its octane rating or octane number. The anti-knocking property
of a fuel cannot be expressed by simple numerical value and hence
an arbitrary scale of octane rating was introduced. According to
this scale, Iso-octane (2,2,4-trimethylpentane) possess higher
anti-knock properties and n-heptane possess lower anti-knock
properties than any commercially used petrol. Arbitrarily, it is
considered that iso-octane has octane rating 100 and for n-heptane,
the rating is 0 (zero). The octane number or octane rating of a
fuel is the % of iso-octane in the mixture of iso-octane and
n-heptane which has same knocking characteristics of a fuel under
consideration in the same set of conditions. Improvement by
Additives to increase octane rating: Addition of some foreign
hydrocarbons to the fuel can enhance the anti-knock properties of
fuel. These additives are called anti-knock agents. Anti-knock
agents, however not recommended due to its toxic and pollutant
nature i) Tetra Ethyl Lead [Et4Pb] or TEL and ii) Diethyl telluride
[(Et)2Te]
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In IC chamber, TEL is ignited which produces Pb and PbO. These
compound acts as chain inhibitors by arresting the chain
propagation process of the explosive chain reaction responsible for
knocking. Ethyl bromide is also requires to add to remove Pb and
PbO as volatile PbBr2. Unleaded Petrol: The octane rating can be
increased by addition of some compound like iso-pentane,
iso-octane, ethyl benzene, methyl tertiary butyl ether (MTBE) etc
which do not contain any lead compound. Q. 15. Explain Reforming
The antiknock characteristics of gasoline can be improved by
reforming. This in effect brings about structural modifications in
the components of feed-stock either by thermally or catalytically.
TEL addition can improve Octane No: Tetraethyl Lead (Et4Pb).
1,2-dibromoethane is requires to remove Pd deposition as PdBr2
volatile and serious pollutant. Therefore no lead petrol is
recommended
The major chemical modifications that occur during reforming
process are: Isomerisation, Alkylation and Cyclisation.
Isomerization
Alkylation Isobutylene produced as a by-product of cracking of
petroleum, alkylates isobutane to form isoocatane in the presence
of c. H2SO4
isobutane
+
Isobutylene
H2SO4
2,2,4-trimethylpentane
Octane No: 100 Aromatization The C6-C8 straight chain alkanes in
the presence of Pt catalyst at 500 C, yield a mixture of benzene,
toluene and xylenes (BTX)
The gasolines prepared by isomerization and alkylation, when
blended with BTX are about 90 octane. This is the fuel that is now
sold as no-lead gasoline.
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Synthetic Fuel
1. Water Gas (Blue Gas): It is mixture of combustible CO and H2
and a little amount of
non-combustible gases like CO2 and N2. Water gas is also called
blue gas as it burns with a blue flame. The average composition of
water gas is: CO: 41%, H2: 51%, N2: 4%, CO2: 4% The calorific value
of water gas is about 2800 kcal/kg Preparation: Water gas is
prepared by passing steam over red-hot bed of coke or coal to a
about 900-1000 C C+ H2O -- CO + H2 - 29 kcal Use: i) Production of
H2 gas, ii) Preparation of synthetic petrol
2. Producer Gas: Producer Gas is a mixture of combustible Carbon
monoxide (CO) gas and non combustible N2 gas. The average
composition of producer gas is: CO: 20-30%, H2: 8-12%, N2: 50-55%,
CO2: 2-3% The calorific value of producer gas is about 900-1300
kcal/kg Preparation: Producer Gas preparation is a two step
process: a) Oxidation: In this step, Carbon of coke is oxidized in
presence of air i) C + O2 ---------- CO2 + 97 kcal ii) C + O2
----------- CO + 53 kcal b) Reduction: In this step CO2 and steam
reacts with Carbon or Coal to produce Hydrogen and CO i) C + CO2
--2CO - 36 kcal ii) C + H2O -- CO + H2 -29 Kcal iii) C + 2H2O --
CO2 + 2H2 -19 kcal Use: Producer gas is generally used as: i)
Reducing agent in metallurgical activities. ii) Fuel for coke oven
plant, open hearth furnace etc.
3. Coal Gas: Coal gas mainly contains H2 and methane. It is
colourless gas having characteristic odour. The average composition
of coal gas is: Hydrogen (H2): 40%, Methane (CH4): 32%, Carbon
monoxide (CO): 7%, Acetylene (C2H2): 25%, Ehtylene (C2H4): 3%,
Nitrogen (N2): 4%, Carbon dioxide (CO2): 1% and other gases The
calorific value of coal gas is about 4900 kcal/m3 Preparation: Coal
gas is prepared by heating coal in absence of air at about 1300 C
Coal ------------- Coke + Coal Gas The coal gas thus produced is
not pure and with the help of different process, its impurity is
removed to make is usable. Use: Coal gas can be used as: I An
illuminating gas for lighting. ii. To produce reducing atmosphere
in metallurgical industries.
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Synthetic Oil Conversion of Coal into Liquid Fuels
Petrol can be synthesized by any one of the following methods:
1. Fisher-Tropsch Method 2. Bergius Process 1. Fisher-Tropsch
Method: The raw material is the hard coke which is converted into
water gas (CO+H2) by passing steam over red hot coke.
A mixture of hydrogen and water gas (CO + H2) is first purified
by passing through Fe2O3 (to remove H2S) and then into a mixture of
Fe2O3+Na2CO3 (to remove organic sulphur compounds). The purified
gas is compressed to 5 to 25 atom and then passed through a
convertor maintained at about 200-300 C. The convertor is packed
with a catalyst, consisting of a mixture of Co, Th, MgO and
Keiselguhr earth. A mixture of saturated and unsaturated
hydrocarbons yield from this process, after condensation liquid
resemble with crude oil. The similar fractional distillation
process needs to repeat to isolate gasoline and high boiling
fractions. The heavy oil can be reused for cracking to get more
gasoline. Bergius Process In this process, finely powdered coal and
a suitable catalyst is made into a paste with Heavy Oil produced in
the process. The coal paste is then preheated and pumped to the
Converter. Here the paste is heated to 450 C and hydrogen bubbled
through it at 250 atm pressure. The coal, which really a mixture of
high molecular complex organic compounds deficient in hydrogen, and
elementary carbon, combines with hydrogen to form higher, saturated
compounds. These as a result of cracking and simultaneous
hydrogenation yield a mixture of alkanes. Thus the vapours leaving
the converter upon condensation yield synthetic Petroleum or Crude
Oil. This crude oil upon fractional distillation produces i) Petrol
ii) Middle Oil and iii) Heavy Oil.
Diesel Oil: It is a mixture of higher hydrocarbons (C15 to C18).
This fraction is obtained between 250 to 320 C. It is used as a
fuel for diesel engine and its calorific value is about 11000
cal/gm.
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Diesel Engine, Ignition Temperature and Ignition Delay: Ignition
Temperature is the minimum temperature at which the combustion is
self-supporting. This also referred to as spontaneous ignition
temperature. In the diesel engine, air is first drawn into the
cylinder and compressed to a pressure of about 500 psi. This
compression is accompanied by a rise in temperature to about 500 C.
Towards the end of the compression stroke; diesel is injected in
the form of finely-divided spray into air in the cylinder heated to
about 500 C by compression. The oil absorbs the heat from the air
and it ignites spontaneously as it attains ignition temperature.
This raises the temperature and pressure. The piston is pushed by
expanding gases in the power stroke. The combustion of fuel in a
diesel engine is not instantaneous, the interval between the start
of fuel injection and its ignition is called the the ignition delay
If the ignition delay is long, it will lead to fuel accumulation in
the engine even before the ignition. When ignited, an explosion
results as the combined effect of increased temperature and
pressure. This is responsible for diesel knock.
Overall, it is desirable to have fuels with short ignition delay
but the ignition delay must be long enough for the compression
stroke to be completed. Ignition delay mostly depends on chemical
nature of the diesel fuel composition e.g., ignition delay is
shorted for paraffinic fuel, than for olefinic, naphthalenic and
aromatic fuels. Define Cetane Number: In order to grade the diesel
fuels, cetane rating is employed. Thus cetane number is a measure
of the ease with which fuels will ignite under compression. Cetane:
C16H34 ( n-hexadecane): Cetane No: 100 Very Short igntion delay
-methyl naphthalene Cetane No: 0 Longer Ignition Delay
CH3
Therefore, Cetane number of a diesel fuel is the percentage of
n-hexadecane (cetane)
in a mixture of n-hexadecane and -methyl naphthalene, which has
same ignition properties as that of a fuel under consideration at
the saem set of conditions. Comparision of Petrol and Diesel
Engines: S. No Description Petrol Engine Diesel Engine 1 Fuel
Petrol + Air mixture Diesel+ Air mixture 2 Ignition By spark plug
Compression of Air 3 Cause of knocking Pre-ignition Delayed-Igntion
4 Knocking Rating Octane Rating Cetane Rating 5 Additives TEL,
Diethyl telluride Alkyl nitrites The cetane number of fuel can be
increased by addition of very small amount of compound called
pre-igntion dopes like Ethyl-nitrate, iso-amyl alcohol, Di-t-Butyl
peroxide etc. Flash Point: Flash Point may be defined as: The
minimum temperature at which an oil gives off enough vapors to form
a momentary flash of light when a flame is brought near its
surface. The fire point is the temperature at which it will
continue to burn for at least 5 seconds after ignition by an open
flame. At the flash point, a lower temperature, a substance will
ignite briefly, but vapor might not be produced at a rate to
sustain the fire. In general the fire points can be assumed to be
about 10 C higher than the flash points. The smoke point of oil is
the temperature at which it begins to break down to glycerol and
free fatty acids, and produce smoke. Considerably above the
temperature of the smoke point is the flash point, the point at
which the vapors from the oil can first ignite when mixed with
air.
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Alterntive Fuels (Proapne, Methanol, Ethanol)
1. Compressed Natural Gas (CNG) is considered as Clean Alternate
Fuels
Natural gas is a fossil fuel found in earths crust. It is
commonly found trapped between liquid petroleum and capping rock.
Although it is found commonly with or near crude oil deposits, it
is not a component of crude oil. India has twice as much as natural
gas reserves as crude oil reserves.
CNG is odourless, colourless, and tasteless. It consists mostly
of methane and is drawn from gas wells or in conjunction with crude
oil production. CNG vehicles store natural gas in high-pressure
fuel cylinders at 3000 to 36000 pounds per square inch. An odorant
is normally added to CNG for safety reasons.
Two types of CNG fuel systems are on the market; dedicated
vehicles, which operate exclusively on natural gas, and dual fule
vehicles, which can use both natural gas and gasoline.
CNG is considered the most promising vehicle fuel and should be
promoted as the fuel of tomorrow. The following points make CNG as
better fuel:
i) Natural gas exists naturally and it is sufficiently
available. ii) CNG provides more energy per kg. iii) Octane rating
is more, therefore thermal efficiency his high. iv) It exhibits
very low particulate emission. v) Life of engine component is
increase, as deposits are less vi) Natural gas is a safe fuel. It
has vapour density nearly three times lighter than air, hence it
rises and dissipates quickly when released. Biodiesel: Biodiesel is
a clean burning, carbon-neutral, renewable fuel which can be used
in any diesel engine and requires no engine modifications.
Biodiesel emissions are significantly lower than those of regular
diesel, and it is 100% biodegradable. A vegetable oil is a
triglyceride extracted from a plant. Biodiesel is made from
vegetable oil, primarily from soybeans or canola.
C19 Unsaturated
C20Saturated It has two main advantages: i) Biodiesel is a
cleaner, environmentally-sound alternative to petroleum diesel. ii)
Biodiesel can prolong the life of your engine by lubricating engine
and fuel systems, thereby reducing engine wear.
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Biodiesel is made using vegetable oil, lye, and alcohol (pure
methanol or ethanol) through a process called trans-esterification.
The most common vegetable oils that are used are soybean oil and
rapeseed oil (canola), biodiesel can also be made from sunflower
oil.
x 100% biodiesel is referred to as B100 x 20% biodiesel, 80%
diesel is labeled B20 x 5% biodiesel, 95% diesel is labeled B5 x 2%
biodiesel, 98% diesel is labeled B2 Blends of 20% biodiesel and
lower can be used in diesel equipment with no, or only minor
modifications, although certain manufacturers do not extend
warranty coverage if equipment is damaged by these blends.
Liquified Natural Gas (LNG) LNG is made by refrigerating (-260 F)
natural gas to condense it into a liquid. The liquefaction process
removes most of the water vapor, butane, propane and other trace
gases, that are usually included in ordinary natural gas. The
resulting LNG is usually more than 98 % pure methane. Liquefied
Petroleum Gas (LPG) LPG is mostly made up of propane. Actually LPG
is made of a mixture of propane and other similar types of
hydrocarbon gases. Different batches of LPG have slightly different
amounts of the different kinds of hydrocarbon molecules. These
hydrocarbons are gases at room temperature, but turn to liquid when
they are compressed. LPG is stored in special tanks that keep it
under pressure, so it stays a liquid. Ethanol and Methanol Fuels
The use of ethanol as a fuel for internal combustion engines,
either alone or in combination with other fuels, has been given
much attention mostly because of its possible environment and
long-term economical advantages over fossil fuel. Both ethanol and
methanol have been considered for this purpose. While both can be
obtained from petroleum or natural gas, ethanol may be the most
interesting because many believe it to be a renewable resource,
easily obtained from sugarcane or corn. When 10% alcohol fuel is
mixed into gasoline, the result is known as Gasohol. When 85%
alcohol fuel is mixed into gasoline, the result is known as E85.
Methanol has been considered as a fuel, mainly in combination with
gasoline. It has received less attention than ethanol because it
has serious toxic concern. However manufacture is easy for
methanol. Since the 1960s, methanol has been the required fuel for
the racing cars. The reason for this is a single chemical entity;
however gasoline composition may vary between batches to batch.
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