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Green Gasoline

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Introduction

     Motor gasoline is one of the key products obtained from a petroleum (crude oil) refinery. It is a complex mixture of light hydrocarbons containing 5 to 10 carbon atoms and having a boiling range of 40 oC to 190 oC.

     Gasoline at the consumer level is called petrol, benzol, motor spirit or gas, depending on the country where it is sold.   At the refinery level, in early stages of crude oil processing, most gasoline components are called naphthas.  To be precise, modern reformulated gasoline is a blend of several refinery streams namely Catalytic Reformate, Straight Run Naphtha(SRN), FCC Gasoline, Visbreaker / Coker Naphtha, Isomerate, Alkylate, Oxygenate etc.  The product application and customer acceptance set detailed specifications for various gasoline properties which in turn determine which refinery streams are suitable for a specific blend.

"In a nutshell, the global trend is towards making gasoline more environment & human friendly or in other words making gasoline, a really green fuel."

     Today most petroleum refineries are facing the challenge of producing motor gasoline having all the desirable properties and also comply with the ever increasing environmental regulations & health restrictions on automotive emissions.   The environmental regulations were created to guard against high levels of lead, aromatics (benzene in particular), olefins, and sulfur in the gasoline.  Reduction in volatile organic compounds (VOCs), toxic and nitrogen oxides (TOx & NOx) in automotive tailpipe emissions, and evaporative and refueling emissions have also assumed high priority.   The European Union had announced its dedication to lower the sulfur content of gasoline to 50 ppm by 2005.  California and Germany are both contemplating a move to a 10 ppm sulfur specification in the near future. 

     Novel technological options are evolving that will improve the quality of gasoline pool streams.  The focus is on the two most important refinery streams: FCC gasoline and catalytic reformate.  FCC gasoline is a major contributor of sulfur and olefins while reformate is the main source of benzene and aromatics.

     We'll explore the properties of gasoline, their impact on the environment, and options for improving the quality of the streams.

Impact of Gasoline on the Environment

     The impact of gasoline on the environment is directly related to its fuel properties and contents.  Table 1 gives a brief account of gasoline properties, their desirable impact on engine performance and their undesirable impact on the environment. 

Table 1: Summary of Gasoline Properties

Gasoline Property

Desirable for

Impact on Environment

Octane Number

Avoid engine knocking; increase fuel-air mix compression ratio, engine power & efficiency.

Octane boosting compounds are not environmentally friendly …
# Lead additives are toxic air pollutants & poison catalytic converter catalysts.
# Benzene is carcinogenic.
# Aromatics produce more smoke & smog.
# Olefins form engine fouling gums , more smoke & smog .

Volatility

( Reid vapor pressure)

Sufficient light components to give adequate vaporization of fuel air mix for easy engine cold start.

# Too many light components result in hydrocarbon loss & result in atmospheric pollution.
# Too many heavy components contribute to chamber deposits & spark plug fouling causing release of unburnt hydrocarbons into the atmosphere.

Sulfur Content

Not desirable at all.

# Sulfur compounds are corrosive, foul smelling, and increase sulfur trioxide emissions.
# Decrease catalytic converter efficiency.
# Adversely affect ignition timing, leading to lower engine efficiency
Olefins Desirable for their octane value # Leads to deposits and gum formation and increased emissions of ozone forming hydrocarbons and toxic compounds.
Aromatics Desirable for their octane value # Increased engine deposits and tailpipe emissions including carbon dioxide
# Produces carcinogenic benzene in exhaust

Stability additives

Reduce valve deposits.

Affect carburetors resulting in higher H/C and CO emissions.


Table 2: Key Characteristics of Unleaded Gasoline

BIS(Bureau of Indian Standards ) , WWFC (World Wide Fuel Charter) , Jan , 2000 & EURO III.

 

  

Proposed by WWFC in January , 2000

  
Characteristics

BIS 2000

Category

Euro III

 

  

I

II

III

IV

  
Sulfur , % w (max)

0.1

0.1

.02

0.003

5-10 ppm

150 ppm
AKI/RON/MON (min)

84/88

-/91/82

-/91/82.5

-/91/82.5

-/91/82.5

90/95
Lead content as Pb , g/l (max)

0.013

0.013

Not detectable

nil
Benzene , %v (max)

5 , 3(Metros)

5

2.5

1.0

1.0

1.0
Aromatics , %v (max)

-

50

40

35

35

42
Olefins , %v (max)

-

-

20

10

10

18

 

Focus on Engine Knocking and Octane Numbers

     A very important feature that allows gasoline engines to run smoothly is a fuel-air mixture that starts burning at a precise time in the combustion cycle.  An electrical spark starts the ignition and a flame moving out from the initial spark should consume the remainder of the compressed fuel-air mixture.  The more the gasoline–air mix is compressed in the cylinder before ignition, the greater the power that the engine can deliver.  But under some conditions this increase in power gets limited because a portion of the fuel air mix will ignite spontaneously instead of waiting for the flame front from the carefully timed spark.  The extra pressure pulsations resulting from the spontaneous combustion are usually audible above the normal sounds of a running engine and give rise to the phenomenon called knock.  Some special attributes of the knocking are called pinging and rumble.  All of these forms of knock are undesirable because they waste power and result in higher amounts of unburnt hydrocarbons in the exhaust leading to air pollution.

     The anti-knock property of a gasoline is generally expressed as its Octane Number.  This number is the percentage by volume of iso-octane (assigned 100 octane) in a blend with n-heptane (assigned zero octane) that matches the knock characteristic of a gasoline sample combusted in a standard engine run under controlled conditions as defined by the American Society for Testing and Materials (ASTM).  One set of conditions produces the Research Octane Number ( RON, indicative of normal road performance) and a more severe set of conditions gives the Motor Octane Number (MON, indicative of high speed performance ).   Octane numbers quoted in literature usually refer to RON, unless stated otherwise.   Generally, it has become practice to label the gasoline with an arithmetic average of both RON and MON ratings (R+M)/2, called the Anti knock Index (AKI). As per the World Wide Fuel Charter (WWFC) , Jan’2000 the proposed specifications are AKI/RON/MON : 86.5/91/82.5.

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Extensive studies of octane numbers of individual compounds have brought to light several general rules.

1.    Normal(n) paraffins have the least desirable knocking characteristics, and these become progressively worse as the molecular weight increases.
2.    Iso (i) paraffins and naphthenes have higher octane than corresponding n-paraffins.
3.    Octane number of i-paraffins increases as the degree of branching of the chain is increased.
4.    Olefins have markedly higher octane numbers than the corresponding paraffins.
5.    Aromatics are hydrocarbons with the highest octane number for the same number of carbon atoms.

Thus it is clear that in order to have a large increase in octane number, it is necessary to transform paraffins and naphthenes into aromatics.

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     In view of strong environmental restrictions on gasoline , the main thrust of technological research has been in the field of finding different options for:

  • Lead phase out and octane enhancement             
    Volatility

         Volatility affects evaporative emissions and drive-ability.  It is this property that must change with location and season.  Fuel for mid-summer would be difficult to use in mid-winter.  Incorrect fuel may result in difficult starting in cold weather, carburetor icing, vapor lock in hot weather, and crankcase oil dilution.
         Volatility is controlled by distillation to Reid vapor pressure specifications.  The higher boiling fractions of the gasoline have significant effects on the emission levels of undesirable hydrocarbons and aldehydes. Also, a reduction of 4 0C in the final boiling point will reduce the levels of benzene, butadiene, formaldehyde and acetaldehyde by 25%, and will reduce HC emissions by 20% .
    Reid Vapor Pressure (RVP)

    • RVP is a measure of how quickly fuel evaporates.
    • RVP reduction provides the majority of VOC emission reductions from RFG.
  • Reduction in sulfur and olefin content
  • Decrease in benzene and aromatic content
  • Reduced tailpipe and evaporation emissions

Options for Lead Phase and Octane Enhancement

     In atmospheric distillation (Fig 1), the fractions identified as light naphtha, medium naphtha and heavy naphtha are the potential gasoline components.
     The clear RON of these components varies from 60 to 70 for light naphtha and 40 to 60 for medium and heavy naphtha. They cannot be used directly as gasoline, since gasoline RON requirements are 90 to 98.  The medium and heavy naptha streams are catalytic reforming feed stocks  and produce reformate having high octane value of 98-105.  Prior to  catalytic reforming, the addition of lead additives (TEL) provided a necessary octane boost. With the exception of a few countries, lead has been phased out due to its carcinogenic dangers .

 


greengas1.gif (20809 bytes)

Figure 1: Atmospheric Crude Distillation Unit

Toward Total Lead (TEL) Phase Out

     In 1922,  Thomas Midgley Jr. discovered that, when added to gasoline in small quantities, Tetra Ethyl Lead (TEL), is an excellent anti-knock material (see Table 2 below).  Alkyl lead added to gasoline interferes with hydrocarbon chain branching in the intermediate temperature ranges where HO2 is the most important radical species.  Lead oxide, either as solid particles, or in the gas phase, reacts with HO2 and removes it from the available radical pool.   This deactivates the major chain branching reaction sequence that results in undesirable, easily-auto ignitable hydrocarbons and thus prevents knocking.   But if you keep adding alkyl lead compounds, the lead response of the gasoline decreases, and so there are economic limits to how much lead should be added.

greengas2.gif (9663 bytes)

     From 1922 until the 1970s, TEL had been added to conventional gasoline for octane boosting.  During the 1970s in the United States, catalystic emission control systems were fitted into new cars to reduce
carbon monoxide and nitrogen dioxide pollutants in automobile exhausts.  The lead antiknock compounds used in gasoline at the time were found to be detrimental to the performance of the catalytic emission control systems.  As a result, unleaded and low-lead gasolines were introduced into the U.S. to supplement the conventional gasolines already available.

     Another drawback to TEL addition was that the lead additive decomposed and was emitted as unconverted particulate lead.  In fact gasoline combustion accounted for 94.8% of atmospheric lead emissions. These lead emissions were toxic and caused slow poisoning of the nervous system, mental retardation in children and other health related problems.

     Over the past three decades, many countries, have passed legislation to decrease the amount of lead emissions with the target of elimating it because of potent health problems in the population.  In the U.S. in 1973, the Environmental Protection Agency (EPA) ordered a gradual reduction in gasoline lead content with a total lead phase out by 1990. As per WWFC lead content has to be lowered to non-detectable levels. At the same time, demand for higher-octane gasoline increased with the development of more efficient automobile engines.

Other Options for Octane Enhancement

     In view of lead phase out schedules adopted, various options for octane enhancement have been explored.

Table 4: Options for Octance Enhancement

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Typical modern refinery processes for producing gasoline blending components are given below:

  • Catalytic Naphtha Reforming - converts saturated, low octane hydrocarbons into higher-octane products containing about 60% aromatics.

  • Fluidised Catalytic cracking - breaks larger, higher-boiling hydrocarbons into gasoline range product containing 30% aromatics and 20-30% olefins.

  • Isomerisation - raises gasoline fraction octane by converting straight chain hydrocarbons into branched isomers.
  • Alkylation - reacts gaseous olefin streams with isobutane to produce liquid high octane iso-alkanes.

     Among all the options for lead phase out, Catalytic Naphtha Reforming and Fluidized Catalytic Cracking have been the most commonly employed processes in refineries to provide gasoline blending high-octane components.

Focus on Catalytic Naphtha Reforming

     Catalytic naphtha reforming as a refinery process to upgrade medium and heavy naphtha into high octane reformate product for gasoline blending, is as important now as it has been for over 50 years of its commercial use.  The process gets its name from its ability to reform or reshape the molecular structure of the feedstock.  Low octane components in virgin naphthas, namely paraffins and naphthenes, are converted into higher octane components such as iso-paraffins and aromatics.  The octane number of a gasoline increases linearly with the increment in aromatic concentration.

     A typical feed to a reforming unit contains 45-70 % paraffins, 20-25 % napthenes, 4-14 % aromatics, and 0- 2 % olefins.   During the reforming reactions, aromatics increase to 60-75%, paraffins and naphthenes decrease to 20-45% and 1-8%, respectively, and olefins virtually disappear.   The main reactions via which these transformations occur are naphthene dehydrogenation, paraffin dehydrocyclization, and paraffin isomerisation.

     The naphtha feed stocks are heated to 500 degrees Celsius and flow through a series of fixed-bed catalytic reactors. Because the reactions are endothermic (absorb heat) additional heaters are installed between reactors to keep the reactants at the proper temperature.

greengas7.gif (5047 bytes)

     The workhorse for the reactions is typically a catalyst composed of minor amounts of several components, including platinum (Pt), supported on an oxide material such as alumina (Al2O3).   To prevent catalyst poisoning, the naphtha feedstock is first hydro-treated to remove any organic sulfur, nitrogen, oxygen and other metallic contaminants.  While catalysts are never consumed in reforming chemical reactions, they can be fouled, making them less effective over time.  The series of reactors used in semi-regenerative type reformers are designed so one may be disconnected and taken out of service for catalyst egeneration while other are still operating.

     In modern day facilities, continuous regenerative reformers operate at such low pressures that the rate of coke deposition is high.  Thus most plants use a continuous circulation and regeneration system for the catalyst.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Focus on Fluidized Catalytic Cracking
     Fluidized Catalytic Cracking (FCC) takes long molecules and breaks them into much smaller molecules. The cracking reaction is very endothermic, and requires large amounts of heat.  Another problem is these reactions quickly foul the silica (SiO2) and alumina (Al2O3) catalyst by forming coke on their surface. However, the catalyst is continuously regenerated by using a fluidized bed to slowly carry the catalyst upwards, and then sending it to a regenerator where the coke can be burned off.  This system has the additional benefit of using the large amounts of heat liberated in the exothermic regeneration reaction to heat the cracking reactor.

      The FCC system is a brilliant reaction scheme, which turns two negatives (heating and fouling) into a positive, thereby making the process extremely economical.

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     For years, Catalytic Reforming and FCC have served the purpose of obtaining motor gasoline with desired octane without addition of any lead additives.  However, in view of stricter regulations on aromatics content, benzene in particular, catalytic reforming has come under attack as the reformate typically contains 60-70 % aromatics and 5-6 % benzene.  FCC has also faced a disadvantage as cracked FCC gasoline contains high levels of aromatics, olefins and sulfur. Operation changes in both the processes as well as development of new processes has been the focus of research in order to meet new motor gasoline specifications.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Options for Benzene and Aromatics Control

     Benzene is one of the key aromatic hydrocarbons desirable in gasoline for its high octane (~100).  It is present in automotive evaporation and refueling vapors as well as in their exhausts.   The positive octane impact has been offset by its tendency to induce severe health hazards as it is a known carcinogenic.
    
     In fact benzene was identified as a potent carcinogen and toxic air pollutant (TAP) by the US Clean Air Act of 1990.  The actual atmospheric benzene levels in the most highly polluted cities range between 50 and 150 ppm (parts per million).  Such high amounts of benzene in the atmosphere are known to cause leukemia, lung, and skin cancer.  Also, children and people in the age group of 50-70 are more prone to the risk of developing breathing problems due to idiopathic pulmonary fibrosis, which hardens the air sacs in the lungs causing thickening and scarring.

     In view of such severe health impact, the European Union has set the safe limit of benzene in air at 10 ppm. To attain such low benzene levels, the World Wide Fuel Charter (WWFC), Jan 2000 has set the maximum limit of benzene content in gasoline at a mere one percent.

     Because 60-70 percent of the total benzene in gasoline is produced in the reforming unit, benzene reduction in the reformate has a major effect in meeting the specification imposed on the component.

     Refineries world wide have adopted three basic approaches for benzene reduction:

  • Limitation of the benzene production in the reformer by diminishing the benzene precursors (C6) content in the reformer feed.

  • Adjustment of reformer operating severity and pressure.  Low pressure Semi-Regeneration and Continuous regeneration type reformers produce lower benzene from reduced hydro-dealkylation reactions.

  • Down stream removal of the benzene produced by the reformer.  Various new processes have been developed for benzene reduction namely:

Reformate Benzene Saturation: Benzene is hydrogenated to cyclo-hexane.  The process can be easily integrated with reforming units.  IFP has developed a process trade named BENFREE™ which can be easily integrated into reforming units.

Reformate Splitting & Benzene Extraction

Alkylation : Removes benzene from the gasoline blending stream via alkylation with light olefin compounds ( C2 – C4).

Pre-fractionation of benzene precursors combined with low pressure reformer operation ( < 100 psig ) will usually produce less than 1 % vol benzene in the reformate regardless of the feed composition.

     The WWFC has proposed a restriction of the total aromatic content in gasoline to about 35 % vol .  Aromatics are the most desirable hydrocarbons for octane improvements but they are also responsible for disproportionate amounts of CO and HC exhaust emissions that lead to higher levels of smoke and smog.

     The aromatics in reformate from Catalytic reforming processes cannot be reduced below certain levels without compromising octane levels.  The development of new reforming catalysts, which isomerise the lighter C6 and C7 hydrocarbons to the branched isomers with higher octane numbers, are very much in demand.

     FCC gasoline is another major contributor of aromatics to the gasoline pool as it contains about 10-20% by volume aromatics on average.  Refiners have several options for lowering aromatics in FCC gasoline: process more naphthenic or paraffinic feedstocks;  lower unit conversion ;  undercut full distillation range gasoline. Undercutting is probably the most desirable choice because the FCCU can then be run to maximize desirable light olefins (C3=, C4=, and C5=) while controlling aromatics.  The light olefins can be converted to excellent blending components for gasoline, e.g. polygasoline, dimate, alkylate, MTBE, tertiary butyl alcohol (TBA), ethyl tertiary butyl ether (ETBE), tertiary amyl methyl ether (TAME), and tertiary amyl ethyl ether (TAEE). Isobutylene and isoamylenes are the olefins in greatest demand.  They are made into MTBE and TAME, the preferred oxygenate blending components for gasoline.  This is called the "aromatic substitution effect".

     Oxygenates are just pre used hydrocarbons having structure that provides a reasonable antiknock value, thus they are good substitutes for aromatics.  For example, MTBE (Methyl Tertiary Butyl ether) works by retarding the progress of the low temperature or cool-flame reactions, consuming radical species responsible for uncontrolled combustion and thus reduce knocking.   Also, as they contain oxygen, fuel combustion is more efficient, reducing hydrocarbons in exhaust gases.  The only disadvantage is that oxygen in the fuel cannot contribute energy;   consequently the fuel has less energy content.  For the same efficiency and power output, more fuel has to be burned.  Oxygenates are also being evaluated for carcinogenicity, and even ethanol and ETBE may be carcinogens.

Options for Sulfur and Olefins Control

     Sulfur in the fuel contributes to corrosion, and when combusted, will form corrosive gases that attack the engine, exhaust and environment.  Sulfur also adversely affects the alkyl lead octane response and will adversely affect exhaust catalysts.  However, monolithic catalysts will recover when the sulfur content of the fuel is reduced, so sulfur is considered an inhibitor rather than a catalyst poison.

     In view of the undesirable effects of sulfur, various options have been explored to reduce sulfur concentrations to undetectable levels.  The sources of sulfur contribution to gasoline include mainly;   FCC gasoline ,Visbreaker / Coker naphtha, and straight run naphtha from high sulfur crude.

     As FCC gasoline generally makes up 40-60% of the total gasoline pool, it contributes as much as 85-95% of the sulfur in motor gasoline and 100% of the olefins.  The sulfur in FCC gasolines in mainly concentrated in the heavier fractions in the form of compounds such as thiophenes, benzo thiophenes, etc.  The lighter fractions contain primarily mercaptans.  Mainly, there are three options for sulfur reduction in FCC gasoline:

  • Post treatment of gasoline using a conventional hydrodesulfurization catalyst.  Severe hydrotreating is not desirable as it saturates the olefins, thereby reducing the octane value.  In general, full range FCC gasoline is split into light cut naptha (LCN) and heavy cut naptha (HCN).  LCN is treated with caustic for mercaptan removal and HCN is actually desulfurized.  Both of the streams are then blended back to the gasoline pool.   Exxon Mobil has offered a process named SCANFining™ (Selective Cat Naptha Hydrofining) which uses a proprietary catalyst (RT 225) and converts sulfur over the full range of FCC gasoline feed to H2S.  This does NOT require extensive fractionating facilities and saves on operating costs.  Exxon Mobil has offered another process called OCTGain™ which first provides complete removal of sulfur and then saturates the olefins.  Finally, the octane value is restored by cracking and isomerization reactions.  OCTGain™ is suitable for refineries with higher gasoline sulfur content which would otherwise require severe hydrotreating.  Some other post treatment technologies include:

    • ISAL Process - UOP

    • PrimeG+ process - IFP

    • S Zorb process - Philips Petroleum

    • Catalytic distillation desulfurization - CDTech

    • S Brane (membrane desulfurization) - Grace Davison

    • Oxidative desulfurization - Unipure

  • Desulfurization of FCC feedstock - This option is better, more cost effective, and is preferred as octane loss due to olefin saturation is avoided.

  • Use of catalyst additives for in-situ conversion of sulfur compounds - The sulfur reduction using this option has been reported as marginal.

     Olefins can also be removed by selective saturation and by isomerisation processes.  With suitable alkylation reactions olefins can be converted to high octane alkylates.

Options for Reduction in Tail Pipe and Evaporative Emissions

      Automobiles emit several pollutants as combustion products out the tailpipe (tailpipe emissions) and as losses due to evaporation (evaporative emissions, refueling emissions).  The volatile organic chemical (VOC) emissions from these sources, along with nitrogen oxides (NOx) emissions from the tailpipe, will react in the presence of ultraviolet (UV) light (wavelengths of less than 430nm) to form ground-level (tropospheric) ozone, which is one of the major components of photochemical smog.  Also from the auto exhausts additional CO2 is added to the atmospheric burden.  More and more scientific evidence is accumulating that global warming is occurring due to the effect of the additional CO2 in the global environment.

     Along with the tail pipe emissions, the hydrocarbons produced by evaporation of the gasoline during distribution, vehicle refueling, and from the vehicle, have become more and more significant.  A recent European study found that 40% of man-made volatile organic compounds came from vehicles.   The health risks to service station workers, who are continuously exposed to refueling emissions remain a concern .

     Exhaust catalysts have offered a post-engine solution that could ensure pollutants are converted to more benign compounds.  As engine management systems and fuel injection systems have developed, the volatility properties (Reid vapor pressure) of the gasoline have been tuned to minimize evaporative emissions, and yet maintain low exhaust emissions.

     The design of the engine can also have very significant effects on the type and quantity of pollutants. Unburned hydrocarbons in the exhaust originate mainly from combustion chamber crevices, such as the gap between the piston and cylinder wall where the combustion flame can not completely use the HCs.

     In a nutshell, the type and amount of unburned hydrocarbon emissions are related to the fuel composition (volatility, olefins, aromatics, final boiling point), as well as state of engine condition, tuning and condition of the engine lubricating oil.

     Future automoblies will be required to trap the refueling emissions in large carbon canisters.  Carbon canister systems can reduce evaporative emissions by 95% from uncontrolled levels.

Conclusions    

1.    Options are available to meet new gasoline specifications.  The solution will be site specific depending upon the refinery configurations and governmental regulations.

2.    Besides considering operational changes in Catalytic Reforming & FCC, the technologies to be considered for the future include:

Alkylation : Alkylate is an excellent blending component for a high octane component free of lead, benzene and olefins.

Isomerisation : Isomerate is a sulfur free, high octane, non-aromatic gasoline blending stock.

Selective gasoline desulfurisation / Olefins saturation processes.

Oxygenate blending : Methyl tertiary butyl ether (MTBE) and Tertiary amyl methyl ether (TAME) are main oxygenates compounds used in gasoline in addition to their high octane numbers .

     To summarize, the drive towards making Green Gasoline is full of challenges.  A joint global effort by refiners, automobile manufacturers and governments can alone provide the desired momentum to make gasoline a really clean burning, non-toxic, and non-polluting fuel and pave the way for cleaner and safer motoring in this "environmental" millennium.

References:

Little , Donald M ; Catalytic Reforming , Penn Well Publishing Company,Oklahoma ,1985, ISBN 0-87814-281-9 .

George J. Antos ,Abdullah M. Aitani , Jose M. Parera ; Catalytic Naphtha Reforming , Marcel Dekker Inc., New York ,1995, ISBN 0-8247-9236-X

A.J.Pahnke and W.E.Bettoney , Role of Lead Antiknocks in Modern Gasolines, SAE Paper 710842 (1971) 32p.

I.S. Al-Mutaz , How to implement a gasoline pool lead phase down , Hydrocarbon Processing , February 1996 , 63-69p.

Michela montesi , Filippo Trivella , Alessandro Brambilla , Massimiliano Dell Agnello , Luciano Paolicchi ; Reduction of benzene precursors in the reformer feed , Petroleum Technology Quarterly , Winter 1998/99 , 107-111p.

H.L.Hoffman , Petroleum and Its Products , Riegel’s Handbook of Industrial Chemistry.

Indian Institute Of Petroleum , Lecture Notes.

Reduction of Sulfur, Aromatics, and Olefins from the Gasoline Pool - A Review of Technological Options, M. Bhaskar, G. Valavarasu, V. Selvavathi, B. Sairam, Chennai Petroleum Corporation Ltd. (R & D Centre)

Case Study – Petroleum Modern Refining http://www3.cems.umn.edu/~aiche_ug/history/h_toc.html

By: Mukesh Sahdev, Associate Content Writer (read the author's Profile)
SAHDEVM@iocl.co.in

 

 

 


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