Prepared by: Kalgi Sheth

Guide: Mr.Chirag Tamboli

Important Additives Used in the Petroleum Fraction

Introduction

What is Additive?

• Complex chemical mixture that are added to fuel, in concentration typically of less than 1% to improve their performance and extend their life.

• To impart desirable properties or to suppress the undesirable properties.

What is the importance of additive in petroleum industries?

• Enhance properties already present.

• Act to reduce the rate at which undesirable changes takes place.

• Aided significantly in the development of prime movers and industrial machinery.

Pirro D.M,Daschner E.Lubrication fundamentals,2nd edition ,Marcel dekkar,37-38

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Speight, J.G.,”The Chemistry and technology of Petroleum” 4th ed.,CRC press Taylor and Francis group783-785

The more commonly used additives are as follows:

• Friction modifiers• Antioxidants• Markers and dyes• Octane boosters• Cetane enhancers• Pour point depressants• Biocides• Viscosity index improvers• Hydrated lime

Comparison of intake valve deposits before and after additive use

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Diesel net technology guide retrieved from https://www.dieselnet.com/tech/fuel_diesel_add.php on 9/1/2016

Additives are added in the fuel at three different stages 1)At the refinery

Fuel refiners must ensure that their products meet specifications and are suitable for the intended use.

2) In the fuel distribution system Fuel properties may be upgraded at the terminal or even at the retail pump. Pipeline operators sometimes inject drag reducing additives and/or corrosion inhibitors.

3) After the fuel has left the control of the producer

These additives are known as aftermarket additives.  Some users use additives to further improve the fuel to meet their particular needs, for instance cold climate operation.

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Friction modifier referred from https://www.corrosionpedia.com/definition/1638/friction-modifier on 10/10/2015

Gasoline additives

Gasoline additives play a vital role in petroleum industry since the rising rates of petroleum and hence gasoline led to development of gasohol, which is 90% unleaded gasoline and 10% ethanol.

1)Friction modifier

• Key component in modern engine oils

• Reduced metal- metal contact point

• Boosting fuel economy

• Reduce engine wear and noise

• Prevent micro pitting of metal surfaces

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Mechanism:

• Typically consists of water soluble end (head) oil soluble end (tail)

• Water soluble end attaches to metal surface.

• Forms sacrificial liquid coating on the metal which serves to minimize the friction.

• Sacrificial coating indicates, friction modifier sacrifice itself to the friction.

Water soluble end

Oil soluble end

6Basic structure of friction modifier

Speight, J.G.,”The Chemistry and technology of Petroleum” 4th ed.,CRC press Taylor and Francis group783

2)Antioxidants

• Prevent gasoline components (particularly olefins) from reacting with oxygen in the air.

• Comprises of phenols, aromatic diamines or mixture of alkyl phenols and aromatic diamines.

• Enhance gasoline stability and inhibit its tendency to deteriorate in storage.

• Gasoline containing a number of unstable species, these can polymerize to form gums and peroxide.

• Peroxides can degrade antiknock quality, cause fuel pump wear.

• Soluble gums can lead to engine deposits.

• Insoluble gums can plug fuel filters.

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Mechanism:

• Oxidation reaction → free radical → chain reaction

• Antioxidants → terminates chain reaction → deactivate metals(oxidizing agent) present in fuel.

antioxidants from https://www.atc-europe.org/public/Doc113%202013-10-01.pdf Referred on 8/10 /20158

diesel additives referred from https://www.atc-europe.org/public/Doc113%202013-10-01.pdf

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Diesel additives

Quality improvement by the addition of additives has also become popular for diesel fuels.

1)Conductivity improvers

•Ultra Low Sulphur Diesel (ULSD) contains less than 15 ppm sulphur.

•ULSD improves exhaust emissions, but removing the sulphur results in a loss of lubricity and conductivity of the fuel.

•Conductivity improvers enhance the conductivity of the blended fuel at very low treat rates.

• Minimum conductivity specification - 25 pS/m (pico-Siemens per meter) by ASTM.

•Typical treat rates are in the range of 1-40 mg/kg.

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Mechanism

Fuels → distribution systems(pipelines) → static charge → risk of fire or explosion hazard.

In order to transport fuels safely, conductivity improvers are added to fuel to dissipate static charge .

2)Biocides

• Used to prevent biological growth.

• Usually in storage tanks of fuel.

• Bacterial growth results in acid environment which can corrode tanks.

• Causes plugging of filter and increase the maintenance of engine.

• Minimizing water content is the best way to prevent growth.

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A complete treatment for biological contamination should involve four steps: 1)Drain all water from the system 2)Treat the entire system with a biocide 3)Filter all fuel (preferably into a clean tank) before use in a diesel engine 4)Clean the contaminated tank.

Thank you

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