UTMUTMUNIVERSITI TEKNOLOGI MALAYSIA

-Gas Processing--Gas Processing--Group -Group

Assignment-Assignment-Group Members:Group Members:

1.1. ASHWENE A/P ASHWENE A/P GENGADHARANGENGADHARAN

2.2. AZLINA MOHD JUSUHAZLINA MOHD JUSUH

3.3. KHALISAH ZAHRIKHALISAH ZAHRI

Group Members:Group Members:

1.1. ASHWENE A/P ASHWENE A/P GENGADHARANGENGADHARAN

2.2. AZLINA MOHD JUSUHAZLINA MOHD JUSUH

3.3. KHALISAH ZAHRIKHALISAH ZAHRI

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UTMUTMUNIVERSITI TEKNOLOGI MALAYSIA

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HYDROCARBONHYDROCARBON

CRACKINGCRACKINGCRACKINGCRACKING

OBJECTIVESOBJECTIVES

4 objectives:

• To give detailed explanation about the type of hydrocarbon cracking

• To specify the discussion on catalytic cracking of hydrocarbon.

• To introduce the type of catalysts used in catalytic cracking and the properties of the catalysts.

• To describe the processes involved in catalytic hydrocarbon cracking.

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RESEARCH METHODOLOGYRESEARCH METHODOLOGY Early studies were done through related materials to

the subject taken from websites available on the internet.

The topic of discussion was chosen based on the simplicity of the scope of the topic .

Detailed research on the topic were done in the university library, Perpustakaan Sultanah Zanariah.

Data for this presentation were collected originally from some journals and books.

Relevant key points are extracted out from the articles taken in the sources mentioned above and rephrase for the simplicity of the presentation and the convenience of viewers.

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WHAT IS HYDROCARBON WHAT IS HYDROCARBON CRACKING?CRACKING?• Hydrocarbon is an organic

compound containing hydrogen and carbon only.

• Cracking of hydrocarbons so called hydrocarbon cracking means that the large hydrocarbon molecules break into smaller molecules when they are heated.

• Thus, cracking is a phenomenon by which higher boiling point (higher molecular weight) constituents in petroleum are converted into lower boiling (lower molecular weight) products.

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TYPES OF HYDROCARBON CRACKINGTYPES OF HYDROCARBON CRACKING

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Thermal crackingThermal cracking

• Thermal cracking is a free radical chain reaction where the free radical reacts with a hydrocarbon by abstracting a hydrogen atom to produce a stable end product and a new free radical.

• Example: Migration of alkyl group. Thermal cracking does not produce any degree of branching in the product.

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Catalytic cracking Catalytic cracking

• Catalytic cracking is the thermal decomposition of petroleum constituents’ hydrocarbon in the presence of a catalyst.

• Example: Gasoline produced is richer in branded paraffins, cycloparaffins, and aromatics. In short, the quality of gasoline is improved.

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DehydrogenationDehydrogenation

• Dehydration is essentially the removal of hydrogen from the parent molecule.

• Example: At 550ºC, n-butane loses hydrogen to produce butene-1 and butene-2.

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DehydrocyclizationDehydrocyclization

• Dehydrocyclization is a catalytic aromatization involving the loss of one mole of hydrogen followed by ring formation and further loss of hydrogen.

• Example: Paraffins (typically n-hexane and n-heptane). n-hexane can be converted to benzene, heptane is converted to toluene,and octane is converted to ethyl benzene and o-xylene.

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TYPES OF CATALYST USED IN CATALYTIC CRACKING

Natural ClaysNatural Clays The first catalysts to be used industrially were natural clays of the

bentonite type. The main component of these type of catalysts is montmorillonite,

hydrated aluminium silicate containing some magnesia. These type of catalyst had to be activated by acid treatment and

hence modified their physical and chemical properties. ADVANTAGES

1. Surface area and porosity increased

2. Surface sites favoring hydrocarbon cracking were formed by ion exchange

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DISADVANTAGES

Existence of impurities

1. These catalysts were very easily poisoned by sulfur derivatives contained in crude feed stocks.

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Natural ClaysNatural Clays

Synthetic CatalystsSynthetic Catalysts Natural clays were replaced by synthetic catalysts

• Consists of amorphous aluminum-silica, produced gasoline with a higher octane rating.

ADVANTAGES

1. These type of catalyst display a very high thermal stability and mechanical strength.

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ZeoliteZeolite Zeolite cracking catalysts

- They are white fine powders whose chemical and physical properties vary with the condition of preparation.

ADVANTAGES

1. Zeolites have molecular sieves which account for the effective pass through of the molecules through certain pores without steric hindrance.

2. Zeolites have a very high stability due to its nature of the compensating cations found in the sodalite structure.

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ZeoliteZeolite3. Have a much larger number of acid sites than the

amorphous alumina-silica catalysts

4. Zeolites formulations are already up to 10000 times more active than conventional catalysts.

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PROPERTIES OF CATALYSTS PROPERTIES OF CATALYSTS USED IN CRACKINGUSED IN CRACKING

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THE THE PROPERTIESPROPERTIES

THE THE PROPERTIESPROPERTIES

Thermal stability and resistance to chemical agents

Thermal stability and resistance to chemical agents

Thermal properties and

mechanical characteristics

Thermal properties and

mechanical characteristics

ActivityActivity

Selectivity Selectivity

EXPLANATIONEXPLANATION Activity

A suitable industrial catalyst must have enough activity to realize a

suitable conversion of the feedstock. This means the catalyst must be

active enough to speed up the reaction to give the desired conversion.

Selectivity

Hydrocarbon mixture is liable to produce different kind of products

due to uncontrollable conversion during the reaction. Hence, a

catalyst should be highly selective to activate those reactions

that yield the wanted or desired products.

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EXPLANATIONEXPLANATION Thermal stability and resistance to chemical agents

Fresh catalyst with the required activity and selectivity will be of

value as long as these properties can be maintained near the optimal

level for a period of time suitable to convenient operation of the

industrial reactor.

Thermal properties and mechanical characteristics

This includes crushing, erosion, attrition and abrasion, specific heat

and thermal conductivity.

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REFINARY REFINARY CATALYTICATALYTIC PROCESSC PROCESS

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THE CATALYTIC CRACKING THE CATALYTIC CRACKING PROCESSPROCESS

The reaction is an endothermic reaction.

The temperature of the mixture is decreasing with time.

During the processing, the solid coke is produced.

During the regeneration, coke is burned off the catalyst to restore its activity. This reaction is exothermic.

The endothermic and exothermic condition balances the heat required to maintain the process.

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THE PROCESS OF CATALYTIC CRACKING WHICH TAKES PART IN

FLUID CATALYTIC CRACKING PROCESS (FCCU)

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Riser reactor Riser reactor

• the most endothermic cracking processes take place.

• producing the product required including coke.

• the riser contains the mixture of catalyst, feed and product.

• The primary feed: atmospheric, vacuum distillation (gas oils), vacuum tower bottoms (vacuum resid; raw, hydrotreated, deasphalted), atmospheric tower resid, coker gas oils and lube extracts

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The StripperThe Stripper

• The coked catalyst from the riser reactor enter it.

• Steam is added.

• Unreacted-reacted hydrocarbon adsorb on the catalyst are released.

• Produced stripped catalyst.

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The Regenerator

The Regenerator

• The stripped catalyst led to the regenerator

• Air is added

• The combustion of coke on catalyst occurs

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CONCLUSIONCONCLUSION

There are 4 types of hydrocarbon process which are thermal cracking, catalytic cracking, dehydrogenation, and dehydrocyclization.

The catalytic cracking discussed in these presentation uses catalysts to speed up the rate of cracking processes.

The mechanism of catalytic process can be divided into 3 components which are riser reactor, stripper and regenerator.

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REFERENCESREFERENCES W.L. Nelson.(1958).”Petroleum Refinery Engineering”.McGraw-

Hill,Inc, 4th Edition(759-819). Daniel Decroocq.(1958).”Catalytic Cracking of Heavy Petroleum

Fractions”.Institut Francais Du Petrole Publications,1st Edition(7-20).

http://www.absorblearning.com/media/item.action?quick=11p

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