Petrochemical feed stocks Presented by: Sarah Al-Houty Ohoud Al-Mutairy Dlal Al-Moulla Hessah Al-Ameer

Introduction The basic petrochemical manufactured by : 1- Aromatics ( Benzene, toluene, xylene,and ethyl benzene ) 2- Un saturates (Olefins,Diolefins ) 3 – Saturates (Paraffin and cyclo paraffin )

Uses of Petrochemical: 1- Plastic production 2- Synthetic fibers 3- Rubber (SBR ) 4-Solvents 5- Polymers

Aromatics Production *Aromatics are obtained mainly from the catalytic reforming of heavy naphtha. * Solvent liquid – liquid extraction method used to separate aromatics from anther hydrocarbons. * Finally the aromatics are separated to produce ( Benzene, toluene, xylene which separated to m- o -p –xylenes, and ethyl benzene )

Solvent extraction of Aromatics : The points important for solvent selection : 1- Good thermal stability. 2- Raid phase separation. 3-Non corrosively. 4 - High capacity ( Solubility of Aromatic ). 5- High selectivity for aromatics versus non aromatics.

Solvent extraction of Aromatics : There are Two major solvent that used to extract aromatics : 1- Sulfolane. 2- Ethylene glycol.

Comparison of Solvent Systems For Aromatics Recovery Extractive splitterExtract recovery column Extraction equipment Wash water wt% 1.442Relative Volatility 33S/L Tetra-ethyleneSulofane

General L-L extraction flow sheet

Solvent extraction of Aromatics :

Aromatics Separation : * Benzene and Toluene can be recovered from the extract product stream of the extraction unit by distillation. * The separation by distillation become more difficult  Because the boiling points of C8 aromatics are so close together. * Solution: by using a combination of distillation and crystallization or adsorption.

o-Xylene m-Xylene p-Xylene Ethyl benzene Toluene Benzene aromatics FoFo Boiling point CoCo

Sequence of Aromatics recovery operation :

For a good desired separation efficiency  the reflux ratio must be high. Disadvantage: it needs more energy so the cost will be higher. Solution : Alkylation Benzene with ethylene to produce ethyl Benzene.

Processing sequence to produce C8 aromatics:

Benzene : * The primary source of benzene is from the reforming unit, but substantial amount of benzene are also produced by hydrodealkylation of toluene *Process flow for a hydrodealkylation unit (HAD): 1-Feed can be to toluene or admixture of to toluene and xylenes. 2-The feed is heated to 1175 f (630 c) at 600psig (4140kpa).

3-The feed charged to an open non catalytic reactor (L/D= reflux ration < 20) where thermal dealkylation of to toluene and xylenes take place during residence time of seconds. 4-The hydrogenation step in the dealkylation reaction is highly exothermic [Q 22,000 Btu/lb-mol] So the temperature is controlled by injection of quench hydrogen at several point along the reactor.

Results : - The hydealkylation reaction results in the conversion of benzene. - Also small amount of polymer is formed, primarily diphenyl. - To prevent catastrophic corrosion of the furnace tubes small amount of hydrogen sulfide is added. - To minimize polymerformation.

Un saturate Production : *Steam cracking of gas oil naphthas is most important process for producing a wide range of unsaturated hydrocarbons for petrochemical use. 1- alkane (single bond) dehydrogenation(-H2) alkene (double bond) Come from 1-ethylene. LBG or flue gas 2-propalene. (C2, C3, C4) 3-Butadiene.

2- Steam – cracking : is the thermal cracking and reforming of hydrocarbons with steam at: a- low pressure. b- High temperature. c- Very short residence times (generally < seconds).

Process of Un saturated - The hydrocarbon is mixed with steam in the steam/ hydrocarbon weight ratio of (0.2 to 0.8) and fed into a steam – cracking furnance. - The residence times in the cracking Zone range from (0.3 to 0.8) seconds - There is a coil with : outlet temperature between 1400 and 1500F, and out let pressure in the rang 10 to 20 psig. - The coil outlet steam is quickly quenched to about 600F to stop the cracking and polymerization reactions, by transfer –line heat exchanger with a low – pressure drop.

- The quenched furnace outlet stream is sent a primary fractionators where it is separated into: a- gas steam. b- Liquid steams according to boiling point range. -The gases are separated into to individual component as desired by compression and high – pressure fractionation. - Paraffin obtained from the dewaxing of lubricating oil base stocks are frequently steam – creaked to produce a wide range of linear olefins.

Steam –Cracking Condition : C3 conversion wt% Steam /HC Pressure psig Coil outlet temp F WaxNaphtha

*If we use wax stream it must be de oiled before being used as a stream –cracker feed stock. *By choosing feed stock with an initial boiling point greater thane the end point of the desired product it will : a) Increase the yield of the desired olefins. b) Makes it possible to separate the product olefins from the feed paraffines by distillation *Results: atypical product stream conditions above 80% mono olefins with only a small percentage less than 11 carbon.

*Linear mono olefins: it is also produced by several catalyst processes: _The overall process consists of: a) Vapor- phase catalytic dehydrogenation unit b) Followed by an extraction unit. -The linear olefins will extract from paraffin hydrocarbons by adsorption on a bed of solid adsorbent material -They use a hydrocarbon as desorbed, it boiling at lower temperature thane olefin product So the separation of olefin product from adsorbent will be easy.

-Then the adsorbant hydrocarbon is recycled in the extraction section. *The results: -The olefin product contains about 96 wt% linear olefins of which about 98%are mono-olefins.

Saturated Paraffin’s 1-Normal paraffin’s: They are recovered from petroleum fractions by vapor phase adsorption on molecular sieves. 2-Cycloparaffin’s: They are prepared by hydrogenation of the corresponding aromatic compounds.

Normal paraffin’s : It uses molecular sieves which are materials containing tiny pores of a precise and uniform size that is used as an adsorbent for gases and liquids. Molecular sieves are often utilized in the petroleum industry.

5 Å pore diameter sieves are used.

1-The adsorption takes place in vapor phase at pressure of (5-10 psig) and temperature of ( o C). 2-AMMONIA is used as a adsorbent. 3-The sieves loses its capacity because of contamination, so it is regenerated by controlled burn-off.

N-paraffin recovery by adsorption:

Cyclo paraffin’s *Example(1): Cyclohexane is prepared by hydrogenation of benzene. *The hydrogenation of benzene is carried out on: *Platinum. *Raney Nickel supported on alumina or silica alumina.

*The hydrogenation reaction is highly exothermic. *The reaction temperature is controlled by recycling and injecting the cyclohexane to the reactor.

*Example (2):Tetralin and Decalin are prepared by hydrogenation of Naphthalene. *The same as hydrogenation of cyclohexane. *The catalyst is Cobalt-molybdenum.

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