Oil Refinery ChemistryOil Refinery Chemistry

Oil Refinery ChemistryOil Refinery Chemistry

Study of Hydrocarbons found in Study of Hydrocarbons found in Crude oilCrude oil Hydrocarbon ClassificationsHydrocarbon Classifications

Study of the chemical and physical Study of the chemical and physical changes taking place in a refinerychanges taking place in a refinery

Study of processes used to separate Study of processes used to separate and chemically alter crude oiland chemically alter crude oil

Organic Chemistry ReviewOrganic Chemistry Review

““Organic” = cOrganic” = carbon arbon basedbased

Carbon forms bonds Carbon forms bonds with many different with many different elements.elements.

Each carbon atoms Each carbon atoms prefers to form 4 prefers to form 4 electron bonds.electron bonds.

Bonding is the force Bonding is the force that holds atoms in a that holds atoms in a molecule togethermolecule together

Organic Chemistry ReviewOrganic Chemistry Review

Define the followingDefine the following:: AlkanesAlkanes (paraffins) (paraffins) AlkenesAlkenes (olefins) (olefins) AlkynesAlkynes AromaticsAromatics NaphthenesNaphthenes (cyclo-paraffins) (cyclo-paraffins)

Organic Chemistry ReviewOrganic Chemistry Review

AlkanesAlkanes ( (ParaffinsParaffins) - Single carbon bonds) - Single carbon bonds Chains, Branched changes (Chains, Branched changes (IsomersIsomers), or ), or

rings (rings (CycloCyclo-)-) AlkenesAlkenes ( (OlefinsOlefins) - Contain at least one ) - Contain at least one

double carbon bonddouble carbon bond AlkynesAlkynes – Triple carbon bonds – Triple carbon bonds Aromatics – Aromatics – Ring-shaped molecules with Ring-shaped molecules with

alternating single- and double-bondsalternating single- and double-bonds NaphthenesNaphthenes – Ring-shaped alkanes – Ring-shaped alkanes

(cyclo-paraffins, single bonds)(cyclo-paraffins, single bonds)

From Crude to your carFrom Crude to your car

Separation,Separation, Reaction,Reaction, More separation,More separation, Blending (mixing)Blending (mixing)

All these processes strive toward the same goal: adding market value to the crude oil we find in the ground. A manufacturing plant is a profit generator.

From Crude to your carFrom Crude to your car

Separation: distillationSeparation: distillation

Separating compounds from a mixture Separating compounds from a mixture based on boiling points – purely a based on boiling points – purely a physicalphysical process, not a process, not a chemicalchemical process process

Each compound in the mixture has a Each compound in the mixture has a different boiling pointdifferent boiling point

If this is an example of a physical process, what would be an example of a chemical process?

Separation: fractionationSeparation: fractionation Recursive distillation Recursive distillation The taller the tower The taller the tower

and more trays aids and more trays aids in separationin separation

Very energy-intensive: Very energy-intensive: crude fractionation crude fractionation alone accounts for alone accounts for about 30% of an oil about 30% of an oil refinery's total energy refinery's total energy usage!usage!

Separation: fractionationSeparation: fractionation

Problem: how to remove sulfur and nitrogen Problem: how to remove sulfur and nitrogen impurities from the crude fractions?impurities from the crude fractions?

MercaptansMercaptans: contain sulfur: contain sulfur AminesAmines: contain nitrogen: contain nitrogen Answer: Answer: hydrotreatinghydrotreating

Add hydrogen gas!Add hydrogen gas! Add heat, pressure, and Add heat, pressure, and

a selective catalyst!a selective catalyst! Produces HProduces H22S and NHS and NH33

H

H

Hc

c

H

H

HMercaptan

S HS

H

H

H

H H

cc

c c

HN

pyrole

Ammonia

HNH

H

H

Hc

c

H

HH

H

Ethane C2H8

H

H

H

H

Hc

c

c

H

H

cHH

H

Butane (n-butane) C4H10

HH

Is hydrotreating exothermic or endothermic? How can we tell?

HH

Reaction: hydrotreatingReaction: hydrotreating

What is the purpose of using a catalyst in the reactor vessel?

What roles do the separators play in this process?

Reaction: hydrotreatingReaction: hydrotreating

All ranges of All ranges of products are products are hydrotreatedhydrotreated NHDS (Naphtha NHDS (Naphtha

Unit)Unit) Treats GasolineTreats Gasoline

DHDS (Diesel Unit)DHDS (Diesel Unit) Treats DieselTreats Diesel

HydrocrackerHydrocracker Treats Gas oilsTreats Gas oils

Isomerization Isomerization process will also process will also treat gasolinetreat gasoline

Caustic washing Caustic washing will remove light will remove light mercaptans and mercaptans and HH22SS

Extracting hydrogen sulfide and Extracting hydrogen sulfide and ammonia after hydrotreatingammonia after hydrotreating

HH22SS

Amine liquid used to Amine liquid used to absorb Habsorb H22S gasS gas

Releases HReleases H22S gas in S gas in

regeneratorsregenerators HH22S is combusted S is combusted

with Hwith H22 and air and air Elemental sulfur is Elemental sulfur is

removed in Claus removed in Claus process, sold as process, sold as byproductbyproduct

NHNH33

Water used to absorb Water used to absorb NHNH

33 and H and H

22S gasesS gases

Sour water is stripped Sour water is stripped with hot steam, with hot steam, removing Hremoving H22S and S and NHNH33 gases gases

Anhydrous ammonia Anhydrous ammonia is separated, sold as is separated, sold as byproductbyproduct

Extracting hydrogen sulfide and Extracting hydrogen sulfide and ammonia after hydrotreatingammonia after hydrotreating

What do you suppose the terms “rich” amine and “lean” amine refer to, in its role as an H

2S absorbant?

What do you think the word “sour” refers to in the “Sour Gas” stream?

Reaction: crackingReaction: cracking Cracking is simple: just Cracking is simple: just

heat the oil to a really heat the oil to a really high temperature!high temperature!

Making high-value light Making high-value light products from less products from less valuable heavy oilsvaluable heavy oils Breaking large molecules Breaking large molecules

into smaller moleculesinto smaller molecules Lighter hydrocarbons have Lighter hydrocarbons have

higher octane values as higher octane values as gasoline feedstocks – more gasoline feedstocks – more $ value$ value

Reaction: catalytic crackingReaction: catalytic cracking

Catalyst beads rest in stationary “beds” through which heated reactants are passed

This is an older technology (first studied in 1923, first built 1936)

What is the purpose of using a catalyst in this reaction?

Reaction: fluid catalytic cracking (FCC)Reaction: fluid catalytic cracking (FCC)

Catalyst powder recirculates in pipes along with reactants, as though it were a fluid itself

This is a proven technology (first built in 1942 to make aviation gasoline for the Allied war effort)

What advantage is there in having the catalyst in powder form rather than beads or pellets?

Reaction: fluid catalytic cracking (FCC)Reaction: fluid catalytic cracking (FCC)

Solid carbon deposits quickly form on the catalyst powder particles, “choking” them off and rendering them ineffective. How is this carbon removed from the catalyst (a process called “regeneration”)?

Molecules cracked in a Molecules cracked in a hydrogen-rich environmenthydrogen-rich environment Catalyst is used to make Catalyst is used to make

reaction conditions less reaction conditions less severesevere

Temperature controls the Temperature controls the rate of reactionrate of reaction

Broken bonds are Broken bonds are saturatedsaturated with hydrogenwith hydrogen

Produces treated paraffinic Produces treated paraffinic (alkane) products for diesel (alkane) products for diesel and jet fuel feedstocksand jet fuel feedstocks

Reaction: hydrocrackingReaction: hydrocracking

Reaction: hydrocrackingReaction: hydrocracking

Hydrocracking is an extremely high-pressure process, usually operating around 2000 PSIG!

Reaction: hydrocrackingReaction: hydrocracking

Reactants Products

Octane (C8H

18) Propane (C

3H

8)

Hydrogen (H2) Pentane (C

5H

12)

Write a balanced hydrocracker reaction showing octane being cracked into propane and pentane

Reaction: hydrogen plantReaction: hydrogen plant Main producer of refinery hydrogen for Main producer of refinery hydrogen for

hydrocracking and other reactive hydrocracking and other reactive processesprocesses

Reactants are steam (HReactants are steam (H22O) and methane O) and methane

(CH(CH44))

Main products are hydrogen (H) and Main products are hydrogen (H) and carbon dioxide (COcarbon dioxide (CO22)) COCO22 sold as waste product or sequestered sold as waste product or sequestered

Write a balanced chemical equation for the conversion of water and methane into hydrogen and carbon dioxide

Reaction: cokingReaction: coking Thermal crackingThermal cracking

Heating oil under pressure to Heating oil under pressure to cracking temperature cracking temperature

Quickly reducing pressure in Quickly reducing pressure in the drums causing oils to crack the drums causing oils to crack into smaller molecules and into smaller molecules and carbon to solidifycarbon to solidify

No hydrogen added, no No hydrogen added, no catalyst employedcatalyst employed

Produces unsaturated Produces unsaturated olefins (alkenes) and solid olefins (alkenes) and solid carbon deposits called carbon deposits called ““coke”coke”

Coke must literally be Coke must literally be drilleddrilled out of the vertical drums!out of the vertical drums!

Reaction: cokingReaction: coking

Why is coking sometimes called a “bottom-of-the-barrel” process?

Reaction: reformingReaction: reforming Reformulates paraffinic Reformulates paraffinic

reactants into higher-octane reactants into higher-octane products including:products including: AromaticsAromatics Iso-paraffinsIso-paraffins Naphthenes (cyclo-paraffins)Naphthenes (cyclo-paraffins)

H HH

HH

c

c

c

c

c

H

H

H

Pentane (n-pentane) C5H12

H

H

H

H

HH

H

H

H

Hc

c

c

H

H

cH

H

c

HH

Iso-pentane(2,methylbutane)

H

H

Hcc

c

cH

H

H

HH

ButeneC4H8

H

H

cc

c c

Hcc

H

H

H

cH

H

Toluene (aromatic)

Reaction: reformingReaction: reforming

Platinum reforming catalyst first economically applied in 1955

Reaction: reformingReaction: reforming

Note the interstage heater passes between reactors. Does this suggest an exothermic or an endothermic reaction?

Reaction: isomerizationReaction: isomerization Produces iso-alkanes, to make high-Produces iso-alkanes, to make high-

octane gasoline without using octane gasoline without using carcinogenic aromatics such as carcinogenic aromatics such as benzenebenzene Benzene saturation – “Bensat” Benzene saturation – “Bensat”

ReactorReactor Re-arrange molecular shape. Re-arrange molecular shape.

Straight Chains to Branched Chains.Straight Chains to Branched Chains.

H HH

HH

c

c

c

c

c

H

H

H

Pentane (n-pentane) C5H12

H

H

H

H

HH

H

H

H

Hc

c

c

H

H

cH

H

c

HH

Iso-pentane(2,methylbutane)

Reaction: isomerizationReaction: isomerization

Does the hydrogen feed become part of the isomerized product? Why or why not, based on what we know about isomers?

Reaction: alkylationReaction: alkylation Produces high-octane gasoline feedstocks, Produces high-octane gasoline feedstocks,

used to blend aviation gasolineused to blend aviation gasoline

Combines an alkene (olefin) with an iso-Combines an alkene (olefin) with an iso-alkane (iso-paraffin) to produce a larger iso-alkane (iso-paraffin) to produce a larger iso-

alkane compoundalkane compound Example: butene (CExample: butene (C

44HH

88) + iso-butane ) + iso-butane

(C(C44HH

1010) ) ➛➛ iso-octane (C iso-octane (C

88HH

1818))

Does an alkylation unit require hydrogen feed like hydrotreating, or release hydrogen as a byproduct like reforming?

Reaction: alkylationReaction: alkylation

Alkylation is a low-temperature, low-pressure refining process, using a highly efficient liquid acid catalyst (either sulfuric or hydrofluoric acid)