The SHELL Olefin Higher Process

SHOP

SHOPThe Oligomerization of ethylene to terminal α–olefins.

C2H4

Ni catalyst

C4 - C8 40%

C10 - C16 40%

C18 + 20%

(ready market)

The 3 fractions are separated by distillation.

The lower and higher olefins are recycled to give more C10-C16 products.

The C10-C16 fraction is used to make other useful products e.g.

CH3(CH2)7-11-CH=CH2

CH3(CH2)8-13-CH2OH

Detergent alcohols

1) Isomerization2) Hydroformylation3) Hydrogenation

SHOP

Catalyst

SHOP C2H4

Ni catalyst

C4 - C8 40%

C10 - C16 40%

C18 + 20%

(ready market)

Ni

Ph

Ph3P

HPh2P

O

CH

CPh

Ni

H

Ph3P

HPh2P

O

CH

CPh

Ph+

Ni

H P

O

From alkene, exchanges with Ph from complex

LabileCatalyst Precursor Active catalyst

Initiation

Vacant site

Can be represented as:

Side product

SHOP

Ni

H P

O

Vacant site

Active catalyst

Alkene occupies here

Ni

H P

ONi

P

O

C

CH

H

H

H

H

Insertion of alkenebetween Ni-H bond

Vacant site regeneratedand another alkene molecule binds, then Inserts between Ni-C bond

SHOP

Ni–(longer chain)

The SHELL HIGHER OLEFIN PROCESS (SHOP)CHEM3162 Learning Objectives

• Draw a catalytic cycle for the oligomerization of ethylene to terminal α–olefins and apply skills for describing a catalytic cycle to this cycle.

• Demonstrate by means of exemplified equations, how the various processes of oligomerization, isomerization, metathesis, hydroformylation* and hydrogenation are utilized by the SHOP process to produce detergent alcohols. (R)

SHOP - Optimization

C2H4

Ni catalyst

C4 - C8 40%

C10 - C16 40%

C18 + 20%

(ready market)

CH3(CH2)1-5 ̶ CH=CH2

CH3(CH2)7-11-CH=CH2

CH3(CH2)13-17 ̶ CH=CH2

Isomerization&Methathesis

Class Activity

Show how H3C(CH2)16-CH2-CH=CH2

may be converted to H3C(CH2)8-CH2=CH2

Hydroformylation

Hydroformylation

• The reaction between an alkene, carbon monoxide and hydrogen, to form an aldehyde containing one more carbon atoms than the original alkene.

Hydroformylation

Aldehydes produced are usually reduced to alcohols which are used as solvents, plasticizers and in the synthesis of detergents.

Co and Rh catalysts are usually employed.

Rh/phosphine catalyst is more active e.g. with RhH(CO)(PPh3)3, hydroformylation occurs at moderate temperatures and pressures (100oC, 1 atm). c.f. Co catalyst at 150oC, 250 atm.

Hydroformylation - Catalyst

Dicobaltoctacarbonyl combines with H2 at high pressure to yield the known tetracarbonylcobalthydride:

Co2(CO)8 + H2 2 [HCo(CO)4]

It is proposed that this complex loses CO to produce the coordinatively unsaturated [HCo(CO)3]:

[HCo(CO)4] [HCo(CO)3] + CO

HCo(CO)4 HCo(CO)3- CO

+ CO

H2CCHCH3

HCo(CO)3

H2C CHCH3

CH2CH2CH3

Co(CO)4

CH2CH2CH3

Co(CO)4

CO

HCCH2CH2CH3

O

+ CO

- CO

CO

H2

a b

c

d

e

Coordination of alkene gives c.

Hydride migration gives d.

CO insertion gives e.

Attack by H2 on e (or acidic [HCo(CO)4]) gives aldehyde and regenerates [HCo(CO)3].

Electron counts: a = 18; b= 16: c= 18; d= 18; e= 18.

Discussion QuestionKinetic studies indicate that the hydroformylation reaction rate is enhanced by an increase in H2 pressure and inhibited by an increase in CO pressure. How is the mechanism in the cycle consistent with these observations?

HCo(CO)4 HCo(CO)3- CO

+ CO

H2CCHCH3

HCo(CO)3

H2C CHCH3

CH2CH2CH3

Co(CO)4

CH2CH2CH3

Co(CO)4

CO

HCCH2CH2CH3

O

+ CO

- CO

CO

H2

a b

c

d

e

Co2(CO)8 + H2 2 [HCo(CO)4]

From these two equations, H2 pressure leads to the conversion of Co2(CO)8 to the more active catalyst, HCo(CO)4, which is necessary to begin the proposed cycle. However, CO is required for the reaction stoichiometry.

CO pressure leads to conversion of the 16e tricarbonyl species to the stable tetracarbonyl species, thus preventing the cycle from going forward.

However, CO is required for the reaction stoichiometry.

Model Response

Hydroformylation: A significant portion of branched aldehydes are also formed:

• The linear aldehydes are preferred e.g. to make linear alcohols for biodegradable detergents.

• Addition of an alkyl phosphine (e.g. PBu3) gives higher selectivity for the linear product. It is proposed that bulky phosphines disfavors formation of sterically crowded, 2o alkyl groups.

The End