Modern Methods in Heterogeneous Catalysis Research

Acid-Base Catalysis Application of Solid Acid-Base Catalysts Annette Trunschke 18 February 2005

Outline 1. Introduction - basic principles 2. Substrates and products 3. Kinds of acid / base catalysts - examples 4. Characterization of surface acidity / basicity - examples 5. Acid catalyzed reactions 6. Base catalyzed reactions 7. Acid-base bifunctional catalysis 8. Summary and outlook

Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

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1. Introduction - Basic definitions concept

acid

base

Brønsted

H2O

OH-

Lewis

FeCl3 +

Cl-

+

H+ [FeCl4]-

Hydrogen transfer reactions intermediates acid-catalyzed

carbenium ions

+ H+

base-catalyzed

Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

+ H+

carbanions

3

1. Introduction - Basic definitions

active species

specific acid / base catalysis

general acid / base catalysis

H3O+ or OH-

undissociated acid or base groups; a variety of species may be simultaneously active

reaction •in solution medium / •on the surface of conditions a hydrated solid

•gas phase reactions •high reaction temperatures

Advantages of solid acid-base catalysts: • • • •

Easier separation from the product Possible reuse and regeneration Fewer disposal problems Non-corrosive and environmentally friendly (but not always!)

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2. Substrates and products solid acid catalysis

solid base catalysis

substrates •Alkanes, aromatics (components of crude petrolium) •Alkenes (products of petrolium cracking (FCC, steam cracking))

•Alkenes •Alkynes •Alkyl aromatics •Carbonyl compounds

products

•Chemical intermediates •Fine chemicals

•Gasoline components •Chemical intermediates •Fine chemicals

Industrial processes in 1999: 103 solid acids worldwide production by catalytic cracking: 500x106 tonnes/y 10 solid bases 14 solid acid-base bifunctional catalysts K.Tanabe, W.F.Hölderich, Applied Catalysis A 181 (1999) 399. Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

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3. Kinds of acid / base catalysts Solid acids

Solid bases

•Zeolites

•Oxides and modified oxides

ZSM-5, Mordenite, Y-zeolite, US-Y, Beta

Al2O3-NaOH-Na, Al2O3-KOH-K, ZrO2-KOH, ZrO2-K2O, MgO, MgO-Al2O3, hydrotalcites

•Oxides, phosphates

•Zeolites SiO2-Al2O3, Al2O3-BF3, SO42-(Mn,Fe)/ZrO2, SrHPO4, CsNaX, CsNaY, microporous FePO4, Li3PO4, phosphoric acid, titanosilicate ETS-10 SAPO-11, SAPO-34 •Mesoporous silicas modified 1.Ion-exchange resins Amberlyst, Nafion

•Clays

with amino groups •Cs/NPC •Oxynitrides

Kaolinite, Montmorillonite, pillared clays

AlPON, AlGaPON, ZrPON

K. Tanabe, W.F. Hölderich, Applied Catalysis A 181 (1999) 399. Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

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3. Kinds of acis / base catalysts - examples

Alumosilicates •Amorphous alumosilicates •Microporous zeolites (ZSM-5) •Mesoporous alumosilicates (MCM-41)

Brønsted acid site H O Al

H Si O Al O Si

O

Si

in H-exchanged zeolites

- H2O Al MFI viewed along [010]

Si O Al O Si

O

Si

MCM-41

d = 5.3x5.6 Å or extraframework Al3+

Lewis acid sites

www.iza-structure.org/databases/ Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

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3. Kinds of acis / base catalysts - examples

Sulfated zirconia Structure of surface sulfates HSO4-/SO42-

S2O72-

A. Hofmann, J. Sauer, J. Phys. Chem B 108 (2004) 14652.

L.M. Kustov, V.B.Kazansky, F.Figueras, D. Tichit, J. Catal. 150 (1994) 143.

Brønsted sites

H

Surface acid sites O

O S

O

O Lewis sites O

Zr O Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

O

Zr

H O

S O

Zr

O O Zr 8

3. Kinds of acis / base catalysts - examples

Resins Styrene-based sulfonic acids (Amberlyst, Dowex, Lewatit) Prepared by copolymerization of styrene and divinylbenzene, sulfonation

Perfluorinated resinsulfonic acid (Nafion) Prepared by copolymerization of perfluorinated vinyl ether and tetrafluoroethylene, sulfonation

•Weak acid sites (Amberlyst-15: H0=2.2) •High number of acid sites, Amberlyst15: surface area 3.35 m2/g, pore volume 4.8 ml/g) •Thermally stable to about 120-140°C

•Strong acid sites (H0=11-13) •Small number of acid sites, surface area 0.02 m2/g, non-porous solid; asseccibility of acid sites improved in nanocomposites with silica •Thermally stable to about 280°C

B. Corain, M. Zecca, K. Jeřábek, J. Mol. Catal. A 177 (2001) 3.

K.A. Mauritz, R.B. Moore, Chem. Rev. 104 (2004) 4535.

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3. Kinds of acis / base catalysts - examples

Resins Morphology of styrene-based sulfonic acids

Hydrated protons in waterswollen ion exchanger catalyst

Undissociated acidic protons in a catalyst swollen in non-aqueous solvent B. Corain, M. Zecca, K. Jeřábek, J. Mol. Catal. A 177 (2001) 3. Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

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3. Kinds of acis / base catalysts - examples

Clays and pillared clays

Al2[Si2O5] (OH)4 Kaolinite

Al2[Si4O10] (OH)2 Montmorillonite

Acid sites: Brønsted (protons) and Lewis (metal ions) Z. Ding, J.T. Kloprogge, R.L. Frost, G.Q. Lu, H.Y. Zhu, Journal of Porous Materials 8 (2001). http://www.ill.fr/dif/3D-crystals/layers.html

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3. Kinds of acis / base catalysts - examples

MgO •Basic sites: •hydroxyl group •surface oxygen anions •Anionic charge of the oxygen is associated to the ionicity of the M-O bond and, therefore, always also to Lewis acidity

ions pairs Mg2+3cO2-3c Sites: •five coordinated sites on flat (001) faces (M2+5c and O2-5c) •four coordinated sites on steps and edges (M2+4c and O2-4c) •three coordinated sites on corners (M2+3c and O2-3c ) (c = coordinatively unsaturated).

progressive water attack on MgO

G. Spoto, E.N. Gribov, G. Ricchiardi, A. Damin, D. Scarano, S. Bordiga, C. Lamberti, A. Zecchina, Progress in Surface Science 76 (2004) 71. S. Coluccia, Stud. Surf. Sci. Catal. 21 (1985) 5. Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

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3. Kinds of acis / base catalysts - examples

Hydrotalcites and MgO-Al2O3 HT

D. Tichit and B. Coq, Cattech 7 (2003) 206.

CHT

[M2+1-xM3+x(OH)2]x+[Ax/n]n-1·mH2O; M2+= Mg2+; M3+=Al3+, A= CO32-, OHTheor. ratio Sample

Al/(Al + Mg)

Mg/Al molar ratio Theor.

Bulk

Surface

(ICP)

(XPS)

SBET 2

Vp

dpa

Cb

3

(m /g)

(cm /g)

(Å)

(wt%)

Weight lossc (wt%)

HT0.6 (MG30)

0.67

0.5

0.6

n.d.

163

0.32

76

1.42

n.a

HT1.4 (MG50)

0.44

1.25

1.4

n.d.

13

0.05

167

1.19

n.a

HT2.2 (MG61)

0.33

2.0

2.2

n.d.

15

0.05

128

2.42

n.a.

HT3.0 (MG70)

0.25

3.0

3.0

n.d.

20

0.10

205

2.27

n.a.

CHT0.6

0.67

0.5

0.6

0.8

257

0.52

81

-

31

CHT1.4

0.44

1.25

1.4

1.4

201

0.23

45

-

36

CHT2.2

0.33

2.0

2.2

2.0

114

0.13

46

-

42

CHT3.0

0.25

3.0

3.0

2.0

-

-

-

52 258

44

-

0.22 0.96

-

MgO

203 75

-

-

Al2O3

-

-

-

-

234

0.54

45

-

-

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3. Kinds of acis / base catalysts - examples

Basic zeolites •Basicity is related to framework oxygen

Na+ Na+ O O O O O Si Al Si Si Al Si

•Exchanging zeolites with a less electronegative charge balancing cation such as Cs+ creates a more basic zeolite (shift to lower O1s binding energies) •Occlusion of alkali metal oxide clusters or alkali metal clusters in zeolite cages •Anchoring organic bases at silanol groups of mesoporous alumosilicates ( e.g. 3-trimethyloxysilyl-propyl(trimethyl)ammonium chloride) – wide distribution of base sites

I. Rodriguez, S. Iborra, A. Corma, F. Rey, J.L. Jordá, Chem. Commun. (1999) 593. Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

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4. Characterization of acid / base properties Indicator methods The color change of an indicator B- is determined by the reaction B- + H+ -

B base indicator BH conjugated acid

BH [B-] H_ = pKBH+ log [BH]

Hammett acidity function

Louis P. Hammett, Alden J. Deyrup, J. Am. Chem. Soc. 54(7) (1932) 2721.

Tanabe et al., Stud. Surf. Sci. Catal. 51 (1989) 21: H_ is equal to the highest among the pKBH values of adsorbed indicators from which the basic site is able to abstract a proton (which can be protonated by the acid site). H_ < -12 „superacid“

H_ > 26 „superbase“

Disadvantages: •Approach is only applicable to Brønsted acid and bases of uniform strength. •Color change is not always related to the acid-base reaction, e.g., formation of charge-transfer complexes, colorless catalyst required Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

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4. Characterization of acid / base properties

FTIR of adsorbed bases

G. Busca, PCCP 1 (1999) 723. Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

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4. Characterization of acid / base properties

Microcalorimetry Q [kJ/mol]

Q [kJ/mol]

Pyridine adsorption 250

S-SZ A-SZ Hβ

200

175

S-SZ A-SZ Hβ

150 125

150

100 100

75 50

50 0 0

200

400

600

800

1000

0

100

200

300

1200

V [µmol/g]

500 Vmid[µmol/g]

70°C in anisole

150°C, gas phase SZ=sulfated zirconia, preparation:

400

S-SZ precipitation of zirconia, sulfation A-SZ sol-gel procedure + S, supercritical drying

Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

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4. Characterization of acid / base properties

Microcalorimetry CO2 adsorption, 40°C, gas phase 160

CHT0.6 CHT1.4 CHT2.2 CHT3.0

CO2, gas phase

140

Qdiff(kJ/mol)

120

Al2O3 MgO

100 80 60 40 20 0 0

40

80

120

160

200

240

CO2 uptake (µmol/g)

CHT = calcined hydrotalcites with Mg/Al ratios from 0.6 to 3 Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

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4. Characterization of acid / base properties

CO2 as probe for basic sites Formation of bicarbonates by reaction of CO2 with basic OH groups H

O H

O C

O

O C

O

O

M

M

Free carbonate and surface carbonates formed by CO2 adsorption 2O

2O

O

O

C

C

O

O

O

M

M

D3h symmetrical

C2v

2O

2O

C

C O

O

M

2O

2O

C

C

O

O M

Cs unidentate

C2v

M

2-

O

O

C

O

O

O

O

M

M

M

M

C2v

Cs

bidentate

M

bridged

polydentate

Other probes: e.g., SO2, pyrrole, CHCl3, CH3CN, B(OCH3)3 J.C. Lavalley, Catal. Today 27 (1996) 377. Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

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4. Characterization of acid / base properties

CO2 TPD

1395

1653 1582 1435

250 200

1231

0.4

T / °C

150 100

2361

3619

ν(OH) in HOCO2-

Absorbance

monodentate or polydentate carbonate (?) δ(OH) in HOCO2

50 0

3500

3000

2500

2000

1500

Wavenumber / cm-1

Adsorption and temperature-programmed desorption of CO2 on MgO-Al2O3 (Mg/Al=0.6)

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4. Characterization of acid / base properties

UV-vis / Photoluminescence Direct measurement of the amount of surface O2-3c anions in defecive positions of MgO by photoluminescence: •To reveal the ion pair Mg2+3c-O2-3c, high pretreatment temperature is required. •At the same time, rearrangement of the surface is going on. •Such competition results in activity maxima as the pretreatment temperature is increased.

high surface low surface water attacked area MgO area MgO MgO

S. Coluccia, Stud. Surf. Sci. Catal. 21 (1985) 5.

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4. Characterization of acid / base properties

Iodine as a visible probe

The visible absorption band of iodine adsorbed on alkali metal-exchanged zeolite blue-shifts with increasing the electropositivity of the countercation and the aluminum content in the framework. S. Y. Choi, Y. S. Park, S. B. Hong, K. B. Yoon, JACS 118 (1996) 9377. Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

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4. Characterization of acid / base properties

Catalytic test reactions Double bond migration – 1-butene isomerization H2C=CH-CH2-CH3

+

H+

H3C-CH-CH2-CH3

H3C-CH=CH-CH3

+

H+

H3C-CH2-CH-CH3

HC H2C

CH2=CH-CH2-CH3 1-butene

CH CH3

+H+ +

-H

-H+ +H+

cis/trans ratio = 1

HC H3C

CH CH3

cis-2-butene

cis/trans ratio >> 1 +

-H+

H C

+H

CH3 CH

H2C

+H+ -H+

H C

CH3 CH

H3C trans-2-butene

H. Hattori, Chem. Rev. 95 (1995) 537. Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

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4. Characterization of acid / base properties

Catalytic test reactions Alcohol decomposition

+ H2O OH

acid

base

O + H2

OH

acid

+ H2O

base + H2O

Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

H. Hattori, Chem. Rev. 95 (1995) 537. 24

5. Acid catalyzed reactions cis-transisomerization


secondary > primary

-12 -16

-19

-21

Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

G.A. Olah, P.v.R. Schleyer, Carbonium Ions, Wiley, NY, 1968, p. 162.; A. Corma et al., J.Catal. 77 (1982) 159. 27

5. Acid catalyzed reactions

Formation of carbenium ion via carbonium ion intermediate

R

+

H C

R' R

H R

H C

R'

+

H2

H

H2 + C R' + H R CH2 R'

+ RCH3 + R'+

H

Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

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5. Acid catalyzed reactions

Examples of alkylcarbonium ions CH5 +

H + H

CH3CH4

R C R R

Methoniumion

+

H-Ethoniumion

CH3 +

H3C

H3C

H

H

H

CH2CH3

+

H C-Cycloproponiumion

H H

H H

CH2

H-Cycloproponiumion

HH H

H H

C-Ethoniumion

H

+

H

+

H

2-C-Butoniumion H

H

H H

H H

Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

H

+

H-Cyclobutoniumion

H

29

5. Acid catalyzed reactions

Intramolecular reactions of carbenium ions Hydride Shift

C

C

C

C

C

+

H~

C

C

H H3 C

O

C

C +

C

H

H H3 C O

Al HO

C

H

CH2 CH2 Si

C

Si OH

C

H3 C CH2

CH

O

O

O Si

CH3

Al HO

Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

Si OH

Si

O Al

HO

Si OH

30

5. Acid catalyzed reactions

Intramolecular reactions of carbenium ions Alkyl Shift C

C

C

C

C

+

C

CH3~

C

C

C

C

C

C +

C

C

+

+

Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

+

+

31

5. Acid catalyzed reactions

Intramolecular reactions of carbenium ions β-Elimination H +

H+

+

β-Scission +

+

+

H +

β-Scission & H-Shift

+

+

Cyclization H+

+

H +

Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

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5. Acid catalyzed reactions

Intermolecular reactions of carbenium ions Hydride Transfer + +

+

H H C +

Disproportionation

+

+ +

+

Addition of alkenes / aromatics R' + CH-CH-CH3

R'+ + R-CH=CH-CH3 R

+ + +

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5. Acid catalyzed reactions

Carbocations on the catalyst surface

H

H C

H

C

H

H C

H

H

O

O Al

HO

CH3

C

H

Si

H

O Si

OH

π-bonding

Si

O Al

HO

CH2

H O Si OH

transition state

Si

O Al

HO

Si OH

σ-bonding

V.B. Kazanskii, I.W. Senchenya, J. Catal. 119 (1989) 108.

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5. Acid catalyzed reactions

Stabilization of carbenium ions on/in solid acids

Low energy adsorption sites for HMB in H-Beta ([100] direction) M. Bjørgen, F. Bonino, S. Kolboe, K.-P. Lillerud, A. Zecchina, S. Bordiga, J. Am. Chem. Soc. 125 (2003) 15863. See also: A.Corma, Topics in Catal. 6 (1998) 127.

FTIR-spectra of hexamethylbenene a) in KBr b) adsorbed on H-Beta c) adsorbed on dealuminated HBeta (free from protons)

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5. Acid catalyzed reactions

Skeletal isomerization of C5+-alkanes formation of a carbenium ion H2 C

H C H2

H2 C C H2

n

H C H2

H2 C

H C H2

m m

Cat: e.g. Pt/ chlorinated Al2O3 Shell Hysomer process: Pt/H-mordenite + H2

H2 C C H

H C C H2

CH

m

n m H

H

3>m≥1

hydride transfer

H

m≥3

n-C5H12 CH3

H2 C

CH C H2

C H2

H C H2

n

CH3 H

H C

H

C H2

H

m

H

CH C H2

isomerized products

C H

m

H

H

Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

CH3

n +

Catalyst deactivation: Formation of unsaturated carbenium ions by hydride transfer between a carbenium ion and an alkene

CH C H2

n

n

+ C5H12

CH3 H2 C

H2 C

H3C C H2

H

m-2

cracked products

36

5. Acid catalyzed reactions

n-Butane isomerization Possible and forbidden rearrangements of the sec-butyl cation CH3

H2 C

H3C

1

C H2

3

b 4 CH3

H3C

a

H2 C

C H

CH2

H

H3C

a

b 4 H2

H3C

1

Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

CH2

C

C2 H

3

CH3

37

5. Acid catalyzed reactions

n-Butane isomerization H3C-CH2-CH2-CH3

H2C=CH2-CH2-CH3

+ H2

CH3 + CH3

C CH3 CH3

CH3 H3C

UOP Butamer process: Pt/chlorinated Al2O3 + H2 Sun Refining: Fe/Mn/sulfated ZrO2

H3C

CH2-CH-CH2-CH3

C

CH3

CH3

http://www.uop.com/refining

H2 C

C

CH3

CH3

CH3 H3C

+

C

H2C

C

CH3

CH3

CH3 + H2

H3C

H C

CH3

CH3

Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

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5. Acid catalyzed reactions

Isomerization of xylenes Mobil Oil: H-ZSM-5

A8 CH3

m

p

CH3

+H

CH3

H H

Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

CH3

-H

CH3

CH3 H

o

H H

CH3

CH3

39

5. Acid catalyzed reactions

Cracking §Initiation:Mechanism depends on: §Reaction conditions §Feed composition §Brønsted- / Lewis site ratio §Propagation: §Ratio of hydride transfer to β-Scission (= product selectivity) can be controlled by catalyst composition §Termination: §β-Elimination (olefines) §Hydrid transfer to the carbenium ion (paraffines) Catalysts, e.g.: 5-40% HY or rare earth exchanged Y + silica/alumina binder + clay filler (UOP) Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

hydride transfer

H

β-scission hydride shift

Schematic catalytic cycle for the bimoleculare cracking of alkanes 40

5. Acid catalyzed reactions

Alkylation of isobutane with alkenes C4 cut from FCCU H2 Removal of Butadiene n-Butane i-Butane n-Butenes i-Butene

Recycle i-Butane

Methanol

Etherification

n-Butane i-Butane n-Butenes

Water Methyl-tert.Butyl Ether (MTBE)

Alkylation

n-Butane

Alkylate

Typical position of an alkylation unit in a modern refinery (FCCU: Fluid catalytic cracking unit) J. Weitkamp, Y. Traa in Handbook of Heterogeneous Catalysis, VCH, Weinheim, 1997, Vol. 4, p. 2049.

Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

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5. Acid catalyzed reactions

Synthesis of MTBE/TAME macroporous sulfonic acid resin catalyst e.g. Amberlyst®-15, Dowex® M32

Chemical reactions to ethers CH3

CH2 + H3C

CH3OH

H3C

CH3

(MTBE)

CH3 CH3

CH2 + H3C

OCH3

C2H5OH

H3C

CH3

OC2H5

(ETBE)

CH3

CH3 H3C

C H

CH3 CH3 +

CH3 H2C

C H2

CH3OH

H3C

OCH3

(TAME)

C2H5 CH3

p=15-20 bar, T=60-80°C Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

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5. Acid catalyzed reactions

Synthesis of MTBE/TAME Reaction steps in etherification Specific acid catalysis R-SO3H

+

CH3OH

CH3OH2

CH3

H3 C CH2 +

CH3OH2

H3C

+

C

H3 C

CH3OH

CH3 CH3H

CH3 H3C

C

+

CH3OH

H3 C

C

O

CH3

CH3

CH3H C

O

CH3

CH3

H3C

+

R-SO3

CH3 + R-SO3

CH3 Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

H3C

C

O

CH3 + R-SO3H

CH3 43

5. Acid catalyzed reactions

Alkylation of isobutane with n-alkenes Isobutane + C3-C5 alkenes = mixture of branched alkanes (alkylate) Conventional catalysts: HF: toxic H2SO4: consumption of 70-100 kg acid/ton alkylate New processes under development: •CF3SO3H/SiO2: Haldor Topsoe / Kellog FBA process •AlCl3/Al2O3 promoted by alkali metal ins + Ni, Pd, Pt (?) = HAL-100: UOP Alkylene process •Faujasite-derived catalyst: Lurgi Eurofuel Process

Zeol.

Isobutane

1-Butene

2,3-Dimethylhexane

Simplest mechanism for the formation of a dimethylhexane J. Weitkamp, Y. Traa in Handbook of Heterogeneous Catalysis, VCH, Weinheim, 1997, Vol. 4, p. 2049.

A. Feller, J. A. Lercher, Adv. Catal. 48 (2004) 229. Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

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5. Acid catalyzed reactions

Friedel-Crafts acylation of aromatics

H3C

C

O + AlCl3

H3C

δ+ C O

δ− AlCl3

H3C

C

O + AlCl4

Cl

Cl

H

O + O C

C

C

CH3

CH3

AlCl3 CH3

O

+ AlCl4- HCl

O H2O

Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

C

CH3

45

5. Acid catalyzed reactions

Solid acids in the acylation of aromatics Test reaction: Benzoylation of anisole O + O

C6H5

O

C6H5 - C6H5COOH

O

O

C6H5

4- and 2-methoxybenzophenone (96 / 4)

100 90 80

Ketone yield [%]

O

50°C, 3 h [solid acid]

71

70

59

60 48

50

Reaction mixture: 12 ml anisole 0.6 g benzoic anhydride 0.2 g solid acid

41

40 30 20

13

10

3

0

H-

mo

rde

Hnit

BE

e

A

K-

10

Am

be

rly

Su lfa ted n-H Batch sto 15 n S Zirco nia ilic a Na

fio

Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

mode

46

5. Acid catalyzed reactions

Alkylation of aromatics R

+ C=C-C

base

acid

radical

R=CH3

R=H

R=CH3

C C

C

C

C

C

C

C

C C

C

cumene

isobutylbenzene

Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

n-butylbenzene

47

5. Acid catalyzed reactions

Alkylation of benzene with ethylene Acid Catalyzed Synthesis of Alkylbenzenes + ArH

CH2=CH2 + HA

CH-CH3 A

[CH3-CH2-ArH] A

CH3-CH2-Ar + HA

Alkylation of benzene with ethylene Conventional catalysts:

New processes:

•

•H-ZSM-5 vapour phase (MobilBadger) •EBZ 500 zeolite liquid phase (UOP/Lummus)

•

Metal chlorides (liquid phase) Friedel-Crafts-catalysts BF3, AlCl3 (Monsanto-Lummus) Mineral acids HF, H2SO4 cumene + H2 C

C H

CH3

Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

•High silica zeolite (Mobile-Badger/Raytheon •H-Beta (Enichem) 48

5. Acid catalyzed reactions

Alkylation of benzene with propylene

ZSM-5

H-Beta

www.accelrys.com/ cases/eniricerche.html

In ZSM-5, the bulkier cumene tends to isomerize to the less bulky n-propylbenzene.

Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

49

5. Acid catalyzed reactions

Alkylation of benzene with propylene Catalyst: H-Beta, EniChem

C. Perego, P. Ignallina, Catalysis Today, 73 (2002) 3. Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

50

6. Base catalyzed reactions RH + H2O → R- + H3O+ Acid

O

pKa

Acid

pKa

7

CH3OH

16

9

CH3CN

25

O H3 C

H

O

O

H

H

CH3COCH3

20

Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

CH3

36

51

6. Base catalyzed reactions

Side-chain alkylation of aromatics Mechanisms of base catalyzed side-chain alkylation of toluene with propylene via a carbanion chain reaction

Initiation

CH3

-

R Na

CH2-Na+

+

+ RH

Addition

+ C=C-C=C

CH3

H2 C C H

CH2+

CH2=CHCH3

C-C-C=C-C

Na/K2CO3

CH2-

AMOCO Chemical, Teijin K.Tanabe, W.F.Hölderich, Applied Catalysis A 181 (1999) 399.

Addition CH3 H2 C C CH2H

CH3 +

Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

CH3 H2 C C CH3 H +

CH2-

52

6. Base catalyzed reactions

C-C Bond Formation – Aldol Condensation H3C

C

CH3

+B

O Acetone H3C

C

C

C

CH2 + H+B

O H3C

CH2

C

+

H3C

O

H3C

O

H3C

H3C

CH3 H2 C C O + H+B

O

O B = e.g. La2O3, ZrO2 H3C

CH3

O

C

CH3 H2 C C O

C

CH3

CH3 H2 C C OH + B

O

CH3

Li/MgO Diacetone Alcohol alkali metal clusters in A-, X-, Y-, L-type zeolites -H O 2

H3C

C

CH3

O

Isophorone Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

(acid sites)

CH3 H3C

C

C H

O Mesityl Oxide

C CH3 53

6. Base catalyzed reactions

Formation of α-β unsaturated compounds Using methanol:

CH3OH

- H2

CH3COCH3 HCHO

CoxMg3-x(OH)4Si2O5

H3 C

-H2O

C

C H

CH2

O Methyl Vinyl Ketone

H2 -H2C C H C N H O O Mg O M O Mg O

Acetonitrile CH3CN

H3COH O

Mg O

M

O

Mg O

-H2O +CH3OH +CH3CN

-H2

Mn-MgO

OH H O

Mg O

M

O

Mg O

+ H2C

C CN H Acrylonitrile

Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

H2C

CH

O-

H C

H O Mg O

N M

O

Mg O

54

6. Base catalyzed reactions

C-C Bond Formation – Knoevenagel Condensation CHO O H3C

+ Benzaldehyde

Reaction of an aldehyde or ketone with an methylene group activated by electronwithdrawing moieties

C

O

H2 C C

OC2H5

Ethyl acetoacetate

- H2O

alkali modified C alkali exchanged Y hydrotalcites CH3 C

HC

C C

O OC2H5 O

Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

55

6. Base catalyzed reactions

C-C Bond Formation – Michael Addition Nucleophilic addition of carbanions to α-β unsaturated carbonyl compounds Yield of Michael adduct (%)

100

CHT0.6 CHT1.4 CHT2.2 CHT3.0

90 80

B

Al2O3 MgO

2-(γ-oxobutyl)-2methylcyclohexane1,3-dione

2-methylcyclohexane-1,3-dione

70 60

methyl vinyl ketone

50

O

40

O H3C

30

Mg

20

+ H+

- H+

+

O

H O

O

O

O H3 C

H3C O

Al

O

O

10 0 0

4

8

12

Time (h)

16

20

solvent : CH3OH

24

Michael addition of 2-methylcyclohexane-1,3-dione to methyl vinyl ketone over calcined hydrotalcites (CHT) with Mg/Al ratios from 0.6 to 3.0, Al2O3 and MgO. Catalyst amounts used were 0.225 g for Al2O3, and MgO and the remaining weight of 0.225 g after calcination at 550 °C for the calcined hydrotalcites; T=21°C.

Mg

O

Mg

H +H O

O

OH

H3C 6-hydroxy-1,6-dimethyl2,9-dioxobicyclo[3.3.1]nonane

Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

+

-H O

O H3C

O

+

H O

O H3 C O

56

7. Acid-base bifunctional catalysis Hydrogenation of benzoic acid to benzaldehyde

HO NaOH/ZrO2

+ H2O

Sumitomo Mitsubishi Kasai ZrO2,doped with Cr2O3 350°C

Acid / base bifunctional mechanism over a zirconia catalyst (Zr4+: acid site; O2- base site) Modern Methods in Heterogeneous Catalysis Research : 18/02/2005

57

8. Summary and outlook •Fine and speciality chemicals will be manufactured in the future to a greater extent using solid acid-base catalysts •Solid acid-base bifunctional catalysis is expected to become more important in the future Problems and needs: •New bases resistant to deactivation (CO2 and water poisoning) need to be developed •Deactivation of catalysts •Development of catalysts other than acidic resins which can be used in aqueous solutuins •Universal acidity / basicity scale for solids

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Acknowledgements Thanks for data and material for illustration to Dr. Jens Deutsch, ACA Zhi-Jian Li , HU Berlin Dr. Hillary A. Prescott, HU Berlin Dr. Veronika Quaschning, BASF AG Dr. Alexander Hofmann, HU Berlin

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