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 2 1. Introduction - Basic definitions
concept acid base
- + Brønsted H2O OH + H
- - Lewis FeCl3 + Cl [FeCl4]
Hydrogen transfer reactions intermediates
acid-catalyzed + H+ carbenium ions
base-catalyzed + H+ carbanions
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 3 1. Introduction - Basic definitions
specific acid / base general acid / base catalysis catalysis + - active H3O or OH undissociated acid or base species groups; a variety of species may be simultaneously active reaction •in solution •gas phase reactions medium / •on the surface of •high reaction temperatures conditions a hydrated solid 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!) Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 4 2. Substrates and products
solid acid catalysis solid base catalysis substrates •Alkanes, aromatics •Alkenes (components of crude •Alkynes petrolium) •Alkyl aromatics •Alkenes (products of •Carbonyl compounds petrolium cracking (FCC, steam cracking)) products •Gasoline components •Chemical intermediates •Chemical intermediates •Fine chemicals •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 5 3. Kinds of acid / base catalysts
Solid acids Solid bases •Zeolites •Oxides and modified oxides
ZSM-5, Mordenite, Y-zeolite, Al2O3-NaOH-Na, Al2O3-KOH-K, US-Y, Beta ZrO2-KOH, ZrO2-K2O, MgO, •Oxides, phosphates MgO-Al2O3, hydrotalcites •Zeolites SiO2-Al2O3, Al2O3-BF3, 2- SO4 (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 with amino groups Amberlystâ, Nafionâ •Cs/NPC •Clays •Oxynitrides Kaolinite, Montmorillonite, AlPON, AlGaPON, ZrPON pillared clays
K. Tanabe, W.F. Hölderich, Applied Catalysis A 181 (1999) 399.
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 6 3. Kinds of acis / base catalysts - examples Alumosilicates
•Amorphous alumosilicates •Microporous zeolites (ZSM-5) Brønsted acid site •Mesoporous alumosilicates (MCM-41) H O Al in H-exchanged H O Si zeolites O O Si Al Si
- H2O
Al O Si MFI viewed O O MCM-41 along [010] Si Al Si d = 5.3x5.6 Å 3+ or extraframework Al Lewis acid sites
www.iza-structure.org/databases/ Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 7 3. Kinds of acis / base catalysts - examples Sulfated zirconia Structure of surface sulfates
- 2- 2- HSO4 /SO4 S2O7
A. Hofmann, J. Sauer, J. Phys. Chem B 108 (2004) 14652.
Surface acid sites H Brønsted sites O O L.M. Kustov, V.B.Kazansky, F.Figueras, D. Tichit, O S O J. Catal. 150 (1994) 143. Lewis sites H O S O O O O Zr Zr Zr Zr O O
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 8 3. Kinds of acis / base catalysts - examples Resins
Styrene-based sulfonic acids Perfluorinated resinsulfonic acid (Amberlystâ, Dowexâ, Lewatitâ) (Nafionâ) Prepared by copolymerization of Prepared by copolymerization of styrene and divinylbenzene, sulfonation perfluorinated vinyl ether and tetrafluoroethylene, sulfonation
•Weak acid sites (Amberlyst-15: •Strong acid sites (H0=11-13)
H0=2.2) •Small number of acid sites, surface •High number of acid sites, Amberlyst- area 0.02 m2/g, non-porous solid; 15: surface area 3.35 m2/g, pore asseccibility of acid sites improved in volume 4.8 ml/g) nanocomposites with silica •Thermally stable to about 120-140°C •Thermally stable to about 280°C B. Corain, M. Zecca, K. Jeřábek, J. Mol. Catal. A K.A. Mauritz, R.B. Moore, Chem. Rev. 104 (2004) 177 (2001) 3. 4535.
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 9 3. Kinds of acis / base catalysts - examples Resins
Morphology of styrene-based Hydrated protons in water- sulfonic acids swollen 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 10 3. Kinds of acis / base catalysts - examples Clays and pillared clays
Al2[Si2O5] (OH)4 Al2[Si4O10] (OH)2 Kaolinite 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
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 11 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 2+ 2- ions pairs Mg 3cO 3c Sites: •five coordinated sites on flat (001) 2+ 2- faces (M 5c and O 5c) •four coordinated sites on steps and 2+ 2- edges (M 4c and O 4c) •three coordinated sites on corners 2+ 2- (M 3c and O 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 12 3. Kinds of acis / base catalysts - examples
Hydrotalcites and MgO-Al2O3 HT CHT D. Tichit and B. Coq, Cattech 7 (2003) 206.
2+ 3+ x+ n-1 2+ 2+ 3+ 3+ 2- - [M 1-xM x(OH)2] [Ax/n] ·mH2O; M = Mg ; M =Al , A= CO3 , OH
Theor. ratio Mg/Al molar ratio a b Weight SBET Vp dp C Sample Al/(Al + Mg) Theor. Bulk Surface lossc (m2/g) (cm3/g) (Å) (wt%) (ICP) (XPS) (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 2.0 203 0.22 52 - 44 MgO - - - - 75 0.96 258 - -
Al2O3 - - - - 234 0.54 45 - -
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 13 3. Kinds of acis / base catalysts - examples Basic zeolites
•Basicity is related to Na+ Na+ O O O O O framework oxygen 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 14 4. Characterization of acid / base properties Indicator methods The color change of an indicator B- is determined by the reaction B- + H+ BH
- - [B ] Hammett acidity B base indicator H_ = pKBH+ log BH conjugated acid [BH] 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 15 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 16 4. Characterization of acid / base properties Microcalorimetry
Pyridine adsorption
175
250 S-SZ S-SZ 150 A-SZ Q [kJ/mol] A-SZ
Q [kJ/mol] 200 Hb Hb 125 150
100 100
75 50
50 0 0 100 200 300 400 500 0 200 400 600 800 1000 1200 m Vmid[ mol/g] V [mmol/g]
150°C, gas phase 70°C in anisole
SZ=sulfated zirconia, preparation: S-SZ precipitation of zirconia, sulfation A-SZ sol-gel procedure + S, supercritical drying
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 17 4. Characterization of acid / base properties Microcalorimetry
CO2 adsorption, 40°C, gas phase
160 CO , gas phase CHT0.6 Al O 2 2 3 CHT1.4 MgO 140 CHT2.2 CHT3.0 120
100
80 (kJ/mol) diff
Q 60
40
20
0 0 40 80 120 160 200 240 CO uptake (µmol/g) 2 CHT = calcined hydrotalcites with Mg/Al ratios from 0.6 to 3
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 18 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 O H O C C O O O M M Free carbonate and surface carbonates formed by CO2 adsorption M M 2- 2- 2- 2- 2- 2- 2- O O O O O O O O O O C C C C M C C C O O O O O O O O O O O
M M M M M M M
D3h C2v Cs C2v Cs C2v
symmetrical unidentate bidentate 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 19 4. Characterization of acid / base properties
CO2 TPD monodentate or polydentate - carbonate (?) d(OH) in HOCO2 T / °C
1653 250 1582 1435 0.4 1395 200
- Absorbance n(OH) in HOCO2
1231 150
100 3619
2361 50
0 3500 3000 2500 2000 1500
Wavenumber / cm-1
Adsorption and temperature-programmed desorption of CO2 on MgO-Al2O3 (Mg/Al=0.6)
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 20 4. Characterization of acid / base properties UV-vis / Photoluminescence
2- Direct measurement of the amount of surface O 3c anions in defecive positions of MgO by photoluminescence:
2+ 2- •To reveal the ion pair Mg 3c-O 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.
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 21 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 22 4. Characterization of acid / base properties Catalytic test reactions
Double bond migration – 1-butene isomerization
+ H2C=CH-CH2-CH3 + H H3C-CH-CH2-CH3 cis/trans ratio = 1
+ H3C-CH=CH-CH3 + H H3C-CH2-CH-CH3
+H+ HC CH HC CH -H+ H2C CH3 H3C CH3 -H+ cis-2-butene +H+ CH2=CH-CH2-CH3 cis/trans ratio >> 1 + -H + 1-butene CH +H CH +H+ H 3 H 3 C CH -H+ C CH H2C H3C trans-2-butene
H. Hattori, Chem. Rev. 95 (1995) 537. Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 23 4. Characterization of acid / base properties Catalytic test reactions
Alcohol decomposition + H2O acid OH
base O
+ H2
+ H O acid 2 OH
base
+ H2O H. Hattori, Chem. Rev. 95 (1995) 537.
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 24 5. Acid catalyzed reactions
cis-trans- double skeleton aromatic xylene cracking isomeri- < bond < isomeri- < alkylation < isomeri- < zation shift zation zation
acid strength of active sites
Carbocation chemistry in superacid solutions:
HF/SbF5 or FSO3H/SbF5 in aprotic solvents
+ - 2 FSO3H + SbF5 [FSO3H2] + [SbF5(FSO3)]
+ - 2 HF + SbF5 [H2F] + [SbF6]
+ RCH=CHR' + H R-CH2-CH-R'
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 25 5. Acid catalyzed reactions Carbocations: Intermediates in hydrocarbon reactions
Formation of Carbenium Ions § Proton addition to an alkene or aromatic molecule
+ H+ § Hydride abstraction from an alkane R-CH-CH -R' + LH R-CH2-CH2-R' + L 2 § Formation via carbonium ion intermediate from an alkane Ø Proton addition to an alkane
+ H+ CH CH + H2 H H
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 26 5. Acid catalyzed reactions Stability of carbenium ions
Strukture DHo (kJ mol-1) Enthalpy differences between +138 aliphatic alkylcarbenium ions in +130 the gas phase at 298 K
+67
+6.3 +2.5 Stability: 0 tertiary > secondary > primary 0
-12
-16
-19
G.A. Olah, P.v.R. Schleyer, Carbonium -21 Ions, Wiley, NY, 1968, p. 162.; A. Corma et al., J.Catal. 77 (1982) 159. Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 27 5. Acid catalyzed reactions Formation of carbenium ion via carbonium ion intermediate
+ H R C R' H R C R' + H2 H H
H2 + R C R' + H + R CH R' 2 + RCH3 + R'
H
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 28 5. Acid catalyzed reactions Examples of alkylcarbonium ions
H + R H + CH5 + C R Methoniumion R H H H-Cycloproponiumion H H H + H-Ethoniumion CH3CH4 H H
+ + H3C CH3 H C-Ethoniumion H H C-Cycloproponiumion H H H H H
+ H3C CH2 CH2CH3 + 2-C-Butoniumion H H H H H-Cyclobutoniumion H H H H H
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 29 5. Acid catalyzed reactions
Intramolecular reactions of carbenium ions
Hydride Shift
C C C C H~ C C C C C C C C + + H H
H H3C CH2 H H3C CH3 CH2 C CH2 CH H3C O O O O O O Si Al Si Si Al Si Si Al Si HO OH HO OH HO OH
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 30 5. Acid catalyzed reactions
Intramolecular reactions of carbenium ions
Alkyl Shift C C C C CH ~ C C C C 3 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
b-Elimination H
+ H+ + b-Scission
+ + + H + + b-Scission & + H-Shift Cyclization
H+ + H +
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 32 5. Acid catalyzed reactions
Intermolecular reactions of carbenium ions
Hydride Transfer + +
+ H H C + Disproportionation + + + +
Addition of alkenes / aromatics R' + + R' + R-CH=CH-CH3 CH-CH-CH3
R
+ +
+ Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 33 5. Acid catalyzed reactions Carbocations on the catalyst surface
H H
C C H H H H H C CH3 C H H H CH2
O O O O O O
Si Al Si Si Al Si Si Al Si
HO OH HO OH HO OH p-bonding transition state s-bonding V.B. Kazanskii, I.W. Senchenya, J. Catal. 119 (1989) 108.
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 34 5. Acid catalyzed reactions Stabilization of carbenium ions on/in solid acids
Low energy adsorption sites for HMB in H-Beta ([100] direction) FTIR-spectra of hexamethylbenene M. Bjørgen, F. Bonino, S. Kolboe, a) in KBr K.-P. Lillerud, A. Zecchina, S. Bordiga, b) adsorbed on H-Beta J. Am. Chem. Soc. 125 (2003) 15863. c) adsorbed on dealuminated H- Beta (free from protons) See also: A.Corma, Topics in Catal. 6 (1998) 127. Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 35 5. Acid catalyzed reactions
Skeletal isomerization of C5+-alkanes
formation of a H H carbenium ion H C C H H2 H2 H2 H2 C C H C C H H C C H H2 CH H2 C C C C C C n m H2 H2 H2 H2 H H2 n m n m m H H Cat: e.g. Pt/ chlorinated Al O 2 3 3>m≥1 m≥3 Shell Hysomer process: hydride transfer n-C H Pt/H-mordenite + H2 5 12
CH3 CH3 CH3 H2 H2 H CH C H CH C H CH C C H C C H H2 H m C CH3 H2 H2 m H2 n n n
+ Catalyst deactivation: + C5H12 H2 H3C C Formation of unsaturated carbenium ions by C H H hydride transfer between a carbenium ion 2 m-2 and an alkene isomerized products cracked products
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 36 5. Acid catalyzed reactions
n-Butane isomerization
Possible and forbidden rearrangements of the sec-butyl cation
CH3
H3C CH2 a a H2 b H2 H3C C 4 H3C C 1 C 3 CH3 C CH2 H 2 H b
H 4H2 H3C C 3 1 C CH3 H 2
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 37 5. Acid catalyzed reactions
n-Butane isomerization
H3C-CH2-CH2-CH3 H2C=CH2-CH2-CH3 + H2
CH3
+ CH3 C
CH3
CH3 CH3 H2 H3C CH2-CH-CH2-CH3 H3C C C C CH3
CH CH UOP Butamer process: CH3 3 3
Pt/chlorinated Al2O3 + H2 CH3
+ H C C CH3 Sun Refining: H3C C 2
Fe/Mn/sulfated ZrO CH3 2 CH3 + H http://www.uop.com/refining 2
H H3C C CH3
CH3
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 38 5. Acid catalyzed reactions
Isomerization of xylenes
Mobil Oil: H-ZSM-5
A 8 o m p
CH3 CH3 CH3 CH3 +H -H CH3
CH3 H H
H CH3 H H CH3
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 39 5. Acid catalyzed reactions
Cracking
§Initiation:Mechanism depends on: §Reaction conditions §Feed composition §Brønsted- / Lewis site ratio hydride transfer §Propagation: §Ratio of hydride transfer to b-Scission (= product selectivity) can be controlled by catalyst composition §Termination: H §b-Elimination (olefines) §Hydrid transfer to the b-scission carbenium ion (paraffines) hydride shift
Catalysts, e.g.: 5-40% HY or rare earth exchanged Y + silica/alumina binder + clay filler Schematic catalytic cycle for the (UOP) bimoleculare cracking of alkanes Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 40 5. Acid catalyzed reactions
Alkylation of isobutane with alkenes
C4 cut from FCCU H2 Removal of Recycle i-Butane Butadiene Methanol
n-Butane n-Butane i-Butane Etherifi- i-Butane n-Butane Alkylation n-Butenes cation n-Butenes i-Butene Water Methyl-tert.- Alkylate Butyl Ether (MTBE) 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 41 5. Acid catalyzed reactions
Synthesis of MTBE/TAME
Chemical reactions to ethers macroporous sulfonic acid resin catalyst
CH3 e.g. Amberlyst®-15, Dowex® M32 CH2 + CH3OH H3C OCH3 (MTBE) H3C CH3 CH3
CH3 CH2 + C2H5OH H3C OC2H5 (ETBE) H3C CH3 CH3
CH3
CH3 H3C C H CH3
+ CH3OH H3C OCH3 (TAME) CH 3 C2H5
CH3 H2C C H2 p=15-20 bar, T=60-80°C Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 42 5. Acid catalyzed reactions
Synthesis of MTBE/TAME
Reaction steps in etherification Specific acid catalysis
R-SO3H + CH3OH R-SO3 + CH3OH2
CH3 H3C + CH OH CH2 + CH3OH2 H3C C 3
H3C CH3
CH3H CH3 H3C C O CH3 H3C C + CH3OH CH3 CH3 CH CH3H 3 H C C O CH + R-SO H H3C C O CH3 + R-SO3 3 3 3 CH CH3 3
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 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 Zeol. development: Isobutane •CF3SO3H/SiO2: Haldor Topsoe / Kellog FBA process
•AlCl3/Al2O3 promoted by alkali metal ins + Ni, Pd, Pt (?) 1-Butene 2,3-Dimethylhexane = HAL-100ä: UOP Alkylene process Simplest mechanism for the formation of a dimethylhexane •Faujasite-derived catalyst: J. Weitkamp, Y. Traa in Handbook of Heterogeneous Catalysis, Lurgi Eurofuel Process 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 44 5. Acid catalyzed reactions
Friedel-Crafts acylation of aromatics
d- d+ - H3C C O + AlCl3 H3C C O AlCl3 H3C C O + AlCl4 Cl Cl
H O O - + AlCl4 + C C CH3 CH3 - HCl
O AlCl3 O C C CH3 H2O CH3
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 45 5. Acid catalyzed reactions
Solid acids in the acylation of aromatics
Test reaction: Benzoylation of anisole 50°C, 3 h O O O [solid acid] + C6H5 C H O C H - C6H5COOH O O 6 5 6 5
100 4- and 2-methoxy- 90 benzophenone (96 / 4) 80 71 70 59 60 50 48 41 Reaction mixture: 40
Ketone yield [%] 30 12 ml anisole 0.6 g benzoic anhydride 20 13 10 3 0.2 g solid acid 0 H-mordeniteH-BEA K-10 Amberlyst-15Nafion-HSulfated on Silica Zirconia Batch mode
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 46 5. Acid catalyzed reactions
Alkylation of aromatics
R
+ C=C-C
acid base radical
R=H R=CH3 R=CH3
C C C C C C C C
C C C
cumene isobutylbenzene n-butylbenzene
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 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: • Metal chlorides (liquid phase) •H-ZSM-5 vapour phase (Mobil- Friedel-Crafts-catalysts Badger) BF3, AlCl3 (Monsanto-Lummus) •EBZ 500 zeolite liquid phase
• Mineral acids HF, H2SO4 (UOP/Lummus)
cumene •High silica zeolite (Mobile-Badger/Raytheon + H2C C CH3 H •H-Beta (Enichem)
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 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 pKa Acid pKa
7 CH3OH 16
O O H3C H O O 9 CH3CN 25
H H
CH3COCH3 20 CH3 36
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 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 CH2 Na R-Na+ + RH + C=C-C=C
Addition C-C-C=C-C CH3 Na/K2CO3 H2 - - CH2 C C CH2 H + CH2=CHCH3 AMOCO Chemical, Teijin
Addition K.Tanabe, W.F.Hölderich, Applied Catalysis A 181 (1999) 399. CH3 CH3 H2 H2 - - C C CH2 CH3 C C CH3 CH2 H H + +
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 52 6. Base catalyzed reactions C-C Bond Formation – Aldol Condensation
+ H3C C CH3 + B H3C C CH2 + H B O O
Acetone CH3 H3C H2 H3C C CH2 + C O H3C C C C O H3C O O CH3 B = e.g. La2O3, ZrO2 CH3 CH3 H2 H + 2 H3C C C C O + H B H3C C C C OH + B
O CH3 O CH3 Li/MgO Diacetone Alcohol alkali metal clusters in A-, X-, Y-, L-type zeolites O - H2O (acid sites) H3C C CH3 CH3 O H C C C C 3 H O CH3 Isophorone Mesityl Oxide Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 53 6. Base catalyzed reactions
Formation of a-b unsaturated compounds
CH3COCH3 Using methanol: - H2 HCHO H3C C C CH2 CH3OH H -H2O CoxMg3-x(OH)4Si2O5 O Methyl Vinyl Ketone
Acetonitrile - H2 H2C H C C CH CN - H3COH 3 H O N O Mg O M O Mg O O Mg O M O Mg O
-H2O +CH3OH -H2 +CH3CN Mn-MgO OH H O Mg O M O Mg O H2C CH O- H C + N H H C C CN O Mg O M O Mg O 2 H Acrylonitrile
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 54 6. Base catalyzed reactions C-C Bond Formation – Knoevenagel Condensation
CHO O O H2 + H3C C C C OC2H5
Benzaldehyde Ethyl acetoacetate
Reaction of an aldehyde or alkali modified C - H2O alkali exchanged Y ketone with an methylene hydrotalcites group activated by electron- withdrawing moieties CH3 C O HC C OC2H5 C 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 a-b unsaturated carbonyl compounds
100 B CHT0.6 Al2O3 90 CHT1.4 MgO 2-(g-oxobutyl)-2- CHT2.2 80 methylcyclohexane- CHT3.0 2-methylcyclohexane-1,3-dione 1,3-dione 70 60 methyl vinyl ketone - H+ + H+ 50 + O O O O O O 40 H3C H H3C H3C 30 O Mg O Al
Yield of Michael adduct (%) 20 O O 10
0 solvent : CH3OH 0 4 8 12 16 20 24 Time (h) Mg O Mg
H Michael addition of 2-methylcyclo- + H+ - H+ hexane-1,3-dione to methyl vinyl ketone H OH O over calcined hydrotalcites (CHT) with O O O O O O H C H3C H3C 3 Mg/Al ratios from 0.6 to 3.0, Al2O3 and 6-hydroxy-1,6-dimethyl- MgO. Catalyst amounts used were 2,9-dioxobicyclo[3.3.1]nonane O 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.
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 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
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 58 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
Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 59