Liquid Phase Aerobic Oxidation Catalysis E-Book
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- Herausgeber: Wiley-VCH
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
The first book to place recent academic developments within the context of real life industrial applications, this is a timely overview of the field of aerobic oxidation reactions in the liquid phase that also illuminates the key challenges that lie ahead. As such, it covers both homogeneous as well as heterogeneous chemocatalysis and biocatalysis, along with examples taken from various industries: bulk chemicals and monomers, specialty chemicals, flavors and fragrances, vitamins, and pharmaceuticals. One chapter is devoted to reactor concepts and engineering aspects of these methods, while another deals with the relevance of aerobic oxidation catalysis for the conversion of renewable feedstock. With chapters written by a team of academic and industrial researchers, this is a valuable reference for synthetic and catalytic chemists at universities as well as those working in the pharmaceutical and fine chemical industries seeking a better understanding of these reactions and how to design large scale processes based on this technology.
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Veröffentlichungsjahr: 2016
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Table of Contents
Cover
Title Page
Copyright
Preface
List of Contributors
Part I: Radical Chain Aerobic Oxidation
Chapter 1: Overview of Radical Chain Oxidation Chemistry
1.1 Introduction
1.2 Chain Initiation
1.3 Chain Propagation
1.4 Formation of Ring-Opened By-Products in the Case of Cyclohexane Oxidation
1.5 Complications in the Case of Olefin Autoxidation
1.6 Summary and Conclusions
References
Chapter 2: Noncatalyzed Radical Chain Oxidation: Cumene Hydroperoxide
2.1 Introduction
2.2 Chemistry and Catalysis
2.3 Process Technology
2.4 New Developments
References
Chapter 3: Cyclohexane Oxidation: History of Transition from Catalyzed to Noncatalyzed
3.1 Introduction
3.2 Chemistry and Catalysis
3.3 Process Technology
3.4 New Developments
Epilogue
References
Chapter 4: Chemistry and Mechanism of Oxidation of para-Xylene to Terephthalic Acid Using Co–Mn–Br Catalyst
4.1 Introduction
4.2 Chemistry and Catalysis
4.3 Process Technology
4.4 New Developments
4.5 Conclusions
References
Part II: Cu-Catalyzed Aerobic Oxidation
Chapter 5: Cu-Catalyzed Aerobic Oxidation: Overview and New Developments
5.1 Introduction
5.2 Chemistry and Catalysis
5.3 Process Technology
5.4 New Developments: Pharmaceutical Applications of Cu-Catalyzed Aerobic Oxidation Reactions
References
Chapter 6: Copper-Catalyzed Aerobic Alcohol Oxidation
6.1 Introduction
6.2 Chemistry and Catalysis
6.3 Prospects for Scale-Up
6.4 Conclusions
References
Chapter 7: Phenol Oxidations
7.1 Polyphenylene Oxides by Oxidative Polymerization of Phenols
7.2 2,3,5-Trimethylhydroquinone as a Vitamin E Intermediate via Oxidation of Methyl-Substituted Phenols
References
Part III: Pd-Catalyzed Aerobic Oxidation
Chapter 8: Pd-Catalyzed Aerobic Oxidation Reactions: Industrial Applications and New Developments
8.1 Introduction
8.2 Chemistry and Catalysis: Industrial Applications
8.3 Chemistry and Catalysis: Applications of Potential Industrial Interest
8.4 Chemistry and Catalysis: New Developments and Opportunities
8.5 Conclusion
References
Chapter 9: Acetaldehyde from Ethylene and Related Wacker-Type Reactions
9.1 Introduction
9.2 Chemistry and Catalysis
9.3 Process Technology (Wacker Process)
9.4 Other Developments
References
Further Reading
Chapter 10: 1,4-Butanediol from 1,3-Butadiene
10.1 Introduction
10.2 Chemistry and Catalysis
10.3 Process Technology
10.4 New Developments
10.5 Summary and Conclusions
References
Chapter 11: Mitsubishi Chemicals Liquid Phase Palladium-Catalyzed Oxidation Technology: Oxidation of Cyclohexene, Acrolein, and Methyl Acrylate to Useful Industrial Chemicals
11.1 Introduction
11.2 Chemistry and Catalysis
11.3 Prospects for Scale-Up
11.4 Conclusion
References
Chapter 12: Oxidative Carbonylation: Diphenyl Carbonate
12.1 Introduction
12.2 Chemistry and Catalysis
12.3 Prospects for Scale-Up
12.4 Conclusions and Outlook
Acknowledgments
References
Chapter 13: Aerobic Oxidative Esterification of Aldehydes with Alcohols: The Evolution from Pd–Pb Intermetallic Catalysts to Au–NiOx Nanoparticle Catalysts for the Production of Methyl Methacrylate
13.1 Introduction
13.2 Chemistry and Catalysis
13.3 Process Technology
13.4 New Developments
13.5 Conclusion and Outlook
References
Part IV: Organocatalytic Aerobic Oxidation
Chapter 14: Quinones in Hydrogen Peroxide Synthesis and Catalytic Aerobic Oxidation Reactions
14.1 Introduction
14.2 Chemistry and Catalysis: Anthraquinone Oxidation (AO) Process
14.3 Process Technology
14.4 Future Developments: Selective Aerobic Oxidation Reactions Catalyzed by Quinones
References
Chapter 15: NOx Cocatalysts for Aerobic Oxidation Reactions: Application to Alcohol Oxidation
15.1 Introduction
15.2 Chemistry and Catalysis
15.3 Prospects for Scale-Up
15.4 Conclusions
References
Chapter 16: N-Hydroxyphthalimide (NHPI)-Organocatalyzed Aerobic Oxidations: Advantages, Limits, and Industrial Perspectives
16.1 Introduction
16.2 Chemistry and Catalysis
16.3 Process Technology
16.4 New Developments
Acknowledgments
References
Chapter 17: Carbon Materials as Nonmetal Catalysts for Aerobic Oxidations: The Industrial Glyphosate Process and New Developments
17.1 Introduction
17.2 Chemistry and Catalysis
17.3 Process Technology
17.4 New Developments
17.5 Concluding Remarks
References
Part V: Biocatalytic Aerobic Oxidation
Chapter 18: Enzyme Catalysis: Exploiting Biocatalysis and Aerobic Oxidations for High-Volume and High-Value Pharmaceutical Syntheses
18.1 Introduction
18.2 Chemistry and Catalysis
18.3 Process Technology
18.4 New Developments
References
Part VI: Oxidative Conversion of Renewable Feedstocks
Chapter 19: From Terephthalic Acid to 2,5-Furandicarboxylic Acid: An Industrial Perspective
19.1 Introduction
19.2 Chemistry and Catalysis
19.3 Process Technology
19.4 New Developments
19.5 Conclusion
References
Chapter 20: Azelaic Acid from Vegetable Feedstock via Oxidative Cleavage with Ozone or Oxygen
20.1 Introduction
20.2 Chemistry and Catalysis
20.3 Prospects for Scale-Up
20.4 Concluding Remarks and Perspectives
References
Chapter 21: Oxidative Conversion of Renewable Feedstock: Carbohydrate Oxidation
21.1 Introduction
21.2 Chemistry and Catalysis
21.3 Prospects for Scale-Up
21.4 Concluding Remarks and Perspectives
References
Part VII: Aerobic Oxidation with Singlet Oxygen
Chapter 22: Industrial Prospects for the Chemical and Photochemical Singlet Oxygenation of Organic Compounds
22.1 Introduction
22.2 Chemistry and Catalysis
22.3 Prospects for Scale-Up
22.4 Conclusion
Acknowledgments
References
Part VIII: Reactor Concepts for Liquid Phase Aerobic Oxidation
Chapter 23: Reactor Concepts for Aerobic Liquid phase Oxidation: Microreactors and Tube Reactors
23.1 Introduction
23.2 Chemistry and Catalysis
23.3 Prospects for Scale-Up
23.4 Conclusions
References
Index
End User License Agreement
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Guide
Cover
Table of Contents
Preface
Part I: Radical Chain Aerobic Oxidation
Begin Reading
List of Illustrations
Chapter 1: Overview of Radical Chain Oxidation Chemistry
Figure 1.1 Oxygen consumption during the autoxidation of cyclohexane at 418 K with and without the addition of cyclohexanone. The red slopes signify the oxidation rate at various stages of the reaction. The initial pressure increase is due to heating, initiated at time 0.
Figure 1.2 Comparison of the unimolecular RO−OH dissociation process and the bimolecular initiation between ROOH and cyclohexanone [11].
Figure 1.3 αH-abstraction from the primary cyclohexyl hydroperoxide product and subsequent chemistry.
Figure 1.4 Effect of the substrate on the solvent-cage efficiency and alcohol-to-ketone ratio.
Figure 1.5 Competing reactions for the cyclohexoxyl radical: formation of the primary ring-opened by-products [22].
Figure 1.6 Addition of peroxyl radical to CC bond of α-pinene and consecutive alkoxyl radical chemistry [23].
Figure 1.7 Competing O
2
addition at higher oxygen partial pressures, leading to a drop in epoxide selectivity and an increase in initiation rate via the formation of labile dialkyl peroxide.
Chapter 2: Noncatalyzed Radical Chain Oxidation: Cumene Hydroperoxide
Figure 2.1 Overview of the cumene route for the production of phenol and acetone.
Figure 2.2 Important side reactions in the cumene oxidation.
Figure 2.3 Block diagram of the cumene oxidation process.
Figure 2.4 Bubble column for the oxidation of cumene.
Figure 2.5 Mass transfer of oxygen (film model).
Figure 2.6 Concentration profiles in a cumene oxidation reactor.
Figure 2.7 Compartment model.
Chapter 4: Chemistry and Mechanism of Oxidation of para-Xylene to Terephthalic Acid Using Co–Mn–Br Catalyst
Figure 4.1 Major oxidation intermediates from pX to TA.
p-
HMBA is
p
-hydroxymethylbenzoic acid, and 4-CBA is 4-carboxybenzaldehyde. Cat.: Co–Mn–Br.
Figure 4.2 Reactive intermediates in liquid phase oxidation of hydrocarbons.
Figure 4.3 Branching sequence in Co–Br and Co–Mn–Br catalysis.
Figure 4.4 Hydrogen abstraction reactions in Co-only and Co–Br-catalyzed oxidation of
p
-toluic acid.
Figure 4.5 Mn-catalyzed reduction of Co(III) by bromide.
Figure 4.6 Equilibria in Co(OAc)
2
–HOAc–HBr system. Solvent ligands surrounding octahedral Co(II) species are not shown.
Figure 4.7 Reduction of Co(III) in its reaction with MBr
2
, (M = Co, Mn).
Figure 4.8 Structures of Co(III)a and Co(III)s (based on Ref. [29]).
Figure 4.9 Current view of MC catalytic mechanism for hydrocarbon oxidation.
Figure 4.10 Mechanism for Co(III)-catalyzed acetic acid combustion.
Figure 4.11 Subsequent reactions of methyl radicals produced in O
2
-deficient or O
2
-rich environment.
Figure 4.12 Process diagram for the oxidation section of conventional BP PTA process. (From Ref. [1].) (a) Oxidation reactor; (b) surge vessel; (c) filter; (d) dryer; (e) residue still; and (f) dehydration column.
Figure 4.13 Process diagram for the purification section of conventional BP PTA process. (From Ref. [1].) (a) Slurry drum; (b) hydrogenation reactor; (c) crystallizers; (d) centrifuge; and (e) dryer.
Chapter 5: Cu-Catalyzed Aerobic Oxidation: Overview and New Developments
Scheme 5.1 Industrially important liquid phase Cu-catalyzed aerobic oxidation reactions.
Scheme 5.2 Proposed mechanism for Cu-catalyzed aerobic decarboxylation of benzoic acid.
Scheme 5.3 Proposed mechanism of DMC formation in the Enichem/Versalis process.
Figure 5.1 Illustration of chloride-free catalysts for the oxidative carbonylation of methanol: (a) 2,2′-bipyrimidine-Cu(OAc)
2
and (b) a Co
II
-Schiff base complex.
Figure 5.2 Reactor scheme for toluene to phenol oxidation.
R
1: toluene oxidation reactor,
A
1: adsorption unit,
C
1: toluene column,
C
2: benzoic acid,
R
2 benzoic acid oxidation reactor,
A
2 adsorption unit,
C
3: crude phenol column,
C
4: benzene column,
C
5: pure phenol column, and
V
1: tar extraction unit.
Figure 5.3 Schematic view of Enichem's slurry reactor.
Scheme 5.4 Chan–Lam coupling reactions and a simplified catalytic cycle.
Scheme 5.5 Efficient preparation of DCPA•HCl outlined by researchers at Bristol-Myers Squibb.
Scheme 5.6 Scalable process for the synthesis of AZD8926 outlined by researchers at AstraZeneca.
Scheme 5.7 Scalable synthesis of 1,2,4-triazoles developed at Hoffman-La Roche: (a) general reaction conditions and (b) scale-up example.
Scheme 5.8 Proposed mechanism of 1,2,4-triazole formation.
Scheme 5.9 Efficient synthesis of imidazo[1,2-
a
]pyridines: (a) general reaction conditions and (b) gram-scale synthesis of zolimidine.
Scheme 5.10 Presumed mechanism of imidazo[1,2-
a
]pyridine formation.
Scheme 5.11 Aerobic Cu-catalyzed α-amination of aldehydes, ketones, and esters: (a) general reaction conditions, (b) multigram-scale coupling, (c) synthesis of Plavix, and (d) synthesis of amfepramone.
Scheme 5.12 Proposed mechanism for the aerobic α-amination of aldehydes, ketones, and esters.
Chapter 6: Copper-Catalyzed Aerobic Alcohol Oxidation
Figure 6.1 Catalyst types developed for copper-catalyzed aerobic alcohol oxidation.
Figure 6.2 Scope of copper(I)/DBED-catalyzed aerobic alcohol oxidation.
Figure 6.3 Common nitroxyl radicals used in copper-catalyzed aerobic alcohol oxidation.
Scheme 6.1 Simplified mechanism of Cu/TEMPO- and oxoammonium-catalyzed aerobic alcohol oxidation.
Scheme 6.2 Production of vanillin via the guaiacol process.
Scheme 6.3 BASF synthesis of vitamin A.
Figure 6.4 Broad-scope Cu/nitroxyl catalyst systems for aerobic alcohol oxidation.
Figure 6.5 Aerobic oxidation of primary alcohols to nitriles by Huang and coworkers [24b].
Scheme 6.4 BASF adaptation of Cu/TEMPO-catalyzed aerobic alcohol oxidation.
Figure 6.6 Cu/DBAD-catalyzed aerobic oxidation reported by Markó.
Figure 6.7 Active site structure of galactose oxidase.
Figure 6.8 Transition state energies providing insight into the selectivity differences between TEMPO and ABNO.
Figure 6.9 Cu/TEMPO-catalyzed aerobic alcohol oxidation by DSM.
Figure 6.10 Zeneca application of Cu/DBAD-catalyzed aerobic alcohol oxidation.
Chapter 7: Phenol Oxidations
Figure 7.1 (a) Resonance structures for the phenoxyl radical; (b) phenol carbon atoms that undergo C−C or C−O coupling reactions; and (c) reaction scheme for the copper-catalyzed oxidative coupling of DMP (R = CH
3
).
Figure 7.2 Schematic representation of the proposed possible initial steps for the oxidative coupling of DMP: (a) ionic pathway [19] and (b) radical pathway [20].
Figure 7.3 Schematic representation of the rearrangement of a quinone-ketal moiety that gives rise to polymer extension [16].
Figure 7.4 Schematic representation of the quinone-ketal rearrangement and redistribution [26].
Figure 7.5 (a)
T
g
of PPO™–PS blends [37] and (b) marketing chart for Noryl® resins.
Scheme 7.1 Synthesis of (all-
rac
)-α-tocopherol (
1
) via phenol oxidation as a key step.
Scheme 7.2 Products formed in the oxidation of 2,3,6-TMP (
3
).
Scheme 7.3 2,6-Dimethylphenol (DMP,
8
) as a starting material for an alternative access to TMHQ (
6
).
Chapter 8: Pd-Catalyzed Aerobic Oxidation Reactions: Industrial Applications and New Developments
Scheme 8.1 Industrial examples of Pd-catalyzed aerobic oxidation.
Scheme 8.2 Additional Pd-catalyzed aerobic oxidations that have been targets of extensive research.
Scheme 8.3 Proposed liquid phase type mechanism in vinyl acetate synthesis [7].
Figure 8.1 Flow diagram of Ube liquid phase process of dibutyl oxalate [18].
Scheme 8.4 Proposed mechanism for oxidative carbonylation of alcohols using alkyl nitrites.
Scheme 8.5 Pd-catalyzed aerobic oxidative coupling of dimethyl phthalate.
Scheme 8.6 Pd-catalyzed oxidative esterification of arenes to aryl esters and phenol derivatives.
Scheme 8.7 Routes for benzyl acetate production.
Scheme 8.8 Proposed mechanism for Pd-based acetoxylation of toluene [[79]b].
Scheme 8.9 Roles of ligands in Pd-catalyzed aerobic oxidations.
Figure 8.2 Representative effective pyridine-based ligands in Pd-catalyzed aerobic oxidations.
Scheme 8.10 Pd-catalyzed aerobic allylic acetoxylation with DAF.
Scheme 8.11 Amino acid–promoted aerobic C−H olefination of phenylacetic acid derivatives.
Scheme 8.12 Ligand-modulated regioselective oxidative Heck reaction for diene synthesis.
Scheme 8.13 Pd-catalyzed aldehyde-selective alkene oxidation and proposed radical model.
Scheme 8.14 Pd-catalyzed aerobic benzene acetoxylation and nitration in the presence of NO
x
[[51, 54]].
Chapter 9: Acetaldehyde from Ethylene and Related Wacker-Type Reactions
Figure 9.1 Relation between pH value and the rate of the reaction of ethylene with aqueous PdCl
2
solutions containing CuCl
2
.
Figure 9.2 Acetaldehyde from ethylene, single-stage process: (a) reactor, (b) separating vessel, (c) cooler, (d) scrubber, (e) crude aldehyde tank, (f) light ends distillation, (g) condenser, (h) purification column, and (i) regeneration unit.
Figure 9.3 Acetaldehyde from ethylene, two-stage process: (a) reactor, (b) expansion tower, (c) catalyst cycle pump, (d) oxidation reactor, (e) exhaust air separator, (f) crude aldehyde column, (g) process water tank, (h) condenser, (i) crude aldehyde container, (j) scrubbers for exhaust gas and air, (k) light ends distillation, (l) purification column, and (m) regeneration.
Chapter 10: 1,4-Butanediol from 1,3-Butadiene
Scheme 10.1
Scheme 10.2
Scheme 10.3
Figure 10.1 Block flow diagram of Mitsubishi Chemical's 1,4-butanediol manufacturing process.
Figure 10.2 Process flow diagram of first generation in oxidative acetoxylation.
Figure 10.3 Process flow diagram of second generation in oxidative acetoxylation.
Chapter 11: Mitsubishi Chemicals Liquid Phase Palladium-Catalyzed Oxidation Technology: Oxidation of Cyclohexene, Acrolein, and Methyl Acrylate to Useful Industrial Chemicals
Figure 11.1 Palladium-catalyzed oxidation of cyclohexene to either cyclohexanone or to 1,4-dioxaspiro[4,5]decane. Cyclohexanone is susceptible to overoxidation, while the 1,4-dioxaspiro[4,5]decane is stable.
Figure 11.2 The simplified proposed mechanism for the catalytic cycle.
Figure 11.3 Three-step synthesis of 1,3-propanediol from acrolein.
Figure 11.4 Hydrolysis and hydrogenation of the by-products (7% Rh/Al
2
O
3
, 2 MPa H
2
, 90 °C, slight excess H
2
O).
Figure 11.5 Pd/Fe/Cu-catalyzed oxidation of methyl acrylate to 3,3-dimethoxy methyl propionate using oxygen as the oxidant [9].
Figure 11.1 Inside reactor temperature increase due to the exothermicity of the oxidation of methyl acrylate to 3,3-dimethoxy methyl propionate [9].
Chart 11.2 Investigation of reaction parameters [9]. (a) Effect of catalyst composition on the reaction rate at different pressures (Pd = 4.4 × 10
−6
mol, MA = 0.11 mol, MeOH = 0.98 mol, 70 °C, 1000 rpm, pure oxygen, varying Cu and Fe amounts). (b) Product selectivity at different reaction temperatures (Pd = 4.4 × 10
−6
, Cu = 2.2 × 10
−3
, Fe = 2.2 × 10
−3
, MA = 0.11 mol, MeOH = 0.98 mol, 1000 rpm, 0.2 MPa pure oxygen, varying reaction temperatures). (c) Conversion curves at different MeOH/Ma ratios (Pd = 4.4 × 10
−6
, Cu = 2.2 × 10
−3
, Fe = 2.2 × 10
−3
, MA = 0.11 mol, 1000 rpm, 70 °C, 0.2 MPa pure oxygen, varying amounts of methanol). (d) Selectivities at different MeOH/MA ratios (Pd = 4.4 × 10
−6
, Cu = 2.2 × 10
−3
, Fe = 2.2 × 10
−3
, MA = 0.11 mol, 1000 rpm, 70 °C, 0.2 MPa pure oxygen, varying amounts of methanol).
Scheme 11.1 The reaction mechanism of palladium-catalyzed oxidation of methyl acrylate to 3,3-dimethoxy methyl propionate [9].
Scheme 11.2 Reaction equations and the corresponding activation energies and pre-experimental factors (MA = methyl acrylate, 3MAC = 3-methoxy acrylate, 33MP = 3,3-dimethoxy methyl propionate, IMP = impurity, 3H3M = 3-hydroxy-3-methoxy methyl propionate, DMM = dimethoxy methylene, and MF = methyl formate) [9].
Chart 11.3 Real experiment versus simulated experiment, ▪ = substrate conversion and ⋄ = product yield.
Chapter 12: Oxidative Carbonylation: Diphenyl Carbonate
Scheme 12.1 Direct synthesis of diphenyl carbonate by oxidative carbonylation.
Scheme 12.2 Pathways of phenol oxidative carbonylation by Pd(II).
Scheme 12.3 Reactions between the main components of lead-based catalytic packages.
Chapter 13: Aerobic Oxidative Esterification of Aldehydes with Alcohols: The Evolution from Pd–Pb Intermetallic Catalysts to Au–NiOx Nanoparticle Catalysts for the Production of Methyl Methacrylate
Figure 13.1 Effect of lead on palladium catalyst. Symbols: (•)
2
Selectivity and (○)
2
Yield. Reaction conditions:
1
(47 mmol), catalyst (5% Pd/CaCO
3
) in methanol (90 ml), and O
2
(1 atm, 5 l/h) at 40 °C for 2 h.
Figure 13.2 Presumed mechanism for synthesis of Pd
3
Pb
1
.
Figure 13.3 Reaction network in oxidative esterification reaction of methacrolein.
Figure 13.4 Precise control of Pd and Pb distribution in the catalyst.
Figure 13.5 The block flow diagram of oxidative esterification process for MMA. (a) TBA oxidation for methacrolein synthesis. (b) Methacrolein absorption by methanol. (c) Oxidative esterification for MMA synthesis. (d) Recovery column for unreacted methacrolein and methanol and removal of low-boiling-point products. (e) High-boiling-point products' separation tower. (f) MMA purification tower.
Figure 13.6 Proposed structure of Au–NiO
x
nanoparticles.
Chapter 14: Quinones in Hydrogen Peroxide Synthesis and Catalytic Aerobic Oxidation Reactions
Scheme 14.1 The anthraquinone oxidation (AO) process for industrial synthesis of H
2
O
2
.
Scheme 14.2 HPPO process for the synthesis of propylene oxide.
Scheme 14.3 Formation of anthrone by-products in the “anthra” system.
Scheme 14.4 Simplified process flow diagram for the production of H
2
O
2
.
Scheme 14.5 Aerobic oxidation of hydroquinone to quinones, a common step in the AO process and in quinone-catalyzed oxidation reactions.
Scheme 14.6 (a) Catalytic oxidation of organic substrates employing catalytic DDQ with molecular oxygen and cocatalytic NO
x
and (b) DDQ-catalyzed and NaNO
2
-cocatalyzed aerobic cross-coupling of diarylpropenes and 1,3-dicarbonyls.
Scheme 14.7 Pd-catalyzed allylic acetoxylation reaction featuring Pd-, quinone-, and metal macrocycle (LM)-coupled catalytic cycles.
Scheme 14.8 Copper amine oxidases carry out (a) the aerobic oxidation of primary amines
in vivo
via a (b) transamination mechanism.
Scheme 14.9 Copper amine oxidase mimics promote the aerobic oxidation of primary amines to imines.
Scheme 14.10 (a) Aerobic phd-catalyzed oxidation of diverse classes of secondary amines through (b) an “addition–elimination” mechanism. (c) Improved reaction efficiency is obtained by replacing Zn
2+
with Ru
2+
and I
−
cocatalyst with Co(salophen).
Chapter 15: NOx Cocatalysts for Aerobic Oxidation Reactions: Application to Alcohol Oxidation
Scheme 15.1 (Top) LCo(III)NO
2
- and Lewis acid-catalyzed aerobic oxidation of benzyl alcohol and cycloheptanol. (Bottom) Proposed mechanism for substrate oxidation.
Scheme 15.2 (a) NO
x
-catalyzed aerobic benzyl alcohol oxidation in TFA. (b) NO
x
-catalyzed aerobic aliphatic alcohol oxidation in perchloric acid.
Scheme 15.3 Amberlyst-15- and NO
x
-catalyzed aerobic benzylic alcohol oxidation.
Scheme 15.4 Proposed catalytic cycle for the amberlyst-15- and NO
x
-catalyzed aerobic oxidation of benzylic alcohols.
Figure 15.1 Examples of common stable nitroxyl radicals.
Scheme 15.5 Generation of
N
-oxoammonium salts from nitroxyl radicals, and the pH-dependent mechanism of oxoammonium reactivity with alcohols: hydride transfer at pH < 5 (Path A) and adduct formation/Cope-type elimination at pH > 5 (Path B).
Scheme 15.6 General proposed catalytic cycles for (a) NO
x
- and nitroxyl-catalyzed aerobic alcohol oxidation and (b) NO
x
-, X
2
-, and nitroxyl-catalyzed aerobic alcohol oxidation.
Scheme 15.7 Minisci's Mn(NO
3
)
2
/Co(NO
3
)
2
/TEMPO-catalyzed aerobic alcohol oxidation and Hu's NaNO
2
/Br
2
/TEMPO-catalyzed aerobic alcohol oxidation.
Scheme 15.8 Catalytic 5-F-AZADO and NaNO
2
aerobic oxidation of a broad array of alcohols.
Scheme 15.9 Catalytic ABNO/keto-ABNO and NaNO
2
for aerobic alcohol oxidation.
Chapter 16: N-Hydroxyphthalimide (NHPI)-Organocatalyzed Aerobic Oxidations: Advantages, Limits, and Industrial Perspectives
Scheme 16.1 Self-decomposition of PINO.
Scheme 16.2 The catalytic cycle of NHPI in the aerobic oxidation of organic substrates.
Scheme 16.3 Radical chain initiation by means of metal (M) salts.
Scheme 16.4 PINO resonance structures.
Scheme 16.5 Aerobic oxidation of adamantane catalyzed by NHPI.
Scheme 16.6 Aerobic oxidation of cyclohexane to adipic acid catalyzed by NHPI.
Scheme 16.7 Aerobic oxidation of cyclohexane in the presence of lipophilic NHPI.
Scheme 16.8 Reaction mechanism for epoxidation of olefins.
Figure 16.1 Process flowchart of NHPI-catalyzed epoxidation in MJOD millireactor system.
Scheme 16.9 Oxidation of cyclohexylbenzene.
Figure 16.2 Process scheme for the NHPI-catalyzed oxidation of cumene.
Figure 16.3 Adsorption of NHPI on A26(Cl) (milligram of catalyst adsorbed per gram of A26(Cl) – (a)) and regeneration of the adsorbing bed using MeCN. CU/CHP = 1.85/1 (mol/mol) (b). Initial NHPI concentration: 2 mg/ml.
Scheme 16.10 Ishii's catalyst
1
and new organocatalyst
2.
Chapter 17: Carbon Materials as Nonmetal Catalysts for Aerobic Oxidations: The Industrial Glyphosate Process and New Developments
Figure 17.1 Three routes toward the production of glyphosate.
Scheme 17.1 The oxidative decarboxylation of
N
-(phosphonomethyl)iminodiacetic acid (PMIDA) toward glyphosate catalyzed by activated carbon.
Scheme 17.2 Possible side reactions during the glyphosate production.
Figure 17.2 Activity (a) and selectivity (b) profiles for glyphosate production by four Norit SXRO activated carbon samples with different pore size distributions ranging from 2 to 8 a.u.
Figure 17.3 Activity (a) and selectivity (b) profiles for glyphosate production by four Norit SXRO activated carbon samples with different H
2
O
2
times ranging from 12 to 60 min (pore size distributions kept constant at 3 a.u.).
Figure 17.4 Activity (a) and selectivity (b) profiles for glyphosate production by eight Norit SXRO activated carbon samples
1–8
prepared with different N-donors (PSD is degree of optimal pore size distribution).
Chart 17.1 Structures accessible via oxygenative and dehydrogenative conversions catalyzed by carbon materials (excluding g-CN). Red and blue bonds refer to oxygenative and dehydrogenative bond formation, respectively. Phenyl rings may contain additional substituents.
Chart 17.2 Structures accessible via oxygenative and dehydrogenative conversions catalyzed by g-CN. Red and blue bonds refer to oxygenative and dehydrogenative bond formation, respectively. Phenyl rings may contain additional substituents.
Figure 17.5 Hypothetical hybrid graphene-type material composed of regions ranging from g-CN to graphene, including B- and N-doped graphene and GeO. The GeO region is based on the Lerf–Klinowski model, g-CN is depicted as its tri-
s
-triazine-based allotrope. Defect holes are included in the structures of GeO and N-doped graphene.
Chapter 18: Enzyme Catalysis: Exploiting Biocatalysis and Aerobic Oxidations for High-Volume and High-Value Pharmaceutical Syntheses
Scheme 18.1 Baeyer–Villiger oxidation of carbonylic substrates catalyzed by BVMOs.
Scheme 18.2 Conversion of cyclohexanone to hexane-6-lactone catalyzed by cyclohexanone monooxygenase (CHMO).
Scheme 18.3 Mechanism of Baeyer–Villiger monooxygenases [36–46].
Figure 18.1 Structures of the proton pump inhibitors omeprazole (racemate) and esomeprazole (
S
-enantiomer).
Scheme 18.4 Synthetic route for the production of omeprazole [52].
Scheme 18.5 Oxidation method developed by Kagan [56, 57] for catalyzing asymmetric sulfoxidation reactions.
Scheme 18.6 Modified Kagan catalytic oxidation for the industrial scale-up of esomeprazole production.
Scheme 18.7 Screening reaction used in the first directed evolution study of a BVMO; (
R
)-5-(2-hydroxyethyl)dihydrofuran-2(3H)-one is formed with 9% ee [62].
Scheme 18.8 Schematic representation of BVMO-mediated enzymatic process for esomeprazole production. During process development, pyrmetazole degradation, esomeprazole degradation and overoxidation, and the production of hydrogen peroxide were identified as side reactions/processes that needed to be minimized or eliminated for successful implementation.
Scheme 18.9 Monoamine oxidase-catalyzed oxidation of amines coupled with catalase disproportionation of hydrogen peroxide to form O
2
and water.
Scheme 18.10 Key disconnections of the peptide bonds of Boceprevir arriving at the bicyclic [3.1.0]proline core.
Scheme 18.11 Comparison of the first- and second-generation retrosynthetic analysis of the bicyclic [3.1.0]proline core.
Scheme 18.12 Third-generation process for the manufacture of the bicyclic [3.1.0]proline featuring an MAO-catalyzed desymmetrization.
Scheme 18.13 HTP approach to screen for MAO activity using an Amplex Red/peroxidase coupled reporter.
Scheme 18.14 Trapping the volatile imine with sodium bisulfite to make the stable sulfone intermediate.
Scheme 18.15 Competition between sulfonation and oxidation of bisulfite.
Scheme 18.16 Synthetic sequence to prepare boceprevir from caronic anhydride.
Scheme 18.17 Hydroxylation reaction catalyzed by cytochrome P450s.
Scheme 18.18 Asymmetric epoxidation reaction catalyzed by styrene monooxygenase.
Scheme 18.19 Biosynthesis of pravastatin using an engineered
E. coli
strain expressing a cytochrome P450 gene.
Chapter 19: From Terephthalic Acid to 2,5-Furandicarboxylic Acid: An Industrial Perspective
Figure 19.1 The five steps that are required to produce PEF starting from glucose.
Figure 19.2 Pathways for three key furanic intermediates with Co/Mn/Br mixtures in acetic acid.
Figure 19.3 Primary radical oxidation pathways for levulinic acid.
Chapter 20: Azelaic Acid from Vegetable Feedstock via Oxidative Cleavage with Ozone or Oxygen
Scheme 20.1 Mechanism of ozonolysis.
Scheme 20.2
Scheme 20.3
Scheme 20.4
Scheme 20.5
Chapter 21: Oxidative Conversion of Renewable Feedstock: Carbohydrate Oxidation
Figure 21.1 Biorefinery concept.
Figure 21.2 Products derived by aerobic oxidation of glucose.
Figure 21.3 Sucralose.
Figure 21.4 Molecular mechanism of glucose oxidation on gold catalyst in the presence of alkali.
Figure 21.5 Mechanism of glucose oxidation on Bi–Pd catalyst.
Figure 21.6 Main chemicals achieved via glucose oxidation.
Figure 21.7 Comparison among Au, Pd, and Pt colloidal nanoparticles in glucose oxidation.
Figure 21.8 Commercial gluconates and uses.
Figure 21.9 Comparison between supported mono- and bimetallic gold platinum catalysts.
Figure 21.10 Structure of disaccharides (sucrose, lactose, and maltose).
Figure 21.11 Products deriving from sucrose.
Figure 21.12 Tricarboxylated sucrose and one of the three possible monocarboxylated isomers.
Figure 21.13 Gold-catalyzed oxidation of cellobiose.
Figure 21.14 Chemoenzymatic oxidation of sugars.
Figure 21.15 Oxidation pattern of polysaccharides.
Chapter 22: Industrial Prospects for the Chemical and Photochemical Singlet Oxygenation of Organic Compounds
Figure 22.1 Higher occupied molecular orbitals of (a) ground-state nitrogen (
1
N
2
, ), (b) ground-state oxygen (
3
O
2
, ), and the (c) and (d) two lowest excited singlet states of oxygen (
1
O
2
,
1
Δ
g
) and (
1
O
2
, ).
Figure 22.2 Jablonski diagram showing the excitation of a photosensitizer
1
Sens into the excited singlet state
1
Sens*, which suffers intersystem crossing (ISC) giving excited triplet state
3
Sens*. The latter may transfer its energy to ground-state oxygen
3
O
2
providing
1
O
2
(type II photooxidation). Alternatively, it may abstract one electron or a H atom from the substrate releasing organic free radicals as well as various reactive oxygen species (ROS) such as O
2
•−
, OH
•
, or H
2
O
2
(type I photooxidation).
Scheme 22.1 Main photosensitizers used to generate photochemically
1
O
2
.
Figure 22.3 Periodic table showing the most effective oxides, hydroxides, and oxoanions able to trigger the formation of
1
O
2
via the oxidation (black boxes) or the disproportionation (gray boxes) of H
2
O
2
in basic aqueous solution.
Scheme 22.2 Influence of the pH value on the chemoselectivity of the oxidation of tiglic acid by the system H
2
O
2
/MoO
4
2−
.
Figure 22.4 Predominance diagram showing prevalent species formed by the interaction between H
2
O
2
and MoO
4
2−
as a function of pH and concentration of free H
2
O
2
(
T
= 0 °C, [Na
2
MoO
4
] = 1 M). The orange area corresponds to the conditions under which the formation of the main precursor of
1
O
2
is favored.
Scheme 22.3 Photooxidation of 1,5-dihydroxynaphthalene into juglone.
Scheme 22.4 Photooxidation of α-pinene into pinocarvone.
Figure 22.5 Schematic representation of the dark singlet oxygenation of a substrate S in a water-in-oil single-phase µem water/surfactant/cosurfactant/solvent by the chemical source hydrogen peroxide/sodium molybdate.
Scheme 22.5 Different types of microemulsion (µem) systems according to the concentration of surfactant and the water/oil interfacial curvature. WI: Winsor I system (O/W µem in equilibrium with excess oil); WII: Winsor II system (W/O µem in equilibrium with excess water); WIII: Winsor III system (µem in equilibrium with excess oil and water); and WIV: Winsor IV (single-phase µem).
Figure 22.6 Three-liquid phase microemulsion (Winsor III) based on the balanced catalytic surfactant bis(dimethyldioctylammonium)molybdate.
Scheme 22.6 Synthesis of the antimalarial artemisinin from artemisinic acid.
Scheme 22.7 Synthesis of rose oxide from β-citronellol.
Chapter 23: Reactor Concepts for Aerobic Liquid phase Oxidation: Microreactors and Tube Reactors
Figure 23.1 Schematic setup of the capillary reactor for gold-catalyzed oxidation reaction of alcohols.
Figure 23.2 General schematic of the XCube™ flow reactor.
Figure 23.3 Schematic diagram of the tube reactor setup for homogeneous copper-catalyzed oxidation of primary alcohols.
Figure 23.4 Schematic diagram of the gas–liquid continuous-flow reactor for the direct aerobic oxidation of 2-benzylpyridines.
Figure 23.5 Schematic flow setup for the through-wall singlet oxygen oxidation of
α
-terpinene to ascaridole.
Figure 23.6 Continuous-flow setup for the conversion of dihydroartemisinic acid (DHAA) into artemisinin.
Figure 23.7 Continuous-flow setup for the visible-light photocatalytic aerobic oxidation of thiols to disulfides.
Figure 23.8 Experimental setup for the metal-free aerobic oxidation of alcohols under three-phase flow conditions.
Figure 23.9 Experimental setup for the aldehyde oxidation under Taylor flow conditions.
Figure 23.10 Integrated three-step continuous-flow system for the preparation of
ortho
-functionalized phenols.
Figure 23.11 Schematic setup for the continuous-flow oxidative acetylene coupling.
Figure 23.12 Schematic representation of the microflow setup for the aerobic C-3 olefination of indoles.
Figure 23.13 Schematic representation of the continuous-flow tube reactor designed for homogeneous Pd-catalyzed aerobic oxidation reactions.
Figure 23.14 Schematic setup for the synthesis of phenylacetaldehydes from styrenes through an aerobic anti-Markovnikov Wacker oxidation.
List of Tables
Chapter 1: Overview of Radical Chain Oxidation Chemistry
Table 1.1 Common initiators for autoxidations and their initiation barriers
Table 1.2 Rate constants (M
−1
s
−1
) for hydrogen abstraction from primary, secondary, and tertiary C−H bonds by various radical species at 400 K (per H-atom) [6–8]
Chapter 7: Phenol Oxidations
Table 7.1 Physical properties of PPO™ [13]
Table 7.2 Catalytic activity of various copper/amine complexes
Chapter 9: Acetaldehyde from Ethylene and Related Wacker-Type Reactions
Table 9.1 Some examples of the oxidation of olefinic compounds with aqueous palladium chloride solution [2, 7, 8]
Chapter 10: 1,4-Butanediol from 1,3-Butadiene
Table 10.1 Ability of Pd–Te–C catalyst to form 1,4-diacetoxy-2-butene.
a
Table 10.2 Addition effect of Se and Te to Pd–C catalyst
Chapter 11: Mitsubishi Chemicals Liquid Phase Palladium-Catalyzed Oxidation Technology: Oxidation of Cyclohexene, Acrolein, and Methyl Acrylate to Useful Industrial Chemicals
Table 11.1 Palladium-catalyzed oxidation of cyclohexene in various solvents showing the importance of 1,4-dioxaspiro[4,5]decane formation in the protection of the product against overoxidation.
a
Table 11.2 Palladium-catalyzed oxidation of cyclohexene with different Cu and Fe cocatalyst compositions showing that the Pd/Cu/Fe combination gives a sTable catalyst which gives clean oxidation
Table 11.3 Various substrates oxidized by the Pd/Cu/Fe-catalyst combination in alcohol solvents using oxygen as the oxidant
Chapter 13: Aerobic Oxidative Esterification of Aldehydes with Alcohols: The Evolution from Pd–Pb Intermetallic Catalysts to Au–NiOx Nanoparticle Catalysts for the Production of Methyl Methacrylate
Table 13.1 Catalytic activity for aerobic oxidative esterification of methacrolein (
1
) with methanol to form methyl methacrylate (
2
).
a
Chapter 15: NOx Cocatalysts for Aerobic Oxidation Reactions: Application to Alcohol Oxidation
Table 15.1 Thermodynamic values associated with O
2
reduction and NO
x
-based redox reactions
Table 15.2 Common NO
x
precursors and pathways to
in situ
NO
x
generation
Chapter 17: Carbon Materials as Nonmetal Catalysts for Aerobic Oxidations: The Industrial Glyphosate Process and New Developments
Table 17.1 Major differences between the three production routes toward glyphosate [2]
Chapter 18: Enzyme Catalysis: Exploiting Biocatalysis and Aerobic Oxidations for High-Volume and High-Value Pharmaceutical Syntheses
Table 18.1 Evolution challenges and strategies for evolving a CHMO enzyme suiTable for the industrial production of esomeprazole
Table 18.2 Process challenges and strategies for developing an industrial process implementing an evolved CHMO enzyme for the production of esomeprazole
Table 18.3 Evolution summary, selection pressures, and results
Chapter 19: From Terephthalic Acid to 2,5-Furandicarboxylic Acid: An Industrial Perspective
Table 19.1 Oxidation of furanics to FDCA over heterogeneous catalysts
Table 19.2 FDCA obtained with Co/Mn/Br catalyst systems
Table 19.3 Oxidation of 5-(methoxymethyl)furfural (MMF)
Chapter 20: Azelaic Acid from Vegetable Feedstock via Oxidative Cleavage with Ozone or Oxygen
Table 20.1 Comparison of different approaches for the synthesis of AA
Chapter 21: Oxidative Conversion of Renewable Feedstock: Carbohydrate Oxidation
Table 21.1 Mono- and bimetallic catalysts tested in glucose oxidation under acidic conditions
Table 21.2 Selective oxidation of disaccharides on Au, Pd, and Pt catalysts
Table 21.3 Comparison between enzymatic and chemical oxidation of glucose
Edited byShannon S. Stahl and Paul L. Alsters
Liquid Phase Aerobic Oxidation Catalysis
Industrial Applications and Academic Perspectives
Editors
Prof. Dr. Shannon S. Stahl
University of Wisconsin-Madison
Department of Chemistry
1101 University Avenue
Madison WI 53706
USA
Dr. Paul L. Alsters
DSM Ahead R&D b.v.
Innovative Synthesis
P.O. Box 1066
6160 BB Geleen
The Netherlands
Cover: Erik de Graaf/iStock
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Preface
Oxidation reactions play a crucial role in the chemical industry, where >90% of the feedstocks derive from hydrocarbons – the most reduced organic chemicals on the planet. Sustainability concerns are demanding a greater shift toward biomass-derived feedstocks; however, oxidation methods will continue to play a major role. For example, even as this book goes to press (March 2016), BASF and Avantium have just announced plans to pursue a joint venture for the production of 2,5-furandicarboxylic acid (FDCA), an important polymer-building block derived from biomass. The proposed 50 000 metric tons per year plant will undoubtedly incorporate liquid phase aerobic oxidation chemistry similar to that described in Chapter 19 of this volume.
Molecular oxygen is the most abundant, most environmentally benign, and least expensive oxidant available. Yet, selective partial oxidation reactions with O2 have long been dominated by the commodity chemical industry, where the scale of the processes typically dictates that O2 or, preferably, air is the only viable oxidant. Over the past 10–15 years, an increasing number of academic research groups have embraced the challenge of developing selective oxidation reactions capable of using O2 as the stoichiometric oxidant. These efforts have led to a growing number of catalytic oxidation methods that are compatible with complex molecules of the type encountered in the fine chemical, agrochemical, and pharmaceutical industries. Invariably, these methods are liquid phase processes, and they employ both homogeneous and heterogeneous catalysts.
We (SSS and PLA) first met at one of the triennial ADHOC conferences (Activation of Dioxygen and Homogeneous Oxidation Catalysis). The unique blend of industrial and academic attendees, who have a shared interest in oxidation chemistry and catalysis, is a special feature of this conference series. Industrial contributors to this conference regularly provide valuable context for the academic research, and often share insights that are not readily available from the open literature.
This volume was conceived with the goal of complementing the growing number of widely available academic review articles that describe research advances in the field of aerobic oxidation catalysis. Our goal was to bring together as many experts as possible, who could provide a perspective on either (i) existing liquid phase aerobic oxidation processes that are practiced in industry or (ii) emerging aerobic oxidation applications of industrial interest, including their prospects for scale-up, where appropriate. In certain cases, we encountered challenges identifying industrial contributors who were both willing to share their (company's) story and had the clearance to do so. Fortunately, we were successful in a number of cases, and the present volume documents these industrial stories and perspectives, together with selected coverage of other relevant topics by academic authors. Twenty-two chapters on aerobic oxidation reactions and processes, beginning with non-catalyzed autoxidations, are complemented by a final chapter on new reactor concepts for liquid phase aerobic oxidations. It was not possible to provide comprehensive coverage, but it is our hope that the content of this volume will provide valuable historical and industrial context for ongoing research efforts within the global research community, and also inspire further advances in the field of aerobic oxidation catalysis.
USA, March 2016
Shannon S. Stahl and Paul L. Alsters
List of Contributors
Victor A. Adamian
BP Petrochemicals
150 West Warrenville Rd.
MC E-1F
Naperville, IL 60563
USA
Paul L. Alsters
DSM Ahead R&D b.v.
Innovative Synthesis
P.O. Box, 1066
6160 BB Geleen
The Netherlands
Jean-Marie Aubry
Université de Lille and ENSCL
Unité de Catalyse et de Chimie du Solide
UCCS CNRS
UMR 8181
59655 Villeneuve d'Ascq
France
Hendrikus J. Baars
Avantium Chemicals
Renewable Chemistries
Zekeringstraat 29
1014 BV Amsterdam
The Netherlands
Annemarie E. W. Beers
Cabot Norit Activated Carbon
Euro Support Catalysts
Kortegracht 26
3811 KH Amersfoort
The Netherlands
Jan-Bernd Grosse Daldrup
INEOS Phenol GmbH
Technology Department
Dechenstrasse 3
45966 Gladbeck
Germany
Ermelinda Falletta
Università degli Studi di Milano
Dipartimento di Chimica
Via G. Golgi 19
20133 Milano
Italy
Patrick Gamez
Institució Catalana de Recerca i Estudis Avançats (ICREA)
Passeig Lluís Companys, 23
08010 Barcelona
Spain
Hannes P. L. Gemoets
Eindhoven University of Technology
Department of Chemical Engineering and Chemistry
Micro Flow Chemistry and Process Technology
Den Dolech 2
5612 AZ Eindhoven
The Netherlands
William H. Gong
1s280 Wisconsin Avenue
Lombard, IL 60147
USA
Gert-Jan M. Gruter
Avantium Chemicals
Renewable Chemistries
Zekeringstraat 29
1014 BV Amsterdam
The Netherlands
Ive Hermans
The University of Wisconsin-Madison
Department of Chemistry
1101 University Avenue
Madison, WI 53706
USA
and
The University of Wisconsin-Madison
Department of Chemical and Biological Engineering
1101 University Avenue
Madison, WI 53706
USA
Volker Hessel
Eindhoven University of Technology
Department of Chemical Engineering and Chemistry
Micro Flow Chemistry and Process Technology
Den Dolech 2
5612 AZ Eindhoven
The Netherlands
Damian Hruszkewycz
University of Wisconsin-Madison
Department of Chemistry
1101 University Avenue
Madison, WI 53706
USA
Yusuke Izawa
Mitsubishi Chemical Corporation
Petrochemicals Technology Laboratory
Toho-cho 1
Yokkaichi-shi Mie 510-8530
Japan
Jonathan N. Jaworski
University of Wisconsin-Madison
Department of Chemistry
1101 University Avenue
Madison, WI 53706
USA
Reinhard Jira
Wacker-Chemie AG
Burghausen
Germany
Angela Köckritz
Department of Heterogeneous Catalytic Processes
Leibniz Institute for Catalysis
Albert-Einstein-Str. 29a
18059 Rostock
Germany
Mark Kuil
Cabot Norit Activated Carbon
P.O. Box 105
3800 AC Amersfoort
The Netherlands
Hans E. B. Lempers
University of Applied Sciences
Department of Chemistry
Institute of Life Sciences and Chemistry
Heidelberglaan 7
3584CS Utrecht
The Netherlands
Etienne Mazoyer
Avantium Chemicals
Renewable Chemistries
Zekeringstraat 29
1014 BV Amsterdam
The Netherlands
Scott McCann
University of Wisconsin-Madison
Department of Chemistry
1101 University Avenue
Madison, WI 53706
USA
Lucio Melone
Politecnico di Milano
Department of Chemistry,
Materials, and Chemical Engineering ``Giulio Natta''
Via Leonardo da Vinci 32
20131 Milano
Italy
and
Università degli Studi e-Campus
Via Isimbardi 10
22060 Novedrate
Como
Italy
Erika M. Milczek
Agem Solutions Inc.
50 Murray St. #2011
New York, NY 10007
USA
Véronique Nardello-Rataj
Université de Lille and ENSCL
Unité de Catalyse et de Chimie du Solide
UCCS CNRS
UMR 8181
59655 Villeneuve d'Ascq
France
Thomas Netscher
DSM Nutritional Products
Research and Development
P.O. Box 2676
CH-4002 Basel
Switzerland
Timothy Noël
Eindhoven University of Technology
Department of Chemical Engineering and Chemistry
Micro Flow Chemistry and Process Technology
Den Dolech 2
5612 AZ Eindhoven
The Netherlands
Robert L. Osborne
Novozymes North America Inc.
77 Perrys Chapel Church Road
Franklinton, NC 27525
USA
Cristina Della Pina
Università degli Studi di Milano
Dipartimento di Chimica
Via G. Golgi 19
20133 Milano
Italy
Carlo Punta
Politecnico di Milano
Department of Chemistry,
Materials, and Chemical Engineering ``Giulio Natta''
Via Leonardo da Vinci 32
20131 Milano
Italy
Michele Rossi
Università degli Studi di Milano
Dipartimento di Chimica
Via G. Golgi 19
20133 Milano
Italy
Jan Schütz
DSM Nutritional Products
Research and Development
P.O. Box 2676
CH-4002 Basel
Switzerland
Tohru Setoyama
Mitsubishi Chemical Corporation
Department of Research & Development
1000 Kamoshida-cho
Aoba-ku
Yokohama 227-8502
Japan
Grigorii L. Soloveichik
General Electric Company
GE Global Research
One Research Circle
Niskayuna, NY 12309
USA
and
Advanced Research Project Agency-Energy (ARPA-E)
1000 Independence Ave
Washington, DC 20585
USA
Shannon S. Stahl
University of Wisconsin-Madison
Department of Chemistry
1101 University Avenue
Madison, WI 53706
USA
Janelle E. Steves
University of Wisconsin-Madison
Department of Chemistry
1101 University Avenue
Madison, WI 53706
USA
Ken Suzuki
Asahi Kasei Chemicals Corporation
Catalyst Laboratory
2767-11 Shionasu Kojima
Kurashiki
Okayama 711-8510
Japan
Jun P. Takahara
Mitsubishi Chemical Corporation
Department of Research & Development
1000 Kamoshida-cho
Aoba-ku
Yokohama 227-8502
Japan
Yoshiyuki Tanaka
Mitsubishi Chemical Corporation
Department of Research & Development
3-10 Ushiodori
Kurashiki
Okayama 712-8054
Japan
Johan Thomas Tinge
Research & Technology
Fibrant BV
Urmonderbaan 22
6167 RD Geleen
The Netherlands
Jan C. van der Waal
Avantium Chemicals
Renewable Chemistries
Zekeringstraat 29
1014 BV Amsterdam
The Netherlands
Dian Wang
University of Wisconsin-Madison
Department of Chemistry
1101 University Avenue
Madison, WI 53706
USA
Manfred Weber
INEOS Phenol GmbH
Technology Department
Dechenstrasse 3
45966 Gladbeck
Germany
Markus Weber
INEOS Phenol GmbH
Technology Department
Dechenstrasse 3
45966 Gladbeck
Germany
Alison E. Wendlandt
University of Wisconsin-Madison
Department of Chemistry
1101 University Avenue
Madison, WI 53706
USA
Setsuo Yamamatsu
Tokyo University and Technology
Department of Chemical Engineering
2-24-16 Nakacho
Koganei
Tokyo 184-8588
Japan
Toshiharu Yokoyama
Mitsubishi Chemical Corporation
C4 Chemical Derivatives Department
1-1 Marunouchi 1-chome
Chiyoda-ku
Tokyo 100-8251
Japan
Susan L. Zultanski
University of Wisconsin-Madison
Department of Chemistry
1101 University Avenue
Madison, WI 53706
USA
Part IRadical Chain Aerobic Oxidation
Chapter 1Overview of Radical Chain Oxidation Chemistry
Ive Hermans
1.1 Introduction
The direct reaction of triplet O2 with hydrocarbons is usually very slow (e.g., H-abstraction), or quantum-chemically forbidden (e.g., the insertion of O2 in a C−H bond to form a hydroperoxide). Nevertheless, those high-energy paths can be bypassed by a more efficient radical mechanism as demonstrated by the pioneering work of Bäckström [1]. Although initial studies were aimed at finding ways of preventing undesired autoxidations, it was soon recognized that the controlled oxidation of hydrocarbons can be a synthetically useful route to a wide range of oxygenated products. In subsequent chapters, some of those industrial processes are discussed in more detail. The goal of this introductory chapter is to provide a mechanistic framework for this rather complex chemistry.
In 1939, Criegee made an important contribution by showing that the primary product of cyclohexene autoxidation is the allylic hydroperoxide [2]. The classical textbook on radical pathway for the thermal autoxidation of a general hydrocarbon RH is summarized in reactions (1.1)–(1.5) [3–5]:
Initiation
Propagation
Termination
In general, an initiation reaction produces radicals from closed-shell molecules. Different types of initiator molecules and their initiation barriers are summarized in Table 1.1. Under normal autoxidation conditions, initiation takes place through O−O cleavage in hydroperoxides (viz., reaction (1.2)). This rate-controlling initiation step is rapidly followed by the fast H-abstraction from the substrate by both alkoxyl and hydroxyl radicals (reaction (1.2)), producing alcohol and water, respectively.
Table 1.1 Common initiators for autoxidations and their initiation barriers
48 kcal/mol
40 kcal/mol
37 kcal/mol
31 kcal/mol
30 kcal/mol
28 kcal/mol
For alkoxyl radicals, a competitive side-reaction can occur in kinetic competition with H-abstraction from the substrate, namely, β C−C cleavage to produce a carbonyl compound and an alkyl radical (viz., RCHx-CR′HO• → RCHx• + CR′HO). We discuss this reaction in Section 1.4.
When no initiators such as peroxides are initially added to a hydrocarbon mixture, an induction period is observed before oxygen consumption takes place. There are several hypotheses on what might happen during this induction–initiation stage: (i) the direct reaction of triplet oxygen with singlet closed-shell molecules (a thermodynamically disfavored reaction), (ii) the R−H homolysis (a reaction that is very slow due to typical C−H bond dissociation energies of 80–110 kcal/mol), and (iii) the termolecular reaction RH + O2 + RH → R• + H2O2 + R• (unlikely to be of any kinetic significance). A more reasonable explanation for the induction–initiation is the presence of (sub)parts per billion levels of compounds that are more easily cleaved. After the induction period, the rate increases very rapidly. Because of this accelerating effect, one refers to this type of reactions as being autocatalytic. However, until recently, the precise reason for this autocatalytic upswing was not very well understood and is discussed in more detail later.
The RO−OH cleavage can also be catalyzed by transition metal ions that are able to undergo one-electron redox switches such as cobalt and manganese, among others. The catalysis of autoxidations is discussed in more detail in chapters dealing with specific industrial processes.
Chain-propagation reactions neither increase nor decrease the radical population. Two elementary propagation reactions can be distinguished: H-abstractions (reactions (1.2) and (1.4)) and O2 addition to a carbon-centered radical (reaction (1.3)). The latter reaction is normally diffusion controlled and hence rarely rate determining. As alkoxyl radicals are significantly more reactive than peroxyl radicals, ROO• are the predominant radical species in the reaction medium and are thus the main participants in the bimolecular propagation reactions. Although the normal rule is that the weakest C−H bond is preferably attacked, the nature of the H-abstracting species also determines the selectivity. Indeed, the more reactive the H-abstracting radical, the lower the selectivity for the weakest C−H bond, as illustrated by the rate data in Table 1.2. Table 1.2 also shows the significant reactivity differences between hydroxyl, alkoxyl, and peroxyl radicals, explaining why only ROO• radicals can be really termed as chain-propagating radicals.
Table 1.2 Rate constants (M−1 s−1) for hydrogen abstraction from primary, secondary, and tertiary C−H bonds by various radical species at 400 K (per H-atom) [6–8]
Attacking radical
Primary C−H
Secondary C−H
Tertiary C−H
•
OH
8.1 × 10
7
(1.0)
3.7 × 10
8
(4.6)
1.1 × 10
9
(13.3)
CH
3
O
•
2.1 × 10
4
(1.0)
2.3 × 10
5
(10.8)
6.0 × 10
5
(28.4)
CH
3
OO
•
2.6 × 10
−2
(1.0)
4.8 × 10
−1
(18.5)
2.7 × 10
1
(1053)
Termination reactions such as (1.5) decrease the number of radicals and produce nonradical products such as alcohols and ketones. Mutual termination reactions of primary and secondary peroxyl radicals have near-zero activation energies but unusually low Arrhenius prefactors, suggesting a strained transition state. The exothermicity of this termination is sufficient to produce electronically excited states of either the carbonyl compound or oxygen. Besides the termination reaction (1.5), peroxyl radicals can also undergo a self-reaction without termination (2ROO• → 2RO• + O2) that is often ignored but is equally important as the termination channel itself [9, 10].
Tertiary alkylperoxyl radicals are generally assumed to combine with tetroxides (ROOOOR) that subsequently decompose to di-tert-alkyl peroxides or tert-alkoxyl radicals. The decomposition of the tertiary tetroxide has a fairly high activation energy, making the termination of tertiary peroxyl radicals slower than that of primary and secondary analogs [5].
The chain termination compensates the chain initiation and leads to a quasi-steady state in peroxyl radicals. Indeed, the characteristic lifetime of ROO• radicals is given by τ = 1/{[ROO•] × 2k5}, with k5 being the rate constant of the termination reaction (1.5). As an example, at 0.1% cyclohexane conversion, the [CyOO•] concentration can be estimated at 5 × 10−8 M (derived from the product formation rate = k4 [CyH] [CyOO•]), leading to a τ as low as ≈2.5 s, given 2kterm = 8.4 × 106 M−1 s−1. We emphasize that τ is much smaller than the timescale of ≈2000 s over which the CyOO• concentration changes significantly, such that [CyOO•] quasi-steady state will indeed be established and maintained throughout the oxidation process. This implies that the rate of chain initiation equals the rate of chain termination, or k1 [CyOOH] = k5[CyOO•]2.
The radical chain mechanism outlined here avoids the ineffective direct reaction of molecular oxygen with the substrate hydrocarbon. The fast propagation reactions produce ROOH that in turn can initiate new radical chains. As the primary product of the reaction initiates new reactions, one ends up with an autocatalytic acceleration. The propagating peroxyl radicals can also mutually terminate and yield one molecule of alcohol and ketone in a one-to-one stoichiometry. The ratio between the rate of propagation and the rate of termination is referred to as the chain length and is of the order of 50–1000. As the desired chain products are more susceptible to oxidation, autoxidations are normally carried out at low conversions in order to keep the selectivity to an economically acceptable level.
In the following sections, we discuss the various reaction sequences in more detail, starting with the chain initiation.
1.2 Chain Initiation
According to reaction (1.1), the ROOH molecule yields radicals upon the unimolecular scission of the 40 kcal/mol O−O bond. However, this reaction is not only slow due to the high barrier but also very inefficient to generate free radicals. Indeed, once the O−O bond has been elongated, the nascent radicals need to diffuse away from each other (i.e., out of their solvent cage in case of liquid phase reactions) before they are really free radicals. This diffusion process faces a significantly higher barrier than the in-cage radical recombination to reform the ROOH molecule. Therefore, only a small fraction of the ROOH molecules that manage to dissociate will effectively lead to free radicals. Moreover, during cyclohexane oxidation, it was observed that the addition of a small amount of cyclohexanone not only eliminates the induction period but also enhances the oxidation rate at a given conversion (i.e., at a certain O2 consumption), as shown in Figure 1.1. This observation clearly indicates that cyclohexanone plays an important role in the chain initiation, hitherto missing in the simple unimolecular mechanisms.
Figure 1.1 Oxygen consumption during the autoxidation of cyclohexane at 418 K with and without the addition of cyclohexanone. The red slopes signify the oxidation rate at various stages of the reaction. The initial pressure increase is due to heating, initiated at time 0.
Based on quantum chemical calculations, a bimolecular chain initiation mechanism was proposed between the ROOH primary product and cyclohexanone [11–13]. In this reaction, the nascent hydroxyl radical, breaking away from the hydroperoxide molecule, abstracts the weakly bonded αH-atom from cyclohexanone, forming water and a resonance-stabilized ketonyl radical (Figure 1.2). This reaction features a significantly lower activation barrier (i.e., 28 kcal/mol) and prevents facile in-cage radical recombination. The theoretically predicted rate constant of this reaction (i.e., 0.6 × 10−4 M−1 s−1 at 418 K) quantitatively agrees with the experimentally determined rate constant (1 × 10−4 M−1 s−1), corroborating this thermal initiation mechanism and explaining the autocatalytic effect of cyclohexanone [11].
Figure 1.2 Comparison of the unimolecular RO−OH dissociation process and the bimolecular initiation between ROOH and cyclohexanone [11].
