Heterogeneously Catalyzed Oxidation Reactions Using ... - CHEC

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CHAPTER 1 oxidation is the most intensively studied reaction (especially for palladium) within liquid phase oxidations. Scheme 1‐3: <strong>Oxidation</strong> reactions over platinum group metals. The interest in gold as a catalyst material has reached out from low‐temperature CO oxidation [7, 23, 24]. From there the use of gold was broadened to liquid phase transformations of course including the selective oxidation of alcohols [25, 26] but gold has also shown interesting activity in epoxidation reactions activating molecular oxygen directly without the need for a sacrificial reductant like H2, hydrocarbons or aldehydes [27‐29]. While a high focus was laid on gold in liquid phase oxidation reactions, the other coinage metals – silver and copper – have received less attention. The literature review in Chapter 2 will show if this is justified highlighting the strengths and opportunities of these lighter coinage metals. Chapter 3 and 4 evaluate the performance of silver catalysts for the oxidation of alcohols and alkyl aromatic compounds, respectively. By a special screening approach an interesting promoter effect of nano‐sized ceria was found which in the case of alcohol oxidation was also observed with palladium and gold catalysts. Whether ceria was a promoter or inhibitor depended on the substrate for the side‐chain oxidation of alkyl aromatic compounds. Ru/Al2O3 R NH2 R NH2 Pt-NPs HO OH O2 O O A fairly new field of research is the use of pressurized – often slightly simplified called “supercritical” 1 – CO2 (Figure 1‐2) as a solvent in combination with molecular oxygen [30, 31]. The use of CO2 can have various advantages; one certainly is the increased safety making last but not least working in the laboratory with oxygen and organic substrates at high pressures considerably more comfortable. The high solubility of oxygen can increase rates of reactions limited by oxygen mass transport though a high oxygen availability can also deactivate the catalyst due to 1 ”Supercritical“ applies strictly speaking only to pure compounds. 4 O 2 10%Pd/C O 2, DMSO O O O
1. Introduction Figure 1‐2: Phase diagram of carbon dioxide. Above the critical temperature liquefaction of CO2 is not possible [37]. overoxidation [32‐36]. Pressurized CO2 is a good solvent for non‐polar organic substrates. The solvent power of CO2 depends on the pressure and hence, all reactants can be present in a single phase (except of course the heterogeneous catalyst) or exist as a multiphasic mixture. This influences reaction rates and therefore knowledge about the phase behavior is desirable. Chapter 5 shows an approach using the Cubic plus Association Equation of State for modeling the phase behavior of ternary mixtures relevant in the oxidation of benzyl alcohol. The usefulness of phase modeling is evaluated in the oxidation of benzyl alcohol over an alumina supported palladium catalyst, a catalytic process which has shown high sensitivity to pressure changes [38, 39]. While catalysts readily catalyze the oxidation of alcohols with molecular oxygen, there are only few analogue examples in epoxidation catalysis. In rare cases, gold catalysts [27, 40] were found to activate oxygen (vide supra) but often a sacrificial reductant is necessary. Also epoxidation in N,N‐ dimethylformamide with cobalt catalysts require no additional sacrificial reductant but there is some debate to what the role of the solvent is. Chapter 6 summarizes investigations with a highly active cobalt‐based metal‐organic framework which give some new insights. In addition, benzaldehyde as a side‐product of olefin epoxidation played a special role activating the catalyst. 5
Page 1 and 2: TECHNICAL UNIVERSITY OF DENMARK (DT
Page 3 and 4: Preface The present dissertation su
Page 5 and 6: the carboxylic acid, ceria inhibite
Page 7 and 8: Resume Denne afhandling giver indle
Page 9 and 10: hvorimod mængden af katalysator ku
Page 11 and 12: 2.3.8 Oxidation of sulfides .......
Page 13 and 14: 5.3.5 Macroscopic mass transport in
Page 15 and 16: Chapter 1 Introduction With its gre
Page 17: 1. Introduction Scheme 1‐1: High
Page 21 and 22: 1. Introduction [28] S. Bawaked, N.
Page 23 and 24: 2.1 Introduction 2.1 Introduction E
Page 25 and 26: 2.2.1 Synthesis of gold catalysts 2
Page 27 and 28: 2.2 Catalyst synthesis for oxidatio
Page 29 and 30: 2.2 Catalyst synthesis for oxidatio
Page 31 and 32: 2.3 Selective liquid‐phase oxidat
Page 33 and 34: Table 2-1: Overview over alcohol ox
Page 45 and 46: Ph O O Ph (4) (5) 2.3 Selective liq
Page 51 and 52: Table 2-4: Side-chain oxidation of
Page 53 and 54: 2.3.4 Oxidation of cyclohexane 2.3
Page 55 and 56: Table 2-5: Oxidatin of cyclohexane.
Page 59 and 60: Table 2-6: Ring hydroxylation of ar
Page 63 and 64: Table 2-7: Aerobic oxidation of ami
Page 65 and 66: Table 2-8: Oxidation of hydroquinon
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Table 2-9: Oxidation of silanes wit
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Table 2-10: Oxidation reactions cat
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2.4 Strengths and opportunities of
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2.6 References 2.6 References [1] M
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2.6 References [56] H. Tumma, N. Na
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2.6 References [113] C. Keresszegi,
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2.6 References [169] Q. Zhu, Y. Lia
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2.6 References [223] M. Fetizon, M.
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Chapter 3 Selective Liquid-Phase Ox
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3.2 Experimental 3.2.1 Catalyst pre
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3.3 Results Scattering amplitudes a
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Absorption (a.u.) 1.2 1.0 0.8 0.6 0
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Conversion (%) 100 90 80 70 60 50 4
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3.3 Results Figure 3‐5: In situ X
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3.3 Results Table 3‐2: Conversion
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3.3 Results In order to gain insigh
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3.3 Results the cost of selectivity
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3.4 Discussion synergetic interacti
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3.5 Conclusions to corroborate the
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3.6 References [29] T. Mitsudome, Y
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Chapter 4 Selective Side-Chain Oxid
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4.2 Experimental single‐step flam
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4.2 Experimental alcohol (Aldrich,
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4.3 Results Scheme 4‐1: Oxidation
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4.3 Results Figure 4‐2: Formation
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4.3 Results oxidation by either 2,6
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Absorption (a.u.) Absorption (a.u.)
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4.3 Results atomic mixing of Ag and
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4.3 Results Figure 4‐7: Influence
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4.4 Discussion and mechanistic cons
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4.5 Conclusions heterogeneous radic
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4.6 References [29] S.I. Zabinsky,
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Chapter 5 Experimental Determinatio
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5.2 Experimental The most important
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5.2 Experimental Eurotherm 2216e te
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Figure 5-1: Schematic view of the e
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(Eq. 5‐5) AB i j ε AB i j β 5.2
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(a) (b) (c) (d) (e) (f) (g) (h) (i)
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5.3 Results two association sites o
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Pressure (bar) 150 145 140 135 5.3
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5.3 Results Figure 5‐7: Oxidation
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Weight (g) 5.3 Results Figure 5‐8
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5.4 Discussion catalytic reactions
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5.4 Discussion corresponding CO2‐
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5.5 Conclusions 5.5 Conclusions The
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5.6 References [29] I. Tsivintzelis
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6.1 Introduction 6.1 Introduction A
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6.2 Experimental [38]. In a typical
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6.3 Results out in 1 mm quartz tube
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6.3 Results Figure 6‐2: Structure
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6.3 Results Figure 6‐4: Epoxidati
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6.3 Results Figure 6‐6: Compariso
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6.3 Results Figure 6‐8: Influence
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6.3 Results investigated the epoxid
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6.3 Results Figure 6‐10: Co‐epo
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6.3 Results Figure 6‐11: EXAFS an
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6.4 Discussion would need to be for
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6.5 Conclusions Formation of the ep
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6.6 References [28] J. Perles, N. S
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Chapter 7 Concluding Remarks 7.1 Co
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7.2 Final remarks and outlook speci
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Acknowledgements Acknowledgements T
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Curriculum Vitae Matthias Josef Bei
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