Heterogeneously Catalyzed Oxidation Reactions Using ... - CHEC

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CHAPTER 2 Figure 2‐6: Procedure for the preparation of Ag nanoparticles on multi‐walled carbon nanotubes (MWNT) with intermediate linker [83]; reprinted with permission from Elsevier © 2007 (no higher image resolution available). Ion‐exchange can also be employed and yields catalysts with ionic Ag [84, 85]. Reducing silver in ion‐exchanged materials in hydrogen atmosphere afforded catalysts with very small silver particles in selected cases [86, 87]. Supported silver particles can also be synthesized by flame‐spray pyrolysis e.g. with Ag/SiO2 (Figure 2‐7) [88, 89]. Addition of CeO2 to the SiO2 support during flame synthesis afforded smaller silver particles [91]. Silver in combination with vanadium in polyoxometallates has attracted considerable attention. This material can be flexibly synthesized so that silver is either in metallic or ionic state (Scheme 2‐1). For metallic silver, vanadium in H5PV2Mo10O40 is first reduced with Zn. Treatment with ionic silver re‐ oxidizes vanadium forming silver particles on the surface [92]. Figure 2‐7: Silver on SiO2 prepared by flame‐spray pyrolysis [90]. 16
2.3 Selective liquid‐phase oxidation reactions The analogue with oxidized silver is prepared by ion exchange either in solution by “metathesis precipitation” (2a) [93] or by calcination of a mixture of a homogeneous mixture of AgNO3 and H5PV2Mo10O40 (2b) [94]. (1) (2a) (2b) Scheme 2‐1: Synthesis strategies for Ag‐doped polyoxometallates [92‐94]. 2.3 Selective liquid-phase oxidation reactions The most intensively studied liquid phase oxidations (Scheme 2‐2) are alcohol oxidation, olefin epoxidation and alkyl aromatics oxidation. Aerobic alcohol oxidation is a prominent field of research in gold catalysis. Silver and copper offer an alternative way by catalyzing the anaerobic dehydrogenation of alcohols achieving other chemoselectivites in selected cases. Olefin epoxidation by molecular oxygen is difficult to achieve in the absence of a sacrificial reductant; there are some examples with Au, but most studies rely on the use of peroxides as oxidants where the reaction rates are considerably higher. The radical side‐chain autoxidation of alkyl aromatic compounds was mainly investigated with silver and copper but gold also showed some potential which may be further deepened in the future. Another important metal‐induced autoxidation is cyclohexane oxidation to K/A oil. Gold was mainly used in combination with oxygen. Literature sees its catalytic activity somewhere between outstanding and almost negligible. Cu catalysts often require tert.‐butyl hydroperoxide (TBHP) as oxidant. Especially for Cu, ring hydroxylation of aryl compounds was extensively studied and is also summarized here. Analogue examples with Ag and Au are rare. Au‐ catalyzed amine oxidation has emerged greatly in the recent years and may also offer opportunities for the other coinage metals. Finally, benzoquinone, sulfide and silane oxidation are fields were the amount of literature is still limited; silane oxidation is remarkable since water could be used as the oxidant. H H5PV2Mo10O40 + Zn 2O Ag ZnH3PV2Mo10O40 Agn-ZnH3PV2Mo10O40 + Na 5PV 2Mo 10O 40 + AgNO 3 Ag 5PV 2Mo 10O 40 + NaNO 3 H 5PV 2Mo 10O 40 + AgNO 3 The comparison of the performance of different catalysts is difficult, since the catalyst activity greatly depends on the chosen reaction conditions and hence, on the degree of optimization of a catalytic reaction. Following the proposition by Mallat and Baiker [7], it will be assumed that the catalysts were tested close to optimal conditions. Where the reported data allow it, turn‐over frequencies (TOFs) will be used to describe and compare the catalytic activity based on the overall 17 Ag 5PV 2Mo 10O 40
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 and 18: 1. Introduction Scheme 1‐1: High
Page 19 and 20: 1. Introduction Figure 1‐2: Phase
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: 2.2 Catalyst synthesis for oxidatio
Page 33 and 34: Table 2-1: Overview over alcohol ox
Page 35 and 36: 2.3 Selective liquid‐phase oxidat
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
Page 69 and 70: Table 2-9: Oxidation of silanes wit
Page 71 and 72: Table 2-10: Oxidation reactions cat
Page 73 and 74: 2.4 Strengths and opportunities of
Page 81 and 82:
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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