Heterogeneously Catalyzed Oxidation Reactions Using ... - CHEC

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Chapter 2 All That Glitters is not Gold – Selective Liquid- Phase <strong>Oxidation</strong> Catalysis with Heterogeneous Copper and Silver Catalysts in Comparison to Gold Abstract 8 Gold as an active material for oxidation catalysis has received a great deal of attention in the recent years. This overview will focus on silver and copper, covering all coinage metals. Both metals also have shown a considerable potential as heterogeneous catalysts for different selective oxidation reactions in the liquid phase. For many oxidation reactions, the efforts which were put in gold‐related research have brought forward gold catalysts with high Coinage metal catalysts. catalytic performance. Cu and Ag can profit from the extensive knowledge on Au catalysts due to similarities between the coinage metals. As an example, alcohol oxidation which was first studied over gold catalysts can also be efficiently catalyzed by silver. Synthesis techniques from gold catalysts can be adapted for copper and silver but their complex chemistry requires specialized routes for catalyst synthesis. Thus, common synthesis techniques will be summarized highlighting important design principles. Available literature on oxidation reactions catalyzed by silver and copper and – if not already described by other recent reviews – gold will be summarized. The strengths and opportunities of the three metals will be discussed and compared stressing out the chances of Cu and Ag thereby showing that the two metals are not necessarily competitors of gold but often complementary. Opportunities for further research will be outlined.
2.1 Introduction 2.1 Introduction Ever since Haruta et al. [1‐3] disproved the prejudice of gold being a beautiful but essentially inert metal in catalysis, a huge run on gold started – first with the in‐depth investigation of the Au catalyzed gas phase CO oxidation proceeding already at room temperature or even below. The use of gold as a potent heterogeneous oxidation catalyst was extended to selective liquid phase oxidations resulting in an immense amount of literature [4‐10]. But the origin of the fascination of gold is also its strongest burden: its low availability and high price (apart from the color and the gold‐digger myths). Despite the tremendous knowledge on gold catalyzed reactions, there are only few examples where gold is industrially competitive [11]. On the other hand, the smaller siblings of gold – silver and copper – have long been applied for important catalytic processes in industry, silver being used in methanol oxidation as well as ethylene epoxidation and copper e.g. for methanol synthesis. However in academics, both silver and copper received far less attention and thus have not made it to step out of the shadow of gold especially in selective liquid‐phase oxidations. Considering that silver is roughly 2 orders and copper even 4 orders of magnitude less expensive than gold makes industrial applications much more likely. Establishing new processes on the background of the discussion on “Green Chemistry” is certainly important and the price of a catalyst is a crucial factor in making a process sustainable. With respect to CO oxidation, both silver [12‐15] and copper [16‐19] have proven their ability to catch up with gold. Applications of heterogeneous copper and silver catalysts in the total oxidation of harmful organic compounds in wastewater effluents [20‐23] underline their potential in liquid phase oxidations. Recently, the potential of the coinage metals mainly in gas phase reactions was summarized in two reviews [4, 10]. This chapter will concentrate on liquid‐phase oxidations and compare heterogeneous silver and copper catalysis with the broad field of gold catalysis. The intention is to show the niches and individual strengths of silver and copper but also supplying a short overview over important features of liquid‐phase gold catalysis. Opportunities for future research will be described, benefitting from the broad knowledge on gold catalysis. Focus has been laid on selective oxidations by intrinsically heterogeneous catalysts. Thus, total oxidations and immobilized complexes being an extensive topic especially for Cu catalysis will only be covered where it supports the argumentation. After providing a short summary of synthesis techniques towards the different catalysts the most important selective oxidation reactions will be described where one or more of the coinage metals play a significant role as a catalyst material. A discussion with respect to important parameters for catalyst synthesis, differences between the catalytic properties and performance of the metals and finally opportunities for future work will complete this chapter. 9
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: 1. Introduction [28] S. Bawaked, N.
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
Page 69 and 70: Table 2-9: Oxidation of silanes wit
Page 71 and 72: 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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