Heterogeneously Catalyzed Oxidation Reactions Using ... - CHEC

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CHAPTER 4 nebulizer. The plasma Ar flow was set to 13 L/min at 800 W RF power and the nebulizer Ar flow was set to 0.80 L/min. The sample solution was injected at a flow rate of 3.0 mL/min. Quantification of Ce and Ag was performed by using multielement ICP‐MS standard solutions (Fluka). Samples for ICP‐MS were prepared via filtering of a hot solution obtained after 3 h reaction time through preheated celite. An aliquot of 1.0 mL of the filtrate was taken. Volatile compounds were removed at 120 °C in vacuo overnight. The residual was treated with 3.5 mL concentrated HNO3 (Merck, p.a.), 0.5 mL HCl (Merck, p.a.) followed by 2 mL double distilled water and digestion in an Anton Paar Microwave Digestion System Multiwave 3000. The solution was neutralized with ammonium hydroxide solution (Sigma‐Aldrich, 28‐30 %), filtered, and diluted with distilled water. The overall dilution ratio was 1:500. Gas adsorption: The specific surface area (SSA) of the catalyst particles were determined by N2 adsorption at 77K using the BET method (Micromeritics Tristar 3000, 5‐point isotherm, 0.05 < p/p0 < 0.25). Transmission electron microscopy (TEM): TEM images were acquired on an FEI Tecnai T20 microscope equipped with a W‐filament as electron source operated at 200kV. High resolution (HR)‐ TEM images were taken on an FEI Titan 80‐300 microscope operated at 300kV. Catalyst samples were dispersed in dry form on lacey carbon film supported on Cu grids. Sample agglomerates overlapping the holes in the support film were imaged using a Gatan US1000 CCD camera. Crystal lattice spacings and particle sizes were analyzed using the Digital Micrograph version GMS 1.8 software package from Gatan Inc. 4.3 Results 4.3.1 Catalytic side chain oxidation of p-xylene by impregnated Ag/SiO2 The oxidation of p‐xylene with an impregnated silica supported Ag catalyst ( imp 10%Ag/SiO2‐900) in the absence of any solvent resulted in the formation of p‐methylbenzyl alcohol, p‐ methylbenzaldehyde and p‐toluic acid at about 3 % yield at 140 °C after 3 h (Scheme 4‐1 and Figure 4‐1) which corresponds to a TON of 43 based on the overall amount of silver. Note, that at this point TONs only serve as a performance comparison being microscopically seen not relevant as the reaction is presumably based on a radical autoxidation mechanism. The addition of CeO2 nanoparticles and a carboxylic acid more than doubled the overall catalytic performance resulting in a combined yield of 7 % after 3 h (TON 100). 106
4.3 Results Scheme 4‐1: <strong>Oxidation</strong> of p‐xylene with molecular oxygen catalyzed by Ag/SiO2 in the presence of ceria and a carboxylic acid. Table 4‐2: <strong>Oxidation</strong> of p‐xylene with silver catalysts in the presence of CeO2 and carboxylic acid. Reaction conditions: 122 mmol p‐xylene, 3 mol‐% p‐toluic acid, 100 mg biphenyl, 100 mg catalyst, oxygen atmosphere, 140 °C, 3 h reaction time. Yields (%) Catalyst 107 Combined TON a Entry imp 10%Ag/SiO2‐900 b 2.1 2.1 2.8 7.0 100 1 imp 10%Ag/SiO2‐ 900 b,c 2.0 2.0 2.8 6.8 100 2 FSP 1%Ag/SiO2 b 0.4 0.6 0.2 1.2 160 3 FSP 1%Ag/10%CeO2‐ SiO2 FSP 1%Ag/10%CeO2‐ SiO2 d FSP 1%Ag/30%CeO2‐ SiO2 FSP 1%Ag/50%CeO2‐ SiO2 SiO2 b O 2 Ag/SiO 2; CeO 2; Carboxylic acid OH O HO O O OH 3.0 2.6 7.8 13.4 1800 4 2.3 2.1 3.3 7.7 1000 5 2.8 2.5 5.2 10.5 1400 6 2.4 2.2 3.8 8.4 1100 7 0.2 0.3 0.3 0.8 ‐ 8 a Based on the number of product molecules with respect to the total amount of silver during one experiment. b 50 mg CeO2 added. c 3 mol‐% benzoic acid used instead of p‐toluic acid. d 1 st re‐use. No difference between benzoic acid and p‐toluic acid could be found with respect to the catalytic performance (Table 4‐2, entry 1 and 2). As underlined by reaction Scheme 4‐1, the second methyl group remained untouched due to the deactivating effect of the electron withdrawing substituent. Some p‐xylene hydroperoxide as an intermediate reaction product was also observed (less than 0.5 %) but no pertoluic acid. Note that the reaction also proceeded in the absence of light in contrast to + O OH +
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TECHNICAL UNIVERSITY OF DENMARK (DT
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Preface The present dissertation su
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the carboxylic acid, ceria inhibite
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Resume Denne afhandling giver indle
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hvorimod mængden af katalysator ku
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2.3.8 Oxidation of sulfides .......
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5.3.5 Macroscopic mass transport in
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Chapter 1 Introduction With its gre
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1. Introduction Scheme 1‐1: High
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1. Introduction Figure 1‐2: Phase
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1. Introduction [28] S. Bawaked, N.
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2.1 Introduction 2.1 Introduction E
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2.2.1 Synthesis of gold catalysts 2
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2.2 Catalyst synthesis for oxidatio
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2.2 Catalyst synthesis for oxidatio
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2.3 Selective liquid‐phase oxidat
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Table 2-1: Overview over alcohol ox
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Ph O O Ph (4) (5) 2.3 Selective liq
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Table 2-4: Side-chain oxidation of
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2.3.4 Oxidation of cyclohexane 2.3
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Table 2-5: Oxidatin of cyclohexane.
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Table 2-6: Ring hydroxylation of ar
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Table 2-7: Aerobic oxidation of ami
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Table 2-8: Oxidation of hydroquinon
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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
Page 83 and 84: 2.6 References [56] H. Tumma, N. Na
Page 85 and 86: 2.6 References [113] C. Keresszegi,
Page 87 and 88: 2.6 References [169] Q. Zhu, Y. Lia
Page 89 and 90: 2.6 References [223] M. Fetizon, M.
Page 91 and 92: Chapter 3 Selective Liquid-Phase Ox
Page 93 and 94: 3.2 Experimental 3.2.1 Catalyst pre
Page 95 and 96: 3.3 Results Scattering amplitudes a
Page 97 and 98: Absorption (a.u.) 1.2 1.0 0.8 0.6 0
Page 99 and 100: Conversion (%) 100 90 80 70 60 50 4
Page 101 and 102: 3.3 Results Figure 3‐5: In situ X
Page 103 and 104: 3.3 Results Table 3‐2: Conversion
Page 105 and 106: 3.3 Results In order to gain insigh
Page 107 and 108: 3.3 Results the cost of selectivity
Page 109 and 110: 3.4 Discussion synergetic interacti
Page 111 and 112: 3.5 Conclusions to corroborate the
Page 113 and 114: 3.6 References [29] T. Mitsudome, Y
Page 115 and 116: Chapter 4 Selective Side-Chain Oxid
Page 117 and 118: 4.2 Experimental single‐step flam
Page 119: 4.2 Experimental alcohol (Aldrich,
Page 123 and 124: 4.3 Results Figure 4‐2: Formation
Page 125 and 126: 4.3 Results oxidation by either 2,6
Page 127 and 128: Absorption (a.u.) Absorption (a.u.)
Page 129 and 130: 4.3 Results atomic mixing of Ag and
Page 131 and 132: 4.3 Results Figure 4‐7: Influence
Page 133 and 134: 4.4 Discussion and mechanistic cons
Page 135 and 136: 4.5 Conclusions heterogeneous radic
Page 137 and 138: 4.6 References [29] S.I. Zabinsky,
Page 139 and 140: Chapter 5 Experimental Determinatio
Page 141 and 142: 5.2 Experimental The most important
Page 143 and 144: 5.2 Experimental Eurotherm 2216e te
Page 145 and 146: Figure 5-1: Schematic view of the e
Page 147 and 148: (Eq. 5‐5) AB i j ε AB i j β 5.2
Page 149 and 150: (a) (b) (c) (d) (e) (f) (g) (h) (i)
Page 151 and 152: 5.3 Results two association sites o
Page 153 and 154: Pressure (bar) 150 145 140 135 5.3
Page 155 and 156: 5.3 Results Figure 5‐7: Oxidation
Page 157 and 158: Weight (g) 5.3 Results Figure 5‐8
Page 159 and 160: 5.4 Discussion catalytic reactions
Page 161 and 162: 5.4 Discussion corresponding CO2‐
Page 163 and 164: 5.5 Conclusions 5.5 Conclusions The
Page 165 and 166: 5.6 References [29] I. Tsivintzelis
Page 167 and 168: 6.1 Introduction 6.1 Introduction A
Page 169 and 170: 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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