Heterogeneously Catalyzed Oxidation Reactions Using ... - CHEC

More documents

Recommendations

Info

CHAPTER 5 (Heidolph MR 2002). Heating of the cell was accomplished by means of an oil‐containing heating jacket controlled by a thermo‐/cryostat (Julabo F25 HD). A sapphire window covering the whole diameter of the cell (26 mm) allowed optical identification of phases. A cold light source applied from the front illuminated the cell. Construction details and the flowchart of the cell can be found in ref. [25]. In this project phase identification was performed without the previously described CCD camera by direct optical identification giving more accurate results when the light source is used in the viewing direction. 5.2.1.2 Continuous reactor for catalytic reactions in pressurized CO2 The setup was based on the design of previous studies [6, 16] with some modifications (Figure 5‐1). Connecting tubes and valves were obtained from Swagelok. CO2 pressurized with a compressor (NWA Loerrach, Germany) to ca. 200‐250 bar was down‐regulated to the desired system pressure by an interconnected reducing valve (TESCOM, stainless steel, P/N 44‐1165‐24). Accordingly, an O2 compressor (NWA Loerrach) supplied O2 via a reducing valve (TESCOM, brass, P/N44‐1115‐24) to a six‐port‐dosing valve (NWA Loerrach). The six‐port‐dosing valve consisted of two coils (Vcoil = 61∙10 ‐6 L) which were alternating filled with oxygen and unloaded to the system. A switching time could be set between 0.1 s ‐ 9.9 s allowing different O2 dosing rates. The pressure difference between the oxygen feed and the system was measured by two pressure gauges (both Yokogawa DPharp transmitter EJX530A, readout VEGAMET 381; accuracy ± 0.5 bar). Risk of back‐flowing of organic compounds into an oxygen‐rich atmosphere was minimized by a check valve. The liquid alcohol was fed to the system by a GILSON 305 HPLC pump. A view cell autoclave (NWA Loerrach) equipped with heating (controlled by a Eurotherm 2216e temperature controller) and stirrer was interconnected in order to monitor the phase behavior of the feed at conditions close to the reactor. The view cell could be set on bypass in order to avoid long equilibration times, which was usually done. The reactor consisted of a 30 cm long 8 mm (e.d.) Swagelok tube equipped with external heating (controlled by a Eurotherm 2216e temperature controller). The reactor was filled with 1.25 g catalyst particles corresponding to a bed length of ca. 15 cm (0.5 % Pd/Al2O3 [shell impregnated], sieve fraction 250 µm ‐ 425 µm, Engelhard 4586, BET surface area 106 m 2 g ‐1 , pore volume 24.3 cm 3 g ‐1 , average pore diameter by BET 9.6 nm, metal dispersion 0.29; data taken from [7]). Note that the Pd‐ containing impregnated shell of the catalyst appeared more brittle, so that the crushing and sieving procedure caused an uncertainty with respect to the actual Pd amount in the catalyst bed. Therefore, the use of TOFs in this study will be avoided. Top and bottom of the reactor were filled with inert particles (e.g. Al2O3) of the same size fraction. Two reduction valves after the reactor allowed stepwise decreasing of the system pressure. The first reduction valve was heatable (controlled by a 128
5.2 Experimental Eurotherm 2216e temperature controller) in order to avoid freezing due to the Joule‐Thomson effect. The effluent gas flow was cooled in a coil immersed in an NaCl/ice bath after which sampling was possible. The gas/liquid separator consisted of a stainless steel reactor (NWA Loerrach, 300 bar pressure rating). A downstream needle valve allowed fine tuning of the overall system gas flow which was measured with a flowmeter calibrated on a daily basis. 5.2.2 Experimental procedures 5.2.2.1 Experimental determination of the phase behavior Leak checks of the view cell were performed weekly. Prior to experiments the cell was thoroughly cleaned with acetone and CO2 and dried in a N2 stream. For experiments the cell was charged with the desired amounts of benzyl alcohol (Aldrich, 99 %+, freshly distilled, stored under argon atmosphere), benzaldehyde (Fluka, 99.5 %+, redistilled, stored under argon atmosphere) and/or water (Fluka, >2 µS/cm) at 288 K. The sealed cell was carefully flushed several times with either O2 or N2 (both PanGas, 5.0) or CO2 (PanGas, 3.0) to remove air and filled with the appropriate amount of O2 or N2 (calculated using data from NIST [26]). CO2 was added by means of a CO2 compressor (NWA Loerrach, Germany) and quantified with a mass flow transmitter (Rheonik Messgeräte GmbH, Germany) at a constant pressure of 100 bar provided by an interconnected reducing valve. The cell was heated to the desired temperature and a pressure significantly higher than the dew point applied by adjusting the cell volume. Under these conditions the cell was equilibrated for an appropriate amount of time (min. 2 h ‐ overnight). After a first rough investigation of the respective system, dew points were determined by changing the pressure in intervals of 0.5 ‐ 2 bar, equilibration (15 min ‐ 2 h) and visual inspection. Accordingly, a pressure interval between a high and a low pressure limit in between which phase separation occurred was noted. Usually, dew points were determined by following the dissolution of droplets. Prior to formation of drops by decreasing the pressure the feed lines were heated by means of a heat gun. The dew point pressures were usually measured three times for each composition and temperature from which a standard deviation was obtained. The uncertainty of the high and low pressure limit around the dew point was then determined by twice the standard deviation plus the uncertainty due to the pressure sensor (± 0.5 bar). The dew point was calculated as the center of the thus obtained pressure interval in which phase separation occurred and the maximum error was considered in order to describe the interval boundaries. Further experimental uncertainties are estimated to be ± 0.02 mol‐% for the molar fraction of each component and ± 0.5 K for the temperature. Batch experiments were conducted in the same cell by adding 0.5 % Pd/Al2O3. 129
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 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 35 and 36:
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
Page 43 and 44:
Page 45 and 46:
Ph O O Ph (4) (5) 2.3 Selective liq
Page 47 and 48:
Page 49 and 50:
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 57 and 58:
Page 59 and 60:
Table 2-6: Ring hydroxylation of ar
Page 61 and 62:
Page 63 and 64:
Table 2-7: Aerobic oxidation of ami
Page 65 and 66:
Table 2-8: Oxidation of hydroquinon
Page 67 and 68:
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 75 and 76:
Page 77 and 78:
Page 79 and 80:
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 and 120: 4.2 Experimental alcohol (Aldrich,
Page 121 and 122: 4.3 Results Scheme 4‐1: Oxidation
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: 5.2 Experimental The most important
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
Page 171 and 172: 6.3 Results out in 1 mm quartz tube
Page 173 and 174: 6.3 Results Figure 6‐2: Structure
Page 175 and 176: 6.3 Results Figure 6‐4: Epoxidati
Page 177 and 178: 6.3 Results Figure 6‐6: Compariso
Page 179 and 180: 6.3 Results Figure 6‐8: Influence
Page 181 and 182: 6.3 Results investigated the epoxid
Page 183 and 184: 6.3 Results Figure 6‐10: Co‐epo
Page 185 and 186: 6.3 Results Figure 6‐11: EXAFS an
Page 187 and 188: 6.4 Discussion would need to be for
Page 189 and 190: 6.5 Conclusions Formation of the ep
Page 191 and 192: 6.6 References [28] J. Perles, N. S
Page 193 and 194:
Chapter 7 Concluding Remarks 7.1 Co
Page 195 and 196:
7.2 Final remarks and outlook speci
Page 197 and 198:
Acknowledgements Acknowledgements T
Page 199:
Curriculum Vitae Matthias Josef Bei
show all

Heterogeneously Catalyzed Oxidation Reactions Using ... - CHEC

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?