Untitled - Technische Universiteit Eindhoven

More documents

Recommendations

Info

2.3. Experimental section 17M TCPMG spin echo train90° 180°exp(-t/T2)spinechorepeated1000 xtmulti-exponential fit(only for calibration samples)exponent12...T 2 [s]0.0701.54...amplitude0.570.31...orspin echo intensity10 410 310 2combined NMRresponse of allH-nuclei in liquidsIntensity [a.u.]CONTINinversion0 1 2 3 4 5 6 7 8time [s]0.01 0.1 1 10T 2 [s]repetition of sequence every 15 minutesyielding time-dependent T 2spectra(not for calibration samples)0.200.15T 2 of the fast (dominant)component in the spectra(extracted using a Gaussian fit)t=3 hT 2 [s]0.10t=2 h0.05t=1 h0.000 2 4 6 8 10 12 14 16time [h]Fig. 2.2: Overview of the CPMG spin-echo train acquisition and data processing.
18 2. Coupled mass transfer and sol-gel reaction in a two-phase bulk systemCPMG measurements and the constant read-out duration result in a varying resolutionof the 1D profiles. Nevertheless, the liquid phases are easily reconstructed and identifiedfrom the profiles. The magnetic susceptibility of water and n-hexadecane is −9.0×10 −6 ,respectively, −8.0×10 −6 [67]. At 4.7 Tesla the resulting frequency mismatch is about 200Hz. With respect to the applied read-out gradient of at least 2.6 kHz mm −1 , susceptibilityartifacts at the interface between n-hexadecane and water are insignificant. The acquisitiontime for each sequence is between 2 and 3 minutes, so that the loop time is about15 minutes (given one Saturation Recovery, one 2D TSE and three CPMG measurementsper loop).In order to measure the gel time of the aqueous phase similar experiments were performedinside glass vials with equal dimensions as the Teflon vials. The vials were placedin a water bath at specific temperatures. By gently tilting the vials at times near the predictedgel time with intervals of 5 minutes, the gel time could be determined by checkingwhether the oil-water interface is still able to follow the tilting motion. The reproducibilitywas checked by using multiple glass vials, and the accuracy of the gel time is about30 minutes.2.4 Results and discussion2.4.1 Calibration resultsViscosity measurementsThe viscosities of TMOS, n-hexadecane and the mixtures were measured in order to checkwhether the relaxation times can be correlated with viscosity and temperature. Figure2.3 shows ln η mix at 25 ◦ C as a function of the mole fraction x (where x = 0 representspure oil, and x = 1 represents pure TMOS). The viscosity for x = 0 is 3.01 ± 0.01 mPas, and it decreases monotonically with x to 0.63 ± 0.01 mPa s when x = 1. The figureshows that ln η mix follows a straight line with increasing mole fraction. The values werefitted with the mixture law (Eq. 2.18) yielding an excellent fit with G = 0.T 1 relaxation in TMOS/n-hexadecane mixturesThe calibrations are used to determine the concentration, φ, of TMOS in n-hexadecanein the two-phase bulk experiments. The Saturation Recovery data of the TMOS/nhexadecanemixtures were evaluated by fitting mono-exponential and bi-exponential decaycurves as given by Eqs. 2.3 and 2.16, respectively. For each concentration and temperaturethe decay appeared to be virtually mono-exponential and a robust bi-exponential fit couldnot be obtained. The individual T 1 -s for TMOS and n-hexadecane in the mixtures areobviously relatively close. Noise present in the spin-echo data results in significant errorsin the fit parameters when applying a multi-exponential fit, even at high signal-to-noiseratios.The Saturation Recovery data of the pure liquids were fitted straightforwardly with asingle exponent. As for the mixtures, a slight deviation from mono-exponential behavior
Page 2: TWO-PHASE REACTIVE TRANSPORTOF AN O
Page 5 and 6: Dit proefschrift is goedgekeurd doo
Page 7 and 8: 4. The effect of pH on mass transfe
Page 9 and 10: Samenvatting . . . . . . . . . . .
Page 11 and 12: 2 1. Introductionproducerbarrierlow
Page 13 and 14: 4 1. IntroductionTwo inter-European
Page 16: Part ITwo-phase bulk systems7
Page 19 and 20: 10 2. Coupled mass transfer and sol
Page 25: 16 2. Coupled mass transfer and sol
Page 41 and 42: 32 3. Interfacial effects during re
Page 53 and 54: 0+,44 4. The effect of pH on mass t
Page 55 and 56: 46 4. The effect of pH on mass tran
Page 67 and 68: 58 5. Cross-linking of silica with
Page 71 and 72: 0+,62 5. Cross-linking of silica wi
Page 77 and 78:
68 5. Cross-linking of silica with
Page 79 and 80:
Page 81 and 82:
Page 84:
Part IIGel placement in porous mate
Page 87 and 88:
78 6. Coupled mass transfer and gel
Page 89 and 90:
Page 91 and 92:
Page 93 and 94:
Page 95 and 96:
Page 97 and 98:
Page 99 and 100:
Page 101 and 102:
Page 103 and 104:
Page 105 and 106:
Page 107 and 108:
98 7. Permeability reduction in por
Page 109 and 110:
100 7. Permeability reduction in po
Page 111 and 112:
Page 113 and 114:
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Page 121 and 122:
Page 123 and 124:
114 8. Model of reactive transport
Page 125 and 126:
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Page 133 and 134:
Page 135 and 136:
Page 137 and 138:
Page 139 and 140:
Page 141 and 142:
132 9. Concluding remarks and outlo
Page 143 and 144:
Page 145 and 146:
Page 147 and 148:
Page 149 and 150:
140
Page 151 and 152:
-142 Appendix A, - C D *, - D
Page 153 and 154:
144 Appendix Awhere S 0 is a consta
Page 155 and 156:
146 Appendix AThe 0.95 Tesla scanne
Page 157 and 158:
148 Appendix B
Page 159 and 160:
150 Appendix CwhereΩ A (θ) = −2
Page 161 and 162:
152 Appendix C
Page 163 and 164:
154 Appendix D
Page 165 and 166:
156 Appendix Eand equal to zero in
Page 167 and 168:
158 Appendix EAs the saturations, d
Page 169 and 170:
160 Bibliography[12] B. Vinot, R. S
Page 171 and 172:
162 Bibliography[40] M. D. Mantle a
Page 173 and 174:
164 Bibliography[70] F. J. M. van d
Page 175 and 176:
166 Bibliography[97] K. Yoshida, A.
Page 177 and 178:
168 Bibliography[127] G. W. Scherer
Page 179 and 180:
170 Bibliography
Page 181 and 182:
172 Summaryand gelation rates. The
Page 183 and 184:
174 Samenvattingwaterfase. De T 1 v
Page 185 and 186:
176 List of publications
Page 187 and 188:
178 Dankwoordimmer opgewekte stemmi
Page 189:
Prior to the speech, Harald Cramér
show all

Untitled - Technische Universiteit Eindhoven

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

Delete template?

Save as template?