HYDRODYNAMIC AND DISPERSION BEHAVIOUR OF AN ANALYTICAL SILICA MONOLITH RECONSTRUCTED FROM SUB-MICROTOMOGRAPHIC SCANS USING COMPUTATIONAL FLUID DYNAMICS VIVEK VASUDEVAN NATIONAL UNIVERSITY OF SINGAPORE 2013 HYDRODYNAMIC AND DISPERSION BEHAVIOUR OF AN ANALYTICAL SILICA MONOLITH RECONSTRUCTED FROM SUB-MICROTOMOGRAPHIC SCANS USING COMPUTATIONAL FLUID DYNAMICS VIVEK VASUDEVAN (M.S., West Virginia University, U.S.A. B. Chem. Eng., University Dept. of Chemical Technology, India) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF CHEMICAL AND BIOMOLECULAR ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2013 ACKNOWLEDGEMENTS I take this opportunity to express my gratitude to many individuals who have had an influence on me and my research work. Firstly, I wish to acknowledge A/P Loh Kai-Chee and thank him for giving me an opportunity to be a part of his diverse research group. He believes in giving his students complete independence of thought, which was one of the keys factors that helped me identify my strengths and weaknesses as a researcher. I also wish to thank Dr. William Krantz for his wonderful inputs on scaling analysis and guidance on simulations from CT images. Some of the most fruitful and exciting discussions that I have had regarding research has been with the diverse group of students in Prof. Loh‘s lab. I wish to thank Dr. Cao Bin, Dr. Sudhir, Mr. Bulbul, Ms. Jia-Jia, Ms. Linh, Ms. Duong, Mr. Prashant and Dr. Xiyu for making the lab a very warm and conducive place to work in. I wish to specially thank Dr. Vignesh and Dr. Satyen Gautam for being very patient sounding boards to my research ideas. I am eternally grateful to the technical staff at the NUS High Performance Computing Centre (HPCC) for being very patient with my queries. Without them, my simulations would never have run. Special thanks to Mr. Wang Junhong (Lead HPC Specialist) at NUS-HPCC for all his time and efforts towards solving my simulation queries. I must also thank the innumerable technical and managerial support personnel at Analyze, Ansys and Fluent for helping me figure out several bottlenecks in my computational efforts. I am deeply grateful to all the lab officers, namely, Mdm Chow Pek, Mdm Alyssa Tay, Mdm Novel and Mr. Wee Siong, for their administrative support. I am thankful to NUS for providing me an opportunity to pursue research on a scholarship. ii I am ever thankful to my wife, Dr. Mrs. Karthiga Nagarajan, for being a source of support and strength and believing in my abilities. I thank my in-laws for always being there for my wife and helping her provide me with constant encouragement and support. I would not have been able to purse a higher level of education if not for my parents‘ encouragement and selflessness to send me away for higher studies. I dedicate this thesis as a small repayment for all their innumerable sacrifices for securing my future. I am grateful to the Almighty and to Karthiga for the most beautiful and precious gift, my son Aaditya, who provided me with the impetus to complete my doctoral studies and look ahead in life. iii TABLE OF CONTENTS ACKNOWLEDGEMENTS II DECLARATION IV TABLE OF CONTENTS V SUMMARY IX LIST OF TABLES XI LIST OF FIGURES XII LIST OF ABBREVIATIONS AND SYMBOLS 1. XVII INTRODUCTION 1.1 BACKGROUND AND MOTIVATION 2. 3. 1.2 RESEARCH OBJECTIVES 11 1.3 THESIS ORGANISATION 12 LITERATURE SURVEY 14 2.1 MONOLITHS AND APPLICATIONS 14 2.2 MODELS FOR POROUS MEDIA 17 2.3 DIRECT IMAGING TECHNIQUES 19 2.4 TRANSPORT IN MODELS RECONSTRUCTED FROM 3D SCANS 20 2.5 EDDY DISPERSION 23 EXPERIMENTAL METHODS 25 3.1 APPARATUS, COLUMNS AND CHEMICALS 25 3.2 PRESSURE DROP MEASUREMENTS 26 3.3 INVERSE SIZE EXCLUSION CHROMATOGRAPHY 26 v 4. 5. 3.4 TOMOGRAPHIC SCAN 26 3.5 MERCURY POROSIMETRY 27 3.6 NON-POROUS DISPERSION 27 3.7 POROUS/NON-RETAINED DISPERSION 28 3.8 RETAINED DISPERSION 28 3.9 DISPERSION DATA ANALYSIS 29 COMPUTATIONAL METHODS 30 4.1 IMAGE ANALYSIS 30 4.2 DEVELOPMENT OF CFD MODEL 31 3.1.1 Hydrodynamics 31 3.1.2 Peak Parking Simulations 33 3.1.3 Dispersion Simulations 35 3.1.4 Retention conditions 38 MODEL VALIDATION FROM HYDRODYNAMICS AND NONPOROUS DISPERSION SIMULATIONS 42 5.1. INTRODUCTION 42 5.2. RESEARCH OBJECTIVES 46 5.3. RESEARCH APPROACH 47 5.4. RESULTS AND DISCUSSIONS 48 5.4.1 Inverse Size Exclusion Chromatography (ISEC) 48 5.4.2 Porosity Analysis 52 5.4.3 Pore and Skeleton Size Distributions 56 5.4.4 Hydrodynamic Simulations 60 5.4.5 Peak Parking Simulations 71 vi 5.4.6 Transient Dispersion Simulations 73 5.4.7 Estimation of Transcolumn Dispersion 77 5.4.8 Estimation of Transchannel and Short-Range interchannel eddy dispersion 84 5.5. CONCLUSIONS 6. 88 MODEL VALIDATION FROM NON-RETAINED AND RETAINED DISPERSION SIMULATIONS 92 6.1. INTRODUCTION 92 6.2. RESEARCH OBJECTIVES 92 6.3. RESEARCH APPROACH 93 6.4. MODEL SETUP 94 5.4.9 Porous Conditions 94 5.4.10 Non-retained conditions 96 5.4.11 Retained conditions 96 6.5. RESULTS AND DISCUSSIONS 5.4.12 Peak Parking Simulations 5.4.13 Transient Dispersion Simulations 5.4.14 Estimation of dispersion due to transcolumn velocity bias and external film mass transfer resistance 97 100 105 5.4.15 Estimation of short-range interchannel eddy dispersion 119 5.4.16 Phenomenological approach to estimate transcolumn dispersion 122 6.6. CONCLUSIONS 7. 97 127 EFFECT OF MACROPOROSITY ON DISPERSION BEHAVIOUR OF SILICA MONOLITHS 130 vii 7.1. INTRODUCTION 130 7.2. RESEARCH OBJECTIVES 132 7.3. RESEARCH APPROACH 132 7.4. GENERATION OF ARTIFICIAL MONOLITHIC MIMICS 133 7.5. RESULTS AND DISCUSSION 134 5.4.17 Pore and Skeleton Size Distributions 134 5.4.18 Hydrodynamic Simulations 137 5.4.19 Peak Parking Simulations 144 5.4.20 Dispersion simulations 146 5.4.21 Estimation of transchannel and short-range interchannel eddy dispersion 5.4.22 Estimation of dispersion due to transcolumn velocity bias and external film mass transfer resistance 8. 155 160 7.6. CONCLUSIONS 166 7.7. IMPROVEMENTS TO MORPHOLOGY 168 CONCLUSIONS AND RECOMMENDATIONS FOR FUTURE WORK 170 8.1 CONCLUSIONS 170 8.2 NOVELTY AND IMPACT 173 8.3 ADVANTAGES AND LIMITATIONS 175 8.4 RECOMMENDATIONS FOR FUTURE WORK 177 BIBLIOGRAPHY 179 LIST OF PUBLICATIONS AND PRESENTATIONS 192 viii SUMMARY Downstream separation of mixtures in a variety of fields such as protein purification, quality control of drugs, pharmacokinetic studies, and determination of pollutants or food additives has traditionally been carried out using particulate HPLC columns where the separation efficiency increases with decreasing particle size, at the cost of higher operating pressures. Monoliths are a class of chromatographic columns cast in the form of tubes, rods or disks as a single and co-continuous block that is porous and permeable. A high external porosity resulting from a regular network of through-macropores and a mesoporous skeleton network provide a combination of low hydraulic resistance to the mobile phase and enhanced mass transfer rates of sample molecules through the column, respectively. In this research, an analysis of the transport properties of the bulk homogeneous core of a silica monolith is presented via direct numerical simulations in a topological model reconstructed from 3D nanotomographic scans. A commercially available silica monolith (Chromolith®) was scanned at three isotropic resolutions to investigate the resolution required to adequately capture the throughpore and skeleton-surface heterogeneity. Hydrodynamic behaviour of the macropore space in domains representative of the bulk porosity was analysed via computational fluid dynamics. A 30 m cubic unit cell at 190 nm scanning resolution was found to be representative of the Darcy permeability, with a ±6% deviation from experimental and reported literature data. Transcolumn eddy dispersion, reported to be the single-most dominant contributor of inefficiency in the first generation of silica monoliths, was estimated from the deviation of axial dispersion simulations under non-porous, porous/non-retained and retained simulations from experiments using ix 3. The current set of geometries has identical domain-sizes and a fairly constant skeleton heterogeneity. CT scans of several different silica monoliths in various formats are required so that a comprehensive study on the effects of varying domain-sizes, heterogeneities and porosities can be explored. A more complete picture and a deeper understanding of the interplay between morphological features and chromatographic performance parameters can then be obtained. 178 BIBLIOGRAPHY Abell, A.B., Willis, K.L. and Lange, D.A. (1999) Mercury Intrusion Porosimetry and Image Analysis of Cement-Based Materials, Journal of Colloid and Interface Science, 211, 39-44. Abia, J. A., Mriziq, K.S. and Guiochon, G.A. (2009) Radial heterogeneity of some analytical columns used in high-performance liquid chromatography, Journal of Chromatography A, 1216, 3185-3191. Afeyan, N.B., Gordon, N.F., Mazsaroff. I., Varady. L., Fulton. S.P., Yang. Y.B. and Regnier. F.E. (1990) Flow-through particles for the high-performance liquid chromatographic separation of biomolecules: perfusion chromatography, Journal of Chromatography A, 519, 1-29. Al-Bokari, M., Cherrak, D. and Guiochon, G. (2002) Determination of the porosities of monolithic columns by inverse size exclusion chromatography, Journal of Chromatography A, 975, 275-284. Baldwin, C.A., Sederman, A.J., Mantle, M.D., Alexander, P. and Gladden, L.F. (1996) Determination and characterization of the structure of a pore space from 3D volume images, Journal of Colloid and Interface Science, 181, 7992. Billen, J., Gzil, P., Baron, G.V. and Desmet, G. (2005) A first principles explanation for the experimentally observed increase in A-term band broadening in small domain silica monoliths and other chromatographic supports, Journal of Chromatography A, 1077, 28-36. Bird, R.B., Stewart, W.E. and Lightfoot, E.N. (2002) Transport Phenomena, 2nd ed., John Wiley and Sons, New York, NY. 179 Bruns, S. and Tallarek, U. (2011) Physical reconstruction of packed beds & their morphological analysis: Core-shell packings as example, Journal of Chromatography A, 1218, 1849-1860. Bruns, S., Hara, T., Smarsly, B.M. and Tallarek, U. (2011) Morphological analysis of physically reconstructed capillary hybrid silica monoliths and correlation with separation efficiency, Journal of Chromatography A, 1218, 5187-5194. Bruns, S., Mullner, T., Kollmann, M., Schachtner, J., Holtzel, A. and Tallarek, U. (2010) Confocal laser scanning microscopy method for quantitative characterization of silica monolith morphology, Analytical Chemistry, 82, 6569-6575. Buchmeiser, M.R. (2001) New Synthetic Ways for the Preparation of HighPerformance Liquid Chromatography Supports, Journal of Chromatography A, 918, 233-266. Cabrera, K. (2004) Applications of silica-based monolithic HPLC columns, Journal of Separation Science, 27, 843-852. Capek, P., Hejtmanek, V., Brabec, L., Zikanova, A. and Kocirik, M. (2009) Stochastic reconstruction of particulate media using simulated annealing: improving pore connectivity, Transport in Porous Media, 76, 179-198. Capek, P., Hejtmanek, V., Kolafa, J. and Brabec, L. (2011) Transport properties of stochastically reconstructed porous media with improved pore connectivity, Transport in Porous Media, 88, 87-106. Chen, Q., Kinzelbach, W. and Oswald, S. (2002) Nuclear magnetic resonance imaging for studies of flow and transport in porous media, Journal of Environmental Quality, 31, 477-486. 180 Courtois, J., Szumski, M., Georgsson, F. and Irgum, K. (2007) Assessing the macroporous structure of monolithic columns by transmission electron microscopy, Analytical Chemistry, 79, 335-344. Desmet, G., Broeckhoven, K., De Smet, J., Deridder, S., Baron, G.V. and Gzil, P. (2008) Errors involved in the existing B-term expressions for the longitudinal diffusion in fully porous chromatographic media Part I: Computational data in ordered pillar arrays and effective medium theory, Journal of Chromatography A, 1118, 171-188. Detobel, F. Gzil, P. and Desmet, G. (2009) Modeling the effect of species retention on the band broadening in perfectly ordered silica monolithic column mimics with variable external porosity and intra-skeleton diffusivity, Journal of Separation Science, 32, 2707-2722. Dong, H. and Blunt, M.J. (2009) Pore-network extraction from micro-computerizedtomography images, Physical Review E, 80, 036307. Geng, A. and Loh, K-C. (2001) Contribution of axial dispersion to band spreading in perfusion chromatography, Journal of Chromatography A, 918, 37-46. Gerbaux, O., Buyens, F., Mourzenko, V.V., Memponteil, A., Vabre, A., Thovert, J.F. and Adler, P.M. (2010) Transport properties of real metallic foams, Journal of Colloid and Interface Science, 342, 155-165. Gerber, F., Krummen, M., Potgeter, H., Roth, A., Siffrin, C. and Spoendlin, C., (2004) Practical aspects of fast reversed-phase high-performance liquid chromatography using 3m particle packed columns and monolithic columns in pharmaceutical development and production working under current good manufacturing practice, Journal of Chromatography A, 1036, 127-133. 181 Giddings, J.C. Dynamics of Chromatography, Part 1: Principles and Theory, Marcel Dekker: New York, NY, 1965. Gritti, F. and Guiochon, G. (2004) Heterogeneity of the surface energy on unused C18Chromolith adsorbents in reversed-phase liquid chromatography, Journal of Chromatography A, 1028, 105-119. Gritti, F. and Guiochon, G. (2006a) General HETP equation for the study of masstransfer mechanisms in RPLC, Analytical Chemistry, 78, 5329-5347. Gritti, F. and Guiochon, G. (2006b) Effect of the surface coverage of C 18-bonded silica particles on the obstructive factor and intraparticle diffusion mechanism, Chemical Engineering Science, 61, 7636-7650. Gritti, F. and Guiochon, G. (2008) Complete Temperature Profiles in Ultra-HighPressure Liquid Chromatography Columns, Analytical Chemistry, 80, 50095020. Gritti, F. and Guiochon, G. (2009a) Mass transfer kinetic mechanism in monolithic columns and application to characterization of new research monolithic samples with different average pore sizes, Journal of Chromatography A, 1216, 4752-4767. Gritti, F. and Guiochon, G. (2009b) Optimization of the thermal environment of columns packed with very fine particles, Journal of Chromatography A, 1216, 1353-1362. Gritti, F. and Guiochon, G. (2010a) Impact of Retention on Trans-Column Velocity Biases in Packed Columns, AIChE Journal, 56, 1495-1509. Gritti, F. and Guiochon, G. (2010b) Relationship between trans-column eddy diffusion and retention in liquid chromatography: Theory and experimental evidence, Journal of Chromatography A, 1217, 6350-6365. 182 Gritti, F. and Guiochon, G. (2011) Measurement of the eddy diffusion term in chromatographic columns. I. Application to the first generation of 4.6 mm I.D. monolithic columns, Journal of Chromatography A, 1218, 5216-5227. Gritti, F. and Guiochon, G. (2012) Measurement of the eddy dispersion term in chromatographic columns: III. Application to new prototypes of 4.6 mm I.D. monolithic columns, Journal of Chromatography A, 1225, 79-90. Guiochon, G. (2007) Monolithic columns in high-performance liquid chromatography, Journal of Chromatography A, 1168, 101-168. Gzil, P., De Smet, J. and Desmet, G. (2006) A discussion of the possible ways to improve the performance of silica monoliths using a kinetic plot analysis of experimental and computational plate height data, Journal of Separation Science, 29, 1675-1685. Gzil, P., Vervoort, N., Baron, G.V. and Desmet, G. (2003) Advantages of Perfectly Ordered 2-D Porous Pillar Arrays over Packed Bed Columns for LC Separations: A Theoretical Analysis, Analytical Chemistry, 75, 6244-6250. Gzil, P., Vervoort, N., Baron, G.V. and Desmet, G. (2004) A computational study of the porosity effects in silica monolithic columns, Journal of Separation Science, 27, 887-896. Hlushkou, D., Bruns, S. and Tallarek, U. (2010a) High-performance computing of flow and transport in physically reconstructed silica monoliths, Journal of Chromatography A, 1217, 3674-3862. Hlushkou, D., Bruns, S., Holtzel, A. and Tallarek, U. (2010b) From pore scale to column scale dispersion in capillary silica monoliths, Analytical Chemistry, 82, 7150-7159. 183 Hlushkou, D., Bruns, S., Seidel-Morgenstern, A. and Tallarek, U. (2011) Morphology–transport relationships for silica monoliths: From physical reconstruction to pore-scale simulations, Journal of Separation Science, 34, 2026-2037. Ho, S.T. and Hutmacher, D.W. (2006) A comparison of micro CT with other techniques used in the characterization of scaffolds, Biomaterials, 27, 13621376. Hormann, K., Mullner, T., Bruns, S., Holtzel, A. and Tallarek, U. (2012) Morphology and separation efficiency of a new generation of analytical silica monoliths, Journal of Chromatography A, 1222, 46-58. Humby, S. J., Biggs, M.J. and Tuzun, U. (2002) Explicit numerical simulation of $uids in reconstructed porous media, Chemical Engineering Science, 57, 1955-1968. Ikegami, T. and Tanaka, N. (2004) Monolithic columns for high-efficiency HPLC separations, Current Opinion in Chemical Biology, 8, 527-533. Jeong, S.J., Kim, W.S. and Sung, S.J. (2007) Numerical investigation on the flow characteristics and aerodynamic force of the upper airway of patient with obstructive sleep apnea using computational fluid dynamics, Medical Engineering and Physics, 29, 637-651. Jinnai, H., Watashiba, H., Kajihara, T. and Takahashi, M. (2003) Connectivity and topology of a phase-separating bicontinuous structure in a polymer mixture: Direct measurements of coordination number, inter-junction distances and Euler characteristic, Journal of Chemical Physics, 119, 7554-7559. Kaviany, M. (1995) Principles of Heat Transfer in Porous Media, 1st Ed.; SpringerVerlag, New York. 184 Kele, M. and Guiochon, G. (2002) Repeatability and reproducibility of retention data and band profiles on six batches of monolithic columns, Journal of Chromatography A, 960, 19-49. Khiverich, S., Holtzel, A., Seidel-Morgenstern, A. and Tallarek, U. (2009) Time and Length Scales of Eddy Dispersion in Chromatographic Beds, Analytical Chemistry, 81, 7057-7066. Knox, J.H. (1973) Hogh Speed Liquid Chromatography, Annual Reviews of Physical Chemistry, 24, 29-49. Koku, H., Maier, R.S., Czymmek, K.J., Schure, M.R. and Lenhoff, A.M. (2011) Modeling of flow in a polymeric chromatographic monolith, Journal of Chromatography A, 1218, 3466-3475. Koku, H., Maier, R.S., Schure, M.R. and Lenhoff, A.M. (2012) Modeling of dispersion in a polymeric chromatographic monolith, Journal of Chromatography A, 1237, 55-63. Kubota, H., Tsuda, S., Murata, M., Yamamoto, T., Tanaka, Y. and Makita, T. (1979) Specific volume and viscosity of methanol-water mixtures under high pressure, The Review of Physical Chemistry of Japan, 49, 59-69. Kutsovsky, Y.E., Scrivem, L.E., Davis, H.T. and Hammer, B.E. (1996) NMR imaging of velocity profiles and velocity distributions in bead packs, Physics of Fluids, 8, 863-871. Langford, J.F., Schure, M.R., Yao, Y., Maloney, S.F. and Lenhoff, A.M. (2006) Effects of pore structure and molecular size on diffusion in chromatographic adsorbents, Journal of Chromatography A, 1126, 95-106. 185 Leinweber, F.C. and Tallarek, U. (2003) Chromatographic performance of monolithic and particulate stationary phases: Hydrodynamics and adsorption capacity, Journal of Chromatography A, 1006, 207-228. Leinweber, F.C., Lubda, D., Cabrera, K. and Tallarek, U. (2002) Characterization of Silica-Based Monoliths with Bimodal Pore Size Distribution, Analytical Chemistry, 74, 2470-2477. Loh, K-C. and Geng, A. (2003) Hydrodynamic dispersion in perfusion chromatography—a network model analysis, Chemical Engineering Science, 58, 3439-3451. Maier, R.S., Kroll, D.M., Bernard, R.S., Howington, S.E., Peters, J.F. and Davis, H.T. (2003) Hydrodynamic dispersion in confined packed beds, Physics of Fluids, 15, 3795-3815. Maier, R.S., Kroll, D.M., Kutsovsky, Y.E., Davis, H.T. and Bernard, R.S. (1998) Simulation of flow through bead packs using the lattice Boltzmann method, Physics of Fluids, 10, 60-74. Meyers, J.J. and Liapis, A.I. (1999) Network modeling of the convective flow and diffusion of molecules adsorbing in monoliths and in porous particles packed in a chromatographic column, Journal of Chromatography A, 852, 3-23. Minakuchi, H., Nakanishi, K., Soga, N. Ishizuka, N. and Tanaka, N. (1998) Effect of domain size on the performance of octadecylsilylated continuous porous silica columns in reversed-phase liquid chromatography, Journal of Chromatography A, 797, 121-131. Minakuchi, H., Nakanishi, K., Soga, N., Ishizuka, N. and Tanaka, N. (1996) Octadecylsilylated Porous Silica Rods as Separation Media for ReversedPhase Liquid Chromatography, Analytical Chemistry, 68, 3498-3501. 186 Minakuchi, H., Nakanishi, K., Soga, N., Ishizuka, N. and Tanaka, N. (1997) Effect of skeleton size on the performance of octadecylsilylated continuous porous silica columns in reversed-phase liquid chromatography, Journal of Chromatography A, 762, 135-146. Mistry, K. and Grinberg, N. (2005) Application of monolithic columns in high performance liquid chromatography, Journal of Liquid Chromatography and Related Technologies, 28, 1056-1074. Miyabe, K. (2008) Evaluation of chromatographic performance of various packing materials having different structural characteristics as stationary phase for fast high performance liquid chromatography by new moment equations, Journal of Chromatography A, 1183, 49-64. Miyabe, K. and Guiochon, G. (2002) The moment equations of chromatography for monolithic stationary phases, Journal of Physical Chemistry B, 106, 88988909. Miyabe, K. and Guiochon, G. (2004) Characterization of monolithic columns for HPLC, Journal of Separation Science, 27, 853-873. Miyabe, K., Ando, N., Nakamura, T. and Guiochon, G. (2010) External Mass Transfer in Silica Monolithic Stationary Phases, Chemical Engineering Science, 65, 5950-5960. Mriziq, K.S., Abia, J.A., Lee, Y. and Guiochon, G. (2008) Structural radial heterogeneity of a silica-based wide-bore monolithic column, Journal of Chromatography A, 1193, 97-103. Nakanishi, K. Minakuchi, H., Soga, N. and Tanaka, N. (1997) Double Pore Silica Gel Monolith Applied to Liquid Chromatography, Journal of Sol-Gel Science and Technology, 8, 547-552. 187 Nakanishi, K., Minakuchi, H., Soga, N. and Tanaka, N. (1998) Structure design of double-pore silica and its application to HPLC, Journal of Sol-Gel Science and Technology, 13, 163-169. Nowak, N., Kakade, P. and Annapragada, A.V. (2003) Computational fluid dynamics simulation of airflow and aerosol deposition in human lungs, Annals of Biomedical Engineering, 31, 374-390. Petrasch, J., Meier, F., Friess, H. and Steinfeld, A. (2008) Tomography based determination of permeability, Dupuit–Forchheimer coefficient, and interfacial heat transfer coefficient in reticulate porous ceramics, International Journal of Heat and Fluid Flow, 29, 315-326. Piller, M., Schena, G., Nolich, M., Favretto, S., Radaelli, F. and Rossi, E. (2009) Analysis of hydraulic permeability in porous media: From high resolution Xray tomography to direct numerical simulation, Transport in Porous Media, 80, 57-78 Podgornik, A., Barut, M., Jaksa, S., Jancar, J. and Strancar, A. (2002) Application of very short monolithic columns for separation of low and high molecular mass substances, Journal of Liquid Chromatography and Related Technologies, 25, 3099-3116. Poling, B.E., Prausnitz, J.M and O‘Connel, J.P. (2001) The Properties of Gases and Liquids, 5th ed., McGraw-Hill, New York, NY. Politis, M.G., Kikkinides, E.S., Kainourgiakis, M.E. and Stubos, A.K. (2008) A hybrid process-based and stochastic reconstruction method of porous media, Microporous and Mesoporous Materials, 110, 92-99. 188 Prodanovic, M., Lindquist, W.B. and Seright, R.S. (2006) Porous structure and fluid partitioning in polyethylene cores from 3D X-ray microtomographic imaging, Journal of Colloid and Interface Science, 298, 282-297. Rodrigues, A.E. (1997) Permeable Packings and Perfusion Chromatography in Protein Separation, Journal of Chromatography B, 699, 47-61. Rodrigues, A.E., Lopes, J.C., Lu, Z.P., Loureiro, J.M. and Dias, M.M. (1992) Importance of Intraparticle Convection in the Performance of Chromatographic Processes, Journal of Chromatography A, 590, 93-100. Sahimi, M. (1995) Flow and Transport in Porous Media and Fractured Rock – From Classical Methods to Modern Approaches, Wiley-VCH, Weinheim. Saito, H, Nakanishi, K., Hirao, K. and Jinnai, H. (2006) Mutual consistency between simulated and measured pressure drops in silica monoliths based on geometrical parameters obtained by three-dimensional laser scanning confocal microscope observations, Journal of Chromatography A, 1119, 95-104. Saito, H., Kanamori, K., Nakanishi, K. and Hirao, K. (2007) Real space observation of silica monoliths in the formation process, Journal of Separation Science, 30, 2881-2887. Schure, M.R., Maier, R.S., Kroll, D.M. and Davis, H.T. (2004) Simulation of ordered packed beds in chromatography, Journal of Chromatography A, 1031, 79-86. Sederman, A.J., Johns, M.L., Alexander, P. and Gladden, L.F. (1998) Structure-flow correlations in packed beds, Chemical Engineering Science, 53, 2117-2128. Sederman, A.J., Johns, M.L., Bramley, A.S., Alexander, P. and Gladden, L.F. (1997) Magnetic resonance imaging of liquid flow and pore structure within packed beds, Chemical Engineering Science, 52, 2239-2250. 189 Selomulya, C., Tran, T.M., Jia, X. and Williams, R.A. (2006) An Integrated Methodology to Evaluate Permeability from Measured Microstructures, AIChE Journal, 52, 3394-3400. Tallarek, U., Bayer, E. and Guiochon, G. (1998) Study of Dispersion in Packed Chromatographic Columns by Pulsed Field Gradient Nuclear Magnetic Resonance, Journal of American Chemical Society, 120, 1494-1505. Tallarek, U., Leinweber, F.C. and Seidel-Morgenstern, A. (2002) Fluid Dynamics in Monolithic Adsorbents: Phenomenological Approach to Equivalent Particle Dimensions, Chemical Engineering and Technology, 25, 1177-1181. Tanaka, N., Kobayashi, H., Ishizuka, N., Minakuchi, H., Nakanishi, K., Hosoya, K. and Ikegami, T. (2002) Monolithic silica columns for high-efficiency chromatographic separations, Journal of Chromatography A, 965, 35-49. Tang, X.W. Cheng, G.C. and Chen, Y.M. (2010) An easy-to-implement multi-scale computation of permeability coefficient for porous materials, Microporous Mesoporous Materials, 130, 274-279. Vervoort, N., Gzil, P., Baron, G.V. and Desmet, G. (2003) A correlation for the pressure drop in monolithic silica columns, Analytical Chemistry, 75, 843-850. Vervoort, N., Gzil, P., Baron, G.V. and Desmet, G. (2004) Model column structure for the analysis of the flow and band-broadening characteristics of silica monoliths, Journal of Chromatography A, 1030, 177-186. Vervoort, N., Saito, H., Nakanishi, K. and Desmet, G. (2005) Experimental validation of the tetrahedral skeleton model pressure drop correlation for silica monoliths and the influence of column heterogeneity, Analytical Chemistry, 77, 39863992. 190 Wilke, C.R. and Chang, P. (1955) Correlation of diffusion coefficients in dilute solutions, AIChE Journal, 1, 264-270. Zabka, M., Minceva, M. and Rodrigues, A.E. (2006) Experimental and modelling study of adsorption in preparative monolithic silica columns, Chemical Engineering and Processing, 45, 150-160. Zabka, M., Minceva, M. and Rodrigues, A.E. (2007) Experimental characterization and modelling of analytical monolithic column, Journal of Biochemical and Biophysical Methods, 70, 95-105. Zhao, X., Yao, J. and Yi, Y. (2007) A new stochastic method of reconstructing porous media, Transport in Porous Media, 69, 1-11. Zubov, A., Pechackova, L., Seda, L., Bobak, M. and Kosek, J. (2010) Transport and reaction in reconstructed porous polypropylene particles: Model validation, Chemical Engineering Science, 65, 2361-2372. 191 LIST OF PUBLICATIONS AND PRESENTATIONS 1. Vasudevan, V. and Loh, K-C. (2013) Hydrodynamic and dispersion behaviour in a non-porous silica monolith through fluid dynamic study of a computational mimic reconstructed from sub-micro-tomographic scans, Journal of Chromatography A, 1274, 65-76. 2. Vasudevan, V. and Loh, K-C. Transcolumn dispersion in a computational mimic of an analytical silica monolith reconstructed from sub-microtomographic scans using computational fluid dynamics (Submitted to Separation and Purification Technology) 3. Vasudevan, V. and Loh, K-C., Theoretical investigation on the effect of external porosity on the hydrodynamic and dispersion behaviour of constant-domain silica monoliths (Under preparation) 4. A realistic 3D model of silica monoliths for CFD simulations, Poster Presentation, Graduate Students‘ Symposium, National University of Singapore, Singapore, December 2008. 5. Development Of A Realistic 3D Model Of Silica Monoliths For CFD Simulations, Oral Presentation, AIChE Annual Meeting, Philadelphia, Pennsylvania, USA, November 2008. 6. Development Of A Realistic 3D Model Of Silica Monoliths For CFD Simulations, Oral Presentation, AIChE Annual Meeting, Salt Lake City, Utah, USA, November 2007. 192 7. Development of a realistic 3D model of silica monoliths for CFD simulations, Poster Presentation, Graduate Students‘ Symposium, National University of Singapore, Singapore, September 2007. 8. Morphological chromatographic representation performance, of silica Poster monoliths Presentation, for simulation Graduate of Students‘ Symposium, National University of Singapore, Singapore, September 2006. 193 [...]... modelling efforts to describe the hydrodynamic and dispersion behaviour of monoliths, iii) non-invasive scanning approaches utilised to capture the morphology of porous media in several applications and iv) use of CT scans and fluid dynamics to capture hydrodynamic and dispersion characteristics of silica and polymer monoliths Chapter three details the materials used and experimental protocols followed... model of a commercially available silica monolith from sub- micron x-ray computed tomography scans and study its hydrodynamic and dispersion behaviour using a commercial computational fluid dynamics program The research work comprised the following: a) Develop a computational model to capture the inherent structural morphology in silica monoliths from non-invasive 3D scans at several resolutions and compare... provide a combination of low 1 hydraulic resistance to the mobile phase, and enhanced mass transfer rates of sample molecules through the column Silica monolithic columns have found many applications in diverse fields such as high throughput analysis of drugs and metabolites, separation of environmentally relevant substances and food additives, separation of enantiomers and separation of complex biological... motivation for modelling the hydrodynamic and dispersion characteristics of monoliths in commercially available CFD software, Ansys Fluent, using geometry reconstructed from sub- micron CT scans This chapter also lists the overall and specific objectives of the research program An extensive literature review follows in chapter two that traces i) the history of the development of monoliths and their applications... after estimation of transcolumn eddy dispersion and external film mass transfer from and , respectively 107 Figure 6.8: Experimental and simulated reduced-plate heights vs reduced-linear velocity under retained conditions Dotted line indicates fit after estimation of transcolumn eddy dispersion and external film mass transfer from and , respectively 107 Figure 6.9: Experimental and simulated... work and (B) Gritti and Guiochon (2011) 114 Figure 6.12: Experimental and simulated reduced-plate heights vs reduced-linear velocity under non-retained conditions Dotted line indicates fit after estimation of transcolumn eddy dispersion and external film mass transfer ( and ) 117 Figure 6.13: Longitudinal diffusion, stationary-phase mass transfer, transchannel and short-range interchannel... identify the transcolumn dispersion contribution – a major source of inefficiency in the current generation of silica monoliths 11 d) Study the effect of external porosity on hydrodynamic and dispersion characteristics of silica monoliths 1.3 Thesis Organisation This thesis comprises of eight chapters The first chapter briefly discusses the role of monoliths in current HPLC practices and provides an insight... inhomogeneities in the macropore network of a silica monolith at lower scanning resolutions We attempt to show that if a lower resolution is able to relate the hydrodynamic and dispersion performance of the silica monolith to its pore structure, without significant loss of accuracy and at an appreciably reduced computational expense, then detailed studies on the dispersion behaviour of the macropore network under... performance than conventional particulate columns in pressure-driven liquid chromatography (Ikegami and Tanaka, 2004) They are cast in the form of tubes, rods or disks as a single and co-continuous block that is porous and permeable An important characteristic of monoliths is their high external porosity resulting from a network of through-macropores (Miyabe and Guiochon, 2004) The regular structure of. .. description of the image analysis techniques, CFD model setup, and numerical analyses and equations employed in this work The model validation via image analyses results and hydrodynamic and non-porous dispersion studies is presented in chapter five Chapter six focuses on extending the model to simulate dispersion under porous and retained conditions with special emphasis on the transcolumn and film mass transfer . HYDRODYNAMIC AND DISPERSION BEHAVIOUR OF AN ANALYTICAL SILICA MONOLITH RECONSTRUCTED FROM SUB-MICROTOMOGRAPHIC SCANS USING COMPUTATIONAL FLUID DYNAMICS VIVEK VASUDEVAN . UNIVERSITY OF SINGAPORE 2013 HYDRODYNAMIC AND DISPERSION BEHAVIOUR OF AN ANALYTICAL SILICA MONOLITH RECONSTRUCTED FROM SUB-MICROTOMOGRAPHIC SCANS USING COMPUTATIONAL FLUID DYNAMICS . Estimation of transchannel and short-range interchannel eddy dispersion 155 5.4.22 Estimation of dispersion due to transcolumn velocity bias and external film mass transfer resistance 160 7.6.