The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
Sean P. Rigby - One of the best experts on this subject based on the ideXlab platform.
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Improving the accuracy of catalyst pore size distributions from mercury Porosimetry using mercury thermoporometry
Chemical Engineering Science, 2016Co-Authors: Paul E. Dim, Rob S. Fletcher, Sean P. RigbyAbstract:Abstract Mercury Porosimetry is still frequently used to obtain the pore size distributions (PSDs) for porous heterogeneous catalyst pellets. However, unless the contact angle in the Washburn equation is correctly calibrated, Porosimetry strictly remains only a relative technique. There is a particular potential issue for catalyst samples containing heavy metals, which may present (relatively) wetting surfaces to mercury, when the standard analysis is based upon the presumption of consistent non-wetting behaviour. Data in the literature on the impact of heavy metals on mercury intrusion is conflicting with some studies suggesting they do impact intrusion and some suggesting they do not. This study uses complementary gas sorption and mercury thermoporometry experiments that were fully serially-integrated with Porosimetry to provide additional information to improve the interpretation of the basic mercury Porosimetry data and validate the pore sizes obtained from it. These complementary data have been used to show that the wetting effect from heavy metals on intrusion may be confined to the smallest nanopores in the sample where the pore wall potentials begin to overlap. It has also been shown that confined mercury shows a significant advanced melting effect during thermoporometry. The thermoporometry studies revealed that the common interpretation of sharp intrusion curves and high entrapment levels in Porosimetry data as implying ink-bottle pore geometries is flawed.
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Combining mercury thermoporometry with integrated gas sorption and mercury Porosimetry to improve accuracy of pore-size distributions for disordered solids
Journal of colloid and interface science, 2014Co-Authors: Buhari Bafarawa, Jiawei Wang, Artjom Nepryahin, Elizabeth M. Holt, Sean P. RigbyAbstract:The typical approach to analysing raw data, from common pore characterization methods such as gas sorption and mercury Porosimetry, to obtain pore size distributions for disordered porous solids generally makes several critical assumptions that impact the accuracy of the void space descriptors thereby obtained. These assumptions can lead to errors in pore size of as much as 500%. In this work, we eliminated these assumptions by employing novel experiments involving fully integrated gas sorption, mercury Porosimetry and mercury thermoporometry techniques. The entrapment of mercury following Porosimetry allowed the isolation (for study) of a particular subset of pores within a much larger interconnected network. Hence, a degree of specificity of findings to particular pores, more commonly associated with use of templated, model porous solids, can also be achieved for disordered materials. Gas sorption experiments were conducted in series, both before and after mercury Porosimetry, on the same sample, and the mercury entrapped following Porosimetry was used as the probe fluid for theromporometry. Hence, even if one technique, on its own, is indirect, requiring unsubstantiated assumptions, the fully integrated combination of techniques described here permits the validation of assumptions used in one technique by another. Using controlled-pore glasses as model materials, mercury Porosimetry scanning curves were used to establish the correct correspondence between the appropriate Gibbs–Thomson parameter, and the nature of the meniscus geometry in melting, for thermoporometry measurements on entrapped mercury. Mercury thermoporometry has been used to validate the pore sizes, for a series of sol–gel silica materials, obtained from mercury Porosimetry data using the independently-calibrated Kloubek correlations. The pore sizes obtained for sol–gel silicas from Porosimetry and thermoporometry have been shown to differ substantially from those obtained via gas sorption and NLDFT analysis. DRIFTS data for the samples studied has suggested that the cause of this discrepancy may arise from significant differences in the surface chemistries between the samples studied here and that used to calibrate the NLDFT potentials.
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MF-DFT and experimental investigations of the origins of hysteresis in mercury Porosimetry of silica materials.
Langmuir : the ACS journal of surfaces and colloids, 2010Co-Authors: Sean P. Rigby, Peter I. ChigadaAbstract:In order to be able to make a proper interpretation of mercury Porosimetry data, to obtain a structural characterization of a porous solid, a full understanding of the causes of hysteresis in mercury Porosimetry is required. Several different theories have previously been proposed, but it is still difficult to make a priori predictions of the level of hysteresis anticipated. In this work, the effect of the degree of smaller scale surface roughness on the hysteresis width has been studied using mean-field density functional simulations and the results obtained confirmed by experiments on silica materials. It has been found that the hysteresis width decreases with increased degree of surface roughness, as characterized experimentally by the surface fractal dimension.
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Integrating Gas Sorption with Mercury Porosimetry
Adsorption-journal of The International Adsorption Society, 2005Co-Authors: Sean P. Rigby, Matthew J. Watt-smith, Robin S. FletcherAbstract:Previous work has shown that it is possible to use intergrated nitrogen sorption and mercury Porosimetry experiments to determine the distribution of average pore length with pore diameter for mesoporous solids. In this work, the previous data analysis method has been generalised such that it is also suitable for application to samples with higher levels of mercury entrapment than before. This generalisation of the theory has facilitated the ability to use a series of progressively larger mercury scanning loops, in integrated gas sorption and Porosimetry experiments, to potentially determine the full pore length distribution for pores of a given diameter, and the distribution of pore co-ordination number. The new analysis has been applied to a silica catalyst support.
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Interfacing Mercury Porosimetry with Nitrogen Sorption
Particle & Particle Systems Characterization, 2004Co-Authors: Sean P. Rigby, Robin S. FletcherAbstract:Combinations of gas sorption and mercury Porosimetry experiments have been run in series on the same sample. This has been achieved by freezing entrapped mercury in place before a subsequent gas sorption experiment was carried out. Several different bidisperse materials with similarly shaped mercury intrusion curves and similar levels of mercury entrapment have been studied. The entrapment of mercury within certain pores in the porous medium can often lead to marked changes in the shape of the gas sorption hysteresis loop between the data obtained prior and subsequent to Porosimetry. It was found that the degree of the change of shape of the sorption hysteresis loops differed markedly between different materials. The analysis of the gas sorption hysteresis loops using percolation theory has allowed information to be obtained on the pore length distribution, and/or the distribution of pore co-ordination number and the spatial arrangement of pores within the sample, in addition to the pore connectivity and lattice size usually obtained. The interfaced experiments have also allowed the internal consistency of analysis methods based on percolation theory to be tested, semi-empirical alternatives to the Washburn Equation for the analysis of raw mercury Porosimetry data to be independently validated, and the mechanisms of mercury entrapment in various samples to be determined.
Jianchao Cai - One of the best experts on this subject based on the ideXlab platform.
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fractal characterization of tight oil reservoir pore structure using nuclear magnetic resonance and mercury intrusion Porosimetry
Fractals, 2018Co-Authors: Fuyong Wang, Kun Yang, Jianchao CaiAbstract:Tight oil sandstones have the characteristics of narrow pore throats, complex pore structures and strong heterogeneities. Using nuclear magnetic resonance (NMR) and mercury intrusion Porosimetry (M...
Yan Zeng - One of the best experts on this subject based on the ideXlab platform.
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petrophysical characterization of tight oil reservoirs using pressure controlled Porosimetry combined with rate controlled Porosimetry
Fuel, 2015Co-Authors: Huawei Zhao, Zhengfu Ning, Qing Wang, Rui Zhang, Tianyi Zhao, Tengfei Niu, Yan ZengAbstract:Abstract Tight oil reservoirs typically show a wide pore size distribution with pore sizes ranging from several nanometers to several hundred microns, requiring a combination of several techniques to properly characterize the pore structures. In this paper, scanning electron microscopy, pressure-controlled Porosimetry and rate-controlled Porosimetry were applied to investigate the pore systems of a tight sandstone oil reservoir in Ordos Basin, Northern China. Pores were identified and classified by scanning electron microscopy; pore size distribution was calculated by pressure-controlled Porosimetry and rate-controlled Porosimetry; main pore sizes were clarified and an empirical permeability estimation model is proposed by extending Winland’s work. Results indicate that four types of pores exist in tight sandstone oil reservoirs, which are residual interparticle pores, grain dissolution pores, clay dominated pores and micro fractures. A combination of pressure-controlled Porosimetry and rate-controlled Porosimetry is proposed as a new method to obtain the overall pore size distribution of tight oil reservoirs with pore radii ranging from 9.2 nm to 500 μm. The overall pore size distribution of tight oil reservoirs is polymodal; pores with radii ranging between 80 and 500 μm and distributed around the right peak are composed of residual interparticle pores, while the left peaks show fluctuation because of complexity in pore types and the multi-scale porosity of clays. The average mercury intrusion saturation of the nanopores is 66.50% and that of mesopores is 24.16%. The nanopores and mesopores are considered to be the main pore types. The new permeability estimation equation indicates a throat radius corresponding to 30% mercury saturation is the dominant throat radius, and shows suitable estimation of permeability with an R 2 value of 0.95542. The proposed method is effective in obtaining the overall pore size distribution of the tight oil reservoirs, and can further be used for storage capacity evaluation and better permeability estimation.
Sandra N. Riley - One of the best experts on this subject based on the ideXlab platform.
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Characterisation of porous solids using integrated nitrogen sorption and mercury Porosimetry
Chemical Engineering Science, 2003Co-Authors: Sean P. Rigby, Robin S. Fletcher, Sandra N. RileyAbstract:Abstract The two different techniques of nitrogen sorption and mercury Porosimetry, which are generally utilised completely separately, have been integrated into the same experiment to improve upon the information obtained from both methods. Nitrogen sorption isotherms have been run both before and after a mercury Porosimetry experiment on the same sample. This experiment has revealed that for a particular type of sol–gel silica catalyst support the entrapped mercury is confined to only the very largest pores in the material. Light micrograph studies have shown that the spatial distribution of entrapped mercury is highly heterogeneous. These results suggest that mercury entrapment within the material is caused by a mechanism involving macroscopic ( >0.1 mm ) heterogeneities in the pore structure. These findings conflict with the usual assumptions generally made in simulations of Porosimetry based on random pore bond network models. The new work has shown that, in conjunction with computer simulations involving the correct mercury retraction mechanism, mercury Porosimetry and nitrogen sorption can be used to study the spatial distribution of all pore sizes within a mesoporous material. A percolation analysis of the nitrogen sorption data, obtained both before and after mercury entrapment, allowed broad features of the spatial disposition of variously sized pores to be determined. The results reported here also support the use of new, semi-empirical alternatives to the Washburn Equation to analyse raw mercury Porosimetry data, rather than the traditional approach.
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Determination of the multiscale percolation properties of porous media using mercury Porosimetry
Industrial & Engineering Chemistry Research, 2002Co-Authors: Sean P. Rigby, Robin S. Fletcher, Sandra N. RileyAbstract:A new technique using mercury Porosimetry to characterize the percolation properties of porous media over several different length scales has been presented. The methodology employed a new theoretical model of a porous medium. The model may be used to represent a highly heterogeneous, porous material, with a wide pore-size distribution, over a broad range of length scales from ∼4 nm to 0.01 m. The characteristic statistical parameters which defined the model were obtained from mercury Porosimetry scanning loop and miniloop experiments. Mercury Porosimetry miniloops have been shown to give rise to so-called “miniloop spectra”. These spectra describe the variation of the value of a characteristic mercury entrapment function with pore size. The shapes of these spectra have been found to be sensitive to both the form of the pore-size probability density function and the pattern of the spatial geometric arrangement of pore sizes in the void space. Additional, complementary information on the pore structure was...
Matthias Thommes - One of the best experts on this subject based on the ideXlab platform.
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insights into the pore structure of kit 6 and sba 15 ordered mesoporous silica recent advances by combining physical adsorption with mercury Porosimetry
New Journal of Chemistry, 2016Co-Authors: Remy Guilletnicolas, R Ahmad, Katie A Cychosz, Freddy Kleitz, Matthias ThommesAbstract:We have performed a systematic study of N2 adsorption at 77 K and Hg Porosimetry experiments at 298 K on highly ordered KIT-6 and SBA-15 silicas exhibiting noticeably different pore structures with pore diameters in the 7–11 nm range. Accurate pore structure analysis was performed by applying appropriate NLDFT methods to the N2 physisorption data. Mercury intrusion/extrusion experiments on KIT-6 silicas (up to 415 000 kPa) showed no collapse of the pore structure quite remarkably. To the best of our knowledge, this is the first successful example of Hg Porosimetry on KIT-6 materials. Hence, it was possible to utilize KIT-6 mesoporous molecular sieves for quantitatively testing the validity of the Washburn equation applied to mercury intrusion for pore size analysis. KIT-6 silicas also allowed investigating the analogies between condensation/evaporation mechanisms of wetting (N2 at 77 K) and non-wetting (Hg at 298 K) fluids as a function of the pore size confirming the thermodynamic consistency between Hg intrusion/extrusion and capillary evaporation/condensation. Contrary to KIT-6 silicas, Hg Porosimetry experiments on SBA-15 materials of identical pore diameters show an inconsistent behavior in a sense that both reversible Hg intrusion/extrusion data and partial collapse of the pore structure were observed. Our work clearly demonstrates that combining advanced physical adsorption and Hg Porosimetry studies provides a more thorough understanding of textural features and shed some light on the fundamental questions concerning the effect of confinement on the phase behavior of wetting and non-wetting fluids.
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surface area and porosity
Handbook of Heterogeneous Catalysis, 2008Co-Authors: Alexander V Neimark, Kenneth S. W. Sing, Matthias ThommesAbstract:The sections in this article are Introduction Physisorption of Gases Determination of Surface Area The BET Method The Standard Isotherm Concept Assessment of Porosity Capillary Condensation and the Kelvin Equation Adsorption Hysteresis Microporosity Micropore Analysis: Dubinin's Theory of Micropore Filling Micropore Analysis: Empirical Methods Other Methods for Micropore Pore Size Analysis Application of Density Functional Theory Adsorption at the Liquid–Solid Interface Adsorption from Solution Heat of Immersion Mercury Porosimetry General Conclusions Keywords: physisorption; pore size; mercury Porosimetry; heat of immersion
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Mercury Porosimetry in Mesoporous Glasses: A Comparison of Experiments with Results from a Molecular Model
Langmuir : the ACS journal of surfaces and colloids, 2007Co-Authors: F Porcheron, Matthias Thommes, Riaz Ahmad, Peter A. MonsonAbstract:We present results from experiments and molecular modeling of mercury Porosimetry into mesoporous Vycor and controlled pore glass (CPG) solid materials. The experimental intrusion/extrusion curves show a transition from a type H2 hysteresis for the Vycor glass to a type H1 hysteresis for the CPG. Mercury entrapment is observed in both materials, but we find that the amount of entrapped mercury depends on the chosen experimental relaxation time. No additional entrapment is found in a second intrusion/extrusion cycle, but hysteresis is still observed. This indicates that hysteresis and entrapment are of different origin. The experimental observations are qualitatively reproduced in theoretical calculations based on lattice models, which provide significant insights of the molecular mechanisms occurring during mercury Porosimetry experiments in these porous glasses.
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Molecular Modeling of mercury Porosimetry
Adsorption-journal of The International Adsorption Society, 2005Co-Authors: F Porcheron, Peter A. Monson, Matthias ThommesAbstract:We present a molecular thermodynamic approach to model mercury Porosimetry. A lattice model is used to describe the intrusion/extrusion of mercury into different pore structures. The non-wetting nature of mercury is modeled by setting the wall-fluid interaction of the lattice model to repulsive values. We perform Mean-Field Density Functional Theory calculations on a mesoporous Vycor glass for different temperatures. The shape of the intrusion/extrusion curves is in good agreement with experimental observations. Visualizations of the liquid distribution in the Vycor glass reveal a fragmentation of mercury along the extrusion curve. The calculations performed on ink-bottle pore show that this fragmentation is caused by the snap-off of mercury from the necks leading to a droplet of mercury entrapped into the bottle part of the pore. This phenomenon is likely to play a role in the mechanism of mercury entrapment frequently observed during experiments.
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Modeling mercury Porosimetry using statistical mechanics.
Langmuir : the ACS journal of surfaces and colloids, 2004Co-Authors: F Porcheron, Peter A. Monson, Matthias ThommesAbstract:We consider mercury Porosimetry from the perspective of the statistical thermodynamics of penetration of a nonwetting liquid into a porous material under an external pressure. We apply density functional theory to a lattice gas model of the system and use this to compute intrusion/extrusion curves. We focus on the specific example of a Vycor glass and show that essential features of mercury Porosimetry experiments can be modeled in this way. The lattice model exhibits a symmetry that provides a direct relationship between intrusion/extrusion curves for a nonwetting fluid and adsorption/desorption isotherms for a wetting fluid. This relationship clarifies the status of methods that are used for transforming mercury intrusion/extrusion curves into gas adsorption/desorption isotherms. We also use Monte Carlo simulations to investigate the nature of the intrusion and extrusion processes.
