Mercury Penetration Research Articles

Mercury penetration studies of porous materials

The process of mercury penetration into porous material is described in terms of the percolation theory.

Hysteresis caused by dimensional changes of porous solids during mercury porosimetry

Hysteresis in mercury porosimetry is often attributed to differences in contact angle and to inkbottle-shaped pores. In this paper, the contribution to hysteresis from dimensional changes in pores is considered. Empty pores are compressed by the applied external mercury pressure. The mercury penetration pressure is related to the dimensions of the compressed pores. After the pores are filled with mercury, the pressure becomes isotropic throughout the solid and the pores revert to their original dimensions. The pressure at which mercury retracts from the pores is related to the original pore dimensions. Using these concepts, the magnitude of the pore dimension changes was determined as a function of the applied mercury pressure, the modulus of elasticity of the solid and the solid porosity. The effect of dimensional changes on the width of the hysteresis loop (P pen - P ret ) was found to be minimal at pressures less than 70 MPa (10 4 psi). At 350 MPa (5 × 10 4 psi), the width of the hysteresis loop caused by dimensional changes can be significant even when the modulus of elasticity is large. The predicted hysteresis loop widths are compared with experimental data reported for model pore systems.

The catalytic hydrogenation of benzene over supported metal catalysts.: III. Gas-phase hydrogenation of benzene over silica-supported Ru-Cu catalysts

A study has been made of the gas-phase hydrogenation of benzene over silica-supported Ru-Cu catalysts in the temperature range from 300 to 400 K and at a total pressure of 130 kPa. Special attention has been given to the catalytic stability and the activity of the catalysts as compared with monometallic supported ruthenium and copper catalysts, described in previous articles. Via a reductive deposition technique, copper was deposited on silica-supported ruthenium catalysts. Two bimetallic catalysts were prepared, one with about 10% of the ruthenium surface covered by copper and one with about 70% copper coverage. The texture of the catalysts was studied by means of mercury penetration, nitrogen physisorption, hydrogen chemisorption and transmission electron microscopy, whereas surface analysis was performed by XPS/AES. At 11% copper coverage a shift in the copper electron binding energy is observed, pointing to a small electron transfer from ruthenium to copper, but at 68% copper coverage this shift has disappeared. Copper deposition on ruthenium increases the lifetime of the catalysts considerably without seriously affecting the activity per ruthenium surface atom. At low copper coverage the reaction kinetics are very similar to the kinetics found with ruthenium, but at high copper coverage the small size of the ruthenium ensembles influences the kinetics considerably.

Comparison of Nitrogen Adsorption and Mercury Penetration Results. Pore Size Distributions for a Series of Mo-A12O3 Catalysis with Increasing MoO3 Content

Scanning electron microscopic data, X-ray diffraction patterns and porosity measurements are consistent with a structure for an Mo-A12O3 catalyst series containing a single surface layer of Mo up to the point where the Mo loadings exceed the amount required for a monolayer. For greater Mo loadings than required for a monolayer, three dimensional orthorhombic MoO3 is also present. The cumulative pore volume, on an alumina basis, does not appear to be significantly altered by MoO3 loadings up to about 15 wt.%. The BET surface area, on an alumina basis, remains constant with Mo loading. However, the apparent surface area calculated from mercury penetration data decreases with Mo loading. For these materials with cylindrical pores, the Broekhoff-deBoer model for the calculation of pore size distributions produced closer agreement to the mercury penetration pore size distribution. This is in contrast to materials composed of nonporous spheres where the Broekhoff-deBoer model provided poorer agreement to mercury penetration results than either the Cohan or a packed sphere model. The results show that, within a factor of two the pore size distributions calculated from nitrogen adsorption and mercury penetration data are comparable.

The catalytic hydrogenation of benzene over supported metal catalysts: I. Gas-phase hydrogenation of benzene over ruthenium-on-silica

A study is reported of the gas-phase hydrogenation of benzene over a ruthenium-on-silica catalyst in the temperature range from 300 to 415 K and at a total pressure of 130 kPa. The texture of the catalyst is studied by TEM, physisorption of nitrogen, chemisorption of hydrogen and by mercury penetration. Surface analysis is performed by XPS/AES. The adsorption enthalpies of the reaction intermediates 1,4-cyclohexadiene and cyclohexene and of cyclohexane on ruthenium are determined. On the basis of the kinetics, a reaction mechanism is proposed in which the rate-determining step shifts from the first hydrogen addition to benzene at low temperatures to the hydrogen addition to cyclohexene at higher temperatures. An approximate diagram is constructed representing the change of the free enthalpy as a function of the extension of the reaction.

水銀圧入法によるAl<SUB>2</SUB>O<SUB>3</SUB>-SiO<SUB>2</SUB>系れんがにおける気孔径の測定とその分布

水銀圧入法によるAl<SUB>2</SUB>O<SUB>3</SUB>-SiO<SUB>2</SUB>系れんがにおける気孔径の測定とその分布

Changes of chemical pulp fibres during recycling.

When a pulp, especially chemical pulp, is repeatedly disintegrated in water, dewatered and dried for several times, the mechanical properties of handsheets are considerably deteriorated. This paper mainly deals with changes in the micro-structure of fibre cell wall by recycling. Changes in recycled fibres were determined by the solute exclusion and the mercury intrusion methods as well as the electron microscopy. Moreover, loading of titanium dioxide in lumina of recycled fibres was investigated. Following results were obtained.(1) Tensile strength of handsheets from recycled fibres could be partly restored by beating.(2) By beating the recycled pulp, the pore volume in cell wall of the pulp fibres could be partly recovered. The mercury penetration volume into the handsheet increased with recycling and decreased by additional beating.(3) It was observed that morphological changes such as delamination and crack formation in cell wall of the recycled fibre were enhanced by additional beating.(4) The amount of TiO2 loaded in pulp fibres increased with recycling upto 3rd time and decreased after 5th time. The amount of TiO2 retained in handsheets seemed to be dependent on bulkness, flexibility and rigidity of fibres.

抄紙機ワイヤーの織りと空隙構造及び脱水性

The behaviour of water removal on fabrics of a paper machine can be divided into three stages, that is, wetting, penetration and draining.In this paper, the open structure and draining properties of paper-making wires were studied by the mercury penetration method and the centrifugal dehydrator.The triple layer fabric had a number of large pores of 300 to 400pm in diameter. On the otherhand, the double layer fabric had pores of 100 to 200pm. The single layer fabrics had smaller net pore volume compared to those of multi layer fabrics.As the results of the centrifugal dehydration, the single layer fabrics showed the lower drainage volume and the triple layer fabrics did the highest draining tendency.Bronze wire of high wettability showed higher drainage volume compared to plastic fabrics.

Effects of drying upon lignite macro-pore structure

The effect of drying upon the macro- and partly meso-pore structure of Greek lignite was investigated. Drying of lignite lumps (∼d p : +3 – 15 mm) placed on a fixed bed arrangement, was carried out under vacuum (∼0.2 Torr) in a constant-temperature (100 – 250 °C) environment, for varying drying times (5 – 180 min). Drying caused a considerable particle contraction (by ∼1/3 of its original size), a minor decrease in the macro- and partly meso-pore volume and a marked increase in the relevant surface area, particularly in the range of high weight losses (35 – 40%). Residual moisture contents ranged from ∼0% to 42%, specific pore volume fell in the range 0.20 – 0.25 cm 3/g (dry sample), and specific surface area in the range 9 – 17 m 2/g (dry sample). Pore volume and surface area frequency distributions, determined from mercury porosimetry (MP) measurements done on raw or partially dried samples, clearly indicate the formation of pores in the size range D p : + 75 – 1500 Å at the expense of pores in the range D p : +1500 – 10 4 Å. This observation might be the result of pore shrinkage and pore emptying due to the counteraction of particle contraction and moisture removal respectively. Mercury penetration — retraction hysteresis was evident in every MP run. Mercury entrapment drop (from 85% to 38%) varied with residual moisture content, an indication that drying favours the formation of a more regular and less complex physical pore structure.

SURFACE AREA OF CALCINED LIMESTONES OBTAINED BY NITROGEN ADSORPTION AND MERCURY PENETRATION MEASUREMENTS

ABSTRACT Two sets of limestones, one from Kentucky and one from Spain, have been used in a study to compare the surface areas from nitrogen adsorption and mercury penetration. As a first approximation for the higher area materials, the surface areas obtained by the two experimental methods are in reasonable agreement and either method could be employed. However, a consistent trend is established when the ratio of surface areas are considered for decreasing nitrogen. The mercury penetration area becomes increasingly greater than the nitrogen area as the nitrogen area becomes smaller.

酸化クロムペレットの水素還元速度

Chromic oxide (Cr2O3) pellets with different pore structures were reduced with hydrogen in the temperature range from 1423 to 1623 K. The pore-radius distributions of unreduced and partially reduced pellets were measured by the mercury penetration method, and fractures of partially reduced pellets were observed by the use of SEM.Since it was observed that the reduction proceeded topochemically under the formation of a relatively clear interface between a reduced sheel and a not reacting core, the reduction rate was analysed on the basis of a not reacting core model, in which the diffusion through the gaseous film around pellet, the intraparticle diffusion and the chemical reaction were taken into account.The rate constant of chemical reaction was increased with the decrease of grain size of Cr2O3 in pellet, while the activation energy was 148∼166 kJ/mol and almost unchanged with the grain size. The intraparticle diffusivity and the labyrinth factor were highly influenced by the pore size, and their temperature-dependence was considerably greater than that in the reduction of iron oxide pellet with hydrogen. In the reduction of pellet composed of fine-grain Cr2O3, pore-shrinkage resulting from sintering occurred in the reduced layer so that the resistance of intraparticle diffusion was larger.

Evolution of pore structure and active surface areas of coal and char during hydrogenation

A Belgian coal (Beringen) has been used in a fundamental study of the changes in pore structure and active surface area during hydrogenation. The coal was devolatilized under N 2 and then hydrogenated at constant temperature up to various conversion yields. Reactivities of the chars were determined by isothermal thermogravimetric analysis. Changes in total surface area, calculated from CO 2 adsorption isotherms at 298 K, and in macropore distribution, obtained by mercury penetration, were found to lead to the same conclusion. In the first reaction stage, the preponderant phenomenon was the opening of previously closed micropores, induced by the material consumed by the reaction. This stopped completely when conversion yield exceeded 55 wt% when the maximum surface area was observed. Then removal of material from pore walls became predominant, pores were enlarged and pore walls disappeared gradually with increasing hydrogenation yields. Oxygen chemisorption capacities were measured at 383 K and 0.1 MPa air to give a relative indication of the concentration of carbon active sites. Active surface area results were compared to total surface area values and correlated with reaction rates.

Properties and structure of oil shale ash pastes I: Composition and physical features

The composition and physical features of oil shale ash pastes were determined and compared with the corresponding properties of portland cement paste. In the first part presented here, the composition, chemically combined water, porosity (total, capillary and gel porosity), pore-size and pore-size distribution, and specific surface area were determined by water vapor adsorption, mercury penetration and X-ray diffraction. It was established that the structural features and the factors which control and determine these features, are essentially the same in both the ash and the portland cement pastes. In the ash paste, however, total porosity remained virtually unchanged with time. This aspect, as well as the mechanical properties of the ash paste, are presented and discussed in the second part of the paper.

Direct transport parameters measurement versus their estimation from mercury penetration in porous solids

It has become widespread practice to rely on mercury penetration data for the determination of pore-size distribution when calculating transport processes occurring in the porous structure of catalysts and adsorbents. The authors, working in independent laboratories, summarize recent results which show that mercury penetration analysis is not reliable. A mean transport-pore model (MTPM) is proposed which requires permeation, steady-state diffusion or pulse chromatographic measurements with several gases or gas pairs and/or at different pressures and temperatures. This method provides basic parameters for calculating the transport processes in catalysis or adsorption, making no direct use of mercury penetration and other textural data.

Texture of manganese nodules used as a catalyst for demetallizing and desulphurizing petroleum residua

The porous texture of oceanic polymetallic nodules used as catalysts for demetallation and desulphurization of petroleum residua in a trickle bed reactor was studied after reaction. Four techniques were considered: analysis of nitrogen physical adsorption—desorption isotherms, X-ray diffractometry, mercury penetration and electronic microscopy. The nodules present a remarkable specific surface area and porosity, which are partially conserved at high temperatures even under the drastic conditions of hydrotreatment.

Precipitation of colloidal silica and pore size distribution in high silica porous glass

Abstract Porous glass was prepared by acid leaching of a phase separated soda borosilicate glass. Fine pores with radius smaller than 15 A and coarse pores with radius larger than 50 A were observed in the glass by nitrogen adsorption and mercury penetration methods, respectively. Effects of the time of heat treatment and the acid/glass ratio, that is, the ratio of volume of leaching acid to the weight of phase separated glass on the characteristics of fine and coarse pores were studied. The size of coarse pores which were ascribed to the phase separated structure was proportional to the cube root of the time of heat treatment. The extraction of silica from specimens by acid solution during leaching increased with increasing acid/glass ratio. The volume of coarse pores was proportional to the amount of extracted silica. These facts are discussed on the basis of the formation of colloidal silica particles from the soluble borate phase during leaching.

A comparison of surface areas derived from mercury penetration and nitrogen adsorption

When considering surface area results for a variety of materials, the mercury penetration method appears to produce higher areas than the BET method does for the surface area range from 100 to 500 m 2 g −1. However, when comparing the results from a range of materials for a single metal oxide, the ratio of mercury penetration areas to nitrogen BET areas, r, gradually decreases with increasing BET surface area and, at higher BET areas, the nitrogen BET area may exceed the mercury penetration area by a factor of two. On a volume, rather than on a mass,comparison, both alumina and silica show a common trend in the decrease of r with increasing BET nitrogen area. For practical comparisons it appears that the two methods can be directly compared. Adjustment of the mercury surface tension or the contact angle between mercury and the material does not provide an adequate compensation to make the two methods comparable over the total BET nitrogen area range.

Empirical correction factors involved in mercury porosimetry

An empirical calculation method has been developed to correct the apparent porosity measured by mercury penetration porosimetry. It was found that the value of the correction depends on the geometry and volume of the sample cell, the volume of mercury in the sample cell, and the pressure applied. The effect of the compressibility of the sample was found to be negligible. Application of this correction enables valid porosity curves to be obtained even at high pressures up to 50,000 psi. Thus, by adopting Rootare and Prenzlow's method for specific surface area, appropriate results can be calculated.

Properties of Fe3O4 porous film catalyst.

An intermetallic compound Fe2Al5 phase was formed on the surface of the original ironplate by aluminum coating followed by heat treating. The alloy plate was processed by a 10 wt% NaOH solution (whole development), and the iron-plate resulted was dried and oxidized in a desiccator. By the procedure described above, a Fe3O4 porous film catalyst was obtained. The catalyst showed activity for reduction of NO with NH3. The following rate equation was obtained: RNO=9.3×103 exp(-7.2×103/RT)•PNOThe pore-size distribution determined by nitrogen adsorption isotherm and mercury penetration was bimodal. A group of micro-pore peaks lay at about 50A, and that of macropore peas at about 1, 300A. The specific surface area of the catalyst was proportional to the thickness of the alloy layer. It was obvious, in this study, that diffusional resistance of capillary began to appear from the alloy layer thickness of ca. 140μm, e. g., the oxide layer was 100μm thick. The effectiveness factor for the sample, whose oxide layer was 120μm thick, was about 0.42 on the basis of a cylindrical pore model.

Porous structure of powdered poly(ethylene terephthalate)

AbstractThe porous structure of both the powdered poly(ethylene terephthalate) and polyamide 6 prepared by reprecipitation from the melt of 6‐caprolactam was studied using the combination of a penetration method and a sorption one. The measurements of the apparent density and of the real one were used for the porosity measurements. The pore size measurement by means of the mercury penetration was used for the pore distribution in the range of macropores (7500–15.8 nm). In the range of mesopores (15.8–1.8 nm), the pore measurement by means of the benzene desorption isotherm at 298 K was used for the pore distribution determination. As for the powdered poly(ethylene terephthalate), the porosity was found in the range from 50 to 80%, the volume of mesopores was in the range from 0.2 to 0.5 cm3 g−1, and the volume of the macropores ranged from 1.5 to 2.8 cm3 g−1. The powdered polyamide 6 did not contain any mesopores and the volume of the macropores was as high as 0.7 cm3 g−1.When using further lactams of ω‐aminoacids, i.e. 2‐pyrrolidone, 8‐capryllactam, 12‐laurinlactam, as melt solvents for a preparation of the powdered poly(ethylene terephthalate), it resulted in decreasing of the specific surface area, porosity and furthermore by an absence of any mesopores.