Search

Determination of the lower limit of flowing porosity for oil recovery from tight oil reservoirs is the key to promoting scientific and economic development of tight oil reservoirs. This study performed a comprehensive analysis based on pore-throat radius distribution measurements, low-temperature nitrogen adsorption measurements, and centrifugation and nuclear magnetic resonance measurements to establish a method for calculating the bound water film thickness and, in turn, the lower limits of pore-throat radius and permeability. The method was applied on rock samples from typical tight oil reservoirs in the Daqing and Changqing oil regions in China. The results indicated that for a given reservoir, bound water film thickness tends to be constant. With decreasing permeability, bound water film thickness showed an L-shaped distribution curve due to the changes in the pore-throat structure and the impact of molecular forces. The flat segment of the distribution curve corresponded to the lower limit of pore-throat radius, while the curve inflection point corresponded to the lower limit of permeability. The pore-throat radius and permeability limits were 22 nm and 0.08 mD for the Daqing tight oil reservoir and 18 nm and 0.03 mD for the Changqing tight oil reservoir, respectively.

Specific surface area based on the BET method in N 2 adsorption has historically posed poor correlation with olefin polymerization activity of heterogeneous Ziegler-Natta (ZN) catalysts. We have investigated the validity of the BET surface area for ZN catalysts based on the α S -plot method, where non-porous core–shell MgO/MgCl 2 /TiCl 4 catalysts were used as a reference material. The α S -plots for typical industrial ZN catalysts clarified the presence of two classes of micropores and resultant difficulty to isolate a multilayer adsorption region for the BET method. The results cast doubt on the application of the BET method to evaluate the surface area of heterogeneous ZN catalysts.

The texture development of a saponite and a montmorillonite, intercalated with zirconium and aluminium oligomers, after calcination at 500 ºC has been studied. Remarkable differences were observed among samples, depending on the source of the intercalating polycations and the parent material. On calcining, the alumina pillared clays suffered noticeable specific surface area and micropore volume losses, which have been related to the interlayer and interpillar distances of the samples. On the contrary, the zirconia pillared clays showed a slight surface area increase, which affected both micropores and mesopores and could be due to the combined effect of the thermal decomposition of the zirconium oligomers and the possible presence of mesoporous ZrO2 particles.En este trabajo se ha estudiado la evolución de las propiedades texturales de una saponita y una montmorillonita intercaladas con disoluciones de circonio y aluminio tras calcinación a 500 ºC. Los sólidos presentaron un diferente comportamiento en función de la naturaleza de la disolución de intercalación y de la arcilla empleada. Tras calcinación, la superficie específica y el volumen microporoso de las arcillas intercaladas con disoluciones de aluminio disminuyeron de manera importante, lo cual se ha relacionado con las distancias interlaminar e interpilar que presentaron los materiales intercalados. Por contra, las superficies específicas de las arcillas intercaladas con disoluciones de circonio aumentaron, probablemente gracias al efecto combinado de la descomposición térmica de los ligandos orgánicos unidos al circonio en los policationes y la posible presencia de partículas mesoporosas de ZrO2 sobre la superficie de los sólidos.

The preparation conditions of heteropolycompounds (HPC) dramatically influence the morphology of the crystals and therefore the heteropolysalts textural properties. When HPC are used as supports it is likely to have a strong influence on the catalytic performances. In this work we try to clarify this point using a perfectly stirred instrumented semi-batch reactor in order to prepare a series of Cs3PMo12O40 Keggin heteropolysalts. Preparation conditions (namely reactants concentrations, reaction and maturation temperature, addition rate and maturation time) have been varied following an experimental design (Hadamard matrix). The aim was to rule out the influence of the preparation conditions on the textural properties of the HPC, which were determined by nitrogen adsorption using the BET and BJH methods. The results show the excellent reproducibility of the supports preparation procedure, as well as the strong effect of the preparation conditions on the textural properties of HPC.

In this presentation we discuss the effect of the presence of small amounts of template and of the nature of the exchangeable cation on the shape of the nitrogen adsorption isotherm of ZSM-5 zeolite samples. It was found that for some exchangeable cations a low-pressure hysteresis loop is shown for Si: Al ratio of 120 but not 80. An explanation of the conditions under which the loop appears is given.

High surface area and thermally stable hierarchically porous zirconia-based composite materials with crystallized framework has been synthesized in a facile process templated from composite surfactants. XRD, nitrogen adsorption analysis, FESEM, FETEM, and EDX were used for the structural characterizations.

We investigate the pore size distributions obtained from the inversion of the adsorption integrals of nitrogen and carbon dioxide on low surface area (-20 m 2 .g -1 ) and medium surface area (∼70 m 2 .g -1 ) carbonaceous materials. Simple single-site (SS) Lennard-Jones models and multiple-site (MS) models incorporating partial charges have been compared for each probe gas. The multiple-site model produced an improved fit for the nitrogen isotherm compared to the single-site model, while the carbon dioxide isotherm was equally well matched by both models. The pore size distribution obtained from the carbon dioxide isotherm was able to successfully predict the nitrogen adsorption isotherm up to moderate pressures for both materials.

Organic-inorganic mesostructured materials were functionalized with titanium by direct synthesis under strong acidic conditions using non-ionic surfactants as structure directing agent and titanocene dichloride as titanium precursor. Materials with different organic content were synthesized with a high mesoscopic order and with incorporation of titanium species in isolated framework positions. The physicochemical properties of the synthesized samples were assessed by different characterization techniques including XRD, 29 Si MAS-NMR, nitrogen adsorption/desorption experiments, and DR UV-VIS spectroscopy. These materials with enhanced hydrophobic properties could have interesting applications in the liquid-phase epoxidation of olefins with organic hydroperoxides.

Mesoporous silica SBA-15 was used as support for the synthesis of π-complexation adsorbents. Samples of mesoporous silica containing variable quantities of AgNO 3 were prepared in order to study changes in the Ag + dispersion produced by different thermal treatments. The samples were activated by heating at different temperatures in air. The solids were characterized by XRD, nitrogen adsorption, EDX, SEM, TEM, FT-IR, TPR and the corresponding propylene equilibrium adsorption curves were obtained. It was found that thermal treatment conducted at about 100°C in air produces high salt dispersion and prevents the transformation in Ag 2 O or Ag o . Activated samples having intermediate values of Ag concentration showed the highest propylene adsorption capacity.

A series of the SBA-15 samples was prepared by varying the time of the first synthesis step, which involved the self-assembly of block copolymer and tetraethylorthosilicate under acidic conditions at 40°C. The time of the second synthesis step, which consisted of the hydrothermal treatment of the gel at 100°C, was varied too. The SBA-15 samples were characterized by nitrogen adsorption, thermogravimetry and small angle X-ray scattering. It was shown that the time of the first synthesis step can be shortened up to two hours, while the hydrothermal treatment should be carried longer.

Nanosized silicalite-1 has been synthesized in only 4 h by microwave synthesis with fumed silica precursor and promoter such as NaH 2 PO 4 . The influence of gel compositions, temperature, aging time and precursor addition on the synthesis of nanosized silicalite-1 were investigated. XRD and nitrogen adsorption showed no structural degradation and high surface area, ≈450 m 2 /g, for nanosized silicalite-1. The formation process of silicalite-1 crystals by using microwave through promoter addition is prior to crystallization rate of hydrothermal synthesis and without promoter. The mean particle sizes were ranged from 150 to 250 nm.

Silica nanospheres were synthesized with diameters in the range from 40 to 170 nm. The size and shape of the spheres were determined by Photon Correlation Spectroscopy (PCS) and Scanning Electron Microscopy (SEM). The nanospheres were agglomerated by centrifugation and solvent evaporation and characterised by SEM and nitrogen adsorption. Partly regular mesostructures could be observed by SEM. However, these structures easily crumbles when they are handle and therefore no surface area related to the formation of mesopores was detected by nitrogen sorption.

The tungsten carbides on FSM-16 were prepared in carburizing of WO 3 /FSM-16 with 20% CH 4 /H 2 and characterized using nitrogen adsorption, XRD, TEM, and NMR. The relationship between the surface properties and the catalytic activity of tungsten carbides on FSM-16 in cyclohexene hydrogenolysis at 250°C was discussed.

Fluorination is effective in chemically modifying and controlling physicochemical properties of carbon materials over a wide range so creating opportunities to prepare carbon alloys with new functionalities. Carbon alloyed nanotubes were prepared by selective fluorination of hidden surfaces of multi-wall carbon nanotubes using a template carbonization technique. Carbon–fluorine bonds are formed on the hidden surfaces of the tubes while internal surfaces retained their sp2-hybridization. Fluorination (as a form of carbon-alloying) significantly affects such properties of hidden surface extents of nitrogen adsorption, hysteresis loops and pore size distributions. Fluorination enhanced the coulomb efficiency of Li/carbon nanotube rechargeable cells in an aprotic medium (with reversible lithium insertion in hidden surfaces) as studied by galvanostatic discharge-charge experiments.

Large pore, high quality MCM-48 silica was synthesized using CTAB as the only template. The pore size could be tailored from 2.6 nm to 4.2 nm by a post-synthesis hydrothermal treatment. Nitrogen adsorption, XRD, TEM and SEM were used to characterize the samples, showing an improved long-range structural order and expanded pore size, which depends on the post-synthesis treatment conditions, such as the aging temperature during the second synthesis step.

Periodic mesoporous organosilicas (PMO) functionalized with sulfonic acid group have been successfully synthesized by co-condensation of bis(triethoxysily)ethane and 3- mercaptopropyltrimethoxysilane in the presence of octadecyltrimethylammonium chloride as the structure-directing agent under basic conditions. The PMO materials have been characterized by nitrogen adsorption, powder X-ray diffraction, IR, and thermogravimetric analysis. The results indicate that the materials exhibit well-ordered mesostructures, high surface areas and solid acid properties.

SBA-15 and MSU-H silicas were synthesized and subjected to calcination at temperatures in the range from 823 to 1273 K. The porous structures of the resulting samples were studied using X-ray diffraction and nitrogen adsorption. The pore connectivity was elucidated using the inverse carbon replication procedure. The structures of carbon inverse replicas were studied using XRD and nitrogen adsorption.

A first stage of a systematic study of the nature of the low-pressure hysteresis loop observed in the nitrogen adsorption isotherms of some MFI zeolites is presented. It was shown that the pressure at which occurrence of this hysteresis loop takes place was linked to the presence of defect sites. The role of the exchangeable cation was also investigated, and it was suggested that in addition to the numbers of defect sites present, the strength of adsorbate-adsorbent interaction, and probably pore shape was also involved.

Ordered Mesoporous Materials (OMS) functionalised with alkyl sulfonic acid groups have been proved to be efficient esterification catalysts. Among them, materials having MCM-41 type structure exhibit the best performance. In this paper we report the synthesis and characterisation of SO 3 H-phenyl-MCM-41 materials and their catalytic activity in the esterification of glycerol with lauric and oleic acids. We have studied several synthesis parameters: the amount of phenyl groups, the presence of additional methyl groups and the sulfonation procedure of the phenyl gorups. The materials obtained have been characterised by XRD, Elemental Analysis, Nitrogen adsorption, TGA and TEM. Finally, it has been studied the influence of the different synthesis parameters on the behaviour of the catalysts in the mentioned reaction of esterification.

Over the years there has been a lot of debate concerning the applicability of the Dubinin-Radushkevich equation on the very low pressure region of isotherms of microporous solids. The experimental downward deviation of the DR-plot for very low pressures is generally attributed to kinetic barriers, especially in the case of nitrogen adsorption at 77 K. This low pressure region of isotherms of various adsorbents can be fitted with the Langmuir equation. Hence it is shown that the downward deviation is not due to experimental factors but reflects a different adsorption mechanism.

This paper presents an overview of the pore structural properties of different mesostructured materials prepared at room temperature, namely MCM-41, MCM-48 and MMS. The stability towards water vapour of some samples is inferred by XRD and nitrogen adsorption after and prior to water adsorption. It is shown that MMS materials are more stable than MCM-41. A new method for the stabilisation of MCM-41 using tetraethoxysilane (TEOS) in hexane as silicification agent is proposed and it is shown to be effective in stabilising the pore structure and to increase significantly the surface hydrophobicity.

The progress in the determination of porosity of various types of materials has arisen over the past ten years from advances in application of new spectroscopy techniques. In the present paper the application of small angle X-ray scattering (SAXS), positronium annihilation lifetime spectroscopy (PALS) and low temperature nitrogen adsorption methods to the characterization of mesoporosity is reviewed using different types of silica gels with chemically modified surface. The results from the three methods are compared and discussed.

The synthesis of MCM-41 type of materials functionalised with (methylmercaptopropyl) and/or methyl groups have been performed by co-condensation of the corresponding alcoxysilanes and tetramethoxysilane, in the presence of hexadecyltrimethylammonium and the aminoacid leucine. The presence of the organic moieties in the resulting material has been assessed by 29Si MAS NMR. Nitrogen adsorption and Transmission electron microscopy (TEM) studies of the samples synthesised from gels containing leucine reveal the presence of large secondary mesopores that permeate the entire bulk of the particles, in addition to the conventional mesopores in hexagonal arrangement. The simultaneous presence of methyl functional groups, and leucine is required for the formation of such secondary mesoporosity.

The post-synthetic galliation of BEA by treatment of dealuminated zeolite with acidic gallium solutions was investigated by means of XRD, 71 Ga MAS NMR, FT-IR and nitrogen adsorption. It was found that the gallium species in the solution are easily incorporated into the framework of dealuminated BEA zeolite by controlling the pH value of the solution below 7. The cumene cracking activity of the galliated BEA zeolite at pH 4 was comparable to that of the galliated BEA zeolite prepared by the direct hydrothermal synthesis method.

Publisher Summary This chapter presents acidic hybrid catalysts prepared by grafting large-pore silica M41S materials. Large-pore mesoporous materials with enhanced textural characteristics are obtained from a pH-adjusted synthesis with a surfactant mixture of hexadecyl- and dodecyltrimethylammonium salts in combination with mesityleneswelling. This material is grafted with phenyl-alkoxysilanes and subsequently sulphonated. Nitrogen adsorption and multinuclear magic angle spinning nuclear magnetic resonance (MAS NMR) are performed to monitor the different synthesis steps.

Publisher Summary This chapter describes the influence of pH of the solution on the realumination of BEA zeolite by means of nitrogen adsorption, X-ray diffraction (XRD), 27Al magic angle spinning nuclear magnetic resonance (MAS NMR), and Fourier transform-infrared (FT-IR). Non-framework aluminum species in the solution are easily reinserted into the framework of dealuminated BEA zeolite by controlling the pH value of the solution below 7. The cumene cracking activity of the realuminated BEA zeolite at pH 5.1 is comparable to that of the parent BEA zeolite. The influence of aluminum species in the solution on the realumination process is also investigated using various aluminum compounds.

Publisher Summary This chapter presents the study of the isopropylation of 2-isopropylnaphthalene over heteropoly acid catalyst supported on mesoporous material. The physico-chemical state of loaded heteropoly acid is investigated using X-ray diffraction (XRD), nitrogen adsorption measurement, and Fourier transform-infrared (FT-IR) techniques. Heteropoly acid is highly dispersed on the wall of mesoporous material, and it retains its Bronsted acidity. The conversion and the selectivity for β, β-diisopropylnaphthalene is very high over the mesoporous material with a large loading amount of heteropoly acid. The treatment of heteropoly acid is helpful for the improvement of the acidity of mesoporous material.

The influence of some characteristics of Nomex [poly(m-phenylene isophthalamide)] fibres on the porous texture of activated carbon fibres (ACFs) prepared from them by pyrolysis and CO2 activation has been comparatively analysed. The features studied were the degree of crystallinity and the presence of dyeing additives on the precursor. The obtained ACFs were characterised by N2 (77 K) and CO2 (273 K) adsorption, and X-ray diffraction. The results show that the texture developed is mainly related to the degree of burn-off (BO) achieved. Crystallinity differences or the presence of carbon black dye in the precursor brought about little differences in porous texture, the main ones appearing at low and high BOs., Financial support from CICYT (project 1FD97-1915), and financial (project PB-MAT97-04) and fellowship support from II PRI Asturias are gratefully acknowledged.

For the characterisation of M41S materials, often only powder X-ray and nitrogen adsorption studies are used. However, the use of transmission electron microscopy in combination with these techniques yields valuable information that is indispensable in order to understand the structure of mesoporous materials.

The recently developed density functional theory method for pore size distribution analysis from nitrogen adsorption and desorption isotherms is extended to materials with pores ranging from 2 to 100 nm. The method is based on the nonlocal density functional theory (NLDFT) of capillary condensation hysteresis in cylindrical pores. It is shown that NLDFT correctly predicts both the adsorption and desorption branches of the hysteretic isotherms in materials with cylindrical pores wider than ca. 5 nm. For pores larger than ca. 6 nm, the NLDFT results agree well with the thermodynamic theory of Derjaguin-Broekhoff-de Boer. When pore-blocking (networking) effects are insignificant, both branches of the experimental isotherm produce identical pore size distributions. The NLDFT method is validated against literature data on capillary condensation in MCM-41 type materials with pores from 5 to 10 nm.

Using a recently developed molecular dynamics procedure, we have prepared a series of models of controlled pore glasses with a range of porosities and pore sizes. Nitrogen adsorption isotherms have been obtained in these models using a parallelized version of the Grand Canonical Monte Carlo simulation technique. These isotherms can be analyzed with standard methods to obtain pore size distributions and surface areas, which can be compared with exact results obtained from the model glasses’ atomic structures. In this study, we also measure the partial structure factors for the gas adsorbed in the model glasses at different pressures, and discuss the relationships between features in these data and the pores’ geometry.

The synthesis of silica mesoporous materials using polyoxyethylene alkyl ether and in particular decaoxyethylene oleyl ether C18H35 (CH2CH20)10 as templating agent has been reported. Characterization of final products by nitrogen adsorption analysis shows that the value of pore diameter depends on several factors such as heating temperature and time, stirring time of micellar solution and pH of the gel. The expansion of pore size with increasing temperature was explained by taking into account the change of surfactant conformation with temperature.

The influences of synthesis conditions (pH) and drying (oven or freeze-drying) on textural and structural properties of titania-aluminas prepared by hydrolysis of alkoxides were studied. Titania-aluminas with a 1:1 molar ratio were prepared by hydrolysis of alcoholic solutions of titanium and aluminium isopropoxides. The syntheses were conducted in acidic (pH 1.4) or basic hydrolysis conditions (pH 9). Solvent and water were removed by freeze-drying or oven-drying at 393 K, followed by calcination at 773 K or 1073 K. The solids were characterized by nitrogen adsorption, X-ray diffraction,27Al NMR, DTA and XPS. The results suggested that the textural properties of titania-aluminas prepared by the sol–gel method were mainly determined by the pH of hydrolysis. However, structural properties were very sensitive to the drying procedure. A less stable structure, with a more random distribution of titanium and aluminum, was formed by freeze-drying than the one obtained by oven-drying, which led to separate alumina and titania domains.

The thermal stability of cloverite, [Ga8P8O31(OH)2](QF)2(H2O)n, was studied by in situ x-ray diffraction (XRD), in situ infrared spectroscopy (IR), thermogravimetric analysis combined with differential thermal analysis (TG/DTA) and nitrogen adsorption measurements. During the heating process the framework remained stable to at least 500°C in air as well as in vacuum. Cooling down to room temperature in ambient air led to a structure break down, while under vacuum the cloverite structure remained stable during the cooling process. When the calcined cloverite is kept at temperatures above 100°C its framework remains intact while storage under aliphatics produces a material similar to cloverite.

Nanometer size SnO 2 was prepared with a sol-gel process followed bysupercritical fluid drying. Their structure, particle size and specific surface area were characterized by XRD. TEM and nitrogen adsorption method. The effect of the preparation parameters is also discussed.

This paper reports a comparison of the structure and catalytic properties of zeolite-Y whendealuminated by hydrothermal and ammonium hexafluorosilicate treatments. Initial results have shown that dealumination using ammonium hexafluorosilicate is highly sensitive to many of the reaction parameters such as reaction temperature, rate of AHFS addition, reaction time, pH, framework Si/Al ratio and also to the extent of washing of the final product. Further, degrees of dealumination beyond 50% are difficult to obtain without causing decreases in framework crystallinity. Structural characterisation of the samples has been performed using X-ray diffraction, X-ray fluorescence spectroscopy, nitrogen adsorption and 27Al MAS NMR. The catalytic properties of the samples were studied using the n-butane cracking reaction. In future work, analysis of the cracking data will be performed as well as a detailed comparison of the deactivation processes occurring within the samples.

Nitrogen adsorption on H-mordenite, H-Y and H-ZSM-5 at low temperatures was studied by in-situ FT-IR. For each zeolites pretreated at higher temperatures (typically above 773 K), two absorption bands were observed at around 2334 and 2352 cm −1 in the νv(NN) region. By examining the effects of water-vapor treatment and the pretreatment temperature, these bands were assigned to the νv(NN) bands of the dinitrogen species adsorbed on Brϕnsted and Lewis acid sites of the zeolites, respectively. For highly siliceous ZSM-5 (without acidity), the νv(NN) band was not observed. Therefore, N 2 species can be used as a probe of acid sites of zeolites. Advantages of N 2 species as a probe are discussed.

A high resolution adsorption apparatus was used to study the effect of occluded organic species on nitrogen adsorption isotherms and B.E.T. surface areas of several three-dimensional zeolites. Three different structure types were investigated: three purely siliceous MFI type, one Beta type and two CLO type gallophosphate samples.

Nitrogen adsorption measurements and small angle neutron scattering (SANS) measurements have been recorded for a series of mesoporous, spherical aluminas with differing particle sizes and capping groups. The results from the two methods are compared and discussed.

Based on the capillary phase-separation concept, or a hindered liquid-liquid equilibrium in narrow pore with curved interface, a method for pore characterization of solids immersed in solvents was proposed. The method is considered to be effective for determination of pore characteristics of swelling/shrinking solids in solvents. The method was tested by comparing the pore size distribution calculated from liquid phase adsorption isotherm and that from nitrogen adsorption on a non-swelling solid. The distribution from liquid phase was able to express the pore characteristics satisfactorily to show the potential power of the method proposed The parametric sensitivity of the method and desirable nature of the probe molecule are also discussed.