Gas Adsorption Method Research Articles

Surface area and microstructure of microwave activated crumb rubber modifier and its influence on high temperature properties of crumb rubber modifier binders

Crumb rubber pretreatment by microwave before blending with an asphalt matrix can address and improve the modification problem of of crumb rubber modifier (CRM) asphalt plant. In this research, the surface area and microstructure of microwave activated CRM and high-temperature performance of CRM asphalt were investigated to characterize the mechanism of interaction between activated CRM blends added and base asphalt. The surface area and microstructure of CRM were measured by gas adsorption method and the scanning electron microscopy (SEM) respectively when CRM was activated using microwave treatment time (30 s, 60 s, 90 s, 120 s and 150 s). The complex shear modulus (G*) and the phase angle (δ) of the CRM asphalt were measured by Dynamic Shear Rheometer (DSR) test. The results indicated that microwave treatment produced more porous structure and agglomeration phenomenon than control one for a given activated time of CRM. The flocculent structure was the most obvious one and agglomeration phenomenon was the most significant one for the particle surface microwave activated 90 s. The δ decreased and G* increased as CRM blends activated time increased before a certain time using the same frequency of microwave treatment. The G*/sinδ of CRM blends was the maximum when CRM activated for 90 s using microwave treatment. Both surface area and microstructure of the CRM influenced the high-temperature performance of CRM binders.

Effects of pore structure on methane adsorption behavior of ductile tectonically deformed coals: An inspiration to coalbed methane exploitation in structurally complex area

The distinctive pore structure of tectonically deformed coals (TDCs) has a considerable influence on their methane adsorption behavior, resulting in higher coalbed methane (CBM) pressure and higher CBM content, and thus increasing the difficulty of CBM development in TDCs distribution area (especially ductile TDCs). In this paper, the supermicropore-microfracture structures of primary structure coals (PSCs) and ductile TDCs from the Suxian mining area were characterized by using mercury intrusion porosimetry (MIP) and gas adsorption methods (N2 and CO2). Methane adsorption test was conducted to study the methane adsorption behavior. Then, the control mechanism of pore structure on methane adsorption behavior of ductile TDCs was investigated. Results show that the supermicropores (<2 nm) surface area generally increases and then decreases. The micropores (2–10 nm) and small transitional pores (10–40 nm) volume of ductile TDCs is slightly larger than that of PSCs, while the volume of big transitional pores (40–100 nm) experiences a steady increase. The mesopores (100–1000 nm) and macropores (1000–10000 nm) volume displays a similar pattern of “steep increase-slightly decrease -stable increase” with the enhancement of deformation. The microfractures (>10000 nm) volume first increases and then decreases from the PSCs to mylonitized coals. Langmuir volume (VL, daf) displays no obvious change rules with the increasing ductile deformation, but the Langmuir pressure (PL, daf) of ductile TDCs is smaller than that of PSCs and gradually decreases to its minimum in the mylonitized coals. The Pearson correlation coefficients show that the volume of big transitional pores (40–100 nm), mesopores and macropores both shows obvious negative correlations with the PL, daf, which indicates that the development of 40–10000 nm pores in ductile TDCs causes a lower PL, daf, resulting in higher CBM pressures and contents in the ductile TDCs distribution area under the in-situ pressure condition.

Characterization of pore structures and gas transport characteristics of Longmaxi shale

Multiscale pore structures of shale conjunctionally determine the gas storage and transport properties of gas shale reservoirs. To investigate the complex pore structures and gas transport in the ultra-tight porous media, a combination of petrophysical and scanning measurements is adopted in this study. Five shale samples of the main productive layers from four wells (Long 11 sub-members of Longmaxi Formation) in southeast Sichuan Basin, China are analyzed. Based on scanning electron microscope (SEM) image, different types of organic pores and inorganic pores are quantitatively analyzed. A method for identification of organic and inorganic pores from SEM images is developed. And a comparison between the pores identified from SEM and gas adsorption (N2 and CO2 adsorption) is conducted. Results show that the main part of inorganic pores are mesopores, and the organic pore size distributions tend to be lognormal with the peak pore size from 10 nm to 30 nm. Results also show that the gas storage space obtained by SEM is several times to several tens of times larger than that obtained by gas adsorption method. The permeability of OM and shale cores is also compared. The permeability is strongly anisotropic and all those samples show a significant non-Darcy effect. Finally, the relationship between the pore structures and gas transport behavior is studied, and the high quality shale samples are identified considering their gas storage and transport behaviors.

Transport properties of H2 confined in carbide-derived carbons with different pore shapes and sizes

Hydrogen adsorption in highly porous carbon with well-defined pores, with three different shapes, and different sizes ranging from sub-to nanometers is investigated. Using a combined approach of volumetric gas adsorption method and in-situ quasi-elastic neutron scattering method the relationship between final macroscopic intake properties, details of the local adsorbent structure and the molecular behaviour of confined hydrogen are established. It is shown that sub-nanometer pores of spherical and cylindrical shape strongly limit the diffusion of H2, and thus, enhance the H2 storage capability of carbons with well-tailored pore structure. In mesoporous carbide-derived carbon, the formation of a hydrogen layer with reduced mobility close to the pore walls is observed. With the increase in the amount of confined hydrogen and the occupation of the centre pore area, the mobility of confined hydrogen increases in a jump–like fashion. Surprisingly, the increase of hydrogen diffusion is also observed at higher hydrogen loadings, indicating that cooperative H2–H2 interactions might play a role.

Exceptionally High CO2 Capture in an Amorphous Polymer with Ultramicropores Studied by Positron Annihilation.

A series of amorphous melamine-based polymer networks synthesized by Schiff base chemistry (SNW) were successfully prepared by varying the strut length. The pore structure was analyzed by gas adsorption and positron annihilation methods. Positron lifetime measurements indicate the existence of ultramicropores and also larger mesopores in the SNW materials. The sizes of micropores and mesopores are almost the same in these samples, which are about 0.7 and 16.5 nm, respectively. The relative number of micropores increases in the order of SNW-1 < SNW-2 < SNW-3, while the number of mesopores increases in the reverse order. N2 adsorption/desorption measurements also reveal micropores and mesopores in these materials. However, it gives an underestimation of the micropore volume. Benefiting from the abundant nitrogen content and high microporosity, the SNW materials exhibit exceptionally high CO2 capture ability, which reaches a maximum value of 18.3 wt % in SNW-3 at 273 K and 1 bar, followed by SNW-2 and SNW-1. This order is exactly the same as the order of micropore volume revealed by positron annihilation measurement, suggesting that micropores play a crucial role in the CO2 uptake. Our results show that positron can provide more precise information about the structure of micropores and thus can offer an accurate prediction for the adsorption capacity of complex porous materials.

A new correction method for mercury injection capillary pressure (MICP) to characterize the pore structure of shale

The economic and accurate measurement of micron or submicron size pores in shale is still a challenge. The mercury injection capillary pressure (MICP) measurement of shale particles is an effective method to evaluate the macropore structure, but it is questionable without proper data interpretation. In this study, the fractal theory was applied to identify the four stages of MICP measurement: Stage A is controlled by the interparticle voids in the particle assemblage; Stage B can reflect mercury intrusion into the pores of the shale; and Stage C and D indicate the shale matrix compression and pore structure change induced by high pressure, respectively. Based on the consistent fractal dimension derived from Stage A, the conformance volume induced by interparticle voids at each pressure step in Stage B was quantitatively simulated using the linear fitting method. The correction results show that simultaneous mercury filling of interparticle voids has an important impact on the pore volume in the pore size range larger than 1 μm. To cover the complete pore size range, the MICP data in Stage C and D were substituted by gas adsorption data.The new correction method for MICP data was verified by the good match between the MICP-gas adsorption combined porosity and the helium porosity of the same sample and by the good agreement between the pore size distribution (PSD) curves from the MICP and N2 adsorption measurements in their overlapped pore size range. Therefore, the MICP and gas adsorption methods can be used in conjunction to characterize the pore structure of shale in the complete pore size range. The application of this method is particularly good for the silty samples of lacustrine shale in the study area compared with the clayey samples. To further improve the convergence of different fluid injection methods, more efforts are needed to determine the optimum particle size class and optimum data interpretation model for different shale lithofacies.

Preparation of hollow glass microspheres@ZnSxSe1−x or copper-/indium-co-doped ZnSxSe1−x composite color pigments with enhanced near-infrared reflectance

To improve the near-infrared (NIR) solar reflectance of ZnSxSe1−x or copper-/indium-co-doped ZnSxSe1−x (ZnSxSe1−x:Cu/In) pigment with various colors, hollow glass microspheres (HGMs)@ZnSxSe1−x or ZnSxSe1−x:Cu/In composite pigments with a litchis-like core-shell structure were prepared with HGMs dispersed and surface-corroded in an alkali-solution under ultrasound and ZnSxSe1−x or ZnSxSe1−x:Cu/In particles deposited on HGMs surface via in-situ co-precipitation and subsequent sintering. The structure, particle size, morphology, color properties and thermal performance of the composite pigments were investigated by X-ray diffraction (XRD), Fourier transfer infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), laser diffraction particle size analysis, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), nitrogen gas adsorption method (BET), ultraviolet-visible-near-infrared (UV-VIS-NIR) spectroscopy and infrared irradiation image analysis. The results show that ultrasound can promote the corrosion of HGMs surface in alkali solution and form a mesh-pore structure, thus providing some heterogeneous nucleation sites on HGMs surface and favoring the nucleation of pigment precursors on HGMs surface in subsequent in-situ co-precipitation reaction. Compared to ZnSxSe1−x or ZnSxSe1−x:Cu/In pigments, HGMs@ZnSxSe1−x or ZnSxSe1−x:Cu/In composite pigments have a higher solar reflectance since the multiple layer reflections occur at the interface between the pigment particles and HGMs, thus leading to a better heat-reflective property. The NIR solar reflectance of HGMs@ZnSxSe1−x or ZnSxSe1−x:Cu/In composite pigments is 90.61 ± 0.052% or 73.13 ± 0.046%. The surface temperature of aluminum plate coated with HGMs@ZnSxSe1−x composite yellow pigment is 3.4 ± 0.2 °C or 9.6 ± 0.2 °C lower than that of aluminum plate coated or uncoated with ZnSxSe1−x pigment. This approach may shed a light on a promising composite structure design for high-performance solar reflective ‘cool materials’.

Electrochemical Capacitors Based on Electrodes Made of Lignocellulosic Waste Materials

Activated carbons have been obtained from the following organic precursors (lignocellulosic waste materials): willow, rapeseed straw, hemp shives, flax shives, switch grass, Virginia mallow and giant miscanthus. The activation process has been performed by using potassium hydroxide at 750 °C. Elemental analysis has been performed in order to determine the presence of heteroatoms in the carbon structure. Boehm titration was used to estimate the functional groups of carbon materials. The surface area was characterized using gas adsorption method. All the obtained samples have been used as electrodes for electrochemical capacitors operated in 1 M H2SO4. The electrochemical characterization was carried out using cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. All measurements proved that carbon materials obtained from different lignocellulosic wastes are suitable for energy storage applications. Moreover, the content of oxygen groups has great influence on the charge storage mechanism. Excessive oxygen content causes the disruption of surface conjugation of the carbon material.Graphical

Fractal study of adsorption-pores in pulverized coals with various metamorphism degrees using N2 adsorption, X-ray scattering and image analysis methods

As a highly heterogeneous material, the porous structure of coal is usually described by fractal dimension, which generally can be obtained by gas adsorption, light scattering and image analysis methods. In this paper, the pore structure (pore volume and specific surface area) and adsorption performance (Langmuir volume and Langmuir pressure) of 12 different rank coal samples were investigated by liquid nitrogen adsorption experiment (LNA) and methane isotherm adsorption experiment. And the fractal characteristics of these coals were studied by three fractal dimensions D1, D2 and D3 acquired from LNA and small angle X-ray scattering (SAXS) and scanning electron microscopy (SEM), respectively. Results indicate that the adsorption pore volume and specific surface area show U-shaped evolutionary trends during the coalification process. The changes of pore volume and specific surface area are dominated by the mechanical compaction and dehydration effects before the second coalification jump (Ro,max = 1.3%), while they are then mainly controlled by concomitant metamorphic pores until the fourth coalification jump (Ro,max = 3.7%). Langmuir volume first increases and then reaches a steady value at the third coalification jump (Ro,max = 2.5%) with the increasing coal rank, however, Langmuir pressure monotonously decreases during the whole coalification process. D1 and D2 exhibit a dramatically increase from Ro,max = 0.6% to Ro,max = 2.0% and then a slowly rise when Ro,max increases from 2.0% to 3.5%, which is relevant to the changes of pore structure and macromolecule structure in coal. D3 increases at a low speed first and then increases at a high speed with the increasing coal rank, which reflects the surface morphology of pores in coal. Fractal dimension D1, D2 and D3 can be used to depict the methane adsorption properties of coal in varying metamorphism degrees. Generally, D2 is larger than D1, which is because N2 adsorption can probe more macropores but SAXS can detect more micropores. Additionally, D1, D2 and D3 are all negatively related to PL. Our investigations also confirm that SAXS may be more superior to character the adsorption capacity of coal according to its highest relativity. This work clarifies the intrinsic sense and difference for characterising the surface irregularity by various methods, and provides an understanding for the experimental means relating to adsorption pores.

Determination of porous structure parameters of coal particles to describe thermal conversion processes

The results of determination of parameters of porous structure of coal and char particles are presented. They were determined using gas adsorption method and thermal decomposition of particles in air oxygen. The porous structure parameters allow predicting char reactivity change at different temperatures as well as during conversion in accordance with Random Pore Model (RPM-model).

Final report of CCQM-K153 Measurement of Specific Adsorption A [mol/kg] of N2 and Kr on nonporous SiO2 at LN temperature (to enable a traceable determination of the Specific Surface Area (BET) following ISO 9277)

CCQM key comparison K-153 Measurement of Specific Adsorption A [mol/kg] of N2 and Kr on nonporous SiO2 at LN temperature (to enable a traceable determination of the Specific Surface Area (BET) following ISO 9277) has been performed by the Surface Analysis Working Group (SAWG) of the Consultative Committee for Amount of Substance (CCQM). The objective of this key comparison is to compare the equivalency of the National Metrology Institutes (NMIs) and Designated Institutes (DIs) for the measurement of specific adsorption, BET specific surface area) of nonporous substances (sorbents, ceramics, catalytic agents, etc) used in advanced technology.In this key comparison, a commercial nonporous silicon dioxide was supplied as a sample. Eight NMIs participated in this key comparison, but only five NMI's have reported in time. All participants used a gas adsorption method, here nitrogen and (or) krypton adsorption at 77.3 K, for analysis according to the international standards ISO 15901-2 and 9277.In this key comparison, the degrees of equivalence uncertainties for specific adsorption nitrogen and krypton, BET specific surface area were established.KEY WORDS FOR SEARCHnonporous SiO2, Specific Adsorption of N2 and Kr, BET specific surface areaMain textTo reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Poly(vinylbenzyl chloride-co-divinyl benzene) polyHIPE monolith-supported o-hydroxynaphthaldehyde propylenediamine Schiff base ligand complex of copper(ii) ions as a catalyst for the epoxidation of cyclohexene.

Poly(vinylbenzyl chloride-co-divinyl benzene)-based polyHIPE monoliths of different porosities were prepared using high-internal-phase emulsions (HIPEs) containing a fixed amount of vinylbenzyl chloride (VBC, 6.0 g, 0.0393 mol) and divinyl benzene (DVB 4.0 g, 0.0308 mol) as the oil phase and different volume ratios of aqueous calcium chloride as the internal phase. Span-80 (2.0 g (4.67 mmol))-stabilized HIPEs were polymerized at 60 °C using potassium persulfate (0.4 g, 1.48 mmol) as the initiator. Upon varying the volume ratio of aqueous calcium chloride from 80 to 90%, the prepared polyHIPE monoliths have shown significant variations in their surface morphology, specific surface area (SA), and pore volumes (Vp) as confirmed by scanning electron microscopy (SEM) and a gas adsorption (BET) method. The prepared polyHIPE monoliths were anchored with o-hydroxynaphthaldehyde propylenediamine Schiff base ligand (HNPn) and then loaded with copper(ii) ions (HNPn–Cu) to act as a catalyst. The structural information of unsupported HNPn–Cu complexes was obtained by recording its FT-IR and UV-visible spectra. The amount of copper(ii) ions loaded onto HNPn ligand-anchored polyHIPE monoliths was determined by atomic absorption spectroscopic analysis. In comparison to unsupported HNPn–Cu catalyst, the polyHIPE monolith-supported HNPn–Cu catalyst has shown high catalytic activity (66.8%), product selectivity for epoxycyclohexane (ECH) (94.8%), high turn over number (0.028 mol mol−1 h−1) and low energy of activation (22.4 kJ mol−1) in the epoxidation of cyclohexene in the presence of hydrogen peroxide (H2O2) as an oxidant at 40 °C. The polyHIPE-supported HNPn–Cu catalyst also shows high reuse applications. Studies show that there is sufficient scope to develop polyHIPE monoliths with various properties for specific applications.

Electrochemical Determination of Porosity and Surface Area of Thin Films of Interconnected Nickel Nanowires

In this work, we demonstrate electrochemical methods for determination of porosity and surface area of thin films of interconnected nickel nanowires. While the standard porosimetry and gas adsorption methods lack sensitivity for characterization of thin metallic films, the electrochemical methods employing coulometry, cyclic voltammetry and electrochemical impedance spectroscopy can be applied to accurately determine textural properties of micron- and sub-micron thick nanostructured materials. Additionally, in this work we evaluated accuracy and precision of five electrochemical signals recorded during cyclic voltammetry and electrochemical impedance spectroscopy, which are commonly used for determination of electrochemical surface area (AECSA) of various nickel electrodes. By verifying the data with two independent surface characterization techniques, we found that the analysis based on surface-limited oxidation of nickel and on capacitive charging of nickel surface during hydrogen evolution reaction give the best accuracy and smallest errors. We also show that experimental conditions play a crucial role in the accurate determination of AECSA of nickel nanomaterials. If the influence of experimental conditions is not corrected for, the electrochemical surface area can differ by over 250% compared to the surface area determined with other methods.

Study of the impact of waste glasses types on pozzolanic activity of cementitious matrix

This paper deals with glass packaging and especially with different types of wastes from its recycling (Valued Product (VP), End-of-Wash Waste (EWW) and Optical Sorting (OS)), in order to make a comparative study of their pozzolanic activity and leaching behaviour for an environmental study. VP is used by industrials in the production of new packaging glass, and EWW and OS are residues which are not currently valued, so considered as undesirable parts. First of all, these three materials have been crushed to obtain a homogeneous particle-size distribution (with d50 = 6.5 µm). Then, they have been physically and chemically characterized by helium pycnometer (absolute density), gas adsorption method (specific surface), X-ray crystallography and X-ray Fluorescence for chemical composition. The second step of this study involves making 4 × 4 × 16 cm specimens according to standard NF EN 196-1 in order to compare a reference mortar (RM) with 100% of cement 42.5 R with samples including the three types of waste glass (VP, EWW and OS) in partial substitution of cement. Leaching tests performed on these wastes according to standard NF EN 12457-2 allowed to highlight a correlation between mobility of silicon, aluminium and calcium, and the mechanical performances obtained. Finally, SEM observations and study of cement paste in fresh state allowed to give an explanation of the results observed in macroscopic scale.

Research on the organic geochemical and mineral composition properties and its influence on pore structure of coal-measure shales in Yushe-Wuxiang Block, South Central Qinshui Basin, China

This paper uses coal-measure shales from Carboniferous-Permian in Yushe-Wuxiang Block as an example to study the physical properties of transitional coal measure shales, including geochemical properties (e.g. total organic carbon content (TOC), organic matter maturity and hydrocarbon generation potential); mineral composition determined by X-ray diffraction (XRD) and pore structure characteristics determined by gas adsorption methods. The results indicated that the transitional coal measure shales in Yushe-Wuxiang area mostly comprise type III kerogen and are mostly in the over-mature stage, with shales in the range of 1.86%–3.36%Ro. The TOC of transitional shales varied significantly, ranging from 0.10% to 34.37%. Clay minerals and quartz are major minerals in transitional shales, while the predominant clay minerals are illite-smectite mixed clay (I/S) and kaolinite. The total pore volume (TPV) and pore specific surface area (SSA) of investigated mud shales varies from 0.0071 to 0.023 cm3/g and 8.4059–18.2888 m2/g, respectively. The transitional shales mostly provide mesopores and macropores, whereas the micropores provide the main SSA. The TOC content has a distinct effect on the porosity and micropores volume but contributes little to the TPV and volumes of macropores and mesopores. Clay minerals are positively correlated with porosity, TPV and volumes of each class of pores, while quartz has an opposite effect. In the over-maturity stage, the increase of organic matter maturity will inhibit the development level of pores in shale. For the coal measure shales, I/S and illite contribute most to the pore development.

Polyoxometalate intercalated layered silicates: Highly efficient catalytic epoxidation of cyclooctene

Polyoxometalates (POMs) are a class of discrete anionic metal oxides with unique physical and chemical properties. Owing to excellent redox activity and structural adjustability, POMs-based catalysts have drawn wide attention during past decades. However, homogenous POMs exhibit high crystallinity behavior, which result in aggregation and/or recycling difficulty. Therefore, appropriate supports are highly needed to achieve well dispersion and stable loading of POMs on supports. Layered silicates are a large family of two-dimensionally arranged cation-exchangeable layered materials, whose frameworks are composed of SiO4 tetrahedral and possess interlayer exchangeable cations that are often hydrated. Most importantly and interestingly, layered silicates can turn to be anion exchangeable materials through covalent modification of imidazolium salts containing terminal triethoxysilyl groups onto interlayer surface. As a result, layered silicates can generate a large variety of interesting structures and properties. Among them, the layered octosilicate (Na8Si32O64(OH)8·32H2O, Oct) is an ideal support due to its optimal arrangement and high density of SiOH/SiO−. It is worthwhile noting that more than 80% of interlayered SiOH/SiO− groups can be silylated with imidazolium salts generally, and are converted to anion exchangeable sites. Herein, the ionic liquid modified layered silicates (IL-Oct) have been synthesized through immobilization of 1-octyl-3-(3-triethoxysilylpropyl)-4,5-dihydroimidazolium-hexafluorophosphate (Oim-PF6) on the interlayered surface of layered silicates. The cation exchangeable sites on layered silicates can be stoichiometrically converted to anion exchangeable sites after modification. Further ion exchange with K7PW11O39·12H2O (PW11), we are able to successfully fabricate the POM-intercalated layered silicates material that can be denoted as PW11-IL-Oct. The resulting PW11-IL-Oct has been fully characterized using a variety of spectroscopy methods including X-ray diffraction (XRD), scanning electron microscope (SEM), high resolution transmission electron microscopy (HRTEM), Brunauer-Emmett-Teller (BET) gas adsorption method, inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and energy dispersive spectrometer (EDS), etc. XRD pattern of PW11-IL-Oct reveals the basal spacing of 2.85 nm. The calculated gallery height value is 2.11 nm by subtracting the thickness of the host layer (0.74 nm). The BET surface areas of IL-Oct and PW11-IL-Oct are 5.7 and 15.4 m2/g, respectively. The loading amount of PW11 in PW11-IL-Oct is 7.34wt% by ICP-AES analysis. SEM images of PW11-IL-Oct show the square plate morphology with distortion and wrinkles on the surface. The SEM Mapping results suggest that the POMs clusters are highly dispersed and orderly arranged in the two-dimensional (2D) confined gallery spaces. Moreover, HRTEM images and EDS result of the PW11-IL-Oct reveal the highly dispersed black spots with the diameter approximately ~1 nm, which is in good agreement with the particle size of PW11 clusters. Epoxides are widely utilized as raw materials for sythesis of biologically important pharmaceuticals and fine chemicals. The application of epoxides is growing fast in the chemical industry, and gives rise to remarkable attention within the scientific community. In this work, by using the expoxidation of cyclooctene as model reaction, we demostrate that the PW11-IL-Oct exhibits excellent activity and stablity. The yield of epoxides product reaches up to 98% in 1 h with >99% selectivity. Moreover, after 10 recycles, no obvious loss of activity can be observed and the loading amount of PW11 in PW11-IL-Oct maintain 7.16wt%. HRTEM and Mapping results show almost no aggreaction of PW11 clusters in the layered silicates after epoxidation reaction. This work paves a pathway for fabrication of novel POMs-based catalysts.

Regularities of Modification of Active Carbons by Oxygen-Containing Manganese Compounds

Composite materials resulted from impregnation of active carbons with aqueous solutions of manganese (II) chloride were studied by the methods of gas adsorption, X-ray powder diffraction, atomic absorption spectrometry, energy-dispersive X-ray spectroscopy, and scanning electron microscopy. The texture and specific characteristics of porosity, microporosity, and composition of the prepared composites were found to change depending on the acidic or basic nature of the surface of initial carbons, conditions of impregnation, subsequent treatment, and calcination temperature. It was shown that, upon the impregnation of the “acidic” carbons, the total pore volume covered 8–11 times the micropore volume, as distinct from the “basic” samples, which showed only a two- or threefold excess. The specific BET surface determined for the “acidic” carbons exceeded the value found for the samples with a “basic” surface. It was confirmed that the prepared composites contained manganese in various manganese-oxide compounds including ramsdellite, hausmannite, manganosite, bixbyite, and partridgeite at concentrations of 23–48 wt %.

Hydrothermal Degradation of Cellulose at Temperature from 200 to 300 °C

Cellulose was treated with subcritical water in a batch reactor within a temperature range of 200–300 °C and reaction time of 5–60 min. The main phases, such as water-soluble fraction, acetone-soluble fraction and solid residue (remaining cellulose or char), were separated and analyzed. The analysis of water-soluble phase was done by HPLC equipped with UV and RI detector, whereas acetone-soluble phase was analyzed by GC–MS. Total sugar content was determined by the phenol-sulfuric acid colorimetric method. The properties of char such as specific surface area, pore volume, and pore diameter were determined by gas adsorption method. A water-soluble phase mainly consists of sugar monomers and monomer degradation products, while acetone-soluble phase, referred to also as bio-oil, consists of furans, phenols, carboxylic acids, aldehydes, ketones, and high molecular compounds. The reaction mechanism of cellulose in subcritical water has been proposed based on the obtained results.

Porosity changes in progressively pulverized anthracite subsamples: Implications for the study of closed pore distribution in coals

Coal samples for low-pressure nitrogen (N2) adsorption measurement in previous work cover a large particle size range (from 0.075 to 4.75 mm). However, minimal attention has been paid to the effect of coal particle size on pore structure using gas adsorption methods. Anthracite coal collected from the Zhina Coalfield, China, was crushed, subsampled, and sieved to eight particle size ranges: 1–2 mesh (8000–25400 µm), 40–50 mesh (270–380 µm), 50–70 mesh (212–270 µm), 70–90 mesh (160–212 µm), 90–160 mesh (96–160 µm), 160–200 mesh (75–96 µm), 200–300 mesh (48–75 µm), and >300 mesh (<48 µm). The adsorption–desorption isotherms of each subsample were measured using N2 at 77.35 K to compare differences in pore structure characteristics. The results of the N2 adsorption tests show that particle size has a significant effect on pore volume, specific surface area, and pore size distribution of coal. Specifically, decreasing coal particle size results in continuous increase in macro- and mesopore volumes and specific surface areas. This can be attributed to the fact that smaller-sized coal particles open more of the previously closed pores, which are then accessible to adsorping gas. The contribution of closed pores to the total pore volume is 94.94% in the pore aperture range of 3.1–370 nm. The volume of closed macropores varies from 48.96 to 84.69% of the total closed pore volume. According to optical microscope and SEM observations of the Zhina Coalfield subsamples, massive gas pores exist in an isolated form with poor connectivity; some plant tissue pores are filled by pyrites and clay minerals, and may be totally occluded. Thus, gas pores contribute the dominant amount of the closed pore volume. In addition, different Zhina Coalfield subsamples show varied hysteresis loop shapes, indicating that closed pores in coal possess a variety of pore morphologies and sizes. To improve the accuracy and comparability of the pore structure of coal, we propose >300 mesh as the preferred particle size of coal for all low-pressure N2 adsorption measurement in future work. Furthermore, caution must be used in evaluating coal bed methane resource recovery potential as coal possesses high closed porosity; failure to account for this will result in an overestimation of the amount of gas that can be recovered from coal seams during production.

Pore characteristics and dominant controlling factors of overmature shales: A case study of the Wangyinpu and Guanyintang Formations in the Jiangxi Xiuwu Basin

Because of the great potential for hydrocarbon generation, the Lower Cambrian Wangyinpu and Guanyintang Formations of the Jiangxi Xiuwu Basin have become the most important targets for shale-gas exploration in the Jiangxi province. We investigate the pore characteristics and main controlling factors of overmature shale using field emission-scanning electron microscopy, image-processing software (i.e., the Particles [Pores] and Crack Analysis System), X-ray diffraction, and gas-adsorption experiments. The results show that the shales have a high abundance of organic matter (OM), over maturity, and highly siliceous mineral content. The kerogen type is identified as type I. OM pores are the most developed, followed by interparticle (interP) pores and intraparticle (intraP) pores. We combine complementary image processing and gas-adsorption methods to reveal that micropores are mainly from OM pores; mesopores are from OM pores and interP pores; and macropores are from OM pores, interP pores, and intraP pores. Although the number of micropores is at a maximum, the total contribution of mesopores and macropores to the pore volume (PV) is larger than that of micropores. However, the specific surface area (SSA) is mainly from the micropores. OM content and maturity are the main controlling factors for the development of pore structures. Because of overmaturity, OM loses its potential for hydrocarbon generation and new pores cannot be produced. Gas loss leads to reservoir pressure drop, and the pores generated during the mature stage collapse and even disappear because they lack support. Therefore, PV, SSA, and porosity decrease when the OM content is more than 10%. When the OM content is less than 10%, most of the OM pores are preserved because they are protected by the skeleton particles.