Gas Physisorption Research Articles

Batch and fixed bed column selective adsorption of C6, C8 and C10 linear α-olefins from binary liquid olefin/paraffin mixtures onto 5A and 13X microporous molecular sieves

The separation of gaseous olefin/paraffin mixtures by physical adsorption and π-complexation chemical adsorption has been widely investigated, while studies on the adsorption of liquid olefin/paraffin are much rarer. One of the most important reasons is that it is difficult to determine the actual adsorption capacity of liquid phase adsorption directly through experiments, and the study of liquid olefin/paraffin mixtures adsorption capacities has not been sufficiently systematic. In this paper, the adsorption of C6, C8 and C10 linear α-olefins onto 5A and 13X molecular sieves from binary liquid olefin/paraffin mixtures in batch and fixed bed column systems was systematically investigated.In batch experiments, a measurement method of actual adsorption capacity was established, and the actual adsorption capacities of 5A and 13X were determined by the liquid phase concentration difference and pore volume correction with the help of gas chromatography (GC) and physisorption apparatus. The adsorption selectivity was obtained through experimental data and the binary liquid adsorption theory. Experimental data were fitted to the Freundlich and Langmuir isotherms to determine the adsorption characteristics. The adsorption kinetics were well fitted with pseudo-second-order and Crank models. In the fixed bed column experiments, breakthrough curves were obtained and the dynamic adsorption characteristics were analyzed through breakthrough curves. The effects of operational conditions, such as adsorbents, flow rate and feed concentration on the column dynamics were examined. Both Thomas and Yoon-Nelson models gave satisfactory fits to the experimental data of dynamic adsorption in a fixed bed column.

Alternative determination of the skeletal density of solids using a manometric gas physisorption apparatus: A systematic and methodological study

Abstract The comparison of skeletal densities determined by standard gas pycnometer and manometric gas physisorption apparatus was performed for 42 solid materials differing in density (1.4–11.3 g/cm3) chemical nature (metals, aluminosilicates, carbons), physical form (granules, powders) and porosity (from non-porous to highly porous). Under nearly identical experimental conditions with helium as probe gas, the use of both types of equipment provides practically the same values of densities (deviations below 8%) for metallic samples and aluminosilicates. The results differ more significantly for porous carbons especially for highly porous materials with the surface area above 400 m2/g (deviations up to 70%). Analysis of possible reasons of this disagreement leads to finding that in gas physisorption apparatus it is necessary to use extra purging with helium and prolong the time of equilibration of the system to achieve results comparable with values obtained by standard procedure with gas pycnometer for highly porous samples. Contrary, the detailed investigation of pressure changes during equilibration stage of measurement (available only with gas physisorption apparatus) of porous carbonaceous samples showed a gradual increase of pressure (consequently decrease of determined density) with the time of equilibration, which is expected to be due to evolution of gases from the porous system even after outgassing. The use of short equilibration time is recommended for such kind of samples to obtain realistic values of skeletal density.

Metal- and halogen-free synthesis of ordered mesoporous carbon materials

Abstract Mesoporous carbon materials are of great interest as catalyst supports. However, the presence of impurities such as the metal or halide ions which are often used to catalyse the polymerisation and condensation reactions in their preparation can be poisonous to the final catalyst product. For this reason, in this work, metal- and halogen-free mesoporous polymer and carbon materials (OMCs) were synthesised using a modified two phase method employing alternative polymerisation and condensation catalysts. The OMC materials synthesised exhibit a highly ordered two dimensional hexagonal arrangement of cylindrical mesopores, as revealed by small angle XRD, gas physisorption and TEM analysis, and have typical specific surface areas of ca. 600 m2/g, pore size of ca. 7.0 nm, and pore volume of approximately 0.60 cm3/g. Their physical evolution with increasing calcination temperature is examined as are the effects of varying synthesis parameters on the nature of the final mesostructure.

Influence of molecular architecture of Si-containing precursors and HF chemical treatment on structural and textural features of silicon oxycarbide (SiOC) materials

Silicon oxycarbide (SiOC) ceramics were obtained from two polymeric precursors to investigate the influence of pyrolysis temperature and HF chemical treatment on their structures and textural features. DVDH polycyclic polymer was prepared from 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, and 2,4,6,8-tetramethylcyclotetrasiloxane, whilst PMFV linear from poly [dimethylsiloxane-co-diphenylsiloxane] divinyl terminated. SiOC-based ceramics were obtained by pyrolysis under argon at 1000 and 1500 °C and also etched in HF solution. FT-IR, TG, XRD, N2 gas physisorption at 77 K and elemental analyses were used to characterize the obtained materials. The results revealed information about controlling chemical structure of SiOC ceramics through the combination of adequate precursor, thermal and chemical treatment. The study demonstrated the dependence of the polymeric precursors structure over the ceramic yield and Cgraphitic and β-SiC crystalline phases produced. HF etching allowed the fabrication of porous materials containing carbon conducting and SiC semiconducting phases more exposed into SiOC matrices, thus revealing potentialities to future electrochemical investigations.

Meltable Mixed-Linker Zeolitic Imidazolate Frameworks and Their Microporous Glasses: From Melting Point Engineering to Selective Hydrocarbon Sorption.

Porous glasses from metal-organic frameworks (MOFs) represent a new class of functional inorganic-organic materials, which have been proposed for applications ranging from solid electrolytes to radioactive waste storage. So far, just a few zeolitic imidazolate frameworks (ZIFs), a subset of MOFs, have been reported to melt and the structural and compositional requirements for MOF melting and glass formation are poorly understood. Here, we show how the melting point of the prototypical ZIF-4/ZIF-62(M) frameworks (composition M(im)2-x(bim)x; M2+ = Co2+, Zn2+; im- = imidazolate; bim- = benzimidazolate) can be controlled systematically by adjusting the molar ratio of the two imidazolate-type linkers im- and bim-. By covering the entire range from x = 0 to 0.35, we unveil a delicate transition from ZIF materials showing sequential amorphization/recrystallization to derivatives exhibiting coherent melting and a liquid phase that is stable over a large temperature window. The melting point of this ZIF system is a direct function of x and can be lowered from ca. 430 °C to only 370 °C, by far the lowest melting point reported for a three-dimensional porous MOF. On the basis of our results, we postulate compositional requirements for ZIF melting and glass formation, which may guide the search for other meltable ZIFs. Moreover, gas physisorption experiments establish that the ZIF glasses adsorb technologically relevant C3 and C4 hydrocarbons. Importantly, the adsorption kinetics are much faster for propylene compared to propane and are also dependent on the im-:bim- ratio, thus demonstrating the potential of these ZIF glasses for applications in gas separation.

Pore connectivity and water accessibility in Upper Permian transitional shales, southern China

Abstract Pore connectivity of shale controls shale gas migration and production behavior. The pore connectivity and water accessibility in clay-rich Upper Permian transitional shales remain unclear. Contrast matching small-angle neutron scattering (CM-SANS) tests were used to determine the accessibility of water to pores in the transitional shales. Complementary analyses with SANS, gas (CO2 and N2) physisorption isotherm, mercury intrusion capillary pressure (MICP), helium ion microscopy (HIM), as well as field emission-scanning electron microscopy (FE-SEM) were conducted to study the pore connectivity and distribution characteristics of closed pores. The results show that closed pores (inaccessible to nitrogen molecules and mercury) are mainly distributed in pore diameters ＜10 nm and associated with organic pores and interlayer spaces of illite-smectite mixed-layer mineral. The pore volume values obtained from MICP and N2 adsorption underestimate the large pores (pore diameters ＞100 nm) in shales. Based on deuterated water CM-SANS tests, 87–98% of the pores (2–200 nm diameters) are water-connected in transitional samples. The low accessibility to water is at pore-sizes of 5–10 nm and 20–30 nm. Results from in-situ gas contents show that closed pores have a certain gas bearing capacity, but micropores (pore diameters ＜2 nm) control the gas occurrence in transitional samples. The connectivity of the organic pore network and between organic pores and surrounding interparticle pores is directly supported by FE-SEM and HIM imaging. Overall, improving pore-fracture connectivity through effective fracturing techniques is a means of mitigating the rapid decline in shale gas production.

Ionization‐Facilitated Formation of 2D (Alumino)Silicate–Noble Gas Clathrate Compounds

AbstractThe nanoscale confinement of noble gases at noncryogenic temperatures is crucial for many applications including noble gas separations, nuclear waste remediation, and the removal of radon. However, this process is extremely difficult primarily due to the weak trapping forces of the host matrices upon noble gas physisorption. Herein, the formation of 2D clathrate compounds, which result from trapping noble gas atoms (Ar, Kr, and Xe) inside nanocages of ultrathin silica and aluminosilicate crystalline nanoporous frameworks at 300 K, is reported. The formation of the 2D clathrate compounds is attributed to a novel activated physisorption mechanism, facilitated by ionization of noble gas atoms. Combined X‐ray photoelectron spectroscopy (XPS) and density functional theory (DFT) studies provide evidence of an initial ionization process that significantly reduces the apparent trapping barrier. Noble gas ions become neutralized upon entering the cages, and their desorption requires unprecedentedly high temperatures, even in ultrahigh vacuum conditions. From 2D aluminosilicate films these temperatures are 348 K (Ar), 498 K (Kr), and 673 K (Xe). DFT calculations also predict that Rn can be trapped in 2D aluminosilicates with an even higher desorption temperature of 775 K. This work highlights a new ionization‐facilitated trapping mechanism resulting in the thinnest family of clathrates ever reported.

3D Mapping of Gas Physisorption for the Spatial Characterisation of Nanoporous Materials.

Nanoporous materials used in industrial applications (e. g., catalysis and separations) draw their functionality from properties at the nanoscale (1-10 Å). When shaped into a technical form these solids reveal spatial variations in the same properties over much larger length scales (1 μm-1 cm). The multiscale characterization of these systems is impaired by the trade-off between sample size and image resolution that is bound to the use of most imaging techniques. We show here the application of X-ray computed tomography for the non-invasive spatial characterization of a zeolite/activated carbon adsorbent bed across three orders of magnitude in scale. Through the unique combination of gas adsorption isotherms measured locally and their interpretation by physisorption analysis, we determine three-dimensional maps of the specific surface area and micropore volume. We further use machine learning to identify and locate the materials within the packed bed. This novel ability to reveal the extent of heterogeneity in technical porous solids will enable a deeper understanding of their function in industrial reactors. Such developments are essential towards bridging the gap between material research and process design.

Large-scale study for the photocatalytic degradation of paracetamol using Fe2O3/TiO2 nanocomposite catalyst and CPC reactor under natural sunlight radiations

Heterogeneous photocatalysis is a promising advanced oxidation process for the degradation of emerging contaminants. In this regard, Hematite (α-Fe2O3) doped TiO2 nanocomposite catalyst was synthesized via sol-gel method. The catalyst was prepared in large quantities (225 g) comparatively with other studies and characterized by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Energy-dispersive X-ray (EDX), and nitrogen gas physisorption studies. The bandgap of the synthesized catalyst was determined using UV–vis diffused reflectance spectroscopy (DRS), and the point of zero charge (PZC) was identified by measuring the zeta potential (ζ-potential) of the nanoparticles. A large-scale study was conducted using a modified Compound Parabolic Collector Reactor (CPCR) for the degradation of paracetamol under natural sunlight irradiations. The operating parameters including the initial concentration of paracetamol, initial pH of the solution, and catalyst loading were optimized using face-centered central composite design (FCCD) based on response surface method (RSM) to obtain the maximum degradation efficiency of paracetamol.•The simplified and direct sol-gel method described helps in the synthesis of a novel nanocomposite catalyst (Fe2O3/TiO2) in large quantities while maintaining good characteristics compared to other methods.•The described treatment method using the modified CPCR will allow the degradation of paracetamol in a more sustainable and green manner.•Optimizing the operating parameters that have a significant influence on the degradation of paracetamol will contribute towards higher degradation rates.

Improved capacitance of NiCo2O4/carbon composite resulted from carbon matrix with multilayered graphene

The optimized electric and ionic conductivity of metal oxides with pseudo-capacitive properties can greatly improve their electrochemical performances and can effectively amplify their applications in super-capacitors. Carbon spheres with multilayered graphene formed in their matrix are prepared by annealing them with sodium metal and they are combined with NiCo2O4 spheres by a simple hydro-thermal treatment. Structures and electrochemical performances of resulted samples are examined with X-ray diffraction, Raman scattering spectra, X-ray photoelectron spectroscopy, infrared spectroscopy, electron microscopy, gas physisorption, cyclic voltammetry and electrochemical impedance spectra, respectively. The largest specific capacitance of resulted composites is measured about 920 F g−1 at 1 A g−1, which is about 3.7 times larger than that of pure carbon spheres and 2.8 times larger than that of pure NiCo2O4 spheres. The formation of multilayered graphene in the matrix of carbon spheres not only increases the high specific capacitance based on electric double layers, but also makes metal oxides combined with them display greatly increased pseudo-capacitance. The electric and ionic conductivity of resulted composites with various weight ratios of NiCo2O4 and carbon spheres are respectively investigated and their effects on their electrochemical performances are also discussed.

Direct solution-based reduction synthesis of Au, Pd, and Pt aerogels

Abstract

Pore structure, wettability and tracer migration in four leading shale formations in the Middle Yangtze Platform, China

Deposited in different sedimentary settings, four leading shale formations (Late Ordovician Wufeng, Early Silurian Longmaxi, Late Permian Dalong, and Early Jurassic Dongyuemiao Shales) are currently the most promising zones for shale gas development in the Middle Yangtze Platform of South China. Based on complementary tests [low pressure gas physisorption, mercury injection capillary pressure (MICP), contact angle measurement, fluid imbibition into initially dry shale, and tracer diffusion into initially fluid-saturated shale followed by tracer mapping with laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS)], this work investigates their pore structure (both geometry and connectivity) and wettability characteristics, as well as the coupled effects of these characteristics on fluid flow and tracer migration.Pores <50 nm account for the majority of the pore volume in these organic shales. The shapes of hysteresis loop from gas physisorption show that the pores are mostly inkbottle-shaped in Wufeng, Longmaxi and Dongyuemiao Shales, while they are mostly narrow plate- or slit-like shaped pores in Dalong Shale. These four organic shales are strongly oil-wetting and moderately water-wetting. According to the imbibition behaviors toward aqueous (deionized water) and oleic (n-decane) phases, hydrophobic pores are better connected than hydrophilic pore networks, which is consistent with the measured contact angles. Diffusion of nano-sized nonsorbing (perrhenate [ReO4−]) and sorbing (cesium [Cs+]) tracers into brine-saturated shales indicates a high spatial variability and limited pore connectivity in these organic shales. The effective diffusion coefficient values are on the order of 10−13 m2/s with an associated geometric tortuosity ranging from 11.1 to 41.4. Due to the limited edge-connected pore spaces and low diffusion coefficients, the migration of hydrocarbons will be very slow from the shale matrix to hydraulically created fractures, with the initially high production of hydrocarbons from connected pore spaces near the sample edge (e.g., fracture face).

Characterization of micro-nano pore networks in shale oil reservoirs of Paleogene Shahejie Formation in Dongying Sag of Bohai Bay Basin, East China

Abstract For typical blocky, laminated and bedded mudrock samples from the Paleogene Shahejie Formation in the Dongying Sag of Bohai Bay Basin, this work systematically focuses on their structure characterization of multiple micro-nano pore networks. A use of mercury injection capillary pressure (MICP) documented the presence of multiple μm-nm pore networks, and obtained their respective porosity, permeability and tortuosity. Different sample sizes (500-841 μm GRI fractions, 1 cm-sized cubes, and 2.54 cm in diameter and 2-3 cm in height core plugs) and approaches (low-pressure N 2 gas physisorption, GRI matrix permeability, MICP, helium pycnometry, and pulse decay permeameter) were used to measure pore size distribution, porosity and permeability. The average porosity and matrix permeability determined from MICP are (6.31±1.64)% and (27.4±31.1)×10 -9 μm 2 , the pore throat diameter of pores is mainly around 5 nm, and the median pore throat diameter based on 50% of final cumulative volume is (8.20±3.01) nm in shale. The pore-throat ratios decrease with a decrease of pore size diameter. Moreover, the permeability of shale samples with lamination is nearly 20 times larger than matrix permeability. The geometrical tortuosity of the nano-scale 2.8−10.0 nm pore networks is 8.44 in these shales, which indicates a poor connectivity of matrix pore network and low flow capability. Overall, the variable and limited pore connectivity of shale samples will affect hydrocarbon preservation and recovery.

Pore Structure Characteristics of Marine–Continental Transitional Shale: A Case Study in the Qinshui Basin, China

Organic shales deposited in a marine–continental transitional environment are well developed in the Qinshui Basin, northern China. However, previous research concerning shales has predominantly focused on marine shales and barely on marine–continental transitional shales. In this study, geochemical and mineralogical analyses were performed on 23 marine–continental transitional shale samples obtained from four wells in a currently active shale gas play, Yushe-Wuxiang area in the Qinshui Basin. Furthermore, the complex pore structure of the transitional shales was well characterized by scanning electron microscopy (SEM), mercury intrusion, and low pressure gas physisorption. The results showed the abundance of organic matter (OM) with an average of 2.03% in the target shales. The dominant minerals in the shale were found to be clay and quartz, and the major clay minerals type is kaolinite and Illite/smectite. SEM images clearly exhibited that the pores in the shale matrix are mainly associated with clay min...

Micro-/Mesoporous Polymer-Derived Ceramic Structures Using Molecular Porogens

Micro-and mesoporous ceramics demonstrate promising properties for applications in energy-and environment-related fields. Due to their high thermal and chemical stability, they are particularly suited for separation in harsh thermal or chemical environments, e.g. as membrane materials for the separation of gas mixtures. In this work, we present the use of a preceramic poly(vinyl)silazane in combination with organic molecular porogens for the generation of micro-/mesoporous non-oxide ceramic structures. Microporosity is generated during the pyrolytic conversion process, while the addition of molecular porogens, to be removed during the heat-treatment, enables further control of the micro-/mesopore structure. A systematic investigation of various porogens showed the suitability of polystyrene for this purpose. Based on these findings, the pore structure and pore connectivity of polysilazane/polystyrene-derived structures were evaluated using gas physisorption and small angle X-ray scattering techniques. This material was further investigated by preparing asymmetric membranes consisting of micro-/mesoporous polysilazane/polystyrene-derived layers on porous ZrO2/TiO2 supports. The potential for gas separation applications was then demonstrated by single-gas permance evaluation of the generated structures at temperatures up to 300 °C.

Pore Structure Characterization of Shale Using Gas Physisorption: Effect of Chemical Compositions

In this study, the pore structure characteristics of Canadian Horn River basin shales with various chemical compositions were evaluated using gas physisorption analyses. The samples used in this research were obtained from two different regions (shallow and deep regions) of rock cuttings during the drilling of the shale gas field located in Horn River basin. The pore size, specific surface area, total pore volume, micropore surface area, and micropore volume of the shale samples were measured using both nitrogen and CO2. The results indicated that the pore size was not a function of chemical composition, while distinct trends were observed for other macroscopic and microscopic pore-related properties. In particular, the greatest specific surface area and total pore volume were observed for silica-rich carbonate shales, while clay-rich siliceous shales exhibited the greatest micropore volume and micropore surface area. The trends clearly suggested that macroscopic and microscopic pore-related properties of the Canadian Horn River basin shales were closely related to their chemical composition. Furthermore, a stronger correlation was observed between the quartz content and the micropore-related physical properties of shales (i.e., the micropore surface area and micropore volume) in comparison to other properties.

Pore characterization of isolated organic matter from high matured gas shale reservoir

Knowledge of pore structure of isolated organic matter (OM) provides guidance for better understanding the origin, distribution and characterization of pore system in gas shale reservoir, and can be used to better comprehend the storage and transport mechanism of natural gas in shale reservoir. Pore structure characteristics of isolated organic matters and its corresponding bulk shales were investigated for five high matured marine shale samples from the Lower Silurian Longmaxi formation in south China using X-ray diffraction (XRD), total organic carbon content (TOC) tests, field emission scanning electron microscope (FE-SEM) observation and ultra-low pressure nitrogen gas physisorption. The results indicate that OM hosted pores are abundant in bulk shale samples under FE-SEM observation. The BET Surface area and the BJH pore volume of isolated OM are approximately three times greater than that of bulk shale samples. Pore size distribution (PSD) of isolated OM from five shale samples show a consistent variation pattern. Additionally, with increasing TOC content, the PSD curves of isolated OM gradually grow down as result of the ductility of OM. Bimodal PSD in surface area and unimodal PSD in pore volume exist in both isolated OM and bulk shale samples, indicating surface area is mainly associated with micropores and fine mesopores (<10nm) and larger pores are the dominate contributor to pore volume. Paralleled variation trends in PSD, especially in the pore size smaller than 4nm, are observed between isolated OM and its corresponding bulk shale samples. However, the PSD divergences at the pore size larger than 10nm between different samples are obvious. Therefore the pore network in gas shale reservoir is predominantly associated with the organic matter, especially small pores, and the mineral compositions are expected to be responsible for lager pores.

Two-Stage Crystallization of Meso- and Macroporous MFI and MEL Zeolites Using Tributylamine-Derived Diquaternary Ammonium Cations as Organic Structure-Directing Agents

Abstract Meso- and/or macroporous zeolites have received particular attention because the presence of secondary meso- and/or macropores, in addition to the intrinsic micropores of zeolites, can provide additional cavities at a nanometer-length scale and shorten molecular diffusion path lengths. Here, synthesis of meso- and macroporous MFI and MEL aluminosilicate zeolites via a two-stage crystallization method using diquaternary ammonium cations (N,N,N,N′,N′,N′-hexabutylheptanediammonium, Bu6-diquat-7) as an organic structure-directing agent (OSDA) is described. In this two-stage process, both low- and high-temperature stages were found to be crucial for the formation of zeolites. By carefully varying the amount of sodium hydroxide in the reactants, both MFI and MEL zeolites can be obtained with the same OSDA. It was revealed that Bu6-diquat-7 was more selective to the formation of MFI and MEL zeolites than its monoquaternary counterpart (i.e., tetrabutylammonium) under the present synthesis conditions. Interestingly, the synthesis time of the first (low temperature) stage highly influenced the particle sizes of the resulting zeolites; zeolites with smaller sizes were obtained when the synthesis time was prolonged. Gas physisorption analyses and scanning transmission electron microscopy observation suggested that the obtained zeolites possessed ink-bottle-like pores consisting of meso- and macroporous internal cavities with very narrow pore necks.

Sol-gel synthesis of less expensive mesoporous titania-tin dioxide systems: Investigation of the influence of tin dioxide on the phase structure, morphology and optical properties

Herein the influence of SnO2 on the optical, morphology and phase structure of mesoporous TiO2-SnO2 composites was examined. Composites with Sn/Ti ratio ranging from 0.1 to 5 were synthesized using less expensive sources in the absence of additives. The obtained samples were examined by XRD, HRTEM, SEM-EDAX, XPS, UV–vis DRS, XRF, TGA and nitrogen gas physisorption studies analyses. The physicochemical properties of the TiO2-SnO2 systems depended mainly on the Sn-to-Ti ratio, calcination temperature and the interaction between Sn4+and Ti4+. XRD results depicted that samples with Sn/Ti=0.1 calcined at ≤600°C exhibited pure anatase TiO2 crystals and the tendency of increasing Sn4+ content facilitated a phase transformation to attain rutile structure. Optical analyses of the samples showed that the absorption of the samples can be extended into the visible region. This study provides a systematic and economical method for large-scale production of TiO2 based composites with desirable properties for various applications.

Adsorption Properties from Pressure-Varying Langmuir Parameters: n-Butane and Isobutane on Activated Carbon

Isothermal adsorption data for n-butane and isobutane on BAX 1500 activated carbon reported by Whittaker et al. [Whittaker, P. B.; Wang, X.; Zimmermann, W.; Regenauer-Lieb, K.; Chua, H. T. Predicting the Integral Heat of Adsorption for Gas Physisorption on Microporous and Mesoporous Adsorbents. J. Phys. Chem. C 2014, 118 (16), 8350−8358, DOI: 10.1021/jp410873v] were modeled with pressure-varying Langmuir adsorption parameters using flexible least squares for pressure-varying linear regression. Coverage varies with pressure and at distinct transitions; when the ratio of uptake to capacity is 0.69 ± 0.04, monolayer coverage is achieved or micropore volume is filled. Monolayer transitions are observed for the 298, 323, and 348 K isotherms, while micropore volume transitions are only apparent for the 298 K isotherms. The resultant adsorbent surface area is 1335 ± 25 cm2 g–1, and the micropore volume is 0.48 ± 0.03 cm3 g–1. Molecular areas, corresponding to excluded adsorbate areas, are dependent upon the temp...