Mesopore Volume Research Articles

Characterizing pore size distribution of high maturity shales and main controlling factors analysis: A case study of Permian Gufeng Formation in the Lower Yangtze region, China

Shale gas resource is heterogeneously distributed in Permian Gufeng Formation in the Xuancheng area, Anhui Province. This research aims to investigate the pore size distribution of the Permian Gufeng shales via 16 core samples analyses, combined with x‐ray diffraction, low‐pressure nitrogen gas adsorption (N2‐GA), CO2 gas adsorption (CO2‐GA) and scanning electron microscopy (SEM). N2‐GA shows that the nanopores (diameter < 10 nm) are dominated and developed in the samples. The Brunauer–Emmett–Teller (BET) specific surface area (SSA) of the samples ranges from 6.7051 to 29.4384 m2/g, with a mean of 16.0931 m2/g. CO2‐GA results illustrate that micropore is well developed, especially the pores with a diameter of 0.5–0.6 and 0.8 nm. The total organic carbon (TOC) content of the Gufeng shale ranges from 0.42% to 12.82% with an average content of 6.44%, which has both positive correlation with pore SSA and pore volume, while carbonate mineral content has a positive correlation with pore SSA and the volume of macropore and mesopore. Clay mineral content is a negative correlation with pore SSA and micropore volume. Therefore, the high‐maturity Permian Gufeng shale could be more preferential high‐quality gas shale reservoir for further exploration and development in the Xuancheng area, which has more than 4% TOC content, relatively higher carbonate mineral content and relatively lower clay mineral content.

Investigation of the transformation of organic matter of carbonate deposits of the Semiluksky–Mendymsky horizon under hydrothermal conditions

The paper presents the results of studies on the transformation of the organic matter of siliceous-clayey carbonate rocks of the Semiluksko–Mendymsky horizon of the Romashkino oil field in a hydrothermal fluid for an hour (with a water-to-rock ratio of 33) at 340°C and 380°C and pressures of 17 and 20 MPa. As a result of hydrothermal treatment, at 340°C and 17 MPa, based on nitrogen porosimetry and electron microscopy data, transformations of rock-forming minerals in the rock are observed. They lead to an increase in the volume and average diameter of mesopores in it and the formation of micropores, as well, which improve its filtration properties. At the same time, the amount of kerogen in the composition of the organic matter decreases and the yield of the petroleum hydrocarbon extract increases, in which, according to the SARA analysis, the content of asphaltenes increases and the content of resins, aromatic and saturated hydrocarbons decreases. In the composition of aroatic hydrocarbons, the proportion of alkyltrimethylbenzenes and dibenzothiophenes increases, phenanthrene homologues appear, and in the composition of saturated hydrocarbons, the amount of iso-structure alkanes decreases relative to the content of linear alkanes. Raising the temperature and pressure of the hydrothermal fluid to 380°С and 20 MPa increases the degree of kerogen conversion from 12.4% to 23.6%. At the same time, changes occurring in the component composition of petroleum hydrocarbon extracts remains similar to the experiments carried out at 340°C and 17 MPa; the content of naphthalenes decreases, the content of dibenzothiophenes increases and C11–C17, C19–C22 alkyltrimethylbenzenes appear. According to IR spectroscopy, with increasing temperature and pressure of the hydrothermal fluid the intensity of the absorption bands of the aromatic ring, aliphatic fragments, and oxygen-containing groups increases in resins; the structural-group composition of asphaltenes changes little: aromaticity and the content of condensed structures slightly increase. The revealed distinctive features in the composition of organic matter after hydrothermal impact on siliceous-clayey carbonate rocks confirm the concept of staged destruction of kerogen, when large structural heteroatomic blocks (asphaltenes) are split off at the initial stages. Changes occurring in the composition of petroleum hydrocarbon extracts indicate their involvement in the process of hydrothermal transformation of organic matter of siliceous-clayey carmbonate rocks with the predominant reactions of dehydrogenation of naphthenic compounds and oxidative polycondensation of aromatic structures. The data of electron microscopy and nitrogen porosimetry of rocks after hydrothermal exposure at 380°С and 20 MPa indicate a deterioration in their reservoir properties. The most optimal thermobaric conditions of the hydrothermal fluid for the generation of petroleum hydrocarbons from kerogen of siliceous-clayey carbonate deposits of the Semiluksko–Mendymsky horizon of the Romashkino field, which improve their reservoir properties, are 340°С and 17 MPa; with implication of hard-to-recover heavy hydrocarbon resources and well-established catalytic methods of in-situ conversion.

Haloacetonitriles adsorption using a low-cost adsorbent derived from canvas fabric

The characteristics of canvas fabric-derived adsorbents and their removal efficiency on five haloacetronitriles (HANs) were investigated. In addition, the effect of chemical activation with ferric chloride (FeCl3) and ferric nitrate (Fe(NO3)3) solutions on HANs removal efficiency was determined. The results indicated that the surface area increased from 262.51 m2/g to 577.25 and 370.83 m2/g, respectively, after being activated with FeCl3 and Fe(NO3)3 solutions. Increases in surface area and pore volume had a direct impact on the effectiveness of HANs removal. As compared to the non-activated adsorbent, the activated adsorbent effectively removed five species of HANs. TCAN was highly removed by the Fe(NO3)3-activated adsorbent (94%) due to the presence of mesoporous pore volume after activation with Fe(NO3)3. On the other hand, MBAN had the lowest removal efficiency of all adsorbents in this study. The activation with FeCl3 and Fe(NO3)3 showed equal removal efficiency for DCAN, BCAN, and DBAN, with percent removal higher than 50%. The hydrophilicity of HANs species affected the removal efficiency. The hydrophilicity order of five HANs species was MBAN, DCAN, BCAN, DBAN, and TCAN, respectively, which well corresponded to the obtained removal efficiency. The canvas fabric-derived adsorbents synthesized in this study were proven to be utilized as low-cost adsorbents to efficiently remove HANs from the environment. Future research will focus on the adsorption mechanism and recycling method to realize the potential for large-scale utilization.

Unravelling the properties of microzonal carbon from waste hard rubber by selective thermal transformation via conventional heating and microwave irradiation

Concerns regarding resource limitations and environmental pollution have led humankind towards a circular economy, where the primary objective is to convert waste into resources. In solidarity with the principles of the circular economy, for the first time, we have reported the synthesis of microzonal carbon by microrecycling of waste hard rubber using a conventional furnace (500 °C - 1500 °C; for 20min) and a microwave furnace (500 °C - 950 °C; for 5min). Microzonal carbon has been unveiled here as a hybrid carbon structure composed of ordered and disordered carbons. This study reveals the aspects of micorzonal carbon and analogises the effectiveness and performance of two different heating methods by way of various material characterisations. The overall analysis summarises that due to selective and rapid heating mechanism, the rate of change of structural properties of microzonal carbon, such as d-spacing (d002), crystallite size (Lc), and ID/IG band ratio, as well as the surface morphology, takes place rapidly in microwave heating than conventional heating. And it has been found that with the rise of temperature, the features of microzonal carbon become more prominent, such as the number of ordered carbon zone and mesopore volume increased, while micropore volume, surface area and interlayer spacing decreased. These evolving adjustments of features with temperature eventually ended up producing near-spherical shaped agglomerated microzonal carbon, with approximately 35–45 nm size. Waste hard rubber can have negative impacts on the environment unless they are disposed of properly. Synthesis of microzonal carbon via microrecycling of waste hard rubber can protect the environment from harsh consequences of waste hard rubber and ensure material sustainability to some extent or another. Therefore, microrecycling of waste hard rubber can fabricate a new horizon in the field of renewable carbon material synthesis, in the form of microzonal carbon.

Insight into the role of mesoporosity in the selective production of propene from methanol

Microporous ZSM-5, hierarchical ZSM-5, and hierarchical ZSM-11 zeolites with different crystalline sizes were prepared to determine the relations of mesoporosity with catalytic performance in methanol-to-propene reaction. The physicochemical properties were investigated by X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, Temperature-Programmed Desorption, and sorption techniques. It was shown that the low pore tortuosity, hierarchical structure, and the reduction of the crystal size all can shorten the diffusion path and reduce the diffusion resistance, leading to the increase of propylene yield. By comparison, the propene yield increase to the increment of mesoporous volume due to the tortuosity is more effective than other aspects. For silica–alumina zeolites, the effective way to reduce the diffusion resistance and increase the selectivity of propylene is to lower the pore tortuosity degree, and then introduce the mesoporous structure and reduce the grain size.

Optimization of photocatalytic degradation of malachite green using nano-scaled V/CeO2-functionalized steel-slag-based catalyst by response surface design approach

The utilization of steel slag with high added value is an important means for sustainable development of the iron and steel industry and environment. A new nano-scaled V/CeO2-functionalized steel-slag-based catalyst (V/CeO2-SC) was prepared. The XPS results revealed that V was embedded in the CeO2 lattice with V4+ and V5+ forms. The regression equation analysis of variance told that the order of influencing factors on malachite green dye degradation rate is: catalyst dosage > V doping amount > malachite green dye concentration. The optimum values of the parameters were dye concentration 10 mg/L, catalyst dosage 0.1 g, and V doping amount 1wt%. Under the optimal condition, the predicted and actual response values of the degradation rate of malachite green dye were 100.00%. UV–Visible light absorption spectroscopy results demonstrated that after the photocatalytic degradation reaction, the absorption peak of the malachite green dye solution almost completely disappeared, indicating that the malachite green dye solution was almost completely degraded. The excellent degradation activity of the 1V/CeO2-SC specimen was attributed to the co-action of the high SBET, large mesoporous volume, and the coupled semiconductors formed by V-doped CeO2 and FeO in the catalyst carrier. A possible photocatalytic degradation mechanism of the V/CeO2-SC specimen was proposed.

Mesopore-dominated porous carbon derived from confinement-region activation strategy toward high capacitive desalination performance

Traditional activated carbon derived from KOH activation method has been used as capacitive deionization electrode. Unfortunately, activated carbon dominated by microporous structures has a poor hydrophilicity and inferior conductivity, which has a serious impact on the desalination capacity. Herein, a novel reduced graphene oxide/porous carbon composite are rational synthesized by compressing KOH, graphene oxide and asphalt into cubic embryo with optimum tableting pressure (10 MPa) and followed by a confinement-region activation strategy. As capacitive deionization material, the reduced graphene oxide/porous carbon has high specific surface areas, abundant mesoporous volume, good hydrophilicity and high conductivity, and resulting in a large desalination capacity (25.1 mg g−1), outstanding linearity (R2 = 0.914) between the desalination capacity and mesopore volume, high maximum salt adsorption rate (0.117 mg g−1 s−1), superior charge efficiency (73.8%) and a long-term cycling stability for 200 cycles (84.9% desalination capacity retention). Furthermore, various density functional theory models of carbon material with different pore sizes (0–12 Å) are rational fabricated to expound the effect of pore size on saline ions adsorption capacity, and showing a large the pore size is, a better the ion adsorption ability. This work provides a unique activation strategy for designing mesopore-dominated composites, which greatly stimulates the clipping development of high-performance capacitive deionization devices applications.

N, P codoped carbon nanosheets derived from rice husk for supercapacitors with high energy density

Supercapacitors (SCs) have been widely used owing to their merits of long cycle life, excellent physiochemical stability and zero-carbon emission. However, the low energy density of SCs restricts their further applications. Herein, the N, P doped carbon nanosheets (NPCNs) were prepared by using silicon-removed carbon as carbon resource derived from rice husk. The as-prepared NPCN not only possesses a large surface area of 1701.6 m2 g−1 and a high ratio of mesopore volume to total pore volume (62.11 %) for adsorption and transfer of electrolyte ions, but also has a suitable nitrogen and phosphorus content for electron conduction and contribution of additional active sites to generate pseudo-capacitance through redox. Therefore, the excellent electrochemical properties have been obtained for NPCN-based SCs in the alkaline electrolyte, e.g. satisfactory capacitance of 396.1 F g−1 at 0.1 A g−1, outstanding rate properties of 319.2 F g−1 at 40 A g−1, long cyclability with capacitance decay of 0.95 % after 30,000 cycles. Additionally, the energy density of the NPCN-based SCs with neutral electrolyte and ionic liquid electrolyte increased 2.67-fold and 11-fold to 33.25 and 137.24 Wh kg−1, respectively. This study opens up a feasible route by crafting heteroatoms and using high voltage window electrolyte to obtain the high energy density for SCs.

Assessing the impact of bioturbation on reservoir quality: Integrated spontaneous imbibition, pressure decay profile permeability and pore-throat characterization study of the Cretaceous Bhuj formation, Kachchh basin, India

The Lower Cretaceous Bhuj Formation in Kachchh basin is well known for its hydrocarbon potentials including proven gas reserves in Kachchh offshore. In the onshore these reservoir equivalent rocks outcrops and includes sandstones (quartz arenites), with higher degree of bioturbations. The present work, deals with determining of impact of variable bioturbation degree sandstones reservoir quality. The petrographic properties were integrated with spot permeability and spontaneous imbibition study to understand petrophysical contrast between burrow and non-burrowed part.In moderately bioturbated samples (BI-3), spot permeability for burrows was 18 times higher than non-burrowed matrix. While in higher bioturbated, samples (BI-4) the permeability contrast between burrows and non-burrowed area was moderately lower (10.26 times). Similarly in highly bioturbated sandstones of BI-5 the permeability contrast between burrow and non-burrow was less up to 5.45 times. Thus, highly bioturbated sandstones appears to be less heterogeneous as compared with moderately bioturbation sandstones. To support this study, qualitative and quantitative investigation of the pore network, pore structure and pore connectivity through Scanning Electron Microcopy (SEM) indicated a larger proportion of intergranular pores in burrow fill than in the surrounding matrix for all types of bioturbation classes. High pressure Mercury Injection (HPMI) data for quantitative validation of these inferences also estimated a higher presence of connected macropore volume in burrowed regions of Bioturbation Index 4 and 5. In contrast, the Bioturbation Index-3 indicated highest connected mesopore volume for the non-burrowed area. The imbibition characteristic corroborated with the better pore connectivity and larger pore throat size in the burrow volume than the non-burrowed matrix estimated from other studies. The Bioturbation Index 4 and 5 had higher initial imbibition rates and imbibition capacities than Bioturbation Index-3. The well-developed and connected pores in the mesopore region tend to form a large transition zone, while a higher proportion of connected pore volume in Bioturbation Index 5 is exhibited in a higher late imbibition rate. In essence, a conceptual model is presented to describe spontaneous imbibition in bioturbated media, in order to understand the enhanced petrophysical quality in bioturbated sandstones.

Effect of litho-facies on nano-pore structure of continental shale in shuinan formation of Jiaolai Basin

Continental shale lithofacies has an important influence on nano-pore structure? However, nano-pore distribution heterogeneity (NDH) in continental shale lithofacies is not well documented. Continental shale was collected from the Shuinan Formation in the Jiaolai Basin, and the shale lithofacies of all samples are identified based on the mineralogical composition and TOC content. Nano-pore size distributions are characterized by LPN2 and CO2GA tests. Then, micro-pore (0.3∼2 nm) and meso-pore (2∼100 nm) distribution heterogeneity of different facies are discussed by single and multi-fractal model. Finally, the pore structure mechanism in shale lithofacies is clarified, and the results are as follows. The lithofacies of all shale samples are classified into three types, (A) calcareous shale lithofacies is characterized by the higher siliceous minerals and highest TOC content; (B) Calcareous/siliceous mixed shale lithofacies is characterized by middle TOC content; (C) Siliceous shale lithofacies is characterized by higher clay minerals and lowest TOC content. Micro- and meso-pore volume and A shale lithofacies NDH is much lower than that of B and C, which indicates that the lithofacies type has a great influence on the nano-pore structure. Felsic mineral and TOC content has a weak negative correlation with nano-pore structure, and there is a linear relationship between clay mineral content and nano-pore volume, indicating that clay mineral content is the main factor that can affect nano-pore structure. Moreover, fractal characteristics of the nitrogen desorption curve have been proved, and there are obvious differences in the fractal values of adsorption and desorption curves among those different lithofacies. Single fractal dimension D1 derived from LPN2 and CO2GA tests has a linear correlation with the multifractal parameter D-10-D0, which shows that a lower pore volume of pore diameter determines NDH variation. In conclusion, siliceous rich shale can provide a larger pore volume and specific surface area, and it acts as the dominant lithofacies for shale gas drainage in the study area.

Features of the deactivation of Mg/HZSM-5 catalysts for the synthesis of lower olefins from dimethyl ether in a slurry reactor

In a slurry reactor, the formation of compaction products on Mg/HZSM-5 catalysts, irrespective of the SiO2 /Al2O3 molar ratio in the zeolite, proceeds predominantly on strong acidic sites. The composition of compaction products (mostly trimethyl- and tetramethylbenzenes) virtually does not change with a growth of the molar ratio; however, their amount decreases, which is related to a growth of the mesopore volume with an increase in the SiO2 /Al2O3 ratio. This leads to a decrease in diffusion limitations and contribution of secondary reactions and enhances the removal of coke precursors from the zeolite surface, thus promoting the catalyst activity (the conversion of DME increases twofold). The composition of reaction products changes only slightly with a growth of the SiO2 /Al2O3 molar ratio, the total selectivity to lower olefins is ca. 70 wt.%. A rapid loss of the Mg/HZSM-5 activity with extending the operation time in a slurry reactor is caused not by coking, but rather by «clogging» of the catalyst with decomposition products of the dispersion medium (polydimethylsiloxane).

Multi-scale deterioration mechanism of shear strength of gypsum-bearing mudstone induced by water-rock reactions

Investigation of water-rock reactions effects on the shear strength of gypsum-bearing mudstone is necessary for underground engineering design and assessment of engineering safety. A comprehensive study of the multi-scale deterioration effects and mechanisms of water-rock reactions on gypsum-bearing mudstone can contribute to developing better engineering applications. The 25 sets of laboratory dissolution tests and 30 sets of conventional rock mechanical compression tests conducted in this study demonstrate the progressive modification of rock properties on multiple scales, including changes in mineralogy, porosity, grain structure, microstructures, and complexity of micropores, with sodium sulfate and gypsum being the most active minerals. Water-rock reactions cause irreversible morphological changes in microstructures. For instance, the number of intracrystalline pores increased, the contact between grains changed from face-to-face contact to line-to-line contact, and the volume of micropores, mesopores and macropores inside the rock increased by a maximum of 80.0%, 59.9% and 71.4% respectively. The maximum increase in the porosity of the samples was 5.33%. The increasing number of microphysical changes leads to defects that develop into weak areas, significantly decreasing the shear strength of gypsum-bearing mudstone. The maximum decrease in the cohesion of the samples was 79.06% throughout the dissolution process. It was found that the decrease in the cohesion of the samples c at the early stage of dissolution is mainly affected by the increase in the micropore volume. In the middle and late stages, the cohesion c of the samples decreased in a straight line, which is mainly caused by the increase in the macropore volume and porosity. The fluctuation in the cumulative pore volume during the whole dissolution process leads to fluctuation in the internal friction angle φ. The multi-scale degradation model of rock samples induced by water-rock reactions should be formulated to accurately evaluate the effect of water-rock reactions on rock shear strength.

Systematic Pore Characterization of Sub-Bituminous Coal from Sohagpur Coalfield, Central India Using Gas Adsorption Coupled with X-ray Scattering and High-Resolution Imaging

Pore characterization helps to estimate the coalbed methane recovery and carbon storage potential of the reservoir. Earlier research on the characteristics of coal pores has shown that coal has high hydrocarbon storage potential in the adsorbed state, but few studies have shown the influence of chemical heterogeneities and depth on the adsorption potential of the coal. With the objective of studying the effect of chemical variation, depth, and surface roughness on gas adsorption potential, this study combines coal composition analysis and adsorption-based pore characterization of coal and shale samples coupled with high-resolution imaging and X-ray scattering measurements. Variation in pore features is correlated with varying depth and composition. A decrease in the mesopore volume and surface area is observed with an increase in the depth and total organic content and inverse behavior is observed for micropores. Scanning electron microscopy images depict the change in the pore shape from semi-spherical OM pores to elongated pores with depth, and samples with high mineral content show a dominance of inter- and intraparticle pores. Fractal dimension values estimated from SAXS are notably higher than N2-LPGA-derived values (i.e.,─DS > DN) due to the incorporation of inaccessible pores, which reflects an increase of up to 62% in SAXS estimated mesopore volume and surface area. This study will provide a better approach to understand the impact of composition, depth, and surface roughness over the gas storage potential in coal reservoirs.

Locking nitrogen dopants in porous carbons through in situ grafting strategy for enhanced oxygen reduction reactions

We report here the synthesis of N-doped porous carbon (PC) through a convenient melamine pre-grafting strategy. The melamine derivative with a monolayer structure was first grafted on the surface of the micropores of PC using a suitable diazotization reaction of melamine in an aqueous solution. After pyrolysis, PC grafting with melamine derivative was converted to the obtained N-doped PC. Meanwhile, more nitrogen dopants were grafted, and nitrogen functionalities were reconstructed to generate more graphitic N and pyridinic N atoms, in which the mesopores volume was consequently enlarged. Because of the unique structures mentioned above, the as-obtained N-doped PC exhibited enhanced oxygen reduction activity under alkaline compared with the N-doped PC from the standard physical mixture of PC and melamine. Besides, the obtained N-doped PC showed a comparable half-wave potential, remarkable durability, and good methanol tolerance compared with the commercial 20% Pt/C electrocatalyst. The results presented here could guide the development of new and improving metal-free nitrogen-doped porous carbon catalysts toward oxygen reduction reaction.

Zr-modified desilicated ZSM-5 catalysts as highly active and recyclable catalysts for production of biodiesel from soybean oil: Insight into improved catalyst properties, acidity and dispersion through desilication

Bio-based fuels, such as biodiesel, have recently gained attention due to concern about ever-increasing energy consumption and global warming. Solid catalysts are key materials in the production of green biodiesel. The use of solid catalysts in the production of biodiesel can lower the cost of the separation and thus reduce biodiesel costs. In the present study, zeolite-supported ZrO2 catalyst (ZrO2/ZSM-5) and a series of desilicated zeolite-supported ZrO2 catalyst [ZrO2/ZSM-5(0.1–0.3 M)] were successfully synthesized by impregnation method and used as new catalysts for the production of soybean oil biodiesel through transesterification. Desilication at various sodium hydroxide concentrations enhances the external surface area and mesoporous volume, without jeopardizing crystallinity or microporosity of the catalysts. The synthesized catalysts were characterized via X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), pyridine-FTIR, scanning electron microscopy, TEM, XRF, TGA and nitrogen adsorption-desorption. Nuclear magnetic resonance (NMR) and gas chromatography-mass spectrometry (GC–MS) were used to characterize the biodiesel that was produced. The as-prepared ZrO2/ZSM-5(0.2 M) catalyst exhibited better catalytic activity in the transesterification of soybean oil with methanol, compared to ZrO2/ZSM-5 catalyst, due to large pore volume, high surface area, and high dispersion of ZrO2 on the desilicated zeolite support with improved acidity and high number of active sites. A biodiesel conversion of 90.1% and 97.84% were obtained for zeolite-supported ZrO2 catalyst and desilicated zeolite-supported ZrO2 catalyst, respectively, under optimum reaction conditions of 1.0 wt% catalyst loading, 1:16 soybean oil/methanol molar ratio at 200 °C in 4 h reaction time. Moreover, the desilicated zeolite-supported ZrO2 catalyst exhibited excellent stability and re-usability giving a biodiesel conversion of 93.8% after three cycles of reuse.

The Adsorption Performance of Porous Activated Carbons Prepared from Iron (II) Precursors Precipitated on the Porous Carbon Matrix Thermolysis

The creation of new compounds featuring high adsorption and catalytic performance with magnetic properties of the material is one of the important fields of magnetochemistry. The typical synthetic schemes of magnetic carbonaceous adsorbents are rather complicated due to the use of inert atmosphere and difficult wet methods of magnetite precipitation. The arising experimental issues prevent industrial production of magnetically activated carbons. In order to overcome these obstacles, we suggested a novel approach to porous carbons: magnetite composite synthesis based on iron (II) salt precipitation on porous carbon and subsequent thermolysis. We facilitated the process at the stage of the material washing. The synthetic route used is simple and can be applied industrially. The present paper is focused on the adsorption performance of a product prepared from commercial activated carbons BAU-A and AG-3. The porous structure was studied with low-temperature nitrogen adsorption that revealed surface area decreased by 26% in the case of BAU-A and 40% in the case of AG-3 with an increase in mesopore volume. Phenol and nitrobenzene adsorption from water solution was tested with magnetic carbon prepared from BAU-A. The adsorption isotherms obtained are described well using the Langmuir model. The limiting adsorption value in the case of magnetic porous carbon is lower than in the case of pristine carbon. The relative decrease in limiting adsorption value is close to the relative decrease in the specific surface area. The adsorption constant remains the same, showing that adsorption centers of phenol and nitrobenzene are the same for porous magnetic carbon and its activated carbon precursor. Thus, we showed in the present study that the magnetically activated carbons we developed almost retain the adsorption performance of their activated carbon precursors.

Organic Mesopore and Micropore Structures and Their Effects on Methane Adsorption in Marine Organic-Rich Shales

Organic pores in organic-rich shale reservoirs can provide major pore space for adsorbed and free gas storage. In this study, the organic micropore and mesopore structures in organic-rich shale reservoirs and their influence on gas adsorption are investigated by comparing CO2, N2, and methane adsorption isotherms for organic matter-combusted and non-combusted organic-rich shale samples taken from the Wufeng–Longmaxi Formation in the Sichuan Basin. Experimental results show that organic pores in organic-rich shales from the Wufeng–Longmaxi Formation in Sichuan Basin are mainly smaller than 15 nm in diameters. Volumes of organic micropores and mesopores are mainly distributed in the diameter size ranges of 0.3–0.9 and 2–8 nm, respectively. Specific surface areas of organic micropores and mesopores are mainly distributed in the diameter size ranges of 0.3–0.7 and 2–4 nm, respectively. Organic pores dominate in the organic-rich shales from the Wufeng–Longmaxi Formation, contributing 49–77% and 50–84% of the entire micropore and mesopore volumes and specific surface areas, respectively. Organic micropores contribute 42–84% and 44–85% of the entire micropore volume and specific surface area, respectively, and organic mesopores contribute 48–84% and 59–89% of the entire mesopore volume and specific surface area, respectively. Organic pores are dominant pore spaces for adsorbed methane in organic-rich shale reservoirs and contribute 75–87% of the total amount of adsorbed methane in shales from the Wufeng–Longmaxi Formation. Outcomes of this study demonstrate that organic matter combustion is a useful method for evaluating organic pores in organic-rich shales mainly according to following lines of evidence: (1) after combustion, samples have low volumes and specific surface areas for micropores and mesopores as well as extremely low contents of adsorbed methane. This suggests that combustion does not result in the generation of <15 nm inorganic micropores and mesopores in clay minerals to provide pore space for adsorbed methane. (2) The total organic carbon content (TOC) positively correlates with the organic pore volume and specific areas as well as the absolute amount of methane adsorption, suggesting that organic pores determined in this study are mainly controlled by TOC values and combustion caused the removal of organic micropores and mesopores.

Fabricating self-templated and N-doped hierarchical porous carbon spheres via microfluidic strategy for enhanced CO2 capture

N-doped porous biochar is a promising material for CO2 capture due to its easy regeneration and high CO2 selectivity. In this study, a new strategy was proposed to design monodisperse porous carbon spheres by microfluidics system with chitosan in-situ grow ZIF-8, utilizing ZIF-8 as a self-sacrificing template and nitrogen dopant. The mesoporous volume and N content of carbon spheres can be adjusted through the ZIF-8 content in the microfluidic system and carbonization temperature, within 0.01 ∼ 0.48 cm3/g and 3.23 ∼ 19.25%, respectively. The optimum sample (CZ2-900) exhibited superior CO2/N2 selectivity at 40. Adsorption kinetics and diffusion resistance indicated that CO2 adsorption in CZ2-900 is controlled by the process of CO2 diffusion from the surface of the basic site to mesopores. This was the first attempt at using a microfluid chip to grow ZIF-8 in chitosan skeleton and pyrolysis approach to synthesize N-doped porous carbon sphere where both additional template agent and activator are non-used, revealing the potential of microfluidic technology for the precise synthesis of highly selective CO2 capture materials.

Comparative study of the adsorption performance of NH2-functionalized metal organic frameworks with activated carbon composites for the treatment of phenolic wastewaters

To better understand the role of the —NH2 group in adsorption process of phenolic wastewaters, NH2-functionalized MIL-53(Al) composites with activated carbon (NH2-M(Al)@(B)AC) were prepared. The results showed that the NH2 group could increase the mesopore volume for composites, which promotes mass transfer and full utilization of active sites, because hierarchical mesopore structure makes the adsorbent easier to enter the internal adsorption sites. Furthermore, the introduction of the NH2 group can improve the adsorption capacity, decrease the activation energy, and enhance the interaction between the adsorbent and p-nitrophenol, demonstrating that the NH2 group plays a crucial role in the adsorption of p-nitrophenol. The density functional theory calculation results show that the H-bond interaction between the —NH2 group in the adsorbent and the NO2 in the p-nitrophenol (adsorption energy of –35.5 kJ·mol−1), and base-acid interaction between the primary —NH2 group in the adsorbent and the acidic OH group in the p-nitrophenol (adsorption energy of –27.3 kJ·mol−1) are predominant mechanisms for adsorption in terms of the NH2-functionalized adsorbent. Both NH2-functionalized M(Al)@AC and M(Al)@BAC composites exhibited higher p-nitrophenol adsorption capacity than corresponding nonfunctionalized composites. Among the composites, the NH2-M(Al)@BAC had the highest p-nitrophenol adsorption capacity of 474 mg·g−1.

Experimental Study on the Distribution and Height of Spontaneous Imbibition Water of Chang 7 Continental Shale Oil

After multi-stage volume hydraulic fracturing in a shale oil reservoir, massive amounts of water can be imbibed into the matrix pores. One of the key imbibition characteristics of a shale reservoir is the imbibition water and its height distribution. Based on high pressure mercury injection (HPMI) experiments and nuclear magnetic resonance (NMR) analyses, this study quantitatively evaluated the pore-size distribution of Chang 7 continental shale oil reservoirs in Yanchang Formation, Ordos Basin. The pores could be divided into three types as micropores (≤0.1 μm), mesopores (0.1–1.0 μm), and macropores (&gt;1.0 μm), while the volume of micropores and mesopores accounted for more than 90%. This demonstrated that there were strong heterogeneity and micro–nano characteristics. According to the spontaneous imbibition (SI) experiments, the cumulative proportion of imbibition water content was the largest in micropores, exceeding 43%, followed by mesopores around 30%, and that of macropores was the lowest, and basically less than 20%. The negative values of stage water content in the macropore or mesopore indicated that these pores became a water supply channel for other dominant imbibition pores. Additionally, combining the fractal theory with the NMR T2 spectrum, the relative imbibition water and actual height were calculated in different pores, while the height distribution varied with cores and shale oil. The shorter the core, the higher was the relative height, while the radius of macropores filled with imbibition water was reduced. This indicates that the height distribution was affected by the pore structure, oil viscosity, and core length.