Micropore Surface Area Research Articles

Evaluation of demineralized lignin and lignin-phenolic resin blends to produce biocoke suitable for blast furnace operation

Metallurgical coke makers could reduce carbon emissions and material costs by introducing waste lignin in coke oven charges. Two approaches have been studied here to increase the use of lignin in the preparation of metallurgical coke: lignin demineralization with H2SO4 and lignin blending with a low rank coal using phenolic resin as binder. The biocoke obtained after carbonization at 1000 °C from the hydrochar of demineralized lignin (350 °C, 6 h, biomass/water = 0.5 wt/wt) had much higher reactivity than the coke obtained from the low rank coking coal, proving that demineralization of lignin prior hydrothermal conversion is not a valid route for biocoke making. In the other approach, it was found that blends containing 70 wt% low rank coal, 24 wt% torrefied lignin (before or after demineralization) and 6 wt% phenolic resin produced biocokes with suitable mechanical strength for handling but higher reactivity than the coke obtained from the low rank coking coal alone. The microporous surface areas of the biocokes studied did not correlate with their reactivity values.

Highly microstructured porous carbon derived from vitex mombassae for high specific capacitance supercapacitors

This study reports on producing highly porous carbon materials by carbonization and activation of biomass (Vitex mombassae) seed wastes. The pore textural properties and microstructures of the synthesized materials are controlled by adjusting the activation temperature from 600 to 800 °C. X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, Raman and nitrogen adsorption and desorption are used to study the physical characteristics of the synthesized materials. The Brunauer–Emmet–Teller surface area, micropore surface area and pore volume increase with activation temperature. At activation temperature of 700 °C, the porous carbon acquires high specific area (2044 m2 g−1). The pore volume increases with increase in activation temperature 0.8–1.1 cm3 g−1 with high self-doping oxygen content. As a result of good physical characteristics, the prepared electrodes exhibit excellent performance with the specific capacitance up to 437 F g−1 at 5 mV s−1 in 6 M KOH electrolyte. The good capacitive behavior of the synthesized porous carbon depends on high surface area, micropore pore volume as well as moderate microstructures. The synthesized sample demonstrates high cyclic stability with capacitance retention of over 90% after 50,000 cycles.

The effect of electrode calendering on the performance of fully printed Zn∣MnO2 batteries

Primary zinc–carbon batteries with a coplanar battery architecture were prepared by screen printing. Prior to battery activation by printing of an acidic zinc chloride electrolyte, printed zinc and manganese dioxide electrodes were compacted by calendering. Material densification of the electodes resulted in electrode layer thickness reduction on both sides, modified micropore surface area and volume on the cathode side. Galvanostatic impedance measurements and chronopotentiometry were used to characterise fabricated batteries with the individually prepared electrode configurations. While calendering of both electrodes of the batteries showed adverse effects by an increase of internal resistances and a reduction of discharge capacities, exclusive calendering of the zinc anode increased the active material utilisation by electrochemical cell reaction and thus the discharge efficiency of the battery.

Promotion effect of KOH surface etching on sucrose-based hydrochar for acetone adsorption

Promotion of porous structures by surface etching plays a key role in the adsorption performance of carbon materials. Herein, we report a detailed research on KOH surface etching of sucrose-based hydrochar and the application in acetone adsorption. The obtained porous carbon (PC) possessed highest specific surface area (2604 m2/g) and maximal microporous surface area (1318 m2/g) with KOH/hydrochar ratio of 3/1. Distributed activation energy model (DAEM) was first introduced to investigate the activation energy during etching process. Moreover, reactions occurred between KOH and hydrochar were also proposed based on analysis of products. When applied to adsorption studies, acetone uptake amount of 443.4 mg/g could be reached. The equilibrium data was well fitted to Redlich-Peterson model, and the adsorption energy calculated by Dubinin-Radushkevich equation was 10.58 kJ/mol. Therefore, acetone molecules were mainly adsorbed in monolayer with little interaction between each other. This study would be useful for the understanding of KOH surface etching on sucrose-based hydrochar, which could open up an alternative for the synthesis of porous carbons as excellent adsorbents.

Comparison of the methane-oxidizing capacity of landfill cover soil amended with biochar produced using different pyrolysis temperatures

The in-situ mitigation of methane (CH4) in landfill gas using landfill cover soil (LCS) is a cost-effective approach, but its efficiency needs to be enhanced. In this study, we incorporated an enriched methane-oxidizing bacteria (MOB) consortium into LCS and established four biochar-amended LCS groups with biochar produced at 300 °C (BC300), 400 °C (BC400), 500 °C (BC500), and 600 °C (BC600). The purpose was to evaluate the CH4 oxidation capacity of biochar-amended LCS after inoculation with MOB and to investigate how the physicochemical properties of biochar that are influenced by the pyrolysis temperature affect the performance and microbial activity of biochar-amended LCS. It was found that a 15% volume ratio (representing a mass ratio of 2.49%–2.78%) for biochar amendment in LCS enhanced CH4 removal efficiency, with the highest removal observed to be 46% for BC400-amended LCS compared to 30% for the original LCS. In addition, CH4 adsorption by the biochar was not observed, and a 15% mass ratio for biochar in the LCS had no or a negative impact. Besides improving the water-holding capacity and gas permeability of LCS, other possible advantages of biochar amendment in terms of CH4 oxidization include greater retention of nutrients, electron acceptors, and exchangeable cations, as well as introducing iron ions. It was also found that CH4 oxidation capacity and the methanotroph activity of biochar-amended LCS did not continue to increase with higher pyrolysis temperatures, even though higher micropore volumes and surface areas were obtained at higher pyrolysis temperatures. From this study, BC400 was identified as the optimal choice for the best performance in terms of enhancing both the CH4 oxidation capacity of the amended LCS and the growth of type II methanotroph Methylocystaceae, which can possibly be attributed to having the highest cation exchange capacity of the four biochars.

Composition effects on pore structure of transitional shale: A case study of the upper Carboniferous Taiyuan Formation in the eastern uplift of the Liaohe Depression, China

Transitional shale is very different from marine shale with respect to mineral composition and pore structure. Insights into the effects of rock composition on pore structure can aid understanding of the storage and migration mechanisms of shale gas in a reservoir. To investigate the compositional effects on pore structure, a combination of geochemical and petrophysical experiments were conducted on four bulk shale samples and their corresponding extracted organic matter (OM) and clay mineral samples. The experimental results show that the removal of OM using H2O2 during clay mineral extraction oxidizes and removes pyrite and siderite from the samples while other inorganic phases remain unaffected. OM hosted more abundant micropores compared with clay minerals, while mesopores and fine-macropores are dominant in clay minerals. Effects of the OM and clay minerals on pore volume and surface area are quantitatively evaluated on the basis of weight-normalized pore-size distribution (PSD) curves of extracted OM and clay mineral samples. In terms of the CO2 adsorption, contribution from OM and clay minerals to micropore volume (MIV) are 19.43–32.92% and 18.75–39.05% respectively, and to micropore surface area (MIS) are 19.30–32.28% and 16.42–35.72%. Other minerals (other than organic matter and clay minerals) account for 34.29–48.93% of the MIV and 39.75–52.98% of the MIS. N2 adsorption results reveal that the pore volume and surface area are mainly attributable to the clay minerals, providing 54.37–80.75% of the BJH pore volume (BJHV) (average 65.83%) and 70.68–87.04% of the BET surface area (BETS) (average 78.71%). The primary medium for pore development in marine shale is OM, whereas pores in the transitional shale are mostly found in the clay and other inorganic minerals. Therefore, the hydraulic fracturing design and drilling-related operations involved in the exploitation of transitional shale gas should be appropriately adjusted and improved in order to accommodate intrinsic characteristics of the transitional shale gas reservoir.

Study on boron and nitrogen co-doped graphene xerogel for high-performance electrosorption application

The search for highly efficient carbon materials with high desalting capacity for the brackish water desalination is still indispensable. In this study, boron and nitrogen co-doped graphene xerogels are prepared by a simple sol-gel method with atmospheric drying and carbonization, in which the rod-like primary particles are attached on the graphene sheets via crosslinking reaction of boric acid-melamine-resorcinol-formaldehyde (BMRF). With the increase in doping ratio, the carbonized BMRF gels display high micropore surface area and abundant doping sites. The maximum doping contents of boron (1.54 at.%) and nitrogen (8.72 at.%) can be achieved in the co-doped graphene xerogel with the molar ratios of C6H6O2 and H3BO3 of 1.2, which displays superior specific capacitance (242 F g−1 at a current density of 0.1 A g−1) and high capacitance retention (92.7% after 5000 cycles at a current density of 2.0 A g−1). The co-doped graphene xerogels are evaluated as electrode materials for the electrochemical desalination of brackish water. Compared to the bare graphene xerogel, the co-doped graphene xerogel displays high electrosorption capacity of 18.45 mg g−1 and high charge efficiency of 45% for NaCl solution under an applied voltage of 1.6 V.

Novel biomass-derived smoke-like carbon as a supercapacitor electrode material.

In this present work, smoke-like carbon was successfully fabricated from a bio-waste fungal substrate crude polysaccharide for the first time. The as-prepared products possess smoke-like structures, ultra-high specific surface area (SBET: 2160 m2 g−1) and a high content of micropores (microporous surface area of 60%, with a nanopore size of 0.70 nm), which can increase the specific capacitance, representing a wonderful structure for electrochemical energy storage devices. The as-prepared sample displayed an excellent specific capacitance of 152 F g−1 at 5 A g−1 in the three-electrode configuration and exhibited maximal densities of 6.8–10.2 W h kg−1 under power outputs of 253.4–24.3 kW kg−1. We believe that this work demonstrates a simple, green and low-cost route by using agricultural residue to prepare applicable carbon materials for use in energy storage devices.

Main factors influencing the development of nanopores in over-mature, organic-rich shales

Shale cores of the Lower Silurian Longmaxi Formation from wells in the Fuling and Changning-Weiyuan shale gas demonstration zones and the Wuxi shale exploration block of the Sichuan Basin were investigated to determine the key factors controlling nanopore development in over-mature, organic-rich shales. These samples were studied using organic, geochemical, and petrological analyses, as well as low pressure nitrogen and carbon dioxide adsorption, and broad ion-beam-field emission scanning electron microscopy (BIB-FESEM). The results show that organic-rich shales of the Lower Silurian Longmaxi Formation have complex pore structures, in which the surface areas of micropores and fine mesopores (diameter < 10 nm), along with the total mesopore volume, are the most important parameters controlling nanopore development. The samples have micropore and fine mesopore surface areas of 10.03–46.47 m2/g (mean 22.65 m2/g), accounting for a significant portion (up to 99%) of the total surface areas. Mesopore volumes of 6.28 × 10−3 to38.35 × 10−3 cm3/g (mean 18.36 × 10−3 cm3/g) also account for a significant portion (up to 77%) of the total pore volume. The development of differently sized pores depends on various factors. For example, pores with a diameter < 10 nm exhibit a significant positive linear correlation with organic matter content and thermal maturity. Total organic carbon (TOC), quartz, clays, and pyrite contents are the main controlling factors in the formation of medium mesopores (10–25 nm). The generation and distribution of coarse mesopores(25–50 nm) are dominantly controlled by clay contents, especially those of illite and mixed-layer minerals of illite and smectite (I/S). Macropores are typically mineral-associated pores (e.g., pores associated with the dissolution of calcite and albite). For organic-rich shales, the development of organic pores can be evaluated using the micropore surface area per unit mass of TOC, such that the results show an increase with increasing maturity from the early mature to the over-mature stage for type I and type IIa kerogen shales, but an obvious inversion or decrease when the vitrinite reflectance (Ro) > 2.5%. For shale samples with type IIb and type III kerogens, the micropore surface area per unit mass of TOC first rises from early mature to the mature stage, and then declines from the mature to over-mature stages of approximately ~2.0% Ro. Therefore, abundant organic matter, type I and type IIa kerogen, relatively high quartz and clay contents (especially illite), and early stage mineral dissolution are favorable factors for the development of nanopores in over-mature shales in the study areas. These findings will help improve our understanding of the development of nanopores in over-mature organic-rich shales.

Facile synthesis of mesoporous zeolite Y using seed gel and amphiphilic organosilane

Abstract Zeolite Y is widely used as an industrial catalyst for catalytic cracking of heavy feedstocks to lighter olefins. However, incorporation of uniform mesoporosity in zeolite Y without compromising the microporous characteristics is required to improve the catalyst efficiency and minimize catalyst deactivation. Here, we report a facile synthesis method for mesoporous zeolite Y (MPY sg ) using seed gel and amphiphilic organosilane, that results in mesoporous zeolite showing a narrow mesopore size distribution (3–4 nm) with high external surface area (110 m 2 g -1 ) and high micropore surface area (654 m 2 g -1 ). During the crystallization of MPY sg , the organosilane acted as a mesopore-generating agent, and the seed gel provided secondary nuclei that created a uniform mesoporous structure in the zeolite Y nanocrystals. Analysis of aluminosilicate precursors collected during the crystallization revealed that the crystallization process starts with a long nucleation period, followed by rapid crystal growth. Due to the highly accessible strong acid sites present on its external surface, MPY sg shows catalytic activity in the decalin cracking reaction higher than that of conventional microporous zeolite Y.

Paleofloral dependence of coal methane sorption capacity

The aim of this study is to reveal key physiochemical factors controlling gas sorption in coals during periods of dramatic coal deposition in Earth's history – the Upper Carboniferous (326–299 Ma) and Permian (299–252 Ma). As a starting point we developed a database of about 1000 entries, including coal-specific parameters such as proximate and ultimate analysis, sample origin, and specific surface area. Our study proposes an innovative approach that links emerging, quantitative organic molecular analyses with more established bulk (bio)geochemical techniques as a context for (1) describing gas–coal (i.e., coalbed methane) formations, (2) sweet-spot identification in terms of methane sorption potential. We found that the main controlling parameter is coal age; Permian coals generally adsorb significantly more methane than Carboniferous coals at comparable maturity. This difference is reflected in micropore surface area and oxygen content of the two sets, with Permian having higher values than the corresponding Carboniferous coals. We attribute this difference in Langmuir volume or surface area to the original plant material, expressed through differences in the molecular structures and surface chemistries of the sorption sites which is also clearly reflected in a lower aromaticity for Permian coals. This leads to a more detailed view on the evolution of original plant material from the Carboniferous to Permian age, coinciding with an evolution in plant material, specifically lignite, changes in climatic conditions towards more arid environments, possible changes in water compositions and bacterial activities.

Evolution of Zeolite Crystals in Self-Supporting Faujasite Blocks: Effects of Hydrothermal Conditions.

In order to prepare self-supporting faujasite (FAU) zeolite, a self-supporting zeolite block was synthesized in situ by hydrothermal treatment of a metakaolin base geopolymer. The effects of hydrothermal conditions such as hydrothermal alkalinity, temperature and time on the phase composition, microstructure and mechanical strength of the hydrothermal samples were investigated and evidenced by a series of characterization methods such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmet-Teller (BET). The results showed that a self-supporting faujasite block could be obtained by hydrothermal treatment of the geopolymer block in 2 M NaOH solution at 90 °C for 24 h, which had high crystallinity, regular morphology and high compressive strength. The self-supporting zeolite block had a compressive strength of 11.7 MPa, a pore volume of 0.24 cm3/g, and an average pore diameter of 7.86 nm. The specific surface area and the microporous specific surface area of the self-supporting faujasite blocks were 80.36 m2/g and 19.7 m2/g, respectively.

CO₂ Adsorption Investigation on an Innovative Nanocomposite Material with Hierarchical Porosity.

A NaX nanozeolite-geopolymer monolith, with hierarchical porosity, has been produced by a one-pot hydrothermal synthesis using metakaolin as alluminosilicate source and a sodium silicate solution as activator. Its final composition, reported in terms of oxides, is 1.3-Na₂O-3.0SiO₂-1Al₂O₃-12H₂O. Its microstructural and chemical features and CO₂ adsorption performance have been investigated. The microstructure of the composite is characterized by NaX zeolite nanocrystals glued by the geopolymeric binder to form a complex three-dimensional network of pores. Overall porosity resulted ~23.5%, whereas compressive strength is 16±0.7 MPa. Monolith showed BET surface area of 350 m²/g, a micropore surface area of 280 m²/g and a mesopore volume, due to the geopolymeric binder, of 0.09 cm³/g. Its CO₂ adsorption capacity has been measured at the temperatures of 7, 25 and 42 °C up to 15 bar using an optimized Sievert-type (volumetric) apparatus. All the adsorption data were evaluated by Toth/Langmuir isotherm model and commercial pure NaX zeolite was used as reference. CO₂ adsorption isotherms show a maximum uptake value around 21 wt% at (~7 °C) that decrease to 18 wt% at high temperature (~42 °C) passing through 19 wt% at room temperature (~25 °C). The homogeneity grade of the surface, as obtained using Toth analysis performed on the adsorption isotherm, is close to t ≅ 0.40, lower than the 0.61 obtained for pure commercial NaX zeolite, as a consequence of the binder formation. Monolith exhibits a notably higher K values and quicker saturation with respect to reference that can be ascribed to the presence of mesoporosity that provides an easier and faster transport of CO₂ in the NaX nanozeolite framework. The produced composite is a potential solid adsorbent candidate in industrial process.

Meso-microporous carbon nanofibers with in-situ embedded Co nanoparticles for catalytic oxidization of azo dyes

To meet the current challenges in the treatment of azo dye wastewater by advanced oxidation processes (AOPs), meso-microporous carbon nanofiber with in-situ embedded Co nanoparticles (Co/P-CNF) is developed by electrospinning Co salt/polyvinylpyrrolidone (PVP)/polyacrylonitrile (PAN) solution followed by carbonization process. The use of PVP as pore-forming agent in PAN solution promotes the formation of meso-microporous structure of P-CNF in carbonization phase, achieving micropore surface area of 98 m2 g−1 and mesopore surface area of 214 m2 g−1 by BET analysis. The heterogeneous catalytic performance of synthesized Co/P-CNF is evaluated by the degradation of Acid Red 1 (AR1) with peroxymonosulfate (PMS). Complete removal of AR1 of 50 × 10−6 M is achieved within 6 min by Co/P-CNF and PMS system. The superior catalytic performance of Co/P-CNF is attributed to both the nanofibrous morphology and meso-microporous structure due to using the pore-forming agent (PVP), which endow the uniform distribution of Co nanoparticles, favor the exposure of active sites and promote electron and mass transfer. Co/P-CNF not only possesses excellent magnetic property but also has good stability and recyclability, which is desirable for the practical application of the treatment of azo dye wastewater. Co/P-CNF is validated to activate PMS using Co0/Co2+/Co3+ for generating sulfate radicals, hydroxyl radical and singlet oxygen and then degrade AR1. Therefore, the combination of electrospun nanofibrous structure and the use of pore-forming agents is a promising strategy for the preparation of high-performance carbon nanofiber supported catalysts.

Reactivity of biomass containing briquettes for metallurgical coke production

The reactivity of cokes from 12 briquettes prepared from ternary blends of coal, three biomasses and four binders was evaluated. In order to determine the effect of the binder, 4 briquettes without biomass were also studied. The gasification tests were carried out by thermogravimetric analysis at 900 °C. Two gas-solid models i.e. the Volumetric model and the Grain model were applied to describe the behaviour of the cokes. Chars and cokes from the briquette components were also tested to determine the degree of synergy. The two models were able to describe the gasification reaction and the predicted conversion fitted the experimental data very well. Reactivity was also determined by means of a greater scale method and a relationship between the two methods was obtained. The ash composition of the briquette components, the micropore surface area and quantitative optical microscopy were used to explain the gasification results obtained.

Reassembly mechanism in Fe-Silicalite during NH4OH post-treatment and relation with the acidity and catalytic reactivity

The treatment in NH4OH of Fe-Silicalite (Fe-MFI) catalysts creates mesopores with a different mechanism with respect to the conventional desilication treatment. A reassembling of Fe-MFI nanocrystals is induced by the creation of isolated defects on the surface of these nanocrystals, as well as a change in the amorphous layer between nanocrystals acting as “glue” to assemble them into larger round-shaped particles occurs. The reassembling process induces also changes in the acidity and hydrophobic character, leading to an enhanced reactivity, and influences the relatives rate constants in the HMF (5-hydroxymethylfurfural) etherification to 5-(ethoxymethyl)furan-2-carbaldehyde (EMF) via acetalization. Moreover, for treatment times with NH4OH longer than 6 h, there is an effective, although minimal, desilication process which leads to a loss of crystallinity, microporous surface area, mesoporosity and acidity characteristics with consequent worsening of the catalytic performances.

Preparation of manganese oxides coated porous carbon and its application for lead ion removal

In this study, porous carbon (PC) was prepared from pyrolysis of sodium carboxymethyl cellulose (CMC) and was further treated with KMnO4 to fabricate manganese oxides coated PC (MnOx/PC). SEM, BET, XPS and FTIR technology were employed to explain their structures. Batch adsorption experiments for Pb(II) were carried out to estimate their adsorption performance. Results showed that manganese oxides coating onto the PC caused the decrease of microporous surface area and microporous volume, while the oxygen content increased greatly. Both PC and MnOx/PC exhibit excellent absorption performance for Pb(II) and their maximum adsorption capacity were 0.6054 and 1.2297 mmol g−1 (about 125.44 and 254.79 mg g−1), respectively. The adsorption process of Pb(II) was quick and pH-dependent. The absorption kinetic and thermodynamic process were fitted well with pseudo-second-order model and Langmuir isotherm model, respectively, suggesting that Pb(II) adsorption onto the sorbents were a chemical process and monolayer adsorption were reached.

Reservoir characteristics and coalbed methane resource evaluation of deep-buried coals: A case study of the No.13–1 coal seam from the Panji Deep Area in Huainan Coalfield, Southern North China

The Panji Deep Area in Huainan Coalfield, Southern North China is a newly discovered deep coal-bearing block with abundant coalbed methane (CBM) resources. To date, systematic geological studies regarding CBM reservoir in this region are still deficient, thereby seriously hindering the further exploitation and utilization of CBM in Huainan Coalfield. Results indicate that No.13–1 coal seam in the Panji Deep Area has good material conditions for CBM accumulation and preservation. All the coal samples from the No.13–1 coal seam are medium ash and medium−high volatile bituminous coals (Ro,max, 0.72–0.82%), which have different proportions of macerals and minerals. Pore structure and morphology analyses indicate that No.13–1 coal samples have various pore types and complex pore structures. Among them, the ink-bottle shaped pores are mainly observed with a pore size diameter of 4 nm. The gas content of No.13–1 coal samples is 16.11–21.83 m3/t (avg. 18.16 m3/t), which is strongly affected by the effective thickness of coal reservoir, reservoir pressure and temperature. Gas content is significantly positively correlated with burial depth, reservoir pressure, and temperature below 700 m, 6 MPa, and 34 °C, respectively. However, the upward trend tends to be constant after these demarcation points. Numberous micropores hold the retention capacity of coal matrix to methane molecules, thus the residual gas content increases along with the volume and surface area of micropores. By contrast, the correlations between gas content and coal thickness and roof thickness are not obvious. The total CBM resource of No.13–1 coal seam is approximately reserve of 205.36 × 108 m3. Moreover, the total CBM resources in the northern and southern parts of the Panji Deep Area are 73.83 × 108 m3 and 131.53 × 108 m3, respectively. On the basis of multi-level fuzzy model and the evaluated factors, the most favorable areas for CBM development of the No.13–1 coal seam were predicted to be around Zhutuan and south Gugou town in the Panji Deep Area.

Assessment of char property on tar catalytic reforming in a fluidized bed reactor for adopting a two-stage gasification process

To well understand the effect of char property on tar catalytic reforming and support the development of two-stage gasification technology for the clean fuel gas production, the roles of pore structure and metal oxide in tar removal behavior were examined and compared on a fluidized bed two-stage reactor. The results show that although both of micro pore and meso pore had a remarkable influence on tar removal efficiency, fuel gas component and distilling fractions in tar, perhaps micro pore played a much more important role. Moreover, the tar removal efficiency did not have a good proportional relationship with the specific surface area of char. For the spent char, the activation treatment in steam was very beneficial to renew the catalytic reforming on tar by increasing the surface area of micro pore and maintain its high gasification activity. Compared to the demineralized char, the char samples that loaded metal oxide by impregnation approach largely promoted the tar removal efficiency, following the rank of Na2O > Fe2O3 > CaO > MgO. For Na2O, it not only had the best catalytic activity on tar, but also greatly promoted the generations of light tar and effective fuel gas, such as H2 and CO. Finally, considering the different effect of pore structure and metal oxide on tar catalytic reforming, a brief mechanism of tar catalytic reforming by char was proposed.

Influences of dynamic entrainer-blended supercritical CO2 fluid exposure on high-pressure methane adsorption on coals

Injecting carbon dioxide (CO2) into unmineable coal reservoirs can reduce CO2 emissions and simultaneously enhance coalbed methane (CBM) recovery. The injected CO2 at the optimum coal seam depth is supercritical fluid, which may affect physicochemical properties and fluid adsorption/desorption performance of coals. Aiming to further elucidate the potential extractive effect of CO2 fluid, the influences of dynamic ethanol-blended supercritical CO2 fluid on physicochemical properties and methane (CH4) adsorption performance of coals are studied. The results indicate that ethanol as entrainer could strengthen extractive power of supercritical CO2 fluid to small organic compounds within coal matrix. Interaction with ethanol-blended supercritical CO2 fluid improves the micropore surface area and volume but decreases the oxygenic functional groups of Tianji coal (VRr = 0.72%) and Datong coal (VRr = 0.83%); however, Shenmu coal (VRr = 0.88%) and Yangquan coal (VRr = 2.62%) give opposite results. They account for increased CH4 adsorption amount of Tianji coal and Datong coal, and decreased CH4 adsorption amount of Shenmu coal and Yangquan coal. The isosteric heat of CH4 adsorption on coals exposed to ethanol-blended supercritical CO2 fluid decreases, further implying that the interaction is viable to weaken adsorbability of coals to CH4. Adsorption kinetics study confirms that ethanol-blended supercritical CO2 fluid exposure causes a rise in both Dmacro/Rmacro and Dmicro/Rmicro of CH4 within coals. Briefly, ethanol as candidate entrainer for supercritical CO2 fluid is expected to enhance CBM recovery and optimize the current CO2-ECBM process.