High-pressure methane adsorption isotherms were measured on five shale core samples obtained during exploratory drilling from three boreholes located in the Colombian Middle Magdalena Valley Basin. The experiments were carried out at 50 and 75 °C and for pressures ranging up to 3.5 MPa under dry conditions through the use of a homemade manometric setup. The effect of the total organic carbon (TOC) content, thermal maturity, clay content, and specific surface area (SSA) on methane adsorption capacity has been discussed. The excess adsorption data were fitted to a three-parameter (n L , p L , and ρ ads ) Langmuir model with the value of the adsorbed phase density, ρ ads , maintained fixed at 421 kg/m 3 , which corresponds to liquid-phase density of methane at a normal boiling point. An excellent fit to the experimental data was achieved. The results show that the temperature has a negative effect on the adsorption capacity, while TOC has a positive effect, even if no linear regression was found between TOC and methane adsorption capacity. No correlation was observed between the clay content and the TOC-normalized adsorption capacity to methane, which indicates that clay minerals do not significantly contribute to methane adsorption in the case of our samples. In addition, there is not a general trend between TOC normalized and thermal maturity. Among the factors investigated in the present study, TOC has the major contribution to the adsorption uptake. A similar contribution is found for the SSA, which is consistent, considering the positive correlation between TOC and SSA. This set of data represents meaningful information for indirect estimations of the gas in place during the future recovery strategies. This study furthers the ongoing projects on the understanding of the adsorption effect on shale gas production and assessment.
The aim of the present work is to study the effect of different activation methods for the production of a biomass-based activated carbon on the CO 2 and CH 4 adsorption. The influence of the activation method on the adsorption uptake was studied using three activated carbons obtained by different activation methods (H 3 PO 4 chemical activation and H 2 O and CO 2 physical activation) of olive stones. Methane and carbon dioxide pure gas adsorption experiments were carried out at two working temperatures (303.15 and 323.15 K). The influence of the activation method on the adsorption uptake was studied in terms of both textural properties and surface chemistry. For the three adsorbents, the CO 2 adsorption was more important than that of CH 4 . The chemically-activated carbon presented a higher specific surface area and micropore volume, which led to a higher adsorption capacity of both CO 2 and CH 4 . For methane adsorption, the presence of mesopores facilitated the diffusion of the gas molecules into the micropores. In the case of carbon dioxide adsorption, the presence of more oxygen groups on the water vapor-activated carbon enhanced its adsorption capacity.
The conversion of biogas to biomethane is an interesting alternative for clean energy production. Although biogas separation by physical adsorption using activated carbons has many advantages, the selectivity for CH 4 /CO 2 adsorption is fairly low. In this work, the surface chemistry of a commercial activated carbon (CNR-115) was modified by a two-step process: oxidative thermal treatment followed by ammonia modification. The activated carbons resulting from each modification step (CNR-115 ox and CNR-115 am , respectively) were characterized texturally and chemically, and their CH 4 /CO 2 equimolar mixture adsorption behaviors were measured. The results showed a significant loss of both surface area and porosity after the modification steps. However, the increased amount of polar surface functionalities leads to a remarkable increase of the selectivity factor (max. selectivity: 2.7 for CNR-115 < 23.4 for CNR-115 ox < 129.0 for CNR-115 am ). The reasons behind the significantly enhanced selectivity are discussed on the basis of the surface chemistries and textural properties of the materials, in relation with molecule characteristics. We demonstrate herein a very efficient surface modification strategy, which allowed to obtain activated carbon adsorbents with oxygen and nitrogen groups that favor a superior CH 4 /CO 2 separation capacity. Furthermore, the stability of the added surface groups and the adsorption behavior was tested, proving the maintenance of the chemical characteristics and the adsorption performance after 10 adsorption/ desorption cycles.
Abstract:The aim of the present study is to provide new insights into the CO 2 and CH 4 adsorption using a set of biomass-based activated carbons obtained by physical and chemical activation of olive-stones. The adsorption behavior is analyzed by means of pure gas adsorption isotherms up to 3.2 MPa at two temperatures (303.15 and 323.15 K).The influence of the activation method on the adsorption uptake is studied in terms of both textural properties and surface chemistry. For three activated carbons the CO 2 adsorption was more important than that of CH 4 . The chemically activation resulted in higher BET surface area and micropore volume that lead to higher adsorption for both CO 2 and CH 4 . For methane the presence of mesopores seems to facilitate the access of the gas molecules into the micropores while for carbon dioxide, the presence of oxygen groups enhanced the adsorption capacity.
The aim of this work is to provide new experimental data of the adsorption equilibrium of pure CH 4 and CO 2 on a set of commercial activated carbons and to express it in terms of textural properties such as BET surface area, total pore volume, and micropore volume. Adsorption isotherms up to 3.5 MPa were performed using a homemade manometric technique at 303.15 and 323.15 K. A higher adsorption capacity was found for carbon dioxide than for methane over the whole pressure range for all of the samples. A contribution to the CO 2 adsorption capacity of the BET surface area and micropore volume was found. The samples were shown to have a comparable adsorption capacity to that of conventional adsorbents used for the separation and storage of CO 2 .
The continuous increase of energy demands based on fossil fuels in the last years have lead to an increase of greenhouse gases (GHG) emission which strongly contribute to global warming. The main strategies to limit this phenomenon are related to the efficient capture of these gases and to the development of renewable energies sources with limited environmental impact. Particularly, carbon dioxide (CO2) and methane (CH4) are the main constituents of greenhouse gases while hydrogen (H2) is considered an alternative clean energy source to fossil fuels. Therefore, tremendous research to store these gases has been reported by several approaches and among them the physisorption on activated carbons (AC) have received significant attention. Their abundance, low cost and tunable porous structure and chemical functionalities with an existing wide range of precursors that includes bio-wastes make them ideal candidates for gas applications. This chapter presents the recent developments on CH4, CO2 and H2 storage by activated carbons with focus on biomass as precursor materials. An analysis of the main carbon properties affecting the AC's adsorption capacity (i.e. specific surface area, pore size and surface chemistry) is discussed in detail herein.
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