scholarly journals Combined Effect of Pressure and Carbon Dioxide Activation on Porous Structure of Lignite Chars

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1326 ◽  
Author(s):  
Natalia Howaniec
Keyword(s):  
Carbon Dioxide ◽  
Porous Structure ◽  
Porous Materials ◽  
Power Plants ◽  
Carbon Materials ◽  
Activated Carbons ◽  
Chemical Activation ◽  
Combined Effect ◽  
Activation Process ◽  
Carbon Dioxide Activation

Lignite is an important natural resource with the application potential covering present and future energy systems, including conventional power plants and gasification systems. Lignite is also a valuable precursor for the production of porous materials of tailored properties for various environmental applications, including the removal of contaminants from gaseous or liquid media. Although the lignite-based activated carbons are commercially available, various approaches to produce carbon materials of desired properties are still being reported, covering temperature, partial oxidation and chemical activation effects on surface and structural properties of these materials. Limited data is, however, available on the effects of pressure as the activation parameter in shaping the porous structure of carbonaceous materials, in particularly lignite-derived. In the study presented the combined effect of carbon dioxide activation and pressure in the range of 1–3 MPa at the temperature of 800 °C on the development of porous structure of lignite chars was reported. The study was also focused on poor-quality resources valorization by using a relatively low calorific value, low volatiles and high ash content lignite as a carbon material precursor. The results showed that the application of pressure in carbon dioxide-activation process at 800 °C results in generation of chars of comparable or higher specific surface area than the carbon materials previously received with demineralization and carbon dioxide activation of lignite. They also proved that the combined pressure and carbon dioxide activation may be effectively applied in conversion of low quality lignite into valuable porous materials.

scholarly journals Computer Analysis of the Effect of Activation Temperature on the Microporous Structure Development of Activated Carbon Derived from Common Polypody

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2951
Author(s):  
Mirosław Kwiatkowski ◽  
Jarosław Serafin ◽  
Andy M. Booth ◽  
Beata Michalkiewicz
Keyword(s):  
Activated Carbon ◽  
Porous Structure ◽  
Computer Analysis ◽  
Density Functional ◽  
Activated Carbons ◽  
Chemical Activation ◽  
Geometrical Parameters ◽  
Activation Process ◽  
Microporous Structure ◽  
Activation Temperature

This paper presents the results of a computer analysis of the effect of activation process temperature on the development of the microporous structure of activated carbon derived from the leaves of common polypody (Polypodium vulgare) via chemical activation with phosphoric acid (H3PO4) at activation temperatures of 700, 800, and 900 °C. An unconventional approach to porous structure analysis, using the new numerical clustering-based adsorption analysis (LBET) method together with the implemented unique gas state equation, was used in this study. The LBET method is based on unique mathematical models that take into account, in addition to surface heterogeneity, the possibility of molecule clusters branching and the geometric and energy limitations of adsorbate cluster formation. It enabled us to determine a set of parameters comprehensively and reliably describing the porous structure of carbon material on the basis of the determined adsorption isotherm. Porous structure analyses using the LBET method were based on nitrogen (N2), carbon dioxide (CO2), and methane (CH4) adsorption isotherms determined for individual activated carbon. The analyses carried out showed the highest CO2 adsorption capacity for activated carbon obtained was at an activation temperature of 900 °C, a value only slightly higher than that obtained for activated carbon prepared at 700 °C, but the values of geometrical parameters determined for these activated carbons showed significant differences. The results of the analyses obtained with the LBET method were also compared with the results of iodine number analysis and the results obtained with the Brunauer–Emmett–Teller (BET), Dubinin–Radushkevich (DR), and quenched solid density functional theory (QSDFT) methods, demonstrating their complementarity.

scholarly journals Highly Selective CO2 Capture on Waste Polyurethane Foam-Based Activated Carbon

Processes ◽  
2019 ◽  
Vol 7 (9) ◽  
pp. 592 ◽  
Author(s):  
Chao Ge ◽  
Dandan Lian ◽  
Shaopeng Cui ◽  
Jie Gao ◽  
Jianjun Lu
Keyword(s):  
Activated Carbon ◽  
Polyurethane Foam ◽  
Co2 Capture ◽  
Carbon Materials ◽  
Activated Carbons ◽  
Chemical Activation ◽  
Physical Activation ◽  
Activation Process ◽  
Co2 Uptake ◽  
High Co2

Low-cost activated carbons were prepared from waste polyurethane foam by physical activation with CO2 for the first time and chemical activation with Ca(OH)2, NaOH, or KOH. The activation conditions were optimized to produce microporous carbons with high CO2 adsorption capacity and CO2/N2 selectivity. The sample prepared by physical activation showed CO2/N2 selectivity of up to 24, much higher than that of chemical activation. This is mainly due to the narrower microporosity and the rich N content produced during the physical activation process. However, physical activation samples showed inferior textural properties compared to chemical activation samples and led to a lower CO2 uptake of 3.37 mmol·g−1 at 273 K. Porous carbons obtained by chemical activation showed a high CO2 uptake of 5.85 mmol·g−1 at 273 K, comparable to the optimum activated carbon materials prepared from other wastes. This is mainly attributed to large volumes of ultra-micropores (<1 nm) up to 0.212 cm3·g−1 and a high surface area of 1360 m2·g−1. Furthermore, in consideration of the presence of fewer contaminants, lower weight losses of physical activation samples, and the excellent recyclability of both physical- and chemical-activated samples, the waste polyurethane foam-based carbon materials exhibited potential application prospects in CO2 capture.

scholarly journals An Evaluation of the Impact of the Amount of Potassium Hydroxide on the Porous Structure Development of Activated Carbons

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2045
Author(s):  
Mirosław Kwiatkowski ◽  
Elżbieta Broniek ◽  
Vanessa Fierro ◽  
Alain Celzard
Keyword(s):  
Density Functional Theory ◽  
Porous Structure ◽  
Potassium Hydroxide ◽  
Density Functional ◽  
Activated Carbons ◽  
Chemical Activation ◽  
Appropriate Technology ◽  
Functional Theory ◽  
Homogeneous Surface ◽  
The Impact

This paper presents the results of an evaluation of the impact of the amount of potassium hydroxide on the obtained porous structure of the activated carbons derived from the shells of pistachios, hazelnuts, and pecans by carbonization and subsequent chemical activation with potassium hydroxide by different adsorption methods: Brunauer–Emmett–Teller, Dubinin–Raduskevich, the new numerical clustering-based adsorption analysis, Quenched Solid Density Functional Theory, and 2D-Non-linear Density Functional Theory for Heterogeneous Surfaces, applied to nitrogen adsorption isotherms at −196 °C. Based on the conducted research, a significant potential for the production of activated carbons from waste materials, such as nut shells, has been demonstrated. All the activated carbons obtained in the present study at the activator/char mass ratio R = 4 exhibited the most developed porous structure, and thus very good adsorption properties. However, activated carbons obtained from pecan shells deserve special attention, as they were characterized by the most homogeneous surface among all the samples analyzed, i.e., by a very desirable feature in most adsorption processes. The paper demonstrates the necessity of using different methods to analyze the porous structure of activated carbons in order to obtain a complete picture of the studied texture. This is because only a full spectrum of information allows for correctly selecting the appropriate technology and conditions for the production of activated carbons dedicated to specific industrial applications. As shown in this work, relying only on the simplest methods of adsorption isotherm analysis can lead to erroneous conclusions due to lack of complete information on the analyzed porous structure. This work thus also explains how and why the usual characterizations of the porous structure of activated carbons derived from lignocellulosic biomass should not be taken at face value. On the contrary, it is advisable to cross reference several models to get a precise idea of the adsorbent properties of these materials, and therefore to propose the most suitable production technology, as well as the conditions of the preparation process.

scholarly journals Computer Analysis of the Porous Structure of Activated Carbons Derived from Various Biomass Materials by Chemical Activation

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4121
Author(s):  
Mirosław Kwiatkowski ◽  
Elżbieta Broniek
Keyword(s):  
Porous Structure ◽  
Adsorption Isotherms ◽  
Computer Analysis ◽  
Activated Carbons ◽  
Chemical Activation ◽  
Adsorbed Layer ◽  
Dry Mass ◽  
Mass Ratio ◽  
Adsorption Volume ◽  
Homogeneous Surface

In this study, the preparation of activated carbons from various materials of biomass origin by activation with potassium hydroxide and a comprehensive computer analysis of their porous structure and adsorption properties based on benzene (C6H6) adsorption isotherms were carried out. In particular, the influence of the mass ratio of the activator’s dry mass to the char mass on the formation of the microporous structure of the obtained activated carbons was analysed. The summary of the analyses carried out based on benzene adsorption isotherms begged the conclusion that activated carbon with a maximum adsorption volume in the first adsorbed layer and homogeneous surface can be obtained from ebony wood at a mass ratio of the activator to the char of R = 3. The obtained results confirmed the superiority of the new numerical-clustering-based adsorption analysis (LBET) method over simple methods of porous structure analysis, such as the Brunauer–Emmett–Teller (BET) and Dubinin–Raduskevich (DR) methods. The LBET method is particularly useful in the evaluation of the influence of the methods and conditions of production of activated carbons on the formation of their porous structure. This method, together with an appropriate economic analysis, can help in the precise selection of methods and conditions for the process of obtaining activated carbons at specific manufacturing costs, and thus makes it possible to obtain materials that can successfully compete with those of other technologies used in industrial practice and everyday life.

Comparison of activated carbons prepared by one-step and two-step chemical activation process based on cotton stalk for supercapacitors application

Energy ◽  
2021 ◽  
Vol 215 ◽  
pp. 119144 ◽  
Author(s):  
Jie Cheng ◽  
Sheng-Chun Hu ◽  
Guo-Tao Sun ◽  
Kang Kang ◽  
Ming-Qiang Zhu ◽  
...  
Keyword(s):  
Activated Carbons ◽  
Chemical Activation ◽  
Activation Process ◽  
Cotton Stalk ◽  
One Step

scholarly journals Jackfruit Seed-Derived Nanoporous Carbons as the Electrode Material for Supercapacitors

2020 ◽  
Vol 6 (4) ◽  
pp. 73 ◽  
Author(s):  
Rashma Chaudhary ◽  
Subrata Maji ◽  
Rekha Goswami Shrestha ◽  
Ram Lal Shrestha ◽  
Timila Shrestha ◽  
...  
Keyword(s):  
Carbon Materials ◽  
Activated Carbons ◽  
High Current Density ◽  
Chemical Activation ◽  
High Surface ◽  
High Surface Area ◽  
Rate Capability ◽  
High Specific Capacitance ◽  
High Rate ◽  
Nanoporous Carbons

Hierarchically porous activated carbon materials from agro-waste, Jackfruit seeds are prepared by a chemical activation method involving the treatment with zinc chloride (ZnCl2) at different temperatures (600–1000 °C). The electrochemical supercapacitance performances of the prepared materials were studied in an aqueous electrolyte (1 M sulfuric acid, H2SO4) in a three-electrode system. Jackfruit seed carbons display nanoporous structures consisting of both micro- and mesopore architectures and they are amorphous in nature and also contain oxygenated surface functional groups, as confirmed by powder X-ray diffraction (pXRD), Raman scattering, and Fourier-transformed infrared (FTIR) spectroscopy, respectively. The surface areas and pore volumes were found to be 1216.0 to 1340.4 m2·g−1 and 0.804 to 1.144 cm3·g−1, respectively, demonstrating the better surface textural properties compared to the commercial activated carbons. Due to the high surface area, large pore volume, and well developed hierarchical micro- and mesoporosity, the optimal sample achieved a high specific capacitance of 292.2 F·g−1 at 5 mV·s−1 and 261.3 F·g−1 at 1 A·g−1 followed by outstanding high rate capability. The electrode sustained 71.6% capacity retention at a high current density of 20 A·g−1. Furthermore, the electrode displayed exceptional cycling stability with small capacitance loss (0.6%) even after 10,000 charging–discharging cycles, suggesting that Jackfruit seed would have potential in low-cost and scalable production of nanoporous carbon materials for supercapacitors applications.

scholarly journals Comparison of Surface and Structural Properties of Carbonaceous Materials Prepared by Chemical Activation of Tomato Paste Waste: The Effects of Activator Type and Impregnation Ratio

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Nurgul Ozbay ◽  
Adife Seyda Yargic
Keyword(s):  
Activated Carbon ◽  
Activated Carbons ◽  
Low Cost ◽  
Chemical Activation ◽  
Nitrogen Adsorption ◽  
Xrd Analysis ◽  
Point Of Zero Charge ◽  
Activation Process ◽  
X Ray ◽  
Tomato Paste

Activated carbons were prepared by carbonization of tomato paste processing industry waste at 500°C followed by chemical activation with KOH, K2CO3, and HCl in N2 atmosphere at low temperature (500°C). The effects of different activating agents and impregnation ratios (25, 50, and 100 wt.%) on the materials’ characteristics were examined. Precursor, carbonized tomato waste (CTW), and activated carbons were characterized by using ultimate and proximate analysis, thermogravimetric analysis (TG/DTG), Fourier transform-infrared (FT-IR) spectroscopy, X-ray fluorescence (XRF) spectroscopy, point of zero charge measurements (pHPZC), particle size analyzer, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, nitrogen adsorption/desorption isotherms, and X-ray diffraction (XRD) analysis. Activation process improved pore formation and changed activated carbons’ surface characteristics. Activated carbon with the highest surface area (283 m3/g) was prepared by using 50 wt.% KOH as an activator. According to the experimental results, tomato paste waste could be used as an alternative precursor to produce low-cost activated carbon.

scholarly journals Activated Carbon Produced by Pyrolysis of Waste Wood and Straw for Potential Wastewater Adsorption

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2047 ◽  
Author(s):  
Katarzyna Januszewicz ◽  
Paweł Kazimierski ◽  
Maciej Klein ◽  
Dariusz Kardaś ◽  
Justyna Łuczak
Keyword(s):  
Activated Carbon ◽  
Surface Area ◽  
Activated Carbons ◽  
Chemical Activation ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Physical Activation ◽  
Activation Process ◽  
Waste Wood ◽  
Carbon Production

Pyrolysis of straw pellets and wood strips was performed in a fixed bed reactor. The chars, solid products of thermal degradation, were used as potential materials for activated carbon production. Chemical and physical activation processes were used to compare properties of the products. The chemical activation agent KOH was chosen and the physical activation was conducted with steam and carbon dioxide as oxidising gases. The effect of the activation process on the surface area, pore volume, structure and composition of the biochar was examined. The samples with the highest surface area (1349.6 and 1194.4 m2/g for straw and wood activated carbons, respectively) were obtained when the chemical activation with KOH solution was applied. The sample with the highest surface area was used as an adsorbent for model wastewater contamination removal.

scholarly journals Investigation of the structural characteristics of the electrodes of energy storage devices used in power plants based on renewable energy sources

2018 ◽  
Vol 161 ◽  
pp. 02007
Author(s):  
Elena Kiseleva ◽  
Fedor Lelin
Keyword(s):  
Porous Structure ◽  
Power Plants ◽  
Electrode Materials ◽  
High Efficiency ◽  
Activated Carbons ◽  
Structural Characteristics ◽  
Renewable Energy Sources ◽  
Electrochemical Characteristics ◽  
Energy Storage Devices ◽  
Excess Value

The porous structure of electrode materials was studied and an experimental analysis of the role of macropores in the electrodes of model double layer supercapacitors was carried out. It is shown that the excess value of the volume of macropores in the electrodes plays a negative role and, on the whole, in a complex manner, decreases the specific electrochemical characteristics of these devices. As a result of the research, high-efficiency activated carbons from wood waste, designed for use in supercapacitors, have been created. Correlations have been established between the parameters of the regime of thermochemical activation of wood, the porous structure of synthesized activated carbons and electrodes based on them and the specific characteristics of supercapacitors.

scholarly journals CO2 and CH4 Adsorption Behavior of Biomass-Based Activated Carbons

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3136 ◽  
Author(s):  
Deneb Peredo-Mancilla ◽  
Imen Ghouma ◽  
Cecile Hort ◽  
Camelia Matei Ghimbeu ◽  
Mejdi Jeguirim ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Activated Carbon ◽  
Adsorption Capacity ◽  
Gas Adsorption ◽  
Activated Carbons ◽  
Chemical Activation ◽  
Textural Properties ◽  
Micropore Volume ◽  
Activation Method ◽  
Physical Activation

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.

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