In this work, the CO(2) capture capacity of different types of carbon nanofibers (platelet, fishbone, and ribbon) and amorphous carbon have been measured at 26 °C as at different pressures. The results showed that the more graphitic carbon materials adsorbed less CO(2) than more amorphous materials. Then, the aim was to improve the CO(2) adsorption capacity of the carbon materials by increasing the porosity during the chemical activation process. After chemical activation process, the amorphous carbon and platelet CNFs increased the CO(2) adsorption capacity 1.6 times, whereas fishbone and ribbon CNFs increased their CO(2) adsorption capacity 1.1 and 8.2 times, respectively. This increase of CO(2) adsorption capacity after chemical activation was due to an increase of BET surface area and pore volume in all carbon materials. Finally, the CO(2) adsorption isotherms showed that activated amorphous carbon exhibited the best CO(2) capture capacity with 72.0 wt % of CO(2) at 26 °C and 8 bar.
"Because CO 2 capture by these adsorbents relies mainly on physical adsorption, research activities have been focused on increasing the surface area of these materials in order to achieve enhanced adsorption capacity . Compared with other adsorbents, porous carbonaceous materials are especially attractive due to their moderate heats of sorption, and inexpensive preparation, and that they are not as sensitive to water vapor as the other CO 2 -philic materials . Therefore, CO 2 adsorption can be considered to be one of the more promising methods, offering potential energy and cost savings . "
[Show abstract][Hide abstract] ABSTRACT: The CO2 adsorption on biochar produced by microwave pyrolysis of rice straw was investigated in this study. A microwave power level of 200 W and a maximum temperature of approximately 300 °C would be the optimal parameters to adsorb the most CO2. The CO2 adsorption capacity was up to 80 mg/g at 20 °C. The adsorption capacity decreased at higher power levels and temperatures possibly owing to the pore destruction. The CO2 adsorption capacity was highly correlated with the specific surface area of biochar. The conventional pyrolysis at 550 °C was optimal to produce the biochar absorbing the most CO2 which, however, was still lower than that of the biochar produced by microwave pyrolysis by about 14%. Low activation energy implies that CO2 adsorption on the biochar is physisorption. The ratio of CO2 quantity versus solid product quantity can almost match the CO2 adsorption capacity of the biochar produced at 200 W microwave power levels, so the microwave pyrolysis without further processes to meet the zero emission of CO2 should be workable. Compared with conventional pyrolysis, microwave pyrolysis could produce the biochar with lower time, cost, and energy consumptions.
Energy 03/2015; 84. DOI:10.1016/j.energy.2015.02.026 · 4.84 Impact Factor
"The application of porous materials in the capture and storage of CO2 has a big potential and wide prospect. There are many kinds of porous materials that can be used as CO2 adsorbents, such as molecular sieves, porous silica, metal organic frameworks (MOFs), and porous carbons [8-18] due to their attractive properties such as high specific surface area and highly developed pore structure. Among these porous materials, porous carbons are especially attractive because they are inexpensive, easy to regenerate, and not sensitive to moisture which may compete with CO2 when adsorption happens [19-21]. "
[Show abstract][Hide abstract] ABSTRACT: A series of carbide-derived carbons (CDCs) with different surface oxygen contents were prepared from TiC powder by chlorination and followed by HNO3 oxidation. The CDCs were characterized systematically by a variety of means such as Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, ultimate analysis, energy dispersive spectroscopy, N2 adsorption, and transmission electron microscopy. CO2 adsorption measurements showed that the oxidation process led to an increase in CO2 adsorption capacity of the porous carbons. Structural characterizations indicated that the adsorbability of the CDCs is not directly associated with its microporosity and specific surface area. As evidenced by elemental analysis, X-ray photoelectron spectroscopy, and energy dispersive spectroscopy, the adsorbability of the CDCs has a linear correlation with their surface oxygen content. The adsorption mechanism was studied using quantum chemical calculation. It is found that the introduction of O atoms into the carbon surface facilitates the hydrogen bonding interactions between the carbon surface and CO2 molecules. This new finding demonstrated that not only the basic N-containing groups but also the acidic O-containing groups can enhance the CO2 adsorbability of porous carbon, thus providing a new approach to design porous materials with superior CO2 adsorption capacity.
Nanoscale Research Letters 04/2014; 9(1):189. DOI:10.1186/1556-276X-9-189 · 2.78 Impact Factor
"Also, high CO 2 uptakes were reported by Wahby et al.  and Silvestre-Albero et al.  for carbon molecular sieves; the aforementioned studies addressed the importance of high surface area and micropore volume, without quantifying the role of ultramicropores in CO 2 adsorption at ambient conditions. The observed enhancement in CO 2 adsorption agrees with recent findings of Nilantha et al.   and others   , indicating that ultramicropores (micropores below $0.7 nm) are mainly responsible for high CO 2 uptake at lower pressures . The ultramicropores attract strongly CO 2 molecules due to overlapping of adsorption forces; namely, the overlapping of interaction potentials of the opposite ultramicropore walls results in a deep well potential that soaks CO 2 molecules . "
[Show abstract][Hide abstract] ABSTRACT: Carbons with high surface area and large volume of ultramicropores were synthesized for CO2 adsorption. First, mesoporous carbons were produced by soft-templating method using triblock copolymer Pluronic F127 as a structure directing agent and formaldehyde and either phloroglucinol or resorcinol as carbon precursors. The resulting carbons were mainly mesoporous with well-developed surface area, large total pore volume, and only moderate CO2 uptake. To improve CO2 adsorption, these carbons were subjected to KOH activation to enhance their microporosity. Activated carbons showed 2-3-fold increase in the specific surface area, resulting from substantial development of microporosity (3-5-fold increase in the micropore volume). KOH activation resulted in enhanced CO2 adsorption at 760 mmHg pressure: 4.4 mrnol g(-1) at 25 degrees C, and 7 mmol g(-1) at 0 degrees C. This substantial increase in the CO2 uptake was achieved due to the development of ultramicroporosity, which was shown to be beneficial for CO2 physisorption at low pressures. The resulting materials were investigated using low-temperature nitrogen physisorption, CO2 sorption, and small-angle powder X-ray diffraction. High CO2 uptake and good cyclability (without noticeable loss in CO2 uptake after five runs) render ultramicroporous carbons as efficient CO2 adsorbents at ambient conditions.
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