The preparation of active carbons from coal by chemical and physical activation

Ahmadpour, Ali; Do, D.D.

doi:10.1016/0008-6223(95)00204-9

Cited by 732 publications

(426 citation statements)

References 22 publications

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“…The agents used commonly in physical activation processes are steam and CO 2 , while KOH and ZnCl 2 are used in chemical activation processes (Ahmadpour, et al, 1996). In this work, steam, CO 2 , and KOH were selected to study the effect of different activation agents on the preparation of activated carbon from unburned carbon.…”

Section: Activation Of Unburned Carbonmentioning

confidence: 99%

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Development of Activated Carbons From Coal Combustion by-Products

Schobert¹,

Maroto‐Valer²,

Lü³

2003

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The increasing role of coal as a source of energy in the 21st century will demand environmental and cost-effective strategies for the use of coal combustion by-products (CCBPs), mainly unburned carbon in fly ash. Unburned carbon is nowadays regarded as a waste product and its fate is mainly disposal, due to the present lack of efficient routes for its utilization. However, unburned carbon is a potential precursor for the production of adsorbent carbons, since it has gone through a devolatilization process while in the combustor, and therefore, only requires to be activated. Accordingly, the principal objective of this work was to characterize and utilize the unburned carbon in fly ash for the production of activated carbons.The unburned carbon samples were collected from different combustion systems, including pulverized utility boilers, a utility cyclone, a stoker, and a fluidized bed combustor.LOI (loss-on-ignition), proximate, ultimate, and petrographic analyses were conducted, and the surface areas of the samples were characterized by N 2 adsorption isotherms at 77K. The LOIs of the unburned carbon samples varied between 21.79-84.52%. The proximate analyses showed that all the samples had very low moisture contents (0.17 to 3.39 wt %), while the volatile matter contents varied between 0.45 to 24.82 wt%. The elemental analyses show that all the unburned carbon samples consist mainly of carbon with very little hydrogen, nitrogen, sulfur and oxygenIn addition, the potential use of unburned carbon as precursor for activated carbon (AC) was investigated. Activated carbons with specific surface area up to 1075m 2 /g were produced from the unburned carbon. The porosity of the resultant activated carbons was related to the properties of the unburned carbon feedstock and the activation conditions used. It was found that not all the unburned carbon samples are equally suited for activation, and furthermore, their potential as activated carbons precursors could be inferred from their physical and chemical properties. The developed porosity of the activated carbon was a function of the oxygen content, porosity and H/C ratio of the parent unburned carbon feedstock. It was observed that extended activation times and high activation temperatures increased the porosity of the produced activated carbon at the expense of the solid yield.

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Section: Activation Of Unburned Carbonmentioning

confidence: 99%

“…Furthermore, prolonged time of activation with higher KOH/carbon ratio, for example 1:1 or 2:1, was recommended to produce activated carbon with well-developed porosity (Ahmadpour, et al, 1996). activation agents on unburned carbon should be explained by further studies.…”

Section: Activation Agentmentioning

confidence: 99%

Development of Activated Carbons From Coal Combustion by-Products

Schobert¹,

Maroto‐Valer²,

Lü³

2003

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“…It is known that porous carbon materials with a high specific surface area can be prepared by chemical activation with metallic compounds. Various chemical agents for porous carbon material activation have been studied, such as zinc chloride [5], and acid [6,7]. Recently, higher-specific-surface-area porous carbon materials with alkaline activation have attracted attention [2].…”

Section: Introductionmentioning

confidence: 99%

Effect of chemical species in alkali agents on pore structure at activated carbon of rice husks

Ono

Akasaka

Toda

et al. 2011

Trans. Mat. Res. Soc. Japan

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To understand effect of chemical reactions of the activation process on pore structures, the activated carbon materials were fabricated by two types of chemical agent for the activation process from rice husk ashes. NaOH and Na 2 CO 3 were used as a chemical agent. And their pore structure and hydrogen storage ability were estimated on temperature range from 77 to 298 K. The porous carbon activated by NaOH involved pores of 0.6, 1.1 and 1.5 nm diameter. The pore sizes in porous carbon activated by Na 2 CO 3 were 0.6 and 1.5 nm in diameter. These results indicated that pore structures could be controlled by chemical agents on the activation. The hydrogen storage ability of the porous carbon material activated by NaOH was the same as that activated by Na 2 CO 3 and the value was about 0.5 wt.% at 298 K. With a decrease in temperature, hydrogen storage ability was increased, and the difference of the maximum amount of stored hydrogen on these two porous carbon materials was made larger. The hydrogen storage ability at 77 K porous carbons activated by NaOH and Na 2 CO 3 indicated 3.7 and that for Na 2 CO 3 was 2.1 wt.%. From pore size distributions and temperature dependence, it was suggested that the size of pore for the hydrogen storage changed from 0.6 nm to both 0.6 and 1.1 nm with decreasing temperature.

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“…Among the solid adsorbents for CO 2 capture, carbon materials, such as activated carbon (AC), carbon aerogels, graphene, and carbon nanotubes, have shown significant advantages because of their highly developed porosities and extended specific surface areas [16][17][18][19][20][21][22][23][24]. AC is of considerable interest because it is inexpensive, readily available, easily tuned, and thermally stable [25][26][27].Surface modification can be performed via a range of treatments, such as chemical or electrochemical oxidation, chemical activation, and thermal treatment [28][29][30]. Chemical activation by ZnCl 2 , NaOH, or KOH is an effective method of controlling the poresize distributions and specific surface areas of carbon supports [31][32][33][34][35].…”

mentioning

confidence: 99%

“…Surface modification can be performed via a range of treatments, such as chemical or electrochemical oxidation, chemical activation, and thermal treatment [28][29][30]. Chemical activation by ZnCl 2 , NaOH, or KOH is an effective method of controlling the poresize distributions and specific surface areas of carbon supports [31][32][33][34][35].…”

mentioning

confidence: 99%

Preparation and characterization of chemically activated carbon materials for CO₂capture

Jeon¹,

Bae²,

Park³

2016

Carbon letters

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Atmospheric carbon dioxide (CO 2 ) exists as a gas at standard temperature and pressure, and it occurs in Earth's atmosphere in this state [1,2]. Rising levels of CO 2 , a greenhouse gas, are a major environmental problem [3]. The main source of CO 2 emissions is the burning of fossil fuels, such as natural gas and coal. The combustion of these fossil fuels, such as natural gas, coal, and oil, is one of the major emission sources of CO 2 [4].In addition to outdoor levels of CO 2 , indoor levels of CO 2 have been extensively investigated because they have a direct impact on human health. Certain levels of CO 2 in indoor spaces cause symptoms such as headaches, vomiting, drowsiness, and dyspnea. Certain indoor spaces, such as automobiles, subways, and aircraft, have high concentrations of CO 2 , which can cause serious health hazards. Thus, an increased CO2 concentration in these types of spaces is considered by many researchers to be a serious problem [5,6].Recently, CO 2 capture and storage technology, including adsorption, absorption, cryogenics, and membranes, has received increased attention motivated by environmental concerns [7][8][9]. Absorption into an alkanolamine solution is a conventional and mature technology; however, this method has major drawbacks, such as high regeneration energy requirements and significant waste. However, adsorption using solid sorbents has attracted widespread interest over recent years because of its low energy consumption, lower regeneration requirements, and ease of conservation and recycling [10]. A wide range of solid adsorbents are currently under investigation, including zeolites, metal organic frameworks, porous carbon materials, macro-porous silica, and certain metal oxides [11][12][13][14][15]. Among the solid adsorbents for CO 2 capture, carbon materials, such as activated carbon (AC), carbon aerogels, graphene, and carbon nanotubes, have shown significant advantages because of their highly developed porosities and extended specific surface areas [16][17][18][19][20][21][22][23][24]. AC is of considerable interest because it is inexpensive, readily available, easily tuned, and thermally stable [25][26][27].Surface modification can be performed via a range of treatments, such as chemical or electrochemical oxidation, chemical activation, and thermal treatment [28][29][30]. Chemical activation by ZnCl 2 , NaOH, or KOH is an effective method of controlling the poresize distributions and specific surface areas of carbon supports [31][32][33][34][35]. In particular, the chemical activation method using KOH has been the most widely studied. Researchers have reported that high specific surface areas and well-developed microporous structures can be obtained. Also, KOH activation is the most effective method in terms of the degree of activation.In this study, we investigated the effects of KOH activation at various ratios on the surface of AC. Samples were prepared to evaluate highly efficient CO 2 capture capacities.The KOH impregnation process was initiated by mixing 1 g of...

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The preparation of active carbons from coal by chemical and physical activation

Cited by 732 publications

References 22 publications

Development of Activated Carbons From Coal Combustion by-Products

Development of Activated Carbons From Coal Combustion by-Products

Effect of chemical species in alkali agents on pore structure at activated carbon of rice husks

Preparation and characterization of chemically activated carbon materials for CO₂capture

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The preparation of active carbons from coal by chemical and physical activation

Cited by 732 publications

References 22 publications

Development of Activated Carbons From Coal Combustion by-Products

Development of Activated Carbons From Coal Combustion by-Products

Effect of chemical species in alkali agents on pore structure at activated carbon of rice husks

Preparation and characterization of chemically activated carbon materials for CO2capture

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Preparation and characterization of chemically activated carbon materials for CO₂capture