Carbon activation with KOH as explored by temperature programmed techniques, and the effects of hydrogen

Lozano‐Castelló, Dolores; Calo, J.M.; Cazorla‐Amorós, Diego; Linares-Solano, Á.

doi:10.1016/j.carbon.2007.08.021

Cited by 350 publications

(156 citation statements)

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“…Apparently, in this case, the R value of AK 1 decreases after KOH activation, implying a decrease in crystallinity and a lower degree of graphitization of AK 1 relative to that of activated carbon, which may be attributed to the breakdown of aligned structural domains in the carbon matrix because of the intercalation of potassium compounds and the oxidation of carbon into carbonate. [17,18,27] SEM images show that activated carbon is composed of agglomerated carbon particles with a size ranging from tens to hundreds of nanometers in diameter (Figure 2 a), whereas AK 1 exhibits a relatively small and homogeneous average particle size of about 50 nm (Figure 2 b). In TEM images, the activated carbon shows a compact surface microstructure (Figure 2 c), whereas AK 1 exhibits a loose surface microstructure with a microporous character (Figure 2 d).…”

Section: Resultsmentioning

confidence: 99%

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Superhydrophobic Activated Carbon‐Coated Sponges for Separation and Absorption

Sun¹,

An²,

Zhu³

et al. 2013

ChemSusChem

194

105

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Highly porous activated carbon with a large surface area and pore volume was synthesized by KOH activation using commercially available activated carbon as a precursor. By modification with polydimethylsiloxane (PDMS), highly porous activated carbon showed superhydrophobicity with a water contact angle of 163.6°. The changes in wettability of PDMS‐ treated highly porous activated carbon were attributed to the deposition of a low‐surface‐energy silicon coating onto activated carbon (confirmed by X‐ray photoelectron spectroscopy), which had microporous characteristics (confirmed by XRD, SEM, and TEM analyses). Using an easy dip‐coating method, superhydrophobic activated carbon‐coated sponges were also fabricated; those exhibited excellent absorption selectivity for the removal of a wide range of organics and oils from water, and also recyclability, thus showing great potential as efficient absorbents for the large‐scale removal of organic contaminants or oil spills from water.

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Section: Resultsmentioning

confidence: 99%

“…[16][17][18] Due to its high surface area, abundant porosity, and sustainability, activated carbon has been widely used as a porous medium for the absorption of metal ions [19] or toxic organic species [20] from water. However, the absorption performance of activated carbon is limited by its finite pore volume and hydrophilic nature.…”

Section: Introductionmentioning

confidence: 99%

Superhydrophobic Activated Carbon‐Coated Sponges for Separation and Absorption

Sun¹,

An²,

Zhu³

et al. 2013

ChemSusChem

194

105

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“…For example, different nitrogen gas flows were used in the lab-scale and scaleup activations. The flow rate is known to have a high impact on the activation process [17,42,43]. It is responsible for eliminating gaseous reaction products which are formed upon chemical activation, thus enhancing the process [17,42,43].…”

Section: Materials Synthesismentioning

confidence: 99%

Scale-up activation of carbon fibres for hydrogen storage

Kunowsky

Marco-Lozar

Cazorla‐Amorós

et al. 2010

International Journal of Hydrogen Energy

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In a previous study, we investigated, at a laboratory scale, the chemical activation of two different carbon fibres (CF), their porosity characterization, and their optimization for hydrogen storage [1]. In the present work, this study is extended to: (i) a larger range of KOH activated carbon fibres, (ii) a larger range of hydrogen adsorption measurements at different temperatures and pressures (i.e. at room temperature, up to 20 MPa, and at 77 K, up to 4 MPa), and (iii) a scaling-up activation approach in which the obtained activated carbon fibres (ACF) are compared with those from laboratory-scale activation. The prepared samples cover a large range of porosities, which is found to govern their ability for hydrogen adsorption. The hydrogen uptake capacities of all the prepared samples have been analysed both in volumetric and in gravimetric bases. Thus, maximum adsorption capacities of around 5 wt.% are obtained at 77 K, and 1.1 wt.% at room temperature, respectively. The packing densities of the materials have been measured, turning out to play an important role in order to estimate the total storage capacity of a tank volume. Maximum values of 17.4 g l −1 at 298 K, and 38.6 g l −1 at 77 K were obtained.

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“…On the other hand, in the case of cellulose and more generally of lignocellulosic biomass, the same synthetic approaches are not feasible because of the insolubility of the cellulosic substrate in water. As a consequence, in order to introduce porosity in the lignocellulosic biomass derived HTC carbons, post-synthesis methods are required.Physical or chemical activation processes are well-known strategies to produce highly porous carbons from coal-derived precursors and it has been largely described in the literature [14][15][16][17][18][19][20]. Their application to lignocellulosic biomass is widely used, but it is not as effective because of poor yields and low porosity development, arising from the excessive degradation of the organic substrate [21][22][23].…”

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Tailoring the porosity of chemically activated hydrothermal carbons: Influence of the precursor and hydrothermal carbonization temperature

Falco

Marco-Lozar

Salinas-Torres

et al. 2013

Carbon

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Advanced porous materials with tailored porosity (extremely high development of microporosity together with a narrow micropore size distribution (MPSD)) are required in energy and environmental related applications. Lignocellulosic biomass derived HTC carbons are good precursors for the synthesis of activated carbons (ACs) via KOH chemical activation. However, more research is needed in order to tailor the microporosity for those specific applications. In the present work, the influence of the precursor and HTC temperature on the porous properties of the resulting ACs is analyzed, remarking that, regardless of the precursor, highly microporous ACs could be generated. The HTC temperature was found to be an extremely influential parameter affecting the porosity development and the MPSD of the ACs. Tuning of the MPSD of the ACs was achived by modification of the HTC temperature. Promising preliminary results in gas storage (i.e. CO 2 capture and high pressure CH 4 storage) were obtained with these materials, showing the effectiveness of this synthesis strategy in converting a low value lignocellulosic biomass into a functional carbon material with high performance in gas storage applications. IntroductionHydrothermal Carbonization (HTC) is now a well-established thermochemical synthesis alternative to produce functional carbon materials with a tunable chemical structure from pure carbohydrates or lignocellulosic biomass [1][2][3].During HTC, biomass-derived precursors are converted into valuable carbon materials using water as reaction medium at mild temperatures (< 200°C) under self-generated pressures [4]. Even though this methodology has been known for almost 100 years [5], its full potential, as a synthetic route for carbon materials having important applications in several fields such as catalysis, energy storage, CO 2 sequestration, water purification, soil remediation, has been revealed only recently, mainly via the work of Dr. Titirici and coworkers [6].Under hydrothermal conditions monosaccharides are dehydrated to 5-hydroxymethylfurfural (5-HMF) via the well-known Lobry de Bruyn-Alberta van Ekstein rearrangement [7]. Once 5-HMF is formed, it is in situ "polymerised" yielding the HTC carbon product [8]. While most of the research efforts focus on the exploitation of HMF for the production of chemicals, bioplastics and biofuels [9], the Titirici´s group rediscovered these processes for the production of green and valuable carbon and carbon-hybrid materials [1,4].One of the main limiting factors, hindering the effective and straightforward exploitation of HTC carbons for several end-applications (eg. catalysis, separation science, energy production and storage), is their low surface area and porosity [10]. In the case of monosaccharide derived HTC carbons, this problem has been elegantly overcome by using hard\soft-templating strategies or by addition of structural directing agents [11][12][13]. Such synthetic routes are effective because of the homogeneous nature of the pre-HTC aqueous reaction mixt...

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Carbon activation with KOH as explored by temperature programmed techniques, and the effects of hydrogen

Cited by 350 publications

References 20 publications

Superhydrophobic Activated Carbon‐Coated Sponges for Separation and Absorption

Superhydrophobic Activated Carbon‐Coated Sponges for Separation and Absorption

Scale-up activation of carbon fibres for hydrogen storage

Tailoring the porosity of chemically activated hydrothermal carbons: Influence of the precursor and hydrothermal carbonization temperature

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