The role of surface chemistry in catalysis with carbons

Figueiredo, José L.; Pereira, M.F.R.

doi:10.1016/j.cattod.2009.04.010

Cited by 583 publications

(407 citation statements)

References 104 publications

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“…Likewise, around 900°C, the desorption of CO 2 evolving groups is virtually completed, with a maximum in the TPD profile around 675°C, which can be attributed to lactones [11,12]. The stability of the oxygen groups is higher for the species that evolve as CO.…”

Section: Activation Conditionsmentioning

confidence: 96%

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Development of porosity upon physical activation of grape seeds char by gas phase oxygen chemisorption–desorption cycles

Jiménez-Cordero

Heras

Alonso-Morales

et al. 2013

Chemical Engineering Journal

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h i g h l i g h t sNovel method of activation by cycles permits good control of porosity development. S BET values above 1000 m 2 /g can be obtained with burn-off values lower than 40%. The low burn-off helps to maintain granular morphology of the activated carbons.Carbons with unique hollow core structure and wall thickness of 250 lm are produced.The activated carbons showed a good mechanical strength during attrition test. a r t i c l e i n f o t r a c tActivation of grape seeds char upon cyclic oxygen chemisorption-desorption permits a controlled development of porosity versus burn-off using air as a cheap activation agent. In this work the influence of chemisorption and desorption temperature and the number of cycles is investigated. A fast increase of BET surface area (S BET ) is obtained in the two first cycles; that increase becomes then lower although the S BET continues increasing upon the successive cycles. Regarding the Dubinin-Astakhov surface area (S DA ) a slow increase was observed from cycle to cycle. The activation process led to the development of both micro and mesoporosity. Under the optimum conditions for surface area development, i.e. an oxidation temperature of 275°C and desorption temperatures between 850 and 950°C, values of 1129-1256 and 1339-1219 m 2 /g were obtained for S BET and S DA , respectively. Porosity was found to increase mainly during the desorption stage, although chemisorption also led to some surface area development. SEM characterization showed that the activated carbon maintained the granular morphology of the seeds even after 10 cycles showing the egg-shell structure of the precursor with longer and deeper cracks at the outer surface. The activated carbons showed a good mechanical strength during attrition tests.

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Section: Activation Conditionsmentioning

confidence: 96%

“…2, the oxygen chemisorbed within the 200-250°C range has a high stability upon heating. At 500°C only 30-40% of the CO 2 -evolving groups are desorbed, that evolution being assessed mainly to carboxylic acid and carboxylic anhydride groups [11,12].…”

Section: Activation Conditionsmentioning

confidence: 99%

Development of porosity upon physical activation of grape seeds char by gas phase oxygen chemisorption–desorption cycles

Jiménez-Cordero

Heras

Alonso-Morales

et al. 2013

Chemical Engineering Journal

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“…The presence of phenol is also possible given the increase in the CO signal in the 650-725 °C ran ge. In the 800-950 °C temperature range, the curve corresponding to the CO evolution shows a peak at around 800 °C which corresponds to carbonyl groups in quinone structures [39,41,44,45]. Moreover, the shape of the curves (Figure 2.a) indicates that at higher temperatures more CO was detected which is indicative of the presence of chromenes and pyrones.…”

Section: Textural and Surface Chemistry Characterizationmentioning

confidence: 95%

“…CO desorption occurs at higher temperatures due to the decomposition of phenols, carbonyl groups, ethers and basic structures such as quinones, chromenes and pyrones (where one C atom is bonded to one oxygen atom) [39][40][41][42][43][44][45]. However, the amount of carboxylic acid groups was not high compared to that of the other surface oxygen functionalities, since gas phase oxidation increased the number of lactone, phenol and carbonyl/quinone surface groups [41].…”

Section: Textural and Surface Chemistry Characterizationmentioning

confidence: 99%

Properties and performance of mesoporous activated carbons from scrap tyres, bituminous wastes and coal

Acevedo

Barriocanal

Lupul

et al. 2015

Fuel

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Tyre wastes and their blends with coal and a bituminous waste material obtained from the benzol distillation column of a by-product section of a coking plant were employed as a precursor for the production of activated carbons (ACs). Pyrolysis up to 850 °C followed by physical activation with CO 2 produced mesoporous carbons with different pore size distributions and surface areas. The surface chemistry of the samples was studied by measuring the point of zero charge (pH pzc ) and by temperature programmed desorption (TPD). The activated carbons obtained contained higher amounts of basic functional groups. Their textural and surface chemistry characteristics make them highly suitable for adsorbing acid dyes of large molecular size, such as Congo red. The adsorption kinetics was found to conform closely to the pseudo-second-order kinetic model. To determine the adsorption mechanism, the kinetic data were also analysed using the Weber and Morris intraparticle diffusion model and the Boyd model to distinguish between the pore and film diffusion steps. The equilibrium isotherms were of the Langmuir isotherm type. The efficiency of the low-cost ACs prepared for the removal of Congo red dye was similar to that reported in the literature for coal-based ACs and greater than that of other low-cost ACs.

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“…While nearly no weight loss was registered for Ox-CS-SWCNTs at temperatures below 500 ºC (due to the previous heat treatment in air), a continuous weight loss reaching ~5 % was detected for the SW-SWCNTs. This weight loss below 500 ºC is probably associated to surface carboxylic acids [15]. Besides, BP4, BP5 and BP6 exhibits redox peaks that are characteristic of the presence of oxygenated surface groups [16,17], which influence the electrochemical interfacial state of the carbon surface and its double-layer properties.…”

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confidence: 99%

Single-walled carbon nanotube buckypapers as electrocatalyst supports for methanol oxidation

Sieben

Ansón‐Casaos

Martı́nez

et al. 2013

Journal of Power Sources

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This work studies the use of various single-walled carbon nanotube (SWCNT) buckypapers as catalyst supports for methanol electro-oxidation in acid media. Buckypapers were obtained by vacuum filtration from pristine and oxidized SWCNT suspensions in different liquid media. Pt-Ru catalysts supported on the buckypapers were prepared by multiple potentiostatic pulses using a diluted solution of Pt and Ru salts (2 mM H 2 PtCl 6 + 2 mM RuCl 3 ) in acid media. The resulting materials were characterized via SEM, TEM, EDX and ICP-OES analysis. Well dispersed rounded nanoparticles between 2 and 15 nm were successfully electrodeposited on the SWCNT buckypapers. The ruthenium content in the bimetallic deposits was between 32 and 48 at. %, while the specific surface areas of the catalysts were in the range of 72 to 113 m 2 g -1 . It was found that the solvent used to prepare the SWCNT buckypaper films has a strong influence on the catalyst dispersion, particle size and metal loading. Cyclic voltammetry and chronoamperometry experiments point out that the most active electrodes for methanol electro-oxidation were prepared with the buckypaper supports that were obtained from SWCNT dispersions in N-methylpyrrolidone.

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The role of surface chemistry in catalysis with carbons

Cited by 583 publications

References 104 publications

Development of porosity upon physical activation of grape seeds char by gas phase oxygen chemisorption–desorption cycles

Development of porosity upon physical activation of grape seeds char by gas phase oxygen chemisorption–desorption cycles

Properties and performance of mesoporous activated carbons from scrap tyres, bituminous wastes and coal

Single-walled carbon nanotube buckypapers as electrocatalyst supports for methanol oxidation

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