Assessment of the surface area and microporosity of activated charcoals from immersion calorimetry and nitrogen adsorption data

Denoyel, Renaud; Fernández‐Colinas, José M.; Grillet, Y.; Rouquérol, J.

doi:10.1021/la00026a025

Cited by 121 publications

(79 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This behaviour is consistent with described by Denoyel [20]. In a similar work, carbonaceous materials were prepared and characterized by immersion calorimetry in benzene and carbon tetrachloride, and a proportionality was found between the enthalpy of immersion and the surface area accessible to the immersion liquid [21].…”

Section: Characterization Of the Materialssupporting

confidence: 83%

Calorimetric study of activated carbons impregnated with CaCl₂

2015

View full text Add to dashboard Cite

Activated carbon monoliths with different surface characteristics were prepared by impregnating oil palm stone with diluted aqueous CaCl 2 solutions (with concentrations between 2 and 7% w/v) without binders. The solids were characterized by determination of nitrogen adsorption isotherms at 77 K and carbon dioxide adsorption isotherms at 273 K using volumetric adsorption equipment. Surface area and micropore volume values were calculated from the nitrogen isotherms using the BET and DR models, respectively, obtaining solids with low percentages of mesoporosity. Immersion enthalpies of the activated carbon monoliths were determined in benzene, with values between -173 and -104 J g -1 , and water, with values between 61 and 30 J g -1 , indicating that the monoliths have a hydrophobic character.

show abstract

Section: Characterization Of the Materialssupporting

confidence: 83%

Calorimetric study of activated carbons impregnated with CaCl₂

2015

View full text Add to dashboard Cite

show abstract

“…The effect is more pronounced when the solution is evaporated because the temperature progressively increases, as it does the concentration of the solution. The partial depolymerisation of lignin decreases the mechanical properties of the particle, thus facilitating its swelling [15], whereas the decomposition of the other components, hemicellulose and cellulose, into smaller units brings about a flow and redistribution of the cellular matter, with a high degree of mobility and migration. In fact, one can observe physical and chemical changes in the particles along impregnation and, additionally, the appearance of micelles in the solution which are converted into tar during evaporation.…”

Section: Discussionmentioning

confidence: 99%

“…The enthalpy of immersion of each carbon into liquids of different molecular dimension was measured at 30ºC. The enthalpy of immersion for a non-porous reference carbon (V3G, 62m 2 /g) was used to calculate the surface area of the carbons accessible to the selected liquids [15]. The micropore size distribution has been determined by plotting the surface area as a function of the minimum kinetic dimension of the liquid: dichloromethane, 0.33nm; benzene, 0.37 nm; 2,2-dimethylbutane, 0.56nm [16,17].…”

Section: Methodsmentioning

confidence: 99%

Modification of the porous structure along the preparation of activated carbon monoliths with H3PO4 and ZnCl2

Nakagawa

Molina‐Sabio

Rodríguez‐Reinoso

2007

Microporous and Mesoporous Materials

147

View full text Add to dashboard Cite

Two series of activated carbon monoliths (discs) have been prepared by chemical activation of olive stones with phosphoric acid or zinc chloride, without the use of any binder. A conforming step was introduced between impregnation with the chemical and heat treatment. Two equivalent series of granular activated carbons were also prepared in order to analyse the effect of conforming pressure on the porosity of the final activated carbon. The evolution of microporosity and the micropore size distribution has been followed by gas adsorption (N 2 at -196ºC and CO 2 at 0ºC) and immersion calorimetry into three liquids with different molecular dimensions (dichloromethane, benzene and 2,2-dimethylbutane). The experimental results indicate that activation by both chemicals produce a large development of microporosity but the differences between the granular and monolithic forms are more noticeable when using phosphoric acid. Thus, there is mainly a reduction in the interparticle space and macroporosity during the formation of the discs prepared using zinc chloride whereas there is an additional reduction in the volume and dimension of the meso-and microporosity when using phosphoric acid. The different behaviour of the two chemicals has been related to their effect on the precursor along the impregnation step.

show abstract

“…Following a technique proposed by Denoyel et al [27], a number of authors (for example [28][29][30][31]) also attempted to derive surface areas from the enthalpy immersion into benzene and other liquids which have no specific interactions with surface groups. This approach is based on the determination of a surface area S(m 2 g À1 ) = D i H/h i , where h i is a specific enthalpy of immersion.…”

Section: Surface Areas From Immersion Calorimetrymentioning

confidence: 99%

“…This approach is based on the determination of a surface area S(m 2 g À1 ) = D i H/h i , where h i is a specific enthalpy of immersion. In the case of benzene, it is suggested to use À0.114 J m À2 , obtained for graphitized carbon blacks [2,27]. However, as shown in Table 1, this approach leads to surface areas which are higher than S mi + S e and the difference increases with the micropore width L o .…”

Section: Surface Areas From Immersion Calorimetrymentioning

confidence: 99%

On the determination of surface areas in activated carbons

Stoeckli

Centeno

2005

Carbon

114

View full text Add to dashboard Cite

The paper examines the validity of two approaches frequently used to determine surface areas in activated carbons, namely the BET method and the use of immersion calorimetry. The study is based on 21 well characterized carbons, whose external and microporous surface areas, S e and S mi , have been determined by a variety of independent techniques. It appears clearly that S BET and the real surface area S mi + S e are in agreement only for carbons with average pore widths L o around 0.8-1.1 nm. Beyond, S BET increases rapidly and S BET À S e is practically the monolayer equivalent of the micropore volume W o . This confirms that a characterization of surface properties based on S BET is, a priori, not reliable. The study of the enthalpy of immersion of the carbons into benzene at 293 K, based on DubininÕs theory, shows that D i H consists of three contributions, namely from the interactions with the micropore walls (À0.136 J m À2 ), the external surface (À0.114 J m À2 ), and from the volume W Ã o of liquid found between the surface layers in the micropores (À141 J cm À3 ). It appears that for carbons where L o > 1 nm, the real surface area cannot be determined in a reliable way from the enthalpy of immersion and a specific heat of wetting alone.

show abstract

Assessment of the surface area and microporosity of activated charcoals from immersion calorimetry and nitrogen adsorption data

Cited by 121 publications

References 2 publications

Calorimetric study of activated carbons impregnated with CaCl₂

Calorimetric study of activated carbons impregnated with CaCl₂

Modification of the porous structure along the preparation of activated carbon monoliths with H3PO4 and ZnCl2

On the determination of surface areas in activated carbons

Contact Info

Product

Resources

About

Assessment of the surface area and microporosity of activated charcoals from immersion calorimetry and nitrogen adsorption data

Cited by 121 publications

References 2 publications

Calorimetric study of activated carbons impregnated with CaCl2

Calorimetric study of activated carbons impregnated with CaCl2

Modification of the porous structure along the preparation of activated carbon monoliths with H3PO4 and ZnCl2

On the determination of surface areas in activated carbons

Contact Info

Product

Resources

About

Calorimetric study of activated carbons impregnated with CaCl₂

Calorimetric study of activated carbons impregnated with CaCl₂