Specific surface area calculations

Specific surface area calculated by multiplot BET method. b Total pore volume calculated by BJH method. c Average pore diameter. 

C. The Meaning of Specific Surface Areas Calculated from... 

Table 5.2 Comparison of specific surface areas calculated from the ascending branch of the water isotherms of selected cellulosic materials by the BET theory, the ct procedure and the Zimm and Lundberg (ZL) cluster theory.

Dl, particle size calculated from the Sherrer equation Sjh, specific surface area calculated assuming cubic particles and a density of LaCo03 equal to 7.29 D2, equivalent cubic particle size calculated from BET surface area. P, perovskite C, cobalt oxide. 

BET surface area m2/g ASTM D 3037 DIN 66131 DIN 66132 total specific surface area calculated from the nitrogen adsorption isotherm by using the BET equation... 

Table E1.5. BET Data for Specific Surface Area Calculation of Ca( OHh.

The specific surface area calculated here only involves the walls of the pores of the bed and excludes the pores within the particles. Therefore, the surface area measured in this method can be much smaller than the total surface area measured by gas adsorption methods [24],... 

Sbet is the specific surface area calculated using standard BET method Vp is the total pore volume computed from adsorption at the maximal p/po value parameters with the DS subscripts were computed using the modified Dubinin-Stoeckli equation [7]. 

Leica Cambridge Stereoscan 360). The SEM micrographs of H-ZSM-5, Zn-H-ZSM-5 and Ga-H-ZSM-5 exhibited the typical crystal form of ZSM-5 zeolite and the average crystal size was 2 pm-4 pm. The quantitative analysis of the Ga and Zn content in the ZSM-5 zeolite was performed by an X-ray fluorescence analyzer X-MET 880 (Outokumpu). The specific surface area of the synthesized zeolite catalysts was determined by nitrogen adsorption using a Sorptomatic 1900 (Carlo Erba Instmments). The specific surface area calculated by the Dubinin method was found to be 427, 445 and 372 m /g for Zn-H-ZSM-5, Ga-H-ZSM-5 and H-ZSM-5, respectively. It was observed from different characterization techniques that the introduction of Ga and Zn by this method did not destroy the structure of the ZSM-5 zeolite. 

The specific surface areas, calculated following the BET method are given in Table 2. 

Dispersion of the emulsion is the degree of distribution of the droplets of the discontinuous phase in the continuous phase. Dispersion is characterized by the diameter of the droplets d, and by D = 1/d (= specific surface area) calculated by dividing the total surface area of the particles by their total volume. 

Specific surface area of C5 polyol-boehmite is also much higher (343 m. g" ) than those of C4 polyol-boehmite (168 m. g ) or even of reference boehmite (144 m. g" ) according to the decrease of particle size previously described. In table 1, these specific surface area values measured from Na adsorption/desorption experiment (Sbet) are compared to geometric specific surface area calculated from particle morphological data (Sga,). Sbet values are slightly lower than Sgeo values probably due to particle aggregation. 

Figure 12.6 Influence of the metal coalescence factor = 1 - Achem/Acaic in PtRu/Sibunit catalysts on the CO stripping peak (top) and the specific current for 0.1M methanol oxidation at 0.4 V after 1800 seconds (bottom). Achem is the specific surface area of Pt-Ru particles determined with CO chemisorption, and Acaic is the specific surface area calculated either from the results of XRD (filled symbols) or from TEM (open symbols). The measurements were performed in O.IM H2SO4 at 323 K, BET surface area of Sibunit carbon 72m /g. (From ref. 178, with permission from the Royal Society of Chemistry.)...

N2 sorption experiments at 77 K were carried out with a Micromeritics ASAP2000 instrument and specific surface areas calculated using the BET method. 

Table 1.8 lists specific surface area values for illitic micas as determined by nitrogen gas adsorption and by negative chloride adsorption.The specific surface areas calculated from N2 gas adsorption with the help of Eq. 1.7 show no particular trend with type of exchangeable cation. The mean value of 5, 11.2 0.5 x 10 m kg", suggests that the mineral forms particles containing seven phyllosilicate layers, as indicated previously. The external surfaces of these particles are expected to repel anions, and therefore the specific surface area determined by negative chloride adsorption should also be around lO m kg" . As shown in Table 1.8, however, the values of 5k, obtained with Eq. 1.18, are always less than 5 and decrease sharply with increasing radius of the... 

This latter observation is clearly highlighted when plotting the TMS surface densities, calculated using both the specific surface areas calculated from nitrogen and CTAB adsorption measurements, versus the surface density of residual silanol groups as depicted on Fig. 1. 

FIGURE 2.33 DTF IPSDs with respect to (a) the pore volume and (b) the specific surface area calculated on the basis of the water adsorption isotherms for nanooxides. (Adapted from Powder TechnoL, 195, Gun ko, V.M., Zarko, V.L, Turov, V.V. et al.. Morphological and structural features of individual and composite nanooxides with alumina, silica, and titania in powders and aqueous suspensions, 245-258, 2009g, Copyright 2009, with permission from Elsevier.)... 

The specific surface area calculated from assuming that the particles are dense, is indicated by the symbol A a. 

Actually, 286 m g was measured. The difference is explained by the fact that around each point of contact between spherical particles there is an area or annular crevice too small to be penetrated by nitrogen molecules during the measurement of specific surface area, the diameter of the nitrogen molecule being 0.4 nm. For larger particles, the specific surface area, calculated from particle size in electron micrographs, is in better agreement with the area measured by adsorption methods (see Chapter 4, Ref. 142). 

According to Eqs. (8) and (9), the specific surface area of the adsorbent can be calculated in the knowledge of the adsorption capacities and the cross-sectional areas. The above method for the determination of the specific surface area has been applied to many systems in the literature, and it has been found that the specific surface areas calculated with the Schay-Nagy extrapolation method for nonswelling and desegregating adsorbents agree very well with the values calculated with the Brunauer-Emmett-Teller (BET) method [1-5]. 

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