Nitrogen adsorption comparison

Fe(lll) surface were used for the rate of the dissociative nitrogen adsorption. Comparison of the calculated ammonia yields with those determined experimentally on a commercial Topsoe KM1 catalyst showed an agreement within a factor better than 2. Figure 12 demonstrates these encouraging results. These conclusions have been confirmed by calculations results of another independent group [121], [209]. 

Comparison of specific surface of anatase and zinc oxide determined by electron microscopy A ) and by nitrogen adsorption A )... 

Comparison of particle diameter of colloidal silica by electron microscopy (cf,). by nitrogen adsorption (d ) and by light scattering (d,)... 

Fig. 2.29 Comparison of nitrogen adsorption at 78 K on a carbon black (Sterling FT) before and after graphitization (a) The amount adsorbed on the ungraphitized sample plotted against the amount x, adsorbed on the graphitized sample, at the same pressure, b) The corresponding isotherms O, adsorption, , desorption on the ungraphitized sample (4 runs) A. adsorption A desorption, on the graphitized sample (4 runs).

Comparison of surface areas determined by mercury porosimetry and by nitrogen adsorption ... 

When the values of the BET monolayer capacity calculated from Type III isotherms are compared with independent estimates (e.g. from nitrogen adsorption) considerable discrepancies are frequently found. A number of typical examples are collected in Table 5.1. Comparison of the value of the monolayer capacity predicted by the BET equation with the corresponding value determined independently (columns (iv) and (v)) show that occasionally, as in line 6, the two agree reasonably well, but that in the majority... 

Brenner, A.M., Adkins, B.D., Spooner, S., and Davis, B.H. 1995. Porosity by small-angle x-ray scattering (SAXS) Comparison with results from mercury penetration and nitrogen adsorption. J. Non-crystal. Solids 185 73-77. 

The pore size distribution in highly activated carbon HSGD measured with low temperature nitrogen adsorption shows absence of the curve maximum in the range of 75-900 A (Fig. 29.6). In comparison with the pore distribution of SCN hemosorbent, HSGD has predominantly meso- and small macroporous structure, with some... 

A good-quality CeMCM-41 material with Si/Ce=50 was synthesized by hydrothermal method. For the purpose of comparison a pure siliceous MCM-41 was prepared using the same composition without cerium. Thermogravimetric curves for the synthesized uncalcined samples exhibit shape characteristic for the MCM-41-type materials. The specific surface area of CeMCM-41 evaluated from nitrogen adsorption was equal to 850 m2/g, whereas the pore width and mesopore volume of this material were equal to 3.8 nm and 0.8 cm3/g, respectively. In contrast to the pure silica MCM-41, the CeMCM-41 material exhibits medium and strong acid sites as revealed by thermogravimetric studies of n-butylamine thermodesorption. 

The total surface area S,0i ofll09m2/g, external surface area Sexi of 110m2/g and mesopore volume Vmc of 0.806 cm3/g were evaluated from the nitrogen adsorption isotherm using the comparison plot method [11], The size of the MCM-41 hexagonal channels can be characterized by their hydraulic diameter Dme, whose size of 3.2 nm was calculated according to the formula... 

Figure 2. (a) PSDs for 3.88 nm MCM-41 [22] calculated from nitrogen adsorption data at 77 K using i) the KJS approach with the BJH algorithm, ii) the hybrid DFT method, iii) the HK-based method with the relation between pore size and condensation pressure described by Eq. 2, and iv) the HK-based Saito-Foley method, (b) Comparison of PSDs for octyldimethylsilyl-bonded MCM-41 calculated from nitrogen adsorption using the KJS-calibrated BJH algorithm with t-curves for reference ODMS-modified silica and unmodified silica. 

Figure 2 shows a comparison of nitrogen adsorption isotherms at 77 K for the organic-inorganic hybrid materials developed for adsorption of mercury ions. The shape of the nitrogen adsorption isotherms indicates that the mesostructure was preserved after chemical modification of the surface. Evaluation of the shift of the capillary condensation step and reduction of its height provide information about formation of the chemically bonded layer inside mesopores. 

Because of their globular shape, carbon black particles were used in some of the earliest attempts to validate the BET method (Emmett and DeWitt, 1941). Comparison of the values of surface area obtained by nitrogen adsorption and electron microscopy appeared to provide sound evidence for the validity of the BET areas (Brunauer, 1945 Gregg and Sing, 1982, p. 64). However, in the light of more recent work (Sing, 1994), it seems likely that the excellent agreement obtained in the early measurements may have been to some extent fortuitous. 

Characterization of particle size. In Figure 12. a comparison is given between particle size determination by the analytical centrifuge, by electron microscope and by nitrogen adsorption on the carefully... 

The estimation of the amount of adsorbent in the column is based on the comparison of the total pore volume (Vptot [niL]) of the adsorbent in the column with the specific pore volume (Vp [mL/g]) of the same adsorbent determined from the full nitrogen adsorption isotherm. The ratio of these two values will give the adsorbent mass. Total pore volume in the column is determined as the difference of the column void volume (Vo) and the interparticle volume (Vip). 

Figure 2 Comparison of isotherms generated by the two-stage HK method (solid lines) and DFT (diamonds) for nitrogen adsorption at 77 K in carbon slit pores of width (fi-om left to right) 10, 15 and 67 A.

This study consists in verifying the coherence of a few commonly used analysis methods of nitrogen adsorption-desorption isotherms. These methods were tested on model samples obtained by mechanically mixing two micro- and mesoporous solids respectively with known mass proportions. Although the individual analysis methods may lead to discrepancies in the interpretation of the isotherms, their systematic comparison allows drawing a coherent picture of the porous texture. 

Data of low-temperature nitrogen adsorption were used to evaluate the parameters characterizing the pore structure of the obtained polymeric materials in dry state. The BET specific surface area, Sbet, and the total pore volume, V, were estimated by applying the standard methods Sbet from the linear BET plots and F/ from adsorption at relative pressure p/po=0.975) [7]. The mesopore structure was characterized by the distribution function of mesopore volume calculated by the Barret-Joyner-Halenda (BJH) method [27]. In Table 2 the values of these parameters are given for both synthesized polymers. The melamine-formaldehyde resin MEA has a more developed pore structure (5 B 7=220mVg, F,=0.45cm /g) and narrower mesopores (D=7.3nm) in comparison to the phenolic-formaldehyde polymer PHD. 

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