Nitrogen adsorption-desorption isotherm

Figure 1. Adsorption-desorption nitrogen isotherms for AC-ref SC-100 and SC-155 Adsorbed volume (cnvVg) vs. p/p .

Xerogel texture is evaluated by thermoporomotry and adsorption-desorption nitrogen isotherms (B.E.T. specific area and mesopore diameter distribution). 

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).

Fig. 230 Adsorption of nitrogen at 77 K on a silica powder a) adsorption isotherms b) /-plot. Broken line, uncompacted powder continuous line, power compacted at 2-00 x 10 N m (130 ton in ). (—>—) adsorption (—<-) desorption. / is the ratio of the amount adsorbed on the powder to the amount adsorbed on the compact at the same relative...

Figure 3.42. Nitrogen adsorption/desorption isotherm for a commercial y-alumina. The arrows denote the mode of changing the pressure, viz. increasing or decreasing pressure.

Catalysts Characterization Catalysts were characterized by nitrogen adsorption-desorption isotherms, XRD, XPS, TEM, and FT-IR. The concentration and the strength of the acid sites were determined using a combination of NHs-chemisorption and FTIR. Detailed procedures are given elsewhere [18, 19]. 

Nitrogen adsorption/desorption isotherms of all the activated carbons are of Type I, i.e. characteristic of basically microporous solids. There is a lack of adsorption/desorption hysteresis. More careful analysis permits to notice significant differences in the porous texture parameters depending on precursor origin. 

Nitrogen adsorption/desorption isotherms on Zeolite and V-Mo-zeolite are very similar and close to a type I characteristic of microporous materials, although the V-Mo-catalysts show small hysterisis loop at higher partial pressures, which reveals some intergranular mesoporosity. Table 1 shows that BET surface area, microporous and porous volumes, decrease after the introduction of Molybdenum and vanadium in zeolite indicating a textural alteration probably because of pore blocking by vanadium or molybdenum species either dispersed in the channels or deposited at the outer surface of the zeolite. The effect is far less important for the catalysts issued from ZSM-5. 

Figure 2 shows us the N2 adsorption-desorption isotherm of Beta/montmorillonite composite. At low relative pressure a sharp adsorption of nitrogen indicates the existence of large amount of micropore. The hysteresis shown in figure 2 is ascribed to type H4 which usually can be observed on layered clay and other materials [2], It is obvious that part of the pore structure in montmorillonite is still preserved after calcination under high temperature and the following hydrothermal crystallization. 

Figure 1. Nitrogen adsorption-desorption isotherms at 77 K on (void squares) SBA-15 synthesized at 403 K, (void lozenges) SBA-15 synthesized at 343 K, (filled triangles) MCM-41.

The X-ray diffraction pattern of the spheres before the immersion in SBF shows the typical diffraction peak ascribable to the (100) reflection of the ordered mesophase with a dioo of 3.45 nm. Nitrogen adsorption-desorption isotherms are of type IV and pore size from DFT model results 2.4 nm (data not reported). 

Nitrogen adsorption-desorption isotherms of MCM-41-IBU after 2 hours of immersion in SBF show the characteristic mesopore filling at p/p° below 0.25 (type IV isotherm). 

Surface Acoustic Waves (SA Ws). The basic idea of this technique is to use the dependence of the frequency and propagation of surface acoustic waves on mass loading in a film. The porous film has to be deposited on a piezoelectric substrate (quartz), which is then placed into a physisorption setup to condense nitrogen at 77 K. Adsorption and condensation of N2 result in a shift of the oscillation frequency, and thus measurements of the oscillation frequency as a function of N2 partial pressure provide an adsorption-desorption isotherm.30 Although the technique has proven to provide a concise characterization of porous films,29,30 the requirement for the deposition directly onto the SAW piezoelectric substrate represents a certain restriction. 

Figure 1.6 Top Low-temperature nitrogen adsorption ( ) and desorption (x) isotherms measured on a calcined SBA-15 mesoporous silica solid prepared using an EO20PO70EO20 block copolymer [54]. Bottom Pore size distribution derived from the adsorption isotherm reported at the top [54]. A high surface area (850 m2/g), a uniform distribution of cylindrical nanopores (diameter —90 A), and a large pore volume (1.17 cm3/g) were all estimated from these data. These properties make this material suitable for use as support in the preparation of high-surface-area solid catalysts. (Reproduced with permission from The American Chemical Society.)...

Figure 4.24 TEM image (left), XRD pattern (middle), and nitrogen adsorption-desorption isotherm (right) of a typical MCM-41 material. (Courtesy of F. Kleitz.)...

Characterization. The high resolution TEM images were obtained on a JEOL 2010 electron microscope with an acceleration voltage of 200 kV. Measurement of nitrogen adsorption-desorption isotherms was performed on a Micromeritics ASAP... 

Figure 12.3 Nitrogen adsorption-desorption isotherms at 77 K showing the pore filling of (a) [Y N(SiHMe2)2 3(THF)2] MCM-412 0 (19) and (h) [Y N(SiHMe2)2 3(THF)2] MCM-41 LP.280 The pore diameters of the parent PMSs are 2.7 (a) and 3.8nm (h). For the former material the isotherm changes from type IV (mesopores) to type I (micropores).

Fig. 4 Nitrogen adsorption-desorption isotherms at 77 K of heat-treated NH4 -exchanged MSU-Ge-2 (solid circles, adsorption data open circles, desorption data). The hysteresis observed at P/Po > 0.8 is due to the voids between the agglomerated particles. (Inset) BJH pore size distribution calculated from the adsorption branch of the isotherm...

Nitrogen physisorption measurements evidence the permanent mesoporosity of the NU-GeSi-A materials (Fig. 11). All the N2 adsorption-desorption isotherms... 

Fig. 11 Nitrogen adsorption-desorption isotherms of mesoporous (a) NU-GeSi-1, (b) NU-GeSi-2, (c) NU-GeSi-3, and (d) NU-GeSi-4 materials. Inset. BJH pore size distribution calculated from the adsorption branch...

Fig. 1. Nitrogen adsorption-desorption isotherms at -196 C for the mesoporous material OH-02-600 and its precursory synthetic hectorite H-02-300. Open symbols adsorption. Solid symbols desorption.

Fig 1A shows the XRD pattern of the calcined MCM-41 sample synthesized from C,6TMAB-silica and aluminosilicate systems with the Si/Al = oo(sample I) and 37(sample II) by using the delayed neutralization process. In both materials, there exist at least 4 sharp XRD peaks, which indicate well-ordered hexagonal structure of MCM-41. It means that the incorporation of aluminum into silica framework could not have significant effect on the arrangement of MCM-41 mesostructure. When the nitrogen adsorption-desorption isotherms... 

The nitrogen adsorption / desorption isotherms (Fig. 2) are typical of well-defined porous frameworks that are characteristic of either supermicroporosity (MSU-1) or a small mesoporosity (MSU-4) without any textural porosity [14]. In these two compounds, the silica walls (deduced from x-ray diffraction and nitrogen isotherms) are quite thick (< 20 A) [5],... 

Figure 2. Nitrogen adsorption ( ) and desorption (O) isotherms of MSU-1 and -4 Silica obtained with Tergitol 15S12 and Tween 20. Nitrogen adsorption isotherms were measured at 77 K on a Micromeretics 2010 Sorptometer using standard continuous procedures and samples degased at 150°C for 15 hours.

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