Textures isotherms

The benefits of the method are appreciated when the textural parameters are compared. Data derived from N2-physisorption isotherms show that Fenton detemplation leads to improved textural parameters, with BET areas around 945 m g for a pore volume of 1.33 cm g , while calcination leads to reduced textural parameters (667m g 0.96cm g ). T-plot analysis, strictly speaking, is not apphcable for these bi-modal materials but it gives a good estimate. It shows that the micropore volume is doubled, which corresponds to an increase in the calculated micropore area from about... 

The BET surface area values are also reported with the distribution of porosity between microporosity (pore diameter <1.8 nm) deduced from N2 adsorption isotherms (t-curves) and mesoporosity (pore diameter > 1.8 nm). The following trend is observed for high atomic M/HPA ratio used for the precipitation, the precipitates exhibited high surface area mainly due to microporosity. However, depending on the nature of the coxmter cation and also of the previous ratio values, the textural characteristics were not similar. In particular, it is interesting to note the presence of mesopores for (NH4)2.4P, CS2.9P, CS2.7P and Cs2.4Si samples. 

Catalyst characterization - Characterization of mixed metal oxides was performed by atomic emission spectroscopy with inductively coupled plasma atomisation (ICP-AES) on a CE Instraments Sorptomatic 1990. NH3-TPD was nsed for the characterization of acid site distribntion. SZ (0.3 g) was heated up to 600°C using He (30 ml min ) to remove adsorbed components. Then, the sample was cooled at room temperatnre and satnrated for 2 h with 100 ml min of 8200 ppm NH3 in He as carrier gas. Snbseqnently, the system was flashed with He at a flowrate of 30 ml min for 2 h. The temperatnre was ramped np to 600°C at a rate of 10°C min. A TCD was used to measure the NH3 desorption profile. Textural properties were established from the N2 adsorption isotherm. Snrface area was calcnlated nsing the BET equation and the pore size was calcnlated nsing the BJH method. The resnlts given in Table 33.4 are in good agreement with varions literature data. 

Nitrogen adsorption isotherms were measured with a sorbtometer Micromeretics Asap 2010 after water desorption at 130°C. The distribution of pore radius was obtained from the adsorption isotherms by the density functional theory. Electron microscopy study was carried out with a scanning electron microscope (SEM) HitachiS800, to image the texture of the fibers and with a transmission electron microscope (TEM) JEOL 2010 to detect and measure metal particle size. The distribution of particles inside the carbon fibers was determined from TEM views taken through ultramicrotome sections across the carbon fiber. 

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 1 shows that the catalysts maintain their mesoporous structure with type IV isotherm. It can be observed a reduction in surface area, pore volume and pore diameter and slight increase in textural porosity as the concentration of aluminum increases (Table 1), due to the increase in the wall thickness in the mesoporous material as we have found previously [3],... 

At 9 hours of immersion, instead, isotherms do not show the pore filling associated with mesopores, which in turn appears again between 25 and 26 hours. After 28 hours of soaking, no mesopore filling is observed (figure 3). The DFT pore size distributions also confirm the presence of mesopores (around 2.2 nm) only at 2 hours of immersion and between 25 and 26 hours. The peak at around 5 nm is probably due to the textural interparticles porosity (figure 3 inset). 

Porous texture characterization of all the samples was performed by physical adsorption of N2 at 77K. and CO2 at 273K, using an automatic adsorption system (Autosorb-6, Quantachrome). The micropore volume, Vpp (N2), was determined by application of Dubinin-Radushkevich equation to the N2 adsorption isotherm at 77K up to P/Po< 0.1. The volume of narrow micropores, Vnpp (DR,C02>, (mean pore size lower than 0.7 nm) was calculated from CO2 adsorption at 273 K. 

Naono, H. Sonoda, J. Oka, K. Hakuman, M. (1993) Evaluation of microporous texture of undecomposed and decomposed p-FeOOH fine particles by means of adsorption isotherms of nitrogen gas and water vapor. Proc. IVth Int. Conf on Fundamentals of Adsorption, Kyoto 1992, 467-474 Naumann, F. (1855) Elemente der Mineralogie. 4. Auflage, Leipzig... 

Chemical composition of fresh HTs was determined in a Perkin Elmer Mod. OPTIMA 3200 Dual Vision by inductively coupled plasma atomic emission spectrometry (ICP-AES). The crystalline structure of the solids was studied by X-ray diffraction (XRD) using a Siemens D-500 diffractometer equipped with a CuKa radiation source. The average crystal sizes were calculated from the (003) and (110) reflections employing the Debye-Scherrer equation. Textural properties of calcined HTs (at 500°C/4h) were analyzed by N2 adsorption-desorption isotherms on an AUTOSORB-I, prior to analysis the samples were outgassed in vacuum (10 Torr) at 300°C for 5 h. The specific surface areas were calculated by using the Brunauer-... 

N2 sorption isotherms were measured for the pure carrier and for all the immobilized complexes, respectively. Sorption isotherms and textural characteristics for pure and loaded samples are compared in Fig. 2.1.6.1 and Table 2.1.6.1. In all cases these isotherms presented the characteristic form of mesoporous materials. It is clear that the N2 adsorbed/desorbed volume was higher in the case of pure carrier than in the case of immobilized complexes. 

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],... 

Texture parameters from adsorption isotherms, i. e, total surface area (Stot), external surface area (Sext), mesopore surface area(Sme). mesopore volume (VTO) and mesopore diameter... 

Figure 3 and Table 1 demonstrate the typical changes in the isotherms and the texture parameters in dependence on several steps leading to dye anchoring. Two groups of isotherms can be distinguished belonging to (i) parent or pre-silylated and (ii) APTES-functionalized and dye-anchored materials. 

Hammami et al. [4.27] determined 0.5 mbar and rSh = 55 °C as the optimum (for quality and operational data) drying conditions for the freeze-drying of apple slices, loaded with 17 kg/m2 and dried in 48-50 h. The rehydration ratio was -0.55 g/g of water removed and the texture loss of rehydrated apples was estimated to be more than 85%. Sa et al. [4.28] used DSC to measure the Tg of freeze-dried Golden Delicious apples after exposure to aw from 0.12 to 0.93. The sorption isotherms are reported. 

The fluorinated carbon-coated AAO film has an interesting adsorption characteristic that has not been reported so far. Figure 3.12 shows N2 adsorption/desorption isotherms at -196°C for the pristine carbon-coated AAO film and the films fluorinated at different temperatures [119]. The isotherm of the pristine film is characterized by the presence of a sharp rise and a hysteresis in a high relative pressure range. Such a steep increase can be ascribed to the capillary condensation of N2 gas into the nanochannels of the AAO films, that is, the inner space of the nanotubes embedded in the AAO films. The amount of N2 adsorbed by the condensation into the fluorinated channels is lower than that of the pristine one. Moreover, the amount drastically decreases with an increase in the severity of fluorination. Since TEM observation revealed that the inner structure of the fluorinated CNTs was not different from that of the pristine nanotubes, the reason why the N2 isotherm was so changed as in Figure 3.12 cannot be attributed to the alteration of the pore texture upon the... 

Physical adsorption of gases is, undoubtedly, the most widely used technique [4], Due to the considerable sensitivity of nitrogen adsorption isotherms to the pore texture in both microporous and mesoporous ranges and to its relative experimental simplicity, measurements of subcritical nitrogen adsorption at 77 K are the most used. However, this technique has some limitations, and other complementary techniques are needed for the characterization of microporous solids. 

Physical adsorption of gases and vapors is a powerful tool for characterizing the porosity of carbon materials. Each system (adsorbate-adsorbent temperature) gives one unique isotherm, which reflects the porous texture of the adsorbent. Many different theories have been developed for obtaining information about the solid under study (pore volume, surface area, adsorbent-adsorbate interaction energy, PSD, etc.) from the adsorption isotherms. When these theories and methods are applied, it is necessary to know their fundamentals, assumptions, and applicability range in order to obtain the correct information. For example, the BET method was developed for type II isotherms therefore, if the BET equation is applied to other types of isotherms, it will not report the surface area but the apparent surface area. 

Potato taste is not characterized by one of the primary taste sensations. Especially sweet, sour or bitter notes are considered off-flavors. However, free amino acids and 5 -nucleotides are important compounds that convey an agreeable basic taste to potato products. The amino acids occur naturally in free form the 5 -nucleotides are liberated during the heat preparation of potatoes by a specific enzymatic degradation of RNA. Starch forms a matrix for all potato preparations. Although it is tasteless, is has an influence on taste quality due to textural characteristics, and due to its pronounced capability to form stable complexes with flavor compounds either in a thermal gradient or under isothermal conditions. 

Malcolm C. Bourne, Food Texture and Viscosity Concept and Measurement. 1982. Hector A. Iglesias and Jorge Chirife, Handbook of Food Isotherms Water Sorption Parameters for Food and Food Components. 1982. 

The main properties of these materials were characterized by means of x-ray diffraction (Siemens D-500 with A.Cu radiation of 1.54 A), Transmission Electron Microscopy (Phillips-CM200) and N2 adsorption (Micromeritics ASAP-2000), 29Si-NMR(MAS). As the textural properties of the catalytic materials, for example the inner pore structure, is a key parameter for their performance, in the present work the N2 adsorption isotherms of the calcined mesoporous Si02-based solids were determined. The solids were prepared using different CTAB surfactant and some co-surfactants based in the light alcohols, i.e. MeOH, EtOH and PrOH. Thus, Figure 15.5 shows the isotherms of the mesoporous solids prepared with MeOH (co-surfactant). In all... 

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