K Pore size

FIGURE 4 Nitrogen adsorption and desorption isotherms at 78 K. Pore size distributions in the micropore range are calculated from the isotherms using the Kelvin equation. 

TSA - total surface area determined by N2 adsorption (BET method) V(N2) and V(C02) - micropore volumes calculated by the application of the Dubinin-Radushkevitch equation to N2 adsorption at 77 K and CO2 adsorption at 273 K pore size determined according to the BJH method - maximum value of the BJH pore size distribution peak calculated from the adsorption branch of the N2 isotherm capacitance values... 

Ishikiriyama, K., Tudoki, M. and Motomura, K., Pore size distribution (PSD) measurements of silica gels by means of differential scanning calorimetry, J. Colloid and Interface Sci., Ill, 92-102 (1995). 

Klein, J., Stock, J., and Vorlop, D.K., Pore size and properties of spherical calcium alginate biocatalysts, Eur. J. Appl. Microbiol. BiotechnoL, 18, 86-91, 1983. 

Figure 4. H-K pore size distribution for cured [HSi03a] [( -C2oH2i)Si03/2]i resin sanq>le.

Horvath G and Kawazoe K 1983 Method for oaloulation of effeotive pore size distribution in moleoular sieve oarbon J. Chem. Eng. Japan 16 470-5... 

Type IV isotherms are often found with inorganic oxide xerogels and other porous solids. With certain qualifications, which will be discussed in this chapter, it is possible to analyse Type IV isotherms (notably those of nitrogen at 77 K) so as to obtain a reasonable estimate of the specific surface and an approximate assessment of the pore size distribution. 

Fig. 3.18 Pore size distributions of a silica geP GSSO, calculated from the desorption branch of the isotherm at 77 K by dilTerent methods. (A) x,...

Fig. 7. The effect of preparation on the pore size distribution (a), titanium dispersion (b), and the activity for epoxidation of cyclohexene (c) of titania—siUca containing 10 wt % titania and calcined in air at 673 K. Sample A, low-temperature aerogel Sample B, high-temperature aerogel Sample C, aerogel.

A more comprehensive purification procedure uses a sequence of steps as follows filtration at 200°C through a stainless steel powder compact filter of 10-jum pore size reduces the oxygen content and removes any solid impurities. Gettering with Zr foil for 46 h at 760°C reduces the oxygen concentration to 200 ppm. The weight ratio of K to Zr is 13 1 with a surface area to volume ratio of Zr to K 4 1. A second gettering with zirconium foil for 72 h at 800°C reduces the oxygen content 50 ppm. 

Thermally stable AI2O3 was synthesized as in ref. 5, by hydrolysis of A1 isopropoxide (99.99+% Aldrich Chemicals) dissolved in 2-methylpentane-2,4-diol. The resulting solid was filtered, washed in 2-propanol, and dried in air at 373 K. Then, it was calcined in flowing dry air, while the temperature was raised at 1 K/min to 733 K, when 2.4% HjO was introduced to the flowing air. Afterwards, the temperature ramp was continued to 973 K. The sample was kept at 973 K for 2 h in 7% water. The isoelectric point of the resulting y-Al Oj was pH 8. The BET surface areas were 205 to 235 mVg, and the average pore size radius was around 8.3 nm... 

The packing material, used for the LEG work was Controlled-Pore Glass (CPG) from Electronucleonics, Fairfield, N.J. with various pore diameters similar to those used by others (6,2 ) (500-10,000 A). Each k.6 mm I.D. x 100 cm column was dry packed with the CPG of a specific pore size by tapping and vibration until a terminal, bed volume was reached. Stainless steel 20-ym frits were used on each end of the column along with the appropriate low-dead volume end-fittings. 

D.W. Aksnes, K. Forland, L. Kimtys 2001, (Pore size distribution in meso-porous materials as studied by H NMR), Phys. Chem. Chem. Phys. 3, 3203. 

Concrete is a composite material composed of cement paste with interspersed coarse and fine aggregates. Cement paste is a porous material with pore sizes ranging from nanometers to micrometers in size. The large pores are known as capillary pores and the smaller pores are gel pores (i.e., pores within the hydrated cement gel). These pores contain water and within the water are a wide variety of dissolved ions. The most common pore solution ions are OH", K+ and Na+ with minor amounts of S042" and Ca2+. The microstructure of the cement paste is a controlling factor for durable concrete under set environmental exposure conditions. 

High performance monolithic columns were prepared from styrene and divinyl-benzene (PSDVB, 200 pm i.d.) (Oberacher et al., 2004). The monoliths possess 5-300 nm pores with porosity of ca. 50% and 20% for external and internal pores, respectively, with specific surface areas of 30-40 m2/g. The column showed permeability K= 3.5 x 10 15m2 in water and slightly less in acetonitrile. The pore size... 

Leinweber, F.C., Lubda, D., Cabrera, K., Tallarek, U. (2002). Characterization of silica-based monoliths with bimodal pore size distribution. Anal. Chem. 74, 2470-2477. 

Motokawa, M., Kobayashi, H., Ishizuka, N., Minakuchi, H., Nakanishi, K., Jinnai, H., Hosoya, K., Ikegami, T., Tanaka, N. (2002). Monolithic silica columns with various skeleton size and through-pore size for capillary liquid chromatography. J. Chromatogr. A 961, 53-63. 

Tanaka, N., Kimata, K., Mikawa, Y., Hosoya, K., Araki, T., Ohtsu, Y., Shiojima, Y., Tsuboi, R., Tsuchiya, H. (1990). Performance of wide-pore silica- and polymer-based packing materials in polypeptide separation the effect of pore size and alkyl chain length. J. Chromatogr. 535, 13-31. 

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