Pore diameter specific

As an extension of Ghadiri s study, a 12-residue cyclic peptide, cyclo[(Gln-D-Ala-Glu-D-Ala),], afforded self-assembled nanotube materials having a uniform 13-A tailored pore diameter. Specifically sized tubular nanostructures with channel structures can expect various applications. ... 

The synthesis conditions have been varied to study their influence on the value of pore diameter and on crystallographic structure. From Table 1, which sums up the synthesis conditions investigated, the crystallographic structure, the value of the pore diameter, specific surface area and pore volume of obtained products. It is clear that both large pore MCM-41 and MCM-48 can be obtained depending on the synthesis conditions used. 

One major advantage of silica xerogel over other support materials is the ease of adjustment and control of mean pore diameter, specific surface area and the specific pore volume. Supports for catalytic applica-... 

Chromatographic stationary phases are usually obtained via the correct attachment of proper ligands to a suitable support, thereby obtaining a bonded phase. The characteristics of both the support and the ligands exert profound impacts on the performance of an IPC separation. Key parameters are the physical features of the support (particle size, pore diameter, specific surface area), the chemical nature of the bonded phase, and its bonding density. 

Pore diameter, specific pore volume. A controlled, macroporous silica can be obtained by hydrolytic polycondensation of polyethoxysiloxane, while silica gel structure modification results from thermal or rather hydrothermal treatment. When hydrothermal treatment is carried out with silica of a pore size of 100 A at 250 C and 50 atm for a period of 15-20 h, formation of silica gel with a homogeneous pore size of 900 A is possible. Of coarse, the increase of pore diameter reduced the surface area thereby the Rf. values are also generally increased in the case of adsorption type chromatography. El Rassi et al. 44] studied the effect of water and that of hydrothermal treatment on the activity of silica gel. 

Gas sorption (nitrogen at 77 K), mercury intrusion (mercury porosimetry) Specific surface area (BET), pore size distribution, average pore diameter, specific pore volume, particle porosity Retention of solutes, mass loadability, column regeneration, column performance, mass loadability, pore and surface accessibility for solutes of given molecular weight, mechanical stability, column pressure drop, pore connectivity... 

Average pore diameter Specific surface area Surface structure... 

Chromatographic behavior is determined mainly by physical parameters, which therefore have to be discussed in more detail. Silica gels used in thin-layer chromatography are porous systems. This is an important prerequisite for suitability as a carrier in chromatography because all substance-ex-change processes, which are responsible for chromatographic separation, take place at the surface or near the surface within the pores. The following parameters serve for the characterization of the pore structure pore diameter, specific pore volume, and specific surface area. 

A number of physical parameters are necessary to standardize chromatographic properties of aluminas in thin-layer chromatography. Because these aluminas are porous materials, the parameters characterize the pore structure and specific surface area. The actual values of pore diameters, specific surface areas, and pore volumes of aluminas most frequently used in thin-layer chromatography are listed in Table 3. 

Adsorbent Pore diameter, nm Particle density, g/cm Specific area, mVg Apphcations... 

Characterization. When siHca gel is used as an adsorbent, the pore stmcture determines the gel adsorption capacity. Pores are characterized by specific surface area, specific pore volume (total volume of pores per gram of solid), average pore diameter, pore size distribution, and the degree to which entrance to larger pores is restricted by smaller pores. These parameters are derived from measuring vapor adsorption isotherms, mercury intmsion, low angle x-ray scattering, electron microscopy, gas permeabiHty, ion or molecule exclusion, or the volume of imbibed Hquid (1). 

Metal Oxide - Since metals are less electrophilic than silicon, metal oxide adsorbents show even stronger selectivity for polar molecules than do siliceous materials. The most commonly used metal oxide adsorbent is activated alumina, used primarily for gas drying. Occasionally, metal oxides find applications in specific chemisorption systems. For example, several processes are under development utilizing lime or limestone for removal of sulfur oxides from flue gases. Activated aluminas have surface areas in the range of 200 to 1,000 ftVft Average pore diameters range from about 30 to 80 A. 

In which the ratio m/n is close to 3. The silane was produced by free radical copolymerization of vinyltriethoxysilane with N-vinylpyrrolidone. Its number-average molecular weight evaluated by vapour-phase osmometry was 3500. Porous silica microballs with a mean pore diameter of 225 A, a specific surface area (Ssp) of 130 m2/g and a pore volume of 0.8 cm3/g were modified by the silane dissolved in dry toluene. After washings and drying, 0.55% by weight of nitrogen and 4.65% of carbon remained on the microballs. Chromatographic tests carried out with a series of proteins have proved the size-exclusion mechanism of their separation. 

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. 

KoTHmex activated carbon fiber fabrics AW-1101 (BET specific surface area of 880m /g, average pore diameter of 2nm) was provided by Taiwan Carbon Technology Co. Ltd. The support is pretreated in a boiling aqueous solution of 6.5wt.% HNO3 for 1 h. Then the support is rinsed with distilled water, air-dried for 12h at room temperature and for 5h at 393 K. BET specific surface area of the ACF is 950m /g. 

Solid palladium scavengers, PVPy, QTU were pmchased from commercial somces. The mesoporous silica material, S102-SH, was prepared via reaction of SBA-15 (110 A pore diameter) with 3-mercaptopropyltrimethoxysilane (16). Specifically, a toluene suspension of SBA-15 and 3-mercaptopropyltrimethoxysilane was heated at reflux for two days under Ar. Water was then added to promote the cross-linking and the mixture was heated at reflux for an additional day. The sohds were filtered and washed with copious amounts of toluene, hexanes, and methanol to remove unreacted silanes. The solids were finally Soxhlet extracted with dichloromethane at reflux temperature for 3 days, dried, and stored in a nitrogen dry box. The final solid contained 7.5 wt% sulfur (2.3 mmole S/g solid). 

Type Composition Character Average Pore Diameter (nm) Specific Specific Solvent Surface Pore Uptake Area Volurc. (g/g) of ( /g) (Ml/g) resin ... 

Type Name Specific Surface Area (m /g) Pore Diameter (nm)... 

---