Effect of pore size

Mangun, C. L., Daley, M. A., Braatz, R. D. and Economy, J., Effect of pore size on adsorption of hydrocarbons in phenolic-based activated carbon fibers. Carbon, 1998,36(12), 123 129. 

Fig. 26. The effect of pore size distribution spread (standard deviation) on the predicted tensile failure [jrobability distribution for grade H-451 graphite.

Generally, optimizing the selectivity by choosing a gel medium of suitable pore size and pore size distribution is the single most important parameter. Examples of the effect of pore size on the separation of a protein mixture are given in Fig. 2.15. The gain in selectivity may then be traded for speed and/ or sample load. However, if the selectivity is limited, other parameters such as eluent velocity, column length, and sample load need to be optimized to yield the separation required. 

IV. PORE SIZE AND PARTICLE SIZE A. Effect of Pore Size... 

This paper will be limited to a discussion of our packed column studies in which we have addressed attention to questions regarding, (a) the role of ionic strength and surfactant effects on both HDC and porous packed column behavior, (b) the effects of pore size and pore size distribution on resolution, and (c) the effects of the light scattering characteristics of polystyrene on signal resolution and particle size distribution determination. 

Table 2 Effect of pore size on initial hydrogenation rate.

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. 

B. Thomas, S. Prathapan, and S. Sugunan, Effect of pore size on the catalytic activities of K-10 clay and H-zeolites for the acetalization of ketones with methanol, Appl. Cat. A Gen., 277 (2004) 247-252. 

The studies of Thomas and Raja [28] showed a remarkable effect of pore size on enantioselectivity (Table 42.3). The immobilized catalysts were more active than the homogeneous ones, but their enantioselectivity increased dramatically on supports which had smaller-diameter pores. This effect was ascribed to more steric confinement of the catalyst-substrate complex in the narrower pores. This confinement will lead to a larger influence of the chiral directing group on the orientation of the substrate. Although pore diffusion limitation can lead to lower hydrogen concentrations in narrow pores with a possible effect on enantioselectivity (see Section 42.2), this seems not to be the case here, because the immobilized catalyst with the smallest pores is the most active one. 

Chem. Soc., Vol. 125, M. Iwamoto, Y. Tanaka, N. Sawamura, S. Namba, Remarkable Effect of Pore Size on the Catalytic Activity of Mesoporous Silica for the Acetalization of Cyclohexanone with Methanol, pp. 13032-13033, Copyright 2003. With permission from American Chemical Society.)... 

The effect of pore size on CEC separation was also studied in detail [70-75]. Figure 9 shows the van Deemter plots for a series of 7-pm ODS particles with pore size ranging from 10 to 400 nm. The best efficiency achieved with the large pore packing led to a conclusion that intraparticle flow contributes to the mass transfer in a way similar to that of perfusion chromatography and considerably improves column efficiency. The effect of pore size is also involved in the CEC separations of synthetic polymers in size-exclusion mode [76]. 

Fig. 9. Effect of pore size on the efficiency of CEC columns. (Reprinted with permission from [70]. Copyright 1997 VCH-Wiley). Conditions field strength 100-500 V/cm, capillary column 75 pm i. d., total length 30 cm, active length 25 cm, isocratic separation using 20 80 acetonitrile-100 mmol/1 phosphate buffer pH = 6.9, marker acetone... 

An example of the effect of pore size on the separation of a set of native proteins is shown in Figure 8.4. The 4%T, 2.67%C gel shown on the left is essentially nonsieving. Proteins in the artificial sample migrate in the gel more or less on the basis of their free mobility. The 8%T, 2.67%C gel on the right sieves the proteins shown and demonstrates the combined effects of charge and size on protein separation. The relative positions of some proteins are shifted in the sieving gel as compared to the nonsieving one. 

Figure 13.9 Effect of pore size on heat of adsorption for alkanes [5, 14],...

Effect of Pore Size and Acid Site Density on Cracking... 

Table V. Effect of Pore Size on GPC Degradation Polystyrene...

The effect of pore size on the retentive capacity of various octadecyl silica bonded phases is illustrated in Fig. 10. Exclusion effects become appreciable when bulky octadecyl groups (see Table V) are attached to the pore wall in 6 nm pore diameter silica (Si-60). As a result, the stationary... 

Effect of pore size on the adsorption of xenon on mesoporous MCM-41 and on the l29Xe NMR chemical shifts a variable temperature study... 

It is the purpose of the present paper to study the effect of pore size on the adsorption of xenon on mesoporous MCM-41 molecular sieves. In particular, much attention will be focused on the temperature variation of l2,Xe NMR chemical shifts at low Xe loading to realize the characteristics of the Xe-wall interactions. 

Effect of Pore Size on the Adsorption of Xenon on Mesoporous MCM-41 and on 517... 

Wheeler<26) considered the problem of chemical selectivity in porous catalysts. Although he employed a cylindrical pore model and restricted his conclusions to the effect of pore size on selectivity, the following discussion will be based on the simple geometrical model of the catalyst pellet introduced earlier (see Fig. 3.2 and Section 3.3.1). 

Fig. 57. Model computation of the effect of pore size on catalyst stability using first-order kinetics and configurational diffusion for a 12.5- A-diameter metal-bearing molecule (Rajago-palan and Luss, 1979).

Fig. 61. Effect of pore size and grain radius on the stability of the macroporous catalyst activity for HDM (Agrawal, 1980).

Hardin, A. H., Ternan, M., and Packwood, R. H., The Effects of Pore Size in MoOrCoO-A1203 Hydroprocessing Catalysts," CANMET Report 81-4E, Energy, Mines and Resources, Canada, 1981 see also ACS Prepr. Div. Petrol. Chem. 23, 1450 (1978). 

Yuan, F., Krol, A. and Tong, S. (2001) Available space and extracellular transport of macromolecules Effects of pore size and connectedness. Ann. Biomed. Eng., 29,1150-1158. 

Consistent with our previous findings using systems consisting of butyl methacrylate, ethylene dimethacrylate, and 2-acrylamido-2-methyl-l-propanesulfonic acid [54,64,72], the column efficiency of quinidine-functionalized monolithic capillaries again clearly depends on the pore size. Fig. 6.30 illustrates that this holds for chiral monoliths prepared by either thermal or UV initiation [60], As previously found for the reversed phase separations of alkylbenzenes, the effect of pore size on the separation of enantiomers is also rather complex and subtleties of these effects remain to be explored in more detail. 

---