Pore size effect

Kennedy VC, Zellweger GW, Jones BF (1974) Filter pore-size effects on the analysis of Al, Fe, Mn, and Ti in water. Water Resource Res 10 785-790... 

Khodakov, A.Y., Griboval-Constant, A., Bechara, R., and Zholobenko, V.L. 2002. Pore size effects in Fischer Tropsch synthesis over cobalt-supported mesoporous silicas. 7. Catal. 206 230-41. 

Figure 4.27 Pore-size effect on the acetalyzation of cyclohexanone with methanol. (Reprinted from J. Am.

This unusual selectivity was explained by the pore size effect of the active carbon. 

This difference was explained by the pore size effect of the active carbon [137]. Non-polar solvents such as toluene are generally choice of solvents for the above-mentioned systems, as they can prevent measurable leaching of POM species during the oxidations. 

Over-cracking of PCC gasoline with either ZSM-5 or REHY results, in both cases, in a preferential loss of heavier olefin components. The major differences between the two zeolites is the increased C3/C4 ratio with ZSM-5 which has been assigned to pore size effects, and enhanced bimolecular hydrogen transfer reactions with REHY, resulting in a higher paraffin/olefin ratio. 

The major effect of ZSM-5 is to convert higher molecular weight iso-olefins into C3/C4 olefins with no discernible change in aromatics other than some dealkylation of the C9+ fraction. Most of the enhanced LPG olefinicity arises from cracking of C7+ olefins and a pore size effect is thought to be responsible for the high C3/C4 ratio compared to REHY. 

The regiochemistry of this reaction is remarkably different from that observed with most homogeneous catalysts, which produce the 1,4-diketone as the major product. This unusual selectivity was ascribed to pore size effects in the carbon support. 

Instead, they proposed a time on stream theory to model the catalyst deactivation. However, in an earlier work by Voorhies (2), a linear correlation between conversion and coke on catalyst for fixed-bed catalytic cracking was derived. Rudershausen and Watson (3) also observed the similar behavior. Coke on catalyst can reduce the activity by covering the active sites and blocking the pores. The effects of pore size on catalyst performance during hydrotreating coal oils in trickle-bed reactors have been studied experimentally by Ahmed and Crynes (4) and by Sooter (5). The pore size effects in other studies are also reported 7, 8). Prasher et al. (9) observed that the effective diffusivities of oils in aged catalysts were severely reduced by coke deposition. 

Because VOCs are often present in streams with excess water, the preferred adsorbents for their selective removal are hydrophobic materials (13). Carbons were and still remain largely used, but HMS is attracting more and more attention. Due to incombustibility, they can be used in a wider temperature range than carbons for regeneration. Additionally, they offer opportunities for selective separation by pore size effects. In contrast, carbons have the efficiency advantage only at higher VOCs concentration and to be of lower cost. 

This paper examines the hydrogenation of aniline, /Moluidinc. and 4-fcrt-butylanilinc over a series of 2.5 % Rh/Si02 catalysts, comparing reaction rates and product selectivities. Further studies concentrated on examining support particle size and average metal crystallite size effects on /Moluidinc hydrogenation and the support pore size effects on 4-tert-butylaniline hydrogenation. 

PORE SIZE EFFECTS IN THE LIQUID PHASE ADSORPTION OF ALKANES... 

Fan, L., Yokota, K. and Fujimoto, K. (1992) Supercritical phase Fischer-Tropsch synthesis Catalyst pore-size effect. AIChE/., 38(10), 1639-1648. 

D. Freilich and G.B. Tanny, Hydrodynamic and microporous support pore size effects on the properties and structure of dynamically formed hydrous Zr(IV)-polyacrylate membranes, Desalination, 1978, 27, 233-251 A.J. van Reenen and R.D. Sanderson, Dynamically formed hydrous zirconium(IV) oxide-polyelectrolyte membranes, VI. Effect of copolymer composition on the stability of poly(acrylic acid - covinyl acetate) and poly(acrylic acid - covinyl alcohol) membranes, Desalination, 1989, 72, 329-338. 

Pore size, effect on adsorption 17-P-07 Pt/MAPSO-31 hydroisomerisation catalyst 26-P-06 ... 

Pore size, effect on isomerisation 25-P-08 Pt/MCM-41 chiral hydrogenation catalyst 23-P-25 ... 

Walters, R.R. (1982) High-performance affinity chromatography. Pore size effects./. Chromatogr., 249, 19-28. 

The original commercial application of TS-1 was the oxidation of phenol in the presence of TS-1 using hydrogen peroxide as the oxidant (45). The main products are a mixture of hydroquinone (p-dihydroxybenzene) and catechol (o-dihydroxyben-zene) (Fig. 10.12). It has been observed that the selectivity and activity of the TS-1 catalyst is tied to the points above. Further, although other titanium-containing zeolites have been investigated [e.g. Ti-Beta (BEA), Ti-ZSM-12 (MTW) Reference 46] none display the activity and selectivity of TS-1. One possible explanation for this is pore size effects another possibility is that the TS-1 samples, which are quite hydrophobic. 

JSnchen et al. [64] have reported that the heats of adsorption of acetonitrile on mesoporous (MCM-41) and microporous (FAU and MFI) molecular sieves are mainly influenced by a specific interaction with the acidic sites, while the adsorption heats of a non-polar molecule like w-hexane are determined by the pore size or density of those materials. However, a pore-size effect, affecting the heats of acetonitrile adsorption on acidic molecular sieves, has to be taken into account when employing those heats as a measurement of acidic strength. The contribution of the pore-size governed dispersion interaction in mesoporous MCM-41 is about 15 kJ mof less than that in the narrow channels of MFI. The adsorption of molecules of different sizes (toluene, xylenes, etc.), and the consecutive adsorption of these same molecules, studied by adsorption microcalorimetry together with reaction tests, can provide useful indications of the pore geometry and reactant accessibility of new zeolitic materials such as MCM-22 [65] or ZSM-11, SSZ-24, ZSM-12, H-M and CIT-1 [66]. 

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