Configurational pore diameter

Surprisingly, an enhanced conductivity is shown for a certain range of confinement, as seen in Figure 19. This can be explained by the decrease in coulombic attractive interaction among the ions in a one-dimensional configuration. But when the pore diameter is... 

Porous Vycor glass tube (in double pipe configuration), wall thickness 3 mm, length 600 mm, outer diameter 15 mm, mean pore diameter 45 A. Feed enters the reactor at shell side, permeate at tube side. ... 

Porous alumina tube externally coated with a MgO/PbO dense film (in double pipe configuration), tube thickness 2.5 mm, outer diameter 4 mm, mean pore diameter 50 nm, active film-coated length 30 mm. Feed enters the reactor at shell side, oxygen at tube side. Oxidative methane coupling, PbO/MgO catalyst in thin film form (see previous column). r-750X,Pr ed 1 bar. Conversion of methane <2%. Selectivity to Cj products > 97%. Omata et al. (1989). The methane conversion is not given. Reported results are calculated from permeability data. 

Diffusion and adsorption studies with Boscan VO-porphyrin extracts and pure VO-TPP in C0M0/AI2O3 catalysts have been reported by Morales and co-workers (Galiasso and Morales, 1983 Morales and Galiasso, 1982 Andreu et al., 1981 Morales et al., 1984). The Boscan extract contained up to 30 wt. % vanadyl DPEP and vanadyl etioporphy-rin. Effective diffusion coefficients at 300°C in a catalyst with an average pore diameter of 150 A (A < 0.1) are on the order of 10-5 cm2/sec. Configurational effects are minor for this system. 

Membrane material Membrane configuration Operation mode Pore diameter (pm) Application Membrane producer References... 

In equations (5) and (6), DM and DK are the molecular and Knudsen diffusivities, respectively, and e and x are the void fraction and the tortuosity of the porous solid, respectively. For pore dimensions significantly larger than the mean free path of the diffusant in the gas phase, the diffusivity is governed by molecular diffusion, but when the pore diameter becomes smaller than the mean free path, diffusion is properly described by Knudsen diffusion. When the pore diameter approaches that of the diffusing species, around 10, one enters the configurational regime. 

Fresh Zeolite. The diffusivities within usual porous catalyst (pore radius a few nm) can be estimated by the parallel pore model (18) or the random pore model (19). However, configurational diffusion occurs within the pores of zeolites (pore diameter < 1 nm) and there are only a few reports on the measurement or estimation methods of the diffusivities of zeolites, especially at higher temperature range (20,21). Here we will review the results of ZSM-5, which first explains the diffusivity of fresh ZSM-5, then the results of coke loaded ZSM-5. 

Relatively speaking, the affinity of the hydrogen-mordenite is greatest for the SO2, then in decreasing order the CO2, N2, and O2 follow. This can be explained by differences in the electronic configurations of these adsorbates no "sieving would be expected in any of these systems since the molecular diameter of these gas molecules is well below the published pore diameters. The sorption of all the species is likely to be physical, since the calculated isosteric heats are all below 5 kcal/mole. 

The rate processes of diffusion and catalytic reaction in simple square stochastic pore networks have also been subject to analysis. The usual second-order diffusion and reaction equation within individual pore segments (as in Fig. 2) is combined with a balance for each node in the network, to yield a square matrix of individual node concentrations. Inversion of this 2A matrix gives (subject to the limitation of equimolar counterdiffusion) the concentration profiles throughout the entire network [14]. Figure 8 shows an illustrative result for a 20 X 20 network at an intermediate value of the Thiele modulus. The same approach has been applied to diffusion (without reaction) in a Wicke-Kallenbach configuration. As a result of large and small pores being randomly juxtaposed inside a network, there is a 2-D distribution of the frequency of pore fluxes with pore diameter. 

Activated surface diffusion or configurational diffusion occurs in molecules with a diameter larger than 60% of the pore diameter, as is the case in pervaporation with zeolite membranes [113]. Diffusion is an activated process and the diffusivity follows an Arrhenius-type equation ... 

Configurational diffusion is a separate class and occurs when the pore diameter is a factor of 1-5 larger than the molecular diameter. 

In the dead ends (inaccessible pore ends) with the normal line of its oil-water interface perpendicular to the flow direction, the residual oil is immovable because it is constrained by the rock configuration. In the experiments shown in Figure 6.16, the cores were flooded with water, glycerin, and HPAM. The pore diameter along the flow streamline was 250 pm. The viscosity of the glycerin or polymer was 30 mPa s. We can see that the portions (depth) of the dead pore flushed by water and glycerin were about the same, although the... 

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