High pressure adsorption

Himeno S., Komatsu T., et al. High-pressure adsorption equilibria of methane and carbon dioxide on several activated carbones. 2005 Journal of Chemical Enginnering Data 50(2) 369-376. 

BaeJ.S. and Bhatia S.K. High-pressure adsorption of methane and carbon dioxide on coal. 2006 Energy Fuels 20(6) 2599-2607. 

R. K. Agarwal and J. A. Schwarz, Analysis of High-Pressure Adsorption of Gases on Activated Carbon by Potential-Theory, Carbon, 26, 873-887 (1988). 

Purging of the adsorbate with an inert gas at much reduced pressure is feasible in high pressure adsorption plants. The adsorption of Example 15.2, for instance, is conducted at 55 atm, so that regeneration could be accomplished at a pressure of only a few atmospheres without heating. If the adsorbate is valuable, some provision must be made for recovering it from the desorbing gas. 

In high-pressure adsorption chromatography, solutes adsorb with different affinities to binding sites in the solid stationary phase. Separation of solutes in a sample mixture occurs because polar solutes adsorb more strongly than nonpolar solutes. Therefore, the various components in a sample are eluted with different retention times from the column. This form of HPLC is usually called normal phase (polar stationary phase and a nonpolar mobile phase). 

Given the ability of the clino ZBS-15 to effect CH4/N2 separation chromatographically, we measured a high pressure adsorption isotherm for N2 and diffusion kinetics for CH4 and N2. A complete isotherm for CH4 was not taken due to slow kinetics, but at low pressures (Pq < psia), CH4 and N2 capacities appeared to be... 

MPa for determining the particle density. [12] The accurate particle density is indispensable to evaluate the high pressure adsorption amount for supercritical gas, in particular, in hydrogen storage problem. Thus, the accurate determination of density is still not easy. 

The high pressure adsorption of single gases and mixtures can be predicted from the low pressure (sub-atmospheric) data for the same systems. The optimum temperature for measuring the aulsorption of single gases is near their critical temperature where both the Henry s constant auid the absolute saturation capacity can be determined accurately. 

High Pressure Adsorption Laboratory, School of Chemical Engineering, Tianjin University,... 

It is well known that the saturation pressure, Ps> the border of subcritical adsorption, beyond which another phenomenon, condensation, happens. It seems there is not a similar border for supercritical adsorption because no matter how high the pressure is, "adsorption isotherms could always be recorded. However, such border must exist considering the cause of adsorption. It is the interaction between gas and solid that causes the density difference between gas phase and adsorbed phase. The strength of the intermolecular (atomic) attraction force is limited, therefore, the density difference resulted must be limited, and the pressure difference corresponds to the density difference must be limited. So, there is no reason to think of supercritical adsorption (or high-pressure adsorption as synonym) as borderless. 

Jiang S. Y., ZoIIweg J. A. and Gubbins K. E. High-pressure adsorption of methane and ethane in activated carbon and carbon fibers, J. Phys. Chem. 98 (1994) pp.5709-5713. 

Run No. Operating conditions Product of Ar in high pressure adsorption step ... 

Figure 1 Flowsheet of hybrid membrane-PSA process. Steps pressurization (PR = PRi + PR2). high-pressure adsorption (HPA), co- and counter-current blowdown (CD, BD), Purge (PG) A stream enriched in less adsorbed component, B-. stream enriched in strongly adsorbed component. Pressure histories of the integrated cycle at CSS.

It is interesting to note that their high pressure adsorption experiments for CO2 and CH4 showed that Henry s law could be applied to pressures of about 15 and 8 bar, respectively for temperatures above 373 K. An interesting implication of this linearity is that if the gas permeation is indeed linearly proportioned to the amount adsorbed, then the Henry s law constant cam be used to calculate the gas fluxes through microporous membranes at high pressures. 

Figure 13. High pressure adsorption isotherms of supercritical N2 at 303 K as a function of pore width w.

Figure 14. The extended DR plots of the high pressure adsorption isotherms of supercritical N2 on ACF.

The thermodynamic description of micropore filling of a supercritical gas introduces the difference in the micropore field strength into the Wl and Poq values. Consequently, if we express the amount of high pressure adsorption per Wl and the equilibrium pressure per Poq, the obtained adsorption isotherms must coincide with each other. Fig. 15 shows the reduced adsorption isotherm. Although the abscissa is 0.5 at best, the isotherm has the type I character. This reduced adsorption isotherm is described by the reduced DR equation ... 

Here, j3Eo = 8.75 kJ/mol, which was obtained from the best fit conditions. This 0Eo agrees with that for micropore filling of vapour N2 at 77 K (7.5-9.3 kJ/mol). This fact also indicates that high pressure adsorption process of supercritical N2 is essentially identical to micropore filling of vapour N2 at 77 K. 

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