scholarly journals Adsorption Potential Distributions for Silicas and Organosilicas

2007 ◽  
Vol 25 (8) ◽  
pp. 573-581 ◽  
Author(s):  
Jerzy Choma ◽  
Mietek Jaroniec
Keyword(s):  
Surface Properties ◽  
Adsorption Isotherms ◽  
Nitrogen Adsorption ◽  
Mesoporous Silicas ◽  
Adsorption Potential ◽  
Carbonaceous Materials ◽  
High Adsorption ◽  
Ordered Mesoporous ◽  
Nitrogen Adsorption Isotherms

Adsorption potential distributions (APDs) were calculated from nitrogen adsorption isotherms for macroporous silicas, and for disordered and ordered mesoporous silicas without and with organic groups attached to the surface. It was shown that the APDs for porous silicas and organosilicas differ significantly from those obtained for carbonaceous materials, especially in the range of high adsorption potentials which correspond to low relative pressures. Although the high adsorption potential portions of APDs for porous siliceous materials are less informative than those for carbons, they are still useful for monitoring the changes in the surface properties due to the attachment of various organic groups.

scholarly journals Surface Characterization of Zn-modified H-ZSM-5 Zeolites

2020 ◽  
Vol 6 (6) ◽  
pp. 48-54
Author(s):  
M. Dziuba ◽  
L. Mushinskii ◽  
R. Brovko ◽  
V. Doluda
Keyword(s):  
Surface Properties ◽  
Adsorption Isotherms ◽  
Surface Characterization ◽  
Technical Problem ◽  
Nitrogen Adsorption ◽  
Correct Choice ◽  
Test Surface ◽  
Frequent Use ◽  
Nitrogen Adsorption Isotherms

The surface properties of microporous aluminosilicates are of primary importance in chemical technology and catalysis. The determination of the surface area, pore volume, and pore size and size distribution for microporous aluminosilicates is a complex scientific and technical problem related to both accurate measurements and the correct choice of a mathematical model that adequately describes the physicochemical processes occurring on the test surface. Currently, t-plot, as-plot, Dubinin-Radushkevich model, Dillimore model and Horvath-Kawazoe model are frequently used, each of which has certain advantages and certain disadvantages, to determine micropores in the material. It should be noted that t-plot model found the most frequent use. This is a consequence of the good correlation of volumes and pore areas obtained with its help with theoretically calculated values for various materials. In this point, the article provides a calculation of Zn-modified zeolite H-ZSM-5 surface properties using the t-plot model, for which nitrogen adsorption isotherms were originally obtained. The nitrogen adsorption isotherms of the initial zeolite H-ZSM-5 can be attributed to the first type of isotherms, and the modified samples to the fourth type of isotherms according to Brunauer’s classification. It was found that the initial zeolite is a typical microporous zeolite of H-ZSM-5 type, while the modified samples are micro- and mesoporous materials. Calculation of nitrogen adsorption isotherms using the t-plot model allows to determine the volume of micro and mesopores, which varied in the range of 0.11–0.14 cm3/g for micropores and 0.04–0.07 cm3/g for mesopores. Based on the obtained data, it can be concluded that when zeolite is modified with zinc at a zinc concentration less than 15 wt.%, micropores are not filled with zinc, while mesopores are predominantly filled and an additional surface of zinc oxide is formed on the external surface of the zeolite.

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