Abstract

SILVA, H. S.; LARSEN, G. F.; VENTURINI, R. B.  and  GONZALEZ, J. E.. Monitoring the thermal stability of the porous structure of hybrid SiO2-TiO2 materials by means of mass transport coefficient calculations. Lat. Am. appl. res. [online]. 2002, vol.32, n.2, pp.183-188. ISSN 0327-0793.

The physical characterization of solids, mainly the surface area measurement and the pore size distribution determination by means of nitrogen adsorption and mercury porosimetry, respectively, might be a matter of controversy in the case of materials that can suffer important structural changes between 77K and their operation temperatures (room or higher), or whose pore structure may be damaged due to the mercury intrusion. The goal of this work is to identify changes in the physical structure of solids when they are exposed to temperatures similar to those used in conventional thermal pretreatments, when they are used as catalysts, by means of mass transfer coefficient measurements. Our working hypothesis is that, if structural changes occur, these should be easily detected via noticeable changes in the mass transfer coefficient for a selected adsorbate. The calculation of relaxation constants, which characterize the transport of cyclohexane through the hybrid materials is carried out by modeling the experimental data corresponding to the transient state of the adsorption tests.

Keywords : Hybrid materials; Structural changes; Mass transfer coefficients; Oscillating Microbalance.

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