Quantum Chemical Modelling Protolytic Equilibrium on Surface Oxide Materials
- Kharkiv National University of Civil Engineering and Architecture 61002, Sumskaya street, 40,Kharkiv, Ukraine
Published in The Second NZAAR International Event Series on Natural and Built Environment, Cities, Sustainability and Advanced Engineering, Kuala Lumpur, Malaysia, 8 December 2016, pages 104 to 108. New Zealand Academy of Applied Research. ISSN 2463-5979 (online), 2463-5960 (print).
Abstract
The results of calculation of the acid and basic properties of a surface of the disperse oxide materials on the basis of SiO 2 , α-Al 2 O 3 , α-Fe 2 O 3 and TiO 2 by the method of quantum chemical modelling are presented in the article. The correspond models of the superficial active centres for this purpose are offered, the constants of their protolytic equilibrium рKa and free Gibbs’s energy deprotonation reactions are calculated. It is established, that acidity of all types of the superficial active centres increases among Al3 + <Fe3 + <Si4 + <Ti4 + depending on the nature of the central element. The acidity of the isolated centres grows at increase of quantity of OH-groups. The vicinal superficial centres Si 2 O 5 (OH) 2 and Ti 2 O 5 (OH) 2 have the greatest acidity from all spectrum of the researched centres. It is established by the results of calculations that the acidity of the active centres grows at increase in quantity of the adsorbed water molecules at surfaces for all disperse oxide materials. This dependence is approximated by the linear equation of a kind рK а = θ ∙ n Н2О + pK a 0, and the free member pK a 0 has real physical sense of an indicator of acidity of the waterless active centres.
Keywords: The Acid And Basic Properties; Quantum Chemical Modelling; The Active Centre; The Disperse Oxide Material
Rights
Copyright © New Zealand Academy of Applied Research Ltd 2016. All rights reserved. Reproduced in the GDI Academy archive from the original proceedings without change to the authors’ text.