Title:	Estudo teórico da adsorção de COVs aromáticos em dióxido de titânio e zircônio
Authors:	Vargas, Marcos dos Reis
Orientador(es)::	Martins, João Batista Lopes
Assunto::	Compostos orgânicos - absorção
Issue Date:	28-Feb-2016
Data de defesa::	10-Dec-2015
Citation:	VARGAS, Marcos dos Reis. Estudo teórico da adsorção de COVs aromáticos em dióxido de titânio e zircônio. 2015. xxiv, 115 f., il. Tese (Doutorado em Química)—Universidade de Brasília, Brasília, 2015.
Abstract:	The theoretical study of the adsorption of volatile organic compounds on metal oxides surfaces, such as TiO2 and ZrO2, is important to understand the structural and electronic changes caused by this interaction. In this work, we studied the adsorption of benzene, toluene, ethylbenzene, o-xylene, m-xylene and p-xylene (known as BTEX) molecules on the (110) surface of rutile TiO2, (101) of anatase TiO2 and (001) of tetragonal ZrO2. The Density Functional Theory with periodic boundary conditions and plane wave basis set with the PW91 and PBE exchange-correlation functional were used. The results showed that 300 eV for the cutoff energy of the plane waves and 3x3x3 k points mesh were appropriate for the BTEX adsorption calculation. A supercell with four layers (3x2) for the (110) rutile TiO2, (3x1) for the (101) anatase TiO2 and (3x3) for the (001) tetragonal ZrO2 were considered for the BTEX-surface complex modeling. The interactions of BTEX molecules indicated that adsorption occurs, most favorable, at a position parallel to the surface. The influence of van der Waals interactions was taken into account by semiempirical DFT-D2 correction, being an important component in the energy of interaction, but without major effects on the geometry. The optimization of the geometry was taken into several steps, so that it leds to a complete optimization system (adsorbate and surface). The adsorption of the benzene molecule on the rutile performed in this study, presented a result of energy closer to the experimental interaction than theoretical studies in the literature. The use of a complete optimization and the inclusion of correction for van der Waals interactions must have contributed to the improvement in the system description, increasing the interaction distance from 3.40 Å, reported in the literature and obtained with a partial optimization using LDA approximation to 4.00 Å, calculated in this work. The methodology was then extended to interaction of other monoaromatic hydrocarbons and the study of interactions with the anatase and the tetragonal ZrO2. The adsorption energies obtained for all complexes showed similar trends between the PW91 and PBE functionals. From the results of the adsorption energies for all systems studied, the interaction of BTEX molecules was higher with the (110) TiO2 rutile surface, followed by (101) of TiO2 anatase, and finally the (001) tetragonal ZrO2. CDD analyses showed an increase on electron density between the BTEX molecules and the rutile and anatase surfaces. For TiO2 and ZrO2, we observed the interaction between hydrogen and oxygen through the CDD and ELF, as evidenced by the decrease of charges of the hydrogen atoms and increased electron density close to bicoordinated surface oxygen atoms. The density of states for all systems studied showed a translation of the states to lower energy regions after adsorption, showing a stabilization of the system to form the complex. The adsorption energies analysis suggest that these materials are promising candidates that could be used as chemical sensors and catalysts for the adsorption of BTEX molecules.
metadata.dc.description.unidade:	Instituto de Química (IQ)
Description:	Tese (doutorado)—Universidade de Brasília, Instituto de Química, Programa de Pós-Graduação em Química, 2015.
metadata.dc.description.ppg:	Programa de Pós-Graduação em Química
Licença::	A concessão da licença deste item refere-se ao termo de autorização impresso assinado pelo autor com as seguintes condições: Na qualidade de titular dos direitos de autor da publicação, autorizo a Universidade de Brasília e o IBICT a disponibilizar por meio dos sites www.bce.unb.br, www.ibict.br, http://hercules.vtls.com/cgi-bin/ndltd/chameleon?lng=pt&skin=ndltd sem ressarcimento dos direitos autorais, de acordo com a Lei nº 9610/98, o texto integral da obra disponibilizada, conforme permissões assinaladas, para fins de leitura, impressão e/ou download, a título de divulgação da produção científica brasileira, a partir desta data.
DOI:	http://dx.doi.org/10.26512/2015.12.T.19612
Appears in Collections:	Teses, dissertações e produtos pós-doutorado

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