Estudo teórico da redução fotocatalítica do gás carbônico a metanol utilizando dióxido de titânio

• Ano de defesa: 2011
• Autor(a) principal: Abdalla Junior, Juarez Valença
• Orientador(a): Dias, Jacques Fernandes
• Banca de defesa: Marques, Mônica Regina da Costa , Chrisman, Erica Christina Ashton Nunes
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade do Estado do Rio de Janeiro
• Programa de Pós-Graduação: Programa de Pós-Graduação em Química
• Departamento: Centro de Tecnologia e Ciências::Instituto de Química
• País: BR
• Palavras-chave em Português: Dióxido de titânio; fotocatálise; dióxido de carbono; mecanismos de reação (Química); química teórica
• Palavras-chave em Inglês: Titanium dioxide; photocatalysis; carbon monoxide; reaction mechanism(Chemistry); theoretical Chemistry
• Área do conhecimento CNPq: CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA::FISICO-QUIMICA::QUIMICA TEORICA
• Link de acesso: http://www.bdtd.uerj.br/handle/1/15725

The concentration increase of greenhouse gases (GHG) emissions from anthropogenic sources, has been one of the main contributions of global warming, threatening the planet life. The carbon dioxide (CO2) is one of the main greenhouse gases and its sources are related to processes that are essential to society, such energy production, transport and many others products. The CO2 conversion to methanol, seems a promising alternative to reduce the emission of this gas in the atmosphere. Of particular interest to this study, the Photoreduction of CO2 to methanol can help to mitigate the problem of greenhouse gases, generating an important feedstock in the chemical industry. Thus, this study aims to use quantum-mechanical calculations, such the Density Functional Theory, in order to investigate the reduction reaction's path of the CO2. The reduction reaction of CO2 to formic acid, formaldehyde and methanol was studied without interaction with the catalyst and under presence of titanium dioxide as a catalyst. Was performed a comparison of theoretical calculations at different levels and different bases, with the experimental data. For calculations involving the TiO2 was used at the B3LYP/6-31G (d,p) level. Vibrational frequencies were also calculated for each step, allowing the identification of possible transition states and estimation of reaction barriers (potential energy). Calculations of intrinsic reaction coordinate (IRC) were used to confirm that the transition states found are related to each studied stage. The comparison of the reduction of carbon dioxide to formic acid, with and without catalyst, showed that the presence of the titanium dioxide decreased more than 25.0% the barrier of this reaction step