Estudo teórico da reação de hidrogenação catalítica do CO2

• Autor(a) principal: Spinelli, Breno Saldanha
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFMT
• Texto Completo: http://ri.ufmt.br/handle/1/1623
• topic: Hidrogenação; CO2; DFT; CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA; Hydrogenation; CO2; DFT

The reaction of catalytic hydrogenation of CO2 was theoretically study at the density theory functional (DFT) level, employing the DGDZVP and 6- 31G(d,p) basis set, for the complex trans-(PNP)X(H)2NO, (where X = Ru or Fe). The solvent effect, applying the continuum polarization model (IEFPCM) was applied. According the mechanism proposal, the first step of the reaction consist on the entrance of the CO2 in the metal complex coordinate sphere, promoting the liberation of the hydride and the formation the formic ion, leading to a pentacoordinated complex. In the following occurs the entrance of the H2 in the complex, forming and T shape bond. At the next step, the bond between the HH coordinated to the metal is broken, transferring the proton to the formic ion producing the formic acid at the cis form. Finally the acid formic isomerizes, reestablishing the catalyst. To solve the interaction problem between the catalyst and the acid formic produced, another acid formic molecule was introduced. This way, when the acid formic is produced, immediately occurs the dimerization, and the catalyst is reestablished. The global reaction analyzed is: H2 + CO2 + HCOOH  (HCOOH)2. The determinant step is the entrance of the H2 molecule at the metal complex penta-coordinated, following its bond scission. On both steps, it is suggested that binder donators may alter the reaction energy, both for the entrance of the H2 at the metal complex and the acid formic formation. The geometry analysis presents the increase on the bond between the H-H distances from the hydrogen molecule coordinated to the metal complex than is free form. Besides, the orbital analysis displays a significant population on the orbital σ antibonding for the H2 molecule coordinated.