Activación de alcanos de seis átomos de carbono

Resumen

During the last decades, partial oxidation of alkanes has received great interest due to their inertness. The main reasons are the strength of the covalent bond C H and C C and the absence in them of double or triple bonds and lone pairs of electrons. In fact, the reactions in which they are involved are usually carried out with strong oxidants, superacids, free radicals or high temperaturas, although the discovery of new catalytic systems in the 60s allowed to carry out selective reactions with alkanes in milder conditions. In this line, it has been attempted to mimic biological systems, which are capable of selectively oxidize paraffins. For example, it is known that monooxygenase enzymes catalyze monooxygenation reactions under very mild conditions, especially the hemoprotein called cytochrome P 450. Therefore, many research groups have tried to find synthetic catalysts in imitation of these cytochromes, metalloporphyrins being the best ones obtained so far Cook y col., 1986; Crabtree, 2001; dA Rocha Gonsalvez and Serra, 2000; Huybrecths y col., 1991a; Lindsay Smith y col., 2006. Metalloporphyrins have been used as homogeneous catalysts because of their shape selectivity. This is achieved by the steric hindrance of their own structure periphery, which also increases significantly their oxidation resistance dA Rocha Gonsalves and Serra, 2000; Groves y col., 1996; Nam y col., 2001; Suslick y col., 1985. Metalloporphyrins have also been supported on various materials. In this way, they have better activity and selectivity and their stability in the reaction medium is increased Aparecido Guedes y col., 2005; Battioni y col., 1989; Campestrini and Meunier, 1992; Costa y col., 2008; das Dores Assis and Lindsay Smith, 1998; Huang y col., 2004; Lindsay Smith y col., 2006; Milaeva y col., 2007. Alkanes partial oxidation has also been carried out using materials with metal incorporated into their framework, such as titanium silicalite1 TS1 Huybrechts y col., 1990; Tatsumi y col., 1990 or vanadium silicalite1 VS1 Shetti y col., 2006. This alternative has the advantage of being cheaper, although it is not as effective as with other catalysts and the experimental conditions are not as mild. The reaction product consists of a mixture of alcohols and ketones, which are not primary Huybrechts y col., 1990; Tatsumi y col., 1990. Furthermore, oxidation of linear and cyclic alkanes has also been achieved at room temperature employing ruthenium catalysts supported on activated carbon. In this case, ketones predominate among the oxidation products Murahasi y col., 1994; Murahasi y col., 2000; Rekkab y col., 2009. In this context, this research focuses on the study of possible catalysts, oxidants and solvents to partially oxidize paraffins of six carbon atoms. These paraffins have been chosen because their oxidation products are of commercial interest and they can be easily synthesized, including their derivatives, which makes the analysis of the reaction products easier. The thesis has been divided into three parts based on the material used as catalyst: biomimetic materials, siliceous materials with metal incorporated into their framework and supported metal materials.