Abstract

PAPA, José et al. Oxidative dehydrogenation of n-butane and its relationship with the oxidation state of the catalyst. Rev. Fac. Ing. UCV [online]. 2009, vol.24, n.3, pp.41-58. ISSN 0798-4065.

In this work the oxidative dehydrogenation (ODH) of n-butane has been studied using the injection by pulse technique on catalysts based on mixtures of vanadium and magnesium oxides in an oxygen free atmosphere. In the presence of molecular oxygen, vacancies generated by the oxidation reaction are rapidly filled by new oxygen ions, while working under anaerobic conditions the concentration of these vacancies increases with each additional n-butane pulse injected. It was found that working under anaerobic conditions the ODH of n-butane presents a higher selectivity toward olefins than when the process is developed in the presence of oxygen, and that the selectivity variation is very small with additional pulses. Nevertheless, the selectivity toward butenes increases and that toward butadiene decreases with decreasing oxidation states of the catalyst. As opposed to what was expected, it was found that the catalyst supported over SiO2 shows a higher selectivity toward butadiene than that supported over α-Al2O3, and that the differences increases with the amount of pulses. It was also found that even when the maximum number of n-butane pulses were added a noticeable amount of mobile oxygen still remains as confirmed by XPS which does not show vanadium oxidation states lower than V+4

Keywords : N-butane; Oxidative dehydrogenation; Vanadium oxide; Silica; Alumina.