Abstract

ARTEAGA, Geomar et al. Effects of the Sn/Ni ratio and the oxidative treatments on properties of Ni-Sn/SiO₂ catalystsEfectos de la relación Sn/Ni y de los tratamientos oxidativos sobre las propiedades de los catalizadores de Ni-Sn/SiO₂. Rev. Téc. Ing. Univ. Zulia [online]. 2007, vol.30, n.Especial, pp.494-503. ISSN 0254-0770.

The influence of the Sn/Ni ratio and the treatments of calcination and oxychlorination on the dispersion, reducibility and dehydrogenation activity of Ni/SiO₂ and Ni-Sn/SiO₂ were studied. The catalysts were characterized by temperature programmed reduction (TPR), CO chemisorption, and cyclohexane dehydrogenation. The results of TPR show that in the untreated monometallic catalysts new species of Ni(NO₃)₂ formed by interacting the salt with the support through silanol groups. These species were thermally less stable. The addition of Sn strongly modified these interactions by displacing the hydrogen atom from such groups. In the case of the calcined catalysts, the presence of tin modified the reductive properties of the nickel oxide and for the oxychlorinated catalysts, the results suggest the simultaneous reduction of oxychlorinated species of Ni and Sn. The treatments of calcination and oxychlorination caused a strong decrease in the dispersion, which was independent of the Sn/Ni ratio. Contrasting with the calcination, oxychlorination produced a strong decrease in the activity of the monometallic catalyst. For untreated and calcined catalysts, the activity reached a maximum and then decreased at higher Sn/Ni ratios. The addition of Sn and Cl at high temperatures produced opposed effects on the activity, causing uniformity in the catalytic behavior of the bimetallic catalysts.

Keywords : Ni-Sn catalysts; CO chemisorption; cyclohexane dehydrogenation; TPR.