Reações De Desidrogenação E Hidrogenólise Do Cicloexano Em Catalisadores De Cobalto Suportados Em Nióbia E Alumina (Cyclohexane Dehydrogenation and Hydrogenolysis Reactions in Cobalt Catalysts Supported on Niobia and Alumina)

Abstract

As propriedades catalíticas dos catalisadores de Co/Nb2O5 e de Co/Al2O3 foram avaliadas na desidrogenação/hidrogenólise do cicloexano. Estudou-se o efeito da temperatura de redução na formação do efeito SMSI para os catalisadores de Co/Nb2O5. A seletividade da reação variou com o tipo de suporte, teor metálico e o SMSI. Os principais produtos foram n-hexano, que provem da hidrogenólise do cicloexano, e o benzeno, que provem da desidrogenação. A seletividade para n-hexano é seriamente afetada na presença do efeito SMSI e pela desativação por coque, confirmando os efeitos geométricos.

Synthesis, Characterization and Catalytic Evaluation of Cobalt and Niobium Oxide Solids Modified with Alkaline Earth Metals

“…Therefore, they remained mainly as oxides species, without activity for dehydrogenation. Thus, the cyclohexane conversion values were due to cobalt atoms, which are active for dehydrogenation [5,13]. Table 2 shows that cyclohexane conversion with CoNb decreased when the modifier was added.…”

“…It presents activity to decomposition, dehydrogenation, hydrogenation, hydrogenolysis and hydrodesulfurization reactions. It is also used in catalysts for cyclohexane oxidation [2], methane decomposition [3,4] , Fischer Tropsch synthesis [5,6], methane or ethanol reforming for hydrogen production [3,4,7,8,9], including fuel cell studies [10], although it shows lower selectivity to hydrogen compared to nickel catalyst [11], pollutant degradation [12] and others. Cobalt catalyst activity and selectivity depends considerably on the support type and preparation method [7,13,14,15].…”

“…Niobium oxide became a widely studied catalyst support, which presents essential catalytic properties such as stability, among others [18]. Besides, it can act as a catalyst in various reactions such as hydrogenation, dehydrogenation, dehydration, esterification and oxidation [5]. Brazil has the largest niobium reserve in the world (above 90%), therefore it is an extra motivation for the development of new technologies that use niobium derivates [16,19].…”