SEM and BET Methods for Investigating the Structure and Morphology of Co - Ce Catalysts for Production of Light Olefins

Abstract

Co–Ce catalysts prepared by the coprecipitation method were tested for production of light olefins. The effect of different preparation conditions including the [Co]/[Ce] molar ratio, aging time, calcination conditions, different supports, and loading of optimum support on the structure and catalytic performance of different catalysts were investigated. It was found that catalyst containing 80% Co/20% Ce/15% SiO2, which was aged for 2 h and calcined at 600°C for 6 h, is the optimum modified catalyst for the conversion of synthesis gas to light olefins. Characterization of both precursors and calcined catalysts (before and after the test) was carried out using scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) specific surface area measurements. The morphology of the catalysts was investigated by SEM and the surface areas of these catalysts were studied by BET. It was shown that all of the different preparation variables influenced the morphology and also the specific surface area of the catalyst precursors and calcined catalysts.

Effect of preparation conditions on the catalytic performance of Co/Ni catalysts for CO hydrogenation

“…In our previous study, we demonstrated the importance of ageing time with respect to catalyst activity for oxidation of CO by mixed copper manganese oxide and mixed copper zinc oxide catalyst (Hutchings et al, 1996(Hutchings et al, , 1998Taylor et al, 1999Taylor et al, , 2003Whittle et al, 2002;Mirzaei et al, 2003aMirzaei et al, ,b,c, 2005a and for hydrogenation of CO by mixed of cobalt-iron oxide, cobalt manganese oxide and cobalt cerium oxide catalysts for FischereTropsch synthesis (Mirzaei et al, 2005a(Mirzaei et al, ,b, 2006a(Mirzaei et al, ,b, 2007(Mirzaei et al, , 2008. The results of all of these investigations have shown that the ageing of the precipitates obtained by co-precipitation leads to phase changes toward forms that are thermodynamically stable.…”

“…In our previous works (Mirzaei et al, , 2008 we demonstrated the importance of calcination conditions with respect to the catalyst activity for the hydrogenation of CO by mixed cobalt cerium oxides. The results of these investigations have shown that the calcination conditions of the precipitates obtained by co-precipitation lead to the phase changes toward forms that are more thermodynamically stable.…”

“…The FischereTropsch synthesis leads to a wide variety of products, whose abundance depends on the catalysts employed, as well as operating conditions (de la Pena O'Shea et al, 2005;Schulz, 1999;Dry, 2002). Although all group VIII metals (Vannice, 1975) display some activity in CeC coupling reaction during CO hydrogenation, the most active metals for FTS are ruthenium, nickel, iron and cobalt de la Pena O'Shea et al, 2007;Davis, 2003;Ding et al, 2008), with iron and cobalt-based catalysts being the most commonly used industrial scale. Cobalt catalysts record higher yields and long life times, producing predominantly linear alkanes and heavy hydrocarbons, with low water gas shift activity (Madon et al, 1993).…”

“…The products derived from the FTS are endowed with a tremendous environmental value because they are not only sulphur and nitrogen free, but also lack of aromatic structures, recognized as harmful substances (Herranz et al, 2006). The FischereTropsch synthesis leads to a wide variety of products, whose abundance depends on the catalysts employed, as well as operating conditions (de la Pena O'Shea et al, 2005;Schulz, 1999;Dry, 2002). Although all group VIII metals (Vannice, 1975) display some activity in CeC coupling reaction during CO hydrogenation, the most active metals for FTS are ruthenium, nickel, iron and cobalt de la Pena O'Shea et al, 2007;Davis, 2003;Ding et al, 2008), with iron and cobalt-based catalysts being the most commonly used industrial scale.…”

Spatial Heterogeneity and Imperfect Mixing in Chemical Reactions: Visualization of Density-Driven Pattern Formation

“…In our previous study, we demonstrated the importance of aging time with respect to catalyst activity for oxidation of CO by mixed copper manganese oxide and mixed copper zinc oxide catalysts [27][28][29][30][31][32][33][34][35] and for hydrogenation of CO by mixed of cobalt-iron oxide, cobalt-manganese oxide, and cobaltcerium oxide catalysts for Fischer-Tropsch synthesis [36][37][38][39][40]. In all of these investigations, our results have shown that the aging of the precipitates obtained by coprecipitation leads to phase changes toward the forms, which are more stable thermodynamically.…”