Effect of catalyst support on cobalt catalysts for ethylene oligomerization into linear olefins

Abstract

Here, we show that the oligomerization activity of a carbon-supported cobalt oxide catalyst is nearly twice as high when it is supported on a less oxidized carbon support. The high temperature treatment (HTT) of carbon reduces the oxygen content of the carbon support whereas the acid wash (AW) treatment of carbon in nitric acid increases the oxygen content and oxidizes the surface functional groups. These surface functional groups lead to isomerization of linear alpha olefins into linear internal olefins which results in lower oligomerization activity. CoO is the cobalt phase on both catalysts after reactions, suggesting the activity difference between these catalysts is not related to the cobalt phase. Increasing the catalyst support particle size to impose more transport restrictions has a minimal impact on product selectivites. The oligomerization activity is higher by a factor of six when the cobalt is supported on a carbon with lower Al, Ca, Fe, and Mg impurities, suggesting at least one of these impurities lowers the oligomerization activity.