Synthesis of cobalt on cobalt-aluminate and its catalytic properties for carbon monoxide hydrogenation

Abstract

The study focused on synthesis of cobalt on cobalt-aluminate catalyst in one-pot via the solvothermal process and its catalytic properties for carbon monoxide hydrogenation. The influence of conditions to synthesize cobalt on cobalt-aluminate catalyst in this study was investigated such as Co/Al molar ratios, time and temperature during synthesis, temperature of calcination, and cobalt precursors. The various samples were characterized using N[subscript 2] physisorption, XRD, SEM/EDX, TEM, TPR and H[subscript 2] chemisorption. CO hydrogenation (H[subscript 2]/CO = 10/1) was also performed to determine the overall activity and selectivity. It was found that when synthesized at 300℃, increased Co/Al molar ratios apparently resulted in increased activities, whereas the holding time during solvothermal synthesis seemed to have only little effect on the activities upon the high molar ratios of Co/Al (1.0 and 2.0). However, at low molar ratio of Co/Al (0.5), the increased holding time can result in dramatically decreased activity. The decreased temperature during solvothermal process for 2 h can result in increased activity. The study of calcination temperature such as 300, 400 and 500℃ for 1 h revealed that the sample calcined at 400℃ exhibited the highest activity among other samples. The cobalt on cobalt-aluminate catalysts apparently exhibited higher activities than that prepared from the conventional solvothermal-derived alumina-supported cobalt catalyst without any changes in product selectivity when prepared with the same amount of cobalt excess. For the study of different cobalt precursors, it revealed that the activity of CoN > CoAC > CoAA > CoCL due to large crystallite size having fewer interactions. CoCL showed higher selectivity to C[subscript 2]-C[subscript 4].