Cobalt catalysts for Fischer-Tropsch synthesis: The effect of support, precipitant and pH value

doi:10.1016/j.cjche.2017.11.001

Abstract

Abstract: In this report, Co-based catalysts supported on ZnO, Al₂O₃ and ZrO₂ as well as the ZrO₂ derived from different precipitants and different pH values were prepared by co-precipitation method. Their catalytic Fischer-Tropsch synthesis (FTS) performance was investigated in a fixed-bed reactor. The results revealed that Co catalyst supported on ZrO₂ exhibited better FTS catalytic performance than that supported on ZnO or Al₂O₃. For the Co/ZrO₂ catalyst, different precipitants showed the following an activity order of NaOH > Na₂CO₃ > NH₄OH, and the best pH value is 13. The catalysts were characterized by N₂ adsorption-desorption, XRF, XRD, H₂-TPR, H₂-TPD and TEM. It was found that the main factor affecting the CO conversion of the catalyst was the amounts of low-temperature active adsorption sites. Moreover, the selectivity of C₅⁺ hydrocarbons had a positive relationship with the peak temperature of the weak hydrogen adsorption sites. The higher the peak temperature, the higher the C₅⁺ selectivity is.

Key words: Fischer-Tropsch synthesis, Co-precipitation, Carbon monoxide, Hydrogenation, ZrO₂

摘要： In this report, Co-based catalysts supported on ZnO, Al₂O₃ and ZrO₂ as well as the ZrO₂ derived from different precipitants and different pH values were prepared by co-precipitation method. Their catalytic Fischer-Tropsch synthesis (FTS) performance was investigated in a fixed-bed reactor. The results revealed that Co catalyst supported on ZrO₂ exhibited better FTS catalytic performance than that supported on ZnO or Al₂O₃. For the Co/ZrO₂ catalyst, different precipitants showed the following an activity order of NaOH > Na₂CO₃ > NH₄OH, and the best pH value is 13. The catalysts were characterized by N₂ adsorption-desorption, XRF, XRD, H₂-TPR, H₂-TPD and TEM. It was found that the main factor affecting the CO conversion of the catalyst was the amounts of low-temperature active adsorption sites. Moreover, the selectivity of C₅⁺ hydrocarbons had a positive relationship with the peak temperature of the weak hydrogen adsorption sites. The higher the peak temperature, the higher the C₅⁺ selectivity is.

关键词: Fischer-Tropsch synthesis, Co-precipitation, Carbon monoxide, Hydrogenation, ZrO₂

Zhenhua Li, Mengyao Si, Li Xin, Renjie Liu, Runxue Liu, Jing Lü. Cobalt catalysts for Fischer-Tropsch synthesis: The effect of support, precipitant and pH value[J]. Chin.J.Chem.Eng., 2018, 26(4): 747-752.

Zhenhua Li, Mengyao Si, Li Xin, Renjie Liu, Runxue Liu, Jing Lü. Cobalt catalysts for Fischer-Tropsch synthesis: The effect of support, precipitant and pH value[J]. Chinese Journal of Chemical Engineering, 2018, 26(4): 747-752.

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