Catalysis Letters, Vol.146, No.1, 61-71, 2016
Impact of Na Promoter on Structural Properties and Catalytic Performance of CoNi/Al2O3 Nanocatalysts for the CO Hydrogenation Process: Fischer-Tropsch Technology
This work deals with the effect of adding Na to bimetallic sol-gel derived alumina supported Co/Ni nanocatalysts in Fischer-Tropsch synthesis. The catalyst activity and selectivity changed with different levels of Na, and the catalyst with 2 % Na loading was selected as an optimal catalyst to compare with un-promoted Co/Ni/Al2O3 catalyst. Na reduced the methane selectivity by increasing the chain-growth probability (alpha-value) at 12 bar. The results of physico-chemical characterizations show that the Na promoter plays a significant role in the catalytic structure. Additionally, the kinetic behavior was considered in absence and presence of Na over CoNi/Al2O3 catalysts. We applied an enolic approach, which was developed based on the interaction between adsorption HCO and dissociated adsorption hydrogen, through the Langmuir-Hinshelwood-Hougen-Watson (LHHW) adsorption theory. Kinetic parameters, including the rate constant (k) and activation energy (E-a) of the catalysts, were also determined. The results show that, by adding Na, the activation energy (E-a) decreases and the reaction rate (-R-CO) increases. [GRAPHICS] .