Fischer–Tropsch synthesis over RuCo catalysts: An effect of ligands on the active phase properties and catalytic activity

High quality synthetic fuels could be obtained using the Fischer–Tropsch process. Development of new catalysts for this process is very important for the selective formation of fuel fractions. RuCo catalysts prepared by modifying the support with ethylenediaminetetraacetic acid, urea, acetone azine, or citric acid was investigated for the first time in order to see the effect of the ligand on the catalytic properties of the bimetallic system. The catalysts were characterized by TEM, STEM, XRF, H2-TPR, NH3-TPD, and XPS. It was assumed that total acidity, reducibility, dispersion and atomic surface composition of the catalysts are dependent on the ligands used. The catalyst obtained after modification of Al2O3 with citric acid was characterized by low activity and the predominant formation of solid paraffins. The use of EDTA resulted in a highly active catalyst with highest selectivity to gasoline. Catalyst modified with acetone azine showed a high α (0.898) as well as a selectivity to the diesel fraction of 64.1 %, but average CO conversion of 23.3 %. The optimal catalytic system among those studied was Ru/Co/Al2O3-urea. This system had a high conversion rate of 37.3 % and a selectivity towards C5+ hydrocarbons of 79.4 %. The diesel fraction was also produced in high yield.