δ-Alumina supported cobalt catalysts promoted by ruthenium for Fischer-Tropsch synthesis

•Reduction of cobalt cations by hydrogen occurs at significantly lower temperatures for the ruthenium-promoted Сo-δAl2O3 catalysts.•FTS was carried out after activation catalyst under the conditions ensuring the comparable extent of cobalt reduction.•Selectivity of Ru-promoted Сo-δAl2O3 catalysts for olefins and high-molecular hydrocarbons is higher in comparison with unpromoted catalysts.•At 0.2 wt.% Ru loading, the major part of ruthenium resides in metallic cobalt particles.•When 0.5–1.0 wt.% of Ru is introduced to catalyst, a part of Ru forms individual ultradisperse particles, which are not active in FTS.