Influence of the Iron Proportion on the Efficiency of an Oil-Soluble Ni–Fe Catalyst Applied in the Co-liquefaction of Lignite and Heavy Residue

Abstract

Developing a fundamental insight into the active phase and the component−activity relationships of catalysts is critical to the successful design of highly efficient catalysts. The influence of the iron proportion on the performance of synthesized Ni−Fe catalysts was investigated to modulate the intrinsic catalytic activity. Furthermore, characterization features of sulfided catalysts and density functional theory methodology were combined for a comprehensive interpretation. The highest hydrogenation efficiency occurred with nickel and iron in an equimolar ratio. A significant increase in the degree of nickel sulfidation was found to coincide with an increase in the proportion of iron, which is ascribed to a lowered thermal decomposition temperature and the promotion of sulfur adsorption. In addition, benefiting from the considerably stronger H adsorption to facilitate H 2 dissociation, the (Fe,Ni) 9 S 8 phases, which exist in all sulfided catalysts, should to be the key component responsible for the observed high hydrogenation activity.