bimetal Nickel catalysts

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Bimetal nanoparticles have moved into the focus of science in recent years to a large part due to their interesting catalytic properties. For many economically important processes the alloying of a second metal offers the possibility to optimize activity, selectivity and long term stability.In this context, the aim of the proposed project is the testing of the hypothesis of a two-parameter optimum of alloy composition and particle size for the catalytic activity and deactivation resistance for Ni-Cu and Ni-Fe.Methanation of carbon monoxide was selected as representative test reaction, which plays an important role in a number of technical processes, such as Fischer-Tropsch- synthesis or upstream of ammonia-synthesis to protect the iron catalyst from deactivation by CO. As alloying elements Fe and Cu were selected, due to promising results in earlier studies. To reach the project goal the investigation of the initial activity and the deactivation behavior of Ni-Cu and Ni-Fe catalysts with highly defined composition and particle size are necessary. For the investigation of the catalytic properties and the deactivation behavior a number of factors of influence need to be taken into account. These are alloy composition, particle size, reaction temperature, reaction time, and gas phase composition. All three target figures, catalytic activity for the desired reaction, the kinetics of coke formation and sintering behavior, are expected to depend on these factors of influence to some extent. A reduction of the experimental matrix is therefore necessary to reduce the number of required experiment. Based on preceding work the gas phase composition of educt gases for the catalytic reaction will therefore be kept constant. The initial activity of the catalysts shall be characterized in dependence on the the Copper- and Iron-concentration in Nickel-based alloyed catalyst particles. The influence of particle size will be observed separately by investigating particles of a set composition but variable particle size. This will be accomplished by the possibility of manipulating the particle size in the spark discharge process and can further be improved by classification in the gasborne state yielding close to monodisperse particles. The loss of catalytic activity with increasing reaction time will be investigated separately for the two dominating mechanisms, particle growth and coking, which is enabled by aerosol processes. Again the parameters composition and particle size will be investigated separately in their influence on the mechanisms.