Effect of potassium in catalysts obtained by the solution combustion synthesis for co-production of hydrogen and carbon nanofibers by catalytic decomposition of methane

A set of catalysts containing 0.25–10 wt% K2O was prepared by solution combustion synthesis. The catalytic systems were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and low-temperature nitrogen adsorption. The catalytic methane decomposition was carried out at 0.5 MPa, 100 LCH4/(h·gcat), and temperature ranging from 550 to 750 °C. It has been found that varying the potassium content led to a change in the phase composition and textural characteristics of the resulting catalysts. The introduction of potassium (0.25 wt% K2O) into the nickel catalyst made it possible to change the particle size distribution towards the formation of smaller particles, from 5 to 30 nm to 5–10 nm, promoting the formation of higher yield of H2. The Ni-0.25 %K2O/Al2O3 и Ni-1 %K2O/Al2O3 catalysts demonstrated the highest hydrogen yield of 11.6 g/gcat and 17.0 g/gcat with a maximum at 675 and 750 °C, respectively. The highest yield of carbon material (51.0 g/gcat) was obtained over Ni-1 %K2O/Al2O3 catalyst.