Methane decomposition over high-loaded Ni-Cu-SiO2 catalysts

The performance of Ni-SiO2 and Ni-Cu-SiO2 during repeated catalytic decomposition of methane (CDM) reactions and subsequent regeneration of the deactivated catalysts with air has been studied. The catalytic activity of the 75%Ni-25%SiO2 catalyst in the second and third CDM was lower than that during the first, while the lifetime of the catalyst did not change significantly. Both the lifetime and the catalytic activity of 65%Ni-10%Cu-25%SiO2 in the second and third CDM reactions decreased significantly. 55%Ni-20%Cu-25%SiO2 showed better performance than the other two catalysts, and its activity and lifetime did not change significantly until the third CDM reaction. The hydrogen yields of 55%Ni-20%Cu-25%SiO2 were 56.8 gH2/gcat., 42.8 gH2/gcat., and 2.4 gH2/gcat. for the first, second, and third CDM reactions, respectively. Spherical carbon structures were observed on the catalysts following all three CDM reactions over 75%Ni-25%SiO2. However, similar carbon structures were only observed following the second and third CDM over 65%Ni-10%Cu-25%SiO2, and only following the third cycle with 55%Ni-20%Cu-25%SiO2. The formation of spherical carbon during the repeated CDM reactions strongly influenced the performance of the catalysts.