Evolution of the Ni-Cu-SiO2 catalyst for methane decomposition to prepare hydrogen

Catalytic decomposition of methane (CDM) is a simple process for the production of high-purity, COX-free hydrogen, and Ni-Cu system catalysts are widely used in the filed of hydrogen production. However, Ni-Cu catalysts easily lose their activities at higher temperatures. To study the methods for facilitating the catalytic performance with Ni-Cu-SiO2 catalysts (Ni:Cu:SiO2 = 65:10:25, mass fraction) during the CDM reaction, and for increasing the utilization rate of the catalyst, a series of kinetic experiments were designed to test and improve the catalytic performance, and the study of generated by-products carbon structures was also carried out. Based on the kinetic experiments, TEM images, XRD data, and Raman spectra, it is found that the introduction of methane into the reactor at lower temperatures prevented the sintering of the catalyst particles into bigger clusters and increased the catalytic activity and lifetime. Moreover, this study also proved that fragmentation process was the key factor contributing to the deactivation of Ni-Cu catalysts at higher temperature. In addition, due to the disordered carbon formed over Ni-Cu-SiO2 catalysts during methane decomposition, the deactivated catalysts exhibit recovered activity at higher temperatures. For the deactivated catalysts recovered activity, the disordered carbon and the pore of generate by-products carbon structures made a big contribution to crack methane at high temperature, and the pores blocked by the generated carbons might cause those catalysts lose activity again.