Characterizations and performances of Ni/diatomite catalysts for methane decomposition to obtain carbon nanotubes and high-purity H₂

Catalytic decomposition of methane (CDM) to produce CO_x-free H₂ along with high-value-added carbon nanomaterials is a unique potential route. However, the cost of catalysts and applications of carbon products are necessary issues that need to be addressed. Directly using natural materials as supporting material catalysts is significant along with the research of green and energy savings. The low-cost natural diatomite was selected as a catalyst support for CDM for the first time. Herein, diatomite support Ni catalysts were synthesized by a facile wet impregnation route, characterized for their structural and chemical properties, and were successfully used for the CDM at low temperatures. The 20 wt% Ni-loaded catalyst had a maximum methane conversion of 33% at a reaction temperature of 500 °C, which was maintained for 120 min. Both low and high Ni loading will affect the reaction activity of the catalyst. The MWCNTs obtained from the reaction were uniformly loaded on the surface of the diatomite support, and this MWCNTs/diatomite composite product could theoretically be used for natural rubber reinforcement, which avoids cleverly the process of separating the carbon product and catalyst. In addition, DRIFTS and CH₄ TPSR spectra demonstrated that the reaction process does not produce CO_x. Our findings provide valuable insight into catalyst and process design for CDM. Meanwhile, it proposes a new approach to solve the utilization of carbon by-products in CDM reactions.