Hydrogen and CNT Production by Methane Cracking Using Ni-Cu and Co-Cu Catalysts Supported on Argan-Derived Carbon

The 21st century arrived with global growth of energy demand caused by population and standard of living increases. In this context, a suitable alternative to produce COx-free H-2 is the catalytic decomposition of methane (CDM), which also allows for obtaining high-value-added carbonaceous nanomaterials (CNMs), such as carbon nanotubes (CNTs). This work presents the results obtained in the co-production of COx-free hydrogen and CNTs by CDM using Ni-Cu and Co-Cu catalysts supported on carbon derived from Argan (Argania spinosa) shell (ArDC). The results show that the operation at 900 degrees C and a feed-ratio CH4:H-2 = 2 with the Ni-Cu/ArDC catalyst is the most active, producing 3.7 g(C)/g(metal) after 2 h of reaction (equivalent to average hydrogen productivity of 0.61 g H-2/g(metal)center dot h). The lower productivity of the Co-Cu/ArDC catalyst (1.4 g(C)/g(metal)) could be caused by the higher proportion of small metallic NPs (<5 nm) that remain confined inside the micropores of the carbonaceous support, hindering the formation and growth of the CNTs. The TEM and Raman results indicate that the Co-Cu catalyst is able to selectively produce CNTs of high quality at temperatures below 850 degrees C, attaining the best results at 800 degrees C. The results obtained in this work also show the elevated potential of Argan residues, as a representative of other lignocellulosic raw materials, in the development of carbonaceous materials and nanomaterials of high added-value.

Automated summary

This study presents the results of co-producing COx-free hydrogen and CNTs through the catalytic decomposition of methane. The Ni-Cu/ArDC catalyst is the most active at 900 degrees Celsius, while the lower productivity of the Co-Cu/ArDC catalyst may be attributed to the hindrance of CNT formation and growth by small metallic nanoparticles.