Hydrogen production by catalytic methane decomposition over rice husk derived silica

Abstract

Methane decomposition (DeCH4) over solid catalysts is an interesting route for the production of hydrogen free of CO2 emissions. Moreover, it could lead to a negative carbon balance if biogas/biomethane is used as feedstock. However, it is limited by the huge amounts of carbon that are deposited over the catalyst causing its deactivation and hindering its regeneration, which makes necessary the development of low-cost and durable catalytic systems. This work reports the use of different silica materials fully produced from rice husk, i.e. without incorporating any external phase or component, as DeCH4 catalysts. The highest catalytic activity has been found for the silica samples showing large BET surface area and amorphous nature. These properties favor the generation of the actual DeCH4 active sites (-Si-C- species), shortening the induction time detected at the beginning of the reaction tests. The nano-silica materials produced from acid-washed rice husk exhibit a remarkable resistance against deactivation, affording an almost constant reaction rate at long times on stream. This fact is assigned to the presence of large mesopores that facilitate the growth of the carbons deposits towards the outer part of the catalyst particles. The results here reported show the great potential of rice husk-derived nano-silica to overcome several of the most relevant limitations that currently exist for the commercial deployment of hydrogen production by catalytic DeCH4, as a consequence of the low cost and durable activity of these sustainable materials.