Hydrogen production through catalytic methane decomposition promoted by pure silica materials

Abstract

This work reports for the first time that DeCH4 reaction can be carried out over pure silica porous solids working under reaction conditions similar to those employed with carbon catalysts. Thereby, a variety of pure silica samples, with different structural and textural properties have been investigated: amorphous silica (am-SiO2), two zeolitic materials with MFI topology (conventional and hierarchical silicalite-1) and two ordered mesoporous silicas (MCM-41 and SBA-15). In all cases, the carbon generation is not observed from the beginning of the methane supply, but the presence of an induction time is noticed. This effect has been assigned to the fact that the real active sites are not present in the raw silica, being formed during the induction time by reaction between methane molecules and defective silica sites to form –Si–C– species. Among the different silica materials, great variations in the DeCH4 catalytic activity are observed. The SBA-15 sample exhibits the highest activity and an exceptional stability against deactivation by carbon deposition. The major benefit derived from the use of silica materials versus ordered mesoporous carbons in DeCH4 is their easier and more economical manufacture at large scale.