Hydrogen production by methane decomposition: A comparative study of supported and bulk ex-hydrotalcite mixed oxide catalysts with Ni, Mg and Al. (17th May 2018)

• Record Type: Journal Article
• Authors: García-Sancho, C.; Guil-López, R.; Sebastián-López, A.; Navarro, R.M.; Fierro, J.L.G.
• Is Part Of: International journal of hydrogen energy. Volume 43:Number 20(2018)
• Page Start: 9607
• Page End: 9621
• Publication Date: 2018-05-17
• Subjects: Hydrogen -- Methane decomposition -- Hydrotalcite -- Nickel catalysts -- Supported catalysts; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2018.04.021
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: A catalytic comparative study of COx -free hydrogen production by methane decomposition was carried out. Catalytic performances of bulk Ni-mixed oxides derived from Ni/Mg/Al-hydrotalcites ( ex -HTs-Ni) were compared with those obtained with Ni supported on mixed oxides derived from Mg/Al-hydrotalcites (Ni/ ex -HTs), or on commercial supports (γ-Al2 O3, MgO and MgO-modified γ-Al2 O3 ). Catalyst characterization and their catalytic performance showed both ex -HTs-Ni and Ni/ ex -HTs appear to be a similar regardless of their method of preparation. Ni/γ-Al2 O3 was the best supported catalyst, although the catalytic performances of the ex -HTs catalysts were better. Higher NiMg interaction in ex -HTs provides higher resistance to deactivation. Characterization by TG, Raman spectroscopy and TEM of spent catalysts in the reaction suggest the degree of ordering of the graphitic layers of the carbon deposit onto the catalyst surface is the key factor in the catalyst deactivation. The higher degree of ordering or graphitization of the carbon produced with the higher concentration of sp2 carbons on the surface of the Ni/γ-Al2 O3 favours its faster deactivation by Ni-coverage than the bulk catalyst ( ex -HT-Ni), in which the MWNT type carbon is mainly obtained. Highlights: Ni/Mg/Al bulk ex -hydrotalcites were the most stable and active catalysts of the study. Ni is incorporated into mixed oxides MgAl matrix to support it on ex -hydrotalcites. Higher stability of ex -hydrotalcite materials allowed reach higher H2 production level. Ni into Mg/Al matrix is better catalyst in the pyrolysis of CH4 than acid Ni/Al2 O3 . The type and order of carbon formed have influence on the catalytic deactivation.