Cu_1−xMg_xAl₃ spinel solid solution as a sustained release catalyst: One-pot green synthesis and catalytic performance in methanol steam reforming

A versatile and green method for the synthesis of an efficient catalyst applied in methanol steam reforming is promising in view of clean energy production. Cu_1−xMg_xAl₃ ternary spinel oxide catalysts have been prepared by a one-pot solid-phase reaction method using Cu(OH)₂, Al₂O₃·xH₂O and MgCO₃ as the raw materials. The structure, reducibility, surface chemical state, and the aluminum ion distribution are comprehensively characterized by XRD, UV–vis, XPS, H₂-TPR, N₂O chemisorption, and ²⁷Al MAS NMR techniques. The performances of the catalysts in methanol steam reforming are evaluated. Compared with binary Cu-Al spinel, the incorporation of Mg into the spinel lattice results in the change of Al³⁺ cation distribution between tetrahedral and octahedral sites, and thus the variation of copper surrounding environment can be inferred. Consequently, the copper releasing rate from the Mg containing spinel structure declines substantially, which is believed to be in favor of maintaining a stable catalytic performance longer. Besides, the ternary spinel oxide might facilitate the in-situ formation of smaller nano copper metals compared to CuAl₃ binary spinel catalyst. Among all the catalysts, Cu_0.9Mg_0.1Al₃ presents the highest activity as well as the best catalytic stability. The findings of this report suggest that introducing a foreign cation into the Cu-Al spinel structure might be a promising way to regulate the copper releasing property for achieving a better sustained release catalyst system.