Enhanced Stability of Spatially Confined Copper Nanoparticles in an Ordered Mesoporous Alumina for Dimethyl Ether Synthesis from Syngas

A spatial confinement effect of copper nanoparticles in an ordered mesoporous γ-Al₂O₃, which is synthesized by an evaporation induced self-assembly (EISA) method, was investigated to verify the enhanced catalytic activity and stability with less aggregation of copper crystallites during direct synthesis of dimethyl ether (DME) from syngas. The surface acidity of the mesoporous Al₂O₃ and the metallic copper surface area significantly altered catalytic activity and stability. The ordered mesopore structures of Al₂O₃ were effective to suppress the aggregation of copper nanoparticles even under reductive CO hydrogenation conditions through the spatial confinement effect of the ordered mesopores of Al₂O₃ as well as the formation of strongly interacted copper nanoparticles with the mesoporous Al₂O₃ surfaces by partial formation of the interfacial CuAl₂O₄ species. The aggregation of copper nanoparticles on the bifunctional Cu/meso-Al₂O₃ having an ordered mesoporous structure was effectively suppressed due to the partial formation of the thermally stable spinel copper aluminate phases, which can further generate new acid sites for dehydration of methanol intermediate to DME.