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

Abstract

A spatial confinement effect of copper nanoparticles in an ordered mesoporous γ-Al 2 O 3, 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 Al 2 O 3 and the metallic copper surface area significantly altered catalytic activity and stability. The ordered mesopore structures of Al 2 O 3 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 Al 2 O 3 as well as the formation of strongly interacted copper nanoparticles with the mesoporous Al 2 O 3 surfaces by partial formation of the interfacial CuAl 2 O 4 species. The aggregation of copper nanoparticles on the bifunctional Cu/meso-Al 2 O 3 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.