Impact of the synthesis route of supported copper catalysts on the performance in the methanol synthesis reaction

Abstract

Two Cu/SiO2 methanol synthesis catalysts were synthesized, one via precipitation and one via impregnation. The copper particle size distribution and local copper weight loading were similar for both catalysts. Electron tomography revealed for the precipitated catalyst a plate-like silica structure with copper particles partially entrapped, whereas for the impregnated catalyst the copper particles were located in the pores between the primary particles of a silica gel. The precipitated catalyst displayed a lower initial copper weight normalized activity and a higher stability in the methanol synthesis reaction (40 bar, 260 ??C). Copper particle growth during reaction, as determined by transmission electron microscopy, was more limited for the precipitated catalyst, in line with the higher catalyst stability, possibly due to the partial entrapment of the copper particles. In addition to copper particle growth, deactivation of both catalysts was ascribed to restructuring of the silica resulting in partial coverage of the copper surface.