LAUSR

Catalyst precursors for methanol synthesis prepared by coprecipitation, such as Cu/Zn‐based hydroxycarbonates, are generally formed within two steps. The initial precipitation phase (nucleation) leads to a suspension from which, in a subsequent aging phase, the final solid precursor is formed, thus providing the structural and morphological features required for later use in catalysis. Combing ultrafast continuous nucleation with sampling from batch‐wise aging opens up the possibility to follow the evolution and transitions of solid phases during suspension aging. The temporal progression of the existence of the different phases in a Cu/ZnO/ZrO2‐based system is investigated by scanning electron microscopy, X‐ray diffraction, and inductive coupled plasma optical emission spectroscopy . According to the findings of this study, the intermediate recrystallization reveals to be a yet unknown two‐step process. The presence of an amorphous transient zinc depot of Na2Zn3(CO3)4 × 3 H2O greatly influences the formation of the relevant zincian malachite catalyst precursor [(Cu,Zn)2(OH)2CO3], which is partly in contrast to reports on Cu/ZnO/Al2O3 systems. Finally, a general mechanism including the relevant transformations during suspension aging in Cu/ZnO/ZrO2 systems is proposed, relying on a general thermodynamic approach, explaining the transient and final species.