Cu,Zn-based catalysts for methanol synthesis: On the effect of calcination conditions and the part of residual carbonates

Abstract

Cu/Zn based catalysts for methanol synthesis derived from zincian malachite and aurichalcite precursor phases were investigated. The decomposition process of the different hydroxy-carbonates to yield the carbonate modified metal oxides (calcined precursor) was studied in detail on the basis of the results of nonisothermal kinetics modeling. It was possible to obtain different amounts of the so-called high temperature carbonate (HT-CO 3 ) in the calcined material after calcination at the same temperature by varying the mass transfer conditions, which resulted in differences in crystallinity, IR spectra and decomposition profile. Large amounts of HT-CO 3 in the calcined material seem to be detrimental, whereas only a small fraction is beneficial and effects phase stability.

Activating a Cu/ZnO : Al Catalyst – Much More than Reduction: Decomposition, Self‐Doping and Polymorphism

“…It is very likely that the reduction to Cu(I) and finally Cu(0), particularly at 150 °C, also contributes to the CO 2 emission since HT‐CO 3 is not exclusively attributed to the Zn‐moieties. These findings imply that the so far controversially discussed role of the Cu/Zn‐HT‐CO 3 is related to the activation period since it decomposes completely . It might have a strong influence on the microstructure due to a slow‐down of the reduction process itself and a possible control of phase separation tendencies.…”

“…This observation is supported by the slightly decreasing charge transfer from ZnO : Al to Cu metal at 250 °C (Figure S2). Generally, the charge transfer from ZnO : Al to Cu and its accumulation at the interface might lead to an additional electrostatic stabilization of the latter and explain the higher stability compared to non‐doped Cu/ZnO catalysts …”

Supercritical Antisolvent Precipitation of Amorphous Copper–Zinc Georgeite and Acetate Precursors for the Preparation of Ambient‐Pressure Water‐Gas‐Shift Copper/Zinc Oxide Catalysts

“…The thermal behaviour of the SAS precipitates was then studied by thermal gravimetric analysis/differential thermal analysis (TGA/DTA) to trial their applicability as suitable precursors for WGS catalysts (Figure 6). Decomposition profiles of these phases are known to be dependent on sample mass [40,41] so the amounts of samples analysed were kept constant. To understand the decomposition of the SAS precipitates, we must consider the thermal decomposition of the as-received copper acetate monohydrate.…”

Preparation of Active Cu/ZnO-based Catalysts for Methanol Synthesis

“…Aside from the metal ratio, the above thermal behavior depends on the heating condition. Schumann et al studied the effect of calcination condition on HT-CO3 of zincian malachite and aurichalcite using different heating rates in TG experiments [49]. After a little weight loss occurred at low temperatures due to water desorption, HT-CO3 was decomposed at ca.…”

“…Prior to the reaction, CuO/ZnO-based catalyst should be reduced to Cu/ZnO-based one, accompanying H2 consumption and concomitant evolution of H2O and CO2 [49]. In this transformation would be changed CuO reduction, mobility of CuO and ZnO, and particle morphology.…”