Structure and activity of Cu/ZnO catalysts co-modified with aluminium and gallium for methanol synthesis

Abstract

This contribution describes the modification in the structure and activity of Cu/ZnO catalyst in the methanol synthesis reaction induced by the co-modification with a low amount of Al and Ga (Al + Ga = 3% atom). To elucidate the effect of the co-modification, the catalysts were characterized by means of variety of techniques (XRD, N2 physisorption, FTIR, TGA, TEM, TPR and N2O chemisorption) and tested in the methanol synthesis reaction carried out in a flow reactor at 250 °C and total pressure of 3 MPa using syngas. The combined characterization and activity tests demonstrated that the co-doping with Al and Ga affects the structure and activity of Cu/ZnO catalysts in a different manner depending on the Al/Ga ratio used. The best catalyst co-loaded with Ga and Al in equal amount shows an improvement in the activity for methanol synthesis respect to the activity obtained on catalysts individually loaded with Al and Ga. The difference in the activity of the samples co-loaded with Al and Ga normalized by N2O chemisorption point to a different participation of the copper surfaces in combination with the defect sites of ZnO depending on the Al and Ga loading.

Methanol Synthesis from CO2: A Review of the Latest Developments in Heterogeneous Catalysis

“…The desired properties in the final catalysts are a high Cu surface area (depending on small particle size and meso-porosity), good Cu–ZnO interaction or even formation of surface Cu–Zn partial oxidized mixed oxides, and minimal contamination from alkali metals (Na + ) introduced during the co-precipitation process [65]. The selective preparation of the hydroxycarbonate precursors involves the control of parameters in the precursor formation as elemental formulation pH, temperature, ageing time [63,64], and complete removal of Na + [63,65,66]. There is some controversy in the literature about which of the hydroxycarbonate phases is the best to obtain an optimal catalyst for the synthesis of methanol from CO 2 .…”

“…In this way, different studies have been carried out with catalysts derived from aurichalcite ((Cu,Zn) 5 (CO 3 ) 2 (OH) 6 ) [62,67], zincian malachite ((Cu,Zn) 2 CO 3 (OH) 2 ) [65,68,69], hydrotalcite (Cu 1−x−y ZnyAlx(OH) 2 (CO 3 ) x/2 ) [70,71], and even the amorphous zincian georgeite phase ((Cu,Zn)(CO 3 )(OH) 2 ) [65,69,72]. The best catalytic performance seems to be linked with the presence of the zincian malachite phase in the hydroxycarbonate precursor with a maximum amount of Zn incorporated into the structure of the malachite [57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72]. However, recent studies also indicate that there is an additional factor to the presence of zincian malachite that is also key to obtaining a good catalyst for the synthesis of methanol.…”

“…The studies about the promoter effect of Ga on the performance of the Cu–Zn–Al catalysts suggest that the concentration of Cu 0 /Cu + species could be regulated by varying the Ga content in the catalysts modifying by this way their catalytic performance [56]. It was shown that Ga is incorporated into the zincian malachite structure during precipitation [66]; moreover, the co-loading with Al 3+ and Ga 3+ increases with the insertion of Ga into malachite precipitates respect to the Al- or Ga-mono-substituted counterparts. The activities of these catalysts (Table 3) suggest a different participation of the copper surfaces in combination with the partially reduced ZnO x sites depending on the load of Al and Ga.…”

“…The sample with an Al/Ga = 1 ratio shows a marked improvement in activity with respect to the Al- or Ga-mono-substituted counterparts. This improvement in activity seems to be related to changes in ZnO defects with the substitution Zn 2+ /Al 3+ /Ga 3+ which was achieved in the sample with the same amount of Ga and Al that produced a surface contact different between Cu and reduced ZnO which resulted in sites with higher activity for methanol synthesis [66].…”

Data on TGA of precursors and SEM of reduced Cu/ZnO catalysts co-modified with aluminium and gallium for methanol synthesis

“…The reduced catalysts were obtained from reduction of calcined precursors under a mixture of H 2 /ArExperimental featuresThermal decomposition of calcined precursors was studied by thermogravimetry analysing the gas produced by mass spectrometry.The nanomorphology and surface composition of the reduced catalysts were obtained by Scanning Electron Microscopy with energy-dispersive X-ray spectroscopy.Data source location Sustainable energy and chemistry Group, Institute of Catalysis and Petrochemistry (CSIC) Madrid, Spain Data accessibility Data are provided in this article Related research article Associated to the research article “Structure and activity of Cu/ZnO catalysts co-modified with aluminium and gallium for methanol synthesis” in Catalysis Today [1]…”