화학공학소재연구정보센터
Catalysis Letters, Vol.130, No.3-4, 481-488, 2009
Bimetallic Au-Cu, Ag-Cu/CrAl3O6 Catalysts for Methanol Synthesis
The influence of silver and gold addition on the activity and physicochemical properties of supported Cu/CrAl3O6 catalysts was the aim of this work. The reduction of CrAl3O6 support shows only one reduction stage attributed to Cr (VI) species reduction originating from previously oxidized binary oxide. Supported copper catalysts reduce in one or two stages depending on copper concentration representing the reduction of copper oxide-CuO, copper oxide chemically combined with Cr(III) oxide as copper chromite-CuCr2O4 and Cr(VI) species originating from surface chromate ions CrO42-. Additionally, the introduction of silver into supported copper catalysts Cu/CrAl3O6 can led to the appearance of silver chromate phase. XRD investigations of support CrAl3O6 alone, supported copper and gold and silver promoted copper supported catalysts calcined at 400, 700 and 900 degrees C indicated the presence of highly amorphous alumina gamma-Al2O3 like structure network in which some of cationic locations of aluminum were occupied by chromium atoms and small quantities of alpha-Cr2O3 phase. Additionally, for copper, silver-copper, and gold-copper supported catalysts the following oxide phases were distinguished: monometallic oxides CuO, Ag2O, binary oxides CuAl2O4, Ag2CrO4, CuCr2O4 and even ternary oxide CuAlCrO4. In the case of gold promoted copper supported catalysts metallic gold phase was detected. Activity tests carried out for these catalysts show that the most active was 20 wt.% Cu/CrAl3O6 catalyst. Promotion of copper catalysts by silver improves the activity in methanol synthesis, what can be assigned to silver chromate formation. The analogical gold chromate like formation was not confirmed.