Effect of metal precursor on Cu/ZnO/Al2O3 synthesized by flame spray pyrolysis for direct DME production

Cu/ZnO/Al2O3 catalysts were synthesized by flame spray pyrolysis (FSP). The effect of different metal precursor types, i.e. metal nitrates and organometallics, on the catalytic properties was investigated. Organometallic precursors are commonly used for flame spray pyrolysis because small nanoparticles can be produced. In this study, we have obtained nanosized copper and zinc oxide clusters also from the nitrate precursors. Characterization was applied to reveal the difference between the clusters obtained from the different precursor types. Both precursors allowed the formation of well-ordered Cu/ZnO/Al2O3 particles with similar size according to TEM investigations. However, the catalyst from metal nitrate precursors possessed a lower reduction temperature, a higher active copper surface area, and a lower overall BET surface area than the one from the organometallic precursor. The catalytic performance of the obtained catalysts was investigated in the direct DME synthesis from synthesis gas. Methanol dehydration catalyst, H-ZSM-5, was therefore admixed to the FSP powders in a pre-defined amount; the FSP powders served as methanol synthesis catalyst in the mixture. The catalyst from metal nitrate precursors showed higher conversion of syngas than the catalyst from the organometallic precursors at same reaction conditions. This effect can be explained mainly by the higher copper surface area. Catalysts with different Cu/Zn ratio were also tested and the best catalyst was further studied by variation of the reaction conditions. In conclusion, we have demonstrated an efficient utilization of less expensive precursor materials for flame spray pyrolysis for production of CugnO/Al2O3 catalysts. (C) 2015 Elsevier Ltd. All rights reserved.