For Cu-ZnO-Al2O3 catalyst, compositional research was on two parameters, namely Cu/ZnO ratio (3/7∼5/5) and content of Al2O3 (0∼33.0 mol%). The influence of each parameter was estimated by DME and MeOH yields for the same catalyst mass. Some Cu-ZnO-Al2O3 catalysts synthesized DME more than MeOH, in which the DME activity was related to specific surface area and existence of broadened ZnO peaks in XRD patterns. In contrast, three other Cu-ZnO catalysts including another oxide (Cr2O3, ZrO2 or Ga2O3) synthesized only MeOH without DME. Content of Al2O3 was more influential on DME synthesis than Cu/ZnO ratio. Physically-admixed (hybrid) catalysts of Cu-ZnO-Ga2O3 for CH3OH synthesis and γ-Al2O3 for its dehydration were experimentally studied, in which the influence of mixing ratio of the two catalysts on both yield and selectivity of DME was mainly examined for the same catalyst mass. The results showed that the developed hybrid catalyst is very effective in producing DME directly from BFG without equilibrium limit of methanol. Interestingly, the yield of DME had a significant dependence of mixing ratio, and the hybrid catalyst with only 5 mass% γ-Al2O3 showed the highest yield with 99.3% selectivity of DME + methanol. This implies that methanol formation governs the rate of this series reaction (BFG→CH3OH→DME) due to fast dehydration of methanol to DME. In conclusion, the most active composition of Cu-ZnO-Al2O3 catalyst for DME synthesis was Cu/ZnO=4/6 with 14.3mol% Al2O3. However catalysts mixture of Cu-ZnO-Ga2O3 (95%) and γ-Al2O3 (5%) showed higher activity.
ASJC Scopus subject areas
- Condensed Matter Physics
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry