Direct conversion of blast furnace gas to dimethyl ether over Cu-ZnO-Ga₂O₃/γ-Al₂O₃ hybrid catalyst: Optimum mass ratio of the catalyst

The objective of this study is to develop a catalyst in a packed-bed reactor for direct synthesis of dimethyl ether ((CH₃)₂O, DME) from blast furnace offgas (CO-CO₂-H₂-N₂, BFG). 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.