Development of Cu/ZnO/Al₂O₃ catalyst for dimethyl ether synthesis from CO-CO₂-H₂ mixture

The objective of this study is to develop a catalyst for direct synthesis of dimethyl ether ((CH₃)₂O, DME) from a CO-CO₂-H₂ mixture such as blast furnace gas. For this purpose, precipitated Cu-ZnO-X (X = Al₂O₃, Cr₂O₃, ZrO₂ or Ga₂O₃) were systematically prepared by changing chemical composition and their catalytic activity was measured. 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. In conclusion, the most active composition of Cu-ZnO-Al₂O₃ catalyst for DME synthesis was Cu/ZnO = 4/6 with 14.3mol% Al₂O₃ and interestingly this composition was included within the range of usual MeOH synthesis catalysts.