Research Of Cu-ZnO-Al₂O₃Catalyzing2-butanol Dehydrgenation

Cu-based catalysts are widespread applied in alcohols dehydrogenation, the synthesis and steam reforming of methanol, esters hydrogenolysis, the synthesis of nitriles from alcohols and ammonia, etc., for their high catalytic activity, low reaction temperature, etc.. However, Cu-based catalysts are easy to sinter at high temperature because of low melting point, leading to shorten lifespan of catalysts. In light of the defects of Cu-based catalysts above, Zn element and proper supporter were added to enhance the reactive stability. Although many researches have been carried out at home and abroad, the roles of Zn element and proper supporter are completely unknown. Herein, Cu-ZnO and CU-Al2O3were studied via TPR, XRD, SEM, N2O decomposition and2-butanol dehydrogenation. And the preparation methods and conditions, alkali metal modification of Cu-ZnO-Al2O3were investigated to their effects on catalytic properties and thermostability.Compared with physical mixing, coprecipition is proper to prepare highly dispersive and active Cu-based catalyst whether they are Cu-ZnO or Cu-Al2O3. Cu0are active sites in2-butanol dehydrogenation. ZnO and Al2O3are unactive for dehydrogenation, but the roles of them are different in Cu-based catalyst. The isomorphous substitution between Zn2+and Cu2+ocurres in aging process, which is in favor of ZnO dispersing Cu species after calcination. Strong interaction between ZnO and Cu0exists, preventing Cu0particles from sintering. Different from Cu-ZnO, copper aluminum hydrotalcite is shaped between Al3+and Cu2+in aging process for Cu-Al2O3system. Al2O3as supporter disperses Cu species, and strong interaction between Al2O3and Cu also exists, which is favorable to hinder Cu0particles from sintering. Cu2Al2O4spinel is formed in Cu-Al2O3, obviously different from Cu-ZnO. Appropriate coprecipitation conditions for Cu-ZnO-Al2O3are basic atmosphere, NaHCO3as precipitant, aging at50℃for4h, calcination temperature at450℃. Cu-ZnO-Al2O3prepared by physical mixing, especially alkali metal modification, exhibits outstanding catalytic property.