Controllable Preparation Of CuAl-NO₃-LDH And Its Catalytic Application

As a kind of anionic layered materials, because of their unique structures and properties, LDHs had a good application prospect in the field of catalysis. As important members of the class hydrotalcite materials, CuAl-LDHs possessed excellent catalytic activity of copper element and made its catalytic application vaster. So CuAl-LDHs controllable synthesis and basic applications research had been the research hot spots. However, at this stage the CuAl-LDHs synthesis study focused on CuAl-CO3-LDH which compounded under higher pH system. At the same time, due to the Jahn-Teller Effect of copper ions, CuAl-LDHs ware poor crystallinity, low purity of product and the difficulty of interlayer anion exchange, so its application ware limited.In this paper, through hydrothermal method by controlling the reaction conditions, we successfully compounded CuAl-NO3-LDH. Besides, with the aid of a variety of characterization methods, we detailedly discussed many influence factors on the synthesis phase. The pure phase CuAl-NO3-LDH had good structure and performance, and was used in one-step efficient catalytic reaction which was benzaldehyde with ethanol to synthesize benzoin ethyl ether, we obtained more efficient catalytic results.In the experiment of synthesis, Cu(NO3)2·3H2O and A1(NO3)3·9H2O as raw materials, CuAl-NO3-LDHs was hydrothermal synthesis by using HMT and Urea as precipitant. Through X-ray powder diffraction, we detailedly investigated the effects of precipitant concentration, hydrothermal temperature, hydrothermal time and Cu2+/Al3+on composite phase. The results showed if precipitant concentration, temperature or time was not suitable for synthesis conditions, CuAl-NO3-LDH samples would contain impurity Cu(NO3)(OH)3, Cu2O or Cu(CO3)(OH)2. Only when Cu2+/Al3+=2～4, c(HMT)=0.1mol/L or c(Urea)=0.2～0.3mol/L and110℃hold on12h, we could compound pure phase CuAl-NO3-LDH.The catalytic experiment results showed when c(Cu2+)=0.3mol/L, c(A13+)=0.1mol/L, c(Urea)=0.2mol/L,110℃hydrothermal temperature and12h hydrothermal time, we compounded pure phase CuAl-NO3-LDH as catalytic and got more better catalytic effect than CuAl-NO3-LDH and other catalytic. When benzaldehyde volume was3mL, ethanol volume was40mL, pure phase CuAl-NO3-LDH(n(Cu):n(Al)=2:1) as catalytic was0.2g, reaction temperature was70℃and reaction time was70min, the balance of benzaldehyde conversion rate was65.83%, benzoin ethyl ether selectivity nearly was100%. At the same time, through parsing the result of catalytic, we infered the possible reaction mechanism.