Guanzhong Lu

Biodiesel synthesis over the CaO–ZrO2 solid base catalyst prepared by a urea–nitrate combustion method

CaO–ZrO2 solid base catalysts with Ca/Zr ratios varying from 4/6 to 9/1 were prepared via a urea–nitrate combustion method and used in the transesterification of soybean oil with methanol to produce biodiesel. The catalysts were characterized using N2 adsorption, XRD, SEM and CO2-TPD techniques, and tested for biodiesel synthesis. The results show that a new phase of CaZrO3 has been formed for the investigated CaO–ZrO2 catalysts. With the increase in Ca/Zr molar ratio, the total basic sites over the catalyst increase and a maximum is obtained over the CaO–ZrO2 catalyst with a Ca/Zr ratio of 8/2. A similar variation trend of biodiesel yield is observed, suggesting that the catalytic activity correlates well with the total basic sites on the catalyst surface. Furthermore, the turnover frequency (TOF) has been calculated for various CaO–ZrO2 catalysts and the result revealed that the catalytic activity also depends on the strength of basic sites. The urea–nitrate combustion method was demonstrated to be a simple, fast and effective method for the preparation of CaO–ZrO2 solid base catalysts, which could be effectively applied for biodiesel synthesis.

Effects of alkaline-earth oxides on the performance of a CuO–ZrO2 catalyst for methanol synthesis via CO2 hydrogenation

CuO–ZrO2 catalysts doped with alkaline-earth oxides were prepared by a urea-nitrate combustion method. The catalysts were characterized with N2 adsorption, N2O titration, XRD, H2-TPR, XPS and CO2-TPD techniques and tested for methanol synthesis from CO2 hydrogenation. With the incorporation of alkaline-earth oxides, the copper surface area increases remarkably, whereas the reducibility of CuO in the catalyst decreases. The doping of alkaline-earth oxides leads to an increase in the strength and contribution of the strong basic site on the catalyst surface. The results of catalytic tests indicate that the conversion of CO2 depends not only on the copper surface area but also on the reducibility of CuO in the catalyst, and the latter is a predominant factor for CaO-, SrO- and BaO-doped CuO–ZrO2 catalysts. The selectivity to methanol is related to the basicity of the catalyst. Moreover, the influence of the doping amount of MgO on the properties of CuO–ZrO2 was investigated, and the optimum catalytic activity is obtained as the amount of MgO doping is 5 mol%.

The effects of PVP-modified SiO2 on the catalytic performance of CO hydrogenation over Rh–Mn–Li/SiO2 catalysts

Rh–Mn–Li catalysts supported on SiO2 prepared by PVP-modified Stober method were used for the synthesis of C2+ oxygenates from CO hydrogenation. The catalysts were characterized by TG, XRD, N2-adsorption–desorption, TEM, H2-TPR, in situ FT-IR, TPSR, and XPS. Activity testing results showed that the Rh–Mn–Li catalyst supported on the SiO2 modified by 1 g PVP exhibited the highest CO conversion and selectivity of C2+ oxygenates compared with other catalysts. Characterization results indicated that the addition of an appropriate amount of PVP is beneficial to the formation of weakly H-bonded hydroxyl groups on the surface of SiO2, which promotes Rh dispersion and weakens the Rh–Mn interaction. Furthermore, the higher Rh dispersion and the weaker Rh–Mn interaction promote CO absorption, enhance the CO dissociation ability and restrain the hydrogenation activity, which are favorable for the CO insertion into the metal–CHX band, finally resulting in excellent catalytic performance for C2+ oxygenates synthesis.