Preparation Characterization And Application Of Hydrotalcite Like Compounds Containing Rare Earth

ZnAlM-Hydrotalcite-Like Compounds (M=La or Ce) were synthesized mainly by a method of varied pH with the materials of Zn(NO3)2 , A1(NO3)3, La(NO3)3 or Ce(NO3)3 and NaOH. NiAlM-Hydrotalcite-Like Compounds (M=La or Ce) were synthesized in the same way with the materials of Zn(NO3)2, A1(NO3)3, La(NO3)3 or Ce(NO3)3. The titration curve of M2+/M3+=2.0, different La3+(Ce3+)/Al3+ ratio mixed salt solution was discussed, the effects of each factor on preparation of ZnAlM-HTLcs and NiAlM-HTLcs were studied systematically, it contains pH domains, different ratios of La3+(Ce3+)/Al3+ of mixed solution, the temperature and time of hydrothermal treatment etc. The phases as to synthetic compounds are detected by XRD, andcrystallinity can be obstained by the peak intensity on it. TG-DTA and XRD results at different temperature calcinations samples are performed to characterized HTLcs thermal decomposition. ICP has been performed in order to determine the metal content of the products. The structure of HTLcs is characterized by FT-IR. The catalytic activity of the products is investigated by the esteiflcation reaction of acetic and n-butanol and the reduction NO reaction. The optimum conditions of preparing HTLcs with the rare earth La or Ce are been found. The precursors of the rare earth composite oxides catalysts can be obtained with the rare earth high-spreading, particle size even.The experiments results showed that the optimal conditions are different according to the type HTLcs. The effect of pH is the heaviest. The products are different on the different pH plateau on the titration curve, the optimal pH domain to obtain unique HTLcs is the second pH plateau. It is distinctly 5.5-6.5(ZnAlLa-HTLcs), 5.3-6.9(ZnAlCe-HTLcs), 5.5-6.7(NiAlLa-HTLcs), 5.5-6.9(NiAlCe-HTLcs).La3+ or Ce3+ can not be replaced A13+ completely, only partly.This is possibly owe to the relative big radium of La3+ or Ce3+, it is difficult to replace A13+. Too high La3+ or Ce3+ content in the starting solution does not results in unique HTLcs. So M2+/M3+=2.0, the optimal La3+ (Ce3+)/Al3+ is 0.07-2.00(ZnAlLa-HTLcs), 0.07-2.75(ZnAlCe-HTLcs), 0.07-0.86(NiAlLa-HTLcs),0.07-0.50(NiAlCe-HTLcs).The temperature and time of the hydrothermal can affect heavily the relative crystallinity of the products. Too low temperature or too short time can lead to poor crystallinity of the products. Too high temperature or too long time may not obtain unique HTLcs. 120℃, 6h hydrothermal as to ZnAlM-HTLcs can obtain the highest relative crystallinity products, while as to NiAlM-HTLcs is 110℃, 5h.TG-DTA curves of all products showed the two endothermaic peaks on the DTA curve and two sharp weight loss accompanied on the TG curve. And they can been distinctly ascribed to losses of interlayer water and OH groups. FT-IR and ICP results with XRD spectrum showed that La or Ce exists in the synthentic tri-HTLcs and not change the layer structure.The catalytic tests exhibited that ZnAlLa-HTLcs have higher catalytic activity and very higher selectivity than ZnAl-HTLcs at the same condition to the esterification of acetic acid with n-butanol. In the domain of 100℃-500℃, the catalytic activity increases with the calcinations temperature, and the best result is at 500℃ calcinations. The catalytic activity of ZnAlLa-HTLcs can be up to 78.7% which was higher than what was reported in the following reaction condition, conditions: Acetic acid/n-Butanol=l/l(mol), 0.8g catalyst (pretreated 2h in N2 at 120℃ before the reaction), 69℃, 5h. Water-carrying agent: cyclohexane. Sovent: Acetophenone.The results of the catalytic reduction NO show that all composite oxides after tri-HTLcs containing La or Ce 700℃ calcinations have higer catalytic activity than those after binary HTLcs calcinations, and the activity of the former can be almost up to 100% in the definite condition for NO conversion, and that of the latter is only 70%, which provides probability in the later research.