Preparation, Characterization and Application of ZnAlLa-Hydrotalcite-Like Compounds

The preparation of ZnAlLa-hydrotalcite-like compounds [ZnAlLa-HTLcs] was studied.ZnAlLa-HTLcs were synthesized by a method of variable pH with the raw materials of Zn(NO3)2.Al(NO3)3, La(NO3)3, and NaOH. The effects of some factors (i.e. pH values, the mole ratio of Al^3- to La^3-.temperature and the period of hydrothermal treatment) on the preparation of HTLcs were discussed systematically. XRD. TG-DTA. FT-IR spectroscopy, and ICP were performed to characterize ZnAlLa-HTLcs samples, and the thermal stability of HTLcs was also discussed. It was shown that unique ZnAlLa-HTLcs with high crystallinity can be prepared, under the conditions of pH=5.5-6.5. n(Zn^2 )/n(Al^3 La^3 )=2 and the atomic ratio of La^3 to Al^3 ranging from 0.07 to 2. hydrothermal treatment at 120℃ for 5 h. When the calcination of the HTLcs is performed at temperatures above 200℃. ZnO phase is detected with Al2O3 and La2O3 spreading on its top. The complex metal oxides derived from ZnAlLa-HTLcs at 500℃ have higher catalytic activity and selectivity than those from ZnAl-HTLcs for the esterification of acetic acid with n-butanol under the same reaction conditions.