The preparation of ZnAlLa-hydrotalcite-like compounds [ZnAlLa-HTLcs] wasstudied. ZnAlLa-HTLcs were synthesized by a method of variable pH with the raw materials ofZn(NO_3)_2, Al(NO_3)_3, La(NO_3)_3, and NaOH. The eS&#...The preparation of ZnAlLa-hydrotalcite-like compounds [ZnAlLa-HTLcs] wasstudied. ZnAlLa-HTLcs were synthesized by a method of variable pH with the raw materials ofZn(NO_3)_2, Al(NO_3)_3, La(NO_3)_3, and NaOH. The eS'ccts of some factors (i.e. pH values, the moleratio of Al^(3+) to La^(3+), temperature and the period of hydrothermal treatment) on thepreparation of HTLcs were discussed systematically. XRD, TG-DTA, FT-IR spectroscopy, and ICP wereperformed to characterize ZnAlLa-HTLcs samples, and the thermal stability of HTLcs was alsodiscussed. It was shown that unique ZnAlLa-HTLcs with high crystallinity can be prepared, under theconditions of pH = 5.5-6.5, n(Zn^(2+))/n(Al^(3+) + La^(3+))=2 and the atomic ratio of La^(3+) toAl^(3+) ranging from 0.07 to 2, hydrothermal treatment at 120 ℃ for 5 h. When the calcination ofthe HTLcs is performed at temperatures above 200 ℃, ZnO phase is detected with Al_2O_3 and La_2O_3spreading on its top. The complex metal oxides derived from ZnAlLa-HTLcs at 500 ℃ have highercatalytic activity and selectivity than those from ZnAl-HTLcs for the esterification of acetic acidwith n-butanol under the same reaction conditions.展开更多
ZnAlLa-CO3 layered double hydroxides （LDHs） with different Zn/Al/La molar ratios were prepared by the constant pH coprecipi- tation method. The synthetic materials were characterized by X-ray diffraction （XRD）, Fo...ZnAlLa-CO3 layered double hydroxides （LDHs） with different Zn/Al/La molar ratios were prepared by the constant pH coprecipi- tation method. The synthetic materials were characterized by X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FTIR）, scan- ning electron microscopy （SEM）, Brunauer-Emmett-Teller method （BET） and particle analysis. The results showed that the hydrotalcite-like materials had a layered structure. The ZnAlLa-CO3-LDHs as stabilizers were mixed with PVC resin. The tests of thermal aging, mass loss test and Congo red for the PVC composites were carried out at 180±1℃, respectively. The results showed that ZnAlLa-CO3- LDHs used as sin- gle thermal stabilizers could enhance both the long-term thermal stability and initial thermal stability of PVC, and 2.4 phr （parts per hundred PVC resin） ZnAlLa-CO3-LDHs with Zn/Al/La （molar ratio）=20/8/2 had a better stabilizing effect on PVC than others. Compared with single thermal stabilizers, the composite thermal stabilizers including 0.3 phr calcium stearate （CaSt2）, 0.4 phr β-diketone and 2.4 phr ZnAlLa-CO3-LDHs significantly enhanced the thermal stability of PVC sample. And rare earth ion could optimize the conformation of PVC and refrain the initiation of the thermal stability and the thermal stable time was over 220 min. The main reason could be concluded to the spe- cial structure of rare earth ion, which had longer atom radius and more coordination numbers. So the rare earth ion （RE3＋） could react with the labile chlorine atoms （Cl-） to form a stable coordinate complex.展开更多
基金Supported by Shanxi Province Natural Science Funds.(20001015)
文摘The preparation of ZnAlLa-hydrotalcite-like compounds [ZnAlLa-HTLcs] wasstudied. ZnAlLa-HTLcs were synthesized by a method of variable pH with the raw materials ofZn(NO_3)_2, Al(NO_3)_3, La(NO_3)_3, and NaOH. The eS'ccts of some factors (i.e. pH values, the moleratio of Al^(3+) to La^(3+), temperature and the period of hydrothermal treatment) on thepreparation of HTLcs were discussed systematically. XRD, TG-DTA, FT-IR spectroscopy, and ICP wereperformed to characterize ZnAlLa-HTLcs samples, and the thermal stability of HTLcs was alsodiscussed. It was shown that unique ZnAlLa-HTLcs with high crystallinity can be prepared, under theconditions of pH = 5.5-6.5, n(Zn^(2+))/n(Al^(3+) + La^(3+))=2 and the atomic ratio of La^(3+) toAl^(3+) ranging from 0.07 to 2, hydrothermal treatment at 120 ℃ for 5 h. When the calcination ofthe HTLcs is performed at temperatures above 200 ℃, ZnO phase is detected with Al_2O_3 and La_2O_3spreading on its top. The complex metal oxides derived from ZnAlLa-HTLcs at 500 ℃ have highercatalytic activity and selectivity than those from ZnAl-HTLcs for the esterification of acetic acidwith n-butanol under the same reaction conditions.
基金Project supported by National Natural Science Foundation of China (91023031)
文摘ZnAlLa-CO3 layered double hydroxides （LDHs） with different Zn/Al/La molar ratios were prepared by the constant pH coprecipi- tation method. The synthetic materials were characterized by X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FTIR）, scan- ning electron microscopy （SEM）, Brunauer-Emmett-Teller method （BET） and particle analysis. The results showed that the hydrotalcite-like materials had a layered structure. The ZnAlLa-CO3-LDHs as stabilizers were mixed with PVC resin. The tests of thermal aging, mass loss test and Congo red for the PVC composites were carried out at 180±1℃, respectively. The results showed that ZnAlLa-CO3- LDHs used as sin- gle thermal stabilizers could enhance both the long-term thermal stability and initial thermal stability of PVC, and 2.4 phr （parts per hundred PVC resin） ZnAlLa-CO3-LDHs with Zn/Al/La （molar ratio）=20/8/2 had a better stabilizing effect on PVC than others. Compared with single thermal stabilizers, the composite thermal stabilizers including 0.3 phr calcium stearate （CaSt2）, 0.4 phr β-diketone and 2.4 phr ZnAlLa-CO3-LDHs significantly enhanced the thermal stability of PVC sample. And rare earth ion could optimize the conformation of PVC and refrain the initiation of the thermal stability and the thermal stable time was over 220 min. The main reason could be concluded to the spe- cial structure of rare earth ion, which had longer atom radius and more coordination numbers. So the rare earth ion （RE3＋） could react with the labile chlorine atoms （Cl-） to form a stable coordinate complex.
