The Basicity and Dispersion State of Alkaline Earth Metal Compounds on the Surface of ZrO_2
ZHU Yuexiang, ZHUANG Wei, JIANG De’en, XIE Youchang(Institute of Physical Chemistry, Peking University, Beijing 100871, China)
The basicity and dispersion state of alkaline earth metal compounds on the surface of ZrO 2 were investigated. The results show that the decomposition of alkaline earth metal nitrates become more difficult as the atomic number increases. Mg(NO 3) 2 can decompose directly to MgO at 550 ℃; Ca(NO 3) 2 and Sr(NO 3) 2 can not decompose directly to respective oxide at 550 ℃, but can decompose after being supported on the surface of ZrO 2. When the content of CaO is low, the resultant is a solid solution of CaO and ZrO 2; a new compound CaZrO 3 shows up with increasing content of CaO. For the system of Sr/ZrO 2, SrO can disperse on the surface of ZrO 2 at low loading, and SrZrO 3 appears when the content of SrO increases. Ba(NO 3) 2 cannot decompose to BaO even in the existence of the support, but to Ba(NO 2) 2 and the latter disperses on the surface of ZrO 2 as a monolayer. CO 2 TPD test shows that ZrO 2 supported alkaline earth metal samples present a wider distribution and a larger amount of basic sites compared with pure ZrO 2, and that the strength of basic sites is also increased a lot, especially for Ca/ZrO 2.
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