文献类型：期刊文献

英文题名：Energetics and structural evolution of Na-Ca exchanged zeolite A during heating

作者：Sun, H.[1];Wu, D.[2,3];Guo, X.[2,3];Navrotsky, A.[2,3]

机构：[1]E China Univ Sci & Technol, State Key Lab Chem Engn, Shanghai 200237, Peoples R China;[2]Univ Calif Davis, Peter A Rock Thermochem Lab, Davis, CA 95616 USA;[3]Univ Calif Davis, NEAT ORU, Davis, CA 95616 USA

年份：2015

卷号：17

期号：14

起止页码：9241

外文期刊名：PHYSICAL CHEMISTRY CHEMICAL PHYSICS

收录：;WOS:【SCI-EXPANDED(收录号:WOS:000351933600080)】；

基金：H.S. is grateful to the National Natural Science Foundation of China for financial support under the National Natural Science Fund for Young Scholar (No. 21201063), the Ministry of Education of Republic of China for financial support under the Research Fund for the Doctoral Program of Higher Education of China (RFDP) (No. 20110074120020) and the Fundamental Research Funds for the Central Universities, and the China Scholarship Council for the State Scholarship Fund (No. 201308310077). The calorimetric work at UC Davis was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, grant DEFG02-97ER14749.

语种：英文

摘要：The properties of zeolite A change significantly upon sodium-calcium exchange. The impact of cation composition on the temperature-induced phase transformations and energetics of Na-Ca exchanged zeolite A was studied systematically using powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and high-temperature oxide melt solution calorimetry. As the temperature increases, the structural evolution of each Na-Ca exchanged zeolite A sample undergoes three distinct stages -dehydration, amorphization, and densification/recrystallization. Initially complete dehydration does not result in framework degradation, but further heating leads to zeolite phase degradation into other aluminosilicate phases. Both amorphization and recrystallization shift to higher temperatures as the calcium content increases. On the other hand, the enthalpies of formation for the high temperature aluminosilicate phases, the amorphous phase (AP) and the dense phase (DP), appear to be a linear function of calcium content (average ionic potential) with diminishing of energetic stability upon increasing the Ca content. 100% Na-A heated at 1200 degrees C has the most exothermic enthalpy of formation from oxides (-65.87 +/- 0.87 kJ mol(-1) - TO2), while 97.9% CaNa-A heated at 945 degrees C has the least exothermic value (-5.26 +/- 0.62 kJ mol(-1) - TO2). For different aluminosilicates with the same chemical composition, the dense phase (DP) assemblage is more stable than the amorphous phase (AP).