Energetics of sodium-calcium exchanged zeolite A.
Energetics of sodium-calcium exchanged zeolite A.
复制标题
DOI：
10.1039/c5cp01133g
复制
发表时间：
2015-04
期刊：
影响因子：
--
通讯作者：
Hui Sun;Di Wu;Xiaofeng Guo;Bin Shen;A. Navrotsky
中科院分区：
文献类型：
--
作者：
Hui Sun;Di Wu;Xiaofeng Guo;Bin Shen;A. Navrotsky
制备了一系列不同交换度的A型沸石钙交换样品。采用粉末x射线衍射（XRD）和差示扫描量热法（DSC）对其进行了表征。高温氧化物熔滴溶液量热法测定了组分氧化物水合沸石CaNa-A的生成焓。水含量与Na-A交换度成线性关系，Na-A交换度为20.54%，can - a交换度为97.9%，水含量为23.77%。水合Na-A沸石在25℃时的生成焓为-74.50±1.21 kJ mol(-1) TO2, 97.9% ca - a沸石的生成焓为-30.79±1.64 kJ mol(-1) TO2。差示扫描量热法测定的Na-A沸石脱水焓为32.0 kJ mol(-1) H2O， 97.9% CaNa-A沸石脱水焓为20.5 kJ mol(-1) H2O。钙交换沸石A的生成焓比Na-A沸石的放热焓小。形成焓与钙取代程度呈线性关系。讨论了ca交换对沸石A的能量效应，重点讨论了沸石骨架、阳离子和水之间的复杂相互作用。
A series of calcium-exchanged zeolite A samples with different degrees of exchange were prepared. They were characterized by powder X-ray diffraction (XRD) and differential scanning calorimetry (DSC). High temperature oxide melt drop solution calorimetry measured the formation enthalpies of hydrated zeolites CaNa-A from constituent oxides. The water content is a linear function of the degree of exchange, ranging from 20.54% for Na-A to 23.77% for 97.9% CaNa-A. The enthalpies of formation (from oxides) at 25 °C are -74.50 ± 1.21 kJ mol(-1) TO2 for hydrated zeolite Na-A and -30.79 ± 1.64 kJ mol(-1) TO2 for hydrated zeolite 97.9% CaNa-A. Dehydration enthalpies obtained from differential scanning calorimetry are 32.0 kJ mol(-1) H2O for hydrated zeolite Na-A and 20.5 kJ mol(-1) H2O for hydrated zeolite 97.9% CaNa-A. Enthalpies of formation of Ca-exchanged zeolites A are less exothermic than for zeolite Na-A. A linear relationship between the formation enthalpy and the extent of calcium substitution was observed. The energetic effect of Ca-exchange on zeolite A is discussed with an emphasis on the complex interactions between the zeolite framework, cations, and water.