摘要
采用ＣＯ２－ＴＰＤ及Ｈａｍｍｅｔ指示剂法测定了ＫＮＯ３／Ａｌ２Ｏ３及Ｋ２ＣＯ３／Ａｌ２Ｏ３样品的碱量和碱强度。当ＫＮＯ３、Ｋ２ＣＯ３的负载量低于其单层分散阈值时，能在Ａｌ２Ｏ３上均匀分布并产生强度（Ｈ－）为１８．４的强碱位；高于其单层分散阈值后则能生成强度（Ｈ－）为２７．０的超强碱位。
Dispersions of KNO_3 or K_2CO_3 loaded on Al_2O_3 was examined by means of XRD and XPS,while the basic properties of these unusually strong solid bases,derived from the Al_2O_3 supported KNO_3 or K_2CO_3,were evaluated by use of CO_2-TPD,titration and the isomerization of butene at 0℃. If the amount of KNO_3 or K_2CO_3 loaded is below its monolayer dispersion threshold on Al_2O_3,all of them can be well disersed and consequently a basic strength(H-) of 18.4 is produced.When the amount loaded is above the threshold,however,a lot of KNO_3 seems to locate in the pore of Al_2O_3 and a new phase such as K_2 Al(NO_3)_5 is formed.Evacuation at 600℃caused not only the decomposition of residual KNO_3 and K_2 Al(NO_3)_5 ,but also the migration of potassium species from the inner to the external surface of Al_2O_3.As a result,sever layers of basic species such as K_2O may overlap on the Al_2O_3,because the KNO_3 dispersed and decomposed has exceeded the monolayer threshold.It is important to find that some superbasic sites iwth a basic strength(H-)of 27.0 are formed on both 20%K_2CO_3/Al_2O_3 and 29%KNO_3/Al_2O_3 smples.Based on the advantages in preparation and storage,these new unusual strong solid bases are expected to be used as the nwe basic catalysts in industrial.
基金
国家教委留学回国人员科研资助
南京大学分别中心测试基金
关键词
固体
超强碱
催化剂
硝酸钾
碳酸钾
氧化铝
Solid superbase\ KNO_3/Al_2O_3\ K_2CO_3/Al_2O_3\ Characterization of basicity
