カオリナイト層間へインターカレートした尿素の熱的挙動

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The thermal behavior of urea intercalated into kaolinite was investigated by changing the experimental conditions such as keeping temperature, keeping time, and atmosphere. The intercalation ratio is increased as with increasing the keeping time and temperature in the closed vessel. The decomposition temperature of the urea-kaolinite complex is lower than that of pure urea, which is found by TG-FTIR measurements. Some kinds of gases are generated simultaneously with the decomposition of the complex. The generated gases are NH_3, CO_2 and isocyan at around 190℃. However in the case of pure urea there are two decomposition stages at 250℃ and at 370℃. The gases generated at the first stage are NH_3 and CO_2, and that at the second stage is only isocyan. The difference between the decomposition of the urea-kaolinite complex and that of pure urea was examined by IR spectrum analysis. The asymmetric and symmetric v (NH_2) stretching frequencies at 3504 and 3389cm^<-1> correspond to NH_2 groups interacting with the oxygens located on the basal tetrahedral layer. Intercalation of urea within the kaolinite structure increases the _ν(CN) stretching frequency from 1468cm^<-1> for the urea to 1477cm^<-1> for intercalated molecules. The _ν(CO) stretching frequency in the urea-kaolinite complex does not appear in the present experiment. The shift of the 1609cm^<-1> absorption to 159lcm^<-1> shows the interaction between the innersur-face OH and the amino groups through weak hydrogen bonding OH…NH_2. These results indicate that the hydrogen bonding of urea molecules intercalated into the interlayer site of kaolinite is weak as compared with the hydrogen bonding of pure urea molecules. Therefore the decomposition temperature of urea in the urea-kaolinite complex seems to be lower than that of pure urea.
日本粘土学会の論文
1995-03-28

カオリナイト層間へインターカレートした尿素の熱的挙動

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