| 초록 |
A series of catalysts, NiSO4/SiO2, for ethylene dimerization were prepared by the impregnation method using aqueous solution of nickel sulfate. Although SiO2 without NiSO4 was inactive as catalyst for ethylene dimerization, the SiO2 with NiSO4 exhibited catalytic activity even at room temperature. The catalytic activities were correlated with the acidity of catalysts measured by the ammonia chemisorption method. The addition of Al2O3 enhanced the acidity, thermal property, and catalytic activities of catalysts, due to the interaction between Al2O3 and SiO2 and due to consequent formation of Al-O-Si bond. The high catalytic activity of NiSO4/SiO2–Al2O3 was closely correlated with the increase of acidity and acid strength due to the addition of Al2O3 and NiSO4. The sample having 15-20 wt% of NiSO4 and calcined at 400-500 °C for 1.5 h exhibited maxima for catalytic activity and acidity. In view of IR results of CO adsorbed on NiSO4/SiO2–Al2O3, it is concluded that the active sites responsible for ethylene dimerization consist of a low-valent nickel, Ni+, and an acid. |
