| Summary: | 碩士 === 淡江大學 === 化學工程學系 === 88 === The methods of precipitation and sol-gel were used to prepare catalysts of SiO2, TiO2 and SiO2-TiO2. The physical properties of catalyst were analyzed by using SEM、FTIR、XRD、EDS、density test and acid test. The catalytic activity of catalysts were tested in the heterogeneous dehydration process of ethanolamine to synthesize ethylenimine. The results were compared to commercial catalysts of SiO2 and Al2O3.
Experimental results showed that the conversion of ethanolamine increased and the selectivity of EI decreased with increasing reaction temperature. Relatively strong acid catalysts such as Al2O3, TiO2, SiO2-TiO2 enhanced the conversion of ethanolamine, but the reaction products were mainly piperazine and pyrazine. Weak acid catalysts such as SiO2 showed higher selectivity of ethylenimine. By addition the metal ions of Li+1, K+1 and Cs+1 to catalysts acidity the effects on the catalytic acidity were examined. The acidity effect is significant and the selectivity of EI for different kinds of cations increased in the order Li+1＜K+1＜Cs+1.Coating a little amount of BaO to SiO2 would lower the acidity of SiO2 catalyst. The catalyst with ratio of Ba/Si 0.08 provided extremely stable catalytic activity in continous flow reaction.
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