焙烧温度对Si-Ba-Cs-P复合氧化物催化剂结构及组成和催化性能的影响

Influence of Calcination Temperature on Structure,Composition and Catalytic Performance of Si-Ba-Cs-P Complex Oxide Catalyst

Si-Ba-Cs-P复合氧化物催化的单乙醇胺分子内脱水反应极易受催化剂焙烧温度条件变化影响.催化剂采用X射线粉晶衍射（XRD）、程序升温脱附（NH3-TPD）及氮吸附等技术进行表征.在550℃焙烧处理的催化剂,虽然单乙醇胺完全转化,但产品乙烯亚胺选择性却不到10%,催化剂中的物相组成主要为CsBa2（PO3）5晶相及Cs4Ba（PO3）6晶相,孔结构主要为介孔;在700-900℃焙烧处理的催化剂,催化剂酸性及BET比表面积明显下降,催化剂中的物相组成主要为α-Cs4P2O7晶相,孔径逐渐减小,虽然单乙醇胺转化率稍有下降,但产品乙烯亚胺选择性却有很大提高.当焙烧温度为800-900℃时,可在保证单乙醇胺转化率大于80%的前提下,得到高于76%的乙烯亚胺选择性.

Monoethanolamine （MEA） intramolecular dehydration catalyzed by Si-Ba-Cs-P complex oxide catalysts is easily influenced by conditions at the time of catalyst calcination. The catalysts were characterized using X-ray powder diffraction （XRD）, fourier-transformed infrared spectroscopy （FT-IR）, and temperature-programmed desorption of ammonia （ NH3-TPD） techniques. When catalyst was ealeinated at 550 ℃, the high MEA interrnolecular dehydration activity was achieved, but ethylenimine （EI） selectivity was low. The active sites on catalyst were mainly CsBa2（ PO3 ）5 phase and CsgBa（ PO3 ）6 phase and pore size was distributed mainly between 10 nm and 75 nm . When catalyst was calcinated at 800 - 900 ℃, both high MEA intramolecular dehydration activity and high EI selectivity could be obtained. The active sites on these weak acidity catalysts were mainly α-Cs4 P2O7 phase and pore size was distributed mainly between 1.7 nm and 4 nm . There is not an obvious relationship between acid amount and MEA intramolecular dehydration activity, but EI selectivity increases with decreasing pore size. The various acidities and pore structures are influenced by phase changes of active sites at different calcination temperatures and result in different reaction activity of MEA dehydration.