催化作用
焦炭
脱氢
尖晶石
化学
差热分析
热重分析
无机化学
傅里叶变换红外光谱
选择性
钯
核化学
有机化学
化学工程
材料科学
冶金
衍射
工程类
物理
光学
作者
Ruixia Jiang,Zaiku Xie,Chengfang Zhang,Qingling Chen
标识
DOI:10.1016/s0926-860x(03)00238-2
摘要
The Pd-La/spinel catalyst for the preparation of 2,6-diisopropylaniline (2,6-DIPA) by gas-phase amination of 2,6-diisopropylphenol (2,6-DIPP) has been studied. The catalysts before and after reaction were characterized by BET, XRD, differential thermal analysis (DTA)-thermo gravimetric analysis (TGA), FTIR, and NH3-TPD techniques. The DTA study results show two kinds of coke deposited on the metal and support of Pd-La/spinel catalyst, and they are combusted at about 242 and 324 °C, respectively. The XRD and FTIR spectra of the Pd-La/spinel catalyst show that the coke contains the aromatic and aliphatic rings, alkyl groups, polynuclear aromatic system, hydroxyl groups, and amine groups. The reason for catalyst deactivation can be expressed as follows: coke formed on palladium metals may move from metal to the interface or boundaries of metal-support and acid sites of the support where further dehydrogenation and polymerization are occurring. The H2 plays a key role in retarding coke formation, but must be in suitable amount to get relatively high selectivity. The rare earth promoter La not only promotes the activity and selectivity by retaining Pd species in the metallic state, but also decreases the formation of carbon by neutralizing the strong acid sites on the catalyst.
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