Characterization and performance of Pd-La/spinel catalyst for preparation of 2,6-diisopropylaniline

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 theraml analysis (DTA)-thermo gravimetric analysis (TGA),FTIR,and NH_3-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 deg C,respectively.The XRD the 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 amino groups.The reason for catalyst deactivation can be expressed as folows: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 adn polymerization are occurring.The H_2 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.