Study On Supported Ni-Re Catalyst For The Monoethanolamine Amination

Ethylene amine is the collective name for ethylenediamine(EDA),piperazine(PIP)etc,which is widely used as important refined chemicals.Reductive amination of monoethanolamine(MEA)for the synthesis of ethylene amine has gained increasing interest.The supported Ni-Re catalyst developed by the group of C1 Chemistry and Fine Chemicals(Dalian Institute of Chemical Physics,Chinese Academy of Sciences)has been applied in industrial production of MEA amination and showed excellent performance.However,the catalytic structure and mechanism are still ambiguous.In this paper,experimental and theoretical methods were used to investigate the role of Re promoter,Ni-Re catalytic mechanism,and Ni particle size effects in supported Ni-Re catalyst for MEA amination.Furthermore,we tried to explore the catalytic performance of other promoters and extend the application of Ni-Re catalyst to the hydrogenation of nitriles.The main research contents were as follows:The effects of Re promoter on the structure of Ni in Ni-Re/Al2O3 catalyst were studied.We found that Re played an important role in resisting the diffusion of Ni2+ in the bulk Al2O3,enhancing the proportion of octahedral Ni2+,and improving the reducibility and dispersion of Ni in Ni-Re/Al2O3 catalyst.The deactivation of monometallic Ni/Al2O3 catalyst was mainly caused by the sintering of Ni particles.In contrast,Ni-Re/Al2O3 catalyst showed good resistance to Ni sintering during MEA amination reaction.The structure of Re in Ni-Re/Al2O3 catalyst was investigated using a combination of experimental and theoretical(DFT)methods.Characterization and simulation results indicated that ReOx(0 ? x<4)species were decorated on the surface of Ni particles to form[ReOx-Ni]surface alloy during amination.Different valent ReOx species played different roles during MEA amination.The high valent ReOx(x>3)distributed on Ni particle surface could decrease the surface energy of Ni.Meanwhile,there was repulsive force between ReOx(x>3)species.As a result,the sintering of Ni particles was inhibited and the lifetime of Ni-Re/Al2O3 catalyst was extended.For low valent ReOx(x<3),the synergistic effect between Ni and ReOx sites could facilitate the dehydrogenation of MEA and improve the catalytic efficiency of Ni-Re/Al2O3 catalyst for MEA amination.The Ni particle size could be adjusted by changing the calcination atmospheres.Ni-Re/SiO2 calcined in flowing NO had the minimum Ni particle size(4.5 nm)and exhibited the highest yield of EDA and PIP(66.4%).The experimental results showed that Ni particle size effects had influence on the MEA amination.The Ni particle size had an impact on the surface Ni sites and electronic property.Increasing the Ni particle size could increase the proportion of terrace Ni and the surface electron density.As a result,large Ni particles were more beneficial for the amination of MEA and NH3 to form EDA in comparison with small particles.According to the study,Mn,La,and Ce promoted Ni-x/SiO2 showed high initial activity for MEA amination.Ni-Cr/SiO2 catalyst had good stability.It is feasible to reduce the costs of Ni-Re catalyst without decreasing activity by using a combination of reducing the amount of Ni-Re and dynamic atmosphere calcination.The Ni-Re/SiO2 catalyst exhibited outstanding catalytic performance for hydrogenation of 3-hydroxypropionitrile(3-HPN).The deactivation was not observed after 1300 h time on stream in the trickle bed reactor.The conversion and the yield of 3-amino-1-propanol were 100%and 90%,respectively.