The Study Of Ni-based Bimetallic Catalysts In Catalytic Amination Of Diethylene Glycol With Tertiarybutylamine

Tertiarybutylaminoethoxyethanol?TBEE?is a severely sterically secondary aminoether alcohol,and TBEE as a selective desulfurization solvent is useful in acid gas scrubbing processes,particularly in the selective removal of H₂S from the natural gas containing CO₂ and H₂S.Desulfurization of natural gas is an important precondition for the wide use of natural gas.The status of desulfurization solvents is extremely important.Compared with other desulfurization solvents,TBEE owns significant advantages and high-efficiency desulfurization effect and which has been proven in industrial applications.Absolutely,TBEE is an industrial product with broad application prospects.A way by utilizing the amination of diethylene glycol?DEG?with tertiarybutylamine?TBA?to produce TBEE has been adopted and proved to be energy-saving and environment protection.Thus far,for the amination of diethylene glycol with tertiarybutylamine,how to design and prepare an efficient catalyst was still crucial issues.In the previous work,Ni shows a good activity to the amination of diethylene glycol?DEG?with tertiarybutylamine?TBA?.Nevertheless,high-Ni loaded catalysts may result in the aggregation of Ni particles and low Ni dispersion during the reduction process,which can be negative effects for the reaction over Ni-based catalysts.As reported,introduction of a second metal to form bimetallic catalysts with Ni is also effective to improve catalytic activities by tailoring their electronic and geometric structures.In this thesis,we focus on the design and preparation of metal catalysts with better performance by using Ni as the main active component and other metal was used as additives.Combined with a series of characterizations,the composition,structure of the catalysts and promotional influence of additives were investigated.The detailed contents and conclusions of this paper are as follows:1.In order to improve the catalytic properties of the monometallic Ni/Al₂O₃catalyst,a series of Ni-M/Al₂O₃ bimetallic catalysts were prepared by the co-impregnation method.In an autoclave reactor,the influence of Fe,Co,Cr,Cu,Ag used as promoters on the activity of Ni/Al₂O₃ catalyst was investigated in the amination of diethylene glycol with tertiarybutylamine.The results show that Co as the additive significantly inhibits the activity of the Ni/Al₂O₃ catalyst.Moreover,Fe,Cr,Cu,Ag were used as additives that all have a promotional effect on Ni/Al₂O₃ to varying degrees.The promotional effect of Cr is little,and Fe as a promoter can increase the DEG conversion,but the selectivity to TBEE is poor,which causes more side reactions to occur.The catalytic activity of the Ni-based bimetallic catalyst modified by Ag is significantly improved.However,the cost of preparation is higher.2.A series of 20%Ni-x%Cu/Al₂O₃ bimetallic catalysts with different Cu content were prepared by the co-impregnation method,the effect of Cu on the catalyst activity was investigated.Among them,the 20%Ni-10%Cu/Al₂O₃ catalyst shows the highest activity for the amination of DEG with TBA.Characterization results show that Ni-Cu alloy is formed in the reduced catalyst.The formation of Ni-Cu alloy can improve the dispersion of Ni species and reduce the overall size of metal particles.In addition,Cu can reduce the reduction temperature of NiO and facilitate the reduction of NiO species.Compared with the monometallic Ni/Al₂O₃catalyst,the formation of Ni-Cu alloy is the key factor for the higher catalytic activity of Ni-Cu/Al₂O₃ catalyst.We confirmed that the Ni-Cu alloy sites were one of the main active centers of the bimetallic catalysts.3.The 20%Ni-10%Cu/Al₂O₃ catalyst with the best catalytic performance was used as the representative catalyst.We investigated the influence of the catalyst treatment processes such as calcined temperature,reduction temperature and metal impregnation sequence on catalytic properties.The reaction temperature was also optimized.Bimetallic catalysts prepared by co-impregnation of Ni and Cu have the best activity.The calcination temperature of the catalyst has an effect on the interaction between the metal oxide and support,while the reduction temperature of the catalyst will affect the metal particles dispersion and ensemble size of metal particles.When the reaction temperature was 230?,the 20%Ni-10%Cu/Al₂O₃catalyst was calcined at 500?for 4 h and reduced at 500?for 2 h,which showed the best catalytic performance,the conversion of DEG was 83.0%,the selectivity to TBEE was 76.4%.