One-step Catalytic Amination Of Naphthalene To Naphthylamine

Polycyclic aromatic amines（PAAs）is a kind of very important organic substances,which have great economic value and great demand in industrial application.Among them,naphthylamine is very important fine chemical materials which have widely applications such as synthesis of dyes,analytical reagents,fluorescence indication,and polyurethane.Especially,1,5-diaminonaphthalene has the highest value for producing1,5-naphthalene diisocyanate（NDI）,which is an important precursor in the synthesis of superior polyurethane.NDI polyurethane exhibits excellent physical properties due to the symmetry,regularity and rigidity of NDI molecules,and it can be applied in high temperature,high grease and high mechanical wear occasion condition in the area of automotive,textile,machinery,petroleum,military,and printing.Nitration of aromatic compounds and the subsequent reduction of the obtained nitro-compounds are the traditional processes for aromatic amines production.However,these processes suffer from high energy consumption and low efficiency due to multi-step reactions and separation,and unfriendly environmental issues result from the nitration and reduction.It is not in line with the idea of green chemistry for the development of sustainable chemical industry.Thus,one-step amination of aromatic compounds to synthesize arylamine by directly introduction of amino groups into aromatic rings could simplify the process,improve atom utilization and reduce environmental pollution.First of all,the amination performance of several catalysts with vanadium as active center was tried in homogeneous system and finally Na VO₃ was selected as the homogeneous catalyst.The effects of the amount of Na VO₃,reaction temperature,reaction time,and material ratio on the reaction were investigated.Finally under the optimized condition:Na VO₃:0.5g;naphthalene:0.1g;HOAC:15ml;H₂O:5ml;and yield of naphthylamine can reach 28.92%.（1,5-diaminonaphthalene:18.0%,1-naphthylamine:9.6%）.Then the supported vanadium catalyst for one-step amination of naphthalene was studied.The effects of different supported catalysts,different Si/Al ratio of HZSM-5,different vanadium loading and different feeding methods on the amination reaction were investigated.It was found that the V₂O₅/HZSM-5 catalyst with 3%vanadium content and Si/Al ratio of HZSM-5=50 had the highest activity by batch feeding method.The conversion of naphthalene is 75.63%and the yield of naphthylamine was69.18%（1,5-diaminonaphthalene:52.31%,1-naphthylamine:11.62%）.Combining with the characterization results and catalytic performances indicate that synergic effect of the Br?nsted acid sites and the polymerized V-O-V and V=O bonds of the monovanadate on V₂O₅/HZSM-5 catalyst could facilitate the naphthalene activation and the formation of NH₃⁺,which help to enhance the yield of naphthylamine.Finally protonated amino radical ion（-NH₃⁺）which act as active aminating species was detected by investigation of real-time IR and in situ DRIFT.Combining with the results of amination a possible reaction path and reaction mechanism was also proposed for reaction.