Study On The Synthesis Of Aliphatic Amines From Aliphatic Alcohols In Two Steps

As significant chemical commodities,aliphatic amines are widely used in agrochemicals,pharmaceuticals,light industries and textile industries which occupied an important position in national economy.However,there are several disadvantages for traditional aliphatic amines synthetic processes such as high energy consumption,high pollution and lower catalyst utilization.With high-quality economic development and progress in chemical industry of China in recent years,exploitation of green processes for aliphatic amines synthesis is in ling with the new economic development concept in China.In this paper,a two-step method was investigated to convert aliphatic alcohols to aliphatic amines by using non noble metal catalysts under a mild condition.First,a catalyst Fe Zn/?-Al₂O₃ was prepared by co-precipitation method for the dehydrogenation-amination of n-amyl alcohol to give n-valeronitrile in a fixed-bed reactor.The optimal reactions were obtaine as follows:atmospheric pressure,ammonia to n-amyl alcohol ratio of 3.5:1,residence time of 13 s,reaction temperature of 390℃.Under the optimal conditions the conversion of n-amyl alcohol was 100%,and the yield of n-valeronitrile was 89.55%.The catalysis of Fe Zn/?-Al₂O₃ deteriorate after on stream for 40 h due to surface carbon deposition.The catalytic activity of the catalyst could be recovered after calcination at 550℃for several hours.Fe Zn/?-Al₂O₃ also showed good performances in other aliphatic alcohols such as n-hexanol and n-octanol.A series of nickel-based catalysts were prepared by changing the types of supports,main catalyst component,cocatalyst component,and the ratios between the components for the hydrogenation of n-valeronitrile to n-amyl amine in a fixed-bed reactor.A catalyst Ni_25.38Co_18.21/Mg O-Al₂O₃-5 with good catalytic performance was obtained.The effects of temperature,the hydrogen to n-valeronitrile molar ratio,the ammonia to n-valeronitrile molar ratio and residence time investigated,from which the optimal reaction conditions were obtained as follows:atmospheric pressure,reaction temperature of 130℃,hydrogen to n-valeronitrile molar ratio of 4:1,ammonia to n-valeronitrile molar ratio of 3:1 and residence time of 5 s.Under the optimal conditions,the conversion of n-valeronitrile reached 100%,the yield of n-amyl amine was 70.82%,and the yield of di-n-amylamine was 25.92%.The Ni_25.38Co_18.21/Mg O-Al₂O₃-5 showed good stalility,and the n-valeronitrile conversion of 100%was maintaine for a long time,meanwhile,the yields of n-amyl amine and total amines only decreased slightly.The characterization results revealed synergistic effect between Ni and Co,which promoting the conversion of n-valeronitrile to n-amyl amine.The catalyst showed great performances in surface area,porosity and active component dispersion after calcination.Besides,this catalyst was only active in the hydrogenation of aliphatic nitriles with low molecular weight to their corresponding aliphatic amines.Finally,based on the experimental data,a workshop was designed for the manufacture of n-amyl amine in 1000 tons productivity per year.