Research On Reaction Process Of One-step Amination Of Naphthalene And Hydroxylamine(Salt) To Naphthylamine

1,5-Diaminonaphthalene（NDA）is an important fine chemical intermediate,which can be used to produce 1,5-naphthalene diisocyanate（NDI）and further produce advanced polyurethane.Due to its special rigid naphthalene ring structure,NDI-type polyurethane has excellent elastic properties,wear resistance and compression resistance,and is widely used in heavy-duty,buffering and other industrial fields.The traditional production process of 1,5-diaminonaphthalene was mainly nitration reduction method.The nitration stage was carried out in a nitric acid mixed acid system,and the reduction stage relied on precious metal catalysts.The process does not conform to the concept of green chemistry.The direct introduction of amino groups into the naphthalene ring to synthesize 1,5-diaminonaphthalene in one step can effectively improve the atomic utilization rate of the reaction,and solve many environmental unfriendly problems existing in the traditional process from the source.In this paper,the direct amination of naphthalene to 1,5-diaminonaphthalene was studied under two different catalytic systems,homogeneous and heterogeneous,using naphthalene as the reaction substrate,hydroxylamine salt as the aminating agent,and aqueous acetic acid as the solvent.Thermodynamic analysis of the following three amination reaction systems was carried out,including amination of naphthalene and hydroxylamine to 1-naphthylamine,further amination of 1-naphthylamine and hydroxylamine to 1,5-diaminonaphthalene,and direct amination of naphthalene and hydroxylamine to 1,5-diaminonaphthalene.The calculation results show that in the investigated temperature range（293.15 K～393.15 K）,the three reaction systems are all exothermic reactions,and the changes of Gibbs free energy are all less than zero,so all three reactions can proceed spontaneously.Among them,the change of Gibbs free energy of naphthalene and hydroxylamine salt to synthesize 1,5-diaminonaphthalene by direct amination is much smaller than that of the former two,and the driving force of the reaction process is the largest.The catalytic activity of several transition metal compounds as homogeneous catalysts for one-step amination of naphthalene with hydroxylamine salt was investigated.Fe SO₄·7H₂O was selected as catalyst and hydroxylamine hydrochloride as aminating agent,and we optimized the amination reaction conditions.The most suitable reaction conditions under this system were:1.5 g catalyst,the molar ratio of naphthalene and hydroxylamine hydrochloride was 1:15,the volume ratio of HOAc and H₂O was 3:1,the total volume was20 m L,and the reaction temperature was 80℃,the reaction time was 4 h,and the yield of1,5-diaminonaphthalene was 16.41%under this condition.A series of heterogeneous Mo O₃ catalysts with different loadings were prepared with molybdenum as the active component,and their catalytic activity for amination was investigated.When 35%Mo O₃/Si O₂ was used as catalyst,the amination of naphthalene can be carried out at a lower temperature.The best reaction condition of this catalytic system was:0.5 g catalyst,the mol ratio of naphthalene and hydroxylamine hydrochloride is 1:10,15 m L HOAc,5 m L H₂O,the reaction temperature is 60℃,and the reaction time is 4 h,the yield of 1,5-diaminonaphthalene is 33.02%.The analysis of reaction mechanism shows that in amination,the activated amino group will preferentially bind to theαposition of naphthalene ring,and in this process,the first substituted amino group will have a positioning effect,which significantly affects the binding site of the second substituted amino group.Acid sites on catalysts played an important role in the formation and protection of amino active species.The effects of catalysts on the decomposition of hydroxylamine hydrochloride under the experimental conditions of amination reaction were preliminarily explored by designing experiments.The experimental results showed that the decomposition rate of hydroxylamine salt was an important factor affecting the amination reaction,and the appropriate decomposition rate of hydroxylamine salt was beneficial to the amination reaction.