Catalytic Characteristics Of Ni Supported γ-Al₂O₃ Catalysts For Naphthalene Hydrogenation To Decalin

Decalin is widely used as an important kind of solvents with two kinds of cis-and trans-isomers,which can dissolve ultra-high molecular weight polyethylene under low temperature and can be used as internal combustion engine fuel and torpedo driver with benzene and ethanol mixture.Therefore,it is necessary to develop the most economical and feasible process for the synthesis of decalin by hydrogenation of naphthalene.In this article,the catalytic activity of the Ni/γ-Al₂O₃ catalyst prepared by impregnation method for the naphthalene hydrogenation reaction was studied in a fixed bed reactor,and the physical and chemical properties of the catalysts were characterized using XRD,BET,TPR and TG-DTA.Firstly,the effect of Ni loading amount,calcination temperature and calcinations time on the catalytic characteristics were presented.The experimental results show that the catalysts reveal high activity when Ni loading was 10%（wt）,calcined at 450℃for 4h.At reaction temperature260℃²75℃,the conversion of naphthalene was close to 100%,the selectivity of decalin was 99.41%and the ratio of trans-decalin to cis-decalin was 3.18.Secondly,the effect of reaction conditions on the naphthalene hydrogenation was studied.The optimum reaction condtions were obtained with the ratio of hydrogenation to oil 300,reaction temperature260℃²90℃,reaction pressure 6MPa⁷MPa,and LHSV 1h^-11.5h^-1.Under this reaction condition,the selectivity of decalin reach to100%.The concentration of naphthalene in feed had a certain influence on the reaction.Thirtly,the effect of reaction conditions on the cis-and trans-isomer was studied.The results showed that the increase of feed rate and reaction pressure was beneficial to the formation of cis-decalin,and the improvement of the ratio of hydrogen to oil and the reaction temperature was beneficial to the formation of trans-decalin.Finally,the stability of the catalyst was investigated.The main reasons for the catalyst deactivation and the decrease of trans-decalin in the product were the sintering or loss of the active component and erosion.