Study On The Synthesis Of Adiponitrile From ε-Caprolactone In Two Steps

Adiponitrile has a wide range of applications in textile industry,engineering materials,medicine and food,mineral flotation and so on with its unique dicyano structure.The industrial manufacture of adiponitrile either involves environmental safety or has the problem of huge consumption of energy.With China’s extensive consensus on environmental protection and energy security,it is of great significance to develop green and simple processes for the synthesis of adiponitrile.In this thesis,adiponitrile was successfully synthesizedd fromε-caprolactone by two-step strategy based on the development of catalysts and investigation on reaction conditions.Firstly,a series of metal oxide catalysts were prepared by kneading and extruding method,and their catalytic performances in the catalytic aminaion ofε-caprolactone to6-hydroxycapronitrile were screened in a fixed-bed reactor,from which Ti O₂was found to be the best catalyst.The optimal reaction conditions were obtained by single-factor control experiments,which are normal pressure,reaction temperature of 270°C,molar ratio ofε-caprolactone to ammonia of 1:6,and residence time of 6 s.Under these conditions,the conversion ofε-caprolactone reach 94.89%with a 6-hydroxycapronitrile selectivity of94.08%.After the catalyst was on stream for 60 h,it was found that the conversion rate ofε-caprolactone and the yield of 6-hydroxycapronitrile began to decline.The catalyst could be regenerated by high temperature oxidation,and its catalytic performances could be recovered.Secondly,a series of bimetallic catalysts were prepared by adjusting the types of catalyst main active metals and their loadings,catalyst support types,catalyst co-metal types and their loadings,the ratio of magnesium-aluminum oxide support,magnesium-aluminum components,and catalyst activation conditions.The catalysts were evaluated in the catalytic amination of 6-hydroxycapronitrile to adiponitrile in a fixed bed reactor,and the catalyst Ni₃₀Fe₁₀/Al₂O₃-Mg O_{（0.8:1.2）}-700-2 showed the best performance in the reaction.The reaction conditions were systematically investigated,and the optimal reaction conditions were obtained,which are normal pressure,reaction temperature of300°C,molar ratios ofε-caprolactone:ammonia:hydrogen were 1:5:2,and residence time of 5 s.Under these conditions,the conversion of 6-hydroxycapronitrile reached 63.06%,and the selectivity towords adiponitrile was 51.49%.The characterization results of the catalysts revealed that the doping of iron into the nickel-based catalyst led to the formation of Ni₃Fe alloy,which improved the catalysis of the catalyst in the catalytic amination of 6-hydroxycapronitrile to adiponitrile.The variation of magnesium-aluminum molar ratio could change the acid characteristics of the catalysts,which affected the selectivity towards adiponitrile in the catalytic reaction.The particle sizes of the active components in the catalysts were strongly affected by the doping of iron in the nickel-based catalyst,the change of the molar ratio of magnesium to aluminum in the support,and the activation conditions of the catalysts.The increase in the diameters of the active components did not lead to obvious decreases in catalytic performances of the catalysts.In addition,carbon deposition took place in the catalytic process,blocking the holes of the catalysts,which led to the deactivation of the catalyst.The deactivated catalyst could be restored by high temperature oxidation.