Study On The Catalysts For Synthesis Of Halogenated Anilines With Halonitrobenzene As Raw Material

Halogenated aniline is an important intermediate of synthetic dyes,pharmaceuticals,pesticides and the like,which is used as a raw material to synthesize anti-infective ciprofloxacin,pesticide bactericide amide azole,herbicide?PUMA?and dye.Currently,there are many production methods of halogenated aniline,such as:iron reduction,alkali reduction,metal hydride reduction,electrolytic reduction,hydrogenation reduction and so on.Among them,such methods like the iron powder reduction and the alkali sulfide reduction method is gradually eliminated,because those have many disadvantages in the preparation process,and the most important ones are serious pollution to the environment and great energy consumption;the used in metal hydride reduction is reducing duo to the expensive and difficult to implement.The energy consumption is too high of electrolytic reduction.Compared with these methods,the catalytic hydrogenation method has attracted much attention for its low pollution,low energy consumption and low cost.Therefore,this paper uses liquid-phase catalytic hydrogenation method to produce 2,4-dichloroaniline with higher selectivity,the main contents are as follows:?1?In this paper,the catalysts of supported precious metals?four single metal catalysts supported on activated carbon:1%Pt/C?3%Pt/C?2%Ru/C?5%Rh/C bimetallic catalysts supported on activated carbon:Pt-Pd/C,Pt-Ru/C;three monometallic catalysts supported on Al₂O₃:1%Pt/Al₂O₃,5%Ru/Al₂O₃,5%Rh/Al₂O₃?were screened.The influence of different noble metals and supported catalysts on the catalytic performance of hydrogenation reaction was investigated.?2?In this paper,the skeleton type Raney nickel catalyst was screened?seven commercially available Raney nickel catalysts were selected according to the particle size and catalytic activity:20-40?m,50?m,150?m,Mc 700,Mc 813,Rc-S-4751-15-3 and Rc-S-4751-18-3.There are also two kinds of redesigned Raney nickel catalysts:T-1 and W-2.?.?3?Studying the reaction conditions of the generation of 2,4-dichloroaniline by liquid-phase catalytic hydrogenation of a skeleton-type Raney nickel.The effects of different catalyst dosages,hydrogenation reaction temperature,hydrogen pressure,stirring speed and reaction time on the hydrogenation reaction were investigated.The optimum conditions for hydrogenation in a 2 L batch autoclave were determined:100 g of raw material,the composition of the mixed solution is 400 g toluene and 50 ganhydrous methanol,the Raney-Ni catalyst is15 g with a particle size of 150?m,reaction temperature 92°C,hydrogen pressure 0.7 Mpa,stirring speed 667r/min.Under the best reaction conditions,the conversion of2,4-dichloronitrobenzene with substituents reached 99.89%,and the corresponding selectivity to2,4-dichloronitroaniline reached 94.80%.?4?Catalytic hydrogenation of 2,4-dichloronitrobenzene with a substituent on the framework-type Mc 813 Raney nickel catalyst was used to prepare the corresponding2,4-dichloroaniline as a probe reaction.The effects of different dehalogenation inhibitors?chemical additives?on the hydrogenation reaction were investigated.