Study On Preparation Of M-toluidine From M-nitrotoluene By Catalytic Hydrogenation In Liqiud Phase

The m-toluidine was synthesized by catalytic hydrogenation fromm-nitrotoluene and then m-cresol and N-ethyl-m-toluidine were prepared fromm-toluidine.Three different catalysts were used in the process of catalytic hydrogenation. Ithas been found that the Raney Ni catalyst which was prepared on the condition thatm(NaOH):m(Al-Ni)=1.7 has the best performance. Under the Condition thatm(catalyst): m(m-nitrotoluene)=0.6:10, methanol as solvent, reaction time was lh,reaction pressure was 1MPa, reaction temperature was 80℃, the conversion ofm-nitrolotuene reached 100%. Ni-B amorphous alloy catalyst which was prepared onthe condition that BH₄^-/Ni²⁺=2 hasthe best performance. Under the condition thatm(catalyst): m(m-nitrotoluene)=3:10, anhydrous ethanol as solvent, reaction timewas 1h, reaction pressure was 1MPa, reaction temperature was 100℃, theconversion of m-nitrolotuene reached 100%. And the Ni-B amorphous alloy wascharacterized by XRD and TEM. The urushibara nickel catalyst which was preparedon the condition that m(Zn):m(NiCl₂·6H₂O)=3:2 and acetic acid as thedevelopingagent has the best performance. Under the condition that re(catalyst):m(m-nitrotoluene)=5:3,methanol as solvent, reaction time was 1.5h and hydrogenvelocity was about 15 mL/min,the conversion of m-nitrolotuene reached 100%.Fresh catalyst's performance just declined after a week's time and the catalyst wasnot obviously deactivated after being used for 10 cycles.It has been found that the three catalysts were superior in catalytichydrogenation, but they have the different trait. Raney Ni was needed less at a timebut it tend to self-ignite; Ni-B amorphous alloy was more stability in air, but thereaction condition was severer than Raney Ni. Reaction in abnormal was the mostnotable advantage of urushibara nickel, and the reaction time was moderate. Theonly fault was that the urushibara nickel required much at a time.The m-cresol was synthesized from m-toluidine by diazotization and hydrolysiswith distillation. The better reaction condition is acquired by the single factoranalysis and orthogonal. Under the reaction condition thatω(H₂SO₄)=25%,ω(NaNO₂)=30%,and reaction time was 35 minutes, the dropwiserate of NaNO₂ in diazotization was 2mL/min,the dropwise rate of diazo salt inhydrolysis was 9mL/min,and the concentration of Sulfuric Acid when hydrolyzingwas 4mol/L,the yield of m-cresol is over 82.5% and the pureness is higher than 99.7%.The N-ethyl-m-toluidine was synthesized from m-toluidine under normalpressure, and used the bromethane as alkyl agent. Effects of proportion of reactant,reaction time and reaction temperature on selectivity of N-ethyl-m-toluidine andconversion of m-nitrotoluene were investigated. Under the optimum reactioncondition that n(m-toluidine):n(bromethane)=3:1, reaction time was 8h and reactiontemperature was 50℃, the conversion of m-nitrotoluene was 80.6% and theselectivity of N-ethyl-m-toluidine reached 84.2%. the pureness is higher than 99.6%.