The Study On The Synthesis Of 2-Amino-4-acetamidoanisole

2-Amino-4-acetamidoanisole（AMA）is a key raw material in the dye industry and is mainly used in the synthesis of more than dozens of disperse dyes such as C.I Disperse Blue 301,C.I Disperse Blue 79:1,C.I Disperse Blue 291G and others.It is widely used because of its good dyeing solidity and dispersibility as a coupling component.The more commonly used synthesis methods are 2,4-dinitrochlorobenzene as raw material,etherification,iron powder reduction,selective acetylation to make AMA.where iron powder reduction pollution is serious,selective acetylation is difficult to control,more by-products,product yield is not high.As the market demands for high quality and green protection are becoming more and more stringent,there is an urgent need to explore more efficient,energy-saving and environmentally friendly synthetic routes to meet the market demand.In this paper,p-aminoanisole（MA）was used as raw material to synthesize AMA by three radical reactions of acetylation,nitration and catalytic hydrogenation.In the process of acetylation reaction,the influence law that the amount of acetic anhydride is much larger than the amount of acetic acid than the reaction temperature is larger than the reaction time was explored through orthogonal test,and the following optimal reaction conditions were obtained through single-factor experiment:reaction temperature 75℃,reaction time 40 min,n（MA）:n（acetic acid）:n（acetic anhydride）=1:1.4:1,under this condition the conversion of MA was 100%,and PMA selectivity was as high as 99.6%.The mother liquor of the acetylation reaction was recycled to save the amount of acetic acid,and the mother liquor was used 10 times with good PMA selectivity.The reaction temperature was controlled during the nitration reaction by controlling the dosing rate and thus the reaction temperature.Under the conditions of n（93%H₂SO₄）:n（PMA）:n（65%HNO₃）=5:1:1.1,reaction temperature of 20±2℃,and stirring for 60 min after the addition of PMA,reaction time of 50 min,the conversion of PMA could reach 99.56%and the selectivity of 2-NMA was 98.1%.The experimental products were identified as the desired target products by IR and~1H-NMR characterization.The mechanism of the nitration reaction was analysed using DFT calculations,and the calculation of the reaction potential barrier led to the formation of 2-NMA with a low potential barrier,which was the main reaction of the nitration reaction,which was consistent with the experimental results.The home-made Ni/SiO₂ catalyst was produced by sol-gel method.The catalysts were characterised by SEM,TEM,NH₃-TPD,H₂-TPR and XRD and applied to the2-NMA hydrogenation reaction to evaluate different loading Ni/Si O₂ catalysts,and the best catalytic performance was finally determined at a loading of 30%,with a reaction time of 2 h,a reaction temperature of 100℃,m（2-NMA）:m（30%Ni/Si O₂）=25:1.25,90m L of methanol and 1.8 MPa of hydrogen pressure,the catalytic performance was determined to be optimal with 99.51%conversion of 2-NMA and 99.26%AMA selectivity.