Preparation Of Catalyst In Heterogeneous Reaction For NMST Oxidation To NMSBA And Study On The Relationship Between Its Catalytic Performance

2-Nitro-4-methylsulfanylbenzoic acid(NMSBA)is an important intermediate for the synthesis of mesotrione which is a highly effective herbicide.At present,the mixed acids method is used to oxidize NMST for preparing NMSBA.But this method has the disadvantages of corrosion equipment,environmental pollution and so on.Therefore,a new green process needs to be developed for improving the above disadvantages.Based on the Co/Mn/Br homogeneous system,a physical-chemical activation method was used to prepare activated carbon from the waste coconut shell to build a Co/Mn/Br/AC heterogeneous system for catalytic oxidation of NMST to NMSBA.Firstly,the conditions for preparing coconut shell activated carbon by physical-chemical activation were explored.The best preparation conditions were as follows:acetic acid impregnation concentration:12 mol/L,impregnation temperature:50℃,impregnation liquid-solid ratio:50 mL acetic acid solution/10 g coconut shell,impregnation time:32 h,carbonization&activation temperature:800℃,carbonization&activation time:6 h.Secondly,the concentration of each component of the Co/Mn/Br/AC catalytic system and the conditions of the liquid-phase air oxidation method were optimized.The best catalytic components were as follow:Co:165 ppm,Mn/Co(the ratio of molar):2.5/1,Br:747 ppm,AC:2.5 g/L.The optimal conditions were as follows:oxygen content:40%,gas flow rate:500 mL/min,stirring speed:200 rpm,pressure:2.0 MPa,temperature:215℃.After 100 minutes of reaction,the conversion of NMST reached 89.7%,the selectivity and the yield of NMSBA reached 97.4%and 88.5%,respectively.Finally,ZnCl2 was used to modify the coconut shell activated carbon to improve the performance of the solid catalyst.The optimal modification conditions were as follows:impregnation concentration:0.5 mol/L,impregnation time:6 h,activation temperature:700℃,activation time:5 h.The characterizations of Fourier transform infrared spectroscopy,Boehm titration and BET revealed that activated carbon modified by ZnCl2 did not introduce new functional groups,but the number of acidic groups increased significantly.In addition,the specific surface area and pore volume of activated carbon have been effectively improved.