Study On Supported PMoA Catalyst For Preparation Of NMSBA By Oxidation Of NMST

NMSBA is an important chemical intermediate for the preparation of herbicide methoxon.NMSBA prepared from oxidation of NMST with nitric acid in industry,but there were many problems,such as serious corrosion and pollution.In order to improve the Co/Mn/Br and PMoA/AC heterogeneous catalyst system,we attempted to prepare catalysis PMoA/AC by competitive adsorption and modified activated carbon by H2C2O4.Firstly,the adsorption behavior of activated carbon on NMST was explored.The effect of activated carbon dose,the initial concentration of NMST and temperature on the adsorption performance of activated carbon were investigated.It was found that the pseudo-second kinetic equation could describe the adsorption process well;the adsorption capacity of activated carbon to NMST reached 252.52 mg/g;the adsorption activation energy was 8.505 kJ/mol,which suggested that adsorption process was mainly physical adsorption;the value of negative AG,indicating that adsorption process proceeded spontaneously.Next,PMoA/AC catalyst was prepared by impregnation using acidic solvent as competitive adsorbent of PMoA.The catalysts were characterized by NH3-TPD and TEM.It was known that H3PO4 was not conducive to the improvement of catalyst performance;the addition of competitive adsorbents H2SO4,HCl,HNO3,CH3COOH and H2C2O4 were beneficial to the dispersion of active components and the improvement of surface acid strength.The optimum concentration of H2SO4,HCl,HNO3,CH3COOH and H2C2O4 was 0.4 mol/L,0.3 mol/L,0.3 mol/L,1.0 mol/L and 0.3 mol/L respectively.The concentration of NMSBA improved 6.97%,7.93%,6.06%,5.17%and 7.51%respectively,compared with the catalyst prepared without acid addition.Finally,this experiment determined the effect of oxalic acid modified activated carbon on the performance of the catalyst.The optimum modification conditions were as follows:oxalic acid impregnation concentration:0.2 mol/L,impregnation time:16 h,activation temperature:450?,activation time:3 h.Activated carbon and catalyst were characterized by FT-IR,XPS,Boehm titration,N2-adsorption desorption.Under the optimal conditions,the total acidic group of modified activated carbon increased by 198.5%,the total specific surface area of the catalyst increased by 5.18%,the NMSBA concentration improved 5.47%and the adsorption capacity of activated carbon to NMST increased by 26.34%.