Study On The Electrochemical Characteristic Of M-NO₂C₆H₅SO₃Na

By electrochemical methods such as cyclic voltammery,potentiostatic polarization, constant current electrolysis,m-NO₂C₆H₆SO₃Na which had good solubility in water was investigatedon its electroreduction behavior and kinetic machanism on Cuelectrode in sulfuric acid. It showed in the research thatm-NO₂C₆H₆SO₃Na was more reductive than nitrobenzene with higherpeak current, which was proved by the calculation of quantum. Theapparent active nenergy of m-NO₂C₆H₆SO₃Na on Cu electrode was 19.07kJ/mol and the diffusion coefficient D of m-NO₂C₆H₆SO₃Na was close to10^-5 cm²/s. As the temperature increased, the reduction current ofm-NO₂C₆H₆SO₃Na increased and the reduction potential became morepositive. The reduction of m-NO₂C₆H₆SO₃Na was irreversible, controlledby diffusion process. The research also showed that acidity affected thereaction a lot. When the concentration of sulfuric acid was between0.02～1 mol/L, the reduction potential had a linearship with the acidity.But when the concentration of sulfuric acid exceeded 1 mol/L, both the current and potential of the reduction had little change, which showedthat the process of protonation was too fast to join in the rate control step.Meanwhile, the different electrochemical behavior ofm-NO₂C₆H₆SO₃Na was investigated according to different medium. Inaprotic media, dimethylformamide(DMF) and tetrabutyl ammoniumperchlorate(TBAP), the reduction-oxidation reaction of ArNO₂/ArNO₂^.-was achieved and controlled by diffusion process; while at more negativepotential, ArNO₂^.- was further reduced to ArNO₂^2-. In protic media,ArNO₂ was directly reduced to ArNHOH. While in mixed media, due tothe higher solvation energy in DMF, ArNO₂H₂⁺ and ArNO₂H·had goodstability so the peak ArNO₂/ArNO₂H·existed well. Then ArNO₂H·easily got protonation and was further reduced to ArNHOH. By thecalculation of quantum, the effect of different medium to thecharacteristic of m-NO₂C₆H₆SO₃Na was known, which was also a goodexplanation to the different electrochemical behavior caused by differentmedium.In the research, m-Aminobenzenesulfonic acid andp-Aminophenol-o-sulfonic acid were produced by constant currentelectrolysis. Sn²⁺ which was recycled produced in electrochemicalreduction acted as the media to directly reduce m-NO₂C₆H₆SO₃Na. Whenthe proper quamtity of SnCl₂ reached 2%, the product yield ofm-Aminobenzenesulfonic acid could reach 90%. In order to getp-Aminophenol-o-sulfonic acid as much as possible, all the effect ofindustrial parameter were considered containing temperature, Current density, concentration of H₂SO₄ and m-NO₂C₆H₆SO₃Na. The currentefficiency reached 68% under following condition: temperature 363 K,concentration of H₂SO₄ 4.6 mol/L, current density 0.15 A/cm²,concentration of m-NO₂C₆H₆SO₃Na 113 g/L.