Kinetic Study On The Degradation Of 4, 4'-Dinitrostilbene-2, 2'-disulfonic Acid

The air oxidation of p-nitrotoluene-o-sulfonic acid (NTS) under aqueous alkaline conditions to prepare 4,4'-dinitrostilbene-2,2'-disulfonic acid (DNS), which is the key procedure in the synthesis of 4,4'-diaminostilbene-2,2'-disulfonic acid (DSD). DSD is a valuable intermediate of fine chemicals. By now, just know that 4,4'-dinitrostilbene-2,2'-disulfonic acid will breakdown under some conditions and little know about kinetics and mechanism of the degradation. Therefore, the objectives of this paper include: the investigation of mechanism and kinetics of the degradation and the optimization of conventional process(air flow).The small scale experiments of DNS degradation process were performed with a home-made reactor with the volume of 4L. By monitoring the reactions with HPLC, the kinetic models of the degradation of 4,4'-dinitrostilbene-2,2'-disulfonic acid under differernt air flow were established, and the reaction order, reaction constant, activation energy and frequency factors were obtained. In addition, the change rules of reaction time, temperatures, hydroxide concentration were investigated by combining the mathematical model and experimental data.Base on carefully investigating the effects of oxygen partial pressure on the degradation ratio, the possible mechanism explaining the degradation of DNS is speculated: The degradation of DNS is a disproportionation reaction under aqueous alkaline conditions as well as reversible reaction. The oxygen in the reaction system will repress the positive reaction, but promote the negative reaction.Base on analysis the effect of air flow on the reaction's rate, discover that appropriately lowering the flow of air within certain limits, will reduce energy consumption and costs.