|
Oxidation of nitro-p-toluene-sulfonic acid (NTS), prepared by condensation of 4,4 '- dinitro - stilbene -2,2' - disulfonic acid (DNS) is a key step in the production process of the DSD acid, due to the reaction of this step side reactions, wastewater volume, low yield, and prone to the phenomenon of red material, so the traditional batch production process has been unable to meet the needs of the development of the situation. Therefore, this subject from the aspects affect the reaction because of cable, the synthesis process, the catalyst reactor forms its research. First, the use of test equipment system, intermittent operation, using high-performance liquid chromatography to track the reaction, and to explore the influence of different process conditions on the reaction. It was found that, NTS oxidation condensation reaction is conducted in two stages, in the intermediate product 4,4 '- dinitro diphenyl ethane -2,2' - disulfonic acid (DND) stage, NTS concentration and the alkali concentration of the reaction the effects are more significant, DND DNS stage is generated, the influence of temperature on the reaction was more significant in the intermediate product; main byproduct of 4 - nitrobenzaldehyde -2 sulfonic acid (NBS) and 4 - nitrobenzoic acid -2 sulfonic acid (NSB) NTS by direct oxidation off key generation occurs, but also by the DNS deep oxidation; phenomenon of the red material is in the high concentration of material and compared with the high temperature conditions, a large number of the NTS, DND rapid accumulation of material viscosity rapidly increases, resulting in the gas dispersing dispersed unevenly, the partial amount of oxygen is insufficient, and a sharp reduction of the effect of the mass transfer, so that the system air local hypoxia caused NTS initiate the polymerization reaction, the main cause the occurrence of the red material. After the occurrence of the phenomenon of red material, the material viscosity is further increased, the air to disperse more uneven, resulting in increased red material phenomenon and byproducts NSB increased dramatically. Secondly, in the proven to affect the condensation reaction of the NTS oxidation process conditions, the use of four autoclaves in series a continuous oxidation process may be synthesized DNS, and the design of the stepped control of process conditions, method for the control of the reaction process. The study found that reasonable control of the temperature, the system of base value by the concentration of the feed, the reaction, it is better able to complete the sub-NTS oxidative condensation reaction conversion. Have a greater impact of the raw material the NTS feed concentration of the oxidation reaction, the concentration of the feed is too high lead NTS direct oxidation of NBS, intensified NSB side reactions, the feed concentration of 20%, the oxidation reaction and the preparation of the product the best results, and reduced by 38.3% compared to traditional batch process, oxidation wastewater, liquid caustic soda consumption is reduced by 48.25%, equipment capacity increased by 79.5%, the production process is more stable. Third, on the basis of four autoclaves in series, and designed two autoclaves in series continuous and single reactor a continuous semi-continuous oxidation process, the generation amount of the single reactor continuously byproducts to be significantly higher than two autoclave continuously, and with the feed concentration increased increased, the generation amount of its DNS is less affected by the concentration of the feed. For two autoclave continuously, the generation amount of the DNS with the feed concentration increases first decreased and then increased and then decreased, the feed concentration was 20%, which generates the largest amount, and the amount of byproducts in the feed concentration for 19% the smallest, is higher than 20%, the percentage content starts to increase. Two kettle continuous to be significantly better than single kettle continuous. Finally, the the NTS oxidative condensation reaction catalyst. The contrast found, before lowering the alkali, the rate of formation of the reaction rate of the NTS and DNS Fe2 catalyzed fastest Cu2-catalyzed slowest Mn2 catalyzed fastest DND generation rate; after descending alkali, generation rate for DNS In Mn2 catalytic fastest Ni2 catalyzed slowest. The total amount of byproducts, The Cu2 catalyzed generation rate is the fastest, the maximum generation amount of Mn2 catalyzed formation rate is slowest at least generation amount gradually increases with increasing atomic number, the amount of byproducts, with The smaller atomic radius increases the amount of byproducts. The composite catalyst does not significantly improve response effect. Airlift loop reactor, gas-liquid two-phase flow simulation, flat-bottomed reactor gas distribution is better significantly better than the bottom of the oval.
|