Preparation of DSD Acid by Catalytic Transfer Reduction Using Aqueous Formate
|Keywords||DNS DSD Sodium Reduction DADB Raney-Ni Inactivation|
4,4 ' - diamino -2, 2' - disulfonic acid ( DSD acid ) is a the bifunctional dye intermediates , widely used in detergent , textile industry, plastics , photographic and paper industry . This paper presents a pass with sodium formate catalytic reduction of 4,4 ' - dinitro -2, 2' - disulfonic acid ( DNS ) Preparation of DSD acid method . The method is characterized DNS catalytic hydrogenation at atmospheric pressure , low equipment requirements , and to overcome the labor-intensive traditional iron reduction , environmental pollution and other issues . The main research contents include: 1 , commonly used in industry Pd / C ( 5 % ) and Raney-Ni catalytic hydrogenation catalyst as the sodium formate catalytic transfer reduction DNS catalyst were investigated their usage and activity on the DNS restore the conversion rate and selectivity . The experimental results show that the Pd / C ( 5 % ) of sodium formate passed restore the catalytic activity is too high , resulting in a large number of byproducts 4,4 ' - diaminobenzidine benzyl -2,2 ' - disulfonic acid ( DADB ) generated . Using Raney-Ni catalyst passivation can effectively inhibit the generation of impurities in the benzyl group , thus also greatly improved the selectivity of the DNS . By single factor experiment and orthogonal experiment to study the impact of various factors on the DNS -reduction reaction , to determine the optimum conditions : passivation Raney-Ni catalyst , the reaction temperature was 80 ° C , the amount of catalyst 0.10 g ( 10%) of the DNS mass ratio of raw materials DNS : sodium formate = 1:8.5 ( mol ratio ) , and the reaction pH value of 5.1 , the use of positive dropwise slow dropwise addition, the raw material liquid . Under these conditions , the DSD acid yield reached more than 96% for the industrial production of new methods and experimental evidence . 3, the experimental verification of the passivation treatment of the Raney-Ni although there is good selectivity , but the repeated use of the performance is not satisfactory , the paper analyzes the Raney-Ni catalyst deactivation was mainly due to a reduction in the number of surface active center . 4 , the preliminary design of a sodium formate Catalytic transfer reduction DNS preparation DSD acid process wastewater treatment process , i.e. by evaporation, sulfuric acid , distillation and other operations to achieve the reuse of formic acid, acetic acid , reducing the production cost for wastewater treatment subsequent experiments a theoretical basis .