Method for preparing DCB reduzate through continuous catalytic hydrogenation reduction

Abstract

The invention provides a method for preparing a DCB reduzate through continuous catalytic hydrogenation reduction. The method comprises the following steps: adding o-nitrochlorobenzene, toluene, caustic soda liquid with a concentration of 30%, desalted water and a Pt / C catalyst into three continuous tank reactors connected in series, and ending a first-stage intermittent reaction until all reactions do not absorb hydrogen; opening overflow discharge valves of the three tank reactors, and simultaneously pumping o-nitrochlorobenzene, methylbenzene, caustic soda liquid with the concentration of 30% and desalted water into the first tank reactor in proportion by using a metering pump; and continuously introducing hydrogen for catalytic hydrogenation to prepare the DCB reduzat, namely, 2,2-dichlorohydrazobenzene. According to the invention, the loss of the catalyst due to frequent filtering in a batch reaction process can be effectively reduced, internal recycling of the catalyst is achieved, and the service life of the catalyst is prolonged; meanwhile, the tank reactors are relatively small in size, reaction stability is good, product dechlorination is relatively low, selectivity is high and relatively few byproducts is produced; and in addition, exhaust emission in the continuous reaction is greatly reduced, so the environmental pollution is greatly reduced.

Description

technical field [0001] The invention relates to the field of organic chemical synthesis, in particular to a method for preparing a DCB reductant (2,2-dichlorohydroazobenzene) by continuous catalytic hydrogenation reduction. Background technique [0002] The chemical name of DCB is 3,3'-dichlorobenzidine, which is an important yellow organic pigment intermediate. Using DCB as the diazo component can synthesize C.I. Pigment Yellow 12, 13, 14, 17, 56, 63, 83 , 87, 106, 124, 127, 152, 170, 171, 172, 174, 176, 188 and orange 13, 14 and other pigment varieties. [0003] The preparation of DCB is generally based on o-nitrochlorobenzene as raw material, which is reduced under alkaline conditions. The reduction methods include catalytic hydrogenation, electrolytic reduction, chemical reduction, and chemical reduction can be divided into zinc powder method and formaldehyde method. , Sodium hydrosulfide method, hydrazine hydrate method, formic acid method, zinc powder method and hydra...

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Problems solved by technology

[0005] 1. The volume of the reactor is large, resulting in high investment in equipment;

[0006] 2. A large amount of steam will be consumed in the reaction process, and the labor intensity is relatively high;

[0007] 3. Due to the unstable reaction control, the by-products in the reaction are relatively high;

[0008] 4. There will be a large amount of toluene-containing waste gas discharged into the air during the reaction, and there will be environmental pollution problems

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