Method for continuous hydrogenation of dinitrobenzene and recycling of reaction heat thereof

Abstract

The invention provides a method for continuous hydrogenation of dinitrobenzene and recycling of reaction heat thereof. The method comprises the following steps: (1) adopting a plurality of stages of hydrogenation reaction kettles which are connected in series, continuously leading the materials dinitrobenzene and methanol to a first stage of a hydrogenation reaction kettle, and simultaneously leading in hydrogen continuously and adding a catalyst, carrying out a liquid-phase catalytic hydrogenation reaction, and continuously feeding the material from the final stage of hydrogenation reaction kettle to a mature kettle to cure and cool; meanwhile, removing hydrogenation reaction heat by water, so as to obtain hot water of 105-120 DEG C; and (2) orderly carrying out continuous sedimentation, filtering and separation on hydrogenation reduction cooling fluid from the mature kettle, and then recovering and mechanically applying the separated catalyst in cycle, and carrying out dealcoholization, dehydration and rectification on the separated hydrogenation reduction fluid to obtain diaminobenzene. Thus, effective utilization of reaction heat energy is achieved on the premise of efficiently producing the diaminobenzene; the aim of saving energy is achieved.

Description

(1) Technical field [0001] The present invention relates to a method for preparing aromatic amines by catalytic hydrogenation of aromatic nitro compounds, more specifically, a method for preparing phenylenediamine by continuous liquid-phase catalytic hydrogenation of dinitrobenzene and recycling heat of hydrogenation reaction method. (2) Background technology [0002] In the industrial application of liquid-phase catalytic hydrogenation of aromatic nitrobenzene, the optimal development of the hydrogenation process is closely related to the structural characteristics of the hydrogenation substrate, the activity and selectivity of the hydrogenation catalyst, and the production equipment such as the hydrogenation reactor. relation. The catalytic hydrogenation reaction of aromatic nitrobenzene is generally a strong exothermic reaction. In the case of severe exothermic reaction of nitro group reduction to amino group, the production efficiency of hydrogenation reaction is greatl...

AI Technical Summary

Problems solved by technology

[0003] The standard heat of formation of dinitrobenzene such as m-dinitrobenzene catalytic hydrogenation reaction reaches 1134.2kJ·mol -1 , too high a reaction temperature not only affects the activity of the catalyst, but also aggravates the occurrence of side reactions

Although the liquid-phase low-temperature hydrogenation reaction reduces the generation of by-products to a certain extent, it also has corresponding shortcomings: the low reaction temperature makes the reaction rate relatively slow; the long residence time of the reaction also increases some additional side reactions ;The hydrogenation reaction is carried out at low temperature, which will reduce the efficiency of circulating water to remove the reaction heat, which will increase the amount of circulating water used for cooling and increase energy consumption; the temperature of circulating water is low, and there is no recycling value

However, the intermittent hydrogenation operation needs to continuously repeat the steps of feeding, heating, and cooling, which leads to cumbersome equipment operation and cannot effectively solve the problems of mass transfer and heat transfer in liquid-phase hydrogenation. Therefore, the heat exchange of the coils in the reactor cannot be completely Satisfying the heat exchange requirements of dinitrobenzene hydrogenation can easily lead to partial overheating of the hydrogenation reactor, uneven mass transfer and heat transfer of the reaction materials, and large mass transfer resistance in the reactor, which affects product quality and catalyst activity, resulting in low production capacity , the catalyst life is short, and the batch process is not conducive to the recovery and utilization of hydrogenation reaction heat

Images