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

A dinitrobenzene hydrogenation reaction technology, applied in chemical recovery, chemical instruments and methods, preparation of amino compounds, etc., can solve the problems of increased circulating water consumption, reduced reaction heat efficiency, and large mass transfer resistance, etc., to achieve reaction Improve the rate and device production efficiency, improve the selectivity and conversion rate, and ensure the effect of quality and yield

Active Publication Date: 2014-12-17
ZHEJIANG HONGSHENG CHEM IND +1
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  • Abstract
  • Description
  • Claims
  • Application Information

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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

Method used

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

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Experimental program
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Effect test

Embodiment 1

[0023] Specific steps are as follows:

[0024] After the hydrogenation kettle (built-in plate heat exchanger and self-priming stirring device) is qualified by nitrogen and hydrogen replacement, add methanol equivalent to 50% of the total volume of the reaction kettle as a base material, and add catalyst skeleton nickel (Raney nickel, made of Nickel-aluminum alloy powder with a nickel content of 40-50% is prepared by activating NaOH solution. Adding 5% of the mass of mixed dinitrobenzene.), hydrogen gas is introduced under the condition of stirring. Methanol and mixed dinitrobenzene (o-, m-, p-nitrobenzene weight percentages are 10%: 88%: 2%) are continuously fed into hydrogenation tanks at various levels to carry out liquid-phase catalytic hydrogenation reaction, wherein methanol The dosage of mixed dinitrobenzene in the primary hydrogenation tank is controlled at 2.67m 3 / h and 1.33m 3 / h, controlled to 1.8m in the secondary hydrogenation tank 3 / h and 1.2m 3 / h, in the th...

Embodiment 2

[0028] After the hydrogenation kettle is qualified by nitrogen and hydrogen replacement, respectively add methanol equivalent to 50% of the total volume of the reaction kettle as a base material, add skeleton nickel (Raney nickel, add according to 5% of the mass of mixed dinitrobenzene), and start stirring In case, hydrogen gas is introduced. Methanol and mixed dinitrobenzene (o-, m-, p-nitrobenzene weight percentages are 11%: 87.5%: 1.5%) are continuously fed into hydrogenation tanks at various levels to carry out liquid-phase catalytic hydrogenation reaction, wherein methanol The dosage of mixed dinitrobenzene in the primary hydrogenation tank is controlled to 3.33m 3 / h, 1.67m 3 / h, respectively controlled to 1.2m in the secondary hydrogenation tank 3 / h, 1.2m 3 / h, respectively controlled to 1.0m in the three-stage hydrogenation tank 3 / h, 1.0m 3 / h, the reaction temperature of the hydrogenation tank is maintained between 115 ~ 122 °C, and the pressure of the reaction...

Embodiment 3

[0032] With reference to the method described in Example 1, the difference is that the mixed dinitrobenzene in Example 1 is replaced with m-dinitrobenzene, and the carrier nickel (SiO 2 The carrier (with a nickel content of 50-65%) replaces the skeleton nickel as a catalyst to carry out continuous catalytic hydrogenation reaction. The conversion rate of dinitrobenzene in the hydrogenation process is 100%, and the product yield based on m-dinitrobenzene reaches 99.3%. After the catalyst is continuously separated, the hydrogenated material is further dealcoholized, dehydrated, and rectified to obtain a qualified m-phenylenediamine product.

[0033] Demineralized soft water is used as circulating cooling water, and the heat of hydrogenation reaction is removed by circulating flow. After heat exchange in hydrogenation tank, the outlet water temperature reaches about 105°C. The hot water from the three hydrogenation tanks is collected and converted by the hot water type lithium bro...

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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...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C07C211/51C07C209/36
CPCY02P20/584
Inventor 何旭斌陶建国朱敬鑫孟明杨日升田景峰孟福庆李建勋黄洪松
Owner ZHEJIANG HONGSHENG CHEM IND
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