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Two step preparation of dinitrotoluene method

A technology for dinitrotoluene and nitrotoluene, applied in the field of two-step preparation of dinitrotoluene, can solve the problems of high energy consumption, inability to prepare DNT, high cost and the like

Inactive Publication Date: 2004-08-25
COVESTRO DEUTSCHLAND AG
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, the method has the following disadvantages: the water taken up by the acid phase formed in the two steps (essentially sulfuric acid) and the high energy consumption
[0006] All of these methods are either cost-prohibitive from a technical or energy point of view, or they do not allow the preparation of DNTs with very few MNTs
Moreover, the problem of DNT or media containing mostly DNT being subjected to high temperature stress remains

Method used

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  • Two step preparation of dinitrotoluene method
  • Two step preparation of dinitrotoluene method
  • Two step preparation of dinitrotoluene method

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0047] use figure 1 device shown. The temperature and composition of the streams are shown in Table 1.

[0048] In the first step of the adiabatic operation, 50.6 kg / h of toluene (stream 1), 63.0 kg / h of 68% by weight nitric acid (stream 2) and 1066.6 kg / h of 76.8% by weight were thoroughly mixed at the inlet of reactor A The spent concentrated acid (stream 3). The dimensions of reactor A are as follows: length (L) = 5 m, diameter (D) = 25 / 80 mm. In a tubular reactor equipped with perforated discs for redispersion, the temperature was raised to 131°C. With an average residence time of 15 minutes, the reaction mixture (stream 4) was separated in phase separator B into 78.1 kg / h organic phase (stream 5) and 1102.1 kg / h acidic aqueous phase (stream 6). The 74.5% by weight of spent acid was concentrated to 76.8% by weight of sulfuric acid in a flash evaporator C operated at 40 mbar. To this end, a small amount of secondary heat is supplied via a heat exchanger at the bottom o...

Embodiment 2

[0053] use figure 2 device shown. The temperature and composition of the streams are shown in Table 2.

[0054] In the first step of the adiabatic operation, 50.6 kg / h of toluene (stream 21), 62.9 kg / h of 68% by weight nitric acid (stream 22) and 736.0 kg / h of 78.6% by weight were thoroughly mixed at the inlet of reactor A of concentrated spent acid (stream 23). The dimensions of reactor A are as follows: length (L) = 8 m, diameter (D) = 80 mm. In a tubular reactor equipped with perforated discs for redispersion, the temperature was raised to 138°C. The reaction mixture (stream 24) is depressurized through nozzles into flasher C operated at 40 mbar, where part of the water and organic components are evaporated. The vapor is then condensed in heat exchanger D. No deposits were formed in the vapor condenser D despite cooling with cold water at 18°C. In phase separator B2, the vapor condensate (stream 29) is separated into an aqueous phase (21.3 kg / h, stream 30) and an org...

Embodiment 3

[0059] use image 3 device shown. The temperature and composition of the streams are shown in Table 3.

[0060] In the first step of the adiabatic operation, 50.6 kg / h of toluene (stream 21), 63.0 kg / h of 68% by weight nitric acid (stream 22) and 1306.6 kg / h of 82.4% by weight were thoroughly mixed at the inlet of reactor A of concentrated spent acid (stream 23). The dimensions of reactor A are as follows: length (L) = 5 m, diameter (D) = 80 mm. In a tubular reactor equipped with perforated discs for redispersion, the temperature was raised to 132°C. The reaction mixture (stream 24) is depressurized through nozzles into flasher C operated at 40 mbar, where part of the water and organic components are evaporated. The vapor is then condensed in heat exchanger D. No deposits were formed in the vapor condenser D despite cooling with cold water at 18°C. In phase separator B2, the vapor condensate (stream 29) is separated into an aqueous phase (18.3 kg / h, stream 30) and an org...

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Abstract

Two-stage nitration of toluene to produce dinitrotoluene involves a first adiabatic stage and a second isothermal stage. Two-stage nitration of toluene to produce dinitrotoluene comprises (1) adiabatically reacting toluene with nitrating acid such that the toluene is at least 90 % reacted and a maximum of 50 % is reacted to dinitrotoluene, separating the mononitrotoluene-containing organic phase and the aqueous sulfuric acid-containing phase, concentrating the acid aqueous phase by flash evaporation and recycling the concentrated sulfuric acid to the first or second stage or to a concentration process in the second stage; and (2) isothermally completing the nitration of the mononitrotoluene-containing organic phase, separating the organic and aqueous sulfuric acid-containing phases, concentrating the acid, aqueous phase by vacuum evaporation and recycling the acid to the first or second stage.

Description

technical field [0001] The invention relates to a method for preparing dinitrotoluene (DNT) by nitrating toluene with nitrating acid in two steps, wherein the first step is carried out adiabatically, and the second step is carried out isothermally. technical background [0002] Dinitrotoluene (DNT) is a precursor of toluene diisocyanate, which is used as a raw material for the preparation of polyurethanes. The conventional industrial process for the preparation of dinitrotoluene is the isothermal two-step reaction of toluene with a nitrating acid, namely a mixture of nitric and sulfuric acids, see Ullmanns Encyklopadie der technischen Chemie, 4th edition, Vol. 17, p. 392, Verlag Chemie, Weinheim 1979. In this method, a mixture of mononitrotoluene (MNT) isomers is first formed and then converted to dinitrotoluene in a separate second step. However, said method suffers from the disadvantages of water uptake by the acid phase formed in the two steps (essentially sulfuric acid...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C07C201/08C07C201/16C07C205/06C07C205/11
CPCC07C201/08C07C201/16C07C205/06E02D3/103
Inventor E·迪特里奇A·西尔舍B·科根霍夫M·凯勒-基里沃德J·穆尼格D·瓦斯迪安
Owner COVESTRO DEUTSCHLAND AG
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