Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C201/00—Preparation of esters of nitric or nitrous acid or of compounds containing nitro or nitroso groups bound to a carbon skeleton
  • C07C201/06—Preparation of nitro compounds
  • C07C201/08—Preparation of nitro compounds by substitution of hydrogen atoms by nitro groups
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C205/00—Compounds containing nitro groups bound to a carbon skeleton
  • C07C205/06—Compounds containing nitro groups bound to a carbon skeleton having nitro groups bound to carbon atoms of six-membered aromatic rings

Definitions

• This invention relates generally to aromatic nitration reactions and, more specifically, to a process for nitrating toluene to dinitrotoluene.
• Nitration reactions of aromatic hydrocarbons are generally conducted in mixed acid systems, such as mixed nitric and sulfuric acids.
• mixed acid systems usually involve reconcentration of the spent sulfuric acid after the nitration reaction. This reconcentration step is time consuming, energy intensive and requires the use of expensive materials of construction.
• sulfuric acid tends to result in significant nitrocreosol and cyanide by-product formation which requires expensive waste-water treatment to remove.
• 4,064,147 discloses the preparation of aromatic mononitro compounds (such as mononitrobenzene) by a liquid phase reaction with nitric acid having an acid concentration of between 70 percent and 100 percent by weight using a reaction temperature of between 0°C and 80°C.
• nitric acid concentration of between 70 and 90 percent by weight is preferred.
• the disclosure of this patent requires a ratio of nitric acid plus water to organic components of not below 3 when using 70 percent nitric acid, and not below 8 when using 100 percent nitric acid.
• Patent 3,928,395 discloses the use of concentrated nitric acid to nitrate aromatic compounds optionally in the presence of a dipolar aprotic solvent that is inert towards the nitrating agent.
• the patent requires that reaction be halted by diluting the resulting mixture with a dipolar aprotic solvent after the desired degree of nitration has been reached.
• the use of such solvents either throughout the reaction or to halt the reaction tends to cause environmental waste disposal problems and waste stream handling problems.
• dinitrotoluene is useful as an intermediate in producing TDI, new processes for the selective manufacture of this intermediate while avoiding the above mentioned problems would be highly desirable to the polyisocyanate manufacturing community.
• the present invention relates to a process for nitrating toluene to produce dinitrotluene by a liquid phase nitration reaction of anhydrous nitric acid with toluene in a reactor at a reaction temperature of between 0°C and 60°C for a reaction time of less than 15 minutes, said reaction employing a molar ratio of nitric acid plus any water to toluene of between 10:1 and 15:1, said reacion being conducted in the absence of sulfuric acid, and in the absence of any aprotic dipolar solvent during the reaction and in the absence of any aprotic dipolar solvent to halt the reaction, to produce mononitrobenzene or dinitrotoluene in a product mixture to produce said dinitrotoluene in a product mixture, followed by vacuum distillation of the product mixture.
• the nitration reaction is conducted using anhydrous nitric acid in the absence of sulfuric acid.
• anhydrous nitric acid is intended to designate nitric acid having an acid concentration of between 95 and 100 weight percent, preferably at least 98 weight percent, the remainder being water. It is desirable to minimize the amount of
• the process of the present invention utilizes a
• reaction in a single phase liquid medium and does not involve the formation of the two phase emulsions observed in conventional, mixed sulfuric/nitric acid nitration processes.
• reaction 25 can be conducted under moderate reaction conditions to provide an excellent yield of the desired mononitrobenzene or dinitrotoluene product.
• the reaction is suitably conducted at a reaction temperature not exceeding 80°C, preferably between 0°C and 60°C,
• reaction 30 more preferably between 10°C and 60°C, most preferably between 20°C and 30°C.
• the reaction is suitably conducted at atmospheric pressure, although superatmospheric pressure can be employed if desired.
• the reaction time is typically less than one-half hour, preferably less than 15 minutes, and more preferably less than 5 minutes.
• the molar ratio of nitric acid plus water to toluene employed is generally between 10:1 and 15:1, preferably between 11:1 and 12:1.
• Suitable distillation temperatures range from 30°C to 60°C.
• Suitable distillation pressures range from 50 mm of Hg to 300 mm of Hg.
• DNT separation from the distillation still bottoms can be effected by phase separation, brought about by the addition of a small quantity of water or dilute nitric acid. Washing with water and a basic solution produces a purified DNT product. These wash waters are free of the nitrocresol impurities observed in the wastewater produced in a conventional, mixed sulfuric/nitric acid DNT process.
• the aqueous nitric acid from the phase separation step can be purified by toluene extraction, the toluene phase being recycled to the reaction step and the 60-70% aqueous nitric acid phase reconcentrated, sold or used in other product manufacture.
• reaction vial was flushed with nitrogen at a rate of 20 cc/min, purging to a 100 ml glass receiving flask immersed in an ice water bath.
• To the reaction vial was fed 50 ml of 98 percent HNO_, 75.0 g, 1.13 mole of HN0 3 and 10 ml, 8.67 g, 0.094 mole
• Feed rates were 0.60 ml HNO_/min and 0.12 ml toluene/min, controlled by Sage Instrument Syringe pumps, Models 351 and 355.
• Reactor content was adjusted to 2 ml, by height adjustment of the reactor exit line in the reaction vial, for a mean reaction residence time of
• the combined toluene extract was extracted with 3 x 15 ml of 5 percent sodium hydroxide solution.
• the combined, yellow caustic extract was cooled, acidified with dilute sulfuric acid, and extracted with 3 x 10 ml of methylene chloride.
• the methylene chloride extract containing the acidic organic species from the original DNT product, was characterized by gas chromatography/mass spectrometry analysis. No mononitro- or dinitro-cresol species were detected (minimum detectability calculated at 2 ppm, based on original weight of DNT produced) .

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Publications (2)

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• 1993
  • 1993-06-01 RU RU94046238A patent/RU2106338C1/ru active
  • 1993-06-01 EP EP93914223A patent/EP0649400A1/de not_active Withdrawn
  • 1993-06-01 AU AU43963/93A patent/AU665843B2/en not_active Ceased
  • 1993-06-01 WO PCT/US1993/005081 patent/WO1993025503A1/en not_active Application Discontinuation
  • 1993-06-01 KR KR1019940704594A patent/KR950701903A/ko not_active Application Discontinuation
  • 1993-06-01 BR BR9306554A patent/BR9306554A/pt active Search and Examination
  • 1993-06-01 CA CA002138391A patent/CA2138391A1/en not_active Abandoned

Patent Citations (4)

Non-Patent Citations (1)

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