WO1990012781A1 - Process for the production of dinitrotoluene using an inorganic salt as a phase separation agent - Google Patents

Process for the production of dinitrotoluene using an inorganic salt as a phase separation agent Download PDF

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Publication number
WO1990012781A1
WO1990012781A1 PCT/US1990/000654 US9000654W WO9012781A1 WO 1990012781 A1 WO1990012781 A1 WO 1990012781A1 US 9000654 W US9000654 W US 9000654W WO 9012781 A1 WO9012781 A1 WO 9012781A1
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WO
WIPO (PCT)
Prior art keywords
inorganic salt
nitric acid
percent
acid
dinitrotoluene
Prior art date
Application number
PCT/US1990/000654
Other languages
French (fr)
Inventor
Robert W. Mason
Peter C. Imm
Kent J. Bordelon
Original Assignee
Olin Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Olin Corporation filed Critical Olin Corporation
Priority to DE69011325T priority Critical patent/DE69011325T2/en
Priority to KR1019910701209A priority patent/KR920701119A/en
Priority to EP90903685A priority patent/EP0468968B1/en
Publication of WO1990012781A1 publication Critical patent/WO1990012781A1/en

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    • 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
    • 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
    • C07C201/16—Separation; Purification; Stabilisation; Use of additives
    • 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

Definitions

  • This invention relates generally to the nitration of toluene and, more specifically, to a process for nitrating toluene to dinitrotoluene employing an inorganic salt as a phase separation agent.
  • 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, requiring expensive wastewater treatment to remove this by-product from the desired product.
  • 2,362,743 discloses a two-step process for the manufacture of dinitrotoluene ("DNT") in the absence of sulfuric acid which comprises (a) nitrating toluene to mononitrotoluene using a nitric acid having a concentration of from about 60 percent to about 75 percent and a mole ratio of toluene to nitric acid of about 1 to about 3.5 and (b) nitrating the mononitrotoluene to dinitrotoluene using nitric acid having a concentration of from about 90 percent to about 100 percent, and a mole ratio of mononitrotoluene to nitric acid of about 1 to about 3.
  • DNT dinitrotoluene
  • step (b) a very high percentage of the nitrated product (up to 25 percent) based upon the amount of toluene reactant employed does not phase separate from the nitric acid medium.
  • step (b) a very high percentage of the nitrated product (up to 25 percent) based upon the amount of toluene reactant employed does not phase separate from the nitric acid medium.
  • the '743 patent teaches vacuum distillation of the product mixture to isolate the desired dinitrotoluene, an expensive and highly energy intensive process step. Since DNT is useful as an intermediate in producing TDI, new processes for the selective manufacture of this intermediate utilizing a more energy efficient phase separation technique would be highly desirable to the polyisocyanate manufacturing community.
  • the present invention relates to a process for producing DNT by a two-step liquid phase nitration reaction of nitric acid with toluene at a reaction temperature not exceeding 80 C in the absence of sulfuric acid and in the absence of a solvent.
  • the process comprises:
  • phase separation of said dinitrotoluene from said unreacted nitric acid in said mixture is suitably effected by adding an inorganic salt to the product mixture.
  • the inorganic salt is preferably soluble in the product mixture.
  • the inorganic salt is generally incorporated into the mixture of dinitrotoluene and unreacted nitric acid in a "phase separation effective amount", i.e., an amount sufficient to cause phase separation of the mixture in order to facilitate isolation of the dinitrotoluene from the unreacted nitric acid in the product mixture.
  • a phase separation effective amount i.e., an amount sufficient to cause phase separation of the mixture in order to facilitate isolation of the dinitrotoluene from the unreacted nitric acid in the product mixture.
  • the inorganic salt is empToyed in a molar amount sufficient to provide between 25 percent and 100 percent of a full saturation concentration of said inorganic salt in said nitric acid, where the full saturation concentration is measured at the reaction temperature employed in step (b) .
  • magnesium nitrate hexahydrate it is preferred to use between 0.2 gram and 0.85 gram of salt per gram of toluene.
  • Particularly advantageous inorganic salts are the inorganic sulfates, inorganic nitrates, and combinations thereof.
  • Illustrative inorganic salts are the alkali metal and alkaline earth metal salts such as sodium nitrate, sodium sulfate, potassium sulfate, potassium nitrate, magnesium nitrate hexahydrate, magnesium nitrate trihydrate, and combinations thereof.
  • the preferred inorganic salts are the nitrate salts, more preferably magnesium nitrate hexahydrate. It is preferred to use inorganic salt(s) which are chemically stable in the presence of the step (a) and step (b) reactions. For example, it is preferred not to use chloride salts due to the formation of chlorine and various nitrogen reaction by-products.
  • the timing of addition of the inorganic salt is not critical and can be effected before, during, or after either step (a) or step (b) of the process of the present invention.
  • the inorganic salt be added to the reaction mixture before step (a) even though the inorganic salt is not necessary for phase separation of the mononitrotoluene from the step (a) intermediate reaction.
  • the inorganic salt is then carried over into the step (b) reaction mixture, and is available in the step (b) product mixture to cause phase separation of the highly soluble dinitrotoluene from the product mixture.
  • step (a) is suitably conducted at a reaction temperature not exceeding 80 C, preferably between about 60 C and about 75 C, more preferably between about 65°C and about 75°C, most preferably about 70°C.
  • the reaction of step (b) is suitably conducted at a reaction temperature not exceeding 80 C, preferably between about 40 C and about 70°C, more preferably between about 60°C and about 70 C, most preferably about 65 C.
  • the reactions are suitably conducted at atmospheric pressure, although subatmospheric pressure can be employed if desired.
  • the reaction time is typically between one and five hours for each of steps (a) and (b), preferably about two hours for each step. After phase separation, washing with water and a basic solution produces a purified DNT product.
  • wash waters are free of the nitrocreosol 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 step (a) reaction and the 60-70% aqueous nitric acid phase reconcentrated, sold or recycled back into the step (a) reaction.
  • the following examples are intended to illustrate, but in no way limit the scope of, the present invention.
  • the HNO_/magnesium nitrate mixture contained 14.4 g of DNT (8.9 percent of total DNT recovered), while the wash water contained 0.78 g of DNT (0.5 percent) .

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

This invention relates to a process for nitrating toluene to dinitrotoluene and phase separation of the product using an inorganic salt as a phase separation agent. The process involves the steps of (a) reacting toluene with nitric acid having an acid concentration of between about 60 and about 75 percent to produce mononitrotoluene, (b) reacting the mononitrotoluene with concentrated nitric acid to produce a mixture of dinitrotoluene and unreacted nitric acid, and (c) incorporating an inorganic salt phase separation agent into the mixture to cause phase separation thereof.

Description

PROCESS FOR THE PRODUCTION OF DINITROTOLUENE USING AN INORGANIC SALT AS A PHASE SEPARATION AGENT
This invention relates generally to the nitration of toluene and, more specifically, to a process for nitrating toluene to dinitrotoluene employing an inorganic salt as a phase separation agent.
Nitration reactions of aromatic hydrocarbons are generally conducted in mixed acid systems, such as mixed nitric and sulfuric acids. However, these 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. In addition, the use of sulfuric acid tends to result in significant nitrocreosol and cyanide by-product formation, requiring expensive wastewater treatment to remove this by-product from the desired product. In view of these disadvantages associated with mixed nitric/sulfuric acid systems, there have been various attempts over the years to perform gas phase or liquid phase nitrations in concentrated nitric acid in the absence of sulfuric acid. By way of illustration, U.S. Patent No. 2,362,743 discloses a two-step process for the manufacture of dinitrotoluene ("DNT") in the absence of sulfuric acid which comprises (a) nitrating toluene to mononitrotoluene using a nitric acid having a concentration of from about 60 percent to about 75 percent and a mole ratio of toluene to nitric acid of about 1 to about 3.5 and (b) nitrating the mononitrotoluene to dinitrotoluene using nitric acid having a concentration of from about 90 percent to about 100 percent, and a mole ratio of mononitrotoluene to nitric acid of about 1 to about 3. Although the process of this '743 patent is advantageously conducted in the absence of sulfuric acid, it has now been found that in step (b) , a very high percentage of the nitrated product (up to 25 percent) based upon the amount of toluene reactant employed does not phase separate from the nitric acid medium. Indeed, the '743 patent teaches vacuum distillation of the product mixture to isolate the desired dinitrotoluene, an expensive and highly energy intensive process step. Since DNT is useful as an intermediate in producing TDI, new processes for the selective manufacture of this intermediate utilizing a more energy efficient phase separation technique would be highly desirable to the polyisocyanate manufacturing community. Heretofore, no process has been disclosed to the knowledge of the present inventors which provides for the nitration of toluene to DNT in the absence of a solvent and in the absence of sulfuric acid while affording enhanced phase separation of the nitrated product from nitric acid without distillation.
The present invention relates to a process for producing DNT by a two-step liquid phase nitration reaction of nitric acid with toluene at a reaction temperature not exceeding 80 C in the absence of sulfuric acid and in the absence of a solvent.
The process comprises:
(a) reacting toluene with nitric acid having an acid concentration of between about 60 and about 75 percent by weight, based upon the total amount of acid plus water, at a reaction temperature of between about 60 C and about 75 C, and employing between about 3 and about 5 moles of nitric acid per mole of toluene, to produce mononitrotoluene, (b) reacting said mononitrotoluene with concentrated nitric acid having an acid concentration of between about 90 and about 100 percent by weight, based upon the total amount of acid plus water therein, at a reaction temperature of between about 40°C and about 70°C, and employing between about 3 and about 4 moles of concentrated nitric acid per mole of mononitrotoluene, to produce a mixture containing dinitrotoluene and unreacted nitric acid, and
(c) incorporating an inorganic salt into said mixture to cause phase separation of said dinitrotoluene from said unreacted nitric acid in said mixture. This and other aspects of the present invention will become apparent upon reading the following detailed description of the invention. The process of the present invention utilizes a two-step reaction in liquid media and does not involve the formation of the two phase emulsions observed in conventional, mixed sulfuric/nitric acid nitration processes or processes which utilize a solvent. Phase separation of the desired dinitrotoluene from the product mixture is suitably effected by adding an inorganic salt to the product mixture. The inorganic salt is preferably soluble in the product mixture.
The inorganic salt is generally incorporated into the mixture of dinitrotoluene and unreacted nitric acid in a "phase separation effective amount", i.e., an amount sufficient to cause phase separation of the mixture in order to facilitate isolation of the dinitrotoluene from the unreacted nitric acid in the product mixture. Preferably, the inorganic salt is empToyed in a molar amount sufficient to provide between 25 percent and 100 percent of a full saturation concentration of said inorganic salt in said nitric acid, where the full saturation concentration is measured at the reaction temperature employed in step (b) . For example, when employing magnesium nitrate hexahydrate as the inorganic salt, it is preferred to use between 0.2 gram and 0.85 gram of salt per gram of toluene.
.Particularly advantageous inorganic salts are the inorganic sulfates, inorganic nitrates, and combinations thereof. Illustrative inorganic salts are the alkali metal and alkaline earth metal salts such as sodium nitrate, sodium sulfate, potassium sulfate, potassium nitrate, magnesium nitrate hexahydrate, magnesium nitrate trihydrate, and combinations thereof.
The preferred inorganic salts are the nitrate salts, more preferably magnesium nitrate hexahydrate. It is preferred to use inorganic salt(s) which are chemically stable in the presence of the step (a) and step (b) reactions. For example, it is preferred not to use chloride salts due to the formation of chlorine and various nitrogen reaction by-products.
The timing of addition of the inorganic salt is not critical and can be effected before, during, or after either step (a) or step (b) of the process of the present invention. For convenience, it is preferred that the inorganic salt be added to the reaction mixture before step (a) even though the inorganic salt is not necessary for phase separation of the mononitrotoluene from the step (a) intermediate reaction. The inorganic salt is then carried over into the step (b) reaction mixture, and is available in the step (b) product mixture to cause phase separation of the highly soluble dinitrotoluene from the product mixture. The reaction of step (a) is suitably conducted at a reaction temperature not exceeding 80 C, preferably between about 60 C and about 75 C, more preferably between about 65°C and about 75°C, most preferably about 70°C. The reaction of step (b) is suitably conducted at a reaction temperature not exceeding 80 C, preferably between about 40 C and about 70°C, more preferably between about 60°C and about 70 C, most preferably about 65 C. The reactions are suitably conducted at atmospheric pressure, although subatmospheric pressure can be employed if desired. The reaction time is typically between one and five hours for each of steps (a) and (b), preferably about two hours for each step. After phase separation, washing with water and a basic solution produces a purified DNT product. These wash waters are free of the nitrocreosol 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 step (a) reaction and the 60-70% aqueous nitric acid phase reconcentrated, sold or recycled back into the step (a) reaction. The following examples are intended to illustrate, but in no way limit the scope of, the present invention.
EXAMPLE 1
Improved Phase Separation of Dinitrotoluene From Nitric Acid Caused bv Magnesium Nitrate Hexahydrate
A mixture of 82.0 g of 59.5 percent HNO-, 64.6 g of Mg(NO_)2.6H20 and 32.9 g of commercial grade dinitrotoluene (mixture of isomers) was added to a separatory funnel and immersed in a water bath at 69°C. After occasional shaking, to dissolve and disperse the components, the layers were allowed to separate. A heavy acid/salt layer (141.4 g) was drawn off the bottom of the funnel, followed by the lighter DNT layer (36.4 g) . After dilution with water and cooling, 2.87 g of dinitrotoluene was recovered from the acid/salt layer equal to 8.7 percent of the original DNT fed. When an analogous mixture, but without added inorganic salt, was phase separated, dinitrotoluene in the acid phase amounted to 27.6 percent of that which was originally fed.
EXAMPLE 2
Two-Step Reaction to Produce Dinitrotoluene and Phase Separation Using Magnesium Nitrate Hexahydrate
A mixture of 92.14 g (1.0 mole) of toluene was reacted with 484.7 g of 65 percent HNO_ (5.0 mole HNO_), in the presence of 412.0 g magnesium nitrite hexahydrate, for two hours at 70°C in a mechanically agitated, jacketed flask. After phase separation of 133.4 g of mononitrotoluene (MNT) product from 827.0 g of spent nitric acid/magnesium nitrate mixture, the MNT was further reacted with 255.9 g (4.0 moles) of 98.5 percent HN0 3 -°- two hours at 70°C. Vacuum distillation of the reaction product removed 102.8 g of 99.4 percent HN03, leaving 255.3 g of DNT/aqueous H 03. This DNT/aqueous HNO_ mixture was combined with the aqueous HNO_/magnesium nitrate mixture from the mononitrate step and phase separated. After washing the DNT with 92.0 g of hot water, 147.4 g of DNT, 895.8 g of HNO_/magnesium nitrate mixture and 119.5 g of wash water were recovered. The wash water and HNO_/magnesium nitrate mixture were diluted with water and chilled to 4°C to crystallize the DNT content of each solution. The HNO_/magnesium nitrate mixture contained 14.4 g of DNT (8.9 percent of total DNT recovered), while the wash water contained 0.78 g of DNT (0.5 percent) . An identical reaction and phase separation sequence, but without added inorganic salt, gave 97.1 g of DNT, 554.3 g of spent HNO_, containing 68.0 g of DNT (40.9 percent of total DNT recovered) and 136.3 g of wash water, containing 1.35 g of DNT (0.8 percent).

Claims

WHAT IS CLAIMED IS:
1. A process for producing dinitrotoluene and causing phase separation of the dinitrotoluene so produced from the product mixture characterized by:
(a) reacting toluene with nitric acid having an acid concentration of between about 60 and about 75 percent by weight, based upon the total amount of acid plus water, at a reaction temperature of between about 60 C and about 75 C, and employing between about 3 and about 5 moles of nitric acid per mole of toluene, to produce mononitrotoluene,
(b) reacting said mononitrotoluene with concentrated nitric acid having an acid concentration of between about 90 and about 100 percent by weight, based upon the total amount of acid plus water therein, at a reaction temperature of between about 40°C and about 70°C, and employing between about 3 and about 4 moles of concentrated nitric acid per mole of mononitrotoluene, to produce a mixture containing dinitrotoluene and unreacted nitric acid, and (c) incorporating an inorganic salt into said mixture to cause phase separation of said dinitrotoluene from said unreacted nitric acid in said mixture.
2. The process of claim 1 characterized in that said inorganic salt is selected from the group consisting of inorganic sulfates, inorganic nitrates, and combinations thereof.
3. The process of claim 1 characterized in that said inorganic salt is selected from the group consisting of sodium nitrate, sodium sulfate, magnesium nitrate hexahydrate, and combinations thereof.
4. The process of claim 1 characterized in that said inorganic salt is added either before, during, or after step (a) or step (b) in order to incorporate said inorganic salt into said mixture to cause said phase separation.
5. The process of claim 1 characterized in that said nitric acid of step (a) has an acid concentration of between about 60 and about 70 percent by weight, based upon the total amount of acid plus water.
6. The process of claim 1 characterized in that said concentrated nitric acid of step (b) has an acid concentration of between about 95 and about 100 percent by weight, based upon the total amount of acid plus water.
7. The process of claim 1 characterized in that said inorganic salt is added before step (a), and characterized in that said salt is employed in a molar amount sufficient to provide between 25 percent and 100 percent of a full saturation concentration of said inorganic salt in said nitric acid step (a).
8. The process of claim 1 characterized in that said inorganic salt is added before step (b) , and characterized in that said inorganic salt is employed in a molar amount sufficient to provide between 25 percent and 100 percent of a full saturation concentration of said inorganic salt in said concentrated nitric acid of step (b) .
9. The process of claim 1 characterized in that step (a) is conducted for a reaction time of between about 1 and about 5 hours.
10. The process of claim 1 characterized in that step (b) is conducted for a reaction time of between about 1 and about 5 hours.
PCT/US1990/000654 1989-04-21 1990-02-09 Process for the production of dinitrotoluene using an inorganic salt as a phase separation agent WO1990012781A1 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
DE69011325T DE69011325T2 (en) 1989-04-21 1990-02-09 METHOD FOR PRODUCING DINITROTOLUOL USING AN INORGANIC SALT AS A PHASE RELEASE AGENT.
KR1019910701209A KR920701119A (en) 1989-04-21 1990-02-09 Process for preparing dinitrotoluene using inorganic salt as phase separator
EP90903685A EP0468968B1 (en) 1989-04-21 1990-02-09 Process for the production of dinitrotoluene using an inorganic salt as a phase separation agent

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US341,447 1989-04-21
US07/341,447 US4918250A (en) 1989-04-21 1989-04-21 Process for the production of dinitrotoluene using an inorganic salt as a phase separation agent

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EP (1) EP0468968B1 (en)
JP (1) JPH04504844A (en)
KR (1) KR920701119A (en)
CN (1) CN1027446C (en)
AU (1) AU5156090A (en)
DE (1) DE69011325T2 (en)
MX (1) MX163846B (en)
PT (1) PT93174B (en)
WO (1) WO1990012781A1 (en)

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US5012019A (en) * 1990-01-26 1991-04-30 Olin Corporation Process for purifying aromatic nitration products
US5099079A (en) * 1990-07-26 1992-03-24 Olin Corporation Process for separating acid from nitro substituted aromatics using a molten nitrate salt
US5057632A (en) * 1990-10-22 1991-10-15 Olin Corporation Process for preparing dinitrotoluene
US5099078A (en) * 1990-12-21 1992-03-24 Olin Corporation Process for preparing dinitrotoluene
US5099080A (en) * 1991-03-08 1992-03-24 Olin Corporation Process for preparing dinitrotoluene
US5245092A (en) * 1991-03-15 1993-09-14 Olin Corporation Process for preparing dinitrotoluene with low by-product content
DE4216416C1 (en) * 1992-05-18 1993-05-13 Bayer Ag, 5090 Leverkusen, De
US5302763A (en) * 1993-03-01 1994-04-12 Olin Corporation Process for preparing dinitrotoluene
DE4437047A1 (en) 1994-10-17 1996-04-18 Bayer Ag Process for the dinitration of aromatic compounds
DE102006033722A1 (en) * 2006-07-21 2008-01-24 Bayer Materialscience Ag Process for the preparation of dinitrotoluene
KR102029504B1 (en) * 2011-08-09 2019-10-07 바스프 에스이 Method for purifying wastewater from reprocessing of crude aromatic nitro compounds
CN110655513A (en) * 2019-10-23 2020-01-07 浙江南郊化学有限公司 Synthetic method of flumioxazin

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US4918250A (en) 1990-04-17
AU5156090A (en) 1990-11-16
PT93174B (en) 1995-12-29
EP0468968A1 (en) 1992-02-05
CN1027446C (en) 1995-01-18
JPH04504844A (en) 1992-08-27
KR920701119A (en) 1992-08-11
MX163846B (en) 1992-06-25
EP0468968B1 (en) 1994-08-03
EP0468968A4 (en) 1992-05-20
DE69011325T2 (en) 1994-12-08
PT93174A (en) 1990-11-20
CN1046521A (en) 1990-10-31
DE69011325D1 (en) 1994-09-08

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