CN108997137A - The method for preparing toluenediamine by catalytic hydrogenation dinitrotoluene (DNT) - Google Patents

Abstract

The present invention relates to a kind of methods for preparing toluenediamine to react dinitrotoluene (DNT) with hydrogen in the presence of a catalyst in the method.It is counted on the basis of the mole of dinitrotoluene (DNT), dinitrotoluene (DNT) needed for this method is such that its content with physical dissolution form or the carbon dioxide for being chemically bonded form is no more than 0.175 mole %.

Description

The method for preparing toluenediamine by catalytic hydrogenation dinitrotoluene (DNT)

Technical field

The present invention relates to a kind of methods for preparing toluenediamine (TDA), in the method, in the presence of a catalyst, make Dinitrotoluene (DNT) (DNT) is reacted with hydrogen, wherein being counted on the basis of the mole of dinitrotoluene (DNT) used, dinitrotoluene (DNT) used The content of the carbon dioxide of the physical dissolution form or chemical bonding form that have is no more than 0.175 mole %.

Background technique

Toluenediamine is the intermediate for preparing toluene di-isocyanate(TDI) (TDI), and the toluene di-isocyanate(TDI) is to be used for Prepare the important primary product with large-scale production of polyurethane.It is by carrying out catalytic hydrogenation to dinitrotoluene (DNT) (DNT) Preparation method be known and be often reported (for example, see being published in Ullmann ' The article of sEnzyklopadiedertechnischenChemie, the 4th edition, volume 7, page 393,1973, The New York VerlagChemieWeinheim/).The industrialized production of toluenediamine mainly will be by being obtained with nitric acid nitrating toluene The isomer mixture of dinitrotoluene (DNT) reacted.

The isomer mixture of commercial dinitrotoluene (DNT) is mainly in two step isothermal nitrifying process in the form of thick DNT In be made, the two steps isothermal nitrifying process is carried out in the presence of sulfuric acid catalyst using nitric acid, and a corresponding nitro is generated Toluene intermediate.They then the step of providing downstream reaction, are mainly collected in washing step, they are very big in this way The sulfuric acid and nitric acid and submember such as cresols and its catabolite of the dissolution formed in reaction step are not contained in degree.

Summary of the invention

The present invention provides a kind of method for preparing toluenediamine, wherein in the presence of a catalyst by dinitrotoluene (DNT) and hydrogen It is reacted, which is characterized in that counted on the basis of the mole of dinitrotoluene (DNT) used, the physics that dinitrotoluene (DNT) used has Dissolved form or the content for being chemically bonded the carbon dioxide of form are less than 0.175 mole %.

A kind of suitable determining physical dissolution form that can be used within the scope of the method for the present invention or chemical bonding form The analysis method of carbon dioxide content is disclosed in detail and is described below in " embodiment " part, entitled " to quantitatively determine dinitro The explanation of the analysis method of physical dissolution or the carbon dioxide of chemical bonding form in base toluene ".Within the scope of the invention, object The content of the carbon dioxide of reason dissolution or chemical bonding form is understood to can exist in the form of physical dissolution and/or chemical bonding Carbon dioxide total content.

In a preferable embodiment of the invention, the method for preparing toluenediamine includes the following steps:

A) it reacts toluene with nitration acids, forms the reaction mixture comprising mononitrotoluene,

B) reaction mixture comprising mononitrotoluene is separated into: the organic phase comprising mononitrotoluene and the water comprising sulfuric acid Phase,

React the organic phase comprising mononitrotoluene with nitration acids, obtaining includes dinitrotoluene (DNT) (i.e. dinitrotoluene (DNT) Isomer mixture) reaction mixture,

D) reaction mixture comprising dinitrotoluene (DNT) is separated into: the organic phase comprising dinitrotoluene (DNT) and the water comprising sulfuric acid Phase,

E) in multistep extraction, purify the organic phase comprising dinitrotoluene (DNT) with water, each step that the multistep extracts all includes It mixes and mutually separates, to obtain the isomer mixture of the dinitrotoluene (DNT) comprising following (i)-(iii): (i) 74-81 weight % 2,4-DNT, the 2,6-DNT of (ii) 17-21 weight %, and (iii) less than the combination of 5.5 weight % 2,3-DNT, 2,5- DNT, 3,4-DNT and 3,5-DNT, wherein (i), the dinitrotoluene (DNT) that the summation of (ii) and (iii) are 100 weight %,

It reacts the isomer mixture of resulting dinitrotoluene (DNT) in the presence of a catalyst with hydrogen, forms toluene two Amine,

Wherein

(1) in each step that the multistep of step e) extracts, it is at least 4 minutes for the mixed residence time and is no more than 60 minutes, and

(2) at least in the final stage of step e) extraction, inert gas is also introduced into the organic phase comprising dinitrotoluene (DNT) and water In mixture, the weight ratio of inert gas and dinitrotoluene (DNT) is: so that being counted on the basis of the mole of dinitrotoluene (DNT), gained The total content of the carbon dioxide of physical dissolution or chemical bonding form that the dinitrotoluene (DNT) of purifying has is to rub less than 0.175 You are %, preferably less than 0.125 mole %, preferably less than 0.075 mole of %.

Specific embodiment

In method of the invention, especially its preferable embodiment (i.e. above-mentioned steps a) arrives g)) in, the system of step a) The standby reaction of mononitrotoluene and the reaction for preparing dinitrotoluene (DNT) of step c), can carry out under insulation or isothermal.Preferably It is the staged stirring container using the cooling for continuously flowing through reaction mixture (cooledstirrervesselcascade) or (series-connected) of series winding cooling ring-reactor isothermally It carries out, these reactors are for example described in EP0903336B1, and the EP patent is considered and is combined reference herein United States Patent (USP) 5,902,910 or DE102004005913A1 are corresponding.Static and dynamic separator be utilized within step b) and D) in mutually separation.It is preferable to use such as static separation device described in EP0903336B1, the EP patent be considered with This combines the United States Patent (USP) 5,902,910 of reference corresponding.

In better method of the invention, the multistep that can carry out step e) to the organic phase that step d) is obtained is extracted, and is returned Receive major amount of nitric acid and/or sulfuric acid contained in organic phase.The recycling can be carried out through single step or multistep process, each Using the water that does not charge on a small quantity in step, or through multistep process, (with described at present opposite), using largely in each step The water of circulation.Suitable process is for example described in EP0279312B1 or EP0736514B1, which is considered distinguishing With herein combine the United States Patent (USP) 5,001,286 and 5,756,867 of reference it is corresponding.

Preferably not recovery acid.Then, in better method of the invention, what step d) was obtained includes dinitrotoluene (DNT) Organic phase is washed in step e) with water with multistep extraction, and each step of multistep extraction all includes mixing and mutually divide From.In a particularly preferred embodiment, extract for dinitrotoluene (DNT) (i.e. the isomer mixture of dinitrotoluene (DNT)) multistep The water taken can have different pH value in different steps.Then, in the step e) for extracting dinitrotoluene (DNT), Alkaline water is used preferably in an at least step, and neutral water is used in an at least step.In the step that extraction includes two steps or more In the case where rapid, alkaline water is used preferably in an at least step, acid water is used in an at least step, and in an at least step Use neutral water.Herein in preferable embodiment, extraction in each step is carried out in a manner of " liquid liquid " extraction.This can be with Ensured and properly selecting the temperature of dinitrotoluene (DNT) used and temperature as the water phase of extractant.

In another preferable embodiment, carried out multistep extraction an at least step in using for mix and The equipment of the liquid of the actually mutually insoluble different specific weight of separation, the equipment are for example described in DE-B-1135425, the DE Patent is considered and combines the United States Patent (USP) 3,162,510 of reference corresponding herein.

Being described in DE-B-1135425(, it is considered and is combined the United States Patent (USP) 3,162,510 of reference opposite herein Answer) equipment be characterized in: extraction or column scrubber form mixed zone, the mixed zone have is aligned to centered on mixed zone Phase separation chamber, leave the mixture of mixed zone and entered in the room by overflow pipe, which has one " shutting off " and wash The circular hollow jacket of column is washed, mixture is separated into two-phase according to density.In order to make in DE-B-1135425(its be considered with Herein in conjunction with reference United States Patent (USP) 3,162,510 it is corresponding) the 2nd column/35-52 row and the 3rd column/1-12 row on The equipment that the equipment of description describes in its structure and on the 3rd column/29-47 row is advantageously functionally used for the present invention at it Method, should in addition assemble in a device it is possible for inert gas to be fed to the device of mixed zone, such as in environment division Bottom section in other opening.

However, extraction, any type of multistep extraction process and extraction can also be used in purification step e) in principle The each step for taking equipment all includes mixing and mutually separating, but condition is: when the stop mixed in each step of step e) extraction Between (time that mixture is handled) be at least 4 minutes and be no more than 60 minutes (see wanting in above-mentioned better method Ask (1))；And at least in the final stage of step e) extraction, inert gas is also introduced into having comprising dinitrotoluene (DNT) and water (see the requirement (2) in above-mentioned better method) in machine phase mixture.The weight ratio of inert gas and dinitrotoluene (DNT) is: so that with It is counted on the basis of the mole of dinitrotoluene (DNT), the physical dissolution or be chemically bonded form that the dinitrotoluene (DNT) of gained purifying has The total content of carbon dioxide is less than 0.175 mole %.

The aequum or required weight ratio of inert gas and dinitrotoluene (DNT) can be by those of ordinary skill in the art easily It determines.The amount or ratio can be readily determined by simply testing, by by the amount of inert gas and dinitrotoluene (DNT) or Weight ratio be increased to physical dissolution or be chemically bonded form carbon dioxide reach aequum until test determined.

After the multistep extraction in purification step e), the dioxy achieved with physical dissolution or chemical bonding form Change the loading capacity (loading) of the dinitro toluene isomers mixture of carbon, can preferably " bottom clearance GC " be relied on, by gas chromatography It is monitored.A kind of suitable determining physical dissolution preferably used within the scope of the method for the present invention or the dioxy for being chemically bonded form The analysis method for changing carbon content is disclosed in the entitled of the application and " quantitatively determines physical dissolution or chemical bonding shape in dinitrotoluene (DNT) In the explanation of the analysis method of the carbon dioxide of formula " part.

Dinitrotoluene (DNT) (isomer mixture of dinitrotoluene (DNT)) obtained so is preferably collected in recipient, by This feeds the step of hydrogenation being preferably carried out continuously in liquid form.Preferably continuously flow into the dinitrotoluene (DNT) of recipient, can be subjected into The gas elution process of one step or different types of carbon dioxide removing processing, this processing can be collected in the dinitrotoluene (DNT) Before recipient, later or they from recipient removing after carry out.The only key factor of the method for the present invention is, It is counted on the basis of the mole of dinitrotoluene (DNT) used, is used to prepare the tool of dinitrotoluene (DNT) used in the catalytic hydrogenation of toluenediamine Some physical dissolutions or the content for being chemically bonded the carbon dioxide of form are less than 0.175 mole %.

The catalytic hydrogenation of dinitrotoluene (DNT) obtained in this way can use atent solvent or the feelings without using solvent at the same time It is carried out under condition.Preferably in the absence of a solvent, it is carried out using the aqueous suspension of catalyst.It can be using the anti-of routine Device is answered to carry out in a manner of being interrupted or is continuous.Its example is stirring container, bubble column (bubblecolumn) or annular reactor (such as annular-Venturi reactor), or the injection annular reactor with inner and outer circuit.

In the preferable embodiment of the method for the present invention, the injection annular reactor with inner and outer circuit used is for example It is described in EP1137623B1, which is considered and is combined the United States Patent (USP) 6,350,911 of reference opposite herein It answers.

In another preferable form of the method for the present invention, is counted, had on the basis of the mole of dinitrotoluene (DNT) used The content of physical dissolution or the carbon dioxide of chemical bonding form is the catalysis hydrogen of the dinitrotoluene (DNT) less than 0.175 mole of % To change, is carried out in the mud phase reaction device with integrated heat exchanger, the reactor is for example described in WO-A-96/11052, The international application is considered and combines the United States Patent (USP) 5,779,995 of reference corresponding herein.This reactor has ring Shape room is covered as heat exchanger, the bottom and top of the doughnut by the reactant in reactor, the doughnut tool There are multiple perpendicular flow slots, for reactant and flows through the coolant of the doughnut between the flowing groove of reactant.Such as WO-A- 96/11052(its be considered with the United States Patent (USP) 5 for being combined reference herein, 779,995 is corresponding) disclosed in, it is this anti- Answer device especially suitable for by the reaction heat discharged in the catalytic hydrogenation of dinitrotoluene mixtures with the shape of useful steam Formula comes out.In the catalytic hydrogenation of the dinitrotoluene (DNT) carried out by the present invention, the operation temperature kept in the reactor is 80-200 DEG C, preferably 100-180 DEG C, pressure are 5-100 bars, preferably 10-50 bars.

In system feed hydrogen preferably by it is following it is this in a manner of carry out, supply the nitro equivalent of corresponding amine compounds Stoichiometry hydrogen needed for reaction, is applicable always, and the content of reactor is also saturated by hydrogen always, herein Particularly contemplate the surface area of used catalyst.This is obtained preferably by following manner: offer preferably uses deflation blender Mud phase reaction device can make the catalyst being suspended in reaction mixture and in the reactive mixture by the reactor The hydrogen of tiny dispersion bubble hydrogen form reaches most of uniform, tiny distribution.

By the content of US publication application 2004/0073066A1, it is advantageous that addition is gaseous state under hydrogenating conditions Inert compound, or with hydrogen establish a suitable flow of purge gas for discharge introducing reactor gaseous contamination Object, so that the purity of hydrogen present in reactor is adjusted to 50-97 volume %, preferably 70-97 volume %, preferably 80-95 volume %.By the content of US publication application 2004/007366A1, very pure hydrogen has strong reacting The tendency gathered in system forms total surface the result is that tiny bubble hydrogen combines immediately in the downstream of dispersion area The small air pocket of product.As disclosed by US publication application 2004/007366A1, it is this be flocked on density of hydrogen it is lower when not The advantages of occurring, but making high surface area due to too low mass transfer in too low density of hydrogen, is eliminated.

In a particularly preferred form of this method, using deflation blender therein in the form of axial conveyer Mud phase reaction device, the reactor are used in particular for gas liquid dispersion, which is for example described in EP0856665B1, and the EP is special Benefit is considered and combines the United States Patent (USP) 6,627,174 of reference corresponding herein.It is special by being carried out to this hybrid element On the one hand fixed selection can achieve very high liquid phase circulation amount, on the other hand can also make reacting in a simple manner The hydrogen of tiny dispersion bubble hydrogen form in mixture reaches required distribution.

As described above, it is excessively high that local concentration should be avoided when dinitrotoluene (DNT) to be metered into catalytic hydrogenation device Phenomenon.Metering can be robbed using spray, the mixing arrangement of nozzle or Mechanical Driven carries out.It, can be by using in preferable mode The agitating device as described in EP1637220A1 carries out, and the EP patent application is considered and the beauty that is combined reference herein State's public patent application 2006/0038306 is corresponding.This agitating device at least by deflation blender and blade-type mixer or Two liquid mixer compositions, they are placed on axis and are respectively provided with inlet and at least one outlet, stirring of deflating The outlet of device and the outlet of one or more liquid mixers are spaced a distance between each other.In agitating device, each The ratio between the diameter " d " of the distance between opening " a " and deflation blender or liquid mixer " a/d " is 0.025-0.5, preferably 0.05-0.3, the ratio between diameter " d " of distance " b " and deflation blender or liquid mixer between each outer ledge " b/d " For 0.01-0.4, preferably 0.02-0.2.Described agitating device becomes anti-especially suitable for mixing gas phase and liquid phase simultaneously Mixture is answered, the mixing of each phase is made to reach optimization, and avoids the nitro equivalent generation office for making to introduce to a certain extent The phenomenon that portion's excessive concentration.

As catalyst, any hydrogenating catalytic of the known catalytic hydrogenation suitable for aromatic nitro compound can be used Agent.It is particularly suitable to or mixtures thereof the metal of the 8th subgroup of the periodic table of elements, they can for example be applied to carrier material such as carbon Or on magnesia, aluminium oxide and/or silica.It is preferred that for example comprising drawing Buddhist nun's iron (Raneyiron), cobalt and/or the catalyst of nickel, Especially nickeliferous catalyst, such as the catalyst of Raney nickel, and the catalyst containing palladium or platinum being loaded on carrier material.System It is standby and use this catalyst as aromatic nitro compound such as nitrobenzene, nitrotoleune, dinitrotoluene (DNT), chlorination nitroaromatic The hydrogenation catalyst of compound etc., this is known and was often reported.For example, see EP0223035B1, EP1066111B1 and EP-A-1512459, these EP patents or patent application are considered and are combined reference herein respectively United States Patent (USP) 4,792,626, United States Patent (USP) 6,395,934 and US publication application 2005/0107251 are corresponding.

In a best embodiment of the method for the present invention, use Raney nickel catalyst as catalyst, it is described to urge Agent is for example described in EP-A-1512459, which is considered and is combined the U.S. Publication of reference special herein Benefit application 2005/0107251 is corresponding.As disclosed therein, the preparation of these better catalysts includes:

1) by 50-95 weight % aluminium, 10-50 weight % nickel, 0-20 weight % iron, 0-15 weight % cerium, cerium mixed metal, vanadium, The alloy melt of niobium, tantalum, chromium, molybdenum or manganese and optional glass formation element is cooled down with the cooling velocity greater than 104K/s, Its process is to be pressed onto the alloy of melting in rotation cooling wheel or be pressed between the cooling wheel that two rotate in opposite directions It is extracted in gap or by melt, and

2) then quick-setting alloy is handled with organic or inorganic alkali.

Compared with conventional Raney nickel catalyst, difference is these preferable catalyst: improving product significantly The working life of selectivity and catalyst, especially when reaction temperature is greater than 120 DEG C.Therefore, when preferably being urged using these When agent, the reaction heat released in the hydrogenation process of dinitrotoluene (DNT), which is advantageously used for generating, is used as heat medium Steam.

From reaction system remove reaction mixture, the reaction system for by charging come catalytic hydrogenation dinitrotoluene (DNT) and Speech preferably continuous operation, preferably catalyst is retained in system while continuous operation.The removing is especially good It is to be carried out by the way of cross-flow filtration, the filtering is for example described in EP0634391B1 in principle, which is considered With the United States Patent (USP) 5 for being combined reference herein, 563,296 is corresponding, or is described in the specific embodiment of EP1137623B1 In, the EP patent be considered with the United States Patent (USP) 6 for being combined reference herein, 350,911 is corresponding.In this product discharge In, part stream in the filter, removes part from removing in reactor and flowing through on cross-flow filter from product stream Amount, while retaining catalyst, finally, being that the reduced part of " concentration " is flowed and is sent back to again for its catalyst content To reactor.

Filtered product has high purity and can be processed, without passing through as described in prior art into one The chemical processing of step forms final product toluenediamine.

In short, the present invention is used to prepare the method for toluenediamine (wherein by dinitro first compared with the method for prior art Benzene is reacted in the presence of at least one catalyst with hydrogen) distinguishing feature be to greatly improve economic benefit.It is logical Crossing using having physical dissolution or being chemically bonded the content of the carbon dioxide of form is less than 0.175 mole %(with dinitro used Counted on the basis of the mole of base toluene) dinitrotoluene (DNT), the selectivity of catalyst can be improved and substantially improve catalyst Working life.

Method of the invention is described in more detail with following preferable embodiment.

Following embodiments further illustrate the details of the method for the present invention.The present invention described in foregoing character is not by this The spirit or scope of a little embodiments are limited.Those skilled in the art will readily appreciate that, following process items can be used The known variation of part.Outer unless otherwise indicated, all temperature are all degree Celsius, what all percentage was by weight Percentage.

Embodiment

Quantitatively determine the explanation of the analysis method of physical dissolution or the carbon dioxide of chemical bonding form in dinitrotoluene (DNT)

In order to quantitatively determine the carbon dioxide of physical dissolution or chemical bonding in dinitrotoluene (DNT) (DNT), by a certain amount of DNT sample Product are placed in the vial at roll-in edge, and the bottle available membrane is sealed in a gas tight manner, and a certain amount of sulfuric acid is added, Then carbon dioxide present in gas chamber is determined with headspace gas chromatography (headspace analysis carried out with gas chromatography) Amount, with external calibration detect thermal conductivity.

Following apparatus is used in analysis method:

HP5890 gas chromatograph with thermal conductivity detectors (Hewlett-Packard)

HP19395A headspace sampler (Hewlett-Packard)

Separation condition:

Stationary phase: silica gel #12, packed column (10 feet × 1/8 inch)

Carrier gas: helium (12.5 ml/min of flow velocity)

Column furnace, temperature: 200 DEG C

Injection block, temperature: 200 DEG C

Detector, temperature: 250 DEG C

Bottom clearance unit: 45 DEG C

Incubation time: 3.0 minutes

Volume injected: 1 milliliter

The completion of quantitative analysis:

It, will be in 1.0 grams ± 0.1 milligram of DNT samples weighing to the vial for having roll-in edge in order to be analyzed.By vial After sealing, 0.50 milliliter of sulfuric acid (w=0.330 g kg) is injected by diaphragm with syringe, is mixed with roller under mild shake Then the content of the vial of flanging edge will have the vial at roll-in edge to be placed in headspace sampler, after tempering, carry out Headspace GC analysis.

Quantitative assessment is carried out with external standard.It is similar with DNT sample analysis, by a certain amount of NaHCO3/ kilograms of content w=0.5 gram The sodium bicarbonate aqueous solution of solution is placed in the vessel, and sulfuric acid is added, and carries out gas chromatographic analysis.

Embodiment 1:

Hydrogenating, there is the dinitrotoluene (DNT) that the content of the carbon dioxide of physical dissolution or chemical bonding is 0.19 mole of % (to be not belonging to The present invention):

Operate continuously laboratory hydrogenation equipment.The composition of the hydrogenation equipment is as follows:

A certain amount of hot DNT covered by one layer of nitrogen,

There is the feed pipe of heat and the DNT metering pump of discharge tube,

- 1 liter of hydrogenation reactor, equipped with heating/cooling jacket, interior cooling coil and heating/cooling linked system, stirring of deflating Device, immersion metering spray is robbed and the fine bore glass material with connection discharge tube, and

Heat separator for mutually separating keeps the row of meter, level measurement meter and the heat for removing product with pressure Put pipeline.

Under nitrogen blanket, 800 grams (are mixed comprising 62 weight % toluenediamines and 38 weight % water with 100 weight % Counted on the basis of object) mixture, be added in the reactor for being preheating to 50 DEG C, 50 grams of water be then added and 7 grams of iron contents are 15 weights Amount %(counted on the basis of the weight of starting alloy) water-wet type Raney nickel/iron catalyst suspension.It is greater than 99.9 with purity The equipment of closing is pressurized to 30 bars absolutes by the hydrogen of volume %, and reactor is heated to 140 DEG C, while operating deflation stirring Device is kept for required temperature 2 hours, makes activation of catalyst, with 30 standard liters per hours of purification speeds (purgerate), Xiang Qing In the atmosphere for changing the bearing area of equipment, inert compound be added is fed.

It will be stored in 75 DEG C of recipients and the content of physical dissolution or the carbon dioxide of chemical bonding form is 0.19 The dinitrotoluene (DNT) of mole %, is metered into the equipment of above-mentioned preparation with 125 Grams Per Hour rates.It is greater than by being passed through purity The hydrogen of 99.9 volume %, remains 30 standard liters per hours for purification speed to keep system pressure, with frit by reactor Horizontal plane be maintained at required horizontal plane, and discharge, will without catalyst reaction mixture collect in downstream separator And it periodically therefrom removes to sample.

With the characteristic of high pressure lipuid chromatography (HPLC) monitoring reaction.It is after 76 hours, no longer to observe completely between in operation Conversion.At this point, chromatogram shows that nitro-amino aromatic compounds breakthrough, test terminate.

Embodiment 2:

Hydrogenating, there is the dinitrotoluene (DNT) that the content of the carbon dioxide of physical dissolution or chemical bonding is 0.045 mole of % (to belong to The present invention):

It is prepared and is tested by method similar described in example 1 above.However, using having physical dissolution or chemical bond The content of the carbon dioxide of conjunction is the dinitrotoluene (DNT) of 0.045 mole of %.

With the characteristic of high pressure lipuid chromatography (HPLC) monitoring reaction.Only in operation between just no longer to observe after 162 hours Complete conversion, chromatogram show nitro-amino aromatic compounds breakthrough.At this point, test just terminates.

Embodiment 3:

Hydrogenating, there is the dinitrotoluene (DNT) that the content of the carbon dioxide of physical dissolution or chemical bonding is 0.18 mole of % (to be not belonging to The present invention):

Becoming to be added continuously 5860 kgs/hr of catalyst suspension, the suspension with nitrogen in inert stirring container Liquid include the iron content of 704 kgs/hr (about 12 weight %, counted on the basis of the weight of suspension) be about 30 weight %(with Counted on the basis of the weight of catalyst) Raney nickel/iron catalyst and the m- TDA of 27.1 weight %, the o- TDA of 0.9 weight %, 37 Weight % isopropanol, 23 weight % water (in each case, above-mentioned weight % is counted on the basis of the total weight of suspension).? Continuously mixed in mixing vessel, be equipped in the mixing vessel: 5876 kilograms have physics molten comprising 99.4 weight % The content of the carbon dioxide of solution or chemical bonding form is that 0.18 mole of %(is counted on the basis of the amount of dinitrotoluene (DNT) used) The commodity dinitrotoluene (DNT) of dinitrotoluene (DNT) (being counted on the basis of the weight of mixture) and 5870 kilograms include 87 weight % isopropyls The solvent of pure and mild 13 weight % water (being counted on the basis of the total weight of the solvent prepared) prepared, the operation temperature of mixing vessel Degree is maintained at 75 DEG C.

Mixture prepared above is continuously taken out from mixing vessel, and is added in high pressure hydrogen equipment, is set at this In standby, in cooling cascade reactor (cooledreactorcascade), reacted under 150 DEG C and 100 bars with hydrogen, institute Cooling cascade reactor is stated to operate continuously for the hydrogen of circulation, and with dinitrotoluene mixtures used It is parallel.After mean residence time is 21 minutes and is cooled to 75 DEG C, reaction mixture leaves the cascade reactor, and Enter phase separator afterwards, is separated into gas phase and liquid phase in the separator.

Gas phase is returned again to the beginning of cascade reactor, and the hydrogen content of gas phase is remained concentration with purge stream Greater than 90 volume %.Liquid phase is continuously taken out from separator, and is put into the filtering recipient of stirring, was therefrom then added to It filters in unit.In filter element, separating mixture in this way: other than obtaining clear filtrate, packet is had also obtained Containing 12 weight % Raney nickels/iron catalyst, the m- TDA of 27.1 weight %, the o- TDA of 0.9 weight %, 37 weight % isopropanols and 23 The catalyst suspension of weight % water.The clear filtrate that separates of distillation processing, prepared by catalyst suspension be then back to Mixing vessel.

With the catalytic activity of gas chromatography monitoring recycling catalyst, it is contemplated that the aging characteristics of used catalyst, by one Quantitative fresh catalyst is continuously added in mixing vessel in the form of 1 weight % suspension in water, passes through periodicity Catalyst suspension obtained keeps catalyst concn needed for reaction chamber in ground discharge filter element.It will keep catalyst The amount of fresh catalyst needed for active (being counted on the basis of the amount of prepared toluenediamine) is known as specific catalyst consumption Amount.

When the content using the carbon dioxide with physical dissolution or chemical bonding form is 0.18 mole of %(with dinitro Counted on the basis of the amount of toluene) dinitrotoluene (DNT) when, specific catalyst consumption reaches 27 grams/double centner TDA.

Embodiment 4:

Hydrogenating, there is the dinitrotoluene (DNT) that the content of the carbon dioxide of physical dissolution or chemical bonding is 0.045 mole of % (to belong to The present invention):

The present embodiment is carried out by method similar described in example 3 above.However, using having physical dissolution or chemical bonding Carbon dioxide content be 0.045 mole of % dinitrotoluene (DNT).

When the content using the carbon dioxide with physical dissolution or chemical bonding form is 0.046 mole of %(with dinitro Counted on the basis of the amount of base toluene) dinitrotoluene (DNT) when, specific catalyst consumption reaches 6 grams/double centner TDA.

Although above-mentioned be for the purpose of illustration described in detail the present invention, these detailed descriptions are only for this purpose, simultaneously And other than being defined by the claims, without departing from the spirit and scope of the present invention, the technology of this field Personnel can be variously modified.

Claims (3)

1. a kind of method for preparing toluenediamine, includes the following steps:

A) it reacts toluene with nitration acids, forms the reaction mixture comprising mononitrotoluene,

B) reaction mixture comprising mononitrotoluene is separated into: the organic phase comprising mononitrotoluene and comprising sulphur The water phase of acid,

It reacts the organic phase comprising mononitrotoluene with nitration acids, obtains the isomers comprising dinitrotoluene (DNT) and mix The reaction mixture of object,

D) reaction mixture of the isomer mixture comprising dinitrotoluene (DNT) is separated into: having comprising dinitrotoluene (DNT) Machine phase and water phase comprising sulfuric acid,

E) in multistep extraction, the organic phase comprising dinitrotoluene (DNT) is purified with water, each step in the multistep extraction All comprising mixing and mutually separating, the isomer mixture of the dinitrotoluene (DNT) comprising following (i)-(iii) is obtained, (i) 74-81 weight 2, the 4- dinitrotoluene (DNT) of %, 2, the 6- dinitrotoluene (DNT) of (ii) 17-21 weight % are measured, and (iii) less than 5.5 weight % dinitros 2,3- isomers, 2,5- isomers, 3, the 4- isomers and 3 of base toluene, 5- isomers, wherein (i), (ii) and (iii) it is total With the dinitrotoluene (DNT) for 100 weight %,

It reacts the isomer mixture of the dinitrotoluene (DNT) in the presence of a catalyst with hydrogen, forms toluene two Amine,

Wherein

(1) it is at least 4 minutes in each step that the multistep of step e) extracts for the mixed residence time, and is no more than 60 Minute, and

(2) at least in the final stage of the extraction of step e), also inert gas is introduced organic comprising dinitrotoluene (DNT) and water In phase mixture, the weight ratio of inert gas and dinitrotoluene (DNT) is: so that being counted on the basis of the mole of dinitrotoluene (DNT), institute The dinitro toluene isomers mixture of the purifying obtained, the carbon dioxide with physical dissolution or chemical bonding form always contain Amount is less than 0.175 mole %.

2. the method as described in claim 1, which is characterized in that in the purification step e), at least the one of multistep extraction There are alkaline waters in step, and there are neutral waters in an at least step for multistep extraction.

3. the method as described in claim 1, which is characterized in that the catalyst includes at least one nickeliferous catalyst.