DE2653641A1 - DIAZOTATION / COUPLING OF AROMATIC AMINES AND REGULATION OF THE NITROGEN OXIDE REACTIONS IN THE RESULTING EXHAUST GASES - Google Patents

Description

Patent attorneys:? R S 3 R A 1

Dr. ! ng. Waiter Abitz .

Dr. Dieter F. Morf *

Dr. Hans-Α. Browns

B Munich SG, Pienzünaaerstr. 28

25 November 1976 PI-0102

EGG. YOU Ρ01ΙΪ DE NEMOURS IM) COMPAM " Wilmington, Delaware / V.St.A.

Diazotization / coupling of aromatic amines and Regulation of the nitrogen dioxide reactions in the resulting exhaust gases

The invention "relates to the preparation of 1,3-diaryltriazenes (e.g. 1,3-Diphenyltriaaen) by diazotization / coupling of primary aromatic monoamines (e.g. aniline) as well as the regulation of nitrogen oxide reactions in the "bei exhaust gases resulting from the diazotization / capping reactions,

1,3-diaryltriazenes (also known as "diazoaminoaryl compounds" by heating, e.g. in the presence of an Eriedel-Crafts catalyst, to rearrange with formation aromatic aminoazo compounds. The latter compounds are obtained by reduction with water

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aromatic diamines, which in turn are used as starting compounds suitable for the synthesis of e.g. polymers or antioxidants.

According to US Pat. No. 2,894,942, aromatic aminoazo compounds are prepared by adding an inorganic nitrite to a mixture of an excess of a primary JLrylmonoamin, a mineral acid and a 3? Riedel-Crafts catalyst at a temperature of 0 to 50 ⁰ C ( preferably 20 to 30 ⁰ C) and the batch is then ^{heated to about 40 to 75 0} C (preferably 45 to 55 ⁰ C). Some of the amine is diazotized and the diazonium salt formed couples with unreacted amine to form the diazoaminoaryl compound, which rearranges to the aminoazo compound under the combined thermal-catalytic action. A disadvantage of this process, which is noticeable in industrial operation, is that the salt formed as a by-product during the diazotization (for example sodium chloride) has to be separated off and disposed of.

For at least a century, there have been publications from time to time showing the diazotization of describe primary aromatic amines with the help of certain nitrogen oxides. Griess reported, for example, in 1862 (Ann. 121, No. 3 »pages 257 to 280) about a synthesis of diazoaminobenzene, in which a so-called "weak stream of nitrous acid" into a cold, alcoholic aniline solution until the whole is used up. Aniline is initiated. Griess used the formula "NO," for the nitrous Acid, without describing the composition or origin of its diazotizing agent.

From US Pat. No. 2,622,078 it is known that the diazotization of aminoaromatic sulfonic acids to diazonium compounds in Carry out water / ketone mixing. Although according to this

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Patent a "nitrous gas" (described as NpCU or a mixture of Ή0 and NOp with an approximately ITpO, corresponding composition) is suitable for the reaction, the gas is introduced at 20 ⁰ C in a mixture of acetone or butanone, water and nitric acid and the amino compound is incorporated into the mixture, which is kept at a temperature of less than 35 ^° C. In addition, according to the patent mentioned, all of the amine is consumed for the synthesis of the diazonium compound, and the latter is not subjected to any coupling.

Lovejoy et al. describe in J. Chem. Soc. (A) (1968), pages 2325-2328 the preparation of a Diazoniumnitrits by reacting a primary aromatic amine with liquid, undissociated dinitrogen trioxide at -85 ⁰ C in an organic solvent, sometimes a small amount of diazoamino compound is isolated. However, the authors describe neither the effect of gaseous nitrogen trioxide on the amines nor the conditions which would be required for the synthesis of a diazoamino compound as the main product.

The diazotization of aromatic amines using NgCU gas in The absence of water (solvent) and the coupling of the diazo compound obtained, which also takes place in the absence of water with phenols or haphthols is disclosed in published Japanese patent application 15,631 / 61 (September 7, 1961).

Primary aromatic amines have also already been diazotized using pure nitrogen oxide in the presence of solvents. G.U. Witt, Tagbl. Catf.-Vers. Baden-Baden 1879, page 194 (Chem. Zentr. 1880, II, page 226) describes the production of benzene diaconium nitrate by converting pure, anhydrous nitrogen tetroxide with aniline in anhydrous

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Benzene solution; B. Houston et al., J. Am. Chem. Soe. 47 (1925), Pages 3011 to 3018 presented a diazoaminobenzene derivative as well as the corresponding diazonium nitrate by the action of pure, anhydrous nitrogen tetroxide on o-, m- and p-nitroaniline in anhydrous benzene solution.

The invention relates to a process for diazotization / Coupling of primary aromatic monoamines by means of a gas mixture containing nitrogen oxide obtained by oxidation of ammonia.

The inventive method "consists in that one after the other

(a) Ammonia using a dilute molecular oxygen containing gas (preferably air) oxidized, resulting in a gas mixture which is a dilute Nitric oxide component in the form of nitrogen dioxide (NOp) or a mixture of nitrogen dioxide and Contains nitrogen oxide, which has the formula HO (in which χ 1 + η, where η is the LTOg fraction of the nitrogen oxide component represents and generally has a value of 1.1 to 2.0), and

(b) the gas mixture - preferably at a temperature in the range of about 25 to 35O ⁰ C - (solvent or diluent free) with a preferably pure aromatic primary monoamine (e.g. "B aniline.) in the liquid phase in such a manner in contact brings, that (vorzugsv / else 40 to 60 ⁰ C) a monoamine temperature in the range of about 25 to 9O ⁰ C during the contact is established, by reacting at least about 5 wt retains .-% (preferably at least about 40 wt .- $) unreacted monoamine .

The accumulation of aromatic diazonium nitrate on any one Place of the reaction system is in the invention

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Procedure undesirable because it creates a risk of explosion can be. The excess monoamine contained in the reaction mixture enables the initially formed Diazonium nitrate immediately couples with the monoamine to form triazene »and thus prevents the accumulation of uncoupled Diazonium nitrate in the reaction mixture. In addition, there is a residual gas, which mainly consists of the diluent (usually nitrogen) of the oxygen-containing gas mixture used to produce the nitrogen oxide-containing gas mixture from ammonia Gas and possibly unreacted NO and unreacted oxygen as well as HpO, monoamine and 1,3-diaryltriazene Contains in the vapor phase, separated from the triazene-containing reaction liquid and passed through a pipeline transferred to an exhaust gas removal system under such conditions that there is no separation of aromatic Diazonium nitrate comes on the pipe walls.

Concerning the prevention of diazonium nitrate accumulation In the pipeline, the invention provides a method that can be used in any process for diazotization primary aromatic monoamine containing an unreacted monoamine and at least one nitric oxide Leaves residual gas, is applicable and consists in the fact that the residual gas under such conditions by a Pipeline transferred to an exhaust gas removal system that no deposition of aromatic diazonium nitrate to the Pipe walls due to

(a) the temperature of the walls (which is, for example, in the range from about 55 to 125 ⁰ C),

(b) the limited residence time of the gas in the pipeline, which depends on the speeds of the reactions, which must take place in the gas before the conditions for the diazonium salt formation are reached (for example on the rate of oxidation of nitric oxide to nitrogen dioxide when molecular oxygen is present is) or

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(c) the absence of nitrogen dioxide in the gas

he follows. In the present context, the term "residual gas" refers to the used gas originating from a gas / liquid reaction system and the vapor formed by the volatilization of a reaction liquid. The method according to the invention for regulating the conversion of the nitrogen oxides contained in the exhaust gas can be used in systems in which amines are diazotized by means of an inorganic urite and a mineral acid, whereby unreacted monoamine and at least one nitrogen oxide-containing vapors can get into the exhaust systems of the reaction vessels; see p. Έ. Filippuichev et al., Anilinokrasochnaya Prom. 3 "351 to 355" Chemical Abstracts 28, 3720. However, as will be explained in more detail below, the diazotization / coupling process according to the invention is preferable to conventional methods; the method for regulating the conversion of the exhaust gas nitrogen oxides can be used in a particularly advantageous manner in this process.

Diazotization / Coupling Process

Although the hot gases formed during ammonia oxidation have so far been in inorganic liquids - for example for Production of ammonium nitrite (US-PSs 2 797 144 and 2 805 122) and sodium nitrite (GB-PS 1 347 909) have been absorbed, there are naturally objections to the association in the professional world a primary aromatic mono * amine (i.e. a strong reducing agent) with that obtained by oxidation of ammonia obtained hot gas, since the controllability of the reactions between such substances appears doubtful. Surprisingly, however, it has been found that the reaction between the obtained by ammonia oxidation hot gas and an aromatic monoamine can be carried out in a smooth and controllable manner.

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In addition to the nitrogen oxide component, the gas mixture containing NO generated by the ammonia oxidation contains an inert diluent (eg nitrogen) and water vapor, the NO _x concentration usually being about 10 to 12 mol. This gas mixture can be brought into contact with the monoamine in unchanged form; this is the preferred mode of operation. Separation of water vapor from the reaction mixture before it comes into contact with the monoamine is of no advantage, although such a procedure is within the scope of the invention.

In order to achieve the highest possible 1,3-diaryltriazene yield, is preferably used in the process according to the invention

(1) Ν0 _χ with χ in the range from about 1.3 to 1.7 »

(2) such a proportion of the gas mixture contacted with the monoamine and a contact time dimensioned such that at least about 60% by weight of the monoamine remain unused, as well

(3) a temperature of the gas mixture immediately prior to its contact with the monoamine in the range of about 110-275 ⁰ C.

In the method according to the invention, ammonia gas and a dilute gas containing molecular oxygen (preferably air) passed over a catalyst at elevated temperature, whereby the NH is oxidized to nitrogen oxide (NO); ; the gas obtained, which is a mixture of nitrogen oxide, oxygen, water vapor and diluent (e.g. nitrogen) represents, is cooled, wherein the nitrogen oxide is completely or (preferably) partially oxidized to nitrogen dioxide (NOp) and a gas mixture is obtained, which nitrogen dioxide (preferably also nitrogen oxide), the diluent, Water vapor and - depending on the respective special

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conditions - possibly contains some residual oxygen. The nitrogen oxide component of the gas mixture, ie NO ₂ or NOg / NO, is given by the formula NO ₇ . reproduced, in which χ (1 + η) and generally has a value of about 1.1 to 2 (n is the NO «content of the nitrogen oxide component). Under the usual conditions, the ITO concentration of the gas mixture produced is about 10 to 12 mol- #. However, as will be explained in more detail below, the concentration can be adjusted to be within the range of about 1 to 20 moles or even up to about 30 moles. Such concentrations are suitable for the diazotization / coupling reaction.

The nitrogen oxide (s) used in the diazotization / coupling reaction is (are) thus in dilute form in the process according to the invention. The diazotization / clutch gas of this process differs as such significantly from that used in conventional diazotization pure N ₂ O, ^ ¹¹¹ ^ ^ 2 ^ 4 * was ^ ^unmenr found that the diazotization / coupling of primary aromatic monoamines by contact with the diluted NO gas mixtures generated by ammonia oxidation can be carried out.

JL.

The use of the diluted gas mixtures does not only have the Advantage that the diazotization gas is more readily available, but also ensures smoother, easier controllable implementation and therefore a reduction in the risk of yield losses caused by an uncontrolled Reaction at the gas / liquid interface. Also in contrast to the conventional nitrite / acid diazotization method In the process according to the invention, there are no salt by-products, which would require costly separation processes require.

The oxidation of ammonia and then of the nitrogen oxide obtained by air at elevated temperature with the formation of NO-

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containing gas mixtures according to the above definition is dealt with comprehensively in the literature. For the oxidation to nitrogen oxide, a platinum or platinum alloy catalyst and temperatures in the range from about 800 to 95O ⁰ C are generally used. Pressures from about atmospheric to 8 »16 atm (120 psiga) are used. Air enriched with oxygen can also be used. The ammonia content of the ammonia / air mixture is generally in the range from about 11 to 13 mol%, the oxygen / ammonia molar ratio in the range from about 1.3: 1 to 1.7: 1. For further details see Mellor's Comprehensive Treatise on Inorganic and Theoretical Chemistry, Vol. YIII, Erg. II, Chap. XXIX or Riegel's Handbook of Industrial Chemistry, 7th edition, Tan Nostrand (1974) »pages 94 bis

In contrast to the oxidation of ammonia, the oxidation of the nitrogen oxide takes place at a lower temperature, for example in the range from about 100 to 500 ^° C., since the rate of oxidation is higher at lower temperatures and higher pressures. The value for χ of the! ^ Component, which is a measure of the oxidation state of the nitrogen oxide component, can be varied by a suitable choice of the pressure, the temperature and the contact time of the gases in the NO oxidation device; the NOg content of the EO produced increases with the contact time. The contact time required to achieve a desired IK ^ fraction can be determined from the known oxidation rates at various temperatures and pressures.

The NO component can consist exclusively of NO «, however, preferably represents a combination of NOp and NO If NO consists only of NOp (i.e. if χ 2), the 1,3-diaryltriazene yield tends to be due to

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(1) Giner competing nitration reaction, soft im The case of aniline, for example, gives p- and o-nitroaniline, and

(2) a rearrangement of the triazenes to the aminoazo compound catalyzed by the nitric acid formed as a by-product

is decreased. Although the nitro and aminoazo products too are utilizable because they can be reduced to diamines is preferred in the diazotization / coupling stage as high a proportion of the monoamine as possible is converted into the triad, which is why a NO with χ <2 preferred

Jv

will. By suppressing the Formation of the aminoazo compounds during diazotization / Coupling will reduce the likelihood of by-product formation, which could subsequently cause problems is reduced.

The vert for χ in NO is at least about 1.1, preferred

X.

indicates * at least about 1.3. When the NO ^ proportion of the mixture decreases, more nitric oxide remains unconsumed, which results in less conversion to triazene. If the NOg content is very low, excessive amounts of unused nitric oxide must be handled, χ preferably has a value of at most about 1.7, so that there is no increased risk of surcharges, nitrations and / or oxidations, which subsequently occur, as mentioned, prove to be bothersome. With regard to a good utilization of the nitrogen oxide i the greatest possible suppression of secondary reactions t ^ n, a NO is particularly preferred in which χ in the vicinity of about 1.5 (50:50 NO ₂ / NO mixtures), for example in the range from about 1.4 to 1.6.

The Xo concentration of the gas mixture produced by air oxidation of nitrogen oxide is generally around 10 to 12

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and depends on the oxygen / ammonia molar ratio and the yield. Higher oxygen / ammonia ratios and yields are associated with higher NO concentrations. Theoretically, up to about $ 17> Ν0 _{χ can be} achieved. A range of about 1 to 20 mol # NO can be achieved, for example, by dilution or steam removal; Mixtures at such concentrations can be used in the diazotization / coupling stage. Mixtures with higher NO "concentrations (eg up to about 30 mol $) can be achieved by combining the 1 to 20 mol $ -containing mixtures with more concentrated mixtures; Such mixtures are also suitable for the diazotization / coupling stage. Concentrations greater than about 12 moles, however, are not preferred because of the added cost of achieving them and the loss of the beneficial effects of dilution on reaction control. Furthermore, no advantage is apparently achieved in the diazotization / coupling by diluting the mixture produced by the NO oxidation or separating off water vapor from this mixture, which is why the NO concentration range of 10 to 12 mol is preferred.

In the inventive process the temperature of the NO-containing gas mixture is immediately before its contact with the monoamine preferably in the range of about 25 to 35O ⁰ C, in particular 110-275 ⁰ C. When the mixture, which corresponds to the usually contains water vapor, prevents a gas temperature of at least about 110 ^° C., the condensation of water vapor from the gas and the associated formation of nitric acid, which catalyzes the rearrangement of the 1,3-diaryltriazene to the aminoazo compound. The oxidative degradation of the monoamine takes place above about 350 ° C. At such temperatures, it becomes more difficult to maintain higher oxidation states of the NO due to the increased rate of decomposition of nitrogen dioxide into nitrogen oxide and oxygen. Temperatures above about 275 ⁰ C are not

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preferred when working with exclusion of oxygen target; Another reason for this is that it is expensive Cooling measures must be taken to keep the 1min to maintain the required temperature range, as will be explained in more detail below. In the method according to the invention the monoamine for diazotization advantageously with a brought in contact with considerably hotter gas than was used in the conventional methods.

The diasotation / coupling temperature or the temperature at which the monoamine is kept during contact with the FO-containing gas mixture is in the range from about 25 to 90 ^° C., preferably from 40 to 60 ^° C., temperatures above about 9O ⁰ C due to the instability of the triazene and therefore not applied to be feared yield losses. The temperature used in the individual case depends on various factors. First, the temperature of the amine increases when it comes into contact with the hot ITO gas mixture due to the heat of reaction and the heat transferred from the hot gas to the amine. It is therefore expedient if the reaction temperature is close to that temperature which results from the aforementioned exothermic and heat transfer and which can easily be maintained by moderate cooling (for example water cooling).

The reaction temperature can also be chosen with a view to the solubility of the triazene and the amount of amine consumed. If a homogeneous product is desired, it can be advantageous to work at a temperature at which the triazene is soluble in the amine at the level of consumption or conversion of the process. 1,3 ~ Diphenyltriazene, for example, has sufficient solubility in aniline at 50 to 55 ° C. for the product to be homogeneous at the temperatures mentioned when about 20 to 40 % of the aniline has been consumed. If the amount used is more than 40 f ° , higher temperatures are

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doors required for homogeneity. In the diazotization / coupling of aniline, a temperature of about 50 "to 55 ^° C. is therefore particularly preferred for proportions used up to about 40 ° C., while higher temperatures are particularly preferred for higher amounts used (for example, amounts used of more than about 4-0 $ temperatures up to about 9O ⁰ C) particularly preferred.

In the diazotization / coupling reaction, low temperatures such as about 25 ^° C. can be used; In the case of aniline, the homogeneity can still be achieved at this temperature with a consumed portion of 20 fo . With regard to all factors to be taken into account, ie the yield, the ease with which the temperature can be maintained, the homogeneity of the product, etc., the temperature range from about 40 to 60 ^° C. is preferred.

The diazotization / coupling process runs at atmospheric pressure satisfactorily, although increased pressures can also be used. In the latter case one usually works at those pressures which are used in the oxidation of nitrogen oxide, for example at pressures up to about 8.4 kp / cm (about 120 psiga).

In the process according to the invention, the NO -containing gas mixture is brought into contact with an excess of the monoamine so that the initially formed diazonium salt (nitrite or nitrate) can immediately couple with unreacted monoamine to form a 1,3-diaryltriazene. "Excess" monoamine means that unused or unreacted monoamine is always present in the reaction mixture; at least about 5 io (preferably at least about 40 fo) of the monoamine remains in unconverted form. When the contact zwisehen NO and the reaction mixture is stopped at a time, non wherein at least about 5 f <> of monoamines

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"needs to lag behind, can be the enrichment of uncoupled Avoid diazonium nitrate in the reaction mixture.

The monoamine is made to react in the liquid phase. In the case of monoamines, which are liquid under the reaction conditions, no solvent or diluent is used needed. For economic reasons, the monoamines are preferably in "pure" form (without solvents or diluents) used. If the monoamine is solid under the reaction conditions, a solvent can be used for it; Examples of suitable solvents are aromatic hydrocarbons such as benzene or xylene and aliphatic Halogenated hydrocarbons such as carbon tetrachloride or methylene dichloride. By the simultaneous presence a liquid acting as a solvent or diluent (such as water) and a liquid monoamine does not affect implementation.

The reaction mixture should contain an amount of liquid sufficient for a stirrable slurry or suspension or solution to be formed with the solid triazene formed. Otherwise, even if there is an excess of monoamine, the diffusion of the gas through the reaction mixture can take place so slowly that the diazonium nitrate can collect on the surface of the solid triazene due to a reaction between the gas and the triazene. Therefore, in the case of an unused monoamine content of only 5 i °, an additional solvent is used to maintain stirrability. If higher proportions of unused monoamine are present, the required flowability of the reaction mixture with pure monoamine can be achieved by using higher reaction temperatures. The reaction product is preferably a homogeneous liquid; if pure monoamine is used »its unused remains is sufficient-

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the proportion therefore made to act as a solvent for the triazene to act.

Regardless of * whether pure, dissolved or diluted monoamine is used, is the contact between the NO gas and the reaction mixture always preferably interrupted at one point in time? wherein at least about 40 wt .- $ (preferably at least about 60 weight "- $) remain the monoamines unspent" The Triazenausbeute decreases due to a rearrangement abruptly _s when the unused monoamine proportion falls below a value of about 40 fo. Even with a reduction in the unused monoamine content below about 60 % , there can be a noticeable loss of yield. The proportion of unconsumed monoamine is preferably no more than about 85% in order to avoid the handling and reprocessing of excessively high volumes of materials having low triazene concentrations. When the process is carried out semi-continuously, the KO gas is incorporated into the monoamine and the addition is terminated when the predetermined monoamine consumption has been reached (which can be determined by analyzing the reaction mixture). In the case of a continuous procedure, the product stream is separated from the gas stream when the predetermined monoamine consumption - as can be determined by analyzing the product stream - has been reached.

The agitation or stirring of the reaction mixture has no noticeable influence on the course of the reaction as such, however, it promotes the distribution of the gas in the monoamine and good contact between the gas and the liquid phase.

The process according to the invention is suitable for diazotization / coupling of unsubstituted primary aromatic monoamines, such as aniline or α- or ß-Käphthylamin, and of

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primary aromatic monoamines with inert to RO Substituents, e.g. halogen atoms, nitro groups or alkyl, Haloalkyl or alkoxy radicals. The alkyl, haloalkyl and alkoxy substituents preferably have 1 to 4 carbon atoms on. Examples of suitable substituted monoamines are o- and m-toluidine, 2,3-, 2,5- »2,6- and 3,5-dimethylaniline, Trifluoromethylaniline, o- and m-chlorine -, - bromine and -fluoroaniline and the nitroanilines.

Regulation of nitrogen oxide conversion in the exhaust gas

The residual gas which is separated from the triazene-containing reaction liquid obtained in the aforementioned reaction consists mainly of the diluent present in the gas containing molecular oxygen used to produce the nitrogen oxide-containing gas mixture from ammonia. As the oxygen-containing gas as commonly used air, there is obtained in the diazotization / coupling reaction residual gas typically mainly of nitrogen and additionally contains small amounts of water, the monoamine, the 1,3-Diaryltriazens, _χ of non-umgesetζtem Ν0 and optionally oxygen. The water, monoamine and triazene content of the residual gas depends on the temperature and pressure in the reaction vessel. If the NO brought into contact with the monoamine is a mixture of nitrogen oxide and nitrogen dioxide, the unconverted NO in the residual gas usually consists only of NO. Unconverted NOp can occur in the residual gas if the Ν0 _χ NOp used and the extent of the gas / liquid contact in the reaction vessel is not sufficient for complete conversion of the NOp. The nitrogen oxide concentration in the residual gas depends on the oxidation state of the starting gas mixture, ie on the value of χ in the NO brought into contact with the monoamine; higher NO concentrations in the residual gas occur at lower values of χ. It was found that the NO concentration

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in the residual gas "at values in the range from 1.3 to 2.0 for χ of the ITO used varies from 0.07 "to 3.2 vol .- $. When χ in the NO used is 1.65, "is the NO concentration $ 0.44

It was found that primary aromatic monoamines, contrary to conventional teaching (cf., for example, RS Drago. Et al., J. Am. Chem. Soc. 83 (1961), pages 1819 Ms 1822) do not react with nitric oxide, and that A diazonium salt "only forms in the residual gas if the residual gas contains nitrogen dioxide. Although nitrogen dioxide, as mentioned, is generally not contained in the residual gas" when it is separated from the reaction liquid, ITOp can form if molecular oxygen and nitrogen oxide are present According to one embodiment of the process according to the invention, molecular oxygen is excluded from the residual gas by using an essentially oxygen-free, SO-containing gas mixture (ie a gas mixture containing less than about 500 ppm of oxygen) for the diazotization / coupling reaction the degree to which the nitrogen oxide contained in the residual gas can be oxidized to nitrogen dioxide due to the low oxygen level The concentration of the gas is reduced to a minimum. In order to achieve the practical absence of oxygen in the gas mixture used for the diazotization / coupling reaction, a gas mixture containing UH ^ / Op with an ammonia concentration as high as possible within the safe working range, e.g. of about 11 to 13 mol #. Further, in the nitrogen oxide oxidation sufficient to ensure a complete SäuerstoffVerbrauchs contact time is applied, and the temperature of the gas mixture produced is at atmospheric pressure not higher than about 275 ⁰ C. In this way, the possibility that the reverse reaction (ie, the

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Splitting of the nitrogen dioxide to nitrogen oxide and oxygen) can take place, largely eliminated.

In other embodiments of the method according to the invention, the residual gas contains molecular oxygen. The deposition of diazonium nitrate on the walls of the pipeline, through which the gas is transferred to a treatment system is avoided in these cases either by one

(a) limit the residence time of the gas in the pipeline so that the gas enters the disposal system (where, for example, the amine is separated from the gas or the gas is exposed to a high temperature gradient) before the diazonium nitrate can form, or by the fact that

(b) keeps the walls of the pipeline at a temperature at which the diazonium nitrate decomposition rate is at least as high as the diazonium nitrate formation rate (for example above about 50 ^° C. in the case of benzene diazonium nitrate).

The time elapsing before diazonium nitrate formation begins depends on the constituents of the gas and their concentrations as well as on the rates of conversion which must take place in the gas before the conditions for diazonium nitrate formation are reached. The earliest arises the diazonium nitrate in the rare case in which the residual gas is separated from the reaction liquid Contains nitrogen dioxide. The reason for this is that the nitrogen dioxide - alone or with the usually present Nitric oxide - quickly with the mono amine to 1,3-diaryltriazene, if the monoamine is present in excess, or to the diazonium nitrate when the nitrogen oxide (s) is present in excess (are) responded. Since the monoamine is consumed quickly,

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which results in an excess of nitric oxide (s), the diazonium nitrate quickly becomes the product of the monoamine / nitric oxide reaction. In this case, the diazonium nitrate can be deposited immediately on the pipe walls, so that measures must be taken to decompose the salt when it is formed, so that salt accumulation is avoided. If the tail gas contains in its separation from the reaction liquid nitrogen, the tube walls must daher.bei a temperature lying above the decomposition temperature of the Diazoniumnitrats (above about 50 ⁰ C in the case of Benzoldiazoniurrmitrat), for example at a temperature in the range of about 55-125 ⁰ C, to be held.

If the residual gas, when it is separated from the reaction liquid, contains molecular oxygen but no nitrogen dioxide, and therefore the nitrogen dioxide contained in the gas flowing through the pipeline comes from the nitrogen oxide / oxygen reaction in the gas, the accumulation of diazonium nitrate can be reduced by regulating the residence time of the gas in prevent the line. The conversion of the nitrogen oxide with the oxygen takes place slowly in relation to the reaction of the amine which results in the diazonium salt or the triazene; No diazonium nitrate separation can take place for a few seconds, the exact time depending on the conditions prevailing in the pipeline. For example, if a 1-fo Yol. nitric oxide, 3 vol .- $ oxygen and 0.5 vol jS aniline-containing residual gas at 50 ⁰ C and one atmosphere by flowing · an exhaust pipe with a wall temperature of 25 to 55 ⁰ C, is carried out the deposition of the benzene diazonium nitrate on the walls after about 5 seconds. In this case, the method according to the invention can therefore be implemented by limiting the residence time of the gas in the line to a maximum of about 4 seconds. The higher the pressure of the gas or the higher the nitrogen oxide or oxygen concentration, the more

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The residence time required to prevent the diazonium nitrate deposition is shorter. Under the aforementioned conditions, the maximum residence time should be reduced, for example, to 2 seconds if the nitrogen oxide concentration is increased to 1.5 °.

It can be achieved that aromatic diazonium nitrates are immediately subject to a smooth thermal decomposition when they are formed in the exhaust gas line if the pipe walls are heated to a temperature above the decomposition temperature of the nitrate the pipeline for the Diazoniumnitratbildung sufficient, the tube walls in the present process are thus maintained above the Kitratzersetzungstemperatur. carried out at a minimum wall temperature, which ensures the immediate decomposition of the entstehbaren certain diazonium salt "means in the case of Benzoldiäzoniumnitrat at about 55 ⁰ C · the maximum temperature depends mainly on the thermal behavior of the other substances contained in the exhaust gas (eg the triazene) and on economic considerations. Taking these factors into account, the wall temperature is generally in the range from about 55 to 125 ^° C., with de r range of about
is preferred.

rich from about 55 to 75 ⁰ C in the case of benzene diaconium nitrate

In a preferred embodiment of a method according to the invention, in which the residual gas contains oxygen, the tube walls are heated in the manner described, and the residence time of the gas in the line is limited in the manner described. This means an accumulation of hatreds to prevent diazonium nitrate accumulation in the pipeline, which - as mentioned - represents a potential source of danger. Of course, you can take either or both of these measures even if that

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Residual gas contains less than 500 ppm oxygen, especially at higher pressures and NO concentrations in the residual gas and oxygen concentrations around 500 ppm. At an oxygen concentration of around 200 ppm, more than 17 seconds can pass before the diazonium nitrate deposition if the ΪΓΟ-Κοη concentration is 2 <fo and the pressure is 0.3 atm (5 psiga). In such an IPaIIe there is generally no need to take any measures which reduce the residence time to a value which is below the level normally prevailing in exhaust pipes. In the case of other combinations of gas concentrations and pressure, use can, however, be made of regulating the residence time and / or the wall temperature.

The following examples are intended to explain the invention in more detail without, however, restricting it.

example

A gas mixture consisting of 4.5 mol-f NO, 6.8 Mbl-ji NO ₂ , 68.8 mol-56 nitrogen and 19.9 mol- $ water vapor (110 concentration = 11.3 mol- ^ j χ) is produced = 1.6) by creating an ammonia / air mixture with a content of 12.1 mol% ammonia, 18.1 mol% oxygen and 1.7 mol% water vapor (from the ambient air) at one pressure of 8.16 atm (120 psi) passes over a ^{heated to 900 0} G mesh catalyst made of a platinum / rhodium alloy (10 $ Rh). and the resulting gas mixture is cooled to 200 ° C and held approximately at the pressure mentioned. Under these conditions, all of the oxygen is consumed within about 3 seconds.

132.4 g of aniline are placed in a 150 ml glass reactor at room temperature entered, which is equipped with a stirrer, external cooling jacket, a heating system (opening near the bottom of the reactor)

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ten sidearm gas inlet capillary tube, a thermocouple and a 150 mm long, water-cooled condenser or capacitor connected, 150 mm long upper Outlet pipe is fitted.

The aforementioned gas mixture is then introduced at an average temperature of 200 ^° C. (175 to 225 ^° C.) and a pressure of 1 atm through the heated gas inlet tube with a throughput of 342 ml / min, into the room temperature aniline. While the gas is being fed in, the aniline is stirred at a speed of about 2000 rpm. The mass temperature of the aniline increases to 45 to 50 ⁰ C; it is kept in this area by air cooling. Exit the reactor through the outlet tube and condenser at a rate of 274 ml / min. Exhaust gases (0.5 to 0.7 vol .- $ NO, no NO ₂ and no oxygen) which are released into the atmosphere. The residence time in the held at 25 ⁰ C and condenser outlet tube is about 11 seconds. No separation of benzene diazonium nitrate is found in the exhaust pipe.

After 180 minutes, the gas flow is interrupted, the reaction mixture is ^{allowed to cool to 30 °} C. and the organic layer is separated off from the aqueous layer. The organic layer (133 »2 g) has the following composition after neutralization: 19» 8% by weight 1,3-diphenyltriazene, 1.63% by weight p-aminoazobenzene, 0.121% by weight o-aminoazobenzene, 0 * 177% by weight of o-, m- and p-aminodiphenyl, 0.086% by weight of HNO, 1.9% by weight of HpO and 73 »1% by weight of aniline. If the total attributable organic products are taken into account, 21.7% of the aniline was converted into products after 180 minutes. On this basis, the yield of 1,3-diphenyltriazene is 91 »1 S ^ (weight of the triazenes divided by the weight of the total attributable, aniline-derived pesticides).

If in the aforementioned process 0- or m-toluidine instead

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■ of aniline is used, is obtained while achieving the corresponding Results 1 »3-o-" or 1,3-m-tolyltriazene.

example

The process of Example 1 is repeated with the exception that the mass temperature of the aniline is kept "at 25 ^° C. by water cooling. The weight of the organic layer obtained" in this case is 139.8 g. Based on a degree of aniline conversion of $ 20.3, the following yields are obtained: 96 * 1 $> 1,3-diphenyltriasene, 3 »8 % p-aminoazobenzene and 0.26 % o-aminoazobenzene. The exhaust gas contains at 25 ⁰ C 0.5 to 7? ° NO, nitrogen, aniline and water (no UO ₂ and no oxygen). During the 11 sec. Residence time lengths having wall of the outlet tube is detected and no capacitor Benzoldiazoniumnitratabscheidung at a temperature of 25 ⁰ C.

example

The procedure of Example 1 is repeated with the exception that a 300 ml reactor and a gas mixture of 10 mol $ NO ₂ and 90 mol $ nitrogen are used. This gas mixture is obtained when the ammonia concentration is 10.7 mol- $ and the oxygen concentration is 18.1 mol- $ and the water vapor is then separated from the product gas. In this case, the gas mixture is introduced ^{into the aniline (199.5 g) at 25 °} C. with a throughput of 375 ml / min. The mass temperature of the aniline increases to 35 ° C. After 204 minutes, the gas flow is interrupted. The weight of the organic layer obtained is 206.7 g. Relative to an aniline conversion efficiency of 16.4 ° i following yields are obtained: 42.4 # 1.3 Diphenyltriazen, 31 '6 $> p-aminoazobenzene, 16.3 $ p-nitroaniline and 9 "9 i ° o-nitroaniline . the

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pi-0102 2 6536 A 1

Exhaust gases (nitrogen, 700 ppm NOP, aniline, water vapor, no oxygen) are cooled in the condenser for condensing the vaporous aniline and triazene at 10 ⁰ C and then discharged. The residence time in the exhaust gas line, which is kept ^{at about 15 ° C., is 8.5 seconds.} No diazonium nitrate deposition is observed.

example

The procedure of Example 1 is repeated with the exception that a gas mixture of 5 »7 mol- £ 10, 5» 7 mol-% FO ₂ , 20.5 mol- $ water vapor and 68.1 mol- ^ nitrogen used. This mixture is obtained when the starting gas has an ammonia content of 12.6 $ and an oxygen content of 18 <p . In this case, the gas mixture is introduced ^{into the aniline (120 g) at an average temperature of 200 °} C. (175 to 225 ^° C.) with a throughput of 750 ml / min. The mass temperature of the aniline rises to 50 ° C. The gas supply is interrupted after 90 minutes. Based on a Anilinuinwandlungsgrad of 31 »$ 3 the following yields are obtained: 90.4% 1,3-Diphenyltriazen, 7» 9% p-aminoazobenzene, 0.49 i ° o-aminoazobenzene, 0.20 $ p-nitroaniline and 0 , 15 $ o-nitroaniline.

example

The procedure of Example 1 is repeated with the exception that a gas mixture of 7 »4 mol _{% HO, 3» 6 mol% UO 2} and 89 mol% nitrogen is used. This mixture is obtained if a starting gas with an ammonia content of 13 × 7 $ and an oxygen content of 17 × 8 5ε is used in the ammonia oxidation and the water vapor is then separated off from the product gas. In this 3? All, the gas mixture is at an average temperature of 200 ⁰ C (175 to 225 ⁰ C) with

- 24 709823/1033

a throughput of 150 ml / min, introduced into a mixture of 66.5 g aniline and 3 * 5 g nitrobenzene (internal standard). The batch is kept at a temperature of 50 to 55 ^° C. After 121 min. interrupted The weight of the organic layer obtained is 68.1 g. Based on an aniline conversion factor of 12.6%, a 1,3-diphenyltriazene yield of 96.8 $ and a p-aminoazobenzene yield of 3.7 $ scored.

example

69.9 g of aniline are placed in a 150 ml glass reactor at room temperature entered, the side arm gas heated with an outer cooling jacket, two (opening near the reactor bottom) inlet capillary tubes, a thermocouple and a 150 mm long, water-cooled condenser.

An existing from 5.4 $> NO _2, 2.9 $ "NO, water vapor, and 17 # 74.7 & nitrogen gas mixture is at a Durchschnittst emperature from 200 ⁰ C (175" to 225 ⁰ C) and a pressure of 1 atm through one of the heated gas inlet tubes with a throughput of 150 ml / min, into the aniline kept at room temperature. Through the second heated gas inlet tube, a second, from 31 ° oxygen and 97 °, is passed through the second heated gas inlet tube with a throughput of 125 ml / min $> nitrogen gas mixture consisting at an average temperature of 200 ⁰ C and a pressure of 1 atm in the aniline a. in this manner will result in a final composition of 2.9 ° i NO ₂ * 1.6 <? o NO, 9.1 1 ° water vapor, 1.4 # O ₂ and 85 # nitrogen. This mixture simulates a gas which has been generated by ammonia oxidation according to the method according to the invention and subsequent dilution with nitrogen up to an NO concentration of 4.5 % is. During the gas

- 25 709823/1033

The aniline feed is stirred at a speed of about 100 rpm. The batch heats up to 45 to 50 ^° C .; this temperature range is maintained by air cooling.

After 211 minutes, the gas supply is interrupted. The weight of the organic layer obtained is 68.2 g. Relative to an aniline conversion efficiency of 24 "8 fo the following yields are obtained: 76.6 <fo 1.3 Diphenyltriazen, 19.3 ° f p-aminoazobenzene, 1.6 $> o-aminoazobenzene, 1.5 ^ p-nitroaniline and 10 o -nitroaniline.

The exhaust gas contains 0.5 "Vol- $ NO and 1.4 Vol- ^ oxygen. During the residence time of the gas in the exhaust pipe, which is about 9 seconds, no benzene diazonium nitrate is deposited on the walls which are kept ^{at 25 ° C.}

example

The process according to the invention is carried out continuously as follows:

(a) Gas mixture containing nitrogen oxide

Nitric oxide and air are at an overpressure of 5> 4 atm (79 psig) with a throughput of 3.31 and 4 »10 l / min. (0.117 to 0.145 standard ft ⁵ / min.) Into a tubular reactor. A sufficient dwell time is provided so that 95 to 97 # of the oxygen supplied is converted, and NO _x is produced in which χ has a value of 1.5. The product gas is heated nitrogen with a throughput of 23 l / min. Slammed (0.82 standard ft ⁵ / min); of the final gas stream contains then 10.8 Mo1- $ NO (at a temperature of 74 ⁰ C) and less als'0,14 mole # residual oxygen. This mixture of gases (with the exception of water) creates that mixture

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"which would be produced by combustion of 12.3 $ ammonia in air with a relative humidity of 80 fi at 3O ⁰ C simulated.

(b) aniline / NO reaction

Aniline and water (the latter in the amount that would be present in the gas obtained by ammonia oxidation described under (a)) are converted into a vapor with throughputs of 110 ml / min and 4.6 ml / min, respectively, via a water-cooled condenser / Liquid separation device, which has devices for continuous drainage or suction, introduced. The solution of 1,3-diphenyltriazene in aniline obtained as a reaction product and the gases formed in the tubular reactor also reach the separating device, from which liquid is continuously withdrawn to maintain a constant level. Part of the withdrawn liquid is recovered, while another part ^{is returned to the tubular reactor through a cooler to maintain a temperature of 40 to 50 0} O with a throughput of about 2300 ml / min.

The nitrogen-containing NO stream generated according to (a) is passed through the reactor simultaneously with the recirculated aniline solution stream. The product (liquid and gas) is transferred to the separation device in the manner described above. The gas is cooled to 16 ^° C. in the condenser, the vaporous aniline and 1,3-diphenyltriazene condensing, and then drained off. The analysis of the exhaust gas shows 1.34 ° NO and no NO ₅ (NO consumption 90 ■ #).

During an operating period of 6 hours 7 minutes, the analysis of periodically taken samples reveals the presence of 19 wt .- # 1,3-diphenyltriazene, 1.2 wt .-% p-amino

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PI-0102

azobenzene and 0.05 wt% aminodiphenylene. The proportion of unreacted aniline "is 76% . On this basis, a 1,3-diphenyltriazene yield of 93 % is achieved.

Example 8

Part of the rose gas stream from a plant serving for nitric acid synthesis for a technical ammonia oxidation process (AOP plant) is continuously withdrawn and reacted with aniline within 155 minutes. In the AOP system is an ammonia / air Geinisch that to 11.6 Μο1-5δ NH, contains due to the regular analysis 11.4 catalytically atm at about 900 ⁰ C and a pressure of from 8.5 (125 psig) Burned over a platinum network catalyst to nitrogen oxide, water vapor, a certain amount (3 V0I-5 &) of unconverted oxygen and nitrous gas containing nitrogen as the remainder. At one point in the AOP system, where the gas was cooled to about 54O ° C., a flow rate of the gas with a throughput of 63> 6 kg / h. (HO lbs / hour) drawn off via a pipeline. The gas is transferred to a heat exchanger where it is cooled within about 1.5 sec. At 190 ⁰ C, and then fed into a tubular reactor, where the recycled aniline solution es.mit at a throughput of 95 ltr./min. (25 gallons / min.). The outlet of the tubular reactor opens into a gas / liquid separating device which is set up for continuous discharge. The solution of 1,3-diphenyltriazene in aniline obtained as a reaction product and the gases generated in the reactor reach the separating device, from which liquid is continuously withdrawn. Fresh aniline is conjoined to the liquid stream withdrawn from the separating device at a throughput of 216 kg / hour. (480 lbs / hour) struck. The product solution is continuously withdrawn so that the material inventory in the reactor and in the separating device remains constant

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pi-0102 ^ ₅ . 26536 A1

Part of the withdrawn liquid is recovered, while another part is returned to the reactor via a cooler (to remove the heat of reaction from the system and to maintain a temperature of 50 to 55 ^° C. in the reactor and in the separating device). the temperature at the tubular reactor inlet is 47 to 50 ⁰ C; the pressure at the reactor inlet 2.4 atm (35 psig) and at the outlet (in the gas / liquid separator) is 0.3 atm (4 psig) the tubular reactor has a volume. of 52 liters (0.186 ft). A liquid supply of about 11 liters (3 gallons) is maintained in the separator (the total volume of which is approximately 45 liters (12 gallons)).

The analysis values of samples of the product solution are shown in the table below. The yield of 1,3-diphenyltriazene, based on aniline, is 89 ° ß> (conversion of aniline to 17% ).

G-ew. -

1,3-diphenyl triazene 16.3 p-aminoazobenzene 1.77 o-aminoazobenzene 0.16 Amino diphenyls 0.07

The exhaust gas exiting the separation apparatus (50 to 55 ⁰ C) containing nitrogen, 0.4 VoIs- NO ^, 3 vol .- $ oxygen, water vapor and aniline (no Itog). The gas flows at a pressure of 0.3 atm (4 psiga) through an exhaust pipe (wall temperature 60 ⁰ C, residence time of 0.05 to 0.1 sec.) In a water scrubber, by the aniline is separated off. No deposition of benzene diazonium nitrate is observed.

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709823/1033

Comparison test

If the abovementioned exhaust gas contains 1 $ NO which has a temperature of 25 ^° C. and the pressure is 1 atm, benzene diazonium nitrate is deposited within 5 seconds. Even if the exhaust gas leaving the separating device has a temperature of 25 ^° C., benzene diazonium nitrate is deposited on the wall of the exhaust gas line within 5 seconds.

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Claims (1)

EGG. DU P (MD DS UEMOURS MD COMPANY PI-0102 Claims Process for the diazotization of a primary aromatic monoamine and coupling of the diazonium salt formed with it unreacted monoamine to form a 1,3-diaryltriazene, characterized in that one successively (a) Ammonia catalytically into a gas mixture with the aid of a dilute gas containing molecular oxygen oxidized, which contains diluted NO, where NO is one of nitrogen dioxide (N0 ") or a mixture represents nitrogen oxide component consisting of nitrogen dioxide and nitrogen oxide and χ is (1 + η), where η is the NOp content of the nitrogen oxide component, and (b) in such a manner bringing the gas mixture in the liquid phase with a primary aromatic monoamine in contact that is established during contact a monoamine temperature in the range of about 25 to 90 ⁰ C, for at least about 5 weight Jo unreacted monoamine be maintained . Process according to Claim 1, characterized in that a residual gas is separated off from the triazene-containing reaction liquid and under such conditions transferred through a pipeline into an exhaust gas removal system that no separation - 31 - 709823/1033 PI-0102 7653641 Aromatic diazonium nitrate is formed on the walls of the pipeline. 3. The method according to claim 2, characterized in that the pipe walls have an elevated temperature, the The residence time of the gas in the pipeline is limited and / or the gas is free of nitrogen dioxide. 4. Process for the preparation of a 1,3-diaryltriazene by Contacting an excess of a primary aromatic monoamines in the liquid phase with a diazotizing agent for this and separation of a residual gas of the triazene-containing reaction liquid, characterized in that that the residual gas under such conditions through a pipeline into an exhaust gas removal system transferred that on the walls of the pipeline due to the temperature of these walls, the limited residence time of the Gas in the pipeline or the absence of nitrogen dioxide in the gas no separation of aromatic Diazoniuran nitrate takes place. 5. The method according to claim 3 or 4, characterized in that that the residual gas, as it is separated from the reaction liquid, contains nitrogen dioxide, and that the Walls of the pipeline at a temperature in the range of holds around 55 to 125 ° C. 6. The method according to claim 3 or 4, characterized in that the residual gas as separated from the reaction liquid contains nitric oxide as well as practically no nitrogen dioxide and practically no molecular oxygen. 7. The method according to claim 3 or 4, characterized in that the residual gas as separated from the reaction liquid becomes, nitric oxide, molecular oxygen and practical - 32 709823/1033 contains no nitrogen dioxide, and that the walls of the pipeline at a temperature in the range of about 55 holds up to 125 ° C. 8. The method according to claim 3 or 4, characterized in that that the residual gas, as it is separated from the reaction liquid, nitrogen oxide, molecular oxygen and practically contains no nitrogen dioxide, and that the residence time of the gas in the pipeline is up to about 4 seconds . 9. Procedure according to. Claim. 7, characterized in that one uses aniline as the primary aromatic monoamine and that said temperature is in the range of about 55 Ms 75 ° C. 10. The method according to claim 6, characterized in that the 1,3-diaryltriazene by Infteruhrunghaben the mono- amines with a practically oxygen-free gas mixture, vrelches by catalytic ^ oxidation of ammonia with a gas containing molecular oxygen and a mixture of nitrogen dioxide and nitric oxide represents. 11. Process for the preparation of a 1,3-diaryltriazene by contact ungTaring an excess of a primary aromatic Monoamine in the liquid phase with a gas mixture, which by catalytic oxidation of ammonia with a diluted molecular oxygen-containing gas and one of nitrogen dioxide or a mixture of Contains nitrogen dioxide and nitrogen oxide, the diluted nitrogen oxide component, and separation of a residual gas of the triazene-containing reaction liquid, thereby characterized in that the residual gas through a pipe, the walls of which at a temperature in the range of about 55 to 125 ° C are held, transferred to an exhaust gas removal system . - 33 709823 / 1.0 33 PI-0102 12. The method according to claim 11, characterized in that the residence time of the gas in the pipeline is up to about 4 seconds. 13 · Method according to claim 11, characterized in that the residual gas as it is separated from the reaction liquid, nitrogen oxide, molecular oxygen and practically does not contain nitrogen dioxide. 14. The method according to claim 1, characterized in that a primary aromatic monoamine is used which is unsubstituted or has at least one substituent which is inert towards NO. 15. The method according to claim 14, characterized in that the primary aromatic monoamine is an unsubstituted, alkyl-substituted or halogen-substituted aniline or naphthylamine is used. 16. The method according to claim 1, characterized in that the ammonia is ^{oxidized at a temperature in the range from 800 to 95O 0} C and the gas obtained is cooled to a temperature below about 500 C to produce the gas mixture. 17. The method according to claim l6, characterized in that air is used as the dilute molecular oxygen-containing gas, and the NO _x content of the gas mixture is about 10 to 12 mol-i and χ in the range of about 1.1 to 2.0 lies. 18. The method according to claim 17, characterized in that the nitrogen oxide component is a mixture of nitrogen dioxide and represents nitric oxide. - 34 - 709823/1033 19 · Method according to claim 18, characterized in that χ ranges from about 1.3 to 1.7. 20. The method according to claim 19 _9, characterized in that
that the gas mixture immediately before its contact with
comprising the monoamine a temperature in the range of about 25 "to 35O ⁰ C. 21. The method according to claim 20, characterized in that the monoamine during its contact with the gas mixture at a temperature in the range of about 40 to
60 ⁰ C holds. 22. The method according to claim 20, characterized by bringing such a proportion of the gas mixture with the monoamine in contact and such contact time dimensioned applies that at least about 40 wt -.% Remain unreacted monoamine. 23. The method according to claim 20, characterized in that the gas mixture is brought into contact with pure (solvent- or diluent-free) monoamine. 24. The method according to claim 23 _3, characterized in that such a proportion of the gas mixture is brought into contact with the monoamine and a contact time is applied such that at least about 60 wt .- # unused monoamine remain. 25. Process for the diazotization of aniline and coupling des
thereby formed diazonium salt with unreacted
Aniline to 1,3-diphenyltriazene, characterized in that
that one after the other - 35 - 709823/1033 PI-0102 (a) Ammonia is oxidized catalytically with the aid of air to a gas mixture which contains dilute NO, where NO is a nitrogen oxide component consisting of a mixture of nitrogen dioxide (NO ») and nitrogen oxide and χ is (1 + η), where η is NO ₂ -Content of the nitrogen oxide component and is in the range of about 1.3 to 1.7, and wherein the NO content of the gas mixture is about 10 to 12 % , and (b) the gas mixture at a temperature in the range of about 25 to 35O ° C in the liquid phase with aniline in such a way that an aniline temperature in the range of about 25 to 90 C is established during the contact, while at least about 40 wt -% of unused aniline remain. 26. The method according to claim 25, characterized in that the gas mixture is brought into contact with pure (solvent-free or diluent-free) aniline and that such a proportion of the gas mixture is brought into contact with the aniline and a contact time dimensioned in this way is used, that at least about 60% by weight of unused aniline remain. 709823/1033