WO2009011665A1

WO2009011665A1 - Method of diphenylamine production from aniline catalyzed by fluoroborates

Info

Publication number: WO2009011665A1
Application number: PCT/SK2008/050012
Authority: WO
Inventors: Jan Uhlar; Milan Kralik; Viera Andruskova; Jaroslav Horak; Oto Seitz; Jozef Mrllak
Original assignee: Duslo, A.S.
Priority date: 2007-07-13
Filing date: 2008-07-11
Publication date: 2009-01-22
Also published as: SK500072007A3

Abstract

The invention concerns a method of diphenylamine production from aniline by a continuous procedure in liquid phase catalysed by thermolabile compounds of fluorine with boron which convert under conditions of diphenylamine formation from aniline to NH4BF4. NH4BF4crystals arising in the reaction medium of the reactor are maintained in uplift during a time,which is at least so long as the dwell time of aniline in the reactor. The maintaining in uplift is ensured by circulation stirring of the reaction mixture with a stirrer of minimum volume-rate of 0.1-multiple ofthe reaction mixture volume per hourand it is realized by mechanical stirring providing turbulent axial-radial flow of the reaction mixture in the reactor. An input overheated water steam is supplied countercurrentlyto the catalyst into the reactor withpressure higher than the sum of saturated vapour tension of the reaction mixture at the working temperature and hydrostatic pressure of the reaction mixture. Aninput reactant aniline is supplied into the reactor countercurrently to the catalyst input with such speed which ensures at least the same residence time of the catalyst in uplift as is the residence time of aniline in the reactor.

Description

Method of diphenylamine production from aniline catalyzed by fluoroborates

Technical Field

The invention concerns a method of diphenylamine production from aniline catalyzed by fluoroborates as an intermediate product of production of antidegradants for rubber, plastics, fuels and lubricants.

Background Art

Many papers have paid attention to compounds, nature of which consists in a complex containing boron and fluorine. Their utilization as catalysts of the synthesis of diphenylamine from aniline is the subject-matter of several patents (Vanier R., Pulvin G., Solianine A.: Co Francaise demateries Colorantes; DE patent application 1 ,116.231 ; Vanier R., Pulvin G., Solianine A.: Co Francaise demateries Colorantes; FR patent 1 ,231.215; Shozo Y., Eiichi G.: Honschu Chem. Co; JP patent 61 16 620; Kehe H.J., Johnson R.T., Driscol W.J.: Goodrich Co; US patent 3,071.619; GB patent 883.084; Vdovin N. M., Vdovin S.N. Safin R.S.: Azot Kemerovo, ZSSR; DE laid-open patent application 2,503.660; CS AO 173.389; Pasek J., Rezabek A.: Difenylamin (Diphenylamine, DPA), Documentation for PU, VUOT at CHZJD Bratislava /1976/; Vdovin N. M., Vdovin S.N. Safin R.S.: SU patent 411.743; Fischer H. M., Bauer D., Qvast H.: Bayer AG/DE laid-open patent application 2,521.293; Timokhin G.A., Kissin B.I., Feskhina N. N., Kurakin E. N.: US patent 547.224) from the period of sixtieth to eightieth years of the past century.

Fluoroborates are obtained by synthesis from the components containing boron (H₃BO₃, B₂O₃) and fluorine (HF, NH₄F, NH₄HF₂), or also directly from BF₃, NH₃, H₂O, or they are formed from these components directly in the process of DPA synthesis. Their composition may be represented by the general formula R⁺[BF_x/OH/_4-χ]^", where R = H⁺, NH₄ ⁺, C₆H₅NH₃ ⁺

Compounds of the type X. BF₃, where X = NH₃, CeH₅NH₂, H₂O, have been also used as catalysts. Compounds of the type R¹R²OB₄Fi₂, where R¹ = NH₄ ⁺ and R² = CeH₅NH₃ ⁺, while R¹ cannot be identical with R², are mentioned in several patents, too. However, these data have been inconsistently commented in other literature (Ryss, J. G., Bogdanova L. P.: Z. Neorg. Chim. 5, 1028-35 /1960/; Swinehardt R.: US patent 2,148.514 /1939/; US patent 2,196.907 /1940/).

Depending on the conditions and composition of the reacting system, individual components of the set of catalysts containing boron and fluorine may undergo a transition into other ones. So the complexes NH₃. BF₃, NH₄BF₃OH, as well as /NH₄/₂B₃O₃F₄OH, form at temperatures over 120 ⁰C NH₄BF₄ (Ryss, J. G., Bogdanova L. P.: Z. Neorg. Chim. 5, 1028-35 /1960/) as the typical catalyst of this type, while yet further components of this system are formed.

Catalysts of the type RVBF₄/^", where R = H⁺, NH₄ ⁺, C₆H₅NH₃ ⁺, which belong to the most active ones, are characterized by their stability under reaction conditions. Other variants of fluoroborate catalysts, for example R-BF_x/OH/_4-x, where x < 4, are in the process of DPA synthesis probably transformed into this stable active type, R⁺[BF₄] (Ryss, J. G., Bogdanova L. P.: Z. Neorg. Chim. 5, 1028- 35 /1960/).

Synthesis of DPA from aniline had been performed in the temperature range of 175 to 450 ⁰C and at such pressures (up to 5 MPa) so that the reaction took place in liquid phase. Concentration of catalysts reached relatively high values, up to 20 weight %, relating to aniline (Kehe H.J., Johnson R.T., Driscol W.J.: /Goodrich Co/ US patent 3,071.619 /1.1.1963/, British patent 883.084 /15.3.1959/).

An increase in aniline conversion can be achieved with shifting the reaction equilibrium by removing ammonia, either by its direct removing from the reaction system through a dephlegmator or by means of supplying an inert gas (for example: dry nitrogen): Vanier R., Pulvin G., Solianine A.: /Co Francaise demateries Colorantes/ NSR patent 1 ,116.231 /8.4.1961/, Vanier R., Pulvin G., Solianine A.: /Co Francaise demateries Colorantes/ French patent 1 ,231.215 /10.4.1959/. In this way the aniline conversion can be increased from 20 % for example even up to 50 %.

The progress of the DPA synthesis from aniline is considerably influenced by the presence of water, either in the form of humidity in the charged aniline or introduced into the reaction system in another way. Its concentration is variable, it may be up to 6 weight %, relating to aniline (Fischer H. M., Bauer D., Qvast H.: /Bayer AG/ NSR patent 2,521.293 / 18.11.1976/), this corresponding to the amount of water dissolved in aniline already at the temperature of 90 ⁰C (Pasek J., Rezabek A.: Difenylamin (Diphenylamine), Documentation for PU, VUOT at

CHZJD Bratislava /1976/). Such concentration of water relating to aniline allows dissolving the catalyst in water (Vdovin N. M., Vdovin S.N. Safin R. S.: /Azot

Kemerovo ZSSR / NSR patent 2,503.660 /5.8.1976/ CSSR author's certificate

173.389 /1975/). Positive influence of water probably consists in supporting ionization of the catalyst of RBF₄ type or in acceleration of formation of thermally more labile intermediate products, for example NH₄BFsOH as follows:

NH₃BF₃ + H₂O → NH₄BF₃OH

4 NH₄BF₃OH → 3 NH₄BF₄ + NH₃ + H₂O + H₃BO₃

(Ryss, J. G., Bogdanova L.P.: Z. Neorg. Chim. 5, 1028-35 /1960/).

The achieved increase in aniline conversion to DPA by adding water to the reaction system is in average 10 % (Fischer H. M., Bauer D., Qvast H.: /Bayer AG/ NSR patent 2,521.293 / 18.11.1976/).

From the technical point of view, method of dosing the catalyst into reaction system is important. If ammonia salt or complex is used as catalyst, this is insufficiently soluble in aniline under the dosing conditions, which causes complications in the continuous production method. As a certain solution, there appears the use of suitable solvent, for example water or aniline, whereby reaction speed is increased, but simultaneously corrosion of the production facility is supported.

In interrelation with the trend of fluoroborate application as catalysts of DPA production, VUCHT Bratislava in cooperation with CHTF-STU Bratislava and Duslo Sal'a became involved in the problem of DPA preparation already in the seventieths of the last century (see for example among others CS AO 188809 /05.08.1977/; 192322 /09.03.1989/; 208303 /15.10.1979/; 200448 /23.11.1978/; 206244 /15.10.1979/; 218720 /30.07.1980/ and 280701). Positive influence of rising atomic ratio of fluorine to boron in starting raw materials on the formation of tetrafluoroborate anion was assumed. The catalysts were prepared from NH₄HF₂ and H₃BO₃.

Prepared catalysts were subsequently checked in discontinuous DPA synthesis from aniline realized in a laboratory reactor Rotamag 100 at the temperature of 340 ⁰C with constant ratio of aniline to catalyst dry mass (Uhlar J.: Vyskum katalyzatorov pre vyrobu difenylaminu z aniline (Research on catalysts for - A - production of diphenylamine from aniline), PhD thesis, CHTF SVST Bratislava /1981/).

Following conclusions were arrived at when evaluating the catalysts from the point of view of their activity for diphenylamine preparation: For lower atomic ratios of fluorine to boron in starting raw materials, i. e. 1 :1 to 2:1 , little efficient catalysts (Fig. 1 ) were prepared containing mostly [BF₂/OH/₂]^". Catalytic activity could be substantially increased by increasing the ratio to 3:1 , but it has not reached the values obtained with the starting ratio of 4:1 , which represents optimum for the given system. Nevertheless, this optimum has not reached activities of pure ammonia tetrafluoroborate. Further increase of the ratio led not to any further rise, but to decreasing the catalyst activity. In the area of ratios 4:1 and higher it has been observed that the activity change corresponds roughly to the content of the ion BF₄ ^" with excessive content of F^" which is inactive.

The checked fluoroborate ammonia salts were catalytically active in the DPA synthesis from aniline, but they have not reached the level of catalytic activity of NH₄BF₄.

However, the advantage of lower fluoroborates is more than two times higher solubility in water than that of NH₄BF₄ (25 weight portions of NH₄BF₄ to 100 weight portions of water at 16 ⁰C). This fact allows injecting much more dry mass of lower fluoroborates into the continuous system at the same temperature as of pure NH₄BF₄. Therefore, it is more preferable to inject aqueous solution of lower fluoroborates which, under the conditions of diphenylamine formation, convert to NH₄BF₄. The problem of catalytic activity of NH₄BF₄ then consists only in the amount of transformed NH₄BF₄ in aniline and in the residence time of NH₄BF₄ and reactants. Substantial disadvantage of such procedure is formation of crystals of arising NH₄BF₄, which are formulated into agglomerates having certain surface, while only the outer surface manifests the catalytic activity. An extreme negative effect is formation of sediments which not only have low activity, but they also reduce the active volume of the reactor, thus also residence time and conversion of aniline.

These and further shortages and disadvantages of the outlined procedures of diphenylamine production from aniline are eliminated by the present invention. Disclosure of Invention

The above shortages of the existing procedures are eliminated by the method of diphenylamine production from aniline using a continuous procedure in liquid phase catalysed by thermolabile compounds of fluorine with boron which convert under conditions of diphenylamine formation from aniline to NH₄BF₄ consisting in that NH₄BF₄ crystals arising in the reaction medium are maintained in uplift during a time which is at least so long as the residence time of aniline in the reactor.

Owing to lower solubility of NH₄BF₄ in the reaction mixture in comparison with the previous compounds of fluorine with boron, the product of thermal decomposition of lower fluoroborates NH₄BF₄ is maintained in uplift during a time which is at least so long as the residence time of aniline in the reactor, thus ensuring its sufficient dissolution in the reaction mixture.

It has been found that prolongation of the residence time can be ensured by circulation stirring of the reaction mixture with a stirrer of minimum volume-rate of 0.1-multiple of the reaction mixture volume per hour, but up to 1000-multiple of the volume. Alternatively it is possible to equip the reactor with a mechanical stirrer with input power ensuring turbulent axial-radial flow of the reaction mixture in the reactor.

It has been further found that the same effect is achieved when contra- currently to the catalyst input overheated water steam is supplied with pressure higher than saturated vapour tension of the reaction mixture at the working temperature plus hydrostatic pressure of the reaction mixture or if input reactant aniline is supplied countercurrently with respect to the catalyst feed into the reactor with such speed and in such direction that the same residence time of the catalyst in uplift as the residence time of aniline in the reactor is ensured.

The advantage of the present preparation method consists especially in that sedimentation of NH₄BF₄ crystals on the walls and bottom of the reactor is prevented, the reaction space of the reactor, as well as the residence time are then not reduced. Prolongation of the residence time of NH₄BF₄ crystals is important to ensure their sufficient dissolution in the reaction mixture, because NH₄BF₄ crystals have lower solubility in the reaction mixture than the previous compounds of fluorine with boron.

Also activity of the catalyst is maintained, because it enters the reaction with its whole surface, while the catalyst deposited on the walls or bottom, takes part in the reaction only by its surface contacting the reaction mixture; the layers inside the catalyst layers are inactive and lead to above mentioned troubles.

Examples of embodiments

Example 1

Aniline in the amount of 400 ml/h and 4 ml of aqueous solution of fluoroborate catalyst with 60 % of dry mass, prepared by mixing orthoboric acid with acidic ammonia fluoride, were injected into continually working laboratory reactor in steady state at the temperature of 345 ⁰C. The reaction mixture was stirred in the reactor only by the flow of dosed aniline.

Composition of the reaction mixture at the outlet of the reactor was as follows (GC analysis): 28.8 weight % of diphenylamine, 69.7 weight % of aniline, 1.15 area % of volatile substances and 0.18 area % of pitches.

Note: Volatile substances are substances which are eluted in the gas chromatograph record between aniline and DPA, and pitches are substances which are eluted in this GC record after DPA.

Catalyst productivity: 57.6 kg of diphenylamine/1 h/1 kg of catalyst dry mass.

When the same experiment was performed with the difference that at about a half of the height of the continuous reactor body suction branch of the centrifugal Hermetic pump CAM 2/1 was opened, the discharge branch of which led into the reactor bottom, and the through-flow in the circulation circuit was set to the value of ten times the reactor volume exchange per hour, reaction mixture after reaching steady state had the following composition: 35.8 weight % of diphenylamine, 62.5 weight % of aniline, 0.32 area % of volatile substances and 0.82 area % of pitches.

Catalyst productivity increased under the influence of circulation stirring, which ensures maintaining NH₄BF₄ crystals in uplift, to 71.5 kg of diphenylamine/1 h/1 kg of catalyst dry mass. Example 2

Reaction mixture of Example 1 without circulation was extracted by ammonia water and water extract was subsequently thickened to dry mass of 40 %. Such solution was then tempered to the temperature of 50 ⁰C and injected into a reactor tempered to the temperature of 345 ⁰C in the amount of 6 ml/h. Aniline was injected into the bottom part of the reactor at a speed of 400 ml/h. Operation of the reactor was stabilized using a circulation pump with the capacity of 16.6- multiple of the reactor volume per hour and in the steady state the following average value of reaction mixture composition at the outlet of the reactor was achieved: 33.6 weight % of diphenylamine, 64.0 weight % of aniline, 0.32 area % of volatile substances, 1.39 area % of pitches. Productivity of the recycled catalyst was 67.22 kg of DPA/1 h/1 kg of dry mass of the recycled catalyst.

Then the circulation pump was stopped and after stabilization of the system without circulation the reaction mixture composition at the reactor outlet was as follows: 16.6 weight % of diphenylamine, 82.2 weight % of aniline, 0.30 area % of volatile substances and 1.40 area % of pitches. After stopping the circulation pump, productivity of the recycled catalyst decreased from 67.22 kg of DPA/1 h/1 kg of dry mass of the recycled catalyst to the value of 33.16 kg of DPA/1 h/1 kg of dry mass.

Example 3

a) 25 l/h of fluoroborate catalyst solution with dry mass as in Example 1 were injected from above into a large capacity reactor tempered to the temperature of 345 ⁰C and co-currently with it also preheated aniline in the amount of 2.5 m³/h. The average concentration of diphenylamine at the outlet of the reactor at operational pressure of 2.3 MPa was 21.0 weight %. Catalyst productivity was 42 kg of DPA/1 h/1 kg of catalyst dry mass. After the reactor was opened, on the walls and bottom of the reactor considerable amounts of crystallized catalyst were found which had to be regularly removed. b) After modification of the aniline input into the reactor so that it was fed countercurrently to the catalyst injection from the reaction bottom tangentially to the reactor wall, to maintain approximately the same average DPA concentration in the reaction mixture (20.8 weight %) as in the above arrangement in this Example 4.5 m³ of aniline were injected per hour. Using this modification the catalyst productivity increased to the value of 72.3 kg of DPA/1 h/1 kg of catalyst dry mass, this value being close to the value obtained from the laboratory reactor with circulation stirring. After opening so operated reactor after three months of continuous operation, no significant amount of catalyst sediment was found.

Example 4

Into the reactor as in Example 3a, steam distributor consisting of a perforated tube of circular shape located ca 5 cm from the reactor wall was installed. In the steady state - as in Example 3a - reduced overheated water steam under pressure of 3.5 MPa was started to be supplied into the reactor. After stabilizing the aniline injection to the value of 3.5 m³/h, the DPA concentration in the reaction mixture at the outlet was ca 20.7 weight %. Thereby the catalyst productivity of 57.96 kg of DPA/1 h/1 kg of catalyst dry mass was reached.

Claims

CLAI MS

1. Method of diphenylamine production from aniline by a continuous procedure in liquid phase catalysed by thermolabile compounds of fluorine with boron which convert under conditions of diphenylamine formation from aniline to NH₄BF₄, characterized in that

NH₄BF₄ crystals arising in the reaction medium of the reactor are maintained in uplift during a time which is at least so long as the dwell time of aniline in the reactor.

2. Method according to claim 1, characterized in that the maintaining in uplift is ensured by circulation stirring of the reaction mixture with a stirrer of minimum volume-rate of 0.1 -multiple of the reaction mixture volume per hour.

3. Method according to claim 1 , characterized in that the maintaining in uplift is realized by mechanical stirring providing turbulent axial- radial flow of the reaction mixture in the reactor.

4. Method according to claim 1, characterized in that countercurrently to the catalyst input overheated water steam is supplied into the reactor with pressure higher than the sum of saturated vapour tension of the reaction mixture at the working temperature and hydrostatic pressure of the reaction mixture.

5. Method according to claim 1, characterized in that the input reactant aniline is supplied into the reactor countercurrently to the catalyst input with such speed which ensures at least the same residence time of the catalyst in uplift as is the residence time of aniline in the reactor.