EP2079685A1 - Method for producing isocyanates - Google Patents

Method for producing isocyanates

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Publication number
EP2079685A1
EP2079685A1 EP07822258A EP07822258A EP2079685A1 EP 2079685 A1 EP2079685 A1 EP 2079685A1 EP 07822258 A EP07822258 A EP 07822258A EP 07822258 A EP07822258 A EP 07822258A EP 2079685 A1 EP2079685 A1 EP 2079685A1
Authority
EP
European Patent Office
Prior art keywords
quench
zone
reaction
reaction mixture
characterized
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP07822258A
Other languages
German (de)
French (fr)
Inventor
Andreas Wölfert
Carsten KNÖSCHE
Andreas Daiss
Eckhard Stroefer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BASF SE
Original Assignee
BASF SE
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to EP06123621 priority Critical
Application filed by BASF SE filed Critical BASF SE
Priority to EP07822258A priority patent/EP2079685A1/en
Priority to PCT/EP2007/061941 priority patent/WO2008055904A1/en
Publication of EP2079685A1 publication Critical patent/EP2079685A1/en
Application status is Withdrawn legal-status Critical

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Classifications

    • CCHEMISTRY; METALLURGY
    • C07ORGANIC CHEMISTRY
    • C07CACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C263/00Preparation of derivatives of isocyanic acid
    • C07C263/10Preparation of derivatives of isocyanic acid by reaction of amines with carbonyl halides, e.g. with phosgene

Abstract

The invention relates to a method for producing isocyanates by reacting amines with phosgene in the gas phase in at least one reaction zone, the reaction mixture being guided to at least one zone in which at least one liquid is injected to terminate the reaction. The invention is characterized by guiding the reaction mixture through a continuous quenching liquid curtain which completely fills the cross-section of the quenching zone.

Description

A process for preparing isocyanates

description

The invention relates to a process for the preparation of isocyanates in the gas phase.

Polyisocyanates are prepared in large quantities and are used primarily as starting materials for preparing polyurethanes. They are usually prepared by reacting the corresponding amines with phosgene.

One possibility of preparing isocyanates is the reaction in the gas phase. The advantages of this procedure, is in a reduced phosgene holdup, the avoidance difficult phosgenate intermediates and increased reaction exploit. Apart from effective mixing of the feed streams to realize a narrow residence and maintenance of a narrow Verweilzeitfensters important prerequisites for the technical feasibility of such a process represent. These requirements can be satisfied with internals, for example through the use of turbulent operated tube reactors or flow tubes.

Various methods for preparing isocyanates by reacting amines with phosgene in the gas phase are known from the prior art. EP-A-593 334 describes a process for the preparation of aromatic diisocyanates in the gas phase, characterized in that the reaction of the diamine with phosgene in a tubular reactor without any moving parts and with a constriction of the walls takes place along the longitudinal axis of the tubular reactor. However, the method is problematic in that the mixing of the reactant streams works alone on a narrowing of the tube wall bad compared to the use of an active mixing element. Poor mixing usually leads to a high undesirable solids formation.

EP-A-699 657 describes a process for the preparation of aromatic diisocyanates in the gas phase, characterized in that the reaction of the corresponding diamine takes place with the phosgene in a two-zone reactor, wherein the first zone, which constitutes 20% to 80% of the total reactor volume is ideally mixed and the second zone, which constitutes 80% to 20% of the total reactor volume, can be characterized by a piston flow. However, since at least 20% of the reaction volume are ideal backmixing, results in an uneven residence time distribution, which can lead to an undesirably increased solids formation.

EP-A-289 840 describes the preparation of diisocyanates by Gasphasenphosge- discrimination, wherein the preparation takes place according to the invention in a turbulent flow at temperatures between 200 0 C and 600 0 C in a cylindrical space without moving parts. By dispensing with moving parts, the risk of phosgene is reduced. Is the turbulent flow in the cylindrical space (tube) apart from the fluid elements close to the wall, a good Strömungsgleich- distribution in the pipe and thus a narrow residence time distribution, which, as described in EP-A-570 799, which to a reduction can result in solids formation.

EP-A-570 799 relates to a process for the preparation of aromatic diisocyanates in the gas phase, characterized in that the reaction of the associated slide mins with the phosgene in a tubular reactor above the boiling point of the slide mins within a mean contact time of 0.5 is carried out up to 5 seconds. As described in Scripture lead to long and to short reaction times to undesirable solids formation. There is therefore disclosed a method in which the average deviation from the average contact time is less than 6%. Compliance with this contact time is achieved in that the reaction is carried out in a pipe flow, which is characterized by either a Reynolds number of above 4,000 or a Bodenstein number of above 100th

EP-A-749 958 describes a process for the preparation of triisocyanates by gas phase phosgenation of (cyclo) aliphatic triamines nogruppen with three primary amino, characterized in that heated the triamine and the phosgene continuously in a 200 0 C to 600 0 C. , s brings cylindrical reaction space at a flow rate of at least 3 m / to react together.

In the explicitly disclosed example, the reaction mixture is passed through a solvent therethrough, which permits only a non-specific separation of the reaction products and resulting in a broad Quenchzeitverteilung.

EP-A-928 785 describes the use of microstructure mixers for the phosgenation of amines in the gas phase. A disadvantage of the use of micro mixers that minute amounts of solids, whose formation is not completely ruled out in the synthesis of the isocyanate already may cause clogging of the mixer, which reduces the temporal availability of the phosgenation.

In all cases, however, it is necessary to effectively stop the reaction after an optimal reaction time in order to prevent the formation of solids by subsequent reactions of the isocyanate.

EP 1403248 A1 describes the rapid cooling of a reaction mixture of iso- cyanate, phosgene and hydrogen chloride, in a cylindrical quench zone. The quench zone consists of at least two nozzle heads which in turn contain one or more individual nozzles. The nozzles are distributed on the outer periphery. In the quenching zone, the reaction gas is mixed with the sprayed liquid droplets. By the evaporation of the liquid, the temperature of the gas mixture is rapidly lowered, so that the loss of the desired isocyanate product is reduced due to high temperatures. Furthermore, an early contact of the hot reaction gas is suppressed with the Quenchzonenwandungen through the nozzle assembly so that the formation of deposits on the surfaces is reduced.

In the disclosed embodiment in the figure shows, however, that remain open under the consideration of the Mitrisses the quench liquid flowing through the reaction mixture in particular on the wall of the quenching chamber channels are passed through the reaction mixture without intimate contact with the quench medium. This results in a proportion ungequenchtem reaction mixture and thus to a broadening of the Quenchzeitverteilung.

A disadvantage of the described method, the quench times of 0.2 to 3.0 s, which lead to a significant loss of isocyanate are avoidable.

The international patent application WO 2005/123665 describes a process for the preparation of isocyanates with a constriction between reaction zone and quench. The there explicitly disclosed example with certain Sauter mean diameter and a certain speed of the injection can be quench times of 0.01 seconds.

With the measures disclosed therein, however, no optimal effect in the quench can be achieved.

The object of the invention is to provide a process for preparing isocyanates in the gas phase, which has reached its optimum dwell time the reaction is stopped within a sufficiently short time and a simple separation of the isocyanate from the other constituents of the reaction mixture reaches advertising can the ,

The object is achieved in that the reaction is carried out in a reaction zone to a conversion of at least 98% and the reaction mixture is led to the discontinuation of the reaction through a zone in which a liquid is injected. In the following, this zone is called quenching. Here, is located between the reaction zone and the zone in which the reaction is stopped is brought about an area which may have a relation to quench and reaction zone modified cross-section. The cross-sectional surface of this area may be smaller or larger than the cross-sectional area of ​​the reaction zone. According to the invention, the gaseous reaction mixture through a curtain of

out quench liquid which fills the entire cross-sectional area of ​​the quench zone. As reaction zone tube reactors, flow tubes can be used with or without internals or plate reactors.

The reaction of the amine with the phosgene in the gas phase can be effected under the known conditions.

The mixing of the reaction components amine and phosgene can occur before or in the reactor. Thus it is possible, connected upstream of the reactor a mixing unit, for example a nozzle, which already reaches a mixed gas stream containing phosgene and amine in the reactor.

In one embodiment of the inventive method, the phosgene stream by means of a distributing element is first on the entire width of the reactor possible liehst homogeneously distributed. The supply of the amine stream takes place at the beginning of the reactor, here a manifold channel with holes or mixing nozzles in the reaction channel is incorporated, said distribution duct preferably extends across the entire width of the reactor. the amine, which is optionally mixed with a I- nertmedium, the phosgene stream is fed from the holes or mixing nozzles.

The inert medium is a medium which is gaseous at the reaction temperature and does not react with the starting materials. For example, nitrogen, noble gases such as helium or argon or aromatics such as chlorobenzene, dichlorobenzene or xylene can be used. Nitrogen is preferably used as the inert medium.

For the inventive method, primary amines, preferably diamines or triamines, and more preferably diamines can be used, which can preferably be converted into the gas phase without decomposition. Particularly suitable are here amines, especially diamines, based on aliphatic or cycloaliphatic hydrocarbons having 1 to 15 carbon atoms. Examples include 1, 6- diaminohexane, 1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane (IPDA), 4,4'-diaminodicyclohexylmethane, 1, 3- or 1, 4- (isocyananatomethyl) cyclohexane (BIC ) and 3 (or 4), 8 (or 9) -bis (aminomethyl) tricyclo [5.2.1.0 26] decane isomer mixtures. is used preferably 1, 6-diaminohexane (HDA).

For the inventive method also can be used aromatic amines which can preferably be converted into the gas phase without decomposition. Examples of preferred aromatic amines are toluenediamine (TDA), preferably 2,4- or 2,6-isomers or mixtures thereof, diaminobenzene, Napthyldiamin (NDA) and 2,4'- or 4,4'-methylene (diphenylamine) (MDA ) or isomer mixtures thereof. In the present process, it is advantageous to use phosgene in excess of the amino groups. Typically, a molar ratio of phosgene to amino groups of 1, 1: 1 to 20: 1, preferably from 1, 2: 1 to 5: 1.

To carry out the process of the invention it may be advantageous to preheat the streams of the reactants prior to mixing, usually at temperatures of 100 to 600 0 C, preferably from 200 to 500 0 C. The reaction in the reaction channel usually takes place at a temperature of 150 to 600 0 C, preferably from 250 to 500 0 C instead. The inventive process is preferably carried out continuously.

The reaction of phosgene with amine in the reaction space is carried out at absolute pressures of from 0.1 bar to less than 20 bar, preferably between 0.5 bar and 15 bar and more preferably between 0.7 and 10 bar. In the case of the reaction of (Cyc- lo) aliphatic amines, the absolute pressure is most preferably between 0.7 bar and 5 bar, in particular from 0.8 to 3 bar, especially from 1 to 2 bar and especially from 1, 1 to 1 , 5 bar.

In a preferred embodiment, the dimensions of the reactor and the flow rates are such that a turbulent flow, ie a flow with a Reynolds number of at least 2300, preferably at least 2700, more preferably is present at least 10,000, wherein the Reynolds number with the hydraulic diameter of the reactor is formed. The Reynolds number determines the flow regime and thus the residence time in the reaction tube firmly (H. Schlichting: boundary layer theory, publishing G. Brown, 1982; M. Baerns: Chemical Reaction Engineering, Georg Thieme Verlag, Stuttgart, 1992). Preferably, the gaseous reactants pass through the reactor at a flow rate of 2 to 220 meters / second, preferably 20 to 150 meters / second, particularly preferably from 30 to 100 meters / second.

In general, in the inventive method, the average contact time is 0.05 to 5 seconds, preferably 0.06 to 1, particularly preferably 0.1 to 0.45 seconds. By average contact time, the time period from the start of mixing of the starting materials is up to the termination of the reaction understood by the quench. In a loading vorzugten embodiment, the flow in the process of this invention by a Bodenstein number of greater than 10, preferably more than 100 and more preferably of more than 500 characterized. The Bodenstein number is a measure of the degree of back-flow of the system. With increasing Bodenstein number backmixing decreases (M. Baerns: Chemical Reaction Engineering, Georg Thieme Verlag, Stuttgart, 1992) As stated above, at the end of the reactor, which can be a turbulent operated tubular reactor, a flow tube with internals or plate reactor, a quench arranged.

As a reaction chamber the volume is described in which at least 98% of the sales, that is, the consumption of the amine used, has occurred, preferably at least 99%, more preferably 99.5%, most preferably 99.7%, in particular 99.9%, and specially 99.99%.

The invention accordingly provides a process for the preparation of isocyanates th by reaction of amines with phosgene in the gas phase in at least one reaction zone, wherein the reaction mixture is led to the termination of the reaction by at least one zone in which a liquid is injected at least in the reaction mixture is passed through a closed curtain of Quenchflüssig- ness, which completely fills the cross section of the quench zone.

The change in the flow cross section between the reaction and quench zone is in this case defined as a function of the other process engineering parameters and the absolute size of the apparatus. So it may nen and / or for example low in highly scale-forming isocyanates at small Apparatedimensio-, an extension of the cross section between reaction and quench zone provided to a blockage of the cross section to avoid the. In case of a cross-sectional enlargement, make sure that the flow takes place without separation, because otherwise is also to be expected with the formation of deposit. The required to achieve a separation-free flow measures, including the requisite angle of transitions within or between the components are known in the art per se.

In the case of sufficiently large apparatus dimensions or only low deposition forming isocyanates, however, is a constant or preferably narrowing flow cross section between reaction zone and quench preferable.

Here, strong scale forming isocyanates particularly monoisocyanates and (cyclo) aliphatic isocyanates, especially 1, 6-hexamethylene diisocyanate.

By contrast, little scale forming isocyanates include aromatic isocyanates, and particularly toluene diisocyanate.

As a general rule, the tendency of isocyanates to form deposits with increasing functionality, increasing reactivity and / or increasing molecular weight increases. A narrowing of the flow cross-section is preferred to be selected so that the reaction gas leaving the constriction is both cooled considerably and on the other hand has a sufficiently high flow rate that provides effective secondary atomization of the quench liquid. Under secondary atomization is understood to mean that z. As liquid droplets produced by means of atomizing nozzles by forces in the gas flow, in particular the aerodynamic forces can be further divided, so that greater heat and mass transfer area is formed.

Both of these requirements can be achieved by adjusting the speeds of the flow of the reaction mixture depending on the boundary conditions of the cross-sections:

In an extension of the flow cross section in the course of flow of the reaction mixture, the Mach number of the flow of the reaction mixture at the inlet into the quench zone is generally from 0.05 to less than 1 can, 0, preferably from 0.1 to less than 1, 0, more preferably 0, 2 to less than 1, 0, and most preferably 0.3 to be less than 1, the 0th

With a narrowing of the flow cross section in the course of flow of the reaction mixture, the Mach number after the cross-sectional constriction can additionally also at least 1, to be 0, for example up to 5.0, preferably up to 3.5, more preferably up to 2.5 and very particularly preferably up to 1; 5. Also conceivable is an adiabatic after-expansion of the reaction mixture after leaving the reaction zone and before meeting with the quench liquid. As a result, the already pre-cooled reaction mixture is subject just before the meeting with the quench a shock wave, the temperature increase will be absorbed by the quench.

Under the Mach number is understood to be the local flow velocity relative to the local sound velocity of the reaction mixture. From the requirements tion to the Mach number directly the size of the inlet cross section in the quench zone is due to the mass balance for a given mass flow, pressure and temperature.

The ratio of the narrowest flow cross-sections in the reaction zone and quench zone is in the case sufficiently large apparatus dimensions or cyanates in iso-, which show a low tendency to form deposits, 1/1 up to 10/1, preferably 1, 2/1 up to 10/1 , more preferably 2/1 to 10/1, and most preferably from 3/1 to 10 / 1. In the case of small clog-prone apparatus dimensions or highly scale forming isocyanates is an extension of the flow cross section between the reaction and quench from 1/1 to 1 / 10, preferably 1/1, 2 to 1/10 min, more preferably from 1/2 to 1/10 and particularly preferably from 1 / 3W to 1 / 10th with respect to the flow cross-sectional area of ​​the reaction tube advantageous.

With the clog-prone dimensions each occurring through the smallest diameter Tenden or gaps are meant, in which deposits can form.

The transition between the reaction and quench zone is preferably designed in the form of a cone. Are also conceivable cone with an oval or elliptical shaped cross-section or concave or convex shaped transitions, thus for example hemisphere spaces.

In the quench zone the reaction mixture from the isocyanate naten substantially, phosgene and hydrogen chloride is intensively mixed with the injected fluid.

The mixing of the reaction mixture and liquid must be carried out according to the invention so that the reaction mixture is not part flows past sigkeit in the bypass at the Quenchflüs-. This ensures that the entire reaction mixture is cooled in a very short time is guaranteed. Further, it is ensured that this cooling is performed uniformly, ie with low deviation from the mean cooling time.

This could not be ensured by the state of the art, as disclosed in the prior art nozzles do not ensure that no channels remain open, can flow through the reaction mixture at the quench medium, or that the time between entry into the quench zone and contact with the quench medium sufficient is short and as uniform as possible.

The mixing is effected such that the temperature of the reaction mixture starting from 150 to 600 0 C, preferably 250 to 500 0 C by 50 to 300 ° C, preferably around 100 to 250 0 C to 100 to 200 ° C, preferably to 140 to 180 ° C is lowered and the isocyanate in the reaction mixture is transferred by condensation fully or partially in the liquid droplets sprayed in while the phosgene and the hydrogen chloride remain essentially completely in the gas phase.

The proportion of the isocyanate contained in the gaseous reaction mixture which passes into the quench zone in the liquid phase, it is preferably 20 to 100% by weight, particularly preferably 50 to 99.5% by weight and in particular 70 to 99 wt%, based given to the reaction mixture isocyanate. The proportion of the hydrogen chloride contained in the gaseous reaction mixture which passes into the quench zone in the liquid phase is preferably less than 20 wt%, more preferably below 15 wt%, most preferably below 10% by weight and especially below 5% by weight.

The proportion of the phosgene contained in the gaseous reaction mixture which passes into the quench zone in the liquid phase is preferably less than 20% by weight, more preferably below 15 wt .-%, most preferably below 10% by weight and especially below 5 wt .-%.

The reaction mixture flows through the quench zone preferably from top to bottom. At the exit of the quench zone is a collection vessel in which the liquid phase is separated, collected and removed through an outlet and then worked up. The remaining gas phase is removed via a second outlet, and also worked up.

The liquid droplets of the quench medium by means of suitable nozzles, for example, one- or Zweistoffzerstäuberdüsen, preferably Einstoffzerstäuberdüsen produced, and preferably have a Sauter mean diameter D32 from 5 to 5000 .mu.m, more preferably 5 to 500 .mu.m and in particular 5 to 250 microns.

The Sauter diameter D32 (Sauter mean diameter, SMD) describes up to a constant factor, the ratio of the average drop volume to medium droplet surface (see K. Schwister: Paperback process engineering, Fachbuch- publisher Leipzig, Carl Hanser Verlag 2003) and is therefore responsible for the quench essential parameter of the droplet size distribution produced. It is the droplet diameter, in which the ratio volume / surface is the same as the sum of all drop in the observed ensemble and gives the fineness of atomization on the reaction surface at

The width of the droplet size distribution should be minimized because too large drops can not cause rapid temperature reduction and only can be separated with increased effort following the flow of gas to small drops yet.

The atomizer nozzles produce, depending on the embodiment, a spray cone of 10 ° to 140 °, preferably from 10 to 120 °, particularly preferably of 10 ° to 100 °. Figure 7 shows the definition of the spray cone angle α (alpha).

As a spray pattern the part surface is referred to a surface perpendicular to the spray axis (at rotationally symmetric nozzle) or perpendicular to the mirror plane (for mirror-symmetrical nozzle) which is flowed through by liquid droplets. The outer contour of the spray pattern is usually circular (full cone nozzles) or annular (in case of hollow cone nozzles). However, it can also be oval or elliptical to rectangular (eg flat jet nozzles).

The envelope of the sprayed droplets is lobe-shaped and forms, as a rule in the vicinity of the nozzle idealized a cone. It is also conceivable a hollow cone. Depending on the shape of the quench zone but also spray nozzles can be used to advantage to produce a non-conical envelope. Furthermore, fan-shaped envelope are conceivable, for example generated through slotted nozzles or flat jet nozzles.

In order to adjust the necessary droplet size Einstoffzerstäuberdüsen usually with an excess pressure relative to the Quenchzonendruck of at least 1 bar, preferably at least 4 bar, more preferably at least 10 bar, most preferably operated at least 20 bar and in particular at least 50 bar.

In the case of Einstoffzerstäuberdüsen a positive pressure of not more than 1000 bar is usually sufficient, preferably not more than 500 bar, more preferably not more than 200 bar, very particularly preferably not more than 100 bar and especially not more than 80 bar.

In the case of Zweistoffzerstäuberdüsen the nozzle can be operated either as a liquid side pressure as well as suction nozzle, that is the liquid form for Quenchzonendruck can be positive or negative relative. usually the atomizing gas has a form which is so high that the ratio of inlet pressure to

Quenchzonendruck is greater than the critical pressure ratio, preferably is greater than twice the critical pressure ratio and most preferably greater than four times the critical pressure ratio. The critical pressure ratio indicates the pressure ratio above which the pressure in the narrowest cross section of the Zerstäubungsgaskanales is independent of the pressure downstream of the nozzle.

The speed with which the droplets emerge from the nozzle, depends on the type of atomisation, and is usually at least 15 m / s, preferably at least 40 m / s and more preferably at least 100 m / s. The upper limit of the overall speed is not critical. Often, a speed up to 350 m / s is sufficient.

Preferably, there is a cross-sectional constriction between the reaction zone and the quench zone, zentrationserniedrigung by a relaxation connected to a con-, the first reactants and temperature reduction of the reaction gas is obtained. Further, the effect of the cross-sectional constriction with increased speed exiting reaction gas stream at the confluence with the Quenchflüssigkeitsspray an additional secondary atomization of the quench liquid

Due to the large specific surface of the liquid droplets and the high relative speeds between the reaction gas and quenching liquid mass and heat exchange between reaction gas and quenching liquid to be intensified. Thus be greatly reduced along with the avoidance of reaction mixture bypass flow required for cooling the reaction mixture contact times and the loss of Isocyanatwertprodukt due to further reaction to by-products th minimized.

The velocity of the reaction gas stream in the narrowest cross-section is preferably more than 20 m / s, particularly preferably more than 50 m / s, particularly more than 100 m / s and is up ULTRASONIC by the speed of sound Reaktionsgasgemi- limited under the respective conditions. In the case of a critical flow through the narrowest cross section occurs behind the narrowest cross section to a post-expansion and further accelerate the reaction gas mixture.

The free flow cross section in the quench zone is based on the free flow cross section in the reaction zone generally 25/1 to 1/2 is preferably 10/1 to 1/1.

The arrangement of the spray nozzles in the quench zone is selected so is that a bypass flow of the reaction mixture to the quench liquid largely by starting avoided. This is achieved in that the Quenchflüssigkeitströpfchen in the quenching zone to form a closed curtain, the one or more entries reaction mixture in the quench zone completely separates the area from the region of the exits from the quench zone. Thus, the entire reaction mixture must have the curtain formed by the quench liquid, so the entirety of the swept in time average of droplet volumes of quench nozzles penetrate and is thus efficiently cooled.

The liquid curtain may be shaped differently depending on the used atomization. So atomizing devices can be used, for example, with a circular spray pattern (for example, conical envelope) or with elliptical spray pattern. In addition, slit-shaped nozzle with an approximately oval or elliptical spray pattern used to rectangular (fan-shaped envelope) can. In the case of conical or elliptical conical wrap-it may be a hollow or a solid cone is further.

The atomizing nozzles are arranged in the quench zone so that the iso-surfaces of the Quenchflüssigkeitsvolumenanteils that define the envelope of the individual nozzles envelop, together with the Quenchzonenwand and the reaction gas inlet, a closed volume. The injection direction of the atomizer, which is defined in the case of cone-shaped nozzle by the central axis of the spray cone and the main direction of flow of the gas in the quench zone can angle of 0 ° to 180 °, preferably from 0 ° to 90 °, particularly preferably from 0 ° to 60 ° lock in. Here means an angle of 0 °, that the Zerstäuberdüsenachse is exactly parallel to the main flow direction and the nozzle in the direction of the main flow is atomized, while an angle of 90 ° means that the Zerstäuberdüsenachse is exactly perpendicular to the main direction of flow in the quenching zone. An angle of 180 ° means that the atomizer nozzle injects the quench liquid exactly opposite to the main flow direction.

The Quenchflüssigkeitsvorhang may be generated by one or more devices for atomization of the quench liquid. The ratio of the number of destruction stäubungseinrichtungen to the number of reaction mixture entrance into the quench zone is well 10/1 to 1/10 preferably 4/1 to 1/4, more preferably 4/1 to 1/1, most preferably 3/1 to 1/1, and more particularly 2/1 to. 1/1

In a preferred embodiment (Figure 1) with a nozzle, the quench nozzle is seated 2 coaxially in the center of a cylindrical or conical quench zone 5. In Figure 1, a quench zone of a cylinder is shown with attached cone. The reaction mixture 3_wird via an annular gap 4 coaxially with the quench nozzle 2 is introduced into the quench zone. 5 The Quenchzonenwand 7 and the spray cones 6 form a narrowing space 8, in which the reaction mixture flows. The reaction mixture must then flow through these constructive measures the curtain formed by the spray cone. In this preferred embodiment, the spray cone angle should be larger than the cone angle of Quenchzonenwand.

In a second preferred embodiment (Figure 2) with a nozzle is also located the nozzle 2 coaxially in the center of a cylindrical or conical quench zone 5. The reaction mixture is here via an inlet 3 at an angle beta (beta) for Sprühdüsenachse into the quench zone is introduced wherein the angle ß 0 ° to 90 ° preferably 45 ° to 90 ° more preferably 70 ° to 90 °. An angle ß of 0 ° means parallel to this Sprühdüsenachse and an angle ß of 90 ° perpendicular to the Sprühdüsenachse. In a particularly preferred arrangement, the reaction mixture flow enters tangentially into the quench zone. This means that the reaction mixture stream is not fed directly to the Sprühdüsenachse, but with the connection axis of the reaction mixture inlet 3 with Sprühdüsenachse an angle of 5 ° to 45 °, preferably 10 ° to 45 °, particularly preferably 20 ° to 45 °, and most preferably 30 ° to 45 ° includes. The reaction mixture then flows back through the narrowing space 8, which is formed by the spray cone 6 and the Quenchzonenwand 7 and finally penetrates the Quenchflüssigkeitsvorhang. In this preferred embodiment, the spray cone angle should be greater than the cone angle of the quench zone wall.

In a further preferred arrangement, a plurality of atomizing devices 2, for example 2 to 10 spray nozzles 2 are seated on a ring around the inlet of the reaction mixture placed 3 (3a and 3b). 3a shows six spray nozzles are exemplified. The spray nozzles thereby produce by superimposition of the individual spray patterns of an elliptical or circular spray pattern 6. In the interior of the ring is the reaction mixture inlet 3. The axis of the spray is conical with respect to the reaction mixture entering direction by the angle y (gamma) employed. Gamma y amounts to 0 °, the injection therefore takes place parallel to the reaction mixture to 90 °, the injection is thus perpendicular to the reaction mixture, preferably 0 ° to 60 ° more preferably from 0 ° to 45 °. Advantage of multiple nozzles is that smaller nozzles can be used, which generally produce smaller droplets so enabling a more rapid quenching of the liquid. Again, it is maintained by proper combination of the Quenchzonenform and arrangement of atomizing, that a closed spray curtain is formed.

Figure 4 shows a variant of the arrangement of Figure 3 with a cross-sectional constriction V \ _ between reaction and quench zone.

This cross-sectional constriction results in an acceleration of the reaction mixture and thereby to a pressure drop, which acts to cool the reaction mixture sawn. By accelerating the reaction mixture in the narrowest cross-section may reach a speed of up to 1, 0 Mach. Behind the narrowest cross-section also Geschwindigkeitem greater than 1, 0 Mach may result.

By this cooling, the reaction mixture is up to quench less thermal stresses. In addition, the increased velocity of the reaction mixture causes a secondary distribution of Quenchtröpfchen ness and thus an improved heat and mass transfer between the reaction gas mixture and Quenchflüssig-. Although the collision of the reaction mixture and Quenchtröpfchen again performs a short time to a temperature increase, but this is absorbed by the quench process of the quench liquid, and thus does not cause any further thermal load of the reaction mixture.

In a further preferred arrangement, the reaction gas mixture passes through a gap on the front side in the quench zone. The gap can thereby be ring-shaped or elliptically or describe another arbitrary curve. The gap width can be variable here, but is preferably constant. On both sides of the gap are depending on the size of the gap or a plurality of atomizer nozzles arranged to inject parallel or at an angle y to the main flow direction of the reaction gas mixture quench liquid. The angle y is from 0 ° to 90 °, preferably 0 ° to 60 ° more preferably from 0 ° to 30 °. Through the spray nozzles on both sides of the gap, a tapered flow channel for the reaction gas mixture overall is formed, which is completed by the meeting of the spray patterns of the spray nozzles. Again, a closed curtain through which the reaction gas mixture must pass, becoming rapidly cooled. It is preferable that the gap is an annular gap through which the reaction mixture is passed and in which inside at least one and the outside depending on the size of the annular gap plurality of spray nozzles, for example 2 to 10, preferably 2 to 8 and more preferably 3 to 6 nozzles , are for the quenching liquid.

In a further preferred embodiment a plurality of reaction gas inlets 3 and a plurality of atomising devices 2, a plurality of sitting Zerstäubungsdü- sen 2 and reaction gas inlet 3 on the front side 1_0 of the quench zone. The atomizing devices 2 and the reaction mixture inlets 3 are preferably evenly distributed (Figure 5). Again, the atomizing devices form a closed curtain similarly as in Figure 3a. Preferred is an arrangement of atomizing devices 2, as shown in Figure 5, where the atomising devices form an outer rim, that is located between the side wall of the quench zone 7 and the reaction mixture inlets 3, so that it is ensured that the reaction mixture not with the wall comes into contact but hits the quench.

A further preferred embodiment is illustrated in figure 6. Therein the reaction gas 3 is guided along the longitudinal axis of the quench zone, four, itself consists in the transverse to the flow direction of the reaction gas, a curtain of several, in Figure 6, overlapping fan-shaped envelope. This overlapping fan-shaped envelope fill out the entire cross section of the quench nozzle, so that the reaction gas comes into contact with the quench liquid.

The Sprühdüsenachsen the quench nozzles which are mounted in the Figure 6 example, the side of the quench zone can, particularly preferably an angle of 90 ° with the longitudinal axis of the quench zone, that are perpendicular to the longitudinal axis of the quench zone. It is however possible that the Sprühdüsenachsen enclose an angle of about -45 ° to + 135 ° with the longitudinal axis, that is against or are preferably aligned with the flow direction of the reaction gas.

the effluent is passed from a reaction zone preferably in the quench zone, but it can be conducted in a quench zone, the effluents from a plurality of reaction zones through one or more inlets. It is also possible to divide the discharge from a reaction zone and lead several inlets in one or more quench zones.

The liquid which is injected via the atomizer nozzles, must have a low hydrogen chloride and / or phosgene good solubility and speed of isocyanates. Preferably, organic solvents are used. In particular, aromatic solvents, which may be substituted with halogen atoms. Examples of such liquids are toluene, benzene, nitrobenzene, anisole, chlorobenzene, dichlorobenzene (ortho, para), trichlorobenzene, xylene, hexane, Diethylisophtha- lat (DEIP), but also tetrahydrofuran (THF), dimethylformamide (DMF) and mixtures thereof.

In a particular embodiment of the method according to the invention is in the liquid sprayed in a mixture of isocyanates, a mixture of isocyanates and solvent or an isocyanate (wherein the quench liquid components used in each case of low boilers, such as HCl and / or phosgene up to 20 wt% , preferably up to 10 wt%, particularly preferably up to 5% by weight may have, and most preferably up to 2 wt%). using the isocyanate is preferably used which is produced in the respective process. Because by the temperature drop in the quenching the reaction stops, side reactions can veringert with the isocyanates sprayed, if not impossible. The advantage of this embodiment is, in particular, can be dispensed to a separation of the solvent.

The temperature of the liquid sprayed is preferably from 0 to 300 0 C, particularly preferably at 50 to 250 0 C and in particular at 70 to 200 ° C, so that when the injected amount of liquid, the desired cooling and condensation of the isocyanate is reached. This requires the wetgehende stop the reaction.

The velocity of the reaction gas in the quench zone is preferably greater than 1 m / s, particularly preferably greater than 10 m / s and in particular greater than 20 m / s.

The velocity of the reaction gas in the quench zone is preferably greater than 1 m / s, particularly preferably greater than 10 m / s and in particular greater than 20 m / s. In case of a cross-sectional constriction between the reaction and quench zone can be reached in the narrowest cross-section up to the speed of sound in the respective system. By a further expansion of the flow between the smallest cross section and quench and flow rates beyond the speed of sound can be achieved then that require a significant cooling of the gas brin- with it. In this case, a shock wave then occurs in the quench zone, leading to a sudden braking and pressure increase of the gas results. A rapid cooling of the gaseous reaction mixture in the quench zone and a quick transfer of the isocyanate into the liquid phase to achieve the droplets of the liquid sprayed need to be quickly spread over the entire flow cross section of the reaction gas fine. The desired temperature drop, and the desired transfer of the isocyanate into the droplet is preferably within up to 10 seconds, particularly preferably carried out in up to 1 second and especially in up to 0.2 seconds. The figures given are mean quench times. The special design of the quench the deviations of the minimum and maximum quench time from this mean value can be kept small. The related to the mean standard deviation. The related to the mean relative standard deviation of the distribution Quenchzeit- is at most 1, preferably at most 0.5, particularly bervorzugt most 0.25 and in particular 0.1. The above times (quench times) are defined as the period between the occurrence of the reaction gas in the quench and the time at which the reaction gas has completed 90% of the temperature change from inlet temperature to the quench for adiabatic final temperature. The adiabatic final temperature is the temperature which is established when the reaction mixture and quench liquid are mixed in the mass flows and entry temperatures under adiabatic conditions and reach the thermodynamic equilibrium. By selected periods a loss of isocyanate by-products or further reactions can be almost completely avoided.

The mass ratio of of injected amount of liquid to the amount of the gaseous reaction mixture is preferably 100: 1 to 1: 10, more preferably 50: 1 to 1: 5 and in particular 10: 1 to 1: 2.

The withdrawn from the quench liquid phase and gas phase are worked up. When using a solvent as the atomized liquid separation of isocyanate and solvent, is carried out, usually by distillation. The gas phase which consists essentially of phosgene, hydrogen chloride and, optionally, not detached isocyanate, may also be preferably decomposed by distillation or adsorption into their constituents, wherein the phosgene may be recycled to the reaction and the hydrogen chloride used either for further chemical reactions, be further processed to form hydrochloric acid, or may be divided into chlorine and hydrogen again.

In the Figures 1 to 5 embodiments of the method according to the invention are shown.

The invention will be explained in more detail by the following examples. Example 1 :

In a tubular reactor with 8 mm diameter with vorgeschaltendem mixing member 20 kg / h of reaction gas were generated, which contained toluene diisocyanate, phosgene and Chlorwas- serstoff.

The reaction gas was then fed via an annular gap with 17 mm inner diameter (Do, ι) and 19 mm outside diameter (Di) of the quench zone. In the quench zone, a one-fluid nozzle, which was located inside the annular gap coaxially (Figure 1) was. The spray cone of the nozzle was 70 °. The nozzle generated thereby drops having a Sauter mean diameter of about 60 microns. The quench zone consisted of a 10 mm (U) long cylindrical part 19 mm in diameter (Di), a subsequent 40 mm long (L_2 - U) conical part, in which an expansion of 19 to 70 mm is done, followed by a 70 mm -length (L3) cylindrical part of 70 mm diameter (D2), and finally a further conical part with a Veren- supply angle of 60 ° and a final diameter of 12 mm (not shown in Figure 1). The amount of liquid sprayed was 17.4 kg / h. The injected Quenchflüs- sigkeit consisted of monochlorobenzene. The temperature of the reaction gas on entry into the quench zone was 363 ° C and the pressure of the gas 1, 35 bar. The inlet temperature of the quenching liquid was 100 0 C, the exit velocity of the liquid-sigkeitströpfchen from the spray nozzle was about 60 m / s. The residence time of the reaction gas in the front conical portion of the quench zone was approximately 0,029s. The temperature of the quench gas dropped to about 156 ° C. The desired temperature reduction was carried out in about 8 ms. The Toluoldiisocyanatmenge in the reaction gas mixture decreased in the quenching zone by 80% compared to the initial concentration.

List of figures:

Figure 1: quench nozzle coaxially over quench zone, metering of the reaction mixture over the annular gap

Figure 2: quench nozzle coaxially over quench zone, metering of the reaction mixture through angle beta (beta)

Figure 3a: dosing with plurality of spray nozzles

3b shows section 1-1 of Figure 3a

Figure 4: cross-sectional constriction between the reaction and quench zone.

Figure 5: Dose plurality of reaction mixture inlets and spray nozzles

Figure 6: Dosage of the quench medium transverse to the flow direction of the reaction gas. Left: side view, right: view perpendicular to the section AA

Figure 7: Definition of the spray cone angle α (alpha)

List of reference drawings in the figures

1 Quenchflüssigkeitszuführung

2 atomizer

3 reaction entry

4 annular gap 5 quench zone

6 spray cone

7 wall

8 enclosed space

9 liquid and the gas outlet end wall 10 of the quench zone

1 1 cross-sectional constriction

Claims

claims
1. A process for preparing isocyanates by reaction of amines with
Phosgene in the gas phase in at least one reaction zone, wherein the reaction mixture is led to the termination of the reaction by at least one zone is injected into the at least one liquid, characterized in that, passing the reaction mixture through a closed curtain of quench liquid of the cross section of the quenching zone to completely fill.
2. A process for preparing isocyanates by reacting amines with phosgene in the gas phase in at least one reaction zone, passing the reaction mixture to terminate the reaction by at least one zone (quench zone), in which one injects at least one liquid (quench liquid), characterized in that the quench zone of cylindrical or konusför- mig is formed and it thus injects the quench liquid, that the spray pattern of the
quench liquid forms a closed space with the wall of the quench zone and passing the reaction mixture in this space.
3. A method according to claim 2, characterized in that the Quenchflüs- sigkeit coaxially aids.
4. The method according to claim 2 or 3, characterized in that ß the reaction mixture in an angle (beta) of 45 ° to 90 ° is introduced into the quench zone to Sprühdüsenachse.
5. The method according to any one of claims 2 to 4, characterized in that the tangentially introducing the reaction mixture in the quench zone.
6. The method according to any one of the preceding claims, characterized in that the quench time is 0.001 to 0.2 seconds.
7. The method according to any one of the preceding claims, characterized in that the relative standard deviation of the quench time is less than the first
8. The method according to any one of the preceding claims, characterized in that the flow of the reaction mixture at the inlet has a velocity of 0.05 to 1, 0 Mach into the quench zone.
9. A method according to any one of claims 1 to 7, characterized in that the flow of the reaction mixture at the inlet has a speed of at least 1, 0 to 5.0 Mach into the quench zone.
10. The method according to any one of the preceding claims, characterized in that the ratio of flow cross-section of the narrowest flow cross section between the reaction zone and quench zone 10/1 bis 1 / 10th weight.
1 1. A method according to any one of the preceding claims, characterized in that the ratio of flow cross-section in the quench zone to free flow cross section in the reaction zone 25/1 to 1/2.
12. The method according to any one of the preceding claims, characterized in that the reaction mixture at a temperature of 150 to 600 0 C in the
Quenching occurs.
13. The method according to any one of the preceding claims, characterized in that the liquid droplets of the quench medium having a Sauter mean diameter D32 from 5 to 5000 microns.
14. A method according to any one of the preceding claims, characterized in that the liquid droplets of the quench the nozzle at a speed of at least 15 m / s exit.
15. The method according to any one of the preceding claims, characterized in that the ratio of the number of atomizers is the number of entries reaction mixture in the quench zone 10/1 to 1/10 min.
EP07822258A 2006-11-07 2007-11-06 Method for producing isocyanates Withdrawn EP2079685A1 (en)

Priority Applications (3)

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EP06123621 2006-11-07
EP07822258A EP2079685A1 (en) 2006-11-07 2007-11-06 Method for producing isocyanates
PCT/EP2007/061941 WO2008055904A1 (en) 2006-11-07 2007-11-06 Method for producing isocyanates

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP07822258A EP2079685A1 (en) 2006-11-07 2007-11-06 Method for producing isocyanates

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JP2010536911A (en) 2007-08-30 2010-12-02 ビーエーエスエフ ソシエタス・ヨーロピアBasf Se Isocyanate production method
KR101560009B1 (en) 2007-09-19 2015-10-13 바스프 에스이 Process for preparing isocyanates
EP2274339B1 (en) * 2008-05-02 2015-11-11 Basf Se Method and device for the continuous production of polymers by radical polymerization
CN102317254B (en) * 2008-07-23 2014-11-19 巴斯夫欧洲公司 Method for producing isocyanates
TW201016702A (en) * 2008-09-25 2010-05-01 Shionogi & Co Novel pyrrolinone derivative and pharmaceutical composition comprising the same
EP2364294B1 (en) * 2008-11-07 2013-07-03 Basf Se Method for producing isocyanates
CN102239142B (en) * 2008-12-03 2015-07-01 拜耳材料科技股份有限公司 Method for modifying diisocyanates
DE102008061686A1 (en) * 2008-12-11 2010-06-17 Bayer Materialscience Ag Process for the preparation of isocyanates in the gas phase
CN102369182B (en) * 2009-04-08 2015-04-08 巴斯夫欧洲公司 Method for producing isocyanates
CN102803206B (en) * 2010-03-18 2015-01-07 巴斯夫欧洲公司 Method for producing isocyanates
US8981145B2 (en) * 2010-03-18 2015-03-17 Basf Se Process for preparing isocyanates
CN103910613B (en) * 2014-04-11 2016-03-23 淄博职业学院 A kind of method utilizing the hydrogen chloride production trimethyl orthoacetate producing tolylene diisocyanate
CN105017079B (en) * 2015-06-24 2016-11-23 青岛科技大学 A kind of method preparing isocyanates in the presence of an inert solvent

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DE10063161A1 (en) * 2000-12-18 2002-06-20 Basf Ag Process for quenching a hot gas mixture containing (meth) acrylic acid
DE10245704A1 (en) * 2002-09-30 2004-04-01 Bayer Ag Process for quenching a gaseous reaction mixture in the gas phase phosgenation of diamines
DE102004030164A1 (en) * 2004-06-22 2006-01-19 Basf Ag Process for the preparation of isocyanates

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US20100056822A1 (en) 2010-03-04
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JP2010508375A (en) 2010-03-18
WO2008055904A1 (en) 2008-05-15

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