Method and device for producing isocyanates

Abstract

The invention relates to a method for producing isocyanates via gas-phase phosgenation of the corresponding amines in a phosgenation system, in which, in particular, problems due to the formation of deposits in apparatus of the phosgenation system, e.g. in particular the reaction section, during the initial operation (start-up) of the method are preferably avoided. The invention also relates to a device for carrying out the method according to the invention, and to a method for starting up a phosgenation system.

Description

[0001] Process and apparatus for producing isocyanates

[0002] The invention relates to a process for producing isocyanates by gas-phase phosgenation of the corresponding amines in a phosgenation plant, in which, in particular, problems resulting from the formation of deposits in equipment of the phosgenation plant, such as in particular the reaction zone, during commissioning (start-up) of the process are avoided as far as possible. Furthermore, the invention relates to an apparatus for carrying out the process according to the invention and to a process for starting up a phosgenation plant.

[0003] The large-scale production of isocyanates by reacting the corresponding amines with phosgene has long been known in the art. The reaction can take place continuously or discontinuously in the gas or liquid phase. Of particular importance are di- or polyisocyanates, which are suitable for the production of polymers such as polyurethanes, polythiourethanes, polyisocyanurates, or polyureas. Both aromatic isocyanates such as methylenediphenyl diisocyanate or its higher homologues, tolylene diisocyanate, and aliphatic isocyanates such as hexamethylene diisocyanate, pentamethylene diisocyanate, or isophorone diisocyanate are used.

[0004] Modern, large-scale production of polyisocyanates is continuous. Planned shutdowns or unplanned process outages occur repeatedly. The reasons for this are diverse and range from equipment or control system failures to disruptions in the raw material supply to economic reasons such as weak demand for the product.

[0005] WO2015 / 144658 A1 explicitly addresses such deviations from normal operation and provides guidance on how, in the case of such deviations, the risk of deposits in the mixing zone for mixing amine and phosgene, or in the reaction zone arranged downstream in terms of flow, can be minimized. For this purpose, it is recommended to always ensure an excess of phosgene compared to the amine. For example, when starting up continuous production, the reactor is first heated with solvent and phosgene and only then starts the amine feed. Or, when shutting down continuous production, the amine feed is first interrupted and only then the phosgene feed.

[0006] However, problems also arise during a plant shutdown in the equipment upstream of the mixing zone and the reaction zone, which is used for amine preparation, such as its tempering, evaporation, or superheating. These problems are not addressed in the aforementioned documents. For example, there are a number of amines that solidify at room temperature, which makes restarting the plant after a shutdown significantly more difficult, as well as cleaning equipment containing such amines, e.g., for maintenance purposes.

[0007] WO2015 / 144681 A1 deals specifically with the commissioning of a gas-phase phosgenation plant. It discloses that the commissioning of such a plant is a critical process step. It describes how this can lead to the formation of amine droplets and solids such as polyureas or amine hydrochlorides, resulting in an increase in the differential pressure required for sufficient flow through the plant. To minimize these problems, it is particularly recommended to coordinate the reactant flows during the commissioning process so that there is always a stoichiometric excess of phosgene relative to the primary amino groups of the amine.

[0008] Furthermore, operational practice has shown, particularly for the phosgenation of amines in the gas phase, that there are amines that more frequently cause problems under less optimal phosgenation conditions, such as those prevailing during process start-up, for example, with a tendency to rapid deposit formation, and others that behave rather well even under these process conditions, such as l-amino-3,5,5-trimethyl-5-aminomethylcyclohexane (IPDA). Even with consistent application of the teachings of WO2015 / 144681 Al and WO2015 / 144658 Al, it cannot be prevented that it can sometimes take an hour or more for the temperature profiles present in continuous operation to be established in the reaction zone. This is due (without being bound to any theory) to the fact that although the phosgenation reactor is heated beforehand, further heating occurs due to the exothermic reaction.Consequently, in the initial phase, parts of the reaction zone are not yet at optimal operating temperature, which can lead to the early and irreversible formation of deposits during the phosgenation of more problematic amines. These deposits, in turn, can cause a significant increase in pressure, for example, in the amine feed line of the amine device. This cannot be resolved by significantly preheating the reactor. Firstly, this is technically difficult to implement, and secondly, the resulting exothermic reaction leads to excessive temperature in the reaction mixture and thus to product damage.

[0009] The phosgenation of mixtures of different amines, where at least one amine contains an aliphatically bonded primary amino group, is disclosed in DE2249459 A1. There, mixtures of amines are phosgenated, and then one of the isocyanates is separated from the reaction mixture. Reference is made to the economic advantage resulting from such a procedure due to the improved plant utilization, particularly for more specialized isocyanates. In all of the reactions disclosed by way of example, a mixture of two or more amines is first prepared in a fixed ratio, and this mixture is then introduced into the phosgenation apparatus. For a continuous process, it is preferable to add the amines as a mixture or at least simultaneously to the phosgene. If the amines are initially introduced as a mixture, on the one hand, the mixing ratio is fixed, and on the other hand, the problems associated with more demanding amines cannot be reliably avoided.

[0010] There is therefore a need for a process and apparatus for producing isocyanates which avoid the problems mentioned and which allow an improved phosgenation process, in particular during commissioning of the phosgenation plant, enable phosgenation of amines in variable mixing ratios and simplify the cleaning of equipment upstream of the phosgenation reactor in the amine pathway.

[0011] The object of the present invention was therefore to provide a process for producing isocyanates by gas-phase phosgenation of the corresponding amines and a phosgenation plant for carrying out this process, thereby eliminating or at least reducing the aforementioned problems. In particular, the process and the device should avoid or at least significantly reduce a pressure increase in the apparatus of the phosgenation plant, such as the amine stream feed line of the amine stream device, especially during commissioning (start-up) of the phosgenation plant, which usually occurs in prior art plants and processes during the production of isocyanates from the corresponding amines, which leads to such a pressure increase. Preferably, such a pressure increase should also be avoided during the production phase or delayed as long as possible.

[0012] Taking this need into account, the present invention relates to a process for the preparation of isocyanates by gas phase phosgenation of the corresponding amines in a phosgenation plant, which

[0013] (a) at least one phosgene stream device for providing a gaseous phosgene stream, optionally comprising, in addition to phosgene, an inert substance in the phosgene stream

[0014] (b) optionally an inert material flow device for providing an inert material flow,

[0015] (c) at least one amine stream device for providing a gaseous amine stream, optionally comprising, in addition to amines, an inert substance in the amine stream;

[0016] (d) comprises or consists of a phosgenation reactor for mixing the streams from (a) to (c) and reacting the amine stream with the phosgene stream, wherein the following steps are carried out to commission the phosgenation plant:

[0017] (A) feeding the phosgenation reactor with the gaseous phosgene stream and optionally the inert material stream and then continuously feeding the gaseous phosgene stream and optionally the inert material stream into the phosgenation reactor,

[0018] (B) Continuous feeding of the amine stream into the phosgenation reactor, characterized in that step (B) comprises a start-up phase, a subsequent reduction phase and a production phase downstream of the reduction phase, wherein during the start-up phase the amine stream comprises at least a first amine and optionally a second amine different from the first amine and the mass fraction of the first amine in the totality of the amines in the amine stream which is fed to the phosgenation reactor amounts to at least 90.0 wt. %, this mass fraction is then reduced to 85.0 wt. % or less during the reduction phase and this mass fraction is then maintained in the production phase, wherein during the start-up phase, the reduction phase and the production phase the remainder of the totality of the amines in the amine stream which is missing to 100 wt. % is made up of the second amine and optionally to a maximum of 1 wt.-% of further organic amines other than the first and second amines, and wherein the first amine is selected from the group comprising or consisting of 1,6-diaminohexane (HDA), l-amino-3,5,5-trimethyl-5-aminomethylcyclohexane (IPDA), bis(p-aminocyclohexyl)methane (PACM) or mixtures thereof; and the second amine is selected from the group comprising or consisting of 1,5-diaminopentane (PDA), 1,3-bis(aminomethyl)benzene (m-XDA), 1,4-bis(aminomethyl)benzene (p-XDA), 1,2-bis(aminomethyl)cyclohexane (1,2-BAC), 1,3-bis(aminomethyl)cyclohexane (1,3-BAC), 1,4-bis(aminomethyl)cyclohexane (1,4-BAC), tetramethylxylylenediamine (TMXDA), 2,5-.

[0019] Bis(aminomethyl)bicyclo[2.2.1]heptane (2,5-NBDA), 2,6-

[0020] Bis(aminomethyl)bicyclo[2.2.1]heptane (2,6-NBDA), neopentanediamine, 2,4,4-trimethylhexamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1-methyl-2,6-diaminocyclohexane and / or l-methyl-2,4-diaminocyclohexane (together or individually H6TDA), 2,5-diamino-2,5-dideoxy-l,4:3,6-dianhydrosorbitol (ISODA), 2,5-diamino-2,5-dideoxy-l,4:3,6-dianhydromannitol (MANDA) and 2,5-diamino-2,5-dideoxy-l,4:3,6-dianhydroiditol (IDDA) or mixtures thereof.

[0021] Furthermore, the invention relates to a phosgenation plant for carrying out the process according to the invention, comprising or consisting of

[0022] (a) at least one phosgene stream device for providing a gaseous phosgene stream, optionally comprising, in addition to phosgene, an inert substance in the phosgene stream;

[0023] (b) optionally an inert material flow device for providing an inert material flow;

[0024] (c) at least one amine stream device for providing a gaseous amine stream, optionally comprising, in addition to amines, an inert substance in the amine stream; and

[0025] (d) a phosgenation reactor for mixing the streams from (a) to (c) and reacting the amine stream with the phosgene stream; characterized in that the amine stream device is designed to provide the amine stream in such a way that in a start-up phase the amine stream comprises at least a first amine and optionally a second amine and the mass fraction of the first amine in the totality of the amines in the amine stream which can be fed to the phosgenation reactor is at least 90.0 wt. %, preferably 95.0 to 100 wt. %, further preferably 97.5 to 100 wt. %, particularly preferably 99.0 to 100.0 wt. %, very particularly preferably 100 wt. %, this mass fraction is then reduced to 85.0 wt. % or less, preferably 0 to 80.0 wt. %, further preferably 0.1 to 50.0 wt. %, particularly preferably 1.0 to 40.0 wt. %, very particularly preferably 5.0 to 30.0 wt.-% and this mass fraction can then be maintained in a production phase following the reduction phase, wherein during the start-up phase, the reduction phase and the production phase the remainder of the total amines in the amine stream which is missing to 100 wt.% is formed by the second amine and optionally to a maximum of 1 wt.%, preferably a maximum of 0.2 wt.% of further organic amines which are different from the first and second amine.

[0026] Furthermore, the invention is directed to a method for starting up a phosgenation plant, which

[0027] (a) at least one phosgene stream device for providing a gaseous phosgene stream, optionally comprising, in addition to phosgene, an inert substance in the phosgene stream;

[0028] (b) optionally an inert material flow device for providing an inert material flow;

[0029] (c) at least one amine stream device for providing a gaseous amine stream, optionally comprising, in addition to amines, an inert substance in the amine stream; and

[0030] (d) a phosgenation reactor for mixing the streams from (a) to (c) and reacting the amine stream with the phosgene stream; comprising or consisting of, the following steps being carried out to commission the phosgenation plant:

[0031] (A) feeding the phosgenation reactor with the gaseous phosgene stream and, if appropriate, the inert material stream and then continuously feeding the gaseous phosgene stream and, if appropriate, the inert material stream into the phosgenation reactor,

[0032] (B) Continuous feeding of the amine stream into the phosgenation reactor, characterized in that step (B) comprises a start-up phase, a subsequent reduction phase and a production phase downstream of the reduction phase, wherein during the start-up phase the amine stream comprises at least a first amine and optionally a second amine different from the first amine and the mass fraction of the first amine in the totality of the amines in the amine stream which is fed to the phosgenation reactor amounts to at least 90.0 wt. %, this mass fraction is then reduced to 85.0 wt. % or less during the reduction phase and this mass fraction is then maintained in the production phase, wherein during the start-up phase, the reduction phase and the production phase the remainder of the totality of the amines in the amine stream which is missing to 100 wt. % is made up of the second amine and optionally to a maximum of 1 wt.-% of further organic amines other than the first and second amines are formed, and the first amine is selected from the group comprising or consisting of 1,6-diaminohexane (HDA), l-amino-3,5,5-trimethyl-5-aminomethylcyclohexane (IPDA), bis(p-aminocyclohexyl)methane (PACM) or mixtures thereof; and the second amine is selected from the group comprising or consisting of 1,5-diaminopentane (PDA), 1,3-bis(aminomethyl)benzene (m-XDA), 1,4-bis(aminomethyl)benzene (p-XDA), 1,2-bis(aminomethyl)cyclohexane (1,2-BAC), 1,3-bis(aminomethyl)cyclohexane (1,3-BAC), 1,4-bis(aminomethyl)cyclohexane (1,4-BAC), tetramethylxylylenediamine (TMXDA), 2,5-bis(aminomethyl)bicyclo[2.2.1]heptane (2,5-NBDA), 2,6-bis(aminomethyl)bicyclo[2.2.1]heptane (2,6-NBDA), neopentanediamine, 2,4,4-trimethylhexamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, l-methyl-2,6-diaminocyclohexane and / or l-methyl-2,4-diaminocyclohexane (together or individually H6TDA), 2,5-diamino-2,5-dideoxy-l,4:3,6-dianhydrosorbitol (ISODA), 2,5-diamino-2,5-dideoxy-l,4:3,6-dianhydromannitol (MANDA) and 2,5-diamino-2,5-dideoxy-l,4:3,6-dianhydroiditol (IDDA) or mixtures thereof.

[0033] In the context of this invention, the word is to be understood as an indefinite article in connection with countable quantities and only as a numeral if this is explicitly stated, for example, by the addition "exactly one." Expressions such as "one heat exchanger" or "one amine stream" therefore do not exclude the possibility of the presence of additional heat exchangers or amine streams.

[0034] The term "gaseous" should be understood to include droplet entrainment. Phosgenation plant:

[0035] The phosgenation plant comprises or consists of

[0036] (a) at least one phosgene stream device for providing a gaseous phosgene stream, optionally comprising, in addition to phosgene, an inert substance in the phosgene stream;

[0037] (b) optionally an inert material flow device for providing an inert material flow;

[0038] (c) at least one amine stream device for providing a gaseous amine stream, optionally comprising, in addition to amines, an inert substance in the amine stream; and

[0039] (d) a phosgenation reactor for mixing the streams from (a) to (c) and reacting the amine stream with the phosgene stream.

[0040] The phosgene flow device, the optional inert material flow device, the amine flow device and the phosgenation reactor can independently comprise further apparatus which are useful for the operation of the phosgnation plant, such as storage vessels for the starting materials, heat exchangers for temperature control or, if necessary, evaporation of starting materials, devices for processing the reaction mixture after the reaction of amine with phosgene has taken place.

[0041] Preferably, the phosgene stream device comprises at least one heat exchanger for heating the phosgene stream and / or the inert material stream.

[0042] The amine stream device is designed to provide the amine stream in such a way that in a start-up phase the amine stream comprises at least a first amine and optionally a second amine and the mass fraction of the first amine in the totality of the amines in the amine stream which can be fed to the phosgenation reactor is at least 90.0 wt. %, preferably 95.0 to 100 wt. %, further preferably 97.5 to 100 wt. %, particularly preferably 99.0 to 100.0 wt. %, very particularly preferably 100 wt. %, this mass fraction is then reduced to 85.0 wt. % or less, preferably 0 to 80.0 wt. %, further preferably 0.1 to 50.0 wt. %, particularly preferably 1.0 to 40.0 wt. %, very particularly preferably 5.0 to 30.0 wt.-% and this mass fraction can then be maintained in a production phase following the reduction phase, wherein during the start-up phase, the reduction phase and the production phase the remainder of the total amines in the amine stream missing to 100 wt.% is formed by the second amine and optionally to a maximum of 1 wt.% by further organic amines which are different from the first and second amine.

[0043] In a preferred embodiment, the amine flow device comprises a metering device for independently variable supply of the amines in terms of mass fractions. In other words, the amine flow device preferably comprises a metering device for each amine (or amine mixture, if, for example, the first or second amine already represents an amine mixture itself), so that the mass flows / mass fractions can be controlled independently of one another. These can be, for example, metering pumps or control valves.

[0044] Furthermore, it is preferred that the amine stream device comprises i. at least one feed vessel each for the first amine and the second amine, ii. at least one metering device downstream of the feed vessels, iii. optionally at least one mixing device downstream of the metering devices, iv. optionally at least one evaporator for evaporating the amine stream, v. optionally a heat exchanger for heating the amine stream. The optional mixing device can, for example, be a T-piece in the pipeline, a mixing chamber, a static mixer or a pump, in particular a mixing pump, or a stirred tank. However, mixing of the amine streams from the metering devices can also take place in the evaporator. An evaporator is used in particular for liquid amines.

[0045] The optional additional organic amines, which are different from the first and second amines, can either be provided via a separate reservoir or mixed with the first and / or second amine. In particular, this also encompasses impurities that may be present in the first and / or second amine. Preferably, the amine flow device comprises at least one flange connection in at least one of the amine-carrying pipelines, which is designed to receive a blanking plate. This makes it possible to reliably prevent the amine flow through the corresponding line by means of the blanking plate, or to reliably disconnect the corresponding amine line.

[0046] Preferably, at least one storage container, and particularly preferably each of the storage containers, is designed to be heatable. This results in the advantage of further improving the efficiency of the system and the process.

[0047] The phosgene stream device, the optional inert material stream device, and the amine stream device are each connected to the phosgenation reactor via at least one feed line. The feed lines can be connected to the phosgenation reactor, for example, via simple pipelines, flange connections, smooth jet nozzles, annular gap nozzles, or a mixing element. The annular gap nozzle can be equipped with two or more, preferably two coaxially arranged channels for the amine stream and the phosgene stream or an inert gas stream, with the amine stream and the phosgene stream only meeting in the phosgenation reactor.Alternatively, particularly in large-scale applications, the amine is added to the phosgenation reactor through an inlet pipe which has a central nozzle at its end and is held in position by a cover and optionally a holder / rectifier, so that an annular space forms around the inlet pipe in the reactor, with the phosgene entering the annular space via a separate inlet and from there via the rectifier into the phosgenation reactor (see also EPI 362847 A2). The phosgenation reactor has a mixing zone where the streams first meet, and a reaction zone where the streams are further reacted. The mixing zone and reaction zone are preferably present in one apparatus. Furthermore, it is preferred that the phosgenation reactor is set up essentially vertically and is preferably connected at the upper end to the phosgene stream device and the amine stream device.

[0048] In addition, the phosgenation plant preferably comprises at least one quench for cooling and at least partially condensing the reaction mixture, which is connected to the phosgenation reactor, preferably at the lower end. The quench is designed in particular for introducing chlorobenzene, o-dichlorobenzene, and / or at least one of the isocyanates produced in the phosgenation plant. In particular, a collecting vessel is assigned to the quench, the collecting vessel preferably being integrated into the quench or separately connected to it.

[0049] Commissioning of the phosgenation plant:

[0050] In the context of the present invention, the term “commissioning of the phosgenation apparatus” comprises all process steps required to convert a phosgenation apparatus that is out of operation, for example after a maintenance-related shutdown, into continuous control operation for the phosgenation of the corresponding amine(s).

[0051] Within the scope of the invention, at least the following steps are carried out to commission (start up) the phosgenation plant:

[0052] (A) feeding the phosgenation reactor with the gaseous phosgene stream and, if appropriate, the inert material stream and then continuously feeding the gaseous phosgene stream and, if appropriate, the inert material stream into the phosgenation reactor,

[0053] (B) Continuous feed of the amine stream into the phosgenation reactor.

[0054] Step (B) comprises a start-up phase, a subsequent reduction phase and a production phase downstream of the reduction phase, wherein during the start-up phase the amine stream comprises at least a first amine and optionally a second amine different from the first amine and the mass fraction of the first amine in the totality of the amines in the amine stream which is fed to the phosgenation reactor amounts to at least 90.0 wt. %, this mass fraction is then reduced to 85.0 wt. % or less during the reduction phase and this mass fraction is then maintained in the production phase, wherein during the start-up phase, the reduction phase and the production phase the remainder of the totality of the amines in the amine stream which is missing to 100 wt. % is formed by the second amine and optionally up to a maximum of 1 wt. % by further organic amines which are different from the first and second amine.

[0055] In a preferred embodiment, a preheating phase takes place before step (A), during which a heated inert gas, preferably nitrogen, is passed through the amine stream feed line and / or the phosgene stream feed line into the reactor. In a preferred embodiment, the mass fraction of the first amine in the total amines in the amine stream during the start-up phase amounts to 95.0 to 100.0 wt. %, preferably 97.5 to 100.0 wt. %, particularly preferably 99.0 to 100.0 wt. %, very particularly preferably 100 wt. In some cases, for example if the first amine and the second amine do not have a separate feed line to the reactor, it may involve a disproportionate amount of purging effort to remove residues of other amines before the phosgenation apparatus is put into operation.Therefore, in such cases, the starting value for the mass fraction of the first amine in the total stream of amines fed to the phosgenation apparatus is at most 99.9%, preferably at most 99.7%, and particularly preferably at most 99.5%. The duration of the start-up phase is preferably at least 5 minutes, preferably 10 to 2880 minutes, more preferably 15 to 1440 minutes, particularly preferably 20 to 240, most preferably 30 to 120 minutes.

[0056] During the reduction phase, it is preferred that the mass fraction of the first amine in the totality of the amines in the amine stream is reduced to 0 to 80.0 wt. %, more preferably to 0.1 to 50.0 wt. %, particularly preferably to 1.0 to 40.0 wt. %, most preferably to 5.0 to 30.0 wt. %. It is further preferred that the reduction in the mass fraction of the first amine in the reduction phase takes place stepwise or continuously. During the reduction phase, the mass fraction of the first amine can also be temporarily reduced below the value maintained in the production phase. The duration of the reduction phase is preferably at least 0.01 minutes, more preferably at least 0.1 to 240 minutes, particularly preferably 0.5 to 60 minutes, very particularly preferably 1 to 30 minutes.

[0057] During charging and continuous feed in step (A), the phosgene stream and optionally the intermediary stream preferably have a temperature of 200°C to 600°C, more preferably 250°C to 500°C, particularly preferably 250°C to 330°C. Step A) can also be referred to as a heating phase. In a preferred embodiment, the phosgene in the phosgenation reactor is present in a molar excess of 30 to 330%, preferably 60 to 300%, and particularly preferably 90 to 270%, based on the amino groups of the amines.

[0058] The amine stream, when fed into the phosgenation reactor in step (B), preferably has a temperature of 200°C to 600°C, more preferably of 250°C to 500°C, most preferably of 250°C to 330°C. In a preferred embodiment, the feed of the amine stream is not started until the phosgenation reactor has been charged with phosgene and, if appropriate, inert material and the desired starting temperature of 230°C to 320°C, preferably 240 to 310°C, has been reached.

[0059] The inert substance is preferably selected from the group comprising or consisting of inert gases, inert solvents, or mixtures thereof. The inert gas can be selected from the group comprising or consisting of nitrogen, argon, or mixtures thereof. The solvent is preferably selected from the group comprising or consisting of aromatic hydrocarbons, preferably chlorobenzene, o-dichlorobenzene, or mixtures thereof.

[0060] If more than one amine is reacted, it is possible to first mix the amines and then vaporize and heat the amine mixture. Alternatively, one or more amines can be vaporized and heated separately. The feed into the phosgenation reactor can also be carried out separately for different amines through different feed devices (feed lines) or by feeding the mixed amine stream. Even if two or more amines are fed separately into the phosgenation reactor, the sum of these amine streams is considered here as the total stream of amines fed to the phosgenation reactor, so that the proportion of the first amine in the total stream of amines refers to this total stream of amines fed to the reactor at a specific time, regardless of whether this occurs as a mixture or in the form of a separate feed / feed line.Preferably, the amines are first mixed from separate storage vessels and then evaporated together, heated, and fed into the phosgenation reactor. Particularly preferably, the storage vessels are heated.

[0061] Amines:

[0062] The first amine is selected from the group comprising or consisting of 1,6-diaminohexane (HDA), l-amino-3,5,5-trimethyl-5-aminomethylcyclohexane (IPDA), bis(p-aminocyclohexyl)methane (PACM) or mixtures thereof

[0063] The second amine is selected from the group comprising or consisting of 1,5-diaminopentane (PDA), 1,3-bis(aminomethyl)benzene (m-XDA), 1,4-bis(aminomethyl)benzene (p-XDA), 1,2-bis(aminomethyl)cyclohexane (1,2-BAC), 1,3-bis(aminomethyl)cyclohexane (1,3-BAC), 1,4-bis(aminomethyl)cyclohexane (1,4-BAC), tetramethylxylylenediamine (TMXDA), 2,5-bis(aminomethyl)bicyclo[2.2.1]heptane (2,5-NBDA), 2,6-

[0064] Bis(aminomethyl)bicyclo[2.2.1]heptane (2,6-NBDA), neopentanediamine, 2,4,4-trimethylhexamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1-methyl-2,6-diaminocyclohexane and / or l-methyl-2,4-diaminocyclohexane (together or individually H6TDA), 2,5-diamino-2,5-dideoxy-l,4:3,6-dianhydrosorbitol (ISODA), 2,5-diamino-2,5-dideoxy-l,4:3,6-dianhydromannitol (MANDA) and 2,5-diamino-2,5-dideoxy-l,4:3,6-dianhydroiditol (IDDA) or mixtures thereof.

[0065] For the purposes of the invention, the optional further organic amines, which differ from the first and second amines, are understood to mean primary, secondary, and tertiary aliphatic, aromatic, and heterocyclic amines. Examples of further organic amines include 1-aminohexane, 1,2-diaminocyclohexane, 1,4-diaminocyclohexane, 6-aminocapronitrile, bis(hexamethylene)triamine, azepane, azepine, 2-aminomethylcyclopentylamine, 2-methylpentamethylenediamine, 2,3,4,5-tetrahydropyridine, piperidine, tri-n-butylamine, or mixtures thereof.

[0066] Embodiments:

[0067] The present invention particularly relates to the following embodiments:

[0068] According to a first embodiment, the invention relates to a process for the preparation of isocyanates by gas phase phosgenation of the corresponding amines in a phosgenation plant which

[0069] (a) at least one phosgene stream device 20 for providing a gaseous phosgene stream, optionally comprising, in addition to phosgene, an inert substance in the phosgene stream

[0070] (b) optionally an inert material flow device for providing an inert material flow,

[0071] (c) at least one amine stream device 10 for providing a gaseous amine stream, optionally comprising, in addition to amines, an inert substance in the amine stream;

[0072] (d) comprises or consists of a phosgenation reactor 1 for mixing the streams from (a) to (c) and reacting the amine stream with the phosgene stream, wherein the following steps are carried out to commission the phosgenation plant:

[0073] (A) feeding the phosgenation reactor 1 with the gaseous phosgene stream and optionally the inert material stream and then continuously feeding the gaseous phosgene stream and optionally the inert material stream into the phosgenation reactor 1,

[0074] (B) Continuous feeding of the amine stream into the phosgenation reactor 1, characterized in that step (B) comprises a start-up phase, a subsequent reduction phase and a production phase downstream of the reduction phase, wherein during the start-up phase the amine stream comprises at least a first amine and optionally a second amine different from the first amine and the mass fraction of the first amine in the totality of the amines in the amine stream which is fed to the phosgenation reactor 1 amounts to at least 90.0 wt. %, this mass fraction is then reduced to 85.0 wt. % or less during the reduction phase and this mass fraction is then maintained in the production phase, wherein during the start-up phase, the reduction phase and the production phase the remainder of the totality of the amines in the amine stream which is missing to 100 wt. % is made up of the second amine and optionally to a maximum of 1 wt.-% of further organic amines other than the first and second amines, and wherein the first amine is selected from the group comprising or consisting of 1,6-diaminohexane (HDA), l-amino-3,5,5-trimethyl-5-aminomethylcyclohexane (IPDA), bis(p-aminocyclohexyl)methane (PACM) or mixtures thereof; and the second amine is selected from the group comprising or consisting of 1,5-diaminopentane (PDA), 1,3-bis(aminomethyl)benzene (m-XDA), 1,4-bis(aminomethyl)benzene (p-XDA), 1,2-bis(aminomethyl)cyclohexane (1,2-BAC), 1,3-bis(aminomethyl)cyclohexane (1,3-BAC), 1,4-bis(aminomethyl)cyclohexane (1,4-BAC), tetramethylxylylenediamine (TMXDA), 2,5-.

[0075] Bis(aminomethyl)bicyclo[2.2.1]heptane (2,5-NBDA), 2,6-

[0076] Bis(aminomethyl)bicyclo[2.2.1]heptane (2,6-NBDA), neopentanediamine, 2,4,4-trimethylhexamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1-methyl-2,6-diaminocyclohexane and / or l-methyl-2,4-diaminocyclohexane (together or individually H6TDA), 2,5-diamino-2,5-dideoxy-l,4:3,6-dianhydrosorbitol (ISODA), 2,5-diamino-2,5-dideoxy-l,4:3,6-dianhydromannitol (MANDA) and 2,5-diamino-2,5-dideoxy-l,4:3,6-dianhydroiditol (IDDA) or mixtures thereof.

[0077] According to a second embodiment, the invention relates to a process according to embodiment 1, characterized in that the duration of the start-up phase is at least 5 minutes, preferably 10 to 2880 minutes, more preferably 15 to 1440 minutes, particularly preferably 20 to 240, most preferably 30 to 120 minutes.

[0078] According to a third embodiment, the invention relates to a process according to embodiment 1 or 2, characterized in that the reduction of the mass fraction of the first amine in the reduction phase takes place stepwise or continuously.

[0079] According to a fourth embodiment, the invention relates to a process according to one of the preceding embodiments, characterized in that the duration of the reduction phase is at least 0.01 minutes, preferably at least 0.1 to 240 minutes, more preferably 0.5 to 60 minutes, particularly preferably 1 to 30 minutes.

[0080] According to a fifth embodiment, the invention relates to a process according to one of the preceding embodiments, characterized in that during the start-up phase the mass fraction of the first amine in the totality of the amines in the amine stream is 95.0 to 100.0 wt.%, preferably 97.5 to 100.0 wt.%, particularly preferably 99.0 to 100.0 wt.%, very particularly preferably 100 wt.%.

[0081] According to a sixth embodiment, the invention relates to a process according to one of the preceding embodiments, characterized in that during the reduction phase the mass fraction of the first amine in the totality of the amines in the amine stream is reduced to 0 to 80.0 wt.%, preferably to 0.1 to 50.0 wt.%, further preferably to 1.0 to 40.0 wt.%, particularly preferably to 5.0 to 30.0 wt.%.

[0082] According to a seventh embodiment, the invention relates to a process according to one of the preceding embodiments, characterized in that the phosgene stream and optionally the inert material stream during charging and continuous feeding in step (A) has a temperature of 200 °C to 600 °C, preferably from 250 °C to 500 °C, very particularly preferably from 250 °C to 330 °C. According to an eighth embodiment, the invention relates to a process according to one of the preceding embodiments, characterized in that the amine stream during feeding into the phosgenation reactor 1 in step (B) has a temperature of 200 °C to 600 °C, preferably from 250 °C to 500 °C, very particularly preferably from 250 °C to 330 °C.

[0083] According to a ninth embodiment, the invention relates to a process according to one of the preceding embodiments, characterized in that the phosgene is present in the phosgenation reactor 1 in a molar excess with respect to the amino groups of the amines of 30 to 330%, preferably 60 to 300% and particularly preferably 90 to 270%.

[0084] According to a tenth embodiment, the invention relates to a process according to one of the preceding embodiments, characterized in that the inert substance is selected from the group comprising or consisting of inert gases, inert solvents or mixtures thereof.

[0085] According to an eleventh embodiment, the invention relates to a process according to embodiment 10, characterized in that the inert substance is selected from the group comprising or consisting of inert gases, inert solvents or mixtures thereof.

[0086] According to a twelfth embodiment, the invention relates to a process according to embodiment 10 or 11, characterized in that the solvent is selected from the group comprising or consisting of aromatic hydrocarbons, preferably chlorobenzene, o-dichlorobenzene or mixtures thereof.

[0087] According to a thirteenth embodiment, the invention relates to a phosgenation plant for carrying out the process according to embodiments 1 to 12, comprising or consisting of

[0088] (a) at least one phosgene stream device 20 for providing a gaseous phosgene stream, optionally comprising, in addition to phosgene, an inert substance in the phosgene stream;

[0089] (b) optionally an inert material flow device for providing an inert material flow;

[0090] (c) at least one amine stream device 10 for providing a gaseous amine stream, optionally comprising, in addition to amines, an inert substance in the amine stream; and (d) a phosgenation reactor 1 for mixing the streams from (a) to (c) and reacting the amine stream with the phosgene stream; characterized in that the amine stream device 10 is designed to provide the amine stream in such a way that in a start-up phase the amine stream comprises at least a first amine and optionally a second amine and the mass fraction of the first amine in the totality of the amines in the amine stream which can be fed to the phosgenation reactor 1 amounts to at least 90.0 wt. %, preferably 95.0 to 100 wt. %, further preferably 97.5 to 100 wt. %, particularly preferably 99.0 to 100.0 wt. %, very particularly preferably 100 wt. %, this mass fraction is then reduced to 85.0 wt. % or less, preferably 0 to 80.0 wt.-%, more preferably 0.1 to 50.0 wt.%, particularly preferably to 1.0 to 40.0 wt.%, very particularly preferably to 5.0 to 30.0 wt.% and this mass fraction can then be maintained in a production phase following the reduction phase, wherein during the start-up phase, the reduction phase and the production phase the remainder of the totality of the amines in the amine stream which is missing to 100 wt.% is formed by the second amine and optionally to a maximum of 1 wt.% by further organic amines which are different from the first and second amine.

[0091] According to a fourteenth embodiment, the invention relates to a device according to embodiment 13, characterized in that the phosgene stream device 20 comprises at least one heat exchanger 21 for heating the phosgene stream and / or the inert material stream.

[0092] According to a fifteenth embodiment, the invention relates to a device according to embodiment 13 or 14, characterized in that the amine stream device 10 comprises a metering device 13 for the independently variable provision of the amines with regard to the mass fractions.

[0093] According to a sixteenth embodiment, the invention relates to a device according to one of the embodiments 13 to 15, characterized in that the amine stream device 10 i. at least one feed container 11, 12 for the first amine and the second amine, preferably the at least one feed container is designed to be heatable, ii. at least one feed container 11, 12 downstream of the feed containers 11, 12

[0094] Dosing device 13, iii. optionally at least one mixing device 14 downstream of the dosing devices 13, iv. optionally at least one evaporator 15 for evaporating the amine stream, v. optionally a heat exchanger 16 for heating the amine stream.

[0095] According to a seventeenth embodiment, the invention relates to a device according to one of embodiments 13 to 16, characterized in that the phosgenation reactor 1 is set up substantially vertically and is preferably connected at the upper end to the phosgene stream device 20 and the amine stream device 10.

[0096] According to an eighteenth embodiment, the invention relates to a device according to one of embodiments 13 to 17, characterized in that the phosgenation plant comprises at least one quencher 2 for cooling and at least partially condensing the reaction mixture, which quencher is connected to the phosgenation reactor 1, preferably at the lower end, wherein the quencher 2 is designed in particular for introducing chlorobenzene, o-dichlorobenzene and / or at least one of the isocyanates produced in the phosgenation plant.

[0097] According to a nineteenth embodiment, the invention relates to a device according to embodiment 18, characterized in that a collecting container is assigned to the quencher 2, wherein the collecting container is in particular integrated in the quencher or separately connected to it.

[0098] According to a twentieth embodiment, the invention relates to a method for starting up a phosgenation plant, which

[0099] (a) at least one phosgene stream device 20 for providing a gaseous phosgene stream, optionally comprising, in addition to phosgene, an inert substance in the phosgene stream;

[0100] (b) optionally an inert material stream device for providing an inert material stream; (c) at least one amine stream device 10 for providing a gaseous amine stream, optionally comprising, in addition to amines, an inert material in the amine stream; and

[0101] (d) a phosgenation reactor 1 for mixing the streams from (a) to (c) and reacting the amine stream with the phosgene stream; comprising or consisting of, the following steps being carried out to commission the phosgenation plant:

[0102] (A) feeding the phosgenation reactor 1 with the gaseous phosgene stream and optionally the inert material stream and then continuously feeding the gaseous phosgene stream and optionally the inert material stream into the phosgenation reactor 1,

[0103] (B) Continuous feeding of the amine stream into the phosgenation reactor 1, characterized in that step (B) comprises a start-up phase, a subsequent reduction phase and a production phase downstream of the reduction phase, wherein during the start-up phase the amine stream comprises at least a first amine and optionally a second amine different from the first amine and the mass fraction of the first amine in the totality of the amines in the amine stream which is fed to the phosgenation reactor 1 amounts to at least 90.0 wt. %, this mass fraction is then reduced to 85.0 wt. % or less during the reduction phase and this mass fraction is then maintained in the production phase, wherein during the start-up phase, the reduction phase and the production phase the remainder of the totality of the amines in the amine stream which is missing to 100 wt. % is made up of the second amine and optionally to a maximum of 1 wt.-% of further organic amines other than the first and second amines are formed, and the first amine is selected from the group comprising or consisting of 1,6-diaminohexane (HDA), l-amino-3,5,5-trimethyl-5-aminomethylcyclohexane (IPDA), bis(p-aminocyclohexyl)methane (PACM) or mixtures thereof; and the second amine is selected from the group comprising or consisting of 1,5-diaminopentane (PDA), 1,3-bis(aminomethyl)benzene (m-XDA), 1,4-bis(aminomethyl)benzene (p-XDA), 1,2-bis(aminomethyl)cyclohexane (1,2-BAC), 1,3-bis(aminomethyl)cyclohexane (1,3-BAC), 1,4-bis(aminomethyl)cyclohexane (1,4-BAC), tetramethylxylylenediamine (TMXDA), 2,5-bis(aminomethyl)bicyclo[2.2.1]heptane (2,5-NBDA), 2,6-bis(aminomethyl)bicyclo[2.2.1]heptane (2,6-NBDA), neopentanediamine, 2,4,4-trimethylhexamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, l-methyl-2,6-diaminocyclohexane and / or l-methyl-2,4-diaminocyclohexane (together or individually H6TDA), 2,5-diamino-2,5-dideoxy-l,4:3,6-dianhydrosorbitol (ISODA), 2,5-diamino-2,5-dideoxy-l,4:3,6-dianhydromannitol (MANDA) and 2,5-diamino-2,5-dideoxy-l,4:3,6-dianhydroiditol (IDDA) or mixtures thereof.

[0104] According to a twenty-first embodiment, the invention relates to a use of a device according to one of embodiments 13 to 19 for carrying out a method according to one of embodiments 1 to 12.

[0105] Examples:

[0106] The present invention is explained below with reference to Figure 1 and the following examples, but is not limited to these.

[0107] Figure 1: a schematic representation of a phosgenation plant according to the invention.

[0108] Figure 1 shows a schematic representation of a phosgenation plant according to the invention. This comprises a vertically arranged tubular reactor / phosgenation reactor (PR) 1 with a residence time section for reacting an amine stream with a phosgene stream, and a downstream quencher (Q) with a collecting vessel 2 for cooling and at least partially condensing the reaction gases generated in the phosgenation reactor 1, an amine stream device 10 for providing the amine stream, and a phosgene stream device 20 for providing the phosgene stream. The quencher 2 has a product outlet 4 for conducting the liquid crude product and a gas outlet 5 for discharging the offgases.

[0109] The amine stream device 10 consists of a first and second feed tank 11, 12 for a first (Al) and a second amine (A2), respectively, as well as a metering device (D) 13 downstream of the feed tanks 11, 12 for independently variable adjustment of the quantitative ratios (or mass fractions) of the amines (Al), (A2) from the first and second feed tanks 11, 12. Downstream of the metering device 13 is a mixing device (M) 14 for mixing the amine streams, with an evaporator (V) 15 for evaporating the amine stream being arranged downstream of the mixing device 14. A heat exchanger (WT) 16 for heating the amine stream is arranged downstream of the evaporator 15.

[0110] The phosgene stream device 20 comprises a heat exchanger (WT) 21 for heating the phosgene stream.

[0111] The amine stream device 10 is connected to the phosgenation reactor 1 via an amine stream feed line 17, and the phosgene stream device 20 is connected via a phosgene stream feed line 22. The feed lines open into an annular nozzle 3 provided in the head region of the phosgenation reactor 1, having two coaxially arranged channels. By feeding the phosgene stream and the amine stream separately, mixing and conversion of these reactants can take place immediately after injection into the phosgenation reactor. The amine stream feed line 17 of the amine stream device 10 is also equipped with a pressure gauge 18 for measuring the pressure in the amine stream feed line 17.

[0112] General working instructions:

[0113] The following examples were carried out in a pilot plant for gas-phase phosgenation according to Figure 1. Phosgene was heated to approximately 340 °C in heat exchanger 21 and introduced at this temperature into the phosgenation reactor 1 via the phosgene stream feed line 22 and the annular gap nozzle 3. On the amine side, the first and / or the second amine were metered from the feed vessels 11 and 12 independently of one another via a metering device 13 as required, so that the desired mass fractions were achieved. After passing through the metering device 13, the amines were mixed in a mixing device 14, subsequently vaporized in an evaporator 15, then superheated to approximately 330 °C in a heat exchanger 16 and introduced at this temperature into the phosgenation reactor 1 via the amine stream feed line 17 and the annular gap nozzle 3. The molar excess of phosgene was, depending on the amine used.The amine mixture used was between 140% and 300%, based on the amine's amino groups. To start the continuous reaction, phosgenation reactor 1 was initially fed with hot phosgene only until a constant temperature was reached. Only then was the addition of amine vapor begun. The reaction proceeded adiabatically, except for unavoidable heat losses. After passing through the residence time zone, the reaction gases were cooled and at least partially condensed in quench 2 by introducing chlorobenzene. The pressure in the amine stream feed line 17 was monitored via a pressure gauge 18.

[0114] Comparison example 1

[0115] Phosgenation reactor 1 was heated to the starting temperature using phosgene vapor as described in the general operating procedure. Then, a 20:80 mixture (weight ratio) of ISODA to IPDA from the two amine receivers was metered via metering devices 13 to mixing device 14, thus starting the phosgenation reaction. Deposits formed in phosgenation reactor 1, leading to a rapid and accelerating increase in pressure in amine stream feed line 17 of amine stream device 10. After approximately 9 minutes, the pressure had risen from an initial level of approximately 1000 mbar to 1500 mbar, and the reaction was terminated. Example 1

[0116] Phosgenation reactor 1 was prepared as in Comparative Example 1. However, after the heating-up phase, in a start-up phase, only IPDA was initially metered via the metering devices 13 to the mixing device 14, i.e., ISODA to IPDA at a ratio of 0:100 (weight ratio), in order to initially start the reaction with IPDA. After 60 minutes of continuous operation, the reduction phase was initiated. The IPDA feed rate was reduced and, at the same time, ISODA feed rates were started until a 10:90 mixture (weight ratio) of ISODA to IPDA was reacted. After a further 30 minutes, the amine feed rates were further adjusted so that the weight ratio of ISODA to IPDA was now 20:80 (weight ratio), i.e., exactly the ratio from Comparative Example 1. Phosgenation was continued for a further 60 minutes at this mixing ratio (production phase) before the reaction was terminated.The pressure in the amine stream feed line 17 of the amine stream device 10 remained almost constant during the reaction and was approximately 1020 mbar at the end (approximately 1000 mbar initially).

[0117] Comparison example 2

[0118] Phosgenation reactor 1 was heated to the starting temperature using phosgene vapor as described in the general operating procedure. The reaction was then started by vaporizing PDA and introducing it into phosgenation reactor 1 via the nozzle, corresponding to a PDA to IPDA weight ratio of 100:0. A rapid increase in pressure was observed in the amine stream feed line 17 of the amine stream device 10, reaching the limit of 1500 mbar (initially approximately 1000 mbar) after just 6 minutes, thus terminating the reaction.

[0119] Example 2

[0120] Phosgenation reactor 1 was prepared as in Comparative Example 2. However, after the heating phase, only IPDA was initially metered via the metering devices 13 to the mixing device 14, i.e., PDA to IPDA at a weight ratio of 0:100, to initially start the reaction with IPDA (start-up phase). After 1.5 hours, the weight ratio of PDA to IPDA was changed in five equal steps (20:80, 40:60, 60:40, 80:20, and 100:0) every 30 minutes to the target value of 100:0 (weight ratio of PDA to IPDA) (reduction phase). The reaction was continued with PDA for another 1.5 hours (production phase) before the experiment was terminated at a pressure of 1090 mbar in the amine stream feed line 17 of the amine stream device 10. The formation of deposits was therefore considerably slower compared to comparative example 2.

[0121] List of reference symbols

[0122] Phosgenation reactor / tubular reactor (PR)

[0123] Quench with collecting container (Q)

[0124] Annular gap nozzle with two coaxially arranged channels

[0125] Product outlet

[0126] Gas outlet

[0127] Amine flow device

[0128] Storage tank for the first amine (Al)

[0129] Storage tank for the second amine (A2)

[0130] Dosing device(s)

[0131] Mixing device (M)

[0132] Evaporator (V) of the amine flow device

[0133] Heat exchanger (WT) of the amine stream device

[0134] Amine stream feed line

[0135] pressure gauge

[0136] Phosgene flow device

[0137] Heat exchanger (WT) of the phosgene flow device

[0138] Phosgene stream feed line

Claims

Patent claims 1. Process for the production of isocyanates by gas-phase phosgenation of the corresponding amines in a phosgenation plant, which (a) at least one phosgene stream device (20) for providing a gaseous phosgene stream, optionally comprising an inert substance in the phosgene stream in addition to phosgene (b) where appropriate an inert material flow device for providing an inert material flow, (c) at least one amine stream device (10) for providing a gaseous amine stream, optionally comprising an inert substance in the amine stream in addition to amines; (d) a phosgenation reactor (1) for mixing the streams from (a) to (c) and reacting the amine stream with the phosgene stream, comprising or consisting of the following steps to put the phosgenation plant into operation: (A) Feeding the phosgenation reactor (1) with the gaseous phosgene stream and optionally the inert material stream, and subsequently continuously supplying the gaseous phosgene stream and optionally the inert material stream into the phosgenation reactor (1), (B) Continuous feed of the amine stream into the phosgenation reactor (1), characterized in that step (B) comprises a start-up phase, a subsequent reduction phase and a production phase following the reduction phase, wherein during the start-up phase the amine stream comprises at least a first amine and optionally a second amine different from the first amine and the mass fraction of the first amine in the totality of amines in the amine stream fed to the phosgenation reactor (1) is at least 90.0 wt.%, this mass fraction is then reduced to 85.0 wt.% or less during the reduction phase and this mass fraction is then maintained in the production phase, wherein during the start-up phase, the reduction phase and the production phase the remaining amount of amines missing to reach 100 wt.% in the totality of amines in the amine stream is supplied by the second amine and optionally to a maximum of 1 wt.%.-% of other organic amines, which differ from the first and second amines, are formed and wherein the first amine is selected from the group comprising or consisting of 1,6-diaminohexane (HDA), l-amino-3,5,5-trimethyl-5-aminomethylcyclohexane (IPDA), bis(p-aminocyclohexyl)methane (PACM) or mixtures thereof; and the second amine is selected from the group comprising or consisting of 1,5-diaminopentane (PDA), 1,3-bis(aminomethyl)benzene (m-XDA), 1,4- Bis(aminomethyl)benzene (p-XDA), 1,2-Bis(aminomethyl)cyclohexane (1,2-BAC), 1,3-Bis(aminomethyl)cyclohexane (1,3-BAC), 1,4- Bis(aminomethyl)cyclohexane (1,4-BAC), tetramethylxylylenediamine (TMXDA), 2.5-Bis(aminomethyl)bicyclo[2.2.1]heptane (2,5-NBDA), 2,6- Bis(aminomethyl)bicyclo[2.2.1]heptane (2,6-NBDA), neopentanediamine, 2,4,4-trimethylhexamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1-methyl-2,6-diaminocyclohexane and / or l-methyl-2,4-diaminocyclohexane (together or individually H6TDA), 2,5-Diamino-2,5-dideoxy-1,4:3,6-dianhydrosorbitol (ISODA), 2,5-Diamino-2,5-dideoxy-1,4:3,6-dianhydromannitol (MANDA), and 2,5-Diamino-2,5-dideoxy-1,4:3,6-dianhydroiditol (IDDA), or mixtures thereof. A process according to claim 1, characterized in that the duration of the start-up phase is at least 5 minutes, preferably 10 to 2880 minutes, more preferably 15 to 1440 minutes, particularly preferably 20 to 240 minutes, most preferably 30 to 120 minutes, and / or that the duration of the reduction phase is at least 0.01 minutes, preferably at least 0.1 to 240 minutes, more preferably 0.5 to 60 minutes, particularly preferably 1 to 30 minutes. Method according to claim 1 or 2, characterized in that during the start-up phase the mass fraction of the first amine in the totality of the amines in the amine stream is 95.0 to 100.0 wt.%, preferably 97.5 to 100.0 wt.%, particularly preferably 99.0 to 100.0 wt.%, most preferably 100 wt.%.Method according to one of the preceding claims, characterized in that during the reduction phase the mass fraction of the first amine in the totality of the amines in the amine stream is reduced to 0 to 80.0 wt.%, preferably to 0.1 to 50.0 wt.%, more preferably to 1.0 to 40.0 wt.%, particularly preferably to 5.0 to 30.0 wt.%. A method according to one of the preceding claims, characterized in that the phosgene stream and optionally the inert material stream has a temperature of 200 °C to 600 °C, preferably 250 °C to 500 °C, most preferably 250 °C to 330 °C during charging and continuous feeding in step (A) and / or that the amine stream has a temperature of 200 °C to 600 °C, preferably 250 °C to 500 °C, most preferably 250 °C to 330 °C during feeding into the phosgenation reactor (1) in step (B). Method according to one of the preceding claims, characterized in that the phosgene in the phosgenation reactor (1) is present in a molar excess with respect to the amino groups of the amines of 30 to 330%, preferably 60 to 300% and particularly preferably 90 to 270%.A process according to any one of the preceding claims, characterized in that the inert substance is selected from the group comprising or consisting of inert gases, inert solvents, or mixtures thereof. A process according to claim 7, characterized in that the inert gas is selected from the group comprising or consisting of nitrogen, argon, or mixtures thereof, and / or that the solvent is selected from the group comprising or consisting of aromatic hydrocarbons, preferably chlorobenzene, o-dichlorobenzene, or mixtures thereof. A phosgenation apparatus for carrying out the process according to claims 1 to 8, comprising or consisting of (a) at least one phosgene stream device (20) for providing a gaseous phosgene stream, optionally comprising an inert substance in the phosgene stream in addition to phosgene; (b) where appropriate, an inert material flow device for providing an inert material flow; (c) at least one amine stream device (10) for providing a gaseous amine stream, optionally comprising an inert substance in the amine stream in addition to amines; and (d) a phosgenation reactor (1) for mixing the streams from (a) to (c) and Reaction of the amine current with the phosgene current; characterized in that the amine stream device (10) is configured to provide the amine stream in such a way that, during a start-up phase, the amine stream comprises at least a first amine and optionally a second amine, and the mass fraction of the first amine in the totality of amines in the amine stream that can be supplied to the phosgenation reactor (1) is at least 90.0 wt.%, preferably 95.0 to 100 wt.%, more preferably 97.5 to 100 wt.%, particularly preferably 99.0 to 100.0 wt.%, and most preferably 100 wt.%, and this mass fraction is then reduced during a reduction phase following the start-up phase to 85.0 wt.% or less, preferably 0 to 80.0 wt.%, more preferably 0.1 to 50.0 wt.%, particularly preferably to 1.0 to 40.0 wt.%, and most preferably to 5.0 to 30.0 wt.%.-% reduced and this mass fraction can then be maintained in a production phase following the reduction phase, wherein during the start-up phase, the reduction phase and the production phase the remaining 100 wt.% of the total amines missing in the amine stream is formed by the second amine and optionally up to a maximum of 1 wt.% by further organic amines, which are different from the first and second amines. Device according to claim 9, characterized in that the phosgene stream device comprises at least one heat exchanger (21) for heating the phosgene stream and / or the inert material stream. Device according to claim 9 or 10, characterized in that the amine stream device comprises a metering device (13) for independently variable provision of the amines with respect to the mass fractions. Device according to one of claims 9 to 11, characterized in that the amine stream device (10) i.at least one storage container (11, 12) each for the first amine and the second amine, ii. at least one dosing device (13) downstream of each storage container (11, 12), iii. optionally at least one mixing device (14) downstream of the dosing devices (13). iv. optionally comprising at least one evaporator (15) for evaporating the amine stream, v. optionally comprising a heat exchanger (16) for heating the amine stream. Device according to any one of claims 9 to 12, characterized in that the phosgenation plant comprises at least one quenche (2) for cooling and at least partially condensing the reaction mixture, which is connected to the phosgenation reactor (1), preferably at the lower end, wherein the quenche (2) is configured in particular for introducing chlorobenzene, o-dichlorobenzene and / or at least one of the isocyanates produced in the phosgenation plant. Device according to claim 13, characterized in that a collection vessel is associated with the quenche (2), wherein the collection vessel is in particular integrated into the quenche (2) or separately connected to it. drive to start up a phosgenation plant which (a) at least one phosgene stream device (20) for providing a gaseous phosgene stream, optionally comprising an inert substance in the phosgene stream in addition to phosgene; (b) where appropriate, an inert material flow device for providing an inert material flow; (c) at least one amine stream device (10) for providing a gaseous amine stream, optionally comprising an inert substance in the amine stream in addition to amines; and (d) a phosgenation reactor (1) for mixing the streams from (a) to (c) and reacting the amine stream with the phosgene stream; comprising or consisting of, the following steps being carried out to put the phosgenation plant into operation: (A) Feeding the phosgenation reactor (1) with the gaseous phosgene stream and optionally the inert material stream, and subsequently continuously supplying the gaseous phosgene stream and optionally the inert material stream into the phosgenation reactor (1), (B) Continuous feed of the amine stream into the phosgenation reactor (1), characterized in that step (B) comprises a start-up phase, a subsequent reduction phase and a production phase following the reduction phase, wherein during the start-up phase the amine stream comprises at least a first amine and optionally a second amine different from the first amine and the mass fraction of the first amine in the totality of amines in the amine stream fed to the phosgenation reactor (1) is at least 90.0 wt.%, this mass fraction is then reduced to 85.0 wt.% or less during the reduction phase and this mass fraction is then maintained in the production phase, wherein during the start-up phase, the reduction phase and the production phase the remaining amount of amines missing to reach 100 wt.% in the totality of amines in the amine stream is supplied by the second amine and optionally to a maximum of 1 wt.%.-% of other organic amines, which are different from the first and second amines, and the first amine is selected from the group comprising or consisting of 1,6-diaminohexane (HDA), l-amino-3,5,5-trimethyl-5-aminomethylcyclohexane (IPDA), bis(p-aminocyclohexyl)methane (PACM) or mixtures thereof; and the second amine is selected from the group comprising or consisting of 1,5-diaminopentane (PDA), 1,3-bis(aminomethyl)benzene (m-XDA), 1,4- Bis(aminomethyl)benzene (p-XDA), 1,2-Bis(aminomethyl)cyclohexane (1,2-BAC), 1,3-Bis(aminomethyl)cyclohexane (1,3-BAC), 1,4- Bis(aminomethyl)cyclohexane (1,4-BAC), tetramethylxylylenediamine (TMXDA), 2.5-Bis(aminomethyl)bicyclo[2.2.1]heptane (2,5-NBDA), 2,6- Bis(aminomethyl)bicyclo[2.2.1]heptane (2,6-NBDA), neopentanediamine, 2,4,4-trimethylhexamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1-methyl-2,6-diaminocyclohexane and / or l-methyl-2,4-diaminocyclohexane (together or individually H6TDA), 2,5-Diamino-2,5-dideoxy-l,4:3,6-dianhydrosorbitol (ISODA), 2,5-Diamino-2,5-dideoxy-l,4:3,6-dianhydromannitol (MANDA) and 2,5-Diamino-2,5-dideoxy-l,4:3,6-dianhydroiditol (IDDA) or mixtures thereof.

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