Method and device for producing isocyanates

Abstract

The invention relates to a method for producing isocyanates by gas-phase phosgenation of the corresponding amines in a phosgenation plant, in particular as far as possible avoiding problems during the start-up (start-up) of the method due to the formation of deposits in the installation of the phosgenation plant, for example in particular in the reaction section. The invention also relates to a device for carrying out the method according to the invention and to a method for starting a phosgenation installation.

Description

[0001] The present invention relates to a process for producing isocyanates by gas-phase phosgenation of the corresponding amines in a phosgenation plant, wherein in particular problems during the start-up (start-up) of the process due to the formation of deposits in the apparatus of the phosgenation plant, such as in particular the reaction stage, are avoided as far as possible. The present invention further relates to an apparatus for carrying out the process according to the invention and to a method for starting up a phosgenation plant.

[0002] The production of isocyanates on an industrial scale by reacting the corresponding amines with phosgene has long been known in the prior art, the reaction being able to be carried out continuously or discontinuously in the gas phase or in the liquid phase. Of particular importance are diisocyanates or polyisocyanates which are suitable for the production of polymers such as polyurethanes, polythiourethanes, polyisocyanurates or polyureas. The isocyanates used here are aromatic isocyanates, for example diphenylmethane diisocyanate or its higher homologues, toluene diisocyanate, or aliphatic isocyanates, for example hexamethylene diisocyanate, pentamethylene diisocyanate or isophorone diisocyanate.

[0003] The modern industrial-scale production of polyisocyanates is carried out continuously. Planned downtimes or unplanned failures are always present in this process. The causes are manifold and range from failures in the plant or control units to interruptions in the supply of raw materials to economic reasons, such as insufficient demand for the product.

[0004] WO 2015 / 144658 A1 explicitly deals with such deviations from normal operation and gives instructions on how the risk of deposits in the mixing zone for mixing amine and phosgene or in the reaction zone arranged downstream thereof in terms of flow technology can be minimized in the case of such deviations. For this purpose, it is recommended to always ensure that there is an excess of phosgene relative to the amine, for example by first heating the reactor only with solvent and phosgene during the start-up of continuous production and then starting to feed in amine, or by first interrupting the feed of amine and then interrupting the feed of phosgene during the shutdown of continuous production.

[0005] However, in the apparatus for preparing the amines upstream of the mixing and reaction zones, i.e., for example, for their temperature control, evaporation or superheating, there are also problems in the event of a plant shutdown which are not discussed in the cited documents. For example, many amines solidify at room temperature, so that restarting after a shutdown becomes significantly more difficult on the one hand and cleaning of the apparatus containing such amines, for example for maintenance purposes, on the other hand.

[0006] WO 2015 / 144681 A1 relates specifically to the start-up of a gas-phase phosgenation facility. It is disclosed that the start-up of such a facility is a critical process step. It is stated that amine droplets and solids such as polyureas or amine hydrochlorides may form, so that the pressure difference required for sufficient flow through the facility increases. In order to minimize these problems, it is particularly recommended to match the reactant streams to one another even during the start-up operation so that phosgene is always present in a stoichiometric excess relative to the primary amino groups of the amine.

[0007] Furthermore, in operating practice, it has been found that some amines, especially for the phosgenation of amines in the gas phase, are more often problematic under non-optimal phosgenation conditions such as those present at process startup, i.e., for example, tend to form deposits quickly, while some amines also exhibit fewer problems under these process conditions, in particular, for example, 1-amino-3,5,5-trimethyl-5-aminomethylcyclohexane (IPDA). Even if the teachings of WO 2015 / 144681 A1 and WO 2015 / 144658 A1 are applied consistently, it cannot be prevented that sometimes one hour or more may be required before the temperature profile present in continuous operation is established in the reaction zone. This is because (without being bound by any theory) the phosgenation reactor, although preheated, is further heated due to the exothermic reaction. Therefore, in the initial stage, some parts of the reaction zone are not yet at the optimal operating temperature, which in the phosgenation of more problematic amines can lead to early and irreversible deposit formation. These deposits in turn can lead to a significant increase in pressure, for example in the amine feed line of the amine plant. This cannot even be solved by a higher preheating of the reactor. Firstly, this is technically difficult to achieve and secondly, the onset of the exothermic reaction subsequently leads to excessively high temperatures in the reaction mixture and thus to damage of the product.

[0008] DE2249459 A1 discloses the phosgenation of a mixture of various amines, wherein at least one amine contains an aliphatic bonded primary amino group. Here, the mixture of amines is phosgenated and one of the isocyanates is then separated from the reaction mixture. The economic advantages brought about by the better utilization of facilities for specific isocyanates in this procedure are pointed out. In all reactions disclosed by way of example, a mixture of two or more amines is first produced in a fixed ratio and then this mixture is introduced into the phosgenation unit. For a continuous process, the amines are preferably added to the phosgene as a mixture or at least simultaneously. If the amines are pre-loaded as a mixture, on the one hand the mixing ratio is fixed and on the other hand the problems associated with the more demanding amines cannot be reliably avoided.

[0009] There is therefore a need for a process and a device for producing isocyanates which avoid the problems mentioned and which make it possible to improve the phosgenation process, in particular during the start-up of a phosgenation plant, to enable phosgenation of amines with variable mixing ratios and to simplify the cleaning of the devices upstream of the phosgenation reactor via the amine route.

[0010] The object of the present invention is therefore to provide a process for producing isocyanates by gas-phase phosgenation of the corresponding amines and a phosgenation plant for carrying out the process which in particular eliminate or at least reduce the above-mentioned problems. In particular, the process and the plant should avoid or at least significantly reduce pressure increases in the amine stream feed lines of the plants of the phosgenation plant, such as the amine stream plant, which usually occur in the production of isocyanates from the corresponding amines which cause such pressure increases in the prior art plants and processes, in particular during the start-up (start-up) of the phosgenation plant. Such pressure increases should preferably be avoided or delayed as long as possible even during the production phase.

[0011] Taking this need into account, the subject of the present invention is a process for producing isocyanates by gas-phase phosgenation of the corresponding amines in a phosgenation plant comprising or consisting of:

[0012] (a) at least one phosgene stream device for providing a gaseous phosgene stream which, in addition to phosgene, optionally comprises inert substances;

[0013] (b) optionally an inert material stream device for providing an inert material stream,

[0014] (c) at least one amine stream device for providing a gaseous amine stream which optionally contains inert substances in addition to the amines,

[0015] (d) a phosgenation reactor for mixing the streams from (a) to (c) and reacting the amine stream with the phosgene stream;

[0016] The phosgenation facility is started up by performing the following steps:

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

[0018] (B) continuously feeding the amine stream into the phosgenation reactor,

[0019] 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 proportion of the first amine in the total amount of amines in the amine stream fed to the phosgenation reactor is at least 90.0% by weight, this mass proportion is then reduced to 85.0% by weight or less during the reduction phase and this mass proportion is then maintained in the production phase, wherein during the start-up phase, the reduction phase and the production phase, the remainder of the total amount of amines in the amine stream to 100% by weight is formed by the second amine and optionally to a maximum of 1% by weight by further organic amines different from the first amine and the second amine, and wherein

[0020] - the first amine is selected from 1,6-diaminohexane (HDA), 1-amino-3,5,5-trimethyl-5-aminomethylcyclohexane (IPDA), bis(p-aminocyclohexyl)methane (PACM) or a mixture thereof; and

[0021] - the second amine is selected from 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), tetramethylphenylenediamine (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), neopentylene diamine, 2 ,4,4-trimethylhexamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1-methyl-2,6-diaminocyclohexane and / or 1-methyl-2,4-diaminocyclohexane (collectively or individually referred to as 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 a mixture thereof.

[0022] The present invention further relates to a phosgenation plant for carrying out the process according to the invention, comprising or consisting of:

[0023] (a) at least one phosgene stream device for providing a gaseous phosgene stream which, in addition to phosgene, optionally comprises inert substances;

[0024] (b) optionally an inert material stream device for providing an inert material stream;

[0025] (c) at least one amine stream device for providing a gaseous amine stream, which optionally contains inert substances in addition to the amine; and

[0026] (d) a phosgenation reactor for mixing the streams from (a) to (c) and reacting the amine stream with the phosgene stream;

[0027] Characterized in that the amine stream device is configured to provide the amine stream so that in the startup phase, the amine stream comprises at least one first amine and optionally a second amine, and the mass proportion of the first amine in the total amount of amines in the amine stream that can be supplied to the phosgenation reactor is at least 90.0% by weight, preferably 95.0% by weight to 100% by weight, further preferably 97.5% by weight to 100% by weight, more preferably 99.0% by weight to 100.0% by weight, most preferably 100% by weight, and this mass proportion can then be reduced to 85.0% by weight during a reduction phase after the startup phase or less, preferably to 0% by weight to 80.0% by weight, further preferably to 0.1% by weight to 50.0% by weight, more preferably to 1.0% by weight to 40.0% by weight, most preferably to 5.0% by weight to 30.0% by weight, and this mass ratio can then be maintained in the production stage downstream of the reduction stage, wherein during the startup phase, the reduction phase and the production phase, the balance to 100% by weight of the total amount of amines in the amine feed stream is formed by the second amine and optionally to a maximum of 1% by weight, preferably to a maximum of 0.2% by weight, by further organic amines different from the first and second amines.

[0028] The invention also relates to a method for starting up a phosgenation plant, the phosgenation plant comprising or consisting of:

[0029] (a) at least one phosgene stream device for providing a gaseous phosgene stream which, in addition to phosgene, optionally comprises inert substances;

[0030] (b) optionally an inert material stream device for providing an inert material stream;

[0031] (c) at least one amine stream device for providing a gaseous amine stream, which optionally contains inert substances in addition to the amine; and

[0032] (d) a phosgenation reactor for mixing the streams from (a) to (c) and reacting the amine stream with the phosgene stream;

[0033] The phosgenation facility is started up by performing the following steps:

[0034] (A) charging the phosgenation reactor with the gaseous phosgene stream and optionally the inert substance stream and then continuously feeding the gaseous phosgene stream and optionally the inert substance stream into the phosgenation reactor,

[0035] (B) continuously feeding the amine stream into the phosgenation reactor,

[0036] 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 one first amine and optionally a second amine different from the first amine, and the mass proportion of the first amine in the total amount of amines in the amine stream fed to the phosgenation reactor is at least 90.0% by weight, this mass proportion is then reduced to 85.0% by weight or less during the reduction phase and this mass proportion is then maintained in the production phase, wherein during the start-up phase, the reduction phase and the production phase, the remainder of the total amount of amines in the amine stream to 100% by weight is formed by the second amine and optionally to a maximum of 1% by weight by further organic amines different from the first and second amines, and

[0037] - the first amine is selected from 1,6-diaminohexane (HDA), 1-amino-3,5,5-trimethyl-5-aminomethylcyclohexane (IPDA), bis(p-aminocyclohexyl)methane (PACM) or a mixture thereof; and

[0038] - the second amine is selected from 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), tetramethylphenylenediamine (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), neopentylene diamine, 2 ,4,4-trimethylhexamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1-methyl-2,6-diaminocyclohexane and / or 1-methyl-2,4-diaminocyclohexane (collectively or individually referred to as 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 a mixture thereof.

[0039] In the present invention, the word "a" or "an" in relation to countable parameters should only be understood as an indefinite article and only when explicitly stated as a quantity, for example by adding "exactly one". Expressions such as "a heat exchanger" or "an amine stream" therefore do not exclude the possibility that further heat exchangers or amine streams are present.

[0040] The term "gaseous" should be understood to include also entrained liquid droplets.

[0041] Phosgenation facilities:

[0042] The phosgenation facility comprises or consists of the following:

[0043] (a) at least one phosgene stream device for providing a gaseous phosgene stream which, in addition to phosgene, optionally comprises inert substances;

[0044] (b) optionally an inert material stream device for providing an inert material stream;

[0045] (c) at least one amine stream device for providing a gaseous amine stream, which optionally contains inert substances in addition to the amine; and

[0046] (d) A phosgenation reactor for mixing the streams from (a) to (c) and reacting the amine stream with the phosgene stream.

[0047] The phosgene stream, the optional inert stream, the amine stream and the phosgenation reactor can, independently of one another, comprise further devices which can be used for operating the phosgenation plant, for example storage containers for starting materials, heat exchangers for temperature control or optional evaporation of starting materials, units for purifying the reaction mixture after the reaction of amine with phosgene is complete.

[0048] The phosgene stream arrangement preferably comprises at least one heat exchanger for heating the phosgene stream and / or the inert stream.

[0049] The amine stream device is configured to provide the amine stream so that in the startup phase, the amine stream comprises at least one first amine and optionally a second amine, and the mass proportion of the first amine in the total amount of amines in the amine stream that can be supplied to the phosgenation reactor is at least 90.0% by weight, preferably 95.0% by weight to 100% by weight, further preferably 97.5% by weight to 100% by weight, more preferably 99.0% by weight to 100.0% by weight, most preferably 100% by weight, and this mass proportion can then be reduced to 85.0% by weight during the reduction phase after the startup phase. % or less, preferably to 0% by weight to 80.0% by weight, further preferably to 0.1% by weight to 50.0% by weight, more preferably to 1.0% by weight to 40.0% by weight, most preferably to 5.0% by weight to 30.0% by weight, and this mass ratio can then be maintained in the production stage downstream of the reduction stage, wherein during the startup phase, the reduction phase and the production phase, the remainder of the total amount of amines in the amine stream to 100% by weight is formed by the second amine and optionally by further organic amines different from the first amine and the second amine to a maximum of 1% by weight.

[0050] In a preferred embodiment, the amine stream device comprises metering units for providing the amines independently of one another in terms of the mass ratio. In other words, the amine stream device preferably comprises one metering unit per amine (or amine mixture, for example if the first amine or the second amine is itself already an amine mixture) so that the mass flows / mass ratios can be controlled independently of one another. These can be, for example, metering pumps or control valves.

[0051] Furthermore, it is preferred that the amine stream device comprises

[0052] i. at least one storage container each for the first amine and the second amine,

[0053] ii. at least one metering unit downstream of the storage container,

[0054] iii. Optionally, at least one mixing unit downstream of the metering unit,

[0055] iv. optionally, at least one evaporator for evaporating the amine stream,

[0056] v. Optionally, a heat exchanger for heating the amine stream.

[0057] The optional mixing unit can be, for example, a T-piece in a pipeline, a mixing chamber, a static mixer or a pump, in particular a mixing pump, or a stirred vessel. However, the amine streams from the metering units can also be mixed in an evaporator. Evaporators are used in particular in the case of liquid amines.

[0058] Optional further organic amines different from the first and second amines can be provided via a separate storage container or mixed with the first and / or second amine. In particular, this also includes impurities that may be present in the first and / or second amine.

[0059] The amine flow device preferably comprises at least one flange connection in at least one of the amine feed lines which is provided for receiving an insert disk. This ensures that the amine flow through the corresponding line is reliably blocked or the corresponding amine line is reliably disconnected by means of the insert disk.

[0060] Preferably, at least one storage container, more preferably each storage container is configured to be heatable. This has the advantage that the efficiency of the facility and the method is further improved.

[0061] Phosgene stream device, optional inert material stream device and amine stream device are connected to phosgenation reactor via at least one feed pipe respectively.Feed pipe and phosgenation reactor connection can be realized for example via simple pipeline, flange connection, smooth jet nozzle, annular gap nozzle or mixing element.Annular gap nozzle can be equipped with two or more passages for amine stream and phosgene stream or inert gas stream, preferably two coaxially arranged passages, wherein amine stream and phosgene stream are not met until phosgenation reactor.Or, especially in industrial scale application, amine is added to phosgenation reactor via the introduction pipe having a central nozzle at its end and being kept in place by a cover and optional fixture / rectifier, to form an annular space around the introduction pipe in the reactor, wherein phosgene enters the annular space via a separate inlet and arrives at phosgenation reactor (also referring to EP1362847 A2) from here via a rectifier.Phosgenation reactor has a mixing zone and a reaction zone, in which streams meet for the first time, and in the reaction zone, streams are further converted. The mixing zone and the reaction zone are preferably in one apparatus. It is furthermore preferred that the phosgenation reactor is essentially vertical and that this is preferably connected at the upper end to an apparatus for the phosgene stream and an apparatus for the amine stream.

[0062] The phosgenation plant also 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, wherein the quench is designed in particular for introducing chlorobenzene, o-dichlorobenzene and / or at least one isocyanate produced in the phosgenation plant. In particular, the quench is assigned a collecting container, wherein the collecting container is preferably integrated into the quench or separately connected to the quench.

[0063] Start-up of the phosgenation facility:

[0064] In the context of the present invention, the expression “startup of a phosgenation plant” comprises all process steps which are required to convert a non-operating phosgenation plant (for example after a maintenance-related shutdown) into continuously controlled operation for the phosgenation of the corresponding amine or corresponding amines.

[0065] In the present invention, the phosgenation facility is started up (start-up) by performing at least the following steps:

[0066] (A) charging the phosgenation reactor with the gaseous phosgene stream and optionally the inert substance stream and then continuously feeding the gaseous phosgene stream and optionally the inert substance stream into the phosgenation reactor,

[0067] (B) continuously feeding the amine stream into the phosgenation reactor.

[0068] 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 one first amine and optionally a second amine different from the first amine, and the mass proportion of the first amine in the total amount of amines in the amine stream fed to the phosgenation reactor is at least 90.0% by weight, this mass proportion is then reduced to 85.0% by weight or less during the reduction phase and this mass proportion is then maintained in the production phase, wherein during the start-up phase, the reduction phase and the production phase, the remainder of the total amount of amines in the amine stream to 100% by weight is formed by the second amine and optionally to a maximum of 1% by weight by further organic amines different from the first and second amines.

[0069] In a preferred embodiment, step (A) is preceded by a preheating phase, during which a heated inert gas, preferably nitrogen, is introduced into the reactor via the amine stream feed line and / or the phosgene stream feed line.

[0070] In a preferred embodiment, during the startup phase, the mass proportion of the first amine in the total amount of amines in the amine stream is 95.0% to 100.0% by weight, preferably 97.5% to 100.0% by weight, more preferably 99.0% to 100.0% by weight, and most preferably 100.0% by weight. In some cases, for example when the first amine and the second amine do not have separate feed lines to the reactor, this may lead to disproportionate cleaning costs for removing residues of other amines before the start-up of the phosgenation unit. Therefore, in such a case, the starting value of the mass proportion of the first amine in the total stream of amines fed to the phosgenation unit is a maximum of 99.9%, preferably a maximum of 99.7%, more preferably a maximum of 99.5%. The duration of the startup phase is preferably at least 5 minutes, preferably 10 to 2880 minutes, further preferably 15 to 1440 minutes, more preferably 20 to 240 minutes, and most preferably 30 to 120 minutes.

[0071] During the reduction phase, the mass proportion of the first amine in the total amount of amines in the amine stream is preferably reduced to 0 wt % to 80.0 wt %, further preferably to 0.1 wt % to 50.0 wt %, more preferably to 1.0 wt % to 40.0 wt %, and most preferably to 5.0 wt % to 30.0 wt %. It is further preferred that the mass proportion of the first amine is gradually or continuously reduced in the reduction phase. During the reduction phase, the mass proportion of the first amine may even be temporarily reduced to a value lower than that maintained in the production phase. The duration of the reduction phase is preferably at least 0.01 minutes, further preferably at least 0.1 to 240 minutes, more preferably 0.5 to 60 minutes, and most preferably 1 to 30 minutes.

[0072] During the loading and continuous feeding in step (A), the phosgene stream and the optional inert material stream preferably have a temperature of 200° C. to 600° C., further preferably 250° C. to 500° C., more preferably 250° C. to 330° C. Step (A) can also be referred to as a heating stage. In a preferred embodiment, phosgene is present in the phosgenation reactor in a molar excess of 30% to 330%, preferably 60% to 300%, more preferably 90% to 270% relative to the amino groups of the amine.

[0073] During the feeding into the phosgenation reactor in step (B), the amine stream preferably has a temperature of 200 to 600° C., further preferably 250 to 500° C. and most preferably 250 to 330° C. In a preferred embodiment, the feeding of the amine stream is started only when the phosgenation reactor has been charged with phosgene and optionally inert substances and has reached the desired starting temperature of 230 to 320° C., preferably 240 to 310° C.

[0074] The inert substance is preferably selected from an inert gas, an inert solvent or a mixture of these. The inert gas may be selected from nitrogen, argon or a mixture of these. The solvent is preferably selected from aromatic hydrocarbons, preferably chlorobenzene, o-dichlorobenzene or a mixture of these.

[0075] If more than one amine is reacted, it is possible to first mix the amines and then evaporate and heat the amine mixture. Alternatively, one or more amines may be evaporated and heated separately. Different amines may also be fed separately to the phosgenation reactor via different feed devices (feed conduits), or may be fed by feeding a mixed amine stream. Even in the case where two or more amines are fed separately to the phosgenation reactor, the sum of these amine streams is considered in the present invention to be the total stream of amines fed to the phosgenation reactor, so that the proportion of the first amine in the total stream of amines is in each case based on the total stream of amines fed to the reactor at a specific time, whether as a mixture or in the form of a separate feed / feed. Preferably, the amines from separate storage containers are first mixed, then evaporated together, heated and fed to the phosgenation reactor. More preferably, the storage container is heated.

[0076] amine:

[0077] The first amine is selected from 1,6-diaminohexane (HDA), 1-amino-3,5,5-trimethyl-5-aminomethylcyclohexane (IPDA), bis(p-aminocyclohexyl)methane (PACM), or a mixture thereof.

[0078] The second amine is selected from 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), tetramethylphenylenediamine (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), neopentyl diamine, 2, 4,4-trimethylhexamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1-methyl-2,6-diaminocyclohexane and / or 1-methyl-2,4-diaminocyclohexane (collectively or individually referred to as 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.

[0079] Optional further organic amines different from the first and second amines are understood in the present invention to be primary, secondary and tertiary aliphatic, aromatic and heterocyclic amines. For example, the further organic amines are 1-aminohexane, 1,2-diaminocyclohexane, 1,4-diaminocyclohexane, 6-aminocapronitrile, bis(hexamethylene)triamine, azepane, azacycloheptatriene, 2-aminomethylcyclopentylamine, 2-methylpentamethylenediamine, 2,3,4,5-tetrahydropyridine, piperidine, tri-n-butylamine or mixtures thereof.

[0080] Implementation plan:

[0081] The present invention particularly relates to the following embodiments:

[0082] In a first embodiment, the invention relates to a process for producing isocyanates by gas-phase phosgenation of the corresponding amines in a phosgenation plant which comprises or consists of:

[0083] (a) at least one phosgene stream device 20 for providing a gaseous phosgene stream which, in addition to phosgene, optionally contains inert substances;

[0084] (b) optionally an inert material stream device for providing an inert material stream,

[0085] (c) at least one amine stream device 10 for providing a gaseous amine stream which optionally contains inert substances in addition to the amines,

[0086] (d) a phosgenation reactor 1 for mixing the streams from (a) to (c) and reacting the amine stream with the phosgene stream;

[0087] The phosgenation facility is started up by performing the following steps:

[0088] (A) loading 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,

[0089] (B) continuously feeding the amine stream into the phosgenation reactor 1,

[0090] 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 one first amine and optionally a second amine different from the first amine, and the mass proportion of the first amine in the total amount of amines in the amine stream fed to the phosgenation reactor 1 is at least 90.0% by weight, this mass proportion is then reduced to 85.0% by weight or less during the reduction phase, and this mass proportion is then maintained in the production phase, wherein during the start-up phase, the reduction phase and the production phase, the remainder of the total amount of amines in the amine stream to 100% by weight is formed by the second amine and optionally to a maximum of 1% by weight by other organic amines different from the first amine and the second amine, and wherein

[0091] - the first amine is selected from 1,6-diaminohexane (HDA), 1-amino-3,5,5-trimethyl-5-aminomethylcyclohexane (IPDA), bis(p-aminocyclohexyl)methane (PACM) or a mixture thereof; and

[0092] - the second amine is selected from 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), tetramethylphenylenediamine (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), neopentylene diamine, 2 ,4,4-trimethylhexamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1-methyl-2,6-diaminocyclohexane and / or 1-methyl-2,4-diaminocyclohexane (collectively or individually referred to as 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 a mixture thereof.

[0093] In a second embodiment, the invention relates to a method according to embodiment 1, characterized in that the duration of the start-up phase is at least 5 minutes, preferably 10 to 2880 minutes, further preferably 15 to 1440 minutes, more preferably 20 to 240, most preferably 30 to 120 minutes.

[0094] In a third embodiment, the invention relates to a process according to embodiment 1 or 2, characterised in that the reduction of the mass proportion of the first amine in the reduction stage is carried out stepwise or continuously.

[0095] In a fourth embodiment, the invention relates to a method according to any 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, further preferably 0.5 to 60 minutes, more preferably 1 to 30 minutes.

[0096] In a fifth embodiment, the present invention relates to a process according to any of the preceding embodiments, characterised in that during the start-up phase, the mass proportion of the first amine in the total amount of amines in the amine stream is from 95.0% to 100.0% by weight, preferably from 97.5% to 100.0% by weight, more preferably from 99.0% to 100.0% by weight and most preferably 100.0% by weight.

[0097] In a sixth embodiment, the present invention relates to a method according to any of the preceding embodiments, characterized in that during the reduction stage, the mass proportion of the first amine in the total amount of amines in the amine feed stream is reduced to 0% by weight to 80.0% by weight, preferably to 0.1% by weight to 50.0% by weight, further preferably to 1.0% by weight to 40.0% by weight, more preferably to 5.0% by weight to 30.0% by weight.

[0098] In a seventh embodiment, the invention relates to a process according to any of the preceding embodiments, characterised in that the phosgene stream and the optional inert stream, when charged and fed continuously in step (A), have a temperature of 200°C to 600°C, preferably 250°C to 500°C, most preferably 250°C to 330°C.

[0099] In an eighth embodiment, the invention relates to a process according to any of the preceding embodiments, characterized in that the amine stream when fed into the phosgenation reactor 1 in step (B) has a temperature of 200 to 600°C, preferably 250 to 500°C, most preferably 250 to 330°C.

[0100] In a ninth embodiment, the invention relates to a process according to any of the preceding embodiments, characterized in that phosgene is present in the phosgenation reactor 1 in a molar excess of 30% to 330%, preferably 60% to 300%, more preferably 90% to 270% relative to the amino groups of the amine.

[0101] In a tenth embodiment, the invention relates to a process according to any one of the preceding embodiments, characterized in that the inert substance is selected from an inert gas, an inert solvent or a mixture of these.

[0102] In an eleventh embodiment, the invention relates to a process according to embodiment 10, characterized in that the inert substance is selected from an inert gas, an inert solvent or a mixture of these.

[0103] In a twelfth embodiment, the invention relates to a process according to embodiment 10 or 11, characterized in that the solvent is selected from aromatic hydrocarbons, preferably chlorobenzene, o-dichlorobenzene or a mixture of these.

[0104] In a thirteenth embodiment, the present invention relates to a phosgenation facility for carrying out the method according to embodiments 1 to 12, comprising or consisting of:

[0105] (a) at least one phosgene stream device 20 for providing a gaseous phosgene stream which, in addition to phosgene, optionally contains inert substances;

[0106] (b) optionally an inert material stream device for providing an inert material stream;

[0107] (c) at least one amine stream device 10 for providing a gaseous amine stream, which optionally contains inert substances in addition to the amine; and

[0108] (d) a phosgenation reactor 1 for mixing the streams from (a) to (c) and reacting the amine stream with the phosgene stream;

[0109] The amine stream device 10 is characterized in that the amine stream is configured to provide the amine stream so that in the startup phase, the amine stream contains at least one first amine and optionally a second amine, and the mass proportion of the first amine in the total amount of amines in the amine stream that can be supplied to the phosgenation reactor 1 is at least 90.0% by weight, preferably 95.0% by weight to 100% by weight, further preferably 97.5% by weight to 100% by weight, more preferably 99.0% by weight to 100.0% by weight, most preferably 100% by weight, and then this mass proportion can be reduced to 100% by weight during the reduction phase after the startup phase. % to 85.0 wt. % or less, preferably to 0 to 80.0 wt. %, further preferably to 0.1 to 50.0 wt. %, more preferably to 1.0 to 40.0 wt. %, most preferably to 5.0 to 30.0 wt. %, and this mass ratio can then be maintained in the production stage downstream of the reduction stage, wherein during the startup phase, the reduction phase and the production phase, the remainder of the total amount of amines in the amine stream to 100 wt. % is formed by the second amine and optionally to a maximum of 1 wt. % by further organic amines different from the first and second amines.

[0110] In a fourteenth embodiment, the invention relates to an apparatus according to embodiment 13, characterized in that the phosgene stream apparatus 20 comprises at least one heat exchanger 21 for heating the phosgene stream and / or the inert stream.

[0111] In a fifteenth embodiment, the invention relates to an apparatus according to embodiment 13 or 14, characterized in that the amine stream apparatus 10 comprises a metering unit 13 for providing amines independently of one another in a variable mass ratio.

[0112] In a sixteenth embodiment, the present invention relates to an apparatus according to any one of embodiments 13 to 15, characterized in that the amine stream apparatus 10 comprises

[0113] i. at least one storage container 11, 12 for the first amine and the second amine, wherein the at least one storage container is preferably heatable,

[0114] ii. at least one metering unit 13 downstream of each storage container 11, 12,

[0115] iii. Optionally, at least one mixing unit 14 downstream of the metering unit 13,

[0116] iv. Optionally, at least one evaporator 15 for evaporating the amine stream,

[0117] v. Optionally, a heat exchanger 16 for heating the amine stream.

[0118] In a seventeenth embodiment, the invention relates to an apparatus according to any one of embodiments 13 to 16, characterized in that the phosgenation reactor 1 is essentially upright and is preferably connected to the phosgene stream device 20 and the amine stream device 10 at the upper end.

[0119] In an eighteenth embodiment, the present invention relates to an apparatus according to any one of embodiments 13 to 17, characterized in that the phosgenation plant comprises at least one quench 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 quench 2 is especially designed for the introduction of chlorobenzene, o-dichlorobenzene and / or at least one isocyanate produced in the phosgenation plant.

[0120] In a nineteenth embodiment, the invention relates to a device according to embodiment 18, characterized in that the quencher 2 is assigned a collecting container, wherein the collecting container is in particular integrated into the quencher and / or is separately connected to the quencher 2.

[0121] In a twentieth embodiment, the invention relates to a method for starting up a phosgenation facility comprising or consisting of:

[0122] (a) at least one phosgene stream device 20 for providing a gaseous phosgene stream which, in addition to phosgene, optionally contains inert substances;

[0123] (b) optionally an inert material stream device for providing an inert material stream;

[0124] (c) at least one amine stream device 10 for providing a gaseous amine stream, which optionally contains inert substances in addition to the amine; and

[0125] (d) a phosgenation reactor 1 for mixing the streams from (a) to (c) and reacting the amine stream with the phosgene stream;

[0126] The phosgenation facility is started up by performing the following steps:

[0127] (A) loading 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,

[0128] (B) continuously feeding the amine stream into the phosgenation reactor 1,

[0129] 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 one first amine and optionally a second amine different from the first amine, and the mass proportion of the first amine in the total amount of amines in the amine stream fed to the phosgenation reactor 1 is at least 90.0% by weight, this mass proportion is then reduced to 85.0% by weight or less during the reduction phase, and this mass proportion is then maintained in the production phase, wherein during the start-up phase, the reduction phase and the production phase, the remainder of the total amount of amines in the amine stream to 100% by weight is formed by the second amine and optionally by other organic amines different from the first amine and the second amine to a maximum of 1% by weight, and

[0130] - the first amine is selected from 1,6-diaminohexane (HDA), 1-amino-3,5,5-trimethyl-5-aminomethylcyclohexane (IPDA), bis(p-aminocyclohexyl)methane (PACM) or a mixture thereof; and

[0131] - the second amine is selected from 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), tetramethylphenylenediamine (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), neopentylene diamine, 2 ,4,4-trimethylhexamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1-methyl-2,6-diaminocyclohexane and / or 1-methyl-2,4-diaminocyclohexane (collectively or individually referred to as 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 a mixture thereof.

[0132] According to a twenty-first embodiment, the present invention relates to the use of the device according to any one of embodiments 13 to 19 for implementing the method according to any one of embodiments 1 to 12. Example:

[0133] Reference now Figure 1 The present invention is illustrated by the following examples, but is not limited thereto. The accompanying drawings show:

[0134] Figure 1 : Schematic diagram of the phosgenation facility of the present invention.

[0135] Figure 1 A schematic diagram of a phosgenation plant according to the invention is shown. This comprises a vertical tubular reactor / phosgenation reactor (PR) 1 with a residence time period for the reaction of an amine stream with a phosgene stream, and a subsequent quench (Q) with a collecting vessel 2 for cooling and at least partially condensing the reaction gases formed in the phosgenation reactor 1, as well as an amine stream device 10 for providing an amine stream and a phosgene stream device 20 for providing a phosgene stream. The quench 2 has a product outlet 4 for conveying a liquid crude product onwards and a gas outlet 5 for conducting off gas.

[0136] The amine stream device 10 is composed of a first and a second storage container 11, 12 for a first amine (A1) and a second amine (A2) and a metering unit (D) 13 downstream of each storage container 11, 12 for independently and variably adjusting the dosage ratio (or mass ratio) of the amines (A1) and (A2) from the first and second storage containers 11, 12. A mixing unit (M) 14 for mixing the amine streams is arranged downstream of the metering unit 13, wherein an evaporator (V) 15 for evaporating the amine streams is provided downstream of the mixing unit 14. A heat exchanger (WT) 16 for heating the amine streams is provided downstream of the evaporator 15.

[0137] The phosgene stream arrangement 20 comprises a heat exchanger (WT) 21 for heating the phosgene stream.

[0138] 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 to the phosgenation reactor 1 via a phosgene stream feed line 22, wherein these feed lines lead to an annular gap nozzle 3 provided in the top region of the phosgenation reactor 1 and having two coaxially arranged channels. By the separate feeding of the phosgene stream and the amine stream, these reactants can be mixed and converted immediately after being injected into the phosgenation reactor. The amine stream feed line 17 of the amine stream device 10 is additionally equipped with a pressure gauge 18 to measure the pressure in the amine stream feed line 17.

[0139] General operating procedures:

[0140] The following embodiments are based on Figure 1The phosgene is heated to about 340° C. in a heat exchanger 21 and introduced into the phosgenation reactor 1 at this temperature via a phosgene feed pipe 22 and an annular gap nozzle 3. As for the amines, the first amine and / or the second amine are metered in from the storage containers 11 and 12 independently of each other via a metering unit 13 as required to achieve the desired mass ratio. After passing through the metering unit 13, the amines are mixed in a mixing unit 14, then evaporated in an evaporator 15, and then superheated to about 330° C. in a heat exchanger 16 and introduced into the phosgenation reactor 1 at this temperature via an amine feed pipe 17 and an annular gap nozzle 3. Depending on each amine used or amine mixture used, the molar excess of phosgene is between 140% and 300%, based on the amino group of the amine. In order to start the continuous reaction, the phosgenation reactor 1 is first loaded with hot phosgene only until a constant temperature is established. Only then does the amine vapor begin to be fed. Except for the unavoidable heat loss, the reaction is adiabatic. After passing the residence period, the reaction gases are cooled and at least partially condensed in the quench 2 by introducing chlorobenzene. The pressure in the amine stream feed line 17 is monitored by means of a pressure gauge 18.

[0141] Comparative Example 1

[0142] The phosgenation reactor 1 is heated to the starting temperature with the aid of phosgene vapor as described in the general operating procedure. Then a 20:80 mixture of ISODA and IPDA (weight ratio) is metered from two amine reservoirs via metering unit 13 into mixing unit 14, whereby the phosgenation reaction is started. Deposits are formed in the phosgenation reactor 1, which leads to a rapid and accelerated increase in the pressure in the amine stream feed line 17 of the amine stream device 10. After about 9 minutes, the pressure has risen from the initial about 1000 mbar to 1500 mbar, and the reaction is terminated.

[0143] Example 1

[0144] The phosgenation reactor 1 was prepared as in comparative example 1. However, after the heating phase, in the startup phase, only IPDA was initially metered into the mixing unit 14 via the metering unit 13, i.e. ISODA to IPDA=0:100 (weight ratio), in order to start the reaction first with IPDA. After a continuous operating time of 60 minutes, the reduction phase began. Here, the IPDA feed rate was reduced and ISODA was metered in at the same time until a 10:90 mixture of ISODA and IPDA (weight ratio) was reacted. After a further 30 minutes, the amine feed rate was further adjusted so that the weight ratio of ISODA to IPDA was then 20:80 (weight ratio), i.e. exactly the ratio of comparative example 1. The phosgenation was continued at this mixing ratio for a further 60 minutes (production phase), and then 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 (initially approximately 1000 mbar) at the end.

[0145] Comparative Example 2

[0146] The phosgenation reactor 1 was heated to the starting temperature by means of phosgene vapor as described in the general operating procedure. The reaction was then started by evaporating PDA and feeding it via a nozzle into the phosgenation reactor 1, corresponding to a weight ratio of PDA to IPDA of 100:0. A rapid increase in the pressure in the amine stream feed line 17 of the amine stream device 10 was observed, wherein a limit of 1500 mbar was reached already after about 6 minutes (initially about 1000 mbar), whereby the reaction was terminated.

[0147] Example 2

[0148] The phosgenation reactor 1 was prepared as in comparative example 2. However, after the heating phase, only IPDA was first metered into the mixing unit 14 via the metering unit 13, i.e. PDA to IPDA=0:100 (weight ratio), in order to start the reaction with IPDA first (start-up phase). After 1.5 hours, the weight ratio of PDA to IPDA was changed to a target value (weight ratio of PDA to IPDA) of 100:0 in 5 equal steps (20:80, 40:60, 60:40, 80:20 and 100:0) from start to finish every 30 minutes (reduction phase). The reaction was continued with PDA for a further 1.5 hours (production phase), and then the experiment was ended at a pressure of 1090 mbar in the amine stream feed line 17 of the amine stream device 10. Compared with comparative example 2, the formation of deposits was significantly slowed down.

[0149] Reference numerals list

[0150] 1 Phosgenation reactor / tubular reactor (PR)

[0151] 2 Quencher with collecting container (Q)

[0152] 3 Annular gap nozzle with two coaxially arranged channels

[0153] 4 Product Export

[0154] 5 Gas outlet

[0155] 10 Amine Flow Unit

[0156] 11. Storage container for first amine (A1)

[0157] 12 Storage container for the second amine (A2)

[0158] 13 (one or more) units of measurement

[0159] 14 Mixing unit (M)

[0160] 15 Evaporator of amine stream unit (V)

[0161] 16 Heat exchanger for amine stream unit (WT)

[0162] 17 Amine feed pipeline

[0163] 18. Pressure gauge

[0164] 20 Phosgene Flow Device

[0165] 21 Heat exchanger for phosgene stream unit (WT)

[0166] 22 Phosgene feed pipe

Claims

1. A process for producing isocyanates by gas-phase phosgenation of the corresponding amines in a phosgenation plant which comprises or consists of: (a) at least one phosgene stream device (20) for providing a gaseous phosgene stream which, in addition to phosgene, optionally comprises inert substances, (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 which optionally contains inert substances in addition to the amines, (d) a phosgenation reactor (1) for mixing the streams from (a) to (c) and reacting the amine stream with the phosgene stream, The phosgenation facility is started up by performing the following steps: (A) charging the phosgenation reactor (1) with the gaseous phosgene stream and optionally the inert substance stream, and then continuously feeding the gaseous phosgene stream and optionally the inert substance stream into the phosgenation reactor (1), (B) continuously feeding 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 proportion of the first amine in the total amount of amines in the amine stream fed to the phosgenation reactor (1) is at least 90.0% by weight, this mass proportion is then reduced to 85.0% by weight or less during the reduction phase and this mass proportion is then maintained in the production phase, wherein during the start-up phase, the reduction phase and the production phase, the remainder of the total amount of amines in the amine stream to 100% by weight is formed by the second amine and optionally to a maximum of 1% by weight by further organic amines different from the first amine and the second amine, and wherein - the first amine is selected from 1,6-diaminohexane (HDA), 1-amino-3,5,5-trimethyl-5-aminomethylcyclohexane (IPDA), bis(p-aminocyclohexyl)methane (PACM) or a mixture thereof; and - the second amine is selected from 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), tetramethylphenylenediamine (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), neopentylene diamine, 2 ,4,4-trimethylhexamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1-methyl-2,6-diaminocyclohexane and / or 1-methyl-2,4-diaminocyclohexane (collectively or individually referred to as 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 a mixture thereof.

2. The method according to claim 1, characterized in that The duration of the startup phase is at least 5 minutes, preferably 10 to 2880 minutes, further preferably 15 to 1440 minutes, more preferably 20 to 240, most preferably 30 to 120 minutes, and / or the duration of the reduction phase is at least 0.01 minute, preferably at least 0.1 to 240 minutes, further preferably 0.5 to 60 minutes, more preferably 1 to 30 minutes.

3. The method according to claim 1 or 2, characterized in that During the startup phase, the mass proportion of the first amine in the total amount of amines in the amine stream is 95.0% to 100.0% by weight, preferably 97.5% to 100.0% by weight, more preferably 99.0% to 100.0% by weight and most preferably 100% by weight.

4. A method according to any one of the preceding claims, characterised in that During the reduction stage, the mass proportion of the first amine in the total amount of amines in the amine stream is reduced to 0% to 80.0% by weight, preferably to 0.1% to 50.0% by weight, further preferably to 1.0% to 40.0% by weight, more preferably to 5.0% to 30.0% by weight.

5. A method according to any one of the preceding claims, characterised in that When charged and fed continuously in step (A), the phosgene stream and the optional inert stream have a temperature of 200 to 600° C., preferably 250 to 500° C., most preferably 250 to 330° C., and / or when fed into the phosgenation reactor (1) in step (B), the amine stream has a temperature of 200 to 600° C., preferably 250 to 500° C., most preferably 250 to 330° C.

6. A method according to any one of the preceding claims, characterised in that Phosgene is present in the phosgenation reactor (1) in a molar excess of 30% to 330%, preferably 60% to 300%, more preferably 90% to 270%, relative to the amino groups of the amine.

7. A method according to any one of the preceding claims, characterised in that The inert substance is selected from an inert gas, an inert solvent or a mixture of these.

8. The method according to claim 7, characterized in that The inert gas is selected from nitrogen, argon or a mixture of these, and / or the solvent is selected from aromatic hydrocarbons, preferably chlorobenzene, o-dichlorobenzene or a mixture of these.

9. A phosgenation plant for carrying out the method according to any one of claims 1 to 8, comprising or consisting of: (a) at least one phosgene stream device (20) for providing a gaseous phosgene stream which, in addition to phosgene, optionally contains inert substances; (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, which optionally contains inert substances in addition to the amine; and (d) a phosgenation reactor (1) for mixing the streams from (a) to (c) and reacting the amine stream with the phosgene stream; The amine stream device (10) is configured to provide the amine stream so that in the startup phase, the amine stream comprises at least one first amine and optionally a second amine, and the mass proportion of the first amine in the total amount of amines in the amine stream that can be supplied to the phosgenation reactor (1) is at least 90.0% by weight, preferably 95.0% by weight to 100% by weight, further preferably 97.5% by weight to 100% by weight, more preferably 99.0% by weight to 100.0% by weight, most preferably 100% by weight, and this mass proportion can then be reduced during the reduction phase after the startup phase. % to 85.0 wt. % or less, preferably to 0 to 80.0 wt. %, further preferably to 0.1 to 50.0 wt. %, more preferably to 1.0 to 40.0 wt. %, most preferably to 5.0 to 30.0 wt. %, and this mass ratio can then be maintained in the production stage downstream of the reduction stage, wherein during the start-up phase, the reduction phase and the production phase, the remainder of the total amount of amines in the amine stream to 100 wt. % is formed by the second amine and optionally to a maximum of 1 wt. % by further organic amines different from the first and second amines.

10. The device according to claim 9, characterized in that The phosgene stream arrangement comprises at least one heat exchanger (21) for heating the phosgene stream and / or the inert stream.

11. The device according to claim 9 or 10, characterized in that The amine stream arrangement comprises a metering unit (13) for providing amines in variable mass ratios independently of one another.

12. The device according to any one of claims 9 to 11, characterized in that The amine stream device (10) comprises i. at least one storage container (11, 12) each for the first amine and the second amine, ii. at least one metering unit (13) downstream of each storage container (11, 12), iii. Optionally, at least one mixing unit (14) downstream of the metering unit (13), iv. Optionally, at least one evaporator (15) for evaporating the amine stream, v. Optionally, a heat exchanger (16) for heating the amine stream.

13. The device according to any one of claims 9 to 12, characterized in that The phosgenation plant comprises at least one quench (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 quench (2) is particularly designed for the introduction of chlorobenzene, o-dichlorobenzene and / or at least one isocyanate produced in the phosgenation plant.

14. The device according to claim 13, characterized in that The quench cooler (2) is assigned a collecting container, wherein the collecting container is in particular integrated into the quench cooler (2) and / or is separately connected to the quench cooler (2).

15. A method for starting up a phosgenation plant, the phosgenation plant comprising or consisting of: (a) at least one phosgene stream device (20) for providing a gaseous phosgene stream which, in addition to phosgene, optionally contains inert substances; (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, which optionally contains inert substances in addition to the amine; and (d) a phosgenation reactor (1) for mixing the streams from (a) to (c) and reacting the amine stream with the phosgene stream; The phosgenation facility is started up by performing the following steps: (A) charging the phosgenation reactor (1) with the gaseous phosgene stream and optionally the inert substance stream, and then continuously feeding the gaseous phosgene stream and optionally the inert substance stream into the phosgenation reactor (1), (B) continuously feeding 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 proportion of the first amine in the total amount of amines in the amine stream fed to the phosgenation reactor (1) is at least 90.0% by weight, this mass proportion is then reduced to 85.0% by weight or less during the reduction phase and this mass proportion is then maintained in the production phase, wherein during the start-up phase, the reduction phase and the production phase, the remainder of the total amount of amines in the amine stream to 100% by weight is formed by the second amine and optionally to a maximum of 1% by weight by further organic amines different from the first amine and the second amine, and - the first amine is selected from 1,6-diaminohexane (HDA), 1-amino-3,5,5-trimethyl-5-aminomethylcyclohexane (IPDA), bis(p-aminocyclohexyl)methane (PACM) or a mixture thereof; and - the second amine is selected from 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), tetramethylphenylenediamine (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), neopentylene diamine, 2 ,4,4-trimethylhexamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1-methyl-2,6-diaminocyclohexane and / or 1-methyl-2,4-diaminocyclohexane (collectively or individually referred to as 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 a mixture thereof.

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