Process for continuous catalytic hydrogenation of MDA

Abstract

The present invention discloses a process for the continuous catalytic hydrogenation of MDA, and specifically discloses an apparatus and a process for the hydrogenation of methylenediphenylamine (MDA) using a hydrogen donor, where i) comprises a collection circuit for a closed first media circuit, a heat exchanger incorporated as at least one heat source into a heat exchanger of a main reactor and / or a separation unit, and a first evaporator, ii) comprises an intermediate circuit for a closed second medium circuit in which the first evaporator, the at least one compressor and the second evaporator are incorporated, and iii) comprises at least one distributor circuit for a closed third medium circuit in which the first evaporator, the at least one compressor and the second evaporator are incorporated, wherein the at least one heat exchanger of the reactor unit, the at least one heat exchanger of the conditioning unit and / or the at least one heat exchanger of the separating unit are combined as a heat sink in a heat exchange manner. The apparatus and process are improved in terms of product conversion and energy efficiency.

Description

Technical Field

[0001] The present invention relates to an apparatus and method for the continuous catalytic hydrogenation of MDA, particularly for the production of methylene bis(cyclohexylamine), especially for example 4,4'-diaminodicyclohexylmethane (PACM). Background Technology

[0002] Methods for hydrogenating organic compounds, especially for hydrogenating aromatic compounds into corresponding cyclohexane derivatives, are known in the art.

[0003] Methylenebis(cyclohexylamine) is an alicyclic amine that exists as a solid or liquid under standard conditions (SATP) and is typically produced by the liquid-phase hydrogenation of MDA. The acronym MDA was historically introduced as an abbreviation for a mixture of products formed in the reaction of aniline and formaldehyde that primarily contained "methylene diphenylamine" (diaminodiphenylmethane), and it is also used to describe the products of this process now produced on an industrial scale. The product of the hydrogenation reaction, primarily containing methylenebis(cyclohexylamine), is therefore often also referred to as H12MDA.

[0004] Due to its production method, MDA is typically a mixture of different diaminodiphenylmethanes. It is primarily composed of 4,4'-diaminodiphenylmethane. However, 2,4' and 2,2' isomers may also be present. MDA may also contain reaction products with three or more aromatic rings formed in the reaction of aniline and formaldehyde, particularly those with three or more phenyl rings. These reaction products with three or more aromatic rings are also known as polynuclear compounds.

[0005] Due to the high proportion of 4,4'-diaminodiphenylmethane in the MDA used, commercially available methylene bis(cyclohexylamine) is primarily composed of 4,4'-diaminodicyclohexylmethane or bis(p-aminocyclohexyl)methane. Since the corresponding 2,4'- and 2,2'-diaminophenylmethane isomers may be present in the MDA, 2,4'-diaminodicyclohexylmethane and 2,2'-diaminodicyclohexylmethane may also be present in methylene bis(cyclohexylamine). Furthermore, hydrogenated MDA may contain (possibly partially) hydrogenated polynuclear compounds in addition to methylene bis(cyclohexylamine).

[0006] US 5,578,546 A discloses a method for producing methylenebis(cyclohexylamine), first described in 1947 and scaled up for industrial use in 1965. The hydrogenation of MDA is highly exothermic. For example, WO 2010 / 069484 A1 indicates a reaction enthalpy of -1600 kJ / mol.

[0007] As a result of hydrogenation, various diastereomers are formed, depending on the method. Here, the product 4,4'-diaminodicyclohexylmethane (PACM), derived from 4,4'-diaminodiphenylmethane, can exist in trans / trans, cis / cis, and cis / trans isomers, and is therefore typically a mixture of these isomers in different proportions. Here, the melting point of the compound increases with increasing trans / trans content. Therefore, the application areas differ significantly depending on the isomer content: methylene bis(cyclohexylamine) with low trans / trans content (e.g., 10-30 wt%) is used in the field of amine and isocyanate crosslinking agents, especially in two-component resins, while those with high trans / trans content (e.g., ≥48 wt%) are mainly used as modifiers in polyamide compounds. The production of products with low trans / trans content is precisely a challenge, as thermodynamic equilibrium is in the region with significantly higher trans / trans content (up to 51.2%), as described in US 3,636,108 A. Furthermore, US2,606,925 A indicates that subsequent heat treatment over a longer period can shift the equilibrium toward a higher proportion of trans / trans isomers.

[0008] The composition of the hydrogenation product also depends on the composition of the MDA used: MDA is typically used in grades from MDA50 to MDA100, where the number between 50 and 100 indicates the diaminodiphenylmethane content in the MDA mixture. MDA50, as explained above, is an MDA grade containing approximately 50% by weight of diaminodiphenylmethane and 50% by weight of polynuclear compounds due to process-related reasons. Depending on the number of aromatic nuclei present, the various polynuclear compounds can be referred to as trinuclear compounds, tetranuclear compounds, etc. MDA50 is the grade produced in the highest quantities and is primarily further processed into methylene dicyclohexyl diisocyanate (MDI). MDA100 is pure MDA or diaminodiphenylmethane without polynuclear compounds. MDA85 or MDA90 are other commercially available grades of medium purity. If the purity of the MDA grade is mentioned in a patent specification relating to a method for producing methylene bis(cyclohexylamine), it is usually MDA100 (e.g., CN 110204447B). In contrast, US2005 / 261525 A1 preferably emphasizes the hydrogenation of MDA50. As shown in US2004 / 162409 A1, hydrogenated oligoamines obtained here as high-boiling-point substances are suitable as crosslinking agents with particularly low vapor pressures for a range of special applications.

[0009] The content of hydrogenated polynuclear compounds in the products (possibly partially) decreases in the order of reactants MDA50, MDA85, MDA90, and MDA100, because the content of polynuclear compounds decreases from MDA50 to MDA100.

[0010] WO 2009 / 153123 A1 discloses a continuous method and reactor for hydrogenating organic compounds in a multiphase, multi-stage system in the presence of a homogeneous or multiphase catalyst. The proposed catalysts particularly include noble metals such as platinum, palladium, ruthenium, and rhodium, or other transition metals such as molybdenum, tungsten, and chromium. The multiphase catalyst may be arranged on a support material such as carbon, alumina, silica, zirconium dioxide, zeolite, aluminosilicate, or a mixture of these support materials. In this method, aromatic compounds containing amino substituents, such as MDA, polymeric MDA, aniline, 2,4-diaminotoluene, 2,6-diaminotoluene, o-phenylenediamine, etc., are preferably used as the substrate. The multiphase catalyst is used in suspension.

[0011] DE 19533718 A1 discloses a method for hydrogenating an aromatic compound in which at least one amino group is bonded to an aromatic core. For this purpose, a heterogeneous catalyst containing ruthenium and optionally at least one metal from a Group I, VII, or VIII subgroup can be used. The support material used is, for example, alumina, silica, titanium dioxide, or zirconium oxide, preferably alumina or zirconium oxide. Only a catalyst containing ruthenium on an alumina support material, rather than zirconium oxide, is taken as an example.

[0012] EP 1337331 A1 discloses a method for the catalytic hydrogenation of aromatic or heteroaromatic amines, wherein ruthenium acts as the active metal, and the catalyst contains at least one additional metal of subgroup I, VII, or VIII, which is applied to a support material. Aromatic compounds used herein particularly include 4,4'-MDA and its isomers. EP 0111238 A1 also discloses a method for the catalytic hydrogenation of 4,4'-MDA, characterized by hydrogenation in the presence of supported ruthenium in the presence of alkali metal nitrates and sulfates and alkaline earth metal nitrates. A similar method is disclosed in EP 1366812 A1, wherein the support materials mentioned particularly include alumina, silicon oxide, titanium oxide, and zirconium oxide.

[0013] WO 2011 / 003899 A1 and WO 2009 / 090179 A1 disclose further methods for hydrogenating organic compounds. A method for hydrogenating aromatic amines with hydrogen gas in the presence of a Ru catalyst, particularly containing a zirconium oxide support material, is disclosed herein.

[0014] Finally, EP 2 883 863 B1 discloses a method and apparatus for hydrogenating 4,4'-methylenediphenylamine (MDA) and / or polymeric MDA with hydrogen in the presence of a catalyst. The catalyst proposed herein is ruthenium applied to a zirconia support material. Regarding the reactor, EP 2 883 863 B1 refers to the reactor or reactor concept of WO 2008 / 015135A1. WO 2008 / 015135A1 discloses a continuous method and apparatus for hydrogenating diisononyl phthalate to diisononyl cyclohexane-1,2-dicarboxylate (DINCH), wherein DINP is hydrogenated with hydrogen as a mixture in an organic solvent at a pressure of up to 325 bar. A series connection of two fixed-bed reactors is proposed herein, each reactor having a stationary fixed bed. To dissipate the heat of reaction from the two reactors, it is proposed to recirculate the sub-feed stream of the mixture downstream of the second fixed-bed reactor and thereby cool it. A similar reactor concept for a series fixed-bed reactor for hydrogenation is also known from EP 1 566 372 B1.

[0015] The drawback of this concept is that the cyclical guidance of the product stream may lead to an increase in the formation of unwanted byproducts and a decrease in the plant's production capacity, which in turn leads to an increase in the energy costs of recycling and cooling the recycled stream.

[0016] As explained, the demand for PACMs with varying proportions of their respective isomers depends on the intended use or subsequent products. For example, PACMs with low trans / trans content of 10% to 30% by weight are preferred in the field of amine and isocyanate crosslinking agents, particularly in the formulation of two-component resins, while PACMs with high trans / trans content exceeding 48% by weight are primarily used as modifiers in polyamide compounds. The weight percentages mentioned here are based on the PACM isomer mixture itself. The production of products with low trans / trans content is precisely a technological challenge, as thermodynamic equilibrium exists in the region of significantly higher trans / trans content, up to 51.2% by weight, as described in US 3,636,108 A. Furthermore, it is known from US 2,606,925 A that subsequent heat treatment for extended periods can shift the balance of PACM isomers toward higher proportions of trans / trans isomers. Summary of the Invention

[0017] Therefore, one object of the present invention is to provide an improved apparatus and an improved method that improves product conversion and energy efficiency, and particularly enables the production of a corresponding proportion of isomers defined in a mixture of isomers.

[0018] According to the present invention, the objective is achieved by the apparatus according to claim 1 and the method according to claim 12.

[0019] This article provides an apparatus for the continuous catalytic hydrogenation of methylenediphenylamine (MDA; reactant 1) using a hydrogen donor (reactant 2), particularly a gaseous hydrogen donor, preferably hydrogen (H2).

[0020] It includes a conditioning unit (104) for reactants, a reactor unit for the synthesis of methylenebis(cyclohexylamine), particularly 4,4'-diaminodicyclohexylmethane (PACM), and a separation unit, wherein

[0021] - The conditioning unit includes a (feed) line for reactant 1, reactant 2 and at least one solvent, at least one heat exchanger in at least one (feed) line, and at least one mixer for mixing the reactant and / or at least one reactant with at least one solvent;

[0022] - The reactor unit includes at least one fixed-bed reactor as a main reactor with a fixed catalyst packing, wherein the at least one main reactor includes:

[0023] - for supplying the material mixture through the first flow path of the fixed catalyst packing and

[0024] -A separate, closed flow path for the heat exchange medium outside the catalyst packing, and wherein

[0025] A heat exchanger is incorporated into the medium circuit;

[0026] - The separation unit includes at least a first separation stage for separating and removing the solvent and a second separation stage for separating at least one reactant and / or at least one byproduct from the product, wherein

[0027] i) Includes a collection loop for a closed first medium loop, wherein at least one heat exchanger, as a heat source, is incorporated into the main reactor's heat exchanger and / or separation unit, and a first evaporator.

[0028] ii) includes an intermediate circuit for a second closed media circuit, wherein a first evaporator, at least one compressor, and a second evaporator are combined, and wherein...

[0029] iii) Includes at least one distributor loop for an additional closed third medium loop, wherein at least one heat exchanger of the reactor unit, at least one heat exchanger of the finishing unit and / or at least one heat exchanger of the separation unit are incorporated as heat sinks in a heat exchange manner.

[0030] In this article,

[0031] - The collection loop includes a branch line leading to the first evaporator or the energy collection line, and a return branch line.

[0032] - The intermediate loop includes a branch line leading to the second evaporator, also known as the steam line, and a return branch line from the second evaporator to the first evaporator, also known as the return line.

[0033] - The distributor loop includes at least one feed line branch (top or steam line) from the second evaporator to the at least one heat exchanger and / or reactor unit that has been incorporated as a heat sink into the second evaporator.

[0034] In this document, a closed loop is understood as a loop in which the respective heat exchange medium can circulate only within that loop, specifically without further transfer to adjacent loops, such that energy exchange with the respective coupled adjacent loops is achieved through indirect heat transfer between the circulating (loop) media, without the exchange of the respective (loop) media. An intermediate loop is here coupled to a collection loop and the at least one distributor loop. The collection loop acts as a heat source for the intermediate loop; the intermediate loop is used to raise the temperature level and acts as a heat source for the distributor loop and the heat exchangers incorporated therein that act as heat sinks, particularly the heat exchangers of the separation unit.

[0035] The liquid material stream from the separation tank is guided via pipeline to the first separation column within the first separation stage of the separation unit. Advantageously, in one embodiment of the apparatus, a pressure relief unit may be provided in the pipeline from the separation tank to the first column. This allows the reactor unit to operate at a first high-pressure level and the first separation stage of the separation unit to operate at a second, lower pressure level.

[0036] This apparatus is preferably used for the continuous catalytic production of methylenebis(cyclohexylamine) of formula (I) as a product, especially for the production of 4,4'-diaminodicyclohexylmethane (PACM).

[0037]

[0038] With the aid of a separate post-reactor, especially an adiabatic post-reactor, the method and apparatus can be optimized for control, thereby enabling selectivity due to the difference in inlet temperature between the post-reactor and the main reactor (outlet). Typically, the inlet temperature of the post-reactor can be provided at the same or slightly lower temperature, which can be up to 30°C lower than the outlet temperature of the main reactor. Therefore, at least temporarily, a temperature increase of 20°C to 40°C, typically 20°C to 30°C, is permissible in the (adiabatic) post-reactor, and thus the desired product quality (isomer ratio) can be selectively adjusted. In this way, a very low and very precise trans / trans isomer ratio can be established in the isomer mixture. The main reactor can be operated at the lowest possible temperature level to achieve a trans / trans ratio of approximately 13% to 20% wt% in the material stream (main reactor outlet), of approximately 13% wt% in the case of new or regenerated catalysts, and 20% wt% in the case of catalysts that have been used for a long time (shortly before replacement / regeneration). Although the main reactor is referred to as “isothermal” in this paper, this ideal state is only achieved to a limited extent in industrial applications. Therefore, due to incomplete heat dissipation, a temperature gradient of approximately 5 to 10 °C forms within the main reactor in both the radial and flow directions. Depending on the stage of the main reactor, it may be at least temporarily meaningful if the inlet temperature of the downstream reactor is 5 to 20 °C higher than that of the main reactor.

[0039] The downstream reactor is fed at a slightly higher temperature via an upstream heat exchanger, allowing the desired residual reaction and isomer transformation to occur, resulting in, for example, a final desired trans / trans ratio of 17% to 23% by weight. The downstream reactor, with its weakly exothermic residual reaction, operates substantially adiabatic, but this should not be understood in an ideal sense. After the downstream reactor, the trans / trans isomer content is further increased to achieve complete conversion of MDA. Advantageously, the MDA concentration downstream of the downstream reactor is less than 1000 ppm. In a preferred embodiment, the trans / trans content in the isomer mixture reaches 10% to 20% by weight downstream of the main reactor, approximately 13% by weight in the case of a fresh, more active catalyst, and approximately 20% by weight in the case of a (previously) loaded catalyst.

[0040] Over time, catalyst activity decreases until replacement or regeneration is required. To address this, the operating temperature is increased in parallel by controlling the cooling loop, i.e., by a small degree of cooling via a heat exchanger incorporated into the cooling loop, to maintain the overall conversion and selectivity at a substantially constant level. This results in a shift in the isomer ratio towards higher trans / trans content in the product. It has proven highly advantageous here that the feed temperature to the downstream reactor can be autonomously controlled, particularly synchronously, using the upstream heat exchanger. Thus, as the operating temperature of the main reactor rises during the catalyst's lifetime, the feed temperature in the downstream reactor's mass stream is reduced.

[0041] From time point t0 (the start of the method after catalyst renewal or regeneration) to time point t4 (the end of the method as determined by catalyst renewal or regeneration), the operating temperature of the main reactor can be increased, and the temperature of the material stream at the inlet (feed) of the downstream reactor can be maintained or decreased. Advantageously, the apparatus is designed to continuously and / or gradually increase or decrease the temperature.

[0042] The main reactor operates isothermally or substantially isothermally, and the downstream reactor operates adiabatally or substantially adiabaticly. At time point t0, i.e., at the start of the method, the catalyst in the downstream reactor, in addition to the main reactor, may have already been renewed or regenerated. Advantageously, the regeneration cycle of the downstream reactor is determined autonomously and independently of the main reactor, especially when the aforementioned interaction between the two reactors is no longer able to produce the desired low trans / trans ratio in the PACM.

[0043] Advantageously, the mixing unit is formed in two parts and includes, for example, a mixing device and a gas saturator. The mixing device can be, in particular, a dynamic or static mixer suitable for the close bonding of MDA (reactant 1) with the solvent. The gas saturator can be, in particular, a small tower or tank containing suitable internal components for strongly dissolving the H2 gas supplied under high pressure in the MDA-solvent stream and / or for uniformly distributing it before it enters the main reactor. The H2 gas pressure is advantageously between 70 bar and 100 bar.

[0044] The terms "immobilized catalyst packing" or "immobilized catalyst" refer to any form of localized catalyst that does not flow or move with the mass stream, such as, in particular, a catalyst bed (granular or coated support) or a fixed internal structure coated with catalyst material. Advantageous internal structures with catalyst coatings can be, for example, grids, plates, or other types arranged in the main reactor.

[0045] In this document, "XY unit" and / or "XY stage" always refer to at least one corresponding device, apparatus, etc., included in the corresponding unit or stage. This refers, for example, to a mixing unit / stage including the at least one mixer / mixing device.

[0046] Unless otherwise explicitly stated otherwise, “heat exchange” or “heat exchanger” in this document always refers to indirect heat exchange and the corresponding design with enclosed material and medium guiding lines.

[0047] This paper primarily considers the following energy coupling (EK), such as integrated energy coupling or direct energy coupling, where integrated EK refers to integrated energy coupling, which is further subdivided into...

[0048] a. Material-based energy coupling (integrated material-based EK) in which at least two material flows are integrated in indirect heat exchange within a heat exchanger, i.e., the structure is integrated into a single heat exchanger (device). This means that where previously two heat exchangers were provided, the two heat transfer functions of the structural unit (heat exchanger) are integrated.

[0049] b. At least two heat exchange media are integrated in the heat exchanger in indirect heat exchange with media-based energy coupling (integrated media-based EK), which means that the structure is integrated in a single heat exchanger (device).

[0050] The aforementioned EK can be designed as a direct energy coupling (direct EK), achieved by providing a series EK or series interconnection of at least two heat exchangers.

[0051] The "condensing unit" of the first separation stage refers to a single heat exchanger or a group of heat exchangers used for at least partial condensation and / or cooling of the low-boiling fraction discharged via the top line. A "condensing unit" as referred to herein does not necessarily have to be a (closed) structural unit. Therefore, in some cases, the terms "condensing unit" and "single heat exchanger" are used synonymously.

[0052] A stage specifically designated as the “first separation stage” is provided, with corresponding equipment and piping, for the (specifically) separation of the solvent from the product-rich material stream, and advantageously, for its return to the reactor unit and / or conditioning unit for use. The first separation stage is defined such that at least 80%, ideally at least 90%, of the solvent is separated. Similarly, a stage designated as the “second separation stage” is meant to be defined, with corresponding equipment and piping to guide the separation of the product from byproducts and reactants, particularly MDA, and to purify the product. In this case, the first and second separation stages may not be completely strictly separated, and there may be overlapping areas or transitional areas where both the solvent and at least one byproduct or at least one reactant are separated from the product. In this context, where the product may be, in particular, PACM, “separation to remove solvent” and “separation of at least one reactant and / or at least one byproduct from the product” in the first separation stage mean that this separation does not imply an absolute boundary between separation stages, but rather “substantially” involves only one or more of the mentioned substances in each case.

[0053] The liquid material stream from the depressurized separation tank (hereinafter referred to as the separation tank (also known in some cases as a "flash vessel")) is guided via pipeline to the first separation column within the first separation stage of the separation unit. The separation tank is characterized by the separation of the incoming material stream into a vapor phase (solvent-rich) and a liquid phase (solvent-lean) through depressurization (pressure reduction), both of which are present in the separation tank during normal operation. The separation tank may additionally have, or be connected to, a bottom feed circulation system with an integrated heat exchanger to increase the separable vapor fraction beyond a pressure-determined fraction by heating the liquid phase. Furthermore, the separation tank may contain internal components or bulk packing to specifically prevent the entrainment of droplets that are not solvent-lean or only partially solvent-lean. Advantageously, in one embodiment of the apparatus, a pressure control unit may be provided in the pipeline from the separation tank to the first column. This allows the reactor unit to operate at a first high-pressure level and the first separation stage of the separation unit to operate at a second lower pressure level. Therefore, in this document, the separation tank (flash vessel) refers to a device in which phase separation is essentially caused by depressurization. In contrast, a separation tower in this paper refers to a device in which separation into a vapor phase and a liquid phase occurs primarily by supplying energy, particularly by incorporating a top circulation system, in which at least a portion of the condensed liquid is guided back into the tower at the top.

[0054] In this document, the term "reactant mixture" refers to the mixture of substances present upon entry into the (first) main reactor, i.e., a mixture of all reactants, solvents, additives, etc. The mixture of substances flowing in any degree of reaction or subsequent purification within and downstream of said at least one reactor is referred to as a "substance stream" or "substance mixture," wherein in some cases adjectives such as "product-rich" or "solvent-rich" are added. However, the material composition of the substance stream at each location in the apparatus is also readily apparent to those skilled in the art from that location in the apparatus and the upstream apparatus components, particularly the process technology equipment of the apparatus. Pure substances, such as the product PACM, and byproducts LB and HB are individually named and identified. "LB" here stands for "low-boiling substance," a valuable mixture of substances that is separately separated from the substance stream and product and has a low boiling point of approximately 240°C to 290°C. Similarly, "HB" stands for "high-boiling substance," a valuable mixture of substances that is separately separated from the substance stream and product and has a high boiling point of >350°C.

[0055] This document specifically claims an apparatus and method for the production of methylenebis(cyclohexylamine) as a product, particularly 4,4'-diaminodicyclohexylmethane (PACM), by the catalytic hydrogenation of methylene diphenylamine. Here, the main product is PACM, obtained by the hydrogenation of 4,4'-diaminodiphenylmethane (4,4'-MDA; the main component of reactant 1), particularly having the aforementioned low trans / trans isomer ratio. Therefore, this apparatus and method are particularly suitable for and adapted for the production of 4,4'-diaminodicyclohexylmethane (PACM) by the continuous catalytic hydrogenation of 4,4'-diaminodiphenylmethane (4,4'-MDA). The additional components of MDA, 2,4'-MDA and 2,2'-MDA, are converted to the reaction product in parallel, at least in small proportions, where these are generally retained in the product mixture. Furthermore, other byproducts can advantageously be purified and separated by this method or apparatus in a second separation stage of a separation unit, particularly in at least one separation column. These are typically secondary (valuable) products, which are generally described and meant in this article as high-boiling-point (HB) and low-boiling-point (LB) products.

[0056] The solvent is advantageously selected from the group consisting of cyclohexane, dioxane, tetrahydrofuran (THF), cyclohexylamine, dicyclohexylamine, methanol, ethanol, isopropanol, n-butanol, 2-butanol, 2-methoxy-2-methylpropane (MTBE), methylcyclohexane, or mixtures thereof. Advantageously, the solvent, especially THF, is supplied in excess to the MDA such that the mass flow ratio of the solvent, especially THF, to the MDA at the inlet of the main reactor is advantageously in the range of 1.0 to 8.0, particularly in the range of 2.0 to 6.0.

[0057] In an advantageous embodiment of the device, it may be that an intermediate loop incorporates a heat exchanger located crosswise in the feed line branch (steam line) and the return line branch to increase the temperature in the feed line branch.

[0058] Advantageously, a heat exchanger having a first internal space, particularly a vapor space, is incorporated in a heat-exchange manner into a feed line branch between a first evaporator and the at least one compressor, particularly the first compressor, wherein a return line branch is incorporated into a second internal space of the heat exchanger, particularly within a WT tube / tube bundle system. In other words, the vapor medium in the feed line flows outside the heat exchanger, for example, into the heat exchanger tubes, while the substantially condensed liquid medium in the return line branch flows inside, for example, the heat exchanger tubes.

[0059] In one implementation, it may be advantageous to provide a (Quer) line between the feed line branch and the return line branch, which originates from the return line branch at one line node and introduces the feed line branch at another line node, wherein this branch is advantageously located between the heat exchanger and the first evaporator, particularly upstream of the pressure relief valve, and the inlet is advantageously connected to...

[0060] - Between the heat exchanger and the at least one compressor, or

[0061] - Between two compressors connected in a branch of the feed line to increase pressure.

[0062] The advantage of cross-interconnection via heat exchangers is that the temperature in the feed line branches is raised by 2 to 10°C through the return medium. This interconnection is used to slightly overheat the feed line branches to prevent condensation from forming at the compressor inlet, which could potentially damage the compressor. By cross-directing the liquid medium from the return line downstream of the compressor via a pressure control unit, especially in the feed line between two compressors, it is advantageous to significantly increase the volumetric flow rate and thus the amount of energy, without increasing the electrical / energy consumption of the forward compressor. The medium supplied via the intermediate feed is depressurized at the pressure control unit and introduced as vapor. This intermediate supply improves the efficiency in the feed line branches by approximately 5% to 10%.

[0063] In another advantageous embodiment of the device, the intermediate loop may incorporate a set of at least two compressors in a branch of the feed line. It has been found advantageous to perform the required pressure increase in multiple stages, as this generally reduces power consumption because the downstream compressors must operate at progressively lower vapor volumetric flow rates, meaning they can have a structurally smaller design.

[0064] In a further advantageous embodiment of the device, a collection tank and a pump may be integrated into the medium loop of the collection circuit, wherein a heat exchanger is located upstream of the collection tank and / or on the suction side of the pump. In one embodiment, the heat exchanger is integrated into the collection tank, and / or the collection tank has an integrated temperature control unit. The advantage here is that the desired temperature level and desired volumetric flow rate of the medium can be provided overall in the feed line branch, regardless of the current input energy of the collection circuit and / or the current energy consumption in the integrated first evaporator. The circulating heat exchange medium in the collection circuit is advantageously water or a substantially aqueous solution.

[0065] In a further advantageous embodiment, the distributor circuit may include a first line branch as a vapor conduction feed line, wherein at least one compressor is incorporated in this line branch, and ideally, a compressor unit comprising two to five compressors, particularly two or three compressors, is provided. The two or more compressors are advantageously connected in series with each other.

[0066] In this way, the temperature of the steam from the second evaporator in the feed line can be increased efficiently by 30 to 150°C, especially by 70 to 120°C. Generally, the distributor circuit is a water circuit, or a circuit in which the heat exchange medium is water or an aqueous solution.

[0067] In a further advantageous embodiment of the device, where there are two or more evaporators in the feed line branch, at least one (bottom feed) line and / or at least one branch of the (bottom feed) line leads from a second evaporator to the suction side of at least one compressor, wherein a pump is integrated into the (bottom feed) line. Advantageously, in one embodiment, the (bottom feed) line and / or at least one branch of the (bottom feed) line guides between each pair of compressors in each case. It has been surprisingly found that, generally energy-advantageously, the liquid medium from the (bottom feed) line is supplied to the feed (vapor) line branch at a slightly lower temperature level, as this achieves a significantly increased mass flow rate without significantly increasing the energy demand of the compressors located downstream. Advantageously, a pressure control unit is provided in the (bottom feed) line or the corresponding branch from the (bottom feed) line to evaporate the liquid medium from the (bottom feed) line by depressurization, so that the feed into the feed line branch is carried out in the form of a vapor medium. Furthermore, the corresponding volumetric flow rate is controlled or, if necessary, completely stopped by means of the pressure control unit.

[0068] In other words, the advantage lies in the fact that the intermediate introduction between the two compressors also achieves the benefits of the second compressor stage. The vapor medium is superheated downstream of the first compressor stage. Despite the material input, this superheating is reduced by supplying lower-temperature vapor in the middle, which reduces the volumetric flow rate to the second compressor stage, thereby reducing the power consumption of the second compressor used for further compression.

[0069] In a further advantageous embodiment of the device, the (bottom material) line may have at least two branches, each branch of which is directed between the two compressors, and at least one branch of the (bottom material) line includes a pressure controller, wherein pressure and / or temperature sensors may be provided alternatively or additionally. A pump operating in the (bottom material) line is advantageously positioned downstream of the second evaporator and upstream of the first branch or a branch of the line used for corresponding intermediate feed.

[0070] In a further advantageous embodiment of the apparatus, a heat exchanger may be incorporated in a heat-exchange manner into the return line branch of the distributor loop, also known as the (return) line. This heat exchanger is incorporated downstream of the line branch used for distributing to the return line branch. This heat exchanger is an on-demand or controlled heat exchanger, through which the medium is ensured to be supplied to the second evaporator at the desired temperature level, regardless of energy consumption or release in the line branch used for distributing. This on-demand or controlled heat exchanger is not distributed to any other equipment in the apparatus, i.e., it is not provided for performing any heat exchange functions other than controlling the feed flow into the second evaporator.

[0071] In a further advantageous embodiment of the device, the distributor circuit may include additional line branches for distributing and / or releasing energy and additional line branches for media recirculation, wherein the line branches for distribution incorporate at least one heat exchanger of the reactor unit, at least one heat exchanger of the conditioning unit, and / or at least one heat exchanger of the separation unit as heat sinks, particularly incorporating multiple corresponding heat exchangers. In a particularly preferred variant, each of these additional line branches for distributing and / or releasing energy is, in its respective case, connected to a branch from the feed line branch, which are associated with different pressure levels. Thus, a first branch may be located downstream of a first compressor, a second branch may be located downstream of a second compressor, etc., and / or a first branch may be located downstream of a first pressure control unit, a second branch may be located downstream of a second pressure control unit, etc.

[0072] This grouping of heat exchangers via additional pipeline branches allows for targeted supply of a single heat exchanger or a group of two or more heat exchangers based on energy demand and temperature level requirements. Therefore, it is advantageous to first discharge heat exchangers or a group of heat exchangers with low temperature levels and / or high exchange power in the flow direction, thereby correspondingly reducing the power consumption of the downstream compressor. As mentioned above, the vapor phase medium can be supplied from the (bottom) line in the feed line branch as needed.

[0073] In a further advantageous embodiment of the device, when there is more than one return line branch in the distributor loop, an on-demand and / or controlled heat exchanger is incorporated into at least one additional return line branch in a heat-exchange manner; ideally, such an on-demand and / or controlled heat exchanger is incorporated into all return line branches.

[0074] In a further advantageous embodiment of the device, it may be that at least some of the heat exchangers incorporated as heat sinks in the distributor loop are connected in parallel. Advantageously, individual heat exchangers or groups of heat exchangers connected in parallel can each be controlled at the inlet or outlet by open-loop and / or closed-loop control. Controllability here specifically relates to the corresponding flow rate of the medium, which is advantageously achieved according to the required temperature gradient and / or required energy transfer in the respective heat exchanger or group of heat exchangers. In a further advantageous embodiment, a single heat exchanger acting as a heat sink or a group of two or more heat exchangers is not incorporated into the distributor loop. When incorporated into the distributor loop, the incorporation of these heat exchangers, particularly the (bottom) heat exchangers from the separation tower of the separation unit, will have an electrical demand on the compressor and / or another compressor equivalent to the direct electric heating of these heat exchangers. It has been found that, overall, direct electric heating is advantageous, even when the energy requirement for direct electric heating of the heat exchanger is increased by 1.2 to 1.3 times compared to that combined with the distributor loop, due to other smaller costs, such as less wear and tear and shorter downtime.

[0075] In a further advantageous embodiment of the apparatus, it may be that heat exchangers acting as heat sources in the collection loop are connected in series. For this purpose, the incorporated heat exchangers are advantageously incorporated into the feed line branch at an elevated temperature level in the flow direction of that branch. The central heat source for the collection loop is a heat exchanger incorporated into the cooling loop of the main reactor and used to dissipate the exothermic energy from the reaction. Other heat sources used are, in particular, the (top) heat exchangers (condensers) of the separation tower, depending on the temperature level of the medium in the respective heat exchanger.

[0076] The liquid material stream from the separator is guided via a (feed) line to the first separation column in the first separation stage of the separation unit. Advantageously, in one embodiment of the apparatus, a pressure relief unit may be provided in the (feed) line from the separator to the first column. In this way, the reactor unit can operate at a first high-pressure level, and the first separation column of the first separation stage can operate at a second lower pressure level, wherein the separator can operate at an intermediate level.

[0077] Furthermore, it may be advantageous to provide a (feed) heat exchanger upstream of the first separation tower of the first separation stage, particularly downstream of the depressurization unit, or between the depressurization unit and the first separation tower. In a particularly advantageous embodiment, energy coupling is provided to operate the condenser downstream of the separator, the condenser of the separation tower of the second separation stage, or the (circulating feed) heat exchanger in the media loop of the at least one main reactor interconnected in heat exchange with the (feed) heat exchanger of the first separation tower. Energy coupling can be achieved through conduction of the media and series interconnection of the individual heat exchangers or through integrated energy coupling in a (structurally) single heat exchanger. If feasible within the space of the device, integrated energy coupling has the advantage that only the temperature gradient for heat transfer needs to be overcome. Thus, it is possible to achieve parallel heating of the (feed) material stream upstream of the first separation tower of the first separation stage via energy transfer, the material stream being at a temperature level of approximately 85 to 95°C downstream of the upstream pressure control unit in the (feed) line. As the main reactor operates at rising temperatures to compensate for declining catalyst activity, it can release increasing energy in parallel to the feed stream upstream of the first separation tower. Consequently, the energy demand in the bottom loop or the heat exchanger incorporated into the first separation tower also decreases continuously.

[0078] In one embodiment of the apparatus, it may be advantageous for the reactor unit to include a first main reactor and at least one downstream, permanent, tandem post-reactor. A particular advantage of the inlet-side temperature control of the post-reactor and its material stream is that, due to the preferred higher inlet temperature compared to the main reactor, the selectivity for controlling the isomer ratio can be optimized in this way.

[0079] Advantageously, the post-reactor is also a fixed-bed reactor, or a reactor with a fixed catalyst, such as a catalyst bed or internal components coated with a catalyst.

[0080] Advantageously, the stationary catalyst comprises ruthenium, either already doped with ruthenium or formed from ruthenium. In an advantageous variation of the method, particularly for achieving a low trans / trans isomer ratio in the isomer mixture, as described more in detail in the context of the method according to the invention, the main reactor is operated at a temperature of 90 to 140°C, ideally 95 to 135°C.

[0081] It has been found particularly advantageous that the catalyst mass ratio in the main reactor to the downstream reactor is in the range of 1.2 to 2, preferably 1.3 to 1.4, and ideally 1.35. It has been surprisingly found that by simply regulating the highly exothermic reaction at the start of the reaction in the main reactor using a strong cooling loop, and by adjusting only the feed temperature at the inlet of the downstream reactor to achieve a moderate temperature increase of approximately 30 to 35°C from inlet to outlet in the downstream reactor, as already stated, there is only a limited and easily reproducible effect on the trans / trans isomer ratio in the material stream or product.

[0082] Perhaps particularly advantageous is that the main reactor is a fixed-bed reactor, which includes

[0083] - For the first flow path of reactant mixtures or substance mixtures, and

[0084] - An additional (closed) flow path, namely the medium circulation system for heat exchange, wherein two heat exchangers for indirect heat exchange are incorporated into the second flow path:

[0085] - The (main) heat exchanger operates as a cooler, and

[0086] - A (secondary) heat exchanger that operates as a heater.

[0087] It has been found to be very effective and advantageous to use the (secondary) heat exchanger to operate the same additional flow path or media circulation system to prepare and start up the main reactor, and to use the (main) heat exchanger to cool the main reaction during the production operation of the main reactor.

[0088] In a further embodiment of the device, it may be advantageous to

[0089] The reactor unit includes another main reactor in the form of a fixed-bed reactor, which includes

[0090] -The first flow path for the mixture of substances, and

[0091] - An additional (closed) flow path, namely a (cooling) medium circulation system for heat exchange, wherein a valve unit is provided upstream of the two main reactors in the (feed) line, thereby allowing the volumetric flow rate of the reactant mixture to be divisible, conductable, and / or fully switchable between the first and other main reactors, and wherein the two main reactors

[0092] - Each is connected to a heat exchanger or

[0093] - Commonly connected to a heat exchanger

[0094] This forms the other (closed) flow path.

[0095] In this case, the two main reactors connected in series are identical or substantially identical in structural design. In particular, the dimensions and / or internal components of the two main reactors are designed to accommodate or contain the same or substantially the same mass and / or volume of catalyst.

[0096] The advantage of these two main reactors is that further thermal decoupling of the highly exothermic first reaction stage, the moderately exothermic second reaction stage, and the lowly exothermic post-reaction is possible. A further advantage is that, with the same plant capacity, each main reactor has a smaller size, thus allowing for easier and more uniform thermal control. Simultaneously, the plant capacity is increased because the unit does not need to be completely shut down during maintenance, such as catalyst replacement. For this purpose, the two main reactors are interconnected via pipeline technology in a manner that allows the mixture of substances to flow individually through each main reactor while bypassing the corresponding other main reactor (bypass 1).

[0097] Hydrogenation under significant cooling in the (isothermal) main reactor can significantly limit temperature-induced isomerization. In the (adiabatic) post-reactor, a sufficiently high temperature level is established in a targeted manner, particularly through heat exchange, in the incoming material stream, thus allowing isomerization to provide just the required trans / trans ratio in the product. In a purely isothermal operation mode with a single main reactor without a post-reactor, excessively low trans / trans ratios and high proportions of unconverted MDA are initially obtained. By allowing the possibility of targeted adiabatic hydrogenation of the material stream, temperature evolution in the post-reactor can be advantageously controlled, and thus isomerization controlled.

[0098] In a further improved variant, the pipeline interconnection technology allows the downstream reactor to be bypassed (bypass 2) even when at least one main reactor is operating, but particularly when two main reactors are operating in series. In the bypass 2 interconnection variant, the downstream reactor, acting as the second main reactor through which fluid flows in the flow direction, at least temporarily assumes the function of the downstream reactor, so that the unit can operate with little or no reduction in production capacity and / or changes in product quality, especially changes in the proportions of isomers in the isomer mixture.

[0099] In a further embodiment of the apparatus, it may be advantageous to arrange at least one common heat exchanger in the pipeline between the at least one main reactor and the second main reactor. This common heat exchanger is positioned in the central branch of the two coolant circulation systems. The routing and interconnection of the pipelines here ensure that, downstream of the common heat exchanger, the cooling medium is first introduced into the first of the two main reactors, where a more exothermic reaction takes place. The heated cooling medium is then introduced downstream via the pipeline into the second main reactor to load the latter with an inflow temperature different from that of the first main reactor.

[0100] The advantage lies in the surprising observation that very precise control, particularly in the first highly exothermic reaction stage, is crucial for product quality, thus eliminating the construction work and control technical complexities involved in a separate, completely independent second cooling loop. Another reason is that complete reaction can be ensured and controlled, especially by controlling the feed temperature of the downstream reactor connected in series downstream of the two main reactors; in particular, the desired low trans / trans isomer ratio can be established.

[0101] In a variant of the device with improved controllability, it may be possible to place a heat exchanger (aftercooler) that can be switched and controlled as needed in a corresponding (cross) line of the cooling loop used to connect the coolant outlet of the first main reactor to the coolant inlet of the second main reactor.

[0102] The bottom circulation system of the separator operates at a temperature of 130°C to 150°C, ideally 135°C to 145°C. A significant advantage of the separator, which is very simple in construction and control technology, is that by reducing the pressure, the boiling point temperature of the mixture is also lowered, so heating in the separator only needs to reach this lowered boiling point temperature. Furthermore, with this measure, approximately 90% of the solvent present in the reactant mixture, especially THF, can be separated and removed. For this purpose, a top loop or return stream as in a column is unnecessary. The material stream further fed to the first separation column therefore advantageously has a residual solvent concentration of only about 20% to 40% by weight, ideally 25% to 35% by weight. Therefore, the first separation column can have a smaller construction design and can operate more energy-efficiently due to the lower quality of the material stream.

[0103] In this way, the temperature of the material stream can be reduced more quickly, thus preventing or reducing any increase in the trans / trans isomer ratio of PACM in the material stream.

[0104] Connect the solvent transfer (return) line to the conditioning unit and / or at least one suitable collection tank.

[0105] The present invention further includes a method for the continuous catalytic hydrogenation of methylene diphenylamine (MDA; reactant 1), particularly 4,4'-diaminodiphenylmethane, using a hydrogen donor (reactant 2), particularly a gaseous hydrogen donor, preferably hydrogen (H2).

[0106] The production is carried out using an industrial apparatus designed according to at least one of the embodiments and variations described herein, wherein the main reactor operates at a temperature in the range of 80°C to 150°C, and wherein, in the intermediate loop, the temperature of the medium in the feed line branch is increased by at least 30°C to 120°C, ideally 50°C to 90°C, by means of the at least one compressor, through vapor compression.

[0107] In a further embodiment of the method, a further advantage is that the at least one main reactor operates at a pressure in the range of 60 to 120 bar, ideally 70 to 110 bar. In a further advantageous embodiment, the pressure in the main reactor may be 70 to 100 bar, ideally 80 to 90 bar. Particularly preferred is a pressure of approximately 85 to 90 bar.

[0108] In a preferred embodiment of this method, the continuous catalytic production of methylenebis(cyclohexylamine), particularly 4,4'-diaminodicyclohexylmethane (PACM), is achieved, preferably 4,4'-diaminodicyclohexylmethane (PACM) with a low trans / trans isomer ratio. In a preferred variation of the method, the continuous catalytic production of methylenebis(cyclohexylamine), particularly PACM, of formula (I) is achieved.

[0109]

[0110] In a further embodiment of the method, a further advantage may be that, from time point t0 (the start of the method after catalyst renewal or regeneration) to time point t4 (the end of the method as determined by catalyst renewal or regeneration), the operating temperature of the main reactor is increased, and the temperature of the material flow at the inlet (feed) of the downstream reactor is maintained or decreased, wherein the increase or decrease in temperature is linear and / or gradual.

[0111] With the aforementioned device variant, the following process could potentially achieve a trans / trans content in PACM of 17% to 25% by weight over time.

[0112] Although the main reactor is referred to as “isothermal” in this paper, this ideal state is only achieved to a limited extent in industrial applications. As a result, due to incomplete heat dissipation, a temperature gradient of approximately 5 to 10 °C is formed within the main reactor in the radial direction and in the flow direction.

[0113] In a further embodiment of the method, a further advantage may be that multi-stage pressure increases are achieved in the distributor circuit and in the feed line branches, wherein an inlet pressure of 1.5 bar to 5 bar and a temperature of 100°C to 150°C are present downstream of the second evaporator and upstream of the first compressor.

[0114] In a further embodiment of the method, a further advantage is that multi-stage pressure increases are achieved in the distributor circuit, in the first pipeline branch, wherein there are pressures of 3 to 30 bar and temperatures of 130°C to 300°C downstream of the final compressor and upstream of the first heat exchanger that acts as a heat sink.

[0115] In a further embodiment of the method, a further advantage is that the energy introduced into the first evaporator by the collection loop via an intermediate loop and the at least one integrated compressor and any heat exchanger that may be cross-integrated is utilized.

[0116] - Increase by at least 1.1 to 2.5 times, and / or

[0117] -Outlet temperature of the first evaporator

[0118] Increased by at least 1.2 to 3.0 times.

[0119] In a further embodiment of the method, a further advantage may be that the MDA (reactant 1) comprises a mixture of the following monomers: 4,4'MDA, 2,4'MDA, and 2,2'MDA, wherein the proportion of 4,4'MDA is advantageously in the range of 75 to 98 mol%, ideally in the range of 85 to 95 mol%, and preferably 90 mol%. The proportion of 2,4'MDA in the reactant mixture is advantageously in the range of 7 to 15 mol%, preferably 8 to 12 mol%, and preferably 9 to 10 mol%.

[0120] Ideally, the proportion of trans / trans-PACM isomers in the product is in the range of 15% to 30% by weight, and ideally 16% to 25% by weight.

[0121] Overall, it is advantageous that the reaction steps in the main reactor are carried out isothermally or substantially isothermally, while the reaction steps in the subsequent reactors are carried out adiabatally or substantially adiabatously. At time point t0, i.e., at the start of the method, the catalyst in the subsequent reactors, in addition to the main reactor, may also be in the form of renewal or regeneration. Advantageously, the regeneration or renewal cycle of the subsequent reactors is determined autonomously and independently of the main reactor, especially when the aforementioned interactions of the reactants in the two reactors are no longer able to produce the desired low trans / trans ratio in the PACM.

[0122] In an advantageous embodiment of the method, the temperature of the reactant stream at the inlet of the main reactor may be 90 to 140°C, ideally 100 to 135°C.

[0123] In a further advantageous implementation of the method, the situation may be that,

[0124] - The temperature at the inlet of the main reactor corresponds substantially to the temperature at the inlet of the downstream reactor, where "substantially" means a range or difference of + / - 10°C, and / or the pressure at the inlet of the main reactor corresponds substantially to the pressure at the inlet of the downstream reactor, where "substantially" means a range or difference of + / - 5 bar.

[0125] In summary, all aspects, advantages, and embodiments related to or mentioned in connection with the device should also apply in kind or similarly to the method, and vice versa, unless otherwise stated and / or there is a technical impossibility related to a similar application.

[0126] The solution according to the present invention will now be described in detail with reference to embodiments. Attached Figure Description

[0127] The attached diagram shows:

[0128] Figure 1 The apparatus is shown as a process flow diagram.

[0129] Figure 2 The first embodiment of two-stage depressurization is shown.

[0130] Figure 3 Another implementation scheme for two-stage depressurization is shown.

[0131] Figure 4 Showing according to Figure 3 A variant of the implementation scheme,

[0132] Figure 5 Showing according to Figure 3 A variant of the implementation scheme,

[0133] Figure 6 Showing according to Figure 3 A variant of the implementation scheme,

[0134] Figure 7 Another embodiment of the reactor unit is shown, and

[0135] Figure 8 Another embodiment of the reactor unit is shown.

[0136] Figure 1This invention illustrates an apparatus 100 for the continuous production of 4,4'-diaminodicyclohexylmethane (PACM) by hydrogenation of methylene diphenylamine (MDA; reactant 1), particularly 4,4'-diaminodiphenylmethane, using a hydrogen donor (reactant 2), wherein the hydrogen donor is supplied in the form of gaseous hydrogen (H2). The apparatus 100 includes a conditioning unit 104 for the reactants, a reactor unit 102, and a separation unit 106.

[0137] Conditioning unit 104, outlined by a dashed line, includes feed lines for reactant 1, hydrogen (reactant 2), and solvent. Furthermore, the conditioning unit includes a compressor unit 150, the compressor mentioned below in the hydrogen supply line 151, and a mixer 152 in the lines supplying the solvent and reactant 1. A pump 156 and a heat exchanger 158 are additionally provided in the line 153 supplying the mixture of reactant 1 and solvent. Lines 151 and 152 lead to a mixing vessel 154 located upstream of the main reactor 200. The mixing vessel 154 is used for thorough mixing of the reactants, and its outlet line forms the inlet line of the main reactor 200.

[0138] Reactor unit 102 is outlined by a dashed line and essentially includes a main reactor 200, a cooling circuit 500, a post-reactor 210, and a heat exchanger 206 in the feed line of the post-reactor 210. The cooling circuit 500 incorporates a pump 204 and the heat exchanger 202, wherein the circulating coolant in the main reactor 200 flows around a carrier element filled with catalyst material. In the illustrated embodiment, the flow direction toward the carrier element filled with catalyst material is a co-current flow direction. The post-reactor 210 is connected via line 211 to separation unit 106, or its first separation stage.

[0139] The heat exchanger 202 in the cooling circuit 500 is shown as an air-cooled heat exchanger 202, but it can also be alternatively designed to control the temperature of the cooling medium in the cooling circuit 500 in an indirect heat exchange, for example, by means of a flowing cooling medium, such as oil, water, or brine. In a variant of the device not shown, the cooling circuit 500 also incorporates a similar... Figure 5 and 6 The heat exchangers 208 and 209 in the middle. Figure 5 and 6 Heat exchangers 208 and 209 operate with a heating medium and are used to regulate the temperature of the main reactor 200 during the start-up step. In an example of the apparatus and method shown, where the objective is to achieve the smallest possible trans / trans isomer ratio of approximately 17% to 23% by weight, the main reactor 200, filled with fresh or regenerated catalyst, is preheated to a temperature of approximately 90°C by means of heat exchanger 208. The main reactor 200 operates at a pressure of 87 to 88 bar.

[0140] Separation unit 106, outlined by dashed lines, includes multiple separation devices for separating the solvent, particularly in the first separation stage, and the PACM product, particularly in the second separation stage, from the remaining reactants and byproducts. The first separation stage (not shown) includes a separation tank 300 (flash vessel) connected to a bottom feed circulation system incorporating a heat exchanger 302 and a pump 306. The top outlet of separation tank 300 is connected to a heat exchanger 304, i.e., a condenser, downstream of which a solvent collection container 310 is provided. Approximately 80% of the solvent (here, THF) is condensed using heat exchanger 304 (condenser) and can be collected or returned. During the flash stage, the heat exchanger 302 in the bottom feed circulation system of separation tank 300 requires approximately 1400 kW of energy.

[0141] Condenser 304 is shown as a heat exchanger in the design of an air-cooled device, but it can also be alternatively designed, for example, by means of a flowing cooling medium, such as cooling water or a medium suitable for thermal integration, to at least partially condense and cool a material stream that is initially in a vapor state in indirect heat exchange.

[0142] The energy amounts mentioned in this article are calculated for the plant output of approximately 3.37 t / h of PACM product in the mentioned synthesis reaction, and the byproduct outputs of approximately 0.4 t / h of HB and approximately 0.05 t / h of LB. The THF to MDA mass flow rate ratio is 4.2 to 4.5.

[0143] Furthermore, the first separation stage of separation unit 106 for further separation and solvent removal includes a first separation tower 320 and a second separation tower 330, wherein the second separation tower 330 is in the form of a stripping tower. For this purpose, nitrogen (N2) is advantageously used as the stripping medium, flowing countercurrently through the tower relative to the material stream. A solvent-lean material stream can be transferred to the first separation tower 320 via line 161 by means of a pump 306 located at the bottom outlet of the separator 300. A pressure relief unit 222 is provided in line 161, which is designed as a controllable valve in the illustrated embodiment. As shown, the material stream is introduced into the first separation tower 320 via a central inlet. An additional (inflow) heat exchanger 327 (shown by dashed lines) is provided upstream of the first separation tower 320, constituting an option for heating the first separation tower 320.

[0144] In the first separation tower 320, the solvent concentration is reduced from 30% by weight in the feed (through the product-rich material stream from line 161) to approximately 2% by weight of residual solvent.

[0145] The first separation tower 320, equipped with (structured) packing material, is connected to a bottom circulation system incorporating a heat exchanger 322 and a pump 326. Furthermore, a top circulation system is provided at the top of the first separation tower 320, incorporating a heat exchanger 324 designed as a condenser. Two discharge lines for the solvent-rich material stream exit from the top circulation system, with one of these discharge lines leading to the top discharge line of the downstream separation tower 330 (stripping tower).

[0146] Specifically, the solvent separated in the first separation stage can be guided via line 311 to a collection tank (not shown) and / or a mixer 152 of the conditioning unit 104. In line 211 leading from the post-reactor 210 to the separation tank 300, there is a pressure relief unit 220, which in this embodiment is designed as a controllable valve.

[0147] A product-rich stream with approximately 2% by weight of residual solvent (THF) is directed from the bottom outlet of the first separation column 320 via line 321 to the top of the second column 330 (stripping column). A heat exchanger 328 is incorporated into line 321. The second column 330 has at least one internal packing, with a gas feed line, particularly an inert gas (stripping gas), positioned below the packing so that the introduced product-rich stream flows through the second column 330 countercurrently to the stripping gas and is further depleted to remove solvent. In the illustrated apparatus example, nitrogen (N2) is used as the stripping gas. The solvent-rich vapor from the second separation column 330 is introduced into a condenser 334 via a top outlet along with the solvent-rich vapor from the top outlet of the first separation column 320. The solvent stream condensed in the heat exchanger 334 is sent back to the recovery unit 104, where the non-condensable portion is removed from the heat exchanger 334 and, for example, completely thermally oxidized.

[0148] The product-rich material stream is fed from the bottom outlet of the second separation tower 330 via a pipeline 331 connected to a pump 336 into the third separation tower 340. The second separation stage 106B of the separation unit 106 is specifically used to separate the by-products LB and / or HB from the product PACM.

[0149] The second separation stage basically comprises three separation towers, with the third separation tower 340, which is the first tower of the second separation stage, being centrally fed with the material stream. The third separation tower is connected to a bottom circulation system incorporating a heat exchanger 342 and a pump 346. The product-rich material stream is guided from the bottom stream outlet to the fourth separation tower 350 via pipeline 341. Furthermore, the third separation tower 340 is connected to a top circulation system incorporating a heat exchanger 344. The condensed LB is drawn off from this top circulation system as a first byproduct.

[0150] The product-rich material stream is centrally fed into the fourth separation tower 350 via line 341. The fourth separation tower 350 is connected to a bottom circulation system incorporating a heat exchanger 352 and a pump 356. Furthermore, the fourth separation tower 350 is connected to a top circulation system incorporating a heat exchanger 354 in the form of a condenser. The product-rich material stream is discharged from the top circulation system as condensate via a top discharge line. In this case, according to the illustrated embodiment, uncondensed vapor and / or gas streams are introduced into the top discharge line of the downstream fifth separation tower 360. Subsequently, the product is further condensed and discharged via another heat exchanger 364 (condenser). A material stream with low product content is discharged via line 351 through the bottom discharge line of the fourth separation tower 350 and introduced into the top of the fifth separation tower 360. This material stream is highly enriched with HB, the second byproduct.

[0151] The fifth separation tower 360 is connected to a bottom material circulation system incorporating a heat exchanger 362 and a pump 366. Furthermore, the separation tower 360 has a top outlet leading to the aforementioned heat exchanger 364 in the form of a condenser. In this condenser 364, another product-rich material stream is condensed and discharged as condensate, while the non-condensable portion is discharged as a gas. The latter can then be completely oxidized.

[0152] Regarding the material flow, reactor unit 102 operates at a first high-pressure level of approximately 60 to 120 bar, the first separation stage 106A of separation unit 106 operates at a second low-pressure level of 4 to 12 bar, and the first separation tower 320 and the second separation tower 330 operate at a third slightly higher pressure level of 1.05 to 2.5 bar. In the illustrated embodiment, the first pressure level is 80 to 90 bar, the second pressure level is 4.5 to 7.5 bar, and the third pressure level is 1.1 to 1.2 bar.

[0153] Direct temperature control of the main reactor 200 via a cooling loop 500 connected in series with the uncooled post-reactor 210 has surprisingly proven to be a reduced energy requirement and a simplified, more stable process control scheme compared to existing technologies. Without being bound by any particular interpretation, this success can be seen in the fact that the cooling loop 500 only needs to be specifically designed to remove the exothermic heat of reaction for the very vigorous initial reaction, where the still significant post-reaction is only regulated by the upstream heat exchanger 206 via the feed temperature. Since the reaction in the post-reactor 210 has been highly attenuated, the material stream is only heated by approximately 5 to 15°C and can be discharged into the separator 300 at this level without any problems.

[0154] Generally, the accompanying drawings illustrate internal components of equipment such as reactors, separation towers, and containers, including packing materials, separation planes, and support elements, using appropriate symbols. These represent respective advantageous embodiments regarding quantity, type, and / or relative position with respect to the corresponding feed or discharge lines. For example, the illustration of the first separation tower 320 thus indicates that, advantageously, the (feed) material flow is introduced via line 161 such that, in each case, at least one (theoretical) separation plane exists between the top circulation system and the bottom circulation system. The specific type and / or number of separation planes are known to those skilled in the art and can be modified or provided in an appropriate manner.

[0155] Figure 2 This first embodiment of the energy interconnection shows three loops: a collection loop 550, an intermediate loop 560, and a distribution loop 570. The collection loop 550 includes a collection tank 180, a first line 551, an evaporator 170, and a second line 552. The first line 551 connects the collection tank 180 to the inlet of the heat exchanger section (WT section) of the evaporator 170, and the second line 552 connects the outlet of the WT section of the evaporator 170 to the collection tank 180. Therefore, only the WT section of the evaporator 170 is part of the collection loop 550.

[0156] The first pipeline 551 incorporates heat exchanger 202 of the coolant loop 500 of the main reactor 200 and heat exchanger 354 of the top circulation system from the fourth separation tower 350 as heat sources, along with pump 182. In the illustrated embodiment, in the second pipeline 552, heat exchanger 182 is incorporated into the feed inlet of the collection tank 180, primarily for adjusting the desired feed temperature (cooling) of the collection tank 180 and / or the temperature in the first pipeline 551 as needed and for control reasons, to ensure the required temperature gradient for cooling the incorporated heat exchangers 202, 354. The first pipeline 551 can also be considered a collection or feed pipeline, while the second pipeline 552 is considered a return pipeline. In the illustrated embodiment, the flow medium provided in this loop is water, although brine or oil can also be used.

[0157] In an advantageous manner, multiple heat sources are "collected" through a collection loop to transfer the energy of the medium (in this case, water) thus collected and guided in the loop to the first evaporator. This significantly reduces design complexity compared to direct interconnection of the heat exchangers involved.

[0158] The intermediate loop 560 includes the aforementioned evaporator 170, a first line 561, two compressors 173 and 174, a (feed) heat exchanger 175, another evaporator 172, another line 562, and a pressure relief unit 178. A portion of the intermediate loop 560 is integrated into the tank section (K section) by the first evaporator 170, and into the WT section by the second evaporator 172, meaning that the heat exchange medium in the intermediate loop 560 flows through it. The (feed) heat exchangers 175 are interconnected to integrate into the second line 562 downstream of the second evaporator 172 and into the inflow line of at least one of the compressors 173 and 174 in the first line 561. Furthermore, a (bridging) line 563 is provided through which the heat exchange medium can be introduced into the first line 561 in a manner that allows it to branch off from the second line 562. The branch of (bridging) line 563 is located downstream of heat exchanger 175 in second line 562, and the introduction into the first feed line occurs between the two compressors 173, 174. The heat exchange medium used is advantageously a more volatile medium than water, such as alcohols having 1 to 6 carbon atoms, particularly methanol, 2-propanol, butanol, or n-butanol. Depressurization unit 178 is located upstream of the inlet of the second line 562 into section K of the first evaporator 170.

[0159] The evaporating medium (in this case, methanol) is guided in the first feed line at a pressure of approximately 2.6 bar and superheated in two compression stages. The pressure is increased to approximately 9.5 bar by compressors 172 and 174, thus superheating the medium stream and resulting in a temperature of approximately 177°C downstream of the second compressor 174. The medium stream is then cooled in the WT section of the second evaporator 172, causing the medium to condense and exist as a liquid phase.

[0160] Besides the potential for significantly higher energy levels, another advantage of the intermediate loop is that the heat exchange medium itself provides additional freedom. This allows for the selection of the working medium to be optimally suited to the process-related temperatures of both the collection and supply loops, resulting in minimal compression costs for compressor operation.

[0161] A distributor circuit 570, incorporating the K portion of the second evaporator 172 (whose WT portion is integrated into the intermediate circuit 560), is connected to the second evaporator 172. The distributor circuit 570 includes a first feed line branch 571, a second distribution line branch or line segment 572, and a third return line branch 573, also referred to as a (return) line. The top discharge port of the evaporator 172 leads to the first line branch 571, wherein, in the illustrated embodiment, three compressors 192, 193, and 194 connected in series are integrated into the first line branch 571. Furthermore, the distributor circuit 570 includes a (bottom material) line 574, which extends from the bottom material outlet of the evaporator 172 through two line nodes to the first line branch 571, wherein a pump 191 is integrated into the (bottom material) line 574. The heating medium is first introduced via a first pipeline node between the first compressor 192 and the second compressor 193; the heating medium is second introduced between the second compressor 193 and the third compressor 194. In each case, controllable valves 196 and 197 are located upstream of the corresponding unmarked pipeline node.

[0162] Distribution line section 572 incorporates heat exchangers that serve as heat sinks, namely heat exchangers 158, 206, 302, 322, 328, 342, 352, and 362 connected in parallel. A central distribution line 572.1 leads to the heat exchangers, all of which are supplied to a central collection line 572.2 and then to a (return) line 573. Distribution line section 572 connects to section K of the second evaporator 172 via the (return) line 573. This (return) line 573 incorporates a heat exchanger 199 and a pressure control unit 195, thereby depressurizing the final pressure of the third compressor 194 (20 bar) back to approximately 2.5 to 3 bar at the level of section K of the second evaporator. The (return) line 573 connects to the inlet of section K of the evaporator 172.

[0163] The two evaporators 170 and 172 are so-called autoclave evaporators, having a heat exchanger section (WT section) closed to a first flowing medium and a tank section (K section) open to another flowing medium. Each WT section has an inlet and an outlet, wherein the heat exchange medium is guided in a closed channel or pipeline, such as at least one tube bundle system. Each K section has at least one inlet and one (top or steam) outlet, wherein the second evaporator 172 also has a (bottom) outlet. Specifically, the medium introduced via the at least one (bottom) inlet is heated by means of the respective WT section or associated heat exchanger and at least partially evaporates. Each K section may be divided into two parts or have two subspaces. A central K section exists therein, into which the heat exchanger of the WT section also extends, and energy is input into the K section. The other subspace is located in a lateral or external K section. This can be advantageously, but not necessarily, determined by the internal components being formed as a calm area relative to the liquid medium and / or by the heat exchanger of the WT section not extending into this subspace.

[0164] The water distributor circuit is at a temperature of 130°C and a pressure of 2.7 bar at the feed line branch immediately downstream of the second evaporator 172. Downstream of the first compressor 192, the pressure is 5.4 bar, achieved with an energy consumption of 238 kW; downstream of the second compressor 192, the pressure is 10.8 bar, achieved with an electrical energy consumption of 295 kW; and downstream of the third compressor 193, the pressure is 20 bar at a temperature of 250°C, achieved through an additional 250 kW of electrical energy consumption for the third compressor 193.

[0165] In order to supply Figure 2 The heat exchangers shown, particularly the bottom heat exchangers of the separation tower, must provide very high temperature levels, so the circulating medium must be cooled again by the on-demand and controlled heat exchanger 199. In the illustrated embodiment, the required cooling output power is approximately 368 kW, which must be provided in the (return) line 573 upstream of the pressure control unit 195 or before entering the second evaporator 172.

[0166] A significant advantage of the distributor loop can be considered as the formation of a central steam loop, allowing steam to be generated centrally and distributed to all heat exchangers operating as consumption devices (heat sinks), rather than directly interconnecting heat sources and heat sinks. Furthermore, if needed (e.g., during startup), the distributor loop, as the central steam loop, can be supplied at least temporarily with the aid of alternative heat or steam sources.

[0167] Figure 3 This illustrates an implementation where the collection loop 550 and the intermediate loop 560 are connected to... Figure 2 Similarly, it is formed. Distributor circuit 570 and according to Figure 2The difference in the implementation scheme is that the pipeline section 572 used to distribute energy to the heat exchanger that functions as a heat sink is divided into three sections, wherein the three sections are connected in parallel with each other:

[0168] - The high-pressure section (HD section) is connected downstream to the third compressor 194.

[0169] - The intermediate pressure section (MD section), which is connected downstream to the second compressor 193, and

[0170] - The low-pressure section (ND section) is connected downstream to the first compressor 192.

[0171] "ND segment / loop" here means that this segment or loop incorporates "fewer compressors and / or lower compressor power" than the HD segment / loop, such that, due to the number and / or design type of the compressors, the possible final pressure and therefore the final temperature (without further heat exchange) in the ND segment / loop is lower than that in the HD segment / loop. In other words, the pressure of the generated vapor is lower than that in the HD segment / loop, which is sufficient to meet the heating task in the ND segment / loop at a lower temperature level. Similarly, the pressure in the MD segment / loop is between that in the ND and HD segments / loops.

[0172] HD segment / loop refers in this document to a segment / loop of such a distributor circuit in which (within the distributor circuit) the maximum possible final pressure and therefore usually the highest final temperature in the distributor circuit can be generated in the medium, which can be achieved by the power and / or number and / or therefore possible output power of the compressors (especially those connected in series).

[0173] Each segment has a dedicated distributor line 572.1, and is connected to the evaporator 172 via feed lines or line branches 576, 577, and 578, which are branches of the feed line branch 571. Furthermore, a common collection line 572.2 supplied to each segment leads to a return line branch 573. If two or more heat exchangers are included, the heat exchangers within each of these segments are connected in parallel with each other.

[0174] In this configuration, the pipeline node where the first (output) pipeline 576 branches off from the central pipeline branch 571 is located between the first compressor 192 and the second compressor 193; the pipeline node where the second (output) pipeline 577 branches off from the central pipeline branch 571 is located between the second compressor 193 and the third compressor 194; and the third (output) pipeline 578, constituting the final section of the central pipeline branch 571, is connected downstream of the third compressor 194. In this configuration, the first (output) pipeline 576 supplies heat exchanger 302 alone, i.e., the ND section of pipeline segment 572; the second (output) pipeline 577 supplies two parallel heat exchangers 322 and 328, i.e., the MD section of pipeline segment 572; and the third (output) pipeline 578 supplies three parallel heat exchangers 342, 352, and 365, i.e., the HD section of pipeline segment 572. Therefore, the three (output) lines 576, 577, and 578 each have different pressure levels and different temperature levels. Similar to... Figure 2 In one embodiment, the liquid medium is fed into the central supply line branch 571 via the (bottom) line 574 or via a branch supply line branch 571, wherein the line nodes of the three (output) lines are positioned upstream of the line node of the corresponding inlet line from the (bottom) line 574 in the flow direction.

[0175] The lower section of the diagram, which incorporates heat exchangers 342, 352, and 362, is maintained at its own pressure level by means of a pressure control unit 585 in the collection line 572.2, while the middle section, which incorporates heat exchangers 322 and 328, is maintained at its own pressure level by means of a pressure control unit 586 in the collection line 572.2. Therefore, gradual depressurization occurs in the collection line 572.2.

[0176] The three sections of the pipeline section 572 used to distribute energy to the heat exchanger that functions as a heat sink lead to the common (return) pipeline 573 and to the evaporator 172.

[0177] This implementation variant is relative to Figure 2 The advantage is that the energy requirements of the second and third compressors 193 and 194 are significantly lower.

[0178] The water distributor loop is also at a temperature of 130°C and 2.7 bar at the feed line branch 571, immediately downstream of the second evaporator 172. Downstream of the first compressor 192, the pressure is 5.4 bar, achieved with the same energy consumption of 238 kW. Downstream of the second compressor 194, the pressure is also 10.8 bar, although achieved with only 145 kW of electrical energy consumption. Similarly, downstream of the third compressor 194, at a temperature of 250°C, the pressure is 20 bar, achieved with only 115 kW of electrical energy consumption for the third compressor 194. This advantage arises from the significant reduction in energy consumption in the second and third compressors 192 and 193. In addition to the energy advantage, this also relates to the fact that the second and third compressors 193 and 194 can have a significantly smaller structural design, which generally also improves maintenance and operation and / or installation.

[0179] In order to supply Figure 3 The heat exchangers shown, particularly the bottom heat exchangers of the separation towers, must provide very high temperature levels, so the circulating medium must be cooled again by the on-demand and controlled heat exchanger 199. In the illustrated embodiment, the required cooling capacity is approximately 368 kW, which must be provided in the (return) line 573 upstream of the pressure control unit 195 or before entering the second evaporator 172.

[0180] In principle, the ND segment incorporating heat exchanger 302 may also incorporate heat exchanger 206 of reaction unit 102 and / or heat exchanger 158 of conditioning unit 104.

[0181] exist Figure 3 In the illustrated embodiment, heat exchanger 304 (condenser), serving as a heat source for energy coupling, is coupled to two heat exchangers 206 and 158 operating as heat sinks. In this case, heat exchanger 206 is integrated into the feed line of the downstream reactor 210 (not shown), and heat exchanger 158 is integrated into the feed line 153 upstream of the main reactor 200. This energy coupling option of direct thermal coupling is shown. Figure 3 The lower left part of the image. For better understanding, heat exchanger 206 and pipe 116 are therefore located in this... Figure 3 It is shown twice. As mentioned above, for example, according to... Figure 2 or Figure 3 Compared to incorporating a heat sink into distributor loop 570, this selective direct interconnection and distribution of heat from condenser 304 results in a 30% to 40% increase in efficiency, especially when at least one energy coupling is an integrated material-based EK, wherein heat exchanger 304 is coupled upstream of the first separation tower 320 of the first separation stage 106B to (feed) heat exchanger 158 and / or (feed) heat exchanger 327 (not shown, similar to) Figure 6 ).

[0182] In this context, unless otherwise stated, "increased efficiency" refers to lower energy consumption. The reference point is self-evident from the context and can be based on the device, separately described segments of the device, or improved equipment, such as by integrating two heat exchangers into a single heat exchanger.

[0183] like Figure 4 The embodiments shown can be regarded as Figure 3 The embodiments are alternatives or improvements because the HD sub-unit has been addressed in an alternative manner. Figure 4 In this embodiment, the distributor circuit 570 includes two sub-circuits. These sub-circuits are the medium-voltage distributor circuit 580 (MD distributor circuit) and the low-voltage distributor circuit 582 (ND distributor circuit). The MD distributor circuit 580 is substantially similar to... Figure 3 An implementation scheme for the intermediate MD segment is formed. This is located downstream of the second compressor 194 and also only provides intermediate feed for the medium flow via the (bottom) line 574 between the two compressors 192 and 194. In the branch line of the ND distributor circuit 582, the pressure downstream of the second compressor 194 is approximately 8 to 12 bar, in this case approximately 10.8 bar. The ND distributor circuit 582 is basically similar to Figure 3 The implementation scheme for the ND segment is formed. This is located downstream of the first compressor 192. In the branch line 591 of the ND distributor circuit 582, the pressure is approximately 5 to 6 bar, in this case 5.4 bar.

[0184] The WT portion of the evaporator 172 is similarly incorporated into the intermediate loop 560, in which a volatile medium, such as methanol or butanol, circulates.

[0185] The ND distributor loop 582 includes a first feed line branch 591, a second distribution line branch 592 (also referred to as line section 592), which leads to a central return line branch 593 (also referred to as (return) line 593). As explained, the feed line branch 591, which incorporates heat exchangers 158, 206, 302 and possibly other heat exchangers connected in parallel as energy sinks, branches off from line branch 571 downstream of the first compressor 192. The (return) line 593 forms a common return line connecting the MD and ND distributor loops 580, 582 to the K section of the second evaporator 172. The (return) line 593 incorporates a heat exchanger 226, by which the return flow temperature required to operate the evaporator 172 and / or preheating steps can be achieved before or during the start-up of the apparatus 100 or the method. In addition, a controllable pressure control unit 195 is incorporated into the (return) line 593 to ensure a low pressure level in the K section of the evaporator 172 at approximately 2.5 to 3.5 bar at approximately 125 to 130°C.

[0186] To maintain an overall favorable efficiency for the device and the three or four interacting loops, a heat exchanger group 584 (WT group 584) is not incorporated and is advantageously energized. Thus, the heat exchangers 342, 352, and 362 of the three associated bottom loops of the separation tower are heated by an electrically heated device, without pipeline connections for the flowing heat exchange medium. The motivation for this is that the electrical conduction requirements for operating the third compressor are comparable in size to direct heating, and therefore it is wise, for example, to provide the slightly higher energy consumption for direct electric heating of the WT group 584 while avoiding the aforementioned disadvantages, in order to avoid maintenance costs, capital costs, etc. Furthermore, since only one power source needs to be secured and the construction volume of the electrically heated heat exchanger is significantly smaller than that of the heat exchanger for the conductive medium, the design and construction complexity of the separation tower involved is also simplified.

[0187] The advantage of dividing distributor circuit 570 into sub-circuits 580 and 582 is that these sub-circuits can operate at different pressure and temperature levels, thus reducing the electrical energy consumption of the compressor, especially the compressor downstream of the first compressor, and allowing for a reduction in their build size. Finally, by using direct electric heating, considering the increase in medium temperature per kW of electrical power supplied by the compressor, the compressor, especially the least efficient compressor, can be completely eliminated. In this embodiment, the electrical cost of compressor operation is minimized through ND and MD distributor circuits 580 and 582 because the temperature level of the circuit is adapted to the required temperature of the heat sink, thus avoiding unnecessary compression stages and / or achieving a corresponding reduction in the volumetric flow rate of the vapor to be compressed.

[0188] like Figure 5 The embodiments shown depict similarities to Figure 2 The implementation scheme, in which the design of distributor circuit 570 is greatly simplified; distributor circuit 570 incorporates only one heat exchanger, in this case heat exchanger 302 from the bottom material circulation system of separator tank 300, which has very high or highest energy requirements for unit 100. Distributor circuit 570 is also simplified because only one heat exchanger 302 relative to the compressor (in which only one compressor 192 is incorporated) is incorporated in the first pipeline branch 571.

[0189] In principle, the distributor circuit 570, which incorporates heat exchanger 302, may also incorporate heat exchanger 206 of reaction unit 102 and / or heat exchanger 158 of conditioning unit 104.

[0190] Figure 5The illustrated embodiment shows an option in which heat exchanger 304 (condenser) is directly connected as a heat source to heat exchanger 206, which acts as a heat sink, to the feed inlet (not shown) of the downstream reactor 210, and to heat exchanger 158, which is integrated into the feed line 153 upstream of the main reactor 200. This direct interconnection option of the various heat exchangers is shown in Figure 5 The lower left part of the image. For better understanding, heat exchanger 206 and pipe 116 are therefore located in this... Figure 5 It is shown twice. As mentioned above, according to... Figure 2 or Figure 3 Compared to incorporating a heat sink into distributor loop 570, this selective direct interconnection and distribution of heat from condenser 304 results in a 30% to 40% increase in efficiency, especially when at least one energy coupling is an integrated material-based EK, wherein heat exchanger 304 is coupled upstream of the first separation tower 320 of the first separation stage 106B to (feed) heat exchanger 158 and / or (feed) heat exchanger 327 (not shown, similar to) Figure 6 ).

[0191] The embodiment in which only heat exchanger 302 is provided in distributor loop 570 constitutes a particularly simple and efficient heat transfer system because only one compressor stage or compressor is required, thus efficiently meeting most heat demands. Efficiency can be increased by approximately 40% simply through this integration compared to direct heating of the heat exchanger. The direct interconnection of heat exchanger 304 as a heat source with heat exchangers 206 and 158 as heat sinks results in an efficiency increase of approximately 28%, i.e., energy savings of 28%. Therefore, through these two measures—the direct interconnection of distributor loop 570 and condenser 304 with heat exchangers 206 and 158—an efficiency increase of approximately 70% is possible.

[0192] Figure 6 Another alternative embodiment is shown. In this case, a (feed) heat exchanger 327 is provided upstream of the first separation tower 320 to reduce the load on and improve the efficiency of the interconnected closed media loops 550, 560, 570. Advantageously, the media stream exiting from the (feed) heat exchanger 206 of the downstream reactor 210 (at a temperature level of approximately 110 to 125°C) is supplied as a heating medium to this (feed) heat exchanger 327. In this way, the energy demand of the heat exchanger 322 in the bottom circulation system of the first separation tower 320 is reduced, and thus the energy demand of the distributor loop 570 is reduced. A particular advantage is achieved when the integrated material base EK of the heat exchanger 304 is used in conjunction with the (feed) heat exchanger 327 upstream of the first separation tower 320 downstream of the pressure control unit 222 and the first separation stage 106B (not shown).

[0193] Figure 7This shows an improved variant of reactor unit 102. Two main reactors 200, 201 are here interchangeably connected in series with each other. Figure 5 Some valves / valve units that can be controlled via open-loop and / or closed-loop control are shown; others can be provided by those skilled in the art as needed to ensure the safe operation of the two main reactors 200, 201. The two main reactors 200, 201 are each integrated into cooling circuits 500, 501, thereby maintaining the fixed-bed reactors 200, 201 at permissible cooling reaction temperatures under their respective conditions. In the interconnection of the main reactors 200, 201 shown and indicated by solid lines, fluid first flows into the first main reactor 200 via line 110 from mixing vessel 154, and the first part of the reaction occurs in this main reactor 200. Downstream, the mixture is introduced into the top of the second main reactor 201 via a lower outlet and line 112, and exits via a bottom outlet and line 115 into a common line 116 as feed into a common downstream reactor 210. The common line 116 is integrated with a heat exchanger 206, thereby ensuring the required temperature level in the downstream reactor 210. The flow sequence through the two main reactors can also be reversed, proceeding from main reactor 201 to main reactor 200. For this purpose, in a similar manner, the fluid first flows through line 111 to main reactor 201, where line 110 leading to the top of main reactor 200 is closed. The mixture exits this fixed-bed reactor via a bottom outlet and (intermediate) line 113, which connects to the top of main reactor 200, where line 115 is closed. Finally, the mixture exits main reactor 200 via a bottom outlet and line 114, which similarly leads to a common line 116 and from there to the downstream reactor 210. Lines 502 and 503 branch off from each of the two cooling circuits 500 and 501, respectively, and are guided through a vessel 212 and 213, which act as pressure balancing vessels, and further to the chimney and / or the complete oxidation unit. Piping and valve / valve units are provided and designed such that each of the main reactors 200, 201 can operate independently and the material flow can completely bypass the corresponding other main reactor. The flow direction of the two cooling loops 500, 501 is indicated by arrows, wherein the two cooling loops 500, 501 are advantageously designed to be identical or substantially identical, since the two main reactors 200, 201 operate alternately as the first or second main reactor relative to the flow direction of the reactant flow or material flow.

[0194] However, cooling circuits 500 and 501 are designed and controllable to meet autonomous cooling capabilities or cooling functions in each case, according to process-related requirements, particularly such as product management and / or product quality. This specifically relates to the volumetric flow rate of the cooling medium per unit time and / or the corresponding temperature level or permissible heating of the cooling medium.

[0195] Figure 7 Optional line 117 is also shown as a dashed line (bypass 2), which can bypass downstream reactor 210—if, for example, it needs maintenance and / or catalyst loading replacement. In this case, the temperature of the second main reactor is controlled, at least in the direction of material flow, to ensure complete reaction at the desired product quality, particularly the desired proportions of the respective isomers. Line branches of line 117 can be provided upstream or downstream of heat exchanger 206 in the flow direction; it is advantageous to provide them upstream of heat exchanger 206 so that they can be bypassed if necessary, and necessary maintenance operations can be performed while the unit is running.

[0196] In operation of the main reactor 201 shown on the right side of the image, flow can bypass the main reactor 200 via pipelines 111, 115, and 116. In operation of the main reactor 200 shown on the left side of the image, flow can bypass the main reactor 201 via pipelines 110, 114, and 116, so that in each case there is no flow through the (crossing) pipelines 112 and 113 between the two main reactors 200 and 201.

[0197] In the illustrated apparatus variant, heat exchangers 208 and 209 are optionally incorporated into the cooling circuits 500 and 501. These operate with a heating medium, particularly steam, and are used to preheat the main reactor 200 to the reaction temperature of the respective main reactor 200 or 201 during the start-up phase. This preheating level is approximately 80 to 100°C, ideally 85 to 95°C. In the illustrated apparatus and method examples, such as... Figure 1 As has been explained, in order to achieve the target of the smallest possible trans / trans isomer ratio of approximately 17% to 23% by weight, it is advantageous to preheat the newly filled catalyst main reactors 200, 201 to a temperature of approximately 90°C by means of their respective heat exchangers 208, 209, or to preheat the respective newly filled catalyst main reactors 200, 201 accordingly.

[0198] Preheating to approximately 85 to 95°C enables the reaction to begin immediately with the catalyst of the present invention, without or with minimal need to recycle the stream of the mixture of substances from the method until the desired reaction temperature is reached.

[0199] like Figure 8The variants of the switchable main reactors 200, 201 shown are based on Figure 7 The variation differs in that the cooling circuit 500 of the first main reactor 200 is also connected in series with the cooling circuit of the second main reactor 201. In this case, only one (cooling) heat exchanger 202 and only one pump 204 are provided for this common cooling and media circulation system, so the flow rate through the common (central) pipeline branch 508 in the two cooling circuits 500, 501 is generally constant and only in one direction, regardless of the interconnection of the two main reactors 200, 201. Of course, the "central" pipeline branch does not actually need to be located between the two main reactors 200, 201 here. This variation is shown in solid lines, in which the reactant mixture is first supplied to the first main reactor 200 (left side) via pipeline 110, and the introduction of (cooling medium) downstream of the heat exchanger 202 and pump 204 is also first achieved via this main reactor 200. Pipelines that do not guide the medium or guide the mixture of substances in this interconnection are shown in dashed lines. In these variations, it is also possible that the mixture of substances and / or (cooling) medium completely bypass the corresponding other main reactor. Therefore, for example, during the filling of one of the two main reactors 200, 201, the corresponding other main reactor can continue to operate at maximum production capacity. The bypass of the material flow or the corresponding main reactor 200, 201 is similar to... Figure 7 The conclusion is as follows.

[0200] In the illustrated exemplary interconnection, fluid flows through a central pipeline branch 508 and heat exchanger 202, and is directed in parallel via pipeline 504 into the media space of the first main reactor 200, where pipeline 505 from the second main reactor 201 to the common pipeline node is blocked. The medium exits the first main reactor 202 at a low outlet via pipeline 506 and is directed to the high inlet (cross pipeline) into the media space of the second reactor 201. The medium also flows in parallel through the media space of the second main reactor 201 and exits at a low outlet via pipeline 509, whereby a branch again leads to the central pipeline branch 508, allowing for re-flow through the loop. Similarly, when pipeline 504 is blocked, fluid first flows through the main reactor 201 shown on the right via pipeline 505. The medium then exits the media space of the second main reactor 201 via pipeline 509 and is directed at the high inlet into the media space of the other main reactor 200. The outlet of the medium space at the low point leads to pipeline 506, and from there it branches into the central pipeline branch 508.

[0201] A particular advantage of the switchable main reactors 200 and 201 is that the main reactor through which the fluid first passes operates at a higher temperature without significantly affecting (i.e., increasing) the possibility of the trans / trans isomer ratio, since the catalyst has already been partially depleted and deactivated. In parallel, a more significantly heated cooling medium is generated in the respective (circulating feed) heat exchangers 202 and 203 of the main reactors 200 and 201 through which the fluid first passes. Due to the higher temperature, this hotter heat exchange medium can be better used in the unit for the integrated media base EK and / or for conventional heat exchange with the reactant feed stream.

[0202] Similar to Figure 7 , Figure 8 The optional pipeline 117 is shown as a dashed line (bypass 2), which allows it to bypass the downstream reactor 210, wherein pipeline 117 branches downstream of the (feed) heat exchanger 206 of the downstream reactor 210.

[0203] Figure 8 A variation of the apparatus (dashed line) is also shown, in which a switchable and controllable heat exchanger 203 (feed cooler) is arranged as needed to achieve greater safety or greater freedom in temperature management in the corresponding (crossing) lines 504 and 505 of the cooling circuits 500 and 501. In the illustrated embodiment, the two heat exchangers 202 are connected in series because, due to the corresponding inactive (crossing) line, in the illustrated embodiment line 505, no heating occurs at the installation location of the heat exchanger 202. In an advantageous variation, the cooling medium line or cooling medium circuit of the heat exchanger 202 can operate in a side flow or via a secondary or auxiliary circuit using a pump 204.

[0204] This document primarily describes the (feed) heat exchanger 206, and in some cases shown in energy couplings where it operates primarily as a heat sink, meaning the material stream conducted within it is heated. By adapting the downstream reactor 210 to the dependent operating mode of the main reactors 200, 201, cooling of the material stream in the (feed) line 116 upstream of the downstream reactor 210 may be necessary, at least temporarily and particularly persistently, because approximately 10% to 20% of the conversion occurs in the (adiabatic) downstream reactor, resulting in the material stream being heated to approximately 140°C as measured at the outlet. Therefore, embodiments and variations of the apparatus and methods described herein can provide energy couplings adapted for cooling (heat exchanger 206 operating as a heat source). Alternatively or additionally, auxiliary cooling can be provided by altered or additional energy couplings.

[0205] The great advantage of this side-flow or secondary / auxiliary loop of coolant via heat exchanger 203 is that this additional cooling capacity only needs to be called up as needed, and with low complexity, it is possible to achieve a greater degree of closed-loop temperature control as needed in the corresponding second of the two series-connected main reactors.

[0206] In general, many conventional open-loop and closed-loop control elements known to those skilled in the art and necessary or desirable for advantageous methodologies, such as sensors (flow, temperature, pressure, etc.), displays, regulating and control elements (especially valves, additional pumps, compressors), collection containers, etc., are not shown, and may be supplemented as needed. In particular, when referring to “one” pump or “one” compressor, this also means a conventional redundant design from at least two parallel units, especially two parallel pumps or two parallel compressors. In a similar manner, “one heat exchanger” should not be construed as limiting, and for the corresponding local heat exchange function, it also refers to the arrangement of heat exchangers connected in series or in parallel, including redundant heat exchangers, which is not understood here as interconnection with at least one other heat exchanger and locally different heat exchange functions.

[0207] Unless otherwise stated, all heat exchangers and condensers are designed in principle to allow indirect heat transfer without physical mixing of reactants, products, byproducts and / or solvents with the (heating / cooling) medium (such as gas, steam, water, oil, brine, etc.).

[0208] Even if components such as valves, pressure control units, and isolators are shown individually or separately in this document for the sake of simplicity, and are not mentioned separately in some cases, this should not be interpreted in a restrictive manner; rather, those skilled in the art can combine two or more of these components in a valve unit or control unit as needed, or instead provide a multi-way valve.

[0209] In this context, unless otherwise stated, "upstream" or "downstream" refers to the arrangement and / or flow direction of the product-rich material flow. Furthermore, unless otherwise stated, "medium," "medium flow," "medium pipeline," etc., always refer to the heating or cooling medium or related pipeline.

[0210] The terms “bottom effluent,” “bottom output,” “bottom discharge,” or “bottom discharge” are used synonymously in some cases, and similarly, the terms “top effluent,” “output,” “discharge,” or “outlet” are also used synonymously in some cases.

[0211] Furthermore, the phrase "heat exchanger operating as a condenser" should be interpreted broadly, and also refers to the incomplete condensation or cooling of the supplied material stream. Therefore, "heat exchanger operating as a condenser" is sometimes also synonymously named "condenser".

[0212] The term "bottom pump" refers to a pump incorporated into the bottom circulation system of equipment (separation tower, container, etc.) and / or a pump downstream of the bottom outlet of the equipment, providing it for conveying the liquid material stream.

[0213] In all embodiments and variations of this apparatus and method, it is generally likely that the second separation tower 340 and the third separation tower 350 are implemented as a single tower, particularly as a partition wall tower (not shown). In this case, the separation function of the second separation tower 340 and the third separation tower 350 can advantageously be implemented at least partially, ideally entirely, by means of a partition wall tower (not shown) as known, for example, from documents EP012 62 88B1 or EP 012 23 67A2.

[0214] In summary, the apparatus and method according to the invention can achieve great energy advantages, namely, the ability to significantly reduce the energy flow supplied from the outside, and in particular, to save a large amount of (external) heating steam.

Claims

1. An apparatus (100) for hydrogenating methylenediphenylamine (MDA; reactant 1) using a hydrogen donor (reactant 2), particularly a gaseous hydrogen donor, preferably hydrogen (H2). It includes a conditioning unit (104) for reactants, particularly a reactor unit (102) for the synthesis of methylenebis(cyclohexylamine), especially 4,4'-diaminodicyclohexylmethane (PACM), and a separation unit (106), wherein - The conditioning unit (104) includes a (feed) line for reactant 1, reactant 2 and at least one solvent, at least one heat exchanger (158) in at least one (feed) line, and at least one mixer (152) for mixing the reactant and / or at least one reactant with at least one solvent. - The reactor unit (102) includes at least one fixed-bed reactor as a main reactor (200, 201) with a fixed catalyst packing, wherein the at least one (first) main reactor (200, 201) includes: - for supplying the material mixture through the first flow path of the fixed catalyst packing and -A separate, closed flow path for the heat exchange medium outside the catalyst packing, and wherein A heat exchanger (202) is incorporated into the medium circuit; - The separation unit (106) includes at least: a first separation stage (106A) for (basically) separating and removing the solvent, and a second separation stage (106B) for separating the at least one reactant and / or at least one byproduct from the product. Its features i) includes a collection loop (550) for a closed first medium loop, wherein at least one heat exchanger (354) of a heat exchanger (202) incorporated into the main reactor (200) and / or a separation unit (106) as at least one heat source, and a first evaporator (170), ii) includes an intermediate circuit (560) for closing a second medium circuit, wherein a first evaporator (170), at least one compressor (173), and a second evaporator (174) are combined, and wherein iii) including at least one distributor circuit (570) for a closed third medium circuit, wherein at least one heat exchanger (206) of the reactor unit (102), at least one heat exchanger (158) of the conditioning unit (104) and / or at least one heat exchanger (302) of the separation unit (106) are incorporated as heat sinks in a heat exchange manner.

2. The apparatus according to claim 1, characterized in that... In the intermediate loop (560), the heat exchanger (175) is cross-connected to the feed line branch (561) and the return line branch (562), wherein the first line branch (561) is connected to the first internal space of the heat exchanger (175) and the return line branch (562) is connected to the second internal space of the heat exchanger (175).

3. The apparatus according to claim 1 or 2, characterized in that... At least two compressors (173, 174) are incorporated in the feed line branch (561) of the intermediate circuit (560).

4. The apparatus according to any one of the preceding claims, characterized in that... In the intermediate loop (560), at least one cross guide line (563) is provided between the feed line branch and the return line branch (561, 562), which branches off from the return line branch (562) at one line node and enters the feed line branch (561) at another line node, wherein the branch is advantageously located between the heat exchanger (175) and the first evaporator (170), and the inlet is incorporated into the feed line branch (561) between the heat exchanger (175) and the at least one compressor (137) or between two compressors (173, 174).

5. The apparatus according to any one of the preceding claims, characterized in that... The collection circuit (550) incorporates a collection tank (180) and a pump (182) in its media circuit, wherein the heat exchanger (182) is located in a return line branch (552) upstream of the collection tank (180) and / or in a feed line branch (551) on the suction side of the pump (182).

6. The apparatus according to any one of the preceding claims, characterized in that... The distributor circuit (570) includes a first line branch (571) as a steam conduction feed, wherein at least one compressor (192, 193, 194) is incorporated in the feed line branch (571).

7. The apparatus according to claim 6, characterized in that... A feed line (574) extends from the second evaporator (172) to the pressure side of one compressor (192) and to the suction side of another downstream compressor (193), wherein a pump (191) is incorporated in this feed line (574), and / or at least one branch of the feed line (574) leads from the second evaporator (172) to a feed line branch (571) between the two compressors (192, 193, 194), and in particular the feed line (574) has at least two branches, wherein each branch of the feed line (574) leads between two of the compressors (192, 193, 194), and wherein at least one branch of the feed line (574) includes a pressure regulator (196, 197).

8. The apparatus according to any one of the preceding claims, characterized in that... The distributor circuit (570) includes an additional pipeline branch (572) for distributing and / or releasing energy and an additional pipeline branch (573) for media recirculation, wherein at least one heat exchanger (206) of the reactor unit (102), at least one heat exchanger (158) of the conditioning unit (104) and / or at least one heat exchanger (302) of the separation unit (106) are incorporated in the pipeline branch (572) as heat sinks, and in particular, multiple corresponding heat exchangers are incorporated.

9. The apparatus according to any one of the preceding claims, characterized in that... The return line branch (573) of the distributor circuit (570) is connected to the heat exchanger (199) in a heat exchange manner.

10. The apparatus according to any one of the preceding claims, characterized in that... At least some of the heat exchangers (158, 206, 302) of the distributor circuit (570) that are incorporated as heat sinks are connected in parallel, in particular each incorporated into the feed line and / or discharge line of the medium and can be controlled by open-loop and / or closed-loop control.

11. The apparatus according to any one of the preceding claims, characterized in that... The heat exchangers (202, 354) that act as heat sources in the collection circuit (550) are connected in series.

12. A method for the catalytic hydrogenation of methylenediphenylamine (MDA; reactant 1) using a hydrogen donor (reactant 2), particularly a gaseous hydrogen donor, preferably hydrogen (H2). Production is carried out using industrial equipment. Its features The apparatus is designed according to at least one of claims 1 to 11, wherein the main reactor (200) operates at a temperature in the range of 80°C to 150°C, and wherein, in the intermediate loop (560), by means of the at least one compressor (173), the temperature of the medium in the feed line branch (561) is increased by at least 30°C to 120°C, ideally 50°C to 90°C, through vapor compression.

13. The method according to claim 12, characterized in that... The temperature of the reactant flow at the inlet of the main reactors (200, 201) is 90 to 140°C, ideally 100 to 135°C.

14. The method according to claim 12 or 13, characterized in that... The at least one main reactor (200) operates at a pressure in the range of 60 bar to 120 bar, ideally in the range of 70 to 110 bar.

15. The method according to any one of the preceding claims, characterized in that... The pressure in the main reactors (200, 201) is 60 to 120 bar, ideally 70 to 110 bar.

16. The method according to any one of the preceding claims, characterized in that... It is carried out continuously and catalytically for the production of methylenebis(cyclohexylamine), especially for the production of 4,4'-diaminodicyclohexylmethane (PACM), preferably 4,4'-diaminodicyclohexylmethane (PACM) with a low trans / trans isomer ratio.

17. The method according to any one of the preceding claims, characterized in that... From time point t0, the start of the method after catalyst renewal or regeneration, to time point t4, the end of the method determined by catalyst renewal or regeneration, the operating temperature of the main reactor is increased, and the temperature of the material flow at the inlet (feed) of the downstream reactor is maintained or decreased, wherein the increase or decrease in temperature is linear and / or gradual.

18. The method according to any one of the preceding claims, characterized in that... In the distributor circuit (570), the pressure in the feed line branch (571) is increased in two or more stages, wherein an inlet pressure of 1.5 bar to 5 bar and a temperature of 100°C to 150°C are present in the first line branch (571) downstream of the second evaporator (172) and upstream of the first compressor (192).

19. The method according to any one of the preceding claims, characterized in that... In the distributor circuit (570), the pressure in the first pipeline branch (571) is increased in two or more stages, wherein there is a pressure of 3 to 30 bar and a temperature of 130°C to 300°C downstream of the final compressor (194) and upstream of the first heat exchangers (302, 362) that act as heat sinks.

20. The method according to any one of the preceding claims, characterized in that... Energy is introduced into the first evaporator (170) by the collection loop (550) via the intermediate loop (560) and the at least one integrated compressor (173, 174) and cross-integrated heat exchanger (175). - Increase by at least 1.1 to 2.5 times, and / or -Outlet temperature of the first evaporator (170) Increased by at least 1.2 to 3.0 times.

21. The method according to any one of the preceding claims, characterized in that... The MDA (reactant 1) comprises or is formed from a mixture of the following monomers: 4,4'MDA, 2,4'MDA and 2,2'MDA, wherein the proportion of 4,4'MDA is advantageously in the range of 75 to 98 mol%, ideally in the range of 85 to 95 mol%.

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