Temperature control in preparation of alicyclic polycarboxylic acids and esters thereof

Abstract

To provide techniques for preparation of alicyclic compounds through a ring hydrogenation of aromatic compounds.SOLUTION: The invention provides a process of preparing alicyclic compounds, preferably alicyclic carboxylic acids and esters thereof, and an apparatus for carrying out the process.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention belongs to the technical field of producing alicyclic compounds by ring hydrogenation of aromatic compounds. The present invention provides a method for producing an alicyclic compound, preferably an alicyclic carboxylic acid and its ester, and an apparatus for carrying out the method.

Background Art

[0002] Alicyclic polycarboxylic acid esters, such as esters of cyclohexane-1,2-dicarboxylic acid, are used as lubricant components and as auxiliaries in metal processing. They are also used as plasticizers for polyolefins and PVC. For plasticizing PVC, esters of phthalic acid, such as dinonyl ester or didecyl ester, are mainly used. The use of these phthalates has increasingly become the subject of discussion among the general public, and their use in plastics may be restricted. Although some of the alicyclic polycarboxylic acid esters have already been described in the literature as plasticizers for plastics, they may be a suitable choice as an alternative to the above-mentioned restricted plasticizers.

[0003] The most economical method for producing alicyclic polycarboxylic acid esters is, in most cases, the ring hydrogenation of the corresponding aromatic polycarboxylic acid esters, such as the above-mentioned phthalates. For this purpose, many methods are known. In Patent Documents 1 and 2, the production of the corresponding alicyclic polycarboxylic acid esters by hydrogenation of aromatic polycarboxylic acid esters is carried out in two reactors connected in series. At this time, the first reactor is operated in a loop operation (partial return of the reactor effluent), and the second reactor is operated in a straight-through operation. The first loop reactor can also be replaced by a plurality of small loop reactors connected in series or in parallel, and these reactors have a common circuit. Patent Document 3 discloses a method for continuous catalytic hydrogenation in at least two reactors connected in series, and the catalyst volume is kept as low as possible. The first reactor is operated in a loop mode, and at least one additional reactor is operated in a straight-through mode. Since hydrogenation is an exothermic process, at the start of such a process using a new catalyst, a fairly high temperature is reached in the first reactor operated in a loop mode. The activity of the catalyst decreases with continuous hydrogenation over time. The decrease in the activity of the catalyst in the first reactor is usually compensated by increasing the temperature in the first reactor. However, increasing the temperature in the first reactor may cause problems in the second reactor operated in a straight-through mode. From the perspective of safety, the temperatures of the first reactor and the second reactor should not be infinitely high. Thereby, there is a possibility that the first reactor can no longer operate at a sufficiently high temperature. Because otherwise, for safety reasons, there is a threat that the first reactor, especially the second reactor, can be shut down due to temperature induction. If the reactor is stopped too early, the yield may decrease and the hydrogenation of the reactants in the product stream from the second reactor may become insufficient.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] Accordingly, an object of the present invention is to provide a method for the catalytic hydrogenation of aromatic compounds, preferably aromatic polycarboxylic acids and their esters, which has a high yield and in which the product stream always contains a high proportion of alicyclic compounds as products of the hydrogenation of the aromatic compounds used.

Means for Solving the Problems

[0006] This main problem is a method for producing one or more alicyclic compounds, comprising the following: (i) providing a stream A(2b) comprising one or more aromatic compounds and a hydrogen-containing hydrogenation gas; (ii) feeding the stream A(2b) to a first hydrogenation unit (1) at a temperature T1 to hydrogenate the one or more aromatic compounds to obtain the corresponding alicyclic compounds; (iii) obtaining a mixture as a first product stream (3) at a temperature T2, comprising the aromatic compounds and the alicyclic compounds; (iv) separating the first product stream (3) obtained in (iii) into a partial stream (8), feeding this to the stream A(2b) in (i), and hydrogenating it again as part of the stream A(2b) in (ii), where a partial stream (6c) is fed to one or more further hydrogenation units (11) at a temperature T3 as stream B(9); (v) hydrogenating the aromatic compounds contained in the stream B(9) in the one or more further hydrogenation units (11) to obtain the corresponding alicyclic compounds; and (vi) obtaining a product stream (12) at a temperature T4, comprising one or more alicyclic compounds corresponding to the one or more aromatic compounds fed in (i); This was achieved by providing a method in which at least temporarily, the temperature T1 is not equal to the temperature T3, or the temperature T1 is higher than the temperature T3.

[0007] In the context of the present invention, the term "alicyclic compound" is understood to mean a compound having an aliphatic structure and a saturated ring system. Such a compound is also known as an alicyclic compound. Preferably, the alicyclic compound obtained as a product in the context of the present invention has a cyclohexane ring.

[0008] In the context of the present invention, the term "aromatic compound" is understood to mean a compound having at least one ring system containing 4n + 2 delocalized electrons in accordance with Hückel's rule, in conjugated double bonds, lone pairs of electrons or unoccupied p-orbitals. Preferably, the aromatic compound used as a starting material in the context of the present invention has a benzene ring.

[0009] In the context of the present invention, the term "hydrogen-containing hydrogenation gas" is a gas containing hydrogen. Hydrogen is used as another reactant in addition to the aromatic compound within the scope of the reaction underlying the present invention. In the hydrogenation reaction carried out, the double bonds of the ring of the aromatic compound used, preferably the benzene ring, are hydrogenated by an addition reaction of hydrogen and thereby broken. The reaction is carried out in the presence of a solid catalyst. The hydrogen molecules in the hydrogen-containing hydrogenation gas form an intermediate bond with the metal atoms of the catalyst, weakening the bond between the two hydrogen atoms in the hydrogen molecule and enabling it to interact with the electron-rich multiple bond (double bond). Hydrogenation is carried out when two hydrogen atoms are formally converted into a double bond. Thereby, the double bond of the aromatic compound is cleaved and an alicyclic compound is obtained. The hydrogenation gas used may be any hydrogen-containing gas mixture that does not contain a catalyst poison such as carbon monoxide or hydrogen sulfide in a harmful amount. In some cases, it is preferred to use hydrogen with a purity of more than 95%, especially more than 98%, of an inert gas. The inert gas fraction may be, for example, nitrogen or methane. The amount of hydrogen present in the hydrogenation unit is preferably present in an excess amount, especially 1% to 200%, preferably 3% to 100%, particularly preferably 5% to 50%, relative to the stoichiometric amount necessary for this hydrogen to achieve the possible or desired conversion in the hydrogenation unit. Adding a sufficiently large excess of hydrogen can be advantageous for the complete hydrogenation of the aromatic bond.

[0010] The term "hydrogenation unit" in the context of the present invention is understood as a hydrogenation reactor, or a plurality of reactors connected in series, a plurality of reactors connected in parallel, or a group of reactors consisting of reactors connected in parallel and in series. That is, in the method process according to the present invention, it is understood as a reactor or a reactor arrangement capable of performing the function as a reactor. New hydrogen can be supplied to each hydrogenation unit. However, in order to minimize the consumption of hydrogen and the discharge loss associated with the exhaust gas, it is convenient to use the exhaust gas from one hydrogenation unit as the hydrogenation gas from another hydrogenation unit or the same hydrogenation unit. Furthermore, the exhaust gas from the hydrogenation unit can be reused as new hydrogen after treatment. For example, in a process carried out in two hydrogenation units connected in series, each having one hydrogenation unit, it is advantageous to supply new hydrogen to the first hydrogenation unit and send the exhaust gas of the first hydrogenation unit into the second hydrogenation unit. In this case, the reactants and the hydrogenation gas flow through the hydrogenation units in the reverse order. In this process, it is advantageous to keep the hydrogen excess below 30%, particularly below 20%, based on the stoichiometric requirement.

[0011] The term "recycle (reuse)" or "loop type" in the context of the present invention means recycling at least partially the product stream of the hydrogenation unit as part of the input stream to the same hydrogenation unit. The product stream or mixture obtained from the hydrogenation unit is split. This means that a partial stream of the hydrogenation effluent (output) or product stream of the first hydrogenation unit is sent as stream A together with fresh reactants to the first hydrogenation unit. The other partial stream of the hydrogenation effluent or product stream of the first hydrogenation unit is preferably hydrogenated in a second hydrogenation unit operated in a once-through mode. Instead of one large loop-type hydrogenation unit, two or more smaller units arranged in series or in parallel may be used. Also, instead of one large hydrogenation unit with a linear through-flow, a plurality of units connected in series or in parallel may be operated. However, it is preferred to use only one hydrogenation unit operated in a loop type and only one unit operated in a once-through mode. This method may be carried out in a tube bundle reactor.

[0012] In the example of FIG. 1, this means that the product stream (3) is fed as input stream or stream A (2b) together with fresh reactants (2a) to the hydrogenation unit (1) via pipelines (4, 8). In the context of the method according to the invention, in step (iv), the recycle ratio is preferably carried out at 1:10 to 1:50, more preferably 1:10 to 1:40, and particularly preferably 1:30. When this ratio is 1:10, for example, it means that 10 tons of the product stream are sent back to the top of the first hydrogenation unit and 1 ton is fed to at least one further hydrogenation unit. The recycle ratio is preferably adjusted such that a conversion rate of 80% to 99%, preferably 85% to 97%, is achieved in the first unit of the hydrogenation units connected in series based on the initial concentration of the compound to be hydrogenated at the inlet of each hydrogenation unit, and a conversion rate of 80% to 100%, preferably 85% to 100%, is achieved in the second hydrogenation unit. When using three or more hydrogenation units, the conversion needs to be adjusted accordingly.

[0013] At least one additional hydrogenation unit can likewise be operated in a loop or once-through mode, i.e., the recycle is not returned to the same hydrogenation unit. Hydrogenation can be carried out in the absence of a solvent or, preferably, in the presence of a solvent. Any liquid that forms a homogeneous solution with the reactants and products, is inert under the hydrogenation conditions, and can be easily separated from the products can be used as the solvent. The solvent can also be a mixture of multiple substances and may contain water. For example, the following substances: linear or cyclic ethers such as tetrahydrofuran and dioxane, and aliphatic alcohols with 1 to 13 carbon atoms in the alkyl group can be used as the solvent. Preferred alcohols are isopropanol, n-butanol, isobutanol, n-pentanol, 2-ethylhexanol, nonanol, industrial nonanol mixture, decanol, industrial decanol mixture, tridecanol. When using an alcohol as the solvent, it may be convenient to use the alcohol or alcohol mixture formed by hydrolysis of the product. This eliminates the formation of by-products by transesterification. A more preferred solvent is the hydrogenation product itself.

[0014] By using a solvent, the concentration of aromatic compounds in the feed to the reactor can be limited, so that the temperature in the reactor can be more appropriately controlled. Thereby, side reactions can be minimized and the product yield can be increased. Preferably, the concentration of aromatic compounds in the reactor feed is 1 to 35% by mass, particularly 5 to 25% by mass, based on the total amount of reactants used. In a reactor operated in a loop mode, the required concentration range can be adjusted by the circulation ratio (the ratio of the recycled hydrogenation effluent to the amount of reactants).

Brief Description of the Drawings

[0015]

Figure 1

DETAILED DESCRIPTION OF THE INVENTION

[0016] The method of the present invention will be described below using an example of the structure shown in FIG. 1. In step (i), a stream A containing at least one aromatic compound and a hydrogen-containing hydrogenation gas is provided as a reactant and sent to the first hydrogenation unit (1) as stream A (2b) via the input stream. The new reactant is fed to the input stream (2a) and sent to the first hydrogenation unit via the input stream (2b). The input stream (2b) is at a temperature T1. In this first hydrogenation unit (1), the hydrogenation of step (ii) is carried out, and in step (iii), at the end of the hydrogenation unit, a mixture containing a hydrogenated compound (alicyclic compound) and a non-hydrogenated compound (aromatic compound) is obtained as the product stream (3). The temperature of this mixture or product stream (3) is T2, and then in step (iv) it is separated into two sub-streams, one of the sub-streams is sent as a partial stream (8) to stream A (2b), and by step (ii), it is subjected to further hydrogenation with the new reactant (2a) in the first hydrogenation unit (1).

[0017] The second partial stream, stream B (6c), is introduced into the second hydrogenation unit (11) via the feed stream (9), and the temperature is T3. This is hydrogenated in at least one further hydrogenation unit (11) in step (v), so that the reactants that were not converted in the first hydrogenation unit (1) are hydrogenated to the corresponding alicyclic compounds in this second hydrogenation unit (11). The temperature of the product mixture obtained as stream (12) in step (vi) is T4. The separation of the product stream in step (vi) may be carried out as stream (4) via a bypass, or may be carried out via a cooling device (7), preferably via a heat exchanger.

[0018] In the product stream (12) at the outlet of at least one further hydrogenation unit, the alicyclic compound used as a reactant is preferably contained in an amount of less than 0.3% by mass, preferably less than 0.1% by mass, particularly less than 0.05% by mass, and particularly preferably less than 0.005% by mass.

[0019] Preferably, process parameters such as the concentrations of the product, by-products, reactants, temperature, etc. are determined by on-line analysis. The on-line analysis preferably acquires each parameter in real time in the product discharge stream of the first hydrogenation unit (3) and / or each further hydrogenation unit (12). Preferably, a measuring method selected from the group consisting of a reaction calorimeter, ATR-FT-IR spectroscopy, Raman spectroscopy, IR spectroscopy, UV and / or UV-VIS spectroscopy, or a combination thereof is used. Based on the process parameters thus determined, after the limit values are determined, the temperature T1 can be specifically adjusted. This setting can also be performed in an automated manner, that is, using computer technology. In connection with the present invention, it is preferable to hydrogenate the aromatic compound obtained in step (i) using the hydrogen-containing gas obtained in step (i). The aromatic compound is provided together with the product obtained in step (i) on one or more solid catalysts arranged in the fixed bed of the hydrogenation unit.

[0020] Furthermore, the solid catalyst preferably contains at least one metal of subgroup 8 of the periodic table of the elements. Preferably, as the active metal, platinum, rhodium, palladium, cobalt, nickel or ruthenium or a mixture of two or more thereof is used, and particularly ruthenium is used as the active metal. In addition to the metals already mentioned, at least one metal of subgroup 1 and / or subgroup 7 of the periodic table of the elements may be included in the catalyst. Preferably, a metal of subgroup 8 of the periodic table of the elements and rhenium and / or copper are used.

[0021] The catalyst used in this process is preferably said metal advantageously applied on a support material. Preferably, the support material used is a material containing micropores (micropores; pore diameter less than 2 nm), mesopores (mesopores; pore diameter 2 - 50 nm) and macropores (macropores; pore diameter greater than 50 nm). For example, regarding the types of pores, the following combinations of pores: a) Mesopores only b) Micropores and mesopores c) Mesopores and macropores d) Micropores, mesopores and macropores e) Micropores and macropores There are support materials that can be used.

[0022] Preferably, as the support material, activated carbon, silicon carbide, aluminum oxide, silicon oxide, aluminosilicate, titanium dioxide, zirconium dioxide, magnesium oxide and / or zinc oxide, or a mixture thereof is used. Preferably, as the support material, a solid that is sufficiently inert under hydrogenation conditions is used. For example, activated carbon, silicon carbide, silicon dioxide, titanium dioxide and / or zirconium dioxide, and mixtures of these compounds can be mentioned. Titanium dioxide is particularly preferred as the support material. Titanium dioxide exists in three forms (anatase, rutile and brookite), of which anatase and rutile are the most common. A preferred support material is Aerolyst 7711 (registered trademark) (Evonik Operations GmbH). The said support material is composed of 15 - 20% by mass of rutile and 80 - 85% by mass of anatase. Further suitable titanium dioxide support materials include those manufactured based on titanium dioxide from the sulfuric acid process. They usually contain 98% or more of anatase.

[0023] The solid catalyst used for the hydrogenation in step (ii) and / or step (v) is particularly preferably a catalyst containing ruthenium as the only metal and titanium dioxide as the carrier material. In a preferred embodiment, the catalysts used for the hydrogenation in step (ii) and / or step (v) are the same, and particularly preferably, it is a catalyst containing ruthenium as the only metal and titanium dioxide as the carrier material.

[0024] In the process according to the invention, the hydrogenation in step (ii) and / or step (v) is carried out in the liquid phase or the gas phase. The hydrogenation can be carried out continuously or discontinuously on a suspended catalyst or a massive catalyst arranged in a fixed bed. In the process according to the invention, preferably, it is a continuous hydrogenation on a catalyst arranged in a fixed bed where the product / reactant phase is mainly in the liquid state under the reaction conditions.

[0025] Preferably, the hydrogenation in step (ii) and / or step (v) is carried out at a pressure of 3 to 300 bar, preferably 15 to 200 bar, and particularly preferably 50 to 150 bar.

[0026] More preferably, the hydrogenation in step (ii) and / or step (v) is carried out at a temperature of 50°C to 250°C, preferably 70 to 200°C. This temperature is in the discharge stream (T2 and T4) of the hydrogenation unit after the hydrogenation is carried out. Since the hydrogenation reaction is an exothermic reaction, the reaction does not occur at a fixed temperature but occurs within the temperature range described herein. Therefore, the temperature of the reaction mixture increases as it passes through the hydrogenation unit. That is, the temperature T1 is always lower than T2, and the temperature T3 is always lower than T4.

[0027] According to the present invention, temperature T1 is not equal to temperature T3, at least temporarily, and preferably, temperature T1 is higher than temperature T3. The term "at least temporarily" in the context of the present invention means that within the scope of the present invention, this state (T1≠T3, preferably T1>T3) does not persist throughout the hydrogenation process but exists only after a certain time. On the other hand, this does not mean a short-term change in the state. Therefore, the term "at least temporarily" means that this state persists for at least 30 minutes, preferably at least 2 hours. Furthermore, the term "at least temporarily" means that at least 1% of the total required time of the process is characterized by this state.

[0028] This state can be achieved as follows. Stream A is sent to the reactor at temperature T1 via the input stream (2b). Due to the exothermic nature of the hydrogenation reaction, the temperature of the reaction mixture in the reactor preferably increases along the length of the reactor. As a result, the temperature T2 of the mixture of the resulting product stream (3) is higher than T1. A partial stream of the temperature T2 of the obtained mixture or product stream (3) is recycled and fed to stream A (2b) together with the new reactant (2a). However, since the temperature T1 of stream A (2b) must be lower than T2, it is necessary to design the process to meet this condition. For example, the temperature of the new reactant can be adjusted to reach temperature T1 during mixing with the recycled sub-stream. However, within the scope of the present invention, preferably, the mixture or product stream (3) obtained from the first hydrogenation unit is cooled from temperature T2 before separating the mixture. For this purpose, preferably, a known cooling device can be suitably used. To utilize the extracted thermal energy at other locations in the process or in a network of multiple systems, preferably, a heat exchanger is used.

[0029] When the mixture obtained from the first hydrogenation unit is cooled, the two sub-streams after separation reach the same temperature. Therefore, the temperatures of T1 and T3 are equal or at most differ by 10%. To achieve the state according to the invention (T1≠T3, preferably T1>T3), different measures can be taken in consideration of this process. Preferably, in order to cool one of the partial streams or to heat one of the partial streams, an additional cooling system or heating system is provided for one of the partial streams. A particularly preferred method in the context of the present invention is to install a bypass (4) upstream of the cooler (7) to the partial stream sent to the first hydrogenation unit. Via the bypass, a predetermined portion of the mixture or product stream (3) obtained from the first hydrogenation unit can be combined with the recirculated partial stream (6b) without being cooled, so that the temperature T1 becomes higher than the temperature T3 of the partial stream (6c) sent to the second hydrogenation unit that has passed completely through the cooler (7). The advantage is that the hydrogenation in the first hydrogenation unit (1) can be carried out at a higher inlet temperature T1, thereby enabling a higher hydrogenation temperature. The decrease in the activity of the catalyst over time is thus compensated. At the same time, the reaction in the second hydrogenation unit can be operated under constant temperature conditions throughout. Therefore, the overall yield and quality of the product stream are kept constant.

[0030] In the present invention, it has been found to be advantageous not to directly supply the product stream (3) at temperature T2 to at least one additional hydrogenation unit, but to cool it and supply it to at least one additional hydrogenation unit at a lower temperature T3. Therefore, particularly preferably, the temperature T2 of the mixture obtained in step (iii) is higher than the temperature T3 of the mixture supplied to the hydrogenation unit in step (iv).

[0031] Furthermore, in the present invention, it has been found to be advantageous that the temperature difference ΔT between T2 and T3 is constant throughout the process. Preferably, the temperature difference ΔT is equal to the reaction enthalpy of the hydrogenation reaction. "Constant" in the context of the present invention means that the maximum deviation of the temperature from the initial temperature is ±10%, preferably ±5%, particularly preferably ±1%.

[0032] Temperature control can be achieved by arranging a device (7) between the discharge stream (3) of the first hydrogenation unit and the input stream (9) of the second hydrogenation unit, which cools the discharge stream (3) to achieve the desired temperatures T1 and T3 in the input stream (2b) to the first hydrogenation unit and the input stream (9) to at least one further hydrogenation unit. Preferably, the cooling is achieved by a heat exchanger. The associated devices are well known to those skilled in the art. It may be present, for example, in the discharge stream (3) of the first hydrogenation unit (1), the input stream (9) to the second hydrogenation unit, or between the two streams. Preferably, one, two, three or more heat exchangers can be used.

[0033] In the context of the method according to the invention, in step (i) one or more aromatic carboxylic acid esters, preferably one or more aromatic mono-, di- and polycarboxylic acid esters are provided. In the method according to the invention, aromatic compounds such as aromatic polycarboxylic acids and / or aromatic monocarboxylic acids or their derivatives, in particular their alkyl esters, can be converted into the corresponding alicyclic polycarboxylic acid compounds. Both complete esters and partial esters can be hydrogenated. A complete ester is a compound in which all acid groups are esterified. A partial ester is a compound having at least one free acid group (or optionally an anhydride group) and at least one ester group. When using polycarboxylic acid esters in the method according to the invention, they preferably have 2, 3 or 4 ester functional groups.

[0034] In the context of the method according to the invention, in step (i), one or more benzene, diphenyl, naphthalene, diphenyl oxide, anthracene dicarboxylic acid esters or polycarboxylic acid esters are provided. The alicyclic polycarboxylic acid or its derivative obtained by the method of the invention consists, in some cases, of one or more C6 rings linked or fused by carbon-carbon bonds.

[0035] In step (i), preferably, there is at least one aromatic carboxylic acid ester having an alcohol component selected from the group consisting of branched or unbranched alkoxyalkyl, cycloalkyl and / or alkyl groups having 1 to 25 carbon atoms, preferably C8-C10 phthalate, C8-C10 terephthalate, C8-C10 isophthalate and C8-C10 trimellitate, particularly preferably di-2-ethylhexyl phthalate, diisononyl phthalate, di-2-ethylhexyl terephthalate, diisononyl terephthalate, di-2-ethylhexyl isophthalate, triisononyl isophthalate, di-2-ethylhexyl trimellitate and triisononyl trimellitate are provided. Here, C8 preferably means 2-ethylhexyl or n-octyl, C9 means isononyl, and C10 means isodecyl or 2-propylheptyl.

[0036] This method is preferably a method of hydrogenating 1,2-; 1,3- or 1,4-benzenedicarboxylic acid ester and / or 1,2,3-; 1,2,4- or 1,3,5-benzenetricarboxylic acid ester, that is, isomers of 1,2-; 1,3- or 1,4-cyclohexanedicarboxylic acid ester or isomers of 1,2,3-; 1,3,5- or 1,2,4-cyclohexanetricarboxylic acid ester are formed.

[0037] In the method according to the invention, for example, the following esters of aromatic carboxylic acids can be used: 1,2-naphthalenedicarboxylic acid, 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 1,7-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, phthalic acid (benzene-1,2-dicarboxylic acid), isophthalic acid (benzene-1,3-dicarboxylic acid), terephthalic acid (benzene-1,4-dicarboxylic acid), benzene-1,2,3-tricarboxylic acid, benzene-1,2,4-tricarboxylic acid (trimellitic acid), benzene-1,3,5-tricarboxylic acid (trimesic acid), benzene-1,2,4,5-tetracarboxylic acid (pyromellitic acid). Further, acids formed from the above acids may be used by substituting one or more hydrogen atoms bonded to the aromatic ring with alkyl, cycloalkyl or alkoxyalkyl groups. Preferably, it is to use alkyl, cycloalkyl and alkoxyalkyl esters of the above acids. For example, these groups are each independently of one another, containing 1 to 25 carbon atoms, especially 3 to 15 carbon atoms, very especially 8 to 13 carbon atoms, especially 9 carbon atoms. These groups may be straight-chain or branched-chain. When there are a plurality of ester groups in the reactant, these groups may be the same or different.

[0038] In the method of the present invention, the following compounds can be mentioned as esters of aromatic polycarboxylic acids: Monomethyl terephthalate, dimethyl terephthalate, diethyl terephthalate, di-n-propyl terephthalate, dibutyl terephthalate, diisobutyl terephthalate, di-tert-butyl terephthalate, dipentyl terephthalate, monoglycol terephthalate, diglycol terephthalate, n-octyl terephthalate, diisooctyl terephthalate, di-2-ethylhexyl terephthalate, di-n-nonyl terephthalate, diisononyl terephthalate, di-2-propylheptyl terephthalate, di-n-decyl terephthalate, di-n-undecyl terephthalate, diisodecyl terephthalate, diisododecyl terephthalate, ditridecyl terephthalate, di-n-octadecyl terephthalate, diisooctadecyl ester terephthalate, di-n-eicosyl terephthalate, monocyclohexyl terephthalate; Monomethyl phthalate, dimethyl phthalate, di-n-propyl phthalate, di-n-butyl phthalate, diisobutyl phthalate, di-tert-butyl phthalate, monoglycol phthalate, diglycol phthalate, di-n-octyl phthalate, diisooctyl phthalate, di-2-ethylhexyl phthalate, di-n-nonyl phthalate, diisononyl phthalate, di-n-decyl phthalate, di-2-propylheptyl ester, diisodecyl phthalate, di-n-undecyl phthalate, diisoundecyl phthalate, ditridecyl phthalate, di-n-octadecyl phthalate, diisooctadecyl phthalate, di-n-eicosyl terephthalate, monocyclohexyl phthalate; Dicyclohexyl phthalate, monomethyl isophthalate, dimethyl isophthalate, diethyl isophthalate, di-n-propyl isophthalate, di-n-butyl isophthalate, diisobutyl isophthalate, di-tert-butyl isophthalate, monoglycol isophthalate; Diglycol isophthalate, di-n-octyl isophthalate, diisooctyl isophthalate, di-2-ethylhexyl isophthalate, di-n-nonyl isophthalate, diisononyl isophthalate, di-n-decyl isophthalate, diisodecyl isophthalate, di-n-undecyl isophthalate, diisododecyl isophthalate, di-n-dodecyl isophthalate, ditridecyl isophthalate, di-n-octadecyl isophthalate, diisooctadecyl isophthalate, di-n-eicosyl isophthalate, monocyclohexyl isophthalate.

[0039] The method of the present invention can in principle also be applied to benzoic acid and its esters. These include alkyl benzoates and benzoates of diols, such as glycol dibenzoate, diethylene glycol benzoate, triethylene glycol dibenzoate or propylene glycol dibenzoate. The carbon atoms of the alcohol component of the alkyl benzoate consist of 1 to 25, preferably 8 to 13, and each may be straight-chain or branched-chain. On an industrial scale, aromatic esters, especially all esters, are often preferably produced from alcohol mixtures. Examples of suitable alcohol mixtures include the following. C5 alcohol mixtures produced by hydroformylation and subsequent hydrogenation from linear butenes; C5 alcohol mixtures produced by hydroformylation and subsequent hydrogenation from butene mixtures containing linear butenes and isobutenes; C6 alcohol mixtures produced by hydroformylation and subsequent hydrogenation from pentenes or from mixtures of two or more pentenes; C7 alcohol mixtures produced by hydroformylation and subsequent hydrogenation from the trimerization of ethylene or the dimerization of propylene or hexene isomers or another mixture of hexene isomers; C8 alcohol mixtures such as 2-ethylhexanol (two isomers), produced by aldol condensation of n-butyl aldehyde and subsequent hydrogenation; C9 alcohol mixtures produced by dimerization, hydroformylation and hydrogenation from C4 olefins. To produce C9 alcohols, one can start from isobutene, or from a mixture of linear butenes, or from a mixture of linear butenes and isobutene. C4 olefins can be dimerized using various catalysts such as protonic acids, zeolites, organometallic nickel compounds or solid nickel-containing catalysts. The hydroformylation of C8 olefin mixtures can be carried out using a rhodium catalyst or a cobalt catalyst. Thus, there are various industrial C9-alcohol mixtures; C10-alcohol mixtures produced by hydroformylation and subsequent hydrogenation from tripropylene; 2-propylheptanol (two isomers) produced by aldol condensation of valeraldehyde and subsequent hydrogenation; C10-alcohol mixtures produced by aldol condensation and subsequent hydrogenation from at least two C5-aldehydes; C13-alcohol mixtures produced by hydroformylation and subsequent hydrogenation from hexaethylene, tetrapropylene or tributene.

[0040] Other alcohol mixtures can be obtained by hydroformylation and subsequent hydrogenation from olefins or olefin mixtures that occur, for example, in Fischer-Tropsch synthesis, dehydrogenation of hydrocarbons, metathesis reactions, polygas processes, or other technical processes. Furthermore, an alcohol mixture can be produced using an olefin mixture containing olefins with different numbers of carbon atoms.

[0041] In the method of the present invention, any ester mixture produced from an aromatic polycarboxylic acid and the above alcohol mixture can be used. According to the present invention, it is preferable to use an ester produced from phthalic acid or phthalic anhydride and terephthalic acid or dimethyl terephthalate and a mixture of isomeric alcohols having 4 to 13 carbon atoms. Preferably, the following steps: (i) Providing a stream A(2b) containing one or more aromatic compounds selected from the group consisting of esters of phthalic acid, isophthalic acid, terephthalic acid and / or trimellitic acid, particularly preferably selected from the group consisting of dipentyl terephthalate, di-2-ethylhexyl terephthalate, diisononyl terephthalate, dipentyl phthalate, di-2-ethylhexyl phthalate, diisononyl phthalate, dipentyl isophthalate, di-2-ethylhexyl isophthalate, diisononyl isophthalate, tripentyl trimellitate, tri-2-ethylhexyl trimellitate, triisononyl trimellitate, or mixtures thereof, and a hydrogen-containing hydrogenation gas; (ii) Supplying the stream A(2b) to a first hydrogenation unit (1) at a temperature T1 to hydrogenate the one or more aromatic compounds to obtain the corresponding alicyclic compounds; (iii) obtaining a mixture as a first product stream (3) at a temperature T2, said mixture comprising the aromatic compound and an alicyclic compound selected from the group consisting of dialkyl cyclohexane-1,2-dicarboxylates, dialkyl cyclohexane-1,3-dicarboxylates, dialkyl cyclohexane-1,4-dicarboxylates and 1,2,4-trimellitic acid esters, particularly preferably dipentyl cyclohexane-1,4-dicarboxylate, di-2-ethylhexyl cyclohexane-1,4-dicarboxylate, diisononyl cyclohexane-1,4-dicarboxylate, dipentyl cyclohexane-1,2-dicarboxylate, di-2-ethylhexyl cyclohexane-1,2-dicarboxylate, diisononyl cyclohexane-1,2-dicarboxylate, dipentyl cyclohexane-1,3-dicarboxylate, di-2-ethylhexyl cyclohexane-1,3-dicarboxylate, diisononyl cyclohexane-1,3-dicarboxylate, tripentyl cyclohexane-1,2,4-tricarboxylate, tri-2-ethylhexyl cyclohexane-1,2,4-tricarboxylate, triisononyl cyclohexane-1,2,4-tricarboxylate; (iv) separating the first product stream (3) obtained in (iii) into a partial stream (8), feeding this to the stream A (2b) in (i), and hydrogenating again as a part of the stream A (2b) in (ii), where a partial stream (6c) is fed as stream B (9) at a temperature T3 to one or more further hydrogenation units (11); (v) hydrogenating the aromatic compounds contained in the stream B (9) in the one or more further hydrogenation units (11) to obtain the corresponding alicyclic compounds; and (vi) One or more alicyclic compounds selected from the group consisting of dialkyl cyclohexane-1,2-dicarboxylates, dialkyl cyclohexane-1,3-dicarboxylates, dialkyl cyclohexane-1,4-dicarboxylates and 1,2,4-trimellitic acid esters, particularly preferably dipentyl cyclohexane-1,4-dicarboxylate, di-2-ethylhexyl cyclohexane-1,4-dicarboxylate, diisononyl cyclohexane-1,4-dicarboxylate, dipentyl cyclohexane-1,2-dicarboxylate, di-2-ethylhexyl cyclohexane-1,2-dicarboxylate, diisononyl cyclohexane-1,2-dicarboxylate, dipentyl cyclohexane-1,3-dicarboxylate, di-2-ethylhexyl cyclohexane-1,3-dicarboxylate, diisononyl cyclohexane-1,3-dicarboxylate, tripentyl cyclohexane-1,2,4-tricarboxylate, tri-2-ethylhexyl cyclohexane-1,2,4-tricarboxylate, triisononyl cyclohexane-1,2,4-tricarboxylate corresponding to the one or more aromatic compounds supplied in (i) above, to obtain a product stream (12) at a temperature of T4; A method for producing one or more alicyclic compounds comprising, wherein, at least temporarily, the temperature T1 is not equal to the temperature T3, or the temperature T1 is higher than the temperature T3. The alicyclic compounds present in the product stream (3) are due to the reactants used. For example, when diisononyl phthalate is used as the starting material, diisononyl cyclohexane-1,2-dicarboxylate is obtained as the product.

[0042] Particularly preferred is a method for producing one or more alicyclic compounds, as follows: (i) Providing a stream A (2b) containing diisononyl phthalate (DINP) or di-2-ethylhexyl phthalate (DEHP) and a hydrogen-containing hydrogenated gas; (ii) Supplying the stream A(2b) to a first hydrogenation unit(1) at a temperature T1 to hydrogenate the one or more aromatic compounds to obtain corresponding alicyclic compounds; (iii) Obtaining a mixture as a first product stream(3) at a temperature T2, which contains diisononyl cyclohexane-1,2-dicarboxylate (DINCH) or di-2-ethylhexyl cyclohexane-1,2-dicarboxylate (DEHCH); (iv) Separating the first product stream(3) obtained in (iii) into a partial stream(8), supplying this to the stream A(2b) in (i), and hydrogenating it again as a part of the stream A(2b), where in (ii), a partial stream(6c) is supplied to one or more further hydrogenation units(11) at a temperature T3 as a stream B(9); (v) Hydrogenating the aromatic compounds contained in the stream B(9) in the one or more further hydrogenation units(11) to obtain corresponding alicyclic compounds; and (vi) Obtaining a product stream(12) at a temperature T4, which contains diisononyl 1,2-cyclohexanedicarboxylate (DINCH) or di-2-ethylhexyl 1,2-cyclohexanedicarboxylate (DEHCH); A method comprising, wherein at least temporarily, the temperature T1 is not equal to the temperature T3, or the temperature T1 is higher than the temperature T3.

[0043] Particularly preferred is further a method for producing one or more alicyclic compounds, comprising the following: (i) Providing a stream A(2b) containing diisononyl terephthalate or di-2-ethylhexyl terephthalate and a hydrogen-containing hydrogenation gas; (ii) Supplying the stream A(2b) to a first hydrogenation unit(1) at a temperature T1 to hydrogenate the one or more aromatic compounds to obtain one or more corresponding alicyclic compounds; (iii) Obtaining a mixture as a first product stream (3) at temperature T2, containing diisononyl 1,4 - cyclohexanedicarboxylate or di - 2 - ethylhexyl 1,4 - cyclohexanedicarboxylate; (iv) Separating the first product stream (3) obtained in (iii) into a partial stream (8), feeding this to the stream A (2b) in (i), and re - hydrogenating it as a part of the stream A (2b) in (ii), where a partial stream (6c) is fed as stream B (9) at temperature T3 to one or more further hydrogenation units (11); (v) Hydrogenating the aromatic compounds contained in the stream B (9) in the one or more further hydrogenation units (11) to obtain the corresponding alicyclic compounds; and (vi) Obtaining a product stream (12) at temperature T4, containing diisononyl 1,4 - cyclohexanedicarboxylate or di - 2 - ethylhexyl 1,4 - cyclohexanedicarboxylate; A method comprising, wherein At least temporarily, the temperature T1 is not equal to the temperature T3, or the temperature T1 is higher than the temperature T3.

[0044] Particularly preferred is further a method for producing one or more alicyclic compounds, comprising the following: (i) Providing a stream A (2b) containing triisononyl trimellitate (TINTM) or tri - 2 - ethylhexyl trimellitate (TOTM) and a hydrogen - containing hydrogenation gas; (ii) Feeding the stream A to a first hydrogenation unit (1) at temperature T1 to hydrogenate the one or more aromatic compounds to obtain the corresponding alicyclic compounds; (iii) Obtaining a mixture as a first product stream (3) at temperature T2, containing triisononyl 1,2,4 - cyclohexanetricarboxylate or tri - 2 - ethylhexyl 1,2,4 - cyclohexanetricarboxylate; (iv) Separating the first product stream (3) obtained in (iii) into a partial stream (8), supplying this to the stream A (2b) in (i), and re-hydrogenating it as a part of the stream A (2b) in (ii), where a partial stream (6c) is supplied to one or more further hydrogenation units (11) at a temperature T3 as stream B (9); (v) Hydrogenating the aromatic compounds contained in the stream B (9) in the one or more further hydrogenation units (11) to obtain the corresponding alicyclic compounds; and (vi) Obtaining a product stream (12) at a temperature T4 containing triisononyl cyclohexane-1,2,4-tricarboxylate or tri-2-ethylhexyl cyclohexane-1,2,4-tricarboxylate; A method comprising, wherein At least temporarily, the temperature T1 is not equal to the temperature T3, or the temperature T1 is higher than the temperature T3.

[0045] The method according to the invention is preferably carried out under the following conditions. In the feed of the first hydrogenation unit (loop type), the concentration of the aromatic compound as a reactant is 5 to 30% by mass, particularly 8 to 15% by mass. In the discharge stream (3) of the first hydrogenation unit, the concentration of the reactant is 0.3 to 8% by mass, particularly 1.5 to 4% by mass. The specific liquid hourly space velocity (LHSV, catalyst loading, liters of new reactant per liter of catalyst per hour) in the first hydrogenation unit (1) is 0.1 to 5 / hour, particularly 0.5 to 3 / hour. The surface area velocity in the first hydrogenation unit (1) is in the range of 25 to 140 m 3 / m 2 / hour, particularly in the range of 50 to 90 m 3 / m 2 / hour. The average hydrogenation temperature in the first hydrogenation unit (1) is 70 to 150 °C, particularly 80 to 120 °C. The hydrogenation pressure in the first hydrogenation unit (1) is 25 to 200 bar, particularly 80 to 110 bar.

[0046] The liquid hourly space velocity (reactant liters / catalyst liters / hour) of the second hydrogenation unit (11) is from 1 to 8 / hour, particularly from 2 to 5 / hour. In the second hydrogenation unit (11), the average temperature is from 70 to 150 °C, particularly from 80 to 120 °C. The hydrogenation pressure in the second hydrogenation unit is from 25 to 200 bar, particularly from 80 to 100 bar.

[0047] This variant method is particularly suitable for the hydrogenation of phthalic esters, in particular diisononyl phthalate (as the isomer mixture "diisononyl phthalate", for example VESTINOL 9 from OXENO GmbH) or di-2-ethylhexyl phthalate.

[0048] A further aspect of the invention is the provision of an apparatus for carrying out the method according to the invention, said apparatus comprising a first hydrogenation unit (1) and one or more further hydrogenation units (11) and one or more heat exchangers (7), wherein the heat exchanger (7) is arranged such that the discharge stream (3) is sent to the heat exchanger (7) via the input stream (5), the temperature of the discharge stream of a further heat exchanger (6a) is lower than the input stream (5), and then it is supplied as an input stream (9) to a further hydrogenation unit (11) via pipelines (6b and 6c), and / or is supplied to one or more further hydrogenation units (11) via the stream (10), and / or is supplied to the input stream to the first hydrogenation unit (1) via the stream (8), preferably the temperatures of the discharge stream (3) and the input stream (9) are different. Preferably, there may be at least one further heat exchanger, which is arranged, for example, in the input stream (9) of at least one further hydrogenation unit (11).

[0049] Regarding the device according to the present invention, the first hydrogenation unit and / or at least one hydrogenation unit (1 and / or 11) has one or more fixed-bed catalysts, preferably, the solid catalyst preferably contains at least one metal from Group 8 of the periodic table, particularly preferably ruthenium. A preferred carrier material is titanium dioxide. The description herein applies equally to the catalysts used.

[0050] Also, the pipeline of the first hydrogenation unit (1) is preferably arranged such that the discharge stream (3) of the first hydrogenation unit (1) can be recycled as an input stream (2b) to the first hydrogenation unit (1) via a bypass (4) or via pipelines (6b, 8). Thereafter, the first hydrogenation unit (1) is operated in a loop.

[0051] In one of the first hydrogenation unit and / or one or more additional hydrogenation units, there is a mixture of an aromatic compound and the corresponding alicyclic compound, or an aromatic carboxylic acid ester and their corresponding alicyclic compounds, and an alcohol component selected from the group consisting of branched or unbranched alkoxyalkyl, cycloalkyl and / or alkyl groups having 1 to 25 carbon atoms, preferably selected from C8 - C10 phthalates, C8 - C10 terephthalates, C8 - C10 isophthalates and C8 - C10 trimellitates, particularly preferably di-2-ethylhexyl phthalate, diisononyl phthalate, di-2-ethylhexyl terephthalate, diisononyl terephthalate, di-2-ethylhexyl isophthalate, triisononyl isophthalate, di-2-ethylhexyl trimellitate and triisononyl trimellitate, diisononyl phthalate and / or didecyl phthalate, diisononyl cyclohexanedicarboxylate and / or didecyl cyclohexanedicarboxylate, and their corresponding alicyclic compounds. The description herein applies equally to the reactants (aromatic compounds) and products (alicyclic compounds).

[0052] Within the scope of the present invention, preferably, the alicyclic polycarboxylic acid ester produced according to the present invention is used as a plasticizer for plastics. Preferred plastics are PVC, ethylene, propylene, butadiene, vinyl acetate, glycidyl acrylate, glycidyl methacrylate, acrylate, acrylate having a branched or unbranched alkyl radical of an alcohol having 1 to 10 carbon atoms bonded to the oxygen atom of the ester group, styrene, acrylonitrile, a homopolymer or copolymer of a cyclic olefin or a homopolymer or copolymer of a copolymer system.

[0053] In addition to the above uses, the alicyclic polycarboxylic acid ester produced according to the present invention can be used as a component of a lubricating oil, a coolant, and a metalworking fluid. They can also be used as components of paints, varnishes, inks, and adhesives.

Example

[0054] The following examples are intended to illustrate the present invention without limiting the scope of the present invention from the description and claims of the present invention. In the following examples, a method for hydrogenating diisononyl phthalate (DINP) to diisononyl 1,2-cyclohexanedicarboxylate (DINCH) is described, in which the final concentration of the discharged DINP at the outlet of the final stage reaches a level of less than 0.05% by weight of the inlet concentration of the first stage. All examples were simulated using Aspen V10 software based on actual process data and the kinetic model based thereon. The hydrogenation unit consisted of a loop-type continuously operating reactor and a subsequent reactor operating in a straight-through manner. In all experiments, the liquid phase and the hydrogenation gas flowed in parallel from top to bottom.

[0055] In Figure 1, the inlet temperature of the first reactor is designated as T1 (2b), the outlet temperature of the second reactor is T2 (3), the inlet temperature of the third reactor is T3 (9), and the outlet temperature of the second reactor is T4 (12). When the reaction is initiated and assuming a plant full load with 100% catalyst activity, the temperature is as follows.

[0056]

Table 1

[0057]

Table 2

[0058] 《Example 1 (Comparative Example)》 Over time, the activity of the catalyst further decreases. Assuming that the catalyst activity is 30% and the plant load is at maximum, the temperature is as follows.

[0059]

Table 3

[0060] 《Example 2 (Example of the Invention)》 Example 2 is carried out using the temperature control according to the present invention, where T1 and T3 can be set independently of each other and the temperature T1 is different from the temperature T3. Assuming that the catalyst activity is 30% and the plant load is at maximum, the temperature is as follows.

[0061]

Table 4

Claims

1. A method for producing one or more alicyclic compounds, comprising the following: (i) providing a stream A comprising one or more aromatic compounds and a hydrogen-containing hydrogenation gas; (ii) supplying the stream A at a temperature T １ to a first hydrogenation unit to hydrogenate the one or more aromatic compounds to obtain corresponding alicyclic compounds; (iii) obtaining a mixture as a first product stream having a temperature of T and containing the aromatic compound and the alicyclic compound; ２ ​ (iv) Separating the first product stream obtained in (iii) into a partial stream (8), supplying this to the stream A in (i), and hydrogenating it again as a part of the stream A in (ii), where the partial stream (6c) is supplied to one or more further hydrogenation units at a temperature T as stream B ３ at which the partial stream (6c) is fed to one or more further hydrogenation units; (v) hydrogenating the aromatic compounds contained in the stream B in the one or more additional hydrogenation units to obtain the corresponding alicyclic compounds; and (vi) obtaining a product stream (12) having a temperature of T and comprising one or more alicyclic compounds corresponding to the one or more aromatic compounds supplied in (i) above ４ thereof; A method comprising, wherein At least temporarily, the temperature T １ is not equal to the temperature T ３ or the temperature T １ is higher than the temperature T ３ method.

2. The method according to claim 1, wherein the hydrogenation of the aromatic compounds supplied in (i) is carried out by reacting with the hydrogen-containing gas supplied in (i) on one or more solid catalysts arranged in the fixed bed of the first hydrogenation unit.

3. The method according to claim 1 or 2, wherein the solid catalyst comprises at least one metal from subgroup 8 of the periodic table or ruthenium.

4. The method according to any one of claims 1 to 3, wherein (vi) is carried out at a circulation ratio of 1:10 to 1:50, 1:10 to 1:40, or 1:

30.

5. The method according to any one of claims 1 to 4, wherein the hydrogenation in (ii) and / or (v) is carried out at a pressure of 3 to 300 bar, 15 to 200 bar, or 100 to 200 bar.

6. The method according to any one of claims 1 to 5, wherein the hydrogenation in (ii) and / or (v) is carried out at a temperature of 50°C to 250°C or 100 to 200°C.

7. The temperature T of the mixture obtained in the above (iii) ２ is higher than the temperature T of the mixture supplied to the hydrogenation unit in the above (iv), and the method according to any one of claims 1 to 6 ３ ​

8. T ２ and T ３ The method according to claim 7, wherein the temperature difference ΔT between and is constant over the course of carrying out the method.

9. The method according to any one of claims 1 to 8, wherein in (i), one or more aromatic carboxylic acid esters, or one or more aromatic mono-, di- and polycarboxylic acid esters are provided.

10. The method according to any one of claims 1 to 9, wherein in (i), one or more benzene-, diphenyl-, naphthalene-, diphenyl oxide, anthracene di- or -polycarboxylic acid esters are provided.

11. In (i), the following: One or more aromatic carboxylic acid esters having an alcohol component selected from the group consisting of branched or unbranched alkoxyalkyl, cycloalkyl and / or alkyl groups having 1 to 25 carbon atoms, preferably C8-C10 phthalate, C8-C10 terephthalate, C8-C10 isophthalate and C8-C10 trimellitate, particularly preferably di-2-ethylhexyl phthalate, diisononyl phthalate, di-2-ethylhexyl terephthalate, diisononyl terephthalate, di-2-ethylhexyl isophthalate, triisononyl isophthalate, di-2-ethylhexyl trimellitate and triisononyl trimellitate, are provided, the method according to any one of claims 1 to 10.

12. An apparatus for carrying out the method according to any one of claims 1 to 11, comprising a first hydrogenation unit and one or more further hydrogenation units (10) and one or more heat exchangers (7), wherein said one or more heat exchangers (7) are arranged such that the exhaust stream (3) is sent to said heat exchanger (7) via the input stream (5), the temperature of the exhaust stream (3) of a further heat exchanger (6a) is lower than the input stream (5), and then it is supplied via pipelines (6b and 6c) as a further input stream (9) to a further hydrogenation unit (10), and / or is supplied via a stream (10) to one or more further hydrogenation units (11), and / or is supplied via a partial stream (8) to the input stream to the first hydrogenation unit (1), preferably the temperatures of said exhaust stream (3) and said further input stream (9) are different, apparatus.

13. One of said first hydrogenation unit and / or one or more further hydrogenation units (11) has one or more fixed bed catalysts, preferably said solid catalyst contains at least one metal from subgroup 8 of the periodic table of the elements or ruthenium, the apparatus according to claim 12.

14. The pipeline of said first hydrogenation unit (1) is arranged such that the exhaust stream (3) of said first hydrogenation unit (1) is sent to said first hydrogenation unit (1) as an input stream (2b) via a bypass (4) or via pipelines (6b, 8), the apparatus according to claim 12 or 13.

15. One of the first hydrogenation unit and / or one or more additional hydrogenation units contains a mixture of an aromatic compound and a corresponding alicyclic compound, or an aromatic carboxylic acid ester and their corresponding alicyclic compounds, and an alcohol component selected from the group consisting of branched or unbranched alkoxyalkyl, cycloalkyl and / or alkyl groups having 1 to 25 carbon atoms. Preferably, it is selected from C8-C10 phthalates, C8-C10 terephthalates, C8-C10 isophthalates and C8-C10 trimellitates. Particularly preferably, it is di-2-ethylhexyl phthalate, diisononyl phthalate, di-2-ethylhexyl terephthalate, diisononyl terephthalate, di-2-ethylhexyl isophthalate, triisononyl isophthalate, di-2-ethylhexyl trimellitate and triisononyl trimellitate, diisononyl phthalate and / or didecyl phthalate, diisononyl cyclohexanedicarboxylate and / or didecyl cyclohexanedicarboxylate, and their corresponding alicyclic compounds are present. The apparatus according to any one of claims 12 to 14.

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