Temperature control in preparation of alicyclic polycarboxylic acids and esters thereof

Abstract

The invention relates to temperature control in the preparation of alicyclic polycarboxylic acids and esters thereof. The invention belongs to the technical field of preparation of alicyclic compounds by cyclohydrogenation of aromatic compounds. The present invention provides a process for the preparation of alicyclic compounds, preferably alicyclic carboxylic acids and esters thereof, as well as an apparatus for carrying out the process.

Description

TECHNICAL FIELD

[0001] The present invention belongs to the technical field of preparing alicyclic compounds by the ring hydrogenation of aromatic compounds. A method for preparing alicyclic compounds, preferably alicyclic carboxylic acids and their esters, and an apparatus for carrying out this method are provided in the present invention. BACKGROUND ART

[0002] Alicyclic polycarboxylic acid esters, such as cyclohexane-1,2-dicarboxylic acid esters, are used as lubricant components and additives in metal processing. They are also used as plasticizers for polyolefins and PVC.

[0003] For the plasticization of PVC, phthalic acid esters, such as dibutyl, dioctyl, dinonyl or didecyl esters, are mainly used. The use of these phthalic acid esters is increasingly controversial in public discussions and may be restricted in the use in plastics. Some of the alicyclic polycarboxylic acid esters that have been described in the literature as plasticizers for plastics can be suitable alternatives as possible substitutes for restricted plasticizers.

[0004] In most cases, the most economical route for preparing alicyclic polycarboxylic acid esters is the ring hydrogenation of the corresponding aromatic polycarboxylic acid esters, such as the above phthalic acid esters. For this, many methods are known to those skilled in the art.

[0005] For example, application EP 1676829 discloses a method for continuous catalytic hydrogenation in at least two series-connected reactors, in which the catalyst volume is kept as low as possible. Here, the first reactor is operated in a loop mode, and at least one additional reactor is operated in a through-flow mode. During the continuous hydrogenation, the temperature rises at the outlet of the first reactor operated in a loop mode. When the obtained mixture is subsequently supplied to the reactor operated in a through-flow mode at the obtained temperature, it may happen that the temperature in the second reactor becomes too high and the reaction has to be stopped. SUMMARY OF THE INVENTION

[0006] Therefore, the 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 method has a high yield and can control the temperature in the second reactor.

[0007] This object is achieved by providing a method for preparing one or more alicyclic compounds, the method comprising the following steps:

[0008] i. Providing a feed stream A, which contains one or more aromatic compounds and a hydrogen-containing hydrogenation gas;

[0009] ii. Supplying the feed stream A having a temperature T1 to a first hydrogenation unit and hydrogenating the one or more aromatic compounds to obtain one or more corresponding alicyclic compounds;

[0010] iii. Obtain a mixture as the first product stream having a temperature T2, which contains aromatic compounds and alicyclic compounds;

[0011] iv. Divide the product stream obtained in step iii. into a sub-stream that is supplied to stream A in step i. and is hydrogenated again as part of stream A in step ii., and a sub-stream that is supplied as stream B to one or more additional hydrogenation units at a temperature T3;

[0012] v. Hydrogenate the aromatic compounds contained in stream B in the one or more additional hydrogenation units to obtain the corresponding alicyclic compounds, and

[0013] vi. Obtain a second product stream having a temperature T4, which contains one or more alicyclic compounds corresponding to the one or more aromatic compounds provided in step i.,

[0014] wherein the temperature T2 is different from the temperature T3, preferably the temperature T2 is higher than T3.

[0015] In the context of the present invention, the term "alicyclic compound" should be understood to refer to those compounds that contain a saturated ring system having an aliphatic structure. Such compounds are also referred to as cycloaliphatic compounds. Preferably, the alicyclic compounds obtained as products in the context of the present invention have a cyclohexane ring.

[0016] In the context of the present invention, "aromatic compound" should be understood to refer to those compounds that have at least one ring system which contains a number of 4n + 2 delocalized electrons in conjugated double bonds, lone electron pairs or unoccupied p-orbitals according to Hückel's rule. Preferably, the aromatic compounds used as reactants in the context of the present invention have a benzene ring.

[0017] "Hydrogen-containing hydrogenation gas" is a gas containing hydrogen. In the case of the reactions underlying the present invention, in addition to the said aromatic compounds, hydrogen is also used as an additional reactant. In the hydrogenation reaction carried out, the double bonds in the ring of the aromatic compounds used, preferably the double bonds of the benzene ring, are hydrogenated by an addition reaction with hydrogen and thus broken. The reaction is carried out in the presence of a solid catalyst. The hydrogen molecules in the hydrogen-containing hydrogenation gas bind to the metal atoms of the catalyst, the bond between the two hydrogen atoms in the hydrogen molecule is weakened, and it can interact with the electron-rich multiple bond (double bond). When two hydrogen atoms are formally transferred to the double bond respectively, hydrogenation occurs. This breaks the double bonds in the said aromatic compounds to obtain alicyclic compounds.

[0018] The hydrogenation gas used can be any hydrogen-containing gas mixture that does not contain any harmful amounts of catalyst poisons, such as carbon monoxide or hydrogen sulfide. The use of an inert gas is optional, and hydrogen with a purity greater than 95%, especially greater than 98%, is preferably used. The inert gas portion can be, for example, nitrogen or methane. Preferably, the amount of hydrogen present in the hydrogenation unit is such that hydrogen is present in excess, especially in excess of 1% to 200%, preferably in excess of 3% to 100%, and particularly preferably in excess of 5% to 50%, based on the stoichiometric amount required to achieve the possible or desired conversion rate in the hydrogenation unit. Setting a sufficient excess of hydrogen can have a favorable effect on the complete hydrogenation of aromatic bonds.

[0019] Each hydrogenation unit can be charged with fresh hydrogen. However, in order to minimize hydrogen consumption and output losses caused by waste gas, it is advisable to use the waste gas of one hydrogenation unit as the hydrogenation gas of another or the same hydrogenation unit. In addition, the waste gas of one hydrogenation unit can be reused as fresh hydrogen after post-treatment. For example, in a process carried out in two series-connected hydrogenation units, it is advantageous to feed fresh hydrogen into the first hydrogenation unit and introduce the waste 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 opposite order. In this process regime, it is advantageous to keep the hydrogen excess below 30%, especially below 20%, based on the stoichiometric required amount.

[0020] In the context of the present invention, "hydrogenation unit" should be understood to mean a hydrogenation reactor or a plurality of reactors connected in series or a plurality of reactors connected in parallel or a reactor group composed of reactors connected in parallel and in series. Therefore, it should be understood to mean a reactor or a reactor combination that can perform the reactor function in the method of the present invention.

[0021] In the context of the present invention, "recycle" or "loop mode" should be understood to mean that at least a part of the product stream of the hydrogenation unit is returned to the same hydrogenation unit as part of the input stream. Here, the product stream or the mixture obtained from the hydrogenation unit is separated. This means that a sub-stream of the hydrogenation output or product stream of the first hydrogenation unit is introduced into the first hydrogenation unit together with the fresh reactants as stream A. Another sub-stream of the hydrogenation output or product stream of the first hydrogenation unit is hydrogenated in the second hydrogenation unit, and the second hydrogenation unit is preferably operated in a straight-through mode. It is also possible to use a plurality of smaller units arranged in series or in parallel instead of a large hydrogenation unit in the loop mode. It is also possible to operate a plurality of units connected in series or in parallel with each other instead of a large hydrogenation unit flowing in a straight-through mode. However, it is preferred to use only one hydrogenation unit operated in the loop mode and one unit operated in the straight-through mode. The method can also be carried out in a tube bundle reactor.

[0022] Preferably, in the method of the present invention, step iv. is carried out at a recycle ratio of 1:10 to 1:50, preferably 1:10 to 1:40, particularly preferably 1:30. This ratio, for example a value of 1:10, means that 10 tons of the first product stream are supplied back to the top of the first hydrogenation unit and 1 ton is supplied to the at least one further hydrogenation unit.

[0023] The recycle ratio is preferably set such that a total conversion of 80% to 99%, preferably 85% to 97%, is achieved in the first of the series of hydrogenation units and a conversion of 80% to 100%, preferably 85% to 100%, is achieved in the second hydrogenation unit, based on the starting concentration of the compound to be hydrogenated at the inlet of the respective hydrogenation unit. If three or more hydrogenation units are used, the conversion rates need to be adjusted accordingly.

[0024] The at least one further hydrogenation unit can also be operated in a loop mode or in a through-flow mode, which means that the recycle does not recycle back to the same hydrogenation unit. The at least one further hydrogenation unit is preferably operated in a through-flow mode.

[0025] The hydrogenation can be carried out in the absence or preferably in the presence of a solvent. The solvent used can be 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. The solvent can also be a mixture of various substances and optionally contain water.

[0026] For example, the following substances can be used as solvents: straight-chain or cyclic ethers such as tetrahydrofuran or dioxane, and aliphatic alcohols in which the alkyl group has 1 to 13 carbon atoms.

[0027] Preferably available alcohols are isopropanol, n-butanol, isobutanol, n-pentanol, 2-ethylhexanol, nonanol, industrial nonanol mixture, decanol, industrial decanol mixture, tridecanol.

[0028] When an alcohol is used as a solvent, it may be advantageous to use the alcohol or alcohol mixture that will be formed during the hydrolysis of the product. This will exclude the formation of by-products due to transesterification. Another preferred solvent is the hydrogenation product itself.

[0029] By using a solvent, the concentration of aromatic compounds in the reactor feed can be limited, thus enabling better temperature control in the reactor. This can minimize side reactions and thus lead to an increased product yield. Preferably, the concentration of aromatic compounds in the reactor feed is 1 wt% to 35 wt%, particularly 5 wt% to 25 wt%, based on the total amount of reactants. In the case of a reactor operated in a loop mode, the required concentration range can be adjusted by the recycle ratio (the ratio of the recycled hydrogenation output to the amount of reactants).

[0030] In step i., at least one aromatic compound and a hydrogen-containing hydrogenation gas are provided as reactants and fed as a feed stream A to the first hydrogenation unit via an input stream. Here, fresh reactants are supplied in the input stream and fed to the first hydrogenation unit via the input stream. The input stream has a temperature T1. Then, the hydrogenation in step ii. takes place in this first hydrogenation unit, and in step iii., a mixture containing a hydrogenated compound (alicyclic compound) and an unhydrogenated compound (aromatic compound) is obtained as a first product stream at the end of the hydrogenation unit. In a preferred embodiment, the product stream from the first hydrogenation unit is pumped to subsequent process steps. Commercially available pumps can be used here. Suitable pumps are known to those skilled in the art.

[0031] The mixture or the first product stream has a temperature T2 and is then split into two sub-streams in step iv., where one sub-stream is introduced as a stream into stream A and undergoes hydrogenation again according to step ii. together with the fresh reactants in the first hydrogenation unit. The second sub-stream is introduced as stream B into the second hydrogenation unit and has a temperature T3. It is hydrogenated in step v. in at least one additional hydrogenation unit so that the reactants not converted in the first hydrogenation unit are hydrogenated in the second hydrogenation unit to obtain the corresponding alicyclic compounds. The product mixture obtained as a stream in step vi. has a temperature T4.

[0032] The separation in step iv. of the process according to the invention is preferably carried out at a known T-piece in the pipeline. Here, valves are advantageously provided at both ends of the T-piece to control the mass flow rate and thus the separation.

[0033] It has been found in the context of the present invention that when the outlet temperature T2 of the first hydrogenation unit and the inlet temperature T3 of the at least one additional hydrogenation unit are set independently of each other, the yield of the process over time can be increased and the temperature in the at least one additional hydrogenation unit can be controlled.

[0034] The second product stream at the outlet of the at least one additional hydrogenation unit preferably contains less than 0.3% by mass, preferably less than 0.1% by mass, in particular less than 0.05% by mass, and particularly preferably 0.005% by mass of the aromatic compound used as a reactant.

[0035] Process parameters, such as product, by-product and reactant concentrations and temperature, are preferably determined by on-line analysis. The on-line analysis obtains the respective parameters in real time, preferably in the product output stream of the first (3) and / or each additional hydrogenation unit (12). Measuring methods selected from the following are preferably used: reaction calorimetry, ATR-FT-IR spectroscopy, Raman spectroscopy, IR spectroscopy, UV and / or UV-VIS spectroscopy or combinations thereof. This setting can also be automated, i.e., by means of computer technology.

[0036] In the context of the present invention, it is preferred that the hydrogenation of the aromatic compound provided in step i. is carried out with the hydrogen-containing gas provided in step i. on one or more solid catalysts provided in the fixed bed of the hydrogenation unit.

[0037] It is further preferred that the solid catalyst contains at least one metal from the eighth subgroup of the periodic table of elements. Platinum, rhodium, palladium, cobalt, nickel or ruthenium or a mixture of two or more thereof is preferably used as the active metal, and ruthenium is particularly used as the active metal.

[0038] In addition to the metals already mentioned, the catalyst preferably further contains at least one metal from the first and / or seventh subgroup of the periodic table of elements. In addition to the metals of the eighth subgroup of the periodic table of elements, rhenium and / or copper are preferably used.

[0039] The catalyst used in the method is preferably a metal as defined above applied to a support material. The support material used is preferably a material containing micropores (pore diameter less than 2 nm), a material containing mesopores (pore diameter from 2 to 50 nm) and a material containing macropores (pore diameter greater than 50 nm). For example, in terms of pore type, support materials having the following pore combinations are available:

[0040] a) Only mesopores,

[0041] b) Micropores and mesopores,

[0042] c) Mesopores and macropores,

[0043] d) Micropores, mesopores and macropores,

[0044] e) Micropores and macropores.

[0045] Activated carbon, silicon carbide, alumina, silica, aluminosilicate, titanium dioxide, zirconium dioxide, magnesium oxide and / or zinc oxide or mixtures thereof are preferably used as the support material.

[0046] Preferably used as the carrier material is a solid that is substantially inert under hydrogenation conditions. Examples of these are activated carbon, silicon carbide, silica, titanium dioxide and / or zirconium dioxide, and mixtures of these compounds. Titanium dioxide is very particularly preferably used as the carrier material. Titanium dioxide occurs in three modifications (anatase, rutile and brookite), of which anatase and rutile are the most common. The preferred carrier material is Aerolyst (Evonik Operations GmbH). The carrier material consists of 15% to 20% by mass of rutile and 80% to 85% by mass of anatase. Other examples of suitable titanium dioxide carrier materials are those prepared by the sulfuric acid process based on titanium oxide. They generally contain >98% anatase.

[0047] Particularly preferably, the solid catalyst used for the hydrogenation in steps ii. and / or v. is a catalyst comprising ruthenium as the sole metal and titanium dioxide as the carrier material. In a preferred embodiment, the same catalyst is used for the hydrogenation in steps ii. and v.; particularly preferably, this is a catalyst comprising ruthenium as the sole metal and titanium dioxide as the carrier material.

[0048] In the process according to the invention, the hydrogenation in steps ii. and / or v. is carried out in the liquid phase or the gas phase. The hydrogenation can be carried out continuously or discontinuously on a catalyst arranged in a fixed bed in suspended or massive form. In the process according to the invention, continuous hydrogenation on a catalyst arranged in a fixed bed is preferred, wherein the product / reactant phase is mainly liquid under the reaction conditions.

[0049] Preferably, the hydrogenation in steps ii. and / or iv. is carried out at a pressure of 3 to 300 bar, preferably 15 to 200 bar, particularly preferably 50 to 150 bar.

[0050] Further preferably, the hydrogenation in steps ii. and / or v. is carried out at a temperature of 50°C to 250°C, preferably 70°C to 200°C. This temperature is present in the output stream of the hydrogenation unit (T2 and T4) after the hydrogenation. Due to the exothermic nature of the hydrogenation reaction, the reaction does not occur at a fixed temperature, but within the temperature range described herein. Thus, the temperature of the reaction mixture increases as it flows through the hydrogenation unit.

[0051] According to the present invention, the temperature T2 is different from the temperature T3, preferably the temperature T2 is higher than T3. It has been found to be particularly advantageous in the context of the present invention that the output stream having the temperature T2 is not directly supplied to the at least one further hydrogenation unit, but is cooled and supplied to the at least one further hydrogenation unit at a lower temperature T3. Thus, it is particularly preferred that the temperature T2 of the obtained mixture is higher than the temperature T3 of the mixture supplied to the hydrogenation unit in step iv.

[0052] The temperature control (T2≠T3, preferably T2>T3) can be achieved by providing a cooling device between the output stream (i.e., the first product stream) of the first hydrogenation unit and the input stream of the second hydrogenation unit, which cools at least a part of the output stream to achieve a temperature T3 different from the temperature T2 in the input stream supplied to the at least one further hydrogenation unit. Preferably, the cooling is achieved via a heat exchanger. Corresponding devices are familiar to those skilled in the art. A heat exchanger is preferably used to utilize the extracted thermal energy elsewhere in the method or in an integrated system of multiple devices.

[0053] Thus, it is possible that the output stream or the first product stream from the hydrogenation in step ii. is cooled after leaving the first hydrogenation device, i.e., the first product stream is cooled before separation in step iv. However, it is also possible that only the part of the output stream (stream B) that is sent to the at least one further hydrogenation unit or the second hydrogenation unit is cooled, i.e., cooled after separation in step iv. In the context of the present invention, it is preferred that the first product stream is cooled before separation in step iv. Particularly preferably, a bypass is provided in the method, which is used to enable a part of the first product stream from the first hydrogenation unit to be mixed into stream B through a side stream before cooling. Thus, a part of the uncooled first product stream can be mixed into stream B to increase the temperature T3. Thus, the temperature T3 can be adjusted independently of the cooling and independently of the temperature of stream A.

[0054] In the method according to the present invention, it is preferred to provide one or more aromatic carboxylic esters in step i., preferably one or more aromatic mono-, di- and polycarboxylic esters.

[0055] In the method according to the present invention, aromatic compounds, such as aromatic polycarboxylic acids and / or monocarboxylic acids or their derivatives, especially their alkyl esters, can be converted into corresponding alicyclic polycarboxylic compounds. Both the peresters and the partial esters can be hydrogenated. A perester should be understood as 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 acid anhydride group) and at least one ester group.

[0056] If polycarboxylic acid esters are used in the process according to the invention, these esters preferably contain 2, 3 or 4 ester functional groups.

[0057] In the process according to the invention, it is preferred that in step i., one or more benzene-, diphenyl-, naphthalene-, diphenyl ether-, anthracene-di- or polycarboxylic acid esters are provided. The alicyclic polycarboxylic acids or their derivatives obtained by the process according to the invention consist of one or more C6 rings which are optionally linked or fused via carbon-carbon bonds.

[0058] Further preferably, in step i., one or more aromatic carboxylic acid esters having an alcohol component selected from branched or unbranched alkoxyalkyl, cycloalkyl and / or alkyl having 1 to 25 carbon atoms are provided, preferably C8-C10 esters of phthalic acid, C8-C10 esters of terephthalic acid, C8-C10 esters of isophthalic acid and C8-C10 esters of trimellitic acid, particularly preferably di-2-ethylhexyl phthalate, diisononyl phthalate, di-2-ethylhexyl terephthalate, diisononyl terephthalate, di-2-ethylhexyl isophthalic acid, diisononyl isophthalic acid, tri-2-ethylhexyl trimellitate and triisononyl trimellitate.

[0059] Here, C8 preferably represents 2-ethylhexyl or n-octyl, C9 represents isononyl, and C10 represents isodecyl or 2-propylheptyl.

[0060] The process is preferably a process for hydrogenating benzene-1,2-, -1,3- or -1,4-dicarboxylic acid esters and / or benzene-1,2,3-, -1,2,4- or -1,3,5-tricarboxylic acid esters, i.e. obtaining isomers of cyclohexane-1,2-, -1,3- or -1,4-dicarboxylic acid esters or cyclohexane-1,2,3-, -1,3,5- or -1,2,4-tricarboxylic acid esters.

[0061] In the process according to the invention, for example, the following aromatic carboxylic acid esters can be used: naphthalene-1,2-dicarboxylic acid, naphthalene-1,3-dicarboxylic acid, naphthalene-1,4-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, naphthalene-1,6-dicarboxylic acid, naphthalene-1,7-dicarboxylic acid, naphthalene-1,8-dicarboxylic 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 (mesitylenetricarboxylic acid), benzene-1,2,3,4-tetracarboxylic acid. Acids formed by substituting one or more hydrogen atoms bonded to the aromatic ring with alkyl, cycloalkyl or alkoxyalkyl can also be used.

[0062] Preference is given to using, for example, alkyl, cycloalkyl and alkoxyalkyl esters of the abovementioned acids, where these groups independently of one another contain from 1 to 25, in particular from 3 to 15, very particularly from 8 to 13 carbon atoms, in particular 9 carbon atoms. These groups can be straight-chain or branched. If the reactant has more than one ester group, these groups can be identical or different.

[0063] Examples of aromatic polycarboxylic esters which can be used in the process according to the invention include the following compounds: monomethyl terephthalate, dimethyl terephthalate, diethyl terephthalate, di-n-propyl terephthalate, di-n-butyl terephthalate, diisobutyl terephthalate, di-tert-butyl terephthalate, di-n-pentyl terephthalate, monoethylene glycol terephthalate, diethylene glycol 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, di-tridecyl terephthalate, di-n-octadecyl terephthalate, diisooctadecyl 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, monoethylene glycol phthalate, diethylene glycol phthalate, n-octyl phthalate, diisooctyl phthalate, di-2-ethylhexyl phthalate, di-n-nonyl phthalate, diisononyl phthalate, di-n-decyl phthalate, di-2-propylheptyl phthalate, diisodecyl phthalate, di-n-undecyl phthalate, diisoundecyl phthalate, di-tridecyl phthalate, di-n-octadecyl phthalate, diisooctadecyl phthalate, di-n-eicosyl phthalate, monocyclohexyl phthalate; dicyclohexyl phthalate, monomethyl isophthalate, dimethyl isophthalate, diethyl isophthalate, di-n-propyl isophthalate, di-n-butyl isophthalate, diisobutyl isophthalate, di-tert-butyl isophthalate, monoethylene glycol isophthalate, diethylene glycol isophthalate, n-octyl isophthalate, diisooctyl isophthalate, 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, di-tridecyl isophthalate, di-n-octadecyl isophthalate, diisooctadecyl isophthalate, di-n-eicosyl isophthalate, monocyclohexyl isophthalate.

[0064] The method according to the invention is in principle also applicable to benzoic acid and its esters. This should be understood to refer not only to alkyl benzoates, but also to benzoates of diols, such as ethylene glycol dibenzoate, diethylene glycol dibenzoate, triethylene glycol dibenzoate or propylene glycol dibenzoate. The alcohol component of the alkyl benzoates can consist of 1 to 25, preferably 8 to 13 carbon atoms, which are in each case straight-chain or branched.

[0065] On an industrial scale, aromatic esters, especially polyester, are preferably usually prepared from alcohol mixtures. Examples of corresponding alcohol mixtures include: C5 alcohol mixtures prepared from linear butenes by hydroformylation and then hydrogenation; C5 alcohol mixtures prepared from butene mixtures containing linear butenes and isobutene by hydroformylation and then hydrogenation; C6 alcohol mixtures prepared from pentenes or from mixtures of two or more pentenes by hydroformylation and then hydrogenation; C7 alcohol mixtures prepared from ethylene trimerization or propylene dimerization or hexene isomers or another mixture of hexene isomers by hydroformylation and then hydrogenation; C8 alcohol mixtures prepared by aldol condensation of n-butyraldehyde and then hydrogenation, such as 2-ethylhexanol (2 isomers); C9 alcohol mixtures prepared from C4 olefins by dimerization, hydroformylation and hydrogenation. The preparation of the C9 alcohol can be carried out from isobutene or from a mixture of linear butenes or from a mixture of linear butenes and isobutene. The C4 olefins can be dimerized with the help of different catalysts, such as proton acids, zeolites, organometallic nickel compounds or solid nickel-containing catalysts. The C8 olefin mixture can be hydroformylated with the help of rhodium or cobalt catalysts. Thus, there are a wide variety of industrial C9 alcohol mixtures; C10 alcohol mixtures prepared from tripropylene by hydroformylation and then hydrogenation; 2-propylheptanol (2 isomers) prepared by aldol condensation of valeraldehyde and then hydrogenation; C10 alcohol mixtures prepared from a mixture of at least two C5 aldehydes by aldol condensation and then hydrogenation; C13 alcohol mixtures prepared from hexavinyl, tetrapropylene or tributene by hydroformylation and then hydrogenation.

[0066] Other alcohol mixtures can be obtained from olefins or olefin mixtures by hydroformylation and then hydrogenation, said olefins or olefin mixtures being produced, for example, in Fischer-Tropsch synthesis, hydrocarbon dehydrogenation, metathesis reactions, polygas processes or other industrial processes. Olefin mixtures containing olefins of different carbon numbers can also be used for the preparation of alcohol mixtures.

[0067] In the process according to the invention, all ester mixtures prepared from aromatic polycarboxylic acids and the above-mentioned alcohol mixtures can be used. According to the invention, preference is given to using esters prepared from phthalic acid or phthalic anhydride and terephthalic acid or dimethyl terephthalate and a mixture of isomeric alcohols having 4 to 13 carbon atoms.

[0068] A preferred method for preparing one or more alicyclic compounds, which comprises the following steps:

[0069] i. Providing a feed stream A, which comprises one or more aromatic compounds selected from the group consisting of phthalates, isophthalates, terephthalates, and / or trimellitates, particularly preferably selected from dipentyl terephthalate, bis(2-ethylhexyl) terephthalate, diisononyl terephthalate, dipentyl phthalate, bis(2-ethylhexyl) phthalate, diisononyl phthalate, dipentyl isophthalate, bis(2-ethylhexyl) isophthalate, diisononyl isophthalate, tripentyl trimellitate, tris(2-ethylhexyl) trimellitate, triisononyl trimellitate, or mixtures thereof,

[0070] and a hydrogen-containing hydrogenation gas;

[0071] ii. Supplying the feed stream A having a temperature T1 to a first hydrogenation unit and hydrogenating the one or more aromatic compounds to obtain one or more corresponding alicyclic compounds;

[0072] iii. Obtaining a mixture as a first product stream having a temperature T2, which comprises aromatic compounds and alicyclic compounds selected from the group consisting of dialkyl cyclohexane-1,2-dicarboxylates, dialkyl cyclohexane-1,3-dicarboxylates, dialkyl cyclohexane-1,4-dicarboxylates, and cyclohexane-1,2,4-tricarboxylates, particularly preferably selected from dipentyl cyclohexane-1,4-dicarboxylate, bis(2-ethylhexyl) cyclohexane-1,4-dicarboxylate, diisononyl cyclohexane-1,4-dicarboxylate, dipentyl cyclohexane-1,2-dicarboxylate, bis(2-ethylhexyl) cyclohexane-1,2-dicarboxylate, diisononyl cyclohexane-1,2-dicarboxylate, dipentyl cyclohexane-1,3-dicarboxylate, bis(2-ethylhexyl) cyclohexane-1,3-dicarboxylate, diisononyl cyclohexane-1,3-dicarboxylate, tripentyl cyclohexane-1,2,4-tricarboxylate, tris(2-ethylhexyl) cyclohexane-1,2,4-tricarboxylate, triisononyl cyclohexane-1,2,4-tricarboxylate;

[0073] iv. Dividing the product stream obtained in step iii. into a sub-stream that is supplied to the feed stream A in step i. and is hydrogenated again as part of the feed stream A in step ii., and a sub-stream that is supplied as a feed stream B to one or more additional hydrogenation units at a temperature T3;

[0074] v. Hydrogenating the aromatic compounds contained in the feed stream B as defined in step i. in the one or more additional hydrogenation units to obtain the corresponding alicyclic compounds, and

[0075] vi. Obtain a second product stream having a temperature T4, which comprises 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-trimesates, particularly preferably selected from dipentyl cyclohexane-1,4-dicarboxylate, bis(2-ethylhexyl) cyclohexane-1,4-dicarboxylate, diisononyl cyclohexane-1,4-dicarboxylate, dipentyl cyclohexane-1,2-dicarboxylate, bis(2-ethylhexyl) cyclohexane-1,2-dicarboxylate, diisononyl cyclohexane-1,2-dicarboxylate, dipentyl cyclohexane-1,3-dicarboxylate, bis(2-ethylhexyl) cyclohexane-1,3-dicarboxylate, diisononyl cyclohexane-1,3-dicarboxylate, tripentyl 1,2,4-trimesate, tris(2-ethylhexyl) 1,2,4-trimesate, tris(isononyl) 1,2,4-trimesate, which corresponds to one or more aromatic compounds provided in step i.,

[0076] wherein the temperature T2 is different from the temperature T3, preferably wherein the temperature T2 is higher than T3.

[0077] The alicyclic compounds contained in the second product stream depend on the reactants used. For example, when using diisononyl phthalate as a reactant, diisononyl cyclohexane-1,2-dicarboxylate is contained as a product.

[0078] Particularly preferred is a method for preparing one or more alicyclic compounds, which comprises the following steps:

[0079] i. Provide a stream A, which contains diisononyl phthalate (DINP) or bis(2-ethylhexyl) phthalate (DEHP) and hydrogenated hydrogen gas;

[0080] ii. Supply the stream A having a temperature T1 to a first hydrogenation unit and hydrogenate the one or more aromatic compounds to obtain one or more corresponding alicyclic compounds;

[0081] vi. Obtain a mixture as a first product stream having a temperature T2, which comprises diisononyl cyclohexane-1,2-dicarboxylate (DINCH) or bis(2-ethylhexyl) cyclohexane-1,2-dicarboxylate (DEHCH);

[0082] iv. Divide the product stream obtained in step iii. into a sub-stream that is supplied to the stream A in step i. and hydrogenated again as part of the stream A in step ii. and a sub-stream that is supplied as a stream B to one or more additional hydrogenation units at a temperature T3;

[0083] v. Hydrogenate the aromatic compounds comprised in stream B in said one or more additional hydrogenation units to obtain the corresponding alicyclic compounds, and

[0084] vi. Obtain a second product stream having a temperature T4 which comprises diisononyl cyclohexane-1,2-dicarboxylate (DINCH) or di-2-ethylhexyl cyclohexane-1,2-dicarboxylate (DEHCH);

[0085] wherein said temperature T2 is different from temperature T3, preferably wherein said temperature T2 is higher than T3.

[0086] Further particularly preferred is a process for preparing one or more alicyclic compounds, which comprises the steps of:

[0087] i. Providing a stream A which contains diisononyl terephthalate or di-2-ethylhexyl terephthalate and a hydrogen-containing hydrogenation gas;

[0088] ii. Supplying said stream A having a temperature T1 to a first hydrogenation unit and hydrogenating said one or more aromatic compounds to obtain one or more corresponding alicyclic compounds;

[0089] vi. Obtaining a mixture as a first product stream having a temperature T2 which comprises diisononyl cyclohexane-1,4-dicarboxylate or di-2-ethylhexyl cyclohexane-1,4-dicarboxylate;

[0090] iv. Dividing the product stream obtained in step iii. into a sub-stream which is supplied to stream A in step i. and hydrogenated again as part of stream A in step ii. and a sub-stream which is supplied as stream B to one or more additional hydrogenation units at a temperature T3;

[0091] v. Hydrogenate the aromatic compounds comprised in stream B in said one or more additional hydrogenation units to obtain the corresponding alicyclic compounds, and

[0092] vi. Obtain a second product stream having a temperature T4 which comprises diisononyl cyclohexane-1,4-dicarboxylate or di-2-ethylhexyl cyclohexane-1,4-dicarboxylate;

[0093] wherein said temperature T2 is different from temperature T3, preferably wherein temperature T2 is higher than T3.

[0094] Further particularly preferred is a process for preparing one or more alicyclic compounds, which comprises the steps of:

[0095] i. Providing a stream A which contains triisononyl trimellitate (TINTM) or tri-2-ethylhexyl trimellitate (TOTM) and a hydrogen-containing hydrogenation gas;

[0096] ii. Supply the stream A having a temperature T1 to the first hydrogenation unit and hydrogenate the one or more aromatic compounds to obtain one or more corresponding alicyclic compounds;

[0097] vi. Obtain a mixture having a temperature T2 as a first product stream, which comprises tris(isononyl) cyclohexane-1,2,4-tricarboxylate or tris(2-ethylhexyl) cyclohexane-1,2,4-tricarboxylate;

[0098] iv. Divide the product stream obtained in step iii. into a sub-stream that is supplied to the stream A in step i. and is hydrogenated again as part of the stream A in step ii. and a sub-stream that is supplied as the stream B to one or more additional hydrogenation units at a temperature T3;

[0099] v. Hydrogenate the aromatic compounds contained in the stream B in the one or more additional hydrogenation units to obtain the corresponding alicyclic compounds, and

[0100] vi. Obtain a second product stream having a temperature T4, which comprises tris(isononyl) cyclohexane-1,2,4-tricarboxylate or tris(2-ethylhexyl) cyclohexane-1,2,4-tricarboxylate;

[0101] wherein the temperature T2 is different from the temperature T3, preferably wherein the temperature T2 is higher than T3.

[0102] The process according to the invention is preferably carried out under the following conditions:

[0103] In the feed to the first hydrogenation unit (in loop mode), the concentration of the aromatic compound as a reactant is 5% to 30% by mass, in particular 8% to 15% by mass. In the output stream from the first hydrogenation unit, the concentration of the reactant is 0.3% to 8% by mass, in particular 1.5% to 4% by mass. The catalyst loading (space velocity based on liquid hourly space velocity, LHSV, liters of fresh reactant per liter of catalyst per hour) in the first hydrogenation unit (1) is 0.1 to 5 h -1 in particular 0.5 to 3 h -1 .

[0104] The surface area loading in the first hydrogenation unit is 25 to 140 m 3 / m 2 / h, in particular 50 to 90 m 3 / m 2 / h.

[0105] The average hydrogenation temperature of the first hydrogenation unit is 70 to 150 °C, in particular 80 to 120 °C.

[0106] The hydrogenation pressure of the first hydrogenation unit is 25 to 200 bar, in particular 80 to 110 bar.

[0107] The catalyst loading (specific liquid hourly space velocity) (liters of reactants per liter of catalyst per hour) in the second hydrogenation unit is 1 to 8 h -1 , in particular 2 to 5 h -1 .

[0108] In the second hydrogenation unit, the average temperature is 70 to 150 °C, in particular 80 to 120 °C.

[0109] The hydrogenation pressure in the second hydrogenation unit is 25 to 200 bar, in particular 80 to 100 bar.

[0110] The process variant is particularly suitable for the hydrogenation of phthalates, in particular diisononyl phthalate (as the isomer mixture "diisononyl phthalate", for example VESTINOL 9 from OXENO GmbH) or di-2-ethylhexyl phthalate.

[0111] Another aspect of the invention is to provide an apparatus for carrying out the process according to the invention, which comprises a first hydrogenation unit and one or more additional hydrogenation units and one or more heat exchangers, wherein the heat exchanger is arranged such that the output stream is introduced into the heat exchanger via the input stream, and the output stream from the heat exchanger has a lower temperature than the input stream, and then is supplied as an input stream to another hydrogenation unit via a pipeline and / or is supplied to one or more additional hydrogenation units in sequence via the stream, preferably wherein the streams 3 and 9 have different temperatures.

[0112] Preferably, there may be at least one additional heat exchanger, which is arranged, for example, in the input stream of the at least one additional hydrogenation unit.

[0113] Preferably, in the apparatus according to the invention, one of the first and / or additional hydrogenation units has one or more fixed bed catalysts, preferably wherein the solid catalyst comprises at least one metal from the eighth subgroup of the periodic table, particularly preferably ruthenium. The preferred support material is titanium dioxide. The content described herein for the catalysts used also applies accordingly.

[0114] It is also preferred that the pipeline of the first hydrogenation unit (1) is arranged such that a part of the first product stream (2) from the first hydrogenation unit (1) can be mixed into stream B through a side stream before passing through the heat exchanger (3). As a result, a part of the uncooled first product stream can be mixed with stream B to increase its temperature.

[0115] Further preferably, a mixture of an aromatic compound and the corresponding alicyclic compound is present in one of the first and / or further hydrogenation units, preferably a mixture of an aromatic carboxylic acid ester having an alcohol component selected from branched or unbranched alkoxyalkyl, cycloalkyl and / or alkyl having 1 to 25 carbon atoms and the corresponding alicyclic compound, and the aromatic carboxylic acid ester and the corresponding alicyclic compound are preferably selected from C8-C 10 esters of phthalic acid, C8-C 10 esters of terephthalic acid, C8-C 10 esters of isophthalic acid, and C8-C 10 esters of trimellitic acid, particularly preferably di-2-ethylhexyl phthalate, diisononyl phthalate, di-2-ethylhexyl terephthalate, diisononyl terephthalate, di-2-ethylhexyl isophthalate, diisononyl isophthalate, tri-2-ethylhexyl trimellitate and triisononyl trimellitate, diisononyl phthalate and / or didodecyl phthalate and diisononyl cyclohexanedicarboxylate and / or didodecyl cyclohexanedicarboxylate and their corresponding alicyclic compounds. What is said herein for the reactant (aromatic compound) and the product (alicyclic compound) applies accordingly.

[0116] In the context of the present invention, it is preferred to use the alicyclic polycarboxylic acid ester prepared according to the present invention as a plasticizer in plastics. Preferred plastics are PVC, homopolymers or copolymers based on ethylene, propylene, butadiene, vinyl acetate, glycidyl acrylate, glycidyl methacrylate, acrylate, acrylate with an alkyl having 1 to 10 carbon atoms, branched or unbranched, bonded to the oxygen atom of the ester group, styrene, acrylonitrile, and homopolymers or copolymers of cycloolefins.

[0117] In addition to the above applications, the alicyclic polycarboxylic acid ester prepared according to the present invention can be used as a lubricating oil component, a component of a coolant and a component of a metalworking fluid. They can also be used as components of paints, coatings, inks and adhesives. Brief Description of the Drawings

[0119] Figure 1 Shows an embodiment of the method according to the present invention.

[0120] Figure 2 Shows an alternative embodiment of the method according to the present invention. Detailed Description

[0121] The method according to the present invention is described below, for example, using the configurations shown in Figure 1 and 2 as examples. Figure 1 and 2 The embodiments shown therein are exemplary embodiments and are not intended to limit the present invention.

[0122] Figure 1 A process embodiment is shown in which in step i., at least one aromatic compound and a hydrogen-containing hydrogenation gas are provided and fed as feed stream A to a first hydrogenation unit (1) via an input stream. The feed stream A has a temperature T1. Then, in this first hydrogenation unit (1), the hydrogenation of step ii. is carried out, and in step iii., a mixture containing hydrogenated compounds (alicyclic compounds) and unhydrogenated compounds (aromatic compounds) is obtained as a first product stream (2) at the end of the hydrogenation unit (2). This mixture or the first product stream (2) has a temperature T2 and is preferably cooled in a cooling device (3), such as a heat exchanger (3). Then, in step iv., the cooled product stream is divided into two sub-streams, where one sub-stream is (optionally again) hydrogenated in the first hydrogenation unit (1) with fresh reactants as feed stream A according to step ii. The second sub-stream is introduced as feed stream B into the second hydrogenation unit (4) and has a temperature T3. Hydrogen-containing hydrogenation gas from the first hydrogenation unit (1) is admixed to this feed stream B. The feed stream is hydrogenated in step v. in at least one additional hydrogenation unit (4) such that the reactants that were not converted in the first hydrogenation unit (1) are hydrogenated in this second hydrogenation unit (4) to obtain the corresponding alicyclic compounds. The product mixture obtained as the second product stream (5) in step vi. has a temperature T4. In this embodiment, a bypass may be present, which allows a part of the first product stream (2) from the first hydrogenation unit (1) to be admixed to the feed stream B via a side stream, as indicated by the dashed arrow. This allows the temperature T3 to be adjusted independently of the cooling.

[0123] Figure 2 An alternative embodiment is shown which largely corresponds to the embodiment according to Figure 1 The only difference is that the first product stream (2) is sent to the cooling device or heat exchanger (3) by a pump (6).

[0124] The product stream (5) at the outlet of the second hydrogenation unit (4) preferably contains less than 0.3% by mass, preferably less than 0.1% by mass, in particular less than 0.05% by mass, and particularly preferably 0.005% by mass of alicyclic compounds used as reactants.

[0125] Process parameters, such as product, by-product and reactant concentrations and temperature, are preferably determined by on-line analysis. The on-line analysis obtains the respective parameters in real time, preferably in the product effluent stream of the first (1) and / or each additional hydrogenation unit (4). Measurement methods selected from the following are preferably used: reaction calorimetry, ATR-FT-IR spectroscopy, Raman spectroscopy, IR spectroscopy, UV and / or UV-VIS spectroscopy or a combination thereof. With the process parameters determined thereby, the temperature T1 can be set specifically after an early determination of the threshold value. The setting can also be achieved automatically, i.e., with the aid of computer technology.

[0126] In the context of the present invention, it is preferred that the hydrogenation of the aromatic compound provided in step i. is carried out with the hydrogen-containing gas provided in step i. on one or more solid catalysts provided in the fixed bed of the hydrogenation unit.

[0127] More preferably, the solid catalyst comprises at least one metal from subgroup VIII of the periodic table of elements. Platinum, rhodium, palladium, cobalt, nickel or ruthenium or a mixture of two or more thereof is preferably used as the active metal, and ruthenium is particularly used as the active metal.

[0128] In addition to the above metals, the catalyst may additionally contain at least one metal from subgroup I and / or VII of the periodic table of elements. In addition to the metals from subgroup VIII of the periodic table of elements, rhenium and / or copper are preferably used.

Claims

1. A method for preparing one or more alicyclic compounds, comprising the following steps: i. providing a feed stream A, which contains one or more aromatic compounds and a hydrogen-containing hydrogenation gas; ii. supplying the feed stream A having a temperature T1 to a first hydrogenation unit and hydrogenating the one or more aromatic compounds to obtain one or more corresponding alicyclic compounds; iii. obtaining a mixture as a first product stream having a temperature T2, which contains aromatic compounds and alicyclic compounds; iv. dividing the product stream obtained in step iii. into a sub-stream that is supplied to the feed stream A in step i. and is hydrogenated again as part of the feed stream A in step ii. and a sub-stream that is supplied to one or more additional hydrogenation units as the feed stream B at a temperature T3; v. hydrogenating the aromatic compounds contained in the feed stream B in the one or more additional hydrogenation units to obtain corresponding alicyclic compounds, and vi. obtaining a second product stream having a temperature T4, which contains one or more alicyclic compounds corresponding to the one or more aromatic compounds provided in step i., wherein the temperature T2 is different from the temperature T3, and preferably the temperature T2 is higher than T3.

2. The method according to claim 1, wherein the hydrogenation of the aromatic compounds provided in step i. is carried out with the hydrogen-containing gas provided in step i. on one or more solid catalysts provided in a fixed bed of a hydrogenation unit.

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

4. The method according to any one of the preceding claims, wherein step ii. is carried out at a recycle ratio of 1:10 to 1:50, preferably 1:10 to 1:40, particularly preferably 1:

30.

5. The method according to any one of the preceding claims, wherein the hydrogenation in step ii. and / or iv. is carried out at a pressure of 3 to 300 bar, preferably 15 to 200 bar, particularly preferably 100 to 200 bar.

6. The method according to any one of the preceding claims, wherein the hydrogenation in step ii. and / or iv. is carried out at a temperature of 50°C to 250°C, preferably 100°C to 200°C.

7. The method according to any one of the preceding claims, wherein the first product stream is cooled before separation in step iv.

8. The method according to claim 7, wherein a bypass is provided, which is used to allow a part of the first product stream to be mixed into the feed stream B through a side stream from the first hydrogenation unit before cooling.

9. The method according to any one of the preceding claims, wherein in step i., one or more aromatic carboxylic esters are provided, preferably one or more aromatic mono-, di- and polycarboxylic esters.

10. The method according to any one of the preceding claims, wherein in step i., one or more benzene-, biphenyl-, naphthalene-, diphenyl ether-, anthracene-di- or polycarboxylic esters are provided.

11. The method according to any one of the preceding claims, wherein in step i., there is provided one or more aromatic carboxylic acid esters having an alcohol component selected from branched or unbranched alkoxyalkyls, cycloalkyls and / or alkyls having 1 to 25 carbon atoms, preferably C8-C 10 esters of phthalic acid, C8-C 10 esters of terephthalic acid, C8-C 10 esters of isophthalic acid, and C8-C 10 esters of trimellitic acid, particularly preferably di-2-ethylhexyl phthalate, diisononyl phthalate, di-2-ethylhexyl terephthalate, diisononyl terephthalate, di-2-ethylhexyl isophthalate, diisononyl isophthalate, tri-2-ethylhexyl trimellitate and triisononyl trimellitate.

12. An apparatus for carrying out the method according to any one of claims 1 to 11, comprising a first hydrogenation unit (1), one or more additional hydrogenation units (4) and one or more heat exchangers (3), wherein the heat exchanger (3) is arranged such that the first product stream (2) is introduced into the heat exchanger (3), and the output stream from the heat exchanger has a lower temperature than stream A and is then partly supplied as stream B through a pipeline to an additional hydrogenation unit (4).

13. The apparatus according to claim 12, wherein one of the first and / or additional hydrogenation units (1, 4) comprises one or more fixed bed catalysts, preferably wherein the solid catalyst comprises at least one metal from subgroup VIII of the periodic table of the elements, particularly preferably ruthenium.

14. The apparatus according to claim 12 or 13, wherein the pipeline of the first hydrogenation unit (1) is arranged such that a part of the first product stream (2) from the first hydrogenation unit (1) can be mixed into stream B through a side stream before passing through the heat exchanger (3).

15. The device according to any one of claims 11 to 14, wherein in one of the first and / or further hydrogenation units there is a mixture of an aromatic compound and the corresponding alicyclic compound, preferably an aromatic carboxylic acid ester having an alcohol component selected from branched or unbranched alkoxyalkyls, cycloalkyls and / or alkyls having 1 to 25 carbon atoms and the corresponding alicyclic compound thereof, the aromatic carboxylic acid ester and the corresponding alicyclic compound thereof preferably being selected from C8-C 10 esters of phthalic acid, C8-C 10 esters of terephthalic acid, C8-C 10 esters of isophthalic acid and C8-C 10 esters of trimellitic acid, particularly preferably di-2-ethylhexyl phthalate, diisononyl phthalate, di-2-ethylhexyl terephthalate, diisononyl terephthalate, di-2-ethylhexyl isophthalate, diisononyl isophthalate, tri-2-ethylhexyl trimellitic acid and triisononyl trimellitic acid, diisononyl phthalate and / or didecyl phthalate and diisononyl cyclohexanedicarboxylate and / or didecyl cyclohexanedicarboxylate and the corresponding alicyclic compounds thereof.

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