Transesterification Process

Abstract

The present invention relates to the field of organic synthesis. More particularly, the present invention relates to a method for producing a compound having at least one C 1~4 The compound containing the carboxylic acid ester group is referred to as C 1~4 The present invention provides a continuous process for transesterification in the presence of an alcohol and a transesterification catalyst, wherein the transesterification step is carried out in at least two subsequent reactors separated by a separation unit.The present invention also relates to a process for preparing diethyl 1,4-cyclohexanedicarboxylate, comprising the steps of transesterifying dimethyl terephthalate in the presence of ethanol and reducing diethyl terephthalate.

Description

[Technical Field]

[0001] The present invention relates to the field of organic synthesis. More particularly, the present invention relates to a method for producing a compound having at least one C 1~4 The compound containing the carboxylic acid ester group is referred to as C 1~4 The present invention provides a continuous process for transesterification in the presence of an alcohol and a transesterification catalyst, wherein the transesterification step is carried out in at least two subsequent reactors separated by a separation unit.The present invention also relates to a process for preparing diethyl 1,4-cyclohexanedicarboxylate, comprising the steps of transesterifying dimethyl terephthalate in the presence of ethanol and reducing diethyl terephthalate.

[0002] Background technology Access to compounds containing carboxylic acid ester groups is highly sought after, as they represent highly desirable scaffolds that can be used as such or as key intermediates to prepare more complex compounds in various fields, such as fragrance, cosmetics, pharmaceuticals, and agricultural chemistry, among others. In this context, numerous methodologies have been developed, such as transesterification. The reactions can be very difficult to carry out on a large scale, as they require long reaction times and large energy consumption while suffering from low productivity.

[0003] Because of the importance of these reactions for producing valuable compounds, new processes that offer improved yields and selectivities and reduced energy consumption are constantly needed.

[0004] The present invention provides a solution to the above problem by carrying out the transesterification under continuous conditions in at least two subsequent reactors separated by a separation unit, in which the alcohol formed during the process is removed.To the best of the inventors' knowledge, the prior art has not reported a continuous process such as that disclosed in this invention. [Brief explanation of the drawings]

[0005] [Figure 1] 1 is a schematic process flow sheet illustrating an embodiment of the present invention.

[0006] Summary of the Invention Surprisingly, it has now been found that by carrying out the transesterification process in a conditional mode in at least two subsequent reactors separated by a separation unit, it is possible to produce significantly higher amounts of the desired product in a shorter time, leading to reduced energy consumption.

[0007] Therefore, the first object of the present invention is to provide at least one C 1~4 The compound containing the carboxylic acid ester group is referred to as C 1~4 A continuous process for transesterification in the presence of an alcohol and a transesterification catalyst, wherein the transesterification step is carried out in at least two subsequent reactors separated by a separation unit. In other words, the first object of the present invention is to provide a continuous process for the transesterification of at least one C 1~4 A continuous process for transesterifying compounds containing carboxylic acid ester groups, comprising: 1~4 A compound containing a carboxylic acid ester group is subjected to a transesterification reaction with C 1~4 It is a continuous process in which the reaction with alcohol and transesterification steps are carried out in at least two subsequent reactors separated by a separation unit.

[0008] For clarity, it is understood that the term "transesterification" is intended to have its ordinary meaning in the art, i.e., that the starting material and the resulting compound contain at least one carboxylic acid ester group. In other words, transesterification can be achieved by, for example, reacting a compound of the formula R-COO-R 1 Starting from a compound of the formula R-COO-R 2 Preparation of a compound of formula (wherein R 1 Groups and R 2 During the process, the C 1~4 Alcohol is a different formula from HOR1 Alcohols are also formed.

[0009] "At least one C 1~4 The term "compound containing a carboxylic acid ester group" refers to a compound having at least one of the formula -COO-R 1 (In the formula, R 1 is C 1~4 In other words, compounds containing at least one C 1~4 Compounds containing a carboxylic acid ester group have the formula R-COO-R 1 (I) (In the formula, R 1 is C 1~4 is an alkyl group, and R is one or more C 1~4 C optionally containing a carboxylic acid ester group 1~18 (It is a hydrocarbon group) is a compound of

[0010] By "...hydrocarbon group..." is meant that the group consists of hydrogen and carbon atoms and may be in the form of an aliphatic hydrocarbon, i.e., a linear or branched saturated hydrocarbon (e.g., an alkyl group), a linear or branched unsaturated hydrocarbon (e.g., an alkenyl or alkynyl group), a saturated cyclic hydrocarbon (e.g., a cycloalkyl), or an unsaturated cyclic hydrocarbon (e.g., a cycloalkenyl or cycloalkynyl), or an aromatic hydrocarbon, i.e., an aryl group, or may be in the form of a mixture of the above types of groups; for example, a particular group may contain linear alkyl, branched alkenyl (e.g., having one or more carbon-carbon double bonds), (poly)cycloalkyl, and aryl moieties, unless a specific limitation to only one type is mentioned. Similarly, in all embodiments of the present invention, when a group is referred to as being in the form of more than one type of topology (e.g., linear, cyclic, or branched) and / or saturated or unsaturated (e.g., alkyl, aromatic, or alkenyl), it also means that the group may contain moieties having any one of the above topologies, or moieties that are saturated or unsaturated, as explained above. Similarly, in any embodiment of the present invention, when a group is referred to as being in one type of saturated or unsaturated form (e.g., alkyl), it means that the group can be of any type of topology (e.g., linear, cyclic, or branched) or can have some moieties with different topologies.

[0011] The term "optionally" is understood to mean that the R group may or may not contain a particular functional group. The term "one or more" means that 1 to 7, preferably 1 to 5, preferably 1 to 3, more preferably 1 to 2 C 1~4 It is understood to include carboxylic acid ester groups.

[0012] "C 1~4 The term "alcohol" refers to a compound of the formula R 2 OH (in the formula, R 2 is C 1~4 C is understood as an alcohol of the alkyl group. 1~4Alcohols contain only one hydroxy group and no other functional groups; i.e., C 1~4 The alcohol is a monoalcohol. 1~4 The alcohol is not glycerin or a fatty alcohol.

[0013] The term "alkyl" is understood to include branched and straight chain alkyl groups.

[0014] The term "separation unit" is understood as any means making it possible to separate molecules from a reaction mixture containing several molecules, in particular to separate molecules with different boiling points. Non-limiting examples of suitable separation units may include distillation columns, rectification units, membranes, pervaporation units, adsorption units, absorption units.

[0015] According to one embodiment of the present invention, at least one C 1~4 A compound containing a carboxylic acid ester group is not a fatty acid ester, monoglyceride, diglyceride, or triglyceride.

[0016] According to one embodiment of the present invention, at least one C 1~4 Compounds containing a carboxylic acid ester group are diester compounds. In particular, diesters are compounds of the formula R 1 -OOC-R'-COO-R 1 (II) (Wherein, both R 1 are independent of each other, C 1~4 alkyl group, and R' is one or more C 1~4 C optionally containing a carboxylic acid ester group 1~18 (It is a hydrocarbon group) is a compound of

[0017] According to any embodiment of the present invention, R 1 is C 1~3 It may be an alkyl group, particularly a methyl or ethyl group, more particularly a methyl group. In other words, the carboxylic acid ester group is C 1~3The alcohol formed / released during the process of the present invention may be a C 1~3 It may be an alcohol, and in particular the carboxylic acid ester group is C 1~2 Carboxylic acid ester group, alcohol is C 1~2 The alcohol, even more particularly the carboxylic acid ester group is a C1 carboxylic acid ester group, the alcohol may be methanol. In particular, the alcohol formed / released during the process of the present invention is not glycerin or ethylene glycol.

[0018] According to any embodiment of the present invention, R may be one or more C 1~4 C optionally containing a carboxylic acid ester group 1~16 In particular, R may be one or more C 1~4 C optionally containing a carboxylic acid ester group 1~14 In particular, R may be one or more C 1~4 C optionally containing a carboxylic acid ester group 1~12 In particular, R may be one or more C 1~4 C optionally containing a carboxylic acid ester group 1~10 In particular, R may be one or more C 1~4 C optionally containing a carboxylic acid ester group 1~8 In particular, each R may be one or more C 1~4 optionally substituted with a carboxylic acid ester group, C 1~8 Alkyl, C 3~8 Cycloalkyl, C 2~8 In particular, each R may be one or more C 1~4 optionally substituted with a carboxylic acid ester group, C 1~6 Alkyl, C 3~6 Cycloalkyl, C 2~6 In particular, R may be an alkenyl group or a phenyl group. 1~4 optionally substituted with a carboxylic acid ester group, C 1~6 Alkyl, C 3~6 Cycloalkyl, C 2~6In particular, R may be an alkenyl group or a phenyl group. 1~4 optionally substituted with a carboxylic acid ester group, C 1~6 Alkyl, C 3~6 Cycloalkyl, C 2~6 R may be an alkenyl group, or a phenyl group. Even more particularly, R may be one C 1~4 optionally substituted with a carboxylic acid ester group, C 1~6 Alkyl, C 5~6 Cycloalkyl, C 2~6 It may be an alkenyl group or a phenyl group.

[0019] According to an optional embodiment of the present invention, R' is C 1~16 In particular, R' can be a hydrocarbon group. 1~14 In particular, R' can be a hydrocarbon group. 1~12 In particular, R' can be a hydrocarbon group. 1~10 In particular, R' can be a hydrocarbon group. 1~8 In particular, R' may be a C 1~8 Alkanediyl, C 3~8 Cycloalkanediyl, C 2~8 In particular, R' may be an alkenediyl group or a phenylene group. 1~6 Alkanediyl, C 3~6 Cycloalkanediyl, C 2~6 In particular, R' may be an alkenediyl group or a phenylene group. 1~6 Alkanediyl, C 5~6 Cycloalkanediyl, C 2~6 It may be an alkenediyl group, or a phenylene group. Even more particularly, R' may be a 1,4-phenylene group.

[0020] According to any embodiment of the present invention, C 1~4 Alcohol is C 2~3 It may be an alcohol, preferably ethanol.

[0021] According to any embodiment of the present invention, at least one C 1~4The alcohol released from the compound containing the carboxylic acid ester, i.e., the compound of formula R 1 The compound of OH is C 1~4 Alcohols, i.e., of formula R 2 It has a lower boiling point than the compounds of C. 1~4 Alcohols, i.e., of formula R 2 The boiling points of compounds of OH and at least one C 1~4 The alcohol released from the compound containing the carboxylic acid ester, i.e., the compound of formula R 1 The difference in boiling points of the OH compounds is comprised between 10 and 30°C, in particular between 10 and 20°C, and even more particularly between 12 and 18°C.

[0022] According to any embodiment of the present invention, at least one C 1~4 The compound containing the carboxylic acid ester group is dimethyl terephthalate or dimethyl 1,4-cyclohexanedicarboxylate.

[0023] According to any embodiment of the present invention, at least one C 1~4 The alcohol released from the compound containing the carboxylic acid ester group is completely or partially removed in the separation unit, resulting in C 1~4 Alcohol is added to each reactor. In particular, C 1~4 The alcohol is the same, i.e., ethanol is added to each reactor.

[0024] According to any embodiment of the present invention, the reactor used in the process of the present invention can be any reactor suitable for a continuous process. The reactors can be the same or different. Non-limiting examples of suitable reactors can include plug flow reactors, continuous stirred tank reactors, laminar flow reactors, loop reactors, microreactors, reactors divided into multiple sections, and combinations thereof. In particular, the reactor can be a plug flow reactor, a continuous stirred tank reactor, and combinations thereof.

[0025] According to an optional embodiment of the present invention, the continuous process is carried out in two reactors. The residence time in each reactor depends on the type of reactor. The residence time can be between 0.01 and 100 hours, in particular between 0.2 and 20 hours.

[0026] According to any embodiment of the present invention, the separation unit may be a distillation column. The distillation column used in the process of the present invention may be any distillation column suitable for a continuous process. The distillation column may contain plates or trays or packing materials. Those skilled in the art can select and size the distillation column as a function of the melting and boiling points of the starting and final products.

[0027] According to any embodiment of the present invention, the distillation may be carried out at atmospheric or reduced pressure, in particular at 200×10 5 Pressures below 200 bar, e.g., 5 x 10 5 Pa~100×10 5 It can be carried out at a pressure comprised between 5 and 100 bar.

[0028] According to an optional embodiment of the present invention, the inventive process comprises: a) in a first reactor, at least one C 1~4 A compound containing a carboxylic acid ester group is subjected to a transesterification reaction with C 1~4 Transesterification with alcohol; b) then distilling the reaction mixture of step a) in a distillation column to completely or partially remove the released alcohol; and c) The reaction mixture is then flowed into a second reactor, C 1~4 Adding alcohol Includes.

[0029] According to an optional embodiment of the present invention, the C added in step a) and step c) 1~4 The alcohol is the same.

[0030] According to an optional embodiment of the present invention, the second reactor is followed by at least one separation unit, 1~4Unreacted or partially reacted compounds containing carboxylic acid ester groups, released alcohol, excess C 1~4 The alcohol and the transesterification catalyst are removed. In particular, the second reactor is followed by two separation units, which are distillation columns.

[0031] According to any embodiment of the present invention, the transesterification catalyst is a Lewis acid, a Bronsted acid or a base, in particular a Lewis acid. Specific, non-limiting examples of transesterification catalysts are tin or titanium organic compounds, tin organic compounds formed in situ by reaction of dialkyltin oxide with the acid of the ester being transesterified, preferably the oxide (C4H9)2SnO, (C8H 17 )2SnO, dialkyltin derivatives such as dibutyltin dilaurate, dicarboxylates such as dioctyltin dicarboxylate, and mixtures thereof.

[0032] The transesterification catalyst may be added to the reaction medium of the process of the present invention in a wide range of concentrations. As a non-limiting example, an acid concentration value of at least one C 1~4 About 0.001 to about 5 mol % of the compound containing a carboxylic acid ester, preferably at least one C 1~4 The range of 0.02 to about 0.5 mol% based on the amount of the compound containing the carboxylic acid ester can be mentioned. As known to those skilled in the art, the optimum concentration of the transesterification catalyst depends on the nature of the transesterification catalyst, the presence of at least one C 1~4 Properties of compounds containing carboxylic acid esters, C 1~4 It depends on the nature of the alcohol, the reaction temperature, and the process flow rate.

[0033] C 1~4 The alcohol may be added to the reaction medium of the process of the present invention in a wide range of concentrations. 1~4 At least one C as alcohol value 1~4 About 2 to about 20 equivalents relative to the amount of the compound containing the carboxylic acid ester, preferably at least one C 1~4A range of at least 5 equivalents relative to the amount of the compound containing the carboxylic acid ester can be mentioned. As known to those skilled in the art, C 1~4 The optimum concentration of alcohol is C 1~4 Alcohol properties, at least one C 1~4 It depends on the nature of the compound containing the carboxylic acid ester, the nature of the transesterification catalyst, the reaction temperature, and the flow rate of the process.

[0034] According to any one of the embodiments of the present invention, C 1~4 Alcohol is added to each reactor of the process of the present invention, in particular at the same C 1~4 Alcohol is added to each reactor.

[0035] According to any one of the embodiments of the present invention, the process of the present invention is carried out at a temperature comprised between 20° C. and 250° C. In particular, the temperature ranges between 70° C. and 200° C. Of course, the skilled person will also be able to select the preferred temperature as a function of the melting and boiling points of the starting and final products and the desired time of the reaction or conversion.

[0036] The process of the present invention 5 Pa~100×10 5 The process can be carried out at a pressure comprised between 0.1 and 100 bar, or even higher if desired. Again, the skilled person will be able to determine the catalyst loading and the at least one C 1~4 It is quite possible to adjust the pressure as a function of the compound containing the carboxylic acid ester. For example, 5 Typical pressures of 1 to 50 bar can be mentioned.

[0037] The process of the present invention may be carried out under an inert atmosphere such as nitrogen and / or argon.

[0038] The process of the present invention can be carried out in the presence or absence of a solvent. If a solvent is required or used for practical reasons, any solvent conventional for the purposes of the present invention can be used in such reaction types. The choice of solvent depends on the presence of at least one C 1~4 It is a function of the nature of the compound containing carboxylic acid ester groups and / or the catalyst, and the skilled person is fully capable of selecting the most suitable solvent in each case to optimize the reaction.

[0039] According to any one of the embodiments of the present invention, C 1~4 The alcohol and transesterification catalyst are recycled.

[0040] Two or more C's 1~4 The process of the present invention for compounds containing carboxylic acid esters involves the formation of a mono-transesterified compound as an intermediate. Such intermediates may be present at a certain level in the final reaction mixture and may be recycled in the process of the present invention. Additionally, unreacted starting materials may also be recycled in the process of the present invention.

[0041] A second object of the present invention is the use of the process defined above for producing a perfume, cosmetic or pharmaceutical product, in particular a perfume, which may in particular be diethyl 1,4-cyclohexanedicarboxylate.

[0042] A further object of the present invention is a process for preparing diethyl 1,4-cyclohexanedicarboxylate, comprising the steps of: a) transesterification of dimethyl terephthalate in the presence of ethanol as defined above to obtain diethyl terephthalate; b) reducing the diethyl terephthalate obtained in step a); It is a process that includes:

[0043] In other words, a further object of the present invention is a process for preparing diethyl 1,4-cyclohexanedicarboxylate, comprising: a) transesterification as defined above, wherein dimethyl terephthalate is reacted with ethanol in the presence of a transesterification catalyst to provide diethyl terephthalate; b) reducing the diethyl terephthalate obtained in step a); It is a process that includes:

[0044] According to any one of the embodiments of the present invention, the reduction is hydrogenation using molecular H and a hydrogenation catalyst. The hydrogenation catalyst may be a metal in elemental metallic form, in particular palladium or ruthenium in elemental metallic form.

[0045] According to any one of the above embodiments of the present invention, the palladium (Pd) or ruthenium (Ru) is supported on a support material.

[0046] For clarity, by support material is intended a material onto which such metals can be deposited and which is inert to the substrate (diethyl terephthalate).

[0047] Specific, non-limiting examples of the support material according to any one of the above embodiments of the present invention are carbon, silica or aluminum oxide. Such supports are well known to those skilled in the art.

[0048] Supported palladium (Pd) or ruthenium (Ru) catalysts are known compounds and commercially available. Those skilled in the art can select the preferred type of metal based on the method of deposition on the support, the proportion of metal on the support material, the form (powder, granules, pellets, extrudates, mousse, etc.), and the surface area of ​​the support. In particular, the hydrogenation catalyst is alumina-supported ruthenium.

[0049] According to any one of the above embodiments of the present invention, the amount of metal relative to the support may range between 0.05% and 25% w / w, or even between 0.4% and 6% by weight on the support used.

[0050] The hydrogenation catalyst can be added to the reaction medium of the process of the present invention in a wide range of concentrations. Non-limiting examples of metal concentration values ​​include values ​​ranging from 0.001 mol% to 1 mol% relative to the total amount of diethyl terephthalate. Preferably, the metal concentration is between 0.02 mol% and 1 mol%, or even between 0.04 mol% and 1 mol%. Those skilled in the art will of course know that the optimum metal concentration depends on the nature of the metal, whether the process is carried out batchwise or continuously, the temperature and pressure of the H2 used during the process, and the desired reaction time.

[0051] The hydrogenation catalyst may be recycled at the end of the process of the present invention, in other words, the hydrogenation catalyst may be recovered at the end of the process of the present invention and used several times in the process of the present invention.

[0052] According to any one of the above embodiments of the present invention, molecular hydrogen can be used either pure or mixed with an inert gas. Specific, non-limiting examples of such inert gases are nitrogen or argon. When molecular hydrogen is used in combination with an inert gas, the H / inert gas volume ratio is between 1 / 1 and 0.01 / 1, and more preferably, the ratio is 0.05 / 1.

[0053] Molecular hydrogen can be added to the reaction medium of the process of the present invention in a wide range of ratios relative to the substrate. By way of non-limiting example, values ​​ranging from 100 mol% to 5000 mol% relative to the amount of diethyl terephthalate can be cited as molecular hydrogen ratio values. Even more preferably, the molecular hydrogen concentration is between 300 mol% and 2000 mol% relative to the amount of diethyl terephthalate. Naturally, a person skilled in the art is fully capable of adjusting the pressure or flow rate of molecular hydrogen (e.g., in a continuous process) batchwise or continuously to obtain this concentration range as a function of the process. A person skilled in the art is also fully capable of adjusting the molecular hydrogen concentration as a function of the catalyst load and the dilution of diethyl terephthalate in the solvent.

[0054] The reduction can be carried out under batch or continuous conditions. According to a particular embodiment of the invention, the reduction is continuous, as this allows for increased productivity.

[0055] The reduction can be carried out in the presence or absence of a solvent. If a solvent is required or used for practical reasons, any solvent conventional for the purposes of the present invention can be used in such reaction types. Non-limiting examples include C 6~12 Aromatic solvents, such as toluene, 1,3-diisopropylbenzene, p-cymene, cumene, pseudocumene, benzyl acetate, xylene or mixtures thereof, C 3~16 Examples of suitable solvents include alkanes such as hexadecane, ether solvents such as tetrahydrofuran, butyl ether, methyltetrahydrofuran, or mixtures thereof, and esters such as ethyl acetate or diethylcyclohexyldicarboxylate (reaction product), with diethylcyclohexyldicarboxylate being the preferred solvent. The choice of solvent is a function of the hydrogenation catalyst, and those skilled in the art are well able to select the most convenient solvent in each case to optimize the reaction.

[0056] The temperature at which the reduction can be carried out is comprised between 90° C. and 300° C., more preferably in the range between 100° C. and 200° C. for a continuous process. Of course, the skilled person will also be able to select the preferred temperature as a function of the melting and boiling points of the starting and final products and the desired time of the reaction or conversion.

[0057] The reduction is 0.1 x 10 5 Pa~100×10 5 The reaction can be carried out at a pressure comprised between 0.1 and 100 bar (0.1 and 100 bar), or even higher if desired. Again, the skilled person is fully capable of adjusting the pressure as a function of the catalyst loading and the desired reaction or conversion time. For example, a pressure of 1 to 50 x 10 5 Typical pressures of 1 to 50 bar can be mentioned.

[0058] According to any one of the above embodiments of the invention, the reduction is carried out in a fixed bed reactor.

[0059] According to any one of the above embodiments of the invention, the reduction is carried out in the absence of a transesterification catalyst.

[0060] A further object of the present invention is a process for preparing diethyl 1,4-cyclohexanedicarboxylate, comprising the steps of: a) reducing dimethyl terephthalate; b) transesterifying the dimethyl 1,4-cyclohexanedicarboxylate obtained in step a) in the presence of ethanol as defined above to obtain diethyl 1,4-cyclohexanedicarboxylate; It is a process that includes:

[0061] Typical modes for carrying out the process of the invention are reported below in the Examples, with reference to the accompanying drawings.

[0062] Example The present invention will now be described in further detail by the following examples, in which abbreviations have their ordinary meaning in the art and temperatures are given in degrees Celsius (°C). The drawings are for illustrative purposes only, and the present invention should not be understood as limited to the precise arrangement and items of equipment shown in the drawings. Moreover, those skilled in the art will appreciate that additional items of equipment not shown in the drawings, such as vacuum pumps, sensors for measuring temperature or pressure, valves, etc., may be required to carry out the processes of the present invention.

[0063] Example 1 Preparation of Diethyl 1,4-Cyclohexanedicarboxylate According to the Continuous Process of the Invention 4,000 gallon (approximately 15 m) tank equipped with agitator and heating system 3In a steady-state mode, 450 kg of molten dimethyl terephthalate (DMT), 45 kg of a recycle solution of tin transesterification catalyst in diethyl terephthalate (DET) (from the bottom of C-3) containing 2 mol% of the catalyst, 70 kg of a recycle mixture of dimethyl terephthalate, ethyl methyl terephthalate (MET), and diethyl terephthalate (DET) from the top of C-3, and 520 kg of recycle ethanol (purity about 90%) from the overhead of C-2 were introduced into the pressure reactor R-1 (C-2) (per hour). The temperature of R-1 was set to 150 °C, the pressure was set to 6 bar, and the liquid level in the reactor was controlled to give an average residence time of 6 hours.

[0064] The product was continuously withdrawn from R-1, and 70 kg / h of methanol-rich distillate was removed in distillation column C-1. The residue from C-1, along with 120 kg / h of fresh ethanol, was continuously introduced into reactor R-2, similar in design to R-1, under similar conditions (pressure, temperature, residence time). The reaction mixture from R-2 was distilled in column C-2 to produce 520 kg / h of recycled ethanol (returned to R-1). The residue from C-2 was separated in column C-3, where 512 kg / h of 99.3% pure diethyl terephthalate was removed as a side draw, with 70 kg / h of overhead cut and 45 kg / h of residue recycled to R-1.

[0065] Diethyl terephthalate was continuously hydrogenated over a supported noble metal catalyst in trickle-bed catalytic reactor R-3 at 55 bar and 120°C, with approximately 75% of the reaction mixture being returned to the top of the reactor to avoid undesirable high temperatures due to the exothermic nature of the hydrogenation. The 530 kg / h effluent, containing approximately 90% diethyl 1,4-cyclohexanedicarboxylate (DECC), 6% unreacted starting materials, and 4% hydrogenation by-products, was distilled in column C-4 to produce 465 kg / h of diethyl 1,4-cyclohexanedicarboxylate as a side-draw stream, and 35 kg / h of diethyl terephthalate was recovered from the bottom and sent to the recycle feed system of reactor R-3.

[0066] Example 2 Preparation of diethyl 1,4-cyclohexanedicarboxylate according to the process of the present invention The process up to the hydrogenation of diethyl terephthalate was carried out as in Example 1, except that instead of continuous hydrogenation in a fixed-bed reactor, diethyl terephthalate was hydrogenated in a high-pressure autoclave at 70 bar / 140° C. for 12 hours. The reaction mixture contained 99.0% 1,4-cyclohexanedicarboxylate, less than 0.05% unreacted diethyl terephthalate, and 1.0% by-products.

[0067] Example 3 Preparation of diethyl terephthalate (comparative example) 21,000 kg of dimethyl terephthalate flakes and a 0.2 mol% soluble tin catalyst were added to a 10,000 gallon (37.5 m) distillation column equipped with a heating system, agitator, and a distillation column. 3 The reactor was charged with dimethyl terephthalate at a pressure rating of 1000 kJ / s. The heating was turned on, and the dimethyl terephthalate melted within 18 hours. The pressure was then set to 3 bar, and 4,000 kg of ethanol was pumped in. As the reaction by-product methanol distilled off (vapor flow to the heater at approximately 500 kg / h), more fresh ethanol was added, gradually enriching the distillate composition with ethanol. After 90 hours, the reaction mixture contained 91% diethyl terephthalate (excluding ethanol and methanol), and approximately 11,000 kg of alcohol by-products (approximately 50% each of methanol and ethanol) had distilled off. After distilling the remaining material in the reactor in a separate still, approximately 17,000 kg of pure diethyl terephthalate was obtained, corresponding to a productivity of 157 kg / h (including melting and reaction time, but excluding charging and preparation time).

Claims

1. At least one C １～４ The compound containing a carboxylic acid ester group is １～４ 1. A continuous process for transesterification in the presence of an alcohol and a transesterification catalyst, wherein said transesterification step is carried out in at least two subsequent reactors separated by a separation unit.

2. The at least one C １～４ The alcohol released from the compound containing a carboxylic acid ester group is completely or partially removed in the separation unit, and the C １～４ 10. The continuous process of claim 1 wherein alcohol is added to each reactor.

3. 3. The continuous process of claim 1 or 2 carried out in two reactors.

4. 4. The continuous process of claim 1, wherein the second reactor is followed by one or two separation units.

5. 5. The continuous process of claim 1, wherein the separation unit is a distillation column.

6. 6. The continuous process of claim 1, wherein the transesterification catalyst is a Lewis acid, a Bronsted acid, or a base.

7. The transesterification catalyst may be a tin or titanium organic compound, a tin organic compound formed in situ by reaction of a dialkyltin oxide with the acid of the ester being transesterified, (C ４ H ９ ) ２ SnO, (C ８ H １７ ) ２ 7. The continuous process of claim 1, wherein the catalyst is selected from the group consisting of SnO, dibutyltin dilaurate, dioctyltin dicarboxylate, and mixtures thereof.

8. The at least one C １～４ 8. The continuous process of claim 1, wherein the compound containing a carboxylic acid ester group is a diester compound.

9. The carboxylic acid ester group is C １ 9. The continuous process of claim 1, wherein the carboxylic acid ester group is a carboxylic acid ester group.

10. The at least one C １～４ 10. The continuous process of claim 1, wherein the compound containing a carboxylic acid ester group is dimethyl terephthalate.

11. The alcohol is C ２～３ 11. A continuous process according to any one of claims 1 to 10, wherein the alcohol is preferably ethanol.

12. 1. A process for preparing diethyl 1,4-cyclohexanedicarboxylate, comprising: a) transesterifying dimethyl terephthalate in the presence of ethanol as defined in claims 1 to 11 to obtain diethyl terephthalate; b) reducing the diethyl terephthalate obtained in step a); The process includes:

13. The process of claim 12, wherein the reduction is carried out under continuous conditions.

14. The reduction is carried out by using molecular H ２ and hydrogenation using a hydrogenation catalyst.

15. 15. The process of any one of claims 12 to 14, wherein the hydrogenation catalyst is selected from the group consisting of supported Ru or Pd metal, more preferably alumina supported ruthenium.

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