Process for hydrofinishing isooctanoic acid

Abstract

The application relates to the chemical process field and discloses a method for hydrofining isooctanoic acid, which comprises the following steps: in the presence of a reduction catalyst, crude isooctanoic acid is contacted with hydrogen to perform a reduction reaction. By using the method for hydrofining isooctanoic acid provided by the application, the product quality can be improved by completely removing substances containing carbon-carbon double bonds and aldehyde ketone carbonyl in the reaction system, the product can keep stable for a long time, the content of isooctanoic acid isooctyl ester in heavy components obtained through rectification is obviously reduced, the residual liquid after separation of isooctanoic acid only contains isooctanoic acid and a catalyst, and the residual liquid can be directly recycled as the catalyst without separation and purification, so that the operation process is simplified.

Description

Technical Field

[0001] This invention relates to the field of chemical processes, and more specifically, to a method for hydrogenating and refining isooctanoic acid. Background Technology

[0002] Isooctanoic acid, also known as 2-ethylhexanoic acid, is an important organic intermediate and a high-value-added fine chemical. Isooctanoic acid readily reacts with metals to form metal salts, including Mn, Co, Ca, and Na salts, which are the main downstream products. Due to its excellent application performance and green, pollution-free characteristics, it can replace some traditional chemical raw materials, promoting the green upgrading of production processes and products. In addition, high-performance cold-resistant plasticizers synthesized from isooctanoic acid also have significant application value.

[0003] Currently, there are two main process routes for producing high-purity isooctanoic acid. Globally, the butyraldehyde condensation method is the most common. First, butyraldehyde is condensed to prepare 2-ethylhexenal, which uses platinum and nickel catalysts, or sometimes palladium and rare earth oxides as catalysts. The support is γ-Al₂O₃ or silica gel. Selective hydrogenation is then used to produce isooctaldehyde, with isooctyl alcohol as a byproduct. Isooctaldehyde is then oxidized to isooctanoic acid using potassium permanganate, Mn acetate, or Co acetate as catalysts. In the above production process, some butyraldehyde and isooctaldehyde will inevitably not be completely converted. Simultaneously, the reaction will produce byproducts such as 3-heptaethyl formate, 3-heptanone, and isooctenoic acid. These byproducts contain unsaturated groups, and these unsaturated impurities have a significant impact on downstream applications such as high-end refrigeration oils. In existing technologies, while introducing excess hydrogen or using a more active catalyst in the isooctaldehyde hydrogenation step can reduce the residual isooctaldehyde and butyraldehyde in the product, it will also lead to excessive hydrogenation of isooctaldehyde to generate isooctyl alcohol, increasing the content of 3-heptanone. Therefore, developing a process for preparing high-purity isooctanoic acid is particularly important.

[0004] Therefore, there is an urgent need for a process to prepare high-purity isooctanoic acid in order to reduce the content of impurities in isooctanoic acid products. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems existing in the prior art and to provide a method for hydrogenating and refining isooctanoic acid.

[0006] To achieve the above objectives, the present invention provides a method for hydrogenating isooctanoic acid, the method comprising: contacting crude isooctanoic acid with hydrogen gas in the presence of a reduction catalyst to carry out a reduction reaction.

[0007] The beneficial effects of the present invention through the above technical solution include at least the following:

[0008] The hydrogenation refining process for isooctanoic acid provided by this invention can improve product quality by completely removing substances containing carbon-carbon double bonds and aldehyde-ketone carbonyl groups from the reaction system, allowing the product to maintain stable properties for a long time. At the same time, it unexpectedly reduces the content of isooctanoic acid isooctyl ester in the heavy fraction residue obtained from distillation, so that the residue remaining after isooctanoic acid separation contains only isooctanoic acid and catalyst, which can be directly recycled as catalyst, simplifying the operation process. Detailed Implementation

[0009] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0010] The first aspect of this invention provides a method for hydrogenating and refining isooctanoic acid. The method includes: contacting crude isooctanoic acid with hydrogen gas in the presence of a reducing catalyst to carry out a reduction reaction. This method can remove substances containing carbon-carbon double bonds and aldehyde / ketone carbonyl groups from the reaction system, improving product quality and allowing the product to maintain stable properties over a long period. Furthermore, and importantly, the byproduct isooctanoate, which was previously present in the distillation residue of heavy components in existing processes, is no longer present, making it easier to recover the catalyst from the heavy components.

[0011] In this invention, the method further includes the step of preparing the crude isooctanoic acid:

[0012] (1) In the presence of a first solvent and a first catalyst, isooctenealdehyde is contacted with hydrogen to carry out a first reaction to obtain a material containing isooctenealdehyde. According to the present invention, a material containing isooctenealdehyde can be extracted from the butanol and octanol unit of Sinopec Anqing Petrochemical Company, which may contain n-butyraldehyde, the raw material for the preparation of butanol and octanol, and isooctol, a reaction byproduct.

[0013] (2) In the presence of a second solvent and a second catalyst, the material containing isooctaldehyde is brought into contact with oxygen to carry out a second reaction to obtain crude isooctanoic acid.

[0014] In this invention, the first solvent can be a C1-C10 alcohol, such as at least one of methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, and decanol, preferably isooctanol.

[0015] In this invention, the volume ratio of the first solvent to the material containing isooctenealdehyde can be (2-10):1, for example, it can be 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, and any range of any two values ​​and any value within the range, preferably (4-7):1.

[0016] In this invention, the first catalyst comprises a support and an active component loaded on the support. Preferably, the support is alumina microspheres coupled with a polyvinyl imidazole polymer, and the active component is Pd. More preferably, the loading of Pd in ​​the first catalyst is 0.005-0.001 wt%.

[0017] In this invention, the molar ratio of hydrogen to isooctene can be (2-20):1, for example, it can be 2:1, 4:1, 6:1, 8:1, 10:1, 12:1, 14:1, 16:1, 18:1, 20:1, and any range of any two values ​​and any value within the range, preferably (5-15):1.

[0018] In this invention, the conditions for the first reaction include: a temperature of 40-60°C, a pressure of 0.5-5 MPa, and a liquid hourly space velocity (LHSV) of hydrogen of 0.05-1 h⁻¹. -1 .

[0019] In this invention, the method for preparing the crude isooctanoic acid may further include: performing a first distillation on the product of the first reaction. The first distillation may be carried out using distillation apparatus and methods commonly used in the art. It may be carried out in a distillation column, and may be continuous or intermittent. According to this invention, the distillation can be carried out by gradually increasing the temperature and collecting the fraction between 100-130°C to obtain the light component (isooctanal). The remaining heavy component is mainly isooctyl alcohol, which can be recovered and recycled.

[0020] In this invention, the second solvent is a C1-C10 carboxylic acid, such as at least one of formic acid, acetic acid, propionic acid, isopropionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, hexanoic acid, isohexanoic acid, octanoic acid, and isooctanoic acid, preferably isooctanoic acid.

[0021] In this invention, the mass ratio of the second solvent to the material containing isooctaldehyde can be (1-10):1, for example, it can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, and any range between any two values ​​and any value within the range.

[0022] In this invention, the second catalyst can be a carboxylate, for example, at least one of the following: alkali metal salt, alkaline earth metal salt, manganese salt, cobalt salt, copper salt, iron salt, and zinc salt of C2-C10 carboxylic acids, preferably isooctanoate, more preferably sodium isooctanoate.

[0023] In this invention, the weight ratio of the second catalyst to the material containing isooctaldehyde can be 1:(100-300), for example, it can be 1:100, 1:130, 1:160, 1:190, 1:220, 1:250, 1:280, 1:300, and any range between any two values ​​and any value within the range.

[0024] In this invention, the molar ratio of oxygen to isooctaldehyde-containing material is (0.5-1):1.

[0025] According to the present invention, the gas containing the oxygen can be a gas conventionally used in the art, for example, it can be provided in the form of pure oxygen, or it can contain other inactive gases, but according to some preferred embodiments of the present invention, the oxygen can be provided using air.

[0026] In this invention, the conditions for the second reaction include: the temperature can be 50-70℃, for example, 50℃, 52℃, 54℃, 56℃, 58℃, 60℃, 62℃, 64℃, 66℃, 68℃, 70℃, and any value between any two of these values; the pressure can be 1-10MPa, for example, 1MPa, 2MPa, 3MPa, 4MPa, 5MPa, 6MPa, 7MPa, 8MPa, 9MPa, 10MPa, and any value between any two of these values; and the time can be 1-10h.

[0027] In this invention, the active component in the reduction catalyst may include at least one of nickel, palladium, ruthenium, rhodium, iridium, manganese, copper, and chromium, preferably nickel and / or palladium. This catalyst can be prepared in-house or commercially available. According to a preferred embodiment of the invention, the reduction catalyst is a palladium-on-carbon catalyst, wherein the palladium content is 5-15 wt%, and the support is activated carbon. According to another preferred embodiment of the invention, the reduction catalyst is a nickel catalyst, with a nickel content >90% and an average particle size <50 μm.

[0028] In this invention, the reduction reaction can be carried out intermittently or continuously. In some preferred embodiments of this invention, the reduction reaction is carried out intermittently, and the mass ratio of the catalyst to crude isooctanoic acid is preferably (0.0001-0.05):1.

[0029] In this invention, the volume ratio of hydrogen gas to the solution containing crude isooctanoic acid can be 1:(0.5-2), for example, it can be 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, and any range of any two values ​​and any value within that range, preferably 1:(0.5-1).

[0030] In this invention, the conditions for the reduction reaction include: the temperature can be 45-90℃, for example, 45℃, 49℃, 53℃, 57℃, 61℃, 65℃, 69℃, 73℃, 77℃, 81℃, 85℃, 90℃, and any value within any two of these ranges; the pressure can be 0.09-6MPa; and the time can be 0.5-10h, for example, 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, and any value within any two of these ranges.

[0031] In this invention, the method further includes: performing a second distillation on the product of the reduction reaction to obtain isooctanoic acid. The second distillation can be carried out using equipment conventionally used in the art, such as at least one of a rotary evaporator, a reflux distiller, and a distillation column. The appropriate equipment can be flexibly selected according to the product purity requirements. The distillation apparatus and process parameters can be designed according to the required purity, for example, by evaporative distillation, which will not be elaborated here.

[0032] According to the most preferred embodiment of the present invention, a method for preparing isooctanoic acid includes:

[0033] (1) Under palladium catalyst conditions, isooctenealdehyde and isooctyl alcohol are mixed at a volume ratio of 1:(4-6), and hydrogen gas is added simultaneously (isooctenaldehyde:hydrogen = 1:(9-11), molar ratio). The reaction temperature is 48-52℃, the reaction pressure is 1.5-2.5MPa, and the liquid hourly space velocity of hydrogen is 0.05-0.15h. -1 The reacted material was distilled to obtain a material containing isooctaldehyde.

[0034] (2) Take materials containing isooctaldehyde, isooctanoic acid and sodium isooctanoate in a weight ratio of (150-175):(600-700):1 and carry out an oxidation reaction at a reaction temperature of 58-62℃, a pressure of 2.5-3.5MPa and a reaction time of 2.8-3.5h to obtain crude isooctanoic acid;

[0035] (3) Hydrogen gas and crude isooctanoic acid are mixed at a volume ratio of 1:(0.7-0.9). The catalyst is a palladium-on-carbon catalyst (palladium content on carbon is 8-12 wt%), and the mass ratio of palladium-on-carbon catalyst to crude isooctanoic acid is (0.003-0.007):1. The reaction temperature is 48-52℃, the reaction pressure is 4.5-5.5 MPa, and the reaction time is 3-5 hours. The product obtained from the reaction is subjected to vacuum distillation to obtain isooctanoic acid product. The isooctanoic acid content in the isooctanoic acid product reaches more than 99 wt%, and the residue after distillation contains only isooctanoic acid and catalyst, without any other substances.

[0036] This invention also relates to a method for reducing the content of isooctanoate in isooctanoic acid products (including the steps described above) or the application of the method described above in reducing the content of isooctanoate in isooctanoic acid products.

[0037] The present invention will be described in detail below through embodiments.

[0038] CN 116041159 B Catalyst prepared in Example 1: Alumina microspheres coupled with polyvinylimidazole, the alumina microspheres having a diameter of 345 μm and a coefficient of variation of 7.2%; the palladium content was 0.0097 wt%.

[0039] Palladium on carbon catalyst: purchased from Beijing Innocare Technology Co., Ltd., item number P1505, supported by activated carbon, with a palladium content of 10wt%.

[0040] Nickel catalyst: purchased from Bailingwei Technology Co., Ltd., item number 984558, nickel catalyst, nickel content >90wt%, average particle size <50μm;

[0041] Ruthenium-carbon catalyst: purchased from Bailingwei Technology Co., Ltd., product number 917027, ruthenium content >5wt%, carrier is activated carbon.

[0042] Example 1

[0043] (1) Isoctenal collected from the butanol and octanol unit was mixed with isooctanol at a volume ratio of 1:5, preheated, and then mixed again with hydrogen (isooctenal:hydrogen = 1:10, molar ratio). The mixture was then introduced into a fixed bed containing 20 mL of the catalyst prepared according to Example 1 of CN 116041159B. The reaction temperature was 50°C, the reaction pressure was 2 MPa, and the liquid hourly space velocity of hydrogen was 0.1 h⁻¹. -1 The reactants were collected, and the material was distilled using a molecular distillation apparatus, and the distillate was collected (the collection and distillation apparatus were purged with nitrogen for 30 minutes beforehand). The distillation column was packed with 100 cm of packing material. During the distillation process, the temperature of the apparatus was gradually increased from 45°C to 165°C (the heating rate was 5°C / min). The fraction before the temperature reached 165°C was collected to obtain the material containing isooctaldehyde.

[0044] (2) Take 20g of material containing isooctaldehyde and mix it with 80g of isooctanoic acid in an oxidation reactor. Add 0.12g of sodium isooctanoate as a catalyst and pass air in as an oxidant. The reaction temperature is 60℃, the pressure is 3MPa, and the reaction time is 3h to obtain crude isooctanoic acid.

[0045] (3) After the reaction, crude isooctanoic acid was mixed with the residual gas from the synthesis of isooctaldehyde (containing hydrogen, with a content of 99 vol%), with a hydrogen to crude isooctanoic acid volume ratio of 1:0.8. This mixture was then introduced into a reactor containing a palladium-on-carbon catalyst, with a palladium-on-carbon catalyst to crude isooctanoic acid mass ratio of 0.005:1. The reaction temperature was 50℃, the reaction pressure was 5 MPa, and the reaction time was 4 hours. After removing the reaction product and reducing the pressure to 10 kPa (abs), the liquid material was distilled using a vacuum distillation apparatus, and the distillate was collected (the collection apparatus and distillation apparatus were purged with nitrogen for 30 min beforehand). During the distillation process, the temperature of the apparatus was gradually increased from 45℃ to 130℃ (the heating rate was 5℃ / min). The fraction with a temperature between 100-130℃ was collected to obtain the isooctanoic acid product. The remaining residue was then evaporated to dryness. The liquid material obtained by condensing the gas volatilized during evaporation was analyzed using a high-resolution gas chromatography-mass spectrometry (GC-MS) instrument. The components and peak area normalization values ​​(in %) of the isooctene aldehyde raw material, isooctanoic acid product (Table 1) and the condensed liquid material were analyzed. The contents of isooctanoic acid and isooctene aldehyde were determined using standards. The conversion rate of isooctene aldehyde and the yield of isooctanoic acid were calculated, as shown in Table 3.

[0046] Example 2

[0047] (1) Isoctenal collected from the butanol and octanol unit was mixed with isooctanol at a volume ratio of 1:6, preheated, and then mixed again with hydrogen (isooctenal:hydrogen = 1:11, molar ratio). The mixture was then introduced into a fixed bed containing 25 mL of the catalyst prepared according to Example 1 of CN 116041159B. The reaction temperature was 48°C, the reaction pressure was 2.5 MPa, and the liquid hourly space velocity of hydrogen was 0.2 h⁻¹. -1 The reactants were collected, and the material was distilled using a molecular distillation apparatus, and the distillate was collected (the collection and distillation apparatus were purged with nitrogen for 30 minutes beforehand). During distillation, the distillation column was packed with 100 cm of packing material, and the temperature of the apparatus was gradually increased from 45°C to 165°C (the heating rate was 5°C / min). The fraction before the temperature reached 165°C was collected to obtain the material containing isooctaldehyde.

[0048] (2) Take 20g of material containing isooctaldehyde and mix it with 85g of isooctanoic acid in an oxidation reactor. Add 0.15g of sodium isooctanoate as a catalyst and pass air in as an oxidant. The reaction temperature is 65℃, the pressure is 2.5MPa, and the reaction time is 2.5h to obtain crude isooctanoic acid.

[0049] (3) After the reaction, crude isooctanoic acid was mixed with the residual gas from the synthesis of isooctaldehyde (containing hydrogen, with a content of 99 vol%) and passed into a reactor containing a nickel catalyst. The volume ratio of hydrogen to crude isooctanoic acid was 1:0.7, and the mass ratio of nickel catalyst to crude isooctanoic acid was 0.005:1. The reaction temperature was 80℃, the reaction pressure was 5 MPa, and the reaction time was 2 hours. After the reaction product was depressurized to 10 kPa (abs), the liquid material was distilled using a vacuum distillation apparatus, and the distillate was collected (the collection apparatus and distillation apparatus were purged with nitrogen for 30 min beforehand). During the distillation process, the temperature of the apparatus was gradually increased from 45℃ to 130℃ (the heating rate was 5℃ / min). The fraction with the temperature between 100-130℃ was collected to obtain the isooctanoic acid product. The remaining residue was then evaporated to dryness. The liquid material obtained by condensing the gas volatilized during evaporation was analyzed using a high-resolution gas chromatography-mass spectrometry (GC-MS) instrument. The composition of the isooctene aldehyde raw material, isooctanoic acid product (Table 1), and the liquid material obtained by condensation were analyzed (Table 2) and the peak area normalization value (in %). The contents of isooctanoic acid and isooctene aldehyde were determined based on the use of standards. The conversion rate of isooctene aldehyde and the yield of isooctanoic acid were calculated, as shown in Table 3.

[0050] Example 3

[0051] Isooctanoic acid was prepared according to the method in Example 1, except that the catalyst used in step (3) was a ruthenium carbon catalyst.

[0052] Example 4

[0053] Isooctanoic acid was prepared according to the method in Example 1, except that the reaction conditions in step (3) were 90°C and atmospheric pressure.

[0054] Comparative Example 1

[0055] Isooctanoic acid was prepared according to the method in Example 1, except that after obtaining crude isooctanoic acid, it was directly distilled according to the method in step (3) without adding a catalyst.

[0056] Table 1

[0057] Compound Name Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Isooctanoic acid 99.61 99.45 99.21 95.98 94.61 3-Heptyl formate 0.14 0.27 0.51 1.34 1.92 3-Hepanotone ND ND ND 0.12 0.23 3-Heptanol 0.06 0.12 0.05 0.04 0.27 2-Ethylhexanol 0.17 0.13 0.15 0.11 0.15 n-Butanol 0.02 0.04 0.02 0.02 0.01 n-Butyraldehyde ND ND ND 0.03 0.03 2-Ethylhexaldehyde ND ND ND 0.05 0.07 2-Ethylhexenal ND ND ND ND 0.03 2-Ethylhexenoic acid ND ND ND ND 0.21 butyric acid ND ND ND ND 0.01 2-Ethylhexanoate-2-ethylhexyl ester ND ND 0.05 2.3 2.45

[0058] Table 2

[0059]

[0060]

[0061] In Table 1-2, ND indicates that the substance was not detected.

[0062] Table 3

[0063] serial number Isooctanoic acid content, wt% Conversion rate of isoocteneal, % Yield of isooctanoic acid, % Example 1 99.61 99.9 95.35 Example 2 99.45 99.9 95.36 Example 3 99.20 99.9 95.29 Example 4 95.76 99.9 95.25 Comparative Example 1 94.61 99.9 95.25

[0064] The data in Table 1 shows that the hydrogenation refining process provided by the present invention can significantly reduce the content of unsaturated impurities in isooctanoic acid products and increase the content of isooctanoic acid in isooctanoic acid products.

[0065] As shown in Table 2, the distillation residue obtained by this invention has high purity of isooctanoic acid and does not contain 2-ethylhexanoate-2-ethylhexyl ester. Therefore, it is not necessary to purify the catalyst from the distillation residue. The distillation residue can be directly used as a catalyst for the subsequent production of isooctanoic acid, and can be directly recycled, making the overall process shorter and the cost lower.

[0066] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for hydrogenating and refining isooctanoic acid, characterized in that, The method includes: reducing crude isooctanoic acid by contacting it with hydrogen in the presence of a reducing catalyst.

2. The method according to claim 1, wherein, The method further includes the step of preparing the crude isooctanoic acid: (1) In the presence of a first solvent and a first catalyst, isooctenealdehyde is brought into contact with hydrogen to carry out a first reaction to obtain a material containing isooctenealdehyde. (2) In the presence of a second solvent and a second catalyst, the material containing isooctaldehyde is brought into contact with oxygen to carry out a second reaction to obtain crude isooctanoic acid.

3. The method according to claim 2, wherein, The first solvent is a C1-C10 alcohol, preferably isooctyl alcohol; And / or, the volume ratio of the first solvent to the material containing the isoocteneal is (2-10):1; And / or, the first catalyst includes a support and an active component supported on the support, preferably, the support is alumina microspheres coupled with a polyvinyl imidazole polymer, and the active component is Pd; And / or, the molar ratio of hydrogen to isooctenealdehyde is (2-20):

1.

4. The method according to claim 2, wherein, The conditions for the first reaction include: a temperature of 40-60℃, a pressure of 0.5-5 MPa, and a liquid hourly space velocity (LHSV) of hydrogen of 0.05-1 h⁻¹. -1 .

5. The method according to claim 2, wherein, The method for preparing the crude isooctanoic acid further includes: subjecting the product of the first reaction to a first distillation.

6. The method according to claim 2, wherein, The second solvent is a C1-C10 carboxylic acid, preferably isooctanoic acid; And / or, the mass ratio of the second solvent to the material containing isooctaldehyde is (1-10):1; And / or, the second catalyst is a carboxylate, preferably isooctanoate, more preferably sodium isooctanoate; And / or, the weight ratio of the second catalyst to the isooctaldehyde-containing material is 1:(100-300); And / or, the molar ratio of oxygen to isooctaldehyde-containing material is (0.5-1):

1.

7. The method according to claim 2, wherein, The conditions for the second reaction include: a temperature of 50-70℃, a pressure of 1-10MPa, and a time of 1-10h.

8. The method according to any one of claims 1-7, wherein, The active component in the reduction catalyst includes at least one of nickel, palladium, ruthenium, rhodium, iridium, manganese, copper, and chromium, preferably nickel and / or palladium.

9. The method according to any one of claims 1-7, wherein, The volume ratio of hydrogen to crude isooctanoic acid is 1:(0.5-2).

10. The method according to any one of claims 1-7, wherein, The conditions for the reduction reaction include a temperature of 45-90℃ and a pressure of 0.09-6MPa.

11. The method according to any one of claims 1-7, wherein, The method further includes: subjecting the product of the reduction reaction to a second distillation to obtain isooctanoic acid.

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