A process for the continuous production of dimethyl cyclohexanedicarboxylate

Abstract

The application provides a process for continuously producing cyclohexane dicarboxylic acid dimethyl ester, comprising: S1. feeding a raw material stream comprising hydrogen, dimethyl phthalate and dimethyl cyclohexane dicarboxylate into a reactor from a bottom inlet of the reactor, and obtaining a post-reaction stream at a top outlet of the reactor; S2. performing gas-liquid separation on the post-reaction stream to obtain circulating hydrogen and a liquid phase stream; S3. circulating part of the circulating hydrogen to the reactor, and removing the remaining part from the reaction zone; S4. circulating part of the liquid phase stream to the reactor, and collecting the remaining part as a product. The application improves the conversion rate of dimethyl phthalate and the selectivity of the target product dimethyl cyclohexane dicarboxylate by improving the traditional feeding mode.

Description

Technical Field

[0001] This invention relates to the field of preparation technology of dimethyl cyclohexanedicarboxylate, and specifically to a process for the continuous production of dimethyl cyclohexanedicarboxylate. Background Technology

[0002] 1,4-Cyclohexanediethanol (CHDM) is an important monomer for synthesizing high-performance polyester resins. Polyester products synthesized from CHDM have better thermal stability, transparency, impact resistance, abrasion resistance, and corrosion resistance than ordinary polyester resins (PET, PBT, etc.).

[0003] Currently, industrial production of CHDM mainly uses dimethyl terephthalate (DMT) as a raw material, which is then produced through a two-step hydrogenation process. The first step involves hydrogenating DMT to produce dimethyl cyclohexanedicarboxylate (DMCD), and the second step involves hydrogenating the ester group of DMCD to obtain CHDM. Therefore, DMCD is an important intermediate in the preparation of CHDM.

[0004] Dimethyl 1,4-cyclohexanedicarboxylate has been prepared as an intermediate in the preparation of CHDM for over 30 years. US 3,334,149 describes a method for preparing dimethyl 1,4-cyclohexanedicarboxylate and 1,4-cyclohexanediethanol from dimethyl terephthalate. This method requires high pressure, for example, greater than 346 bar, during the hydrogenation of dimethyl terephthalate to produce dimethyl 1,4-cyclohexanedicarboxylate.

[0005] CN 105056996 A discloses a catalyst for the selective hydrogenation of dimethyl terephthalate to dimethyl 1,4-cyclohexanedicarboxylate, as well as its preparation and application methods. The catalyst is composed of Ru particles, and the surface of the Ru particles is modified with Ru-S and Ru-O coordination bonds. The preparation steps include: solution preparation, reduction reaction, precipitation washing, molecular modification, and post-treatment. Compared with existing technologies, the catalyst of this invention exhibits better catalytic activity and target product selectivity for the selective hydrogenation of dimethyl terephthalate to dimethyl 1,4-cyclohexanedicarboxylate, with milder hydrogenation conditions and shorter reaction time. This technical solution does not improve the preparation process of dimethyl 1,4-cyclohexanedicarboxylate.

[0006] CN 111187167 A discloses a method for preparing dimethyl 1,4-cyclohexanedicarboxylate, comprising: providing a continuous reactor filled with a plurality of Ru / Al₂O₃ catalyst particles with a particle size of 1.5 to 5.0 mm, wherein the Ru / Al₂O₃ catalyst particles in the continuous reactor have a packing density of 0.4 to 0.7 g / cm², and wherein the ruthenium metal dispersion of the plurality of Ru / Al₂O₃ catalyst particles is 13% or more; and in the continuous reactor, subjecting a reactant solution containing dimethyl terephthalate and dimethyl 1,4-cyclohexanedicarboxylate to a hydrogenation reaction with hydrogen gas at a pressure of 20 to 30 kg / cm² to obtain dimethyl 1,4-cyclohexanedicarboxylate. The method provided by this invention can effectively improve the conversion rate, exhibits excellent catalytic activity during hydrogenation, and reduces post-processing costs, making it valuable for industrial applications. This technical solution mainly focuses on the distribution mode of the catalyst, without considering the influence of the feeding method. Summary of the Invention

[0007] In view of the problems existing in the prior art, the purpose of the present invention is to provide a process for continuous production of dimethyl cyclohexanedicarboxylate, which improves the conversion rate of dimethyl phthalate and the selectivity of the target product dimethyl cyclohexanedicarboxylate by improving the traditional feeding method.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A process for the continuous production of dimethyl cyclohexanedicarboxylate, comprising:

[0010] S1. A feed stream containing hydrogen, dimethyl phthalate and dimethyl cyclohexanedicarboxylate is fed into the reactor from the bottom inlet, and a post-reaction stream is obtained at the top outlet of the reactor.

[0011] S2. Perform gas-liquid separation on the reaction post-flow to obtain recycled hydrogen and liquid phase flow;

[0012] S3. A portion of the circulating hydrogen is recycled back to the reactor, while the remainder is removed from the reaction zone;

[0013] S4. A portion of the liquid phase stream is recycled back to the reactor, and the remainder is collected as a product.

[0014] In some preferred embodiments of the present invention, the weight ratio of circulating hydrogen gas to the reactor to circulating hydrogen gas removed from the reaction zone is (90-100):(0-10).

[0015] In some preferred embodiments of the present invention, the weight ratio of the liquid phase material recycled to the reactor to the liquid phase stream collected as a product is (50-98):(2-50).

[0016] In some preferred embodiments of the present invention, in step S1, the hydrogen in the raw material stream is fresh hydrogen and / or recycled hydrogen from step S2.

[0017] In some preferred embodiments of the present invention, in step S1, the dimethyl phthalate in the raw material stream is dimethyl phthalate from fresh raw material and / or dimethyl phthalate from the circulating liquid stream of step S4.

[0018] In some preferred embodiments of the present invention, in step S1, the dimethyl cyclohexanedicarboxylate in the raw material stream is dimethyl cyclohexanedicarboxylate from fresh raw materials and / or dimethyl cyclohexanedicarboxylate from the circulating liquid phase stream of step S4.

[0019] According to the present invention, the raw material stream includes fresh raw materials, fresh hydrogen, recycled liquid phase materials, and recycled hydrogen.

[0020] In the context of this invention, fresh ingredients refer to freshly added ingredients.

[0021] In some preferred embodiments of the present invention, in step S1, the mass ratio of dimethyl phthalate to dimethyl cyclohexanedicarboxylate in the fresh raw material is (1-5):(5-9), preferably (2-4):(6-8).

[0022] According to the present invention, in the post-reaction stream, the conversion rate of dimethyl phthalate to dimethyl cyclohexanedicarboxylate by hydrogenation is greater than or equal to 98% molar.

[0023] In some preferred embodiments of the present invention, in step S1, the weight ratio of dimethyl phthalate and dimethyl cyclohexanedicarboxylate in the raw material stream is 1:(1-99), preferably 1:(5-50), more preferably 1:(10-50), and even more preferably 1:(15-50).

[0024] In some preferred embodiments of the present invention, in step S1, the molar ratio of hydrogen to dimethyl phthalate is controlled to be (10-100):1, preferably (10-50):1, and more preferably (10-35):1.

[0025] In some preferred embodiments of the present invention, in step S1, the liquid space velocity of the dimethyl phthalate is controlled to be 0.01 h⁻¹. -1 ~1h -1 Preferably 0.1h -1 ~1h-1 Further preferably 0.1h -1 ~0.5h -1 .

[0026] In some preferred embodiments of the present invention, in step S1, controlling the reaction conditions of the reactor includes: a pressure of 1 MPa to 10 MPa and a temperature of 100°C to 160°C.

[0027] In some preferred embodiments of the present invention, the reactor is a bubble-type reactor, more preferably a bubble-type fixed-bed reactor.

[0028] In some preferred embodiments of the present invention, the reactor is filled with a hydrogenation catalyst, the hydrogenation catalyst comprising a support and an active component and an auxiliary component supported on the support, the support being selected from at least one of alumina and silica, the active component comprising ruthenium, and the auxiliary component being selected from at least one of alkali metal oxides and alkaline earth metal oxides.

[0029] In some preferred embodiments of the present invention, based on the total weight of the hydrogenation catalyst, the content of the support is 75wt% to 99.3wt%, the content of the active component is 0.2wt% to 5wt%, and the content of the auxiliary component is 0.5wt% to 20wt%.

[0030] In some preferred embodiments of the present invention, the specific surface area of ​​the carrier is 80–230 m². 2 / g; and / or pore size of 5–20 nm; and / or pore volume of 0.3–0.8 cm³ 3 / g.

[0031] In some preferred embodiments of the present invention, the chlorine content in the catalyst is less than 1.0% of the total weight of the catalyst.

[0032] In some preferred embodiments of the present invention, the catalyst is prepared by calcination in air at a temperature range of 350°C to 550°C, and / or the catalyst is selected from a chlorine-free ruthenium precursor, and / or the catalyst is washed with an alkaline liquid so that the chlorine content in the catalyst is less than 1.0% of the total weight of the catalyst.

[0033] In some preferred embodiments of the present invention, the dimethyl phthalate is dimethyl terephthalate, dimethyl isophthalate, or dimethyl phthalate, and correspondingly, the dimethyl cyclohexanedicarboxylate is 1,4-cyclohexanedicarboxylate, 1,3-cyclohexanedicarboxylate, or 1,2-cyclohexanedicarboxylate. Preferably, the dimethyl phthalate is dimethyl terephthalate, and the dimethyl cyclohexanedicarboxylate is 1,4-cyclohexanedicarboxylate.

[0034] The beneficial effects of the present invention are at least as follows: by improving the feeding method, the present invention can achieve a conversion rate of over 99% for dimethyl phthalate, while the selectivity of the target product, dimethyl cyclohexanedicarboxylate, can reach over 95%. Attached Figure Description

[0035] Figure 1 This is a process flow diagram of Embodiment 1 of this application.

[0036] Explanation of reference numerals in the attached diagram: 1-Fresh dimethyl phthalate feed line; 2-Fresh hydrogen feed line; 3-Mixed feed line; 4-Circulating hydrogen feed line; 5-Reactor; 6-Gas-liquid separator; 7-Condenser; 8-Post-reaction material discharge line; 9-Condenser discharge line; 10-Circulating liquid phase material feed line; 11-Product liquid phase material discharge line. Detailed Implementation

[0037] The present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited to the following description.

[0038] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0039] In the following embodiments, unless otherwise specified, the reactor used is a bubble-type fixed-bed reactor of conventional size; the catalyst used is 2%Ru-1%CaO / Al2O3 (wherein, the Ru content is calculated as Ru elemental, and is 2wt% of the carrier content; the CaO content is calculated as Ca elemental, and is 1wt% of the carrier content), the chlorine content is <0.5wt%, and the specific surface area of ​​the carrier is 135m². 2 / g; and / or a pore size of 12.5nm; and / or a pore volume of 0.5cm³. 3 / g.

[0040] In the following implementation method, the formula for calculating the DMT conversion rate is:

[0041] Conversion rate = 1 - (Dimethyl phthalate content in the liquid product discharge pipeline / Dimethyl phthalate content in the fresh dimethyl phthalate feed stream).

[0042] In the following embodiments, the formula for calculating DMCD selectivity is:

[0043] Selectivity = Amount of dimethyl cyclohexanedicarboxylate in the product liquid discharge line / (Amount of dimethyl phthalate in the fresh dimethyl phthalate feed stream - Amount of dimethyl phthalate in the product liquid discharge line).

[0044] Example 1

[0045] The process flow of this embodiment is as follows: Figure 1 As shown, fresh dimethyl phthalate is mixed with the circulating liquid phase stream via pipeline 10 and enters pipeline 3. Fresh hydrogen is mixed with circulating hydrogen via pipeline 2 and pipeline 4, and then mixed with the liquid phase material in pipeline 3 before entering reactor 5. The feed stream flows in from the bottom and out from the top of reactor 5. After the reaction, the liquid phase product and hydrogen enter gas-liquid separator 6 via condenser 7. After separation, the hydrogen is used as circulating hydrogen and mixed with fresh hydrogen via pipeline 4. A portion of the liquid phase product is used as circulating liquid phase stream via pipeline 10 and mixed with the fresh dimethyl phthalate in pipeline 1. The other portion of the liquid phase stream is collected as product.

[0046] The weight ratio of the liquid phase material recycled to the reactor to the liquid phase stream collected as product is 90:10; the weight ratio of dimethyl phthalate to dimethyl cyclohexanedicarboxylate in the fresh dimethyl phthalate feed is 3:7; the weight ratio of dimethyl phthalate to dimethyl cyclohexanedicarboxylate in the feed stream obtained after mixing the recycled liquid phase stream via pipeline 1 and pipeline 10 is 3:97; the operating temperature is 140℃, 6MPa, and the DMT liquid hourly space velocity is 0.15h. -1 The reaction was carried out under the condition that the H2 / DMT molar ratio was 30.

[0047] The product showed a DMT conversion rate of 99.3% and a DMCD selectivity of 95.5%.

[0048] Example 2

[0049] The only difference between this embodiment and Example 1 is that the weight ratio of the liquid phase material recycled to the reactor to the liquid phase stream collected as product is 98:2. Under the same conditions, the DMT conversion rate was 99.9% and the DMCD selectivity was 95.3% in the product.

[0050] Example 3

[0051] The only difference between this embodiment and Example 1 is that the weight ratio of the liquid phase material recycled to the reactor to the liquid phase stream collected as product is 70:30. Under the same conditions, the DMT conversion rate was 99.3% and the DMCD selectivity was 95.5% in the product.

[0052] Example 4

[0053] The only difference between this embodiment and Example 1 is that the weight ratio of the liquid phase material recycled to the reactor to the liquid phase stream collected as product is 50:50. Under the same conditions, the DMT conversion rate was 99.1% and the DMCD selectivity was 95.0% in the product.

[0054] Example 5

[0055] The only difference between this embodiment and Example 1 is that the weight ratio of the liquid phase material recycled to the reactor to the liquid phase stream collected as product is 30:70. Under the same conditions, the DMT conversion rate was 99.0% and the DMCD selectivity was 91.5% in the product.

[0056] Example 6

[0057] The only difference between this embodiment and Example 1 is that the ratio of DMT and DMCD in the fresh raw material is adjusted so that the weight ratio of dimethyl phthalate and dimethyl cyclohexanedicarboxylate in the raw material stream is 2:98. Under the same conditions, the DMT conversion rate in the product is 99.8% and the DMCD selectivity is 95.4%.

[0058] Example 7

[0059] The only difference between this embodiment and Example 1 is that the ratio of DMT and DMCD in the fresh raw material is adjusted so that the weight ratio of dimethyl phthalate and dimethyl cyclohexanedicarboxylate in the raw material stream is 1:99. Under the same conditions, the DMT conversion rate in the product is 99.9% and the DMCD selectivity is 95.4%.

[0060] Example 8

[0061] The only difference between this embodiment and Example 1 is that the ratio of DMT and DMCD in the fresh raw material is adjusted so that the weight ratio of dimethyl phthalate and dimethyl cyclohexanedicarboxylate in the raw material stream is 5:95. Under the same conditions, the DMT conversion rate in the product is 99.2% and the DMCD selectivity is 95.0%.

[0062] Example 9

[0063] The only difference between this embodiment and Example 1 is that the ratio of DMT and DMCD in the fresh raw material is adjusted so that the weight ratio of dimethyl phthalate and dimethyl cyclohexanedicarboxylate in the raw material stream is 7:93. 7%. Under the same conditions, the DMT conversion rate in the product was measured to be 99.0% and the DMCD selectivity to be 93.2%.

[0064] Comparative Example 1

[0065] The only difference between this embodiment and Example 1 is that the feed stream flows in from the top and out from the bottom of reactor 5. Under otherwise identical conditions, the product showed a DMT conversion of 99.0% and a DMCD selectivity of 88.5%.

[0066] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A process for the continuous production of dimethyl cyclohexanedicarboxylate, comprising: S1. A feed stream containing hydrogen, dimethyl phthalate and dimethyl cyclohexanedicarboxylate is fed into the reactor from the bottom inlet, and a post-reaction stream is obtained at the top outlet of the reactor. S2. Perform gas-liquid separation on the post-reaction stream to obtain recycled hydrogen and liquid stream; S3. A portion of the circulating hydrogen is recycled back to the reactor, and the remaining portion is removed from the reaction zone; the weight ratio of the circulating hydrogen recycled back to the reactor to the circulating hydrogen removed from the reaction zone is (90~100):(0~10); S4. A portion of the liquid stream is recycled back to the reactor, and the remainder is collected as a product; In step S1, the weight ratio of dimethyl phthalate and dimethyl cyclohexanedicarboxylate in the raw material stream is (7:93) ~ (1:99). The reactor is filled with a hydrogenation catalyst, which includes a support and an active component and an auxiliary component supported on the support, wherein the active component includes ruthenium.

2. The process according to claim 1, characterized in that, In step S4, the weight ratio of the liquid phase material recycled to the reactor to the liquid phase stream collected as a product is (50~98):(2~50).

3. The process according to claim 1, characterized in that, In step S1, the hydrogen in the raw material stream is fresh hydrogen and / or recycled hydrogen from step S2; and / or the dimethyl phthalate in the raw material stream is dimethyl phthalate from fresh raw materials and / or dimethyl phthalate from the recycled liquid phase stream of step S4; and / or the dimethyl cyclohexanedicarboxylate in the raw material stream is dimethyl cyclohexanedicarboxylate from fresh raw materials and / or dimethyl cyclohexanedicarboxylate from the recycled liquid phase stream of step S4.

4. The process according to claim 3, characterized in that, The mass ratio of dimethyl phthalate to dimethyl cyclohexanedicarboxylate in the fresh raw material is (1~5):(5~9).

5. The process according to claim 4, characterized in that, The mass ratio of dimethyl phthalate to dimethyl cyclohexanedicarboxylate in the fresh raw material is (2~4):(6~8).

6. The process according to claim 1, characterized in that, In step S1, the weight ratio of dimethyl phthalate and dimethyl cyclohexanedicarboxylate in the raw material stream is 1:(15~50).

7. The process according to claim 1, characterized in that, In step S1, the molar ratio of hydrogen to dimethyl phthalate is controlled to be (10~100):1; and / or the liquid hourly space velocity of dimethyl phthalate is controlled to be 0.01 h⁻¹. -1 ~1h -1 ; And / or control the reaction conditions of the reactor, including: a pressure of 1 MPa to 10 MPa and a temperature of 100°C to 160°C.

8. The process according to claim 7, characterized in that, In step S1, the molar ratio of hydrogen to dimethyl phthalate is controlled to be (10~50):1; and / or the liquid hourly space velocity of dimethyl phthalate is controlled to be 0.1 h⁻¹. -1 ~1h -1 .

9. The process according to claim 7, characterized in that, In step S1, the molar ratio of hydrogen to dimethyl phthalate is controlled to be (10~35):1; and / or the liquid hourly space velocity of dimethyl phthalate is controlled to be 0.1 h⁻¹. -1 ~0.5h -1 .

10. The process according to any one of claims 1-9, characterized in that, The reactor is a bubble-type reactor.

11. The process according to claim 10, characterized in that, The reactor is a bubble-type fixed-bed reactor.

12. The process according to any one of claims 1-9, characterized in that, The carrier is selected from at least one of alumina and silicon dioxide. And / or the auxiliary component is selected from at least one of alkali metal oxides and alkaline earth metal oxides.

13. The process according to any one of claims 1-9, characterized in that, Based on the total weight of the hydrogenation catalyst, the content of the support is 75wt%~99.3wt%, the content of the active component is 0.2wt%~5wt%, and the content of the auxiliary component is 0.5wt%~20wt%.

14. The process according to any one of claims 1-9, characterized in that, The specific surface area of ​​the carrier is 80~230 m². 2 / g; and / or pore size of 5~20 nm; and / or pore volume of 0.3~0.8 cm³ 3 / g.

15. The process according to any one of claims 1-9, characterized in that, The chlorine content in the catalyst is less than 1.0% of the total weight of the catalyst.

16. The process according to any one of claims 1-9, characterized in that, The catalyst is prepared by calcination in air at a temperature range of 350°C to 550°C, and / or the catalyst is made from a chlorine-free ruthenium precursor, and / or the catalyst is washed with an alkaline liquid so that the chlorine content in the catalyst is less than 1.0% of the total weight of the catalyst.

17. The process according to any one of claims 1-9, characterized in that, The dimethyl phthalate is dimethyl terephthalate, dimethyl isophthalate, or dimethyl phthalate, and correspondingly, the dimethyl cyclohexanedicarboxylate is 1,4-cyclohexanedicarboxylate, 1,3-cyclohexanedicarboxylate, or 1,2-cyclohexanedicarboxylate.

18. The process according to claim 17, characterized in that, The dimethyl phthalate is dimethyl terephthalate, and the dimethyl cyclohexanedicarboxylate is dimethyl 1,4-cyclohexanedicarboxylate.

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