阅读说明：本技术 一种连续化生产1,4-环己烷二甲酸二甲酯的方法 (Method for continuously producing 1, 4-cyclohexane dimethyl phthalate ) 是由 武金丹 刘喆 邴威瀚 杨光 靳权 张立兴 白世杰 王聪 刘新伟 杨克俭 梁秀霞 于 2020-11-26 设计创作，主要内容包括：本发明提供了一种连续化生产1,4-环己烷二甲酸二甲酯的方法,包括依次串联连通的配料系统、连续化反应系统及固液分离器,所述固液分离器再与配料系统连通；所述连续化反应系统包括串联连通的第一塔式反应器及第二塔式反应器,所述配料系统包括DMT溶解釜,所述DMT溶解釜与第一塔式反应器连通。本发明提供的连续化生产1,4-环己烷二甲酸二甲酯的方法,实现了连续化生产,采用两台串联的塔式反应器,确保气液固三相能够在反应器中充分接触,在较低压力下、较短时间内即完成反应,同时能确保反应完全,有效提高了反应效率。(The invention provides a method for continuously producing 1, 4-cyclohexane dimethyl phthalate, which comprises a batching system, a continuous reaction system and a solid-liquid separator which are sequentially communicated in series, wherein the solid-liquid separator is communicated with the batching system; the continuous reaction system comprises a first tower reactor and a second tower reactor which are communicated in series, the batching system comprises a DMT dissolving kettle, and the DMT dissolving kettle is communicated with the first tower reactor. The method for continuously producing the 1, 4-cyclohexane dimethyl phthalate realizes continuous production, adopts two tower reactors connected in series, ensures that gas, liquid and solid phases can be fully contacted in the reactors, completes the reaction under lower pressure in shorter time, ensures complete reaction and effectively improves the reaction efficiency.)

1. A method for continuously producing 1, 4-cyclohexane dimethyl phthalate is characterized in that: the device comprises a batching system, a continuous reaction system and a solid-liquid separator which are sequentially communicated in series, wherein the solid-liquid separator is communicated with the batching system; the continuous reaction system comprises a first tower reactor and a second tower reactor which are communicated in series, the batching system comprises a DMT dissolving kettle, and the DMT dissolving kettle is communicated with the first tower reactor.

2. The process according to claim 1, wherein the reaction mixture comprises dimethyl 1, 4-cyclohexanedicarboxylate and at least one of: the height-diameter ratio of the first tower reactor to the second tower reactor is 10-20: 1.

3. the process according to claim 1, wherein the reaction mixture comprises dimethyl 1, 4-cyclohexanedicarboxylate and at least one of: the preparation method comprises the following steps:

(1) dissolving DMT solid in a DMT dissolving kettle by using DMCD to obtain DMT mixed solution;

(2) introducing the DMT mixed solution and a catalyst into a first tower reactor simultaneously, and introducing hydrogen from the bottoms of the first tower reactor and a second tower reactor simultaneously; reacting the materials in the first tower reactor, and then entering the second tower reactor for continuous reaction;

(3) and (3) feeding the material reacted by the second tower reactor into a solid-liquid separator to realize solid-liquid separation, wherein the solid obtained by the solid-liquid separation is a catalyst, the mother liquor is a DMCD solution, the catalyst is collected for recycling, one part of the mother liquor is fed into a product tank, the other part of the mother liquor is fed into a DMT dissolving kettle to dissolve newly added DMT solid, and then feeding the dissolved material into a continuous reaction system to realize continuous production.

4. The process according to claim 3, wherein the reaction mixture comprises dimethyl 1, 4-cyclohexanedicarboxylate and at least one of: the catalyst is selected from Ru-Pd/Al₂O₃、Ru-Pd/C、Ru-Ni/Al₂O₃、Ru-Ni/C。

5. The process according to claim 3, wherein the reaction mixture comprises dimethyl 1, 4-cyclohexanedicarboxylate and at least one of: the mass ratio of the DMT solid to the DMCD added in the step (1) is as follows: 1: 0.8-1.2.

6. The process according to claim 3, wherein the reaction mixture comprises dimethyl 1, 4-cyclohexanedicarboxylate and at least one of: after the preparation in the step (2) is started, the mass ratio of the introduced hydrogen to the DMT solid put into the DMT dissolving kettle each time is as follows: 0.05-0.12: 1.

7. The process according to claim 3, wherein the reaction mixture comprises dimethyl 1, 4-cyclohexanedicarboxylate and at least one of: after the preparation in the step (2) is started, the mass ratio of the catalyst introduced into the continuous reaction system to the DMT solid fed into the DMT dissolution kettle each time is as follows: 1: 8-12.

8. The process according to claim 3, wherein the reaction mixture comprises dimethyl 1, 4-cyclohexanedicarboxylate and at least one of: and (3) the mass ratio of the mother liquor entering the DMT dissolving kettle to the mother liquor entering the product tank in the solid-liquid separator is as follows: 0.4-0.6: 0.4-0.6.

9. The process according to claim 1, wherein the reaction mixture comprises dimethyl 1, 4-cyclohexanedicarboxylate and at least one of: the temperature for dissolving DMT solid in the DMT dissolving kettle is 100-140 ℃.

10. The process according to claim 1, wherein the reaction mixture comprises dimethyl 1, 4-cyclohexanedicarboxylate and at least one of: the reaction temperature of the continuous reaction system is 100-140 ℃, the reaction pressure is 0.5-2.0 MPa, and the total reaction time is 20-50 min.

Technical Field

The invention belongs to the technical field of chemical production, and particularly relates to a method for continuously producing 1, 4-cyclohexane dimethyl phthalate.

Background

Dimethyl 1, 4-cyclohexanedicarboxylate (DMCD) is not only a commonly used polymer modifying material, but also an intermediate for the preparation of 1, 4-Cyclohexanedimethanol (CHDM). Currently, as the market demand for CHDM downstream products, such as novel polyester materials PCT, modified copolyester PETG, etc., increases, higher demands are placed on the production of DMCD.

In the existing DMCD production process, a catalyst loaded with noble metals such as Pd, Ru, Rh and the like is adopted to react in an autoclave or a fixed bed reactor. In order to obtain a better reaction effect, higher pressure is often needed to accelerate the reaction; meanwhile, the control of the reaction temperature is also particularly critical due to the large exothermic amount of the reaction. CN 1915494 describes a kettle type reaction with supported Ru as a catalyst, and the pressure is up to 5.0MPa under the condition of higher catalyst content, and the reaction can be completed within 1-1.5 h. CN102795967 adopts a fixed bed reactor, the reaction temperature is 140 ℃, the pressure is as high as 4.0MPa, and the mass space velocity is only 0.2-0.4h^-1。

In the prior art, higher reaction pressure puts higher requirements on equipment, and meanwhile, the reaction efficiency is lower, so that the large-scale production is not facilitated.

Disclosure of Invention

In order to solve the defects of the prior art, the invention provides a method for continuously producing dimethyl 1, 4-cyclohexanedicarboxylate, so as to improve the production efficiency.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

a method for continuously producing 1, 4-cyclohexane dimethyl phthalate comprises a batching system, a continuous reaction system and a solid-liquid separator which are sequentially communicated in series, wherein the solid-liquid separator is communicated with the batching system, one part of DMCD (dimethyl phthalate) separated by the solid-liquid separator is collected as a product, the other part of DMCD is returned to the batching system to dissolve DMT, and the separated catalyst is returned to the continuous reaction system to continuously participate in reaction; the continuous reaction system comprises a first tower reactor and a second tower reactor which are communicated in series, the batching system comprises a DMT dissolving kettle and a DMT raw material tank, the DMT dissolving kettle, the DMT raw material tank and the first tower reactor are communicated in sequence, DMT solid and DMCD returned by a solid-liquid separator are mixed, stirred and dissolved in the DMT dissolving kettle, enter the DMT raw material tank after the DMT is dissolved, and are pumped into the first tower reactor through a pipeline; the DMT raw material tank is provided with a flow meter and a valve for controlling the amount of the materials entering the continuous reaction system.

The height-diameter ratio of the first tower reactor to the second tower reactor is 10-20: 1.

the preparation method comprises the following steps:

(1) dissolving DMT solid in a DMT dissolving kettle by using DMCD to obtain DMT mixed solution, and then pumping the DMT mixed solution into a DMT raw material tank;

(2) adding DMCD solution as a bottom material into a first tower reactor and a second tower reactor before preparation, introducing a catalyst and a DMT mixed solution in a DMT raw material tank into the first tower reactor simultaneously, and introducing hydrogen from the bottoms of the first tower reactor and the second tower reactor simultaneously after preparation is started; reacting the materials in the first tower reactor, and then entering the second tower reactor for continuous reaction; the first tower reactor and the second tower reactor are respectively provided with a liquid phase feed inlet, a liquid phase discharge outlet, a gas phase feed inlet and a gas phase discharge outlet, the liquid phase feed inlet is arranged at a position close to the bottom, the liquid phase discharge outlet is arranged at a position close to the top, the gas phase feed inlet is arranged at the bottom, the gas phase discharge outlet is arranged at the top, hydrogen enters the reactor from the gas phase feed inlet at the bottom of the tower reactor, reaction materials enter the reactor from the liquid phase feed inlet, and the materials are discharged from the liquid phase discharge outlet after the reaction and enter the next step; a catalyst inlet is also arranged at the position of the first tower reactor close to the bottom;

(3) the materials reacted by the second tower reactor are pumped into a solid-liquid separator to realize solid-liquid separation, the solid obtained by the solid-liquid separation is used as a catalyst, the mother liquor is DMCD solution, the catalyst is collected for recycling, one part of the mother liquor is input into a product tank, the other part of the mother liquor is input into a DMT dissolution kettle to dissolve newly added DMT solid, and the dissolved materials are pumped into a continuous reaction system to realize continuous production; preferably, the solid-liquid separator comprises a mother liquor tank and a centrifuge or a decanter, a reaction product of the continuous reaction system is subjected to solid-liquid separation by the centrifuge or the decanter, the solid catalyst returns to the continuous reaction system, the mother liquor is pumped into a buffer tank by a pump, substances in the mother liquor are mainly DMCD, and the buffer tank is respectively communicated with the DMT dissolving kettle and the product tank through pipelines; preferably, the buffer tank is provided with two sets of flow meters and valves for respectively controlling the amount of the mother liquor entering the DMT dissolving kettle and the product tank;

further, the catalyst is selected from Ru-Pd/Al₂O₃、Ru-Pd/C、Ru-Ni/Al₂O₃、Ru-Ni/C。

Further, the mass ratio of the DMT solid to the DMCD added in the step (1) is as follows: 1: 0.8-1.2.

Further, after the preparation in the step (2) is started, the mass ratio of the introduced hydrogen to the mass of DMT solid fed into the DMT dissolution kettle each time is as follows: 0.05-0.12: 1.

Further, after the preparation in the step (2) is started, the mass ratio of the catalyst introduced into the continuous reaction system to the DMT solid charged into the DMT dissolution kettle each time is as follows: 1: 8-12.

Further, the mass ratio of the mother liquor entering the DMT dissolving kettle and the product tank in the solid-liquid separator in the step (3) is as follows: 0.4-0.6: 0.4-0.6.

Further, the temperature for dissolving DMT solid in the DMT dissolving kettle is 100-140 ℃.

Further, the reaction temperature of the continuous reaction system is 100-140 ℃, the reaction pressure is 0.5-2.0 MPa, and the total reaction time is 20-50 min.

Compared with the prior art, the method for continuously producing the 1, 4-cyclohexane dimethyl phthalate has the following advantages: the method adopts a tower reactor with a certain height-diameter ratio, realizes the high-efficiency circulating continuous production of the DMCD by recycling the product DMCD, stabilizes the product quality and is simple to operate; meanwhile, two tower reactors connected in series are used as a continuous production system, so that the condition of incomplete reaction of flying materials after hydrogen is introduced is avoided, and the complete reaction is ensured; the improvement enables the gas phase, the liquid phase and the solid phase to be fully contacted, can complete the reaction under lower pressure and with shorter retention time, and improves the reaction efficiency.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention.

FIG. 1 is a process flow diagram of the present invention.

Detailed Description

The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

The first embodiment is as follows:

dissolving 2.00kg of DMT solid in 2.40kg of mother liquor in a DMT dissolving kettle, stirring at 110 ℃ for 25min to obtain DMT mixed solution, and introducing the DMT mixed solution into a DMT raw material tank; before production, DMCD is added into a first tower reactor and a second tower reactor as a bottom material, and after the preparation is started, the DMT mixed solution and Ru-Pd/Al are mixed₂O₃The catalyst is prepared according to the following steps of 20: 1, introducing hydrogen from the bottoms of the first tower reactor and the second tower reactor simultaneously, wherein the introduction amount of the hydrogen in each tower reactor is 0.12kg, and the materials reacted in the first tower reactor enter the second tower reactor for continuous reaction; the height of each pipe of the first tower reactor and the second tower reactor is 1000mm, the effective diameter is 60mm, the reaction temperature is maintained within the range of 113-117 ℃, the reaction pressure is 0.8MPa, and the total reaction time in the two tower reactors is 42 min. The conversion of DMT was found to be 99.3% and the selectivity of DMCD was found to be 98.1%. Pumping the reaction product in the second tower reactor into a centrifuge at 10000rpm for 3min to obtain 0.22kg of catalyst solid and 4.46kg of DMCD mother liquor with the purity of more than 99.0%. Pumping the mother liquor into a buffer tank by a pump, wherein 2.06kg of the mother liquor enters a product tank, and 2.40kg of the mother liquor returns to a DMT dissolving kettle to continuously dissolve newly added DMT solid raw materials.

Example two:

dissolving 3.00kg of DMT solid in 3.60kg of mother liquor in a DMT dissolving kettle, stirring at 115 ℃ for 30min to obtain DMT mixed solution, and introducing the DMT mixed solution into a DMT raw material tank; before production, DMCD is added into a first tower reactor and a second tower reactor as a bottom material, and after the preparation is started, the DMT mixed solution and Ru-Pd/Al are mixed₂O₃The catalyst was prepared as follows: 1, introducing hydrogen from the bottoms of the first tower reactor and the second tower reactor simultaneously, wherein the introduction amount of the hydrogen in each tower reactor is 0.18kg, and the materials reacted in the first tower reactor enter the second tower reactor for continuous reaction; the height of each pipe of the first tower reactor and the second tower reactor is 1000mm, the effective diameter is 60mm, the reaction temperature is maintained within the range of 113-117 ℃, the reaction pressure is 0.8MPa, and the total reaction time in the two tower reactors is 50 min. The conversion of DMT was found to be 99.4% and the selectivity of DMCD was found to be 98.2%. Pumping the reaction product in the second tower reactor into a centrifuge at 10000rpm for 3min to obtain 0.266kg of catalyst solid and 6.69kg of DMCD mother liquor with purity of more than 99.0%. Pumping the mother liquor into a buffer tank by a pump, wherein 3.09kg of the mother liquor enters a product tank, and 3.6 kg of the mother liquor enters a product tank0kg of DMT solution is returned to the DMT dissolution kettle to dissolve the newly added DMT solid raw material continuously.

Example three:

dissolving 4.00kg of DMT solid in 4.80kg of mother solution in a DMT dissolving kettle, stirring at 125 ℃ for 28min to obtain DMT mixed solution, and introducing the DMT mixed solution into a DMT raw material tank; before production, DMCD is added into a first tower reactor and a second tower reactor as a bottom material, and after preparation is started, the DMT mixed solution and the Ru-Pd/C catalyst are mixed according to the proportion of 20: 1, introducing hydrogen from the bottoms of the first tower reactor and the second tower reactor simultaneously, wherein the introduction amount of the hydrogen in each tower reactor is 0.24kg, and the materials reacted in the first tower reactor enter the second tower reactor for continuous reaction; the height of each pipe of the first tower reactor and the second tower reactor is 1200mm, the effective diameter is 65mm, the reaction temperature is maintained within the range of 112-118 ℃, the reaction pressure is 0.8MPa, and the total reaction time in the two tower reactors is 40 min. The conversion of DMT was found to be 99.2% and the selectivity of DMCD was found to be 97.9%. Pumping the reaction product in the second tower reactor into a centrifuge at 10000rpm for 3min to obtain 0.45kg of catalyst solid and 8.92kg of DMCD mother liquor with the purity of more than 99.0%. Pumping the mother liquor into a buffer tank by a pump, wherein 4.12kg of the mother liquor enters a product tank, and 4.80kg of the mother liquor returns to a DMT dissolution kettle to continuously dissolve newly added DMT solid raw materials.

Example four:

dissolving 0.50kg of DMT solid in 0.60kg of mother liquor in a DMT dissolving kettle, stirring at 110 ℃ for 25min to obtain a DMT mixed solution, and introducing the DMT mixed solution into a DMT raw material tank; before production, DMCD is added into a first tower reactor and a second tower reactor as a bottom material, and after the preparation is started, the DMT mixed solution and Ru-Pd/Al are mixed₂O₃The catalyst is prepared according to the following steps of 20: 1, introducing hydrogen from the bottoms of the first tower reactor and the second tower reactor simultaneously, wherein the introduction amount of the hydrogen in each tower reactor is 0.03kg, and the materials reacted in the first tower reactor enter the second tower reactor for continuous reaction; the height of each pipe of the first tower reactor and the second tower reactor is 860mm, the effective diameter is 75mm, and the reaction temperature is maintained at 118-122 DEG CWithin the range, the reaction pressure is 0.8MPa, and the total reaction time in the two tower reactors is 37 min. The conversion of DMT was found to be 99.5% and the selectivity of DMCD was found to be 98.5%. Pumping the reaction product in the second tower reactor into a centrifuge at 10000rpm for 3min to obtain 0.055kg of catalyst solid and 1.12kg of DMCD mother liquor with purity of more than 99.0%. Pumping the mother liquor into a buffer tank by a pump, wherein 0.52kg of the mother liquor enters a product tank, and 0.60kg of the mother liquor returns to a DMT dissolving kettle to continuously dissolve newly added DMT solid raw materials.

Example five:

dissolving 1.00kg of DMT solid in 1.20kg of mother liquor in a DMT dissolving kettle, stirring at 108 ℃ for 20min to obtain a DMT mixed solution, and introducing the DMT mixed solution into a DMT raw material tank; before production, DMCD is added into a first tower reactor and a second tower reactor as a bottom material, and after the preparation is started, the DMT mixed solution and Ru-Pd/Al are mixed₂O₃The catalyst was prepared as follows 23.1: 1, introducing hydrogen from the bottoms of the first tower reactor and the second tower reactor simultaneously, wherein the introduction amount of the hydrogen in each tower reactor is 0.06kg, and the materials reacted in the first tower reactor enter the second tower reactor for continuous reaction; the height of each pipe of the first tower reactor and the second tower reactor is 1000mm, the effective diameter is 60mm, the reaction temperature is maintained within the range of 112-116 ℃, the reaction pressure is 1.6MPa, and the total reaction time in the two tower reactors is 39 min. The conversion of DMT was found to be 99.1% and the selectivity of DMCD was found to be 98.6%. Pumping the reaction product in the second tower reactor into a centrifuge at 9000rpm for 4min to obtain 0.095kg of catalyst solid and 2.23kg of DMCD mother liquor with purity of more than 99.0%. Pumping the mother liquor into a buffer tank by a pump, wherein 1.03kg of the mother liquor enters a product tank, and 1.20kg of the mother liquor returns to a DMT dissolution kettle to continuously dissolve newly added DMT solid raw materials.

Example six:

dissolving 2.00kg of DMT solid in 2.00kg of mother liquor in a DMT dissolving kettle, stirring for 24min at 110 ℃ to obtain DMT mixed solution, and introducing the DMT mixed solution into a DMT raw material tank; before production, DMCD is added into the first tower reactor and the second tower reactor as a bottom material, and the process is startedAfter preparation, the DMT mixed solution and Ru-Ni/Al are mixed₂O₃The catalyst was prepared as follows 19.0: 1, introducing hydrogen from the bottoms of the first tower reactor and the second tower reactor simultaneously, wherein the introduction amount of the hydrogen in each tower reactor is 0.06kg, and the materials reacted in the first tower reactor enter the second tower reactor for continuous reaction; the height of each pipe of the first tower reactor and the second tower reactor is 1000mm, the effective diameter is 60mm, the reaction temperature is maintained within the range of 113-117 ℃, the reaction pressure is 0.8MPa, and the total reaction time of the two tower reactors is 47 min. The conversion of DMT was found to be 99.3% and the selectivity of DMCD was found to be 98.4%. Pumping the reaction product in the second tower reactor into a centrifuge at 8000rpm for 5min to obtain 0.21kg of catalyst solid and 4.06kg of DMCD mother liquor with purity of more than 99.0%. Pumping the mother liquor into a buffer tank by a pump, wherein 2.06kg of the mother liquor enters a product tank, and 2.00kg of the mother liquor returns to a DMT dissolving kettle to continuously dissolve newly added DMT solid raw materials.

Example seven:

dissolving 2.00kg of DMT solid in 2.20kg of mother liquor in a DMT dissolving kettle, stirring for 24min at 120 ℃ to obtain DMT mixed solution, and introducing the DMT mixed solution into a DMT raw material tank; before production, DMCD is added into a first tower reactor and a second tower reactor as a bottom material, and after preparation is started, a DMT mixed solution and a Ru-Ni/C catalyst are mixed according to the proportion of 19.1: 1, introducing hydrogen from the bottoms of the first tower reactor and the second tower reactor simultaneously, wherein the introduction amount of the hydrogen in each tower reactor is 0.12kg, and the materials reacted in the first tower reactor enter the second tower reactor for continuous reaction; the height of the first tower reactor is 1000mm, the effective diameter is 60mm, the height of the second tower reactor is 950mm, the effective diameter is 50mm, the reaction temperature is maintained within the range of 110-119 ℃, the reaction pressure is 0.8MPa, and the total reaction time of the two tower reactors is 40 min. The conversion of DMT was found to be 99.3% and the selectivity of DMCD was found to be 98.3%. Pumping the reaction product in the second tower reactor into a centrifuge at 10000rpm for 3min to obtain 0.22kg of catalyst solid and 4.26kg of DMCD mother liquor with the purity of more than 99.0%. Pumping the mother liquor into a buffer tank by a pump, wherein 2.06kg of the mother liquor enters a product tank, and 2.20kg of the mother liquor returns to a DMT dissolving kettle to continuously dissolve newly added DMT solid raw materials.

Example eight:

dissolving 2.40kg of DMT solid in 2.00kg of mother liquor in a DMT dissolving kettle, stirring at 115 ℃ for 27min to obtain DMT mixed solution, and introducing the DMT mixed solution into a DMT raw material tank; before production, DMCD is added into a first tower reactor and a second tower reactor as a bottom material, and after preparation is started, a DMT mixed solution and a Ru-Ni/C catalyst are mixed according to the proportion of 14.7: 1, introducing hydrogen from the bottoms of the first tower reactor and the second tower reactor simultaneously, wherein the introduction amount of the hydrogen in each tower reactor is 0.12kg, and the materials reacted in the first tower reactor enter the second tower reactor for continuous reaction; the height of each pipe of the first tower reactor and the second tower reactor is 1100mm, the effective diameter is 80mm, the reaction temperature is maintained within the range of 112-120 ℃, the reaction pressure is 0.8MPa, and the total reaction time in the two tower reactors is 43 min. The conversion of DMT was found to be 99.1% and the selectivity of DMCD was found to be 98.1%. Pumping the reaction product in the second tower reactor into a centrifuge at the centrifugal speed of 11000rpm for 2min to finally obtain 0.30kg of catalyst solid and 4.47kg of DMCD mother liquor with the purity of more than 99.0 percent. Pumping the mother liquor into a buffer tank by a pump, wherein 2.47kg of the mother liquor enters a product tank, and 2.00kg of the mother liquor returns to a DMT dissolution kettle to continuously dissolve newly added DMT solid raw materials.

Comparative example one:

2.00kg DMT, 2.40kg DMCD and 0.22kg Ru-Pd/Al₂O₃The catalyst is placed in a 5.0L autoclave and reacts for 80min under the conditions of the reaction temperature of 111-117 ℃, the pressure of 0.8MPa and the rotating speed of 1000 rpm. After the reaction was complete, the DMT conversion was only 54.0% and the DMCD selectivity was only 93.1%. Compared with the two phases of the example, the conversion rate is lower even if longer reaction time is passed due to the change of the reactor form and the gas-liquid-solid mixing state.

Comparative example two:

2.00kg DMT, 2.40kg DMCD and 0.22kg Ru-Pd/Al₂O₃The catalyst was placed in a 5.0L autoclave at the reaction temperatureReacting for 80min at the temperature of 113-119 ℃, the pressure of 6.0MPa and the rotating speed of 1000 rpm. After the reaction was complete, the conversion of DMT was determined to be 96.1% and the selectivity of DMCD was only 94.0%. Compared with the second embodiment and the first comparative example, the pressure of the kettle type reaction is increased, the reaction can be accelerated, but the requirement on equipment is increased; an increase in reaction time may increase conversion, but may result in a decrease in selectivity.

The conversion and selectivity of comparative examples one to eight and comparative examples one, two are shown in the following table:

TABLE 1 comparative table of conversion and selectivity of examples and comparative examples

It can be seen from the examples I to eight and the comparative examples I and II that the tower reactors with specific height-diameter ratio are adopted to realize the efficient circulating continuous production of the 1, 4-dimethyl cyclohexanedicarboxylate, and meanwhile, the two tower reactors connected in series are adopted as a continuous production system to avoid the incomplete reaction of flying materials after the hydrogen is introduced, thereby ensuring the complete reaction. The mutual cooperation of the whole system ensures that gas, liquid and solid phases are fully contacted, can effectively reduce the reaction pressure, reduce the retention time and improve the reaction efficiency and the selectivity of target products.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.