Energy-saving method for producing cyclododecanone

Abstract

The invention discloses an energy-saving method for producing cyclododecanone, which is characterized in that 9, 10-epoxy-1, 5-cyclododecadiene is used as a raw material, and cyclododecanone is prepared through pre-hydrogenation, secondary hydrogenation, refining and dehydrogenation. The method comprises the following steps: carrying out pre-hydrogenation on 9, 10-epoxy-1, 5-cyclododecene and hydrogen collected by refining and dehydrogenation, carrying out secondary hydrogenation on a pre-hydrogenation reaction liquid to continuously hydrogenate to obtain a reaction liquid containing cyclododecanol, carrying out refining to obtain a high-purity cyclododecanol product, and finally feeding cyclododecanol into a dehydrogenation reactor to prepare cyclododecanone. A large amount of high-purity hydrogen can be collected in the refining and dehydrogenation processes, and the part of hydrogen is used as a pre-hydrogenation raw material, so that process materials can be fully utilized, more than 90% of waste gas output is reduced, the production cost is reduced, the selectivity of cyclododecanol is improved, and meanwhile, stable control of heat release of a secondary hydrogenation reaction is facilitated; and safe production and economic benefits of the device are ensured.

Description

Technical Field

[0001] The present application belongs to the field of fine chemicals and flavors and fragrances, and specifically relates to an energy-saving method for producing cyclododecanone. Background Art

[0002] Cyclododecanone (CDON) is a very important chemical product in the fragrance industry and engineering plastics field. It is an important intermediate in the nylon 12 industry chain. Its preparation can use cyclododecane, cyclododecene, epoxycyclododecane, epoxycyclododecadiene, cyclododecanol, etc. as initial raw materials.

[0003] Patent CN1167657C oxidizes cyclododecane to cyclododecyl hydroperoxide, which is then decomposed into cyclododecanol and cyclododecanone using a chromium catalyst. The chromium catalyst used in this method is toxic, and the peroxide itself is very unstable, posing significant process safety challenges. Patent CN105315146A oxidizes cyclododecene to epoxycyclododecane, which is then rearranged to cyclododecanone. The reaction byproduct, cyclododecanol, is then dehydrogenated to produce cyclododecanone. This method results in complex oxidation reaction products, poor selectivity, low yield of the target product, and difficulty in separation.

[0004] In contrast, CN116730809A uses cyclododecanol as a raw material and dehydrogenates it to produce cyclododecanone over a copper-zinc catalyst. This method offers a long catalyst life, high cyclododecanone yield, and excellent safety. Furthermore, the raw cyclododecanol can be prepared using the catalyst and process described in patent CN110882724B. Patent CN110882724B utilizes polyamide-amine supramolecular grafted graphene foam as a carrier and platinum as the active component to highly selectively hydrogenate 9,10-epoxy-1,5-cyclododecadiene to cyclododecanol. The resulting cyclododecanol is of higher purity and contains fewer metallic impurities, making it more suitable for dehydrogenation to produce cyclododecanone.

[0005] Patent CN117623886A uses 9,10-epoxy-1,5-cyclododecadiene as a raw material, and obtains cyclododecanone after hydrogenation, distillation desolventization, gas stripping desolventization, and dehydrogenation. The process route is reasonable and the product yield is high. The hydrogen generated by dehydrogenation is recycled to the gas stripping desolventization link, avoiding the use of inert gas, greatly reducing the amount of tail gas, and saving tail gas treatment costs. In addition, the hydrogen generated by dehydrogenation contains high-freezing point materials, which can be absorbed by cyclododecanol after entering the gas stripping tower, avoiding the risk of material solidification and blockage in the gas phase pipeline. It is a set of green and environmentally friendly process flow. However, this process flow still has shortcomings. The hydrogen generated by dehydrogenation is used as gas stripping gas, which still needs to be incinerated later. The processing cost of this part of hydrogen still exists. In addition, hydrogen is flammable and explosive, and its safety needs to be strictly controlled compared with inert gas. In addition, during the hydrogenation of 9,10-epoxy-1,5-cyclododecadiene to prepare cyclododecanol, two sets of carbon-carbon double bonds and one set of epoxy bonds need to be hydrogenated in one reactor. The reaction releases a large amount of heat and the temperature rises, which poses certain safety risks and poses severe challenges to the selection, design and control of the reactor. At the same time, the higher reaction temperature will trigger more side reactions, reducing the selectivity of the target product. Summary of the Invention

[0006] In response to the problems of low target product yield, high post-processing cost and process safety challenges in the existing technology, the present application provides an energy-saving production method of cyclododecanone with safer process, lower production cost and higher comprehensive yield. 9,10-epoxy-1,5-cyclododecadiene is used as raw material, and cyclododecanone is prepared through pre-hydrogenation, secondary hydrogenation, refining and dehydrogenation. This method can fully utilize process materials, reduce waste gas generation, reduce production costs, improve cyclododecanol selectivity, and improve economic benefits; at the same time, it can also improve the controllability of the reaction process and reduce the risk of reaction out of control.

[0007] To achieve the above object, the technical solutions adopted by the present invention are as follows:

[0008] An energy-saving method for producing cyclododecanone, the method comprising the steps of:

[0009] 1) Pre-hydrogenation: reacting 9,10-epoxy-1,5-cyclododecadiene with hydrogen in the presence of a solvent and a hydrogenation catalyst to obtain a pre-hydrogenation reaction liquid;

[0010] 2) Secondary hydrogenation: secondary hydrogenation of the pre-hydrogenation reaction liquid with hydrogen in the presence of a hydrogenation catalyst to obtain a secondary hydrogenation reaction liquid containing cyclododecanol;

[0011] 3) Refining: The secondary hydrogenation reaction liquid is passed through a desolventizing tower and a product refining tower to obtain the cyclododecanol product, wherein the hydrogen collected at the top of the desolventizing tower is returned to the pre-hydrogenation step for hydrogenation reaction;

[0012] 4) Dehydrogenation: The cyclododecanol product is dehydrogenated in a dehydrogenation reactor to produce cyclododecanone, and the hydrogen produced by dehydrogenation is returned to the pre-hydrogenation step for hydrogenation reaction.

[0013] In the method of the present invention, the solvent in step 1) is a small molecule alcohol, which is selected from at least one of methanol, ethanol, and isopropanol. Preferably, the amount of the small molecule alcohol added is 1 to 10 times the initial mass of 9,10-epoxy-1,5-cyclododecadiene.

[0014] In the method of the present invention, the pre-hydrogenation reaction temperature in step 1) is 30-120°C, the reaction pressure is 0.1-3 MPaG, the molar ratio of the total amount of hydrogen in step 1) to the initial amount of 9,10-epoxy-1,5-cyclododecadiene is 1.0-1.5, and the mass space velocity is 0.1-1.0h-1 based on the initial raw material 9,10-epoxy-1,5-cyclododecadiene. -1 .

[0015] In the method of the present invention, the hydrogen pre-hydrogenated in step 1) comes from the desolventizing tower in step 3) and the dehydrogenation reactor in step 4).

[0016] In a specific embodiment, when the amount of hydrogen recycled in the desolventizing tower in step 3) and the dehydrogenation reactor in step 4) is insufficient, fresh hydrogen is added in step 1) to meet the aforementioned pre-hydrogenation conditions.

[0017] In the method of the present invention, the hydrogenation catalyst in step 1) and step 2) can be selected from one or more of nickel catalysts, cobalt catalysts, palladium catalysts, platinum catalysts, ruthenium catalysts, and rhodium catalysts, preferably one or more of supported nickel catalysts, cobalt catalysts, palladium catalysts, and platinum catalysts.

[0018] In the method of the present invention, the secondary hydrogenation reaction temperature in step 2) is 50-150° C., the reaction pressure is 8-16 MPaG, the molar ratio of the amount of hydrogen in the secondary hydrogenation in step 2) to the initial amount of 9,10-epoxy-1,5-cyclododecadiene is 2-2.14, and the mass space velocity is 0.10-0.25 h-1 based on the initial raw material 9,10-epoxy-1,5-cyclododecadiene for the pre-hydrogenation reaction. -1 .

[0019] In the method of the present invention, the hydrogenation reactor in step 1) and step 2) can be selected from a kettle or tubular reactor, preferably selected from a batch-operated stirred kettle, a continuously operated stirred kettle or a continuously operated tubular reactor, more preferably a continuously operated stirred kettle or a continuously operated tubular reactor.

[0020] In the method of the present invention, the operating pressure of the desolventizing tower in step 3) is 60kPaG to 1200kPaG, preferably 60kPaG to 120kPaG, and the tower bottom temperature is 145°C to 200°C; the hydrogen temperature at the top of the desolventizing tower is 35°C to 45°C, the hydrogen pressure is 60kPaG to 1000kPaG, preferably 60kPaG to 120kPaG, and the hydrogen purity is ≥99.5% (mol).

[0021] In the method of the present invention, the operating pressure of the product refining tower in step 3) is -75kPaG to 10kPaG, preferably -75kPaG to -50kPaG, the tower bottom temperature is 140°C to 180°C, and the content of small molecular alcohol in the tower kettle is controlled below 40ppm.

[0022] In the method of the present invention, a copper catalyst, preferably a supported copper catalyst, is used as the dehydrogenation catalyst in step 4). The temperature of the dehydrogenation reactor in step 4) is 195° C. to 290° C., and the reaction pressure is 80 to 125 kPaA. The temperature of hydrogen generated during the dehydrogenation process is 70° C. to 170° C., and the purity of the hydrogen is ≥99.9% (mol).

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The large amount of high-purity waste hydrogen generated in the hydrorefining and dehydrogenation processes is used as the raw material for the pre-hydrogenation process, which can fully utilize the hydrogen, reduce the amount of waste gas generated by at least 90%, reduce the cost of waste gas treatment, and improve economic benefits;

[0025] (2) The heat released by hydrogenating 9,10-epoxy-1,5-cyclododecadiene to produce cyclododecanol is divided into two parts: pre-hydrogenation and secondary hydrogenation. Pre-hydrogenation accounts for at least 25% of the total heat release, which is conducive to the stable control of the heat release of the secondary hydrogenation reaction and effectively reduces the risk of temperature runaway.

[0026] (3) The process of hydrogenating 9,10-epoxy-1,5-cyclododecadiene to prepare cyclododecanol is divided into two steps. The pre-hydrogenation process is carried out under relatively mild conditions, and the secondary hydrogenation conditions are also milder than the hydrogenation reaction in the prior art, which is beneficial to reducing over-hydrogenation and hydrogenolysis side reactions, and improving the selectivity of the hydrogenated target product cyclododecanol by at least 1%. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the production process of cyclododecanone according to an embodiment of the present invention;

[0028] Figure 2 Schematic diagram of the production process of cyclododecanone in comparative example. DETAILED DESCRIPTION

[0029] In order to better understand the technical solution of the present application, the following examples will further illustrate the method provided by the present invention, but the present invention is not limited to the listed examples, and should also include any other known changes within the scope of the claims of the present invention.

[0030] Hydrogenation catalyst: the catalyst of Example 1 of CN110882724B was used.

[0031] Dehydrogenation catalyst: the catalyst of Example 4 of CN116730809A was used.

[0032] Example 1

[0033] according to Figure 1 The process shown is based on an 80,000-ton / year cyclododecanone production unit as an example.

[0034] 1) Pre-hydrogenation: The pre-hydrogenation reactor adopts a continuously operated tubular reactor, which is filled with 20 tons of activated hydrogenation catalyst, the pre-hydrogenation reaction temperature is 75 ° C, the reaction pressure is 1.5 MPaG, the initial raw material 9,10-epoxy-1,5-cyclododecadiene and solvent methanol are prepared into a raw material liquid in a mass ratio of 3:7 and then introduced into the pre-hydrogenation reactor. The raw material (9,10-epoxy-1,5-cyclododecadiene, the same below) has a mass space velocity of 0.50h -1 , reacting with the high-purity hydrogen collected from the desolventizing tower and the dehydrogenation process. The purity of the hydrogen from the desolventizing tower is 99.7% (mol), and the flow rate is 180Nm 3 / h, the purity of hydrogen from the dehydrogenation part is 99.9% (mol), and the flow rate is 1231Nm 3 / h, the molar ratio of the total amount of recycled hydrogen to the initial raw material 9,10-epoxy-1,5-cyclododecadiene is 1.12, and after pre-hydrogenation, a pre-hydrogenation reaction liquid with epoxycyclododecane as the main component (excluding solvent methanol) is obtained. The heat transfer power of the pre-hydrogenation reactor is 1590kW, and the exhaust gas of the pre-hydrogenation reactor is 127Nm 3 / h;

[0035] 2) Secondary hydrogenation: The secondary hydrogenation reactor adopts a continuously operated tubular reactor, in which 40 tons of activated hydrogenation catalyst is loaded. The pre-hydrogenation reaction liquid is heated at a mass space velocity of 0.25h -1 (calculated based on the initial raw material 9,10-epoxy-1,5-cyclododecadiene, the same below) is pumped into a secondary hydrogenation reactor, the secondary hydrogenation temperature is 100°C, the reaction pressure is 12 MPaG, the molar ratio of hydrogen to the raw material 9,10-epoxy-1,5-cyclododecadiene (calculated based on the initial amount) is 2, and after the secondary hydrogenation, a secondary hydrogenation reaction liquid with cyclododecanol as the main component (excluding the solvent methanol) is obtained, wherein the selectivity of cyclododecanol is 99.1%, and the heat transfer power of the secondary hydrogenation reactor is 4340 kW;

[0036] 3) Refining: The secondary hydrogenation reaction liquid is fed to a desolventizing tower. The operating conditions of the desolventizing tower are: pressure 60 kPaG, tower bottom temperature 198°C, reflux ratio 0.5, and solvent methanol and non-condensable hydrogen are obtained at the top of the tower. The solvent methanol is reused, and the hydrogen (99.7%, mol) is cooled to 45°C and 60 kPaG and then fed to a pre-hydrogenation reactor. The bottom of the desolventizing tower contains a crude cyclododecanol product containing a small amount of methanol. This crude product is fed to a product refining tower. Under the conditions of tower pressure -75 kPaG and tower bottom temperature 142°C, the methanol content in the tower bottom material can be controlled to be less than 20 ppm. The bottom of the product refining tower contains a high-purity cyclododecanol product with a purity of ≥99.3 wt%;

[0037] 4) Dehydrogenation: The high-purity cyclododecanol product is pumped into a dehydrogenation reactor at a reaction temperature of 235°C and a reaction pressure of 83 kPaA. Cyclododecanone is produced in the presence of a dehydrogenation catalyst, while high-purity hydrogen (99.9% mol) is produced as a by-product. The hydrogen produced by dehydrogenation is cooled to 70°C and atmospheric pressure and then sent to a pre-hydrogenation reactor to fully utilize the hydrogen produced by dehydrogenation.

[0038] Example 2

[0039] according to Figure 1 The process shown is based on an 80,000-ton / year cyclododecanone production unit as an example.

[0040] 1) Pre-hydrogenation: The pre-hydrogenation reactor adopts a continuously operated tubular reactor, which is filled with 10 tons of activated hydrogenation catalyst, the pre-hydrogenation reaction temperature is 30 ° C, the reaction pressure is 3 MPaG, the initial raw material 9,10-epoxy-1,5-cyclododecadiene and solvent isopropanol are prepared into a raw material liquid in a mass ratio of 1:1, and then introduced into the pre-hydrogenation reactor. The raw material mass space velocity is 1.0h -1 , reacting with the high-purity hydrogen collected from the desolventizing tower and the dehydrogenation process. The purity of the hydrogen from the desolventizing tower is 99.6% (mol), and the flow rate is 310Nm 3 / h, hydrogen purity from the dehydrogenation part is 99.9% (mol), flow rate is 1285Nm 3 / h, the molar ratio of the total amount of recycled hydrogen to the initial raw material 9,10-epoxy-1,5-cyclododecadiene is 1.27, and after pre-hydrogenation, a pre-hydrogenation reaction liquid with epoxycyclododecane as the main component (excluding the solvent isopropanol) is obtained. The heat transfer power of the pre-hydrogenation reactor is 1769kW, and the exhaust gas of the pre-hydrogenation reactor is 166Nm 3 / h;

[0041] 2) Secondary hydrogenation: The secondary hydrogenation reactor adopts a continuously operated tubular reactor, in which 50 tons of activated hydrogenation catalyst is loaded. The pre-hydrogenation reaction liquid is heated at a mass space velocity of 0.20h -1(calculated based on the initial raw material 9,10-epoxy-1,5-cyclododecadiene) was pumped into a secondary hydrogenation reactor at a secondary hydrogenation temperature of 150° C., a reaction pressure of 8 MPaG, a molar ratio of hydrogen to the raw material 9,10-epoxy-1,5-cyclododecadiene (calculated based on the initial amount) of 2.11, and after secondary hydrogenation, a secondary hydrogenation reaction liquid with cyclododecanol as the main component (excluding the solvent isopropanol) was obtained, wherein the selectivity of cyclododecanol was 98.7%, and the heat transfer power of the secondary hydrogenation reactor was 4161 kW;

[0042] 3) Refining: The secondary hydrogenation reaction liquid is fed to a desolventizing tower. The desolventizing tower is operated under the following conditions: pressure of 70 kPaG, tower bottom temperature of 193° C., and reflux ratio of 0.5. Isopropyl alcohol and non-condensable hydrogen are obtained at the top of the tower. The isopropyl alcohol is recycled, and the hydrogen (99.6% mol) is cooled to 35° C. and 60 kPaG before being fed to a pre-hydrogenation reactor. The bottom of the desolventizing tower contains a crude cyclododecanol product containing a small amount of isopropyl alcohol. The crude product is fed to a product refining tower. Under the conditions of a tower pressure of -70 kPaG and a bottom temperature of 145° C., the isopropyl alcohol content in the bottom material can be controlled to be less than 30 ppm. The bottom of the product refining tower contains a high-purity cyclododecanol product with a purity of ≥99.3 wt%;

[0043] 4) Dehydrogenation: The high-purity cyclododecanol product is pumped into a dehydrogenation reactor at a reaction temperature of 220° C. and a reaction pressure of 125 kPaA. Cyclododecanone is produced in the presence of a dehydrogenation catalyst, while high-purity hydrogen (99.9% mol) is produced as a by-product. The hydrogen produced by dehydrogenation is cooled to 143° C. and atmospheric pressure and then sent to a pre-hydrogenation reactor to fully utilize the hydrogen produced by dehydrogenation.

[0044] Example 3

[0045] according to Figure 1 The process shown is based on an 80,000-ton / year cyclododecanone production unit as an example.

[0046] 1) Pre-hydrogenation: The pre-hydrogenation reactor adopts a continuously operated tubular reactor, which is filled with 30 tons of activated hydrogenation catalyst, the pre-hydrogenation reaction temperature is 120 ° C, the reaction pressure is 0.1 MPaG, the initial raw material 9,10-epoxy-1,5-cyclododecadiene and solvent isopropanol are prepared into a raw material liquid in a mass ratio of 1:10, and then introduced into the pre-hydrogenation reactor, and the raw material mass space velocity is 0.33h -1 , reacting with the high-purity hydrogen collected from the desolventizing tower and the dehydrogenation process. The purity of the hydrogen from the desolventizing tower is 99.8% (mol), and the flow rate is 430Nm 3 / h, the purity of hydrogen from the dehydrogenation part is 99.9% (mol), and the flow rate is 1374Nm 3 / h, the molar ratio of the total amount of recycled hydrogen to the initial raw material 9,10-epoxy-1,5-cyclododecadiene is 1.43, and after pre-hydrogenation, a pre-hydrogenation reaction liquid with epoxycyclododecane as the main component (excluding the solvent isopropanol) is obtained. The heat transfer power of the pre-hydrogenation reactor is 2005kW, and the exhaust gas from the pre-hydrogenation reactor is 185Nm 3 / h;

[0047] 2) Secondary hydrogenation: The secondary hydrogenation reactor adopts a continuously operated tubular reactor, which is filled with 60 tons of activated hydrogenation catalyst. The pre-hydrogenation reaction liquid is heated at a mass space velocity of 0.17h -1 (calculated based on the initial raw material 9,10-epoxy-1,5-cyclododecadiene) is pumped into a secondary hydrogenation reactor, the secondary hydrogenation temperature is 90° C., the reaction pressure is 10 MPaG, the molar ratio of hydrogen to the raw material 9,10-epoxy-1,5-cyclododecadiene (calculated based on the initial amount) is 2, and after the secondary hydrogenation, a secondary hydrogenation reaction liquid with cyclododecanol as the main component (excluding the solvent isopropanol) is obtained, wherein the selectivity of cyclododecanol is 99.0%, and the heat transfer power of the secondary hydrogenation reactor is 3925 kW;

[0048] 3) Refining: The secondary hydrogenation reaction liquid is fed to a desolventizing tower. The desolventizing tower is operated under the following conditions: pressure of 100 kPaG, tower bottom temperature of 189° C., and reflux ratio of 0.5. Isopropyl alcohol and non-condensable hydrogen are obtained at the top of the tower. The isopropyl alcohol is recycled, and the hydrogen (99.8% mol) is cooled to 35° C. and 60 kPaG before being fed to a pre-hydrogenation reactor. The bottom of the desolventizing tower contains a crude cyclododecanol product containing a small amount of isopropyl alcohol. The crude product is fed to a product refining tower. Under the conditions of a tower pressure of -73 kPaG and a bottom temperature of 144° C., the isopropyl alcohol content in the bottom material can be controlled to be less than 30 ppm. The bottom of the product refining tower contains a high-purity cyclododecanol product with a purity of ≥99.3 wt%;

[0049] 4) Dehydrogenation: The high-purity cyclododecanol product is pumped into a dehydrogenation reactor at a reaction temperature of 195° C. and a reaction pressure of 117 kPaA. Cyclododecanone is produced in the presence of a dehydrogenation catalyst, while high-purity hydrogen (99.9% mol) is produced as a by-product. The hydrogen produced by dehydrogenation is cooled to 102° C. and atmospheric pressure and then sent to a pre-hydrogenation reactor to fully utilize the hydrogen produced by dehydrogenation.

[0050] Example 4

[0051] according to Figure 1 The process shown is based on an 80,000-ton / year cyclododecanone production unit as an example.

[0052] 1) Pre-hydrogenation: The pre-hydrogenation reactor adopts a continuously operated tubular reactor, which is filled with 100 tons of activated hydrogenation catalyst, the pre-hydrogenation reaction temperature is 90 ° C, the reaction pressure is 2 MPaG, the initial raw material 9,10-epoxy-1,5-cyclododecadiene and solvent ethanol are prepared into a raw material liquid in a mass ratio of 1:9 and then introduced into the pre-hydrogenation reactor, the raw material mass space velocity is 0.10h -1 , reacting with the high-purity hydrogen collected from the desolventizing tower and the dehydrogenation process. The purity of the hydrogen from the desolventizing tower is 99.5% (mol), and the flow rate is 150Nm 3 / h, the purity of hydrogen from the dehydrogenation part is 99.9% (mol), and the flow rate is 1398Nm 3 / h, the molar ratio of the total amount of recycled hydrogen to the initial raw material 9,10-epoxy-1,5-cyclododecadiene is 1.23, and after pre-hydrogenation, a pre-hydrogenation reaction liquid with epoxycyclododecane as the main component (excluding solvent ethanol) is obtained. The heat transfer power of the pre-hydrogenation reactor is 1751kW, and the exhaust gas of the pre-hydrogenation reactor is 134Nm 3 / h;

[0053] 2) Secondary hydrogenation: The secondary hydrogenation reactor adopts a continuously operated tubular reactor, in which 100 tons of activated hydrogenation catalyst is loaded. The pre-hydrogenation reaction liquid is heated at a mass space velocity of 0.10h -1 (calculated based on the initial raw material 9,10-epoxy-1,5-cyclododecadiene) was pumped into a secondary hydrogenation reactor at a secondary hydrogenation temperature of 50° C., a reaction pressure of 16 MPaG, a molar ratio of hydrogen to the raw material 9,10-epoxy-1,5-cyclododecadiene (calculated based on the initial amount) of 2.14, and after secondary hydrogenation, a secondary hydrogenation reaction liquid with cyclododecanol as the main component (excluding the solvent ethanol) was obtained, wherein the selectivity of cyclododecanol was 98.8%, and the heat transfer power of the secondary hydrogenation reactor was 4179 kW;

[0054] 3) Refining: The secondary hydrogenation reaction liquid is fed to a desolventizing tower. The operating conditions of the desolventizing tower are: pressure 60 kPaG, tower bottom temperature 198° C., reflux ratio 0.5, and solvent ethanol and non-condensable hydrogen are obtained at the top of the tower. The solvent ethanol is reused, and the hydrogen (99.5%, mol) is cooled to 38° C. and 60 kPaG before being fed to a pre-hydrogenation reactor. The bottom of the desolventizing tower contains a crude cyclododecanol product containing a small amount of ethanol. This crude product is fed to a product refining tower. Under the conditions of a tower pressure of -55 kPaG and a tower bottom temperature of 160° C., the ethanol content in the tower bottom material can be controlled to be less than 20 ppm. The bottom of the product refining tower contains a high-purity cyclododecanol product with a purity of ≥99.3 wt%;

[0055] 4) Dehydrogenation: The high-purity cyclododecanol product is pumped into a dehydrogenation reactor at a reaction temperature of 290° C. and a reaction pressure of 80 kPaA. Cyclododecanone is produced in the presence of a dehydrogenation catalyst, while high-purity hydrogen (99.9% mol) is produced as a by-product. The hydrogen produced by dehydrogenation is cooled to 170° C. and atmospheric pressure and then sent to a pre-hydrogenation reactor to fully utilize the hydrogen produced by dehydrogenation.

[0056] Comparative Example 1

[0057] according to Figure 2 The process shown is based on an 80,000-ton / year cyclododecanone production unit as an example.

[0058] 1) Hydrogenation: The hydrogenation reactor adopts a continuously operated tubular reactor, which is filled with 60 tons of activated hydrogenation catalyst. The raw material 9,10-epoxy-1,5-cyclododecadiene and the solvent methanol are prepared into a raw material liquid in a mass ratio of 3:7 and then introduced into the hydrogenation reactor. The raw material liquid mass space velocity is 0.17h -1 , hydrogenation reaction temperature 155℃, reaction pressure 18MPaG, fresh hydrogen flow rate 4365Nm 3 / h, and after high-pressure hydrogenation, a hydrogenation reaction liquid with cyclododecanol as the main component (excluding the solvent methanol) is obtained, wherein the cyclododecanol selectivity is 97.3%, and the heat transfer power of the hydrogenation reactor is 5930kW;

[0059] 2) Refining: The hydrogenation reaction liquid is sent to the desolventizing tower. The operating conditions of the desolventizing tower are: pressure 60kPaG, tower bottom temperature 198℃, reflux ratio 0.5, and solvent methanol and non-condensable hydrogen are obtained at the top of the tower. The solvent methanol is recycled and the hydrogen is sent for incineration. The hydrogen flow rate of this part is 594Nm 3 / h; the desolventizing tower kettle contains a crude cyclododecanol product containing a small amount of methanol, which is fed to the product refining tower. Under the conditions of a tower pressure of -75kPaG and a kettle temperature of 142°C, the methanol content in the kettle material can be controlled to be less than 30ppm. The cyclododecanol product in the kettle of the product refining tower is cyclododecanol, and the purity of the cyclododecanol product is ≥99.0wt%;

[0060] 3) Dehydrogenation: The cyclododecanol product is pumped into the dehydrogenation reactor at a reaction temperature of 235°C and a reaction pressure of 83 kPaA. While cyclododecanone is generated under the dehydrogenation catalyst, high-purity hydrogen is produced as a by-product. The by-product hydrogen flow rate is 1207 Nm 3 / h, and sent for incineration.

[0061] In Comparative Example 1, 1801 Nm of waste hydrogen was generated which needed to be incinerated. 3 / h, while in Example 1 of the present invention, the waste hydrogen gas to be incinerated is only 127Nm 3 / h, the waste hydrogen treatment volume is reduced by 1674Nm 3 / h, accounting for 92.9%, and saving about RMB 40 million annually. In addition, the heat removal power of the secondary hydrogenation reactor of the embodiment using the method of the present invention is at least 25% lower than that of the comparative example 1, and the selectivity of cyclododecanol in the embodiment is also significantly higher than that in the comparative example 1.

[0062] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description is not intended to limit the present invention. Those skilled in the art will appreciate that, based on the teachings of this specification, modifications or adjustments may be made to the present application. Such modifications or adjustments should also be within the scope defined by the claims of this application.

Claims

1. An energy-saving method for producing cyclododecanone, characterized in that the method include: 1) Pre-hydrogenation: in the presence of a solvent and a hydrogenation catalyst, 9,10-epoxy-1,5-cyclododecadiene reacts with hydrogen to obtain a pre-hydrogenation reaction liquid; 2) Secondary hydrogenation: secondary hydrogenation of the pre-hydrogenation reaction liquid and hydrogen in the presence of a hydrogenation catalyst to obtain a secondary hydrogenation reaction liquid containing cyclododecanol; 3) Refining: The secondary hydrogenation reaction liquid is passed through a desolventizing tower and a product refining tower to obtain a cyclododecyl alcohol product, wherein the hydrogen collected at the top of the desolventizing tower is returned to the pre-hydrogenation step for hydrogenation reaction; 4) Dehydrogenation: The cyclododecanol product is dehydrogenated in a dehydrogenation reactor to produce cyclododecanone, and the hydrogen produced by the dehydrogenation is returned to the pre-hydrogenation step for hydrogenation reaction.

2. The method according to claim 1, characterized in that In step 1), the solvent is a small molecule alcohol, selected from at least one of methanol, ethanol and isopropanol. Preferably, the amount of the small molecule alcohol added is 1 to 10 times the initial mass of the raw material 9,10-epoxy-1,5-cyclododecadiene.

3. The method according to claim 1, characterized in that In step 1), the pre-hydrogenation reaction temperature is 30-120° C. and the reaction pressure is 0.1-3 MpaG; Preferably, the molar ratio of the amount of hydrogen to the initial content of 9,10-epoxy-1,5-cyclododecadiene in step 1) is 1.0 to 1.5, and the mass space velocity calculated based on the initial content of 9,10-epoxy-1,5-cyclododecadiene is 0.1 to 1.0 h -1 .

4. The method according to any one of claims 1 to 3, characterized in that: In step 1) and step 2), the hydrogenation catalyst is selected from one or more of a nickel catalyst, a cobalt catalyst, a palladium catalyst, a platinum catalyst, a ruthenium catalyst, and a rhodium catalyst, preferably one or more of a supported nickel catalyst, a cobalt catalyst, a palladium catalyst, and a platinum catalyst.

5. The method according to claim 1, characterized in that In step 2), the secondary hydrogenation reaction temperature is 50-150°C and the reaction pressure is 8-16MpaG; Preferably, the molar ratio of the amount of hydrogen to the initial amount of 9,10-epoxy-1,5-cyclododecadiene in step 2) is 2 to 2.14, and the mass space velocity is 0.10 to 0.25 h / min based on the initial content of 9,10-epoxy-1,5-cyclododecadiene. -1 .

6. The method according to any one of claims 1 to 5, characterized in that: In step 1) and step 2), the hydrogenation reactor is selected from a kettle or a tubular reactor, preferably selected from an intermittently operated stirred kettle, a continuously operated stirred kettle or a continuously operated tubular reactor, more preferably a continuously operated stirred kettle or a continuously operated tubular reactor.

7. The method according to claim 1, characterized in that In step 3), the operating pressure of the desolventizing tower is 60 kPaG to 1200 kPaG, preferably 60 kPaG to 120 kPaG, and the tower bottom temperature is 145° C. to 200° C.; Preferably, in step 3), the hydrogen temperature at the top of the desolventizing tower is 35°C to 45°C, the pressure is 60kPaG to 1000kPaG, preferably 60kPaG to 120kPaG, and the hydrogen purity is ≥99.5% (mol).

8. The method according to claim 1, characterized in that In step 3), the operating pressure of the product refining tower is -75kPaG to 10kPaG, preferably -75kPaG to -50kPaG, the tower bottom temperature is 140°C to 180°C, and the small molecular alcohol content in the tower kettle is controlled below 40ppm.

9. The method according to claim 1, characterized in that: In step 4), the dehydrogenation catalyst uses a copper catalyst, preferably a supported copper catalyst; Preferably, in step 4), the temperature of the dehydrogenation reactor is 195°C to 290°C, and the reaction pressure is 80 to 125 kPaA; Preferably, in step 4), the temperature of hydrogen generated during the dehydrogenation process is 70° C. to 170° C., and the purity of the hydrogen is ≥ 99.9% (mol).

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