A method for preparing CDON by EPO or ECDA catalytic hydrogenation and dehydrogenation

Abstract

This invention discloses a method for preparing CDOL via EPO / ECDA catalytic hydrogenation, followed by purification and dehydrogenation to prepare CDON. Common small-molecule alcohols are used as solvents in the hydrogenation reaction. The hydrogenation reaction mixture is separated by distillation and stripping, with the small-molecule alcohol solvent recycled, resulting in high-purity CDOL. CDOL, as a reactant, undergoes catalytic dehydrogenation to produce hydrogen and CDON. The gaseous mixture from the dehydrogenation reaction is condensed in a condenser to separate the product CDON and the byproduct hydrogen. The byproduct hydrogen is used as stripping gas for the purification of the CDOL product. This specially designed process allows for the full utilization of process materials, reduces waste gas, lowers energy consumption, saves operating costs, and improves the stability of the equipment operation.

Description

Technical Field

[0001] This invention relates to the field of separation technology in chemical processes, specifically to a process and method for the catalytic hydrogenation of EPO / ECDA to obtain CDOL, and the dehydrogenation of CDOL to prepare CDON. Background Technology

[0002] CDOL (cyclododecanol, CAS No. 1724-39-6, molecular formula C) 12 H 24 O) is an important intermediate in the Nylon 12 (PA12) industrial chain. Its main use is in the dehydrogenation preparation of CDON (cyclododecanone, CAS No. 830-13-7, molecular formula C). 12 H 22 O).

[0003] Patent CN105315146A describes a method for preparing cyclododecanone: cyclododecanene (CDEN) is oxidized to cyclododecane oxide, and the cyclododecane oxide is rearranged to cyclododecanone (CDON). During the reaction, cyclododecyl alcohol (CDOL) is generated as a byproduct, and CDOL is dehydrogenated to obtain cyclododecanone (CDON). Patent CN105315140A describes a method for preparing CDON, oxidizing cyclododecene (CDEN) to cyclododecane oxide (ECDA), rearranging the cyclododecane oxide to cyclododecanone (CDON), and oxidizing the byproduct cycloeicosane to CDON. Patent CN 103055880A describes a catalyst for the dehydrogenation of cyclododecyl alcohol to prepare ketones and its preparation method, disclosing a catalyst whose main active component is copper, with zinc as a support, and a reaction temperature of 230°C. Patent CN 103864591A discloses a method for separating a mixture of CDOL and CDON.

[0004] The above-mentioned processes for preparing CDON have some insurmountable drawbacks: the oxidation of cyclododecane to cyclododecone has poor reaction selectivity, complex reaction products, low yield of the target product, and is difficult to separate and purify. The hydrogenation of CDT (1,5,9-cyclododecanetriene) to CDEN has harsh reaction conditions, high exothermic reaction, and poor safety. The epoxidation of CDEN to ECDA, followed by rearrangement of ECDA to CDON, is difficult to separate from CDDA, and produces complex byproducts.

[0005] This invention discloses a process for the hydrogenation of EPO / ECDA to obtain CDOL, and the dehydrogenation of CDOL to prepare CDON. EPO (9,10-epoxy-1,5-cyclododecadiene, CAS No. 943-93-1) can be prepared by the epoxidation reaction of CDT. The overall yield from EPO to CDON can reach over 98%, with higher selectivity and yield than the oxidation reaction process, improving the atom economy of the process. The EPO / ECDA hydrogenation reaction, by selecting a suitable solvent, can improve the controllability of the reaction process and reduce the risk of runaway reaction. Optimizing and coupling the above process route using chemical systems engineering methods and theories can reduce waste gas, make on-site operation more user-friendly, and improve process competitiveness. Summary of the Invention

[0006] The purpose of this invention is to provide a system and method for the preparation of CDOL by catalytic hydrogenation of EPO / ECDA and the preparation of CDON by dehydrogenation of CDOL. Through system optimization, the cost of separating CDOL from the hydrogenation reaction mother liquor and the small molecule alcohol solvent can be reduced, while the process materials entrained in the tail gas of the dehydrogenation reactor can be reduced, thereby improving competitiveness.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] The first aspect of the present invention provides a system for preparing CDON:

[0009] The system described in this invention includes: a solvent stripping tower, a solvent stripping tower, a dehydrogenation reactor, and a tail gas cooler, etc.

[0010] The bottom material outlet of the solvent stripping tower is connected to the top liquid inlet of the solvent stripping tower, the bottom product outlet of the solvent stripping tower is connected to the inlet of the dehydrogenation reactor (a buffer tank can be installed in between), the liquid outlet of the dehydrogenation reactor is connected to the downstream refining and separation system, the gas outlet of the dehydrogenation reactor is connected to the tail gas cooler, and the gas outlet of the tail gas cooler is connected to the bottom of the solvent stripping tower.

[0011] The top material outlet of the solvent stripping tower is connected to the solvent recovery system. After the gas phase at the top of the solvent stripping tower is cooled, the liquid phase enters the solvent stripping tower, and the gas phase tail gas is used to recover hydrogen or sent for appropriate treatment.

[0012] In a second aspect, the present invention provides a method for preparing CDOL by catalytic hydrogenation of EPO / ECDA and for preparing CDON by dehydrogenation of CDOL.

[0013] The method for preparing CDOL by EPO / ECDA catalytic hydrogenation and CDOL dehydrogenation to prepare CDON according to the present invention includes:

[0014] 1) Using small molecule alcohols as solvents, hydrogenation reaction mother liquor containing CDOL is obtained by catalytic hydrogenation of 9,10-epoxy-1,5-cyclododecadiene (EPO) or epoxycyclododecane (ECDA);

[0015] 2) The mother liquor from the hydrogenation reaction enters the desolventizing tower to remove and recover most of the small molecule alcohol solvent;

[0016] 3) The mother liquor from the bottom of the solvent stripping tower then enters the solvent stripping tower to further remove the remaining small molecule alcohol solvent by stripping, thus meeting the feed requirements of the downstream dehydrogenation reactor. The bottom of the solvent stripping tower yields CDOL product.

[0017] 4) CDOL is pumped into the dehydrogenation reactor, where an endothermic dehydrogenation reaction occurs under specific temperature and pressure conditions. The reactor outlet yields CDON, hydrogen, and unreacted CDOL. The liquid phase enters the downstream refining and separation system, while the gas phase enters the tail gas cooler for CDOL / CDON recovery before being fed into the solvent stripping tower as stripped gas. Due to the high temperature of the dehydrogenation reaction, the gas phase contains a significant amount of CDON / CDOL. The tail gas enters the tail gas cooler for condensation, recovering process materials. By controlling parameters such as the temperature of the condensed tail gas, it can be used as stripped gas for solvent removal in the upstream solvent stripping tower. To improve the efficiency of the entire process, this tail gas can be appropriately pressurized, and its temperature, pressure, and composition can be controlled.

[0018] The hydrogenation reaction mother liquor refers to a solution using a small molecule alcohol as a solvent, which catalyzes the reaction of 9,10-epoxy-1,5-cyclododecadiene (CAS No. 943-93-1, molecular formula C...). 12 H 18 O) or epoxycyclododecane (CAS No. 286-99-7, molecular formula C) 12 H 22 The reaction solution containing CDOL obtained by hydrogenation (O) catalyzes the hydrogenation of 9,10-epoxy-1,5-cyclododecadiene or cyclododecane. This reaction involves high pressure, a large hydrogen circulation volume, harsh conditions, and the release of significant heat. Diluting the reaction raw materials with small-molecule alcohols (such as methanol, ethanol, and isopropanol) as solvents can effectively improve the safety and controllability of the hydrogenation reaction, enhance its selectivity, and improve the economic competitiveness of the process. Furthermore, small-molecule alcohols can increase the solubility of hydrogen in the liquid phase and enhance mass transfer in the hydrogenation reaction. The amount of small-molecule alcohol added is 1 to 10 times the mass of EPO / ECDA.

[0019] The above-mentioned hydrogenation reaction mother liquor is subjected to distillation, gas stripping and separation to obtain CDOL product with high purity that meets the requirements of dehydrogenation reaction feed. CDOL is then used as raw material to prepare CDON through catalytic dehydrogenation.

[0020] The aforementioned hydrogenation reaction mother liquor is a mixture containing CDOL and a small molecule alcohol solvent. If the small molecule alcohol enters the dehydrogenation system, it will undergo side reactions on the dehydrogenation catalyst, causing coking and adhesion to the catalyst, affecting its performance and shortening its lifespan. Therefore, the solvent needs to be removed before entering the dehydrogenation reactor. CDOL has a boiling point exceeding 270℃ at atmospheric pressure, while commonly used small molecule alcohols have a boiling point below 100℃ at atmospheric pressure, a significant difference in boiling points. According to the principle of phase equilibrium, if the two components are separated solely through distillation, the temperature difference between the top and bottom of the column will be substantial. If the distillation column operates under atmospheric or pressurized conditions, the CDOL concentration and temperature at the bottom will be very high, resulting in extremely high costs and reduced safety for heating utilities. If operated under vacuum conditions, the purity of the small molecule alcohol at the top of the column will be very high, requiring low-temperature utilities, which are also extremely costly. Therefore, considering the characteristics of this process material, a combination of distillation (solvent removal column) and stripping (solvent stripping column) for solvent removal is the preferred solution.

[0021] The solvent removal column recovers most of the small-molecule alcohol solvent from the hydrogenation reaction mother liquor. The column operates under suitable pressure, with the top containing high-purity, appropriately heated small-molecule alcohol solvent, while the bottom contains a mixture of solvent and CDOL. Because the bottom contains a certain amount of small-molecule alcohol solvent, its temperature is relatively low, allowing the use of low-grade steam as a heat source to reduce bottom heat source costs.

[0022] The content of small molecule alcohol solvent in the bottom product of the solvent stripping tower is already low. The bottom product enters the solvent stripping tower, where the remaining small molecule alcohol solvent is removed by gas stripping, ensuring that the solvent content in CDOL meets the process requirements.

[0023] For the stripping gas used in solvent stripping towers, inert gases such as nitrogen are typically used. However, using nitrogen as the stripping gas introduces nitrogen components into the system, generating waste gas containing trace amounts of process materials and small-molecule alcohol solvents, which is then sent for incineration. The introduction of nitrogen increases operating costs. This application, through system coupling, controls the composition of the cooled tail gas discharged from the dehydrogenation reactor at specific temperature, pressure, and composition, returning it to the solvent stripping tower as stripping gas. Furthermore, through proper design, the tail gas can be used to improve the vacuum level of the stripping system, enhance the stripping effect, and further reduce the small-molecule alcohols in CDOL products.

[0024] On the other hand, after cooling, most of the CDOL / CDON in the gaseous phase of the dehydrogenation reactor condenses into a liquid phase. According to phase equilibrium calculations, approximately 1.5% CDOL / CDON by mass remains in the tail gas. This CDOL / CDON mixture in the tail gas has a high freezing point, and if operated for a long period, it may gradually solidify on pipelines, valves, and fittings, clogging pipes and affecting valve operation. Using the dehydrogenation reactor tail gas as stripping gas absorbs the high-freezing-point CDOL / CDON, significantly reducing its content and significantly decreasing the risk of clogging subsequent pipelines, thus contributing to the stable, long-term, and high-efficiency operation of the unit.

[0025] In one specific implementation, in step 1), the hydrogenation reaction temperature is 50–200°C, the reaction pressure is 6–18 MPaG, the catalyst is preferably a carbon-supported nickel catalyst, a carbon-supported palladium catalyst, or a nickel-aluminum alloy catalyst, and the mass hourly space velocity is 0.03–0.25 g / gcat / h; the catalyst can be one of the catalysts in patents such as CN 107649149 A, CN 109225261 A, CN 106140195 A, CN 104607207 A, and CN 103977819 A.

[0026] In one specific implementation, in step 2), the operating pressure of the desolventizing tower is -50 kPaG to 10 barG, and the bottom temperature of the tower is 140 to 195°C. By controlling the concentration of small molecule alcohol solvent in the bottom material of the tower, the bottom temperature of the reaction vessel is controlled below 195°C.

[0027] In a preferred embodiment, in step 3), the operating pressure of the solvent stripping tower is -80 kPaG to 20 kPaG, and the molar ratio of stripping gas to the liquid feed at the top of the tower can be controlled to be 0.5:1 to 3:1, so as to control the content of small molecule alcohol in the bottom of the tower to below 20 ppm. The tail gas can be cooled, separated and then recycled according to the actual situation.

[0028] The stripping gas used in the stripping process comes from the tail gas cooler. After being condensed by the tail gas cooler, the gas phase material stream (stripping gas) entering the solvent stripping tower has a temperature of 75-150°C, a pressure of 95-115 kPaA, and a CDOL / CDON content of 0.8-4 wt%.

[0029] In a preferred embodiment, two stripping towers with different operating pressures can be set up. The tail gas from the dehydrogenation reactor and the process material flow countercurrently or in parallel gas phase through the two stripping towers to improve the stripping effect. A preheater or cooler can be set between the two towers.

[0030] In a preferred embodiment, the stripping gas can be vacuumed by jetting and then fed into the stripping tower to provide the vacuum required for stripping and enhance the stripping effect.

[0031] In a preferred embodiment, the feed to the solvent stripping tower may be preheated as needed.

[0032] In one specific implementation, in step 4), the reaction temperature of the dehydrogenation reactor is 190–270°C, and the reaction pressure is 90–120 kPaA; the main active component of the catalyst is copper, and zinc can be used as a support, such as catalysts CN 103055880A, CN101733130A, and CN102271808A, with a space velocity of 0.3–1.5 g / gcat / h;

[0033] In one specific implementation, the temperature of the gaseous stream of reaction products entering the exhaust gas cooler is 190–270°C, and the pressure is 90–120 kPaA (absolute pressure); the inlet temperature of the refrigerant used in the exhaust gas cooler is 70–75°C, and the outlet temperature is 80–85°C; preferably, the refrigerant is selected from circulating water or hot water exchange.

[0034] In summary, the positive effects of the present invention are as follows:

[0035] 1) This invention avoids the introduction of inert stripping gases, such as nitrogen, into the hydrogenation mother liquor refining system through integrated process design, thereby reducing costs.

[0036] 2) Through the integrated design of the process, this invention absorbs the material in the tail gas of the dehydrogenation reactor containing high freezing point materials, thus avoiding the risk of material solidification in the gas phase pipeline.

[0037] 3) The hydrogen obtained from the exhaust gas of this invention has high purity, and the by-product hydrogen can be recovered and refined at a low cost, resulting in high economic benefits. Furthermore, the amount of exhaust gas generated is significantly reduced, making it a more environmentally friendly process. Attached Figure Description

[0038] Figure 1 , Figure 2 This is a schematic diagram of the CDOL catalytic dehydrogenation process for the preparation of CDON according to the present invention.

[0039] Among them, 1 is the solvent removal tower, 2 is the solvent stripping tower, 3 is the dehydrogenation reactor, and 4 is the tail gas cooler. Detailed Implementation

[0040] To better understand the technical solution of the present invention, the following embodiments will further illustrate the method provided by the present invention. However, the present invention is not limited to the listed embodiments, but should also include any other known modifications within the scope of the claims of the present invention.

[0041] Skeletal nickel catalyst: The catalyst used is from Example 1 of patent CN 107649149 A.

[0042] Dehydrogenation catalyst: The catalyst of Example 2 of patent CN101733130A is used.

[0043] Example 1

[0044] according to Figure 1 The process shown is based on an 80,000-ton / year production unit as an example.

[0045] 1) The hydrogenation reaction feedstock EPO and methanol solvent were prepared into a solution at a mass ratio of 1:3. The catalyst used was the catalyst in Example 1 of CN107649149A. The material space velocity was 0.08 g / gcat / h. After high-pressure hydrogenation (reaction temperature 160℃, reaction pressure 16MPa), a mixture of CDOL and small molecule alcohol solvent was obtained.

[0046] 2) The reaction mixture enters the desolventizing column. The operating conditions of the desolventizing column are: pressure -50 kPaG, column bottom temperature 180℃, reflux ratio 0.4. Through distillation separation, the solvent methanol obtained at the top of the column is recycled, and CDOL product containing a certain amount of methanol solvent is obtained at the bottom of the column.

[0047] 3) The material from the bottom of the solvent stripping tower enters the solvent stripping tower, which consists of two sections. The upper section operates at a pressure of -60 kPaG and a temperature of approximately 175°C. The material flows by gravity into the lower section, where the operating pressure is -80 kPaG and the temperature is approximately 175°C. The lower section is evacuated using an ejector, and qualified CDOL is obtained from the bottom of the tower, with its methanol content controlled to be below 10 ppm.

[0048] 4) The qualified CDOL product enters the dehydrogenation reactor, the reaction temperature is 200℃, the reaction pressure is atmospheric pressure, the catalyst is the catalyst of Example 2 of patent CN101733130A, the space velocity is 1g / gcat / h, CDON is generated, and hydrogen is produced as a by-product.

[0049] 5) After cooling, the hydrogen tail gas is controlled at a temperature of 75°C and a pressure of atmospheric pressure, with a CDOL / CDON content of 0.8%. The tail gas is pressurized to 7 barG and sent to the stripping tower. The pressure in the lower section is controlled at -80 kPaG by vacuum injection. The material at the ejector outlet enters the upper section of the stripping tower as stripping gas to achieve the function of solvent removal.

[0050] The molar yield from EPO to CDON can reach 98.5%. Through process coupling and enhancement, the amount of nitrogen used for stripping can be reduced by 700 Nm3 / h, the amount of exhaust gas discharged from the unit can be reduced by 1928 Nm3 / h, the annual operating cost can be saved by about RMB 1 million, and the risk of hydrogen pipeline blockage can be greatly reduced.

[0051] Example 2

[0052] according to Figure 2 The process shown is based on an 80,000-ton / year production unit as an example.

[0053] 1) The hydrogenation reaction feedstock EPO and methanol solvent were prepared into a solution at a ratio of 1:2. After high-pressure hydrogenation, the mixture was subjected to a reaction temperature of 170°C and a reaction pressure of 15 MPa. The catalyst used was the catalyst of Example 1 of CN 107649149 A. The mass hourly space velocity of the material was 0.12 g / gcat / h, and a mixture of CDOL and methanol solvent was obtained.

[0054] 2) The reaction mixture enters the desolventizing column. The operating conditions of the desolventizing column are: pressure 50 kPaG, column bottom temperature 185℃, reflux ratio 0.2. Through distillation separation, the solvent is recycled at the top of the column, and CDOL product containing a certain amount of methanol solvent is obtained at the bottom of the column.

[0055] 3) The material from the bottom of the solvent stripping tower enters the solvent stripping tower, which consists of two stages. The operating conditions for the first tower are: pressure -50 kPaG and bottom temperature approximately 180°C; the operating conditions for the second tower are: pressure -70 kPaG and bottom temperature 185°C. The material from the bottom of the first tower is heated to 195°C before entering the second tower. The methanol content in the bottom product of the second tower can be controlled to be below 10 ppm.

[0056] 4) The qualified CDOL product obtained enters the dehydrogenation reactor. The reaction temperature is 260℃, the reaction pressure is atmospheric pressure, the catalyst used is the catalyst of Example 1 (CN 103055880A), and the space velocity is 1.2 g / gcat / h. CDON is generated and hydrogen is produced as a byproduct.

[0057] 5) To achieve better gas stripping effect, the tail gas of the dehydrogenation reactor is cooled to 100°C and the pressure is atmospheric pressure. The CDON / CDOL content in the gas phase is 2.5%. It is then sent to a two-stage gas stripping tower, where CDON / CDOL in the tail gas is removed by washing.

[0058] The molar yield from EPO to CDON can reach 98.2%. Through process coupling and enhancement, the amount of nitrogen used for stripping can be reduced by 1300 Nm3 / h, the amount of exhaust gas discharged from the unit can be reduced by 2528 Nm3 / h, the annual operating cost can be saved by about RMB 1.85 million, and the risk of hydrogen pipeline blockage is greatly reduced.

[0059] Although the present invention has been described in detail through the preferred embodiments described above, it should be understood that the above description should not be considered as a limitation of the present invention. Those skilled in the art will understand that modifications or adjustments can be made to the present invention based on the teachings of this specification. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A method for preparing CDON, using a system as described below, the system comprising: Solvent stripping tower, solvent stripping tower, dehydrogenation reactor, tail gas cooler; The bottom material outlet of the solvent stripping tower is connected to the top liquid inlet of the solvent stripping tower, the bottom product outlet of the solvent stripping tower is connected to the inlet of the dehydrogenation reactor, the liquid outlet of the dehydrogenation reactor is connected to the downstream refining and separation system, the gas outlet of the dehydrogenation reactor is connected to the tail gas cooler, and the gas outlet of the tail gas cooler is connected to the bottom of the solvent stripping tower. The method for preparing CDON includes: 1) Using small molecule alcohols as solvents, hydrogenation reaction mother liquor containing CDOL is obtained by catalytic hydrogenation of 9,10-epoxy-1,5-cyclododecadiene or epoxycyclododecane. 2) The mother liquor from the hydrogenation reaction enters the desolventizing tower to remove and recover most of the small molecule alcohol solvent; 3) The mother liquor from the bottom of the solvent stripping tower enters the solvent stripping tower, where the remaining small molecule alcohol solvent is further removed by stripping. The bottom of the solvent stripping tower yields CDOL product. 4) CDOL product is fed into the dehydrogenation reactor, where an endothermic dehydrogenation reaction occurs under certain temperature and pressure conditions. The dehydrogenation reactor outlet yields CDON product, hydrogen, and unreacted CDOL. The liquid phase enters the downstream refining and separation system, while the gas phase enters the tail gas cooler to cool and recover CDOL / CDON before entering the bottom of the solvent stripping tower as stripped gas.

2. The method according to claim 1, wherein, The top material outlet of the solvent stripping tower is connected to the solvent recovery system. After the gas phase at the top of the solvent stripping tower is cooled, the liquid phase enters the solvent stripping tower, and the gas phase tail gas is recovered or sent for appropriate treatment.

3. The method according to claim 1, wherein, Step 1) The small molecule alcohol is selected from at least one of methanol, ethanol, and isopropanol.

4. The method according to claim 3, wherein, Step 1) The amount of small molecule alcohol added is 1 to 10 times the mass of EPO / ECDA.

5. The method according to claim 1 or 2, wherein, In step 1), the hydrogenation reaction temperature is 50–200°C and the reaction pressure is 6–18 MPaG; the catalyst is a carbon-supported nickel catalyst, a carbon-supported palladium catalyst, or a nickel-aluminum alloy catalyst.

6. The method according to claim 5, wherein, In step 1), the mass hourly space velocity is 0.03–0.25 g / gcat / h.

7. The method according to any one of claims 1-2, wherein, In step 2), the operating pressure of the desolventizing tower is -50 kPaG to 10 barG, and the bottom temperature of the tower is 140 to 195°C.

8. The method according to any one of claims 1-2, wherein, In step 3), the operating pressure of the solvent stripping tower is -80 kPaG to 20 kPaG, and the content of small molecule alcohols in the tower bottom is controlled below 20 ppm.

9. The method according to any one of claims 1-2, wherein, In step 3), two solvent stripping towers are set.

10. The method according to any one of claims 1-2, wherein, In step 3), the stripping gas used comes from the tail gas cooler, with a temperature of 75-150℃, a pressure of 95-115 kPaA, and a CDOL / CDON content of 0.8-4 wt%.

11. The method according to any one of claims 1-2, wherein, In step 4), the reaction temperature of the dehydrogenation reactor is 190–270 °C and the reaction pressure is 90–120 kPaA.

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