Method and device for preparing cyclohexene by partial hydrogenation of benzene

Abstract

The invention discloses a method and a device for preparing cyclohexene by partial hydrogenation of benzene. The device is formed by connecting 2-3 reaction units in series, the reaction unit comprises a reaction kettle and a split-phase kettle; a material outlet of the reaction kettle is connected with a material inlet of a guide cylinder at the top of the split-phase kettle through a guide pipe, the spherical kettle top of the reaction kettle is communicated with the top of the split-phase kettle through a gas phase balance pipe, and the spherical kettle bottom of the split-phase kettle is communicated with the spherical kettle bottom of the reaction kettle through a circulating pump; a split-phase kettle stirring paddle driven by a motor is arranged on the split-phase kettle along a vertical central axis; and the stirring paddle is positioned between water-phase baffles filled with a catalyst at the bottom of the split-phase kettle. When the device is used for preparing cyclohexene, the catalyst in the water phase is promoted to be uniformly distributed on the premise of ensuring that the oil phase and the water phase are not backmixed, so that the separation effect is ensured, the catalytic efficiency is also improved, and the industrial production requirement that the single set of cyclohexene is more than 300,000 tons per year can be met.

Description

Technical Field

[0001] The invention relates to a method for preparing cyclohexene, in particular to a method and device for preparing cyclohexene by partial hydrogenation of benzene, and belongs to the field of petrochemical technology development. Background Art

[0002] Cyclohexene is an important organic chemical raw material, widely used in the production of medicines, pesticides, dyes, detergents, feed additives, polyester and polyamide products; traditional cyclohexene production methods include cyclohexanol dehydration, cyclohexane dehydrohalogenation, cyclohexane dehydrogenation, etc. Due to the use of high-cost cyclohexanol and cyclohexane as raw materials, cyclohexene produced by the above methods can only be used for the production of a few high-value-added fine chemical products such as L-lysine and cyclohexene oxide. Benzene is abundant and inexpensive, so the preparation of cyclohexene by partial hydrogenation of benzene is the first choice for modern industrial production.

[0003] In the 1990s, Asahi Kasei of Japan took the lead in realizing the industrial production of cyclohexene by partial hydrogenation of benzene, using ruthenium as a catalyst and zinc sulfate aqueous solution as a circulating phase. Benzene and hydrogen were partially hydrogenated in a reactor to obtain cyclohexene. Shenma Group was the first to introduce this technology in China, and Shijiazhuang Coking Group also introduced Asahi Kasei's process in the early 21st century. With the in-depth research in China, many patents have been applied for in the catalysts and reaction devices of the cyclohexene preparation process.

[0004] Invention patent CN1696087A discloses a device for producing cyclohexene by hydrogenating benzene. The design of the oil-water phase separator is complex, which increases the difficulty of production. In addition, in order to ensure the uniform distribution of the catalyst in the water phase during operation, a short residence time is designed, resulting in a difference in oil and water phases, and the oil phase entrains the catalyst, which increases the consumption of the catalyst. On the contrary, in order to ensure the oil-water phase effect, the residence time must be increased, which will lead to catalyst deposition and uneven distribution.

[0005] Invention patent CN101850225B discloses a tubular reactor and membrane catalyst recovery system. Although the tubular reactor has a simple structure, it has limitations in the four-phase mass transfer reaction of partial hydrogenation of benzene, which is not conducive to improving the conversion rate; in addition, the membrane is difficult to operate and maintain in multiphase filtration.

[0006] Invention patent CN102241558B discloses a reaction device and process for preparing cyclohexene by selective hydrogenation of benzene. The invention mainly emphasizes the external static mixing of materials benzene, hydrogen, and circulating water phase. Since the gas-liquid-liquid-solid four phases are difficult to simply mix and maintain uniformity, the effect is not obvious; in addition, the catalyst in the water phase will be unevenly distributed in the sedimentation tank, resulting in changes in the catalyst concentration.

[0007] Invention patent CN112023852B discloses a production device for preparing cyclohexene by partial hydrogenation of benzene. The invention adopts three-stage series-connected reactors and a separation reactor with stirring to carry out partial hydrogenation of benzene to prepare cyclohexene. Although the conversion rate of benzene and the selectivity of cyclohexene are improved, the radial flow requirements of the reactor are high, which is specifically manifested in a large height-to-diameter ratio, which is not conducive to larger-scale industrial production.

[0008] Utility model patent CN202860529U discloses a reaction device for partial hydrogenation of benzene to produce cyclohexene. The utility model is characterized in that upper and lower guide tubes are added to the reactor, and a phase separation zone is generated at the upper part of the reactor to make the catalyst produce internal circulation. The disadvantage is that the oil-water ratio of the reactor is difficult to control, and the selectivity of cyclohexene is reduced.

[0009] Utility model patents CN202460629U and CN206103913U disclose a reaction device for synthesizing cyclohexene by partial hydrogenation of benzene. The characteristic of the utility model is that hydrogen is introduced at multiple points in the reactor to improve the dispersion of hydrogen and the speed of hydrogen absorption. The disadvantage is that the conversion rate is increased and the selectivity of cyclohexene is reduced. Summary of the invention

[0010] In view of the problems existing in the prior art, the first object of the present invention is to provide a method for preparing cyclohexene by partial hydrogenation of benzene. The method adopts a multi-stage reaction unit connected in series to improve the selectivity of cyclohexene and the conversion rate of benzene without reducing the height-to-diameter ratio of the reactor. In the phase separation reactor, a low-speed stirring method is adopted to promote the uniform distribution of the catalyst in the water phase while ensuring that the oil and water phases are not mixed back, thereby ensuring the separation effect and improving the catalytic efficiency, and can meet the industrial production requirements of more than 300,000 tons / year of cyclohexene in a single set.

[0011] The second object of the present invention is to provide a device for preparing cyclohexene by partial hydrogenation of benzene, which is composed of multi-stage reaction units connected in series, each reaction unit includes a reactor and a phase separation reactor, and a low-speed stirring paddle is provided at the bottom of the phase separation reactor. Compared with the static separation method, the low-speed dynamic separation method can avoid the oil-water back-mixing phenomenon, and can also improve the dispersion of the catalyst in the water phase, improve the catalytic efficiency, and reduce the amount of catalyst. The device has the advantages of simple structure, long material residence time and easy operation, and is suitable for continuous production of cyclohexene.

[0012] To achieve the above technical purpose, the present invention provides a device for preparing cyclohexene by partial hydrogenation of benzene, which is composed of 2 to 3 reaction units connected in series; the reaction units include a reactor (1) and a phase separation reactor (2); a reactor overflow weir (7) is provided on the upper part of the reactor wall of the reactor, and the material outlet at the reactor overflow weir is connected to the material inlet of the guide tube (8) at the top of the phase separation reactor through a conduit; the spherical reactor top of the reactor is connected to the top of the phase separation reactor through a gas phase balance pipe (15), and the spherical reactor bottom of the phase separation reactor is connected to the spherical reactor bottom of the reactor through a circulation pump (13);

[0013] The phase separation kettle is provided with a phase separation kettle stirring paddle (10) driven by a motor (14) along the vertical center axis, and the stirring paddle is located between water phase baffles (9) containing catalyst at the bottom of the phase separation kettle;

[0014] An overflow weir of the phase separation kettle is arranged at the upper part of the kettle wall of the phase separation kettle, an oil phase outlet is opened at the overflow weir of the phase separation kettle, and an oil-water interface meter (12) is arranged at the middle and lower part of the kettle wall of the phase separation kettle.

[0015] As a preferred solution, the reactor is provided with a stirring shaft driven by a motor (14) along the vertical central axis, and a plurality of stirring paddles (3) are provided on the stirring shaft at equal heights, and a heat exchange coil (4) is provided between the plurality of stirring paddles, and the bottom stirring paddle is located on the plane with the largest cross-sectional area of ​​the spherical bottom of the reactor.

[0016] As a preferred solution, a liquid-phase feed distributor (5) and a gas-phase feed distributor (6) are inserted into the spherical top of the reactor.

[0017] As a preferred solution, the liquid-phase feed distributor and the gas-phase feed distributor are inserted from the top of the spherical reactor to below the bottommost stirring paddle of the multi-machine stirring paddle.

[0018] As a preferred solution, the height-to-diameter ratio of the reactor is 1 to 2.5:1.

[0019] As a preferred solution, the multi-stage stirring paddles and heat exchange coils in the reactor are both 2 to 3 stages.

[0020] As a preferred solution, the reactor wall is further provided with 4 to 6 spoiler baffles.

[0021] As a preferred solution, the bottom of the multi-stage stirring paddle is propulsion stirring, and the middle and / or upper part is radial flow stirring.

[0022] As a preferred solution, there are 4 to 8 water phase baffles inside the phase separation kettle.

[0023] As a preferred solution, the water phase baffles are evenly distributed around the stirring paddle of the phase separation kettle.

[0024] The present invention also provides a method for preparing cyclohexene by partial hydrogenation of benzene, which is implemented by any of the above-mentioned devices, and the process is as follows:

[0025] 1) Add the catalyst solution into the reactor and turn on the multi-stage stirring paddles and heat exchange coils of the reactor;

[0026] 2) feeding multiple series reaction units through the liquid phase feed distributor and gas phase feed distributor of the reaction kettle of each unit, and turning on the stirring paddle of the phase separation kettle;

[0027] 3) After the feed of each reaction unit is stable, the feed amount and reaction temperature of each unit are adjusted, and cyclohexene is discharged through the oil phase outlet of the phase separation kettle of the last reaction unit;

[0028] In each of the reaction units, the gas phase feed amount of the latter reaction unit is 0.5 to 1.0 times the gas phase feed amount of the former reaction unit.

[0029] As a preferred solution, the catalyst solution is an aqueous solution of zinc sulfate containing a ruthenium catalyst.

[0030] As a preferred solution, the rotation speed of the multi-stage stirring paddles of the reactor is 110 rpm.

[0031] As a preferred solution, the liquid phase feed rate of the first reaction unit in the plurality of series reaction units is 60 to 100 m 3 / h, gas phase feed rate is 11000~15000Nm 3 / h, water phase circulation volume is 140~180m 3 / h.

[0032] As a preferred solution, in the multiple series reaction units, the water phase circulation amount of the latter reaction unit is 0.9 to 1.1 times the water phase circulation amount of the former reaction unit.

[0033] As a preferred solution, in the plurality of series reaction units, the oil-water interface of the phase separation kettle is 30-40%.

[0034] As a preferred solution, the gas phase pressure of each unit reactor in the multiple series reaction units is 45 bar, and the reaction temperature is 130-140°C.

[0035] Each reaction unit of the present invention is a complete separation unit. The phase separation kettle in each unit adopts a low-speed stirring method. Through dynamic mixing, the dispersibility of the catalyst in the water phase is improved, and the amount of the catalyst is greatly reduced. Furthermore, when the oil phase enters the next reaction unit, the diffusion processes of benzene and cyclohexene in the oil phase and the water phase are changed. From an overall perspective, the residence time of the material is effectively extended, thereby improving the conversion rate and selectivity of the raw materials.

[0036] Compared with the prior art, the beneficial technical effects of the present invention are:

[0037] 1) In the method for preparing cyclohexene by partial hydrogenation of benzene provided by the present invention, a multi-stage reaction unit is connected in series, so that the oil-water phase has a complete separation process in each reaction unit; after the oil phase enters the next reaction unit, the diffusion movement speed of benzene and cyclohexene in the oil phase and the water phase is changed; experiments show that: without reducing the height-to-diameter ratio of the reactor, the selectivity of cyclohexene and the conversion rate of benzene are improved, which can meet the industrial production requirements of more than 300,000 tons / year of cyclohexene in a single set.

[0038] 2) The device for preparing cyclohexene by partial hydrogenation of benzene provided by the present invention is composed of multiple reaction units connected in series, each reaction unit includes a reactor and a phase separation reactor, and a low-speed stirring paddle is provided at the bottom of the phase separation reactor. Compared with the static separation method, the low-speed dynamic separation method can avoid the oil-water back-mixing phenomenon, and can also improve the dispersion of the catalyst in the water phase, improve the catalytic efficiency, and reduce the amount of catalyst. The device has the advantages of simple structure, long material residence time and easy operation, and is suitable for continuous production of cyclohexene. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A schematic diagram of a reaction unit process of a method and device for preparing cyclohexene by partial hydrogenation of benzene according to the present invention;

[0040] Among them: 1. Reactor; 2. Phase separation kettle; 3. Stirring paddle; 4. Heat exchange coil; 5. Liquid feed distributor; 6. Gas feed distributor; 7. Overflow weir; 8. Guide tube; 9. Water baffle; 10. Stirring paddle; 11. Overflow weir; 12. Oil-water interface meter; 13. Circulation pump; 14. Motor; 15. Gas phase balance pipe. DETAILED DESCRIPTION

[0041] The present invention is described in detail below with reference to the accompanying drawings and embodiments, but the embodiments do not limit the present invention.

[0042] like Figure 1As shown, the present invention provides a production device for preparing cyclohexene by partial hydrogenation of benzene, which is composed of 2 to 3 reaction units connected in series; the reaction unit reactor 1 and the phase separation reactor 2, the reactor 1 is provided with a three-stage heat exchange coil 4 and a three-stage stirring paddle 3, the heat exchange coil 4 and the three-stage stirring paddle 3 are axially spaced and combined with the temperature point in the reactor 1 to control the reaction temperature, the lower part of the three-stage stirring paddle 3 adopts propulsion stirring, and the middle and upper parts adopt radial flow stirring, which is driven by a motor 14 arranged on the top of the reactor 1. A gas phase feed distributor 6 and a liquid phase feed distributor 5 are provided at the bottom of the reactor 1, and a reactor overflow weir 7 is also provided in the reactor 1. A material outlet is provided at the reactor overflow weir to enter the phase separation reactor 2; an inlet material guide tube 8 and an overflow weir 11 are provided in the phase separation reactor 2, a gas phase balance hole is provided on the upper part of the guide tube, an oil phase outlet is provided at the overflow weir 11 to enter the next-stage reaction unit reactor or discharge cyclohexene, a phase separation reactor stirring paddle 10 is provided in the water phase at the bottom of the phase separation reactor 2, the phase separation reactor stirring paddle 10 is a radial flow stirrer driven by a motor provided on the top of the phase separation reactor 2, 4 to 6 evenly distributed water phase baffles 9 are provided around the stirring paddle 11, a water phase outlet containing a catalyst is provided at the bottom of the phase separation reactor 2, and the water phase returns to the reactor 1 through a circulation pump 13, and the phase separation reactor is provided with two oil-water interface meters 12.

[0043] The reactor is connected to the upper part of the phase separation reactor through a gas phase balance pipeline 15, and is connected to the gas phase balance pipeline of the next stage reaction unit. The oil phase discharge of the phase separation reactor of the last stage reaction unit is sent to the subsequent refining unit as a product to obtain a cyclohexene product.

[0044] In this embodiment, the reaction kettle 1 and the phase separation kettle 2 are made of Hastelloy or a steel plate lined with Hastelloy.

[0045] Example 1

[0046] The cyclohexene production unit consists of two reaction units connected in series. The effective volume of the reactor in each reaction unit is 50m 3 The reactor has a height-to-diameter ratio of 1.5 and an effective volume of 30 m 3 , add 40 ml of zinc sulfate aqueous solution containing a certain concentration of ruthenium catalyst into the reactor. 3 , control the stirring speed of the reactor to 110rpm, the stirring speed of the phase separation reactor to 10rpm, increase the hydrogen pressure of the reactor to 45bar, and use the desalted water heat exchange coil to increase the temperature to 130℃; after the system is stable, 80m of benzene is introduced into the first unit reactor 3 / h, hydrogen intake 13400N m 3 / h, water phase circulation volume 160m 3 / h, the hydrogen input of the secondary unit reactor is 9400N m 3 / h, water phase circulation volume 160m 3 / h, the oil-water interface of the phase separation kettle is controlled at 30%-40%, and the desalted water coil heat exchange is used to control the upper, middle and lower temperatures of the reactor between 130 and 140°C. The conversion rate of benzene is 55%, the selectivity of cyclohexene is 82%, and the catalyst dosage is 1.3g / ton of cyclohexene.

[0047] Comparative Example 1

[0048] The cyclohexene production unit consists of an effective volume of 50m 3 Two reactors in series and an effective volume of 25m 3 The non-stirred phase separation reactor has a height-to-diameter ratio of 2. 80 ml of zinc sulfate aqueous solution containing a certain concentration of ruthenium catalyst is added to the reactor. 3 , control the stirring speed of the reactor to 110rpm, increase the hydrogen pressure of the reactor to 45bar, and use the desalted water heat exchange coil to increase the temperature to 130℃; after the system stabilizes, 80m3 of benzene is introduced into the first reactor 3 / h, hydrogen intake 11000Nm 3 / h, hydrogen input to the secondary reactor 8900N m 3 / h, water phase circulation volume 160m3 / h, phase separation kettle oil-water interface control at 30% ~ 40%, desalted water coil heat exchange control reactor upper, middle and lower temperatures between 130 ~ 140 ℃, benzene conversion rate 40%, cyclohexene selectivity 78%, catalyst dosage is 1.8g / ton cyclohexene.

[0049] Comparative Example 2

[0050] The cyclohexene production unit consists of an effective volume of 50m 3 Two reactors in series and an effective volume of 25m 3 The non-stirred phase separation tank has a reactor height-to-diameter ratio of 2. 80 ml of zinc sulfate aqueous solution containing a certain concentration of ruthenium catalyst is added to the reactor. 3 , control the stirring speed of the reactor to 110rpm, increase the hydrogen pressure of the reactor to 45bar, and use the desalted water heat exchange coil to increase the temperature to 130℃; after the system stabilizes, 80m3 of benzene is introduced into the first reactor 3 / h, hydrogen intake 13400Nm 3 / h, hydrogen input to the secondary reactor: 9500Nm 3 / h, water phase circulation volume 160m 3 / h, the oil-water interface of the phase separation kettle is controlled at 30%-40%, and the upper, middle and lower temperatures of the reactor are controlled between 130 and 140°C by using desalted water coil heat exchange. The conversion rate of benzene is 50%, the selectivity of cyclohexene is 70%, and the catalyst dosage is 2.0g / ton of cyclohexene.

[0051] It can be seen from Example 1 that the device and method provided by the present invention are used to partially hydrogenate benzene to produce cyclohexene, and the conversion rate of benzene is 55%, the selectivity of cyclohexene is 82%, and the catalyst dosage is 1.3 g / ton of cyclohexene; it can be seen from Comparative Example 1 and Example 1 that when a multi-stage series reaction kettle and a low-speed stirring phase-separation kettle are used to form a production device, the conversion rate of benzene and the selectivity of cyclohexene are significantly reduced, and the amount of catalyst used is increased. It can be seen from Comparative Example 2 and Comparative Example 1 that when the low-speed stirring phase-separation kettle is replaced with a static phase-separation tank, although the conversion rate of benzene is increased, it is difficult to achieve uniform dispersion of the catalyst in the static phase-separation tank, which leads to a significant decrease in the selectivity of cyclohexene and a significant increase in the catalyst dosage. In summary, only by strictly following the device and process steps provided by the present invention can the corresponding technical effects be achieved.

Claims

1. A device for preparing cyclohexene by partial hydrogenation of benzene, characterized in that: The invention is composed of 2 to 3 reaction units connected in series; the reaction units include a reaction kettle (1) and a phase separation kettle (2); a reaction kettle overflow weir (7) is provided on the upper part of the reaction kettle wall, and the material outlet at the reaction kettle overflow weir is connected to the material inlet of the guide tube (8) at the top of the phase separation kettle through a conduit; the spherical kettle top of the reaction kettle is connected to the top of the phase separation kettle through a gas phase balance pipe (15), and the spherical kettle bottom of the phase separation kettle is connected to the spherical kettle bottom of the reaction kettle through a circulation pump (13); The phase separation kettle is provided with a phase separation kettle stirring paddle (10) driven by a motor (14) along the vertical center axis, and the stirring paddle is located between water phase baffles (9) containing catalyst at the bottom of the phase separation kettle; An overflow weir of the phase separation kettle is arranged at the upper part of the kettle wall of the phase separation kettle, an oil phase outlet is opened at the overflow weir of the phase separation kettle, and an oil-water interface meter (12) is arranged at the middle and lower part of the kettle wall of the phase separation kettle.

2. The device for preparing cyclohexene by partial hydrogenation of benzene according to claim 1, characterized in that: The reactor is provided with a stirring shaft driven by a motor (14) along the vertical center axis, and multi-stage stirring paddles (3) are provided on the stirring shaft at equal heights. Heat exchange coils (4) are provided between the multi-stage stirring paddles, and the bottom stirring paddle is located on the plane with the largest cross-sectional area of ​​the spherical bottom of the reactor.

3. The device for preparing cyclohexene by partial hydrogenation of benzene according to claim 2, characterized in that: A liquid phase feed distributor (5) and a gas phase feed distributor (6) are inserted into the top of the spherical reactor. The liquid phase feed distributor and the gas phase feed distributor are inserted from the top of the spherical reactor to below the bottommost stirring paddle of the multi-machine stirring paddle.

4. The device for preparing cyclohexene by partial hydrogenation of benzene according to claim 2, characterized in that: The height-to-diameter ratio of the reactor is 1-2.5:1; the multi-stage stirring blades and heat exchange coils in the reactor are both 2-3 stages.

5. The device for preparing cyclohexene by partial hydrogenation of benzene according to claim 4, characterized in that: The reactor wall is also provided with 4 to 6 spoiler baffles; the bottom of the multi-stage stirring paddle is propulsion stirring, and the middle and / or upper part is radial flow stirring.

6. The device for preparing cyclohexene by partial hydrogenation of benzene according to claim 1, characterized in that: There are 4 to 8 water phase baffles inside the phase separation kettle; the water phase baffles are evenly distributed around the stirring paddle of the phase separation kettle.

7. A method for preparing cyclohexene by partial hydrogenation of benzene, characterized in that: The process is implemented by the device according to any one of claims 1 to 6: 1) Add the catalyst solution into the reactor and turn on the multi-stage stirring paddles and heat exchange coils of the reactor; 2) feeding multiple series reaction units through the liquid phase feed distributor and gas phase feed distributor of the reaction kettle of each unit, and turning on the stirring paddle of the phase separation kettle; 3) After the feed of each reaction unit is stable, the feed amount and reaction temperature of each unit are adjusted, and cyclohexene is discharged through the oil phase outlet of the phase separation kettle of the last reaction unit; In each of the reaction units, the gas phase feed amount of the latter reaction unit is 0.5 to 1.0 times the gas phase feed amount of the former reaction unit.

8. The method for preparing cyclohexene by partial hydrogenation of benzene according to claim 7, characterized in that: The catalyst solution is a zinc sulfate aqueous solution containing a ruthenium catalyst; the rotation speed of the multi-stage stirring paddle of the reactor is 110 rpm.

9. The method for preparing cyclohexene by partial hydrogenation of benzene according to claim 7, characterized in that: The liquid phase feed amount of the first reaction unit in the plurality of series reaction units is 60 to 100 m 3 / h, gas phase feed rate is 11000~15000Nm 3 / h, water phase circulation volume is 140~180m 3 / h.

10. The method for preparing cyclohexene by partial hydrogenation of benzene according to claim 9, characterized in that: In the plurality of reaction units connected in series, the water phase circulation amount of the latter reaction unit is 0.9 to 1.1 times the water phase circulation amount of the former reaction unit.

11. The method for preparing cyclohexene by partial hydrogenation of benzene according to claim 7, characterized in that: In the plurality of series reaction units, the oil-water interface of the phase separation kettle is 30-40%.

12. The method for preparing cyclohexene by partial hydrogenation of benzene according to claim 7, characterized in that: The gas phase pressure of each unit reactor in the multiple series reaction units is 45 bar, and the reaction temperature is 130-140°C.

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