Method for producing epoxypropane by hydrogen peroxide direct oxidation method

Abstract

The invention provides a method for producing epoxypropane through a hydrogen peroxide direct oxidation method, and relates to the technical field of chemical synthesis. The method is carried out in a single reaction unit or N reaction units connected in series; wherein the reaction unit comprises a reactor and a liquid-liquid phase splitting device, and N is at least 2; when the reaction is carried out in a single reaction unit, after the materials after the reaction are subjected to phase separation through a liquid-liquid phase separation device, an obtained propylene-rich phase returns to the reactor, and an obtained solvent-rich phase is input into a subsequent separation process; and when the reaction is carried out in N reaction units which are connected in series, a rich solvent phase obtained by phase splitting of the liquid-liquid phase splitting device of the previous reaction unit is input into the reactor of the next reaction unit for reaction, and a rich solvent phase obtained by the liquid-liquid phase splitting device of the last reaction unit is input into a subsequent separation process. According to the method, the circulation amount of propylene and the solvent in the separation process is reduced, the raw material conversion rate and yield are high, operation is safe and stable, and remarkable economic benefits are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of chemical synthesis, and in particular to a method for producing propylene oxide by direct oxidation of hydrogen peroxide. Background Art

[0002] Propylene oxide (PO) is an important basic organic chemical raw material and the third largest propylene derivative after polypropylene and acrylonitrile. It is mainly used to produce chemical products such as polyether polyols, propylene glycol and propylene glycol ethers, and is widely used in insulation materials, construction materials, automobiles, food, medicine, cosmetics, coatings, adhesives, etc. These applications not only reflect the diversity and importance of propylene oxide, but also provide a solid foundation for its market demand.

[0003] In recent years, the preparation technology of propylene oxide has developed rapidly. Among them, the direct oxidation method of propylene oxide with hydrogen peroxide (HPPO) has the advantages of simple process, small environmental impact, mild reaction conditions, and high raw material utilization efficiency. It is gradually replacing the traditional production process of propylene oxide.

[0004] The HPPO process is a process in which propylene and hydrogen peroxide are directly oxidized in a reactor in a circulating solvent under relatively mild conditions and catalyzed by titanium silicalite (TS-1) to produce propylene oxide. A large number of studies have been conducted on the HPPO process at home and abroad. For example, patent US2003009040A1 discloses an olefin epoxidation process, which uses a multiphase mixed system consisting of a liquid phase rich in hydrogen peroxide and solvent and a propylene-rich organic liquid phase, which can significantly improve the selectivity of propylene oxide without affecting the conversion rate of hydrogen peroxide. However, the patent does not involve the subsequent separation process of the two-phase system. Patent CN103641800A discloses a method for producing propylene oxide, which involves a method for producing propylene oxide by connecting three reactors in series, distributing the load of a single reactor to the first two reactors, and recycling the excess propylene and methanol in the first reactor in the second reactor by maintaining the molar ratio of methanol / propylene / hydrogen peroxide input to the single reactor, thereby reducing the propylene circulation amount and the methanol circulation amount, but the final reaction stream still needs to be separated from the solvent and propylene by high energy consumption methods such as distillation and then recycled back to the reactor. Patent CN101693703A discloses an energy-saving and emission-reduction process for producing propylene oxide by epoxidation of propylene with hydrogen peroxide, wherein propylene and hydrogen peroxide undergo epoxidation reaction under medium pressure and low temperature through titanium silicon molecular sieve, and the reaction product realizes the separation of unreacted propylene in the propylene distillation tower, and the circulating solvent is separated at the top of the solvent distillation tower; although the bottom stream of the propylene tower is used as part of the heat source of the subsequent distillation tower and part of the energy is recovered, the separation process still consumes a large amount of fresh steam.

[0005] It is worth noting that in the actual process, in order to improve the conversion rate of hydrogen peroxide and the yield of propylene oxide, reduce safety hazards such as combustion and explosion, and inhibit the occurrence of side reactions, in addition to using highly selective catalysts, excess propylene and a large amount of circulating solvent should be provided; and in the subsequent reaction product separation process, it is necessary to go through complex procedures to separate and purify the excess propylene and solvent separately and then return them to the epoxidation reactor for recycling. This separation is mainly carried out by distillation, which requires a large amount of energy and seriously affects the economic efficiency of the process. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention discloses a method for producing propylene oxide by direct oxidation of hydrogen peroxide. The method has high hydrogen peroxide conversion rate and propylene oxide yield, so that the circulation amount of propylene and solvent in the subsequent separation process is low, the operation is safe and stable, energy-saving and consumption-reducing, and the method is suitable for large-scale promotion and application.

[0007] In order to achieve the above technical objectives, the present invention provides a method for producing propylene oxide by direct oxidation of hydrogen peroxide, which is carried out in a single reaction unit, or N reaction units connected in series; wherein the reaction unit includes a reactor and a liquid-liquid phase separation device, and N is at least 2; When the method is carried out in a single reaction unit, the solvent, propylene and hydrogen peroxide are input into the reactor for reaction, and after the reaction is completed, the materials are separated by a liquid-liquid phase separation device, and the obtained propylene-rich phase is returned to the reactor, and the obtained solvent-rich phase is input into a subsequent separation process; When the method is carried out in N reaction units connected in series, the solvent is input into the reactor of the first reaction unit, and propylene and hydrogen peroxide are respectively input into the reactors of each reaction unit; the propylene-rich phase obtained by phase separation in the liquid-liquid phase separation device of any reaction unit is returned to the reactor in the same reaction unit, the solvent-rich phase obtained by phase separation in the liquid-liquid phase separation device of the previous reaction unit is input into the reactor of the next reaction unit for reaction, and the solvent-rich phase obtained by the liquid-liquid phase separation device of the last reaction unit is input into the subsequent separation process.

[0008] In the above technical solution, in any single reaction unit, the solvent and the raw materials propylene and hydrogen peroxide (aqueous solution of hydrogen peroxide) are input into the reactor, and the following reaction occurs under the action of the catalyst in the reactor: CH3CH=CH2+H2O2→CH3CH(O)CH2+H2O The materials after the reaction are input into the liquid-liquid phase separation device for phase separation to obtain a propylene-rich phase and a solvent-rich phase, wherein the propylene-rich phase includes propylene, solvent and propylene oxide, with propylene accounting for the largest mass proportion; the solvent-rich phase includes methanol, water, propylene and propylene oxide, with the solvent accounting for the largest mass proportion. When the epoxidation reaction is carried out in a single reaction unit, the propylene-rich phase obtained by phase separation is returned to the reactor to continue the reaction, thereby effectively reducing the circulation amount of propylene and solvent in the subsequent separation process, thereby reducing the energy consumption of the separation process; in addition, the solvent-rich phase is input into the subsequent separation process to separate the product, solvent, propylene and remove moisture, and the phase separation operation enriches the propylene oxide in the solvent-rich phase, thereby further reducing the difficulty of the subsequent separation process and saving energy and reducing consumption. When the epoxidation reaction is carried out in N reaction units, the propylene-rich phase obtained after the phase separation operation in each reaction section is returned, which reduces the proportion of propylene and solvent in the solvent-rich phase output by the liquid-liquid phase separation device of the last reaction unit, thereby reducing the load of the subsequent separation unit and reducing energy consumption; in addition, through the multiple reaction units connected in series, the excess solvent and propylene in the previous group of reaction units continue to be input into the next group of reaction units in the form of solvent-rich phase, reducing the input amount of fresh propylene and solvent in the next group of reaction units, thereby reducing the overall propylene and solvent flow entering the subsequent separation process, further reducing the energy consumption of the subsequent separation process and reducing the difficulty of separation.

[0009] The embodiments and comparative examples of the present invention illustrate a process for producing propylene oxide by direct oxidation of hydrogen peroxide including a single reaction unit and N reaction units.

[0010] In a further example of the present invention, the ratio of the solvent to the reaction raw materials in any reactor is explored and optimized. Optionally, in the reactor of any of the reaction units, the molar ratio of the solvent, the propylene and the hydrogen peroxide in the hydrogen peroxide is (4~10): (2~5): 1. By exploring the solvent and the reaction raw materials in each reactor, it is beneficial for the reaction materials to effectively contact the catalyst surface, improve the reaction efficiency and promote the full conversion of hydrogen peroxide. In addition, the materials after the reaction are effectively separated in the liquid-liquid phase separation device to obtain a propylene-rich phase and a solvent-rich phase, so that the technical effect of reducing the circulation amount of propylene and solvent in the subsequent separation process and enriching propylene oxide can be achieved by outputting two streams. In an optional example of the present invention, the molar ratio of the solvent, the propylene and the hydrogen peroxide in the hydrogen peroxide is preferably (5~9): (3~4): 1. Within this molar ratio range, the energy-saving and consumption-reducing advantages of the technical solution of the present invention can be further exerted.

[0011] In a further example of the present invention, the control conditions of each reactor are explored and optimized. Optionally, in any of the reaction units, the reaction temperature of the reactor is 15~80°C, and the reaction pressure is 1.0~5.0MPaG. Suitable reaction conditions are conducive to the propylene epoxidation reaction. Combined with appropriate reaction pressure, propylene participates in the reaction in liquid phase, thereby facilitating the subsequent liquid-liquid phase separation operation. In an optional example of the present invention, the reaction temperature of the reactor is preferably 20~70°C, and the reaction pressure is preferably 1.5~4.0MPaG; in an optional example of the present invention, the reaction temperature of the reactor is further preferably 25~60°C, and the reaction pressure is further preferably 2.0~3.0MPaG; in an optional example of the present invention, the reaction temperature of the reactor is preferably 45°C~50°C, and the reaction pressure is preferably 2.4~2.8MPaG.

[0012] In a further example of the present invention, the temperature of the phase separation operation is explored. Optionally, the temperature of the phase separation operation is 20-70°C, more preferably 25-40°C, under which the density difference between the liquid-liquid phases can be increased, which helps to speed up the stratification speed and improve the separation efficiency.

[0013] In a further example of the present invention, the mass ratio of the propylene-rich phase and the solvent-rich phase output by the liquid-liquid phase separation device is explored and optimized. Optionally, in any of the reaction units, the mass ratio of the propylene-rich phase and the solvent-rich phase obtained by the liquid-liquid phase separation device is (1~30):1. As mentioned above, in order to promote the full reaction of hydrogen peroxide, the amount of propylene and solvent used is excessive relative to hydrogen peroxide. Therefore, the present invention can optionally regulate the output of the propylene-rich phase and the solvent-rich phase output by the liquid-liquid phase separation operation within the above larger mass ratio range, and most of the propylene phase and the solvent contained in the propylene-rich phase can be recycled, thereby significantly reducing the circulation amount of propylene and solvent in the subsequent separation process. In an optional example of the present invention, the mass ratio of the propylene-rich phase and the solvent-rich phase obtained by the liquid-liquid phase separation device is preferably (2~15):1, and further preferably (4~10):1.

[0014] Furthermore, in the propylene-rich phase obtained by phase separation in any of the liquid-liquid phase separation devices, the mass proportion of propylene is not less than 50%, preferably not less than 65%. By exploring and optimizing the propylene content in the propylene-rich phase, it is beneficial to regulate the propylene and solvent flow rates of the reactor.

[0015] In a further example of the present invention, the catalyst used for the reaction is explored. Optionally, any reactor is filled with a TS-1 titanium silicon molecular sieve catalyst, and the titanium-silicon ratio of the TS-1 titanium silicon molecular sieve (referring to the molar ratio of silicon dioxide to titanium dioxide in the molecular sieve) is 10 to 80, preferably 20 to 50. Furthermore, the mass space velocity of the catalyst is 0.05 to 1.2 h -1 .

[0016] In a further example of the present invention, the mass concentration of hydrogen peroxide is explored and optimized. Optionally, the concentration of hydrogen peroxide is 25wt%-70wt%. In the actual process, hydrogen peroxide of a suitable concentration can be selected as needed to carry out the propylene epoxidation reaction. In an optional example of the present invention, the concentration of hydrogen peroxide is preferably 30wt%-50wt%.

[0017] In a further example of the present invention, the type of solvent is explored and optimized. Optionally, the solvent includes at least one of methanol, acetone, and tetrahydrofuran, which can be selected by those skilled in the art as needed; in a further example of the present invention, the solvent is preferably methanol.

[0018] In a further example of the present invention, the material to be input into the reactor is subjected to multiphase liquid distribution before being input into the corresponding reactor. This operation is conducive to promoting uniform distribution of the reaction materials in a large industrial reactor, thereby achieving efficient reaction under the action of the catalyst in the reactor.

[0019] In a further example of the present invention, the propylene and solvent separated in the subsequent separation process are returned to the reaction unit for recycling, thereby saving costs and improving process economy.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The method for producing propylene oxide by direct oxidation of hydrogen peroxide of the present invention comprises the following steps: after liquid-liquid phase separation of materials outputted from reactors in various reaction units, the propylene-rich phase is returned to the reactor for further reaction, the solvent-rich phase is inputted into the reactor of the next-stage reaction unit for further reaction, and the solvent-rich phase outputted from the liquid-liquid phase separation device in the last reaction unit is inputted into a subsequent separation process, thereby most of the propylene and part of the solvent in the materials after the reaction are reused, the circulation amount of propylene and the solvent in the subsequent separation process is reduced, and the energy consumption is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1A structural diagram showing a device used in the method for producing propylene oxide by direct oxidation of hydrogen peroxide according to the present invention; Figure 2 Another structural diagram showing the device used in the method for producing propylene oxide by direct oxidation of hydrogen peroxide of the present invention; Figure 3 Another structural diagram showing the device used in the method for producing propylene oxide by direct oxidation of hydrogen peroxide of the present invention; Figure 4 Another structural diagram showing the apparatus used in the method for producing propylene oxide by direct oxidation of hydrogen peroxide according to the present invention.

[0022] The above drawings include the following reference numerals: 1-reactor, 11-first reactor, 12-second reactor, 2-liquid-liquid phase separation device, 21-first liquid-liquid phase separation device, 22-second liquid-liquid phase separation device, 3-cooler, 31-first cooler, 32-second cooler. DETAILED DESCRIPTION

[0023] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively below, and preferred embodiments of the present invention are given. However, it should be understood that these embodiments are only used for more detailed description and should not be understood as limiting the present invention in any form, i.e., not intended to limit the scope of protection of the present invention.

[0024] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods, unless otherwise specified, are all conventional methods.

[0025] Example 1 A method for producing propylene oxide by direct oxidation of hydrogen peroxide, the method being carried out in a single reaction unit, or N reaction units connected in series; wherein the reaction unit comprises a reactor and a liquid-liquid phase separation device, and N is at least 2; When the method is carried out in a single reaction unit, the solvent, propylene and hydrogen peroxide are input into the reactor for reaction, and after the reaction is completed, the materials are separated by a liquid-liquid phase separation device, and the obtained propylene-rich phase is returned to the reactor, and the obtained solvent-rich phase is input into a subsequent separation process; When the method is carried out in N reaction units connected in series, the solvent is input into the reactor of the first reaction unit, and propylene and hydrogen peroxide are respectively input into the reactors of each reaction unit; the propylene-rich phase obtained by phase separation in the liquid-liquid phase separation device of any reaction unit is returned to the reactor in the same reaction unit, the solvent-rich phase obtained by phase separation in the liquid-liquid phase separation device of the previous reaction unit is input into the reactor of the next reaction unit for reaction, and the solvent-rich phase obtained by the liquid-liquid phase separation device of the last reaction unit is input into the subsequent separation process.

[0026] The method of this embodiment is as follows Figure 1 The device for producing propylene oxide by direct oxidation of hydrogen peroxide is shown, and the device includes a single reaction unit, and the reaction unit includes a reactor 1 and a liquid-liquid phase separation device 2. The reactor 1 is used for reacting propylene with hydrogen peroxide under the action of a catalyst to obtain propylene oxide, and the liquid-liquid phase separation device 2 is used for liquid-liquid phase separation of the material after the reaction in the reactor 1 to obtain a propylene-rich phase containing propylene and a solvent, and a solvent-rich phase containing a solvent and water.

[0027] The feed port of the reactor 1 is connected to the solvent input pipe, the hydrogen peroxide input pipe and the propylene input pipe, and the discharge port of the reactor 1 is connected to the feed port of the liquid-liquid phase separation device 2; the propylene-rich phase outlet of the liquid-liquid phase separation device 2 is connected to the feed port of the reactor 1, and the solvent-rich phase outlet of the liquid-liquid phase separation device 2 is connected to the subsequent separation unit.

[0028] Furthermore, the reactor 1 of any reaction unit is independently selected from a shell-and-tube reactor, a tank reactor, or a tower reactor. In the actual process, a suitable type of reactor 1 can be selected according to needs.

[0029] The present invention does not limit the position where the reaction materials are fed into the reactor 1. In a further example of the present invention, the reactor 1 is fed from the top, bottom or side, and a suitable feeding position is selected according to needs in the specific process.

[0030] Furthermore, a liquid distribution device is provided in any of the reaction units to evenly distribute the material input into the reactor 1, thereby promoting uniform mixing and sufficient contact of the reactants. It should be noted that the present invention is not limited to the specific structure of the liquid distribution device, and those skilled in the art can select a device or setting that can promote the distribution of two-phase or multi-phase liquids as needed, and the protection scope of the present invention is not limited thereby.

[0031] Furthermore, in any of the reaction units, a cooler 3 and / or a filtering device is arranged on the pipeline connecting the discharge port of the reactor 1 and the feed port of the liquid-liquid phase separation device 2, so that under specific operating conditions, the temperature of the material output from the reactor 1 can be adjusted by the cooler 3 to improve the efficiency of the subsequent phase separation operation, or the entrained catalyst particles can be separated by the filtering device to protect the stability of the downstream settings and the operation of the device. Figure 2 A structure of an apparatus for producing propylene oxide by direct oxidation of hydrogen peroxide according to the present invention comprising a cooler is shown.

[0032] Furthermore, the reactor 1 and the liquid-liquid phase separation device 2 in the same reaction unit are an integrated device or a separate device. In the actual process, the reactor 1 and the liquid-liquid phase separation device 2 can be set separately according to needs, or operated as an integrated device, which can meet the needs of more working conditions.

[0033] Furthermore, the liquid-liquid phase separation device 2 may be selected as a static phase separation device or a dynamic phase separation device, and those skilled in the art may select according to needs. In an optional embodiment of the present invention, the liquid-liquid phase separation device 2 is preferably a static phase separation device.

[0034] Example 2 A method for producing propylene oxide by direct oxidation of hydrogen peroxide. Figure 2 The unit shown is in operation with a propylene oxide production scale of 150,000 tons.

[0035] Specifically: the molar ratio of methanol: propylene: hydrogen peroxide in reactor 1 is 6.2:3:1, of which the methanol feed flow rate is 69.2 t / h, the 50% hydrogen peroxide aqueous solution feed flow rate is 24.6 t / h, the propylene feed flow rate is 31.5 t / h, and the propylene-rich phase flow rate returned from the liquid-liquid phase separation device 2 is 20.2 t / h. Reactor 1 is a tube-in-tube fixed bed reactor, equipped with a liquid distribution device for uniformly distributing the feed material. Subsequently, in reactor 1, under the catalytic action of titanium silicon molecular sieve TS-1 (titanium silicon ratio is SiO2:TiO2=25), epoxidation reaction is carried out at 45°C and 2.4 MPaG; the mass space velocity of the catalyst is 0.05~1.2h -1 .

[0036] The outlet logistics of reactor 1 is cooled to 35°C by discharge cooler 3 and enters liquid-liquid phase separation device 2 for phase separation; the flow rate of the separated propylene-rich phase is 20.2 t / h, including propylene, methanol, and propylene oxide with mass contents of approximately 70.2%, 13.9%, and 15.9%, respectively. This part of the material is returned to the inlet of reactor 1; the flow rate of the solvent-rich phase is 125.2 t / h, including methanol, water, propylene, and propylene oxide with mass contents of 55.1%, 14.7%, 13.8%, and 15.3%, respectively, as well as some other impurities. This part of the material enters the subsequent separation unit to separate methanol, propylene, and propylene oxide products.

[0037] After separation in the subsequent separation unit, the final product of propylene oxide in this embodiment is 18.75 t / h, and the separated and purified methanol and propylene are recycled back to the reaction unit to continue the reaction, and the circulation flow rates are 68.9 t / h and 17.3 t / h respectively (excluding separation loss). The subsequent separation unit in this embodiment includes a methanol second-effect separation tower and a propylene separation tower, wherein the 2.5 MPaG steam consumption of the methanol second-effect separation tower is 59.7 t / h, and the 0.5 MPaG steam consumption of the propylene separation tower is 4.93 t / h.

[0038] Comparative Example 1 This comparative example shows a process for preparing propylene oxide by direct oxidation of propylene with hydrogen peroxide. The production scale of propylene oxide is 150,000 tons. Specifically: The molar ratio of methanol:propylene:hydrogen peroxide in the reactor is 6.2:3:1, wherein the methanol feed flow rate is 72.0 t / h, the 50% hydrogen peroxide aqueous solution feed flow rate is 24.6 t / h, and the propylene feed flow rate is 45.7 t / h. The reactor is a tube-and-tube fixed bed reactor, and a liquid distribution device is provided for mixing the feed materials of the reactor. In the reactor, under the catalytic action of titanium silicon molecular sieve TS-1 (titanium silicon ratio is SiO2:TiO2=25), the epoxidation reaction is carried out at 45°C and 2.4 MPaG; the mass space velocity of the catalyst is the same as the mass space velocity of the catalyst in Example 2.

[0039] The reactor outlet stream is cooled to 35°C by the discharge cooler 3 and enters the liquid-liquid phase separation device 2 for phase separation. The flow rate of the separated propylene-rich phase is 19.8 t / h, in which the mass contents of propylene, methanol and propylene oxide are 71.8%, 14.3% and 13.9% respectively; the flow rate of the solvent-rich phase is 122.4 t / h, in which the mass contents of methanol, water, propylene and propylene oxide are 56.4%, 14.9%, 14.2% and 13.3% respectively, and some other impurities. Both the propylene-rich phase stream and the solvent-rich phase stream enter the subsequent separation unit to separate the methanol, propylene and propylene oxide products.

[0040] In this comparative example, the final product of propylene oxide is 18.75 t / h, and the purified methanol and propylene are recycled to the reaction unit, with circulation flow rates of 71.7 t / h and 31.5 t / h respectively (excluding separation loss). The subsequent separation units include a methanol second-effect separation tower and a propylene separation tower, wherein the 2.5 MPaG steam consumption of the methanol second-effect separation tower is 61.7 t / h, and the 0.5 MPaG steam consumption of the propylene separation tower is 8.98 t / h.

[0041] Combining Example 2 with Comparative Example 1, it can be verified that in order to achieve the same propylene oxide yield, the process of Comparative Example 1 needs to increase the input of propylene and solvent methanol; at the same time, after the reaction is completed, the propylene and solvent streams input to the subsequent separation unit of Comparative Example 1 are larger than those of Example 1; it can be inferred that the subsequent separation process of Comparative Example 1 will generate higher energy consumption. By comparing and analyzing the distillation tower energy consumption of the subsequent separation process of Example 1 and Comparative Example 1, it is confirmed that the method for producing propylene oxide by direct oxidation of hydrogen peroxide in Example 1 can significantly reduce the process operation energy consumption and operate stably and safely.

[0042] Comparative Example 2 A process for preparing propylene oxide by direct oxidation of propylene with hydrogen peroxide, the propylene oxide production scale is 150,000 tons, specifically: The molar ratio of methanol:propylene:hydrogen peroxide in the reactor is 15:3:1, wherein the methanol feed rate is 173.5 t / h, the 50% hydrogen peroxide aqueous solution feed rate is 24.6 t / h, and the propylene feed rate is 45.7 t / h. The reactor is a tubular fixed bed reactor, and the epoxidation reaction is carried out at 50°C and 2.4 MPaG under the catalytic action of titanium silicon molecular sieve TS-1 (titanium silicon ratio is SiO2:TiO2=25); the mass space velocity of the catalyst is the same as the mass space velocity of the catalyst in Example 2.

[0043] Since the solvent feed flow is relatively high, the materials after the reaction cannot undergo obvious liquid-liquid phase separation, so the homogeneous flow output from the reactor outlet enters the subsequent separation unit to separate methanol, propylene and propylene oxide products.

[0044] The final product of propylene oxide in this comparative example is 18.75t / h. The purified methanol and propylene are recycled to the reaction unit with circulation flow rates of 173.2t / h and 31.5t / h respectively (excluding separation loss). The subsequent 2.5MPaG steam consumption of the methanol secondary separation tower is 132.2t / h, and the 0.5MPaG steam consumption of the propylene separation tower is 8.98t / h.

[0045] Combining Example 2 with Comparative Example 2, it can be confirmed that in order to achieve the same propylene oxide yield, the method for producing propylene oxide by direct oxidation of hydrogen peroxide of the present invention can promote the phase separation of the materials after the reaction by optimizing the ratio of the feed materials to the reactor, and can reduce the circulation flow of propylene and the solvent in combination with the phase separation operation, and significantly reduce the energy consumption of the subsequent separation process, which has important advantages in large-scale, continuous industrial production and is worthy of promotion and application.

[0046] Example 3 Based on the method for producing propylene oxide by direct oxidation of hydrogen peroxide shown in Example 1, the method for producing propylene oxide by direct oxidation of hydrogen peroxide in this embodiment is carried out in another device for producing propylene oxide by direct oxidation of hydrogen peroxide. The device in this embodiment is Figure 1 The difference between the device shown is that in this embodiment, it includes N reaction units connected in series, and N is at least 2.

[0047] Among them, the feed port of the reactor 1 in the first reaction unit is connected to the solvent input pipe, the feed port of the reactor 1 in any reaction unit is connected to the hydrogen peroxide input pipe and the propylene input pipe, and the discharge port is connected to the feed port of the liquid-liquid phase separation device 2; the propylene-rich outlet of the liquid-liquid phase separation device 2 in any reaction unit is connected to the feed port of the reactor 1 in the same reaction unit, the solvent-rich phase outlet of the liquid-liquid phase separation device 2 in the previous reaction unit is connected to the feed port of the reactor 1 in the next reaction unit, and the solvent-rich phase outlet of the liquid-liquid phase separation device 2 in the last reaction unit is connected to the subsequent separation unit.

[0048] Figure 3 An example of an apparatus for producing propylene oxide by the direct oxidation method of hydrogen peroxide of this embodiment including two reaction units is shown. As shown in the figure, raw materials hydrogen peroxide and propylene, and a solvent are input into the first reactor 11 of the first reaction unit for epoxidation reaction, and the materials obtained by the reaction are input into the first liquid-liquid phase separation device 21 for phase separation; the propylene-rich phase obtained by phase separation is returned to the feed port of the first reactor 11, and the obtained solvent-rich phase is input into the second reactor 12 of the second reaction unit; newly input hydrogen peroxide and propylene undergo epoxidation reaction in the second reactor 12, and the materials obtained by the reaction are input into the second liquid-liquid phase separation device 21 for phase separation, the propylene-rich phase obtained by phase separation is returned to the feed port of the second reactor 12, and the obtained solvent-rich phase is input into the subsequent separation unit.

[0049] Figure 4 The device for producing propylene oxide by direct oxidation of hydrogen peroxide is shown, which comprises a first cooler 31 and a second cooler 32. Specifically, the reacted material output from the first reactor 11 is cooled by the first cooler 31 and then input into the first liquid-liquid phase separation device 21, and the reacted material output from the second reactor 12 is cooled by the second cooler 32 and then input into the second liquid-liquid phase separation device 21.

[0050] It should be noted that when the device includes N reaction units, the present invention is not limited to whether the types of any two reactors are the same. The types of any two reactors can be the same or different. In a further example of the present invention, the types of reactors in the N reaction units are the same, thereby improving the operability of the overall process.

[0051] Example 4 A method for producing propylene oxide by direct oxidation of hydrogen peroxide. Figure 4 The unit shown is in operation with a propylene oxide production scale of 150,000 tons.

[0052] Specifically: the molar ratio of methanol:propylene:hydrogen peroxide in the first reactor 11 is 6.2:3:1. The load of the first reactor 11 is 50% of the total amount, of which the methanol feed flow rate is 34.6 t / h, the 50% hydrogen peroxide aqueous solution feed flow rate is 12.3 t / h, the propylene feed flow rate is 15.6 t / h, and the propylene-rich phase flow rate returned from the first liquid-liquid phase separation device 21 is 10.1 t / h. The first reactor 11 is a tubular fixed bed reactor, which is equipped with a liquid distribution device for mixing the feed materials. Under the catalytic action of titanium silicon molecular sieve TS-1 (titanium silicon ratio is SiO2:TiO2=25), the epoxidation reaction is carried out at 45°C and 2.4 MPaG; the mass space velocity of the catalyst is 0.3h -1 .

[0053] The outlet logistics of the first reactor 11 is cooled to 35°C by the first discharge cooler 31, and enters the first liquid-liquid phase separation device 21 for phase separation, and the flow rate of the propylene-rich phase is 10.1 t / h, wherein the mass contents of propylene, methanol and propylene oxide are 70.2%, 13.9% and 15.9% respectively, and returns to the inlet of the first reactor 11; the flow rate of the solvent-rich phase obtained by phase separation is 62.6 t / h, wherein the mass contents of methanol, water, propylene and propylene oxide are 55.1%, 14.7%, 13.8% and 15.3% respectively, and some other impurities, and this part of the solvent-rich phase enters the second reactor 12 of the second reaction unit to continue the reaction.

[0054] The molar ratio of methanol:propylene:hydrogen peroxide in the second reactor 12 is 5.8:3:1. The feed rate of 50% hydrogen peroxide aqueous solution is 12.3 t / h, the feed rate of propylene is 7.6 t / h, the flow rate of the rich solvent phase sent from the first reaction unit is 62.6 t / h, and the flow rate of the propylene-rich phase returned from the second liquid-liquid phase separation device 21 is 11.1 t / h. The second reactor 12 is a tube-in-tube fixed bed reactor, equipped with a liquid distribution device. Under the catalytic action of titanium silicon molecular sieve TS-1 (titanium silicon ratio is SiO2:TiO2=25), the epoxidation reaction is carried out at 45°C and 2.4 MPaG; the mass space velocity of the catalyst is 0.3h -1 .

[0055] The outlet logistics of the second reactor 12 is cooled to 35°C by the second discharge cooler 32, and enters the second liquid-liquid phase separation device 21 for phase separation. The flow rate of the propylene-rich phase is 11.1 t / h, in which the mass contents of propylene, methanol and propylene oxide are 69.9%, 12.6% and 17.5% respectively, and returns to the inlet of the second reactor 12; the flow rate of the solvent-rich phase is 82.5 t / h, in which the mass contents of methanol, water, propylene and propylene oxide are 41.6%, 22.4%, 10.6% and 23.8% respectively, and enters the subsequent separation process to separate methanol, propylene and propylene oxide products.

[0056] In this embodiment, the final product of propylene oxide is 18.75 t / h; the purified methanol and propylene are recycled to the reaction unit, and the circulation flow rates are 34.4 t / h and 9.0 t / h respectively (excluding separation loss). In the subsequent separation process, the 2.5 MPaG steam consumption of the methanol second-effect separation tower is 35.7 t / h, and the 0.5 MPaG steam consumption of the propylene separation tower is 2.57 t / h.

[0057] Example 5 A method for producing propylene oxide by direct oxidation of hydrogen peroxide. Figure 3 The unit shown is in operation with a propylene oxide production scale of 150,000 tons.

[0058] Specifically: the molar ratio of methanol: propylene: hydrogen peroxide in the first reactor 11 is 6.2:3:1. The load of the first reactor 11 is 50% of the total amount, of which the methanol feed flow rate is 35.0 t / h, the 50% hydrogen peroxide aqueous solution feed flow rate is 12.3 t / h, the propylene feed flow rate is 19.1 t / h, and the propylene-rich phase flow rate returned from the first liquid-liquid phase separation device 21 is 5.3 t / h. The first reactor 11 is a tube-in-tube fixed bed reactor, and a liquid distribution device is provided for mixing the feed materials. Under the catalytic action of titanium silicon molecular sieve TS-1 (titanium silicon ratio is SiO2:TiO2=25), the epoxidation reaction is carried out at 50°C and 2.8 MPaG; the mass space velocity of the catalyst is 0.3h -1 .

[0059] The outlet logistics of the first reactor 11 enters the first liquid-liquid phase separation device 21 for phase separation, and the flow rate of the propylene-rich phase is 5.3 t / h, wherein the mass contents of propylene, methanol and propylene oxide are 68.3%, 15.3% and 16.4% respectively, and returns to the inlet of the first reactor 11; the flow rate of the solvent-rich phase obtained by phase separation is 66.4 t / h, wherein the mass contents of methanol, water, propylene and propylene oxide are 52.6%, 13.8%, 18.2% and 14.3% respectively, and this part of the solvent-rich phase enters the second reactor 12 of the second reaction unit to continue the reaction.

[0060] The molar ratio of methanol:propylene:hydrogen peroxide in the second reactor 12 is 5.8:3:1. The feed flow rate of 50% hydrogen peroxide aqueous solution is 12.3 t / h, the feed flow rate of propylene is 8.1 t / h, the flow rate of the rich solvent phase sent from the first reaction unit is 66.4 t / h, and the flow rate of the propylene-rich phase returned from the second liquid-liquid phase separation device 21 is 6.5 t / h. The second reactor 12 is a tube-in-tube fixed bed reactor, equipped with a liquid distribution device, and the epoxidation reaction is carried out at 50°C and 2.8 MPaG under the catalytic action of titanium silicon molecular sieve TS-1 (titanium silicon ratio is SiO2:TiO2=25); the mass space velocity of the catalyst is 0.3h -1 .

[0061] The logistics at the outlet of the second reactor 12 enters the second liquid-liquid phase separation device 21 for phase separation. The flow rate of the propylene-rich phase is 6.5 t / h, in which the mass contents of propylene, methanol and propylene oxide are 68.1%, 13.6% and 18.3% respectively, and returns to the inlet of the second reactor 12; the flow rate of the solvent-rich phase is 86.8 t / h, in which the mass contents of methanol, water, propylene and propylene oxide are 40.1%, 21.4%, 14.5% and 22.6% respectively, and some other impurities enter the subsequent separation unit to separate methanol, propylene and propylene oxide products.

[0062] In this embodiment, the final product of propylene oxide is 18.75 t / h; the purified methanol and propylene are recycled to the reaction unit, and the circulation flow rates are 34.7 t / h and 12.6 t / h respectively (excluding separation loss). In the subsequent separation process, the 2.5 MPaG steam consumption of the methanol second-effect separation tower is 36.1 t / h, and the 0.5 MPaG steam consumption of the propylene separation tower is 3.60 t / h.

[0063] It should be noted that the above contents are further detailed descriptions of the present invention in combination with specific implementation methods, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple improvements can be made without departing from the concept of the present invention, which should be regarded as falling within the scope of protection of the present invention.

Claims

1. A method for producing propylene oxide by direct oxidation of hydrogen peroxide, characterized in that: The method is carried out in a single reaction unit, or N reaction units connected in series; wherein the reaction unit comprises a reactor and a liquid-liquid phase separation device, and N is at least 2; When the method is carried out in a single reaction unit, the solvent, propylene and hydrogen peroxide are input into the reactor for reaction, and after the reaction is completed, the materials are separated by a liquid-liquid phase separation device, and the obtained propylene-rich phase is returned to the reactor, and the obtained solvent-rich phase is input into a subsequent separation process; When the method is carried out in N reaction units connected in series, the solvent is input into the reactor of the first reaction unit, and propylene and hydrogen peroxide are respectively input into the reactors of each reaction unit; the propylene-rich phase obtained by phase separation in the liquid-liquid phase separation device of any reaction unit is returned to the reactor in the same reaction unit, the solvent-rich phase obtained by phase separation in the liquid-liquid phase separation device of the previous reaction unit is input into the reactor of the next reaction unit for reaction, and the solvent-rich phase obtained by the liquid-liquid phase separation device of the last reaction unit is input into the subsequent separation process.

2. The method for producing propylene oxide by direct oxidation of hydrogen peroxide according to claim 1, characterized in that: In the reactor of any one of the reaction units, the molar ratio of the solvent, the propylene and the hydrogen peroxide in the hydrogen peroxide is (4-10):(2-5):

1.

3. The method for producing propylene oxide by direct oxidation of hydrogen peroxide according to claim 2, characterized in that: The molar ratio of the solvent, the propylene and the hydrogen peroxide in the hydrogen peroxide is (5-9):(3-4):

1.

4. The method for producing propylene oxide by direct oxidation of hydrogen peroxide according to claim 1, characterized in that: In any of the reaction units, the reaction temperature of the reactor is 15-80° C., and the reaction pressure is 1.0-5.0 MPaG.

5. The method for producing propylene oxide by direct oxidation of hydrogen peroxide according to claim 4, characterized in that: In any of the reaction units, the reaction temperature of the reactor is 20-70° C., and the reaction pressure is 1.5-4.0 MPaG.

6. The method for producing propylene oxide by direct oxidation of hydrogen peroxide according to claim 1, characterized in that: The temperature of the phase separation operation is 20-70°C.

7. The method for producing propylene oxide by direct oxidation of hydrogen peroxide according to claim 1, characterized in that: In any of the reaction units, the mass ratio of the propylene-rich phase to the solvent-rich phase obtained by the liquid-liquid phase separation device is (1-30):

1.

8. The method for producing propylene oxide by direct oxidation of hydrogen peroxide according to claim 1, characterized in that: In the propylene-rich phase obtained by phase separation in any of the liquid-liquid phase separation devices, the mass proportion of propylene is not less than 50%.

9. The method for producing propylene oxide by direct oxidation of hydrogen peroxide according to claim 1, characterized in that: Any reactor is filled with a TS-1 titanium-silicon molecular sieve catalyst, wherein the titanium-silicon ratio of the TS-1 titanium-silicon molecular sieve is 10 to 80; And / or, the mass space velocity of the catalyst is 0.05~1.2h -1 .

10. The method for producing propylene oxide by direct oxidation of hydrogen peroxide according to claim 1, characterized in that: The concentration of the hydrogen peroxide is 25wt%-70wt%; And / or, the solvent includes at least one of methanol, acetone and tetrahydrofuran.

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