CN101314596A - A method for continuous production of propylene oxide - Google Patents

Abstract

The invention discloses a method for continuously producing propylene oxide, which is characterized in that the original powdery titanium-silicon molecular sieve is used as a catalyst, and the reaction raw materials containing propylene and hydrogen peroxide are continuously injected into the reaction system through a feed port, and the titanium-silicon molecular sieve and The reaction materials are uniformly mixed and react in a slurry state. Under the action of the internal and external pressure difference, the molecular sieve and the liquid reaction material are separated from the solid and liquid in the separation system, and the molecular sieve continues to circulate in the circulation pipeline composed of the reactor and the separation system, while part of the liquid The product flows out of the reaction system to obtain the target product. The reaction and separation coupling of the method can effectively and timely remove the liquid product from the reaction zone, reduce the occurrence of side reactions, the conversion rate of hydrogen peroxide is greater than 95%, and the selectivity of propylene oxide is higher than 90%.

Description

A method for continuous production of propylene oxide

technical field

The invention relates to a method for producing propylene oxide, more specifically to a method for continuously producing propylene oxide by epoxidation of propylene and hydrogen peroxide in the presence of titanium-silicon molecular sieves.

Background technique

Propylene oxide is an important organic chemical raw material, second only to polypropylene and acrylonitrile among propylene derivatives. It is mainly used to produce polyurethane, propylene glycol, polyether polyol, oilfield demulsifier, surfactant, etc. At present, the industrial production of propylene oxide mainly adopts the chlorohydrin method and the co-oxygen method. The disadvantage of the chlorohydrin method is that a large amount of waste water is generated, which seriously pollutes the environment; while the co-oxygen method has a large investment and co-production of other low-cost The question of value-added products.

The discovery of titanium-silicon molecular sieves has opened up a green road for the epoxidation of propylene to produce propylene oxide.

Titanium silicate molecular sieve catalyzes the reaction of propylene and hydrogen peroxide epoxidation to produce propylene oxide. There are two types of reaction equipment currently used. One is developed by the American ARCO company (EP 0659473) and is suitable for forming large particle catalysts. The other is a fixed bed reactor, and the other is a slurry bed reactor suitable for the original powdery titanium-silicon molecular sieve.

Titanium-silicon molecular sieves must be formed when they are used in fixed-bed reactors. The binders added during the forming process have a certain negative impact on the catalytic performance of titanium-silicon molecular sieves. Moreover, the thermal effect of the propylene epoxidation reaction is relatively large, and the formed titanium-silicon Molecular sieve catalysts are not conducive to heat transfer and mass transfer, which is the main cause of catalyst deactivation. In order to control the temperature of the catalyst bed in actual production, the method of increasing the space velocity is generally used, but this method has high energy consumption and poor economic efficiency.

The slurry bed reactor is applied to the epoxidation reaction of propylene, and the titanium silicon molecular sieve does not need to be shaped, which can overcome the defects of the fixed bed reactor.

CN1256273A discloses a shell and tube circulating flow reaction device suitable for fine-grained titanium-silicon molecular sieves. The equipment is composed of a tube-and-tube reaction section mainly for the reaction process, a tube-and-tube cooling section for heat exchange, and a gas-liquid separation section. It is characterized by the tube-and-tube reaction section and the tube-and-tube reaction section The cooling sections are placed side by side, and the upper and lower ends are connected by a U-shaped connecting section to form a closed circuit. During the epoxidation reaction of propylene and hydrogen peroxide, the catalyst is continuously added from the inlet, mixed with the continuously input raw materials, and circulates in the closed loop in a slurry state in the order of the reaction section, gas-liquid separation section, and cooling section. The reactants are withdrawn from the bottom of the gas-liquid separation section along with the solvent containing the catalyst, while the tail gas flows out from the top.

CN1631538A discloses a membrane separation device applied to the regeneration and washing of titanium-silicon molecular sieves. During the regeneration and washing process of titanium-silicon molecular sieves, a pump is used to continuously add materials containing catalyst particles, regeneration liquid or washing liquid to a membrane separator with a certain aperture In the membrane separator, the regenerated liquid or washing liquid is obtained on the permeation side of the membrane separator, and the retentate and catalyst are obtained at the outlet of the membrane separator, and are returned to the regeneration or washing processor under the action of the pressure difference, so that the regeneration of the titanium-silicon molecular sieve can be realized washing.

Contents of the invention

The purpose of the present invention is to provide a method suitable for the continuous production of propylene oxide through the epoxidation of propylene and hydrogen peroxide suitable for the original powdery titanium-silicon molecular sieve.

The method for continuously producing propylene oxide provided by the present invention is characterized in that the original powdery titanium-silicon molecular sieve is used as a catalyst, and the reaction raw materials containing propylene and hydrogen peroxide are continuously injected into the reaction system through the feed port, and the titanium-silicon molecular sieve and the reaction material Mix evenly and react in a slurry state. Under the action of the internal and external pressure difference, the molecular sieve and the liquid reaction material realize solid-liquid separation in the separation system, and the molecular sieve continues to circulate in the circulation pipeline composed of the reactor and the separation system, while part of the liquid product flows out reaction system to obtain the target product, wherein the pressure of the reaction system is 0.1-3.0MPa, the temperature is 30-60°C, the space time is 0.5-3h ^-1 , and the molar ratio of propylene to hydrogen peroxide is (0.5-4.0):1, The molar ratio of the solvent to the hydrogen peroxide is (10-60): 1, and the concentration of the titanium-silicon molecular sieve catalyst in the reaction system is 1.0-30 g/L.

In the method provided by the present invention, the titanium-silicon molecular sieve is preferably a titanium-silicon molecular sieve with an MFI structure.

In the method provided by the present invention, the propylene epoxidation slurry reaction equipment is mainly composed of three parts: a reactor, a separation system and a backwashing system, wherein the reactor and the separation system form a circulation pipeline, which is also the main body of the reaction equipment, and the circulation pipeline The pump in the pump drives the materials to circulate in the whole system, which not only plays the role of mixing materials, but also is the heat source for the normal reaction. A cooling jacket can be installed outside the reactor and the circulation pipeline, and the size of the cooling water is controlled by the temperature of the reaction system, which makes the temperature of the reaction system easier to control.

In the method provided by the present invention, said separation system is a solid-liquid separator composed of a separation membrane tube, the membrane tube aperture is smaller than the particle size of the titanium-silicon molecular sieve, and one or more solid-liquid separators are connected in parallel, which can be processed by actual separation Quantity selected. The slurry material flowing through the separation membrane tube realizes the solid-liquid separation of the catalyst and the liquid under the action of the pressure difference inside and outside the membrane tube. A part of the separated supernatant is backwashed by the backwashing system to the membrane tube.

In the method provided by the present invention, methanol or a mixture of methanol and water is preferably used as a solvent, and a certain amount of titanium-silicon molecular sieve is dissolved in the methanol solvent of hydrogen peroxide to form a slurry-like feed liquid, which is injected into the reaction system from the catalyst feeding port until Fill the entire circulation line. Turn on the circulating pump, and turn on the propylene and liquid-phase raw material feed pumps respectively after the system temperature reaches a predetermined value. Adjust the opening of the back pressure valve until the system pressure reaches the set value. After the whole system is stabilized, the product flows out from the product outlet of the stabilization tank.

In the method provided by the present invention, in order to prevent the catalyst from clogging the pores of the membrane tube, the solid-liquid separator should be backwashed regularly, and the molecular sieve attached to the membrane tube should be washed back into the reaction system. 0.5 ~ 3h.

The method provided by the invention has the following advantages:

(1) The coupling and integration of the reactor and the solid-liquid separator can realize the continuous production of propylene oxide in the epoxidation of propylene, and the titanium-silicon molecular sieve is separated from the solvent containing the product on-line, so that the target product propylene oxide can be removed from the reaction system in time , reduce the occurrence of side reactions, and the selectivity of the target product propylene oxide is high.

(2) The process is simple, the equipment investment is small, and it is easy to operate.

Description of drawings

Fig. 1 is a schematic flow chart of the method provided by the present invention.

Among them, 01 Catalyst feeding port, 02 Electromagnetic flowmeter, 03 Exhaust valve, 04 Temperature sensor, 05 Pressure gauge, 06 Check valve, 07 Pressure gauge, 08 Rotameter, 09 Back pressure valve, 10 Condenser, 11 Sampling valve, 12 exhaust valve, 13 product outlet, 14 liquid storage tank, 15 liquid level gauge, 16 pressure gauge, 17 cooling water inlet, 18 catalyst discharge port, 19 cooling water outlet, 20 regulating valve, 21 one-way valve, 22 hydrogen peroxide feed port, 23 propylene feed port, 24 vent port, 25 safety valve, 26 liquid level transmitter, 27 pressure sensor, R-1 reactor, P01 circulation pump, P02 backwash pump, F-1 separation device, F-2 separator.

Figure 2 is a schematic diagram of a solid-liquid separator.

Detailed ways

The method provided by the present invention will be described in detail below in conjunction with the schematic flow chart 1 .

Reactor (R-1), circulation pump (P01) and separators (F-1, F-2) form a circulation pipeline, in which separators F-1 and F-2 are connected in parallel in the circulation pipeline, containing molecular sieve The slurry fluid of the reaction mixture is driven by the circulation pump (P01), and the catalytic oxidation reaction occurs in the entire circulation pipeline. The thermal effect of the reaction is controlled by the circulation pump (P01) and the cooling water flow regulating valve (20). The flow rate of the fluid can be adjusted by the frequency conversion controller that controls the speed of the circulating pump (P01). The opening of the cooling water flow regulating valve (20) Controlled by temperature sensor (04). The slurry fluid flowing through the separator realizes the solid-liquid separation of the molecular sieve and the epoxidation product containing olefin under the action of the pressure difference inside and outside the separator, in which the molecular sieve remains in the circulation pipeline, and a part of the clear liquid flows out of the reaction system after reaction .

The separator is shown in Figure 2, and its main working part is the ceramic membrane tube. When the equipment is in normal operation, the membrane separator needs to be backwashed regularly to prevent the original powdery catalyst from clogging the membrane pores. The specific implementation process will be described in detail in conjunction with Figure 1. as follows:

When the backwash pump P02 is turned on, the solenoid valve (09) is in the closed state (the pump P02 is closed, and the solenoid valve (09) is in the normally open state), and the cleaning liquid used for backflushing in the storage tank is pumped into the separator by the pump P02 ( F-1, F-2), the pressure difference inside and outside the membrane tube of the separator increases rapidly, and under the action of pressure, the cleaning liquid permeates the membrane tube wall and flushes the catalyst attached to it back to the reaction system to complete the backwashing process. The best recoil time is 1-3s, and the recoil interval is 0.5-3h.

The method provided by the present invention will be further described below in conjunction with the examples, but the content of the present invention is not limited thereby.

The titanium-silicon molecular sieve (prepared by the method disclosed in CN1132699C) catalyst used in the examples is produced by Hunan Jianchang Company, and the trade name is HTS. The number of separators depends on the actual processing capacity. In the following examples, two parallel separators are used, and the volume of the entire circulation pipeline is 2.5L.

Example 1

Weigh 50g of HTS molecular sieve and place it in the methanol solution of hydrogen peroxide, stir to form a slurry, and then inject it into the reaction system through the catalyst feeding port. Open the feed valve of the liquid-phase raw material (methanol solution of hydrogen peroxide) and backpressure until the system pressure is 2.0 MPa, then open the feed valve of propylene and control the reaction temperature to 40°C. In the reaction system, the molar ratio of methanol to hydrogen peroxide in the liquid phase raw material is 40:1, the molar ratio of propylene to hydrogen peroxide is 2:1, and the space time is 1.5h.

The results of regular sampling analysis are: the conversion rate of hydrogen peroxide is greater than 98%, the selectivity of propylene oxide is 93%, the selectivity of 1-methoxyl-2-propanol is 2.3%, the selectivity of 2-methoxyl-1-propanol The selectivity to alcohol was 3.2%, and the selectivity to propylene glycol was 1.5%.

Example 2

Weigh 40g of HTS titanium-silicon molecular sieve and place it in the methanol solution of hydrogen peroxide, stir to form a slurry, and then inject it into the reaction system through the catalyst feeding port. Open the feed valve of the liquid-phase raw material, when the back pressure reaches a system pressure of 2.0 MPa, open the propylene feed valve after the system pressure is stable, and control the reaction temperature at 35°C. The molar ratio of methanol and hydrogen peroxide in the liquid phase raw material is 40:1, the molar ratio of propylene and hydrogen peroxide is 2:1, and the reaction space time is 2.0h.

The results of regular sampling analysis are: the conversion rate of hydrogen peroxide is greater than 98%, the selectivity of propylene oxide is 95%, the selectivity of 1-methoxyl-2-propanol is 1.7%, the selectivity of 2-methoxyl-1-propanol The selectivity to alcohol was 2.3%, and the selectivity to propylene glycol was 1.0%.

Example 3

Weigh 50g of HTS titanium-silicon molecular sieve and place it in the methanol solution of hydrogen peroxide, stir to form a slurry, and then inject it into the reaction system through the catalyst feeding port. Open the feed valve of the liquid-phase raw material, when the back pressure reaches a system pressure of 2.0 MPa, open the propylene feed valve after the system pressure is stable, and control the reaction temperature at 35°C. The molar ratio of methanol to hydrogen peroxide in the liquid phase raw material is 40:1, the molar ratio of propylene to hydrogen peroxide is 2:1, and the reaction space time is 3.0h.

The results of regular sampling analysis are: the conversion rate of hydrogen peroxide is greater than 98%, the selectivity of propylene oxide is 91%, the selectivity of 1-methoxyl-2-propanol is 2.0%, the selectivity of 2-methoxyl-1-propanol is Alcohol selectivity was 5.5%, propylene glycol selectivity was 1.5%.

Example 4

Weigh 50g of HTS titanium-silicon molecular sieve and place it in the methanol solution of hydrogen peroxide, stir to form a slurry, and then inject it into the reaction system through the catalyst feeding port. Open the feed valve of the liquid-phase raw material, back pressure until the system pressure is 1.5 MPa, and open the propylene feed valve after the pressure is stable. The reaction temperature was controlled at 30°C. The molar ratio of methanol to hydrogen peroxide in the liquid phase raw material is 20:1, the molar ratio of propylene to hydrogen peroxide is 3:1, and the reaction space time is 1.0h.

The results of regular sampling analysis are: the conversion rate of hydrogen peroxide is greater than 98%, the selectivity of propylene oxide is 98%, the selectivity of 1-methoxyl-2-propanol is 0.5%, the selectivity of 2-methoxyl-1-propanol is The selectivity to alcohol was 0.8%, and the selectivity to propylene glycol was 0.7%.

Example 5

Weigh 50g of HTS titanium-silicon molecular sieve and place it in the methanol solution of hydrogen peroxide, stir to form a slurry, and then inject it into the reaction system through the catalyst feeding port. Open the feed valve of the liquid-phase raw material, and when the back pressure reaches a system pressure of 3.0 MPa, open the propylene feed valve after the pressure stabilizes. The reaction temperature was controlled at 35°C. The molar ratio of methanol and hydrogen peroxide in the liquid phase raw material is 60:1, the molar ratio of propylene and hydrogen peroxide is 1:1, and the reaction space time is 2.5h.

The results of regular sampling analysis are: the conversion rate of hydrogen peroxide is greater than 95%, the selectivity of propylene oxide is 95%, the selectivity of 1-methoxyl-2-propanol is 2.0%, the selectivity of 2-methoxyl-1-propanol The selectivity to alcohol was 1.7%, and the selectivity to propylene glycol was 1.3%.

Claims (5)

1. A method for continuous production of propylene oxide, characterized in that the former powdery titanium-silicon molecular sieve is used as a catalyst, and the reaction raw materials containing propylene and hydrogen peroxide are continuously injected into the reaction system by the feed port, and the titanium-silicon molecular sieve and the reaction material Mix evenly and react in a slurry state. Under the action of the internal and external pressure difference, the molecular sieve and the liquid reaction material realize solid-liquid separation in the separation system, and the molecular sieve continues to circulate in the circulation pipeline composed of the reactor and the separation system, while part of the liquid product flows out Reaction system, obtain target product, wherein, the pressure of reaction system is 0.1-3.0MPa, temperature is 30-60 ℃, space time is 0.5-3h, the mol ratio of propylene and hydrogen peroxide is (0.5-4.0): 1, solvent and The molar ratio of the hydrogen peroxide is (10-60): 1, and the concentration of the titanium-silicon molecular sieve catalyst in the reaction system is 1.0-30 g/L. 2. according to the method for claim 1, it is characterized in that described titanium silicon molecular sieve is the titanium silicon molecular sieve with MFI structure. 3. according to the method for claim 1, it is characterized in that said separation system is the solid-liquid separator that separation membrane tube is formed, and membrane tube aperture is less than the particle diameter of titanium-silicon molecular sieve, and solid-liquid separator is one or more parallel connections . 4. The method according to claim 3, characterized in that the solid-liquid separator is regularly recoiled, and the molecular sieve attached to the membrane tube is flushed back to the reaction system, the recoil time is 1-3s, and the recoil interval is 0.5-3h. 5. A process according to claim 1, characterized in that said solvent is methanol or a mixture of methanol and water.

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