Method for preparing isoamylene

Abstract

The invention belongs to the technical field of isopentene preparation, and particularly relates to a method for preparing isopentene, which comprises the following steps: S1, carrying out etherification reaction on tert-amyl methyl ether serving as a raw material in a gas phase through a catalyst bed layer at the reaction temperature of 140-290 DEG C, S2, removing methanol from an etherification reaction product to obtain a crude isopentene material, and S3, separating the crude isopentene material from the crude isopentene material to obtain the isopentene. S3, adding a mixture of tert-butyl alcohol and water into the crude isopentene material, uniformly stirring the mixture through mixing equipment to uniformly disperse the tert-butyl alcohol into the crude isopentene material, adding the mixture of tert-butyl alcohol and water before the crude isopentene is subjected to isomerization reaction through a catalyst bed layer, controlling the reaction temperature to be 20-45 DEG C, and carrying out reaction for 2-3 hours; the condition that the isopentene is cracked due to too high temperature is reduced, and the production quality of the isopentene is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of isopentene preparation, in particular to a method for preparing isopentene. Background Art

[0002] Isoamylene is an organic compound with the chemical formula C5H10, also known as 3-methyl-1-butene or isopropylethylene, which is mainly used in organic synthesis.

[0003] In the current prior art, a patent application with publication number CN109232156A discloses a method for preparing isopentene, wherein isopentane and butene are mixed, dissolved in an organic acid, and isopentane is converted into isopentene under the action of an acidic catalyst. The reaction materials can be separated to obtain a mixed C5 product rich in isopentene, and organic acid sec-butyl ester can also be produced as a by-product. The conversion reaction conditions are mild, the energy consumption is low, the process is simple, the requirements for equipment and facilities are low, and the production cost can be significantly reduced.

[0004] Isoamylene is a colorless, volatile liquid with an extremely low melting point of about -168°C and a boiling point of about 20.1°C. It is insoluble in water but soluble in most organic solvents such as ethanol, ether, and benzene. The preparation of isopentene mainly includes separation of by-products from petroleum refining, co-dimerization of ethylene and propylene, and reaction of the residual carbon five after hydrogenation with methanol. The residual carbon five after hydrogenation reacts with methanol to produce tert-amyl methyl ether, and the separated and purified tert-amyl methyl ether is cracked at high temperature to produce isopentene.

[0005] In the existing method for preparing isopentene, the conditions of the preparation method require a relatively high temperature environment. Isopentene may undergo cracking reactions in a high temperature environment, thereby affecting the production quality of isopentene.

[0006] To this end, the present invention provides a method for preparing isopentene. Summary of the invention

[0007] In order to make up for the deficiencies of the prior art, at least one technical problem raised in the background technology is solved.

[0008] The technical solution adopted by the present invention to solve the technical problem is as follows: a method for preparing isopentene according to the present invention comprises: S1: using methyl tert-amyl ether as a raw material, performing an etherification reaction in a gas phase through a catalyst bed, and the reaction temperature is 140-290° C.; S2: removing methanol from the etherification reaction product to obtain a crude isopentene material; S3: adding a mixture of tert-butyl alcohol and water to the crude isopentene material, and stirring the mixture uniformly through a mixing device to uniformly disperse the tert-butyl alcohol in the crude isopentene material; S4: performing an isomerization reaction on the mixed crude isopentene material through a catalyst bed to convert 2-methyl-1-butene in the crude isopentene into 2-methyl-2-butene; the mass exchange capacity of the sulfonic acid cation exchange resin-1 is 3.5-5 mol / g, the reaction temperature is 20-45° C., the reaction pressure is 0.3-1.0 MPa, and the isomerization reaction is performed in a stainless steel tubular fixed bed reactor, and the reactor 50 grams of spherical sulfonic acid cation exchange resin catalyst is loaded into the fixed bed catalyst bed to form a fixed bed catalyst bed, the mass exchange capacity of the resin is 3.5-5.5 mmol / g, the outside of the reactor is controlled by a circulating hot water temperature jacket, and a temperature measuring element is installed in the catalyst bed. The reaction materials of the isomerization reaction pass through the fixed bed according to the set feed amount, and the isomerization reaction is carried out according to the set reaction conditions. Before the crude isopentene passes through the catalyst bed for isomerization reaction, a mixture of tert-butyl alcohol and water is added, and the reaction temperature is controlled between 20-45° C. to reduce the situation that the isopentene is cracked due to excessive temperature, thereby improving the quality of isopentene production. The comparative example has the same reaction conditions as the comparative example, except that the mixture of tert-butyl alcohol and water is not added. After the reaction is completed, sampling is performed for detection. The reaction pressure in the comparative example is 0.3 MPa and the reaction temperature is 22° C., and the reaction pressure in the comparative example is 0.5 MPa and the reaction temperature is 32° C., and the mass space velocity ratio is 1:8.

[0009] Preferably, the catalyst for the etherification reaction is changed from sulfuric acid to Ni / Al2O3, which provides a higher surface area and increases the activity of the catalyst.

[0010] Preferably, the product obtained from the isomerization reaction is passed into a distillation tower for further distillation treatment, and the distillation tower produces refined isopentene and impurities respectively.

[0011] Preferably, the distillation step comprises: a: placing the mixed crude isopentene mixture into a tubular reactor for pre-reaction, reacting tert-butyl alcohol with part of tert-amyl methyl ether under the action of a catalyst to generate a mixed solution of 2-methyl-1-butene and 2-methyl-2-butene; b: the mixed solution enters a distillation tower, and under the action of gravity, most of the 2-methyl-1-butene, the catalyst and part of the water enter the stripping section of the distillation tower, and most of the tert-butyl alcohol, 2-methyl-2-butene and the remaining water enter the distillation section of the distillation tower; c: sending the mixture obtained at the top of the reaction distillation tower to a phase separation tank, and obtaining an oil phase mixture of isopentene, light components and other by-products at the top of the phase separation tank, and obtaining a water phase mixture containing tert-butyl alcohol at the bottom of the phase separation tank; d: sending the water phase mixture to a water treatment tower, and separating tert-butyl alcohol from the top of the tower. , the separated sewage is sent to the sewage treatment device e: the oil phase mixture separated by the phase separation tank is sent to the separation tower, and the light component mixture is separated at the top of the separation tower. The separation tower kettle is sent to the isopentene distillation tower, and the heavy component mixture is obtained by the separation tower kettle. The isopentene mixture is distilled by a distillation tower to improve the production efficiency of isopentene, reduce the material requirements of the water phase treatment unit for equipment, reduce the energy consumption of production, and improve the economy of production. Before the distillation operation step, the temperature and pressure of the distillation tower are set, wherein the kettle temperature is set to 126°C and the pressure is set to 0.5MPa. A comparative example is added, and the kettle temperature in the comparative example is set to 117°C and the pressure is set to 0.1MPa. The produced refined isopentene is detected by chromatography, and the reflux ratio with comparative example 2 is 3:1.

[0012] Preferably, the temperature in the separation tower is 20-45°C. During the reaction, since isopentene is an organic compound, it may undergo thermal decomposition at high temperature. During this process, double bonds may break, resulting in changes in the molecular structure. By reasonably controlling the reaction temperature, it is possible to effectively avoid the situation where the temperature is too high, which causes the decomposition of isopentene and affects the reaction. The situation where the isopentene production is reduced due to the cracking of isopentene due to excessive temperature is reduced, thereby improving the quality of isopentene production.

[0013] Preferably, the mass exchange capacity of the sulfonic acid cation exchange resin-1 is 3.5-5 mol / g.

[0014] Preferably, the reaction temperature is 140-290° C. By controlling the reaction temperature, the reaction rate can be increased while the overly high temperature that affects the reaction efficiency can be effectively avoided.

[0015] Preferably, the distillation tower is a plate tower, which is a graded contact mass transfer equipment for gas-liquid or liquid-liquid systems, and consists of a cylindrical tower body and a number of tower plates horizontally arranged in the tower at a certain interval. The plate tower can make the gas and liquid phases fully contact on the tower plates, provide the largest possible mass transfer area and mass transfer coefficient, thereby enhancing the mass transfer effect. At the same time, compared with traditional packed towers, plate towers usually have a larger production capacity, which means that they can process more materials. Since the plate efficiency of plate towers is usually high, this means that higher separation efficiency can be achieved per unit plate height.

[0016] The beneficial effects of the present invention are as follows:

[0017] 1. In the method for preparing isopentene described in the present invention, a mixture of tert-butyl alcohol and water is added to crude isopentene before the isomerization reaction is carried out through a catalyst bed, and the reaction temperature is controlled between 20-45° C. to reduce the cracking of isopentene caused by excessively high temperature, thereby improving the quality of isopentene production.

[0018] 2. The method for preparing isopentene described in the present invention performs distillation treatment on an isopentene mixture through a distillation tower, thereby improving the production efficiency of isopentene, reducing the material requirements of the water phase treatment unit for equipment, reducing production energy consumption, and improving production economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described below in conjunction with the accompanying drawings.

[0020] Figure 1 is a flow chart of the preparation of isopentene according to the present invention;

[0021] Figure 2 It is a flow chart of the distillation step of the present invention. DETAILED DESCRIPTION

[0022] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0023] Example 1

[0024] like Figure 1As shown, a method for preparing isopentene according to an embodiment of the present invention comprises: S1: using methyl tert-amyl ether as a raw material, and performing an etherification reaction in a gas phase through a catalyst bed, and the reaction temperature is 140-290° C., S2: removing methanol from the etherification reaction product to obtain a crude isopentene material, S3: adding a mixture of tert-butyl alcohol and water to the crude isopentene material, and stirring the mixture evenly through a mixing device to uniformly disperse the tert-butyl alcohol in the crude isopentene material, S4: passing the mixed crude isopentene material through a catalyst bed for an isomerization reaction to convert 2-methyl-1-butene in the crude isopentene into 2-methyl-2-butene, the mass exchange capacity of the sulfonic acid cation exchange resin-1 is 3.5-5 mol / g, the reaction temperature is 20-45° C., and the reaction pressure is 0.3-1.0 MPa. During the operation, using methyl tert-amyl ether as a raw material, The etherification reaction is carried out through a catalyst bed, the reaction temperature is controlled between 140-290° C., the product after the etherification reaction is subjected to a methanol removal operation, tert-butyl alcohol and water are added to the crude isopentene material, and then an isomerization reaction is carried out through the catalyst bed to convert 2-methyl-1-butene in the crude isopentene into 2-methyl-2-butene, and finally a mass exchange of a sulfonic acid cation exchange resin-1 is carried out. The isomerization reaction is carried out in a stainless steel tubular fixed bed reactor, 50 grams of a spherical sulfonic acid cation exchange resin catalyst is loaded into the reactor to form a fixed bed catalyst bed, the mass exchange capacity of the resin is 3.5-5.5 mmol / g, the outside of the reactor is controlled by a circulating hot water temperature jacket, and a temperature measuring element is provided in the catalyst bed. The reaction materials of the isomerization reaction pass through the fixed bed according to a set feed amount, and the isomerization reaction is carried out according to set reaction conditions.

[0025] like Figure 1 As shown, the catalyst for the etherification reaction is changed from sulfuric acid to Ni / Al2O3, which provides a higher surface area and increases the activity of the catalyst.

[0026] like Figure 1 As shown, the product obtained from the isomerization reaction described above is passed into a distillation tower for further distillation treatment, and the distillation tower produces refined isopentene and impurities respectively.

[0027] Example 2

[0028] like Figure 2As shown, the distillation step comprises: a: the mixed crude isopentene mixture is placed in a tubular reactor for pre-reaction, tert-butyl alcohol reacts with part of methyl tert-amyl ether under the action of a catalyst to generate a mixed liquid of 2-methyl-1-butene and 2-methyl-2-butene; b: the mixed liquid enters a distillation tower, and under the action of gravity, most of the 2-methyl-1-butene, the catalyst and part of the water enter the stripping section of the distillation tower, and most of the tert-butyl alcohol, 2-methyl-2-butene and the remaining water enter the distillation section of the distillation tower; c: the mixture obtained at the top of the reaction distillation tower is sent to a phase separation tank, and the oil phase mixture of isopentene, light components and other by-products obtained at the top of the phase separation tank is sent to the bottom of the phase separation tank. The crude isopentylene mixture is pre-reacted, and the catalyst causes the tert-butanol to react with part of the methyl tert-amyl ether to obtain a mixed liquid, which is then sent to a distillation tower for distillation treatment, and isopentylene is obtained by reaction in a phase separation tank, and then the light component and the heavy component in the oil phase mixture are separated by the phase separation tank to obtain pure isopentylene.

[0029] like Figure 2 As shown, the temperature in the separation tower is 20-45°C. The temperature in the separation tower is controlled between 20-45°C. During the reaction, since isopentene is an organic compound, isopentene may undergo thermal decomposition at high temperatures. During this process, double bonds may break, resulting in changes in the molecular structure. By reasonably controlling the reaction temperature, it is possible to effectively avoid the situation where the temperature is too high, which may cause isopentene to decompose and affect the reaction.

[0030] like Figure 1 As shown, the mass exchange capacity of the sulfonic acid cation exchange resin-1 is 3.5-5 mol / g.

[0031] like Figure 1 As shown, the reaction temperature mentioned above is 140-290°C. During the preparation of isopentene, the reaction rate will increase with the increase of temperature. If the reaction temperature is too high, it may cause the reaction equilibrium to shift to the left, that is, to the direction of the reactants, thereby reducing the yield of the target product. By controlling the reaction temperature, while increasing the reaction rate, it is possible to effectively avoid the situation where the temperature is too high and the reaction efficiency is affected.

[0032] like Figure 2As shown, the distillation tower is a plate tower, which is a graded contact mass transfer equipment for gas-liquid or liquid-liquid systems. It consists of a cylindrical tower body and a number of plates horizontally arranged in the tower at a certain interval. The plate tower can make the gas and liquid phases fully contact on the plates, provide the largest possible mass transfer area and mass transfer coefficient, thereby enhancing the mass transfer effect. At the same time, compared with traditional packed towers, plate towers usually have a larger production capacity, which means that they can process more materials. Since the plate efficiency of plate towers is usually high, this means that higher separation efficiency can be achieved per unit plate height.

[0033] Comparative Example 1

[0034] The reaction conditions are the same as those in Example 1, except that the mixture of tert-butyl alcohol and water is not added. After the reaction is completed, sampling is performed. The reaction pressure in Example 1 is 0.3 MPa and the reaction temperature is 22° C., while the reaction pressure in the comparative example is 0.5 MPa and the reaction temperature is 32° C., and the mass space velocity ratio is 1:8.

[0035] Comparative Example 2

[0036] Before performing the distillation operation steps, the temperature and pressure of the distillation tower are set, wherein the bottom temperature of the tower in Example 2 is set to 126°C and the pressure is set to 0.5 MPa, and the bottom temperature of the tower in the comparative example is set to 117°C and the pressure is set to 0.1 MPa. The component of the produced refined isopentene is detected by chromatography, and the reflux ratio of Example 2 to Comparative Example 2 is 3:1.

[0037] Working principle: using methyl tert-amyl ether as raw material, carrying out etherification reaction through a catalyst bed, removing impurities from the product of the etherification reaction to obtain a crude isopentene material, and then carrying out an isomerization reaction on the crude isopentene material. The obtained product is then sent to a distillation tower for distillation treatment to obtain isopentene and impurities, which are separated by a phase separation tank to obtain an isopentene product. During the reaction, since isopentene is an organic compound, it may undergo thermal decomposition at high temperatures. In this process, double bonds may break, resulting in changes in the molecular structure. By reasonably controlling the reaction temperature, it is effectively avoided that the temperature is too high, which may cause isopentene to decompose and affect the reaction. In the process of isopentene preparation, the reaction rate will accelerate with the increase of temperature. If the reaction temperature is too high, it may It can cause the reaction equilibrium to move to the left, that is, to the direction of the reactants, thereby reducing the yield of the target product. By controlling the reaction temperature, while increasing the reaction rate, it can effectively avoid the situation where the temperature is too high and affects the reaction efficiency. The plate tower is a graded contact mass transfer equipment used for gas-liquid or liquid-liquid systems. It consists of a cylindrical tower body and a number of tower plates horizontally arranged in the tower at a certain interval. The plate tower can make the gas and liquid phases fully contact on the tower plate, provide the largest possible mass transfer area and mass transfer coefficient, thereby enhancing the mass transfer effect. At the same time, compared with traditional packed towers, plate towers usually have a larger production capacity, which means that they can handle more materials. Since the plate efficiency of plate towers is usually high, this means that higher separation efficiency can be achieved per unit plate height.

[0038] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing isopentene, characterized in that: The preparation method comprises: S1: Using tert-amyl methyl ether as raw material, the gas phase passes through the catalyst bed to carry out ether decomposition reaction, the reaction temperature is 140-290℃, S2: removing methanol from the etherification reaction product to obtain crude isopentene material, S3: adding a mixture of tert-butyl alcohol and water to the crude isopentene material, and stirring the mixture evenly by a mixing device to make the tert-butyl alcohol evenly dispersed in the crude isopentene material. S4: the mixed crude isopentene material is passed through a catalyst bed for isomerization reaction to convert 2-methyl-1-butene in the crude isopentene into 2-methyl-2-butene. The mass exchange capacity of the sulfonic acid cation exchange resin-1 is 3.5-5 mol / g, the reaction temperature is 20-45°C, and the reaction pressure is 0.3-1.0 MPa.

2. A method for preparing isopentene according to claim 1, characterized in that: The catalyst for the etherification reaction in S1 is changed from sulfuric acid to Ni / Al2O3.

3. A method for preparing isopentene according to claim 1, characterized in that: The product obtained from the isomerization reaction described in S4 is passed into a distillation tower for further distillation treatment, and the distillation tower produces refined isopentene and impurities respectively.

4. A method for preparing isopentene according to claim 3, characterized in that: The distillation step comprises: a: The mixed crude isopentene mixture is placed in a tubular reactor for pre-reaction. Under the action of a catalyst, tert-butyl alcohol reacts with part of tert-amyl methyl ether to generate a mixed liquid of 2-methyl-1-butene and 2-methyl-2-butene. b: The mixed liquid enters the distillation tower. Under the action of gravity, most of the 2-methyl-1-butene, catalyst and part of the water enter the stripping section of the distillation tower, and most of the tert-butyl alcohol, 2-methyl-2-butene and the remaining water enter the distillation section of the distillation tower. c: The mixture obtained at the top of the reaction distillation tower is sent to a phase separation tank, and an oil phase mixture of isopentene, light components and other by-products is obtained at the top of the phase separation tank, and a water phase mixture containing tert-butyl alcohol is obtained at the bottom of the phase separation tank. d: The aqueous phase mixture is sent to a water treatment tower, tert-butyl alcohol is separated from the top of the tower, and the separated wastewater is sent to a wastewater treatment device. e: The oil phase mixture separated in the phase separation tank is sent to the separation tower, and the light component mixture is separated at the top of the separation tower and sent to the isopentene distillation tower in the separation tower kettle, and the heavy component mixture is obtained in the separation tower kettle.

5. A method for preparing isopentene according to claim 1, characterized in that: The temperature in the separation tower is 20-45°C.

6. A method for preparing isopentene according to claim 1, characterized in that: The mass exchange capacity of the sulfonic acid cation exchange resin-1 described in S4 is 3.5-5 mol / g.

7. A method for preparing isopentene according to claim 1, characterized in that: The reaction temperature described in S1 is 140-290°C.

8. A method for preparing isopentene according to claim 4, characterized in that: The distillation tower is a plate tower.

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