A method for isomerizing trans-2-pentene to cis-2-pentene

Abstract

This invention relates to the field of organic synthesis, specifically to a method for isoformation of trans-2-pentene into cis-2-pentene. The method comprises the following steps: extractive distillation of 2-pentene to obtain cis-2-pentene and trans-2-pentene; mixing trans-2-pentene with water, heating the mixture, and then feeding it into a reactor containing alumina particles as catalyst for reaction; after the reaction, the resulting product is condensed and sequentially passed through a light-weight removal tower T-01 and a heavy-weight removal tower T-02 to obtain the cis-2-pentene product.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis, and more specifically, to a method for isoforming trans-2-pentene into cis-2-pentene. Background Technology

[0002] The industrial route for preparing diethyl ketone from cis-2-pentene is both clean and environmentally friendly. In this production process, trans-2-pentene yields almost no target product; therefore, isolating and isomerizing trans-2-pentene can save significant material and energy costs. Summary of the Invention

[0003] In view of this, the present invention aims to provide a method for isoformation of trans-2-pentene into cis-2-pentene, which is a clean, environmentally friendly, and mild industrial route.

[0004] To solve the above-mentioned technical problems, this application is implemented as follows:

[0005] This invention provides a method for isomerizing trans-2-pentene into cis-2-pentene, characterized by comprising the following steps:

[0006] Extractive distillation of 2-pentene yields cis-2-pentene and trans-2-pentene.

[0007] Trans-2-pentene and water are mixed, heated, and then fed into a reactor containing a γ-crystalline alumina catalyst for reaction.

[0008] After the reaction is complete, the product is condensed and then passed through light-removal tower T-01 and heavy-removal tower T-02 in sequence to obtain cis-2-pentene product.

[0009] In this invention, the method for isomerizing trans-2-pentene into cis-2-pentene specifically includes:

[0010] (1) Extractive distillation was performed on 2-pentene to separate cis-2-pentene and trans-2-pentene;

[0011] (2) Trans-2-pentene is mixed with water, heated to a certain temperature by a preheater and vaporizer, and then enters the reactor to react. The reactor is filled with γ-crystalline alumina catalyst. After the reaction is completed, the product is subjected to secondary condensation.

[0012] (3) The reaction products in step (2) above are sequentially fed into the light removal tower T-01 and the heavy removal tower T-02 to obtain cis-2-pentene product.

[0013] In some specific embodiments, the specific methods of extraction and distillation include:

[0014] 2-Pentene was directly fed into an extractive distillation column with 60 trays for separation. The top temperature of the extractive distillation column was 63°C, the bottom temperature was 66°C, and the top pressure was 0.1 MPa. The reflux ratio of the distillation column was controlled at 5:1 to 10:1, and the ratio of the extractant N-methylpyrrolidone to cis-2-pentene was 16:1 to 25:1. Trans-2-pentene with a purity of over 97.0% was obtained at the top of the column, and cis-2-pentene was obtained after desorption from the bottom of the column.

[0015] In this invention, the 2-pentene raw material is generally a mixture of cis-2-pentene and trans-2-pentene, and the content of trans-2-pentene in 2-pentene is not specifically limited.

[0016] In some specific embodiments, the molar ratio of trans-2-pentene to water is 1:1 to 1.5.

[0017] In some specific embodiments, the heating temperature is 240–270°C.

[0018] In some specific embodiments, the reaction temperature is 300–350°C.

[0019] Through extensive experiments, the inventors discovered that the following three factors affect the yield and conversion rate of cis-2-pentene: 1) The amount of deionized water added to the raw materials. Too little deionized water can easily cause coking during the reaction, while too much deionized water not only increases energy consumption but also hinders the reaction; 2) The temperature of the material after being heated by the preheater and vaporizer. If the temperature is too low, the reaction conversion rate will be low; if the temperature is too high, the energy consumption will be high, and excessively high temperatures will not have a significant impact on the reaction conversion rate; 3) The constant temperature of the reactor. If the temperature is too low, the reaction conversion rate will be low; if the temperature is too high, the material will coke, resulting in a low reaction yield.

[0020] The beneficial technical effects of the present invention through the above technical solution are as follows:

[0021] The method for isoformation of trans-2-pentene into cis-2-pentene provided by this invention is a clean, environmentally friendly industrial route with mild conditions. Detailed Implementation

[0022] The present invention will be further described in detail below through examples. All raw materials used in the examples are commercially available.

[0023] In the following embodiments, the light-light removal tower T-01 has 40 plates, an operating pressure of 0.1 MPa (gauge pressure), a top temperature of 52°C, a bottom temperature of 55°C, and a reflux ratio of 16.

[0024] Heavy removal tower T-02: theoretical plate number is 45, operating pressure is 0.1MPa (gauge pressure), tower top temperature is 53℃, tower bottom temperature is 56℃, and reflux ratio is 14.

[0025] Methods for isomerizing trans-2-pentene into cis-2-pentene include:

[0026] (1) 2-Pentene (as determined by gas chromatography, the content of trans-2-pentene is 97.23 wt%, the content of cis-2-pentene is 2.69 wt%, and the content of other impurities is 0.08 wt%) is directly fed into an extractive distillation column with 60 trays for separation. The top temperature of the extractive distillation column is 63℃, the bottom temperature of the extractive distillation column is 66℃, the top pressure of the extractive distillation column is 0.1 MPa, the reflux ratio of the distillation column is controlled at 5:1 to 10:1, and the ratio of the extractant N-methylpyrrolidone to cis-2-pentene is 16:1 to 25:1. The trans-2-pentene product with a purity of more than 97.0% is obtained at the top of the column, and the cis-2-pentene is obtained after analysis at the bottom of the column.

[0027] (2) Trans-2-pentene is mixed with water, heated to a certain temperature by a preheater and vaporizer, and then enters the reactor to react. The reactor contains 360g of aluminum granules. After the reaction is completed, the product is subjected to secondary condensation.

[0028] (3) The reaction products in step (2) above are sequentially fed into the light removal tower T-01 and the heavy removal tower T-02 to obtain cis-2-pentene product.

[0029] Table 1 shows the parameters, product conversion rate, and yield in the examples.

[0030] Table 1

[0031]

[0032] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for isoforming trans-2-pentene into cis-2-pentene, characterized in that, Includes the following steps: Extractive distillation of 2-pentene yields cis-2-pentene and trans-2-pentene. Trans-2-pentene and water are mixed, heated, and then fed into a reactor containing a γ-crystalline alumina catalyst for reaction. After the reaction is complete, the product is condensed and then passed through light-removal tower T-01 and heavy-removal tower T-02 in sequence to obtain cis-2-pentene product.

2. The method for isoformation of trans-2-pentene into cis-2-pentene according to claim 1, characterized in that, The molar ratio of trans-2-pentene to water is 1:1 to 1.

5.

3. The method for isoformation of trans-2-pentene into cis-2-pentene according to claim 1, characterized in that, The heating temperature is 240–270°C.

4. The method for isoformation of trans-2-pentene into cis-2-pentene according to claim 1, characterized in that, The reaction temperature is 300–350°C.

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