A reaction process for synthesizing cyclohexyl acetate by esterification of cyclohexene with acetic acid

Abstract

This invention discloses a reaction process for synthesizing cyclohexene acetate by esterification of cyclohexene and acetic acid. The process comprises a two-stage synthesis of cyclohexene acetate from cyclohexene and acetic acid via a moving bed pre-reaction and catalytic reactive distillation. In this two-stage process, the pre-reactor and the catalytic reactive distillation column are filled with the same macroporous resin solid acid catalyst, simplifying catalyst processing, use, and waste catalyst disposal. Furthermore, the pre-reactor utilizes a moving bed reactor, allowing for flexible adjustment of the raw material processing load and product yield within a certain range while ensuring the quality of the cyclohexene acetate product. It is also applicable to a wider range of cyclohexene content in the reaction feedstock; thus, this process offers the advantages of a wide applicable range of cyclohexene content in the feedstock and a broad range of adjustable processing loads.

Description

Technical Field

[0001] This invention relates to the field of esterification reaction synthesis technology, and in particular to a reaction process for synthesizing cyclohexene and acetate by esterification. Background Technology

[0002] Cyclohexyl acetate is an important chemical intermediate and fine chemical with an elegant fruity aroma. It is widely used in food and cosmetic fragrances. It is also a high-performance environmentally friendly solvent and a key precursor for the synthesis of cyclohexanol and ethanol. Cyclohexanol is an important upstream raw material for the production of nylon-6 and nylon-66.

[0003] Traditional industrial production of cyclohexyl acetate mainly involves the esterification of cyclohexanol and acetic acid under concentrated sulfuric acid catalysis. This method suffers from inherent drawbacks such as severe equipment corrosion, excessive emissions of waste gas, complex side reactions, and difficulties in product separation, which does not align with the development direction of modern green chemistry. With the maturation of selective hydrogenation technology for cyclohexene from benzene, the highly atom-economical route for the direct esterification of cyclohexene and acetic acid to synthesize cyclohexyl acetate has attracted widespread attention.

[0004] Patent CN103739485B discloses a method for producing cyclohexyl acetate and the catalytic reactive distillation column used therein. Its characteristic is the use of excess acetic acid to react with cyclohexene in a reactive distillation column to produce and separate cyclohexyl acetate. The raw material is a mixture containing cyclohexene, cyclohexane, and benzene obtained by hydrogenating benzene. The top product of the column is cyclohexane and benzene containing acetic acid, with a yield generally below 92.5%. Another example is patent CN110105208A, which discloses a processing technology using a fixed-bed reactor combined with subsequent distillation. Although the catalyst is easily separated, the reaction and separation units are independent, resulting in higher energy consumption and requiring high purity raw materials. Patent CN103664587A discloses a two-stage reaction process combining pre-reaction and catalytic reactive distillation to produce cyclohexyl acetate from acetic acid via cyclohexene esterification. This process achieves good reaction performance, yielding high-purity cyclohexyl acetate at the bottom of the reactive distillation column. The pre-reactor can be a tubular fixed-bed, stirred-tank, fluidized-bed, or boiling-bed reactor. However, the different catalysts used in the pre-reaction and catalytic reactive distillation stages cause some inconvenience in application. Furthermore, the catalyst is another key factor limiting the widespread industrial application of this process. Heteropoly acids (such as phosphotungstic acid) have high activity but are difficult to separate and recover from the product; ordinary cation exchange resins have limited acid strength, are prone to swelling and breakage, and lack long-term operational stability. Patent CN116851034A attempts to enhance resin sulfonation, while CN118459336A designs a supported composite catalyst.

[0005] How to combine high-performance catalysts with better reaction processes to achieve high-efficiency, low-cost, flexible and adjustable continuous production remains a technical problem that needs to be solved in this field. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a reaction process for synthesizing cyclohexene acetate by esterification of cyclohexene and acetate, achieving high-efficiency, low-cost, flexible, and adjustable continuous production of cyclohexene acetate.

[0007] The present invention adopts the following technical solution: A reaction process for synthesizing cyclohexyl acetate by esterification of cyclohexene and acetate includes a pre-esterification reaction stage and an esterification reaction stage. In the pre-esterification reaction stage, the reactants, consisting of acetic acid and cyclohexene, first enter a pre-reactor containing a solid acid catalyst for pre-esterification. In the esterification reaction stage, the effluent from the pre-reactor enters a catalytic reactive distillation column containing a solid acid catalyst for esterification. High-purity cyclohexyl acetate is obtained at the bottom of the catalytic reactive distillation column, and an additional mixture is obtained at the top. Finally, the materials are separated.

[0008] As a further optimization of the above-mentioned reaction process for synthesizing cyclohexene acetate by esterification of cyclohexene and acetate, the cyclohexene material is any one of the following: a mixture of cyclohexene and cyclohexane, a mixture of cyclohexene and benzene, or a mixture of cyclohexene, cyclohexane, and benzene, wherein the cyclohexene content in the cyclohexene material is 5%-60%.

[0009] As a further optimization of the above-mentioned reaction process for synthesizing cyclohexene acetate by esterification of cyclohexene and acetate, the pre-reactor includes either a moving bed pre-reactor or a fixed bed pre-reactor, and the reaction conditions are as follows: reaction temperature of 40~200℃, reaction pressure of 0.1~15MPa, acid-to-olefin molar ratio of 1:1~50:1 in the pre-esterification reaction, liquid feed space velocity of 0.05~50 / h, and catalyst bed moving rate to catalyst bed height ratio of 0.001~0.5 / d.

[0010] As a further optimization of the above-mentioned reaction process for synthesizing cyclohexene acetate by esterification of cyclohexene and acetate, the theoretical plate number of the catalytic reactive distillation column is 8~220. 2~50 plates are selected near the median theoretical plate number to load the solid acid catalyst. Based on the total catalyst loading volume, the liquid feed space velocity is 0.05~40 / h, the operating pressure of the reactive distillation column is -0.1MPa to 8MPa, the temperature of the catalyst bed loading zone is 30~230℃, and the reflux ratio is 0.03:1~160:1.

[0011] As a further optimization of the above-mentioned reaction process for synthesizing cyclohexene acetate by esterification of cyclohexene and acetate, the pre-reactor and the catalytic reaction distillation column are filled with the same macroporous resin solid acid catalyst, which is one or both of spherical particles and hollow spherical particles, with an outer diameter of 1~25 mm.

[0012] As a further optimization of the above-mentioned reaction process for synthesizing cyclohexyl acetate by esterification of cyclohexene and acetate, the purity of the cyclohexyl acetate obtained from the bottom of the catalytic reactive distillation column is ≥99.5%.

[0013] As a further optimization of the above-mentioned reaction process for synthesizing cyclohexyl acetate by esterification of cyclohexene and acetate, the additional mixture obtained at the top of the catalytic reactive distillation column is a mixture of acetic acid, cyclohexane and / or benzene.

[0014] Beneficial effects Compared with the prior art, the present invention has significant advantages and beneficial effects, achieving considerable technological progress and practicality, and possessing broad application value. It has at least the following advantages: 1. The process of the present invention includes a two-stage synthesis process for preparing cyclohexyl acetate from cyclohexene and acetic acid through pre-reaction and catalytic reactive distillation. In the two-stage reaction process, the same macroporous resin solid acid catalyst is packed in the pre-reactor and the catalytic reactive distillation column, which makes the catalyst processing, use and waste catalyst treatment simpler.

[0015] 2. The pre-reactor of the present invention adopts a moving bed reactor, which can flexibly adjust the raw material processing load and product yield of the pre-reaction and the overall package within a certain range while ensuring the quality of cyclohexyl acetate product. It can also be applied to reaction raw materials with a wider range of cyclohexene content.

[0016] 3. The process of this invention has the advantages of a wide range of applicable cyclohexene content in raw materials and a wide range of adjustable processing load. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of protection. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort, such as formal modifications to the technical solutions described in the following embodiments or equivalent substitutions for some technical features, within the scope of the present invention's conceptual framework, are within the scope of protection of the present invention.

[0018] The present invention will now be described in detail with reference to the embodiments.

[0019] Example 1: A mixture of cyclohexene (containing 30 mg% cyclohexene) and benzene was mixed with acetic acid and fed into a moving bed pre-reactor packed with a 10 mm outer diameter spherical macroporous resin solid acid catalyst. The pre-reaction conditions were: temperature 100 °C, pressure 2 MPa, acid-to-olefin molar ratio 3:1, liquid feed space velocity 8 h⁻¹, and catalyst bed movement rate to catalyst bed height ratio 0.1 / d. The pre-reactor outlet material was fed into a catalytic reactive distillation column with 32 theoretical plates. A 10 mm outer diameter spherical macroporous resin solid acid catalyst was packed between the 14th and 20th theoretical plates. The catalytic reactive distillation conditions were: liquid feed space velocity 12 h⁻¹, operating pressure of the reactive distillation column -0.05 MPa, catalyst bed packing temperature 120 °C, and reflux ratio 20:1. The purity of the cyclohexyl acetate obtained from the bottom of the catalytic distillation reactor was 99.7%.

[0020] Example 2: A mixture of cyclohexene and cyclohexane containing 6% cyclohexene was mixed with acetic acid and fed into a moving bed pre-reactor packed with a 25mm outer diameter spherical and hollow sphere macroporous resin solid acid catalyst. The pre-reaction conditions were: temperature 45℃, pressure 14.5 MPa, acid-to-olefin molar ratio 1:1, liquid feed hourly space velocity (LHSV) 49 / h, and catalyst bed movement rate to catalyst bed height ratio 0.003 / d. The pre-reactor outlet material was fed into a catalytic reactive distillation column with 210 theoretical plates. The 25mm outer diameter spherical and hollow sphere macroporous resin solid acid catalyst was packed between the 100th and 150th theoretical plates. The catalytic reactive distillation conditions were: liquid feed hourly space velocity 0.05 / h, operating pressure 4 MPa, catalyst bed temperature 220℃, and reflux ratio 155:1. The purity of the cyclohexyl acetate obtained from the bottom of the catalytic distillation reactor was 99.9%.

[0021] Example 3: A mixture of cyclohexene (60 mg / L) with cyclohexane and benzene was fed into a fixed-bed pre-reactor containing a 1.5 mm outer diameter hollow spherical macroporous resin solid acid catalyst. The pre-reaction conditions were: temperature 195 °C, pressure 0.15 MPa, acid-to-olefin molar ratio 6:1, liquid feed space velocity 0.1 h⁻¹, and catalyst bed movement rate to catalyst bed height ratio 0.5 / d. The pre-reactor outlet material was fed into a catalytic reactive distillation column with 9 theoretical plates. A 1.5 mm outer diameter hollow spherical macroporous resin solid acid catalyst was packed between the 4th and 5th theoretical plates. The catalytic reactive distillation conditions were: liquid feed space velocity 40 h⁻¹, operating pressure 8 MPa, catalyst bed packing temperature 50 °C, and reflux ratio 0.1:1. The purity of the cyclohexyl acetate obtained from the bottom of the catalytic distillation reactor was 99.5%.

[0022] Example 4: A mixture of cyclohexene (containing 10 mg / mL cyclohexene), cyclohexane, and benzene, and acetic acid was fed into a fixed-bed pre-reactor packed with a 1.5 mm outer diameter spherical macroporous resin solid acid catalyst. The pre-reaction conditions were: temperature 145 °C, pressure 0.15 MPa, acid-to-olefin molar ratio 50:1, liquid feed space velocity 12 h / h, and catalyst bed movement rate to catalyst bed height ratio 0.3 / d. The pre-reactor outlet material was fed into a catalytic reactive distillation column with 20 theoretical plates. A 1.5 mm outer diameter spherical macroporous resin solid acid catalyst was packed between the 8th and 13th theoretical plates. The catalytic reactive distillation conditions were: liquid feed space velocity 8 h / h, operating pressure of the reactive distillation column 8 MPa, catalyst bed temperature around 98 °C, and reflux ratio 5:1. The purity of the cyclohexyl acetate obtained from the bottom of the catalytic distillation reactor was 99.6%.

[0023] The preferred embodiments and specific implementations of the present invention have been described in detail above with reference to the examples. However, the present invention is not limited to the above-described embodiments and examples. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the concept of the present invention.

Claims

1. A process for the synthesis of cyclohexyl acetate by esterification of cyclohexene with acetic acid, characterized in that: The method comprises a pre-esterification reaction stage and an esterification reaction stage, the pre-esterification reaction stage is that the reactant material composed of acetic acid and cyclohexene material is firstly introduced into a pre-reactor provided with a solid acid catalyst to perform a pre-esterification reaction, and the esterification reaction stage is that the pre-reactor effluent is introduced into a catalytic reaction rectifying tower provided with a solid acid catalyst to perform an esterification reaction, high-purity cyclohexyl acetate is obtained at the bottom of the catalytic reaction rectifying tower, and an additional mixture is obtained at the top of the catalytic reaction rectifying tower, and finally, the material is separated.

2. The reaction process for synthesizing cyclohexene acetate by esterification of cyclohexene with acetate as described in claim 1, characterized in that: The cyclohexene material is any one of a cyclohexene and cyclohexane mixture, a cyclohexene and benzene mixture, and a cyclohexene, cyclohexane and benzene mixture, and the content of cyclohexene in the cyclohexene material is 5%-60%.

3. The process for the synthesis of cyclohexyl acetate from cyclohexene and acetic acid according to claim 1, characterized in that: The pre-reactor comprises any one of a moving bed pre-reactor and a fixed bed pre-reactor, and the reaction conditions are as follows: the reaction temperature is 40-200℃, the reaction pressure is 0.1-15Mpa, the acid-alkene molar ratio of the pre-esterification reaction is 1:1-50:1, the liquid feed space velocity is 0.05-50 / h, and the ratio of the catalyst bed moving speed to the catalyst bed height is 0.001-0.5 / d.

4. The process for the synthesis of cyclohexyl acetate from cyclohexene and acetic acid according to claim 1, characterized in that: The catalytic reaction rectifying tower has a theoretical plate number of 8-220, 2-50 plates are selected to load the solid acid catalyst near the middle of the theoretical plate number, the liquid material feed space velocity is 0.05-40 / h based on the total volume of the catalyst loading, the operation pressure of the reaction rectifying tower is -0.1MPa to 8MPa, the temperature of the catalyst bed loading area is 30-230℃, and the reflux ratio is 0.03:1-160:

1.

5. The process for the synthesis of cyclohexyl acetate from cyclohexene and acetic acid according to claim 1, characterized in that: The same kind of macroporous resin solid acid catalyst is loaded in the pre-reactor and the catalytic reaction rectifying tower, the macroporous resin solid acid catalyst is one or both of a spherical particle and a hollow spherical particle, and the particle outer diameter is 1-25 mm.

6. The process for the synthesis of cyclohexyl acetate from cyclohexene and acetic acid according to claim 1, characterized in that: The purity of the cyclohexyl acetate obtained at the bottom of the catalytic reaction rectifying tower is ≥99.5%.

7. The reaction process for synthesizing cyclohexene acetate by esterification of cyclohexene with acetate as described in claim 1, characterized in that: The additional mixture obtained at the top of the catalytic reaction rectifying tower is a mixture composed of acetic acid and cyclohexane and / or benzene.