A process for the preparation of cyclopentylbenzene

Abstract

The application discloses a preparation method of cyclopentylbenzene. The method is that cyclopentene and benzene are subjected to alkylation catalytic reaction, the alkylation reaction product is subjected to fractionation and rectification in sequence to obtain cyclopentylbenzene, the heavy component obtained by rectification is subjected to heavy component removal to recover a polysubstituted cyclopentylbenzene component, the polysubstituted cyclopentylbenzene component is subjected to transposition alkylation catalytic reaction with benzene, and the transposition alkylation catalytic reaction product is subjected to fractionation and rectification with the alkylation reaction product. The method has the advantages of high selectivity, high yield, strong continuity and the like, and the unreacted raw materials in one reaction can be recycled and utilized, thereby saving cost and meeting the green chemical concept.

Description

Technical Field

[0001] This invention relates to a method for preparing cyclopentylbenzene, specifically a method for producing cyclopentylbenzene by alkylation of benzene and cyclopentene, belonging to the field of molecular sieves. Background Technology

[0002] Cyclopentylbenzene is an important organic chemical raw material. It serves not only as an excellent solvent but also as a raw material for the co-production of phenol and cyclopentanone via an oxidative-acidolysis reaction. Due to the increasing global demand for phenol, higher ketones, and their derivative bisphenol A, the industrial production capacity required for cyclopentylbenzene will continue to grow. The production method of cyclopentylbenzene is similar to that of cumene, both involving the alkylation reaction of benzene and olefins. Therefore, most engineers have developed cyclopentylbenzene processes based on the cumene process. However, due to the different physicochemical properties of the reactants, the cyclopentylbenzene processes developed based on the cumene process face problems such as low yield, low selectivity, and high byproduct levels. Currently, cyclopentylbenzene is not only an excellent solvent; more importantly, it can be used as a raw material to co-produce phenol and cyclopentanone via an oxidative-acidolysis reaction. Compared to the traditional route for producing phenol / acetone from propylene / benzene via the Hock reaction, this route effectively reduces the production cost of phenol. Simultaneously, it can co-produce high-value cyclopentanone, thus replacing the old process with low atom utilization of cyclopentanone produced by high-temperature decarboxylation of adipic acid. The produced cyclopentanone can be used to develop high-value products such as valeramide and PA5. In the oxidative-acidolysis reaction of cyclopentylbenzene to produce phenol and cyclopentanone, the quality of the cyclopentylbenzene feedstock directly affects the yield and quality of the phenol and cyclopentanone products.

[0003] Currently, the mainstream production method for cyclopentylbenzene is the catalytic alkylation synthesis using benzene and cyclopentene as raw materials. This method suffers from problems such as low selectivity for monosubstituted cyclopentylbenzene, high content of polysubstituted cyclopentylbenzene and other heavy component byproducts, and low purity of cyclopentylbenzene. Therefore, there is an urgent industrial need to develop a method for preparing cyclopentylbenzene with high reaction selectivity, high separation, and high purification yield. Summary of the Invention

[0004] To address the problems existing in the prior art, the purpose of this invention is to provide a process for preparing cyclopentylbenzene. This process for preparing cyclopentylbenzene has advantages such as high selectivity, high yield, and strong continuity. Furthermore, unreacted raw materials in one reaction can be recovered and recycled, thereby saving costs and conforming to the concept of green chemical engineering.

[0005] To achieve the above-mentioned objective, this invention provides a method for preparing cyclopentylbenzene. The method involves catalytically reacting cyclopentene and benzene with an alkylation reaction. The alkylation reaction product is then subjected to fractionation and distillation to obtain cyclopentylbenzene. The heavy component obtained from distillation is then subjected to deweighting to recover the polysubstituted cyclopentylbenzene component. The polysubstituted cyclopentylbenzene component is then subjected to a transposition alkylation catalytic reaction with benzene. The transposition alkylation catalytic reaction product is incorporated into the alkylation reaction product and then subjected to fractionation and distillation.

[0006] The present invention provides a method for the catalytic alkylation of cyclopentene and benzene. By controlling the reaction temperature, pressure, space velocity, and other conditions, monosubstituted cyclopentylbenzene with a selectivity greater than 92% is obtained. The reaction product is sequentially purified by a light-weight removal tower (I), a benzene removal tower (II), and a cyclopentylbenzene refining tower to obtain pure cyclopentylbenzene. The polysubstituted cyclopentylbenzene is separated in a heavy-weight removal tower, and the transposition alkylation reaction product is returned to the tower system for further purification, thereby increasing the cyclopentylbenzene yield. Benzene is recovered and recycled as raw material. This method features high product selectivity and high yield; it is an industrial-scale method for the continuous production of cyclopentylbenzene.

[0007] As a preferred embodiment, the mass ratio of cyclopentene to benzene in the alkylation catalytic reaction is 1:10 to 1:3.

[0008] As a preferred embodiment, the alkylation catalytic reaction is carried out in an alkylation reactor under the following conditions: a volume hourly space velocity (VHSV) of 0.5–5 h⁻¹. -1 The reaction temperature is 120–220℃ and the reaction pressure is 0.5–4.0 MPa.

[0009] As a further preferred embodiment, the mass ratio of cyclopentene to benzene in the alkylation catalytic reaction is 1:10 to 1:3, and the volume hourly space velocity is 1 to 4 h⁻¹. -1 The reaction temperature is 160–200℃ and the reaction pressure is 1.5–3 MPa.

[0010] As a preferred embodiment, the catalyst used in the alkylation catalytic reaction is at least one of Y-type zeolite molecular sieve, hierarchical β-type zeolite molecular sieve, and MCM-41 strip molecular sieve.

[0011] The alkylation reaction described in this invention is a catalytic alkylation reaction. Using catalysts such as Y-type zeolite molecular sieves at specific temperatures and pressures, the olefinic bonds in cyclopentene are broken, leading to a displacement reaction with hydrogen on the benzene ring to form cyclopentylbenzene. The temperature, pressure, and mass hourly space velocity (MHV) of the reaction vessel affect the selectivity and yield of the product. Too low a MHV results in an increase in polycyclopentylbenzene, which is detrimental to subsequent separation; too high a MHV leads to incomplete reaction and a low yield. Therefore, all process parameters of the reaction vessel must be strictly controlled within the specified range. However, the amount of cyclopentene on the benzene ring cannot be completely controlled during the reaction, so some polycyclopentylbenzene will still be present. Further processing is required to separate polycyclopentylbenzene from monocyclopentylbenzene.

[0012] As a preferred embodiment, the fractionation is achieved using a series of light-light component removal towers: Tower I (light-light component removal), Tower II (benzene removal), and Tower III (light-light component removal). The conditions for Tower I are controlled as follows: atmospheric pressure and temperature 80–120°C; the conditions for Tower II are controlled as: atmospheric pressure and temperature 160–250°C; and the conditions for Tower III are controlled as: vacuum 3–10 kPa and temperature 110–160°C. The light components from Tower I are substances with boiling points between cyclopentene and benzene, such as cyclopentene and cyclopentane (C5 monomers). The light components from Tower II are substances with boiling points between benzene and cyclopentylbenzene, such as tetrahydrodicyclopentadiene. During the fractionation process, unreacted substances, reaction byproducts, and other impurities from the alkylation reaction are distilled off separately. This process purifies the reaction products, facilitating subsequent distillation of cyclopentylbenzene.

[0013] As a preferred embodiment, the distillation is achieved through a refining column; the refining column conditions are controlled as follows: temperature 130–170℃, vacuum 1–5 kPa. The distillation column is a packed column, with feed entering from the lower section and exiting from the top; the refining section has 36 trays, and the stripping section has 12 trays, for a total of 48 trays; the packing is 5mm stainless steel θ-rings. Simple distillation can achieve some separation, but it cannot separate the mixture into a high-purity product, while distillation can achieve this. Because cyclopentylbenzene is prone to decomposition or isomerization when heated to its boiling point under normal pressure, reducing the product's selectivity and yield, this invention employs vacuum distillation. After distillation, the selectivity of monosubstituted cyclopentylbenzene is greater than 92%, and the purity of cyclopentylbenzene is 99.9%. At this point, a portion of polysubstituted cyclopentylbenzene is still mixed in the distillation column bottoms. To improve the yield of monosubstituted cyclopentylbenzene, further deweighting and transposition hydrocarbonation treatment of the distillation column bottoms feed is still required.

[0014] As a preferred embodiment, the heavy residue removal is achieved by a heavy residue removal tower; the tower conditions are controlled as follows: temperature 140–180℃, vacuum 0.5 kPa–3 kPa. The heavy residue removal tower is a packed tower, and its packing material is 5 mm stainless steel θ rings. After heavy residue removal, the heavy residue is discharged through the bottom of the tower, while the polysubstituted cyclopentylbenzene is recovered through the top of the tower. The polysubstituted cyclopentylbenzene is then reconstituted into monosubstituted cyclopentylbenzene through a subsequent transposition alkylation reaction.

[0015] As a preferred embodiment, the mass ratio of polysubstituted cyclopentylbenzene to benzene in the transposition alkylation catalytic reaction is 1:14 to 1:6.

[0016] As a preferred embodiment, the transposition alkylation catalytic reaction is carried out in a hydrocarbon conversion reactor, and the conditions for the transposition alkylation catalytic reaction are: a reaction temperature of 160–240 °C and a volume hourly space velocity of 0.5–8 h⁻¹. -1 The reaction pressure is 1.0–3.0 MPa. The transposition alkylation reaction can convert about 6% of polysubstituted cyclopentylbenzene into monosubstituted cyclopentylbenzene, further increasing the yield of monosubstituted cyclopentylbenzene.

[0017] As a preferred embodiment, the catalyst used in the transposition alkylation catalytic reaction is at least one of Y-type zeolite molecular sieve, hierarchical β-type zeolite molecular sieve, and MCM-41 strip molecular sieve, and the catalyst is purchased from Tianjin Nankai University Catalyst Factory.

[0018] Compared with the prior art, the beneficial technical effects of the technical solution of the present invention are reflected in the following aspects:

[0019] (1) The present invention provides a complete production process and method for producing cyclopentylbenzene by alkylation of cyclopentene and benzene, which has high selectivity and conversion rate; by controlling the reaction process parameters, such as benzene-to-olefin ratio, temperature, pressure, and space velocity, the conversion rate of cyclopentene and the selectivity of cyclopentylbenzene are improved.

[0020] (2) About 6% of the polysubstituted cyclopentylbenzene was converted into monosubstituted cyclopentylbenzene by transposition alkylation reaction, thereby increasing the yield of cyclopentylbenzene. The yield of cyclopentylbenzene after transposition alkylation reaction was greater than 98%.

[0021] (3) The process flow and technical control parameters described in this invention are designed according to the working scenario of continuous reaction in industry. They can be applied to continuous industrial production and have the advantages of simple process, easy operation, safety and stability. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a preparation process for cyclopentylbenzene according to the present invention.

[0023] 1. Alkylation reactor; 2. Transposition alkylation reactor; 3. Light molecule removal I tower; 4. Main separation tower; 5. Light molecule removal II tower; 6. Cyclopentylbenzene distillation tower; 7. Heavy molecule removal tower. Detailed Implementation

[0024] The present invention will be described in detail below with reference to the embodiments and accompanying drawings, but the embodiments do not constitute a limitation on the present invention.

[0025] All catalysts in the embodiments of this invention are from the catalyst factory of Nankai University in Tianjin.

[0026] The equipment used in the embodiments of the present invention is as follows: Figure 1 As shown, the specific parameters are:

[0027] The alkylation reactor and the transposition hydrocarbonation reactor are fixed-bed reactors with a diameter of DN40×1500mm and a capacity of 1300ml of molecular sieve catalyst. The separation tower parameters are shown in Table 1.

[0028] Table 1 Separation tower parameters in the embodiment

[0029]

[0030]

[0031] The tower is equipped with 5mm stainless steel theta rings.

[0032] The preparation process of cyclopentylbenzene according to the present invention is as follows: Raw materials from the cyclopentene tank and benzene tank are pumped into the alkylation reactor from the top at a certain mass ratio, and the temperature and pressure are controlled; the reactor effluent is pressurized into the light component removal tower 1, and the bottom temperature and reflux ratio are controlled, with light component 1 flowing out from the top of the tower; the bottom material is pumped into the benzene removal tower, and the bottom temperature and reflux ratio are controlled, with benzene recovery flowing out from the top of the tower; the bottom material is pumped into the light component removal tower 2, and the bottom temperature, reflux ratio, and vacuum degree are controlled, with light component 2 flowing out from the top of the tower; the bottom material is pumped into the cyclopentylbenzene refining tower, and the bottom temperature, reflux ratio, and vacuum degree are controlled, with purified cyclopentylbenzene flowing out from the top of the tower; the bottom material is pumped into the heavy component removal tower, and the bottom temperature, reflux ratio, and vacuum degree are controlled, with polysubstituted cyclopentylbenzene flowing out from the top of the tower, and heavy residues being discharged from the bottom. The vacuum degree of the three towers—light component removal tower 2, cyclopentylbenzene refining tower, and heavy component removal tower—is maintained at a gradient difference. The polysubstituted cyclopentylbenzene flowing out from the top of the deweighting tower is fed into the transposition hydrocarbonation reactor at a certain mass ratio, with temperature and pressure controlled; it is converted into monosubstituted cyclopentylbenzene and then recycled into the purification system for further purification.

[0033] Example 1

[0034] A continuous reactor for the preparation of cyclopentylbenzene was loaded with 1300 ml of Y-type zeolite molecular sieve catalyst. Benzene and cyclopentene were fed separately using horizontal flow pumps at a mass ratio of 8:1, with a total volumetric space velocity of 3.7 h⁻¹. -1The catalyst bed reaction temperature is 175℃ and the pressure is 2.35 MPa. The reaction product enters the first light component removal tower, with the bottom temperature controlled at 88℃ and a reflux ratio of 30:2. After light component removal, the bottom material enters the benzene removal tower, with the bottom temperature controlled at 225℃ and a reflux ratio of 2:8. Excess benzene is recovered to the raw benzene tank. The bottom material enters the second light component removal tower, with the bottom temperature controlled at 136℃, a vacuum of 8 kPa, and a reflux ratio of 4:60. The bottom material enters the cyclopentylbenzene refining tower, with the bottom temperature controlled at 139℃, a vacuum of 3 kPa, and a reflux ratio of 5:10. The top product of the tower is cyclopentylbenzene; the bottom product enters the heavy residue removal tower, with the bottom temperature controlled at 160℃, vacuum at 1 kPa, and reflux ratio at 4:10. The bottom product is heavy residue, and the top product is polysubstituted cyclopentylbenzene, which enters the transposition alkylation reactor. The transposition alkylation reactor is filled with Y-type zeolite molecular sieve catalyst. The mass ratio of polysubstituted cyclopentylbenzene to benzene is 1:10. The catalyst bed reaction temperature is 170℃ and the pressure is 2.0 MPa, which converts polysubstituted cyclopentylbenzene into monosubstituted cyclopentylbenzene, which is returned to the light residue removal tower and purified using the same process as the reaction product.

[0035] The analytical results showed that the cyclopentene conversion rate was 99.8% and the cyclopentylbenzene selectivity was 92.5%.

[0036] 6% of polysubstituted cyclopentylbenzene was converted to monosubstituted cyclopentylbenzene via a transposition alkylation reaction.

[0037] Cyclopentylbenzene yield ≥ 98% (yield = conversion * selectivity).

[0038] Cyclopentylbenzene purity: 99.9%.

[0039] Example 2

[0040] A continuous reactor for the preparation of cyclopentylbenzene was loaded with 1300 ml of Y-type zeolite molecular sieve catalyst. Benzene and cyclopentene were fed separately using horizontal flow pumps at a mass ratio of 10:1, with a total volume hourly space velocity (VHSV) of 4 h⁻¹. -1The catalyst bed reaction temperature is 180℃, and the pressure is 2.2 MPa. The reaction product enters the first light component removal tower, with the bottom temperature controlled at 87℃ and a reflux ratio of 30:2. After light component removal, the bottom material enters the benzene removal tower, with the bottom temperature controlled at 224℃ and a reflux ratio of 2:8. Excess benzene is recovered to the raw benzene tank. The bottom material enters the second light component removal tower, with the bottom temperature controlled at 137℃, a vacuum of 10 kPa, and a reflux ratio of 4:60. The bottom material enters the cyclopentylbenzene refining tower, with the bottom temperature controlled at 140℃, a vacuum of 3 kPa, and a reflux ratio of 5:10. The top product of the tower is cyclopentylbenzene; the bottom product enters the heavy residue removal tower, with the bottom temperature controlled at 150℃, vacuum at 0.5 kPa, and reflux ratio at 4:10. The bottom product is heavy residue, and the top product is polysubstituted cyclopentylbenzene, which enters the transposition alkylation reactor. The transposition alkylation reactor is filled with Y-type zeolite molecular sieve catalyst. The mass ratio of polysubstituted cyclopentylbenzene to benzene is 1:8. The catalyst bed reaction temperature is 180℃ and the pressure is 2.2 MPa, which converts polysubstituted cyclopentylbenzene into monosubstituted cyclopentylbenzene, which is returned to the light residue removal tower and purified using the same process as the reaction product.

[0041] The analysis results showed that the cyclopentene conversion rate was 99.9% and the cyclopentylbenzene selectivity was 93.0%.

[0042] Cyclopentylbenzene yield ≥ 98%; cyclopentylbenzene purity: 99.9%.

Claims

1. A method for preparing cyclopentylbenzene, characterized in that: Cyclopentene and benzene undergo alkylation catalytic reaction. The alkylation reaction product is successively fractionated and distilled to obtain cyclopentylbenzene. The heavy component obtained by distillation is deweighted to recover the polysubstituted cyclopentylbenzene component. The polysubstituted cyclopentylbenzene component is then subjected to transhydroalkylation catalytic reaction with benzene. The transhydroalkylation catalytic reaction product is incorporated into the alkylation reaction product and enters the fractionation and distillation process. The fractionation is achieved by a series of light component removal towers I, benzene removal tower, and light component removal tower II. The conditions for light component removal tower I are controlled as follows: atmospheric pressure and temperature 80~120℃; the conditions for benzene removal tower are controlled as follows: atmospheric pressure and temperature 160~250℃; and the conditions for light component removal tower II are controlled as follows: vacuum degree 3KPa~10KPa and temperature 110~160℃. The distillation is achieved through a refining column; the conditions of the refining column are controlled as follows: temperature 130~170℃, vacuum degree 1KPa~5KPa; The transposition alkylation catalytic reaction is carried out in a hydrocarbon conversion reactor under the following conditions: reaction temperature of 160–240 °C and volume hourly space velocity of 0.5–8 h⁻¹. -1 The reaction pressure is 1.0~3.0MPa.

2. The method for preparing cyclopentylbenzene according to claim 1, characterized in that: The mass ratio of cyclopentene to benzene in the alkylation catalytic reaction is 1:10 to 1:

3.

3. The method for preparing cyclopentylbenzene according to claim 1, characterized in that: The alkylation catalytic reaction is carried out in an alkylation reactor under the following conditions: volume hourly space velocity (VHSV) of 0.5–5 h⁻¹. -1 The reaction temperature is 120~220℃ and the reaction pressure is 0.5~4.0MPa.

4. The method for preparing cyclopentylbenzene according to claim 1, characterized in that: The catalyst used in the alkylation catalytic reaction is at least one of Y-type zeolite molecular sieve, hierarchical β-type zeolite molecular sieve, and MCM-41 strip molecular sieve.

5. The method for preparing cyclopentylbenzene according to claim 1, characterized in that: The deweighting is achieved by a deweighting tower; the conditions of the deweighting tower are controlled as follows: temperature 140~180℃, vacuum degree 0.5kPa~3kPa.

6. The method for preparing cyclopentylbenzene according to claim 1, characterized in that: In the transposition alkylation catalytic reaction, the mass ratio of polysubstituted cyclopentylbenzene to benzene is 1:14 to 1:

6.

7. The method for preparing cyclopentylbenzene according to claim 1, characterized in that: The catalyst used in the transposition alkylation catalytic reaction is at least one of Y-type zeolite molecular sieve, hierarchical β-type zeolite molecular sieve, and MCM-41 strip molecular sieve.

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