Preparation method of isobutylbenzene
By using a composite catalytic system and stepwise alkylation-isomerization reaction, combined with ultrasonic assistance and multi-stage distillation, the problems of low purity and yield in the preparation of isobutylbenzene were solved, and efficient and low-energy-consumption isobutylbenzene production was achieved.
Patent Information
- Application Number
- CN202511511870.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-22
- Publication Date
- 2026-01-09
AI Technical Summary
Existing processes for preparing isobutylbenzene are difficult to achieve high purity and high yield, and traditional acidic catalysts are prone to corrosion. Propylene polymerization at high temperatures results in severe side reactions and numerous byproducts.
A composite catalytic system, including a composite support of alkali metals, potassium carbonate and rare earth elements, is used to optimize reaction conditions and separation processes through stepwise alkylation and isomerization reactions, combined with ultrasonic-assisted and multi-stage distillation techniques.
It improves the purity and yield of isobutylbenzene, extends catalyst life, reduces distillation energy consumption, and reduces by-product generation and raw material waste.
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Figure CN121293076A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the chemical technology field, and in particular to a preparation method of isobutylbenzene. BACKGROUND
[0002] As a key organic chemical intermediate, isobutylbenzene has irreplaceable use in the industrial field: its core application scenario is as a raw material of phenol-acetone co-production device, which can be efficiently converted into phenol and acetone by cumene hydroperoxide method, and the phenol and acetone are basic raw materials for synthesizing resins, plastics and pharmaceutical intermediates; at the same time, in the fine chemical industry, isobutylbenzene can be further derived into isobutylbenzaldehyde and other perfume intermediates, or used as a precursor of anti-inflammatory pharmaceutical products, and can also be used as a high-boiling solvent for the production of high-end coatings and inks.
[0003] Since the downstream products have strict requirements on the purity of raw materials (such as the demand for purity ≥ 99% for pharmaceutical grade), the preparation process level of isobutylbenzene directly determines the product quality and production cost of the downstream industry chain, so the development of a preparation process with high efficiency, high purity and high yield has become an important demand in the industry. SUMMARY
[0004] The present application aims to overcome the shortcomings of the prior art and provide a preparation method of isobutylbenzene.
[0005] The specific technical solution is as follows: a preparation method of isobutylbenzene, which uses toluene and propylene as raw materials and performs step-by-step alkylation reaction in the presence of a composite catalyst system, including the following steps:
[0006] (1) Benzylation reaction: toluene and propylene are reacted at 180-210℃ and 1.5-3.0 MPa for 1-3 hours to generate intermediate benzyltoluene;
[0007] (2) Isomerization reaction: benzyltoluene is reacted at 200-230℃ and 0.5-1.5 MPa for 2-4 hours under the assistance of ultrasonic waves to generate isobutylbenzene;
[0008] (3) Product separation: unreacted toluene and propylene are recovered by multi-stage rectification to obtain isobutylbenzene finished product.
[0009] As a further technical solution, the composite catalyst system is a composite carrier of alkali metal, potassium carbonate and rare earth elements, and its preparation method includes:
[0010] S1: 100-300 mesh potassium carbonate powder, sodium metal block and rare earth element compound are mixed in a mass ratio of 1:10-14:0.2-0.4, and a molten alloy is formed by stirring at 225-250℃ under the protection of inert atmosphere for 2-3 hours;
[0011] S2 adding dispersant into the molten alloy, the adding amount is 0.3-0.8% of the mass of toluene, the stirring speed is raised to 800-1200r / min, and the solid catalyst is obtained after cooling;
[0012] S3 loading the solid catalyst on the porous silica carrier, the loading amount is 5.5-5.8% of the total mass of the catalyst, so as to improve the catalytic selectivity.
[0013] As a further technical solution, the rare earth element compound in step S1 is selected from at least one of lanthanum oxide, cerium nitrate and praseodymium oxide, and the purity of the rare earth element is ≥99.9%, and the synergistic effect of the rare earth element compound and the sodium block can reduce the content of isomerization by-products of benzyl toluene.
[0014] As a further technical solution, the inert atmosphere in step S1 is nitrogen.
[0015] As a further technical solution, the dispersant in step S2 is polyethylene glycol with a molecular weight of 5000-10000, and the adding amount is 0.5-0.6% of the mass of toluene.
[0016] As a further technical solution, in the stirring process in step S2, programmed temperature rising is adopted: from room temperature to 150℃ at a rate of 5-6℃ / min, then incubated for 1 hour, and then cooled to room temperature at a rate of 3-5℃ / min.
[0017] As a further technical solution, the specific surface area of the porous silica carrier in step S3 is 200-300m² / g.
[0018] As a further technical solution, the ultrasonic auxiliary conditions in the isomerization reaction are: frequency 30-50kHz, power 100-150W, and the ultrasonic wave is applied in an intermittent mode: pause for 10-12 seconds after continuous working for 50-60 seconds, and cycle until the reaction is completed.
[0019] As a further technical solution, the process parameters of the step-by-step alkylation reaction meet:
[0020] (1) Benzylization stage: the molar ratio of propylene to toluene is 0.8-1.2:1, the stirring rate is 600-1000r / min, and the adding amount of the composite catalytic system is 2.0-3.0% of the mass of toluene;
[0021] (2) Isomerization stage: introducing 0.1-0.2vol.% of trace water vapor into the reaction system, linearly reducing the reaction pressure from the initial 1.5MPa to 0.5MPa, and the pressure gradient is controlled at 0.1-0.2MPa / h.
[0022] As a further technical solution, the specific operation parameters of the multi-stage rectification are as follows: the primary rectification tower is used for recovering propylene, the number of its plates is 20-30, the reflux ratio is 1.5-2.5, and the tower top temperature is 30-40 DEG C; the secondary rectification tower is used for recovering toluene, the number of its plates is 15-20, the reflux ratio is 1.0-2.0, and the tower top temperature is 110-115 DEG C; and the final rectification tower is used for purifying isobutylbenzene, the number of its plates is 25-30, the reflux ratio is 2.0-3.0, and the tower top temperature is 170-175 DEG C.
[0023] Compared with the prior art, the present application has the following beneficial effects:
[0024] The process steps of the present application are optimized, and compared with the traditional preparation process, the purity and yield of isobutylbenzene are obviously improved. The present application takes a composite catalytic system as the core, and the components synergize: the basic site can activate the benzyl hydrogen of toluene to generate a benzyl negative ion intermediate, thereby promoting the alkylation reaction with propylene and avoiding the corrosion problem of traditional acid catalysts; the metallic sodium can act as a strong electron donor to stabilize the benzyl negative ion intermediate, thereby reducing the activation energy of the benzylization reaction, making the reaction proceed under mild conditions of about 200 DEG C, and reducing the propylene polymerization side reaction caused by high temperature; the rare earth compound provides Lewis acid sites, which helps to adjust the reaction selectivity and inhibit the multi-alkylation side reaction, and on the other hand, forms a coordination structure with the metallic sodium and potassium carbonate, reducing the volatilization and loss of active components; the porous silica carrier uniformly disperses the composite active components by virtue of the high specific surface area, avoids the agglomeration of active sites, and guarantees the catalytic selectivity. The step-by-step alkylation process controls the "benzylation, isomerization" in stages, first directionally generates a high-purity benzyl toluene intermediate, and then converts it into the target product through isomerization, avoiding the generation of by-products in the multi-path competition in one-step reaction; the ultrasonic wave assistance can improve the mass transfer conditions through cavitation effect, thereby improving the isomerization efficiency, and the batch mode can also avoid local overheating and reduce coking impurities; the multi-stage rectification precisely controls the plate number, reflux ratio and temperature according to the boiling point difference of each component, realizes a high recovery rate of toluene and propylene, purifies the product, and obtains high-purity isobutylbenzene.
[0025] The temperature-programmed stirring of the present application forms a uniform active layer of the solid catalyst, cooperates with the dispersion effect of the porous carrier, reduces the loss of active components, and prolongs the service life of the catalyst to more than 7 cycles; the pressure gradient control and the introduction of trace water vapor in the isomerization stage can adjust the polarity of the system, further promote the directional isomerization reaction, and reduce the generation of non-target isomers. In addition, the reaction and separation links are synergistically optimized: the high selectivity reaction reduces the generation of impurities, reduces the load of rectification separation, and reduces the energy consumption of rectification; the efficient recovery of raw materials realizes the process circulation and reduces the waste of raw materials. BRIEF DESCRIPTION OF DRAWINGS
[0026] Figure 1The preparation method of isobutylbenzene of the present application is shown in the flow chart. DETAILED DESCRIPTION
[0027] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.
[0028] The present application provides a preparation method of isobutylbenzene, which comprises the following steps: using toluene and propylene as raw materials, and performing step-by-step alkylation reaction in the presence of a composite catalyst system, specifically including the following four core links: composite catalyst system preparation, benzylation reaction, isomerization reaction, and product separation, and finally obtaining high-purity isobutylbenzene finished product.
[0029] In the present application, the sources of raw materials and auxiliary materials are as follows: toluene is industrial-grade toluene with a purity of ≥99.5%, and is a conventional product on the market; propylene is polymer-grade propylene with a purity of ≥99.9%; potassium carbonate powder is analytical pure, with a particle size of 100-300 mesh, and is a standard reagent on the market; sodium metal is industrial-grade, with a purity of ≥99.0%, and is a conventional metal raw material; rare earth compounds (lanthanum oxide, cerium nitrate, praseodymium oxide) are all analytical pure, and are commercially available; porous silica carrier has a specific surface area of 200-300 m² / g, and is a special carrier for catalysts; and the dispersant polyethylene glycol has a molecular weight of 5000-10000, and is an industrial-grade polymer. The above-mentioned raw materials do not need special pretreatment and can be directly used.
[0030] General preparation process of composite catalyst system
[0031] The 100-300 mesh potassium carbonate powder, sodium metal block and rare earth element compound (at least one selected from lanthanum oxide, cerium nitrate and praseodymium oxide) are weighed according to the mass ratio, and the mass ratio of the three is controlled to be 1:10-14:0.2-0.4.
[0032] The above-mentioned materials are placed in a reaction kettle, nitrogen gas is introduced as an inert protective atmosphere, the temperature is raised to 225-250℃, and stirring is performed for 2-3 hours to form a uniform molten alloy.
[0033] The dispersant polyethylene glycol is added to the molten alloy, the addition amount is 0.3-0.8% of the mass of the subsequent toluene involved in the reaction, preferably 0.5-0.6%, the stirring speed is increased to 800-1200 r / min, and at the same time, the temperature is raised by programming: from room temperature to 150℃ at a rate of 5-6℃ / min, and then kept for 1 hour, and then cooled to room temperature at a rate of 3-5℃ / min, to obtain a solid catalyst.
[0034] The solid catalyst is loaded on a porous silica carrier, and the loading amount is controlled to be 5.5-5.8% of the total mass of the catalyst, and is placed for standby use.
[0035] The following is a specific embodiment:
[0036] Example 1
[0037] Preparation of a composite catalyst body
[0038] 10 g of potassium carbonate powder with a particle size of 200 mesh, 120 g of sodium metal block, and 3 g of lanthanum oxide (mass ratio 1:12:0.3) were weighed and placed in a reaction kettle, nitrogen was introduced for protection, and the temperature was raised to 240°C and stirred for 2.5 hours to form a molten alloy; polyethylene glycol (molecular weight 8000) was added to the molten alloy, the amount of addition was 0.5% of the subsequent toluene mass, the stirring speed was adjusted to 1000 r / min, and the temperature was raised according to the program: 5.5°C / min from room temperature to 150°C for 1 hour, and then cooled to room temperature at a rate of 4°C / min, to obtain a solid catalyst; the solid catalyst was loaded on a porous silica carrier (specific surface area 250 m² / g), and the loading amount was 5.6%, for standby use.
[0039] Benzylization reaction
[0040] Toluene 1000 g was added to the reaction kettle, and 25 g of the composite catalyst system prepared above (2.5% of the mass of toluene) was added, propylene was introduced, the molar ratio of propylene to toluene was controlled to be 1.0:1, the reaction kettle was closed, the temperature was raised to 200°C, the pressure was raised to 2.0 MPa, the stirring rate was adjusted to 800 r / min, and the reaction was carried out for 2 hours to generate the intermediate benzyl toluene.
[0041] Isomerization reaction
[0042] The temperature of the reaction kettle was maintained at 220°C, the pressure was reduced to 1.0 MPa, 0.15 vol.% of trace water vapor was introduced into the reaction system, and the pressure was linearly reduced from 1.5 MPa to 0.5 MPa at a gradient of 0.15 MPa / h; the ultrasonic wave assistance was turned on, the frequency was set to 40 kHz, the power was set to 120 W, and the intermittent application mode was adopted: after 55 seconds of continuous operation, it was paused for 11 seconds, and the reaction was continued for 3 hours to generate a crude isobutyl benzene product.
[0043] Product separation
[0044] The crude product was sent to a multi-stage rectification system: the first-stage rectification tower had 25 plates, the reflux ratio was 2.0, and the overhead temperature was 35°C, and unreacted propylene was recovered; the secondary rectification tower had 18 plates, the reflux ratio was 1.5, and the overhead temperature was 112°C, and unreacted toluene was recovered; the final rectification tower had 28 plates, the reflux ratio was 2.5, and the overhead temperature was 172°C, and the product was collected at the bottom of the tower to obtain the isobutyl benzene product.
[0045] Example 2
[0046] Preparation of composite catalyst
[0047] Take 10 g of potassium carbonate powder with a particle size of 150 mesh, 100 g of sodium metal block, and 2 g of cerium nitrate (mass ratio 1:10:0.2), and place them in a reaction kettle. Protect them by introducing nitrogen gas, and heat them to 225°C. Stir them for 2 hours to form a molten alloy. Add polyethylene glycol (molecular weight 5000) to the molten alloy, with an addition amount of 0.3% of the subsequent toluene mass. Adjust the stirring speed to 800 r / min, and follow the programmed temperature increase: increase the temperature from room temperature to 150°C at a rate of 5°C / min, and maintain it for 1 hour. Then, cool it down to room temperature at a rate of 3°C / min. Obtain the solid catalyst. Load the solid catalyst on a porous silica carrier (specific surface area 250 m² / g), with a loading amount of 5.5%, and reserve it for use.
[0048] Benzylation reaction
[0049] Add 1000 g of toluene to the reaction kettle, and add 20 g of the composite catalyst system (2.0% of the toluene mass). Introduce propylene, and control the molar ratio of propylene to toluene to be 0.8:1. Close the reaction kettle, heat it to 180°C, increase the pressure to 1.5 MPa, and adjust the stirring speed to 600 r / min. React for 1 hour to generate the intermediate benzyl toluene.
[0050] Isomerization reaction
[0051] Increase the temperature of the reaction kettle to 200°C, and reduce the pressure to 0.5 MPa. Introduce 0.1 vol.% of trace water vapor into the system, and control the pressure to decrease linearly from 1.5 MPa to 0.5 MPa at a gradient of 0.1 MPa / h. Turn on the ultrasonic assistance, and set the frequency to 30 kHz and the power to 100 W. Use the intermittent mode: pause for 10 seconds after each continuous operation of 50 seconds. Continue the reaction for 2 hours to generate the crude isobutyl benzene.
[0052] Product separation
[0053] Multi-stage rectification parameters: primary rectification column plate number 20, reflux ratio 1.5, column top temperature 30°C; secondary rectification column plate number 15, reflux ratio 1.0, column top temperature 110°C; tertiary rectification column plate number 25, reflux ratio 2.0, column top temperature 170°C. Collect the bottom product to obtain the isobutyl benzene finished product.
[0054] Example 3
[0055] Preparation of composite catalyst
[0056] Take the particle size of 300 potassium carbonate powder 10 g, metal sodium block 140 g, praseodymium oxide 4 g (mass ratio 1:14:0.4), placed in the reaction kettle, nitrogen protection, heating to 250 ℃, stirring for 3 hours to form a molten alloy; to the molten alloy is added polyethylene glycol (molecular weight 10000), the amount of 0.8% of the subsequent toluene mass, the stirring speed is adjusted to 1200 r / min, the temperature is programmed to rise: room temperature to 150 ℃ at 6 ℃ / min, 1 h, then cooled to room temperature at 5 ℃ / min, to get solid catalyst; the solid catalyst is loaded on the porous silica carrier (specific surface area 250 m² / g), the loading amount is 5.8%, ready for use.
[0057] Benzylization reaction
[0058] The reaction kettle is added with toluene 1000 g, and the composite catalyst system 30 g (3.0% of the mass of toluene) is added, and propylene is introduced, and the molar ratio of propylene to toluene is controlled to be 1.2:1. The reaction kettle is closed, heated to 210 ℃, and the pressure is increased to 3.0 MPa. The stirring speed is adjusted to 1000 r / min, and the reaction is carried out for 3 hours to generate the intermediate benzyl toluene.
[0059] Isomerization reaction
[0060] The temperature of the reaction kettle is increased to 230 ℃, the pressure is decreased to 1.5 MPa, and 0.2 vol.% of trace water vapor is introduced into the system. The pressure is linearly decreased from 1.5 MPa to 0.5 MPa at a gradient of 0.2 MPa / h. The ultrasonic auxiliary is turned on, and the frequency is set to 50 kHz and the power is set to 150 W. The intermittent mode is: after 60 seconds of continuous operation, pause for 12 seconds. The reaction is continued for 4 hours to generate the crude isobutyl benzene.
[0061] Product separation
[0062] The parameters of multi-stage rectification are as follows: the primary rectification column has 30 plates, the reflux ratio is 2.5, and the overhead temperature is 40 ℃; the secondary rectification column has 20 plates, the reflux ratio is 2.0, and the overhead temperature is 115 ℃; the final rectification column has 30 plates, the reflux ratio is 3.0, and the overhead temperature is 175 ℃. The bottom product is collected to obtain the finished isobutyl benzene.
[0063] Example 4
[0064] Preparation of composite catalyst
[0065] Take the particle size of 250 potassium carbonate powder 10 g, 130 g of sodium metal block, lanthanum oxide 2.5 g and cerium nitrate 1.5 g (mixed rare earth, total mass ratio 1:13:0.4), placed in the reaction kettle, nitrogen protection, heating to 235 ℃, stirring for 2.5 hours to form a molten alloy; to the molten alloy, add polyethylene glycol (molecular weight 7000), the amount of 0.6% of the subsequent toluene mass, the stirring speed is adjusted to 1100 r / min, the temperature is programmed to rise: room temperature to 150 ℃ at 5.5 ℃ / min, 1 h, then cooled to room temperature at 4.5 ℃ / min, to get solid catalyst; the solid catalyst is loaded on the porous silica carrier (specific surface area 250 m² / g), the loading amount is 5.7%, ready for use.
[0066] Benzylization reaction
[0067] Into the reaction kettle, add toluene 1000 g, add 28 g of composite catalyst system (2.8% of toluene mass), introduce propylene, control the molar ratio of propylene to toluene to be 1.1:1, close the reaction kettle, heat to 195 ℃, increase the pressure to 2.5 MPa, adjust the stirring rate to 900 r / min, react for 2.5 hours, to generate intermediate benzyl toluene.
[0068] Isomerization reaction
[0069] The temperature of the reaction kettle is raised to 215 ℃, the pressure is reduced to 1.2 MPa, 0.18 vol.% of trace water vapor is introduced into the system, and the pressure is linearly reduced from 1.5 MPa to 0.5 MPa at a gradient of 0.18 MPa / h; open the ultrasonic auxiliary, set the frequency to 45 kHz, the power to 140 W, intermittent mode: pause for 11.5 seconds after each continuous working for 58 seconds, continue to react for 3.5 hours, to generate crude isobutyl benzene.
[0070] Product separation
[0071] Multistage rectification parameters: the first rectification column has 28 plates, a reflux ratio of 2.2, and a top temperature of 38 ℃; the secondary rectification column has 17 plates, a reflux ratio of 1.8, and a top temperature of 113 ℃; the final rectification column has 27 plates, a reflux ratio of 2.8, and a top temperature of 174 ℃, the bottom product is collected, and the isobutyl benzene product is obtained.
[0072] Example 5
[0073] Composite catalyst preparation
[0074] Take the particle size of 180 of potassium carbonate powder 10 g, metal sodium block 110 g, cerium nitrate 1.5 g and praseodymium oxide 1.5 g (mixed rare earth, total mass ratio 1:11:0.3), put into the reaction kettle, protect by nitrogen, heat to 230℃, stir for 2.2 hours to form a molten alloy; add polyethylene glycol (molecular weight 6000) to the molten alloy, the addition amount is 0.4% of the subsequent toluene mass, adjust the stirring speed to 900 r / min, program heating: room temperature to 150℃ at 5.2℃ / min, keep for 1 hour, then cool to room temperature at 3.5℃ / min, get solid catalyst; load the solid catalyst on porous silica carrier (specific surface area 250 m² / g), loading capacity 5.6%, ready for use.
[0075] Benzylation reaction
[0076] Add toluene 1000 g to the reaction kettle, add composite catalyst system 22 g (2.2% of toluene mass), introduce propylene, control the molar ratio of propylene to toluene to be 0.9:1, close the reaction kettle, heat to 190℃, increase the pressure to 1.8 MPa, adjust the stirring rate to 700 r / min, react for 1.5 hours to generate intermediate benzyl toluene.
[0077] Isomerization reaction
[0078] Increase the temperature of the reaction kettle to 210℃, reduce the pressure to 0.8 MPa, introduce 0.12 vol.% of trace water vapor into the system, control the pressure to decrease linearly from 1.5 MPa to 0.5 MPa at a gradient of 0.12 MPa / h; open the ultrasonic auxiliary, set the frequency to 35 kHz, the power to 110 W, intermittent mode: pause for 10.5 seconds after 52 seconds of continuous operation, continue to react for 2.5 hours to generate crude isobutyl benzene.
[0079] Product separation
[0080] Multistage rectification parameters: primary rectification column plate number 22, reflux ratio 1.8, column top temperature 32℃; secondary rectification column plate number 16, reflux ratio 1.2, column top temperature 111℃; tertiary rectification column plate number 26, reflux ratio 2.2, column top temperature 171℃, collect the bottom product to obtain isobutyl benzene finished product.
[0081] Comparative example 1
[0082] Catalyst preparation
[0083] Only take the particle size of 200 of potassium carbonate powder 10 g, directly load on porous silica carrier (specific surface area 250 m² / g), loading capacity 5.6%, ready for use (without metal sodium and rare earth compounds).
[0084] Benzylation reaction
[0085] The same as Example 1: 1000 g of toluene was added to a reaction kettle, 25 g of the above potassium carbonate catalyst was added, propylene was introduced (molar ratio 1.0:1), the temperature was raised to 200°C, the pressure was raised to 2.0 MPa, the stirring rate was 800 r / min, and the reaction was carried out for 2 hours.
[0086] Isomerization reaction
[0087] The same as Example 1: temperature 220°C, pressure 1.0 MPa, introduction of 0.15 vol.% water vapor, pressure gradient 0.15 MPa / h, ultrasonic assistance (40 kHz, 120 W, intermittent mode), reaction for 3 hours.
[0088] Product separation
[0089] The same as Example 1, the multi-stage rectification parameters were collected, and the bottom product was collected.
[0090] Comparative Example 2
[0091] Preparation of composite catalyst
[0092] The same as Example 1: mass ratio of potassium carbonate, sodium metal, and lanthanum oxide 1:12:0.3, nitrogen protection, stirring at 240°C for 2.5 hours, polyethylene glycol addition amount 0.5%, and loading amount 5.6%.
[0093] Benzylization reaction
[0094] The same as Example 1: 1000 g of toluene, 25 g of catalyst, propylene molar ratio 1.0:1, 200°C, 2.0 MPa, stirring 800 r / min, reaction for 2 hours.
[0095] Isomerization reaction
[0096] Only the ultrasonic assistance was cancelled, and the rest was the same as Example 1: temperature 220°C, pressure 1.0 MPa, introduction of 0.15 vol.% water vapor, pressure gradient 0.15 MPa / h, continuous stirring for 3 hours.
[0097] Product separation
[0098] The same as Example 1, the multi-stage rectification parameters were collected, and the bottom product was collected.
[0099] Test
[0100] Test 1: detection of isobutylbenzene purity
[0101] Test method
[0102] Refer to GB / T3144-2019 "Determination of Purity of Organic Chemical Products by Gas Chromatography", use gas chromatograph (model: Agilent 7890A), chromatographic column is HP-5 capillary column (30m x 0.32mm x 0.25um); column temperature program: initial temperature 60℃, hold for 2min, increase to 200℃ at 10℃ / min, hold for 5min; injection port temperature 250℃, detector (FID) temperature 280℃; carrier gas is nitrogen, flow rate 1.0mL / min; injection volume 1uL, split ratio 10:1. Calculate the purity of isobutylbenzene by area normalization method, the results are as follows:
[0103] Table 1
[0104] Group Isobutylbenzene purity (%) Example 1 99.2 Example 2 98.8 Example 3 99.5 Example 4 99.3 Example 5 99.0 Comparative Example 1 85.3 Comparative Example 2 90.5
[0105] As can be seen from Table 1, the purity of isobutylbenzene of Examples 1-5 is all ≥98.8%, mainly through the synergistic effect of "potassium carbonate, metallic sodium, rare earth compound" in the composite catalytic system: metallic sodium can enhance the efficiency of electron transfer, promote the directional progress of benzylation reaction, rare earth compounds can provide more active sites, inhibit side reactions such as polyalkylation, isomerization impurity generation; At the same time, ultrasonic assisted isomerization can improve the mass transfer efficiency, ensure that benzyltoluene is completely converted into isobutylbenzene.
[0106] Test 2: Activity life test of composite catalytic system
[0107] Test method
[0108] Refer to GB / T37248-2018 "General Test Method for Catalyst Activity", the catalysts of each example and comparative example are repeatedly used for benzylation-isomerization cycle reaction, after each reaction, the catalyst is recovered (blown by nitrogen, dried), re-put into the next round of reaction, record the isobutylbenzene yield of each reaction (yield = actual yield / theoretical yield x 100%), when the yield is reduced to 80% of the initial yield, stop the cycle, record the cycle number (i.e. activity life), the results are as follows:
[0109] Table 2
[0110] Group Initial yield (%) Active life (number of cycles) Yield at the nth cycle (%) Example 1 92.5 8 74.2 (8th) Example 2 90.3 7 72.5 (7th) Example 3 94.1 9 75.3 (9th) Example 4 93.2 8 74.6 (8th) Example 5 91.8 7 73.4 (7th) Comparative Example 1 65.8 3 52.7 (3rd) Comparative Example 2 88.6 4 70.9 (4th)
[0111] As can be seen from Table 2, the activity life of the catalytic system of Examples 1-5 is all ≥7 cycles, the key lies in the structural stability of the composite catalytic system: the high specific surface area of porous silica carrier can uniformly disperse the active components, avoiding the agglomeration of active sites; Rare earth compounds can also inhibit the loss of active components, such as volatilization of metallic sodium and dissolution of potassium carbonate, prolonging the catalytic life.
[0112] The preferred embodiments of the application disclosed above are only to facilitate the elucidation of the application. The preferred embodiments do not describe all the details of the application, nor limit the application to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of the present specification.
Claims
1. A process for the preparation of isobutylbenzene, characterized in that, The stepwise alkylation reaction is carried out in the presence of a composite catalyst system, using toluene and propylene as raw materials, and includes the following steps: (1) benzylization reaction: toluene and propylene are reacted at 180-210℃ and 1.5-3.0 MPa for 1-3 hours to generate intermediate benzyl toluene; (2) isomerization reaction: the benzyl toluene is reacted at 200-230℃ and 0.5-1.5 MPa for 2-4 hours under the assistance of ultrasonic waves to generate isobutyl benzene; (3) product separation: unreacted toluene and propylene are recovered by multi-stage rectification to obtain isobutyl benzene product.
2. The method of claim 1, wherein, The composite catalyst system is a composite carrier of alkali metal, potassium carbonate and rare earth elements, and its preparation method includes: S1: 100-300 mesh potassium carbonate powder, sodium metal block and rare earth element compound are mixed in a mass ratio of 1:10-14:0.2-0.4, and a molten alloy is formed under stirring at 225-250℃ in an inert atmosphere protection for 2-3 hours; S2: a dispersing agent is added to the molten alloy, the addition amount is 0.3-0.8% of the mass of toluene, and the stirring speed is increased to 800-1200 r / min, and a solid catalyst is obtained after cooling; S3: the solid catalyst is loaded on a porous silica carrier, and the loading amount is 5.5-5.8% of the total mass of the catalyst.
3. The method of claim 2, wherein, The rare earth element compound in step S1 is selected from at least one of lanthanum oxide, cerium nitrate and praseodymium oxide.
4. The method of claim 2, wherein, The inert atmosphere in step S1 is nitrogen.
5. The method of claim 2, wherein, The dispersing agent in step S2 is polyethylene glycol with a molecular weight of 5000-10000, and the addition amount is 0.5-0.6% of the mass of toluene.
6. The method of claim 2, wherein, In the stirring process in step S2, programmed temperature rising is adopted: from room temperature to 150℃ at a rate of 5-6℃ / min, and then kept for 1 hour, and then cooled to room temperature at a rate of 3-5℃ / min.
7. The method of claim 2, wherein, The specific surface area of the porous silica carrier in step S3 is 200-300 m² / g.
8. The method of claim 1, wherein, The ultrasonic wave assistance conditions in the isomerization reaction are: frequency 30-50 kHz, power 100-150 W, and the ultrasonic wave is applied in an intermittent mode: pause for 10-12 seconds after continuous working for 50-60 seconds, and cycle until the reaction is completed.
9. The method of claim 1, wherein, The process parameters of the stepwise alkylation reaction meet the following conditions: (1) benzylization stage: the molar ratio of propylene to toluene is 0.8-1.2:1, the stirring speed is 600-1000 r / min, and the addition amount of the composite catalyst system is 2.0-3.0% of the mass of toluene; (2) isomerization stage: 0.1-0.2 vol.% of trace water vapor is introduced into the reaction system, the reaction pressure is linearly reduced from the initial 1.5 MPa to 0.5 MPa, and the pressure gradient is controlled at 0.1-0.2 MPa / h.
10. The method of claim 1, wherein, The specific operation parameters of the multi-stage rectification are: the number of plates of the primary rectification tower is 20-30, the reflux ratio is 1.5-2.5, and the tower top temperature is 30-40℃; the number of plates of the secondary rectification tower is 15-20, the reflux ratio is 1.0-2.0, and the tower top temperature is 110-115℃; the number of plates of the final rectification tower is 25-30, the reflux ratio is 2.0-3.0, and the tower top temperature is 170-175℃.