A method for preparing styrene co-benzofuran

Abstract

The application discloses a method for preparing styrene and benzofuran, which comprises the following steps: taking ethylbenzene and oxygen as raw materials, and performing catalytic oxidation reaction to obtain reaction liquid and carbon oxide; and performing rectification separation on the reaction liquid to obtain benzofuran and styrene. x The synergistic catalysis effect between the active component FeO and the alkaline earth metal oxide additive promotes the generation of high value-added products. The gas-solid phase selective oxidation reaction route not only reduces the energy consumption of styrene production, but also does not need to introduce halogen for the production of benzofuran, greatly improves the product added value, and is easy to realize continuous production, simple and easy to operate, and is conducive to realizing large-scale production. In addition, ethylbenzene, styrene and benzofuran are easy to separate by rectification, and the operation cost is low, so the reaction path and the catalyst provided by the application have industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of chemical catalysis technology, specifically relating to a method for the combined gas-solid phase production of styrene and benzofuran. Background Technology

[0002] Styrene is an important chemical monomer for the production of rubber and resins, and is widely used in construction, automobiles, electronics, and other fields. With the booming development of downstream products, the demand for styrene has been increasing year by year. Globally, the annual consumption of styrene remains enormous, and this huge consumption gap places higher demands on industrial production. Currently, styrene is mainly produced industrially through the direct dehydrogenation of ethylbenzene. This is a thermodynamically limited reaction, requiring high temperatures (600-700℃) and excess water vapor (S / O = 1.5-2.0), resulting in high energy consumption (Applied Catalysis A: General, 1995, 133, 219).

[0003] The selective oxidation of ethylbenzene to styrene in the gas-solid phase is currently the most promising alternative method for styrene production because it is not limited by thermodynamic equilibrium, has a low reaction temperature (400-550℃), and can effectively reduce energy consumption (ACS Catalysis, 2020, 10, 6697–6706). However, under oxygen conditions, the selective oxidation of ethylbenzene to styrene involves varying degrees of oxidation side reactions, generating numerous byproducts such as benzofuran, benzaldehyde (Journal of Catalysis, 2021, 400, 265-273), acetophenone, and large amounts of carbon monoxide and carbon dioxide. This leads to complex and energy-intensive subsequent styrene product separation processes.

[0004] In fact, benzofuran, benzaldehyde, and acetophenone are all high-value-added products urgently needed by the chemical industry. Benzofuran, in particular, is a high-value oxygen-containing compound with excellent biological activity and high potential to become a drug molecule. It is an intermediate in the preparation of amiodarone and oxyindene resin (Organic Letters, 2013, 15, 4742-4745). Amiodarone is a Class III antiarrhythmic drug, and oxyindene resin is mainly used to replace natural resins in the formulation of insulating and anti-rust coatings. Currently, traditional synthetic methods are complex and cumbersome, mainly divided into organic synthesis methods and extraction methods (Phytochemistry, 1983, 22 2335-2348). These synthetic methods usually require the introduction of halogens at specific positions and are carried out under specific acidic or alkaline conditions (catalysis, hydroxylation, coupling cyclization). The batch reaction process is cumbersome, and the catalysts are highly toxic and expensive, still some distance from meeting the requirements of efficient, environmentally friendly, and economical green synthesis.

[0005] Our research group previously reported an example of catalyst modification for the co-production of styrene and benzaldehyde by the oxidative dehydrogenation of ethylbenzene. Inspired by this technology, if we can achieve a one-step direct synthesis of benzofuran co-production of styrene by the gas-solid phase catalytic oxidative dehydrogenation of ethylbenzene through catalyst modification, it will have the advantages of being green, efficient, and environmentally friendly. Summary of the Invention

[0006] The purpose of this invention is to develop a method for the selective oxidation of ethylbenzene in a gas-solid phase to co-produce styrene and benzofuran. Addressing the problems of high energy consumption in industrial styrene production and the presence of halogens in benzofuran products, this invention proposes a gas-solid phase co-production method for styrene and benzofuran. This invention reduces energy consumption in both reaction and separation, enables continuous operation, and simultaneously yields high-value-added products.

[0007] The technical solution of the present invention:

[0008] A method for preparing styrene and co-producing benzofuran involves using ethylbenzene and oxygen as raw materials, and carrying out a catalytic oxidation reaction to obtain a reaction solution (ethylbenzene, styrene, benzofuran, and benzaldehyde) and CO. x (Carbon oxides) are used to separate the reaction liquid by distillation to obtain benzofuran and styrene.

[0009] The catalyst used in the catalytic oxidation reaction includes a support, an active component, and an auxiliary agent. The support is porous silica, and the active component is FeO. x The additive is an alkali metal oxide or an alkaline earth metal oxide.

[0010] The molar ratio of oxygen to ethylbenzene is 0.5–6:1, and the temperature of the catalytic oxidation reaction is 450–510℃.

[0011] The total gas flow rate used in the reaction was 30 mL / min.

[0012] The active component FeO x The loading (mass) is 0.1% to 50 wt% of the porous silica mass; furthermore, FeO x The loading amount is 1% to 8 wt% of the porous silica mass.

[0013] The additives are specifically Li2O, MgO, CaO, and SrO; more specifically, the additives are alkaline earth metal oxides SrO.

[0014] The loading (mass) of the additive is 0.1% to 8 wt% of the porous silica.

[0015] The preferred reactor is an atmospheric pressure fixed-bed reactor.

[0016] The beneficial effects of this invention are as follows: Compared with the prior art, this invention provides a method for the selective oxidation of ethylbenzene in a gas-solid phase to co-produce styrene and benzofuran, which can simultaneously obtain two high-value-added products. The active component FeO on porous silica... x The synergistic catalytic effect between the species and alkaline earth metal oxide promoters promoted the generation of high-value-added products, with a selectivity of up to 77% for styrene, 16% for benzofuran, and CO. x The selectivity for (carbon oxides) is only 4%. This gas-solid phase selective oxidation reaction route not only reduces the energy consumption in styrene production, but also eliminates the need for halogens in the production of benzofuran, greatly increasing the added value of the product. Furthermore, the gas-solid phase reaction is easier to implement for continuous production, is simple and easy to carry out, and is conducive to large-scale production. In addition, ethylbenzene, styrene, and benzofuran are easily separated by distillation, resulting in low operating costs. Therefore, the reaction route and catalyst provided by this invention have promising prospects for industrial application. Detailed Implementation

[0017] The specific embodiments of the present invention will be further described below in conjunction with the technical solution.

[0018] Catalyst using yMO x / zFeO x / SiO2 indicates that: MO x denoted as alkali metal or alkaline earth metal oxide; x represents the possible coordination number of the metal and oxygen in the metal oxide, ranging from 0.5 to 1.5; y represents the percentage of alkali metal or alkaline earth metal oxide loading (mass) to the catalyst support mass, ranging from 0.1% to 8%; z represents FeO. x The loading (mass) as a percentage of the catalyst support mass is 1% to 8%; SiO2 represents porous silica.

[0019] The specific gas-solid phase co-production method for styrene and benzofuran includes the following steps: placing a catalyst in a reactor; pre-mixing an N2 / O2 (N2 / O2 = 2-20, vol) gas mixture; introducing ethylbenzene into the reactor via a bubbler for catalytic reaction; and distilling the reaction mixture (ethylbenzene, styrene, benzofuran, benzaldehyde) to obtain the product.

[0020] Comparative Example 1

[0021] Porous silica

[0022] Commercial porous silica was dried in a 120°C airflow oven for 2 hours to remove surface physically adsorbed water, and was labeled as SiO2, corresponding to number 1 in Table 1.

[0023] Example 1

[0024] Different FeO xFeO loading x / SiO2 catalyst

[0025] (1) Take SiO2 support and dry it in a 120℃ airflow oven for 2 hours to remove the surface physically adsorbed water; use water to determine the saturated water absorption rate of the porous silica support.

[0026] (2) At 25℃, take ferric nitrate aqueous solutions with concentrations of 0.042, 0.21 and 0.336 g / mL and immerse them in equal volumes on the SiO2 support obtained after drying in step (1) and let them stand for 2 hours.

[0027] (3) The mixture obtained after step (2) is allowed to stand is dried in an oven at 100°C for 12 hours to obtain the catalyst precursor;

[0028] (4) The catalyst precursor obtained in step (3) is calcined in a muffle furnace at 600°C for 2 hours to obtain zFeO. x / SiO2 catalyst, corresponding to numbers 2 to 4 in Table 1.

[0029] Table 1 Different FeO x Correspondence between catalyst loading and preparation conditions

[0030]

[0031] Example 2

[0032] 1MO x / 1FeO x / SiO2 catalyst

[0033] The preparation process is the same as in Example 1, and the 1FeO obtained in Example 1... x An alkali metal or alkaline earth metal salt aqueous solution is loaded onto a SiO2 catalyst using an equal-volume impregnation method and allowed to stand for 2 hours to obtain a mixture. This mixture is then dried in an oven at 100°C for 12 hours to obtain a catalyst precursor. The catalyst precursor is then calcined in a muffle furnace at 600°C for 2 hours to obtain MO. x / 1FeO x / SiO2 catalyst, MO x The loading amount is 1 wt% of the porous silica mass.

[0034] The alkali metal and alkaline earth metal salt solutions are their respective nitrate aqueous solutions, and the concentration of the alkali metal salt or alkaline earth metal salt aqueous solution is determined according to the loading of the alkali metal or alkaline earth metal oxide additive.

[0035] Example 3

[0036] Effects of different catalysts on ethylbenzene conversion, styrene and benzofuran selectivity

[0037] The selective oxidative dehydrogenation reaction performance was evaluated in a fixed-bed reactor using ethylbenzene and oxygen as raw materials. The reaction conditions were as follows: 0.1 g of catalyst was packed into a fixed-bed reactor with an inner diameter of 8 mm; atmospheric pressure; reaction temperature of 450 °C; N2 / O2 = 9 (vol); ethylbenzene partial pressure of 5.6 kPa; and oxygen / ethylbenzene ratio of 2 (mol). After the reaction stabilized, the reactants and products were analyzed by online chromatography. The correlation between different catalysts and catalytic activities is shown in Tables 2 and 3.

[0038] Compare the different FeO values ​​numbered 2 to 4 in Table 2. x Catalytic performance of catalyst with varying loading, 1FeO x The styrene and benzofuran selectivity of the / SiO2 catalyst is significantly higher than that of other supported catalysts, and its CO x The selectivity was also the lowest. Comparing catalysts numbered 2-5 in Table 3, the selected alkaline earth metal oxide promoters significantly improved the selectivity of the high-value-added product benzofuran. Among them, catalyst number 7, with the addition of strontium oxide promoter, exhibited even higher benzofuran selectivity and simultaneously reduced the peroxidation product CO. x The selectivity.

[0039] In summary, FeO on porous silica supports x Synergistic catalytic effects exist between species and alkaline earth metal oxides, promoting the formation of the high-value-added product benzofuran. Among them, the catalyst modified with strontium oxide-supported promoter showed the greatest improvement in selectivity for benzofuran and exhibited the best modification in catalytic performance.

[0040] Table 2 Different FeO x Correlation between catalyst loading and ethylbenzene conversion and styrene and benzofuran selectivity

[0041]

[0042] Table 3. Correspondence between catalysts modified with different alkali additives and ethylbenzene conversion and styrene and benzofuran selectivity.

[0043]

[0044] Example 4

[0045] 1FeO x Effect of different strontium oxide loadings on SiO2 catalysts on ethylbenzene conversion and styrene and benzofuran selectivity.

[0046] The selective oxidative dehydrogenation reaction performance was evaluated in a fixed-bed reactor using ethylbenzene and oxygen as raw materials. The reaction conditions were as follows: 0.1 g of catalyst with different strontium oxide loadings were loaded into a fixed-bed reactor with an inner diameter of 8 mm; the reaction was carried out at atmospheric pressure, a reaction temperature of 450 °C, an N2 / O2 ratio of 9 (vol), an ethylbenzene partial pressure of 5.6 kPa, and an oxygen / ethylbenzene ratio of 2 (mol). After the reaction stabilized, the reactants and products were analyzed by online chromatography. The relationship between strontium oxide loading and catalyst activity is shown in Table 4.

[0047] Table 4. Correspondence between ethylbenzene conversion and styrene and benzofuran selectivity for catalysts with different strontium oxide loadings.

[0048]

[0049]

[0050] Comparing the catalysts with different strontium oxide loadings (numbered 1-7) in Table 4, the selectivity of benzofuran exhibits a volcano-shaped curve distribution with respect to loading. As the loading increases, the selectivity of benzofuran first increases and then decreases.

[0051] In summary, in the active component FeO x The synergistic effect of species and strontium oxide as an auxiliary agent is required to promote the formation of benzofuran, a high-value-added product, and the effect is better when the loading is 1 than that of other catalysts.

[0052] Example 5

[0053] 1SrO / 1FeO x Effect of reaction temperature on SiO2 catalyst on ethylbenzene conversion and selectivity for styrene and benzofuran

[0054] The selective oxidative dehydrogenation reaction performance was evaluated in a fixed-bed reactor using ethylbenzene and oxygen as raw materials. The reaction conditions were as follows: a fixed-bed reactor with an inner diameter of 8 mm was charged with 1SrO / 1FeO. x The reaction was carried out at a SiO2 catalyst concentration of 0.1 g, under normal pressure, at a reaction temperature of 450–510 °C, with an N2 / O2 ratio of 9 (vol), an ethylbenzene partial pressure of 5.6 kPa, and an oxygen / ethylbenzene ratio of 2 (mol). After the reaction stabilized, the reactants and products were analyzed using online chromatography. The relationship between reaction temperature and catalytic activity is shown in Table 5.

[0055] Table 5. Relationship between reaction temperature and ethylbenzene conversion and styrene and benzofuran selectivity

[0056]

[0057] Example 6

[0058] 1SrO / 1FeO x Effect of the oxygen to ethylbenzene ratio (O2 / EB) on the selectivity of styrene and benzofuran on the SiO2 catalyst

[0059] The selective oxidative dehydrogenation reaction performance was evaluated in a fixed-bed reactor using ethylbenzene and oxygen as raw materials. The reaction conditions were as follows: a fixed-bed reactor with an inner diameter of 8 mm was charged with 1SrO / 1FeO. x The reaction was carried out at 0.1 g of SiO2 catalyst under normal pressure and at a reaction temperature of 450 °C. The N2 / O2 ratio was 2–20 (vol), the partial pressure of ethylbenzene was 5.6 kPa, and the oxygen / ethylbenzene ratio was 0.5–6 (mol). After the reaction stabilized, the reactants and products were analyzed by online chromatography. The relationship between the oxygen / ethylbenzene ratio (O2 / EB) and the catalytic activity is shown in Table 6.

[0060] Table 6. Correspondence between O2 / EB (mol) and ethylbenzene conversion and styrene and benzofuran selectivity

[0061]

[0062] In summary, the porous silica-supported FeO x After the catalyst is modified with an alkaline earth metal oxide promoter, its FeO x The synergistic effect between species and alkaline earth metal oxides can catalyze gas-solid phase selective oxidation reactions to co-produce two high-value-added products, styrene and benzofuran; optimizing catalyst composition and evaluation conditions can further improve catalyst performance.

Claims

1. A method for preparing styrene and co-producing benzofuran, characterized in that, Using ethylbenzene and oxygen as raw materials, a catalytic oxidation reaction is carried out to obtain a reaction solution and carbon oxides. The reaction solution is then separated by distillation to obtain benzofuran and styrene. The catalyst used in the catalytic oxidation reaction includes a support, an active component, and an auxiliary agent. The support is porous silica, and the active component is FeO. x The additives are alkali metal oxides or alkaline earth metal oxides; The active component FeO x It is either Fe2O3 or Fe3O4.

2. The method for preparing styrene and benzofuran according to claim 1, characterized in that, The loading of the active component is 0.1% to 50 wt% of the porous silica mass.

3. The method for preparing styrene and benzofuran according to claim 2, characterized in that, The loading of the active component is 1% to 8 wt% of the porous silica mass.

4. The method for preparing styrene and benzofuran according to any one of claims 1-3, characterized in that, The molar ratio of oxygen to ethylbenzene is 0.5~6:1, the temperature of the catalytic oxidation reaction is 450~510 ℃, and the total gas flow rate is 30 mL / min.

5. The method for preparing styrene and benzofuran according to any one of claims 1-3, characterized in that, The additives are Li2O, MgO, CaO, and SrO.

6. The method for preparing styrene and benzofuran according to any one of claims 1-3, characterized in that, The loading of the additive is 0.1% to 8 wt% of the porous silica mass.

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