A method for preparing styrene by dehydrogenating ethylbenzene

Abstract

The present invention relates to a method for producing styrene by dehydrogenating ethylbenzene. The method comprises contacting an ethylbenzene-containing feedstock with a dehydrogenation catalyst in the presence of water vapor and O2 to carry out a dehydrogenation reaction, thereby producing a styrene-containing product. The catalyst of the present invention is used in the dehydrogenation of ethylbenzene to produce styrene at a low water ratio, making the catalyst less susceptible to carbon deposition and exhibiting high activity and stability.

Description

Technical Field

[0001] The present invention relates to a method for preparing styrene by dehydrogenating ethylbenzene, and in particular to a method for preparing styrene by dehydrogenating ethylbenzene with a low water ratio. Background Art

[0002] Styrene monomer is a key raw material for the synthetic rubber and plastics industries and plays a vital role in the national economy. Catalytic dehydrogenation of ethylbenzene has long been the dominant technology for producing styrene, accounting for over 85% of total styrene production capacity. To improve the efficiency of ethylbenzene dehydrogenation, the industry typically introduces large amounts of high-temperature steam. Steam plays a variety of important roles in the reaction, such as providing the required heat, shifting the chemical equilibrium toward styrene, removing carbon deposits on the catalyst surface through the water-gas shift reaction, and maintaining catalyst activity by oxidizing the catalyst surface. However, the use of large amounts of superheated steam as the dehydrogenation medium results in high energy consumption, large product condensation volumes, and high process equipment costs, resulting in high production costs. Developing a method for dehydrogenating ethylbenzene to produce styrene using a low water ratio to achieve energy savings and reduce production costs in styrene plants is an urgent need for styrene companies.

[0003] Hydrocarbon dehydrogenation can be divided into oxidative dehydrogenation and non-oxidative dehydrogenation, i.e., direct dehydrogenation, two types. The non-oxidative dehydrogenation catalytic process has been realized for industrial application. This process is limited by thermodynamic equilibrium and has the disadvantages of high reaction temperature, large water vapor consumption, large energy consumption, and easy and rapid carbon deposition of catalyst, which reduces activity. This type of catalyst is mostly based on Fe-K-Ce, in which Fe-K oxide is the main active phase, and Ce is the main auxiliary agent, and also contains structural stabilizers and electronic auxiliary agents such as oxides of Mg, Mo, W and Ca. Currently disclosed low water ratio ethylbenzene dehydrogenation catalysts mainly adopt methods such as improving catalyst structural stability and modifying catalyst surface properties to improve the stability, activity and selectivity of catalyst under low water ratio conditions. CN106582678A discloses that on the basis of a Fe-K-Ce-W catalyst, by introducing Ba, Sn and rare earth oxides (Sm, Eu, Gd), the catalyst active phase is stabilized to improve the activity and stability of catalyst under low water ratio conditions.

[0004] In the oxidative dehydrogenation catalytic process, iron or vanadium oxides are often used as catalysts, and ethylbenzene is oxidatively dehydrogenated in an atmosphere such as air, oxygen or CO2. The oxidative dehydrogenation process breaks the limitations of thermodynamic equilibrium, but it also has disadvantages such as low catalyst activity, poor styrene selectivity, severe deep oxidation reaction, and more by-products. The oxidative dehydrogenation process of ethylbenzene has not yet been industrialized. Zhu Xing et al. published "A tailored multi-functional catalyst for ultra-efficient styrene production under a cyclic redox scheme" in Nature Communications (Nature Communications.2021, 12, 1329) and reported a multifunctional (Ca / Mn) 1-x The redox-oxidative dehydrogenation (redox-ODH) strategy over O@KFeO2 core-shell redox catalysts can be used for the efficient production of styrene. While the oxidative dehydrogenation of ethylbenzene does not require the injection of large amounts of steam, oxygen is not introduced into the reactor simultaneously with the feedstock, requiring frequent catalyst regeneration. Furthermore, the ethylbenzene throughput per pass is limited by the amount of lattice oxygen available in the catalyst, making it difficult to improve production efficiency.

[0005] Current styrene production technology is developing towards large-scale equipment and comprehensive energy utilization. To improve the economic efficiency of ethylbenzene dehydrogenation to styrene, it is necessary to develop an ethylbenzene dehydrogenation catalyst and reaction process suitable for operation under low water ratio conditions, with high activity and improved stability. Summary of the Invention

[0006] The present invention aims to address the technical problems of existing non-oxidative dehydrogenation catalysts for ethylbenzene dehydrogenation to styrene, which suffer from high water vapor and energy consumption, rapid carbon deposition on the catalyst, and low activity and poor stability during the dehydrogenation process. The present invention provides a method for ethylbenzene dehydrogenation to styrene. This method, used in ethylbenzene dehydrogenation reactions under low water ratio conditions, reduces carbon deposition on the catalyst and exhibits high reactivity and stability.

[0007] The present invention provides a method for preparing styrene by dehydrogenating ethylbenzene, the method comprising:

[0008] The ethylbenzene-containing raw material is brought into contact with a dehydrogenation catalyst in the presence of water vapor and O2 to undergo a dehydrogenation reaction to obtain a styrene-containing product.

[0009] In the above technical solution, when water vapor is added, the water is preheated to become water vapor before entering the reactor and is fully mixed with the ethylbenzene-containing raw material and O2.

[0010] In the above technical solution, the molar ratio of ethylbenzene to O2 is 4:1 to 100:1, preferably 5:1 to 20:1.

[0011] In the above technical solution, the dehydrogenation reaction is ethylbenzene dehydrogenation at a low water ratio; the low water ratio is 0.8 or less, preferably 0.2 to 0.8, and more preferably 0.2 to 0.6. The water ratio is the weight ratio of water to ethylbenzene.

[0012] In the above technical solution, the reaction temperature of the dehydrogenation reaction is 520℃~620℃, the absolute pressure is 20~100kPa, and the mass space velocity of ethylbenzene is 0.2~2.0h -1 .

[0013] In the above technical solution, the dehydrogenation catalyst includes Fe2O3, K2O, CeO2, MoO3, Bi2O3, and CaO.

[0014] In the above technical solution, the dehydrogenation catalyst, based on the total mass of the dehydrogenation catalyst, comprises the following components in terms of mass fraction:

[0015] (a) 60% to 85% Fe2O3;

[0016] (b) 8% to 16% K2O;

[0017] (c) 4% to 12% CeO2;

[0018] (d) 0.5% to 5% MoO3;

[0019] (e) 0.1% to 4% Bi2O3;

[0020] (f) 0.2% to 3% CaO.

[0021] In the above technical solution, the dehydrogenation catalyst further includes oxides of Sm and / or Eu.

[0022] In the above technical solution, preferably, based on the total mass of the dehydrogenation catalyst, the dehydrogenation catalyst contains 0.01% to 1.0% of Sm and / or Eu oxides in terms of mass fraction.

[0023] In the above technical solution, the preparation method of the dehydrogenation catalyst comprises the following steps:

[0024] The Fe source, K source, Ce source, Mo source, Bi source, Ca source and an optional porogen are uniformly mixed, kneaded into a mold, and calcined to obtain the dehydrogenation catalyst.

[0025] In the above technical solution, in the preparation method of the dehydrogenation catalyst, the raw materials further contain a Sm source and / or a Eu source; the Sm source and / or Eu source are uniformly mixed with an Fe source, a K source, a Ce source, a Mo source, a Bi source, a Ca source, and an optional porogen and then added. The Sm source is added in the form of a Sm salt or oxide; the Sm salt is either one or both of samarium nitrate and samarium chloride. The Eu source is added in the form of a Eu salt or oxide; the Eu salt is either one or both of europium nitrate and europium chloride.

[0026] In the above technical solution, in the preparation method of the dehydrogenation catalyst, an appropriate amount of water may be added during the kneading process. The water addition method is to add water slowly. The amount of water added is not particularly limited and can be adjusted according to the dryness of the material. Generally, the amount of water added accounts for 15% to 35% of the mass of the catalyst raw material.

[0027] In the above technical solution, in the preparation method of the dehydrogenation catalyst, the molding can be performed by extrusion molding, and the strips can be particles with a diameter of 2 to 5 mm and a length of 3 to 10 mm.

[0028] In the above technical solution, in the preparation method of the dehydrogenation catalyst, the calcination temperature is 600-1000° C., and the calcination time is 2-8 hours.

[0029] In the above technical solution, in the preparation method of the dehydrogenation catalyst, a two-step calcination is preferably used, for example but not limited to calcination at 600-800°C for 2-4 hours, followed by calcination at 900-1000°C for 2-4 hours. The calcination is performed in a muffle furnace.

[0030] In the above technical solution, in the preparation method of the dehydrogenation catalyst, the formed material may be subjected to a drying step before being calcined. The drying temperature is 30 to 200° C. and the drying time is 1 to 24 hours.

[0031] In the above technical solution, in the preparation method of the dehydrogenation catalyst, the Fe source is added in the form of the oxide Fe2O3. The Fe source is preferably selected from red iron oxide and / or yellow iron oxide, and more preferably a combination of red iron oxide and yellow iron oxide. The K source is added in the form of a potassium salt; the potassium salt is selected from any one or more of potassium carbonate, potassium nitrate, and potassium bicarbonate. The Ce source is added in the form of a cerium salt; the cerium salt is any one or two of cerium oxalate, cerium nitrate, and cerium carbonate. The Mo source is added in the form of a molybdenum salt or oxide; the molybdenum salt is ammonium molybdate; the Bi source is added in the form of a bismuth salt or oxide; the bismuth salt is bismuth nitrate; and the Ca source is added in the form of an oxide or hydroxide. The porogen is any one or more of activated carbon, graphite, sodium hydroxymethyl cellulose, and polystyrene microspheres. The amount of the porogen added is 0.01% to 5% of the mass of the dehydrogenation catalyst.

[0032] Compared with the prior art, the present invention has significant advantages and outstanding effects, as follows:

[0033] 1. Typically, the oxidative dehydrogenation of ethylbenzene is a highly exothermic reaction that is not constrained by thermodynamic equilibrium, resulting in a relatively low reaction bed inlet temperature, but low styrene selectivity. The nonoxidative dehydrogenation of ethylbenzene is an endothermic reaction that is constrained by thermodynamic equilibrium, resulting in a relatively high reaction bed inlet temperature, low ethylbenzene conversion, and a high water vapor consumption. These two dehydrogenation methods differ in their thermal effects, placing different requirements on catalysts and process conditions. The present invention overcomes the limitations of conventional oxidative dehydrogenation and nonoxidative dehydrogenation processes by combining oxidative dehydrogenation with nonoxidative direct dehydrogenation under aerobic conditions with low O₂ content to catalyze the dehydrogenation of ethylbenzene to produce styrene. This reaction process introduces a small amount of oxygen into the direct dehydrogenation process, maintaining high styrene selectivity. The addition of a small amount of oxygen also disrupts the thermodynamic equilibrium of the reaction, shifting the chemical equilibrium toward dehydrogenation to produce styrene, significantly improving the reaction conversion rate. The addition of oxygen also activates the dehydrogenation catalyst surface and eliminates carbon deposits, replacing the role of high-temperature water vapor, reducing carbon deposits, extending the life of the dehydrogenation catalyst, and reducing the amount of water vapor used. The oxidative dehydrogenation of some ethylbenzene produces water, a highly exothermic reaction. This heat compensation lowers the bed inlet temperature required for the direct dehydrogenation reaction, reducing the overall energy consumption of the reaction process. Furthermore, the low oxygen concentration involved in the oxidative dehydrogenation reaction also limits the occurrence of deep oxidation side reactions, maintaining the high selectivity of the dehydrogenation reaction. Consequently, these reaction process conditions improve reaction efficiency, significantly reduce water vapor usage, significantly lower energy consumption, reduce production costs, and enhance catalyst activity and stability, achieving excellent technical results.

[0034] 2. The dehydrogenation catalyst employed in the present invention is a multifunctional dehydrogenation catalyst that exhibits excellent catalytic performance in the direct dehydrogenation of ethylbenzene and possesses abundant active lattice oxygen, enabling efficient and stable catalysis of the oxidative dehydrogenation of ethylbenzene. The appropriate amount of oxygen introduced during the reaction replenishes the lattice oxygen in the dehydrogenation catalyst, maintaining its high performance in the oxidative dehydrogenation reaction.

[0035] The evaluation results of the method for preparing styrene by dehydrogenating ethylbenzene using the technical solution of the present invention show that the activity evaluation is carried out in an isothermal fixed bed at 40 kPa (absolute pressure) and a mass space velocity of 1.0 h -1Under the conditions of 600°C, 0.5% water ratio, the ethylbenzene conversion reached 82.6% and the styrene selectivity reached 95.2% after 100 hours of reaction. After 1000 hours of operation, the dehydrogenation catalyst performance remained stable, with no significant change in catalyst activity or target product selectivity, and minimal carbon deposits. This demonstrates that the dehydrogenation catalyst of the present invention significantly improves the activity, selectivity, and stability of the dehydrogenation catalyst under low water ratio conditions, achieving excellent technical results. DETAILED DESCRIPTION

[0036] The present invention will be further described below by way of examples, but the protection scope of the present invention is not limited by the examples.

[0037] In the present invention, the dehydrogenation catalyst of the present invention is evaluated for ethylbenzene dehydrogenation performance in an isothermal fixed bed. The process is briefly described as follows:

[0038] The reactor is a stainless steel tube with an inner diameter of 1", filled with 50-150 ml of dehydrogenation catalyst with a diameter of 3-10 mm. Deionized water, O2, and ethylbenzene are respectively fed into a preheating mixer via metering pumps. After preheating and mixing into a gaseous state, they enter the reactor. The reactor is heated by a heating wire to reach the predetermined temperature. The reactants flowing out of the reactor are condensed with water and their composition is analyzed by gas chromatography.

[0039] Ethylbenzene conversion and styrene selectivity are calculated according to the following formula:

[0040]

[0041]

[0042] The present invention uses thermogravimetric (TG) analysis to determine the amount of carbon deposited on the catalyst. A TA-4000 (TGA-2050) thermal analyzer from TA Instruments (USA) is used. A 2-3 mg sample of dried material is placed in a 40 mL / min air flow and heated from room temperature to 800°C at a rate of 20°C / min. The catalyst weight loss curve is then monitored, and the amount of carbon deposited on the catalyst is calculated based on the catalyst weight loss.

[0043] Carbon deposit amount (wt%) = catalyst weight loss / catalyst initial weight × 100%.

[0044] [Example 1]

[0045] Weigh 48.2 parts of red iron oxide (equivalent to Fe₂O₃), 22.6 parts of yellow iron oxide (equivalent to Fe₂O₃), 11.6 parts of potassium carbonate (equivalent to K₂O), 9.2 parts of cerium nitrate (equivalent to CeO₂), 3.5 parts of ammonium molybdate (equivalent to MoO₃), 2.8 parts of Bi₂O₃, 1.8 parts of calcium hydroxide (equivalent to CaO), 0.1 parts of Sm₂O₃, 0.2 parts of europium chloride (equivalent to Eu₂O₃), and 2.4 parts of polystyrene microspheres in a mixer and stir for 2 hours until uniformly mixed. Deionized water (24% by weight of the total weight of the dehydrogenation catalyst raw materials) was then added and mixed for 2 hours. The mixture was then extruded and pelletized to obtain pellets 3 mm in diameter and 6 mm in length. The pellets were then dried in an oven at 80°C for 4 hours and 160°C for 4 hours. The pellets were then calcined in a muffle furnace at 650°C for 2 hours and 900°C for 2 hours to obtain the finished dehydrogenation catalyst. The composition of the dehydrogenation catalyst is listed in Table 1.

[0046] 100 ml of dehydrogenation catalyst was loaded into the reactor and the reaction mixture was heated at 40 kPa (absolute pressure) and a mass space velocity of 1.0 h-1 for ethylbenzene. -1 The performance evaluation was carried out under the conditions of reaction temperature 600℃, water ratio 0.5 (wt%), and molar ratio of ethylbenzene and O2 of 20:1. The test results of reaction time 100h are listed in Table 1, and the test results of reaction time 1000h are listed in Table 2.

[0047] [Example 2]

[0048] Weigh 38.9 parts of red iron oxide (equivalent to 38.9 parts of Fe2O3), 22.2 parts of yellow iron oxide (equivalent to 22.2 parts of Fe2O3), 15.5 parts of potassium carbonate (equivalent to 15.5 parts of K2O), 11.2 parts of cerium nitrate (equivalent to 11.2 parts of CeO2), 4.9 parts of ammonium molybdate (equivalent to 4.9 parts of MoO3), 3.6 parts of Bi2O3, 2.7 parts of calcium hydroxide (equivalent to 0.5 parts of CaO), 0.5 parts of Sm2O3, 0.5 parts of europium chloride (equivalent to 0.5 parts of Eu2O3), and 2.4 parts of polystyrene microspheres in a mixer and stir for 2 hours until uniformly mixed. Deionized water (24% by weight of the total weight of the dehydrogenation catalyst raw materials) was then added and mixed for 2 hours. The mixture was then extruded and pelletized to obtain pellets with a diameter of 3 mm and a length of 6 mm. The pellets were then dried in an oven at 50°C for 4 hours and then at 160°C for 4 hours. The finished dehydrogenation catalyst was then calcined in a muffle furnace at 600°C for 4 hours and then at 900°C for 2 hours. The composition of the dehydrogenation catalyst is listed in Table 1.

[0049] 100 ml of dehydrogenation catalyst was loaded into the reactor and the reaction mixture was heated at 40 kPa (absolute pressure) and a mass space velocity of 1.0 h-1 for ethylbenzene. -1 The performance evaluation was carried out under the conditions of reaction temperature of 600℃, water ratio of 0.25 (wt%), and molar ratio of ethylbenzene to O2 of 4:1. The test results after 100h of reaction are listed in Table 1.

[0050] [Example 3]

[0051] Weigh 45.2 parts of red iron oxide (equivalent to 45.2 parts of Fe2O3), 25.4 parts of yellow iron oxide (equivalent to 25.4 parts of Fe2O3), 10.2 parts of potassium carbonate (equivalent to 10.2 parts of K2O), 11.5 parts of cerium nitrate (equivalent to 11.5 parts of CeO2), 3.25 parts of ammonium molybdate (equivalent to 3.25 parts of MoO3), 3.9 parts of Bi2O3, 0.5 parts of calcium hydroxide (equivalent to 0.5 parts of CaO), 0.05 parts of Sm2O3, and 0.5 parts of polystyrene microspheres in a mixer and stir for 2 hours until uniformly mixed. Deionized water (24% by weight of the total weight of the dehydrogenation catalyst raw materials) was then added and mixed for 2 hours. The mixture was then extruded and pelletized to obtain pellets 3 mm in diameter and 6 mm in length. These pellets were then dried in an oven at 80°C for 4 hours and 160°C for 4 hours. The finished dehydrogenation catalyst was then calcined in a muffle furnace at 650°C for 2 hours and 1000°C for 2 hours. The dehydrogenation catalyst composition is listed in Table 1.

[0052] 100 ml of dehydrogenation catalyst was loaded into the reactor and the reaction mixture was heated at 40 kPa (absolute pressure) and a mass space velocity of 1.0 h-1 for ethylbenzene. -1 The performance evaluation was carried out under the conditions of reaction temperature of 600℃, water ratio of 0.6 (wt%), and molar ratio of ethylbenzene to O2 of 5:1. The test results of reaction time of 100h are listed in Table 1.

[0053] [Example 4]

[0054] Weigh 51.2 parts of red iron oxide (equivalent to Fe₂O₃), 32.6 parts of yellow iron oxide (equivalent to Fe₂O₃), 8.2 parts of potassium carbonate (equivalent to K₂O), 4.6 parts of cerium nitrate (equivalent to CeO₂), 2.2 parts of ammonium molybdate (equivalent to MoO₃), 0.2 parts of Bi₂O₃, 0.6 parts of calcium hydroxide (equivalent to CaO), 0.4 parts of Sm₂O₃, and 4.6 parts of polystyrene microspheres in a mixer and stir for 2 hours until uniformly mixed. Deionized water (24% by weight of the total weight of the dehydrogenation catalyst raw materials) was then added and mixed for 2 hours. The mixture was then extruded and pelletized to obtain pellets 3 mm in diameter and 6 mm in length. These pellets were then dried in an oven at 80°C for 4 hours and 160°C for 4 hours. The mixture was then calcined in a muffle furnace at 650°C for 2 hours and 950°C for 2 hours to obtain the finished dehydrogenation catalyst. The composition of the dehydrogenation catalyst is listed in Table 1.

[0055] 100 ml of dehydrogenation catalyst was loaded into the reactor and the reaction mixture was heated at 40 kPa (absolute pressure) and a mass space velocity of 1.0 h-1 for ethylbenzene. -1 The performance evaluation was carried out under the conditions of reaction temperature of 600℃, water ratio of 0.75 (wt%), and molar ratio of ethylbenzene to O2 of 50:1. The test results after 100h of reaction are listed in Table 1.

[0056] [Example 5]

[0057] Weigh 46.1 parts of red iron oxide (equivalent to Fe₂O₃), 23.5 parts of yellow iron oxide (equivalent to Fe₂O₃), 13.8 parts of potassium carbonate (equivalent to K₂O), 11.8 parts of cerium nitrate (equivalent to CeO₂), 0.6 parts of ammonium molybdate (equivalent to MoO₃), 3.5 parts of Bi₂O₃, 0.5 parts of calcium hydroxide (equivalent to CaO), 0.2 parts of europium chloride (equivalent to Eu₂O₃), and 2.1 parts of polystyrene microspheres in a mixer and stir for 2 hours until uniformly mixed. Deionized water (24% by weight of the total weight of the dehydrogenation catalyst raw materials) was then added and mixed for 2 hours. The mixture was then extruded and pelletized to obtain pellets 3 mm in diameter and 6 mm in length. The pellets were then dried in an oven at 80°C for 4 hours and 160°C for 4 hours. The pellets were then calcined in a muffle furnace at 650°C for 2 hours and 900°C for 2 hours to obtain the finished dehydrogenation catalyst. The composition of the dehydrogenation catalyst is listed in Table 1.

[0058] 100 ml of dehydrogenation catalyst was loaded into the reactor and the reaction mixture was heated at 40 kPa (absolute pressure) and a mass space velocity of 1.0 h-1 for ethylbenzene. -1 The performance evaluation was carried out under the conditions of reaction temperature of 600℃, water ratio of 0.78 (wt%), and molar ratio of ethylbenzene to O2 of 95:1. The test results after 100h of reaction are listed in Table 1.

[0059] [Example 6]

[0060] Weigh 47.6 parts of red iron oxide (equivalent to 47.6 parts of Fe2O3), 23.1 parts of yellow iron oxide (equivalent to 23.1 parts of Fe2O3), 12.4 parts of potassium carbonate (equivalent to 12.4 parts of K2O), 10.3 parts of cerium nitrate (equivalent to 10.3 parts of CeO2), 2.7 parts of ammonium molybdate (equivalent to 2.7 parts of MoO3), 3.2 parts of Bi2O3, 0.2 parts of calcium hydroxide (equivalent to 0.2 parts of CaO), 0.5 parts of Sm2O3, and 1.4 parts of polystyrene microspheres in a mixer and stir for 2 hours until uniformly mixed. Deionized water (24% by weight of the total weight of the dehydrogenation catalyst raw materials) is then added and mixed for 2 hours. The mixture is then extruded and pelletized to obtain pellets 3 mm in diameter and 6 mm in length. These pellets are then dried in an oven at 80°C for 4 hours and 160°C for 4 hours. The finished dehydrogenation catalyst is then calcined in a muffle furnace at 650°C for 2 hours and 900°C for 2 hours. The dehydrogenation catalyst composition is listed in Table 1.

[0061] 100 ml of dehydrogenation catalyst was loaded into the reactor and the reaction mixture was heated at 40 kPa (absolute pressure) and a mass space velocity of 1.0 h-1 for ethylbenzene. -1 The performance evaluation was carried out under the conditions of reaction temperature 600℃, water ratio 0.5 (wt%), and molar ratio of ethylbenzene and O2 of 20:1. The test results of reaction time 100h are listed in Table 1, and the test results of reaction time 1000h are listed in Table 2.

[0062] [Example 7]

[0063] Weigh 46.8 parts of red iron oxide (Fe2O3), 23.8 parts of yellow iron oxide (Fe2O3), 10.2 parts of potassium carbonate (K2O), 10.0 parts of cerium nitrate (CeO2), 2.5 parts of ammonium molybdate (MoO3), 3.1 parts of Bi2O3, 2.9 parts of calcium hydroxide (CaO), 0.7 parts of Sm2O3, and 3.2 parts of polystyrene microspheres in a mixer and stir for 2 hours until uniformly mixed. Deionized water (24% by weight of the total weight of the dehydrogenation catalyst raw materials) was then added and mixed for 2 hours. The mixture was then extruded and pelletized to obtain pellets 3 mm in diameter and 6 mm in length. The pellets were then dried in an oven at 80°C for 4 hours and 160°C for 4 hours. The pellets were then calcined in a muffle furnace at 650°C for 2 hours and 900°C for 2 hours to obtain the finished dehydrogenation catalyst. The composition of the dehydrogenation catalyst is listed in Table 1.

[0064] 100 ml of dehydrogenation catalyst was loaded into the reactor and the reaction mixture was heated at 40 kPa (absolute pressure) and a mass space velocity of 1.0 h-1 for ethylbenzene. -1 The performance evaluation was carried out under the conditions of reaction temperature 600℃, water ratio 0.5 (wt%), and molar ratio of ethylbenzene to O2 of 20:1. The test results after 100h of reaction are listed in Table 1.

[0065] [Example 8]

[0066] Weigh 48.2 parts of red iron oxide (Fe2O3), 22.6 parts of yellow iron oxide (Fe2O3), 11.6 parts of potassium nitrate (K2O), 9.2 parts of cerium nitrate (CeO2), 3.5 parts of ammonium molybdate (MoO3), 2.8 parts of bismuth nitrate (Bi2O3), 1.8 parts of calcium hydroxide (CaO), 0.1 parts of Sm2O3, 0.2 parts of europium chloride (Eu2O3), and 2.4 parts of polystyrene microspheres in a mixer and stir for 2 hours until uniformly mixed. Deionized water (24% by weight of the total dehydrogenation catalyst raw materials) was then added and mixed for 2 hours. The mixture was then extruded and pelletized to obtain pellets with a diameter of 3 mm and a length of 6 mm. The pellets were then dried in an oven at 80°C for 4 hours and 160°C for 4 hours. The pellets were then calcined in a muffle furnace at 650°C for 2 hours and 900°C for 2 hours to obtain the finished dehydrogenation catalyst. The composition of the dehydrogenation catalyst is listed in Table 1.

[0067] 100 ml of dehydrogenation catalyst was loaded into the reactor and the reaction mixture was heated at 40 kPa (absolute pressure) and a mass space velocity of 1.0 h-1 for ethylbenzene. -1 The performance evaluation was carried out under the conditions of reaction temperature 600℃, water ratio 0.5 (wt%), and molar ratio of ethylbenzene to O2 of 20:1. The test results after 100h of reaction are listed in Table 1.

[0068] [Example 9]

[0069] Weigh 48.2 parts of red iron oxide (equivalent to 48.2 parts of Fe2O3), 22.6 parts of yellow iron oxide (equivalent to 22.6 parts of Fe2O3), 11.6 parts of potassium bicarbonate (equivalent to 11.6 parts of K2O), 9.2 parts of cerium nitrate (equivalent to 9.2 parts of CeO2), 3.5 parts of ammonium molybdate (equivalent to 3.5 parts of MoO3), 2.8 parts of Bi2O3, 1.8 parts of CaO, 0.1 parts of Sm2O3, 0.2 parts of europium chloride (equivalent to 0.2 parts of Eu2O3), and 2.4 parts of polystyrene microspheres in a mixer and stir for 2 hours until uniformly mixed. Deionized water (24% by weight of the total weight of the dehydrogenation catalyst raw materials) is then added and mixed for 2 hours. The mixture is then extruded and pelletized to obtain pellets 3 mm in diameter and 6 mm in length. These pellets are then dried in an oven at 80°C for 4 hours and 160°C for 4 hours. The finished dehydrogenation catalyst is then calcined in a muffle furnace at 650°C for 2 hours and 900°C for 2 hours. The dehydrogenation catalyst composition is listed in Table 1.

[0070] 100 ml of dehydrogenation catalyst was loaded into the reactor and the reaction mixture was heated at 40 kPa (absolute pressure) and a mass space velocity of 1.0 h-1 for ethylbenzene. -1 The performance evaluation was carried out under the conditions of reaction temperature 600℃, water ratio 0.5 (wt%), and molar ratio of ethylbenzene to O2 of 20:1. The test results after 100h of reaction are listed in Table 1.

[0071] [Example 10]

[0072] Weigh 48.2 parts of red iron oxide (equivalent to 48.2 parts of Fe2O3), 22.6 parts of yellow iron oxide (equivalent to 22.6 parts of Fe2O3), 11.6 parts of potassium carbonate (equivalent to 11.6 parts of K2O), 9.2 parts of cerium oxalate (equivalent to 9.2 parts of CeO2), 3.5 parts of ammonium molybdate (equivalent to 3.5 parts of MoO3), 2.8 parts of Bi2O3, 1.8 parts of calcium hydroxide (equivalent to 1.8 parts of CaO), 0.1 parts of Sm2O3, 0.2 parts of europium chloride (equivalent to 0.2 parts of Eu2O3), and 2.4 parts of graphite in a mixer and stir for 2 hours until uniformly mixed. Deionized water (24% by weight of the total weight of the dehydrogenation catalyst raw materials) was then added and mixed for 2 hours. The mixture was then extruded and pelletized to obtain pellets 3 mm in diameter and 6 mm in length. The pellets were then dried in an oven at 80°C for 4 hours and 160°C for 4 hours. The pellets were then calcined in a muffle furnace at 650°C for 2 hours and 900°C for 2 hours to obtain the finished dehydrogenation catalyst. The composition of the dehydrogenation catalyst is listed in Table 1.

[0073] 100 ml of dehydrogenation catalyst was loaded into the reactor and the reaction mixture was heated at 40 kPa (absolute pressure) and a mass space velocity of 1.0 h-1 for ethylbenzene. -1 The performance evaluation was carried out under the conditions of reaction temperature 600℃, water ratio 0.5 (wt%), and molar ratio of ethylbenzene to O2 of 20:1. The test results after 100h of reaction are listed in Table 1.

[0074] [Example 11]

[0075] Weigh 48.2 parts of red iron oxide (equivalent to 48.2 parts of Fe2O3), 22.6 parts of yellow iron oxide (equivalent to 22.6 parts of Fe2O3), 11.6 parts of potassium carbonate (equivalent to 11.6 parts of K2O), 9.2 parts of cerium carbonate (equivalent to 9.2 parts of CeO2), 3.5 parts of ammonium molybdate (equivalent to 3.5 parts of MoO3), 2.8 parts of Bi2O3, 1.8 parts of calcium hydroxide (equivalent to 1.8 parts of CaO), 0.1 parts of Sm2O3, 0.2 parts of europium chloride (equivalent to 0.2 parts of Eu2O3), and 2.4 parts of activated carbon in a mixer and stir for 2 hours until uniformly mixed. Deionized water (24% by weight of the total weight of the dehydrogenation catalyst raw materials) was then added and mixed for 2 hours. The mixture was then extruded and pelletized to obtain pellets 3 mm in diameter and 6 mm in length. The pellets were then dried in an oven at 80°C for 4 hours and 160°C for 4 hours. The finished dehydrogenation catalyst was then calcined in a muffle furnace at 650°C for 2 hours and 900°C for 2 hours. The dehydrogenation catalyst composition is listed in Table 1.

[0076] 100 ml of dehydrogenation catalyst was loaded into the reactor and the reaction mixture was heated at 40 kPa (absolute pressure) and a mass space velocity of 1.0 h-1 for ethylbenzene. -1 The performance evaluation was carried out under the conditions of reaction temperature 600℃, water ratio 0.5 (wt%), and molar ratio of ethylbenzene to O2 of 20:1. The test results after 100h of reaction are listed in Table 1.

[0077] [Example 12]

[0078] Weigh 48.2 parts of red iron oxide (equivalent to 48.2 parts of Fe2O3), 22.6 parts of yellow iron oxide (equivalent to 22.6 parts of Fe2O3), 11.6 parts of potassium carbonate (equivalent to 11.6 parts of K2O), 9.2 parts of cerium nitrate (equivalent to 9.2 parts of CeO2), 3.5 parts of MoO3, 2.8 parts of Bi2O3, 1.8 parts of calcium hydroxide (equivalent to 1.8 parts of CaO), 0.1 parts of Sm2O3, 0.2 parts of europium chloride (equivalent to 0.2 parts of Eu2O3), and 2.4 parts of sodium hydroxymethylcellulose in a mixer and stir for 2 hours until uniformly mixed. Deionized water (24% by weight of the total weight of the dehydrogenation catalyst raw materials) is then added and mixed for 2 hours. The mixture is then extruded and pelletized to obtain pellets 3 mm in diameter and 6 mm in length. These pellets are then dried in an oven at 80°C for 4 hours and 160°C for 4 hours. The finished dehydrogenation catalyst is then calcined in a muffle furnace at 650°C for 2 hours and 900°C for 2 hours. The dehydrogenation catalyst composition is listed in Table 1.

[0079] 100 ml of dehydrogenation catalyst was loaded into the reactor and the reaction mixture was heated at 40 kPa (absolute pressure) and a mass space velocity of 1.0 h-1 for ethylbenzene. -1 The performance evaluation was carried out under the conditions of reaction temperature 600℃, water ratio 0.5 (wt%), and molar ratio of ethylbenzene and O2 of 20:1. The test results of reaction time 100h are listed in Table 1, and the test results of reaction time 1000h are listed in Table 2.

[0080] [Comparative Example 1]

[0081] Weigh 48.2 parts of red iron oxide (Fe2O3), 22.6 parts of yellow iron oxide (Fe2O3), 11.6 parts of potassium carbonate (K2O), 9.2 parts of cerium nitrate (CeO2), 3.5 parts of ammonium molybdate (MoO3), 1.8 parts of calcium hydroxide (CaO), and 2.4 parts of polystyrene microspheres in a mixer and stir for 2 hours until uniformly mixed. Add the same amount of water as in Example 1 to the mixer and stir for 2 hours until uniformly mixed. The mixture is then extruded and pelletized to obtain pellets 3 mm in diameter and 6 mm in length. These pellets are then dried in an oven at 80°C for 4 hours and then at 160°C for 4 hours. The resulting pellets are then calcined in a muffle furnace at 650°C for 2 hours and then at 900°C for 2 hours to obtain the finished dehydrogenation catalyst. The composition of the dehydrogenation catalyst is listed in Table 1.

[0082] 100 ml of dehydrogenation catalyst was loaded into the reactor and the reaction mixture was heated at 40 kPa (absolute pressure) and a mass space velocity of 1.0 h-1 for ethylbenzene. -1 The performance evaluation was carried out under the condition of reaction temperature of 600℃. The test results of reaction time of 100h are listed in Table 1, and the test results of reaction time of 1000h are listed in Table 2.

[0083] Table 1 Dehydrogenation catalyst compositions and evaluation results of Examples and Comparative Examples

[0084]

[0085] Note: * Ethylbenzene conversion and styrene selectivity after 100h reaction

[0086] Table 2 Dehydrogenation catalyst stability evaluation results of Examples and Comparative Examples

[0087]

[0088]

[0089] [Comparative Examples 2 to 4]

[0090] 100 ml of the dehydrogenation catalyst obtained in Example 1 was loaded into the reactor and heated at 40 kPa (absolute pressure) and a mass space velocity of ethylbenzene of 1.0 h -1 The performance evaluation was carried out under the conditions of reaction temperature 600℃ and water ratio 0.5 (wt%). The reaction results are listed in Table 3.

[0091] Table 3

[0092]

[0093] Combining the results in Tables 1, 2, and 3, it can be seen that the method for producing styrene by dehydrogenating ethylbenzene of the present invention significantly reduces the amount of water vapor used, has high ethylbenzene conversion and styrene selectivity, and has good stability. After the dehydrogenation reaction has been running for 1000 hours, the ethylbenzene conversion and styrene selectivity have not decreased significantly.

[0094] The above describes in detail the specific embodiments of the present invention, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as the contents disclosed by the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing styrene by dehydrogenating ethylbenzene, characterized in that: The method comprises: contacting a raw material containing ethylbenzene with a dehydrogenation catalyst in the presence of water vapor and O2 to carry out a dehydrogenation reaction to obtain a product containing styrene; The dehydrogenation reaction adopts a low water ratio; the low water ratio means that the weight ratio of water to ethylbenzene is less than 0.8; The dehydrogenation catalyst, based on the total mass of the dehydrogenation catalyst, comprises the following components in terms of mass fraction: (a) 60% to 85% Fe2O3; (b) 8% to 16% K2O; (c) 4% to 12% CeO2; (d) 0.5% to 5% MoO3; (e) 0.1% to 4% Bi2O3; (f) 0.2% to 3% CaO.

2. The method according to claim 1, characterized in that The molar ratio of ethylbenzene to O2 is 4:1 to 100:

1.

3. The method according to claim 1, characterized in that The molar ratio of ethylbenzene to O2 is 5:1 to 20:

1.

4. The method according to claim 1 or 2, characterized in that The weight ratio of water to ethylbenzene is 0.2 to 0.

8.

5. The method according to claim 4, characterized in that: The weight ratio of water to ethylbenzene is 0.2 to 0.

6.

6. The method according to claim 1 or 5, characterized in that The reaction temperature of the dehydrogenation reaction is 520°C to 620°C, the absolute pressure is 20 to 100 kPa; the mass space velocity of ethylbenzene is 0.2 to 2.0 h -1 .

7. The method according to claim 1, characterized in that: The dehydrogenation catalyst further comprises oxides of Sm and / or Eu.

8. The method according to claim 7, characterized in that: Based on the total mass of the dehydrogenation catalyst, the dehydrogenation catalyst contains 0.01% to 1.0% of Sm and / or Eu oxides in terms of mass fraction.

Images