Process for producing styrene

Abstract

The present invention provides a method for producing styrene, comprising the following steps: passing reaction raw materials through a plurality of reactors connected in series in sequence to obtain a product; wherein the reaction raw materials include at least ethylbenzene and water; a catalyst II is loaded in the last reactor connected in series, and the relative void ratio of the catalyst II is not less than 1.01, based on the void ratio of the cylindrical catalyst being 1. The method for producing styrene provided by the present invention performs a reaction through a plurality of reactors connected in series, and designs the catalyst in the last reactor so that the raw materials react fully, which can effectively increase the specific surface area of ​​the reaction, and at the same time reduce the bed pressure drop, increase the raw material conversion rate and styrene selectivity, thereby improving the overall reaction effect and the yield of styrene.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical industry, and in particular relates to a method for producing styrene. Background Art

[0002] Styrene is an important bulk basic organic raw material, mainly used in the production of synthetic resins and rubber. More than 85% of the industrial production method is the catalytic dehydrogenation of ethylbenzene. Based on the wide range of uses of styrene, styrene production in countries around the world has developed rapidly. According to the statistics of global styrene production capacity in 2018, the total production capacity was 33.979 million tons, mainly concentrated in the five major regions of Northeast Asia, North America, Western Europe, the Middle East, and Southeast Asia, with a total production capacity of 32.268 million tons, accounting for as high as 95%, and the production capacity in other regions is relatively small. In 2019, my country's production capacity was 9.255 million tons, making it the world's largest styrene producer.

[0003] For the important petrochemical catalytic process of ethylbenzene dehydrogenation to styrene, the catalyst plays a key role in the production of styrene, and the quality of the catalyst determines the economic efficiency of the dehydrogenation process. The research, development and replacement of ethylbenzene dehydrogenation catalysts have been continuously developed since the 1930s. The basic composition of the current catalysts is a composite / mixed oxide of Fe / K / Ce / Mo. The performance of commercial ethylbenzene dehydrogenation to styrene catalysts is relatively close to the thermodynamic equilibrium value and has reached a very high level. It is not easy to continue to improve the performance of the catalyst to a large extent through the improvement of the catalyst formulation.

[0004] Chinese patent CN1209194C discloses a catalyst for the dehydrogenation of ethylbenzene to produce styrene and its preparation method, which can enhance the lateral pressure strength of the catalyst by adding vanadium, cobalt, manganese and titanium oxides to the Fe / K / Ce / Mo / Mg system and optimizing the preparation process. However, the catalyst contains vanadium, which will cause environmental pollution.

[0005] Chinese patent CN100443170C discloses a catalyst for dehydrogenating ethylbenzene to produce styrene and a preparation method thereof. The catalyst has a lateral pressure strength of not less than 25 N / mm. However, since 1%-9% of cement and silica gel are added to the catalyst as reinforcing agents, and these reinforcing agents are generally acidic substances, they are prone to cause side reactions such as cracking, thereby affecting the selectivity of the catalyst.

[0006] On the other hand, styrene plants have tended to be large-scale, and the expansion and transformation of the original old plants often adopts the method of adding a reactor and changing two stages to three stages. The dehydrogenation of ethylbenzene to produce styrene is a reaction of increasing the number of molecules. The higher the vacuum degree of the plant, the more favorable it is for the production of styrene. With the increase of catalyst bed thickness or the poor compressive strength of the catalyst, it is easy to pulverize, resulting in an increase in bed pressure drop, which directly affects the conversion rate. In addition, most of the early introduced styrene plants in China have more or less problems such as aging of compressors and serious blockage of combined heat exchangers, making it difficult to fully utilize the catalyst conversion rate and selectivity level, and high energy consumption and material consumption of the plants.

[0007] Therefore, it is urgent to propose a method for producing styrene that can design a catalyst, combine the characteristics of various catalysts, and optimize the process, so as to reduce the cost of the production equipment, reduce energy consumption, and be suitable for higher reaction pressures. Summary of the invention

[0008] The technical problem to be solved by the present invention is that the existing device for producing styrene in the prior art has high energy consumption, poor effect and is not suitable for the situation where the reaction pressure is too high. A method for producing styrene is provided, which can ensure a high raw material conversion rate and styrene yield under a high pressure, and also has high selectivity, and can reduce the device cost and energy consumption.

[0009] To achieve the purpose of the present invention, in a first aspect, the present invention provides a method for producing styrene, comprising the following steps: passing the reaction raw materials through a plurality of reactors connected in series in sequence to obtain a product; wherein the reaction raw materials include at least ethylbenzene and water; and the last reactor connected in series is filled with a catalyst II, and the relative porosity of the catalyst II is not less than 1.01, based on the porosity of the cylindrical catalyst being 1.

[0010] Preferably, the relative porosity of the catalyst II is not greater than 1.25.

[0011] By designing the relative porosity of Catalyst II, a catalyst bed with a smaller bulk density is obtained, which can maintain a certain activity under a higher pressure and effectively increase the specific surface area of ​​the reaction, thereby ensuring a higher raw material conversion rate and styrene yield under a higher pressure while also having a high selectivity.

[0012] The method for producing styrene provided by the present invention performs the reaction through a plurality of reactors connected in series, and designs the catalyst in the last reactor so that the raw materials react fully, which can effectively increase the specific surface area of ​​the reaction, reduce the bed pressure drop, and increase the raw material conversion rate and styrene selectivity, thereby improving the overall reaction effect and the yield of styrene.

[0013] As a specific embodiment of the present invention, the outlet pressure of the last reactor is in the range of 40 kPaA to 101 kPaA, such as 60 kPaA to 101 kPaA, 70 kPaA to 80 kPaA, 40 kPaA, 50 kPaA, 60 kPaA, 70 kPaA, 80 kPaA, 90 kPaA, 101 kPaA and any combination thereof. The pressures described in the present invention all refer to absolute pressures.

[0014] By carrying out a preliminary reaction on the raw materials through multiple reactors connected in series, the temperature of the material entering the last reactor can be made to have a suitable reaction temperature when entering the reactor, thereby improving the efficiency of the reaction.

[0015] Preferably, the plurality of reactors is two reactors.

[0016] As a specific embodiment of the present invention, the temperature in each reactor can be set to between 570°C and 640°C, such as 590°C to 620°C, 600°C to 610°C, 570°C to 590°C, 575°C, 585°C, 595°C, 605°C, 615°C, 625°C, 635°C and any combination thereof. The temperature of each reactor can be the same or different, all within the scope of the present invention.

[0017] In addition, in order to ensure the temperature of the material at the entrance of the last reactor, a heating system can be set between the reactors connected in series. Specifically, the heating system can be a conventional heating device in the art, such as an interstage heater. The heating temperature of the heater can be further adjusted. For example, the temperature of the reaction raw materials after passing through the heating system is not less than 590°C, thereby ensuring that the material reaches a suitable reaction temperature at the entrance of the last reactor.

[0018] The catalyst in the other reactors except the last reactor can be the same catalyst as catalyst II, or can be an existing conventional catalyst, which is not particularly limited in the present invention. Any catalyst conventional in the art suitable for the reaction of producing styrene is within the protection scope of the present invention.

[0019] In a preferred embodiment of the present invention, at least two reactors are filled with catalyst II.

[0020] In a preferred embodiment of the present invention, each reactor is filled with catalyst II.

[0021] Since the pressure of the last reactor is relatively high, in order to make the catalyst suitable for a higher pressure range, the catalyst II in the present invention adopts a special-shaped catalyst, for example, it can be selected from at least one of a butterfly shape, a hollow cylinder, a rhombus shape, a honeycomb shape, a clover shape, a four-leaf clover shape, a five-leaf clover shape, a sphere, a wheel shape, a gear shape, a star shape, a cross shape and a plum blossom shape.

[0022] Preferably, the catalyst II is at least selected from a clover shape, a five-plum blossom shape and a five-gear shape.

[0023] It is well known to those skilled in the art that the shaped catalyst has the defects of low strength and high abrasion. In order to reduce the abrasion of the catalyst and increase its strength, the inventors further defined the lateral pressure strength and abrasion rate of Catalyst II.

[0024] Specifically, the lateral compression strength of Catalyst II is not less than 120N / 5mm, for example, in the range of 130N / 5mm, 140N / 5mm, 150N / 5mm, 160N / 5mm, 170N / 5mm, 180N / 5mm, 190N / 5mm, 200N / 5mm and any combination thereof.

[0025] As a specific embodiment of the present invention, the attrition rate of Catalyst II is in the range of 0.3%-2.5%, for example, 0.3%-2.5%, 0.8%-2%, 1.3%-1.7%, 0.3%, 0.8%, 1.3%, 1.8%, 2.5% and any combination thereof.

[0026] In addition, the inventors found during the research that adjusting the content and form of Ce in the catalyst can also appropriately adjust the physical properties of the catalyst. For example, adding CeO2 to Catalyst II can improve the strength of the catalyst and reduce its wear while ensuring the activity of the catalyst.

[0027] The particle size of CeO2 can be further adjusted to the range of 10nm-60nm, for example, 20nm-50nm, 30nm-40nm, 15nm, 25nm, 35nm, 45nm, 55nm and any combination thereof, so as to further improve the strength of the catalyst and reduce abrasion.

[0028] As a specific embodiment of the present invention, based on the mass of the catalyst II, the catalyst II includes the following components in percentage by mass: Fe2O3 60%-85%, K2O 6%-14%, CeO2 6%-16%, MoO3 0.5%-5%, CaO 0.2%-5% and MnO2 0.1%-2%.

[0029] Preferably, the weight ratio of CaO to MnO2 is 1-10:1, such as 2-8:1, 1-5:1, 5-10:1.

[0030] As a specific embodiment of the present invention, when two reactors are arranged in series, the catalyst in the first reactor may include the following components in percentage by mass, based on the mass of the catalyst: Fe2O3 65%-80%, K2O 6%-14%, CeO2 9%-16%, MoO3 0.5%-5%, CaO 0.2%-5% and TiO2 0.01%-1%.

[0031] As a specific embodiment of the present invention, the catalyst II at least includes CeO2 prepared using cerium nitrate as a precursor.

[0032] Preferably, in the catalyst II, the mass of CeO2 prepared from the cerium nitrate accounts for 5%-50% of the total mass of Ce oxides prepared from all Ce-containing precursors, for example, in the range of 10%-40%, 20%-30%, 5%, 15%, 25%, 35%, 45% and any combination thereof.

[0033] As a specific embodiment of the present invention, the volume ratio of the catalyst in the last reactor to the catalyst in other reactors is independently set to 1:1-1:1.3, for example, 1:1, 1:1.1, 1:1.2, 1:1.3 and any combination thereof, that is, the volume ratio of the catalyst in the last reactor to the catalyst in other reactors may be the same or different, both within the scope of protection of the present invention.

[0034] As a specific embodiment of the present invention, in the raw material, the weight ratio of water to ethylbenzene is 0.9-2:1, for example, 1.3-1.8:1, 0.9:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2:1 and any combination thereof.

[0035] Preferably, the ethylbenzene liquid volume space velocity is 0.1h -1 -1h -1 , for example 0.3h -1 -0.5h -1 , for example 0.1h -1 , 0.2h -1 , 0.3h -1 , 0.4h -1 , 0.5h -1 , 0.6h -1 , 0.7h -1 , 0.8h -1 , 0.9h -1 , 1h -1and any combination thereof. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with specific embodiments, but they do not constitute any limitation to the present invention.

[0037] The testing methods in the following examples and comparative examples are as follows:

[0038] 1. Calculation of void ratio

[0039] Void ratio = (1-bulk density of catalyst / apparent density of catalyst) × 100%;

[0040] Relative porosity = porosity of shaped catalyst / porosity of cylindrical catalyst.

[0041] The bulk density of the catalyst is measured in accordance with the relevant provisions of GB / T 6286.

[0042] The apparent density of the catalyst is determined by the pycnometer method, that is, first weigh the mass of the sample, then inject distilled water into the pycnometer, plug it tightly with a stopper (to ensure that the volume of distilled water is equal to the volume of the pycnometer), and weigh it. Finally, put the weighed sample into the pycnometer filled with distilled water and weigh it, and then calculate the apparent density of the sample.

[0043] 2. Side pressure strength of catalyst

[0044] The test was carried out according to the standard HG / T2782-1996, using the DL-II intelligent particle strength tester. The sample length was 5 mm, and 40 particles were tested in a group. The arithmetic mean of the test results was taken as the final mechanical strength value, and Newton (N) was used as the unit of mechanical strength.

[0045] 3. Catalyst attrition rate

[0046] The determination method is: the percentage of the original weight of the sample between the accurate weight of the sample after being dried at 200°C for 2 hours and the accurate weight of the particles taken out through a 20-mesh sieve after the sample was abraded 5000 times on an abrasion tester.

[0047] 4. CeO2 grain size of catalyst

[0048] According to the XRD test results, it is calculated by Scherrer formula. The XRD test was carried out on a Bruker D8advance X-ray powder diffractometer with a tube voltage of 40 kV, a tube current of 250 mA, a Cu target, a scanning range of 4°-70°, a scanning speed of 6° / min, and a solid detector.

[0049] [Example 1]

[0050] Example 1 provides a method for producing styrene, comprising the following steps: passing the reaction raw materials through a first reactor and a second reactor connected in series in sequence to obtain a product.

[0051] The first reactor was filled with 750 mL of catalyst I, the second reactor was filled with 750 mL of catalyst II, the temperature T1 in the first reactor and the temperature T2 in the second reactor were 615° C. / 620° C. respectively, and the outlet pressure P2 of the second reactor was 60 kPa.

[0052] Catalyst II is clover-shaped, has a lateral compression strength of 145 N / 5 mm, and an abrasion rate of 1.1%. The CeO2 grain size and composition of the catalyst are listed in Table 1.

[0053] Catalyst II is prepared by adding, based on the weight of the oxides, 60.44 parts of red iron oxide equivalent to Fe2O3, 12.09 parts of yellow iron oxide equivalent to Fe2O3, 11.45 parts of potassium carbonate equivalent to K2O, 9.14 parts of cerium oxalate equivalent to CeO2, 1.07 parts of ammonium molybdate equivalent to MoO3, 2.15 parts of calcium hydroxide equivalent to CaO, 0.58 parts of MnO2, 0.03 parts of TiO2 and 5.5 parts of carboxymethyl Sodium cellulose was stirred in a kneader for 1.5 hours, cerium nitrate equivalent to 3.05 parts of CeO2 was added to deionized water accounting for 23.5% of the total weight of the catalyst raw material to dissolve, and then the cerium nitrate aqueous solution was added to the kneader and stirred for 0.7 hours, and the extruded strips were taken out and extruded into particles with a diameter of 3 mm and a length of 5 mm, which were placed in an oven and baked at 50°C for 6 hours, 120°C for 12 hours, and then calcined at 350°C for 7 hours, and then calcined at 850°C for 4 hours to obtain Catalyst II. The catalyst composition is listed in Table 1.

[0054] Catalyst I can be a Fe2O3-K2O catalyst used in the prior art for dehydrogenation of ethylbenzene to produce styrene (such as GS series ethylbenzene dehydrogenation catalyst). In this embodiment, the composition of catalyst I is the same as that of catalyst II, except that the shape of catalyst I is cylindrical. When the volume space velocity (V) of ethylbenzene liquid is 0.5h -1 The evaluation was carried out under the condition that the weight ratio of water to ethylbenzene (D) was 1.3:1. The test results are listed in Table 2.

[0055] [Example 2]

[0056] Example 2 provides a method for producing styrene. The only difference between Example 2 and Example 1 is that the catalyst II in Example 2 is in the shape of a five-plum blossom, and the other parameters and steps are the same.

[0057] When the volume space velocity (V) of ethylbenzene liquid is 0.5h -1The evaluation was carried out under the condition that the weight ratio of water to ethylbenzene (D) was 1.3:1. The test results are listed in Table 2.

[0058] [Example 3]

[0059] Example 3 provides a method for producing styrene. The only difference between Example 3 and Example 1 is that the catalyst II in Example 3 is in the shape of five gears, and the other parameters and steps are the same.

[0060] When the volume space velocity (V) of ethylbenzene liquid is 0.5h -1 The evaluation was carried out under the condition that the weight ratio of water to ethylbenzene (D) was 1.3:1. The test results are listed in Table 2.

[0061] [Example 4]

[0062] Example 4 provides a method for producing styrene. The only difference between Example 4 and Example 1 is that the outlet pressure of the second reactor in Example 4 is 70 kPaA, and the other parameters and steps are the same.

[0063] When the volume space velocity (V) of ethylbenzene liquid is 0.5h -1 The evaluation was carried out under the condition that the weight ratio of water to ethylbenzene (D) was 1.3:1. The test results are listed in Table 2.

[0064] [Example 5]

[0065] Example 5 provides a method for producing styrene. The only difference between Example 5 and Example 1 is that the outlet pressure of the second reactor in Example 5 is 80 kPaA, and the other parameters and steps are the same.

[0066] When the volume space velocity (V) of ethylbenzene liquid is 0.5h -1 The evaluation was carried out under the condition that the weight ratio of water to ethylbenzene (D) was 1.3:1. The test results are listed in Table 2.

[0067] [Example 6]

[0068] Example 6 provides a method for producing styrene. The only difference between Example 6 and Example 1 is that the first reactor in Example 6 is loaded with catalyst II, and the other parameters and steps are the same.

[0069] When the volume space velocity (V) of ethylbenzene liquid is 0.5h -1 The evaluation was carried out under the condition that the weight ratio of water to ethylbenzene (D) was 1.3:1. The test results are listed in Table 2.

[0070] [Example 7]

[0071] Example 7 provides a method for producing styrene. The only difference between Example 7 and Example 1 is that in Example 7, the first reactor is filled with 680 mL of catalyst I, and the second reactor is filled with 820 mL of catalyst II. The other parameters and steps are the same.

[0072] When the volume space velocity (V) of ethylbenzene liquid is 0.5h -1 The evaluation was carried out under the condition that the weight ratio of water to ethylbenzene (D) was 1.3:1. The test results are listed in Table 2.

[0073] [Example 8]

[0074] Example 8 provides a method for producing styrene. The only difference between Example 8 and Example 1 is that the composition of the catalyst in Example 8 is different, and the other parameters and steps are the same.

[0075] Catalyst II is prepared by stirring red iron oxide equivalent to 68.91 parts of Fe2O3, potassium carbonate equivalent to 13.42 parts of K2O, cerium carbonate equivalent to 0.97 parts of CeO2, ammonium molybdate equivalent to 2.81 parts of MoO3, calcium carbonate equivalent to 4.78 parts of CaO, 0.50 parts of MnO2, 0.01 parts of TiO2 and 5.8 parts of hydroxyethyl cellulose in a kneader for 1.5 hours, adding cerium nitrate equivalent to 8.60 parts of CeO2 into deionized water accounting for 21.5% of the total weight of the catalyst raw materials and dissolving them, then adding the cerium nitrate aqueous solution into the kneader, stirring for 0.5 hours, taking out the extruded strips, extruding into particles with a diameter of 3 mm and a length of 5 mm, putting them into an oven, baking at 45°C for 8 hours, baking at 120°C for 10 hours, then roasting at 360°C for 7 hours, and then roasting at 820°C for 5 hours to obtain Catalyst II. The catalyst composition is listed in Table 1.

[0076] The composition of catalyst I is the same as that of catalyst II, except that catalyst I is cylindrical in shape.

[0077] When the volume space velocity (V) of ethylbenzene liquid is 0.5h -1 The evaluation was carried out under the condition that the weight ratio of water to ethylbenzene (D) was 1.3:1. The test results are listed in Table 2.

[0078] [Comparative Example 1]

[0079] Comparative Example 1 provides a method for producing styrene. The only difference between Comparative Example 1 and Example 1 is that the second reactor in Comparative Example 1 is filled with cylindrical catalyst I, and the other parameters and steps are the same.

[0080] When the volume space velocity (V) of ethylbenzene liquid is 0.5h -1 The evaluation was carried out under the condition that the weight ratio of water to ethylbenzene (D) was 1.3:1. The test results are listed in Table 2.

[0081] [Comparative Example 2]

[0082] Comparative Example 2 provides a method for producing styrene. The only difference between Comparative Example 2 and Example 1 is that the first reactor in Comparative Example 2 is filled with clover-shaped catalyst II, and the second reactor is filled with cylindrical catalyst I. The remaining parameters and steps are the same.

[0083] When the volume space velocity (V) of ethylbenzene liquid is 0.5h -1 The evaluation was carried out under the condition that the weight ratio of water to ethylbenzene (D) was 1.3:1. The test results are listed in Table 2.

[0084] [Comparative Example 3]

[0085] Comparative Example 3 provides a method for producing styrene. The only difference between Comparative Example 3 and Example 2 is that the first reactor in Comparative Example 3 is filled with five-plum blossom-shaped catalyst II, and the second reactor is filled with cylindrical catalyst I. The other parameters and steps are the same.

[0086] When the volume space velocity (V) of ethylbenzene liquid is 0.5h -1 The evaluation was carried out under the condition that the weight ratio of water to ethylbenzene (D) was 1.3:1. The test results are listed in Table 2.

[0087] [Comparative Example 4]

[0088] Comparative Example 4 provides a method for producing styrene. The only difference between Comparative Example 4 and Example 3 is that the first reactor in Comparative Example 4 is filled with five-gear-shaped catalyst II, and the second reactor is filled with cylindrical catalyst I. The other parameters and steps are the same.

[0089] When the volume space velocity (V) of ethylbenzene liquid is 0.5h -1 The evaluation was carried out under the condition that the weight ratio of water to ethylbenzene (D) was 1.3:1. The test results are listed in Table 2.

[0090] [Comparative Example 5]

[0091] Comparative Example 5 provides a method for producing styrene. The only difference between Comparative Example 5 and Example 4 is that the first reactor in Comparative Example 5 is filled with trilobate catalyst II, and the second reactor is filled with cylindrical catalyst I. The other parameters and steps are the same.

[0092] When the volume space velocity (V) of ethylbenzene liquid is 0.5h -1 The evaluation was carried out under the condition that the weight ratio of water to ethylbenzene (D) was 1.3:1. The test results are listed in Table 2.

[0093] [Comparative Example 6]

[0094] Comparative Example 6 provides a method for producing styrene. The only difference between Comparative Example 6 and Example 5 is that the first reactor in Comparative Example 6 is filled with trilobate catalyst II, and the second reactor is filled with cylindrical catalyst I. The other parameters and steps are the same.

[0095] When the volume space velocity (V) of ethylbenzene liquid is 0.5h -1 The evaluation was carried out under the condition that the weight ratio of water to ethylbenzene (D) was 1.3:1. The test results are listed in Table 2.

[0096]

[0097] Table 2

[0098]

[0099]

[0100] Note: The first-reaction catalyst shape refers to the catalyst shape in the first reactor, and the second-reaction catalyst shape refers to the catalyst shape in the second reactor.

[0101] The obtained catalyst was evaluated for activity in a two-stage adiabatic fixed bed. The process of activity evaluation of ethylbenzene dehydrogenation to styrene is briefly described as follows:

[0102] The reaction raw materials are respectively fed into the preheating mixer through metering pumps, and after being preheated and mixed into gaseous state, they enter the two reactors in sequence. The reactants flowing out of the reactors are condensed with water and their composition is analyzed by gas chromatography.

[0103] Ethylbenzene conversion, styrene selectivity and styrene yield were calculated according to the following formula:

[0104]

[0105]

[0106] Styrene yield % = ethylbenzene conversion × styrene selectivity

[0107] It can be seen from Table 1 and Table 2 that, compared with the comparative example, the method for producing styrene in the embodiment of the present invention can effectively improve the raw material conversion rate and styrene selectivity, thereby improving the yield of styrene.

[0108] Any numerical value mentioned in the present invention, if there is only an interval of two units between any minimum value and any maximum value, includes all values ​​from the minimum value to the maximum value each time increasing by one unit. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, time, etc. is declared to be 50-90, in this specification it means that 51-89, 52-88... and 69-71 and 70-71 are specifically listed. For non-integer values, 0.1, 0.01, 0.001 or 0.0001 can be appropriately considered as a unit. These are just some specially specified examples. In this application, in a similar manner, all possible combinations of numerical values ​​between the listed minimum and maximum values ​​are considered to have been disclosed.

[0109] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A method for producing styrene, characterized in that: The method comprises the following steps: passing the reaction raw materials through a plurality of reactors connected in series in sequence to obtain a product; the plurality of reactors are two reactors; The reaction raw materials include at least ethylbenzene and water; the last reactor connected in series is filled with catalyst II, and the relative void ratio of the catalyst II is not less than 1.01, based on the void ratio of the cylindrical catalyst being 1; the relative void ratio of the catalyst II is not greater than 1.25; Based on the mass of the catalyst II, the catalyst II comprises the following components in percentage by mass: Fe2O3 60%-85%, K2O 6%-14%, CeO2 6%-16%, MoO3 0.5%-5%, CaO 0.2%-5% and MnO2 0.1%-2%. The grain size of CeO2 in the catalyst II is 10nm-60nm. The catalyst II is selected from one of a five-plum blossom shape and a five-gear shape, The reactor is an adiabatic fixed bed reactor, The outlet pressure of the last reactor is 60 kPaA~70 kPaA, The lateral pressure strength of the catalyst II is 120N / 5mm-138N / 5mm; the wear rate of the catalyst II is 0.3%-2.5%, The catalyst in the first reactor includes the following components in percentage by mass based on the mass of the catalyst: Fe2O3 65%-80%, K2O 6%-14%, CeO2 9%-16%, MoO3 0.5%-5%, CaO 0.2%-5% and TiO2 0.01%-1%.

2. The method for producing styrene according to claim 1, characterized in that The temperatures of the multiple reactors were independently set to 570°C-640°C.

3. The method for producing styrene according to claim 2, characterized in that A heating system is also included before the last reactor.

4. The method for producing styrene according to claim 2, characterized in that The temperature of the reaction raw materials when entering the last reactor is not less than 590°C.

5. The method for producing styrene according to claim 1, characterized in that Each reactor was filled with catalyst II.

6. The method for producing styrene according to claim 1, characterized in that In catalyst II, the weight ratio of CaO to MnO2 is 1-10:

1.

7. The method for producing styrene according to any one of claims 1 to 2, characterized in that The catalyst II at least includes CeO2 prepared using cerium nitrate as a precursor.

8. The method for producing styrene according to claim 7, characterized in that In the catalyst II, the mass of CeO2 prepared from the cerium nitrate accounts for 5%-50% of the total mass of Ce oxides prepared from all Ce-containing precursors.

9. The method for producing styrene according to any one of claims 1 to 2, characterized in that: The volume ratio of the catalyst in the last reactor to the catalyst in each of the other reactors was independently set to 1-1.3:

1.

10. The method for producing styrene according to any one of claims 1 to 2, characterized in that: In the raw material, the weight ratio of water to ethylbenzene is 0.9-2:1, and / or the liquid volume space velocity of ethylbenzene is 0.1 h -1 -1 h -1 .

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