Catalyst for catalytic hydrodealkylation of aromatic hydrocarbons and method for its preparation and use

Abstract

The application discloses an aromatic hydrocarbon catalytic dealkylation catalyst, a preparation method and application thereof. The catalyst composition comprises alumina, a first modified metal, a second modified metal and a rare earth metal element. The first modified metal is Cr, the second modified metal comprises at least one of Co, Ni and Rh, and the rare earth metal element comprises at least one of La, Ce and Re. The application solves the problem of non-uniformity of the hydrogen hydrocarbon ratio of the reaction catalyst bed layer caused by the reaction, and also achieves the purposes of reducing the reaction temperature rise, improving the safety of the operation of the device and the heat exchanger, and improving the selectivity of the target product and the aromatic hydrocarbon conversion rate.

Description

Technical Field

[0001] This invention belongs to the field of aromatic catalytic conversion, specifically relating to an aromatic catalytic hydrogenation dealkylation catalyst, its preparation method, and its application. Background Technology

[0002] In recent years, the continuous increase in the operating rate and new capacity of styrene, phenol, and caprolactam plants in China has led to a surge in the market demand for benzene, causing its price to rise steadily. Consequently, the demand for efficient benzene production technologies is constantly increasing. Currently, aromatic hydrocarbon hydrodealkylation technology for benzene production uses alkylbenzene as a raw material, removing side-chain substituents through a hydrodealkylation reaction to convert it into benzene. This is a highly efficient benzene production technology. Currently, aromatic hydrocarbon dealkylation technologies include thermal hydrodealkylation and catalytic hydrodealkylation processes. Thermal hydrodealkylation requires an operating temperature of 750–780℃, while catalytic hydrodealkylation offers advantages such as lower operating temperature (600–650℃), higher benzene product selectivity, and lower aromatic ring loss rate, making it widely favored by enterprises.

[0003] Existing aromatic catalytic hydrogenation dealkylation catalyst systems include: (1) modified molecular sieve catalysts; (2) composite oxide catalysts. Among them, modified molecular sieves have strong ability to remove C2 and above side chain alkyl groups and have low reaction temperature, but weak demethylation ability. CN113171793A discloses a hydrogenation dealkylation catalyst and its preparation method, using heavy aromatics as raw materials and NiMo modified hierarchical ZSM-5 molecular sieve as catalyst, mainly removing C2 and above side chain alkyl groups, with xylene as the main product. Although this type of catalyst has a low reaction temperature, its activity for removing methyl groups is low, and the benzene yield is limited. Composite oxide catalysts have strong methyl removal ability and can meet the demand for deep demethylation to produce benzene, but the high reaction activation energy makes the reaction start temperature high, and the inlet temperature needs to reach about 600℃ when toluene is used as raw material. The operating temperature of UOP's Hydeal aromatic hydrogenation dealkylation process is as high as 600~650℃, using Cr2O3 / Al2O3 composite oxide catalyst, which can remove toluene and above aromatics (C7) + A) Conversion to benzene. Furthermore, this reaction is strongly exothermic, resulting in a temperature rise of approximately 100°C in fixed-bed catalytic hydrodealkylation technology, which can significantly impact the safety of the outlet and heat exchanger operations. Simultaneously, the high thermodynamic equilibrium constant of this reaction leads to high conversion rates. These high conversion rates and temperature rises cause a continuous decrease in the hydrogen-to-hydrogen ratio in the catalyst bed, hindering the overall performance of the catalyst. Therefore, reasonable catalyst and reaction process design to further reduce the reaction temperature and temperature rise, and to achieve a uniform hydrogen-to-hydrogen ratio in each catalyst bed, is crucial for the research of catalytic hydrodealkylation technology. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides an aromatic catalytic hydrogenation dealkylation catalyst, its preparation method, and its application. This application solves the problem of uneven hydrogen-to-hydrogen ratio in the catalyst bed caused by the reaction proceeding, while also reducing reaction temperature rise, improving the safety of the equipment and heat exchanger operation, and enhancing the selectivity of the target product and the conversion rate of aromatics.

[0005] The first aspect of this invention provides a catalyst for the catalytic hydrogenation and dealkylation of aromatic hydrocarbons. The catalyst is a composite metal-modified alumina; the catalyst composition includes alumina, a first modifying metal, a second modifying metal, and rare earth metal elements.

[0006] According to the present invention, the first modified metal is Cr; the second modified metal includes at least one of Co, Ni, and Rh; and the rare earth metal element includes at least one of La, Ce, and Re.

[0007] According to the present invention, preferably, the mass of the catalyst is used as a basis.

[0008] The alumina content, calculated as oxide, is 78% to 98.8%, preferably 78% to 94%.

[0009] The content of the first modified metal, calculated as oxide, is 1% to 20%, preferably 5% to 15%;

[0010] The content of the second modified metal, calculated as oxide, is 0.01% to 10%, preferably 0.1% to 5%;

[0011] The content of the rare earth metal oxide, calculated as oxide, is 0.1% to 4%, preferably 0.5% to 2.0%.

[0012] A second aspect of the present invention provides a method for preparing the above-mentioned catalyst. The method includes:

[0013] (1) Alumina is impregnated with an impregnation solution containing rare earth metal elements, and then dried and calcined to obtain rare earth modified alumina.

[0014] (2) The rare earth modified alumina obtained in step (1) is treated under steam conditions;

[0015] (3) The product obtained in step (2) is impregnated in an impregnation solution containing the first modified metal and the second modified metal, dried, and calcined to obtain the catalyst.

[0016] According to the present invention, the immersion conditions in step (1) are: immersion temperature 25-50°C, and immersion time 1-24 h. The immersion solution in step (1) includes a rare earth metal source. The rare earth metal source is a rare earth metal salt, preferably a nitrate.

[0017] According to the present invention, the calcination conditions in step (1) are: calcination temperature 550-700℃, calcination time 1-10h. The drying conditions in step (1) are: drying temperature 90-150℃, drying time 1-10h.

[0018] According to the present invention, the conditions for steam treatment in step (2) are: treatment temperature of 550-700°C and treatment time of 2-10 hours. The steam treatment method is to place the object to be treated under steam conditions. After steam treatment, drying can be carried out, and the drying conditions are: drying temperature of 90-150°C and drying time of 1-10 hours.

[0019] According to the present invention, the impregnation conditions in step (3) are: impregnation temperature 20-50°C, time 1-24 hours. The drying temperature in step (3) is 90-150°C, and the drying time is 1-10 hours. The calcination temperature is 550-700°C, and the calcination time is 1-10 hours.

[0020] According to the present invention, the impregnation solution in step (3) includes a first modified metal source and a second modified metal source. The first modified metal source is a first modified metal salt, preferably a nitrate. The second modified metal source is a second modified metal salt, preferably a nitrate.

[0021] The third aspect of the present invention provides the application of the above-described catalyst or the catalyst prepared by the above-described method in the catalytic hydrogenation and dealkylation reaction of aromatics.

[0022] According to the present invention, the method of application includes:

[0023] In the presence of hydrogen, the aromatic feedstock reacts with the catalyst in a reactor to produce a benzene-containing stream.

[0024] According to the present invention, the reactor is provided with at least two catalyst beds; hydrogen gas is introduced from above each catalyst bed; each catalyst bed is filled with the catalyst; preferably, the amount of hydrogen gas introduced into each catalyst bed is the same.

[0025] Preferably, a cooling feedstock is introduced near the reactor outlet; the cooling feedstock is mixed with the reaction product and then enters the separation system to obtain a benzene-containing stream.

[0026] According to the present invention, preferably, the number of catalyst beds is 2 to 5, more preferably 3 to 4.

[0027] According to the present invention, hydrogen and / or cooling feedstock are introduced via a bypass. The reactor is a fixed-bed reactor.

[0028] According to the present invention, the cooling raw material is an aromatic hydrocarbon, such as an alkylbenzene; the aromatic hydrocarbon includes toluene, C8 aromatic hydrocarbons, and C9 aromatic hydrocarbons. +At least one of the aromatic hydrocarbons; wherein, C9 + Aromatic hydrocarbons are aromatic hydrocarbons with 9 or more carbon atoms; further, C9... + The aromatic hydrocarbon is a monocyclic aromatic hydrocarbon with 9 to 15 carbon atoms, preferably 9 to 10.

[0029] According to the present invention, the aromatic raw materials include toluene, C8 aromatics, and C9 aromatics. + At least one of the aromatic hydrocarbons; wherein, C9 + Aromatic hydrocarbons are aromatic hydrocarbons with 9 or more carbon atoms; further, C9... + The aromatic hydrocarbon is a monocyclic aromatic hydrocarbon with 9 to 15 carbon atoms, preferably 9 to 10.

[0030] According to the present invention, the reaction conditions include: a reaction temperature of 450–750°C; and a weight hourly space velocity (WHSV) of 0.5–2 h⁻¹ for the aromatic feedstock. -1 The total hydrogen content / molar ratio of aromatic feedstock is 2–8; the reaction pressure is 2–6 MPa.

[0031] According to the present invention, preferably, the reaction conditions include: a reaction temperature of 550–600°C; and a weight hourly space velocity (WHSV) of 0.5–1 h⁻¹ for the aromatic feedstock. -1 The total hydrogen volume / aromatic feedstock molar ratio is 3–6; the reaction pressure is 3–4 MPa. The total hydrogen volume is the sum of the hydrogen flow rates to each catalyst bed. Hydrogen is evenly distributed above each catalyst bed. For example, along the flow path, for the first catalyst bed, the hydrogen flow rate is between the reactor inlet and the first catalyst bed. The remaining hydrogen is introduced between every two catalyst beds.

[0032] According to the present invention, preferably, the amount of cooling raw material introduced is 5 wt% to 20 wt% of the mass of the aromatic raw material, preferably 5 wt% to 18 wt%.

[0033] Compared with the prior art, the present invention achieves the following outstanding technical effects:

[0034] 1. The catalyst of this invention comprises alumina, a first modified metal, a second modified metal, and a rare earth metal element; the first modified metal is Cr; the second modified metal is at least one selected from Co, Ni, and Rh; and the rare earth metal element includes at least one selected from La, Ce, and Re. The catalyst is suitable for the catalytic hydrogenation and dealkylation of aromatics. Particularly under suitable application conditions, it can significantly reduce temperature rise and improve the conversion rate of aromatics and the selectivity of benzene.

[0035] 2. The preparation method of the catalyst of the present invention includes: (1) impregnating alumina with an impregnation solution containing rare earth metal elements, and then drying and calcining to obtain rare earth modified alumina; (2) treating the rare earth modified alumina obtained in step (1) under steam conditions; (3) impregnating the product obtained in step (2) in an impregnation solution containing a first modified metal and a second modified metal, drying, and calcining to obtain the catalyst. The catalyst prepared by the method is suitable for the catalytic hydrogenation and dealkylation reaction of aromatics. Especially under suitable application conditions, it can significantly reduce the temperature rise, improve the conversion rate of aromatics and the selectivity of benzene.

[0036] 3. In the application of the catalyst of this invention, staged hydrogen feeding solves the problem of uneven hydrogen-to-hydrogen ratio in the catalyst bed caused by the reaction, improving the reaction uniformity of each bed. This also reduces the reaction temperature rise and improves the conversion rate of aromatics and the selectivity of benzene. Furthermore, introducing cooling feedstock at the reactor outlet lowers the reactor outlet temperature, improves the safety of the equipment and heat exchanger operation, and further enhances the conversion rate and benzene selectivity. Attached Figure Description

[0037] Figure 1 The process flow diagrams are shown for the catalytic hydrogenation and dealkylation reactions of aromatic hydrocarbons in Examples 1 to 4 of this invention.

[0038] The main reference numerals are as follows:

[0039] 1-Aromatic feedstock, 2-First hydrogen gas, 3-Second hydrogen gas, 4-Third hydrogen gas, 5-Fourth hydrogen gas, 6-Cooling feedstock, 7-Reaction effluent, 8-Fixed bed reactor. Detailed Implementation

[0040] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0041] In this invention, in various embodiments: aromatic feedstock 1 enters a fixed-bed reactor 8 and reacts with a catalyst packed on a catalyst bed in the presence of hydrogen. Hydrogen is injected evenly in four stages from a bypass above each catalyst bed. The reaction product, near the reactor outlet, mixes with the cooled feedstock 6 introduced from the bypass, and the resulting effluent 7 exits the reactor, then enters a separation system to obtain a benzene-containing stream.

[0042] In this invention, the maximum temperature rise of the bed in each example means that the temperature difference between the first catalyst bed (near the beginning of the flow) and the last catalyst bed (near the end of the flow) in the reactor along the flow direction is the maximum temperature rise of the bed.

[0043] In this invention, the impregnation conditions for the rare earth elements, the first modified metal, and the second modified metal in each example are: impregnation at room temperature (25°C) for 10 hours.

[0044] Example 1

[0045] 1. Take 100g of alumina and impregnate it with lanthanum nitrate by the equal volume impregnation method. After completion, dry it at 120℃ for 5 hours and then calcine it at 700℃ for 5 hours to obtain lanthanum-modified alumina.

[0046] The above-mentioned lanthanum-modified alumina was treated with steam at 700°C for 2 hours, and then dried at 120°C for 5 hours after treatment to obtain composite-modified alumina.

[0047] The above-mentioned composite modified alumina was impregnated with chromium nitrate and nickel nitrate by equal volume impregnation method. After completion, it was dried at 90°C for 10 hours and then calcined at 700°C for 5 hours to obtain an aromatic catalytic hydrogenation dealkylation catalyst.

[0048] The catalyst comprises: 80.5% alumina, 15% Cr2O3, 2.5% NiO, and 2% La2O3.

[0049] 2. Using aromatic hydrocarbon catalytic hydrogenation dealkylation catalysts for toluene catalytic hydrogenation dealkylation reactions.

[0050] The reaction conditions were as follows: toluene was used as the raw material, the reaction temperature was 590°C, and the toluene weight hourly space velocity (WHSV) was 1.0 h⁻¹. -1 The reaction pressure is 3 MPa, and the molar ratio of total hydrogen to toluene feedstock is 3.5. In this example, there are four catalyst beds, with hydrogen introduced in four separate stages via bypasses to the top of the catalyst beds. Cooling feedstock is introduced near the reactor outlet. The cooling feedstock is 5% of the aromatic feedstock mass. In this example, the cooling feedstock is the same as the aromatic feedstock, using toluene.

[0051] The catalyst evaluation results for this example are shown in Table 1.

[0052] Example 2

[0053] 1. Take 100g of alumina and impregnate it with ammonium perrhenate by the equal volume impregnation method. After completion, dry it at 90℃ for 10 hours and then calcine it at 550℃ for 8 hours to obtain Re-modified alumina.

[0054] The Re-modified alumina was treated with steam at 550°C for 10 hours, and then dried at 90°C for 10 hours to obtain composite modified alumina.

[0055] The above-mentioned composite modified alumina was impregnated with chromium nitrate and rhodium chloride by equal volume impregnation. After completion, it was dried at 100°C for 8 hours and then calcined at 650°C for 8 hours to obtain an aromatic catalytic hydrogenation dealkylation catalyst.

[0056] The catalyst comprises 89.8% alumina, 10% Cr2O3, 0.1% Rh2O3 and 0.1% Re2O3.

[0057] 2. Using aromatic hydrocarbon catalytic hydrogenation dealkylation catalysts for C9 + Catalytic hydrogenation and dealkylation of heavy aromatics

[0058] The reaction conditions are: using C9 + Heavy aromatics are used as raw materials. Among them, C9 + Heavy aromatic hydrocarbons are monocyclic aromatic hydrocarbons with 9 to 10 carbon atoms. The reaction temperature is 550℃, C9 + The weight hourly space velocity (WHSV) of heavy aromatics is 1.0 h⁻¹. -1 The reaction pressure is 4 MPa, and the total amount of hydrogen is C9. + The molar ratio of heavy aromatics is 6. In this example, there are four catalyst beds, and hydrogen is introduced into the top of the catalyst beds in four separate stages via bypasses. Cooling feedstock is introduced near the reactor outlet. The cooling feedstock is 18% of the aromatic feedstock mass. In this example, the cooling feedstock is the same as the aromatic feedstock, both using C9 hydrocarbons. + Heavy aromatic hydrocarbons.

[0059] The catalyst evaluation results for this example are shown in Table 1.

[0060] Example 3

[0061] 1. Take 100g of alumina and impregnate it with cerium nitrate by the equal volume impregnation method. After completion, dry it at 120℃ for 5 hours and then calcine it at 600℃ for 5 hours to obtain Ce-modified alumina.

[0062] The Ce-modified alumina was treated with steam at 600°C for 10 hours, and then dried at 100°C for 8 hours to obtain composite modified alumina.

[0063] The above-mentioned composite modified alumina was impregnated with chromium nitrate and cobalt nitrate by equal volume impregnation method. After completion, it was dried at 120°C for 5 hours and then calcined at 600°C for 10 hours to obtain an aromatic catalytic hydrogenation dealkylation catalyst.

[0064] The catalyst comprises 89.5% alumina, 5% Cr2O3, 5% Co2O3 and 0.5% CeO2.

[0065] 2. Using aromatic catalytic hydrogenation dealkylation catalysts for C8 aromatic catalytic hydrogenation dealkylation reactions.

[0066] The reaction conditions were as follows: using C8 aromatics as raw materials; the reaction temperature was 550°C; and the weight hourly space velocity (WHSV) of the C8 aromatics was 0.5 h⁻¹. -1 The reaction pressure is 3 MPa, and the molar ratio of total hydrogen to C8 aromatics is 4.

[0067] In this example, there are four catalyst beds, with hydrogen introduced in four separate stages via bypasses to the top of the catalyst beds. A cooling feedstock is introduced near the reactor outlet. The cooling feedstock is 10% of the aromatic feedstock mass. In this example, the cooling feedstock is the same as the aromatic feedstock, both using C8 aromatics.

[0068] The catalyst evaluation results for this example are shown in Table 1.

[0069] Example 4

[0070] 1. Take 100g of alumina and impregnate it with cerium nitrate using the equal volume impregnation method. After completion, dry it at 120℃ for 5 hours and then calcine it at 550℃ for 10 hours to obtain cerium-modified alumina.

[0071] The cerium-modified alumina was treated with steam at 550°C for 10 hours, and then dried at 120°C for 5 hours to obtain composite modified alumina.

[0072] The above-mentioned composite modified alumina was impregnated with chromium nitrate and nickel nitrate by equal volume impregnation method. After completion, it was dried at 90°C for 10 hours and then calcined at 700°C for 5 hours to obtain an aromatic catalytic hydrogenation dealkylation catalyst.

[0073] The catalyst comprises: 78.5% alumina, 15% Cr2O3, 2.5% NiO, and 4% CeO2.

[0074] 2. Using aromatic hydrocarbon catalytic hydrogenation dealkylation catalysts for toluene catalytic hydrogenation dealkylation reactions.

[0075] The reaction conditions were as follows: toluene was used as the raw material, the reaction temperature was 600°C, and the toluene weight hourly space velocity (WHSV) was 1.0 h⁻¹. -1 The reaction pressure is 3 MPa, and the molar ratio of total hydrogen to toluene is 5. In this example, there are four catalyst beds, and hydrogen is introduced into the top of the catalyst beds in four separate stages via bypasses. Cooling feedstock is introduced near the reactor outlet. The cooling feedstock is 5% of the aromatic feedstock mass. In this example, the cooling feedstock is the same as the aromatic feedstock, which is toluene.

[0076] The catalyst evaluation results for this example are shown in Table 1.

[0077] Example 5

[0078] The catalyst preparation was the same as in Example 1. The difference in catalyst evaluation conditions compared to Example 1 was that the cooling feedstock was 20% of the mass of the aromatic feedstock.

[0079] Comparative Example 1

[0080] The difference from Example 1 is that hydrogen was not fed in stages during the reaction process.

[0081] 1. Take 100g of alumina and impregnate it with lanthanum nitrate by the equal volume impregnation method. After completion, dry it at 120℃ for 5 hours and then calcine it at 700℃ for 5 hours to obtain lanthanum-modified alumina.

[0082] The above-mentioned lanthanum-modified alumina was treated with steam at 700°C for 2 hours, and then dried at 120°C for 5 hours after treatment to obtain composite-modified alumina.

[0083] The above-mentioned composite modified alumina was impregnated with chromium nitrate and nickel nitrate by equal volume impregnation method. After completion, it was dried at 90°C for 10 hours and then calcined at 700°C for 5 hours to obtain an aromatic catalytic hydrogenation dealkylation catalyst.

[0084] The catalyst comprises: 80.5% alumina, 15% Cr2O3, 2.5% NiO, and 2% La2O3.

[0085] 2. Using aromatic hydrocarbon catalytic hydrogenation dealkylation catalysts for toluene catalytic hydrogenation dealkylation reactions.

[0086] The reaction conditions were as follows: toluene was used as the raw material, the reaction temperature was 590°C, and the toluene weight hourly space velocity (WHSV) was 1.0 h⁻¹. -1 The reaction pressure is 3 MPa, and the molar ratio of total hydrogen to toluene feedstock is 3.5. In this example, there are four catalyst beds; along the feed direction, all hydrogen is fed from above the first catalyst bed.

[0087] Inside the reactor, a cooling feedstock is introduced near the reactor outlet. The cooling feedstock is 5% of the aromatic feedstock mass. In this example, the cooling feedstock is the same as the aromatic feedstock, which is toluene.

[0088] The catalyst evaluation results for this example are shown in Table 1.

[0089] Comparative Example 2

[0090] The difference from Example 1 is that no water vapor treatment was performed during the catalyst preparation process.

[0091] 1. Take 100g of alumina and impregnate it with lanthanum nitrate by the equal volume impregnation method. After completion, dry it at 120℃ for 5 hours and then calcine it at 700℃ for 5 hours to obtain lanthanum-modified alumina.

[0092] The modified alumina was impregnated with chromium nitrate and nickel nitrate by an equal-volume impregnation method. After the impregnation was completed, it was dried at 90°C for 10 hours and then calcined at 700°C for 5 hours to obtain an aromatic catalytic hydrogenation dealkylation catalyst.

[0093] The catalyst comprises: 80.5% alumina, 15% Cr2O3, 2.5% NiO, and 2% La2O3.

[0094] 2. Using aromatic hydrocarbon catalytic hydrogenation dealkylation catalysts for toluene catalytic hydrogenation dealkylation reactions.

[0095] The catalyst was tested under the same conditions as in Example 1, and the evaluation results are shown in Table 1.

[0096] Comparative Example 3

[0097] The difference from Example 1 is that the catalyst does not contain rare earth elements.

[0098] 1. Take 100g of alumina and treat it under 700℃ steam for 2 hours. After treatment, dry it at 120℃ for 5 hours to obtain modified alumina.

[0099] The modified alumina was impregnated with chromium nitrate and nickel nitrate by an equal-volume impregnation method. After the impregnation was completed, it was dried at 90°C for 10 hours and then calcined at 700°C for 5 hours to obtain an aromatic catalytic hydrogenation dealkylation catalyst.

[0100] The catalyst comprises 15% Cr2O3, 2.5% NiO, and the balance being alumina.

[0101] 2. Using aromatic hydrocarbon catalytic hydrogenation dealkylation catalysts for toluene catalytic hydrogenation dealkylation reactions.

[0102] The test was conducted under the same conditions as in Example 1, and the test results are shown in Table 1.

[0103] Comparative Example 4

[0104] The difference from Example 1 is that only a single metal active center is used in the catalyst preparation process.

[0105] 1. Take 100g of alumina and impregnate it with lanthanum nitrate by the equal volume impregnation method. After completion, dry it at 120℃ for 5 hours and then calcine it at 700℃ for 5 hours to obtain lanthanum-modified alumina.

[0106] The above-mentioned lanthanum-modified alumina was treated with steam at 700°C for 2 hours, and then dried at 120°C for 5 hours after treatment to obtain composite-modified alumina.

[0107] The above-mentioned composite modified alumina was impregnated with chromium nitrate by an equal-volume impregnation method. After completion, it was dried at 90°C for 10 hours and then calcined at 700°C for 5 hours to obtain an aromatic catalytic hydrogenation dealkylation catalyst.

[0108] The catalyst comprises 15% Cr2O3, 2% La2O3, and the balance being alumina.

[0109] 2. Using aromatic hydrocarbon catalytic hydrogenation dealkylation catalysts for toluene catalytic hydrogenation dealkylation reactions.

[0110] The test was conducted under the same conditions as in Example 1, and the test results are shown in Table 1.

[0111] Comparative Example 5

[0112] The difference from Example 1 is that only a single metal active center is used in the catalyst preparation process.

[0113] 1. Take 100g of alumina and impregnate it with lanthanum nitrate by the equal volume impregnation method. After completion, dry it at 120℃ for 5 hours and then calcine it at 700℃ for 5 hours to obtain lanthanum-modified alumina.

[0114] The above-mentioned lanthanum-modified alumina was treated with steam at 700°C for 2 hours, and then dried at 120°C for 5 hours after treatment to obtain composite-modified alumina.

[0115] The above-mentioned composite modified alumina was impregnated with nickel nitrate by an equal-volume impregnation method. After completion, it was dried at 90°C for 10 hours and then calcined at 700°C for 5 hours to obtain an aromatic catalytic hydrogenation dealkylation catalyst.

[0116] The catalyst comprises 2.5% NiO, 2% La2O3, and the balance being alumina.

[0117] 2. Using aromatic hydrocarbon catalytic hydrogenation dealkylation catalysts for toluene catalytic hydrogenation dealkylation reactions.

[0118] The test was conducted under the same conditions as in Example 1, and the test results are shown in Table 1.

[0119] Comparative Example 6

[0120] The difference from Example 1 is that toluene feedstock is not introduced near the reactor outlet to reduce the outlet temperature.

[0121] 1. The catalyst was prepared using the same method as in Example 1. The catalyst composition included: 80.5% alumina, 2% La2O3, 15% Cr2O3, and 2.5% NiO.

[0122] 2. Using aromatic hydrocarbon catalytic hydrogenation dealkylation catalysts for toluene catalytic hydrogenation dealkylation reactions.

[0123] The reaction conditions were as follows: toluene was used as the raw material, the reaction temperature was 590°C, and the toluene weight hourly space velocity (WHSV) was 1.0 h⁻¹. -1 The reaction pressure was 3 MPa, and the total molar ratio of hydrogen to toluene was 3.5. In this example, there were four catalyst beds, and hydrogen was introduced into the top of the catalyst beds through four separate bypasses.

[0124] Inside the reactor, no cooling feedstock is introduced near the reactor outlet to reduce the material outlet temperature. The catalyst evaluation results for this example are shown in Table 1.

[0125] Table 1 Performance of Aromatic Hydrogenation Dealkylation Reaction

[0126]

[0127] The specific embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. The application of a catalyst in the catalytic hydrogenation and dealkylation reaction of aromatics, characterized in that, The aromatic hydrocarbon catalytic hydrogenation dealkylation catalyst used in the application comprises alumina, a first modified metal, a second modified metal, and rare earth metal elements. The first modified metal is Cr; The second modified metal includes at least one of Co, Ni, and Rh; The rare earth metal element includes at least one of La, Ce, and Re; Based on the mass of the catalyst, the catalyst comprises: The alumina content, calculated as oxides, is 78% to 98.8%. The content of the first modified metal, calculated as oxide, is 1% to 20%; The content of the second modified metal, calculated as oxide, is 0.01% to 10%. The content of the rare earth metal oxide, calculated as oxide, is 0.1% to 4%. The method for preparing the catalyst includes the following steps: (1) Alumina is impregnated with an impregnation solution containing rare earth metal elements, and then dried and calcined to obtain rare earth modified alumina; (2) The rare earth modified alumina obtained in step (1) is treated under steam conditions; (3) The product obtained in step (2) is impregnated in an impregnation solution containing the first modified metal and the second modified metal, dried, and calcined to obtain the catalyst; The conditions for steam treatment in step (2) are: treatment temperature 550~700℃, treatment time 2~10 hours.

2. The application according to claim 1, characterized in that, In the presence of hydrogen, the aromatic feedstock reacts with the catalyst in a reactor to produce a benzene-containing stream.

3. The application according to claim 2, characterized in that, The reactor is provided with at least two catalyst beds; hydrogen is introduced from above each catalyst bed; each catalyst bed is filled with the catalyst.

4. The application according to claim 3, characterized in that, The same amount of hydrogen is introduced into each catalyst bed.

5. The application according to claim 3, characterized in that, The number of catalyst beds is 2 to 5.

6. The application according to claim 3, characterized in that, The catalyst bed consists of 3 to 4 layers.

7. The application according to any one of claims 1 to 6, characterized in that, Cooling feedstock is introduced near the reactor outlet; the cooling feedstock is mixed with the reaction products and then enters the separation system to obtain a benzene-containing stream.

8. The application according to claim 7, characterized in that, The cooling feedstock is an aromatic hydrocarbon; the aromatic hydrocarbon includes toluene, C8 aromatic hydrocarbons, and C9 aromatic hydrocarbons. + At least one of the aromatic hydrocarbons.

9. The application according to claim 8, characterized in that, The amount of cooling feedstock introduced is 5 wt% to 20 wt% of the mass of the aromatic feedstock.

10. The application according to claim 9, characterized in that, The amount of cooling feedstock introduced is 5 wt% to 18 wt% of the mass of the aromatic feedstock.

11. The application according to claim 1, characterized in that, The reaction conditions include: a reaction temperature of 450~750℃; and a weight hourly space velocity (WHSV) of 0.5~2h for the aromatic feedstock. -1 The total hydrogen content / molar ratio of aromatic feedstock is 2~8; the reaction pressure is 2~6 MPa.

12. The application according to claim 11, characterized in that, The reaction conditions include: a reaction temperature of 550~600℃; and a weight hourly space velocity (WHSV) of 0.5~1 h⁻¹ for the aromatic feedstock. -1 The total hydrogen content / molar ratio of aromatic feedstock is 3~6; the reaction pressure is 3~4 MPa.

13. The application according to claim 1, characterized in that, Based on the mass of the catalyst, the catalyst comprises: The content of alumina, calculated as oxides, is 78% to 94%. The content of the first modified metal, calculated as oxide, is 5% to 15%; The content of the second modified metal, calculated as oxide, is 0.1% to 5%; The content of the rare earth metal oxide is 0.5% to 2.0% based on oxides.

14. The application according to claim 1, characterized in that, The calcination conditions in step (1) are: calcination temperature 550~700℃, calcination time 1~10h.

15. The application according to claim 1, characterized in that, The conditions for immersion in step (3) are: immersion temperature 20~50℃, time 1~24h; And / or, the drying temperature in step (3) is 90~150℃ and the drying time is 1~10 hours; And / or, the roasting temperature in step (3) is 550~700℃ and the roasting time is 1~10 hours.

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