Method for improving stability and selectivity of aromatic hydrocarbon hydrodealkylation catalyst
By pre-reaction treatment of the aromatic hydrodealkylation catalyst, the problem of catalyst accumulation at high temperatures is solved, and the stability of the catalyst and the selectivity of light aromatic hydrocarbons are improved.
Patent Information
- Application Number
- CN202311226230.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-09-21
- Publication Date
- 2025-03-21
AI Technical Summary
The existing aromatic hydrodealkylation catalysts are used at high temperatures, resulting in the catalyst's carbon accumulation, affecting its stability and selectivity.
Pretreatment of the catalyst by pre-reaction, including contacting the catalyst with hydrogen and aromatic feedstock, or pre-reactioning the catalyst with nitrogen and aromatic feedstock, with the aim of covering the high active position of the catalyst and reducing the inactivation rate.
The stability of aromatic hydrodealkylation catalyst and the selectivity of light aromatic hydrocarbons are improved, and the carbon deposit phenomenon of catalysts is reduced.
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Abstract
Description
Technical Field
[0001] The invention relates to the field of catalytic conversion of aromatic hydrocarbons, and more particularly to a method for improving the stability and selectivity of an aromatic hydrocarbon hydrodealkylation catalyst. Background Art
[0002] In recent years, the load of styrene, phenol, caprolactam and other equipment in China and the newly built production capacity have been continuously increasing, which has led to an increasing market demand for benzene and a continuous rise in the market price of benzene. Therefore, there is a growing demand for efficient technologies for producing light aromatics such as benzene. At present, the technology for producing benzene by hydrodealkylation of aromatics uses alkylbenzene as raw material, removes the side chain substituents of alkylbenzene through hydrodealkylation reaction, and then converts them into light aromatics benzene, toluene and xylene. At present, aromatic dealkylation technology includes thermal hydrodealkylation and catalytic hydrodealkylation processes, of which the operating temperature of thermal hydrodealkylation is 750-780°C, while catalytic hydrodealkylation has the characteristics of low operating temperature (600-650°C), high selectivity of light aromatic products, and low aromatic ring loss rate, and is widely favored by enterprises.
[0003] The reaction temperature of the composite metal oxide aromatic catalytic hydrodealkylation catalyst in the existing aromatic catalytic hydrodealkylation catalyst system is high, and the aromatic raw material inevitably causes carbon deposition on the catalyst, affecting its stability. There are two commonly used methods at present: (1) modifying the Cr2O3 / Al2O3 catalyst, such as introducing KF to change the type and number of acid centers to improve the catalyst performance and stability (Development of poly-functional catalyst forbenzene production from pyrolysis gasoline. Appl. Catal. A, 2003, 238 (2): 279-287), and introducing CeO2 to improve the catalyst's anti-coking ability and stability (Development of a new type of catalyst for benzene production by hydrodealkylation [J]. Petrochemicals, 1990, 19 (5): 283-287); (2) reducing the severity of operating conditions and frequent catalyst burning and regeneration, such as (Countermeasures and inspiration for the early activity decline of the hydrogenation catalyst in Baosteel Letoll hydrogenation unit [J]. Modern Chemical Industry, 2010, 30 (1): 71-73). The above two methods have the problems of complex additive modification and frequent regeneration affecting production progress. Summary of the invention
[0004] In view of the problems in the prior art that the temperature of the catalytic hydrodealkylation reaction of aromatics is high, the aromatic raw materials inevitably cause carbon deposition on the catalyst, and affect its stability, the present invention provides a method for improving the stability and selectivity of the aromatic hydrodealkylation catalyst. The method effectively covers the high activity sites of the catalyst, reduces the catalyst deactivation rate, and thus improves the stability of the aromatic hydrodealkylation catalyst and the selectivity of light aromatics.
[0005] The present invention provides a method for improving the stability and selectivity of an aromatic hydrocarbon hydrodealkylation catalyst, the method comprising the following steps:
[0006] (a) Using at least one of the methods (a1), (a2), and (a3):
[0007] (a1) contacting an aromatic hydrocarbon catalytic hydrodealkylation catalyst with hydrogen and an aromatic hydrocarbon feedstock to conduct a pre-reaction, wherein the reaction temperature is T1, the hydrogen-to-hydrocarbon molar ratio is H1, the aromatic hydrocarbon feedstock mass space velocity is W1, the reaction pressure is P1, and the reaction time is t1;
[0008] (a2) contacting an aromatic hydrocarbon catalytic hydrodealkylation catalyst with hydrogen and an aromatic hydrocarbon feedstock to conduct a pre-reaction, wherein the reaction temperature is T3, the hydrogen-to-hydrocarbon molar ratio is H2, the aromatic hydrocarbon feedstock mass space velocity is W1, the reaction pressure is P2, and the reaction time is t2;
[0009] (a3) contacting an aromatic hydrocarbon catalytic hydrodealkylation catalyst with nitrogen and an aromatic hydrocarbon feedstock to conduct a pre-reaction, wherein the reaction temperature is T2, the nitrogen-to-hydrocarbon molar ratio is N1, the aromatic hydrocarbon feedstock mass space velocity is W2, the reaction pressure is P1, and the reaction time is t3;
[0010] (b) contacting the catalyst after the pre-reaction in step (a) with an aromatic hydrocarbon feedstock under hydrogenation conditions to carry out a hydrodealkylation reaction, wherein the reaction temperature is T2, the hydrogen-to-hydrocarbon molar ratio is H2, the mass space velocity of the aromatic hydrocarbon feedstock is W1, and the reaction pressure is P1;
[0011] In the method, 10°C≤T2-T1≤100°C; 1≤H2-H1≤5; 10°C≤T3-T2≤100°C; 1≤N1 / H2≤5; 1.5≤P2 / P1≤2; 0.01≤W2 / W1≤0.05; t2 <t1。
[0012] Furthermore, in the method, the reaction time t1 of step (a1) is 10 to 200 hours, preferably 24 to 48 hours.
[0013] Furthermore, in the method, the reaction time t2 of step (a2) is 1 to 48 hours, preferably 10 to 24 hours.
[0014] Furthermore, in the method, 12h≤t1-t2≤24h
[0015] Furthermore, in the method, the reaction time t3 of step (a3) is 0.5 to 20 hours, preferably 1 to 3 hours.
[0016] Furthermore, in the method, 20°C≤T2-T1≤40°C; 2≤H2-H1≤3.
[0017] Furthermore, in the method, 30°C≤T3-T2≤50°C.
[0018] Furthermore, in the method, 1.5≤N1 / H2≤3.
[0019] Furthermore, in the method, the value of W1 in steps (a1), (a2) and (b) may be the same or different.
[0020] Furthermore, in the method, the value of P1 in steps (a1), (a3) and (b) may be the same or different.
[0021] Furthermore, in the method, the aromatic hydrocarbon catalytic hydrodealkylation catalyst in step (b) comprises an active component Cr2O3 and a carrier alumina, the mass content of Cr2O3 in the catalyst is 10% to 15%, and the mass content of alumina in the catalyst is 85% to 90%.
[0022] Furthermore, the preparation method of the aromatic hydrocarbon catalytic hydrodealkylation catalyst can be prepared by conventional methods, preferably by impregnating alumina with active metal, drying, and calcining to obtain the catalyst. Among them, the drying and calcining can be carried out under conventional conditions in the art. The active metal can be impregnated to reach the loading amount.
[0023] Furthermore, the aromatic hydrocarbon catalytic hydrogenation dealkylation reaction product is subjected to gas-liquid separation to obtain gas phase and liquid phase products respectively.
[0024] Furthermore, in the method, the aromatic hydrocarbons in the aromatic hydrocarbon feedstock are monocyclic aromatic hydrocarbons, which can be selected from toluene, C8 aromatic hydrocarbons, C9 / C 10 At least one of aromatic hydrocarbons, preferably C9 / C 10 Aromatics (i.e. C9 aromatics and / or C 10 Aromatic hydrocarbons). Wherein, the C9 / C 10 The source of aromatic hydrocarbons is not particularly limited, for example, but not limited to at least one of the products from catalytic reforming, pyrolysis gasoline hydrogenation, hydrocracking, etc., wherein the aromatic hydrocarbon raw materials include C9 aromatic hydrocarbons and C 10 The mass content of aromatics is more than 95%.
[0025] Furthermore, in the method, the reaction conditions of step (b) are: the reaction temperature T2 is 500-800°C, the weight space velocity W1 of the aromatic hydrocarbon feedstock is 0.5-5h-1 , the hydrogen-to-hydrocarbon molar ratio H2 is 1 to 10, the reaction pressure P1 is 1 to 10 MPa; preferably, the reaction temperature T2 is 550 to 650°C, and the weight space velocity W1 of the aromatic hydrocarbon feedstock is 1 to 2 h -1 , the hydrogen-to-hydrocarbon molar ratio H2 is 5 to 7, and the reaction pressure P1 is 4 to 6 MPa.
[0026] Compared with the prior art, the advantages of the present invention are:
[0027] The method of the present invention pretreats the catalyst for catalytic hydrogenation and dealkylation of aromatics through a pre-reaction, and then performs a hydrogenation and dealkylation reaction under normal conditions. The inventors find that the high-activity defect sites of the Cr2O3 active center after the pretreatment are covered to an appropriate degree, which can suppress the saturated hydrogenation side reaction of aromatics caused by the defect sites on the one hand, and avoid the continuous growth of carbon dendrites at the high-activity defect sites during the dealkylation reaction to cover the metal oxide active center on the other hand, thereby improving the stability of the catalyst for catalytic hydrogenation and dealkylation of aromatics and improving the selectivity of light aromatics (benzene, toluene, xylene). BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1 is the reaction conversion rate of the embodiments and comparative examples;
[0029] Figure 2 It is the reaction selectivity of the embodiment and the comparative example. DETAILED DESCRIPTION
[0030] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.
[0031] The raw materials used in the examples and comparative examples of the present invention are commercially available and have an analytical purity (AR).
[0032] Example 1
[0033] Take 100g of alumina and use the equal volume impregnation method to impregnate chromium nitrate to dissolve it. After the impregnation is completed, air dry it at 120°C for 5 hours and air roast it at 650°C for 3 hours to obtain an aromatic catalytic hydrogenation dealkylation catalyst. The mass content of Cr2O3 in the catalyst is 15%, and the mass content of alumina in the catalyst is 85%.
[0034] The above catalyst is placed in a fixed bed reaction tube, and aromatic raw materials and hydrogen are introduced. The aromatic raw materials are C9 / C 10 , among which C9 aromatics and C 10 The mass content of aromatics is 100%.10 The weight space velocity of aromatic feedstock is 1h -1 , reaction temperature 580 ℃, hydrogen hydrocarbon molar ratio of 2, reaction pressure 5.0MPa, pre-reaction 48 hours. After the pre-reaction, the reaction was carried out under the following conditions: C9 / C 10 The weight space velocity of aromatic feedstock is 1h -1 , reaction temperature 610℃, hydrogen-to-hydrocarbon molar ratio 5, reaction pressure 5.0MPa, reaction performance results are shown in Figure 1 and Figure 2 .
[0035] Example 2
[0036] Take 100g of alumina and use the equal volume impregnation method to impregnate chromium nitrate to dissolve it. After the impregnation is completed, air dry it at 120°C for 5 hours and air roast it at 650°C for 3 hours to obtain a catalytic hydrogenation and dealkylation catalyst for aromatics. The mass content of Cr2O3 in the catalyst is 10%, and the mass content of alumina in the catalyst is 90%.
[0037] The above catalyst was placed in a fixed bed reaction tube, and aromatic hydrocarbon feedstock (same as in Example 1) and hydrogen were introduced, C9 / C 10 The weight space velocity of aromatic feedstock is 1h -1 , reaction temperature 660 ℃, hydrogen hydrocarbon molar ratio of 5, reaction pressure 10.0MPa, pre-reaction 10 hours. After the pre-reaction, the reaction was carried out under the following conditions: C9 / C 10 The weight space velocity of aromatic feedstock is 1h -1 , reaction temperature 610℃, hydrogen-to-hydrocarbon molar ratio 5, reaction pressure 5.0MPa, reaction performance results are shown in Figure 1 and Figure 2 .
[0038] Example 3
[0039] Take 100g of alumina and use the equal volume impregnation method to impregnate chromium nitrate to dissolve it. After the impregnation is completed, air dry it at 120°C for 5 hours and air roast it at 650°C for 3 hours to obtain a catalytic hydrogenation and dealkylation catalyst for aromatics. The content of Cr2O3 in the catalyst is 12%, and the mass content of alumina in the catalyst is 88%.
[0040] The above catalyst was placed in a fixed bed reaction tube, and aromatic hydrocarbon feedstock (same as in Example 1) and nitrogen were introduced. 10 The weight space velocity of aromatic feedstock is 0.05h -1 , reaction temperature 610 ℃, nitrogen hydrocarbon molar ratio of 10, reaction pressure 5.0MPa, pre-reaction for 1 hour. After the pre-reaction, nitrogen was replaced with hydrogen, so that the reaction was carried out under the following conditions: C9 / C 10 The weight space velocity of aromatic feedstock is 1h-1 , reaction temperature 610℃, hydrogen-to-hydrocarbon molar ratio 5, reaction pressure 5.0MPa, reaction performance results are shown in Figure 1 and Figure 2 .
[0041] Example 4
[0042] Take 100g of alumina and use the equal volume impregnation method to impregnate chromium nitrate to dissolve it. After the impregnation is completed, air dry it at 120°C for 5 hours and air roast it at 650°C for 3 hours to obtain an aromatic catalytic hydrogenation dealkylation catalyst. The mass content of Cr2O3 in the catalyst is 12%, and the mass content of alumina in the catalyst is 88%.
[0043] The above catalyst was placed in a fixed bed reaction tube, and aromatic hydrocarbon feedstock (same as in Example 1) and hydrogen were introduced, C9 / C 10 The weight space velocity of aromatic feedstock is 1h -1 The reaction temperature was 580°C, the hydrogen-to-hydrocarbon molar ratio was 2, and the reaction pressure was 5.0 MPa. The pre-reaction was carried out for 24 hours. Then the hydrogen was switched to nitrogen. 10 The weight space velocity of aromatic feedstock is 0.05h -1 , reaction temperature 610 ℃, nitrogen hydrocarbon molar ratio of 15, reaction pressure 5.0MPa, pre-reaction for 3 hours. After the pre-reaction, nitrogen was replaced with hydrogen, so that the reaction was carried out under the following conditions: C9 / C 10 The weight space velocity of aromatic feedstock is 1h -1 , reaction temperature 610℃, hydrogen-to-hydrocarbon molar ratio 5, reaction pressure 5.0MPa, reaction performance results are shown in Figure 1 and Figure 2 .
[0044] Comparative Example 1
[0045] Take 100g of alumina and use the equal volume impregnation method to impregnate chromium nitrate to dissolve it. After the impregnation is completed, air dry it at 120°C for 5 hours and air roast it at 650°C for 3 hours to obtain an aromatic catalytic hydrogenation dealkylation catalyst. The mass content of Cr2O3 in the catalyst is 15%, and the mass content of alumina in the catalyst is 85%.
[0046] The above catalyst was placed in a fixed bed reaction tube, and aromatic hydrocarbon feedstock (same as in Example 1) and hydrogen were introduced, C9 / C 10 The weight space velocity of aromatic feedstock is 1h -1 , reaction temperature 610 ℃, hydrogen hydrocarbon molar ratio of 5, reaction pressure 5.0MPa, the reaction performance results are shown in Figure 1 and Figure 2 .
[0047] Comparative Example 2
[0048] Take 100g of alumina and use the equal volume impregnation method to impregnate chromium nitrate to dissolve it. After the impregnation is completed, air dry it at 120°C for 5 hours and air roast it at 650°C for 3 hours to obtain an aromatic catalytic hydrogenation dealkylation catalyst. The mass content of Cr2O3 in the catalyst is 15%, and the mass content of alumina in the catalyst is 85%.
[0049] The above catalyst was placed in a fixed bed reaction tube, and aromatic hydrocarbon feedstock (same as in Example 1) and hydrogen were introduced, C9 / C 10 The weight space velocity of aromatic feedstock is 1h -1 , reaction temperature 620 ℃, hydrogen hydrocarbon molar ratio of 2, reaction pressure 5.0MPa, pre-reaction 48 hours. After the pre-reaction, the reaction was carried out under the following conditions: C9 / C 10 The weight space velocity of aromatic feedstock is 1h -1 , reaction temperature 610℃, hydrogen-to-hydrocarbon molar ratio 5, reaction pressure 5.0MPa, reaction performance results are shown in Figure 1 and Figure 2 .
[0050] Comparative Example 3
[0051] Take 100g of alumina and use the equal volume impregnation method to impregnate chromium nitrate to dissolve it. After the impregnation is completed, air dry it at 120°C for 5 hours and air roast it at 650°C for 3 hours to obtain a catalytic hydrogenation and dealkylation catalyst for aromatics. The mass content of Cr2O3 in the catalyst is 10%, and the mass content of alumina in the catalyst is 90%.
[0052] The above catalyst was placed in a fixed bed reaction tube, and aromatic hydrocarbon feedstock (same as in Example 1) and hydrogen were introduced, C9 / C 10 The weight space velocity of aromatic feedstock is 1h -1 , reaction temperature 660 ° C, hydrogen hydrocarbon molar ratio of 5, reaction pressure 6.0MPa, pre-reaction for 10 hours. After the pre-reaction, the reaction was carried out under the following conditions: C9 / C 10 The weight space velocity of aromatic feedstock is 1h -1 , reaction temperature 610℃, hydrogen-to-hydrocarbon molar ratio 5, reaction pressure 5.0MPa, reaction performance results are shown in Figure 1 and Figure 2 .
[0053] Comparative Example 4
[0054] Take 100g of alumina and use the equal volume impregnation method to impregnate chromium nitrate to dissolve it. After the impregnation is completed, air dry it at 120°C for 5 hours and air roast it at 650°C for 3 hours to obtain a catalytic hydrogenation and dealkylation catalyst for aromatics. The content of Cr2O3 in the catalyst is 12%, and the mass content of alumina in the catalyst is 88%.
[0055] The above catalyst was placed in a fixed bed reaction tube, and aromatic hydrocarbon feedstock (same as in Example 1) and nitrogen were introduced. 10 The weight space velocity of aromatic feedstock is 0.08h -1 , reaction temperature 610 ° C, nitrogen hydrocarbon molar ratio of 5, reaction pressure 5.0MPa, pre-reaction for 1 hour. After the pre-reaction, nitrogen was replaced with hydrogen, so that the reaction was carried out under the following conditions: C9 / C 10 The weight space velocity of aromatic feedstock is 1h -1 , reaction temperature 610℃, hydrogen-to-hydrocarbon molar ratio 5, reaction pressure 5.0MPa, reaction performance results are shown in Figure 1 and Figure 2 .
[0056] The above detailed description of the specific implementation of the present invention, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the various technical features are combined in any other suitable manner, these simple modifications and combinations should also be regarded as the contents disclosed by the present invention, all belong to the protection scope of the present invention.
Claims
1. A method for improving the stability and selectivity of an aromatics hydrodealkylation catalyst, the method comprising the following steps: (a) Using at least one of the methods (a1), (a2), and (a3): (a1) contacting an aromatic hydrocarbon catalytic hydrodealkylation catalyst with hydrogen and an aromatic hydrocarbon feedstock to conduct a pre-reaction, wherein the reaction temperature is T1, the hydrogen-to-hydrocarbon molar ratio is H1, the aromatic hydrocarbon feedstock mass space velocity is W1, the reaction pressure is P1, and the reaction time is t1; (a2) contacting an aromatic hydrocarbon catalytic hydrodealkylation catalyst with hydrogen and an aromatic hydrocarbon feedstock to conduct a pre-reaction, wherein the reaction temperature is T3, the hydrogen-to-hydrocarbon molar ratio is H2, the aromatic hydrocarbon feedstock mass space velocity is W1, the reaction pressure is P2, and the reaction time is t2; (a3) contacting an aromatic hydrocarbon catalytic hydrodealkylation catalyst with nitrogen and an aromatic hydrocarbon feedstock to conduct a pre-reaction, wherein the reaction temperature is T2, the nitrogen-to-hydrocarbon molar ratio is N1, the aromatic hydrocarbon feedstock mass space velocity is W2, the reaction pressure is P1, and the reaction time is t3; (b) contacting the catalyst after the pre-reaction in step (a) with an aromatic hydrocarbon feedstock for a hydrogenation dealkylation reaction under hydrogenation conditions, wherein the reaction temperature is T2, the hydrogen-to-hydrocarbon molar ratio is H2, the mass space velocity of the aromatic hydrocarbon feedstock is W1, and the reaction pressure is P1; In the method, 10°C≤T2-T1≤100°C; 1≤H2-H1≤5; 10°C≤T3-T2≤100°C; 1≤N1 / H2≤5; 1.5≤P2 / P1≤2; 0.01≤W2 / W1≤0.05; t2 <t1。 2. The method according to claim 1, characterized in that The reaction time t1 of step (a1) is 10 to 200 hours, preferably 24 to 48 hours; optionally, the reaction time t2 of (a2) is 1 to 48 hours, preferably 10 to 24 hours; optionally, the reaction time t3 of step (a3) is 0.5 to 20 hours, preferably 1 to 3 hours.
3. The method according to claim 1, characterized in that In the method, 20°C≤T2-T1≤40°C; 2≤H2-H1≤3.
4. The method according to claim 1, characterized in that: In the method, 30°C≤T3-T2≤50°C.
5. The method according to claim 1, characterized in that In the method, 1.5≤N1 / H2≤3.
6. The method according to claim 1, characterized in that The aromatic hydrocarbon catalytic hydrodealkylation catalyst comprises an active component Cr2O3 and a carrier alumina.
7. The method according to claim 6, characterized in that The mass content of the Cr2O3 in the catalyst is 10% to 15%; optionally, the mass content of the aluminum oxide in the catalyst is 85% to 90%.
8. The method according to claim 1, characterized in that In the method, the aromatic raw materials are toluene, C8 aromatics, C9 / C 10 At least one of aromatic hydrocarbons, preferably C9 / C 10 Aromatic hydrocarbons.
9. The method according to claim 1, characterized in that: The reaction conditions of step (b) are: reaction temperature T2 is 500-800°C, and the weight space velocity W1 of the aromatic hydrocarbon feedstock is 0.5-5h -1 , the hydrogen-to-hydrocarbon molar ratio H2 is 1 to 10, and the reaction pressure P1 is 1 to 10 MPa.
10. The method according to claim 1, characterized in that The reaction conditions of step (b) are: reaction temperature T2 is 550-650°C, and the weight space velocity W1 of the aromatic hydrocarbon feedstock is 1-2h -1 , the hydrogen-to-hydrocarbon molar ratio H2 is 5 to 7, and the reaction pressure P1 is 4 to 6 MPa.