Process for producing paraxylene and co-producing dimethylnaphthalene

Abstract

The present application relates to the field of paraxylene production, and discloses a method for producing paraxylene and co-producing dimethylnaphthalene. The method comprises: separating C5 + raw materials to obtain C6, C7 and C8 + components; selectively performing hydrodealkylation reaction on the C8 + component to obtain C8 + product; performing aromatic hydrocarbon separation on the C8 + product to obtain C8 component, C9-C 10 component and C 10 + component; performing disproportionation and transalkylation reaction on at least part of the C9-C 10 component and the C7 component to obtain a product rich in dimethylbenzene; performing demethylation reaction on the C 10 + component to obtain C 10 -C 11 component and C 12 + component; performing transalkylation reaction on the C 10 -C 11 component and the remaining part of the C9-C 10 component to obtain a product rich in 2,6-dimethylnaphthalene. The method can realize high-value utilization of by-product naphthalene series and co-production of 2,6-dimethylnaphthalene.

Description

Technical Field

[0001] This invention relates to the field of para-xylene production, and more specifically to a method for producing para-xylene and concurrently producing dimethylnaphthalene. Background Technology

[0002] Traditional aromatics complexes include reforming, aromatics extraction, disproportionation and alkyl transfer units, C8 aromatics isomerization units, and p-xylene separation units (PX separation units), with the main target products being p-xylene and benzene. The disproportionation and alkyl transfer unit utilizes toluene and C9... + The production of benzene and thermodynamically balanced xylene is generally a hydrogen-gaseous gas-phase reaction. For example, CN103121915A discloses a method for the disproportionation and alkyl transfer of toluene with heavy aromatics. In this method, an auxiliary agent selected from alkaline earth metals or rare earth metals is introduced into the molecular sieve system. This reduces the strong acid centers on the surface of the molecular sieve, thereby weakening the deep demethylation reaction of the product xylene by the strong acid centers and achieving the goal of increasing the xylene yield.

[0003] The isomerization unit converts PX-depleted C8 aromatic hydrocarbon feedstocks into thermodynamically balanced C8 aromatic hydrocarbons, typically a gas-phase reaction. Based on different conversion routes for ethylbenzene, it is divided into two technologies: ethylbenzene conversion type and deethylation type. The former converts ethylbenzene to xylene, while the latter converts ethylbenzene to benzene through a deethylation reaction. CN110218142A discloses a method for preparing p-xylene by isomerization of m-xylene and o-xylene, using a metal-modified molecular sieve Me / HZSM-5 as a catalyst, where Me is Pt, Ag, Ni, Fe, Co, or Ga, achieving a high yield of p-xylene. CN112023978A discloses a xylene isomerization catalyst and its preparation method, comprising a composite support and platinum in a content of 0.01-0.1% by mass based on the composite support. The composite support comprises 30-90% by mass of HZSM-5 molecular sieve modified with Group IIA metals and 10-70% by mass of alumina. The catalyst can suppress the occurrence of disproportionation side reactions and has higher xylene yield and isomerization activity.

[0004] The main shortcomings of traditional aromatics complexes lie in the fact that the reforming products still contain 5-10% naphthalene compounds and other polycyclic aromatic hydrocarbons. These naphthalene compounds cannot be effectively utilized in the aromatics complex, reducing the economic efficiency of the unit. In addition, the operating energy and material consumption is relatively high. For example, the reactions that occur in the disproportionation and alkyl transfer and C8 aromatics isomerization units are all high-temperature gas-phase reactions, requiring a large amount of hydrogen circulation, resulting in high operating energy consumption and aromatics losses. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems existing in the prior art and provide a method for producing p-xylene and concurrently producing dimethylnaphthalene. The method provided by this invention enables high-value utilization of the byproduct naphthalene compounds, specifically the high-value byproduct 2,6-dimethylnaphthalene.

[0006] To achieve the above objectives, the present invention provides a method for producing p-xylene and co-producing dimethylnaphthalene, the method comprising the following steps:

[0007] (1) C5 containing aromatics + The raw materials were separated to obtain C6, C7 and C8. + Components; the C8 + The component undergoes selective hydrogenation and dealkylation to yield C8 compounds rich in polymethylbenzene and polymethylnaphthalene. + product;

[0008] (2) The C8 compound rich in polymethylbenzene and polymethylnaphthalene + The product was subjected to aromatic separation to obtain C8 fraction and C9-C fraction. 10 Components and C rich in naphthalene compounds 10 + Components;

[0009] (3) C9-C 10 At least a portion of the component undergoes disproportionation and alkyl transfer reaction with the C7 component to obtain a xylene-rich product; the xylene-rich product is then returned to the selective hydrogenation-dealkylation reaction in step (1);

[0010] (4) C rich in naphthalene compounds 10 + The component undergoes a demethylation reaction to yield C360 rich in naphthalene and methylnaphthalene. 10 -C 11 Components and C 12 + Components; the C-containing compound rich in naphthalene and methylnaphthalene 10 -C 11 Components and C9-C 10 The remaining portion of the component undergoes an alkyl transfer reaction to yield a product rich in 2,6-dimethylnaphthalene.

[0011] The beneficial effects of the present invention through the above technical solution include:

[0012] The method provided by this invention enables high-value utilization of naphthalene compounds, producing high-purity 2,6-dimethylnaphthalene as a byproduct, and has a higher utilization rate of heavy aromatic hydrocarbon resources.

[0013] In preferred cases, by employing liquid-phase disproportionation and alkyl transfer and liquid-phase aromatic isomerization reactions, the energy and material consumption of the equipment can be effectively reduced, and higher yields of benzene and p-xylene can be achieved. Attached Figure Description

[0014] Figure 1 This is the process flow provided by the present invention. Detailed Implementation

[0015] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0016] This invention provides a method for producing p-xylene and dimethylnaphthalene, the method comprising the following steps:

[0017] (1) C5 containing aromatics + The raw materials were separated to obtain C6, C7 and C8. + Components; the C8 + The component undergoes selective hydrogenation and dealkylation to yield C8 compounds rich in polymethylbenzene and polymethylnaphthalene. + product;

[0018] (2) The C8 compound rich in polymethylbenzene and polymethylnaphthalene + The product was subjected to aromatic separation to obtain C8 fraction and C9-C fraction. 10 Components and C rich in naphthalene compounds 10 + Components;

[0019] (3) C9-C 10 At least a portion of the component undergoes disproportionation and alkyl transfer reaction with the C7 component to obtain a xylene-rich product; the xylene-rich product is then returned to the selective hydrogenation-dealkylation reaction in step (1);

[0020] (4) C rich in naphthalene compounds 10 + The component undergoes a demethylation reaction to yield C360 rich in naphthalene and methylnaphthalene. 10 -C 11 Components and C 12 + Components; the C-containing compound rich in naphthalene and methylnaphthalene 10 -C 11 Components and C9-C 10 The remaining portion of the component undergoes an alkyl transfer reaction to yield a product rich in 2,6-dimethylnaphthalene.

[0021] Traditional aromatics complexes include reforming, aromatics extraction, disproportionation and alkyl transfer units, C8 aromatics isomerization units, and PX separation units, with the main target products being p-xylene and benzene. The main shortcomings of traditional aromatics complexes lie in the fact that the reforming products contain 5-10% condensed-ring aromatics such as naphthalene derivatives, which cannot be effectively utilized in the aromatics complex, reducing the economic efficiency of the unit. In addition, the operating energy and material consumption is high. For example, the reactions in the disproportionation and alkyl transfer units and the C8 aromatics isomerization units are high-temperature gas-phase reactions, requiring large amounts of hydrogen circulation, resulting in high operating energy consumption and aromatics losses. This invention provides a new method for producing p-xylene and concurrently producing 2,6-dimethylnaphthalene, by using reforming product oil (containing aromatics from C5...)... + The raw material first undergoes a selective hydrogenation-dealkylation reaction to remove C2 and above side-chain alkyl groups (e.g., ethyl, propyl, etc.), generating a product rich in polymethylbenzene and polymethylnaphthalene. A portion of the polymethylbenzene is converted to xylene via disproportionation and alkyl transfer reactions, while the polymethylnaphthalene reacts with the remaining polymethylbenzene via alkyl transfer reactions to generate a product rich in 2,6-dimethylnaphthalene. Compared to conventional processes, this invention's process produces C... 10 + Component A is significantly reduced, resulting in higher utilization of heavy aromatic hydrocarbon resources. In preferred cases, by employing liquid-phase disproportionation and alkyl transfer reactions as well as liquid-phase aromatic hydrocarbon isomerization reactions, energy and material consumption of the unit can be effectively reduced, and higher yields of benzene and p-xylene can be achieved.

[0022] According to the present invention, preferably, at least a portion of C9-C is involved in step (2). 10 Components and the remaining C9-C in step (4) 10 The mass flow ratio of the components is 1:0.1-1, specifically 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, and any range of two of these values, preferably 1:0.2-0.5. This preferred embodiment maximizes the production of p-xylene and 2,6-dimethylnaphthalene.

[0023] According to the present invention, preferably, the C6 component obtained in step (1) is subjected to aromatic extraction to obtain benzene. Using this preferred embodiment, a benzene product can be obtained.

[0024] The present invention does not particularly limit the specific method for the extraction of aromatics, and conventional methods in the art can be used. The present invention will not describe it in detail here.

[0025] According to the present invention, preferably, the C8 component obtained in step (2) is subjected to p-xylene separation to obtain p-xylene and C8 aromatic hydrocarbons containing p-xylene-depleted.

[0026] The present invention does not particularly limit the method of separating p-xylene, and conventional methods in the art can be used, such as adsorption separation, crystallization separation, etc.

[0027] More preferably, the C8 aromatic hydrocarbon containing p-xylene is subjected to an isomerization reaction and then returned to the aromatic hydrocarbon separation in step (2).

[0028] The isomerization reaction of this invention can be a gas-phase reaction or a liquid-phase reaction. Preferably, the isomerization reaction is a liquid-phase reaction. This preferred embodiment effectively reduces aromatic hydrocarbon loss; hydrogen does not require recycling, thus reducing operating energy consumption.

[0029] More preferably, the reaction temperature of the isomerization reaction is 200-500℃, more preferably 200-300℃.

[0030] The isomerization reaction described in this invention has a low temperature and requires less hydrogen, which helps reduce operating energy consumption and aromatic hydrocarbon loss. According to this invention, preferably, the reaction conditions for the isomerization reaction include: a reaction temperature of 200-500℃, preferably 200-300℃; a reaction pressure of 1-5 MPa; a hydrogen-to-hydrogen molecular ratio of 0.1-3; and a feed weight hourly space velocity of 3-15 h⁻¹. -1 .

[0031] According to the present invention, preferably, the isomerization reaction is carried out in the presence of a fifth catalyst.

[0032] The fifth catalyst described in this invention can be a conventional choice in the art. Preferably, the fifth catalyst comprises a fifth support and a noble metal supported on the fifth support, the fifth support comprising a molecular sieve selected from at least one of ZSM-5, EU-1, and MOR molecular sieves; the noble metal is preferably Pt and / or Pd.

[0033] According to the present invention, preferably, in the fifth carrier, the silicon-to-aluminum molar ratio of the molecular sieve is 3-60.

[0034] According to the present invention, preferably, the content of noble metals in the fifth catalyst, calculated as oxides, is 0.02-0.5% by weight, and more preferably 0.05-0.2% by weight.

[0035] According to the present invention, preferably, the fifth carrier further contains a heat-resistant inorganic oxide.

[0036] According to the present invention, preferably, based on the total weight of the fifth carrier, the content of the molecular sieve is 60-90% by weight, and the content of the heat-resistant inorganic oxide is 10-40% by weight.

[0037] The present invention has a wide range of choices for the types of heat-resistant inorganic oxides. Preferably, in the fifth carrier, the heat-resistant inorganic oxide is selected from at least one of silicon oxide, aluminum oxide, zirconium oxide and titanium oxide.

[0038] According to the present invention, preferably, the C8 + The component undergoes selective hydrogenation and dealkylation to yield C8 compounds rich in polymethylbenzene and polymethylnaphthalene. + Products and C7 - Components.

[0039] According to the present invention, preferably, the C7 - The components are returned to the separation process described in step (1).

[0040] According to the present invention, preferably, the reaction conditions for the selective hydrogenation dealkylation reaction in step (2) include: a reaction temperature of 350-450°C, a reaction pressure of 1-5 MPa, a hydrogen-to-hydrocarbon molecular ratio of 1-10, and a feed weight hourly space velocity of 3-20 h⁻¹. -1 .

[0041] According to the present invention, preferably, the selective hydrogenation dealkylation reaction in step (2) is carried out under the action of a first catalyst.

[0042] According to the present invention, preferably, the first catalyst comprises a first support and a first active component supported on the first support, the first support comprising a molecular sieve having ten-membered ring channels, preferably ZSM-5 and / or ZSM-11; the first active component is selected from at least one of Pt, Pd, Re and Ni.

[0043] According to the present invention, preferably, in the first carrier, the silicon-to-aluminum molar ratio of the molecular sieve is 10-80.

[0044] According to the present invention, preferably, the content of the first active component in the first catalyst, based on oxides, is 0.05-5% by weight, and more preferably 0.1-2% by weight.

[0045] According to the present invention, preferably, the first carrier further contains a heat-resistant inorganic oxide.

[0046] According to the present invention, preferably, based on the total weight of the first carrier, the content of the molecular sieve is 60-90% by weight, and the content of the heat-resistant inorganic oxide is 10-40% by weight.

[0047] The present invention has a wide range of choices for the types of heat-resistant inorganic oxides. Preferably, in the first carrier, the heat-resistant inorganic oxide is selected from at least one of silicon oxide, aluminum oxide, zirconium oxide and titanium oxide.

[0048] The disproportionation and alkyl transfer reaction of this invention can be a gas-phase reaction or a liquid-phase reaction. Preferably, the disproportionation and alkyl transfer reaction is a liquid-phase reaction. Using this preferred embodiment, aromatic hydrocarbon loss can be further reduced; hydrogen does not need to be recycled, and operating energy consumption is reduced.

[0049] More preferably, the reaction temperature of the disproportionation and alkyl transfer reaction in step (3) is 200-500℃, preferably 200-310℃.

[0050] According to the present invention, preferably, the reaction conditions for the disproportionation and alkyl transfer reaction in step (3) include: a reaction temperature of 200-500°C, preferably 200-310°C; a reaction pressure of 2-5 MPa; a hydrogen-to-hydrocarbon molecular ratio of 0.1-5; and a feed weight hourly space velocity of 1-5 h⁻¹. -1 .

[0051] According to the present invention, preferably, at least a portion of C9-C 10 The mass flow rate ratio of component C7 to component C7 is 0.2-5:1, preferably 0.5-2:1.

[0052] According to the present invention, preferably, the disproportionation and alkyl transfer reaction in step (3) is carried out under the action of a second catalyst.

[0053] According to the present invention, preferably, the second catalyst comprises a second support and a second active component supported on the second support, the second active component being selected from at least one of Ni, Pt, Mo and Pd; the second support comprises a molecular sieve having twelve-membered ring channels, preferably selected from at least one of MOR molecular sieve, BETA molecular sieve and Y molecular sieve.

[0054] Preferably, in the second carrier, the silicon-to-aluminum molar ratio of the molecular sieve is 3-50.

[0055] According to the present invention, preferably, the content of the second active component in the second catalyst, based on oxides, is 0.02-8% by weight, and more preferably 0.05-5% by weight.

[0056] According to the present invention, preferably, the second carrier further contains a heat-resistant inorganic oxide.

[0057] According to the present invention, preferably, based on the total weight of the second carrier, the content of the molecular sieve is 60-90% by weight, and the content of the heat-resistant inorganic oxide is 10-40% by weight.

[0058] The present invention has a wide range of choices for the types of heat-resistant inorganic oxides. Preferably, in the second carrier, the heat-resistant inorganic oxide is selected from at least one of silicon oxide, aluminum oxide, zirconium oxide and titanium oxide.

[0059] According to the present invention, preferably, the reaction conditions for the demethylation reaction in step (4) include: a reaction temperature of 500-700℃, a reaction pressure of 3-7 MPa, a hydrogen-to-hydrocarbon molecular ratio of 3-8, and a feed weight hourly space velocity of 0.5-2 h⁻¹. -1 .

[0060] According to the present invention, preferably, the demethylation reaction in step (4) is carried out under the action of a third catalyst, the third catalyst comprising a third support and a third active component supported on the third support, the third active component being selected from at least one of Cr, Pt and Ni; the third support is a heat-resistant inorganic oxide, preferably selected from at least one of silicon oxide, aluminum oxide, zirconium oxide and titanium oxide.

[0061] According to the present invention, preferably, the content of the third active component in the third catalyst, based on oxides, is 0.1-30% by weight, preferably 0.2-20% by weight.

[0062] According to the present invention, preferably, the reaction conditions for the alkyl transfer reaction in step (4) include: a reaction temperature of 250-450°C, a reaction pressure of 2-5 MPa, a hydrogen-to-hydrocarbon molecular ratio of 2-6, and a feed weight hourly space velocity of 0.5-3 h⁻¹. -1 .

[0063] According to the present invention, preferably, the C-rich naphthalene and methylnaphthalene-rich C-rich naphthalene ... 10 -C 11 Components and Remaining C9-C 10 The mass flow ratio of the components is 0.2-5:1, specifically 0.2:1, 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, and any two of these values ​​within a range, preferably 0.2-1.5:1.

[0064] According to the present invention, preferably, the alkyl transfer reaction in step (4) is carried out under the action of a fourth catalyst.

[0065] According to the present invention, preferably, the fourth catalyst comprises a fourth support and a fourth active component supported on the fourth support, the fourth active component being selected from at least one of Ni, Mo and Re; the fourth support comprises a molecular sieve having twelve-membered ring channels, preferably selected from at least one of MOR molecular sieve, BETA molecular sieve and Y molecular sieve.

[0066] Preferably, in the fourth carrier, the silicon-to-aluminum molar ratio of the molecular sieve is 3-50.

[0067] According to the present invention, preferably, the content of the fourth active component in the fourth catalyst, based on oxides, is 0.2-10% by weight, preferably 0.3-8% by weight.

[0068] According to the present invention, preferably, the fourth carrier further contains a heat-resistant inorganic oxide.

[0069] According to the present invention, preferably, based on the total weight of the fourth carrier, the content of the molecular sieve is 60-90% by weight, and the content of the heat-resistant inorganic oxide is 10-40% by weight.

[0070] The present invention has a wide range of choices for the types of heat-resistant inorganic oxides in the fourth carrier. Preferably, the heat-resistant inorganic oxides in the fourth carrier are selected from at least one of silicon oxide, aluminum oxide, zirconium oxide and titanium oxide.

[0071] The fourth catalyst described in this invention may also incorporate silicon, magnesium, and phosphorus elements. Generally, the performance of the fourth catalyst is improved by surface modification of the fourth support.

[0072] According to the present invention, preferably, the product rich in 2,6-dimethylnaphthalene obtained in step (4) is separated to obtain the 2,6-dimethylnaphthalene product.

[0073] The present invention does not particularly limit the separation method, and conventional separation methods in the art can be used. Preferably, the separation is distillation separation and / or crystallization separation.

[0074] The method described in this invention can obtain a high-purity 2,6-dimethylnaphthalene product. Preferably, the purity of the 2,6-dimethylnaphthalene product is greater than 95%, and more preferably greater than 98%.

[0075] Preferably, the method further includes: taking the C obtained in step (4) 12 + Component discharge system.

[0076] According to the present invention, preferably, C5 containing aromatic hydrocarbons + The raw materials contain 50-100 wt% aromatic hydrocarbons.

[0077] This invention relates to the C5 aromatic hydrocarbon-containing compounds. + There are no particular restrictions on the source of the raw materials; they can be C5 hydrocarbons containing aromatics obtained through various methods. + Raw materials. Preferably, the aromatic C5... + The feedstock is derived from at least one of the following: catalytic reforming products, catalytic gasoline, cracked gasoline, hydrogenated components of residual oil and / or heavy oil, and coal-based hydrocarbon compounds.

[0078] In this invention, the terms "first", "second", "third", "fourth" and "fifth" do not limit the substances and operations, but are only used to distinguish the substances introduced in different steps and the operations performed in different stages.

[0079] According to a specific embodiment of the present invention, refer to Figure 1 C5 containing aromatics + The feedstock (reformed oil) is separated in the reformed oil separation unit to obtain C6, C7 and C8. + The components, of which C6 component enters the aromatics extraction unit for aromatics extraction to obtain high-purity benzene, C7 component enters the aromatics conversion unit, and C8 component enters the aromatics conversion unit. + The component enters the dealkylation unit for selective hydrogenation dealkylation to remove C2 and above side chain alkyl groups, yielding C8 compounds rich in polymethylbenzene and polymethylnaphthalene. + Products and C7 - Components. The above C7 - The components are returned to the reforming product oil separation unit; the above-mentioned C8 oil rich in polymethylbenzene and polymethylnaphthalene + The product enters the aromatics separation unit for aromatics separation to obtain C8 components and C9-C4 components. 10 Components and C rich in naphthalene compounds 10 + Components. The C8 component is separated into PX products and C8 aromatics containing p-xylene-lean compounds via a PX separation unit. These p-xylene-lean C8 aromatics then undergo isomerization in an isomerization unit and are subsequently returned to the aromatics separation unit. Partial C9-C 10 The component, along with the C7 component, enters the aromatic conversion unit to undergo disproportionation and alkyl transfer reactions, increasing xylene production. It is rich in naphthalene compounds (C7). 10 + The component enters the demethylation unit and undergoes a demethylation reaction to generate C-type compounds rich in naphthalene and methylnaphthalene. 10 -C 11 Components and C 12 + Component, C 12 + Component discharge system. The above-mentioned C-type compounds rich in naphthalene and methylnaphthalene. 10 -C 11 Components and Remaining C9-C 10 The components enter the alkyl transfer unit of the naphthalene series together to undergo an alkyl transfer reaction, generating a product rich in 2,6-dimethylnaphthalene, which is then separated to obtain a high-purity 2,6-dimethylnaphthalene product.

[0080] The present invention will be described in detail below through embodiments.

[0081] Example 1

[0082] according to Figure 1The aforementioned process flow originates from a 100-ton / hour C5 catalytic reforming process. + The raw materials (composition shown in Table 1) enter the reforming-derived oil separation unit, and the reaction products are shown in Table 2.

[0083] Selective dealkylation catalyst: ZSM-5 molecular sieve (silicon-to-aluminum molar ratio 30) and pseudoboehmite (70wt% Al2O3) were mixed uniformly at a dry weight ratio of 70:30. Appropriate amounts of nitric acid and water were added, and the mixture was extruded into strips with a diameter of 1.6 mm. These strips were then dried, calcined, and granulated into supports with a length of 2-3 mm. The supports were then impregnated in a 1 g / L aqueous solution of chloroplatinic acid, dried at 120°C for 4 hours, and calcined in air at 550°C for 3 hours to obtain a 0.05 wt% Pt / ZSM-5 catalyst.

[0084] The reaction conditions were: reaction temperature 380℃, reaction pressure 3MPa, hydrogen-to-hydrocarbon molecular ratio 3, and feed weight hourly space velocity 5h⁻¹. -1 .

[0085] Aromatic hydrocarbon conversion unit catalyst: Beta molecular sieve (silicon-to-aluminum molar ratio 25) and pseudoboehmite (70 wt% Al2O3) were mixed uniformly at a dry basis mass ratio of 70:30. Appropriate amounts of nitric acid and water were added, and the mixture was extruded into strips with a diameter of 1.6 mm. These strips were then dried, calcined, and granulated into supports with a length of 2-3 mm. The supports were impregnated in a 10 g / L nickel nitrate aqueous solution, dried at 120 °C for 4 hours, and calcined in air at 550 °C for 3 hours to obtain a 0.5 wt% Ni / Beta catalyst.

[0086] The reaction conditions were: reaction pressure 3 MPa, hydrogen-to-hydrogen ratio 3, reaction inlet temperature 340℃, and liquid feedstock weight hourly space velocity 3 h⁻¹. -1 .

[0087] At least some C9-C 10 The mass flow rate ratio of component C7 to component C7 is 0.5:1. At least a portion of the C9-C atoms are introduced into the aromatic conversion unit. 10 The remaining C9-C components and alkyl transfer units introduced into naphthalene compounds 10 The mass flow rate ratio of the components is 1:0.3.

[0088] Isomerization reaction unit catalyst: ZSM-5 molecular sieve (silicon-to-aluminum molar ratio 20) and pseudoboehmite (70wt% Al2O3) were mixed uniformly at a dry basis mass ratio of 70:30. Appropriate amounts of nitric acid and water were added, and the mixture was extruded into strips with a diameter of 1.6 mm. These strips were then dried, calcined, and granulated into supports with a length of 2-3 mm. The supports were impregnated in a 1 g / L aqueous solution of chloroplatinic acid, dried at 120°C for 4 hours, calcined in air at 500°C for 3 hours, and then reduced with hydrogen at 500°C for 3 hours to obtain the desired catalyst.

[0089] 0.05wt% Pt / ZSM-5 catalyst.

[0090] The reaction conditions were: reaction pressure 2 MPa, hydrogen-to-hydrogen ratio 1.5, reaction inlet temperature 350 °C, and liquid feedstock weight hourly space velocity (WHSV) 8 h⁻¹. -1 .

[0091] Aromatic demethylation unit catalyst: An Al2O3 support was impregnated in a 100 g / L aqueous solution of chromium nitrate, then dried at 120 °C for 4 hours and calcined at 550 °C for 3 hours in air atmosphere to obtain a 15 wt% Cr / Al2O3 catalyst.

[0092] The reaction conditions were: reaction pressure 5 MPa, hydrogen-to-hydrogen ratio 4, reactor inlet temperature 580℃, and liquid feed weight hourly space velocity (WHSV) 2 h⁻¹. -1 .

[0093] Naphthalene-based alkyl transfer unit catalyst: MOR molecular sieve (silicon-to-aluminum molar ratio 15) and pseudoboehmite (70 wt% Al2O3) were mixed uniformly at a dry weight ratio of 70:30. Appropriate amounts of nitric acid and water were added, and the mixture was extruded into strips with a diameter of 1.6 mm. These strips were then dried, calcined, and granulated into supports with a length of 2-3 mm. The supports were impregnated in a 50 g / L ammonium heptamolybdate aqueous solution, dried at 120 °C for 4 hours, and calcined in air at 550 °C for 3 hours to obtain a 3 wt% Mo / MOR catalyst.

[0094] The reaction conditions were: reaction pressure 4 MPa, hydrogen-to-hydrogen ratio 3, reactor inlet temperature 380℃, and liquid feed weight hourly space velocity 2 h⁻¹. -1 .

[0095] The C-rich naphthalene and methylnaphthalene 10 -C 11 Components and Remaining C9-C 10 The mass flow rate ratio of the components is 0.2:1.

[0096] Example 2

[0097] according to Figure 1 The aforementioned process flow originates from a 100-ton / hour C5 catalytic reforming process.+ The raw materials (composition shown in Table 1) enter the reforming-derived oil separation unit, and the reaction products are shown in Table 2.

[0098] Selective dealkylation catalyst: ZSM-5 molecular sieve (silicon-to-aluminum molar ratio 30) and pseudoboehmite (70wt% Al2O3) were mixed uniformly at a dry weight ratio of 70:30. Appropriate amounts of nitric acid and water were added, and the mixture was extruded into strips with a diameter of 1.6 mm. These strips were then dried, calcined, and granulated into supports with a length of 2-3 mm. The supports were then impregnated in a 1 g / L aqueous solution of chloroplatinic acid, dried at 120°C for 4 hours, and calcined in air at 550°C for 3 hours to obtain a 0.05 wt% Pt / ZSM-5 catalyst.

[0099] The reaction conditions were: reaction temperature 380℃, reaction pressure 3MPa, hydrogen-to-hydrocarbon molecular ratio 3, and feed weight hourly space velocity 5h⁻¹. -1 .

[0100] Aromatic hydrocarbon conversion unit catalyst: Beta molecular sieve (silicon-to-aluminum molar ratio 15) and pseudoboehmite (70 wt% Al2O3) were mixed uniformly at a dry basis mass ratio of 70:30. Appropriate amounts of nitric acid and water were added, and the mixture was extruded into strips with a diameter of 1.6 mm. These strips were then dried, calcined, and granulated into supports with a length of 2-3 mm. The supports were impregnated in a 10 g / L nickel nitrate aqueous solution, dried at 120 °C for 4 hours, and calcined in air at 550 °C for 3 hours to obtain a 0.5 wt% Ni / Beta catalyst.

[0101] The reaction conditions were: reaction pressure 4 MPa, hydrogen-to-hydrogen ratio 0.3, reaction inlet temperature 290℃, and liquid feedstock weight hourly space velocity 2 h⁻¹. -1 .

[0102] At least some C9-C 10 The mass flow ratio of component C7 to component C7 is 1:1. At least a portion of the C9-C fraction is introduced into the aromatics conversion unit. 10 The remaining C9-C components and alkyl transfer units introduced into naphthalene compounds 10 The mass flow rate ratio of the components is 1:0.2.

[0103] Isomerization reaction unit catalyst: ZSM-5 molecular sieve (silicon-to-aluminum molar ratio 10) and pseudoboehmite (70wt% Al2O3) were mixed uniformly at a dry basis mass ratio of 70:30. Appropriate amounts of nitric acid and water were added, and the mixture was extruded into strips with a diameter of 1.6 mm. These strips were then dried, calcined, and granulated into supports with a length of 2-3 mm. The supports were impregnated in a 1 g / L aqueous solution of chloroplatinic acid, dried at 120°C for 4 hours, calcined in air at 500°C for 3 hours, and then reduced with hydrogen at 500°C for 3 hours to obtain the desired catalyst.

[0104] 0.05wt% Pt / ZSM-5 catalyst.

[0105] The reaction conditions were: reaction pressure 3 MPa, hydrogen-to-hydrogen ratio 0.2, reaction inlet temperature 250 °C, and liquid feedstock weight hourly space velocity 4 h⁻¹. -1 .

[0106] Aromatic demethylation unit catalyst: An Al2O3 support was impregnated in a 100 g / L aqueous solution of chromium nitrate, then dried at 120 °C for 4 hours and calcined at 550 °C for 3 hours in air atmosphere to obtain a 15 wt% Cr / Al2O3 catalyst.

[0107] The reaction conditions were: reaction pressure 5 MPa, hydrogen-to-hydrogen ratio 4, reactor inlet temperature 580℃, and liquid feed weight hourly space velocity (WHSV) 1.5 h⁻¹. -1 .

[0108] Naphthalene-based alkyl transfer unit catalyst: MOR molecular sieve (silicon-to-aluminum molar ratio 20) and pseudoboehmite (70 wt% Al2O3) were mixed uniformly at a dry weight ratio of 70:30. Appropriate amounts of nitric acid and water were added, and the mixture was extruded into strips with a diameter of 1.6 mm. These strips were then dried, calcined, and granulated into supports 2-3 mm in length. The supports were impregnated in a 50 g / L ammonium heptamolybdate aqueous solution, dried at 120 °C for 4 hours, and calcined in air at 550 °C for 3 hours to obtain a 3 wt% Mo / MOR catalyst.

[0109] The reaction conditions were: reaction pressure 3 MPa, hydrogen-to-hydrogen ratio 3, reactor inlet temperature 330℃, and liquid feed weight hourly space velocity 2 h⁻¹. -1 .

[0110] The C-rich naphthalene and methylnaphthalene 10 -C 11 Components and Remaining C9-C 10 The mass flow rate ratio of the components is 0.5:1.

[0111] Comparative Example 1

[0112] 100 tons / hour of C5 from catalytic reforming + The raw materials (composition shown in Table 1) were separated by a heptane removal column to obtain C6-C7 components and C8 components. + The C6-C7 fractions are separated in the aromatics extraction unit to obtain benzene and toluene, with benzene being collected as the product and toluene being returned to the aromatics conversion unit. C8... + The components were separated by a xylene separator to obtain C8 aromatics and C9 aromatics. + Aromatics. C8 aromatics are processed through a PX separation unit and an isomerization unit to obtain PX products, C9... + Aromatics were separated by a heavy aromatics column to obtain C9-C 10Aromatics and C 11 + Aromatic hydrocarbons. Among them, C... 11 + Aromatic hydrocarbons are discharged outside the boundary, C9-C 10 The aromatics were returned to the aromatics conversion unit and, together with toluene, underwent disproportionation and alkyl transfer reactions. The resulting products were sequentially separated to obtain benzene and C8 aromatics. The obtained C8 aromatics were returned to the xylene separation tower. The results are shown in Table 2.

[0113] The aromatic hydrocarbon conversion unit catalyst was prepared by uniformly mixing Beta molecular sieve (silicon-to-aluminum molar ratio 25) and boehmite (70 wt% Al2O3) at a dry weight ratio of 70:30, adding appropriate amounts of nitric acid and water, extruding into strips with a diameter of 1.6 mm, drying, calcining, and granulating into supports of 2-3 mm in length. The supports were then impregnated in a 10 g / L nickel nitrate aqueous solution, dried at 120 °C for 4 hours, and calcined in air at 550 °C for 3 hours to obtain a 0.5 wt% Ni / Beta catalyst.

[0114] The reaction conditions were: reaction pressure 3 MPa, hydrogen-to-hydrogen ratio 3, reaction inlet temperature 340℃, and liquid feedstock weight hourly space velocity 3 h⁻¹. -1 .

[0115] Isomerization reaction unit catalyst: ZSM-5 molecular sieve (silicon-to-aluminum molar ratio 20) and pseudoboehmite (70wt% Al2O3) were mixed uniformly at a dry basis mass ratio of 70:30. Appropriate amounts of nitric acid and water were added, and the mixture was extruded into strips with a diameter of 1.6 mm. These strips were then dried, calcined, and granulated into supports with a length of 2-3 mm. The supports were impregnated in a 1 g / L aqueous solution of chloroplatinic acid, dried at 120°C for 4 hours, calcined in air at 500°C for 3 hours, and then reduced with hydrogen at 500°C for 3 hours to obtain the desired catalyst.

[0116] 0.05wt% Pt / ZSM-5 catalyst.

[0117] The reaction conditions were: reaction pressure 2 MPa, hydrogen-to-hydrogen ratio 1.5, reaction inlet temperature 350 °C, and liquid feedstock weight hourly space velocity (WHSV) 8 h⁻¹. -1 .

[0118] Table 1

[0119] <![CDATA[C5 + Raw material composition]]> Content, wt% Non-aromatic hydrocarbons 15.3 benzene 5.8 Toluene 17.9 Ethylbenzene 3.3 p-xylene 4.7 m-xylene 9.9 o-xylene 6.1 <![CDATA[C9A]]> 21.5 <![CDATA[C 10 + A]]> 15.5

[0120] Table 2

[0121]

[0122]

[0123] As can be seen from the results in Table 2, compared to Comparative Example 1, the method provided in this embodiment of the invention produces C as a byproduct. 10 + The A component is significantly reduced, resulting in higher utilization of heavy aromatic hydrocarbon resources. In particular, this invention employs liquid-phase disproportionation, alkyl transfer, and liquid-phase aromatic hydrocarbon isomerization reactions, which reduces aromatic hydrocarbon loss and yields higher benzene and p-xylene yields; moreover, it eliminates the need for hydrogen recycling, effectively reducing energy and material consumption of the equipment.

[0124] The preferred 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 combinations of 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. A method for producing p-xylene in conjunction with dimethylnaphthalene, characterized in that, The method includes the following steps: (1) C5 containing aromatics + The raw materials were separated to obtain C6, C7 and C8. + Components; the C8 + The component undergoes selective hydrogenation and dealkylation to yield C8 compounds rich in polymethylbenzene and polymethylnaphthalene. + product; (2) The C8 compound rich in polymethylbenzene and polymethylnaphthalene + The product was subjected to aromatic separation to obtain C8 fraction and C9-C fraction. 10 Components and C rich in naphthalene compounds 10 + Components; (3) C9-C 10 At least a portion of the component undergoes disproportionation and alkyl transfer reaction with the C7 component to obtain a xylene-rich product; the xylene-rich product is then returned to the selective hydrogenation-dealkylation reaction in step (1); (4) C rich in naphthalene compounds 10 + The component undergoes a demethylation reaction to yield C360 rich in naphthalene and methylnaphthalene. 10 -C 11 Components and C 12 + Components; the C-containing compound rich in naphthalene and methylnaphthalene 10 -C 11 Components and C9-C 10 The remaining portion of the component undergoes an alkyl transfer reaction to yield a product rich in 2,6-dimethylnaphthalene.

2. The method according to claim 1, wherein, At least part of C9-C in step (2) 10 Components and the remaining C9-C in step (4) 10 The mass flow ratio of the components is 1:0.1-1, preferably 1:0.2-0.5; Preferably, the C6 component obtained in step (1) is subjected to aromatic extraction to obtain benzene; Preferably, the C8 component obtained in step (2) is subjected to p-xylene separation to obtain p-xylene and C8 aromatic hydrocarbons containing p-xylene-lean; More preferably, the C8 aromatic hydrocarbon containing p-xylene is subjected to an isomerization reaction and then returned to the aromatic hydrocarbon separation in step (2).

3. The method according to claim 2, wherein, The conditions for the isomerization reaction include: a reaction temperature of 200-500℃, preferably 200-300℃; a reaction pressure of 1-5 MPa; a hydrogen-to-hydrocarbon molecular ratio of 0.1-3; and a feed weight hourly space velocity of 3-15 h⁻¹. -1 ; Preferably, the isomerization reaction is carried out under the action of a fifth catalyst; Preferably, the fifth catalyst comprises a fifth support and a noble metal supported on the fifth support, the fifth support comprising a molecular sieve selected from at least one of ZSM-5, EU-1 and MOR molecular sieves; the noble metal is preferably Pt and / or Pd. Preferably, in the fifth carrier, the silicon-to-aluminum molar ratio of the molecular sieve is 3-60; Preferably, in the fifth catalyst, the content of noble metal, calculated as oxide, is 0.02-0.5% by weight, and more preferably 0.05-0.2% by weight.

4. The method according to claim 3, wherein, The fifth carrier further contains a heat-resistant inorganic oxide, which is selected from at least one of silicon oxide, aluminum oxide, zirconium oxide, and titanium oxide; Preferably, based on the total weight of the fifth carrier, the content of the molecular sieve is 60-90% by weight, and the content of the heat-resistant inorganic oxide is 10-40% by weight.

5. The method according to any one of claims 1-4, wherein, The reaction conditions for the selective hydrogenation dealkylation reaction in step (2) include: a reaction temperature of 350-450℃, a reaction pressure of 1-5 MPa, a hydrogen-to-hydrocarbon molecular ratio of 1-10, and a feed weight hourly space velocity of 3-20 h⁻¹. -1 ; Preferably, the selective hydrogenation-dealkylation reaction in step (2) is carried out under the action of a first catalyst; Preferably, the first catalyst comprises a first support and a first active component supported on the first support, wherein the first support comprises a molecular sieve having ten-membered ring channels, preferably ZSM-5 and / or ZSM-11; and the first active component is selected from at least one of Pt, Pd, Re and Ni. Preferably, in the first carrier, the silicon-to-aluminum molar ratio of the molecular sieve is 10-80; Preferably, in the first catalyst, the content of the first active component, calculated as oxide, is 0.05-5% by weight, preferably 0.1-2% by weight.

6. The method according to claim 5, wherein, The first carrier further contains a heat-resistant inorganic oxide, wherein the heat-resistant inorganic oxide is selected from at least one of silicon oxide, aluminum oxide, zirconium oxide, and titanium oxide; Preferably, based on the total weight of the first carrier, the content of the molecular sieve is 60-90% by weight, and the content of the heat-resistant inorganic oxide is 10-40% by weight.

7. The method according to any one of claims 1-6, wherein, The reaction conditions for the disproportionation and alkyl transfer reaction in step (3) include: a reaction temperature of 200-500℃, preferably 200-310℃; a reaction pressure of 2-5 MPa; a hydrogen-to-hydrocarbon molecular ratio of 0.1-5; and a feed weight hourly space velocity of 1-5 h⁻¹. -1 ; Preferably, at least a portion of C9-C 10 The mass flow rate ratio of component C7 to component C7 is 0.2-5:1, preferably 0.5-2:

1.

8. The method according to any one of claims 1-7, wherein, The disproportionation and alkyl transfer reaction described in step (3) is carried out under the action of a second catalyst; Preferably, the second catalyst comprises a second support and a second active component supported on the second support, the second active component being selected from at least one of Ni, Pt, Mo and Pd; the second support comprises a molecular sieve having twelve-membered ring channels, preferably selected from at least one of MOR molecular sieve, BETA molecular sieve and Y molecular sieve; Preferably, in the second carrier, the silicon-to-aluminum molar ratio of the molecular sieve is 3-50; Preferably, in the second catalyst, the content of the second active component, calculated as oxide, is 0.02-8% by weight, preferably 0.05-5% by weight.

9. The method according to claim 8, wherein, The second carrier further contains a heat-resistant inorganic oxide, which is selected from at least one of silicon oxide, aluminum oxide, zirconium oxide, and titanium oxide; Preferably, based on the total weight of the second carrier, the content of the molecular sieve is 60-90% by weight, and the content of the heat-resistant inorganic oxide is 10-40% by weight.

10. The method according to any one of claims 1-9, wherein, The reaction conditions for the demethylation reaction in step (4) include: a reaction temperature of 500-700℃, a reaction pressure of 3-7 MPa, a hydrogen-to-hydrocarbon molecular ratio of 3-8, and a feed weight hourly space velocity of 0.5-2 h⁻¹. -1 ; Preferably, the demethylation reaction in step (4) is carried out under the action of a third catalyst, the third catalyst comprising a third support and a third active component supported on the third support, the third active component being selected from at least one of Cr, Pt and Ni; the third support is a heat-resistant inorganic oxide, preferably selected from at least one of silicon oxide, aluminum oxide, zirconium oxide and titanium oxide; Preferably, in the third catalyst, the content of the third active component, calculated as oxide, is 0.1-30% by weight, preferably 0.2-20% by weight.

11. The method according to any one of claims 1-10, wherein, The reaction conditions for the alkyl transfer reaction in step (4) include: a reaction temperature of 250-450℃, a reaction pressure of 2-5 MPa, a hydrogen-to-hydrocarbon molecular ratio of 2-6, and a feed weight hourly space velocity of 0.5-3 h⁻¹. -1 ; Preferably, the C-type compound rich in naphthalene and methylnaphthalene... 10 -C 11 Components and Remaining C9-C 10 The mass flow ratio of the components is 0.2-5:1, preferably 0.2-1.5:

1.

12. The method according to any one of claims 1-11, wherein, The alkyl transfer reaction in step (4) is carried out in the presence of a fourth catalyst; Preferably, the fourth catalyst comprises a fourth support and a fourth active component supported on the fourth support, the fourth active component being selected from at least one of Ni, Mo and Re; the fourth support comprises a molecular sieve having twelve-membered ring channels, preferably selected from at least one of MOR molecular sieve, BETA molecular sieve and Y molecular sieve; Preferably, in the fourth carrier, the silicon-to-aluminum molar ratio of the molecular sieve is 3-50; Preferably, in the fourth catalyst, the content of the fourth active component, calculated as oxide, is 0.2-10% by weight, preferably 0.3-8% by weight.

13. The method according to claim 12, wherein, The fourth carrier further contains a heat-resistant inorganic oxide, which is selected from at least one of silicon oxide, aluminum oxide, zirconium oxide, and titanium oxide; Preferably, based on the total weight of the fourth carrier, the content of the molecular sieve is 60-90% by weight, and the content of the heat-resistant inorganic oxide is 10-40% by weight.

14. The method according to any one of claims 1-13, wherein, The product rich in 2,6-dimethylnaphthalene obtained in step (4) is separated to obtain the 2,6-dimethylnaphthalene product; the separation is preferably distillation separation and / or crystallization separation; Preferably, the purity of the 2,6-dimethylnaphthalene product is greater than 95%, and more preferably greater than 98%.

15. The method according to any one of claims 1-14, wherein, C5 containing aromatics + The aromatic hydrocarbon content in the raw materials is 50-100 wt%. Preferably, the aromatic C5 + The feedstock is derived from at least one of coal-based hydrocarbon compounds, catalytic reforming products, and hydrogenated components of catalytic gasoline, cracked gasoline, and heavy oil.

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