Method and system for preparing benzene and p-xylene by taking naphtha as raw material

Abstract

The invention provides a method and a system for preparing benzene and p-xylene by taking naphtha as a raw material, and the method comprises the following steps: (1) feeding the naphtha raw material to a first reaction zone, and carrying out a first catalytic reaction in the presence of a first catalyst to obtain a first material flow containing benzene, toluene, p-xylene and byproducts; (2) feeding toluene to a second reaction zone, and carrying out a second catalytic reaction in the presence of a second catalyst to obtain a second material flow containing benzene, toluene, p-xylene and by-products; (3) sending the first material flow and / or the second material flow to a separation system for separation to obtain a toluene-rich component, a byproduct-rich component, and a benzene-rich component and a p-xylene-rich component which are used as products; and (4) returning the separated toluene-rich component to the step (2) as a toluene source. The invention further provides a corresponding system. According to the method and the system, the naphtha raw material is used for preparing the benzene and the p-xylene, and the selectivity of the benzene and the p-xylene is remarkably improved through toluene reprocessing.

Description

Technical Field

[0001] The invention belongs to the field of chemical industry, and in particular relates to a method and a system for preparing benzene and p-xylene by taking naphtha as raw material. Background Art

[0002] Aromatic hydrocarbons represented by benzene, toluene, xylene and other BTX are basic petrochemical chemicals. Among them, benzene is a basic petrochemical raw material, which can synthesize a series of benzene derivatives: a series of compounds generated by benzene through substitution reaction, addition reaction, oxidation reaction, etc., can be used as raw materials for making plastics, rubber, fiber, dye, detergent, pesticide, etc. About 10% of benzene is used as the basic raw material for making benzene intermediates. The output of benzene and the technical level of production are one of the signs of a country's petrochemical development level. The industrial chain of my country's pure benzene industry is relatively complete, and the downstream derivative fields are extremely extensive, mainly including styrene, caprolactam, phenol, adipic acid, aniline, chlorobenzene, nitrobenzene, maleic anhydride, rubber, plastic, fiber, detergent, etc., among which the largest downstream product is styrene, accounting for about 39%. Paraxylene (PX) is the most concerned product among aromatic hydrocarbons. As the key connection point between oil refining and chemical industry, it is not only the most important product among the three xylene isomers, but also the main raw material of the polyester industry. The downstream products of p-xylene (PX) are mainly purified terephthalic acid (PTA), which is then used to produce polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT) and polytrimethylene terephthalate (PTT). A small part of it is used in other fields such as pharmaceutical intermediate dimethyl terephthalate (DMT) and coatings. In recent years, the extensive application of polyester in the fields of textiles, clothing, beverage packaging, etc. has driven the rapid growth of the production and consumption of purified terephthalic acid (PTA) and its upstream product p-xylene (PX). Taking the chemical fiber industry as an example, synthetic fibers in my country currently account for 70% of textile fiber production, of which polyester fibers produced with p-xylene (PX) account for more than 80% of the total synthetic fiber production.

[0003] Industrially, benzene and paraxylene (PX) are mainly produced from naphtha through a catalytic reforming / aromatics combined unit. First, mixed aromatics are obtained through catalytic reforming of naphtha, and benzene, toluene and mixed xylenes are obtained after separation. The mixed xylenes are then separated from the xylene isomer mixture with extremely similar boiling points by multi-stage deep cold crystallization separation or molecular sieve simulated moving bed adsorption separation technology. Limited by thermodynamic equilibrium, the content of paraxylene (PX) in the xylene mixture is relatively low (~24%). The demand for paraxylene (PX) is growing, and direct extraction and separation of paraxylene (PX) from reformed oil and pyrolysis gasoline can no longer meet the demand. Toluene disproportionation and transalkylation, xylene isomerization technology is often used to increase the production of paraxylene (PX). However, the insufficient number of methyl groups in the reformed naphtha feedstock and the thermodynamic equilibrium distribution of the produced xylene (PX is only about 24wt%) are still the main factors that hinder the traditional catalytic reforming / aromatics combined unit from significantly increasing the production of para-xylene (PX) and simplifying the process flow. Therefore, in order to solve the above problems, it is particularly important to develop new technologies for preparing benzene and para-xylene. Summary of the invention

[0004] The first object of the present invention is to provide a method for preparing benzene and para-xylene using naphtha as a raw material, which method can improve the selectivity of benzene and para-xylene in the preparation process, thereby increasing the production of benzene and para-xylene;

[0005] A second object of the present invention is to provide a system for use in the aforementioned method.

[0006] To achieve the first object of the present invention, the following technical solutions are adopted:

[0007] A method for preparing benzene and p-xylene using naphtha as a raw material, the method comprising:

[0008] (1) delivering a naphtha feedstock to a first reaction zone and performing a first catalytic reaction in the presence of a first catalyst to obtain a first stream; wherein the first stream comprises benzene, toluene, para-xylene and by-products;

[0009] (2) sending toluene to a second reaction zone and performing a second catalytic reaction in the presence of a second catalyst to obtain a second stream; wherein the second stream comprises benzene, toluene, para-xylene and by-products;

[0010] (3) sending the first logistics obtained in step (1) and / or the second logistics obtained in step (2) to a separation system for separation to obtain a toluene-rich component, a by-product-rich component, a benzene-rich component as a product, and a para-xylene-rich component, respectively;

[0011] (4) The toluene-rich component separated in step (3) is returned to step (2) as a source of toluene.

[0012] In the method of the present invention, preferably, in step (3), the first logistics obtained in step (1) and the second logistics obtained in step (2) are sent to a separation system for separation to obtain a benzene-rich component, a toluene-rich component, a para-xylene-rich component and a by-product-rich component.

[0013] In the method of the present invention, preferably, the separation system comprises a first separation system and a second separation system;

[0014] In step (3), the first logistics obtained in step (1) is sent to a first separation system for separation to obtain a first benzene-rich component, a first toluene-rich component, a first p-xylene-rich component and a first by-product-rich component; and the second logistics obtained in step (2) is sent to a second separation system for separation to obtain a second benzene-rich component, a second toluene-rich component, a second p-xylene-rich component and a second by-product-rich component; wherein,

[0015] The benzene-rich component obtained in step (3) comprises a first benzene-rich component and a second benzene-rich component;

[0016] The toluene-rich component obtained in step (3) comprises a first toluene-rich component and a second toluene-rich component;

[0017] The p-xylene-rich component obtained in step (3) comprises a first p-xylene-rich component and a second p-xylene-rich component;

[0018] The by-product-rich component obtained in step (3) comprises a first by-product-rich component and a second by-product-rich component.

[0019] In the method of the present invention, preferably, in step (3), the first logistics obtained in step (1) is sent to a first separation system for separation to obtain a first benzene-rich component, a first toluene-rich component, a first p-xylene-rich component and a first by-product-rich component; and the first benzene-rich component, the first p-xylene-rich component and the first by-product-rich component output by the first separation system and the second logistics obtained in step (2) are sent to a second separation system for separation to obtain a second benzene-rich component, a second toluene-rich component, a second p-xylene-rich component and a second by-product-rich component.

[0020] In the method of the present invention, preferably, in step (3), the second logistics obtained in step (2) is sent to a separation system for separation to obtain a benzene-rich component, a toluene-rich component, a para-xylene-rich component and a by-product-rich component, respectively.

[0021] The method of the present invention preferably further comprises step (5), sending the first logistics obtained in step (1) to step (2) as a source of toluene.

[0022] In the method of the present invention, preferably, among the first catalyst and the second catalyst, the first catalyst is selected from any one or more combinations of metal-modified ZSM-5 molecular sieve catalysts; and / or

[0023] The second catalyst is selected from any one or more combinations of ZSM-5 molecular sieve catalysts modified by silanization and metal modification; preferably, the second catalyst is selected from any one or more combinations of ZSM-5 molecular sieve catalysts modified by metal modification and silanization in sequence.

[0024] In the method of the present invention, preferably, the metal modification is bimetallic modification, and the first metal is selected from any one of La, Ce, Mg and Ca, and the second metal is selected from any one of Ga and Zn.

[0025] In the method of the present invention, preferably, in step (1), the conditions of the first catalytic reaction include:

[0026] The reaction temperature is 300 to 600° C.; and / or,

[0027] The reaction pressure is 0.1-0.5 MPa; and / or,

[0028] The feed weight space velocity of the naphtha raw material I is 0.1 to 10 h -1 .

[0029] In the method of the present invention, preferably, in step (2), the conditions of the second catalytic reaction include:

[0030] The reaction temperature is 300 to 600° C.; and / or,

[0031] The reaction pressure is 0.1-0.5 MPa; and / or,

[0032] The feed weight space velocity of toluene is 0.1~6h -1 .

[0033] In the method of the present invention, preferably, the second catalyst is prepared in situ in the second reaction zone.

[0034] The method of the present invention is preferably an in-situ preparation method as follows: the first catalyst is loaded into the second reaction zone, a silanization reagent is introduced into the second reaction zone to contact the first catalyst, and the catalyst is calcined at a high temperature to obtain the second catalyst in-situ.

[0035] In the method of the present invention, preferably, the calcination temperature is 500-700° C.; and / or the calcination time is 2-8 hours.

[0036] In the method of the present invention, preferably, after the calcination is completed, the second reaction zone is directly cooled to its reaction temperature to carry out the second catalytic reaction.

[0037] To achieve the second object of the present invention, a system for the above method is provided.

[0038] The beneficial effects of the present invention are:

[0039] (1) The method and system of the present invention for preparing benzene and para-xylene using naphtha as raw material utilizes naphtha as raw material to prepare benzene and para-xylene, and adjusts the product distribution through toluene recycling, thereby significantly improving the selectivity of benzene and para-xylene, as well as the yield of benzene and para-xylene.

[0040] (2) The method and system of the present invention for preparing benzene and para-xylene using naphtha as raw material utilizes naphtha as raw material to prepare benzene and para-xylene. Since the toluene contained in the first stream and / or the second stream obtained by the catalytic reaction is returned to the second reaction zone, material recycling is achieved and economic benefits are improved.

[0041] (3) The method and system of the present invention for preparing benzene and para-xylene using naphtha as raw material have simple process and strong feasibility, and can greatly improve the selectivity and yield of benzene and para-xylene, providing a new way to efficiently produce benzene and para-xylene from naphtha, and has important application value.

[0042] (4) In the method and system for preparing benzene and paraxylene using naphtha as raw material of the present invention, the second catalyst can be prepared in situ in the second reaction zone, so that after the roasting in the in situ preparation process is completed, the second reaction zone can be directly cooled to its reaction temperature to carry out the second catalytic reaction, thereby avoiding heat loss; compared with the inherent production method in the chemical industry, the second catalyst of the present invention is prepared in situ in the second reaction zone, which saves the washing and separation process after catalyst modification, the catalyst cooling process to room temperature after roasting, the catalyst transportation step, the catalyst loading step, the high-temperature pre-activation step after the catalyst is loaded into the reactor, etc., greatly improving the production efficiency and avoiding the safety problems that may occur in the above-mentioned saved steps; more importantly, the second reaction zone can start the second catalytic reaction after the roasting temperature is cooled to its reaction temperature, the thermal energy is fully utilized, and the energy consumption in production is greatly saved. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a schematic flow diagram of a method for preparing benzene and para-xylene using naphtha as a raw material in a first embodiment of the present invention;

[0044] Figure 2 is a schematic flow chart of a second embodiment of the method for preparing benzene and p-xylene using naphtha as a raw material according to the present invention;

[0045] Figure 3It is a schematic flow diagram of a method for preparing benzene and p-xylene using naphtha as a raw material in a third embodiment of the present invention;

[0046] Figure 4 It is a schematic flow chart of the method for preparing benzene and p-xylene using naphtha as raw material in Comparative Example 1. DETAILED DESCRIPTION

[0047] The technical scheme and its effects of the present invention are further described below in conjunction with specific implementation modes / examples and drawings. The following implementation modes / examples are only used to illustrate the contents of the present invention, and the invention is not limited to the following implementation modes or examples. Simple changes made to the present invention by applying the concept of the present invention are within the scope of protection claimed by the present invention.

[0048] The present invention provides a method and system for preparing benzene and p-xylene using naphtha as raw material. Figure 1-3 As shown, the method includes:

[0049] (1) delivering a naphtha feedstock to a first reaction zone and performing a first catalytic reaction in the presence of a first catalyst to obtain a first stream; wherein the first stream comprises benzene, toluene, para-xylene and by-products;

[0050] (2) sending toluene to a second reaction zone and performing a second catalytic reaction in the presence of a second catalyst to obtain a second stream; wherein the second stream comprises benzene, toluene, para-xylene and by-products;

[0051] (3) sending the first stream obtained in step (1) and / or the second stream obtained in step (2) to a separation system for separation to obtain a toluene-rich component, a by-product-rich component, a benzene-rich component as a product, and a p-xylene-rich component, respectively;

[0052] (4) The toluene-rich component separated in step (3) is returned to step (2) as a source of benzene and toluene.

[0053] The method and system for preparing benzene and para-xylene by using naphtha as raw material of the present invention utilizes naphtha raw material to prepare benzene and para-xylene, and adjusts product distribution by toluene recycling, thereby significantly improving the selectivity of benzene and para-xylene; and by returning toluene in the first stream obtained by naphtha conversion to the second reaction zone for selective alkylation reaction, the recycling of materials is realized, the yield of benzene and para-xylene is effectively improved, and the economic benefit is improved.

[0054] In one embodiment, Figure 1 As shown, in step (3), the first logistics obtained in step (1) and the second logistics obtained in step (2) are sent to a separation system for separation to obtain a benzene-rich component, a toluene-rich component, a para-xylene-rich component and a by-product-rich component.

[0055] In one embodiment, Figure 2 As shown, the separation system includes a first separation system and a second separation system;

[0056] In step (3), the first logistics obtained in step (1) is sent to a first separation system for separation to obtain a first benzene-rich component, a first toluene-rich component, a first p-xylene-rich component and a first by-product-rich component; and the second logistics obtained in step (2) is sent to a second separation system for separation to obtain a second benzene-rich component, a second toluene-rich component, a second p-xylene-rich component and a second by-product-rich component; wherein,

[0057] The benzene-rich component obtained in step (3) comprises a first benzene-rich component and a second benzene-rich component;

[0058] The toluene-rich component obtained in step (3) comprises a first toluene-rich component and a second toluene-rich component;

[0059] The p-xylene-rich component obtained in step (3) comprises a first p-xylene-rich component and a second p-xylene-rich component;

[0060] The by-product-rich component obtained in step (3) comprises a first by-product-rich component and a second by-product-rich component.

[0061] In a preferred embodiment, Figure 2 As shown, in step (3), the first logistics obtained in step (1) is sent to a first separation system for separation to obtain a first benzene-rich component, a first toluene-rich component, a first para-xylene-rich component and a first by-product-rich component; and the first benzene-rich component, the first para-xylene-rich component and the first by-product-rich component output by the first separation system and the second logistics obtained in step (2) are sent to a second separation system for separation to obtain a second benzene-rich component, a second toluene-rich component, a second para-xylene-rich component and a second by-product-rich component.

[0062] In one embodiment, Figure 3 As shown, in step (3), the second logistics obtained in step (2) is sent to a separation system for separation to obtain a benzene-rich component, a toluene-rich component, a para-xylene-rich component and a by-product-rich component, respectively.

[0063] In a preferred embodiment, Figure 3 As shown, the method further includes step (5), sending the first logistics obtained in step (1) to step (2) as a source of toluene.

[0064] Those skilled in the art will appreciate that, in the present invention, when the first logistics obtained in step (1) is sent to the first separation system for separation and the separated toluene is sent to the second reaction zone, only the toluene required for the second reaction zone can be separated, while the benzene, p-xylene and by-products therein may not be separated, but instead enter the second separation system together with the second logistics obtained in step (2) for separation.

[0065] The method for preparing benzene and para-xylene by using naphtha as raw material of the present invention utilizes naphtha raw material to prepare benzene and para-xylene. Since the toluene contained in the first logistics and / or the second logistics obtained by the catalytic reaction is returned to the second reaction zone, the material recycling is realized and the economic benefit is improved. In addition, the process is simple and the feasibility is strong, and the selectivity and yield of benzene and para-xylene can be greatly improved, thereby providing a new way to efficiently produce benzene and para-xylene from naphtha, and having important application value.

[0066] In one embodiment, the first catalyst is selected from any one or more combinations of metal-modified ZSM-5 molecular sieve catalysts, that is, the first catalyst is obtained by metal-modifying the ZSM-5 molecular sieve.

[0067] In one embodiment, the second catalyst is selected from any one or more combinations of ZSM-5 molecular sieve catalysts modified by silanization and metal modification; preferably, the second catalyst is selected from any one or more combinations of ZSM-5 molecular sieve catalysts modified by metal modification and silanization in sequence, that is, the ZSM-5 molecular sieve is first metal-modified and then the ZSM-5 molecular sieve obtained by metal modification is silanized.

[0068] In one embodiment, in the first catalyst and the second catalyst, the metal modification is a bimetallic modification, and the first metal is selected from any one of La, Ce, Mg and Ca, and the second metal is selected from any one of Ga and Zn.

[0069] The present invention can improve the selectivity of para-xylene (PX) in the xylene product by adopting a selective catalyst, can greatly reduce the processing volume of the xylene isomerization unit, and simplifies the xylene separation process, and develops a new route for preparing benzene and para-xylene.

[0070] In one embodiment, the metal modification is performed by impregnation.

[0071] In one embodiment, the ZSM-5 molecular sieve is metal-modified by an impregnation method, which specifically comprises the following steps:

[0072] (i) preparing an aqueous solution of a soluble metal salt;

[0073] (ii) impregnating the ZSM-5 molecular sieve in the aqueous solution of the soluble metal salt obtained in step (i) to obtain an impregnated molecular sieve;

[0074] (iii) The impregnated molecular sieve obtained in step (ii) is dried and calcined to obtain the metal-modified ZSM-5 molecular sieve catalyst.

[0075] In one embodiment, in step (ii), the impregnation conditions include:

[0076] The immersion time is 2 to 10 hours, such as 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours and 10 hours, and any value and numerical range within this range; and / or the immersion temperature is 60 to 90°C, such as 60°C, 65°C, 70°C, 75°C, 80°C, 85°C and 90°C, and any value and numerical range within this range.

[0077] In one embodiment, in step (iii),

[0078] Drying conditions include: air atmosphere, temperature of 110-150°C, such as 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C and 150°C and any value and range of values ​​within the range; and / or,

[0079] The calcination conditions include: air atmosphere, a temperature of 500-700°C, such as 500°C, 525°C, 550°C, 575°C, 600°C, 625°C, 650°C, 675°C and 700°C and any value and range of values ​​within this range.

[0080] In one embodiment, the silanization agent used in the silanization modification is selected from at least one of the compounds of the structure shown in Formula I:

[0081]

[0082] Wherein, R1, R2, R3 and R4 are each independently selected from any one of C1-C10 alkyl groups and C1-C10 alkoxy groups.

[0083] In one embodiment, optionally, in Formula I, at least one of R1, R2, R3 and R4 is selected from any one of C1-10 alkoxy groups.

[0084] In the present invention, the "C1-C10" refers to the number of carbon atoms contained in the group;

[0085] The "alkyl" is a group formed by losing any hydrogen atom from an alkane compound molecule; the alkane compound includes straight-chain alkanes, branched-chain alkanes, cycloalkanes, and branched cycloalkanes;

[0086] The "alkoxy group" is a group formed by losing the hydrogen atom on the hydroxyl group in the alkyl alcohol compound molecule.

[0087] In one embodiment, optionally, the silanization agent is tetraethyl silicate and / or tetramethyl silicate.

[0088] In one embodiment, optionally, the ZSM-5 molecular sieve is a shaped ZSM-5 molecular sieve formed according to the reactor type; the shaped ZSM-5 molecular sieve consists of ZSM-5 molecular sieve; or the shaped ZSM-5 molecular sieve contains ZSM-5 molecular sieve and a binder.

[0089] In one embodiment, optionally, the shaped ZSM-5 molecular sieve is prepared by a method selected from the group consisting of: tabletting and crushing the ZSM-5 molecular sieve, mixing the ZSM-5 molecular sieve with a binder and extruding the resulting strips, and then breaking the resulting strips, and spray-drying the ZSM-5 molecular sieve with a binder.

[0090] In one embodiment, the silicon-to-aluminum ratio in the ZSM-5 molecular sieve is Si / Al=10-200, such as 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190 and 200, and any value and range of values ​​within this range.

[0091] In one embodiment, in step (1), the conditions of the first catalytic reaction include:

[0092] The reaction temperature is 300-600°C, such as 300°C, 350°C, 400°C, 450°C, 500°C, 550°C and 600°C and any value and range of values ​​within the range; and / or,

[0093] The reaction pressure is 0.1 to 0.5 MPa, such as 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa and 0.5 MPa; and / or,

[0094] The feed weight space velocity of the naphtha raw material I is 0.1 to 10 h -1 , for example 0.1h -1 , 0.5h -1 , 1h -1 , 2h -1 , 3h -1 , 4h -1 , 5h -1 , 6h -1 , 7h -1 , 8h -1 , 9h -1 and 10h-1 and any numerical value and numerical range within this range.

[0095] In one embodiment, in step (2), the conditions of the second catalytic reaction include:

[0096] The reaction temperature is 300-600°C, such as 300°C, 350°C, 400°C, 450°C, 500°C, 550°C and 600°C and any value and range of values ​​within the range; and / or,

[0097] The reaction pressure is 0.1 to 0.5 MPa, such as 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa and 0.5 MPa; and / or,

[0098] The feed weight space velocity of toluene is 0.1~6h -1 , for example 0.1h -1 、0.5h -1 , 1h -1 , 2h -1 , 3h -1 , 4h -1 , 5h -1 and 6h -1 and any numerical value and numerical range within this range.

[0099] In one embodiment, the second catalyst is prepared in situ in the second reaction zone;

[0100] Preferably, the in-situ method is as follows: the first catalyst is loaded into the second reaction zone, a silanization agent is introduced to contact the first catalyst, and the catalyst is calcined at a high temperature to obtain the second catalyst in-situ.

[0101] In one embodiment, during the in-situ preparation process, the calcination temperature is 500-700°C, such as 500°C, 525°C, 550°C, 575°C, 600°C, 625°C, 650°C, 675°C and 700°C, and any value and numerical range within this range; and / or the calcination time is 2-8h, such as 2h, 3h, 4h, 5h, 6h, 7h and 8h, and any value and numerical range within this range.

[0102] In one embodiment, during the in-situ preparation process, after the calcination is completed, the second reaction zone is directly cooled to its reaction temperature to carry out the second catalytic reaction.

[0103] In the method for preparing benzene and paraxylene using naphtha as raw material of the present invention, the second catalyst can be prepared in situ in the second reaction zone, so that after the roasting in the in situ preparation process is completed, the second reaction zone can be directly cooled to its reaction temperature to carry out the second catalytic reaction, thereby avoiding heat loss; compared with the inherent production method in the chemical industry, the second catalyst of the present invention is prepared in situ in the second reaction zone, which saves the washing and separation process after catalyst modification, the catalyst cooling process to room temperature after roasting, the catalyst transportation step, the catalyst filling step, the step of high-temperature pre-activation of the catalyst after loading into the reactor, etc., greatly improves the production efficiency and avoids the safety problems that may occur in the above-mentioned saved steps; more importantly, the second reaction zone can start the second catalytic reaction when it is cooled from the roasting temperature to its reaction temperature, the thermal energy is fully utilized, and the energy consumption in production is greatly saved.

[0104] In the present invention, the first catalytic reaction carried out in the first reaction zone is a conversion reaction of naphtha, and the second catalytic reaction carried out in the second reaction zone is a shape-selective alkylation reaction.

[0105] The present invention also provides a system for the above method, Figure 1 , 2 , as shown in Figure 3.

[0106] In one embodiment, Figure 1 , 2 As shown in , 3, the system comprises a first reaction zone 1, a second reaction zone 2 and a separation system 3; wherein,

[0107] The inlet of the first reaction zone 1 is connected to a naphtha raw material feed pipeline, and the outlet is connected to the inlet of the second reaction zone 2, for introducing naphtha raw material and causing a first catalytic reaction in the presence of a first catalyst therein, to obtain a first stream containing benzene, toluene, p-xylene and by-products and send the first stream to the second reaction zone 2;

[0108] The inlet of the second reaction zone 2 is connected to a toluene feed pipeline, and the outlet is connected to the inlet of the separation system 3, for introducing toluene and causing a second catalytic reaction in the presence of a second catalyst therein, to obtain a second stream containing benzene, toluene, p-xylene and by-products and send the second stream to the separation system 3;

[0109] The toluene-rich component outlet of the separation system 3 is connected to the toluene feed pipeline of the second reaction zone 2, so as to return the toluene-rich component outputted from the separation system 3 to the second reaction zone 2 as a source of toluene;

[0110] The benzene product outlet and the para-xylene product outlet of the separation system 3 are connected to the benzene product line and the para-xylene product line respectively, so as to output the benzene product and the para-xylene product of the separation system 3 .

[0111] In one embodiment, Figure 1 As shown, the outlet of the first reaction zone 1 is connected to the inlet of the separation system 3 , and is connected to the inlet of the second reaction zone 2 through the toluene-rich component outlet of the separation system 3 .

[0112] Specifically, in one embodiment, Figure 1 As shown, the system comprises a first reaction zone 1, a second reaction zone 2 and a separation system 3; wherein,

[0113] The inlet of the first reaction zone 1 is connected to a naphtha raw material feed pipeline, and the outlet is connected to the inlet of the separation system 3, for introducing naphtha raw material and causing a first catalytic reaction in the presence of a first catalyst therein, to obtain a first stream containing benzene, toluene, p-xylene and by-products and send the first stream to the separation system 3;

[0114] The inlet of the second reaction zone 2 is connected to a toluene feed pipeline, and the outlet is connected to the inlet of the separation system 3, for introducing toluene and causing a second catalytic reaction in the presence of a second catalyst therein, to obtain a second stream containing benzene, toluene, p-xylene and by-products and send the second stream to the separation system 3;

[0115] The toluene-rich component outlet of the separation system 3 is connected to the toluene feed pipeline of the second reaction zone 2, so as to return the toluene-rich component outputted from the separation system 3 to the second reaction zone 2 as a source of toluene;

[0116] The benzene product outlet and the para-xylene product outlet of the separation system 3 are connected to the benzene product line and the para-xylene product line respectively, so as to output the benzene product and the para-xylene product of the separation system 3 .

[0117] In such Figure 1 In the system shown, the first reaction zone 1 first performs a first catalytic reaction, and is connected to the separation system 3 for first logistics separation. The separated toluene-rich component enters the inlet of the second reaction zone 2 for a second catalytic reaction, and the second logistics enters the separation system 3 for product separation again. The separated toluene-rich component then enters the inlet of the second reaction zone 2 for circulation.

[0118] Specifically, in one embodiment, Figure 2 As shown, the system includes a first reaction zone 1, a second reaction zone 2 and a separation system 3, wherein the separation system 3 includes a first separation system 301 and a second separation system 302; wherein,

[0119] The inlet of the first reaction zone 1 is connected to a naphtha raw material feed pipeline, and the outlet is connected to the inlet of the first separation system 301, for introducing naphtha raw material and causing a first catalytic reaction in the presence of a first catalyst therein, to obtain a first stream containing benzene, toluene, p-xylene and by-products, and to send the first stream to the first separation system 301, and to separate and output a first benzene-rich component, a first toluene-rich component, a first p-xylene-rich component and a first by-product-rich component;

[0120] The inlet of the second reaction zone 2 is connected to a toluene feed pipeline, and the toluene feed pipeline is connected to the first toluene-rich component outlet of the first separation system 301. The outlet of the second reaction zone 2 and the first benzene-rich component outlet, the first p-xylene-rich component outlet and the first by-product-rich component outlet of the first separation system 301 are respectively connected to the inlet of the second separation system 302, so as to introduce toluene into the second reaction zone 2, and return the first toluene-rich component outputted by the first separation system 301 to the second reaction zone 2 as a source of toluene, and cause a second catalytic reaction in the presence of a second catalyst therein, so as to obtain a second logistics comprising benzene, toluene, p-xylene and by-products, and send the second logistics to the second separation system 302, and separate and output a second benzene-rich component, a second toluene-rich component, a second p-xylene-rich component and a second by-product-rich component;

[0121] The second toluene-rich component outlet of the second separation system 302 is connected to the toluene feed pipeline of the second reaction zone 2, so as to return the second toluene-rich component outputted from the second separation system 302 to the second reaction zone 2 as a source of toluene;

[0122] The benzene product outlet and the para-xylene product outlet of the second separation system 302 are connected to the benzene product line and the para-xylene product line respectively, so as to output the benzene product and the para-xylene product of the second separation system 302 .

[0123] In such Figure 2 In the system shown, the first logistics produced by the first catalytic reaction in the first reaction zone 1 first passes through the first separation system 301 for the first separation, and the separated first toluene-rich component enters the entrance of the second reaction zone 2 for the second catalytic reaction, and the separated first benzene-rich component, the first para-xylene-rich component and the first by-product-rich component are sent to the second separation system 302; the second logistics produced after the reaction in the second reaction zone 2 is connected to the second separation system 302 and is also sent to the second separation system 302 for separation, and the separated second toluene-rich component is returned to the entrance of the second reaction zone 2 for circulation, the separated second benzene-rich component is output as a benzene product, and the separated second para-xylene-rich component is output as a para-xylene product.

[0124] Specifically, in one embodiment, Figure 3As shown, the system comprises a first reaction zone 1, a second reaction zone 2 and a separation system 3; wherein,

[0125] The inlet of the first reaction zone 1 is connected to a naphtha raw material feed pipeline, and the outlet is connected to the inlet of the second reaction zone 2, for introducing naphtha raw material and causing a first catalytic reaction in the presence of a first catalyst therein, to obtain a first stream containing benzene, toluene, p-xylene and by-products and send the first stream to the second reaction zone 2;

[0126] The inlet of the second reaction zone 2 is connected to a toluene feed pipeline, and the outlet is connected to the inlet of the separation system 3, for introducing toluene and causing a second catalytic reaction in the presence of a second catalyst therein, to obtain a second stream containing benzene, toluene, p-xylene and by-products and send the second stream to the separation system 3;

[0127] The toluene-rich component outlet of the separation system 3 is connected to the toluene feed pipeline of the second reaction zone 2, so as to return the toluene-rich component outputted from the separation system 3 to the second reaction zone 2 as a source of toluene;

[0128] The benzene product outlet and the para-xylene product outlet of the separation system 3 are connected to the benzene product line and the para-xylene product line respectively, so as to output the benzene product and the para-xylene product of the separation system 3 .

[0129] In such Figure 3 In the system shown, the first logistics produced by the first catalytic reaction in the first reaction zone 1 is not separated by the separation system 3, but directly enters the second reaction zone 2 for the second catalytic reaction. The second logistics produced by the reaction in the second reaction zone 2 is connected with the separation system 3 and sent to the separation system 3 for separation. The toluene-rich component separated by the separation system 3 enters the inlet of the second reaction zone 2 for circulation, and the separated benzene-rich component is output as a benzene product, and the separated paraxylene-rich component is output as a paraxylene product.

[0130] In one embodiment, the first reaction zone 1 comprises one reactor or a plurality of reactors connected in series and / or in parallel.

[0131] In one embodiment, the second reaction zone 2 comprises one reactor or a plurality of reactors connected in series and / or in parallel.

[0132] In one embodiment, the reactor is at least one of a fixed bed, a fluidized bed or a moving bed.

[0133] In one embodiment, the first reaction zone 1 and the second reaction zone 2 are in the same reactor.

[0134] The system for preparing benzene and para-xylene from naphtha as raw material of the present invention utilizes naphtha raw material to prepare benzene and para-xylene, and adjusts product distribution through toluene recycling, thereby significantly improving the selectivity of benzene and para-xylene; since toluene contained in the first logistics and / or the second logistics obtained by the catalytic reaction is returned to the second reaction zone, material recycling is achieved, the yield of benzene and para-xylene is improved, and the economic benefit is improved; the process is simple and has strong feasibility, and the selectivity and yield of benzene and para-xylene can be greatly improved, thereby providing a new way to efficiently produce benzene and para-xylene from naphtha, and having important application value.

[0135] Raw materials used in the following examples / comparative examples:

[0136] Unless otherwise specified, the raw materials and reagents used in the present invention were purchased from commercial sources and used directly without treatment.

[0137] In the embodiment of the present invention, the type of naphtha raw material is coal direct liquefaction full-fraction naphtha, and its specific composition is as shown in Table 1.

[0138] Table 1 Composition of full-fraction naphtha from direct coal liquefaction

[0139] Carbon number Normal alkanes Isoalkanes Cycloalkanes Aromatics 4 0.67 0.25 / / 5 3.24 2.01 1.36 / 6 3.11 4.05 14.48 0.25 7 2.47 1.84 24.00 0.63 8 2.15 1.53 19.32 1.07 9 0.00 1.84 9.90 0.15 10 0.24 0.52 1.58 0.06 <![CDATA[11 + ]]> 0.01 2.54 0.73 0.01 total 11.88 14.58 71.37 2.17

[0140] In the examples, the catalyst wear index is measured using a MS-C wear index tester manufactured by Shenyang Hexing Machinery & Electronics Co., Ltd.

[0141] In the embodiment, the inner diameter of the fixed bed reactor is 1.5 cm; the inner diameter of the fixed fluidized bed reactor is 3 cm; and the inner diameter of the circulating fluidized bed reactor is 12 cm.

[0142] System and method

[0143] Example a1 (Sa1)

[0144] Use Figure 1 The system and preparation process shown in the figure prepares the p-xylene product, as follows:

[0145] (1) delivering naphtha feedstock to a first reaction zone 1, and performing a first catalytic reaction in the presence of a first catalyst to obtain a first stream; wherein the first stream comprises benzene, toluene, para-xylene and by-products;

[0146] (2) sending toluene to a second reaction zone 2 and performing a second catalytic reaction in the presence of a second catalyst to obtain a second stream; wherein the second stream comprises benzene, toluene, para-xylene and by-products;

[0147] (3) sending the first stream obtained in step (1) and the second stream obtained in step (2) to a separation system 3 for separation to obtain a toluene-rich component, a by-product-rich component, a benzene-rich component as a benzene product, and a para-xylene-rich component as a para-xylene product;

[0148] (4) The toluene-rich component separated in step (3) is returned to step (2) as a source of toluene.

[0149] Example a2 (Sa2)

[0150] Use Figure 2 The system and preparation process shown in the figure prepares the p-xylene product, as follows:

[0151] (1) delivering naphtha feedstock to a first reaction zone 1, and performing a first catalytic reaction in the presence of a first catalyst to obtain a first stream; wherein the first stream comprises benzene, toluene, para-xylene and by-products;

[0152] (2) sending toluene to a second reaction zone 2 and performing a second catalytic reaction in the presence of a second catalyst to obtain a second stream; wherein the second stream comprises benzene, toluene, para-xylene and by-products;

[0153] (3) sending the first logistics obtained in step (1) to the first separation system 301 for separation to obtain a first benzene-rich component, a first toluene-rich component, a first p-xylene-rich component and a first by-product-rich component; and sending the second logistics obtained in step (2) to the second separation system 302 for separation to obtain a second toluene-rich component, a second by-product-rich component, a second benzene-rich component as a benzene product and a second p-xylene-rich component as a p-xylene product;

[0154] (4) The first toluene-rich component separated by the first separation system 301 in step (3) and the second toluene-rich component separated by the second separation system 302 are returned to step (2) as a source of toluene.

[0155] Example a3 (Sa3)

[0156] Use Figure 3 The system and preparation process shown in the figure prepares the p-xylene product, as follows:

[0157] (1) delivering naphtha feedstock to a first reaction zone 1, and performing a first catalytic reaction in the presence of a first catalyst to obtain a first stream; wherein the first stream comprises benzene, toluene, para-xylene and by-products;

[0158] (2) sending toluene to a second reaction zone 2 and performing a second catalytic reaction in the presence of a second catalyst to obtain a second stream; wherein the second stream comprises benzene, toluene, para-xylene and by-products;

[0159] (3) sending the second stream obtained in step (2) to a separation system 3 for separation to obtain a toluene-rich component, a by-product-rich component, a benzene-rich component as a benzene product, and a para-xylene-rich component as a para-xylene product;

[0160] (4) The toluene-rich component separated in step (3) is returned to step (2) as a source of toluene.

[0161] Comparative Example a1 (Da1)

[0162] Use Figure 4 The system and preparation process shown prepare benzene products and paraxylene products, as follows:

[0163] (1) delivering naphtha feedstock to a first reaction zone 1, and performing a first catalytic reaction in the presence of a first catalyst to obtain a first stream; wherein the first stream comprises benzene, toluene, para-xylene and by-products;

[0164] (2) The first logistics obtained in step (1) is sent to a separation system 3 for separation to obtain a toluene-rich component, a by-product-rich component, a benzene-rich component as a benzene product, and a para-xylene-rich component as a para-xylene product.

[0165] Catalyst preparation

[0166] Example b1 (Sb1) Fixed bed lanthanum gallium modified ZSM-5 molecular sieve

[0167] The ZSM-5 molecular sieve was modified by metal impregnation to prepare [10% La5% Ga] ZSM-5 (i.e., the first catalyst C1) and FX-[10% La5% Ga] ZSM-5 (i.e., the first catalyst C1). 颗粒 ), specifically including the following steps:

[0168] (i) preparing a soluble metal salt aqueous solution of lanthanum nitrate and gallium nitrate, wherein the La content is 10% of the amount of the ZSM-5 molecular sieve used, the Ga content is 5% of the amount of the ZSM-5 molecular sieve used, and the water content is the saturated water absorption of the ZSM-5 molecular sieve used;

[0169] (ii) impregnating 100 g of ZSM-5 molecular sieve (Nankai University Catalyst Plant, silicon-aluminum ratio is Si / Al=20 in terms of atomic ratio) in the soluble metal salt aqueous solution obtained in step (i) to obtain an impregnated molecular sieve; wherein:

[0170] The impregnation conditions include: impregnation temperature of 80°C and impregnation time of 6h;

[0171] (iii) The impregnated molecular sieve obtained in step (ii) is dried and calcined to obtain the metal-modified ZSM-5 molecular sieve catalyst - [10% La5% Ga] ZSM-5 (i.e., the first catalyst C1), which is then tableted, crushed, and sieved to obtain shaped molecular sieve catalyst particles with a particle size of 40 to 60 meshes, recorded as FX-[10% La5% Ga] ZSM-5 (i.e., the first catalyst C1). 颗粒 );in,

[0172] Drying conditions include: drying at 120°C for 4 h in air atmosphere;

[0173] The calcination conditions include: calcination at 550° C. for 4 h in an air atmosphere.

[0174] Example b2 (Sb2) Fixed bed lanthanum gallium modified ZSM-5 molecular sieve

[0175] [10% La10% Ga] ZSM-5 (i.e., the first catalyst C2) and FX-[10% La10% Ga] ZSM-5 (i.e., the first catalyst C2) were prepared according to the method of Example b1 (Sb1). 颗粒 ), wherein the difference between it and embodiment b1 (Sb1) is only that:

[0176] In step (i), a soluble metal salt aqueous solution of lanthanum nitrate and gallium nitrate is prepared so that the La content is 10% of the amount of ZSM-5 molecular sieve used, the Ga content is 10% of the amount of ZSM-5 molecular sieve used, and the water content is the saturated water absorption capacity of the ZSM-5 molecular sieve used.

[0177] Example b3 (Sb3) Fixed bed lanthanum zinc modified ZSM-5 molecular sieve

[0178] [10% La 5% Zn] ZSM-5 (i.e., the first catalyst C3) and FX-[10% La 5% Zn] ZSM-5 (i.e., the first catalyst C3) were prepared according to the method of Example b1 (Sb1). 颗粒 ), wherein the difference between it and embodiment b1 (Sb1) is only that:

[0179] In step (i), a soluble metal salt aqueous solution of lanthanum nitrate and zinc nitrate is prepared so that the La content is 10% of the amount of ZSM-5 molecular sieve used, the Zn content is 5% of the amount of ZSM-5 molecular sieve used, and the water content is the saturated water absorption of the ZSM-5 molecular sieve used.

[0180] Example b4 (Sb4) Fixed bed lanthanum zinc modified ZSM-5 molecular sieve

[0181] [5%La5%Zn]ZSM-5 (i.e., the first catalyst C4) and FX-[5%La5%Zn]ZSM-5 (i.e., the first catalyst C4) were prepared according to the method of Example b1 (Sb1). 颗粒 ), wherein the difference between it and embodiment b1 (Sb1) is only that:

[0182] In step (i), a soluble metal salt aqueous solution of lanthanum nitrate and zinc nitrate is prepared so that the La content is 5% of the amount of ZSM-5 molecular sieve used, the Zn content is 5% of the amount of ZSM-5 molecular sieve used, and the water content is the saturated water absorption of the ZSM-5 molecular sieve used.

[0183] Example b5 (Sb5) Fluidized bed lanthanum zinc modified and silanized ZSM-5 molecular sieve

[0184] The [10% La 5% Zn] ZSM-5 (i.e., the first catalyst C3) prepared in Example b3 (Sb3) is mixed with an amorphous binder containing aluminum or silicon and spray-dried to form a mold. The specific steps are as follows:

[0185] [10%La5%Zn]ZSM-5 (i.e., the first catalyst C3), kaolin, pseudo-boehmite, silica sol, alumina sol, xanthan gum (i.e., bio-gum) and water are uniformly mixed, and a slurry is obtained by beating, grinding and defoaming. The weight proportions of the components in the slurry are as follows:

[0186]

[0187] The obtained slurry is spray-dried to obtain a microsphere particle sample with a particle size distribution of 20 to 100 μm;

[0188] The obtained microsphere particle sample was calcined at 550°C in a muffle furnace for 4 hours to obtain a [10%La5%Zn]ZSM-5 shaped molecular sieve with an abrasion index of 0.9, which was recorded as FL-[10%La5%Zn]ZSM-5 (i.e., the first catalyst C5).

[0189] Preparation and reaction evaluation of benzene and p-xylene

[0190] Example c1 (Sc1)

[0191] The first catalyst C1 prepared by using the system and preparation process of Example a1 (Sa1) and Example b1 (Sb1) 颗粒 (i.e., FX-[10%La5%Ga]ZSM-5) was used to prepare benzene product N1 and para-xylene product P1, as follows:

[0192] (1) delivering naphtha feedstock to a first reaction zone 1, and performing a first catalytic reaction in the presence of a first catalyst to obtain a first stream; wherein the first stream comprises benzene, toluene, para-xylene and by-products;

[0193] (2) sending toluene to a second reaction zone 2 and performing a second catalytic reaction in the presence of a second catalyst to obtain a second stream; wherein the second stream comprises benzene, toluene, para-xylene and by-products;

[0194] (3) sending the first stream obtained in step (1) and the second stream obtained in step (2) to a separation system 3 for separation to obtain a toluene-rich component, a by-product-rich component, a benzene-rich component as a benzene product N1, and a para-xylene-rich component as a para-xylene product P1;

[0195] (4) returning the toluene-rich component separated in step (3) to step (2) as a source of toluene; wherein:

[0196] In step (1), after the first catalyst is loaded in the first reaction zone 1, it is first treated with 50 mL / min nitrogen at 550° C. for 1 h, and then cooled to 525° C. under a nitrogen atmosphere;

[0197] The first catalyst is the first catalyst C1 prepared in Example b1 (Sb1) 颗粒 , the dosage is 5g;

[0198] The naphtha raw material is fed by a micro-feed pump, and the weight space velocity of the naphtha raw material is 4.0h -1 , reaction pressure 0.1MPa;

[0199] In step (2), after the first catalyst (5 g) is loaded in the second reaction zone 2, it is first treated with 50 mL / min nitrogen at 550° C. for 1 hour, and then cooled to 400° C. under a nitrogen atmosphere; then tetraethyl silicate is fed with a micro-feed pump, and the weight space velocity of tetraethyl silicate is 0.1 h -1 , normal pressure, stop feeding after 60 minutes, purge with nitrogen, heat to 550°C, calcine for 4 hours in air atmosphere, and prepare FX-[10%La5%Ga]ZSM-5-T in situ, i.e., the second catalyst; then cool to 400°C for the second catalytic reaction;

[0200] The feed weight space velocity of toluene is 1.5h -1 .

[0201] Reaction evaluation:

[0202] The second logistics of the second reaction zone was analyzed by online Agilent 7890 gas chromatography. Samples were taken for analysis after 30 minutes of reaction. The product distribution after deducting the toluene component (toluene raw material of the second reaction zone) was shown in Table 2.

[0203] The first stream of the first reaction zone and the second stream of the second reaction zone were mixed and analyzed by online Agilent 7890 gas chromatography. Samples were taken for analysis after 30 minutes of reaction. The product distribution after deducting the toluene component is shown in Table 3.

[0204] Table 2 Product distribution of the second stream

[0205]

[0206] Table 3 Product distribution after mixing the first and second logistics

[0207]

[0208] a Aliphatic hydrocarbons with carbon numbers greater than 4 in the reaction products are used as naphtha raw materials.

[0209] Example c2 (Sc2)

[0210] The first catalyst C2 prepared by using the system and preparation process of Example a1 (Sa1) and Example b2 (Sb2) 颗粒 (i.e., FX-[10%La10%Ga]ZSM-5) to prepare benzene product N2 and para-xylene product P2; the only difference between it and Example c1 (Sc1) is that:

[0211] In step (1), the first catalyst is the first catalyst C2 obtained in Example b2 (Sb2) 颗粒 , the dosage is 5g;

[0212] In step (2), the first catalyst is the first catalyst C2 obtained in Example b2 (Sb2) 颗粒 , the dosage is 5g; the first catalyst is in situ prepared FX-[10%La10%Ga]ZSM-5-T, which is the second catalyst.

[0213] Reaction evaluation:

[0214] The second logistics of the second reaction zone was analyzed by online Agilent 7890 gas chromatography. Samples were taken for analysis after 30 minutes of reaction. The product distribution after deducting the toluene component (toluene raw material of the second reaction zone) was shown in Table 4.

[0215] The first stream of the first reaction zone and the second stream of the second reaction zone were mixed and analyzed by online Agilent 7890 gas chromatography. Samples were taken for analysis after 30 minutes of reaction. The product distribution after deducting the toluene component is shown in Table 5.

[0216] Table 4 Product distribution of the second stream

[0217]

[0218]

[0219] Table 5 Product distribution after mixing the first and second logistics

[0220]

[0221] a Aliphatic hydrocarbons with carbon numbers greater than 4 in the reaction products are used as naphtha raw materials.

[0222] Example c3 (Sc3)

[0223] The first catalyst C3 prepared by using the system and preparation process of Example a1 (Sa1) and Example b3 (Sb3) 颗粒 (i.e., FX-[10%La5%Zn]ZSM-5) to prepare benzene product N3 and para-xylene product P3; the only difference between it and Example c1 (Sc1) is that:

[0224] In step (1), the first catalyst is the first catalyst C3 obtained in Example b3 (Sb3) 颗粒 , the dosage is 5g;

[0225] In step (2), the first catalyst is the first catalyst C3 obtained in Example b3 (Sb3) 颗粒 , the dosage is 5g; the first catalyst is in situ prepared FX-[10%La5%Zn]ZSM-5-T, which is the second catalyst.

[0226] Reaction evaluation:

[0227] The second logistics of the second reaction zone was analyzed by online Agilent7890 gas chromatography. Samples were taken for analysis after 30 minutes of reaction. The product distribution after deducting the toluene component (toluene raw material of the second reaction zone) was shown in Table 6.

[0228] The first logistics of the first reaction zone and the second logistics of the second reaction zone were mixed and analyzed by online Agilent7890 gas chromatography. Samples were taken for analysis after 30 minutes of reaction. The product distribution after deducting the toluene component is shown in Table 7.

[0229] Table 6 Product distribution of the second stream

[0230]

[0231] Table 7 Product distribution after mixing the first and second logistics

[0232]

[0233]

[0234] a Aliphatic hydrocarbons with carbon numbers greater than 4 in the reaction products are used as naphtha raw materials.

[0235] Example c4 (Sc4)

[0236] The system and preparation process of Example a1 (Sa1) and the first catalyst C5 (i.e., FL-[10%La5%Zn]ZSM-5) prepared in Example b5 (Sb5) are used to prepare benzene product N4 and para-xylene product P4; the only difference between it and Example c1 (Sc1) is that:

[0237] In step (1), the first catalyst is the first catalyst C5 prepared in Example b5 (Sb5), and the amount used is 5 g;

[0238] In step (2), the first catalyst is the first catalyst C5 prepared in Example b5 (Sb5), and the amount used is 5 g; the first catalyst is in situ prepared FL-[10%La5%Zn]ZSM-5-T, that is, the second catalyst.

[0239] Reaction evaluation:

[0240] The second logistics of the second reaction zone was analyzed by online Agilent7890 gas chromatography. Samples were taken for analysis after 30 minutes of reaction. The product distribution after deducting the toluene component (toluene raw material of the second reaction zone) was shown in Table 8.

[0241] The first logistics of the first reaction zone and the second logistics of the second reaction zone were mixed and analyzed by online Agilent7890 gas chromatography. Samples were taken for analysis after 30 minutes of reaction. The product distribution after deducting the toluene component is shown in Table 9.

[0242] Table 8 Product distribution of the second logistics

[0243]

[0244]

[0245] Table 9 Product distribution after mixing the first and second logistics

[0246]

[0247] a Aliphatic hydrocarbons with carbon numbers greater than 4 in the reaction products are used as naphtha raw materials.

[0248] Example c5 (Sc5)

[0249] The first catalyst C4 prepared by using the system and preparation process of Example a1 (Sa1) and Example b4 (Sb4) 颗粒 (i.e., FX-[5%La5%Zn]ZSM-5) to prepare benzene product N5 and para-xylene product P5; the only difference between it and Example c1 (Sc1) is that:

[0250] In step (1), the first catalyst is the first catalyst C4 obtained in Example b4 (Sb4) 颗粒 , the dosage is 5g;

[0251] In step (2), the first catalyst is the first catalyst C4 obtained in Example b4 (Sb4) 颗粒 , the dosage is 5g; the first catalyst is in situ prepared FX-[5%La5%Zn]ZSM-5-T, which is the second catalyst.

[0252] Reaction evaluation:

[0253] The second logistics of the second reaction zone was analyzed by online Agilent7890 gas chromatography. Samples were taken for analysis after 30 minutes of reaction. The product distribution after deducting the toluene component (toluene raw material of the second reaction zone) was shown in Table 10.

[0254] The first logistics of the first reaction zone and the second logistics of the second reaction zone were mixed and analyzed by online Agilent7890 gas chromatography. Samples were taken for analysis after 30 minutes of reaction. The product distribution after deducting the toluene component is shown in Table 11.

[0255] Table 10 Product distribution of the second stream

[0256]

[0257] Table 11 Product distribution after mixing the first and second logistics

[0258]

[0259] a Aliphatic hydrocarbons with carbon numbers greater than 4 in the reaction products are used as naphtha raw materials.

[0260] Comparative Example c1 (Dc1)

[0261] The first catalyst C1 prepared by using the system and preparation process of comparative example a1 (Da1) and example b1 (Sb1) 颗粒 (i.e., FX-[10%La5%Ga]ZSM-5) is used to prepare benzene product N1' and p-xylene product P1', as follows:

[0262] (1) delivering naphtha feedstock to a first reaction zone 1, and performing a first catalytic reaction in the presence of a first catalyst to obtain a first stream; wherein the first stream comprises benzene, toluene, para-xylene and by-products;

[0263] (2) sending the first stream obtained in step (1) to a separation system 3 for separation to obtain a toluene-rich component, a by-product-rich component, a benzene-rich component as a benzene product N1', and a para-xylene-rich component as a para-xylene product P1'; wherein:

[0264] In step (1), after the first catalyst is loaded in the first reaction zone 1, it is first treated with 50 mL / min nitrogen at 550° C. for 1 h, and then cooled to 525° C. under a nitrogen atmosphere;

[0265] The first catalyst is the first catalyst C1 prepared in Example b1 (Sb1) 颗粒 , the dosage is 5g;

[0266] The naphtha raw material is fed by a micro-feed pump, and the weight space velocity of the naphtha raw material is 4.0h -1 , reaction pressure 0.1MPa.

[0267] Reaction evaluation:

[0268] The first logistics of the first reaction zone was analyzed by online Agilent7890 gas chromatography. Samples were taken for analysis after 30 minutes of reaction. The product distribution is shown in Table 12.

[0269] Table 12 Product distribution of the first stream

[0270]

[0271] a Aliphatic hydrocarbons with carbon numbers greater than 4 in the reaction products are used as naphtha raw materials.

[0272] Comparative Example c2 (Dc2)

[0273] The first catalyst C2 prepared by using the system and preparation process of comparative example a1 (Da1) and example b2 (Sb2) 颗粒 (i.e., FX-[10%La10%Ga]ZSM-5) to prepare benzene product N2' and para-xylene P2'; the only difference between it and comparative example c1 (Dc1) is that:

[0274] In step (1), the first catalyst is the first catalyst C2 obtained in Example b2 (Sb2) 颗粒 , the dosage is 5g.

[0275] Reaction evaluation:

[0276] The first logistics of the first reaction zone was analyzed by online Agilent7890 gas chromatography. Samples were taken for analysis after 30 minutes of reaction. The product distribution is shown in Table 13.

[0277] Table 13 Product distribution of the first stream

[0278]

[0279] a Aliphatic hydrocarbons with carbon numbers greater than 4 in the reaction products are used as naphtha raw materials.

[0280] Comparative Example c3 (Dc3)

[0281] The first catalyst C3 prepared by using the system and preparation process of comparative example a1 (Da1) and example b3 (Sb3) 颗粒 (i.e., FX-[10%La5%Zn]ZSM-5) was used to prepare benzene product N3' and para-xylene P3'; the only difference between it and comparative example c1 (Dc1) is that:

[0282] In step (1), the first catalyst is the first catalyst C3 obtained in Example b3 (Sb3) 颗粒 , the dosage is 5g.

[0283] Reaction evaluation:

[0284] The first logistics of the first reaction zone was analyzed by online Agilent7890 gas chromatography. Samples were taken for analysis after 30 minutes of reaction. The product distribution is shown in Table 14.

[0285] Table 14 Product distribution of the first stream

[0286]

[0287] a The aliphatic hydrocarbons with carbon number greater than 4 in the reaction products are used as naphtha raw materials.

[0288] Comparative Example c4 (Dc4)

[0289] The system and preparation process of Comparative Example a1 (Da1) and the first catalyst C5 (i.e., FL-[10%La5%Zn]ZSM-5) prepared in Example b5 (Sb5) were used to prepare benzene product N4' and para-xylene P4'; the only difference between it and Comparative Example c1 (Dc1) is that:

[0290] In step (1), the first catalyst is the first catalyst C5 prepared in Example b5 (Sb5), and the amount used is 5 g.

[0291] Reaction evaluation:

[0292] The first logistics of the first reaction zone was analyzed by online Agilent7890 gas chromatography. Samples were taken for analysis after 30 minutes of reaction. The product distribution is shown in Table 15.

[0293] Table 15 Product distribution of the first stream

[0294]

[0295]

[0296] a Aliphatic hydrocarbons with carbon numbers greater than 4 in the reaction products are used as naphtha raw materials.

[0297] Comparative Example c5 (Dc5)

[0298] The first catalyst C4 prepared by using the system and preparation process of comparative example a1 (Da1) and example b4 (Sb4) 颗粒 (i.e., FX-[5%La5%Zn]ZSM-5) was used to prepare benzene product N5' and para-xylene P5'; the only difference between it and comparative example c1 (Dc1) is that:

[0299] In step (1), the first catalyst is the first catalyst C4 obtained in Example b4 (Sb4) 颗粒 , the dosage is 5g.

[0300] Reaction evaluation:

[0301] The first logistics of the first reaction zone was analyzed by online Agilent7890 gas chromatography. Samples were taken for analysis after 30 minutes of reaction. The product distribution is shown in Table 16.

[0302] Table 16 Product distribution of the first stream

[0303]

[0304]

[0305] a Aliphatic hydrocarbons with carbon numbers greater than 4 in the reaction products are used as naphtha raw materials.

[0306] According to the comparison between the embodiment and the comparative example:

[0307] Under the same other conditions, compared with the existing preparation process, the method of the present invention can significantly improve the selectivity of (benzene + PX) in the product and the selectivity of PX in the xylene product.

Claims

1. A method for preparing benzene and p-xylene using naphtha as raw material, characterized in that: The method comprises: (1) delivering a naphtha feedstock to a first reaction zone and performing a first catalytic reaction in the presence of a first catalyst to obtain mixed aromatic hydrocarbons as a first stream; wherein the first stream comprises benzene, toluene, para-xylene and by-products; (2) sending toluene to a second reaction zone and performing a second catalytic reaction in the presence of a second catalyst to obtain a second stream; wherein the second stream comprises benzene, toluene, para-xylene and by-products; (3) sending the first logistics obtained in step (1) and / or the second logistics obtained in step (2) to a separation system for separation to obtain a toluene-rich component, a by-product-rich component, a benzene-rich component as a product, and a para-xylene-rich component, respectively; (4) The toluene-rich component separated in step (3) is returned to step (2) as a source of toluene.

2. The method according to claim 1, characterized in that In step (3), the first logistics obtained in step (1) and the second logistics obtained in step (2) are sent to a separation system for separation to obtain a benzene-rich component, a toluene-rich component, a para-xylene-rich component and a by-product-rich component.

3. The method according to claim 1, characterized in that The separation system comprises a first separation system and a second separation system; In step (3), the first stream obtained in step (1) is sent to a first separation system for separation to obtain a first benzene-rich component, a first toluene-rich component, a first p-xylene-rich component and a first by-product-rich component; The second stream obtained in step (2) is sent to a second separation system for separation to obtain a second benzene-rich component, a second toluene-rich component, a second p-xylene-rich component and a second by-product-rich component; wherein: The benzene-rich component obtained in step (3) comprises a first benzene-rich component and a second benzene-rich component; The toluene-rich component obtained in step (3) comprises a first toluene-rich component and a second toluene-rich component; The p-xylene-rich component obtained in step (3) comprises a first p-xylene-rich component and a second p-xylene-rich component; The by-product-rich component obtained in step (3) comprises a first by-product-rich component and a second by-product-rich component.

4. The method according to claim 3, characterized in that In step (3), the first stream obtained in step (1) is sent to a first separation system for separation to obtain a first benzene-rich component, a first toluene-rich component, a first p-xylene-rich component and a first by-product-rich component; The first benzene-rich component, the first para-xylene-rich component and the first by-product-rich component output by the first separation system and the second logistics obtained in step (2) are sent to the second separation system for separation to obtain a second benzene-rich component, a second toluene-rich component, a second para-xylene-rich component and a second by-product-rich component.

5. The method according to claim 1, characterized in that In step (3), the second stream obtained in step (2) is sent to a separation system for separation to obtain a benzene-rich component, a toluene-rich component, a p-xylene-rich component and a by-product-rich component respectively; Preferably, the method further comprises a step (5), sending the first logistics obtained in the step (1) to the step (2) as a source of toluene.

6. The method according to any one of claims 1 to 5, characterized in that The first catalyst is selected from any one or more combinations of metal-modified ZSM-5 molecular sieve catalysts; and / or The second catalyst is selected from any one or more combinations of ZSM-5 molecular sieve catalysts modified by silanization and metal modification; preferably, the second catalyst is selected from any one or more combinations of ZSM-5 molecular sieve catalysts modified by metal modification and silanization in sequence; Preferably, in the first catalyst and the second catalyst, the metal modification is bimetallic modification, and the first metal is selected from any one of La, Ce, Mg and Ca, and the second metal is selected from any one of Ga and Zn.

7. The method according to any one of claims 1 to 6, characterized in that In step (1), the conditions of the first catalytic reaction include: The reaction temperature is 300 to 600° C.; and / or, The reaction pressure is 0.1-0.5 MPa; and / or, The feed weight space velocity of the naphtha raw material I is 0.1 to 10 h -1 .

8. The method according to any one of claims 1 to 7, characterized in that In step (2), the conditions of the second catalytic reaction include: The reaction temperature is 300 to 600° C.; and / or, The reaction pressure is 0.1-0.5 MPa MPa; and / or, The feed weight space velocity of toluene is 0.1~6h -1 .

9. The method according to any one of claims 1 to 8, characterized in that The second catalyst is prepared in situ in the second reaction zone; Preferably, the in-situ preparation method is as follows: the first catalyst is loaded into the second reaction zone, a silanization agent is introduced to contact the first catalyst, and the catalyst is calcined at a high temperature to obtain the second catalyst in-situ; Preferably, the calcination temperature is 500-700°C; and / or the calcination time is 2-8h; Preferably, after the calcination is completed, the second reaction zone is directly cooled to its reaction temperature to carry out the second catalytic reaction.

10. A system for use in the method according to any one of claims 1 to 9.

Images