Method for producing toluene and xylene

Abstract

The invention relates to the field of petrochemical industry production, and discloses a method for producing toluene and xylene. The method comprises the following steps: in the presence of hydrogen and an alkylation catalyst, alkane and benzene are subjected to a contact reaction in n catalyst bed layers connected in series to obtain toluene and xylene, wherein the hydrogen and the benzene are introduced from the uppermost layer of the n catalyst bed layers connected in series from top to bottom; the alkane is divided into N parts, the N parts of alkane are respectively introduced into n catalyst bed layers connected in series, and n is a positive integer and is greater than or equal to 2; the alkylation catalyst comprises a molecular sieve, a binder and an active component loaded on the binder, on the basis of the total amount of the alkyl catalyst, the content of the active component in terms of oxide is 0.05-5 wt%. The method can effectively solve the problems of conversion of benzene and efficient utilization of alkane in industry, improve the selectivity of target products toluene and xylene, reduce side reactions and reaction energy consumption, improve the reaction performance and prolong the service life.

Description

Technical Field

[0001] The invention relates to the technical field of petrochemical production, and in particular to a method for producing toluene and xylene. Background Art

[0002] In recent years, with the development of clean fuels, the limit of benzene content in gasoline has become an important issue, because it is discharged into the atmosphere due to incomplete combustion, which is potentially carcinogenic to human health. Today, with the upgrade of China's gasoline (GB17930-2019), the benzene content in fuel is limited to less than 0.8%, which is stricter than the European standard (<1%). In the future, with the improvement of national environmental protection standards, the benzene content in fuel will be further restricted. At present, the main source of benzene is the catalytic reforming unit of the refinery. The methods for reducing the benzene content in the reforming liquid include extraction, distillation, adsorption, hydroisomerization and alkylation. Among these methods, benzene alkylation technology has attracted much attention due to its high conversion rate and strong flexibility. Generally speaking, the alkylating agents used in benzene alkylation technology are alcohols, olefins and halogenated alkanes. However, these alkylating agents all have some disadvantages, such as the introduction of alcohols leading to low product quality and the generation of wastewater. Olefins as alkylating agents cannot be methylated, which can easily cause the catalyst to coke and deactivate quickly. Halogenated alkanes as alkylating agents are prone to produce halogenated acids that affect product quality and corrode equipment. Compared with traditional alkylating agents, directly using alkanes as alkylating agents has great advantages: (1) The reaction system is halogen-free, which reduces the impact of equipment corrosion; (2) The raw materials are cheap and easy to obtain from the residual liquid; (3) The catalyst is not easily deactivated, which reduces the formation of coke. All these advantages greatly enhance the potential research value of alkanes as alkylating agents. In addition, mixing the raw materials benzene and alkanes in proportion and then reacting them in a fixed bed reactor will lead to an increase in side reaction methane and heavy aromatics, and the catalyst has low selectivity for the target product. Summary of the invention

[0003] The purpose of the present invention is to overcome the problems existing in the prior art and provide a method for producing toluene and xylene, which can effectively solve the industrial conversion of excess benzene and the efficient utilization of alkanes, improve the selectivity of the target products toluene and xylene, reduce side reactions and reaction energy consumption, and improve reaction performance and service life.

[0004] In order to achieve the above object, the present invention provides a method for producing toluene and xylene, wherein the method comprises: in the presence of hydrogen and an alkylation catalyst, contacting alkanes and benzene in n catalyst beds connected in series to obtain toluene and xylene; wherein the hydrogen and benzene are introduced from the top to the bottom of the uppermost layer of the n catalyst beds connected in series; the alkane is divided into N parts, and the N parts of the alkane are respectively introduced into the n catalyst beds connected in series, wherein n is a positive integer and n≥2; the alkylation catalyst comprises a molecular sieve, a binder and an active component supported on the binder; and the content of the active component is 0.05-5% by weight based on the total amount of the alkylation catalyst.

[0005] Preferably, the preparation method of the alkylation catalyst comprises the following steps:

[0006] (1) treating a molecular sieve precursor in an acid to obtain a molecular sieve;

[0007] (2) The binder is immersed in the active component precursor solution, mixed with the molecular sieve of step (1) after a first drying and a first calcination, and then aged, dried and calcined for a second time to obtain an alkylation catalyst.

[0008] The present invention adopts a method of coupling benzene alkylation reaction by using alkane protonation cracking, and directly uses alkane as an alkylation agent, thereby having a cost advantage in terms of raw materials. At the same time, the alkane is introduced into the corresponding catalyst bed in N portions, which effectively solves the problems of uneven mixing of bed materials and single-pass conversion rate, and achieves excellent results.

[0009] The total acid amount of the alkylation catalyst selected in the method provided by the present invention is less reduced than the total acid amount of the modified molecular sieve, which can ensure the acid amount of the alkylation catalyst, improve the performance of the alkylation catalyst, and further improve the selectivity of the target product.

[0010] The method provided by the present invention, under preferred circumstances, firstly performs modification treatment with an acid to obtain a modified molecular sieve to increase the total acid content of the modified molecular sieve, and then directly loads the active component on a binder and then mixes it with the modified molecular sieve to form a mixture, thereby increasing the total acid content of the zeolite molecular sieve while avoiding the influence of the interaction between the active component and the zeolite on the total acid content of the catalyst, so as to maintain a suitable total acid content of the alkylation catalyst, and at the same time separate the active component from the hydrogenation metal phase, thereby effectively improving the performance of the alkylation catalyst and the selectivity of the target product.

[0011] In the present invention, preferably, the catalyst within the preferred range of the present invention is used for grading, which can improve the conversion rate of the raw material and the selectivity of the target product. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1It is a schematic diagram of the method provided by the present invention.

[0013] Description of Reference Numerals

[0014] A-Hydrogen B-Benzene

[0015] D-Alkane E-High score tank DETAILED DESCRIPTION

[0016] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0017] In the present invention, the total pyridine infrared acid content, B acid, and L acid of the alkylation catalyst, molecular sieve, and molecular sieve precursor are determined by using a Nicolet Nexsus TM infrared spectrometer (FT-IR) to perform pyridine infrared adsorption and diffuse reflectance method. The specific test conditions are: weigh about 15 mg of the sample, press the body into a tablet, and The circular slice was placed in a quartz sample cell frame and heated at 400°C, 1.3×10 -5 kPa vacuum conditions, dehydrated for 2 hours to 200℃, then adsorbed pyridine for 10 minutes, balanced for 5 minutes, low vacuum pumped for 10 minutes, high vacuum pumped for 30 minutes for desorption and IR scanning, then raised to 300℃ at 10℃ / min, balanced for 5 minutes, and IR scanning; then raised to 400℃ at 10℃ / min, balanced for 5 minutes, and IR scanning. The amount of B acid and L acid was calculated according to the obtained spectrum at 1540cm -1 and 1450cm -1 Calculation of the absorption peak area of ​​the attachment.

[0018] In the present invention, the molecular sieve precursor molar ratio is measured by the S4 PIONEER X-ray fluorescence spectrometry (XRF) method of Bruker, Germany. The specific test conditions are: the powder sample needs to be at least 3-5g, and the primary X-rays emitted by the X-ray tube of the X-ray fluorescence spectrometry are injected into the sample to excite the characteristic spectral lines of each element in the sample.

[0019] The invention provides a method for producing toluene and xylene, wherein the method comprises: in the presence of hydrogen and an alkylation catalyst, contacting alkanes and benzene in n catalyst beds connected in series to react, so as to obtain toluene and xylene; wherein the hydrogen and benzene are introduced from the top of the n catalyst beds connected in series from top to bottom; the alkanes are divided into N parts, and the N parts of alkanes are respectively introduced into the n catalyst beds connected in series, wherein n is a positive integer, and n≥2; the alkylation catalyst comprises a molecular sieve, a binder and an active component loaded on the binder; and based on the total amount of the alkylation catalyst, the content of the active component is 0.05-5% by weight.

[0020] In the present invention, there is no particular limitation on the amount of alkane used. Preferably, the alkane is equally divided into N parts and introduced into the corresponding n catalyst beds connected in series.

[0021] In the present invention, there is no particular limitation on the loading method and amount of the catalyst. Preferably, n catalyst beds connected in series are respectively loaded with an equal amount of alkylation catalyst.

[0022] In the present invention, preferably, n is 2-10, and n is a positive integer. Through this preferred implementation, the problems of uneven mixing of bed materials and single-pass conversion rate can be effectively solved, and excellent results are achieved.

[0023] In the present invention, the total acid amount of the alkylation catalyst is slightly lower than that of the molecular sieve, but can still maintain a high acid amount to improve the conversion rate of the raw material. Preferably, the total acid amount of the alkylation catalyst is reduced by 10-40%, preferably 14-30% compared to the molecular sieve.

[0024] In the present invention, preferably, the B acid content of the alkylation catalyst is 0.1-1 mmol / g, the L acid content is 0.05-0.3 mmol / g, and the total acid content is 0.15-1.3 mmol / g; further preferably, the B acid content of the alkylation catalyst is 0.2-1 mmol / g, the L acid content is 0.1-0.3 mmol / g, and the total acid content is 0.4-1.25 mmol / g. The advantage of adopting this preferred embodiment is that the alkylation catalyst can fully crack the reaction alkane while maintaining a suitable acid content, and the cracking product undergoes an alkylation reaction with benzene at the B acid site, thereby increasing the yield of toluene and xylene.

[0025] In the present invention, there is no particular limitation on the type of active component, and it can be any active component conventionally defined in the art. Preferably, the active component is selected from at least one of Group IIIA metal elements, Group VIII metal elements, Group IIB metal elements, and Group VIB metal elements, and is further preferably selected from at least one of Mo, Ni, Ga, Zn, and Pt.

[0026] In the present invention, there is no particular limitation on the type of binder. Preferably, the binder is aluminum oxide and / or silicon oxide, and more preferably aluminum oxide.

[0027] In the present invention, preferably, the molecular sieve is an MFI type molecular sieve and / or an MWW type molecular sieve, preferably an MFI type molecular sieve. The advantage of adopting this preferred embodiment is that the MFI type molecular sieve has good pores and acidity, which is conducive to the reaction cracking and alkylation.

[0028] In the present invention, preferably, the content of the active component calculated as oxide is 1-2% by weight.

[0029] It should be noted that when the active component is Ga, the content of the active component in the catalyst is calculated as Ga2O3.

[0030] In the present invention, preferably, based on the total amount of the alkylation catalyst, the content of the molecular sieve is 60-85% by weight, and the content of the binder is 10-35% by weight based on a dry basis.

[0031] In the present invention, the content of each component in the catalyst is calculated by the feed amount.

[0032] In the present invention, preferably, along the logistics direction, n catalyst beds connected in series are all loaded with alkylation catalysts. In the present invention, the types of alkylation catalysts loaded in the n catalyst beds connected in series may be the same or different, preferably different, and more preferably the total acid amount of each alkylation catalyst loaded in the n catalyst beds connected in series is gradually reduced, preferably reduced by 0.1-0.95 mmol / g, and more preferably reduced by 0.12-0.7 mmol / g. The advantage of adopting this preferred embodiment is that the grading method of gradually lowering the acidity of the bed is adopted, which can reduce the excessive cracking and conversion of the target products toluene and xylene into benzene in the subsequent bed on the one hand, and can also reduce the excessive methane generation on the other hand.

[0033] In a preferred embodiment, the preparation method of the alkylation catalyst comprises the following steps:

[0034] (1) treating a molecular sieve precursor in an acid to obtain a molecular sieve;

[0035] (2) The binder is immersed in the active component precursor solution, mixed with the molecular sieve of step (1) after a first drying and a first calcination, and then aged, dried and calcined for a second time to obtain an alkylation catalyst.

[0036] In the present invention, the total acid content of the molecular sieve is increased by first subjecting the molecular sieve precursor to acid treatment, and then the active component is first impregnated on a binder and then mixed with the molecular sieve to form a mixture, thereby ensuring the acid content of the molecular sieve while reducing the loss of the acid content of the alkylation catalyst, thereby ensuring the performance of the alkylation catalyst, and improving the conversion rate of the raw material and the selectivity of the target product.

[0037] In the present invention, preferably, in step (1), the molecular sieve precursor is an MFI type structure molecular sieve and / or an MWW type structure molecular sieve, preferably an MFI type structure molecular sieve. The advantage of adopting this preferred embodiment is that the MFI type structure molecular sieve has good pores and acidity, which is conducive to the reaction cracking and alkylation.

[0038] In the present invention, preferably, in step (1), the silicon-aluminum molar ratio of the molecular sieve precursor is 25-90, more preferably 25-50. The advantage of adopting this preferred embodiment is that the silicon-aluminum molar ratio is directly related to the acid properties, and the low silicon-aluminum zeolite molecular sieve has a strong acidity and acid amount, which is conducive to improving the selectivity of the target products toluene and xylene.

[0039] In the present invention, preferably, in step (1), the B acid content of the molecular sieve precursor is 0.15-1.25 mmol / g, the L acid content is 0.1-0.4 mmol / g, and the total acid content is 0.25-1.65 mmol / g; further preferably, in step (1), the B acid content of the molecular sieve precursor is 0.3-1.25 mmol / g, the L acid content is 0.15-0.4 mmol / g, and the total acid content is 0.45-1.5 mmol / g.

[0040] In the present invention, the binder is a substance that can be converted into oxides by calcination, and the present invention does not make any specific limitation to this.

[0041] In the present invention, preferably, the amounts of the molecular sieve precursor, the binder and the active component are used so that in the prepared alkylation catalyst, based on the total amount of the alkylation catalyst, the content of the active component calculated as oxide is 0.05-5% by weight, the content of the molecular sieve is 60-85% by weight, and the content of the binder calculated on a dry basis is 10-35% by weight.

[0042] In the present invention, there is no particular limitation on the type of acid. Preferably, in step (1), the acid is an organic acid and / or an inorganic acid.

[0043] In the present invention, when the acid is an organic acid, it can be an organic acid conventionally defined in the art. Preferably, in step (1), the organic acid is selected from at least one of oxalic acid, citric acid and butyl acetate.

[0044] In the present invention, when the acid is an inorganic acid, it can be an inorganic acid conventionally defined in the art. Preferably, in step (1), the inorganic acid is selected from at least one of nitric acid, phosphoric acid, hydrochloric acid and boric acid.

[0045] In the present invention, preferably, in step (1), the concentration of the acid is 0.1-1 mol / L, more preferably 0.1-0.5 mol / L. The advantage of adopting this preferred embodiment is to effectively adjust the content of B acid and L acid of the zeolite catalyst and improve the selectivity of the target product.

[0046] In the present invention, the acid treatment conditions have a wide range of selection. Preferably, in step (1), the acid treatment conditions include: a temperature of 25-60°C and a time of 2-8 hours.

[0047] In the present invention, the acid content of the molecular sieve can be increased by acid treatment of the molecular sieve precursor. Preferably, in step (1), the B acid content of the molecular sieve is 0.16-1.15 mmol / g, the L acid content is 0.08-0.35 mmol / g, and the total acid content is 0.24-1.5 mmol / g; further preferably, in step (1), the B acid content of the molecular sieve is 0.25-1.15 mmol / g, the L acid content is 0.1-0.3 mmol / g, and the total acid content is 0.35-1.45 mmol / g.

[0048] In the present invention, the selection range of the active component precursor is relatively wide. Preferably, in step (2), the active component precursor is selected from at least one of soluble salts containing metal elements of Group IIIA, Group VIII, Group IIB and Group VIB, and is further preferably selected from at least one of soluble salts containing Mo, Ni, Ga, Zn and Pt. For example, it can be at least one of molybdenum nitrate, nickel nitrate, nickel chloride, gallium nitrate, zinc nitrate, zinc chloride and palladium chloride.

[0049] In the present invention, the range of selection of the conditions for the first drying is relatively wide. Preferably, in step (2), the conditions for the first drying include: a temperature of 80-130°C and a time of 2-24 hours.

[0050] In the present invention, the range of selection of the conditions for the first calcination is relatively wide. Preferably, in step (2), the conditions for the first calcination include: a temperature of 450-600°C and a time of 2-8h.

[0051] In the present invention, the range of selection of aging treatment conditions is relatively wide. Preferably, in step (2), the aging conditions include: a temperature of 25-60°C and a time of 12-24h.

[0052] In the present invention, the second drying conditions have a wide range of selection. Preferably, in step (2), the second drying conditions include: a temperature of 80-130°C and a time of 2-24 hours.

[0053] In the present invention, the second calcination conditions have a wide range of selection. Preferably, in step (2), the second calcination conditions include: a temperature of 400-600°C and a time of 2-8h.

[0054] In the present invention, the specific type of alkane can be selected in a wide range. Preferably, the alkane is C5-C 16 Alkanes, more preferably C5-C 16 At least one of normal alkanes, isoalkanes and cycloalkanes.

[0055] In the present invention, the contact reaction conditions can be selected in a wide range. Preferably, the contact reaction conditions include: a reaction temperature of 400-600°C, a reaction pressure of 1-7 MPa, and a weight space velocity of 0.5-10 h -1 , the mass ratio of benzene to alkane is 1-9:1, and the volume ratio of hydrogen to oil is 200-2000:1. It should be noted that the weight space velocity refers to the ratio of the total mass flow rate of benzene and alkane to the total loading amount of the catalyst.

[0056] In the present invention, the reaction method is as follows Figure 1 As shown in the figure, hydrogen A and benzene B are introduced from the top of the top layer of n catalyst beds in series, the alkane is D, and the alkane is evenly divided into N1-N n The n catalyst beds in series are respectively loaded with alkylation catalysts C1-C n (not shown in the figure), wherein the loading amount of catalyst on each catalyst bed is the same. After the reaction is completed, the gas phase product and the liquid phase product are separated by the high separation tank E. It should be noted that C1-C n It represents the catalyst corresponding to n catalyst beds connected in series.

[0057] The present invention will be described in detail below by way of examples. In the following examples, unless otherwise specified, all raw materials used are commercially available. In the following examples, unless otherwise specified, room temperature refers to 25±5°C.

[0058] Benzene single-pass conversion rate = (reaction feed benzene - reaction discharge benzene) / reaction feed benzene * 100%;

[0059] Toluene selectivity = toluene production / benzene conversion × 100%;

[0060] Xylene selectivity = xylene production / benzene conversion × 100%.

[0061] Example 1

[0062] (1) 40 g of ZSM-5 (H type, SiO2 / Al2O3=25, molecular sieve precursor) was added to 160 g of sulfuric acid aqueous solution (0.1 mol / L), stirred at room temperature for 4 h, filtered and separated, and dried in an oven at 120° C. to obtain acid-modified ZSM-5-25 (molecular sieve);

[0063] (2) dissolving 0.01 mol of zinc nitrate hexahydrate in 7 g of an aqueous solution to form a zinc nitrate aqueous solution;

[0064] (3) adding the prepared zinc nitrate aqueous solution to 10 g of pseudo-boehmite on a dry basis, drying in an oven at 120° C., and calcining at 550° C. for 3 h to obtain a Zn-loaded binder;

[0065] (4) The acid-modified ZSM-5-25 and the Zn-loaded binder were uniformly mixed and kneaded into a mold, aged at room temperature for 4 h, then placed in an oven for drying at 120° C., and calcined at 550° C. for 3 h to obtain catalyst C1.

[0066] Catalyst C2 was prepared in the same manner as C1, except that an H-type ZSM-5 molecular sieve precursor with SiO2 / Al2O3=38 was selected.

[0067] The properties of the molecular sieve precursor, acid-modified molecular sieve and catalyst are shown in Table 1.

[0068] according to Figure 1 As shown, hydrogen A and raw benzene B are introduced into the alkylation reactor from top to bottom through the top of two catalyst beds connected in series, the alkane N is methylcyclohexane, the alkane is divided into N1 and N2 parts and introduced into corresponding catalyst beds (first catalyst bed and second catalyst bed) respectively, the two catalyst beds connected in series are respectively loaded with alkylation catalysts, C1 is the first bed catalyst, C2 is the second bed catalyst, methylcyclohexane is the alkane raw material and benzene is alkylated, the reaction temperature is 500°C, the reaction pressure is 3MPa, the hydrogen-to-oil volume ratio is 600, the total catalyst loading is 6g, the first catalyst bed and the second catalyst bed are each loaded with 3g, the benzene feed rate is 30g / h, the methylcyclohexane feed rate per stage is 5g / h, and the reaction results of measuring the reaction for 24h are shown in Table 2.

[0069] Example 2

[0070] (1) 40 g of ZSM-5 (H type, SiO2 / Al2O3=25, molecular sieve precursor) was added to 160 g of nitric acid aqueous solution (0.1 mol / L), stirred at room temperature for 4 h, filtered and separated, and dried in an oven at 120° C. to obtain acid-modified ZSM-5-25 (molecular sieve);

[0071] (2) dissolving 0.01 mol of zinc nitrate hexahydrate in 12 g of an aqueous solution to form a zinc nitrate aqueous solution;

[0072] (3) adding the prepared zinc nitrate aqueous solution to 17 g of pseudo-boehmite on a dry basis, drying in an oven at 120° C., and calcining at 550° C. for 3 h to obtain a Zn-loaded binder;

[0073] (4) The acid-modified ZSM-5-25 and the Zn-loaded binder were uniformly mixed and kneaded into a mold, aged at room temperature for 4 h, then placed in an oven for drying at 120° C., and calcined at 550° C. for 3 h to obtain catalyst C3.

[0074] The properties of the molecular sieve precursor, molecular sieve and catalyst are shown in Table 1.

[0075] With C1 as the first bed catalyst and C3 as the second bed catalyst, the reaction was carried out according to the method and conditions of Example 1. The reaction results are shown in Table 2.

[0076] Example 3

[0077] (1) 40 g of ZSM-5 (H type, SiO2 / Al2O3=25, molecular sieve precursor) was added to 160 g of nitric acid aqueous solution (0.1 mol / L), stirred at room temperature for 4 h, filtered and separated, and dried in an oven at 120° C. to obtain acid-modified ZSM-5-25 (molecular sieve);

[0078] (2) dissolving 0.01 mol of hydrated gallium nitrate in 7 g of aqueous solution to form an aqueous zinc nitrate solution;

[0079] (3) adding the prepared gallium nitrate aqueous solution to 7 g of pseudo-boehmite on a dry basis, drying in an oven at 120° C., and calcining at 550° C. for 3 h to obtain a Ga-loaded binder;

[0080] (4) The acid-modified ZSM-5-25 and the Ga-loaded binder were uniformly mixed and kneaded into a mold, aged at room temperature for 4 hours, then placed in an oven for drying at 120°C, and calcined at 550°C for 3 hours to obtain catalyst C4.

[0081] Catalyst C5 was prepared in the same manner as C4, except that an H-type ZSM-5 molecular sieve precursor with SiO2 / Al2O3=38 was selected.

[0082] The properties of the molecular sieve precursor, molecular sieve and catalyst are shown in Table 1.

[0083] Using C4 as the first bed catalyst, C5 as the second bed catalyst, n-heptane as the alkane feedstock and benzene for alkylation, according to the method and reaction conditions of Example 1, the reaction results are shown in Table 2.

[0084] Example 4

[0085] (1) 40 g of dry ZSM-5 (H type, SiO2 / Al2O3=50) was added to 160 g of sulfuric acid aqueous solution (0.1 mol / L), stirred at room temperature for 4 h, filtered and separated, and dried in an oven at 120° C. to obtain acid-modified ZSM-5-50;

[0086] (2) dissolving 0.01 mol of hydrated gallium nitrate in 7 g of aqueous solution to form a gallium nitrate aqueous solution;

[0087] (3) adding the prepared gallium nitrate aqueous solution to 10 g of pseudo-boehmite on a dry basis, drying in an oven at 120° C., and calcining at 550° C. for 3 h to obtain a Ga-loaded binder;

[0088] (4) The acid-modified ZSM-5-50 and the Ga-loaded binder were uniformly mixed and kneaded into a mold, aged at room temperature for 4 hours, then placed in an oven at 120°C for drying, and calcined at 550°C for 3 hours to obtain catalyst C6.

[0089] The properties of the molecular sieve precursor, molecular sieve and catalyst are shown in Table 1.

[0090] With C1 as the first bed catalyst and C6 as the second bed catalyst, the reaction was carried out according to the method and conditions of Example 1. The reaction results are shown in Table 2.

[0091] Example 5

[0092] The method of Example 1 is followed, except that each catalyst bed layer uses the same alkylation catalyst C1.

[0093] The properties of the molecular sieve precursor, molecular sieve and catalyst are shown in Table 1.

[0094] The reaction was carried out according to the method and conditions of Example 1. The reaction results are shown in Table 2.

[0095] Example 6

[0096] The method of Example 1 was followed, except that a H-type ZSM-5 molecular sieve precursor with SiO2 / Al2O3=87 was selected to obtain catalyst C7;

[0097] The properties of the molecular sieve precursor, molecular sieve and catalyst are shown in Table 1.

[0098] With C1 as the first bed catalyst and C7 as the second bed catalyst, the reaction was carried out according to the method and conditions of Example 1. The reaction results are shown in Table 2.

[0099] Example 7

[0100] The reaction was carried out according to the method and conditions of Implementation 1, except that three catalyst beds were used. From top to bottom, the first bed was filled with catalyst C4, the second bed was filled with catalyst C1, and the third bed was filled with catalyst C3.

[0101] According to the method of Example 1, the reaction temperature is 500°C, the reaction pressure is 3 MPa, the hydrogen-to-oil volume ratio is 600, the total catalyst loading is 9 g, the benzene feed rate is 45 g / h, the methylcyclohexane feed rate per stage is 5 g / h, and the reaction results after 24 hours of reaction are shown in Table 2.

[0102] Example 8

[0103] (1) 40 g of ZSM-5 (H type, SiO2 / Al2O3=25, molecular sieve precursor) was added to 160 g of sulfuric acid aqueous solution (0.1 mol / L), stirred at room temperature for 4 h, filtered and separated, and dried in an oven at 120° C. to obtain acid-modified ZSM-5-25 (molecular sieve), which was then mixed with 10 g of pseudo-boehmite to form a uniform mixture, dried in an oven at 120° C., and calcined at 550° C. for 3 h to obtain a catalyst body;

[0104] (2) dissolving 0.01 mol of hydrated gallium nitrate in 35 g of aqueous solution to form a gallium nitrate aqueous solution;

[0105] (3) The catalyst body was impregnated with a metal gallium solution, placed in an oven at 120° C. for drying, and calcined at 550° C. for 3 h to obtain catalyst C8.

[0106] The properties of the molecular sieve precursor, molecular sieve and catalyst are shown in Table 1.

[0107] Using C8 as the first bed catalyst and the second bed catalyst, the reaction was carried out according to the method and conditions of Example 1. The reaction results are shown in Table 2.

[0108] Example 9

[0109] The method of Example 1 is followed, except that the first bed catalyst is C1 and the second bed catalyst is C8.

[0110] The properties of the molecular sieve precursor, molecular sieve and catalyst are shown in Table 1.

[0111] The reaction was carried out according to the method and conditions of Example 1. The reaction results are shown in Table 2.

[0112] Table 1

[0113]

[0114]

[0115] Table 2

[0116]

[0117] It can be seen from Tables 1 and 2 above that when the alkylation catalyst within the preferred range of the present invention is graded and used in conjunction with the method of the present invention, the single-pass conversion rate of benzene and the total selectivity of toluene and xylene can be improved.

[0118] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for producing toluene and xylene, characterized in that: The method comprises: in the presence of hydrogen and an alkylation catalyst, contacting alkanes and benzene in n series-connected catalyst beds to obtain toluene and xylene; wherein the hydrogen and benzene are introduced from the top to the bottom of the uppermost layer of the n series-connected catalyst beds; the alkane is divided into N parts, and the N parts of the alkane are respectively introduced into the n series-connected catalyst beds, wherein n is a positive integer and n≥2; the alkylation catalyst comprises a molecular sieve, a binder and an active component loaded on the binder; and based on the total amount of the alkylation catalyst, the content of the active component in terms of oxide is 0.05-5% by weight.

2. The method according to claim 1, wherein: n is 2-10, n is a positive integer; Preferably, compared to molecular sieves, the total acid content of the alkylation catalyst is reduced by 10-40%, preferably 14-30%; Preferably, the alkylation catalyst has a B acid content of 0.1-1 mmol / g, an L acid content of 0.05-0.3 mmol / g, and a total acid content of 0.15-1.3 mmol / g; More preferably, the alkylation catalyst has a B acid content of 0.2-1 mmol / g, an L acid content of 0.1-0.3 mmol / g, and a total acid content of 0.4-1.25 mmol / g.

3. The method according to claim 1 or 2, wherein: The active component is selected from at least one of Group IIIA metal elements, Group VIII metal elements, Group IIB metal elements and Group VIB metal elements, preferably selected from at least one of Mo, Ni, Ga, Zn and Pt; Preferably, the binder is aluminum oxide and / or silicon oxide, more preferably aluminum oxide; Preferably, the molecular sieve is an MFI type structure molecular sieve and / or an MWW type structure molecular sieve, preferably an MFI type structure molecular sieve.

4. The method according to any one of claims 1 to 3, wherein: The content of the active component in terms of oxide is 1-2% by weight based on the total amount of the alkyl catalyst; Preferably, based on the total amount of the alkylation catalyst, the content of the molecular sieve is 60-85% by weight, and the content of the binder on a dry basis is 10-35% by weight; Preferably, along the logistics direction, the n catalyst beds connected in series are all loaded with alkylation catalysts, and the total acid amount of each loaded alkylation catalyst gradually decreases, preferably decreasing by 0.1-0.95 mmol / g, and more preferably decreasing by 0.12-0.7 mmol / g.

5. The method according to any one of claims 1 to 4, wherein: The preparation method of the alkylation catalyst comprises the following steps: (1) treating a molecular sieve precursor in an acid to obtain a molecular sieve; (2) The binder is immersed in the active component precursor solution, mixed with the molecular sieve of step (1) after a first drying and a first calcination, and then aged, dried and calcined for a second time to obtain an alkylation catalyst.

6. The method according to claim 5, wherein: In step (1), the molecular sieve precursor is an MFI type structure molecular sieve and / or an MWW type structure molecular sieve, preferably an MFI type structure molecular sieve; Preferably, in step (1), the molar ratio of silicon oxide to aluminum oxide in the molecular sieve precursor is 25-90, more preferably 25-50; Preferably, in step (1), the B acid content of the molecular sieve precursor is 0.15-1.25 mmol / g, the L acid content is 0.1-0.4 mmol / g, and the total acid content is 0.25-1.65 mmol / g; Further preferably, in step (1), the B acid content of the molecular sieve precursor is 0.3-1.25 mmol / g, the L acid content is 0.15-0.4 mmol / g, and the total acid content is 0.45-1.5 mmol / g.

7. The method according to claim 5, wherein: In step (1), the acid is an organic acid and / or an inorganic acid; Preferably, in step (1), the organic acid is selected from at least one of oxalic acid, citric acid and acetic acid; Preferably, in step (1), the inorganic acid is selected from at least one of nitric acid, phosphoric acid, hydrochloric acid and boric acid; Preferably, in step (1), the concentration of the acid is 0.1-1 mol / L, more preferably 0.1-0.5 mol / L; Preferably, in step (1), the acid treatment conditions include: temperature of 25-60°C and time of 2-8h; Preferably, in step (1), the molecular sieve has a B acid content of 0.16-1.15 mmol / g, an L acid content of 0.08-0.35 mmol / g, and a total acid content of 0.24-1.5 mmol / g; Further preferably, in step (1), the molecular sieve has a B acid content of 0.25-1.15 mmol / g, an L acid content of 0.1-0.3 mmol / g, and a total acid content of 0.35-1.45 mmol / g.

8. The method according to claim 5, wherein: In step (2), the active component precursor is selected from at least one soluble salt containing Group IIIA metal elements, Group VIII metal elements, Group IIB metal elements and Group VIB metal elements, preferably selected from at least one soluble salt containing Mo, Ni, Ga, Zn and Pt.

9. The method according to claim 5, wherein: In step (2), the first calcination conditions include: temperature of 450-600° C. and time of 2-8 h; Preferably, in step (2), the aging conditions include: temperature of 25-60°C and time of 2-24h; Preferably, in step (2), the conditions for the second calcination include: a temperature of 400-600° C. and a time of 2-8 h.

10. The method according to any one of claims 1 to 9, wherein: The alkane is C5-C 16 Alkanes, preferably C5-C 16 At least one of normal alkanes, isoalkanes and cycloalkanes; Preferably, the contact reaction conditions include: reaction temperature of 400-600°C, reaction pressure of 1-7MPa, and weight space velocity of 0.5-10h -1 , the mass ratio of benzene to alkane is 1-9:1, and the volume ratio of hydrogen to oil is 200-2000:1.

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