Method for producing BTX from diesel raw materials

Abstract

The present disclosure relates to a method for producing BTX from a diesel feedstock. The method comprises: contacting the diesel feedstock with a hydrorefining catalyst to perform a hydrorefining reaction; contacting the hydrorefining reaction product with a first hydrocracking catalyst to perform a first hydrocracking reaction to obtain a first hydrocracking reaction product; separating the first hydrocracking reaction product to obtain a first BTX fraction, a first intermediate aromatics-rich fraction, and a first tail oil fraction; contacting the first intermediate aromatics-rich fraction with a second hydrocracking catalyst to perform a second hydrocracking reaction; wherein the second hydrocracking catalyst comprises a third support and a third active metal component supported on the third support; the third support comprises an acidic component and a matrix, and the acidic component is a molecular sieve having a BX value greater than 1. This method can effectively improve the selectivity and yield of BTX.

Description

Technical Field

[0001] The present disclosure relates to a method for producing BTX from a diesel feedstock. Background Art

[0002] In my country's refineries, catalytic cracking technology, the main means of converting heavy oil to light oil, is widely used, with a processing capacity of over 150 million tons / year. This results in a high proportion of catalytic cracking diesel (hereinafter referred to as LCO) in the diesel pool, with an output of 35 million tons, reaching more than 30%. The typical characteristics of LCO are high content of impurities such as sulfur and nitrogen, high content of aromatics, and low cetane number. Especially when the catalytic cracking unit adopts the MIP process or DCC process to reduce olefins, the aromatic content in LCO increases significantly. With the implementation of more stringent diesel quality standards such as National VI and even Beijing VII, a large amount of aromatic saturation is required, hydrogen consumption is high, and operating conditions are harsh, which will inevitably lead to a substantial increase in investment and energy consumption. Therefore, LCO is the main bottleneck restricting the Chinese petrochemical industry from achieving diesel quality upgrades with high efficiency and low consumption. In order to improve the economic benefits of refineries, this part of low-quality LCO urgently needs to find a way out.

[0003] Taking advantage of LCO's high aromatic content and combining it with the hydrocarbon evolution during the hydrocracking reaction, controlled aromatic hydrogenation allows for efficient conversion of large, low-value aromatics in LCO into smaller aromatics such as benzene, toluene, and xylene. This represents an ideal LCO processing and utilization approach. The development and industrial application of this technology could provide a new technical route for LCO processing and utilization and the production of aromatics feedstock.

[0004] CN105085154B discloses a method for increasing the production of aromatic raw materials from inferior heavy aromatics. This method involves mixing the crude oil with hydrogen, followed by hydrorefining and hydrocracking reactions. The hydrocracking effluent is fractionated to produce a light fraction, an intermediate cut fraction, and a heavy fraction. The intermediate cut fraction has a boiling point range of 100-240°C. The intermediate cut fraction, recycled toluene, and recycled C9+A fraction are mixed with hydrogen and then fed into an intermediate cut fraction conversion reactor for reaction. Part or all of the heavy fraction is recycled back to the hydrocracking reactor. This method directly produces benzene and xylene from inferior heavy aromatics. CN106047404B discloses a combined process for increasing the production of high-octane gasoline from inferior catalytic cracking diesel. In this method, catalytically cracked diesel first undergoes a hydrorefining reaction to selectively hydrogenate condensed aromatics and undergo desulfurization and denitrification. The refined liquid product is then mixed with reformed C10+ heavy aromatics and fed into a lightweighting reactor equipped with a precious metal catalyst for hydrogenation and lightweighting. After separation and fractionation, dry gas and liquefied gas, a gasoline fraction, and a diesel fraction are obtained; the diesel fraction is partially or entirely recycled back to the lightweighting reactor, ultimately achieving the goal of producing more high-octane gasoline. However, when using the above-mentioned existing technology to process low-quality diesel to produce high-octane gasoline or small-molecule aromatics, although the yield of the gasoline fraction is improved to a certain extent, the utilization rate of the aromatics in the feedstock is not maximized, and a large amount of aromatics still exists in the diesel fraction and is not effectively converted. Summary of the Invention

[0005] The purpose of the present disclosure is to provide a method for producing BTX from diesel feedstock, which can effectively improve the selectivity and yield of BTX.

[0006] To achieve the above objectives, the present disclosure provides a method for producing BTX from a diesel feedstock, the method comprising:

[0007] contacting the diesel feedstock with a hydrotreating catalyst to perform a hydrotreating reaction to obtain a hydrotreating reaction product;

[0008] contacting the hydrotreating reaction product with a first hydrocracking catalyst to carry out a first hydrocracking reaction to obtain a first hydrocracking reaction product, and separating the first hydrocracking reaction product to obtain a first BTX fraction, a first intermediate aromatic-rich fraction, and a first tail oil fraction;

[0009] contacting the first intermediate aromatic-rich fraction with a second hydrocracking catalyst to perform a second hydrocracking reaction to obtain a second hydrocracking reaction product, and separating the second hydrocracking reaction product to obtain a second BTX fraction, a second intermediate aromatic-rich fraction, and a second tail oil fraction;

[0010] The second hydrocracking catalyst includes a third carrier and a third active metal component supported on the third carrier; the third active metal component includes a Group VIII metal element and a Group VIB metal element; the third carrier is composed of an acidic component and a matrix, and the acidic component is a molecular sieve with a BX value greater than 1; the BX value of a certain molecular sieve to be tested is defined as the ratio of the adsorption amount of benzene by the molecular sieve to be tested to the adsorption amount of butylbenzene by the molecular sieve to be tested.

[0011] Optionally, the BX value of the molecular sieve is 1 to 100, preferably 1 to 10;

[0012] Optionally, the pore volume of the molecular sieve is 0.4 to 0.8 cm 3 / g, acid density is 0.8~2.5μmol / m 2 ;

[0013] Optionally, based on the total weight of the third carrier, the content of the acidic component is 30-90 wt%, preferably 45-80 wt%; the content of the matrix is 10-70 wt%, preferably 20-55 wt%.

[0014] Optionally, based on the total weight of the second hydrocracking catalyst, calculated as oxides, the second hydrocracking catalyst contains 1 to 10 weight percent of Group VIII metal elements and 2 to 40 weight percent of Group VIB metal elements; preferably, the second hydrocracking catalyst contains 1 to 6 weight percent of Group VIII metal components and 5 to 25 weight percent of Group VIB metal components.

[0015] Optionally, the molecular sieve is at least one selected from PKU-16 molecular sieve, SCM-15 molecular sieve, ITQ-4 molecular sieve, JU-64 molecular sieve, Beryllophosphate-H molecular sieve and UCSB-10GaZn molecular sieve;

[0016] Optionally, the matrix is selected from at least one of alumina, silica and silica-alumina.

[0017] Optionally, the diesel feedstock has a boiling point range of 165-400° C., a total aromatics content higher than 60% by weight, and a content of bicyclic and higher aromatics higher than 40% by weight.

[0018] Optionally, the distillation range of the first BTX fraction and the second BTX fraction is independently 50-180° C., and the sulfur content of the first BTX fraction and the second BTX fraction is independently less than 10 μg / g;

[0019] The distillation range of the first intermediate aromatic-rich fraction and the second intermediate aromatic-rich fraction is independently 150-280° C., the total aromatic content of the first intermediate aromatic-rich fraction and the second intermediate aromatic-rich fraction is independently higher than 50% by weight, wherein the content of alkylbenzenes and tetralin monocyclic aromatic hydrocarbons is independently higher than 45% by weight;

[0020] The cutting points of the first middle aromatic-rich fraction and the first tail oil fraction, the second middle aromatic-rich fraction and the second tail oil fraction are independently in the range of 170 to 280°C.

[0021] Optionally, the method further comprises: based on the total weight of the first tail oil fraction and the second tail oil fraction, at least 20 weight % of the first tail oil fraction and / or the second tail oil fraction is recycled for the hydrofining reaction.

[0022] Optionally, the conditions of the hydrofining reaction include: hydrogen partial pressure of 3.5-10 MPa, reaction temperature of 300-450°C, hydrogen-to-oil volume ratio of 400-2500 Nm 3 / m 3 , liquid hourly volumetric space velocity is 0.2~6h -1 .

[0023] Optionally, the hydrogen partial pressure of the second hydrocracking reaction is 0.5 to 6 MPa lower than that of the first hydrocracking reaction.

[0024] Preferably, the conditions of the first hydrocracking reaction include: hydrogen partial pressure of 4-12 MPa, reaction temperature of 300-450°C, hydrogen-to-oil volume ratio of 400-2500 Nm 3 / m 3 , liquid hourly volumetric space velocity is 0.2~5h -1 ;

[0025] Preferably, the conditions of the second hydrocracking reaction include: hydrogen partial pressure of 2.5-6 MPa, reaction temperature of 300-450°C, hydrogen to oil volume ratio of 400-2200 Nm 3 / m 3 , liquid hourly volumetric space velocity is 0.2~10h -1 .

[0026] Optionally, the hydrorefining catalyst comprises a first support and a first active metal component, and the hydrorefining catalyst contains 1 to 10 weight percent of a Group VIII metal element, 10 to 45 weight percent of a Group VIB metal element, and the balance is the first support, calculated as oxides and based on the total weight of the hydrorefining catalyst;

[0027] Optionally, the first hydrocracking catalyst contains a second carrier and a second active metal component; calculated as oxide and based on the total weight of the first hydrocracking catalyst, the first hydrocracking catalyst contains 50 to 90 weight percent of the second carrier, 1 to 10 weight percent of Group VIII metal elements, and 5 to 40 weight percent of Group VIB metal elements; based on the total weight of the second carrier, the second carrier includes 0.5 to 95 weight percent of MoNi-containing Y-type zeolite and 5 to 99.5 weight percent of alumina.

[0028] Through the above technical solution, the present invention performs a first hydrocracking reaction and a second hydrocracking reaction in sequence after the diesel feedstock is subjected to a hydrorefining reaction, and a new hydrocracking catalyst is used in the second hydrocracking reaction, which can effectively improve the selectivity and yield of BTX, maximize the utilization rate of aromatics in the feedstock oil, and reduce the total aromatics loss.

[0029] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following detailed description, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0031] Figure 1 Schematic diagram of the process for producing BTX from diesel feedstock provided by the present disclosure.

[0032] Description of Reference Numerals

[0033] 1 Hydrofining reactor 2 First hydrocracking reactor

[0034] 3. First high-pressure separator 4. Second hydrocracking reactor

[0035] 5 Second high pressure separator 6 Low pressure separator

[0036] 7 Fractionation system 8 Low-quality diesel raw materials

[0037] 9 Hydrotreating reaction product 10 The first part of the tail oil fraction

[0038] 11 First hydrocracking reaction product 12 First hydrogen-rich gas

[0039] 13 First liquid product 14 Second hydrocracking reaction product

[0040] 15 Second hydrogen-rich gas 16 Third liquid product

[0041] 17 Low-gas 18 Second liquid product

[0042] 19 light components 20 BTX fraction

[0043] 21 Intermediate aromatic fraction 22 Tail oil fraction

[0044] 23 The second part of the tail oil fraction DETAILED DESCRIPTION

[0045] The following describes the specific embodiments of the present disclosure in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure and are not intended to limit the present disclosure.

[0046] The present disclosure provides a method for producing BTX from a diesel feedstock, the method comprising:

[0047] contacting the diesel feedstock with a hydrotreating catalyst to perform a hydrotreating reaction to obtain a hydrotreating reaction product;

[0048] contacting the hydrotreating reaction product with a first hydrocracking catalyst to carry out a first hydrocracking reaction to obtain a first hydrocracking reaction product, and separating the first hydrocracking reaction product to obtain a first BTX fraction, a first intermediate aromatic-rich fraction, and a first tail oil fraction;

[0049] The intermediate aromatic-rich fraction is contacted with a second hydrocracking catalyst to carry out a second hydrocracking reaction to obtain a second hydrocracking reaction product, and the second hydrocracking reaction product is separated to obtain a second BTX fraction, a second intermediate aromatic-rich fraction and a second tail oil fraction.

[0050] According to the present disclosure, the diesel feedstock may have a boiling point range of 165-400°C, a total aromatic content greater than 60% by weight, preferably greater than 65% by weight, wherein the content of dicyclic and larger aromatics is greater than 40% by weight, preferably greater than 45% by weight. The diesel feedstock may be selected from one or a mixture of catalytic cracking light cycle oil, straight-run diesel from naphthenic crude oil, coker diesel from naphthenic crude oil, diesel fraction from direct coal liquefaction oil, and diesel fraction from coal tar.

[0051] According to the present disclosure, BTX (Benzene-Toluene-Xylene) refers to a mixture of benzene, toluene, and xylene, and the first BTX fraction and the second BTX fraction are fractions containing BTX, respectively.

[0052] In the hydrofining reaction zone, the low-quality diesel feedstock contacts and reacts with the hydrofining catalyst. After hydrodesulfurization, hydrodenitrogenation and selective hydrogenation of aromatics, sulfides and nitrogen compounds are effectively removed, and the two-ring or higher aromatic hydrocarbons in the low-quality diesel feedstock are hydrogenated and saturated into alkylbenzene-type single-ring aromatic hydrocarbons and tetralin-type single-ring aromatic hydrocarbons. The conditions of the hydrofining reaction may include: a hydrogen partial pressure of 3.5 to 10 MPa, preferably 5 to 10 MPa; a reaction temperature of 300 to 450°C, preferably 340 to 420°C; a hydrogen-to-oil volume ratio of 400 to 2500 Nm 3 / m 3 , preferably 600~2000Nm 3 / m 3 , liquid hourly volumetric space velocity is 0.2~6.0h -1 , preferably 0.8 to 3 hours -1 . The hydrorefining catalyst used is preferably a hydrorefining catalyst with good denitrogenation performance, excellent hydrogenation saturation performance for two-ring or higher aromatic hydrocarbons, and poor hydrogenation saturation performance for monocyclic aromatic hydrocarbons. For example, the hydrorefining catalyst may include a first carrier and a first active metal component, and the first active metal component includes at least one of a Group VIII metal element and a Group VIB metal element; further, calculated as oxide and based on the total weight of the hydrorefining catalyst, the hydrorefining catalyst may contain 1 to 10 weight % of a Group VIII metal element, 10 to 45 weight % of a Group VIB metal element, and the remainder is the first carrier. Preferably, the Group VIII metal element is nickel and the Group VIB metal element is molybdenum.

[0053] The hydrofining reaction product enters the first hydrocracking reaction zone without any intermediate separation, where it contacts the first hydrocracking catalyst and undergoes the first hydrocracking reaction, including selective ring-opening and alkyl side-chain cracking of tetralin-type monocyclic aromatics and alkyl side-chain cracking of alkylbenzene-type monocyclic aromatics. In the hydrofining reaction zone and the first hydrocracking reaction zone, the two-ring or higher aromatics in the low-quality diesel feedstock are effectively converted into alkylbenzene-type monocyclic aromatics, as well as some tetralin-type monocyclic aromatics.

[0054] The first hydrocracking catalyst may contain a second carrier and a second active metal component, the second active metal component including at least one of a Group VIII metal element and a Group VIB metal element, and the second carrier may contain a Y-type zeolite containing MoNi and alumina. Further, calculated as oxides and based on the total weight of the first hydrocracking catalyst, the first hydrocracking catalyst contains 50-90 weight percent of the second carrier, 1-10 weight percent of the Group VIII metal element, and 5-40 weight percent of the Group VIB metal element. More preferably, the first hydrocracking catalyst contains 60-85 weight percent of the second carrier, 1.5-6 weight percent of the Group VIII metal element, and 7-30 weight percent of the Group VIB metal element. Based on the total weight of the second carrier, the second carrier comprises 0.5-95 weight percent of the Y-type zeolite containing MoNi and 5-99.5 weight percent of alumina. Preferably, the second carrier comprises 1-80 weight percent of the Y-type zeolite containing MoNi and 20-99 weight percent of alumina. The Y-type zeolite containing MoNi is obtained by a Y-type zeolite modified with MoNi. In terms of oxide and based on the dry basis of the zeolite, the content of the MoNi component in the Y-type zeolite of MoNi can be 1 to 50% by weight, preferably 1 to 40% by weight. The first hydrocracking catalyst has excellent selective ring-opening cracking function and alkyl side chain cracking function, and has good selectivity for reactions such as the scission of the alkyl side chains of monocyclic aromatic hydrocarbons, the selective ring-opening of tetralin, and the breaking of side chains, so that the monocyclic aromatic hydrocarbons in the diesel fraction undergo selective cracking reaction to generate benzene, toluene, xylene, etc. In addition, the first hydrocracking catalyst weakens the hydrogenation saturation performance of the monocyclic aromatic hydrocarbons, which can effectively avoid further hydrogenation saturation of small molecule monocyclic aromatic hydrocarbons such as benzene and toluene.

[0055] The conditions of the first hydrocracking reaction may include: a hydrogen partial pressure of 4 to 12 MPa, preferably 5 to 10 MPa, a reaction temperature of 300 to 450° C., preferably 350 to 420° C., a hydrogen to oil volume ratio of 400 to 2500 Nm 3 / m 3 , preferably 700~2000Nm 3 / m 3 Based on the mixed oil of fresh material and tail oil fraction entering the first hydrocracking reaction zone, the liquid hourly volume space velocity of the first hydrocracking reaction zone is 0.2~5h -1 , preferably 0.5 to 3 hours -1 .

[0056] The reaction effluent from the first hydrocracking reaction zone is cooled and separated in a high-pressure separator to obtain hydrogen-rich gas and liquid products. The hydrogen-rich gas can be recycled, and the liquid products can be separated in a low-pressure separator and a fractionation system to obtain light components, a first BTX fraction, a first intermediate aromatic-rich fraction and a first tail oil fraction.

[0057] The light component refers to a component with a distillation dry point of less than 50°C. The first BTX fraction refers to a fraction with a distillation range of 50-180°C, preferably 50-170°C. The sulfur content of the first BTX fraction is less than 10 μg / g, and the BTX (benzene, toluene, and xylene) content is greater than 30% by weight. The first intermediate aromatic-rich fraction refers to a fraction with a distillation range of 150-280°C, preferably 160-260°C. The total aromatic content of the first intermediate aromatic-rich fraction is greater than 50% by weight, preferably greater than 55% by weight, and the content of monocyclic aromatic hydrocarbons such as alkylbenzenes and tetralin is greater than 45% by weight, preferably greater than 50% by weight. The cut point between the first intermediate aromatic-rich fraction and the first tail oil fraction can be between 170-280°C.

[0058] The first intermediate aromatic-rich fraction is rich in alkylbenzene-type monocyclic aromatic hydrocarbons and part of tetralin-type monocyclic aromatic hydrocarbons, enters the second hydrocracking reaction zone, contacts with the second hydrocracking catalyst, and undergoes the second hydrocracking reaction.

[0059] According to the present disclosure, the second hydrocracking catalyst includes a third carrier and a third active metal component supported on the third carrier; the third active metal component includes a Group VIII metal element and a Group VIB metal element; the third carrier is composed of an acidic component and a matrix, and the acidic component is a molecular sieve with a BX value greater than 1; wherein the BX value of a certain molecular sieve to be tested is defined as the ratio of the adsorption amount of the molecular sieve to be tested on benzene to the adsorption amount of the molecular sieve to be tested on butylbenzene.

[0060] The present disclosure utilizes a molecular sieve with a high BX value, significantly improving the second hydrocracking catalyst's adsorption capacity for reactants, diffusion capacity for intermediates, and product desorption capacity, thereby increasing BTX selectivity. By tailoring the molecular sieve's pore structure to match the reaction intermediates and target products, the second hydrocracking catalyst enhances the side chain scission reaction of long-chain alkylbenzenes and improves the yield of BTX products.

[0061] The BX value of the present disclosure is determined by the adsorption molar ratio test method, specifically: first accurately measure benzene and butylbenzene (100 ml, room temperature), then add a certain amount of molecular sieve material (5 g), and stir at a constant temperature of 360°C under inert gas (N2) protection, 1 atmosphere, and then filter. The filtrate is re-concentrated and cooled to room temperature. The solution volume is measured again with a graduated cylinder to obtain the adsorption volume difference ΔV. 测试分子筛_丁基苯 , ΔV 测试分子筛_苯 The calculation formula of BX value is:

[0062] BX=ΔV 测试分子筛_苯 / ΔV 测试分子筛_丁基苯

[0063] where ΔV 测试分子筛_丁基苯 Must be greater than 0.

[0064] In a preferred embodiment of the present disclosure, the BX value of the molecular sieve is 1 to 100, preferably 1 to 10; the pore volume of the molecular sieve in the present disclosure can be 0.4 to 0.8 cm 3 / g, the acid density can be 0.8~2.5μmol / m 2 .

[0065] According to the present disclosure, based on the total weight of the third carrier, the content of the acidic component can be 30-90 wt%, preferably 45-80 wt%; the content of the matrix can be 10-70 wt%, preferably 20-55 wt%.

[0066] According to the present disclosure, based on the total weight of the second hydrocracking catalyst, calculated as oxides, the second hydrocracking catalyst may contain 1 to 10 wt% of Group VIII metal elements and 2 to 40 wt% of Group VIB metal elements; preferably, the second hydrocracking catalyst may contain 1 to 6 wt% of Group VIII metal components and 5 to 25 wt% of Group VIB metal components.

[0067] According to the present disclosure, the molecular sieve may be selected from at least one of PKU-16 molecular sieve, SCM-15 molecular sieve, ITQ-4 molecular sieve, JU-64 molecular sieve, Beryllophosphate-H molecular sieve and UCSB-10GaZn molecular sieve.

[0068] According to the present disclosure, the matrix can be selected from at least one of alumina, silica, and silica-alumina. The alumina described in the present disclosure is selected from one or more transition phase alumina selected from γ, η, θ, δ, and χ, and can also be one or more transition phase alumina selected from γ, η, θ, δ, and χ containing one or more additive components selected from silicon, titanium, magnesium, boron, zirconium, thorium, niobium, and rare earth elements, preferably γ-alumina and γ-alumina containing one or more additive components selected from silicon, phosphorus, titanium, magnesium, boron, zirconium, thorium, niobium, and rare earth elements. They can be commercially available products or obtained by any existing method. The silica-alumina preferably has a pseudo-boehmite structure, and can also be a commercially available product or prepared by any existing technology. For example, the Siral series of commercial silica-alumina produced by Condea, Germany, has a pseudo-boehmite structure and can be used in the present disclosure.

[0069] According to the present disclosure, the preparation method of the second hydrocracking catalyst may include:

[0070] S1, mixing the matrix and the molecular sieve, kneading and extruding to obtain an extruded strip; performing a first drying and a first calcination on the extruded strip to obtain a third carrier;

[0071] S2. Impregnating the third support with an aqueous solution containing a compound of a Group VIII metal and a compound of a Group VIB metal to obtain an impregnated third support; and subjecting the impregnated third support to a second drying and activation treatment.

[0072] Wherein, the weight ratio of the matrix to the molecular sieve may be 3-7:7-3.

[0073] According to the present disclosure, in step S1, the conditions for the first drying treatment may include: a drying temperature of 80 to 300°C, preferably 100 to 200°C; a drying time of 1 to 12 hours, preferably 2 to 8 hours; the conditions for the first roasting may include: a roasting temperature of 350 to 850°C, preferably 450 to 650°C; a roasting time of 1 to 12 hours, preferably 2 to 6 hours; in step S2, the conditions for the impregnation may include: an impregnation temperature of 20 to 150°C, and an impregnation time of 1 to 6 hours; the conditions for the second drying may include: a temperature of 100 to 300°C, preferably 100 to 200°C; a time of 2 to 8 hours; the conditions for the activation treatment may include: a temperature of 250 to 650°C, preferably 300 to 500°C; a time of 1 to 12 hours, preferably 2 to 6 hours.

[0074] According to the present disclosure, the hydrogen partial pressure of the second hydrocracking reaction can be 0.5-6 MPa lower than that of the first hydrocracking reaction. Preferably, the conditions of the second hydrocracking reaction may include: a hydrogen partial pressure of 2.5-6 MPa, a reaction temperature of 300-450°C, a hydrogen-to-oil volume ratio of 400-2200 Nm 3 / m 3 Based on the intermediate aromatic fraction entering the second hydrocracking reaction zone, the liquid hourly volume space velocity in the second hydrocracking reaction zone is 0.2 to 10 h -1 .

[0075] The reaction products of the second hydrocracking reaction zone can be subjected to gas-liquid separation in a high-pressure separator to produce hydrogen-rich gas and liquid products. The hydrogen-rich gas can be recycled, and the resulting liquid products can be returned to the low-pressure separator and fractionation system to separate into a second BTX fraction, a second intermediate aromatic-rich fraction, and a second tail oil fraction. The second hydrocracking reaction zone and the first hydrocracking reaction zone can share the same low-pressure separator and fractionation system.

[0076] The second BTX fraction has a distillation range of 50-180°C, preferably 50-170°C. The sulfur content of the second BTX fraction is less than 10 μg / g, and the BTX (benzene, toluene, and xylene) content is greater than 30% by weight. The second intermediate aromatic-rich fraction has a distillation range of 150-280°C, preferably 160-260°C. The total aromatic content of the second intermediate aromatic-rich fraction is greater than 50% by weight, preferably greater than 55% by weight, and the content of monocyclic aromatic hydrocarbons such as alkylbenzenes and tetralin is greater than 45% by weight, preferably greater than 50% by weight. The cut point between the second intermediate aromatic-rich fraction and the first tail oil fraction can be between 170-280°C. The second intermediate aromatic-rich fraction is returned to the second hydrocracking reaction.

[0077] According to the present disclosure, the method may further include: recycling at least 20 wt % of the first tail oil fraction and / or the second tail oil fraction for the hydrotreating reaction, based on the total weight of the first tail oil fraction and the second tail oil fraction. In addition, the remaining tail oil fraction can be used as a clean diesel blending component.

[0078] According to the present disclosure, the first BTX fraction and the second BTX fraction are the target BTX products. Using the method disclosed herein, BTX can be produced from diesel feedstock with a BTX selectivity of over 40% and a BTX yield of over 30%.

[0079] The method provided by the present disclosure is further described below with reference to the accompanying drawings. Figure 1 This is a schematic diagram of the process flow of the present invention. Many equipment, such as pumps, heat exchangers, compressors, etc., are omitted in the figure, but they are well known to ordinary technicians in this field.

[0080] like Figure 1As shown, the inferior diesel feedstock 8 and the hydrogen-rich gas enter the hydrotreating reactor 1 and contact with the hydrotreating catalyst to carry out a hydrotreating reaction. The obtained hydrotreating reaction product 9 is mixed with the first part of the tail oil fraction 10 from the fractionation system 7 and enters the first hydrocracking reactor 2 to contact with the first hydrocracking catalyst to carry out a first hydrocracking reaction to obtain a first hydrocracking reaction product 11. The first hydrocracking reaction product 11 enters the first high-pressure separator 3 for gas-liquid separation to obtain a first hydrogen-rich gas 12 and a first liquid product 13. The first hydrogen-rich gas 12 is recycled (the hydrogen circulation system is omitted here), and the first liquid product 13 is recycled. Enter the low-pressure separator 6 for separation, and obtain low-fraction gas 17 and second liquid product 18. The second liquid product 18 enters the fractionation system 7 to obtain light components (dry gas + liquefied gas) 19, BTX fraction 20, intermediate aromatic-rich fraction 21 and tail oil fraction 22. The intermediate aromatic-rich fraction 21 enters the second hydrocracking reactor 4, contacts with the second hydrocracking catalyst, and undergoes a second hydrocracking reaction. The resulting second hydrocracking reaction product 14 enters the second high-pressure separator 5 for gas-liquid separation, and obtains a second hydrogen-rich gas 15 and a third liquid product 16. The third liquid product 16 enters the low-pressure separator 6 for separation. The first part of the tail oil fraction 10 enters the hydrotreating reactor 1, and the second part of the tail oil fraction 23 is used as a clean diesel product.

[0081] The present disclosure is further illustrated by the following examples, but the present disclosure is not limited thereto. Unless otherwise specified, all reagents used in the examples are chemically pure reagents.

[0082] In the embodiment, the commercial brand of the hydrorefining catalyst A is RN-411; the commercial brand of the first hydrocracking catalyst B is RHC-100.

[0083] The preparation process of the second hydrocracking catalyst C1 is as follows:

[0084] Weigh 130.2 g of pseudo-boehmite (Catalyst Changling Branch) with a dry basis of 70% and 115.2 g of PKU-16 molecular sieve with a dry basis of 82%, extrude them into three-leaf strips with an circumscribed circle diameter of 1.6 mm on an extruder, dry them at 120°C for 3 hours, and calcine them at 600°C for 4 hours to obtain catalyst carrier Z1.

[0085] 100 g of carrier Z1 was impregnated for 3 hours with 80 ml of a mixed solution of molybdenum trioxide, basic nickel carbonate, and phosphoric acid containing 187.5 g / L MoO3, 37.5 g / L NiO, and 37.5 g / L P2O5, respectively. The catalyst was dried at 120°C for 2 hours and then calcined at 450°C for 3 hours to obtain catalyst C1.

[0086] The preparation process of the second hydrocracking catalyst C2 is as follows:

[0087] Weigh 130.2 g of pseudo-boehmite (Catalyst Changling Branch) with a dry basis of 70% and 114.6 g of SCM-15 molecular sieve (marked as A) with a dry basis of 82%, extrude them into three-leaf strips with an circumscribed circle diameter of 1.6 mm on an extruder, dry them at 120°C for 3 hours, and calcine them at 600°C for 4 hours to obtain catalyst carrier Z2.

[0088] 100 g of carrier Z2 was impregnated for 3 hours with 80 ml of a mixed solution of molybdenum trioxide, basic nickel carbonate, and phosphoric acid containing 187.5 g / L MoO3, 37.5 g / L NiO, and 37.5 g / L P2O5, respectively. The catalyst was dried at 120°C for 2 hours and then calcined at 450°C for 3 hours to obtain catalyst C2.

[0089] The adsorption molar ratio test method involves accurately measuring a benzene and butylbenzene solution (100 ml, room temperature) and then adding a predetermined amount of molecular sieve material (5 g). The mixture is then sealed and stirred at 360°C under an inert atmosphere (N2) at 1 atm for 10 hours. The mixture is then filtered, the filtrate is brought back to volume, cooled to room temperature, and the solution volume is measured again using a graduated cylinder. The pore volume is determined by BET, and the acid content by NH3-TPD. The results are shown in Table 1. The composition of the calcined catalyst is shown in Table 2.

[0090] Table 1

[0091] Molecular sieve number <![CDATA[Pore volume / (cm 3 / g)]]> <![CDATA[Acid density / (mmol / m 2 )]]> BX value PKU-16 0.532 1.812 1.857 SCM-15 0.624 1.988 1.734

[0092] Table 2

[0093]

[0094] Example 1

[0095] Feedstock E (properties shown in Table 3) enters the hydrorefining reaction zone along with hydrogen, where it contacts and reacts with hydrorefining catalyst A. The reaction effluent from the hydrorefining reaction zone and the tail oil fraction enter the first hydrocracking reaction zone, where they contact and react with the first hydrocracking catalyst B. The reaction effluent from the first hydrocracking reaction zone sequentially enters separation facilities, including a first high-pressure separator, a low-pressure separator, and a fractionating tower. After cooling, separation, and fractional distillation, dry gas, liquefied gas (distillation range <60°C), a BTX fraction (distillation range 60-170°C, sulfur content 8 μg / g), an intermediate aromatics-rich fraction (distillation range 170-260°C, total aromatics content 58% by weight, including 54% by weight of monocyclic aromatic hydrocarbons such as alkylbenzenes and tetralins), and a tail oil fraction (distillation range >260°C). The entire intermediate aromatic-rich fraction enters the second hydrocracking reaction zone, where it contacts and reacts with the second hydrocracking catalyst C1. 50% by weight of the tail oil fraction is recycled back to the hydrotreating reaction zone. The reaction effluent from the second hydrocracking reaction zone enters the second high-pressure separator, and the resulting liquid is returned to the low-pressure separator and fractionation system. The reaction conditions are shown in Table 4. The BTX yield and selectivity were calculated using the following formula, with the results shown in Table 5.

[0096] BTX yield (%) = BTX content in BTX fraction × BTX fraction yield × 100%

[0097] BTX selectivity (%) = BTX yield / (total aromatic hydrocarbon content in the raw material - aromatic hydrocarbon content above C10 in the product) × 100%

[0098] Among them, the BTX content in the BTX fraction is determined according to the naphtha monomer hydrocarbon and PIONA composition method, and the aromatic hydrocarbon content in the intermediate aromatic-rich fraction and the tail oil fraction is determined according to the coal diesel fraction hydrocarbon composition mass spectrometry method.

[0099] Example 2

[0100] BTX is produced from diesel feedstock according to the method of Example 1, except that the second hydrocracking catalyst is C2. A fractionating tower obtains dry gas, liquefied gas (boiling range < 50°C), a BTX fraction (boiling range 50-165°C, a sulfur content of 5 μg / g), an intermediate aromatic fraction (boiling range 165-270°C, a total aromatic content of 52% by weight, wherein the alkylbenzene and tetralin monocyclic aromatic hydrocarbon content is 49% by weight), and a tail oil fraction (boiling range > 270°C). The intermediate aromatic fraction oil all enters the second hydrocracking reaction zone, contacts and reacts with the second hydrocracking catalyst C2, and 30% by weight of the tail oil fraction is recycled back to the first hydrocracking reaction zone. Reaction conditions are shown in Table 4, and product yield and properties are shown in Table 5.

[0101] Comparative Example 1

[0102] BTX was produced from a diesel feedstock according to the method of Example 1, except that a second hydrocracking catalytic reaction zone was not provided. A fractionating tower was used to obtain dry gas, liquefied gas (boiling range < 50°C), a BTX fraction (boiling range 50-170°C, with a sulfur content of 80 μg / g), an intermediate aromatic fraction (boiling range 170-260°C, with a total aromatic content of 60% by weight, wherein the content of alkylbenzenes and tetralin monocyclic aromatic hydrocarbons was 53% by weight), and a tail oil fraction (boiling range > 260°C). Reaction conditions are shown in Table 4, and product yield and properties are shown in Table 5.

[0103] Comparative Example 2

[0104] BTX is produced from diesel feedstock according to the method of Example 1, except that the second hydrocracking catalyst is identical to the first hydrocracking catalyst. Fractional distillation tower obtains dry gas, liquefied gas (boiling range < 60 ℃), BTX fraction (boiling range 60-165 ℃, sulfur content is 44 μg / g), intermediate aromatic fraction (boiling range 165-270 ℃, total aromatic content is 61 wt %, wherein alkylbenzene and tetralin monocyclic aromatic hydrocarbon content is 56 wt %) and tail oil fraction (boiling range > 270 ℃). Reaction conditions are as shown in Table 4, and product yield and properties are as shown in Table 5.

[0105] Table 3

[0106]

[0107]

[0108] Table 4

[0109] Comparative Example 1 Comparative Example 2 Example 1 Example 2 crude oil E E E E Hydrorefining reaction zone: catalyst A A A A Hydrogen partial pressure, MPa 7.0 6.5 6.0 5.8 Reaction temperature, °C 360 370 370 360 <![CDATA[Space velocity, h -1 > 2.0 1.5 1.5 1.0 <![CDATA[Hydrogen-oil volume ratio, Nm 3 / m 3 > 800 1000 1000 1000 First hydrocracking reaction zone: catalyst B B B B Hydrogen partial pressure, MPa 7.0 6.5 6.0 5.8 Reaction temperature, °C 400 403 400 400 <![CDATA[Space velocity, h -1 > 0.8 1.0 1.0 0.8 <![CDATA[Hydrogen-oil volume ratio, Nm 3 / m 3 > 1500 1500 1200 1200 Second hydrocracking reaction zone: catalyst none B C1 C2 Hydrogen partial pressure, MPa / 4.0 4.0 5.0 Reaction temperature, °C / 390 390 400 <![CDATA[Space velocity, h -1 > / 2.0 1.5 2.0 <![CDATA[Hydrogen-to-oil volume ratio, Nm 3 / m 3 > / 1000 1000 1000

[0110] Table 5

[0111]

[0112]

[0113] It can be seen from Table 5 that, compared with the prior art, the method provided by the present disclosure is used to produce BTX by hydrocracking of inferior diesel, which can effectively improve the BTX yield and selectivity.

[0114] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings. However, the present disclosure is not limited to the specific details of the above embodiments. Within the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the scope of protection of the present disclosure.

[0115] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0116] In addition, the various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A method for producing BTX from diesel feedstock, characterized in that: The method includes: contacting the diesel feedstock with a hydrotreating catalyst to perform a hydrotreating reaction to obtain a hydrotreating reaction product; contacting the hydrotreating reaction product with a first hydrocracking catalyst to carry out a first hydrocracking reaction to obtain a first hydrocracking reaction product, and separating the first hydrocracking reaction product to obtain a first BTX fraction, a first intermediate aromatic-rich fraction, and a first tail oil fraction; contacting the first intermediate aromatic-rich fraction with a second hydrocracking catalyst to perform a second hydrocracking reaction to obtain a second hydrocracking reaction product; and separating the second hydrocracking reaction product to obtain a second BTX fraction, a second intermediate aromatic-rich fraction, and a second tail oil fraction; wherein the sulfur content of the first BTX fraction and the second BTX fraction is independently less than 10 μg / g; Based on the total weight of the first tail oil fraction and the second tail oil fraction, at least 20 weight percent of the first tail oil fraction and / or the second tail oil fraction is recycled for the hydrofining reaction; The second hydrocracking catalyst includes a third carrier and a third active metal component supported on the third carrier; the third active metal component includes a Group VIII metal element and a Group VIB metal element; the third carrier is composed of an acidic component and a matrix, the acidic component is a molecular sieve having a ratio of the adsorption amount of benzene to the adsorption amount of butylbenzene greater than 1, and the molecular sieve is selected from at least one of PKU-16 molecular sieve, SCM-15 molecular sieve, ITQ-4 molecular sieve, JU-64 molecular sieve, Beryllophosphate-H molecular sieve and UCSB-10GaZn molecular sieve.

2. The method according to claim 1, wherein The ratio of the molecular sieve's adsorption capacity for benzene to that for p-butylbenzene is 1-100.

3. The method according to claim 2, wherein: The ratio of the molecular sieve's adsorption capacity for benzene to that for p-butylbenzene is 1-10.

4. The method according to claim 1, wherein The pore volume of the molecular sieve is 0.4 to 0.8 cm 3 / g, acid density is 0.8~2.5μmol / m 2 .

5. The method according to claim 1, wherein Based on the total weight of the third carrier, the content of the acidic component is 30 to 90 weight %, and the content of the matrix is 10 to 70 weight %.

6. The method according to claim 5, wherein: Based on the total weight of the third carrier, the content of the acidic component is 45 to 80 weight %, and the content of the matrix is 20 to 55 weight %.

7. The method according to claim 1, wherein Based on the total weight of the second hydrocracking catalyst, the second hydrocracking catalyst contains 1 to 10 weight percent of Group VIII metal elements and 2 to 40 weight percent of Group VIB metal elements in terms of oxides.

8. The method according to claim 7, wherein: Based on the total weight of the second hydrocracking catalyst, the second hydrocracking catalyst contains 1 to 6 weight percent of a Group VIII metal component and 5 to 25 weight percent of a Group VIB metal component in terms of oxides.

9. The method according to claim 1, wherein The matrix is selected from at least one of alumina, silica, and silica-alumina.

10. The method according to claim 1, wherein The boiling point range of the diesel feedstock is 165-400° C., the total aromatic hydrocarbon content is higher than 60% by weight, and the content of bicyclic and higher aromatic hydrocarbons is higher than 40% by weight.

11. The method according to claim 1, wherein The distillation range of the first BTX fraction and the second BTX fraction is independently 50 to 180° C.; The distillation range of the first intermediate aromatic-rich fraction and the second intermediate aromatic-rich fraction is independently 150-280° C., the total aromatic content of the first intermediate aromatic-rich fraction and the second intermediate aromatic-rich fraction is independently higher than 50% by weight, wherein the content of alkylbenzenes and tetralin monocyclic aromatic hydrocarbons is independently higher than 45% by weight; The cutting points of the first middle aromatic-rich fraction and the first tail oil fraction, the second middle aromatic-rich fraction and the second tail oil fraction are independently in the range of 170 to 280°C.

12. The method according to claim 1, wherein The conditions of the hydrofining reaction include: hydrogen partial pressure of 3.5-10 MPa, reaction temperature of 300-450°C, hydrogen-to-oil volume ratio of 400-2500 Nm 3 / m 3 , liquid hourly volumetric space velocity is 0.2~6h -1 .

13. The method according to claim 1, wherein The hydrogen partial pressure of the second hydrocracking reaction is 0.5 to 6 MPa lower than that of the first hydrocracking reaction.

14. The method according to claim 13, wherein The conditions of the first hydrocracking reaction include: hydrogen partial pressure of 4-12 MPa, reaction temperature of 300-450°C, hydrogen to oil volume ratio of 400-2500 Nm 3 / m 3 , liquid hourly volumetric space velocity is 0.2~5h -1 ; The conditions of the second hydrocracking reaction include: hydrogen partial pressure of 2.5-6 MPa, reaction temperature of 300-450°C, hydrogen to oil volume ratio of 400-2200 Nm 3 / m 3 , liquid hourly volumetric space velocity is 0.2~10h -1 .

15. The method according to claim 1, wherein The hydrotreating catalyst includes a first carrier and a first active metal component. Calculated as oxides and based on the total weight of the hydrotreating catalyst, the hydrotreating catalyst contains 1 to 10 weight percent of Group VIII metal elements, 10 to 45 weight percent of Group VIB metal elements, and the remainder is the first carrier.

16. The method according to claim 1, wherein The first hydrocracking catalyst contains a second carrier and a second active metal component; calculated as oxides and based on the total weight of the first hydrocracking catalyst, the first hydrocracking catalyst contains 50 to 90 weight percent of the second carrier, 1 to 10 weight percent of a Group VIII metal element, and 5 to 40 weight percent of a Group VIB metal element; based on the total weight of the second carrier, the second carrier comprises 0.5 to 95 weight percent of a MoNi-containing Y-type zeolite and 5 to 99.5 weight percent of alumina.

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