A hydrocracking catalyst and its conversion method and system and application for producing aromatics from catalytic diesel

Abstract

The present application relates to a kind of hydrocracking catalyst, its preparation method and the conversion method and application of producing aromatic hydrocarbon from catalytic diesel.The hydrocracking catalyst includes: a) twelve-membered ring zeolite, b) ten-membered ring zeolite, c) VIB group metal oxide, d) VIB group metal sulfide, e) VIII group metal, f) binder;The conversion method for producing aromatic hydrocarbon from catalytic diesel includes that catalytic diesel is subjected to hydrofining, separates impurity, hydrocracking, and the >200 ℃ heavy tail oil obtained by hydrocracking is sent into catalytic cracking device fractionating column, and the superheavy aromatic hydrocarbon is separated, enters catalytic diesel stream as conversion raw material.The present application realizes the high efficiency conversion of catalytic diesel to aromatic hydrocarbon, solves the problem of affecting device long-period stable operation and catalyst stability due to superheavy aromatic hydrocarbon.

Description

Technical Field

[0001] This invention pertains to hydrocracking technology in the field of petroleum refining, specifically relating to a hydrocracking catalyst and its conversion method, system, and application for producing aromatics from catalytic diesel. Background Technology

[0002] The main component of catalytic diesel (LCO) is carbon. 11 + Alkylbenzenes and polycyclic aromatic hydrocarbons (PAHs) represent a potential source of aromatic hydrocarbons. However, due to their high PAH content, processing them into diesel fuel results in high hydrogen consumption and poor economic efficiency. Currently, the main processing methods for catalytic diesel fuel include hydrorefining-hydrocracking tandem (see patent CN101724454A) and hydrorefining-catalytic cracking combined processes (see patent CN110551526A), with the primary target product being high-octane gasoline. However, the C8, C9, and C4 hydrocarbons produced by these processes... 10 The aromatic content of the fraction is too low to meet the standards for reformed oil, making it difficult to use it as a feedstock for the production of benzene and paraxylene in the aromatics complex.

[0003] With stagnant growth in diesel demand, there is an urgent need to develop efficient conversion technologies to transform catalytic diesel into light aromatics and olefin feedstocks via hydrocracking. This integrated refining and chemical process would reduce costs and increase efficiency in the refining-aromatics-olefins industry. Patent CN112322348A discloses a method for producing high-quality aromatics from catalytic diesel, employing a two-stage hydrorefining-hydrocracking process. This solves the problem of low aromatic purity in single-stage tandem processes, producing C8 aromatics at 136-144℃, C9 aromatics at 145-170℃, and C4 aromatics at 171-210℃. 10 The purity of the aromatics meets the requirements of the aromatics complex.

[0004] However, in the conversion of catalytic diesel to light aromatics, both the feedstock and the conversion products are rich in aromatics. During the conversion, condensation and side-chain cyclization reactions inevitably occur, producing tetracyclic or higher-weighted heavy aromatics (HPNAs). These HPNAs cannot enter the zeolite channels for conversion. Under low hydrogen partial pressure, high conversion rate, and high temperature conditions, HPNA formation accelerates, depositing in areas such as heat exchangers and affecting the operability of the unit. Direct recycling of unconverted oil will affect the long-term stability of the catalyst. Therefore, it is necessary to study conversion methods for producing aromatics from catalytic diesel to solve the problems caused by the formation of HPNAs. Summary of the Invention

[0005] To address the problems of existing technologies, the inventors have discovered that tetracyclic and higher-order heavy aromatic hydrocarbons (HPNAs) are found in the fraction range above 350°C. After separation, the hydrocracking products yield fractions including C2-C4 alkanes, C5-C6 alkanes, benzene-toluene-containing streams, C8 aromatic streams, and streams containing C9 and C10 aromatics. At the bottom of the separation zone, a fraction containing C... 10 The tail oil containing the above heavy aromatics is recycled back to the fractionation system of the catalytic cracking unit. The 200-360℃ fraction enters the catalytic diesel stream, while the tetracyclic and above ultra-heavy aromatics (HPNA) enter the heavy cycle oil or catalytic slurry, thus solving the problem of their impact on the long-term stable operation of the unit and the stability of the catalyst.

[0006] The light aromatic hydrocarbons described in this invention refer to aromatic hydrocarbons with 10 or fewer carbon atoms, including C6 aromatic hydrocarbons, such as benzene; C7 aromatic hydrocarbons, such as toluene; C8 aromatic hydrocarbons, such as ethylbenzene and xylene; C9 aromatic hydrocarbons, such as methylbenzene, propylbenzene, and trimethylbenzene; C 10 Aromatic hydrocarbons, such as tetramethylbenzene, dimethylethylbenzene, diethylbenzene, etc. Accordingly, the C of the present invention... 10 The above heavy aromatic hydrocarbons refer to aromatic hydrocarbons with more than 10 carbon atoms.

[0007] One objective of this invention is to provide a hydrocracking catalyst, which, by weight, comprises: a) 10-60 parts of twelve-membered ring zeolite, b) 5-50 parts of ten-membered ring zeolite, c) 2-20 parts of Group VIB metal oxides, d) 2-10 parts of Group VIB metal sulfides, e) 0.5-10 parts of Group VIII metals, and f) 25-70 parts of binder; preferably, by weight, the hydrocracking catalyst comprises: a) 15-50 parts of twelve-membered ring zeolite, b) 10-45 parts of ten-membered ring zeolite, c) 4-15 parts of Group VIB metal oxides, d) 2.1-8 parts of Group VIB metal sulfides, e) 1-6 parts of Group VIII metals, and f) 25-70 parts of binder.

[0008] In the aforementioned hydrocracking catalyst, the twelve-membered ring zeolite exhibits strong selective ring-opening ability for tetrahydronaphthalene compounds, while the ten-membered ring zeolite demonstrates strong cracking ability for non-aromatic hydrocarbons. The combination of twelve-membered and ten-membered ring zeolites endows the catalyst with both excellent tetrahydronaphthalene and non-aromatic hydrocarbon conversion capabilities, significantly improving single-pass conversion rate and the quality of light aromatic hydrocarbon products. Preferably, the weight ratio of twelve-membered ring zeolite to ten-membered ring zeolite in the hydrocracking catalyst is between 1:5 and 12:1, more preferably 1:3 to 5:1, and even more preferably 1:2 to 2:1.

[0009] In a preferred embodiment of the present invention, the hydrocracking catalyst contains:

[0010] The twelve-membered ring zeolite is selected from BEA topological structure zeolites, preferably from β zeolites with a silica-to-alumina ratio between 10 and 200, and more preferably from β zeolites with a silica-to-alumina ratio between 15 and 150; the ten-membered ring zeolite is selected from MFI topological structure zeolites, preferably from ZSM-5 zeolites with a silica-to-alumina ratio between 10 and 100; the group VIB metal is selected from at least one of Mo and W; the group VIII metal is selected from at least one of Co and Ni; and the binder is selected from alumina.

[0011] A second objective of this invention is to provide a method for producing aromatics from catalytic diesel, comprising the step of contacting the hydrocracking catalyst described above with hydrorefined catalytic diesel under conversion conditions.

[0012] In a preferred embodiment of the present invention, the conversion method includes hydrorefining and gas-liquid separation of catalytic diesel obtained from the fractionation tower of a catalytic cracking unit, followed by hydrocracking of the separated liquid stream, and then separating the hydrocracking products containing C. 10 The above steps describe the process of feeding heavy aromatic hydrocarbons into the fractionation tower of the catalytic cracking unit.

[0013] In a more preferred embodiment of the present invention, the conversion method specifically includes the following steps:

[0014] 1) The catalytic diesel obtained from the fractionation tower of the catalytic cracking unit enters the first reaction zone for hydrorefining and gas-liquid separation to obtain the first stream;

[0015] 2) The first stream is introduced into the second reaction zone and hydrocracking is carried out in the presence of a hydrocracking catalyst to obtain the second stream;

[0016] 3) The second stream is separated in the first separation zone, and C-containing material is obtained at the bottom of the separation zone. 10 The above are the third-party logistics of heavy aromatics;

[0017] 4) The third stream is fed to the fractionation tower of the catalytic cracking unit, wherein the 200-360°C fraction enters the first reaction zone along with the catalytic diesel.

[0018] In step 1) of the above conversion method, the catalytic diesel oil, used as feedstock, undergoes hydrorefining under hydrogen-exposed conditions in the first reaction zone. The catalytic diesel oil stream and hydrogen gas contact the hydrorefining catalyst for desulfurization and denitrogenation, resulting in a selective saturation reaction of polycyclic aromatic hydrocarbons retaining one aromatic ring. The hydrorefining can be carried out in any manner and method conventionally known in the art, as long as the catalytic diesel oil is desulfurized and denitrogenated, and the polycyclic aromatic hydrocarbons are hydrogenated to retain one aromatic ring; there are no particular limitations. The first stream obtained after hydrorefining the catalytic diesel oil mainly contains refined catalytic diesel oil from which most sulfur and nitrogen impurities have been removed.

[0019] In step 1) of the above conversion method, catalytic diesel oil, used as feedstock, and hydrogen are contacted with a hydrorefining catalyst in the first reaction zone to undergo a hydrorefining reaction. The hydrorefining reaction is a well-known catalytic diesel hydrorefining technology in the art. The hydrorefining reaction conditions can be those known in the art for catalytic diesel hydrorefining; the hydrorefining catalyst can be any type of hydrorefining catalyst already available in the art, as long as it can achieve the catalytic diesel hydrorefining objective of step 1).

[0020] In step 1) of the above conversion method, the preferred hydrogenation purification reaction conditions in the first reaction zone include:

[0021] Hydrogen-to-oil volume ratio 500–3000 Nm 3 / m 3 Preferably 800-2000 Nm 3 / m 3 More preferably 1000-1500 Nm 3 / m 3 ; and / or:

[0022] Reactor inlet temperature 280-420℃, preferably 300-410℃, more preferably 310-390℃; and / or:

[0023] The partial pressure of hydrogen is 5–15 MPa, preferably 6–10 MPa, more preferably 7–9 MPa; and / or:

[0024] Airspeed 0.5–2.0 h -1 Preferably 0.6 to 1.5 hours -1 More preferably 0.8 to 1.2 hours -1 .

[0025] In the conversion method of the present invention, the hydrorefining catalyst in step 1) is preferably as follows:

[0026] The mixture comprises, by weight parts: a1) 60 to 99.9 parts, preferably 65 to 99.9 parts, more preferably 70 to 99.9 parts, and more preferably 75 to 99.9 parts of a support; and b1) a hydrogenated metal oxide, wherein the hydrogenated metal oxide comprises 0.1 to 40 parts by weight, preferably 0.1 to 35 parts, more preferably 0.1 to 30 parts, and more preferably 0.1 to 25 parts; based on the total weight parts of the support and the hydrogenated metal oxide.

[0027] In one exemplary embodiment, the carrier comprises, by weight, 60 to 100 parts of alumina; 0 to 40 parts of silicon oxide; and the total weight of the alumina and silicon oxide.

[0028] In one exemplary embodiment, the hydrogenated metal is selected from at least one of the group consisting of nickel, cobalt, molybdenum, tungsten, and iron. The hydrogenated metal is sulfided after loading.

[0029] The aforementioned hydrorefining catalyst can be prepared using any method known in the art; for example, the support can be prepared using methods such as extrusion, ball rolling, or oil column forming. In one embodiment, the catalyst can be prepared by forming a support and then impregnating it with metal.

[0030] In step 2) of the above conversion method, the first stream undergoes hydrocracking under hydrogen-containing conditions in the second reaction zone. The second stream obtained in step 2) mainly includes dry gas (including methane and ethane), dry gas, C3-C4 alkanes, C5-C6 alkanes, benzene-toluene-containing streams, C8 aromatic streams, C9 and C10 aromatic streams, and a third stream containing heavy aromatics of C10 or more. One of the purposes of hydrocracking in step 2) is to conduct hydrocracking while retaining one aromatic ring of the polycyclic aromatic hydrocarbons in the heavy aromatics of the first stream, effectively controlling the saturation and ring-opening position, while also allowing the large non-aromatic molecules in the first stream to undergo isomerization and cracking; maximizing the production of light aromatics with economical hydrogen consumption.

[0031] In a preferred embodiment of the present invention, the hydrocracking catalyst of the present invention can be prepared using any method known in the art. For example, the support can be prepared by methods such as extrusion, ball rolling, or oil column forming. In one embodiment, the catalyst can be prepared by forming a support and then impregnating it with metal. In one embodiment, the hydrocracking catalyst can be prepared by a method including the following steps:

[0032] The zeolite is mixed with a binder, then kneaded, extruded, and dried at 60–150°C. After calcination in air at 500–600°C for 3–6 hours, the desired catalyst support is obtained. A composite metal aqueous solution is prepared using Group VIII and Group VIB metal compounds. This solution is then impregnated with the catalyst support using an equal-volume impregnation method. After drying at 60–150°C, the catalyst is calcined in air at 450–520°C for 1–4 hours to obtain the catalyst precursor. The catalyst precursor is reduced in a hydrogen atmosphere at 300–450°C for 2–8 hours, and then sulfided to obtain the desired hydrocracking catalyst. This catalyst contains a considerable amount of Group VIB metal sulfides and Group VIB metal oxides, providing moderate hydrogenation activity while maintaining the selectivity for monocyclic aromatic hydrocarbons and improving the conversion ability to polycyclic aromatic hydrocarbons. This is beneficial for improving the conversion efficiency and selectivity of catalytic diesel to monocyclic aromatic hydrocarbons. Preferably, the content ratio (by weight) of group VIB metal oxides and group VIB metal sulfides in the catalyst is 1:5 to 10:1, more preferably 1:4 to 7:1, and even more preferably 1:1 to 3:1.

[0033] In step 2) of the above conversion method, the reaction conditions in the second reaction zone can adopt the reaction conditions of conventional hydrocracking reactions in the art.

[0034] Specifically, the preferred reaction conditions for hydrocracking in the second reaction zone include:

[0035] Hydrogen-to-oil volume ratio 500–5000 Nm 3 / m 3 Preferably 800-4000 Nm 3 / m 3 More preferably 1000-3000 Nm 3 / m 3 ;

[0036] The reactor inlet temperature is 280–450°C, preferably 300–430°C, and more preferably 310–420°C;

[0037] The partial pressure of hydrogen is 5-15 MPa, preferably 6-12 MPa, and more preferably 7-10 MPa;

[0038] Airspeed 0.5–2.0 h -1 Preferably 0.6 to 1.5 hours -1 More preferably 0.8 to 1.2 hours -1 .

[0039] In step 3) of the above conversion method, the second stream undergoes a first separation in the first separation zone, and the resulting stream, in addition to the third stream, includes dry gas, C3-C4 alkanes, C5-C6 alkanes, a benzene-toluene-containing stream, a C8 aromatic stream, and a stream containing C9 aromatics and C... 10 The fraction includes aromatic hydrocarbon streams, wherein the benzene-toluene hydrocarbon stream is a mixture of C6 non-aromatic hydrocarbons, C7 non-aromatic hydrocarbons, C8 non-aromatic hydrocarbons and benzene and toluene, and the C8 aromatic hydrocarbon stream is a mixture of ethylbenzene, p-xylene, m-xylene and o-xylene.

[0040] In step 3) of the above conversion method, the first separation of the second stream preferably includes gas-liquid separation, distillation and extraction; the distillation preferably includes C5-C6 alkane separation, heptane removal, xylene removal and heavy aromatics removal; wherein preferably, the stream rich in benzene-toluene fraction obtained by heptane removal is extracted and separated.

[0041] Specifically, the second stream undergoes gas-liquid separation to separate dry gas and liquid phase. The dry gas is released externally, and then the released C3-C4 and C5-C6 light hydrocarbon fractions are separated. A heptane stripper separates a stream rich in benzene-toluene fractions and a bottom stream from the heptane stripper. This bottom stream from the heptane stripper is sent to a xylene stripper. The top of the xylene stripper separates a mixed xylene product and a bottom stream from the xylene stripper. This bottom stream from the xylene stripper undergoes heavy aromatics removal. The heavy aromatics removal process separates out-of-bounds C9-C6 hydrocarbons. 10 The third stream separated from the bottom of the tower. This third stream contains C. 10 The above-mentioned heavy tail oil containing heavy aromatics. The above-mentioned deheptane tower separates a stream rich in benzene-toluene fractions. This stream is preferably further extracted to separate pure benzene-toluene mixed aromatics. The extracted C6-C8 alkanes are mainly cycloalkanes, which can be used as high-quality reforming feedstock. The gas-liquid separation, extraction, and distillation described above can all be carried out using extraction and distillation methods commonly used in the art. The third stream obtained after separation from the second stream obtained by the hydrocracking process of this invention preferably has a higher aromatic content than non-aromatic content; more preferably, the aromatic content of the third stream of this invention can reach 80 wt% or more, and most preferably 90 wt% or more.

[0042] In step 4) of the above conversion method, the C-containing material obtained in step 3) is... 10 The above-mentioned heavy aromatics are sent to the fractionation tower of the catalytic cracking unit. The 200-360℃ fraction enters the catalytic diesel stream, while the tetracyclic and above ultra-heavy aromatics (HPNA) enter the heavy cycle oil or catalytic slurry.

[0043] In the method for producing aromatics from catalytic diesel oil according to the present invention, the catalytic diesel oil used as feedstock can be obtained from a catalytic cracking unit in the art. Preferably, the catalytic diesel oil has an initial boiling point at atmospheric pressure between 160 and 220°C, and a 95% distillation temperature between 300 and 360°C. The total sulfur content of the first stream is less than 500 ppm, and the organic nitrogen content of the first stream is less than 20 ppm. The single-pass conversion rate of the >200°C fraction in the hydrocracking reaction of the second reaction zone is greater than 80 wt%.

[0044] This invention does not specifically limit the composition of the catalytic diesel oil, and it can be derived from crude oil from different origins, resulting in varying compositions. However, as an example, the catalytic diesel oil mainly contains alkanes, cycloalkanes, alkenes, sulfur-containing hydrocarbons, nitrogen-containing hydrocarbons, and C64 hydrocarbons. 11 + Components include alkylbenzenes and polycyclic aromatic hydrocarbons. Among them, C... 11 +The content of alkylbenzenes ranges from 10 to 40 wt%, the content of polycyclic aromatic hydrocarbons ranges from 15 to 50 wt%, the content of sulfur ranges from 200 to 15000 wt ppm, the content of nitrogen ranges from 100 to 1500 wt ppm, and the rest are high-boiling alkanes, cycloalkanes and alkenes.

[0045] A third objective of this invention is to provide a system for producing aromatics from catalytic diesel fuel using the above-mentioned conversion method, comprising:

[0046] A first reaction zone; configured to receive the catalytic diesel fuel and the first emission stream;

[0047] A second reaction zone; configured to receive the first material stream and discharge the second material stream;

[0048] A first separation zone; configured to receive the second stream; emissions including the C6-C8 alkane stream, benzene-toluene stream, C8 aromatic stream, C9 aromatic stream, and C6-C8 aromatic stream. 10 The logistics of aromatics, and C-containing compounds 10 The fraction including the third stream of the above heavy aromatics;

[0049] A fractionation column of a catalytic cracking unit: configured to receive the third stream and discharge the fourth stream;

[0050] A first conduit; configured to circulate the fourth material flow to the first reaction zone.

[0051] In the above-mentioned system for producing aromatics from catalytic diesel:

[0052] The reactor in the first reaction zone is a fixed-bed reaction system;

[0053] The reactor in the second reaction zone is a fixed-bed reaction system;

[0054] The first separation zone includes a gas-liquid separator, a distillation column, and an extraction column connected in sequence, for sequentially separating dry gas, C3-C4 alkanes, C5-C6 alkanes, benzene-toluene-containing hydrocarbon streams, C8 aromatic streams, C9 aromatic streams, and C4 aromatic streams. 10 Fractions including aromatics and C 10 The above-mentioned heavy aromatics third stream; preferably, the distillation column includes a depentane column, a deheptane column, a xylene column and a heavy aromatics column connected in sequence, and the deheptane column includes a benzene-toluene fraction extraction device to separate the stream rich in benzene-toluene fraction separated from the deheptane column.

[0055] The fourth objective of this invention is to apply the above-described conversion method for producing aromatics from catalytic diesel or the above-described system for producing aromatics from catalytic diesel to the production of aromatics from catalytic diesel.

[0056] In the technical solution described in this invention, after hydrorefining in the first reaction zone, the saturation rate of polycyclic aromatic hydrocarbons in the catalytic diesel stream is greater than 50%, the total sulfur content is reduced to below 500 ppm, the organic nitrogen content is reduced to below 20 ppm, and the final boiling point is reduced by more than 10°C. After the catalytic diesel stream passes through the hydrorefining unit in the first reaction zone and the hydrocracking unit in the second reaction zone, it is converted into monocyclic aromatic hydrocarbons and light hydrocarbons of C10 and below, with a conversion rate greater than 80%.

[0057] Compared with existing technologies, the hydrocracking catalyst of this invention can effectively control saturation and ring-opening positions, while also enabling the isomerization and cracking of large non-aromatic hydrocarbons in the first stream; maximizing the production of light aromatics with economical hydrogen consumption. The technical solution of this invention employs a two-stage process of hydrorefining-hydrocracking to convert catalytic diesel. The unconverted oil containing heavy aromatics of C10 or more is sent to the fractionation tower of the catalytic cracking unit, where the diesel fraction enters the catalytic diesel stream and serves as feedstock for hydrorefining. Four-ring and above ultra-heavy aromatics (HPNA) are discharged into the heavy cycle oil or catalytic slurry, without entering the hydrorefining and hydrocracking reactors. This method achieves complete conversion of catalytic diesel to aromatics without increasing equipment, solving the problems caused by ultra-heavy aromatics affecting the long-term stable operation of the unit and catalyst stability. Attached Figure Description

[0058] Figure 1 This is a process flow diagram of the method for converting diesel fuel into aromatics according to the present invention.

[0059] Explanation of reference numerals in the attached figures:

[0060] 1 is feedstock oil - catalytic diesel

[0061] 2 is the first reaction zone - hydrorefining reactor.

[0062] 3 is the first reaction zone export logistics - First Logistics

[0063] 4 is the second reaction zone - hydrocracking reactor.

[0064] 5 is the product of hydrocracking reaction - second stream.

[0065] 6 represents the first separation zone, which may include dry gas separation, light hydrocarbon separation, distillation, and extraction.

[0066] 7 represents the dry gas, C3-C4 alkanes, and C5-C6 alkanes separated from the first separation zone.

[0067] 8 is the first separation zone where C6-C8 alkane streams are separated.

[0068] 9 represents the benzene-toluene stream separated from the first separation zone.

[0069] 10 represents the C8 aromatic hydrocarbon material separated from the first separation zone.

[0070] 11 represents the C9 aromatics and C... separated from the first separation zone. 10 Aromatics logistics

[0071] 12 represents the heavy tail oil discharged from the first separation zone.

[0072] 13 is the fractionation tower of the catalytic cracking unit. Detailed Implementation

[0073] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0074] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In the event of inconsistency or conflict, the definitions in this specification shall prevail.

[0075] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0076] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values; such ranges or values ​​should be understood to include values ​​close to them. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In principle, various technical solutions can be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0077] The following describes in detail the specific embodiments of the present invention. However, the present invention is not limited to the specific details described in the embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0078] It should also be noted that the various specific technical features described in the following embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the various possible combinations will not be described separately in this invention.

[0079] Furthermore, various embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention. The resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0080] Unless otherwise specified, the pressure mentioned in this manual is gauge pressure.

[0081] Unless otherwise specified, the air velocity mentioned in this specification is the liquid time air velocity (LHSV).

[0082] Unless otherwise specified, all percentages, parts, ratios, etc. mentioned in this specification are based on weight, unless being based on weight would not be in accordance with the common understanding of those skilled in the art.

[0083] Figure 1 This is a schematic process flow diagram of an exemplary embodiment of the method for converting diesel fuel to aromatics according to the present invention. Many conventional equipment items, such as pumps, compressors, heat exchangers, extraction devices, and hydrogen pipelines, are omitted in the diagram, but these items are well known to those skilled in the art. Figure 1 As shown, a detailed description of the flow of an exemplary embodiment of the method described in this invention is as follows:

[0084] Catalytic diesel 1, used as feedstock, enters the hydrorefining unit in the first reaction zone 2 to obtain refined catalytic diesel 3 (first stream), which is the outlet stream of the first reaction zone, after the separation of hydrogen sulfide and ammonia. The first stream then enters the hydrocracking unit in the second reaction zone 4. It is rich in light aromatics such as benzene, toluene, and xylene, as well as C9A and C6A hydrocarbons. 10 The A fraction and heavy tail oil exit stream 5 (second stream) enters the first separation zone 6, where it is separated to obtain dry gas, C3-C4 and C5-C6 light hydrocarbon stream 7, C6-C8 alkane stream 8, benzene-toluene stream 9, C8 aromatic stream 10, including C9A / C 10 Aromatic hydrocarbon stream 11, and C-containing 10 The above-mentioned heavy aromatics heavy tail oil third stream 12. The third stream 12 enters the fractionation tower 13 of the catalytic cracking unit, in which the diesel fraction stream enters the hydrorefining reaction zone (first reaction zone) as feedstock along with the catalytic diesel.

[0085] Specifically, the first separation zone 6 includes sequentially connected distillation columns such as a gas-liquid separator, a light hydrocarbon separator, a heptane removal column, a xylene column, and a heavy aromatics column, as well as a benzene-toluene fraction extraction device (not shown in the attached drawings).

[0086] The compositional analysis of the catalysts involved in this invention employs analytical methods known in the art. For example, the composition of the hydrocracking catalyst can be analyzed using ICP (inductively coupled plasma) and XRF (X-ray fluorescence). The compositional ratio of group VIB metal oxides and metal sulfides is determined using XPS (X-ray photoelectron spectroscopy). ICP testing was performed using a Varian 700-ES series XPS instrument. XRF testing was performed using a Rigaku ZSX 100e XRF instrument. XPS testing conditions included: a Perkin Elmer PHI 5000C ESCA X-ray photoelectron spectrometer, using a MgK excitation source, operating voltage 10 kV, current 40 mA, and vacuum degree 4.0 × 10⁻⁸ Pa.

[0087] In this invention, the composition of reaction streams (such as hydrocracking products) is determined by gas chromatography. The chromatograph is an Agilent 7890A, equipped with an FID detector, and an FFAP capillary column is used for separation. The column is programmed with an initial temperature of 90°C, held for 15 minutes, and then increased to 220°C at a rate of 15°C / min, held for 45 minutes.

[0088] The calculation formula in the method described in this invention is as follows:

[0089] 1. The formula for calculating the overall conversion rate (single-pass conversion rate of fractions above 200℃) is as follows:

[0090]

[0091] 3. The formula for calculating the yield of light aromatics is:

[0092]

[0093] The catalyst raw materials used in the embodiments of this invention are all commercially available.

[0094] Comparative Example 1

[0095] A two-stage hydrorefining-selective conversion process is used to process catalytic diesel (see Chinese patent CN112322348A for the specific process flow diagram). The catalytic diesel, used as feedstock, undergoes hydrorefining and impurity separation, followed by hydrocracking. The hydrocracking products are then separated into benzene-toluene, xylene, and C9A / C by a gas-liquid separation and distillation system. 10 Products such as heavy aromatics and heavy tail oil are recycled directly back to the hydrorefining reactor.

[0096] Table 1 shows the analytical data of the catalytic diesel feedstock and hydrorefining products. The aromatic content of the catalytic diesel is 87.15 wt%. Table 2 lists the hydrorefining catalyst used and its reaction conditions. The hydrorefining catalyst used is a nickel-molybdenum type diesel hydrorefining catalyst from Sinopec Catalyst Branch. After mixing the catalytic diesel with hydrogen, it enters the hydrorefining reactor to remove most of the sulfur and nitrogen impurities. The polycyclic aromatic hydrocarbons are saturated and converted into hydrocarbons containing only one aromatic ring. Table 1 also lists the sulfur and nitrogen content, density, aromatic hydrocarbon content, and fraction distribution of the hydrorefined products. The first stream of catalytic diesel after hydrorefining undergoes impurity separation and nitrogen stripping to fully remove dissolved hydrogen sulfide and ammonia, yielding the first stream. The sulfur and nitrogen contents of the hydrorefined products are 126 ppm and 7.6 ppm, respectively.

[0097] Hydrocracking catalyst C-0 and its preparation: Hydrogen-form β-zeolite was obtained from Sinopec Catalyst Branch, with a silica-to-alumina ratio (SAR) of 50.5. Hydrogen-form ZSM-5 zeolite was also obtained from Sinopec Catalyst Branch, with a silica-to-alumina ratio (SAR) of 36.5. 40 kg of hydrogen-form β-zeolite (95% dry basis), 20 kg of hydrogen-form ZSM-5 zeolite (95% dry basis), and 50 kg of pseudoboehmite (70% Al2O3 dry basis) were thoroughly mixed, kneaded, extruded, dried at 120°C, and calcined in air at 550°C for 4 hours to obtain the desired catalyst support. A 50 L aqueous solution was prepared using 5.8 kg of nickel acetate, 1.5 kg of ammonium sulfate, and 7.8 kg of ammonium heptamolybdate. More than 50 L of the metal solution was uniformly added to 75 kg of the support, and the catalyst support was impregnated by an equal-volume impregnation method. After drying at 120°C, the catalyst precursor was calcined in air at 500°C for 2 hours to obtain the catalyst precursor. Reduction at 400℃ in a hydrogen atmosphere for 3 hours yielded a hydrocracking catalyst C-0, with a composition of 1.7 parts Ni, 1.3 parts MoS2, and 5.0 parts MoO. x / 37.6 parts β zeolite - 18.8 parts ZSM-5 zeolite - balance 34.6 parts Al2O3, where x value is 2.38.

[0098] Table 1. Composition of catalytic diesel and hydrorefining products

[0099] project Catalytic diesel feedstock Hydrogenation Refining Products Density (4℃) 0.953 0.926 Sulfur (wtppm) 1070 126 Nitrogen (wtppm) 632 7.6 Non-aromatic hydrocarbons (wt) 10.85 17.68 Monocyclic aromatic hydrocarbons (wt%) 37.40 56.65 Polycyclic aromatic hydrocarbons (wt%) 51.75 25.67 Distillation test (D-86) ℃ ℃ Initial boiling point 195 189 5％ 212 210 10％ 237 223 30％ 245 236 50％ 289 272 70％ 318 311 90％ 344 336 95％ 354 348 Final boiling point 367 356

[0100] Table 2. Hydrorefining catalysts and reaction conditions

[0101]

[0102] Hydrocracking catalyst CO was loaded into a multi-stage fixed-bed reactor. The first stream was fed into the hydrocracking reactor, and the reaction conditions were: hydrogen-to-oil volume ratio of 2800 Nm³. 3 / m3 The inlet temperature of each hydrocracking catalyst bed is 350℃, the hydrogen partial pressure is 8.0 MPa, and the space velocity is 0.9 h⁻¹. -1 .

[0103] After establishing a stable reaction, the second stream of hydrocracking products is separated into benzene-toluene, xylene, C9A aromatics, and C6A aromatics by gas-liquid separation, distillation, and aromatics extraction systems. 10 Aromatic hydrocarbons. Contain C. 10 The above heavy tail oil is recycled back to the hydrorefining reactor. After 100 hours, samples are taken for analysis. Calculations show that the total conversion rate of the hydrocracking unit is 75.64%, producing benzene-toluene, xylene, C9A aromatics, and C... 10 The yield of monocyclic light aromatic hydrocarbons, including A aromatics, was 31.54 wt%, containing C. 10 The amount of tetracyclic or higher-order ultra-heavy polycyclic aromatic hydrocarbons in the third stream of the above heavy aromatics was 95 ppm. After 2000 hours of unit operation, sample analysis showed that the total conversion rate of the hydrocracking unit was 67.69%, with benzene-toluene, xylene, C9A aromatics, and C... 10 The yield of monocyclic light aromatic hydrocarbons, including A aromatics, was 25.65 wt%, containing C. 10 The amount of tetracyclic or higher-order ultra-heavy pyrocyclic aromatics in the third stream of the above heavy aromatics increased to 4930 ppm. The significant increase in the amount of ultra-heavy pyrocyclic aromatics generated during the conversion process has an adverse effect on the stability of the hydrocracking catalyst, making it impossible for the unit to operate stably for a long period of time.

[0104] Comparative Example 2

[0105] A two-stage hydrorefining-selective conversion process is used to process catalytic diesel (see Chinese patent CN112322348A for the specific process flow diagram). The catalytic diesel, used as feedstock, undergoes hydrorefining and impurity separation, followed by hydrocracking. The hydrocracking products are then separated into benzene-toluene, xylene, and C9A / C by a gas-liquid separation and distillation system. 10 Products such as heavy aromatics and heavy tail oil are recycled directly back to the hydrorefining reactor.

[0106] Hydrocracking catalyst C-1 and its preparation: Hydrogen-form β-zeolite was obtained from Sinopec Catalyst Branch, with a silica-to-alumina ratio (SAR) of 50.5. Hydrogen-form ZSM-5 zeolite was also obtained from Sinopec Catalyst Branch, with a silica-to-alumina ratio (SAR) of 36.5. 40 kg of hydrogen-form β-zeolite (95% dry basis), 20 kg of hydrogen-form ZSM-5 zeolite (95% dry basis), and 50 kg of pseudoboehmite (70% Al2O3 dry basis) were thoroughly mixed, kneaded, extruded, dried at 120°C, and calcined in air at 550°C for 4 hours to obtain the desired catalyst support. A 50 L aqueous solution was prepared using 5.8 kg of nickel acetate, 3 kg of ammonium sulfate, and 7.8 kg of ammonium heptamolybdate. More than 50 L of the metal solution was uniformly added to 75 kg of the support, and the catalyst support was impregnated by an equal-volume impregnation method. After drying at 120°C, the catalyst precursor was calcined in air at 500°C for 2 hours to obtain the catalyst precursor. Reduction at 400℃ in a hydrogen atmosphere for 3 hours yielded hydrocracking catalyst C-1, with a composition of 1.7 parts Ni, 2.2 parts MoS2, and 5.1 parts MoO. x / 37.6 parts β zeolite - 18.8 parts ZSM-5 zeolite - balance 34.6 parts Al2O3, where x value is 2.38.

[0107] Hydrocracking catalyst C1 was loaded into a multi-stage fixed-bed reactor. The first stream was fed into the hydrocracking reactor, and the reaction conditions were: hydrogen-to-oil volume ratio of 2800 Nm³. 3 / m 3 The inlet temperature of each hydrocracking catalyst bed is 350℃, the hydrogen partial pressure is 8.0 MPa, and the space velocity is 0.9 h⁻¹. -1 .

[0108] After establishing a stable reaction, the second stream of hydrocracking products is subjected to gas-liquid separation, distillation, and aromatics extraction systems to obtain benzene-toluene, xylene, and C9A aromatics. 10 Aromatic hydrocarbons, containing C 10 The above heavy tail oil. Heavy tail oil containing more than C10 is recycled back to the hydrorefining reactor.

[0109] Sampling and analysis after 100 hours showed that the total conversion rate of the hydrocracking unit was 91.64%, producing benzene-toluene, xylene, C9A aromatics, and C... 10 The yield of monocyclic light aromatic hydrocarbons, including A aromatics, was 38.56 wt%, containing C. 10 The amount of tetracyclic or higher polycyclic aromatic hydrocarbons in the third stream of the above heavy aromatics was 92 ppm. After 2000 hours of unit operation, sample analysis showed that the total conversion rate of the hydrocracking unit was 83.76%, with benzene-toluene, xylene, C9A aromatics, and C... 10 The yield of monocyclic light aromatic hydrocarbons, including A aromatics, was 35.47 wt%, containing C. 10In the third stream of the above heavy aromatics, the amount of extra-heavy fused-ring aromatics with four or more rings increased to 2658 ppm. Although the initial conversion rate was high, the amount of extra-heavy fused-ring aromatics produced during the conversion process increased significantly as the reaction progressed. After long-term operation, the catalyst conversion rate decreased significantly, and the stability was poor.

[0110] Example 1

[0111] The flowchart of the conversion method for producing aromatics from catalytic diesel in this embodiment is as follows: Figure 1 As shown. This includes hydrorefining catalytic diesel, separating impurities, and hydrocracking. The heavy tail oil (>200℃) obtained from hydrocracking is fed into the fractionation tower of the catalytic cracking unit to separate ultra-heavy aromatics. The diesel fraction enters the catalytic diesel stream as a conversion feedstock. Specifically:

[0112] Catalytic diesel 1, used as feedstock, enters the hydrorefining unit in the first reaction zone 2 to obtain refined catalytic diesel 3 (first stream), which is the outlet stream of the first reaction zone, after the separation of hydrogen sulfide and ammonia. The first stream then enters the hydrocracking unit in the second reaction zone 4. It is rich in light aromatics such as benzene, toluene, and xylene, as well as C9A and C6A hydrocarbons. 10 The A fraction and heavy tail oil exit stream 5 (second stream) enters the first separation zone 6, where it is separated to obtain dry gas, C3-C4 and C5-C6 light hydrocarbon stream 7, C6-C8 alkane stream 8, benzene-toluene stream 9, C8 aromatic stream 10, including C9A / C 10 Aromatic hydrocarbon stream 11, and C-containing 10 The above-mentioned heavy aromatics heavy tail oil third stream 12. Third stream 12 enters the fractionation 13 of the catalytic cracking unit, wherein the diesel fraction stream enters the hydrorefining reaction zone as feedstock along with the catalytic diesel.

[0113] The hydrorefining catalyst and reaction conditions are the same as in Comparative Example 1. The hydrocracking catalyst C-1 and its preparation are the same as in Comparative Example 2.

[0114] Hydrocracking catalyst C1 was loaded into a multi-stage fixed-bed reactor. The first stream was fed into the hydrocracking reactor, and the reaction conditions were: hydrogen-to-oil volume ratio of 2800 Nm³. 3 / m 3 The inlet temperature of each hydrocracking catalyst bed is 350℃, the hydrogen partial pressure is 8.0 MPa, and the space velocity is 0.9 h⁻¹. -1 .

[0115] After establishing a stable reaction, the second stream of hydrocracking products is subjected to gas-liquid separation, distillation, and aromatics extraction systems to obtain benzene-toluene, xylene, and C9A aromatics. 10 Aromatic hydrocarbons, containing C 10 The above are heavy tail oils. Contains C. 10The above heavy tail oil is sent to the fractionation tower of the catalytic cracking unit, where the 200-360℃ fraction enters the first reaction zone along with the catalytic diesel.

[0116] Sampling and analysis after 100 hours showed that the total conversion rate of the hydrocracking unit was 92.75%, producing benzene-toluene, xylene, C9A aromatics, and C... 10 The yield of monocyclic light aromatic hydrocarbons, including A aromatics, was 39.06 wt%, containing C. 10 The amount of tetracyclic or higher polycyclic aromatic hydrocarbons in the third stream of the above heavy aromatics was 88 ppm. After 2000 hours of unit operation, sample analysis showed that the total conversion rate of the hydrocracking unit was 90.37%, with benzene-toluene, xylene, C9A aromatics, and C... 10 The yield of monocyclic light aromatic hydrocarbons, including A aromatics, was 38.21 wt%, containing C. 10 In the third stream of the above heavy aromatics, the amount of tetracyclic or higher-order ultra-heavy fused-ring aromatics increased to 91 ppm. The ultra-heavy fused-ring aromatics generated during the conversion process did not increase significantly with the progress of the reaction, indicating good catalyst stability.

[0117] Example 2

[0118] The flow chart for the conversion of catalytic diesel to aromatics in this embodiment is as follows: Figure 1 As shown, the process includes hydrorefining catalytic diesel, separating impurities, and hydrocracking. The heavy tail oil obtained from hydrocracking (>200°C) is fed into the fractionation tower of the catalytic cracking unit to separate ultra-heavy aromatics. The diesel fraction enters the catalytic diesel stream as a conversion feedstock, as in Example 1.

[0119] The catalyst and reaction conditions for hydrogenation purification were the same as those in Comparative Example 1.

[0120] Hydrocracking catalyst C-2 and its preparation: Hydrogen-form β-zeolite was obtained from Sinopec Catalyst Branch, with a silica-to-alumina ratio (SAR) of 28.1. Hydrogen-form ZSM-5 zeolite was also obtained from Sinopec Catalyst Branch, with a silica-to-alumina ratio (SAR) of 55. 20 kg of hydrogen-form β-zeolite (95% dry basis), 40 kg of hydrogen-form ZSM-5 zeolite (95% dry basis), and 40 kg of pseudoboehmite (70% Al2O3 dry basis) were thoroughly mixed, kneaded, extruded, dried at 120°C, and then calcined in air at 550°C for 4 hours to obtain the desired catalyst support. A 50-liter aqueous solution was prepared using 5.8 kg of cobalt nitrate, 3.6 kg of ammonium persulfate, 10.5 kg of ammonium heptamolybdate, and 6 kg of succinic acid. More than 50 liters of molten metal were uniformly added to a 75 kg support, and the catalyst support was impregnated by an equal-volume impregnation method. After drying at 120 °C, the catalyst precursor was calcined in air at 500 °C for 2 hours to obtain the catalyst precursor. Reduction in hydrogen atmosphere at 400 °C for 3 hours yielded hydrocracking catalyst C-2, with a composition of 1.4 parts Co, 4.2 parts MoS2, and 4.7 parts MoO. x / 20.1 parts β zeolite - 40.1 parts ZSM-5 zeolite - balance 29.5 parts Al2O3, where x value is 2.57.

[0121] Hydrocracking catalyst C2 was loaded into a multi-stage fixed-bed reactor. The first stream was fed into the hydrocracking reactor, and the reaction conditions were: hydrogen-to-oil volume ratio of 2400 Nm³. 3 / m 3 The inlet temperature of each hydrocracking catalyst bed is 355℃, the hydrogen partial pressure is 8.5 MPa, and the space velocity is 1.1 h⁻¹. -1 .

[0122] After establishing a stable reaction, the second stream of hydrocracking products is separated into benzene-toluene, xylene, C9A aromatics, and C6A aromatics by gas-liquid separation, distillation, and aromatics extraction systems. 10 Aromatic hydrocarbons, containing C 10 The above are heavy tail oils. Contains C. 10 The above heavy tail oil is sent to the fractionation tower of the catalytic cracking unit, where the 200-360℃ fraction enters the first reaction zone along with the catalytic diesel.

[0123] Sampling and analysis after 100 hours showed that the total conversion rate of the hydrocracking unit was 83.24%, producing benzene-toluene, xylene, C9A aromatics, and C... 10 The yield of monocyclic light aromatic hydrocarbons, including A aromatics, was 36.87 wt%, containing C. 10 The amount of tetracyclic or higher-order ultra-heavy polycyclic aromatic hydrocarbons in the third stream of the above heavy aromatics was 129 ppm. After 2000 hours of unit operation, sample analysis showed that the total conversion rate of the hydrocracking unit was 81.53%, with benzene-toluene, xylene, C9A aromatics, and C... 10 The yield of monocyclic light aromatic hydrocarbons, including A aromatics, was 33.85 wt%, containing C. 10 In the third stream of the above heavy aromatics, the amount of tetracyclic or higher-order ultra-heavy fused-ring aromatics increased to 136 ppm. The ultra-heavy fused-ring aromatics generated during the conversion process did not increase significantly with the progress of the reaction, indicating good catalyst stability.

Claims

1. A method for producing aromatics from catalytic diesel fuel, comprising the step of contacting a hydrocracking catalyst with hydrorefined catalytic diesel fuel under conversion conditions, wherein the conversion method specifically includes the following steps: 1) The catalytic diesel obtained from the fractionation tower of the catalytic cracking unit enters the first reaction zone for hydrorefining and gas-liquid separation to obtain the first stream; 2) The first stream is introduced into the second reaction zone and hydrocracking is carried out in the presence of a hydrocracking catalyst to obtain the second stream; 3) The second stream is separated in the first separation zone, and C-containing material is obtained at the bottom of the separation zone. 10 The above are the third-party logistics of heavy aromatics; 4) The third stream is fed to the fractionation tower of the catalytic cracking unit, wherein the 200~360℃ fraction enters the first reaction zone along with the catalytic diesel; The hydrocracking catalyst, by weight, comprises: a) 15-50 parts of 12-membered ring zeolite, b) 10-45 parts of 10-membered ring zeolite, c) 4-15 parts of Group VIB metal oxides, d) 2.1-8 parts of Group VIB metal sulfides, e) 1-6 parts of Group VIII metals, and f) 25-70 parts of binder; wherein the 12-membered ring zeolite is selected from β-zeolite with a silica-alumina ratio between 10 and 200, and the 10-membered ring zeolite is selected from ZSM-5 zeolite with a silica-alumina ratio between 10 and 100.

2. The conversion method according to claim 1, characterized in that, The VIB group metal is selected from at least one of Mo and W; and / or, The group VIII metal is selected from at least one of Co and Ni; and / or, The adhesive is selected from aluminum oxide.

3. The conversion method according to claim 1, characterized in that, The initial boiling point of the catalytic diesel is between 160 and 220°C, and the 95% distillation temperature is between 300 and 360°C.

4. The conversion method according to claim 1, characterized in that, In step 2), the single-pass conversion rate of the hydrocracking reaction >200℃ fraction is greater than 80 wt%; and / or, The reaction conditions for hydrocracking in step 2) include: The hydrogen-to-oil volume ratio is 500~5000 Nm 3 / m 3 ; and / or, The reactor inlet temperature is 280~450℃; and / or, The partial pressure of hydrogen is 5~15 MPa; and / or, Airspeed is 0.5~2.0 h / h -1 .

5. The conversion method according to claim 4, characterized in that, The reaction conditions for hydrocracking in step 2) include: The hydrogen-to-oil volume ratio is 800~4000 Nm 3 / m 3 ; and / or, The reactor inlet temperature is 300~430℃; and / or, The partial pressure of hydrogen is 6~12 MPa; and / or, Airspeed is 0.6~1.5 h / h -1 .

6. The conversion method according to claim 1, characterized in that, The separation in step 3) includes gas-liquid separation, distillation, and extraction; and / or, In step 3), the streams separated in the first separation zone, in addition to the third stream, also include dry gas, C3-C4 alkanes, C5-C6 alkanes, benzene-toluene-containing streams, C8 aromatic streams, and streams containing C9 aromatics and C... 10 Fractions including aromatic hydrocarbon streams.

7. The conversion method according to claim 6, characterized in that, The distillation process includes C5-C6 alkane separation, heptane removal, xylene removal, and heavy aromatic hydrocarbon removal; and / or, The benzene-toluene hydrocarbon stream is a mixture of C6 non-aromatic hydrocarbons, C7 non-aromatic hydrocarbons, C8 non-aromatic hydrocarbons, and benzene and toluene; and / or, The C8 aromatic stream is a mixture of ethylbenzene, p-xylene, m-xylene, and o-xylene.

8. The conversion method according to claim 7, characterized in that, The stream obtained from the removal of heptane, which is rich in benzene-toluene fraction, needs to be extracted and separated.

9. The conversion method for producing aromatics from catalytic diesel according to any one of claims 1 to 8 is applied to the production of aromatics from catalytic diesel.

Images