A method for producing chemical raw materials by hydrocracking diesel oil

Abstract

The present invention discloses a method for producing chemical raw materials by hydrocracking of diesel. The method includes: (1) mixing diesel with hydrogen and passing through a normal paraffin conversion reaction zone to carry out a normal paraffin conversion reaction, and controlling the mass content of C7 + normal paraffins in the reaction effluent to be 0.5 wt% to 3.0 wt%; (2) in the presence of hydrogen, the normal paraffin conversion reaction effluent from step (1) enters a hydrocracking reaction zone to carry out a hydrocracking reaction, and then the hydrocracking reaction effluent is separated to obtain chemical raw materials; the chemical raw materials include raw materials for preparing low-carbon olefins and reforming raw materials; the reaction pressure in the normal paraffin conversion reaction zone in step (1) is 6 to 12 MPa; the reaction pressure in the hydrocracking reaction zone in step (2) is 6 to 12 MPa. This method uses diesel as a raw material for hydrocracking to produce chemical raw materials, which can greatly improve the yield and quality of ethylene raw materials and reforming raw materials.

Description

Technical Field

[0001] The present invention belongs to the field of diesel hydrocracking, and particularly relates to a method for producing chemical raw materials by diesel hydrocracking. Background Art

[0002] Driven by the continuous optimization of China's economic structure, China's refining industry is shifting from the high-speed development stage since the beginning of this century to the high-quality development stage. The main characteristics of the high-quality development of the refining industry include refining-chemical integration, large-scale units, base and park-based production capacity layout, and cleaner, lower-carbon and intelligent production processes. The consumption of petroleum has increased from 224 million tons in 2000 to 625 million tons in 2018. From the perspective of petroleum consumption trends, in recent years, the growth rate of China's refined oil consumption has generally slowed down, and diesel consumption has entered a plateau period. The demand for chemical raw materials such as naphtha and light hydrocarbons continues to grow. The changes in the total demand and consumption structure of petroleum products are driving the structural adjustment and transformation and upgrading of the refining industry. Therefore, converting diesel fractions into high-quality chemical raw materials has become a beneficial technical path for refining enterprises to optimize product structure and improve economic benefits.

[0003] Hydrocracking technology has the characteristics of strong feedstock adaptability, large flexibility in production operation and product scheme, and good product quality. It can directly convert various heavy and inferior feeds into high-quality jet fuels, diesel oils, lubricating oil bases, chemical naphtha, and ethylene raw materials for steam cracking of tail oil, which are in urgent need in the market. It has become one of the most important deep hydrocarbon processing processes in modern refining and petrochemical industries and has been increasingly widely used in various countries in the world.

[0004] CN201580070326.4 discloses a method for preparing LPG and BTX, comprising: a) subjecting a mixed hydrocarbon stream to a first hydrocracking in the presence of a first hydrocracking catalyst to prepare a first hydrocracking product stream; b) separating the first hydrocracking product stream to provide at least one light hydrocarbon stream containing at least C2 and C3 hydrocarbons, an intermediate hydrocarbon stream composed of C4 and / or C5 hydrocarbons, and a heavy hydrocarbon stream containing at least C6+ hydrocarbons, and c) subjecting the heavy hydrocarbon stream to a second hydrocracking in the presence of a second hydrocracking catalyst to prepare a second hydrocracking product stream containing BTX, wherein the second hydrocracking is more severe than the first hydrocracking, d) wherein, in the presence of a C4 hydrocracking catalyst, at least part of the intermediate hydrocarbon stream is subjected to C4 hydrocracking to prepare a C4 hydrocracking product stream, and the C4 hydrocracking is optimized for converting C4 hydrocarbons into C3 hydrocarbons.

[0005] CN201480037272.7 discloses a method for producing light olefin hydrocarbon compounds from hydrocarbon raw materials, comprising the following steps: (a) feeding the hydrocarbon raw materials into a reaction zone for ring opening; (b) separating the reaction products generated from the reaction zone into an overhead stream and a side stream; (c) feeding the side stream from (b) into a gasoline hydrocracking (GHC) unit; (d) separating the reaction products of the GHC in step (c) into an overhead stream containing hydrogen, methane, ethane and liquefied petroleum gas and a stream containing aromatic hydrocarbon compounds and a small amount of hydrogen and non-aromatic hydrocarbon compounds; (e) feeding the overhead stream from the gasoline hydrocracking (GHC) unit into a steam cracking unit.

[0006] The above method is mainly used for producing LPG and BTX, and has defects of low target product yield and poor quality when producing low-carbon olefins. Therefore, it is worthy of in-depth research by those skilled in the art to develop a hydrocracking method suitable for producing high-quality chemical raw materials from diesel. Summary of the Invention

[0007] Aiming at the problems existing in the prior art, the object of the present invention is to provide a method for producing chemical raw materials by hydrocracking diesel. This method uses diesel as a raw material for hydrocracking to produce chemical raw materials, and can greatly improve the yield and quality of ethylene raw materials and reforming raw materials.

[0008] The present invention provides a method for producing chemical raw materials by hydrocracking diesel, and the method comprises:

[0009] (1) Diesel is mixed with hydrogen and undergoes a normal paraffin conversion reaction in a normal paraffin conversion reaction zone, and the mass content of C7 + normal paraffins in the reaction effluent is controlled to be 0.5 wt% to 3.0 wt%;

[0010] (2) In the presence of hydrogen, the normal paraffin conversion reaction effluent from step (1) enters a hydrocracking reaction zone for hydrocracking reaction, and then the hydrocracking reaction effluent is subjected to distillation separation to obtain chemical raw materials; the chemical raw materials include ethylene raw materials for preparing low-carbon olefins and reforming raw materials.

[0011] According to the present invention, a catalyst is loaded in the normal paraffin conversion reaction zone in step (1); specifically, a hydrofining catalyst and a first hydrocracking catalyst are loaded in sequence along the material flow direction. The first hydrocracking catalyst can be one or more catalysts. The hydrofining catalyst can be one or more catalysts. The loading ratio of the hydrofining catalyst to the first hydrocracking catalyst is 0.5 to 5:1, by volume.

[0012] According to the present invention, the hydrofining catalyst described in step (1) can adopt a conventional hydrofining catalyst, which is mainly used for hydrodesulfurization, hydrodenitrogenation and other impurities. The hydrofining catalyst includes a carrier and a hydrogenation active metal, wherein the carrier is an inorganic refractory oxide, generally selected from one or more of alumina, amorphous silica-alumina, silica or titanium oxide, etc.; the hydrogenation active metal includes Group VIB and / or Group VIII metal components. Further preferably, in the hydrofining catalyst, the Group VIB metal is preferably selected from tungsten and / or molybdenum, and its content in the catalyst is 5 wt% to 30 wt% based on the mass of the oxide, preferably 10 wt% to 20 wt%; the Group VIII metal is preferably selected from nickel and / or cobalt, and its content in the catalyst is 1 wt% to 6 wt% based on the mass of the oxide, preferably 1.5 wt% to 5 wt%. The content of the carrier in the catalyst is 64 wt% to 94 wt%, preferably 75 wt% to 88.5 wt%.

[0013] According to the present invention, in step (1), the first hydrocracking catalyst includes an active metal component and a carrier; the carrier includes a molecular sieve having selective cracking of normal paraffins, preferably selected from one or more of ZSM-5 molecular sieve, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35 and ZSM-38 molecular sieves, preferably ZSM-5 molecular sieve. The carrier may also include a binder. Preferably, the binder is alumina. The active metal component includes at least one of metals in Group VIB and Group VIII. The Group VIB metal is preferably molybdenum and / or tungsten, and the Group VIII metal is preferably cobalt and / or nickel.

[0014] According to the present invention, in step (1), preferably, in the first hydrocracking catalyst, based on the weight of the catalyst, the content of the Group VIB metal (calculated as the oxide) is 5.0% to 15.0%, the content of the Group VIII metal (calculated as the oxide) is 2.0% to 5.0%, and the content of the carrier is 80.0% to 93.0%.

[0015] According to the present invention, in step (1), preferably, in the carrier of the first hydrocracking catalyst, based on the weight of the carrier, the content of the binder is 8% to 60%, and the content of the molecular sieve is 40% to 92%.

[0016] According to the present invention, in step (1), preferably, the specific surface area of the first hydrocracking catalyst is 200 - 400 m 2 / g, and the pore volume is 0.25 - 0.45 mL / g.

[0017] According to the present invention, the preparation method of the first hydrocracking catalyst in step (1) can be prepared according to the conventional methods in the art. The preparation method includes the preparation of the support and the loading of the active metal components. The process of preparing the support is as follows: The shape-selective cracking molecular sieve and the binder are mechanically mixed, formed, and then dried and calcined to obtain the catalyst support. The drying and calcination of the support can be carried out under conventional conditions. The conditions for drying are: drying at 100°C to 150°C for 1 to 12 hours. The conditions for calcination are: calcining at 450°C to 550°C for 2.5 to 6.0 hours.

[0018] According to the present invention, in step (1), in the preparation method of the first hydrocracking catalyst, the method for loading the active metal components is a conventional method, such as the kneading method, the impregnation method, etc., and the impregnation method is preferred. The impregnation method can be the saturated impregnation method, the excess impregnation method or the complex impregnation method, that is, the catalyst support is impregnated with a solution containing the required active components, and then dried and calcined to obtain the first hydrocracking catalyst. The conditions for drying are: drying at 100°C to 150°C for 1 to 12 hours. The conditions for calcination are: calcining at 450°C to 550°C for 2.5 to 6.0 hours.

[0019] According to the present invention, in step (1), the nitrogen content in the reaction effluent is below 50 mg / kg, and more preferably below 20 mg / kg.

[0020] According to the present invention, the diesel oil in step (1) can be straight-run diesel oil, coking diesel oil and other diesel fractions with a relatively high content of n-alkanes. The content of n-alkanes in the diesel oil is 10 wt% to 60 wt%, preferably 20 wt% to 50 wt%; the initial boiling point of the diesel oil is 180°C to 280°C, preferably 200°C to 260°C; the final boiling point is 300°C to 400°C, preferably 340°C to 380°C.

[0021] According to the present invention, in the diesel oil in step (1), the mass content of the cyclic hydrocarbons is 30 wt% to 80 wt%, and the cyclic hydrocarbons are the sum of naphthenes and aromatics.

[0022] According to the present invention, the reaction conditions in the n-alkane conversion reaction zone in step (1) are as follows: the reaction pressure is 6 to 12 MPa.

[0023] According to the present invention, the reaction conditions in the n-alkane conversion reaction zone in step (1) are as follows: the average reaction temperature is 250 to 450°C, preferably 300 to 400°C; the liquid hourly space velocity is 0.1 to 15.0 h -1 , preferably 1.0 to 5.0 h -1 ; the hydrogen-oil volume ratio is 100:1 to 2500:1, preferably 400:1 to 2000:1.

[0024] According to the present invention, in step (2), a second hydrocracking catalyst is loaded in the hydrocracking reaction zone. The second hydrocracking catalyst can be one or more catalysts.

[0025] According to the present invention, the hydrocracking reaction effluent obtained in step (2) is a hydrocracking product containing monocyclic cyclic hydrocarbons. In the hydrocracking reaction effluent of step (2), the mass ratio of C6-C8 monocyclic cyclic hydrocarbons to the total mass of cyclic hydrocarbons in the feedstock is 0.20-0.40, preferably 0.30-0.35.

[0026] According to the present invention, in step (2), the chemical raw materials include ethylene raw materials and reforming raw materials. The chemical raw materials include ethane, propane, butane, light naphtha and heavy naphtha. Among them, heavy naphtha is used as a reforming raw material to produce BTX, and ethane, propane, butane and light naphtha are used as ethylene raw materials to produce light olefins, such as ethylene produced as a steam cracking raw material. Propane and butane can also be directly dehydrogenated to produce propylene and butadiene. Among them, light olefins refer to olefins with four or fewer carbon atoms, especially ethylene, propylene and butadiene.

[0027] According to the present invention, in step (2), in the chemical raw materials, based on the total mass of ethane, propane, butane and light naphtha, the normal paraffins account for 60%-80%, preferably 65%-75%. Based on the total mass of ethane, propane, butane and light naphtha, after entering the steam cracking to ethylene unit, the yield of triolefins (including ethylene, propylene and butadiene) reaches more than 50%, and further can reach 50%-60%.

[0028] According to the present invention, after the hydrocracking reaction effluent obtained in step (2) is subjected to distillation separation, tail oil is also obtained. The tail oil can be recycled to the normal paraffin conversion reaction zone of step (1) and / or recycled to the hydrocracking reaction zone of step (2).

[0029] According to the present invention, in step (2), the second hydrocracking catalyst has the functions of ring opening and cracking of polycyclic cyclic hydrocarbons, selectively cracking isoparaffins or side chains of cyclic hydrocarbons and retaining monocyclic cyclic hydrocarbons. The second hydrocracking catalyst includes a cracking component, a hydrogenation component and a binder. The second hydrocracking catalyst can be a commercially available product or prepared according to the prior art. The hydrogenation component is at least one of a metal, a metal oxide, and a metal sulfide of an active metal component; the active metal component includes metals of Group VIB and / or Group VIII; the active metal component is more preferably at least one of iron, chromium, molybdenum, tungsten, cobalt, and nickel. In the second hydrocracking catalyst, the binder is alumina and / or silica; the cracking component includes an acidic molecular sieve, preferably at least one of Beta molecular sieve and Y molecular sieve.

[0030] According to the present invention, preferably, in step (2), the hydrocracking reaction zone is filled with a catalyst with Y zeolite as the cracking component and a catalyst with Beta zeolite as the cracking component in sequence along the material flow direction; preferably, the volume ratio of the catalyst with Y zeolite as the cracking component to the catalyst with Beta zeolite as the cracking component is 1:1 to 1:5, preferably 1:2 to 1:4.

[0031] According to the present invention, for the second hydrocracking catalyst in step (2), based on the weight of the second hydrocracking catalyst, the content of the hydrogenation component in terms of oxide is 5 wt% to 40 wt%, preferably 10 wt% to 30 wt%; the content of the cracking component is 10 wt% to 80 wt%, preferably 20 wt% to 60 wt%; the content of the binder is 5 wt% to 85 wt%, preferably 10 wt% to 50 wt%.

[0032] According to the present invention, in step (2), the preparation method of the second hydrocracking catalyst can be prepared according to the conventional methods in the art. The preparation method includes the preparation of the carrier and the loading of the hydrogenation component. The process of preparing the carrier is as follows: mechanically mix the cracking component and the binder, shape, and then dry and calcine to make the catalyst carrier. The drying and calcining of the carrier can adopt conventional conditions. The conditions for drying are: drying at 100°C to 150°C for 1 to 12 hours. The conditions for calcining are: calcining at 450°C to 550°C for 2.5 to 6.0 hours.

[0033] According to the present invention, in step (2), in the preparation method of the second hydrocracking catalyst, the method for loading the hydrogenation component is a conventional method, such as the kneading method, the impregnation method, etc., preferably the impregnation method. The impregnation method can be the saturated impregnation method, the excess impregnation method or the complex impregnation method, that is, impregnate the catalyst carrier with a solution containing the required hydrogenation component, and then dry and calcine to obtain the second hydrocracking catalyst. The conditions for drying are: drying at 100°C to 150°C for 1 to 12 hours. The conditions for calcining are: calcining at 450°C to 550°C for 2.5 to 6.0 hours.

[0034] According to the present invention, in step (2), the reaction conditions in the hydrocracking reaction zone are as follows: the reaction pressure is 6 to 12 MPa.

[0035] According to the present invention, in step (2), the reaction conditions in the hydrocracking reaction zone are as follows: the average reaction temperature is 250 to 450°C, preferably 300 to 400°C; the liquid hourly space velocity is 0.1 to 15.0 h -1 , preferably 1.0 to 5.0 h -1 ; the hydrogen-oil volume ratio is 100:1 to 2500:1, preferably 400:1 to 2000:1.

[0036] According to the present invention, preferably, the normal paraffin conversion reaction zone and the hydrocracking reaction zone adopt the same pressure.

[0037] According to the present invention, preferably, in step (2), the second hydrocracking reaction effluent is subjected to supplementary hydrorefining. The supplementary hydrorefining can be carried out by loading hydrorefining catalyst at the bottom of the hydrocracking reaction zone, or the effluent can enter a separate hydrorefining reaction zone.

[0038] According to the present invention, preferably, in step (2), the second hydrocracking reaction effluent can also directly enter the fractionation system, and the heavy naphtha component obtained by separation is subjected to supplementary hydrorefining.

[0039] According to the present invention, the ethane, propane, butane and light naphtha obtained in step (2) can be directly used as the feed for the steam cracking to produce ethylene unit. Generally, the operating conditions of the steam cracking to produce ethylene unit are as follows: reaction temperature 750°C to 900°C, reaction pressure 0.1 to 0.5 MPa, and mass ratio of water to oil 0.2 to 0.6.

[0040] According to the present invention, preferably, the propane obtained in step (2) can also be directly used as the feed for the propane dehydrogenation to produce propylene unit. Generally, the operating conditions of the propane dehydrogenation unit are as follows: reaction temperature 600°C to 680°C, preferably 620°C to 650°C; reaction pressure 0.1 MPa to 0.5 MPa, preferably 0.2 MPa to 0.3 MPa; volumetric space velocity 0.2 h -1 ~8.0 h -1 。

[0041] According to the present invention, preferably, the heavy naphtha obtained in step (2) is used as the feed for the catalytic reforming unit after hydrorefining. The catalytic reforming can be semi-regenerative reforming, continuous reforming or cyclic regenerative reforming. The main operating conditions are as follows: reaction temperature 480 to 530°C, reaction pressure 0.35 to 1.5 MPa, hydrogen-hydrocarbon molar ratio 2 to 8, volumetric space velocity 1 to 6 h -1. In the prior art, a catalytic reforming unit generally includes three reaction zones, namely, a dehydrogenation reaction zone for six-membered rings, an isomerization dehydrogenation reaction zone for five-membered rings, and a cyclization and dehydrogenation reaction zone for paraffins. In the present invention, preferably, the cyclization and dehydrogenation reaction zone for paraffins is cancelled in the catalytic reforming unit, and only the dehydrogenation reaction zone for six-membered rings and the isomerization dehydrogenation reaction zone for five-membered rings are provided. After the heavy naphtha undergoes catalytic reforming reaction, it enters an aromatics extraction unit to separate and obtain BTX components. The aromatics extraction can adopt the prior art, and the conventional aromatics extraction methods mainly include: liquid-liquid extraction method or extractive distillation method. The present invention preferably adopts the liquid-liquid extraction method, and the extraction solvent is one or more of diethylene glycol, triethylene glycol, tetraethylene glycol, sulfolane, N-methylpyrrolidone, and dimethyl sulfoxide. The extraction conditions are as follows: extraction temperature is 20°C to 200°C, preferably 50°C to 150°C; the mass ratio of the solvent to the heavy naphtha is 1:1 to 8:1, preferably 3:1 to 5:1; the pressure is 0 to 2 MPa, preferably 0.1 to 0.5 MPa.

[0042] Petroleum hydrocarbons have a complex composition, mainly including paraffins, naphthenes, and aromatics. High-quality ethylene raw materials are small-molecule normal paraffins, and reforming raw materials are monocyclic naphthenes and aromatics. The inventors have found through research that the technical solution of the present invention can selectively generate small-molecule normal paraffins, thereby realizing the efficient enrichment of small-molecule normal paraffins in ethylene raw materials, and at the same time, retaining monocyclic hydrocarbons in heavy naphtha as much as possible to achieve the efficient enrichment of high-quality reforming raw materials. In this way, the purpose of greatly improving the yields of chemical raw materials (i.e., ethylene raw materials and reforming raw materials) and the quality of ethylene raw materials and reforming raw materials can be achieved, and thus the present invention is completed.

[0043] Compared with the prior art, the present invention has the following beneficial technical effects:

[0044] (1) In the hydrocracking method for producing chemical raw materials from diesel oil of the present invention, the diesel oil raw material and hydrogen enter the normal hydrocarbon conversion reaction zone, mainly selectively cracking the normal paraffins in the raw material and the long straight chains of isoparaffins and naphthenes containing long straight chains to generate small-molecule normal paraffins, so that the content of C7 normal paraffins in the effluent of the normal hydrocarbon conversion reaction is 0.5 wt% to 3 wt%. The effluent of the normal hydrocarbon conversion reaction enters the hydrocracking reaction zone, mainly to open and crack the polycyclic hydrocarbons and retain the monocyclic hydrocarbons and further break the side chains in each hydrocarbon to generate small-molecule hydrocarbons. In this way, a large amount of the linear paraffins in the raw material can be converted into gas and light naphtha components, that is, enriched in ethylene raw materials, while the monocyclic hydrocarbons are retained in the heavy naphtha fraction, that is, enriched in reforming raw materials. Through simple fractionation, the efficient separation of paraffins and cyclic hydrocarbons can be achieved, increasing the production of high-quality ethylene cracking feedstock while improving the quality of heavy naphtha as a catalytic reforming feedstock. + The content of normal paraffins is 0.5 wt% to 3 wt%. The effluent of the normal hydrocarbon conversion reaction enters the hydrocracking reaction zone, mainly to open and crack the polycyclic hydrocarbons and retain the monocyclic hydrocarbons and further break the side chains in each hydrocarbon to generate small-molecule hydrocarbons. In this way, a large amount of the linear paraffins in the raw material can be converted into gas and light naphtha components, that is, enriched in ethylene raw materials, while the monocyclic hydrocarbons are retained in the heavy naphtha fraction, that is, enriched in reforming raw materials. Through simple fractionation, the efficient separation of paraffins and cyclic hydrocarbons can be achieved, increasing the production of high-quality ethylene cracking feedstock while improving the quality of heavy naphtha as a catalytic reforming feedstock.

[0045] (2) The content of monocyclic cyclic hydrocarbons in the heavy naphtha obtained by the method of the present invention is high. As the feed for the catalytic reforming unit, the paraffin cyclization and dehydrogenation unit in the catalytic reforming unit can be cancelled, which can greatly reduce the investment and energy consumption of the catalytic reforming unit. At the same time, since the hydrocracking reaction follows the carbocation reaction mechanism, the side-chain breaking reaction of cyclic hydrocarbons with more than C9 can be selectively achieved, so that the C6-C8 cyclic hydrocarbons in the product have a higher enrichment degree, and the BTX yield can be greatly increased after catalytic reforming and aromatics extraction.

[0046] (3) The method of the present invention selectively converts the paraffins in diesel into small-molecule paraffins. This process consumes a certain amount of hydrogen, but the light hydrocarbons also have a high hydrogen yield as the raw material for the ethylene unit. The lower the carbon number, the higher the hydrogen yield. Therefore, most of the hydrogen consumed in the hydrogenation process can be recovered after passing through the ethylene unit. At the same time, the light hydrocarbons as the ethylene raw material can greatly increase the yields of ethylene, propylene and butadiene, and extend the cleaning cycle of the ethylene unit, significantly improving the economic benefits of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 is a schematic process flow diagram of Examples 1-4 of the present invention;

[0048] MAIN REFERENCE NUMERAL DESCRIPTION:

[0049] 1 - Diesel, 2 - Hydrogen, 3 - Normal hydrocarbon conversion reaction zone, 4 - Normal hydrocarbon conversion reaction effluent, 5 - Hydrocracking reaction zone, 6 - Hydrocracking reaction effluent, 7 - Separator, 8 - Gas-phase stream rich in hydrogen gas, 9 - Liquid-phase stream, 10 - Fractionating tower, 11 - Gas fraction, 12 - Light naphtha, 13 - Heavy naphtha, 14 - Tail oil. DETAILED DESCRIPTION OF THE INVENTION

[0050] The functions and effects of the present invention will be further illustrated by the following examples, but the following examples do not limit the method of the present invention.

[0051] In the present invention, % is the mass fraction unless otherwise specified.

[0052] The overall volume space velocity in the examples and comparative examples is the ratio of the fresh feed volume to the total volume of the catalyst.

[0053] The method of the present invention, as Figure 1 shown, includes: Diesel 1 and hydrogen 2 are mixed and enter the normal hydrocarbon conversion reaction zone 3 for normal hydrocarbon conversion reaction. The normal hydrocarbon conversion reaction effluent 4 enters the hydrocracking reaction zone 5 for hydrocracking reaction. The hydrocracking reaction effluent 6 enters the separator 7. The separated gas-phase stream rich in hydrogen gas 8 is recycled for use. The liquid-phase stream 9 enters the fractionating tower 10, and is fractionated to obtain a gas fraction 11, light naphtha 12, heavy naphtha 13 and tail oil 14. The tail oil 14 is recycled to the hydrocracking reaction zone 5.

[0054] In the present invention, the first hydrocracking catalyst in each example is represented by Cat-A plus a number, such as Cat-A1, Cat-A2, Cat-A3, and Cat-A4. The first hydrocracking catalyst is prepared by a conventional active metal saturation impregnation method, and the physicochemical properties of the obtained catalyst are shown in Table 1.

[0055] In the present invention, the second hydrocracking catalyst in each example is represented by Cat-B plus a number, such as Cat-B1 and Cat-B2. The physicochemical properties of the catalyst are shown in Table 2. The second hydrocracking catalyst in each example is prepared by a conventional active metal saturation impregnation method. Among them, the properties of the Beta zeolite used in Cat-B1 are as follows: the SiO2 / Al2O3 molar ratio is 30, the specific surface area is 350 m 2 / g, and the pore volume is 0.32 cm 3 / g. The properties of the Y zeolite used in Cat-B2 are as follows: the SiO2 / Al2O3 molar ratio is 15, the specific surface area is 400 m 2 / g, and the pore volume is 0.30 cm 3 / g.

[0056] In the present invention, in Examples 1 to 3, Cat-B2 and Cat-B1 are successively loaded in the hydrocracking reaction zone along the material flow direction.

[0057] In the present invention, the hydrofining catalyst in each example is represented by Cat-J. The properties of the hydrofining catalyst are shown in Table 3.

[0058] In the present invention, the feedstock oil in each example is diesel, and its main properties are shown in Table 4.

[0059] In the present invention, the loading ratio of the hydrofining catalyst and the first hydrocracking catalyst in each example is 1:2.

[0060] In the present invention, in each example, the nitrogen content in the reaction effluent in step (1) is below 20 mg / kg.

[0061] In each example of the present invention, ethane, propane, butane, and light naphtha obtained by hydrocracking enter the steam cracking to ethylene unit to obtain the main target products ethylene, propylene, and butadiene. The yield of the three olefins is the sum of the yields of ethylene, propylene, and butadiene and the feed amount of ethane, propane, butane, and light naphtha, calculated by mass. The operating conditions for the steam cracking to ethylene are as follows: reaction temperature 880 °C, reaction pressure 0.2 MPa, and water / oil mass ratio 0.4.

[0062] In each example of the present invention, the heavy naphtha obtained by hydrocracking enters the catalytic reforming unit after supplementary refining. The operating conditions for catalytic reforming are as follows: 500 °C, reaction pressure 0.8 MPa, hydrogen / hydrocarbon molar ratio 5, and volume space velocity 4 h-1 ; The reformate enters the aromatics extraction unit, and the extraction solvent is sulfolane. The operating conditions for aromatics extraction are as follows: extraction temperature 80 °C; solvent: heavy naphtha mass ratio 4:1; pressure 0.3 MPa. The BTX yield obtained from aromatics extraction is the percentage of the C6-C8 aromatics production in the feed of the catalytic reforming heavy naphtha.

[0063] In the present invention, the ethylene feedstocks in Table 5 are ethane, propane, butane, and light naphtha.

[0064] In the present invention, the distillation range of light naphtha is the liquid component with a boiling range less than 60 °C, the distillation range of heavy naphtha is 60 - 175 °C, and the distillation range of the tail oil is the component with a boiling range > 175 °C.

[0065] In the present invention, the yield of the ethylene feedstock refers to the mass ratio of ethane, propane, butane, and light naphtha in the hydrocracking product to the fresh hydrocracking feedstock (diesel), and the yield of heavy naphtha refers to the mass ratio of heavy naphtha in the hydrocracking product to the fresh hydrocracking feedstock.

[0066] Examples 1 - 4

[0067] The method for producing chemical raw materials by diesel hydrocracking adopts the process as Figure 1 shown in the flow chart. The specific method includes:

[0068] (1) Diesel is mixed with hydrogen and undergoes a normal paraffin conversion reaction in the normal paraffin conversion reaction zone, and the mass content of C7 normal paraffins in the reaction effluent is controlled; the normal paraffin conversion reaction zone is filled with catalysts; along the flow direction of the material, the catalysts are filled with a hydrofining catalyst and a first hydrocracking catalyst in sequence; + The normal paraffin conversion reaction zone is filled with catalysts; along the flow direction of the material, the catalysts are filled with a hydrofining catalyst and a first hydrocracking catalyst in sequence;

[0069] (2) In the presence of hydrogen, the normal paraffin conversion reaction effluent from step (1) enters the hydrocracking reaction zone for a hydrocracking reaction, and then the hydrocracking reaction effluent is subjected to distillation separation to obtain chemical raw materials and tail oil; the chemical raw materials include the raw materials for preparing low-carbon olefins and the reforming raw materials. The hydrocracking reaction zone is filled with a second hydrocracking catalyst. The separated tail oil is recycled to the hydrocracking reaction zone.

[0070] The chemical raw materials mainly include ethane, propane, butane, light naphtha, and heavy naphtha. Among them, ethane, propane, butane, and light naphtha are directly used as the feed for the steam cracking ethylene unit to produce low-carbon olefins; the heavy naphtha is used as the feed for the catalytic reforming unit to produce BTX after supplementary refining.

[0071] The process conditions and hydrocracking effects of each example are shown in Table 5.

[0072] Comparative Example 1

[0073] The difference from Example 1 is that the feedstock oil directly enters the hydrocracking reaction zone after hydrofining.

[0074] The process conditions and hydrotreating effects in this example are shown in Table 5.

[0075] Comparative Example 2

[0076] The difference from Example 1 is that in step (1), the content of C7 normal paraffin in the effluent of the normal paraffin conversion reaction is controlled. + The content of normal paraffin is 4%.

[0077] The process conditions and hydrotreating effects in this example are shown in Table 5.

[0078] Comparative Example 3

[0079] The difference from Example 1 is that the catalyst loading order in the hydrocracking reaction zone is different from that in Example 1. In this example, the order of catalysts Cat-B2 and Cat-B1 is exchanged.

[0080] Specifically, in this example, the hydrocracking reaction zone is filled with catalyst Cat-B1 and catalyst Cat-B2 in sequence along the material flow direction.

[0081] The process conditions and hydrotreating effects in this example are shown in Table 5.

[0082] Table 1 Physicochemical properties of the first hydrocracking catalyst

[0083] Catalyst Cat-A1 Cat-A2 Cat-A3 Cat-A4 <![CDATA[Pore volume, cm 3 / g]]> 0.35 0.45 0.25 0.30 <![CDATA[Specific surface area, m 2 / g]]> 300 200 400 350 Content, wt%, based on the weight of the support ZSM-5 58 42 85 75 Aluminum oxide 42 58 15 25 Active metal content in the catalyst, wt% <![CDATA[MoO3]]> 10.0 15.0 5.0 12.5 NiO 3.5 2.0 5.0 4.0 <![CDATA[SiO2 / Al2O3 molar ratio of ZSM-5]]> 40 60 20 50

[0084] Table 2 Physicochemical properties of the second hydrocracking catalyst

[0085] Catalyst properties Cat-B1 Cat-B2 <![CDATA[Pore volume, cm 3 / g]]> 0.35 0.35 <![CDATA[Specific surface area, m 2 / g]]> 300 300 Catalyst composition and content Beta, wt% 50 - Y, wt% - 30 <![CDATA[MoO3, wt%]]> 10 20 NiO, wt% 5 5 Aluminum oxide, wt% 35 45

[0086] Table 3 Hydrofining catalyst

[0087] Catalyst properties Cat-J <![CDATA[Pore volume, cm 3 / g]]> 0.35 <![CDATA[Specific surface area, m 2 / g]]> 200 Catalyst composition and content <![CDATA[MoO3, wt%]]> 22 NiO, wt% 4.5 Aluminum oxide, wt% 73.5

[0088] Table 4 Main properties of the feedstock oil

[0089] Name of feedstock Diesel <![CDATA[Density (20 °C) / kg·m -3 > 853.9 Distillation range / °C (ASTM D86) IBP / 10% 206 / 265 30％ / 50％ 292 / 308 70％ / 90％ 322 / 340 95% / EBP 348 / 353 n-alkane, wt% 26.6 Cyclic hydrocarbon, wt% 53.8 Nitrogen content, mg / kg 200

[0090] Table 5 Process conditions and hydrotreating effects of each example

[0091]

[0092]

[0093] Continued Table 5

[0094]

[0095] Note: Catalyst volume ratio *, in Comparative Examples 1, 2, and 4, it is the volume ratio of Cat-B2 to Cat-B1; in Comparative Example 3, it is the volume ratio of Cat-B1 to Cat-B2.

Claims

1. A method for producing chemical raw materials by diesel hydrocracking, characterized in that, The method includes: (1) Diesel is mixed with hydrogen and undergoes a normal paraffin conversion reaction in the normal paraffin conversion reaction zone, and the mass content of C7 + normal paraffins in the reaction effluent is 0.5 wt% to 3.0 wt%; (2) In the presence of hydrogen, the effluent from the normal paraffin conversion reaction in step (1) enters the hydrocracking reaction zone for hydrocracking reaction, and then the effluent from the hydrocracking reaction is separated to obtain chemical raw materials; the chemical raw materials include raw materials for preparing light olefins and reforming raw materials; In step (1), the reaction pressure in the normal paraffin conversion reaction zone is 6 - 12 MPa; In step (2), the reaction pressure in the hydrocracking reaction zone is 6 - 12 MPa; In step (1), a catalyst is loaded in the normal paraffin conversion reaction zone; specifically, a hydrofining catalyst and a first hydrocracking catalyst are loaded in sequence along the material flow direction; The first hydrocracking catalyst includes an active metal component and a carrier; the carrier includes one or more of ZSM-5 zeolite, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35, and ZSM-38 zeolites; the active metal component includes at least one of metals in Group VIB and Group VIII; for the first hydrocracking catalyst, based on the weight of the catalyst, the content of the Group VIB metal in terms of oxide is 5.0% - 15.0%, the content of the Group VIII metal in terms of oxide is 2.0% - 5.0%, and the content of the carrier is 80.0% - 93.0%; in the carrier of the first hydrocracking catalyst, based on the weight of the carrier, the content of the zeolite is 40% - 92%; In step (2), a second hydrocracking catalyst is loaded in the hydrocracking reaction zone; the second hydrocracking catalyst includes a cracking component, a hydrogenation component, and a binder; based on the weight of the second hydrocracking catalyst, the content of the hydrogenation component in terms of oxide is 5wt% - 40wt%; the content of the cracking component is 10wt% - 80wt%; and the content of the binder is 5wt% - 85wt%; Heavy naphtha is used as a reforming raw material to produce BTX; ethane, propane, butane, and light naphtha are used as ethylene raw materials to produce light olefins; in the chemical raw materials, based on the total mass of ethane, propane, butane, and light naphtha, the normal paraffins account for 60% - 80%; In step (2), in the hydrocracking reaction zone, a catalyst with Y zeolite as the cracking component and a catalyst with Beta zeolite as the cracking component are loaded in sequence along the material flow direction.

2. The method according to claim 1, wherein The loading volume ratio of the hydrofining catalyst to the first hydrocracking catalyst is 0.5 - 5:1; and / or, in step (1), the nitrogen content in the reaction effluent is below 50 mg / kg.

3. The method according to claim 2, characterized in that In step (1), the nitrogen content in the reaction effluent is below 20 mg / kg.

4. The method according to claim 1 or 2, characterized in that The hydrofining catalyst includes a carrier and a hydrogenation active metal; wherein: The carrier is an inorganic refractory oxide; and / or, the hydrogenation active metal includes Group VIB and / or Group VIII metal components.

5. The method according to claim 4, wherein In the hydrofining catalyst, the carrier is selected from one or several of alumina, amorphous silica-alumina, silica, and titanium oxide.

6. The method according to claim 4, wherein In the hydrofining catalyst, the content of Group VIB metal in the catalyst, calculated based on the mass of the oxide, is 5 wt% to 30 wt%; and / or, the content of Group VIII metal in the catalyst, calculated based on the mass of the oxide, is 1 wt% to 6 wt%; and / or, the content of the carrier in the catalyst is 64 wt% to 94 wt%.

7. The method according to claim 6, wherein In the hydrofining catalyst, the content of Group VIB metal in the catalyst, calculated based on the mass of the oxide, is 10 wt% to 20 wt%; and / or, the content of Group VIII metal in the catalyst, calculated based on the mass of the oxide, is 1.5 wt% to 5 wt%; and / or, the content of the carrier in the catalyst is 75 wt% to 88.5 wt%.

8. The method according to claim 6, wherein In the hydrofining catalyst, Group VIB is selected from tungsten and / or molybdenum, and Group VIII is selected from nickel and / or cobalt.

9. The method according to claim 1 or 2, characterized in that, The molecular sieve of the first hydrocracking catalyst is ZSM-5 molecular sieve; and / or, the Group VIB metal is molybdenum and / or tungsten, and the Group VIII metal is cobalt and / or nickel.

10. The method according to claim 1, characterized in that, The diesel oil in step (1) includes at least one of straight-run diesel oil and coker diesel oil; and / or, the content of n-alkanes in the diesel oil is 10 wt% to 60 wt%; and / or, in the diesel oil, the mass content of cyclic hydrocarbons is 20 wt% to 90 wt%; and / or, the initial boiling point of the diesel oil is 180 °C to 280 °C; the final boiling point is 300 °C to 400 °C.

11. The method according to claim 10, wherein The content of n-alkanes in the diesel oil in step (1) is 20 wt% to 50 wt%; and / or, the initial boiling point of the diesel oil is 200 °C to 260 °C; the final boiling point is 340 °C to 380 °C.

12. The method according to claim 1, wherein The reaction conditions in the normal paraffin conversion reaction zone in step (1) are as follows: the average reaction temperature is 250 to 450 °C; and / or, the liquid hourly space velocity is 0.1 to 15.0 h -1 ; and / or, the hydrogen-oil volume ratio is 100:1 to 2500:

1.

13. The method according to claim 12, wherein The reaction conditions in the normal paraffin conversion reaction zone in step (1) are as follows: the average reaction temperature is 300-400 °C; and / or, the liquid hourly space velocity is 1.0-5.0 h -1 ; and / or, the hydrogen-oil volume ratio is 400:1-2000:

1.

14. The method according to claim 1, characterized in that In step (2), based on the weight of the second hydrocracking catalyst, the content of the hydrogenation component, calculated as the oxide, is 10 wt% to 20 wt%; the content of the cracking component is 20 wt% to 60 wt%; the content of the binder is 10 wt% to 50 wt%; and / or, in the second hydrocracking catalyst, the hydrogenation component is at least one of the metal, metal oxide, and metal sulfide of the active metal component; the active metal component includes Group VIB and / or Group VIII metal; and / or, in the second hydrocracking catalyst, the binder is alumina and / or silica.

15. The method according to claim 14, wherein The volume ratio of the catalyst with Y molecular sieve as the cracking component to the catalyst with Beta molecular sieve as the cracking component is 1:1 to 1:

5.

16. The method according to claim 15, characterized in that The volume ratio of the catalyst with Y molecular sieve as the cracking component to the catalyst with Beta molecular sieve as the cracking component is 1:2 to 1:

4.

17. The method according to claim 14, wherein In the second hydrocracking catalyst in step (2), the active metal component is at least one of iron, chromium, molybdenum, tungsten, cobalt, and nickel.

18. The method according to claim 1, wherein In step (2), the reaction conditions in the hydrocracking reaction zone are as follows: the average reaction temperature is 250 to 450 °C; and / or, the liquid hourly space velocity is 0.1 to 15.0 h -1 ; and / or, the hydrogen-to-oil volume ratio is 100:1 to 2500:

1.

19. The method according to claim 18, wherein In step (2), the reaction conditions in the hydrocracking reaction zone are as follows: the average reaction temperature is 300 to 400 °C; and / or, the liquid hourly space velocity is 1.0 to 5.0 h -1 ; and / or, the hydrogen-to-oil volume ratio is 400:1 to 2000:

1.

20. The method according to claim 1, characterized in that, The hydrocracking reaction effluent obtained in step (2) is a hydrocracking product containing monocyclic cyclic hydrocarbons.

21. The method according to claim 20, wherein In the hydrocracking reaction effluent of step (2), the mass ratio of C6-C8 monocyclic cyclic hydrocarbons to the total mass of cyclic hydrocarbons in the feedstock is 0.20 to 0.

40.

22. The method according to claim 21, wherein In the hydrocracking reaction effluent of step (2), the mass ratio of C6-C8 monocyclic cyclic hydrocarbons to the total mass of cyclic hydrocarbons in the feedstock is 0.30 to 0.

35.

23. The method according to claim 1, characterized in that, The normal paraffin conversion reaction zone in step (1) and the hydrocracking reaction zone in step (2) adopt the same pressure.

Images