A hydrocracking method for producing chemical raw materials

Abstract

The present invention discloses a hydrocracking method for producing chemical raw materials. The method includes: (1) in the presence of hydrogen, a hydrocarbon oil raw material enters a first hydrocracking reaction zone to selectively crack the n-alkanes in the hydrocarbon oil raw material to obtain a first hydrocracking product; wherein, in the first hydrocracking product, the mass content of C7 + n-alkanes is controlled below 5.0%; (2) in the presence of hydrogen, the first hydrocracking product enters a second hydrocracking reaction zone to obtain a second hydrocracking product containing monocyclic cyclic hydrocarbons; (3) the second hydrocracking product is separated and fractionated to obtain a gas fraction, light naphtha, and heavy naphtha. When using the hydrocarbon oil as a raw material to produce chemical raw materials, this method can significantly improve the yield and quality of chemical raw materials.

Description

Technical Field

[0001] The present invention belongs to the field of hydrocarbon oil hydrocracking, and particularly relates to a hydrocracking method for producing chemical raw materials, wherein the chemical raw materials are particularly propane, butane, light naphtha, and high-quality heavy naphtha. Background Art

[0002] The ethylene industry is the core of the petrochemical industry. Ethylene products account for more than 75% of petrochemical products and are one of the important indicators to measure the petrochemical development level of a country. Therefore, improving the production capacity of ethylene is an important way for petrochemical technology and product innovation. Ethylene cracking raw materials include liquid raw materials such as naphtha and light hydrocarbon gas raw materials. Comparatively speaking, light hydrocarbon gas raw materials are more advantageous and have greater potential for increasing efficiency.

[0003] Heavy naphtha, as the main raw material of the catalytic reforming unit, has a relatively high content of paraffins in its composition. Paraffins are difficult to undergo cyclization dehydrogenation reactions and are not beneficial raw material components for the reforming unit.

[0004] Hydrocracking technology has the characteristics of strong raw material adaptability, great 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 base stocks, chemical naphtha, and feedstocks for steam cracking of tail oil to produce ethylene, etc., which are in urgent need in the market. It has become one of the most important hydrocarbon oil deep processing processes in modern refinery and petrochemical industries and is increasingly widely used in various countries in the world.

[0005] 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 hydrocracked product stream; b) separating the first hydrocracked 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 hydrocracked 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 undergoes C4 hydrocracking to prepare a C4 hydrocracked product stream, and the C4 hydrocracking is optimized for converting C4 hydrocarbons into C3 hydrocarbons.

[0006] CN201480037272.7 discloses a method for producing light olefin hydrocarbon compounds from a hydrocarbon raw material, comprising the following steps: (a) feeding the hydrocarbon raw material into a reaction zone for ring opening; (b) separating the reaction product 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 product 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.

[0007] The above method is mainly for using hydrocarbon raw materials to produce LPG and BTX, but the yield of triolefins is relatively low. Therefore, it is of great significance to develop a hydrocracking method suitable for producing high-quality chemical raw materials from hydrocarbon oils. Summary of the Invention

[0008] Aiming at the problems existing in the prior art, the object of the present invention is to provide a hydrocracking method for producing chemical raw materials. This method uses hydrocarbon oil as the raw material, preferably heavy naphtha raw material, and can significantly improve the yield and quality of chemical raw materials (i.e., light olefin raw materials and reforming raw materials).

[0009] The present invention provides a hydrocracking method for producing chemical raw materials, wherein the chemical raw materials include light olefin raw materials and reforming raw materials, and the method comprises:

[0010] (1) In the presence of hydrogen, the hydrocarbon oil raw material enters the first hydrocracking reaction zone, and selectively cracks the n-alkanes in the hydrocarbon oil raw material to obtain a first hydrocracking product; wherein, in the first hydrocracking product, the mass content of C7 + n-alkanes is controlled below 5.0%.

[0011] (2) In the presence of hydrogen, the first hydrocracking product enters the second hydrocracking reaction zone to obtain a second hydrocracking product containing monocyclic cyclic hydrocarbons;

[0012] (3) The second hydrocracking product is separated and fractionated to obtain a gas fraction, light naphtha and heavy naphtha.

[0013] According to the present invention, preferably, in step (1), the mass content of C7 + n-alkanes is controlled at 1% - 5%.

[0014] According to the present invention, in step (1), the first hydrocracking reaction zone is filled with a first hydrocracking catalyst, and in step (2), the second hydrocracking reaction zone is filled with a second hydrocracking catalyst. Among them, the first hydrocracking catalyst can be one or more catalysts, and the second hydrocracking catalyst can be one or more catalysts.

[0015] According to the present invention, the chemical raw materials mainly include ethane, propane, butane, and light naphtha, and may also include heavy naphtha. Among them, the heavy naphtha is used as a reforming raw material to produce BTX, and ethane, propane, butane, and light naphtha are used as raw materials for producing light olefins. For example, they are used as steam cracking raw materials to produce ethylene, and propane and butane can also be directly dehydrogenated to produce propylene and butene. Among them, light olefins refer to olefins with four or fewer carbon atoms, especially ethylene, propylene, and butadiene.

[0016] According to the present invention, the hydrocarbon oil raw material includes one or more selected from heavy naphtha, diesel, and kerosene, and preferably the heavy naphtha raw material. The heavy naphtha raw material can be a naphtha fraction with a relatively high content of normal paraffins, such as straight-run naphtha, coker naphtha, fluidized-bed residue hydrotreating naphtha, and coal chemical naphtha; the initial boiling point is 40°C to 80°C, preferably 50°C to 70°C; the final boiling point is 150°C to 200°C, preferably 160°C to 180°C.

[0017] According to the present invention, when the hydrocarbon oil raw material is a heavy naphtha raw material, the chemical raw materials produced are ethane, propane, butane, light naphtha, and heavy naphtha. When the hydrocarbon oil raw material is a heavy naphtha raw material, it can selectively crack the long straight-chain hydrocarbons in the heavy naphtha and retain the broken-side-chain cyclic hydrocarbons. After hydrocracking, the heavy naphtha has a high enrichment degree of cyclic hydrocarbons, and is basically mainly composed of C6-C8 single-ring cyclic hydrocarbons. Preferably, when the hydrocarbon oil raw material is a heavy naphtha raw material, the mass ratio of the C6-C8 single-ring cyclic hydrocarbons in the second hydrocracking product in step (2) to the total mass of the cyclic hydrocarbons in the raw material is 0.40 to 0.80, preferably 0.45 to 0.60.

[0018] According to the present invention, when the hydrocarbon oil raw material is diesel or kerosene, the chemical raw materials produced are ethane, propane, butane, light naphtha, and heavy naphtha.

[0019] According to the present invention, in the hydrocarbon oil raw material, the mass content of C7 + normal paraffins is 6% to 60%, preferably 10% to 40%.

[0020] According to the present invention, in the hydrocarbon oil raw material, the mass content of cyclic hydrocarbons is 20% to 90%, and the cyclic hydrocarbons are the sum of naphthenes and aromatics.

[0021] According to the present invention, in the obtained chemical raw materials, based on the total mass of ethane, propane, butane and light naphtha, the normal paraffins account for 50% to 70%, preferably 55% to 65%. Based on the total mass of ethane, propane, butane and light naphtha, after entering the steam cracking to ethylene unit, the yield of trienes (including ethylene, propylene and butadiene) reaches more than 50%, and further can reach 50% to 60%.

[0022] According to the present invention, the hydrocarbon oil may contain impurities such as sulfur, nitrogen, etc. According to actual needs, a hydrofining catalyst may be provided upstream of the first hydrocracking catalyst to remove impurities such as sulfur and nitrogen. Among them, the nitrogen content in the reaction stream in contact with the first hydrocracking catalyst is preferably below 50 mg / kg, and more preferably below 20 mg / kg.

[0023] According to the present invention, the hydrofining catalyst described above may adopt a conventional hydrofining catalyst, which is mainly used for hydrodesulfurization, denitrification 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. In the hydrofining catalyst, Group VIB is preferably selected from tungsten and / or molybdenum, and its content in the catalyst based on the mass of the oxide is 5% to 30%, preferably 10% to 20%, and Group VIII is preferably selected from nickel and / or cobalt, and its content in the catalyst based on the mass of the oxide is 1% to 6%, preferably 1.5% to 5%.

[0024] 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, and more preferably ZSM-5 molecular sieve. The SiO2 / Al2O3 molar ratio of the ZSM-5 molecular sieve is 20 to 60. 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.

[0025] According to the present invention, in step (1), preferably, for 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%.

[0026] 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%.

[0027] According to the present invention, in step (1), the specific surface area of the first hydrocracking catalyst is 200 to 400 m 2 / g, and the pore volume is 0.25 to 0.45 mL / g.

[0028] According to the present invention, in step (1), the preparation method of the first 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 active metal components. The preparation process of the carrier is as follows: The shape-selective cracking molecular sieve and the binder are mechanically mixed, formed, and then dried and calcined 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.

[0029] 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 carrier 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 calcining are: calcining at 450°C to 550°C for 2.5 to 6.0 hours.

[0030] According to the present invention, in step (2), the second hydrocracking catalyst has the function of selectively cracking the side chains of isoparaffins or cyclic hydrocarbons and retaining the 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 the 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, and more preferably Beta molecular sieve.

[0031] According to the present invention, in step (2), for the second hydrocracking catalyst, 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 20 wt%; the content of the cracking component is 20 wt% to 80 wt%, preferably 30 wt% to 70 wt%; the content of the binder is 5 wt% to 75 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 support and the loading of the hydrogenation component. The process of preparing the support is as follows: mechanically mix the cracking component and the binder, shape it, and then dry and calcine it to make the catalyst support. The drying and calcination of the support can adopt 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.

[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 support with a solution containing the required hydrogenation component, and then dry and calcine it 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 calcination are: calcining at 450°C to 550°C for 2.5 to 6.0 hours.

[0034] According to the present invention, in step (1), the reaction conditions for the first hydrocracking reaction are as follows: the reaction pressure is 1.0 to 25.0 MPa, preferably 2.0 to 18.0 MPa. When using heavy naphtha as the raw material, the reaction pressure is preferably 1.0 to 5.0 MPa.

[0035] According to the present invention, in step (1), the reaction conditions for the first hydrocracking reaction 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, in step (2), the reaction conditions for the second hydrocracking reaction are as follows: the reaction pressure is 1.0 to 25.0 MPa, preferably 2.0 to 18.0 MPa. When using heavy naphtha as the raw material, the reaction pressure is preferably 1.0 to 5.0 MPa.

[0037] According to the present invention, the reaction conditions of the second hydrocracking reaction in step (2) 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.

[0038] According to the present invention, preferably, the first hydrocracking reaction zone and the second hydrocracking reaction zone adopt the same pressure.

[0039] According to the present invention, preferably, the first hydrocracking product in step (2) is subjected to supplementary hydrofining. The supplementary hydrofining can be carried out by loading a hydrofining catalyst at the bottom of the first hydrocracking reaction zone, or it can enter a separate hydrofining reaction zone.

[0040] According to the present invention, preferably, the first hydrocracking product in step (2) can also directly enter the fractionation system, and the separated heavy naphtha component is subjected to supplementary hydrofining.

[0041] According to the present invention, when using a raw material heavier than heavy naphtha, the product in step (3) also includes tail oil. The tail oil obtained by fractionation in step (3) is preferably recycled to step (1) and / or step (2).

[0042] According to the present invention, the ethane, propane, butane, and light naphtha obtained in step (3) 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: the reaction temperature is 750 °C to 900 °C, the reaction pressure is 0.1 to 0.5 MPa, and the water-oil mass ratio is 0.2 to 0.6.

[0043] According to the present invention, preferably, the propane obtained in step (3) 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: the reaction temperature is 600 °C to 680 °C, preferably 620 °C to 650 °C; the reaction pressure is 0.1 MPa to 0.5 MPa, preferably 0.2 MPa to 0.3 MPa; the volume space velocity is 0.2 h -1 ~8.0 h -1 .

[0044] According to the present invention, preferably, the heavy naphtha obtained in step (3) is used as the feed for the catalytic reforming unit after hydrofining. The catalytic reforming can be semi-regenerative reforming, continuous reforming, or cyclic regenerative reforming. The main operating conditions are as follows: the reaction temperature is 480 to 530 °C, the reaction pressure is 0.35 to 1.5 MPa, the hydrogen-hydrocarbon molar ratio is 2 to 8, and the volume space velocity is 1 to 6 h -1. In the prior art, the catalytic reforming device generally includes three reaction zones, namely, a six-membered ring dehydrogenation reaction zone, a five-membered ring isomerization dehydrogenation reaction zone, and a chain alkane cyclization and dehydrogenation reaction zone. In the present invention, it is preferred that the chain alkane cyclization and dehydrogenation reaction zone be eliminated from the catalytic reforming device, and only a six-membered ring dehydrogenation reaction zone and a five-membered ring isomerization dehydrogenation reaction zone are provided. After the catalytic reforming reaction, the heavy naphtha enters the aromatic extraction device for separation to obtain the BTX component. The aromatic extraction can adopt the existing technology, and the conventional aromatic extraction methods mainly include: liquid-liquid extraction method or extractive distillation method. The present invention preferably uses the liquid-liquid extraction method, and the extraction solvent is one or more of diethylene glycol, triethylene glycol, tetraethylene glycol, cyclobutane sulfone, N-methylpyrrolidone, and dimethyl sulfoxide. The extraction conditions are as follows: extraction temperature 20°C to 200°C, preferably 50°C to 150°C; solvent: heavy naphtha mass ratio 1:1 to 8:1, preferably 3:1 to 5:1; pressure 0 to 2MPa, preferably 0.1 to 0.5MPa.

[0045] Petroleum hydrocarbons have a complex composition, mainly including chain alkanes, cycloalkanes and aromatics, while high-quality ethylene raw materials are small molecular normal alkanes, and reforming raw materials are monocyclic cycloalkanes and aromatics. The inventors have found through research that hydrocarbon oil raw materials can be highly selectively generated by selective cracking of straight-chain alkanes, ring-opening cracking of polycyclic cyclic hydrocarbons, and selective hydrocracking of long side chains on isomeric hydrocarbons or cyclic hydrocarbons to retain monocyclic cyclic hydrocarbons as much as possible, thereby achieving efficient enrichment of small molecular normal alkanes in low-carbon olefin raw materials, while retaining monocyclic cyclic hydrocarbons in heavy naphtha as much as possible to achieve efficient enrichment of high-quality reforming raw materials, so that the purpose of greatly improving the yield of chemical raw materials (i.e., low-carbon olefin raw materials and reforming raw materials) and the quality of low-carbon olefin raw materials and reforming raw materials can be achieved, thereby completing the present invention.

[0046] Compared with the prior art, the present invention has the following beneficial technical effects:

[0047] (1) In the hydrocracking method for producing chemical raw materials from hydrocarbon oil of the present invention, the hydrocarbon oil raw material (especially heavy naphtha raw material) and hydrogen enter the first hydrocracking reaction zone, mainly to selectively crack the normal alkanes and the long straight-chain isoalkanes and cycloalkanes containing long straight-chain hydrocarbons in the raw material to produce small molecular normal alkanes, so that the C7 +The content of normal paraffin is below 5%. The first hydrocracking product enters the second hydrocracking reaction zone, mainly to selectively crack the isomer side chains on isoparaffins and cyclic hydrocarbons, and retain the monocyclic cyclic hydrocarbons. In this way, a large amount of linear paraffins in the raw material can be converted into gas and light naphtha components, that is, enriched in the raw material of the ethylene plant, while the monocyclic cyclic hydrocarbons are retained in the heavy naphtha fraction, that is, enriched in the reforming raw material. Through simple fractionation, the efficient separation of paraffins and cyclic hydrocarbons can be achieved. While increasing the production of high-quality ethylene cracking feedstock, the quality of heavy naphtha as catalytic reforming feedstock is improved. Particularly, the present invention sets a second hydrocracking process after the first hydrocracking process. After the second hydrocracking treatment, the ethylene raw material yield in the product is further increased.

[0048] (2) The content of monocyclic cyclic hydrocarbons in the heavy naphtha obtained by the method of the present invention is high. As the feedstock of the catalytic reforming unit, the linear paraffin cyclization and dehydrogenation unit in the catalytic reforming unit can be cancelled, and the investment and energy consumption of the catalytic reforming unit can be greatly reduced. At the same time, since the hydrocracking reaction follows the carbocation reaction mechanism, the side chain breaking reaction of cyclic hydrocarbons above C9 can be selectively realized, so that the C6-C8 cyclic hydrocarbons in the product have a high enrichment degree. After catalytic reforming and aromatics extraction, the BTX yield can be greatly increased.

[0049] (3) The present invention selectively converts the linear paraffins in the hydrocarbon oil into small molecule paraffins. This process will consume a certain amount of hydrogen, but the light hydrocarbons also have a high hydrogen yield as the raw material of the ethylene plant. 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 plant. At the same time, the light hydrocarbons as ethylene raw materials can greatly increase the yields of ethylene, propylene and butadiene, and extend the cleaning cycle of the ethylene plant, significantly improving the economic benefits of the plant. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 is a schematic process flow diagram of the process method of the present invention;

[0051] Main reference numeral description:

[0052] 1 - Hydrocarbon oil raw material, 2 - Hydrogen, 3 - First hydrocracking reaction zone, 4 - First hydrocracking product, 5 - Second hydrocracking reaction zone, 6 - Second hydrocracking product, 7 - Separator, 8 - Gas-phase stream rich 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

[0053] The functions and effects of the present invention will be further described below through examples, but the following examples do not limit the method of the present invention.

[0054] In the present invention, % is by mass fraction unless otherwise specified.

[0055] The total volume space velocity in the examples and comparative examples is the ratio of the fresh feed volume to the total catalyst volume.

[0056] The method of the present invention, as Figure 1 shown, comprises: a hydrocarbon oil feedstock 1 (a feedstock heavier than heavy naphtha) is mixed with hydrogen 2 and enters the first hydrocracking reaction zone 3 for the first hydrocracking reaction. The first hydrocracking product 4 enters the second hydrocracking reaction zone 5 for the second hydrocracking reaction. The second hydrocracking product 6 enters a separator 7. The separated gas-phase stream, the hydrogen-rich gas 8, is recycled for use. The liquid-phase stream 9 enters a fractionating tower 10, and gas fractions 11, light naphtha 12, heavy naphtha 13, and tail oil 14 are fractionated. The tail oil 14 is recycled to the second hydrocracking reaction zone 5. When using heavy naphtha as the feedstock, after separation and fractionation of the second hydrocracking product 6, gas fractions 11, light naphtha 12, and heavy naphtha 13 are obtained.

[0057] 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. 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.

[0058] In the present invention, the second hydrocracking catalyst in each example is represented by Cat-B plus a number, such as Cat-B1, 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, 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, the pore volume is 0.30 cm 3 / g, and the physicochemical properties of the obtained catalyst are shown in Table 2.

[0059] In each example of the present invention, the ethylene raw material in each example refers to the gas fraction (ethane, propane, butane) and light naphtha obtained after separation and fractionation of the effluent from the second hydrocracking reaction. Ethane, propane, butane, and light naphtha can be directly used as raw materials for steam cracking to produce ethylene. The ethane, propane, butane, and light naphtha obtained through 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 steam cracking to produce ethylene are: reaction temperature 880°C, reaction pressure 0.2 MPa, and mass ratio of water to oil 0.4.

[0060] In each example of the present invention, the heavy naphtha obtained through hydrocracking enters the catalytic reforming unit after supplementary refining. The operating conditions for catalytic reforming are: 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. The extraction solvent is sulfolane. The operating conditions for aromatics extraction are: extraction temperature 80°C; mass ratio of solvent to heavy naphtha is 4:1; pressure is 0.3 MPa. The yield of BTX obtained from aromatics extraction is the percentage of the yield of C6-C8 aromatics in the feed of catalytic reforming heavy naphtha.

[0061] In the present invention, the raw material oil in each example uses heavy naphtha as the raw material, and its main properties are shown in Table 3.

[0062] In the present invention, the distillation range of light naphtha is the liquid component with a boiling point less than 60°C, and the distillation range of heavy naphtha is 60-175°C.

[0063] In the present invention, the yield of the ethylene raw material refers to the mass ratio of ethane, propane, butane, and light naphtha in the hydrocracking product to the fresh feed of hydrocracking. The yield of heavy naphtha refers to the mass ratio of heavy naphtha in the hydrocracking product to the fresh feed of hydrocracking.

[0064] Example 1

[0065] The hydrocracking method includes:

[0066] (1) The raw material oil is mixed with hydrogen and sequentially enters the first hydrocracking reaction zone and the second hydrocracking reaction zone; the first hydrocracking reaction zone is filled with the first hydrocracking catalyst Cat-A1; the second hydrocracking reaction zone is filled with the second hydrocracking catalyst Cat-B1; in step (1), the content of n-alkanes in the first hydrocracking product with C7 + is 1%.

[0067] (2) The reaction effluent of the second hydrocracking reaction zone in step (1) is separated into a gas-phase stream and a liquid-phase stream. The gas-phase stream is recycled, and the liquid-phase stream enters a fractionating column, where gas fractions, light naphtha, and heavy naphtha are fractionated. The process conditions and hydrocracking effects in this example are shown in Table 4.

[0068] Example 2

[0069] The hydrocracking method includes:

[0070] (1) The feedstock oil is mixed with hydrogen and sequentially enters a first hydrocracking reaction zone and a second hydrocracking reaction zone. The first hydrocracking reaction zone is filled with a first hydrocracking catalyst Cat-A2; the second hydrocracking reaction zone is filled with a second hydrocracking catalyst Cat-B2. In step (1), the content of C7 + n-alkanes in the first hydrocracking product is 2%.

[0071] (2) The reaction effluent of the second hydrocracking reaction zone in step (1) is separated into a gas-phase stream and a liquid-phase stream. The gas-phase stream is recycled, and the liquid-phase stream enters a fractionating column, where gas fractions, light naphtha, and heavy naphtha are fractionated. The process conditions and hydrocracking effects in this example are shown in Table 4.

[0072] Example 3

[0073] The hydrocracking method includes:

[0074] (1) The feedstock oil is mixed with hydrogen and sequentially enters a first hydrocracking reaction zone and a second hydrocracking reaction zone. The first hydrocracking reaction zone is filled with a first hydrocracking catalyst Cat-A3; the second hydrocracking reaction zone is filled with a second hydrocracking catalyst Cat-B1. In step (1), the content of C7 + n-alkanes in the first hydrocracking product is 5%.

[0075] (2) The reaction effluent of the second hydrocracking reaction zone in step (1) is separated into a gas-phase stream and a liquid-phase stream. The gas-phase stream is recycled, and the liquid-phase stream enters a fractionating column, where gas fractions, light naphtha, and heavy naphtha are fractionated. The process conditions and hydrocracking effects in this example are shown in Table 4.

[0076] Example 4

[0077] The first hydrocracking reaction zone is filled with the same first hydrocracking catalyst Cat-A1 as in Example 1.

[0078] The second hydrocracking reaction zone is filled with a second hydrocracking catalyst Cat-B2.

[0079] The hydrocracking method includes:

[0080] (1) The feedstock oil is mixed with hydrogen and successively enters the first hydrocracking reaction zone and the second hydrocracking reaction zone; the first hydrocracking reaction zone is filled with the first hydrocracking catalyst Cat-A1; the second hydrocracking reaction zone is filled with the second hydrocracking catalyst Cat-B2; in step (1), the content of C7 + normal paraffin in the first hydrocracking product is controlled to be 1%.

[0081] (2) The reaction effluent from the second hydrocracking reaction zone in step (1) is separated into a gas-phase stream and a liquid-phase stream by gas-liquid separation. The gas-phase stream is recycled, and the liquid-phase stream enters the fractionating tower, where gas fractions, light naphtha, and heavy naphtha are fractionated.

[0082] In this example, the process conditions and the hydrocracking effect are shown in Table 4.

[0083] Comparative Example 1

[0084] The difference from Example 1 is that the feedstock oil directly enters the second hydrocracking reaction zone and reacts with the Cat-B1 catalyst.

[0085] In this example, the process conditions and the hydrocracking effect are shown in Table 4.

[0086] Comparative Example 2

[0087] The difference from Example 1 is that in step (1), the content of C7 + normal paraffin in the first hydrocracking product is controlled to be 6%.

[0088] In this example, the process conditions and the hydrocracking effect are shown in Table 4.

[0089] Comparative Example 3

[0090] The difference from Example 3 is that the first hydrocracking reaction zone is filled with the catalyst Cat-B2.

[0091] In this example, the process conditions and the hydrocracking effect are shown in Table 4.

[0092] Comparative Example 4

[0093] The difference from Example 1 is that the first hydrocracking reaction zone is filled with the catalyst Cat-B1 and the second hydrocracking reaction zone is filled with the catalyst Cat-B2.

[0094] In this example, the process conditions and the hydrocracking effect are shown in Table 4.

[0095] Table 1 Physical and Chemical Properties of the First Hydrocracking Catalyst

[0096] Catalyst Cat-A1 Cat-A2 Cat-A3 <![CDATA[Pore volume, cm 3 / g]]> 0.35 0.45 0.25 <![CDATA[Specific surface area, m 2 / g]]> 300 200 400 Content, wt%, based on the weight of the support ZSM-5 58 42 85 Aluminum oxide 42 58 15 Active metal content in the catalyst, wt% <![CDATA[MoO3]]> 10.0 15.0 5.0 NiO 3.5 2.0 5.0 <![CDATA[SiO2 / Al2O3 molar ratio of ZSM-5]]> 40 60 20

[0097] Table 2 Physical and Chemical Properties of the Second Hydrocracking Catalyst

[0098] 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% - 50 <![CDATA[MoO3, wt%]]> 10 10 NiO, wt% 5 5 Aluminum oxide, wt% 35 35

[0099] Table 3 Main Properties of Raw Materials

[0100]

[0101]

[0102] Table 4 Hydrogenation Effect

[0103]

[0104] Continued Table 4

[0105]

[0106] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. 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, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A hydrocracking method for producing chemical raw materials, wherein, The chemical raw materials include low-carbon olefin raw materials and reforming raw materials, and the method includes: (1) In the presence of hydrogen, a hydrocarbon oil feedstock enters a first hydrocracking reaction zone to selectively crack the normal paraffins in the hydrocarbon oil feedstock, obtaining a first hydrocracking product; wherein, in the first hydrocracking product, the mass content of C7 + normal paraffins is controlled to be below 5.0%; (2) In the presence of hydrogen, the first hydrocracking product enters the second hydrocracking reaction zone to obtain a second hydrocracking product containing monocyclic cyclic hydrocarbons; (3) The second hydrocracking product is separated and fractionated to obtain a gas fraction, light naphtha, and heavy naphtha; Among them, the first hydrocracking reaction zone is filled with a first hydrocracking catalyst, and the second hydrocracking reaction zone is filled with a second hydrocracking catalyst; The first hydrocracking catalyst includes an active metal component and a carrier; the active metal component includes at least one of metals in Group VIB and Group VIII; the carrier in the first hydrocracking catalyst includes one or more of ZSM-5 zeolite, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35, and ZSM-38 zeolites; 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%; The cracking component in the second hydrocracking catalyst includes at least one of Beta zeolite and Y zeolite; For the second hydrocracking catalyst, 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 20wt% - 80wt%, and the content of the binder is 5wt% - 75wt%; The hydrocarbon oil raw material includes one or more selected from heavy naphtha, diesel, and kerosene; 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 raw materials for producing low-carbon olefins; In the obtained chemical raw materials, based on the total mass of ethane, propane, butane, and light naphtha, the normal paraffin accounts for 50% - 70%.

2. The method according to claim 1, characterized in that The product in step (3) also includes tail oil; the obtained tail oil is recycled to the first hydrocracking reaction zone in step (1) and / or recycled to the second hydrocracking reaction zone in step (2).

3. The method according to claim 1, characterized in that, The hydrocarbon oil raw material is a heavy naphtha raw material.

4. The method according to claim 3, wherein The heavy naphtha raw material includes at least one of straight-run naphtha, coker naphtha, ebullated bed residue hydrotreating naphtha, and coal chemical naphtha; and / or, the initial boiling point of the heavy naphtha raw material is 40°C - 80°C; the final boiling point is 150°C - 200°C.

5. The method according to claim 3, wherein The initial boiling point of the heavy naphtha raw material is 50°C - 70°C; the final boiling point is 160°C - 180°C.

6. The method according to claim 1, wherein In the hydrocarbon oil feedstock described above, C7 + The mass content of n-alkanes is 6% to 60%.

7. The method according to claim 1, characterized in that, In the hydrocarbon oil feedstock described above, the mass content of C7 + n-alkanes is 10% to 40%.

8. The method according to claim 1, characterized in that, In the hydrocarbon oil raw material described, the mass content of cyclic hydrocarbons is 20% - 90%.

9. The method according to claim 1, wherein The nitrogen content in the reaction fluid in contact with the hydrocracking catalyst filled in the first hydrocracking reaction zone is below 50mg / kg.

10. The method according to claim 9, characterized in that, The nitrogen content in the reaction fluid in contact with the hydrocracking catalyst filled in the first hydrocracking reaction zone is below 20mg / kg.

11. The method according to claim 1, wherein In step (1), the carrier of the first hydrocracking catalyst includes ZSM-5 molecular sieve.

12. The method according to claim 1, wherein In step (1), in the first hydrocracking catalyst, the Group VIB metals are molybdenum and / or tungsten, and the Group VIII metals are cobalt and / or nickel.

13. The method according to claim 1, characterized in that In step (2), for the second hydrocracking catalyst, based on the weight of the second hydrocracking catalyst, the content of the hydrogenation component calculated as the oxide is 10 wt% - 20 wt%, the content of the cracking component is 30 wt% - 70 wt%, and the content of the binder is 10 wt% - 50 wt%.

14. The method according to claim 1, wherein In step (1), the reaction conditions of the first hydrocracking reaction are as follows: The reaction pressure is 1.0 - 25.0 MPa; The average reaction temperature is 250 - 450 °C; The hourly space velocity of the liquid is 0.1 to 15.0 h -1 ; The hydrogen-oil volume ratio is 100:1 - 2500:

1.

15. The method according to claim 1, wherein In step (1), the reaction conditions of the first hydrocracking reaction are as follows: The reaction pressure is 2.0 - 18.0 MPa; The average reaction temperature is 300 - 400 °C; The hourly space velocity of the liquid is 1.0~5.0 h -1 ; The hydrogen-oil volume ratio is 400:1 - 2000:

1.

16. The method according to claim 1, wherein In step (2), the reaction conditions of the second hydrocracking reaction are as follows: The reaction pressure is 1.0 - 25.0 MPa; The average reaction temperature is 250 - 450 °C; The hourly space velocity of the liquid is 0.1~15.0 h -1 ; The hydrogen-oil volume ratio is 100:1 - 2500:

1.

17. The method according to claim 1, characterized in that In step (2), the reaction conditions of the second hydrocracking reaction are as follows: The reaction pressure is 2.0 - 18.0 MPa; The average reaction temperature is 300 - 400 °C; The hourly space velocity of the liquid is 1.0 to 5.0 h -1 ; The hydrogen-oil volume ratio is 400:1 - 2000:

1.

18. The method according to claim 1, characterized in that In the second hydrocracking product described in step (2), the mass ratio of the C6 - C8 monocyclic cyclic hydrocarbons to the total cyclic hydrocarbon mass in the raw material is 0.40 - 0.

80.

19. The method according to claim 1, wherein In the second hydrocracking product described in step (2), the mass ratio of the C6 - C8 monocyclic cyclic hydrocarbons to the total cyclic hydrocarbon mass in the raw material is 0.45 - 0.

60.

20. The method according to claim 1, wherein In the obtained chemical raw material, based on the total mass of ethane, propane, butane, and light naphtha, the normal paraffins account for 55% - 65%.

21. The method according to claim 1 or 20, characterized in that, Based on the total mass of ethane, propane, butane, and light naphtha, after entering the steam cracking unit for ethylene production, the yields of the three olefins, namely ethylene, propylene, and butadiene, are above 50%.

22. The method according to claim 21, wherein Based on the total mass of ethane, propane, butane, and light naphtha, after entering the steam cracking unit for ethylene production, the yields of the three olefins, namely ethylene, propylene, and butadiene, are 50% - 60%.

23. A method for jointly producing BTX by hydrocracking and catalytic reforming, characterized in that, Use the heavy naphtha of the chemical raw material obtained by any of the methods of claims 1 - 22 as the feed for the catalytic reforming unit.

24. The method according to claim 23, wherein The catalytic reforming is semi-regenerative reforming, continuous reforming or cyclic regenerative reforming, and the main operating conditions are as follows: reaction temperature 480-530 °C, reaction pressure 0.35-1.5 MPa, hydrogen-hydrocarbon molar ratio 2-8, volumetric space velocity 1-6 h -1 .

25. The method according to claim 23 or 24, characterized in that, The catalytic reforming unit cancels the alkane cyclization and dehydrogenation reaction zone, and only sets up the dehydrogenation reaction zone for six-membered rings and the isomerization dehydrogenation reaction zone for five-membered rings.

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