A two-stage hydrocracking method for producing chemical raw materials from heavy distillate oil

Abstract

The present invention discloses a two-stage hydrocracking method for producing chemical raw materials from heavy distillate oil. The method comprises that the heavy distillate oil is mixed with hydrogen and sequentially enters a hydrofining reaction zone, a first hydrocracking reaction zone and a second hydrocracking reaction zone. The product of the second hydrocracking is separated and fractionated to obtain gas, light naphtha, heavy naphtha and tail oil. Then the tail oil is mixed with hydrogen again and enters a third hydrocracking reaction zone, and the product of the third hydrocracking enters a separation and fractionation system to obtain gas, light naphtha and heavy naphtha. Among them, the reaction pressure of the first hydrocracking reaction zone is 1-6 MPa higher than that of the third hydrocracking reaction zone. This method can significantly improve the quality and yield of chemical raw materials.

Description

Technical Field

[0001] The present invention belongs to the field of hydrocarbon oil hydrocracking, and particularly relates to a two-stage hydrocracking method for producing chemical raw materials from heavy oil, especially a hydrocracking method for producing high-quality chemical raw materials from heavy distillate oil with a relatively wide boiling range. Background Art

[0002] In recent years, the trend of crude oil being heavier and of lower quality has been obvious, and the processing of heavy oil has become more difficult. Progress has been mainly made in aspects such as technical optimization and catalyst upgrading in the deep processing technology of heavy oil; technologies for refineries to increase the production of chemical raw materials such as low-carbon olefins and aromatics have developed rapidly along with the refining-chemical integration strategy; alternative energy technologies have received high attention and entered the stage of large-scale industrial application.

[0003] 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. The hydrocracking technology has the characteristics of strong feedstock 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 fuel, diesel, lubricating oil base stock, and chemical naphtha and tail oil for steam cracking to produce ethylene raw materials. It has become one of the most important heavy oil deep processing processes in modern refining and petrochemical industries and has been increasingly widely used at home and abroad. With the current decrease in the demand for the fuel oil market in China, converting the maximum amount of heavy distillate oil fraction into high-quality chemical raw materials has become a beneficial technical path for refining enterprises to optimize their product structure and improve economic benefits.

[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. At the same time, when producing ethylene raw materials, the content of normal paraffins in the ethylene raw materials is low, which will also result in a relatively low yield of triolefins in the steam cracking to ethylene unit. Therefore, it is of great significance to develop a hydrocracking method suitable for producing high-quality chemical raw materials from heavy distillate oil. Summary of the Invention

[0007] Aiming at the problems existing in the prior art, the object of the present invention is to provide a two-stage hydrocracking method for producing chemical raw materials from heavy distillate oil. This method can significantly improve the quality and yield of chemical raw materials by hydrocracking heavy distillate oil as the raw material.

[0008] The present invention provides a two-stage hydrocracking method for producing chemical raw materials from heavy distillate oil, and the method comprises:

[0009] (1) Mixing heavy distillate oil with hydrogen and entering a hydrotreating reaction zone, and then performing gas-liquid separation to obtain a gas-phase stream and a liquid-phase stream; controlling the nitrogen content in the liquid-phase stream in step (1) to be 50 mg / kg to 100 mg / kg;

[0010] (2) In the presence of hydrogen, the liquid-phase stream obtained in step (1) enters a first hydrocracking reaction zone to selectively crack the normal paraffins in the heavy distillate oil raw material to obtain a first hydrocracking product; wherein, in the first hydrocracking product, control the mass content of C7 + normal paraffins to be not higher than 3.0%;

[0011] (3) In the presence of hydrogen, the first hydrocracking product enters a second hydrocracking reaction zone. After the second hydrocracking product is subjected to gas-liquid separation through a separator, the hydrogen-rich gas obtained is used as recycle hydrogen, and the liquid phase enters a fractionation system for fractionation to obtain gas, light naphtha, heavy naphtha and tail oil.

[0012] (4) The tail oil from step (3) is mixed with hydrogen and enters the third hydrocracking reaction zone to obtain a third hydrocracking product containing monocyclic cyclic hydrocarbons; the third hydrocracking product enters a separation and fractionation system to obtain gas, light naphtha, and heavy naphtha;

[0013] In step (2), the reaction pressure in the first hydrocracking reaction zone is 1 - 6 MPa higher than the reaction pressure in the third hydrocracking reaction zone in step (4).

[0014] According to the present invention, the gaseous stream obtained in step (1) is input into the hydrotreating reaction zone for recycling.

[0015] According to the present invention, the nitrogen content in the liquid stream described in step (1) is controlled to be 60 mg / kg - 80 mg / kg.

[0016] According to the present invention, the chemical raw materials include low - carbon olefin raw materials and reforming raw materials. Specifically, the chemical raw materials mainly include ethane, propane, butane, light naphtha, and may also include 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. 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, low - carbon olefins refer to olefins with four or fewer carbon atoms, especially ethylene, propylene, and butadiene.

[0017] According to the present invention, a hydrotreating catalyst is loaded in the hydrotreating reaction zone of step (1). The hydrotreating catalyst described in step (1) can adopt a conventional hydrotreating catalyst, which is mainly used for hydrodesulfurization, denitrification, and other impurities. The hydrotreating catalyst includes a carrier and a hydrogenation active metal. Among them, 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. Preferably, in the hydrotreating catalyst, the Group VIB metal is preferably selected from tungsten and / or molybdenum, and its content in the catalyst based on the mass of the oxide is 10% - 50%, preferably 20% - 30%; the Group VIII metal is preferably selected from nickel and / or cobalt, and its content in the catalyst based on the mass of the oxide is 2% - 10%, preferably 3% - 8%; the content of the carrier is 42% - 88%, preferably 62% - 77%.

[0018] According to the present invention, in the heavy - fraction oil described in step (1), the mass content of cyclic hydrocarbons is 40% - 90%, where the cyclic hydrocarbons are the sum of naphthenes and aromatics. In the heavy - fraction oil, the mass content of normal paraffins is 5% - 50%, preferably 10% - 30%. The heavy - fraction oil is at least one of coal tar and shale oil. The distillation range of the heavy - fraction oil is 100 °C - 750 °C; the density is 0.88 g / cm 3 ~1.20 g / cm3 The nitrogen mass content is 0.6% to 2.0%, preferably 0.8% to 1.5%; the oxygen mass content is 0.5% to 1.5%, preferably 0.6% to 1.0%.

[0019] According to the present invention, in step (1), the reaction conditions in the hydrofining reaction zone are as follows: the reaction pressure is 10.0 to 25.0 MPa, preferably 15.0 to 20.0 MPa.

[0020] According to the present invention, in step (1), the reaction conditions in the hydrofining reaction zone are as follows: the average reaction temperature is 300 to 450 °C, preferably 350 to 420 °C; the liquid hourly space velocity is 1.0 to 15.0 h -1 , preferably 5.0 to 10.0 h -1 ; the hydrogen-oil volume ratio is 100:1 to 2500:1, preferably 400:1 to 2000:1.

[0021] According to the present invention, preferably, in step (2), the mass content of C7 + n-alkanes is 1.0% to 3.0%.

[0022] According to the present invention, in the third hydrocracking product of step (4), the ratio of the mass of C6-C8 monocyclic cyclic hydrocarbons to the total mass of cyclic hydrocarbons in the raw material is 0.15 to 0.35, preferably 0.29 to 0.34. The raw material is the heavy distillate oil.

[0023] According to the present invention, in step (2), the first hydrocracking reaction zone is filled with a first hydrocracking catalyst. The first hydrocracking catalyst can be one or more catalysts. In step (2), the first hydrocracking catalyst includes an active metal component and a carrier; the carrier includes a molecular sieve having selective cracking of n-alkanes, 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 SiO2 / Al2O3 molar ratio of the ZSM-5 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 of Group VIB and Group VIII. The metal of Group VIB is preferably molybdenum and / or tungsten, and the metal of Group VIII is preferably cobalt and / or nickel.

[0024] According to the present invention, in step (2), 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%.

[0025] According to the present invention, in step (2), preferably, in the carrier of the first hydrocracking catalyst, based on the weight of the carrier, the binder content is 8% to 60%, and the molecular sieve content is 40% to 92%.

[0026] According to the present invention, in step (2), 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.

[0027] According to the present invention, in step (2), 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 process of preparing the carrier 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 carrier. The drying and calcination of the carrier can adopt conventional conditions. The drying conditions are: drying at 100°C to 150°C for 1 to 12 hours. The calcination conditions are: calcining at 450°C to 550°C for 2.5 to 6.0 hours.

[0028] According to the present invention, in step (2), in the preparation method of the first hydrocracking catalyst, the method of 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 drying conditions are: drying at 100°C to 150°C for 1 to 12 hours. The calcination conditions are: calcining at 450°C to 550°C for 2.5 to 6.0 hours.

[0029] According to the present invention, the reaction conditions in the first hydrocracking reaction zone in step (2) are as follows: the reaction pressure is 10.0 to 25.0 MPa, preferably 15.0 to 20.0 MPa.

[0030] According to the present invention, the reaction conditions in the first hydrocracking reaction zone in step (2) are as follows: the average reaction temperature is 300 to 450°C, preferably 350 to 420°C; the liquid hourly space velocity is 1.0 to 15.0 h [[ID=^19]] -1 , preferably 5.0 to 10.0 h -1 ; the hydrogen-oil volume ratio is 100:1 to 2500:1, preferably 400:1 to 2000:1.

[0031] According to the present invention, in step (3), the second hydrocracking reaction zone is filled with a second hydrocracking catalyst. The second hydrocracking catalyst can be one or more catalysts. The second hydrocracking catalyst has the function of selectively cracking polycyclic cyclic hydrocarbons.

[0032] According to the present invention, the second hydrocracking catalyst in step (3) comprises 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 comprises a Group VIB and / or Group VIII metal; the active metal component is more preferably at least one of iron, chromium, molybdenum, tungsten, cobalt, and nickel. The binder is alumina and / or silica; the cracking component comprises an acidic molecular sieve, preferably at least one of Beta zeolite and Y zeolite.

[0033] According to the present invention, it is further preferred that the cracking component of the second hydrocracking catalyst in step (3) is Y zeolite.

[0034] According to the present invention, in the second hydrocracking catalyst in step (3), based on the mass of the catalyst, the content of the hydrogenation component calculated as the 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%; and the content of the binder is 5 wt% to 85 wt%, preferably 10 wt% to 50 wt%.

[0035] According to the present invention, the preparation method of the second hydrocracking catalyst in step (3) can be prepared according to the conventional methods in the art. The preparation method includes the preparation of a carrier and the loading of a hydrogenation component. The process of preparing the carrier is as follows: the cracking component and the binder are mechanically mixed, shaped, and then dried and calcined to form a catalyst carrier. The drying and calcination of the carrier 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.

[0036] According to the present invention, in the preparation method of the second hydrocracking catalyst in step (3), 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, the catalyst carrier is impregnated with a solution containing the required hydrogenation component, and then dried and calcined 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.

[0037] According to the present invention, the reaction conditions in the second hydrocracking reaction zone in step (3) are as follows: the reaction pressure is 100 to 25.0 MPa, preferably 10.0 to 20.0 MPa.

[0038] According to the present invention, the reaction conditions of the second hydrocracking reaction in step (3) are as follows: the average reaction temperature is 300 to 450 °C, preferably 350 to 420 °C; the liquid hourly space velocity is 1.0 to 15.0 h -1 , preferably 5.0 to 10.0 h -1 ; the hydrogen-oil volume ratio is 100:1 to 2500:1, preferably 400:1 to 2000:1.

[0039] According to the present invention, preferably, the hydrofining zone, the first hydrocracking reaction zone, and the second hydrocracking reaction zone adopt the same reaction pressure.

[0040] According to the present invention, in step (4), the third hydrocracking reaction zone is filled with a third hydrocracking catalyst. The third hydrocracking catalyst can be one or more catalysts. The third hydrocracking catalyst has the function of selectively cracking the side chains of isoparaffins or cyclic hydrocarbons and retaining the monocyclic cyclic hydrocarbons.

[0041] According to the present invention, in step (4), the third hydrocracking catalyst includes a hydrogenation component, a cracking component, and a binder. The isoparaffin conversion 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. The binder is alumina and / or silica; the cracking component includes an acidic molecular sieve, preferably at least one of Beta zeolite and Y zeolite, and more preferably Beta zeolite.

[0042] According to the present invention, in the third hydrocracking catalyst in step (4), based on the mass of the catalyst and in terms of oxides, the content of the hydrogenation component 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%.

[0043] According to the present invention, the preparation method of the third hydrocracking catalyst in step (4) can be prepared according to the conventional methods in the art. The preparation method includes the preparation of a carrier and the loading of a hydrogenation component, wherein the preparation process of the carrier is as follows: the cracking component and the binder are mechanically mixed, formed, and then dried and calcined to make a catalyst carrier. The drying and calcination of the carrier can adopt conventional conditions. The drying conditions are: drying at 100 °C to 150 °C for 1 to 12 hours. The calcination conditions are: calcining at 450 °C to 550 °C for 2.5 to 6.0 hours.

[0044] According to the present invention, in the preparation method of the third hydrocracking catalyst in step (4), the method for loading the hydrogenation component is a conventional method, such as kneading method, impregnation method, etc., and the impregnation method is preferred. The impregnation method can be saturated impregnation method, excess impregnation method or complex impregnation method, that is, the catalyst support is impregnated with a solution containing the required hydrogenation component, and then dried and calcined to obtain the third hydrocracking catalyst. The conditions for the drying are: drying at 100°C to 150°C for 1 to 12 hours. The conditions for the calcination are: calcining at 450°C to 550°C for 2.5 to 6.0 hours.

[0045] According to the present invention, in step (4), the reaction conditions in the third hydrocracking reaction zone are as follows: the reaction pressure is 10.0 to 20.0 MPa, preferably 10.0 to 16.0 MPa.

[0046] According to the present invention, in step (4), the reaction conditions for the third hydrocracking reaction are as follows: the average reaction temperature is 300 to 450°C, preferably 350 to 420°C; the liquid hourly space velocity is 1.0 to 15.0 h -1 , preferably 5.0 to 10.0 h -1 ; the hydrogen-oil volume ratio is 100:1 to 2500:1, preferably 400:1 to 2000:1.

[0047] According to the present invention, preferably, the reaction pressure in the first hydrocracking reaction zone in step (2) is the same as the reaction pressure in the second hydrocracking reaction zone in step (3).

[0048] According to the present invention, preferably, the reaction pressure in the first hydrocracking reaction zone in step (2) is 2 to 5 MPa higher than the reaction pressure in the third hydrocracking reaction zone in step (4).

[0049] According to the present invention, preferably, the effluent from the third hydrocracking reaction in step (4) is subjected to supplementary hydrofining. The supplementary hydrofining can be carried out by loading a hydrofining catalyst at the bottom of the third hydrocracking reaction zone, or it can enter a separate hydrofining reaction zone.

[0050] According to the present invention, preferably, the effluent from the third hydrocracking reaction in step (4) can also first enter the fractionation system, and the separated heavy naphtha component is subjected to supplementary hydrofining.

[0051] According to the present invention, preferably, the products of the third hydrocracking in step (4) and the products of the second hydrocracking in step (3) share the same set of separation and fractionation systems.

[0052] Petroleum hydrocarbons have a complex composition, mainly including alkanes, cycloalkanes and aromatics. High-quality ethylene feedstock is small-molecule normal alkanes, and reforming feedstock is monocyclic cycloalkanes and aromatics. Through research, the inventors found that the technical solution of the present invention can selectively generate small-molecule normal alkanes, so as to efficiently enrich small-molecule normal alkanes in the light olefin feedstock, and at the same time retain monocyclic cyclic hydrocarbons in heavy naphtha as much as possible to achieve efficient enrichment of high-quality reforming feedstock. In this way, the yield of chemical raw materials (i.e., light olefin feedstock and reforming feedstock) and the quality of light olefin feedstock and reforming feedstock can be greatly improved, thereby completing the present invention.

[0053] Compared with the prior art, the present invention has the following beneficial technical effects:

[0054] (1) In the two-stage hydrocracking method for producing chemical raw materials from heavy distillate oil of the present invention, the heavy distillate oil is mixed with hydrogen and enters the hydrotreating reaction zone, and the nitrogen content in the liquid-phase product is controlled, which is beneficial to controlling an appropriate hydrotreating reaction temperature and preventing the rapid deactivation of the catalyst caused by too high a hydrotreating reaction temperature. Then, the raw material and hydrogen enter the first hydrocracking reaction zone, mainly selectively cracking the normal alkanes in the raw material and the long straight chains of isoparaffins and cycloalkanes containing long straight chains to generate small-molecule normal alkanes, so that the content of C7 + normal alkanes in the effluent of the first hydrocracking reaction is not higher than 3.0%. The effluent of the first hydrocracking reaction enters the second hydrocracking reaction zone, mainly to crack the polycyclic cyclic hydrocarbons in the heavy raw material to form more monocyclic cyclic hydrocarbons. The effluent of the second hydrocracking reaction enters the third hydrocracking reaction zone to selectively crack the long side chains of isoparaffins and cyclic hydrocarbons. In this way, a large amount of the chain alkanes in the raw material can be converted into gas and light naphtha components, that is, enriched in the light olefin feedstock, while the monocyclic cyclic hydrocarbons are retained in the heavy naphtha fraction, that is, enriched in the reforming feedstock. Through simple fractionation, the efficient separation of alkanes 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.

[0055] (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 alkane 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 above C9 can be selectively realized, so that the C6-C8 cyclic hydrocarbons in the product have a high enrichment degree, and the BTX yield can be greatly improved after catalytic reforming and aromatics extraction.

[0056] (3) The present invention selectively converts the chain alkanes in the heavy distillate oil into small molecular alkanes. This process consumes a certain amount of hydrogen, but the hydrogen yield of light hydrocarbons as raw materials for ethylene plants is also high. 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, light hydrocarbons as ethylene raw materials can greatly increase the yields of ethylene, propylene and butadiene, and extend the rubber cleaning cycle of the ethylene plant, significantly improving the economic benefits of the plant. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 Schematic diagram of the process flow of Examples 1 to 4 of the present invention;

[0058] Description of main reference numerals:

[0059] 1-heavy distillate oil, 2-hydrogen, 3-hydrorefining reaction zone, 4-hydrorefining reaction effluent, 5-separator, 6-gas stream hydrogen-rich gas, 7-liquid stream, 8-first hydrocracking reaction zone, 9-first hydrocracking reaction effluent, 10-second hydrocracking reaction zone, 11-second hydrocracking reaction effluent, 12-separator, 13-gas stream hydrogen-rich gas, 14-liquid stream, 15-fractionation tower, 16-gas fraction, 17-light naphtha, 18-heavy naphtha, 19-tail oil, 20-third hydrocracking reaction zone, 21-third hydrocracking reaction zone effluent. DETAILED DESCRIPTION

[0060] The effects and benefits of the present invention are further illustrated below by way of examples, but the following examples do not limit the method of the present invention.

[0061] Unless otherwise specified, % in the present invention refers to mass fraction.

[0062] The total volume space velocity in the Examples and Comparative Examples is the ratio of the volume of fresh feed to the total volume of the catalyst.

[0063] In the present invention, Figure 1 As shown, heavy distillate oil 1 is mixed with hydrogen 2 and enters hydrorefining reaction zone 3, hydrorefining reaction effluent 4 enters separator 5, and is separated to obtain hydrogen-rich gas 6 for recycling, liquid stream 7 is mixed with hydrogen 2 and enters first hydrocracking reaction zone 8 for hydrocracking reaction, first hydrocracking reaction effluent 9 enters second hydrocracking reaction zone 10 for hydrocracking reaction, second hydrocracking reaction effluent 11 enters separator 12, and hydrogen-rich gas 13 obtained by separation is recycled, liquid 14 enters fractionating tower 15, and is separated to obtain gas 16, light naphtha 17, heavy naphtha 18 and tail oil 19, tail oil 19 is mixed with hydrogen 2 and enters third hydrocracking reaction zone 20, and third hydrocracking reaction effluent 21 enters separator 12 for separation and fractionation.

[0064] In the present invention, each example of the hydrofining catalyst is denoted by Cat-E, and the hydrofining catalyst is prepared by the conventional active metal saturation impregnation method. The physicochemical properties of the obtained catalyst are shown in Table 3.

[0065] In the present invention, each example of the first hydrocracking catalyst is denoted by Cat-A plus a number, such as Cat-A1, Cat-A2, and Cat-A3. The first hydrocracking catalyst is prepared by the conventional active metal saturation impregnation method. The physicochemical properties of the obtained catalyst are shown in Table 1.

[0066] In the present invention, the physicochemical properties of the second hydrocracking catalyst Cat-B in each example are shown in Table 2. Each example of the second hydrocracking catalyst is prepared by the conventional active metal saturation impregnation method. Among them, the properties of the Y zeolite used in the catalyst Cat-B 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. The physicochemical properties of the obtained catalyst are shown in Table 2.

[0067] In the present invention, the physicochemical properties of the isoparaffin conversion catalyst Cat-C in the third hydrocracking catalyst in each example are shown in Table 2. The properties of the Beta zeolite used in the catalyst Cat-C 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.

[0068] In the present invention, the feedstock oil in each example uses a heavy distillate oil feedstock, and its main properties are shown in Table 4.

[0069] In the present invention, the ethylene feedstock in each example refers to ethane, propane, butane, and light naphtha obtained in step (3). Ethane, propane, butane, and light naphtha can be directly used as feedstocks for steam cracking to produce ethylene.

[0070] 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.

[0071] 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 (the liquid-phase stream obtained in step (1)), and the yield of heavy naphtha refers to the mass ratio of heavy naphtha in the hydrocracking product to the fresh hydrocracking feedstock (the liquid-phase stream obtained in step (1)).

[0072] Examples 1 - 4

[0073] The two-stage hydrocracking method for producing chemical raw materials from the heavy distillate oil adopts the following Figure 1 process, including:

[0074] (1) The heavy distillate oil is mixed with hydrogen and enters the hydrofining reaction zone, and then gas-liquid separation is carried out to obtain a gas-phase stream and a liquid-phase stream; the nitrogen content in the liquid-phase stream described in step (1) is controlled.

[0075] (2) In the presence of hydrogen, the liquid-phase stream obtained in step (1) enters the first hydrocracking reaction zone to obtain a first hydrocracking product; the first hydrocracking reaction zone is filled with a first hydrocracking catalyst; and the mass content of C7 + n-alkane in the effluent of the first hydrocracking reaction is controlled.

[0076] (3) In the presence of hydrogen, the first hydrocracking product enters the second hydrocracking reaction zone, the second hydrocracking reaction zone is filled with a second hydrocracking catalyst, and the effluent of the second hydrocracking reaction is separated and fractionated to obtain a gas fraction, light naphtha, heavy naphtha and tail oil.

[0077] (4) The tail oil in step (3) is mixed with hydrogen and enters the third hydrocracking reaction zone, the third hydrocracking reaction zone is filled with a third hydrocracking catalyst, and the effluent of the third hydrocracking reaction shares a set of separation and fractionation systems with the effluent of the second hydrocracking reaction.

[0078] The specific process conditions and hydrotreating effects are shown in Table 5.

[0079] Comparative Example 1

[0080] The difference from Example 1 is that step (2) is omitted, that is, the liquid-phase stream obtained in step (1) directly enters the second hydrocracking reaction zone. The process conditions and hydrotreating effects in this example are shown in Table 5.

[0081] Comparative Example 2

[0082] The difference from Example 1 is that in step (2), the content of C7 + n-alkane in the effluent of the first hydrocracking reaction is 4%.

[0083] The process conditions and hydrotreating effects in this example are shown in Table 5.

[0084] Comparative Example 3

[0085] The difference from Example 1 is that the reaction pressure in the first hydrocracking reaction zone is the same as the reaction pressure in the third hydrocracking reaction zone.

[0086] The process conditions and hydrotreating effects in this example are shown in Table 5.

[0087] Comparative Example 4

[0088] The difference from Example 1 is that the nitrogen content in the liquid-phase stream described in step (1) is controlled to be 200 mg / kg.

[0089] In this example, the process conditions and the hydrogenation effect are shown in Table 5.

[0090] Table 1 Physicochemical properties of the first hydrocracking catalyst

[0091] 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 Support content, wt% 86.5 83.0 90.0 83.5 <![CDATA[SiO2 / Al2O3 molar ratio of ZSM-5]]> 40 60 20 50

[0092] Table 2 Physicochemical properties of the second and third hydrocracking catalysts

[0093] Catalyst properties Cat-B Cat-C <![CDATA[Pore volume, cm 3 / g]]> 0.35 0.35 <![CDATA[Specific surface area, m 2 / g]]> 300 300 Catalyst composition Beta, wt% - 50 Y, wt% 50 - <![CDATA[MoO3, wt%]]> 10 10 NiO, wt% 5 5 Aluminum oxide, wt% 35 35 ZSM-5, wt% - -

[0094] Table 3 Physicochemical properties of the hydrofining catalyst

[0095] Catalyst properties Cat-E <![CDATA[Pore volume, cm 3 / g]]> 0.35 <![CDATA[Specific surface area, m 2 / g]]> 300 Catalyst composition <![CDATA[MoO3, wt%]]> 25 NiO, wt% 5 Aluminum oxide support, wt% 70

[0096] Table 4 Main properties of the raw materials

[0097] Name of feedstock Heavy distillate oil <![CDATA[Density (20 °C), g / cm -3 > 0.8933 Distillation range / °C (ASTM D86) IBP / 10% 167 / 248 30％ / 50％ 316 / 374 70％ / 90％ 428 / 501 95% / EBP - / 663 n-alkane, wt% 18 Cyclic hydrocarbon, wt% 71 Nitrogen content, wt% 1.09 Oxygen content, wt% 0.85

[0098] Table 5 Hydrogenation effect

[0099]

[0100]

[0101] Continued Table 5

[0102]

[0103]

[0104] 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 two-stage hydrocracking method for producing chemical raw materials from heavy distillate oil, the method comprising: (1) Mixing heavy distillate oil with hydrogen and entering a hydrotreating reaction zone, followed by gas-liquid separation to obtain a gas-phase stream and a liquid-phase stream; Controlling the nitrogen content in the liquid-phase stream in step (1) to be 50 mg / kg to 100 mg / kg; (2) In the presence of hydrogen, the liquid-phase stream obtained in step (1) enters the first hydrocracking reaction zone to selectively crack the n-alkanes in the heavy distillate oil feedstock, obtaining a first hydrocracking product; wherein, in the first hydrocracking product, the mass content of C7 + n-alkanes is not higher than 3.0%; (3) In the presence of hydrogen, the first hydrocracking product enters the second hydrocracking reaction zone. After the second hydrocracking product undergoes gas-liquid separation in a separator, the hydrogen-rich gas obtained is used as recycle hydrogen, and the liquid phase enters a fractionation system for fractionation to obtain gas, light naphtha, heavy naphtha, and tail oil; (4) The tail oil from step (3) is mixed with hydrogen and enters the third hydrocracking reaction zone to obtain a third hydrocracking product containing monocyclic cyclic hydrocarbons; the third hydrocracking product enters a separation and fractionation system to obtain gas, light naphtha, and heavy naphtha; wherein, the reaction pressure in the first hydrocracking reaction zone is 1 to 6 MPa higher than the reaction pressure in the third hydrocracking reaction zone; In step (2), the first hydrocracking reaction zone is filled with a first hydrocracking catalyst; the first hydrocracking catalyst includes an active metal component and a support; the support includes a molecular sieve having selective cracking of normal paraffins, and the molecular sieve is 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; the active metal component includes at least one of Group VIB metals and Group VIII metals; For the first hydrocracking catalyst in step (2), based on the weight of the catalyst, the content of the Group VIB metal in terms of oxide is 5.0% to 15.0%, the content of the Group VIII metal in terms of oxide is 2.0% to 5.0%, and the content of the support is 80.0% to 93.0%; in the support of the first hydrocracking catalyst, based on the weight of the support, the content of the binder is 8% to 60%, and the content of the molecular sieve is 40% to 92%; In step (3), the second hydrocracking reaction zone is filled with a second hydrocracking catalyst; the second hydrocracking catalyst includes a cracking component, a hydrogenation component, and a binder; the cracking component is Y molecular sieve; In the second hydrocracking catalyst in step (3), based on the mass of the catalyst, the content of the hydrogenation component in terms of oxide is 5 wt% to 40 wt%; the content of the cracking component is 10 wt% to 80 wt%; the content of the binder is 5 wt% to 85 wt%; In step (4), the third hydrocracking reaction zone is filled with a third hydrocracking catalyst; the third hydrocracking catalyst includes a cracking component, a hydrogenation component, and a binder; the cracking component is Beta molecular sieve; In the third hydrocracking catalyst in step (4), based on the mass of the catalyst, in terms of oxide, the content of the hydrogenation component is 5 wt% to 40 wt%; the content of the cracking component is 20 wt% to 80 wt%; the content of the binder is 5 wt% to 75 wt%; 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 lower olefins.

2. The method according to claim 1, wherein The nitrogen content in the liquid-phase stream in control step (1) is 60 mg / kg to 80 mg / kg.

3. The method according to claim 1, wherein In the heavy distillate oil in step (1), the mass content of cyclic hydrocarbons is 40% to 90%, where the cyclic hydrocarbons are the sum of naphthenes and aromatics, and the mass content of normal paraffins is 5% to 50%.

4. The method according to claim 1, characterized in that, In the heavy distillate oil in step (1), the mass content of normal paraffins is 10% to 30%.

5. The method according to claim 1, wherein The heavy distillate oil is at least one of coal tar and shale oil.

6. The method according to claim 1, characterized in that The reaction conditions in the hydrofining reaction zone in step (1) are as follows: the reaction pressure is 10.0 - 25.0 MPa; the average reaction temperature is 300 - 450 °C; the liquid hourly space velocity is 1.0 - 15.0 h -1 ; the hydrogen-oil volume ratio is 100:1 - 2500:

1.

7. The method according to claim 1, wherein The reaction conditions in the hydrofining reaction zone in step (1) are as follows: the reaction pressure is 15.0 - 20.0 MPa; the average reaction temperature is 350 - 420 °C; the liquid hourly space velocity is 5.0 - 10.0 h -1 ; the hydrogen-to-oil volume ratio is 400:1 - 2000:

1.

8. The method according to claim 1, wherein Control C7 in step (2) + The mass content of the normal paraffin is 1.0% to 3.0%.

9. The method according to claim 1, wherein In the first hydrocracking product of step (2), the ratio of the mass of C6-C8 single-ring cyclic hydrocarbons to the total mass of cyclic hydrocarbons in the raw material is 0.15 to 0.

35.

10. The method according to claim 1, wherein In the first hydrocracking product of step (2), the ratio of the mass of C6-C8 single-ring cyclic hydrocarbons to the total mass of cyclic hydrocarbons in the raw material is 0.29 to 0.

34.

11. The method according to claim 1, wherein In the first hydrocracking catalyst in step (2), the molecular sieve is ZSM-5 molecular sieve.

12. The method according to claim 1, characterized in that 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.

13. The method according to claim 1, wherein The reaction conditions in the first hydrocracking reaction zone in step (2) are as follows: the reaction pressure is 10.0 - 25.0 MPa; the average reaction temperature is 300 - 450 °C; the liquid hourly space velocity is 1.0 - 15.0 h -1 ; the hydrogen-oil volume ratio is 100:1 - 2500:

1.

14. The method according to claim 1, characterized in that, The reaction conditions in the first hydrocracking reaction zone in step (2) are as follows: the reaction pressure is 15.0 - 20.0 MPa; the average reaction temperature is 350 - 420 °C; the liquid hourly space velocity is 5.0 - 10.0 h -1 ; the hydrogen-oil volume ratio is 400:1 - 2000:

1.

15. The method according to claim 1, wherein In the second hydrocracking catalyst in step (3), based on the mass of the catalyst, the content of the hydrogenation component in terms of oxide is 10 wt% to 30 wt%; the content of the cracking component is 20 wt% to 60 wt%; the content of the binder is 10 wt% to 50 wt%.

16. The method according to claim 1, characterized in that The reaction conditions in the second hydrocracking reaction zone in step (3) are as follows: the reaction pressure is 10.0 - 25.0 MPa; the average reaction temperature is 300 - 450 °C; the liquid hourly space velocity is 1.0 - 15.0 h -1 ; the hydrogen-to-oil volume ratio is 100:1 - 2500:

1.

17. The method according to claim 1, wherein The reaction conditions in the second hydrocracking reaction zone in step (3) are as follows: the reaction pressure is 10.0~20.0 MPa; the average reaction temperature is 350~420 °C; the liquid hourly space velocity is 5.0~10.0 h -1 ; the hydrogen-oil volume ratio is 400:1~2000:

1.

18. The method according to claim 1, characterized in that, In the third hydrocracking catalyst in step (4), based on the mass of the catalyst, in terms of oxide, the content of the hydrogenation component is 10 wt% to 20 wt%; the content of the cracking component is 30 wt% to 70 wt%; the content of the binder is 10 wt% to 50 wt%.

19. The method according to claim 1, wherein In step (4), the reaction conditions in the third hydrocracking reaction zone are as follows: the reaction pressure is 10.0 - 20.0 MPa; the average reaction temperature is 300 - 450 °C; the liquid hourly space velocity is 1.0 - 15.0 h -1 ; the hydrogen-to-oil volume ratio is 100:1 - 2500:

1.

20. The method according to claim 1, characterized in that In step (4), the reaction conditions in the third hydrocracking reaction zone are as follows: the reaction pressure is 10.0 - 16.0 MPa; the average reaction temperature is 350 - 420 °C; the liquid hourly space velocity is 5.0 - 10.0 h -1 ; the hydrogen-oil volume ratio is 400:1 - 2000:

1.

21. The method according to claim 1, wherein The hydrofining reaction zone, the first hydrocracking reaction zone and the second hydrocracking reaction zone adopt the same pressure.

22. The method according to claim 1, wherein The reaction pressure of the first hydrocracking reaction zone is 2 to 5 MPa higher than the reaction pressure of the third hydrocracking reaction zone.

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