A method for producing chemical raw materials by two-stage hydrocracking of wax oil

Abstract

The present invention discloses a method for producing chemical raw materials by two-stage hydrocracking of wax oil. The method comprises: hydrocracking the wax oil raw material in the presence of hydrogen to first obtain a first hydrocracking product with a low polycyclic alkane content; then selectively cracking the normal paraffins in the first hydrocracking product to obtain a second hydrocracking product; separating and fractionating the second hydrocracking product to obtain gas, light naphtha, heavy naphtha, and tail oil; finally, mixing the tail oil with hydrogen and hydrocracking it to convert it into a third hydrocracking product containing monocyclic cyclic hydrocarbons; separating and fractionating the third hydrocracking product to obtain a gas fraction, light naphtha, and heavy naphtha; wherein the reaction pressure of the first hydrocracking reaction zone is 2.0 to 5.0 MPa higher than the reaction pressure of the third hydrocracking reaction zone. This method can significantly improve the yield and quality of chemical raw materials when using wax oil as a raw material for two-stage hydrocracking production of chemical raw materials.

Description

Technical Field

[0001] The invention belongs to the field of wax oil hydrocracking, and specifically relates to a method for producing chemical raw materials through two-stage hydrocracking of wax oil. Background Art

[0002] Using light hydrocarbons as feedstock for steam cracking to ethylene plants offers significant advantages over liquid feedstocks, including high hydrogen yields, low feedstock costs, high ethylene selectivity, and low yields of difficult-to-process, low-value-added products such as naphtha and ethylene tar. Therefore, further optimizing the feedstock mix, exploring the potential for integrated efficiency gains, and increasing the proportion of light and low-grade feedstocks in ethylene cracking feeds remain key tasks for steam cracking to reduce olefin production costs.

[0003] 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 produce a first hydrocracked product stream; b) separating the first hydrocracked product stream to provide at least one light hydrocarbon stream comprising at least C2 and C3 hydrocarbons, an intermediate hydrocarbon stream consisting of C4 and / or C5 hydrocarbons, and a heavy hydrocarbon stream comprising at least C6+ hydrocarbons, and c) subjecting the heavy hydrocarbon stream to a second hydrocracking in the presence of a second hydrocracking catalyst to produce a second hydrocracked product stream comprising BTX, wherein the second hydrocracking is more severe than the first hydrocracking, d) wherein, in the presence of a C4 hydrocracking catalyst, at least a portion of the intermediate hydrocarbon stream is subjected to C4 hydrocracking to produce a C4 hydrocracking product stream, and the C4 hydrocracking is optimized for converting C4 hydrocarbons into C3 hydrocarbons.

[0004] CN201480037272.7 discloses a method for producing light olefin hydrocarbon compounds from hydrocarbon feedstocks, comprising the following steps: (a) feeding the hydrocarbon feedstock to a reaction zone for ring opening; (b) separating the reaction product produced by the reaction zone into an overhead stream and a side stream; (c) feeding the side stream from (b) to a gasoline hydrocracker (GHC) unit; (d) separating the reaction product of the GHC of step (c) into an overhead stream comprising hydrogen, methane, ethane and liquefied petroleum gas and a stream comprising aromatic hydrocarbon compounds and a small amount of hydrogen and non-aromatic hydrocarbon compounds; (e) feeding the overhead stream from the gasoline hydrocracker (GHC) unit to a steam cracker unit.

[0005] In summary, existing technologies for converting petroleum fractions fail to efficiently and selectively enrich paraffins (including long side chains on cyclic hydrocarbons) into ethylene feedstocks and cyclic hydrocarbons into reforming feedstocks. Therefore, to address these issues, developing a hydrocracking process suitable for producing high-quality chemical feedstocks from wax oils is of great significance. Summary of the Invention

[0006] In response to the problems of the prior art, the present invention aims to provide a method for producing chemical raw materials by two-stage hydrocracking of wax oil. This method uses wax oil as a raw material to produce chemical raw materials by hydrocracking, which can significantly improve the yield and quality of chemical raw materials (i.e., ethylene raw materials and reforming raw materials).

[0007] The present invention provides a method for producing chemical raw materials by two-stage hydrocracking of wax oil, the method comprising:

[0008] (1) In the presence of hydrogen, the wax oil feedstock enters the first hydrocracking reaction zone to obtain a first hydrocracking product with a low polycycloalkane content;

[0009] (2) In the presence of hydrogen, the first hydrocracking product enters the second hydrocracking reaction zone, and the normal alkanes in the first hydrocracking product are selectively cracked to obtain a second hydrocracking product; wherein, in the second hydrocracking product, C7 + The mass content of normal alkanes is controlled below 2.0%;

[0010] (3) The second hydrocracking product is separated into gas and liquid by a separator to obtain hydrogen-rich gas which is used as circulating hydrogen, and the liquid phase enters the fractionation system for fractionation to obtain gas, light naphtha, heavy naphtha and tail oil;

[0011] (4) The tail oil in step (3) is mixed with hydrogen and enters a third hydrocracking reaction zone to obtain a third hydrocracking product containing monocyclic hydrocarbons. The third hydrocracking product enters a separation and fractionation system to obtain gas, light naphtha, and heavy naphtha;

[0012] The reaction pressure of the first hydrocracking reaction zone is 2.0 to 5.0 MPa higher than the reaction pressure of the third hydrocracking reaction zone.

[0013] According to the present invention, the content of polycycloalkanes in the first hydrocracking product of step (1) is controlled at 2% to 8%, preferably 3% to 6%; the polycycloalkanes are tricyclic or higher-ring cyclic hydrocarbons, preferably 3-6-ring cyclic hydrocarbons.

[0014] According to the present invention, preferably, the reaction pressure of the first hydrocracking reaction zone in step (1) is 2.0 to 3.0 MPa higher than the reaction pressure of the third hydrocracking reaction zone in step (3).

[0015] According to the present invention, the chemical raw materials primarily include ethane, propane, butane, and light naphtha, and may also include heavy naphtha. Heavy naphtha is used as a reforming feedstock to produce BTX. Ethane, propane, butane, and light naphtha are used as ethylene feedstocks to produce light olefins, such as steam cracking feedstocks to produce ethylene. Propane and butane can also be directly dehydrogenated to produce propylene and butene. Light olefins refer to olefins with a carbon content of four or less, particularly ethylene, propylene, and butadiene.

[0016] According to the present invention, the obtained chemical raw materials have a normal alkanes content of 50% to 70%, preferably 54% to 70%, based on the total mass of ethane, propane, butane and light naphtha. After entering the steam cracking process to produce an ethylene unit, the triene (including ethylene, propylene and butadiene) yield reaches over 50%, and can further reach 50% to 60%, based on the total mass of ethane, propane, butane and light naphtha.

[0017] According to the present invention, in the wax oil raw material described in step (1), the mass content of cyclic hydrocarbons is 50% to 90%, wherein cyclic hydrocarbons are the sum of cycloalkanes and aromatic hydrocarbons. The wax oil raw material can be a wax oil fraction with a high content of normal alkanes, such as straight-run wax oil and coker wax oil, and the mass content of normal alkanes is 5% to 40%, preferably 10% to 30%; preferably, the wax oil is a vacuum wax oil raw material, and the vacuum wax oil is generally vacuum gas oil (VGO); the dry point of the wax oil does not exceed 600°C, preferably 450 to 600°C, and the density is not more than 0.95g / cm 3 Preferably 0.85 to 0.95 g / cm 3 The nitrogen content does not exceed 3000μg / g, preferably 500~3000μg / g, the C7 insoluble matter is not more than 300μg / g, preferably 0.1~300μg / g, and the sum of Fe, Ca, Ni and V contents does not exceed 3.0μg / g, preferably 0.5μg / g~3.0μg / g.

[0018] According to the present invention, the wax oil may contain impurities such as sulfur and nitrogen. If necessary, a hydrorefining catalyst may be installed upstream of the first hydrocracking catalyst to remove impurities such as sulfur and nitrogen. The nitrogen content in the reactant stream in contact with the first hydrocracking catalyst is preferably less than 50 mg / kg, more preferably less than 20 mg / kg.

[0019] According to the present invention, in step (1), the first hydrocracking reaction zone is loaded with a first hydrocracking catalyst, wherein the first hydrocracking catalyst can be one or more catalysts. The first hydrocracking catalyst has the function of ring-opening cracking of polycyclic cyclic hydrocarbons. The first hydrocracking catalyst comprises a cracking component, a hydrogenation component and a binder. The first hydrocracking catalyst can be a commercially available product or prepared according to existing technology. The hydrogenation component is at least one of the metal, metal oxide, and metal sulfide of the active metal component; the active metal component comprises a VIB and / or VIII group metal; the active metal component is more preferably at least one of iron, chromium, molybdenum, tungsten, cobalt, and nickel. In the first hydrocracking catalyst, the binder is alumina and / or silica; the cracking component comprises an acidic molecular sieve, preferably at least one of Beta molecular sieve and Y molecular sieve, more preferably Y molecular sieve.

[0020] According to the present invention, in step (1), the first hydrocracking catalyst has a hydrogenation component content of 5 wt% to 40 wt%, preferably 10 wt% to 30 wt%, calculated as oxide, based on the weight of the first hydrocracking catalyst; a cracking component content of 10 wt% to 50 wt%, preferably 20 wt% to 40 wt%; and a binder content of 10 wt% to 85 wt%, preferably 30 wt% to 50 wt%.

[0021] According to the present invention, the preparation method of the first hydrocracking catalyst in step (1) can be prepared according to conventional methods in the art. The preparation method includes the preparation of a carrier and the loading of the hydrogenation component, wherein the carrier preparation process is as follows: the cracking component and the binder are mechanically mixed, formed, and then dried and calcined to form 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.

[0022] According to the present invention, in step (1), the reaction conditions of the first hydrocracking reaction zone are as follows: the reaction pressure is 14 to 20 MPa.

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

[0024] According to the present invention, preferably, in step (2), C7 + The mass content of normal alkanes is controlled at 0.2% to 1.0%.

[0025] According to the present invention, in step (2), the second hydrocracking reaction zone is loaded with a second hydrocracking catalyst, which can be one or more catalysts. In step (2), the second hydrocracking catalyst includes an active metal component and a carrier; the carrier includes a molecular sieve having the ability to selectively crack normal alkanes, preferably one or more selected from 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 molecular sieve is 20 to 60. The carrier may further include a binder. Preferably, the binder is alumina. The active metal component includes at least one of a metal from Group VIB and a metal from Group VIII, preferably molybdenum and / or tungsten from Group VIB, and preferably cobalt and / or nickel from Group VIII.

[0026] According to the present invention, in step (2), preferably, the second hydrocracking catalyst has, based on the weight of the catalyst, a content of Group VIB metal (calculated as oxide) of 5.0% to 15.0%, a content of Group VIII metal (calculated as oxide) of 2.0% to 5.0%, and a content of the carrier of 80.0% to 93.0%.

[0027] According to the present invention, in step (2), preferably, in the carrier of the second hydrocracking catalyst, the content of the binder is 8% to 60%, and the content of the molecular sieve is 40% to 92%, based on the weight of the carrier.

[0028] According to the present invention, in step (2), the specific surface area of the second hydrocracking catalyst is 200 to 400 m 2 / g, pore volume is 0.25~0.45cm 3 / g.

[0029] According to the present invention, the preparation method of the second hydrocracking catalyst in step (2) can be prepared according to conventional methods in the art. The preparation method includes preparing a carrier and loading the active metal component, wherein the carrier preparation process is as follows: mechanically mixing the shape-selective cracking molecular sieve and the binder, forming, and then drying and calcining to form a catalyst carrier. The drying and calcining of the carrier can adopt conventional conditions. The drying conditions are: drying at 100°C to 150°C for 1 to 12 hours. The calcining conditions are: calcining at 450°C to 550°C for 2.5 to 6.0 hours.

[0030] According to the present invention, in step (2), in the preparation method of the second hydrocracking catalyst, the method for loading the active metal component is a conventional method, such as a kneading method, an impregnation method, etc., preferably an impregnation method. The impregnation method can be a saturation impregnation method, an excess impregnation method, or a complex impregnation method, that is, the catalyst support is impregnated with a solution containing the desired active component, and then dried and calcined to obtain the second 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.

[0031] According to the present invention, the reaction conditions of the second hydrocracking reaction zone in step (2) are as follows: the reaction pressure is 14 to 20 MPa.

[0032] According to the present invention, the reaction pressure of the second hydrocracking reaction zone in step (2) is the same as the reaction pressure of the first hydrocracking reaction zone.

[0033] According to the present invention, the reaction conditions of the second hydrocracking reaction in step (2) are as follows: the average reaction temperature is 250-450°C, preferably 300-400°C; the liquid hourly volume space velocity is 0.1-15.0h -1 , preferably 1.0~5.0h -1 ; The volume ratio of hydrogen to oil is 100:1 to 2500:1, preferably 400:1 to 2000:1.

[0034] According to the present invention, the ratio of the mass of C6-C8 monocyclic cyclic hydrocarbons in the third hydrocracking product of step (4) to the mass of the total cyclic hydrocarbons in the feedstock is 0.10-0.30, preferably 0.22-0.28. The feedstock is wax oil.

[0035] According to the present invention, the third hydrocracking reaction zone in step (4) is loaded with a third hydrocracking catalyst, which may be one or more catalysts. The third hydrocracking catalyst in step (4) has the function of selectively cracking the side chains of isomeric hydrocarbons or cyclic hydrocarbons and retaining monocyclic cyclic hydrocarbons. The third hydrocracking catalyst comprises a cracking component, a hydrogenation component and a binder. The third hydrocracking catalyst may be a commercially available product or prepared according to existing technology. The hydrogenation component is at least one of the metal, metal oxide, and metal sulfide of the active metal component; the active metal component comprises a VIB and / or VIII group metal; the active metal component is more preferably at least one of iron, chromium, molybdenum, tungsten, cobalt, and nickel. In the third hydrocracking catalyst, the binder is alumina and / or silica; the cracking component comprises an acidic molecular sieve, preferably at least one of a Beta molecular sieve and a Y molecular sieve, and more preferably a Beta molecular sieve.

[0036] According to the present invention, the third hydrocracking catalyst in step (4) has a hydrogenation component content of 5 wt% to 40 wt%, preferably 10 wt% to 20 wt%, calculated as oxide, based on the weight of the third hydrocracking catalyst; a cracking component content of 20 wt% to 80 wt%, preferably 30 wt% to 70 wt%; and a binder content of 5 wt% to 75 wt%, preferably 10 wt% to 50 wt%.

[0037] According to the present invention, the preparation method of the third hydrocracking catalyst in step (4) can be prepared according to conventional methods in the art. The preparation method includes the preparation of a carrier and the loading of the 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 form 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.

[0038] According to the present invention, in step (4), in the preparation method of the third hydrocracking catalyst, the method for loading the hydrogenation component is a conventional method, such as a kneading method, an impregnation method, etc., preferably an impregnation method. The impregnation method can be a saturation impregnation method, an excess impregnation method, or a complex impregnation method, that is, the catalyst support is impregnated with a solution containing the desired hydrogenation component, and then dried and calcined to obtain the third 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.

[0039] According to the present invention, the reaction conditions of the third hydrocracking reaction zone in step (4) are as follows: the reaction pressure is 10 to 15 MPa.

[0040] According to the present invention, the reaction conditions of the third hydrocracking reaction in step (4) are as follows: the average reaction temperature is 250-450°C, preferably 300-400°C; the liquid hourly volume space velocity is 0.1-15.0h -1 , preferably 1.0~5.0h -1 ; The volume ratio of hydrogen to oil is 100:1 to 2500:1, preferably 400:1 to 2000:1.

[0041] 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 performed by loading a hydrofining catalyst at the bottom of the third hydrocracking reaction zone, or by entering a separate hydrofining reaction zone.

[0042] According to the present invention, the separation and fractionation of the second hydrocracking product of step (2) and the third hydrocracking product of step (4) preferably share a set of separation and fractionation systems.

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

[0044] (1) In the hydrocracking method for producing chemical raw materials from wax oil of the present invention, the wax oil raw material and hydrogen enter the first hydrocracking reaction zone, selectively cracking polycyclic hydrocarbons to convert more of them into monocyclic hydrocarbons while retaining the side chains on the cyclic hydrocarbons; the effluent from the first hydrocracking reaction enters the second hydrocracking reaction zone, which mainly selectively cracks the normal alkanes and the long straight-chain isoalkanes and cycloalkanes in the raw material to produce small molecular normal alkanes, so that the C7 + The content of normal alkanes is below 2%. The effluent from the second hydrocracking reaction enters the third hydrocracking reaction zone, which mainly breaks the side chains of each hydrocarbon to generate small-molecule hydrocarbons. In this way, a large amount of chain alkanes in the feedstock can be converted into gas and light naphtha components, that is, they are enriched in the ethylene feedstock, while the monocyclic cyclic hydrocarbons are retained in the heavy naphtha fraction, that is, they are enriched in the reforming feedstock. Through simple distillation, efficient separation of chain alkanes and cyclic hydrocarbons can be achieved, thereby increasing the production of high-quality ethylene cracking feed and improving the quality of heavy naphtha as catalytic reforming feed.

[0045] Petroleum hydrocarbons are complex, primarily comprising paraffins, cycloalkanes, and aromatics. High-quality ethylene feedstocks are small-molecule normal alkanes, while reforming feedstocks are monocyclic cycloalkanes and aromatics. The inventors discovered through research that the technical solution of the present invention can maximize the retention of monocyclic cyclic hydrocarbons and produce small-molecule normal alkanes with high selectivity, thereby achieving efficient enrichment of small-molecule normal alkanes in light olefin feedstocks. Simultaneously, it maximizes the retention of monocyclic cyclic hydrocarbons in heavy naphtha, thereby achieving efficient enrichment of high-quality reforming feedstocks. This significantly improves the yield and quality of chemical feedstocks (i.e., ethylene feedstock and reforming feedstock), thereby completing the present invention.

[0046] (2) The heavy naphtha obtained by the method of the present invention has a high content of monocyclic cyclic hydrocarbons. When used as feed for a catalytic reforming unit, the cyclization and dehydrogenation units of the paraffins in the catalytic reforming unit can be eliminated, thereby significantly reducing the investment and energy consumption of the catalytic reforming unit. At the same time, since the hydrocracking reaction follows the positive carbon ion reaction mechanism, the cyclic hydrocarbons above C9 can be selectively subjected to side chain scission reactions, 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 significantly increased.

[0047] (3) The present invention selectively converts the chain alkanes in the wax 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

[0048] Figure 1 Schematic diagram of the process flow of Examples 1 to 4 of the present invention;

[0049] Description of main reference numerals:

[0050] 1-wax oil, 2-hydrogen, 3-first hydrocracking reaction zone, 4-first hydrocracking reaction effluent, 5-second hydrocracking reaction zone, 6-second hydrocracking reaction effluent, 7-separator, 8-gas stream hydrogen-rich gas, 9-liquid stream, 10-fractionation tower, 11-gas fraction, 12-light naphtha, 13-heavy naphtha, 14-tail oil, 15-third hydrocracking reaction zone, 16-third hydrocracking reaction zone effluent. DETAILED DESCRIPTION

[0051] The effects and benefits of the present invention are further illustrated below by way of examples, but the following examples do not constitute a limitation to the method of the present invention.

[0052] Unless otherwise specified, % in the present invention refers to mass fraction.

[0053] 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.

[0054] The method of the present invention, such as Figure 1 As shown, the process includes: diesel 1 and hydrogen 2 are mixed and enter the first hydrocracking reaction zone 3 for hydrocracking reaction, the first hydrocracking reaction effluent 4 enters the second hydrocracking reaction zone 5, the second hydrocracking reaction effluent 6 enters the separator 7, the separated gaseous phase stream hydrogen-rich gas 8 is recycled, the liquid phase stream 9 enters the fractionation tower 10, and the fractionation obtains the gas fraction 11, light naphtha 12, heavy naphtha 13 and tail oil 14, the tail oil 14 is mixed with hydrogen 2 and enters the third hydrocracking reaction zone 15, and the third hydrocracking reaction effluent 16 enters the separator 7 for separation and fractionation.

[0055] In the present invention, the first hydrocracking catalyst in each example is represented by Cat-A. The physicochemical properties of the catalyst are shown in Table 2. The first hydrocracking catalyst in each example is prepared by a conventional active metal saturation impregnation method. The properties of the Y molecular sieve used in the first hydrocracking catalyst Cat-A are as follows: SiO2 / Al2O3 molar ratio is 15, specific surface area is 400m 2 / g, pore volume is 0.30cm 3 The physicochemical properties of the obtained catalyst are shown in Table 2.

[0056] 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, and Cat-B3. The second hydrocracking catalyst is prepared by a conventional active metal saturation impregnation method. The physicochemical properties of the obtained catalyst are shown in Table 1.

[0057] In the present invention, the third hydrocracking catalyst in each example is represented by Cat-C. The physicochemical properties of the catalyst are shown in Table 2. The third hydrocracking catalyst in each example is prepared by a conventional active metal saturation impregnation method. The properties of the Beta molecular sieve used in the third hydrocracking catalyst Cat-C are as follows: SiO2 / Al2O3 molar ratio is 30, specific surface area is 350m 2 / g, pore volume is 0.32cm 3 / g, and the physicochemical properties of the obtained catalyst are shown in Table 2.

[0058] In the present invention, the raw oil in each example adopts wax oil raw material, and its main properties are shown in Table 3.

[0059] In the present invention, the nitrogen content in the reactant stream in contact with the first hydrocracking catalyst in each example is less than 20 mg / kg.

[0060] In the present invention, the ethylene raw materials in each example refer to the ethane, propane, butane and light naphtha obtained in step (2). Ethane, propane, butane and light naphtha can be directly used as raw materials for steam cracking to produce ethylene.

[0061] In the present invention, the distillation range of light naphtha is the liquid component less than 60°C, and the distillation range of heavy naphtha is 60-175°C.

[0062] In the present invention, the yield of ethylene feedstock refers to the mass ratio of ethane, propane, butane and light naphtha in the hydrocracking product to the fresh hydrocracking feedstock, and the yield of heavy naphtha refers to the mass ratio of heavy naphtha in the hydrocracking product to the fresh hydrocracking feedstock.

[0063] Examples 1 to 4

[0064] The method in this example is as follows Figure 1 Process, including:

[0065] (1) The feedstock oil is mixed with hydrogen and sequentially enters the first hydrocracking reaction zone, the second hydrocracking reaction zone and the third hydrocracking reaction zone; the first hydrocracking reaction zone is filled with the first hydrocracking catalyst; the second hydrocracking reaction zone is filled with the second hydrocracking catalyst; in step (1), the C7 + n-Alkanes content.

[0066] (2) The hydrogen-rich gas obtained after separation and fractionation of the second hydrocracking product is used as circulating hydrogen, and the liquid phase enters the fractionation tower for fractionation to obtain gas, light naphtha, heavy naphtha and tail oil;

[0067] (3) The tail oil of step (2) enters the third hydrocracking reaction zone, and the third hydrocracking reaction zone is loaded with a third hydrocracking catalyst; the third hydrocracking reaction effluent and the second hydrocracking reaction effluent share a set of separation and fractionation systems.

[0068] The process conditions and hydrogenation effects of each case are shown in Table 4.

[0069] Comparative Example 1

[0070] The difference from Example 1 is that the feedstock enters the third hydrocracking zone directly after passing through the first hydrocracking zone, without a second hydrocracking zone. The first hydrocracking zone is loaded with Cat-A catalyst, and the third hydrocracking zone is loaded with Cat-C catalyst.

[0071] The process conditions and hydrogenation effects in this example are shown in Table 4.

[0072] Comparative Example 2

[0073] The difference from Example 1 is that in step (1), the C7 + The normal alkane content is 3%.

[0074] The process conditions and hydrogenation effects in this example are shown in Table 4.

[0075] Comparative Example 3

[0076] The difference from Example 1 is that the first hydrocracking reaction zone is filled with catalyst Cat-C, and the third hydrocracking reaction zone is filled with catalyst Cat-A.

[0077] The process conditions and hydrogenation effects in this example are shown in Table 4.

[0078] Comparative Example 4

[0079] The difference from Example 1 is that the reaction pressure of the first hydrocracking reaction zone is the same as the reaction pressure of the third hydrocracking reaction zone.

[0080] The process conditions and hydrogenation effects in this example are shown in Table 4.

[0081] Table 1 Physicochemical properties of the second hydrocracking catalyst

[0082]

[0083]

[0084] Table 2 Physicochemical properties of the first hydrocracking catalyst and the third hydrocracking catalyst

[0085] Catalyst properties Cat-A Cat-C <![CDATA[Pore volume, cm 3 / g]]> 0.35 0.35 <![CDATA[Specific surface area, m 2 / g]]> 300 300 Catalyst composition and content Beta, wt% - 50 Y, wt% 30 - <![CDATA[MoO3,wt%]]> 25 10 NiO, wt% 5 5 Alumina, wt% 40 35

[0086] Table 3 Main properties of crude oil

[0087] Raw oil name wax oil <![CDATA[Density (20 °C) / g / cm -3 > 0.9004 Dry point, ℃ 517 Distillation range / ℃(ASTM D86) IBP / 10% 293 / 353 30％ / 50％ 379 / 400 70％ / 90％ 429 / 476 95% / EBP 497 / 517 Normal alkanes, wt% 11 Cyclic hydrocarbons, wt% 78 <![CDATA[N / μg·g -1 ]]> 926 <![CDATA[C7 insolubles, μg / g]]> <1 Fe+Ca+Ni+V,μg / g <1

[0088] Table 4 Hydrogenation effect

[0089]

[0090]

[0091] Table 4

[0092]

[0093]

[0094] The above describes in detail the specific embodiments of the present invention, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as the contents disclosed by the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for producing chemical raw materials by two-stage hydrocracking of wax oil, the method comprising: (1) In the presence of hydrogen, the wax oil feedstock enters the first hydrocracking reaction zone to obtain a first hydrocracking product with a low polycycloalkane content; (2) In the presence of hydrogen, the first hydrocracking product enters the second hydrocracking reaction zone, selectively cracking the normal alkanes in the first hydrocracking product to obtain the second hydrocracking product; wherein, in the second hydrocracking product, C7 + The mass content of normal alkanes is controlled below 2.0%; (3) The second hydrocracking product is separated into gas and liquid by a separator, and the hydrogen-rich gas obtained is used as circulating hydrogen. The liquid phase enters the fractionation system for fractionation to obtain gas, light naphtha, heavy naphtha and tail oil; (4) The tail oil in step (3) is mixed with hydrogen and enters the third hydrocracking reaction zone to obtain a third hydrocracking product containing monocyclic hydrocarbons. The third hydrocracking product enters the separation and fractionation system to obtain gas, light naphtha, and heavy naphtha; The reaction pressure of the first hydrocracking reaction zone is 2.0-5.0 MPa higher than the reaction pressure of the third hydrocracking reaction zone; In the first hydrocracking product of step (1), the polycycloalkane content is controlled at 2% to 8%; In step (1), the first hydrocracking reaction zone is filled with a first hydrocracking catalyst; the first hydrocracking catalyst comprises a cracking component, a hydrogenation component and a binder, and the cracking component is a Y molecular sieve; In step (1), the first hydrocracking catalyst has a hydrogenation component content of 5 wt% to 40 wt% in terms of oxides, a cracking component content of 10 wt% to 50 wt% and a binder content of 10 wt% to 85 wt% based on the weight of the first hydrocracking catalyst. In step (2), the second hydrocracking reaction zone is loaded with a second hydrocracking catalyst; the second hydrocracking catalyst comprises an active metal component and a carrier; the carrier comprises a molecular sieve having the ability to selectively crack normal alkanes, the molecular sieve being 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 comprises at least one of a Group VIB metal and a Group VIII metal; In step (2), in the second hydrocracking catalyst, 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 carrier is 80.0% to 93.0%; in the carrier of the second 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%; The third hydrocracking reaction zone in step (4) is loaded with a third hydrocracking catalyst; the third hydrocracking catalyst comprises a cracking component, a hydrogenation component and a binder, and the cracking component is a Beta molecular sieve; The third hydrocracking catalyst has a hydrogenation component content of 5 wt% to 40 wt% in terms of oxides, a cracking component content of 20 wt% to 80 wt% and a binder content of 5 wt% to 75 wt% based on the weight of the third hydrocracking catalyst. The chemical raw materials include ethane, propane, butane, light naphtha and heavy naphtha, wherein heavy naphtha is used as a reforming raw material to produce BTX, and ethane, propane, butane and light naphtha are used as raw materials to produce low-carbon olefins.

2. The method according to claim 1, characterized in that The reaction pressure of the first hydrocracking reaction zone in step (1) is 2.0 to 3.0 MPa higher than the reaction pressure of the third hydrocracking reaction zone in step (3).

3. The method according to claim 1, characterized in that In the first hydrocracking product of step (1), the polycycloalkanes content is controlled at 3% to 6%.

4. The method according to claim 1, characterized in that The mass content of cyclic hydrocarbons in the wax oil raw material described in step (1) is 50% to 90%; and / or the mass content of normal alkanes in the wax oil raw material is 5% to 40%.

5. The method according to claim 1, characterized in that: The mass content of normal alkanes in the wax oil raw material is 10% to 30%.

6. The method according to claim 1, characterized in that The first hydrocracking catalyst has the function of ring-opening cracking of polycyclic cyclic hydrocarbons.

7. The method according to claim 1, characterized in that: In step (1), the first hydrocracking catalyst has a hydrogenation component content of 10 wt% to 30 wt% in terms of oxides, a cracking component content of 20 wt% to 40 wt% and a binder content of 30 wt% to 50 wt%, based on the weight of the first hydrocracking catalyst.

8. The method according to claim 1, characterized in that: In step (1), the reaction pressure of the first hydrocracking reaction zone is 14-20 MPa.

9. The method according to claim 1, characterized in that: The reaction conditions of the first hydrocracking reaction zone in step (1) are as follows: average reaction temperature of 250-450°C; liquid hourly volume space velocity of 0.1-15.0h -1 ;The volume ratio of hydrogen to oil is 100:1~2500:

1.

10. The method according to claim 1, characterized in that: The reaction conditions of the first hydrocracking reaction zone in step (1) are as follows: average reaction temperature of 300-400°C; liquid hourly volume space velocity of 1.0-5.0h -1 ;The volume ratio of hydrogen to oil is 400:1~2000:

1.

11. The method according to claim 1, characterized in that: C7 in step (2) + The mass content of normal alkanes is controlled at 0.2%~1%.

12. The method according to claim 1, characterized in that: In the second hydrocracking catalyst in step (2), the molecular sieve is ZSM-5 molecular sieve.

13. The method according to claim 1, characterized in that: The reaction pressure of the second hydrocracking reaction zone in step (2) is 14-20 MPa.

14. The method according to claim 1 or 10, characterized in that: The reaction conditions of the second hydrocracking reaction zone in step (2) are as follows: average reaction temperature of 250-450°C; liquid hourly volume space velocity of 0.1-15.0h -1 ;The volume ratio of hydrogen to oil is 100:1~2500:

1.

15. The method according to claim 1 or 10, characterized in that: The reaction conditions of the second hydrocracking reaction zone in step (2) are as follows: average reaction temperature of 300-400°C; liquid hourly volume space velocity of 1.0-5.0h -1 ;The volume ratio of hydrogen to oil is 400:1~2000:

1.

16. The method according to claim 1, wherein: In the third hydrocracking product of step (4), the mass ratio of C6-C8 monocyclic cyclic hydrocarbons to the mass ratio of the total cyclic hydrocarbons in the feedstock is 0.10-0.

30.

17. The method according to claim 1, characterized in that: In the third hydrocracking product of step (4), the mass ratio of C6-C8 monocyclic cyclic hydrocarbons to the mass ratio of total cyclic hydrocarbons in the feedstock is 0.22-0.

28.

18. The method according to claim 1, wherein: The third hydrocracking catalyst has the function of selectively cracking the side chains of isomeric hydrocarbons or cyclic hydrocarbons and retaining monocyclic cyclic hydrocarbons.

19. The method according to claim 1, wherein: The third hydrocracking catalyst has, based on the weight of the third hydrocracking catalyst, a hydrogenation component content in terms of oxides of 10 wt% to 20 wt%; a cracking component content of 30 wt% to 70 wt%; and a binder content of 10 wt% to 50 wt%.

20. The method according to claim 1, wherein: The reaction pressure of the third hydrocracking reaction zone in step (4) is 10-15 MPa.

21. The method according to claim 1, wherein: The reaction conditions of the third hydrocracking reaction zone in step (4) are as follows: average reaction temperature of 250-450°C; liquid hourly volume space velocity of 0.1-15.0h -1 ;The volume ratio of hydrogen to oil is 100:1~2500:

1.

22. The method according to claim 1, wherein: The reaction conditions of the third hydrocracking reaction zone in step (4) are as follows: average reaction temperature of 300-400°C; liquid hourly volume space velocity of 1.0-5.0h -1 ;The volume ratio of hydrogen to oil is 400:1~2000:1.

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