A two-stage hydrocracking process and system for producing reforming raw materials

Abstract

The present invention discloses a two-stage hydrocracking process and system for producing reforming raw materials, the process comprising the following steps: (1) the raw oil and hydrogen are mixed and then enter a first hydrocracking reaction zone, where they are contacted with a hydrofining catalyst and a hydrocracking catalyst for reaction, and a first hydrocracking product oil is obtained after the reaction; (2) the first hydrocracking product oil obtained in step (1) enters a separation unit for separation to obtain gas products, light naphtha, heavy naphtha, light circulating tail oil, and heavy circulating tail oil; (3) the light circulating tail oil and heavy circulating tail oil obtained in step (2) enter a second hydrocracking reaction zone for reaction, and the second hydrocracking product oil after the reaction is circulated for treatment. A hydrocracking system for producing reforming raw materials is provided, comprising a first hydrocracking reaction zone, a separation unit, and a second hydrocracking reaction zone connected in sequence. The heavy naphtha selectivity of the device is improved, and the problem that the two-stage full-cycle hydrocracking process easily leads to the accumulation of polycyclic aromatic hydrocarbons is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of petrochemical industry, and relates to a hydrocracking process and system, in particular to a two-stage full-cycle hydrocracking process and system with the main purpose of producing reforming raw materials. Background Art

[0002] In recent years, the domestic refining and chemical market has undergone tremendous changes, showing an overall trend of product structure adjustment and large-scale equipment. In terms of product structure adjustment, the market demand for conventional fuels such as diesel has dropped significantly, while the demand for chemical raw materials such as benzene, toluene, and xylene has risen against the trend. Catalytic reforming units have become the most economically valuable units for major refining and chemical companies. Hydrocracking units have become key units for increasing the production of reforming raw materials in major refineries due to their inherent advantages in adjusting product structure. At the same time, in order to cooperate with the large-scale trend of units, the two-stage full-cycle hydrocracking process has attracted widespread attention. This process has a large raw material processing volume and can convert the maximum amount of wax oil raw materials into heavy naphtha fractions that can be used as reforming raw materials. However, the two-stage full-cycle hydrocracking process of wax oil has some technical bottlenecks in daily production and experimental research, which has troubled refinery production personnel and related researchers. One is that there is an upper limit to the selectivity of heavy naphtha. Under the trend of large-scale development, even if the yield of heavy naphtha is only slightly improved, it will bring significant economic benefits. It is difficult to break through the 70% barrier for the increase in heavy naphtha yield by relying solely on catalyst optimization and process parameter adjustment. Secondly, in the conventional wax oil two-stage full-cycle hydrocracking process, the second-stage circulating oil no longer undergoes a refining process but is directly circulated to the distillation part, resulting in the accumulation of some difficult-to-react polycyclic aromatic hydrocarbons in the system, which ultimately affects the overall reaction activity of the device and product properties.

[0003] CN103773463B discloses a two-stage hydrocracking process method, which is characterized in that two different types of hydrocracking catalysts are graded and loaded in the cracking section to achieve the purpose of broadening the adaptability of process raw materials and improving product quality.

[0004] CN1952067A discloses a two-stage hydrocracking method. The first hydrocracking reactor of the patent adopts a single-stage two-dose idea to load two catalysts, with the upper part loaded with refined catalyst and the lower part loaded with hydrocracking catalyst. The method of the present invention not only maintains the advantages of the single-stage two-dose hydrocracking technology, such as high yield of middle distillate oil, low chemical hydrogen consumption and low total catalyst cost, but also has the characteristics of the single-stage series hydrocracking technology, such as strong adaptability to raw oil, long catalyst operation cycle and good quality of hydrocracking products. However, the device realizes the maximum production of middle distillate oil, which does not conform to the current trend of refining enterprises to reduce the diesel-gasoline ratio. Summary of the invention

[0005] During the research process, the applicant found that there are some difficult-to-overcome technical bottlenecks when using the existing two-stage full-cycle hydrocracking process to produce reforming raw materials: (1) Unlike the single-stage full-cycle process that can circulate the unconverted oil to the inlet of the refining reactor, the two-stage full-cycle hydrocracking process directly enters the separation system because the unconverted oil from the second stage cracking does not go through the hydrorefining reaction zone. This will cause some polycyclic aromatic hydrocarbons that are difficult to undergo hydrocracking reactions to circulate in the system and accumulate to a certain amount, affecting the overall technical effect of the device; (2) The existing two-stage full-cycle process is difficult to break through the 70% mark in heavy naphtha selectivity by relying solely on catalyst upgrades. Increasing the reaction depth will lead to an increase in the yield of light naphtha and gas products, resulting in a decrease in the overall heavy naphtha selectivity.

[0006] In view of the above problems existing in the prior art, the main purpose of the present invention is to provide a two-stage hydrocracking process and system for producing reforming raw materials. The two-stage hydrocracking process is achieved by setting a two-stage hydrorefining reaction zone in the lower part of the two-stage hydrocracking reactor, and at the same time, the original one-stage circulating oil in the distillation tower is changed into two streams of light circulating oil and heavy circulating oil, and one-stage light naphtha product is changed into part of light naphtha product and part of light petroleum circulating oil. The heavy circulating oil enters from the top of the two-stage hydrocracking reactor, while the light circulating oil and light petroleum circulating oil enter the reactor from the lower part of the two-stage hydrorefining reaction zone. It not only improves the heavy naphtha selectivity of the device, but also solves the inherent problem that the two-stage full-cycle hydrocracking process is prone to cause the accumulation of polycyclic aromatic hydrocarbons, providing favorable technical support for the physical efficiency improvement of enterprises.

[0007] In order to achieve the above-mentioned object of the invention, the present invention first provides a two-stage hydrocracking process for producing reforming feedstock, comprising the following steps:

[0008] (1) The feedstock oil and hydrogen are mixed and then enter a primary hydrocracking reaction zone, which includes a hydrofining reactor and a hydrocracking reactor, and are contacted with a hydrofining catalyst and a hydrocracking catalyst therein to react, and a primary hydrocracking product oil is obtained after the reaction;

[0009] (2) The primary hydrocracking product oil obtained in step (1) enters a separation unit for separation to obtain gas products, light naphtha, heavy naphtha, light circulating tail oil, and heavy circulating tail oil;

[0010] (3) The light circulating tail oil and heavy circulating tail oil obtained in step (2) enter the second-stage hydrocracking reaction zone, the second-stage hydrocracking reaction zone includes a hydrocracking reactor, the reactor includes an upper hydrocracking catalyst bed, a hydrorefining catalyst bed and a lower hydrocracking catalyst bed, the second-stage hydrocracking reactor is provided with at least two feed ports, wherein the first feed port is at the top of the reactor, and the second feed port is on the reactor shell below the hydrorefining catalyst bed; wherein the heavy circulating tail oil enters the second-stage hydrocracking reaction zone through the first feed port, and the light circulating tail oil enters the second-stage hydrocracking reaction zone through the second feed port, and the oil generated by the second-stage hydrocracking after the reaction is circulated for treatment.

[0011] Preferably, in the above-mentioned two-stage hydrocracking process for producing reforming raw materials, the distillation range of the raw oil is generally 350°C to 520°C, and there is usually no special restriction on the sulfur and nitrogen content. Under normal circumstances, the sulfur content is not more than 3.0wt% and the nitrogen content is not more than 2000ppm. More specifically, the raw oil can be selected from one or a mixture of straight-run wax oil, boiling bed wax oil, coker wax oil, etc.

[0012] Preferably, in the above-mentioned two-stage hydrocracking process for producing reforming raw materials, the separation in step (2) includes gas-liquid separation and fractionation, and the first-stage hydrocracking product oil obtained in step (1) is first subjected to gas-liquid separation to obtain a gas phase stream and a liquid phase stream after separation; the obtained liquid phase stream is further fractionated to obtain gas products, light naphtha, heavy naphtha, light circulating tail oil, and heavy circulating tail oil. The gas phase stream obtained by gas-liquid separation is further purified and compressed by a circulating hydrogen compressor to obtain hydrogen, which can be circulated back to the first-stage hydrocracking reaction zone and / or the second-stage hydrocracking reaction zone for use. Generally, the purification treatment refers to the removal of sulfur-containing compounds (hydrogen sulfide) in the gas phase stream, and the purification treatment can adopt any of the existing processes for removing hydrogen sulfide.

[0013] Preferably, in the above two-stage hydrocracking process for producing reforming feedstock, the splitting temperature of the light circulating tail oil and the heavy circulating tail oil in step (2) is 250-350°C, preferably 290-320°C.

[0014] Preferably, in the above-mentioned two-stage hydrocracking process for producing reforming raw materials, light naphtha can partially enter the second-stage hydrocracking reaction zone, partially as a product, or all enter the second-stage hydrocracking reaction zone, preferably entering the second-stage hydrocracking reaction zone from the second feed port together with the light circulating tail oil. Furthermore, when the light naphtha partially enters the second-stage hydrocracking reaction zone, the amount of light naphtha entering the second-stage hydrocracking reaction zone is 5wt% to 95wt% (wt) of the light naphtha product, preferably 15wt% to 75wt%.

[0015] Preferably, in the above-mentioned two-stage hydrocracking process for producing reforming raw materials, the hydrorefining reactor of the first hydrocracking reaction zone in step (1) is filled with at least one hydrorefining catalyst, preferably comprising 1 to 3 hydrorefining catalysts. Generally, the hydrorefining catalyst includes a carrier and a hydrogenation active metal component, the hydrogenation active metal component is loaded on the carrier, and the hydrogenation active metal can be at least one selected from the metal elements of Group VIB, Group VIIB, and Group VIII, preferably two or more metals selected from Co, Mo, Ni, and W as active components. Specifically, commercial hydrorefining catalysts such as FF-12, FF-56, FF-66, and FHUDS-8 developed by Dalian (Fushun) Petrochemical Research Institute of China Petroleum and Chemical Corporation can be selected, and can also be prepared according to the common sense in the field as needed.

[0016] Preferably, in the above-mentioned two-stage hydrocracking process for producing reforming raw materials, at least one hydrocracking catalyst is loaded in the hydrocracking reactor of the first hydrocracking reaction zone in step (1), and the hydrocracking catalyst includes a hydrogenation metal component and a carrier. The hydrogenation metal component can generally be selected from at least one of the metal elements of Group VIB, Group VIIB, and Group VIII, preferably two or more of Co, Mo, Ni, and W; the carrier is selected from at least one of Y molecular sieve, β molecular sieve, modified Y molecular sieve, modified β molecular sieve, alumina, and amorphous silicon aluminum. Usually, based on the weight of the catalyst, the content of the hydrogenation metal component in terms of oxide is 18wt% to 40wt%, preferably 20wt% to 30wt%. Specifically, commercial hydrocracking catalysts such as FC-52 and FC-32 developed by Dalian (Fushun) Petrochemical Research Institute of China Petroleum and Chemical Corporation can be selected, and can also be prepared according to common sense in the field as needed.

[0017] Preferably, in the above two-stage hydrocracking process for producing reforming feedstock, the process conditions of the hydrotreating reactor in the first hydrocracking reaction zone in step (1) are generally as follows: reaction temperature is 320-420°C, preferably 350-400°C; reaction pressure is 8.0-18.0 MPa, preferably 12.0-17.0 MPa; volume space velocity is 0.5-10.0 h -1 , preferably 0.8~2.0h -1 ; The volume ratio of hydrogen to oil is 100 to 2500, preferably 600 to 1200.

[0018] Preferably, in the above two-stage hydrocracking process for producing reforming feedstock, the process conditions of the hydrocracking reactor in the first hydrocracking reaction zone in step (1) are generally as follows: reaction temperature is 330-425°C, preferably 360-410°C; reaction pressure is 8.0-18.0 MPa, preferably 12.0-17.0 MPa; volume space velocity is 0.6-8.0 h -1 , preferably 0.8~2.0h -1 ; The volume ratio of hydrogen to oil is 100 to 2500, preferably 600 to 1500.

[0019] Preferably, in the above-mentioned two-stage hydrocracking process for producing reforming feedstock, the second-stage hydrocracking reaction zone includes a hydrocracking reactor, and the reactor includes an upper hydrocracking catalyst bed, a hydrorefining catalyst bed and a lower hydrocracking catalyst bed; the hydrorefining catalyst bed is arranged between the upper hydrocracking catalyst bed and the lower hydrocracking catalyst bed, and the volume ratio of the hydrorefining catalyst bed to the catalyst bed in the entire reactor is 2% to 32%, preferably 5% to 15%; further, the bottom of the hydrorefining catalyst bed is located at 50% to 90% of the reactor height (from top to bottom), and further preferably 75% to 85% of the reactor height.

[0020] Preferably, in the above two-stage hydrocracking process for producing reforming raw materials, the process conditions of the second-stage hydrocracking reaction zone are generally as follows: reaction temperature is 320-410°C, preferably 340-390°C; reaction pressure is 8.0-18.0 MPa, preferably 12.0-17.0 MPa; volume space velocity is 0.6-8.0 h -1 , preferably 1.0 to 2.5 hours -1 ; The volume ratio of hydrogen to oil is 500 to 2000, preferably 600 to 1500.

[0021] Preferably, in the above-mentioned two-stage hydrocracking process for producing reforming raw materials, at least one hydrocracking catalyst is loaded in the second-stage hydrocracking reaction zone, and the hydrocracking catalyst can be the same as or different from the hydrocracking catalyst loaded in the first-stage hydrocracking reaction zone. The hydrocracking catalyst includes a hydrogenation metal component and a carrier. The hydrogenation metal component can generally be selected from at least one of the metal elements of Group VIB, Group VIIB, and Group VIII, preferably two or more of Co, Mo, Ni, and W; the carrier is selected from at least one of Y molecular sieve, β molecular sieve, modified Y molecular sieve, modified β molecular sieve, alumina, and amorphous silicon aluminum. Usually, based on the weight of the catalyst, the content of the hydrogenation metal component in terms of oxide is 15wt% to 35wt%, preferably 18wt% to 28wt%. It is further preferred that the hydrogenation metal component of the upper hydrocracking catalyst of the second-stage hydrocracking reaction zone has an oxide content of 23wt% to 28wt%, and the hydrogenation metal component of the lower hydrocracking catalyst of the second-stage hydrocracking reaction zone has an oxide content of 18wt% to 25wt%. Specifically, commercial hydrocracking catalysts such as FC-76 and FC-50 developed by Fushun Research Institute of Petrochemicals (FRIPP) of Sinopec can be selected, and can also be prepared according to common knowledge in the field as needed.

[0022] Preferably, in the above-mentioned two-stage hydrocracking process for producing reforming raw materials, at least one hydrorefining catalyst is loaded in the second-stage hydrocracking reaction zone, and the hydrorefining catalyst can be the same as or different from the hydrorefining catalyst loaded in the first-stage hydrocracking reaction zone. In general, the hydrorefining catalyst includes a carrier and a hydrogenation active metal component, the hydrogenation active metal component is loaded on the carrier, and the hydrogenation active metal can be at least one selected from the metal elements of Group VIB, Group VIIB, and Group VIII, preferably two or more metals of Co, Mo, Ni, and W as active components. Specifically, commercial hydrorefining catalysts such as FF-56, FF-66, FHUDS-7, and FHUDS-8 developed by Dalian (Fushun) Petrochemical Research Institute of China Petroleum and Chemical Corporation can be selected, and can also be prepared according to common sense in the field as needed.

[0023] In order to achieve the above-mentioned object of the invention, the present invention provides a hydrocracking system for producing reforming feedstock, comprising a first-stage hydrocracking reaction zone, a separation unit, and a second-stage hydrocracking reaction zone connected in sequence: wherein:

[0024] A first-stage hydrocracking reaction zone, wherein the first-stage hydrocracking reaction zone includes a hydrofining reactor and a hydrocracking reactor, wherein the feedstock oil and hydrogen are mixed and then contacted with the hydrofining catalyst and the hydrocracking catalyst therein to react, and a first-stage hydrocracking product oil is obtained after the reaction;

[0025] A separation unit, wherein the separation unit comprises a gas-liquid separator and a fractionation tower, wherein the first stage hydrocracking generated oil first enters the gas-liquid separator, and after separation, a gas phase feed stream and a liquid phase feed stream are obtained, and the liquid phase feed stream enters the fractionation tower and after separation, a gas product, light naphtha, heavy naphtha, light circulating tail oil, and heavy circulating tail oil are obtained;

[0026] The second-stage hydrocracking reaction zone comprises a hydrocracking reactor, wherein the reactor comprises an upper hydrocracking catalyst bed, a hydrofining catalyst bed and a lower hydrocracking catalyst bed, and the second-stage hydrocracking reactor is provided with at least two feed ports, wherein the first feed port is at the top of the reactor, and the second feed port is on the reactor shell at the lower part of the hydrofining catalyst bed; wherein the heavy circulating tail oil enters the second-stage hydrocracking reaction zone from the first feed port, and the light circulating tail oil enters the second-stage hydrocracking reaction zone from the second feed port, and the oil generated by the second-stage hydrocracking after the reaction is returned to the fractionation tower in the separation unit for treatment.

[0027] Preferably, in the above-mentioned hydrocracking system for producing reforming raw materials, the gas-liquid separator generally includes one or more of a hot high-pressure separator, a hot low-pressure separator, a cold high-pressure separator, and a cold low-pressure separator according to actual conditions. The type of the separator, the type of the distillation tower, the connection method between the separators and between the separators and the distillation tower, etc., can be freely selected by technical personnel in this field according to actual needs.

[0028] Preferably, the above-mentioned hydrocracking system for producing reforming feedstock further includes a purification unit, which is used to receive the gaseous phase stream separated by the gas-liquid separator in the separation unit, and obtain purified hydrogen after purification treatment. The purified hydrogen can be circulated back to the first hydrocracking reaction zone and / or the second hydrocracking reaction zone as circulating hydrogen after being compressed by a circulating hydrogen compressor. Usually, the purification treatment refers to removing sulfur-containing compounds (hydrogen sulfide) in the gaseous phase stream, and the purification treatment can adopt any of the existing processes for removing hydrogen sulfide.

[0029] Compared with the existing two-stage hydrocracking process, the technical advantages and effects of the two-stage hydrocracking process and system for producing reforming raw materials provided by the present invention are mainly reflected in the following aspects:

[0030] (1) In the two-stage hydrocracking process for producing reforming raw materials provided by the present invention, the applicant proposes to set a hydrorefining catalyst bed in the lower part of the reactor of the second-stage hydrocracking reaction zone, so that the polycyclic aromatic hydrocarbons accumulated in the second-stage reaction zone can be partially saturated with aromatic hydrocarbons, thereby solving the problem of polycyclic aromatic hydrocarbon accumulation inherent in the traditional two-stage full-circulation wax oil hydrocracking process, and at the same time, it can also improve the heavy naphtha selectivity, thereby achieving two positive improvements: preventing the accumulation of polycyclic aromatic hydrocarbons and improving the heavy naphtha selectivity.

[0031] (2) At the same time, the applicant discovered during the research process that the hydrocracking reaction has a dynamic inhibition-guiding phenomenon in the cracking reaction area, that is, in the hydrocracking process of the full-fraction reactants, the introduction of substances with a distillation range of A to B°C will promote the reaction of substances with a distillation range of <B°C, while inhibiting the reaction of substances with a distillation range of >B°C. Based on the above phenomenon, the applicant optimized the functional area of ​​the second-stage hydrocracking reaction and the hydrocracking reaction path, thereby improving the selectivity of the target product while solving the adverse effects of the accumulation of polycyclic aromatic hydrocarbons. By allowing light naphtha and light circulating tail oil to enter the second-stage hydrocracking reaction zone from the second feed port, the light circulating oil does not pass through the hydrorefining catalyst bed in the second-stage hydrocracking reaction zone, and forms a high-concentration zone of light circulating oil reactants in the lower hydrocracking catalyst bed of the second-stage hydrocracking reaction zone, promoting the occurrence of conversion reactions toward heavy naphtha. At the same time, due to the introduction of light naphtha fractions, the tendency of heavy naphtha fractions to react toward light naphtha fractions will be reduced according to the dynamic inhibition guidance theory, further increasing the selectivity of heavy naphtha products. At the same time, light naphtha enters the second-stage hydrocracking reaction zone to continue the hydrocracking reaction. Combining the hydrocracking carbon ion reaction mechanism and the β-position chain breaking principle, the isomerization degree of light naphtha products is further improved, and high-octane light naphtha is obtained, increasing its economic value as a gasoline blending component.

[0032] (3) In the two-stage hydrocracking process for producing reforming raw materials provided by the present invention, the feed to the upper hydrocracking catalyst bed area of ​​the second-stage hydrocracking reaction zone is only heavy cycle oil, and a region with low space velocity and high hydrocracking reaction activity is created in this region, which reduces the processing difficulty and helps to reduce the inlet reaction temperature of the second-stage hydrocracking reaction zone, which is beneficial to the long-term operation of the device and reduces the overall energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A schematic diagram of a two-stage hydrocracking process and system for producing reforming feedstock according to an embodiment of the present invention.

[0034] Figure 2 This is a schematic diagram of a two-stage hydrocracking process and system for producing reforming feedstock in a comparative example of the present invention. DETAILED DESCRIPTION

[0035] The technical scheme and technical effects of the present invention are further described below in conjunction with the accompanying drawings and specific implementation methods.

[0036] Unless explicitly stated otherwise, throughout the specification and claims, the term “comprise” or variations such as “include” or “comprising”, etc., will be understood to include the stated elements or components but not to exclude other elements or components.

[0037] In this document, for the convenience of description, spatial relative terms such as "below", "below", "down", "above", "above", "upper", etc. may be used to describe the relationship between one element or feature and another element or feature in the accompanying drawings. It should be understood that the spatial relative terms are intended to include different directions of objects in use or operation in addition to the directions drawn in the drawings. For example, if the object in the figure is turned over, the elements described as being "below" or "below" other elements or features will be oriented "above" the elements or features. Therefore, the exemplary term "below" can include both below and above directions. Objects may also have other orientations (rotated 90 degrees or other orientations) and the spatial relative terms used in this document should be interpreted accordingly.

[0038] In this document, the terms "first", "second", etc. are used to distinguish two different elements or parts, and are not used to limit a specific position or relative relationship. In other words, in some embodiments, the terms "first", "second", etc. can also be interchangeable.

[0039]

[0043] All numerical values ​​for parameters (eg, amounts or conditions) herein are to be understood as being modified in all instances by the term "about", whether or not "about" actually appears before the numerical value.

[0040] the following Figure 1 The specific implementation methods of the process and system provided by the present invention are further described as follows: Figure 1 As shown, the two-stage hydrocracking process of producing reforming raw materials of the present invention is as follows: under the condition of the presence of new hydrogen 18, the wax oil raw material 1 is mixed with the circulating hydrogen 17 and enters the first hydrorefining reactor 2 in the first hydrocracking reaction zone for reaction, and the refined product 3 obtained after the reaction enters the first hydrocracking reactor 4 in the first hydrocracking reaction zone for reaction, and the first hydrocracking generated oil 16 obtained after the reaction enters the gas-liquid separation unit 5 to obtain a gas phase stream and a liquid phase stream 6 after gas-liquid separation, wherein the gas phase stream is circulated as the circulating hydrogen 17 after the action of the circulating hydrogen compressor 15, and the liquid phase stream 6 enters the fractionation unit 7 for separation to obtain gas 8 and light naphtha 9, heavy naphtha 10, light circulating tail oil 11 and heavy circulating tail oil 12, the heavy circulating tail oil 12 enters the second hydrocracking reactor 13 in the second-stage hydrocracking reaction zone from the first feed port at the top of the reactor, the light circulating tail oil 11 and optional part or all of the light naphtha 9-1 enter the second hydrocracking reactor from the second feed port located on the reactor shell at the lower part of the hydrorefining catalyst bed in the second hydrocracking reactor, the reactor includes an upper hydrocracking catalyst bed, a hydrorefining catalyst bed and a lower hydrocracking catalyst bed, and the second-stage hydrocracking product oil 14 obtained after the reaction is circulated back to the gas-liquid separation unit 5 for treatment.

[0041] The properties of the raw oil used in the examples of the present invention and the comparative examples are shown in Table 1.

[0042] Table 1 Raw oil properties

[0043]

[0044] Example 1

[0045] use Figure 1 The two-stage hydrocracking process flow for producing reforming raw materials is shown in Table 1. The first hydrorefining reactor is filled with FF-66 catalyst, the first hydrocracking reactor is filled with FC-52 catalyst, the upper hydrocracking catalyst in the second hydrocracking reactor is FC-52, the hydrorefining catalyst is FF-66, and the lower hydrocracking catalyst is FC-52; the volume of the hydrorefining catalyst in the second hydrocracking reactor accounts for 12% (v). The bottom end of the hydrorefining catalyst bed is located at 75% of the height (from top to bottom) of the second hydrocracking reactor. The split temperature of light circulating tail oil and heavy circulating tail oil is 300℃, and the amount of light naphtha entering the second-stage hydrocracking reaction zone is 25% (wt) of the light naphtha product. The reaction conditions of the first hydrorefining reactor are as follows: reaction pressure is 16.0 MPa, reaction temperature is 370℃, volume space velocity is 1.2h -1 , the hydrogen-to-oil volume ratio is 1200. The reaction conditions of the first hydrocracking reactor are as follows: reaction pressure is 16.0 MPa, reaction temperature is 380°C, volume space velocity is 1.6 h -1 , the hydrogen-to-oil volume ratio is 1200. The reaction conditions of the second hydrocracking reactor are as follows: reaction pressure is 16.0 MPa, reaction temperature is 360°C, volume space velocity is 2.0 h -1 , the volume ratio of hydrogen to oil is 1300. The reaction results are shown in Table 2.

[0046] Example 2

[0047] use Figure 1The two-stage hydrocracking process flow for producing reforming raw materials is shown in Table 1. The properties of the processed wax oil raw materials are shown in Table 1. The first hydrorefining reactor is filled with FF-56 and FF-66 catalysts in a graded manner according to the flow direction of the liquid phase material. The first hydrocracking reactor is filled with FC-32A catalyst. The upper hydrocracking catalyst in the second hydrocracking reactor is FC-76, the hydrorefining catalyst is FF-12, and the lower hydrocracking catalyst is FC-76. The hydrorefining catalyst in the second hydrocracking reactor accounts for 15% (v). The bottom end of the hydrorefining catalyst bed is located at 85% of the height (from top to bottom) of the second hydrocracking reactor. The split temperature of light circulating tail oil and heavy circulating tail oil is 290°C, and the amount of light naphtha entering the second-stage hydrocracking reaction zone is 50% (wt) of the light naphtha product. The reaction conditions of the first hydrorefining reactor are as follows: reaction pressure is 14.7 MPa, reaction temperature is 380°C, and volume space velocity is 0.8h -1 , the hydrogen-to-oil volume ratio is 1000. The reaction conditions of the first hydrocracking reactor are as follows: reaction pressure is 14.7 MPa, reaction temperature is 385°C, volume space velocity is 1.2h -1 , the hydrogen-to-oil volume ratio is 1500. The reaction conditions of the second hydrocracking reactor are as follows: reaction pressure is 15.0 MPa, reaction temperature is 368°C, volume space velocity is 1.5h -1 , the volume ratio of hydrogen to oil is 1500. The reaction results are shown in Table 2.

[0048] Example 3

[0049] use Figure 1 The two-stage hydrocracking process flow for producing reforming raw materials is shown in Table 1. The properties of the processed wax oil raw materials are shown in Table 1. The first hydrorefining reactor is filled with FF-66 and FF-12 catalysts in a graded manner according to the flow direction of the liquid phase material. The first hydrocracking reactor is filled with FC-52 and FC-32A catalysts in a graded manner according to the flow direction of the liquid phase material. The upper hydrocracking catalyst in the second hydrocracking reactor is FC-76, the hydrorefining catalyst is FTX, and the lower hydrocracking catalyst is FC-80. The hydrorefining catalyst in the second hydrocracking reactor accounts for 5% (v), and the bottom end of the hydrorefining catalyst bed is located at 75% of the height (from top to bottom) of the second hydrocracking reactor. The splitting temperature of light circulating tail oil and heavy circulating tail oil is 320°C, and the amount of light naphtha entering the second-stage hydrocracking reaction zone is 55% (wt) of the light naphtha product. The reaction conditions of the first hydrofining reactor are as follows: reaction pressure is 17.0 MPa, reaction temperature is 365°C, volumetric space velocity is 1.8 h -1 , the hydrogen-to-oil volume ratio is 900. The reaction conditions of the first hydrocracking reactor are as follows: reaction pressure is 17.0 MPa, reaction temperature is 378°C, volume space velocity is 1.8 h -1, the hydrogen-to-oil volume ratio is 1100. The reaction conditions of the second hydrocracking reactor are as follows: reaction pressure is 17.0 MPa, reaction temperature is 362°C, volume space velocity is 1.2 h -1 , the volume ratio of hydrogen to oil is 1000. The reaction results are shown in Table 2.

[0050] Comparative Example 1

[0051] use Figure 2 The two-stage hydrocracking process flow for producing reforming feedstock is shown in FIG. 1 , and the properties of the processed wax oil feedstock are shown in Table 1. Figure 2 As shown, the two-stage hydrocracking process for producing reforming raw materials in Comparative Example 1 is as follows: in the presence of new hydrogen 18, the wax oil raw material 1 is mixed with the circulating hydrogen 17 and enters the first hydrocracking refining reactor 2 in the first hydrocracking reaction zone for reaction, and the refined product 3 obtained after the reaction is reacted in the first hydrocracking reactor 4 in the first hydrocracking reaction zone, and the first hydrocracking product oil 16 obtained after the reaction enters the gas-liquid separation unit 5 to obtain a gas phase stream 14 and a liquid phase stream 6 after gas-liquid separation, wherein the gas phase stream 14 is recycled as the circulating hydrogen 17 after the action of the circulating hydrogen compressor 15, and the liquid phase stream 6 enters the fractionation unit 7 for separation to obtain gas 8, light naphtha 9, heavy naphtha 10, and tail oil 11, and the tail oil 11 enters the second hydrocracking reactor 12 in the second hydrocracking reaction zone from the feed port at the top of the reactor, and the second hydrocracking product oil 13 obtained after the reaction is circulated back to the gas-liquid separation unit 5 for treatment.

[0052] The first hydrofining reactor is filled with FF-66 catalyst, the first hydrocracking reactor is filled with FC-52 catalyst, and the hydrocracking catalyst in the second hydrocracking reactor is FC-52 catalyst. The reaction conditions of the first hydrofining reactor are as follows: reaction pressure is 16.0 MPa, reaction temperature is 370 ° C, volume space velocity is 1.2 h -1 , the hydrogen-to-oil volume ratio is 1200. The reaction conditions of the first hydrocracking reactor are as follows: reaction pressure is 16.0 MPa, reaction temperature is 380°C, volume space velocity is 1.6h -1 , the hydrogen-to-oil volume ratio is 1200. The reaction conditions of the second hydrocracking reactor are as follows: reaction pressure is 16.0 MPa, reaction temperature is 360 °C, volume space velocity is 2.0 h -1 , the volume ratio of hydrogen to oil is 1300. The reaction results are shown in Table 3.

[0053] Comparative Example 2

[0054] use Figure 1The two-stage hydrocracking process flow for producing reforming raw materials shown in the figure is different in that a hydrorefining catalyst is loaded at the top of the second hydrocracking reactor. The properties of the processed wax oil raw materials are shown in Table 1. The first hydrorefining reactor is filled with FF-56 and FF-66 catalysts in a graded manner according to the flow direction of the liquid phase material, and the first hydrocracking reactor is filled with FC-32A catalyst. The catalyst loading method in the second hydrocracking reactor is different from that in the embodiment. According to the flow direction of the liquid phase material, the hydrorefining catalyst and the hydrocracking catalyst are loaded in sequence, wherein the hydrorefining catalyst is FF-12, and the hydrocracking catalyst is FC-76. The volume of the hydrorefining catalyst in the second hydrocracking reactor accounts for 15% (v). The hydrorefining catalyst bed is located at the top of the second hydrocracking reactor. The reaction conditions of the first hydrorefining reactor are as follows: the reaction pressure is 14.7MPa, the reaction temperature is 380°C, and the volume space velocity is 0.8h -1 , the hydrogen-to-oil volume ratio is 1000. The reaction conditions of the first hydrocracking reactor are as follows: reaction pressure is 14.7 MPa, reaction temperature is 385 °C, volume space velocity is 1.2 h -1 , the hydrogen-to-oil volume ratio is 1500. The reaction conditions of the second hydrocracking reactor are as follows: reaction pressure is 15.0 MPa, reaction temperature is 368°C, volume space velocity is 1.5 h -1 , the volume ratio of hydrogen to oil is 1500. The reaction results are shown in Table 2. The reaction results show that a hydrorefining catalyst bed is set on the top of the reactor in the second-stage hydrocracking reaction zone, and some light aromatics are saturated and then pass through the subsequent hydrocracking reaction zone. Excessive hydrocracking reaction will lead to an increase in the yield of gas and light naphtha products, thereby affecting the overall economic benefits.

[0055] Comparative Example 3

[0056] use Figure 1 The two-stage hydrocracking process flow for producing reforming raw materials shown in the figure is basically the same as that in Example 3, except that the light naphtha is not circulated, and the second hydrocracking reactor is not provided with a hydrorefining catalyst. The properties of the processed wax oil raw materials are shown in Table 1. FF-66 and FF-12 catalysts are graded in the first hydrorefining reactor according to the flow direction of the liquid phase material, and FC-52 and FC-32A catalysts are graded in the first hydrocracking reactor according to the flow direction of the liquid phase material. The upper hydrocracking catalyst in the second hydrocracking reactor is FC-76, accounting for 70% by volume; the lower hydrocracking catalyst is FC-80, and a light cycle oil feed port is provided between the two hydrocracking catalyst beds. The splitting temperature of the light cycle tail oil and the heavy cycle tail oil is 320°C. The reaction conditions of the first hydrorefining reactor are as follows: the reaction pressure is 17.0MPa, the reaction temperature is 365°C, and the volume space velocity is 1.8h -1, the hydrogen-to-oil volume ratio is 900. The reaction conditions of the first hydrocracking reactor are as follows: reaction pressure is 17.0 MPa, reaction temperature is 378°C, volume space velocity is 1.8 h -1 , the hydrogen-to-oil volume ratio is 1100. The reaction conditions of the second hydrocracking reactor are as follows: reaction pressure is 17.0 MPa, reaction temperature is 362 °C, volume space velocity is 1.2 h -1 , the volume ratio of hydrogen to oil is 1000. The reaction results are shown in Table 2.

[0057] Table 2 Example reaction results

[0058]

[0059] Table 3 Comparative Example Reaction Results

[0060]

[0061] The experimental results of the above embodiments and comparative examples show that in the two-stage hydrocracking process for producing reforming raw materials provided in the present invention, the yield of heavy naphtha is significantly increased, the octane number of light naphtha is also improved, and the problem of accumulation of circulating oil aromatics during long-term operation of the two-stage circulating hydrocracking process can be solved at the same time. Under the general trend of "oil conversion", this method will help refining enterprises improve quality and efficiency and bring significant economic benefits to refineries.

Claims

1. A two-stage hydrocracking process for producing reforming feedstock, comprising the following steps: (1) The feedstock oil and hydrogen are mixed and then enter a primary hydrocracking reaction zone, which includes a hydrofining reactor and a hydrocracking reactor, and are contacted with a hydrofining catalyst and a hydrocracking catalyst therein to react, and a primary hydrocracking product oil is obtained after the reaction; (2) The primary hydrocracking oil obtained in step (1) enters a separation unit for separation to obtain gas products, light naphtha, heavy naphtha, light circulating tail oil, and heavy circulating tail oil; the splitting temperature of the light circulating tail oil and the heavy circulating tail oil is 250-350°C; (3) The light circulating tail oil and heavy circulating tail oil obtained in step (2) enter the second-stage hydrocracking reaction zone. The second-stage hydrocracking reaction zone includes a hydrocracking reactor. The reactor includes an upper hydrocracking catalyst bed, a hydrorefining catalyst bed and a lower hydrocracking catalyst bed. The hydrorefining catalyst bed is arranged between the upper hydrocracking catalyst bed and the lower hydrocracking catalyst bed. The second-stage hydrocracking reactor is provided with at least two feed inlets, wherein: The first feed port is at the top of the reactor, and the second feed port is on the reactor shell at the bottom of the hydrotreating catalyst bed; the heavy circulating tail oil enters the second-stage hydrocracking reaction zone from the first feed port, and the light naphtha and the light circulating tail oil enter the second-stage hydrocracking reaction zone from the second feed port, and the oil generated by the second-stage hydrocracking after the reaction is circulated for treatment.

2. The two-stage hydrocracking process for producing reforming feedstock according to claim 1, characterized in that: The distillation range of the raw oil is 350°C to 520°C, the sulfur content is not more than 3.0wt%, and the nitrogen content is not more than 2000ppm.

3. The two-stage hydrocracking process for producing reforming feedstock according to claim 1, characterized in that: The raw material oil is selected from one or more of straight-run wax oil, fluidized bed wax oil and coking wax oil.

4. The two-stage hydrocracking process for producing reforming feedstock according to claim 1, characterized in that: The separation in step (2) includes gas-liquid separation and fractionation. The first-stage hydrocracking product oil obtained in step (1) is first subjected to gas-liquid separation to obtain a gas phase feed stream and a liquid phase feed stream after separation; the liquid phase feed stream is fractionated to obtain a gas product, light naphtha, heavy naphtha, light circulating tail oil, and heavy circulating tail oil.

5. The two-stage hydrocracking process for producing reforming feedstock according to claim 1, characterized in that: In step (2), the separation temperature of the light circulating tail oil and the heavy circulating tail oil is 290-320°C.

6. The two-stage hydrocracking process for producing reforming feedstock according to claim 1, characterized in that: Part of the light naphtha enters the second-stage hydrocracking reaction zone, and part is used as a product.

7. The two-stage hydrocracking process for producing reforming feedstock according to claim 1, characterized in that: The hydrotreating reactor of the first hydrocracking reaction zone in step (1) is filled with at least one hydrotreating catalyst.

8. The two-stage hydrocracking process for producing reforming feedstock according to claim 1, characterized in that: The hydrotreating reactor of the first hydrocracking reaction zone in step (1) is loaded with 1 to 3 types of hydrotreating catalysts.

9. The two-stage hydrocracking process for producing reforming feedstock according to claim 1, characterized in that: The hydrocracking reactor of the first hydrocracking reaction zone in step (1) is filled with at least one hydrocracking catalyst.

10. The two-stage hydrocracking process for producing reforming feedstock according to claim 1, characterized in that: The process conditions of the hydrotreating reactor in the first hydrocracking reaction zone in step (1) are as follows: reaction temperature of 320-420°C, reaction pressure of 8.0-18.0 MPa, volume space velocity of 0.5-10.0 h -1 , the volume ratio of hydrogen to oil is 100~2500.

11. The two-stage hydrocracking process for producing reforming feedstock according to claim 1, characterized in that: The process conditions of the hydrotreating reactor in the first hydrocracking reaction zone in step (1) are as follows: reaction temperature of 350-400°C, reaction pressure of 12.0-17.0 MPa, volume space velocity of 0.8-2.0 h -1 , the volume ratio of hydrogen to oil is 600-1500.

12. The two-stage hydrocracking process for producing reforming feedstock according to claim 1, characterized in that: The process conditions of the hydrocracking reactor in the first hydrocracking reaction zone in step (1) are as follows: reaction temperature of 330-425°C, reaction pressure of 8.0-18.0 MPa, volume space velocity of 0.6-8.0 h -1 , the volume ratio of hydrogen to oil is 100~2500.

13. The two-stage hydrocracking process for producing reforming feedstock according to claim 1, characterized in that: The process conditions of the hydrocracking reactor in the first hydrocracking reaction zone in step (1) are as follows: reaction temperature is 360-410°C, reaction pressure is 12.0-17.0 MPa, volume space velocity is 0.8-2.0 h -1 , the volume ratio of hydrogen to oil is 600-1200.

14. The two-stage hydrocracking process for producing reforming feedstock according to claim 1, characterized in that: The volume ratio of the hydrotreating catalyst bed to the catalyst bed in the entire reactor is 2% to 32%.

15. The two-stage hydrocracking process for producing reforming feedstock according to claim 1, characterized in that: The volume ratio of the hydrotreating catalyst bed to the catalyst bed in the entire reactor is 5% to 15%.

16. The two-stage hydrocracking process for producing reforming feedstock according to claim 1, characterized in that: The bottom of the hydrotreating catalyst bed is located at 50% to 90% of the reactor height.

17. The two-stage hydrocracking process for producing reforming feedstock according to claim 1, characterized in that: The bottom of the hydrotreating catalyst bed is located at 75% to 85% of the reactor height.

18. The two-stage hydrocracking process for producing reforming feedstock according to claim 1, characterized in that: The process conditions of the second-stage hydrocracking reaction zone are as follows: reaction temperature is 320-410°C, reaction pressure is 8.0-18.0 MPa, and volume space velocity is 0.6-8.0 h -1 , the volume ratio of hydrogen to oil is 500~2000.

19. The two-stage hydrocracking process for producing reforming feedstock according to claim 1, characterized in that: The process conditions of the second-stage hydrocracking reaction zone are as follows: reaction temperature is 340-390°C, reaction pressure is 12.0-17.0 MPa, volume space velocity is 1.0-2.5 h -1 , the volume ratio of hydrogen to oil is 600-1500.

20. The two-stage hydrocracking process for producing reforming feedstock according to claim 1, characterized in that: The second-stage hydrocracking reaction zone is filled with at least one hydrocracking catalyst, and the hydrocracking catalyst is the same as or different from the hydrocracking catalyst filled in the first-stage hydrocracking reaction zone.

21. The two-stage hydrocracking process for producing reforming feedstock according to claim 1, characterized in that: The second-stage hydrocracking reaction zone is filled with at least one hydrorefining catalyst, and the hydrorefining catalyst is the same as or different from the hydrorefining catalyst filled in the first-stage hydrocracking reaction zone.

22. A hydrocracking system for producing reforming raw materials that realizes the two-stage hydrocracking process for producing reforming raw materials as described in any one of claims 1 to 21, comprising a first-stage hydrocracking reaction zone, a separation unit, and a second-stage hydrocracking reaction zone connected in sequence: wherein: A first-stage hydrocracking reaction zone, wherein the first-stage hydrocracking reaction zone includes a hydrofining reactor and a hydrocracking reactor, wherein the feedstock oil and hydrogen are mixed and then contacted with the hydrofining catalyst and the hydrocracking catalyst therein to react, and a first-stage hydrocracking product oil is obtained after the reaction; A separation unit, wherein the separation unit comprises a gas-liquid separator and a fractionation tower, wherein the first stage hydrocracking generated oil first enters the gas-liquid separator, and after separation, a gas phase feed stream and a liquid phase feed stream are obtained, and the liquid phase feed stream enters the fractionation tower and after separation, a gas product, light naphtha, heavy naphtha, light circulating tail oil, and heavy circulating tail oil are obtained; The second-stage hydrocracking reaction zone comprises a hydrocracking reactor, wherein the reactor comprises an upper hydrocracking catalyst bed, a hydrorefining catalyst bed and a lower hydrocracking catalyst bed, wherein the hydrorefining catalyst bed is arranged between the upper hydrocracking catalyst bed and the lower hydrocracking catalyst bed; the second-stage hydrocracking reactor is provided with at least two feed ports, wherein the first feed port is at the top of the reactor, and the second feed port is on the reactor shell at the lower part of the hydrorefining catalyst bed; wherein the heavy circulating tail oil enters the second-stage hydrocracking reaction zone from the first feed port, and the light naphtha and the light circulating tail oil enter the second-stage hydrocracking reaction zone from the second feed port, and the oil generated by the second-stage hydrocracking after the reaction is returned to the fractionation tower in the separation unit for treatment.

23. The hydrocracking system for producing reforming feedstock according to claim 22, characterized in that: The gas-liquid separator includes one or more of a hot high-pressure separator, a hot low-pressure separator, a cold high-pressure separator, and a cold low-pressure separator.

24. The hydrocracking system for producing reforming feedstock according to claim 22, characterized in that: It includes a purification unit, which is used to receive the gas phase material flow separated by the gas-liquid separator in the separation unit, obtain purified hydrogen after purification, and the purified hydrogen is compressed by a circulating hydrogen compressor and circulated back to the first stage hydrocracking reaction zone and / or the second stage hydrocracking reaction zone for use as circulating hydrogen.

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