A hydrocracking method for producing heavy naphtha

Abstract

The present invention discloses a hydrocracking method for producing heavy naphtha. The method comprises a hydropretreatment reaction zone and a hydrocracking reaction zone, and the process comprises: a wax oil-containing raw material and hydrogen pass through the hydropretreatment reaction zone for hydropretreatment, the nitrogen content of the effluent of the hydropretreatment reaction zone is controlled to be below 30 mg / kg, the effluent of the hydropretreatment reaction zone is mixed with the circulating oil and then enters the hydrocracking reaction zone for reaction, and the effluent of the hydrocracking reaction zone is separated and fractionated to obtain dry gas, liquefied gas, light naphtha, heavy naphtha and tail oil, wherein the tail oil, at least part of the liquefied gas and at least part of the light naphtha are circulated back to the hydrocracking reaction zone as the circulating oil. The method of the present invention is suitable for processing conventional hydrocracking raw materials, and can realize the maximum production of heavy naphtha by single-stage full-cycle processing of hydrocarbon raw materials.

Description

Technical Field

[0001] The present invention relates to a hydrocracking method, in particular to a hydrocracking method for producing heavy naphtha. Background Art

[0002] In recent years, China's refining primary processing capacity has increased year by year, reaching 860 million tons / year by 2019, of which 652 million tons / year were processed crude oil. China's total apparent consumption of refined oil products has basically stabilized at 300 million tons / year, of which diesel apparent consumption has been stable and declining, and gasoline apparent consumption growth has slowed down. In the future, only the growth rate of jet fuel apparent consumption will remain above 10%, and competition in the refined oil consumption market will intensify. Compared with fuel oil, the consumption of major chemical products will continue to grow in the next few decades, and the shortage of raw materials is the biggest bottleneck restricting the development of the ethylene and aromatics industries. The continuous increase in refining processing capacity and the lack of consumption demand in the oil market have led to the need for refineries to shift to the direction of producing more chemical raw materials such as aromatics and ethylene. The transformation and upgrading of refineries from "fuel type" to "chemical type" is an inevitable development trend, and processing petroleum derivatives into aromatics and ethylene raw materials is a general trend.

[0003] The hydrocracking process is one of the two key units for lightening oil and changing product structure. It is a powerful tool for the transformation of oil refining to chemical industry. Due to its good product quality and flexible operation, it is bound to play a huge role in adjusting the product structure of refineries, increasing the proportion of high value-added products, increasing benefits, and enhancing corporate competitiveness. How to make good use of hydrocracking units to process oil products and produce heavy naphtha as a reforming raw material in large quantities is an important manifestation of technological progress and advancement.

[0004] When using the hydrocracking process to produce more heavy naphtha, there are many factors to consider, including the characteristics of the raw materials, catalyst optimization, process selection, parameter setting, etc. How to sort out the relationship between them and reasonably choose the match, use the experimental process to explore the influencing laws and summarize and refine them, and form a method to produce more heavy naphtha, is a direction that requires effort and progress. In the process of refining and chemical transformation, the most critical task is to reduce the diesel-to-gasoline ratio, so how to reduce it or even convert more into chemical materials requires serious study.

[0005] CN201711119101.0 discloses a hydrocracking method for improving the yield of heavy naphtha. The raw oil is mixed with hydrogen and then enters a hydrotreating reactor. It contacts a hydrotreating catalyst to undergo hydrodesulfurization, hydrodenitrogenation, aromatic saturation and other refining reactions. The obtained generated oil is mixed with the hydrogenated tail oil and enters a hydrocracking reactor for hydrocracking reaction. It is mixed with the circulating oil between different beds and continues to react. The obtained generated oil enters a separation system, the obtained hydrogen is recycled, and the obtained generated distillate oil enters a fractionation system to obtain gas, light naphtha, heavy naphtha, middle distillate oil, and hydrogenated tail oil. The hydrogenated tail oil is circulated to the entrance of the hydrocracking reactor, and the middle distillate oil returns to the catalyst bed of the hydrocracking reactor. This method cannot avoid the problem that the circulating oil component is single, excessive cracking is prone to occur, and the yield of heavy naphtha is low.

[0006] CN201811279948.X discloses a hydrocracking method for producing heavy naphtha and jet fuel fractions. After the raw oil is mixed with hydrogen, it passes through the hydrofining reaction zone and the hydrocracking reaction zone in sequence to obtain the reaction product, which is separated to obtain a light naphtha fraction, a heavy naphtha fraction, a jet fuel fraction, a diesel fraction and a tail oil fraction, and part of the diesel fraction is circulated to the hydrocracking reaction zone. The hydrocracking reaction zone is loaded with hydrocracking catalyst I and hydrocracking catalyst II from top to bottom. This method can take into account the activity and stability of the hydrocracking catalyst, and produce heavy naphtha and jet fuel components at a high conversion rate. However, there is also a single circulating oil component from the reaction raw material, and it is impossible to suppress its excessive cracking to the maximum extent.

[0007] In the above methods, either the fraction heavier than heavy naphtha is used as circulating oil to achieve heavy naphtha production, or the performance of the catalyst is improved to achieve maximum production of heavy naphtha. However, further research is still needed on how to produce heavy naphtha. Summary of the invention

[0008] When a conventional single-stage hydrocracking method is used to produce heavy naphtha, it is usually considered to circulate the fraction heavier than heavy naphtha to the hydrocracking reactor for further cracking to increase the production of heavy naphtha, which is generally called a single-stage full-cycle hydrocracking process. The inventors of the present invention have found through extensive research that, on the basis of the single-stage full-cycle hydrocracking process, part of the liquefied gas and light naphtha fractions are used as the circulating oil of the hydrocracking reactor and the circulating amount is controlled. The circulating liquefied gas and light naphtha fractions can be completely dissolved in the circulating oil, and non-ideal processes such as gasification will not be caused. The reaction balance of the whole fraction can be effectively controlled, and the purpose of increasing the production of heavy naphtha and improving the quality of heavy naphtha can be achieved, thereby realizing the present invention.

[0009] In view of the problems existing in the prior art, the present invention provides a hydrocracking method for producing heavy naphtha. The method of the present invention is suitable for processing conventional hydrocracking raw materials and can realize single-stage full-cycle processing of hydrocarbon raw materials to produce heavy naphtha in maximum quantity.

[0010] The present invention provides a hydrocracking method for producing heavy naphtha, the method comprising a hydropretreatment reaction zone and a hydrocracking reaction zone, and the process comprises:

[0011] (1) The wax oil-containing feedstock and hydrogen are passed through a hydrogenation pretreatment reaction zone for hydrogenation pretreatment, and the nitrogen content of the effluent from the hydrogenation pretreatment reaction zone is controlled to be below 30 mg / kg, preferably 5 to 25 mg / kg.

[0012] (2) The effluent from the hydrotreating reaction zone is mixed with the circulating oil and then enters the hydrocracking reaction zone for reaction. The effluent from the hydrocracking reaction zone is separated and fractionated to obtain dry gas, liquefied gas, light naphtha, heavy naphtha and tail oil;

[0013] The tail oil, at least part of the liquefied gas and at least part of the light naphtha are circulated back to the hydrocracking reaction zone as the circulating oil.

[0014] In the hydrocracking method, the tail oil is a fraction heavier than heavy naphtha, generally a fraction with an initial distillation point higher than 175°C.

[0015] In the hydrocracking method, the hydrocracking reaction zone is provided with a plurality of hydrocracking catalyst beds, preferably more than 4, and further preferably 5 to 7. The beds can be divided by a cold hydrogen box.

[0016] In the hydrocracking method, hydrogen is separated at the top of the separation system and can be circulated back to the hydrogenation pretreatment reaction zone and the hydrocracking reaction zone as circulating hydrogen.

[0017] In the hydrocracking method, the hydropretreatment reaction zone is filled with a hydropretreatment catalyst. The hydropretreatment catalyst includes a carrier and a hydrogenation active metal; the hydrogenation active metal includes a Group VIB metal and / or a Group VIII metal, and the carrier is an inorganic refractory oxide, which can be selected from one or more of alumina, amorphous silica-alumina, silicon dioxide, titanium oxide, etc. The Group VIB metal is preferably W and / or Mo, and the Group VIII metal is preferably Ni and / or Co. Based on the weight of the catalyst, the content of the Group VIB metal in terms of oxide is 12% to 37%, preferably 15% to 32%, and the content of the Group VIII metal in terms of oxide is 0.5% to 7.5%, preferably 1% to 7%. The hydropretreatment catalyst can be selected from various existing conventional commercial catalysts, such as FF-36, FF-46, FF-56, FF-66 and other hydrocracking pretreatment catalysts developed by Dalian Petrochemical Research Institute; it can also be prepared according to the common sense in the field according to actual needs.

[0018] In the hydrocracking method, the hydrocracking reaction zone is loaded with a hydrocracking catalyst. The hydrocracking catalyst includes a cracking component, a hydrogenation component and a binder. The cracking component includes amorphous silica-alumina and / or a molecular sieve, and the molecular sieve includes but is not limited to a Y-type molecular sieve, such as a USY-type molecular sieve, and the binder can be alumina or silicon oxide. The hydrogenation component is selected from one or more of the metals, metal oxides or metal sulfides of Group VI, Group VII, and Group VIII, preferably one or more of iron, chromium, molybdenum, tungsten, cobalt, nickel, or their sulfides or oxides. Based on the weight of the catalyst, the content of the hydrogenation component is 10wt% to 40wt% in terms of oxide, preferably 15wt% to 35wt%, and the content of the molecular sieve is 30wt% to 70wt%, preferably 31wt% to 70wt%. The hydrocracking catalyst can be selected from an existing commercial hydrocracking catalyst, or a specific hydrocracking catalyst can be prepared as needed. The main commercial hydrocracking catalysts are: HC-185, HC-680 from UOP and FC-46, FC-52 developed by Dalian Petrochemical Research Institute.

[0019] In the hydrocracking method, in the raw material containing wax oil, the wax oil can be derived from at least one of light vacuum wax oil (LVGO), vacuum wax oil (VGO), heavy vacuum wax oil (HVGO), heavy coker wax oil (HCGO), coker wax oil (CGO), and ebullated bed hydrogenated wax oil. The raw material containing wax oil can also include one or more of catalytic light cycle oil (LCO), deasphalted oil (DAO), ebullated bed hydrogenated diesel, coker diesel, etc. Preferably, the wax oil accounts for more than 30wt% of the total mass of the raw material containing wax oil, and further 35wt% to 100wt%.

[0020] In the hydrocracking method, the nitrogen content of the wax oil is generally below 0.20wt%, preferably below 0.18wt%, further 0.01wt% to 0.18wt%, the sulfur content is not particularly required, the initial boiling point is generally 280 to 340°C, the final boiling point is generally 470 to 580°C, and the aromatic content is 15wt% to 50wt%, preferably 20wt% to 45wt%. The wax oil can be selected from one or more of various vacuum wax oils (VGO) obtained by processing Middle East crude oil, such as one or more of Iranian VGO, Saudi VGO, etc., or one or more of various vacuum wax oils (VGO) obtained by processing Daqing crude oil or Liaohe crude oil. Any liquid wax oil product suitable as a raw material for a hydrocracking unit is within the applicable scope.

[0021] In order to further reduce the concentrated cracking of saturated hydrocarbons when producing heavy naphtha from raw materials, an aromatic component can be blended, preferably, catalytic diesel rich in various aromatic structures is added to the raw materials, preferably, the aromatic component accounts for less than 65wt% of the total mass of the wax oil-containing raw material, preferably 1wt% to 65wt%. The aromatic component can be catalytic diesel, whose initial distillation point is generally 120 to 240°C, preferably 130 to 220°C, and the final distillation point is generally 320 to 400°C, preferably 350 to 380°C, and the aromatic content is above 60wt%, preferably above 65wt%, and further 66wt% to 90wt%. The density (20°C) of the catalytic diesel is generally 0.90g·cm -3 Above, preferably 0.92 g·cm -3 Above, further 0.92 g·cm -3 ~0.97g·cm -3 The catalytic diesel raw material can be selected from catalytic cracking products obtained by processing any base oil, for example, it can be selected from catalytic diesel obtained by processing Middle East crude oil, specifically, it can be a catalytic diesel component obtained by processing Iranian crude oil, Saudi crude oil, etc.

[0022] In the hydrocracking method, the main process conditions of the hydrotreating pretreatment reaction zone include: average reaction temperature of 310°C to 445°C, inlet hydrogen-oil volume ratio of 400:1 to 1000:1, operating pressure of 10.0MPa to 16.5MPa, liquid hourly volume space velocity of 0.3h -1 ~4.5h -1 Preferably, the average reaction temperature is 330°C to 420°C, the inlet hydrogen-oil volume ratio is 500:1 to 900:1, the operating pressure is 11.0MPa to 15.0MPa, and the liquid hourly volume space velocity is 0.5h -1 ~4.0h -1 .

[0023] In the hydrocracking method, the main process conditions of the hydrocracking reaction zone include: average reaction temperature of 330°C to 450°C, inlet hydrogen-oil volume ratio of 700:1 to 1400:1, operating pressure of 10.0MPa to 16.5MPa, liquid hourly volume space velocity of 0.3h -1 ~4.0h -1 Preferably, the average reaction temperature is 340°C to 420°C, the inlet hydrogen-oil volume ratio is 800:1 to 1300:1, the operating pressure is 11.0MPa to 15.0MPa, and the liquid hourly volume space velocity is 0.5h -1 ~3.5h -1 .

[0024] In the hydrocracking method, the operations of separation and fractionation systems are well known to those skilled in the art and need not be described in detail.

[0025] In the hydrocracking method, the main components of the liquefied gas are C3 and C4, and the light naphtha is preferably a fraction of the hydrocracking product with a distillation temperature higher than the liquefied gas and less than 65° C. Based on the output quality of heavy naphtha, the mass fractions of the liquefied gas and light naphtha respectively account for 6wt% to 9wt% and 12wt% to 16wt%.

[0026] Compared with the prior art, it has the following beneficial effects:

[0027] (1) The hydrocracking method of the present invention adopts a full-cycle single-stage hydrocracking process, and uses part of the liquefied gas and light naphtha as the circulating oil in the hydrocracking reaction zone. The circulating liquefied gas and light naphtha fraction can be completely dissolved in the circulating oil, and will not cause non-ideal processes such as gasification. The reaction balance of the entire fraction can be effectively controlled, and the purpose of increasing the production of heavy naphtha and improving the quality of heavy naphtha can be achieved.

[0028] (2) The present invention preferably introduces aromatic-rich components into the processed hydrocracking feedstock, thereby achieving differentiation of the feedstock structure, reducing excessive cracking of saturated components, and improving the yield of the target product.

[0029] (3) The present invention uses a hydrocracking catalyst with a high molecular sieve content and multiple hydrocracking catalyst beds, which optimizes the hot spot temperature and curbs the conditions for the occurrence of side reactions. This not only prolongs the operating cycle of the device, but also increases the yield of heavy naphtha.

[0030] (4) The hydrocracking method of the present invention can achieve the purpose of maximizing the production of heavy naphtha without any additional auxiliary measures. It has the advantages of simple implementation, minimal investment, easy operation, flexible adjustment means, and obvious effect. It can follow the current development trend of increasing the production of chemical materials to design new devices or transform existing devices, conform to the law of market demand, and has strong application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the process flow of the present invention. DETAILED DESCRIPTION

[0032] The method of the present invention is described below in conjunction with the accompanying drawings. Some conventional unit diagrams that are not necessary for description are integrated and summarized as a separation system and a fractionation system.

[0033] like Figure 1 As shown, the process flow of the present invention is as follows:

[0034] The feedstock oil 1 and the circulating hydrogen 7 are mixed and then enter the hydrotreating reaction zone 2 filled with a hydrotreating catalyst for hydrotreating. The reaction effluent 3 enters the hydrocracking reaction zone 4 filled with a plurality of hydrocracking catalyst beds for hydrocracking reaction. The reaction effluent 5 enters the separation system 6 for separation, and the circulating hydrogen 7 is obtained at the top. The reaction stream 8 discharged from the bottom enters the subsequent fractionation system 9 for product fractionation and circulation process. From top to bottom, dry gas 10, liquefied gas 11, light naphtha 12, heavy naphtha 13 and tail oil 14 are obtained in sequence, wherein the liquefied gas 11 and part of the light naphtha 12 are mixed with the tail oil 14 to obtain the circulating oil 15, which is returned to the hydrocracking reaction zone 4 for reaction. The final output product of the present invention is mainly heavy naphtha 13, thereby achieving the increase of heavy naphtha production.

[0035] The method of the present invention is further described below with reference to the embodiments and comparative examples.

[0036] In the present invention, unless otherwise specified, percentages refer to mass fractions.

[0037] The process of the method of the present invention is as follows: Figure 1 The properties of the raw oil involved are shown in Table 1, the main physical and chemical properties of the catalyst are shown in Table 2, the relevant control conditions are shown in Table 3, and the effect comparison is shown in Table 4.

[0038] Example 1

[0039] This embodiment is based on the method and Figure 1 The process operation is to process the feedstock 1 shown in Table 1, the hydrotreating reaction zone is filled with FF-66 and the hydrocracking reaction zone is filled with FC-52, and the liquid hourly volume space velocity in the hydrotreating reaction zone is 1.0 h -1The reaction pressure is 13.5MPa, the reaction temperature is 365℃, the hydrogen-oil volume ratio is 800, the nitrogen content of the hydropretreatment oil is controlled to be 5mg / kg, the hydropretreatment oil obtained after the raw oil reacts in the hydropretreatment reaction zone enters the hydrocracking reaction zone from the top of the hydrocracking reactor, and 5 hydrocracking catalyst beds are set in the hydrocracking reaction zone. The reaction conditions are liquid hourly volume space velocity of 1.5h -1 , the reaction temperature is 383°C, the reaction pressure is 13.2MPa, the hydrogen-to-oil volume ratio is 1200, the single-pass conversion rate is 65%, and the product enters the subsequent separation and fractionation system to obtain dry gas, liquefied gas, light naphtha, heavy naphtha and tail oil components. The tail oil, part of the liquefied gas and part of the light naphtha are circulated back to the hydrocracking reactor from the top of the hydrocracking reactor as circulating oil for hydrocracking reaction, wherein the circulating liquefied gas accounts for 7% of the weight of the heavy naphtha, and the circulating light naphtha accounts for 13% of the weight of the heavy naphtha.

[0040] Example 2

[0041] This embodiment is based on the method and Figure 1 The process operation is to process the feedstock 2 shown in Table 1, the hydrotreating reaction zone is filled with FF-66 and the hydrocracking reaction zone is filled with FC-52, and the liquid hourly volume space velocity in the hydrotreating reaction zone is 1.0h -1 The reaction pressure is 13.5MPa, the reaction temperature is 369℃, the hydrogen-oil volume ratio is 800, the nitrogen content of the hydropretreatment oil is controlled to be 5mg / kg, the hydropretreatment oil obtained after the feed oil reacts in the hydropretreatment reaction zone enters the hydrocracking reaction zone from the top of the hydrocracking reactor, and 5 hydrocracking catalyst beds are set in the hydrocracking reaction zone. The reaction conditions are liquid hourly volume space velocity of 1.5h -1 The reaction temperature is 387°C, the reaction pressure is 13.2MPa, the hydrogen-to-oil volume ratio is 1200, the single-pass conversion rate is 65%, and the product enters the subsequent separation and fractionation system to obtain dry gas, liquefied gas, light naphtha, heavy naphtha and tail oil components. The tail oil, part of the liquefied gas and part of the light naphtha are circulated back to the hydrocracking reactor from the top of the hydrocracking reactor as circulating oil for hydrocracking reaction, wherein the circulating liquefied gas accounts for 7% of the weight of the heavy naphtha, and the circulating light naphtha accounts for 13% of the weight of the heavy naphtha.

[0042] Example 3

[0043] This embodiment is based on the method and Figure 1 The process operation is to process the feedstock 1 shown in Table 1, the hydrotreating reaction zone is filled with FF-66 and the hydrocracking reaction zone is filled with FC-52, and the liquid hourly volume space velocity in the hydrotreating reaction zone is 1.2h -1The reaction pressure is 11.5MPa, the reaction temperature is 375℃, the hydrogen-oil volume ratio is 800, the nitrogen content of the hydropretreatment oil is controlled to be 5mg / kg, the hydropretreatment oil obtained after the feed oil reacts in the hydropretreatment reaction zone enters the hydrocracking reaction zone from the top of the hydrocracking reactor, and 5 hydrocracking catalyst beds are set in the hydrocracking reaction zone. The reaction conditions are liquid hourly volume space velocity of 1.5h -1 The reaction temperature is 393°C, the reaction pressure is 11.2MPa, the hydrogen-to-oil volume ratio is 1200, the single-pass conversion rate is 65%, and the product enters the subsequent separation and fractionation system to obtain dry gas, liquefied gas, light naphtha, heavy naphtha and tail oil components. The tail oil, part of the liquefied gas and part of the light naphtha are recycled from the top of the hydrocracking reactor to the hydrocracking reactor as circulating oil for hydrocracking reaction, wherein the circulating liquefied gas accounts for 7% of the weight of the heavy naphtha, and the circulating light naphtha accounts for 13% of the weight of the heavy naphtha.

[0044] Example 4

[0045] This embodiment is based on the method and Figure 1 The process operation is to process the feedstock 1 shown in Table 1, the hydrotreating reaction zone is filled with FF-66 and the hydrocracking reaction zone is filled with FC-52, and the liquid hourly volume space velocity in the hydrotreating reaction zone is 1.0 h -1 The reaction pressure is 13.5MPa, the reaction temperature is 363℃, the hydrogen-oil volume ratio is 800, the nitrogen content of the hydropretreatment oil is controlled to be 8mg / kg, the hydropretreatment oil obtained after the feed oil reacts in the hydropretreatment reaction zone enters the hydrocracking reaction zone from the top of the hydrocracking reactor, and 5 hydrocracking catalyst beds are set in the hydrocracking reaction zone. The reaction conditions are liquid hourly volume space velocity of 1.5h -1 , the reaction temperature is 384°C, the reaction pressure is 13.2MPa, the hydrogen-to-oil volume ratio is 1200, the single-pass conversion rate is 65%, and the product enters the subsequent separation and fractionation system to obtain dry gas, liquefied gas, light naphtha, heavy naphtha and tail oil components. The tail oil, part of the liquefied gas and part of the light naphtha are recycled from the top of the hydrocracking reactor to the hydrocracking reactor as circulating oil for hydrocracking reaction, wherein the circulating liquefied gas accounts for 8% of the weight of the heavy naphtha, and the circulating light naphtha accounts for 14% of the weight of the heavy naphtha.

[0046] Comparative Example 1

[0047] According to the conventional single-stage full-cycle method, the raw material 1 shown in Table 1 is processed, the hydrogenation pretreatment reaction zone is filled with FF-66 and the hydrocracking reaction zone is filled with FC-52, the raw oil and hydrogen are fed from the top of the hydrogenation pretreatment reaction zone, and the liquid hourly volume space velocity of the hydrogenation pretreatment reaction zone is 1.0h -1The reaction pressure is 13.5MPa, the reaction temperature is 365℃, the hydrogen-oil volume ratio is 800, the nitrogen content of the hydropretreatment oil is controlled to be 5mg / kg, the hydropretreatment oil obtained after the raw oil reacts in the hydropretreatment reaction zone enters the hydrocracking reaction zone from the top of the hydrocracking reactor, and 5 hydrocracking catalyst beds are set in the hydrocracking reaction zone. The reaction conditions are liquid hourly volume space velocity of 1.5h -1 The reaction temperature is 383°C, the reaction pressure is 13.2MPa, the hydrogen-to-oil volume ratio is 1200, the single-pass conversion rate is 65%, and the product enters the subsequent separation and fractionation system to obtain dry gas, liquefied gas, light naphtha, heavy naphtha and tail oil components. The tail oil is circulated back to the hydrocracking reactor from the top of the hydrocracking reactor as circulating oil for hydrocracking reaction.

[0048] Comparative Example 2

[0049] This comparative example is based on the method of the present invention and Figure 1 The process operation is to process the feedstock 1 shown in Table 1, the hydrotreating reaction zone is filled with FF-66 and the hydrocracking reaction zone is filled with FC-52, and the liquid hourly volume space velocity in the hydrotreating reaction zone is 1.0 h -1 The reaction pressure is 13.5MPa, the reaction temperature is 365℃, the hydrogen-oil volume ratio is 800, the nitrogen content of the hydropretreatment oil is controlled to be 5mg / kg, the hydropretreatment oil obtained after the raw oil reacts in the hydropretreatment reaction zone enters the hydrocracking reaction zone from the top of the hydrocracking reactor, and 5 hydrocracking catalyst beds are set in the hydrocracking reaction zone. The reaction conditions are liquid hourly volume space velocity of 1.5h -1 , the reaction temperature is 383°C, the reaction pressure is 13.2MPa, the hydrogen-to-oil volume ratio is 1200, the single-pass conversion rate is 65%, and the product enters the subsequent separation and fractionation system to obtain dry gas, liquefied gas, light naphtha, heavy naphtha and tail oil components. The tail oil, part of the liquefied gas and part of the light naphtha are circulated back to the hydrocracking reactor from the top of the hydrocracking reactor as circulating oil for hydrocracking reaction, wherein the circulating liquefied gas accounts for 2% of the weight of the heavy naphtha, and the circulating light naphtha accounts for 5% of the weight of the heavy naphtha.

[0050] Table 1 Raw oil properties

[0051] Source of raw materials Mixed raw materials* Vacuum wax oil Catalytic diesel serial number Crude oil 1 Crude oil 2 Crude oil 3 <![CDATA[Density (20 °C) / g·cm -3 > 0.9210 0.9168 0.9440 Distillation range / ℃ 215～544 336～542 136～371 <![CDATA[Sulfur / mg·kg -1 > 14300 15900 8100 <![CDATA[Nitrogen / mg·kg -1 > 1474 1681 914 Aromatic content, % 51.9 45.3 78.3

[0052] *The mixed stock consists of 20% catalytic diesel and 80% vacuum gas oil in Table 1.

[0053] Table 2 Main physical and chemical properties of catalysts

[0054] project FF-66 FC-52 Chemical composition Mo-Ni Mo-Ni Physical properties Appearance and shape Shamrock Strips Cylindrical Bar Crushing strength, N / cm ≥150 >130 Particle diameter, mm 1.0～1.4 1.5～1.7 Molecular sieve type / content, wt% -- Y-type molecular sieve / 50

[0055] Table 3 Main reaction conditions for each example

[0056]

[0057] Table 4 Comparison of the effects obtained in each case

[0058]

Claims

1. A hydrocracking process for producing heavy naphtha, the process comprising a hydrotreating reaction zone and a hydrocracking reaction zone, the process comprising: (1) The wax oil-containing raw material and hydrogen are passed through the hydrogenation pretreatment reaction zone for hydrogenation pretreatment, and the nitrogen content of the effluent from the hydrogenation pretreatment reaction zone is controlled to be below 30 mg / kg. (2) The effluent from the hydrotreating reaction zone is mixed with the circulating oil and then enters the hydrocracking reaction zone for reaction. The effluent from the hydrocracking reaction zone is separated and fractionated to obtain dry gas, liquefied gas, light naphtha, heavy naphtha and tail oil; wherein the tail oil, at least part of the liquefied gas and at least part of the light naphtha are circulated back to the hydrocracking reaction zone as the circulating oil; The hydrocracking reaction zone is provided with more than 4 hydrocracking catalyst beds; Based on the output quality of heavy naphtha, the mass fractions of liquefied gas and light naphtha are 6wt%~9wt% and 12wt%~16wt% respectively; Aromatic-rich components are blended into the wax-containing oil raw material, wherein the aromatic-rich components account for less than 65wt% of the total mass of the wax-containing oil raw material, and the aromatic content of the aromatic-rich components is more than 60wt%.

2. The method according to claim 1, characterized in that: The wax oil-containing raw material and hydrogen are passed through a hydrogenation pretreatment reaction zone for hydrogenation pretreatment, and the nitrogen content of the effluent from the hydrogenation pretreatment reaction zone is controlled to be 5-25 mg / kg.

3. The method according to claim 1, characterized in that The tail oil is a fraction heavier than heavy naphtha, and has an initial distillation point higher than 175°C.

4. The method according to claim 1, characterized in that: The hydrocracking reaction zone is provided with 5 to 7 hydrocracking catalyst beds.

5. The method according to claim 1, characterized in that The effluent from the hydrocracking reaction zone is separated by a separation system, and hydrogen separated from the top of the separation system is used as circulating hydrogen to circulate back to the hydrogenation pretreatment reaction zone and the hydrocracking reaction zone.

6. The method according to claim 1, characterized in that The hydrogenation pretreatment reaction zone is filled with a hydrogenation pretreatment catalyst; based on the weight of the catalyst, the content of the Group VIB metal in terms of oxide is 12% to 37%, and the content of the Group VIII metal in terms of oxide is 0.5% to 7.5%.

7. The method according to claim 6, characterized in that The hydrogenation pretreatment reaction zone is filled with a hydrogenation pretreatment catalyst; based on the weight of the catalyst, the content of the Group VIB metal in terms of oxide is 15% to 32%, and the content of the Group VIII metal in terms of oxide is 1% to 7%.

8. The method according to claim 1, characterized in that: The hydrocracking reaction zone is filled with a hydrocracking catalyst; based on the weight of the catalyst, the content of the hydrogenation component is 10wt%~40wt% in terms of oxide, and the content of the molecular sieve is 30wt%~70wt%; the hydrogenation component is selected from one or more of the metals, metal oxides or metal sulfides of Group VIB, Group VIIB and Group VIII.

9. The method according to claim 8, characterized in that The hydrocracking reaction zone is filled with a hydrocracking catalyst; based on the weight of the catalyst, the content of the hydrogenation component is 15wt% to 35wt% in terms of oxide; and the content of the molecular sieve is 31wt% to 70wt%.

10. The method according to claim 1, characterized in that In the wax oil-containing raw material, the wax oil comes from at least one of vacuum wax oil, coking wax oil, and fluidized bed hydrogenated wax oil; the wax oil accounts for more than 30wt% of the total mass of the wax oil-containing raw material.

11. The method according to claim 10, characterized in that In the wax oil-containing raw materials, the wax oil is derived from at least one of light vacuum wax oil, heavy vacuum wax oil, and heavy coking wax oil.

12. The method according to claim 10, characterized in that The waxy oil-containing raw materials also include one or more of catalytic light cycle oil, deasphalted oil, ebullated bed hydrogenated diesel, and coker diesel; the waxy oil accounts for 35wt% to 100wt% of the total mass of the waxy oil-containing raw materials.

13. The method according to claim 10, characterized in that The wax oil has a nitrogen content of less than 0.20 wt %, an initial distillation point of 280-340° C., a final distillation point of 470-580° C., and an aromatic hydrocarbon content of 15 wt %-50 wt %.

14. The method according to claim 13, characterized in that In the wax oil, the nitrogen content is below 0.18wt% and the aromatic hydrocarbon content is 20wt%~45wt%.

15. The method according to claim 1, characterized in that Aromatic-rich components are blended into the waxy oil-containing raw material, and the aromatic-rich components account for 1wt% to 65wt% of the total mass of the waxy oil-containing raw material.

16. The method according to claim 15, characterized in that The aromatic component is catalytic diesel; the initial distillation point of catalytic diesel is 120-240°C, the final distillation point is 320-400°C, the aromatic content is above 65wt%; the density is 0.90g·cm -3 above.

17. The method according to claim 16, characterized in that The aromatic content of the catalytic diesel is 66wt%~90wt%; the density is 0.92g·cm -3 above.

18. The method according to claim 17, characterized in that The density of the catalytic diesel is 0.92 g·cm -3 ~0.97g·cm -3 .

19. The method according to claim 1, characterized in that The process conditions of the hydrogenation pretreatment reaction zone include: average reaction temperature 310℃~445℃, inlet hydrogen-oil volume ratio 400:1~1000:1, operating pressure 10.0MPa~16.5MPa, liquid hourly volume space velocity 0.3h -1 ~4.5h -1 .

20. The method according to claim 19, characterized in that The process conditions of the hydrogenation pretreatment reaction zone include: average reaction temperature 330℃~420℃, inlet hydrogen-oil volume ratio 500:1~900:1, operating pressure 11.0MPa~15.0MPa, liquid hourly volume space velocity 0.5h -1 ~4.0h -1 .

21. The method according to claim 1, characterized in that The process conditions of the hydrocracking reaction zone include: average reaction temperature 330℃~450℃, inlet hydrogen-oil volume ratio 700:1~1400:1, operating pressure 10.0MPa~16.5MPa, liquid hourly volume space velocity 0.3h -1 ~4.0h -1 .

22. The method according to claim 21, characterized in that The process conditions of the hydrocracking reaction zone include: average reaction temperature 340℃~420℃, inlet hydrogen oil volume ratio 800:1~1300:1, operating pressure 11.0MPa~15.0MPa, liquid hourly volume space velocity 0.5h -1 ~3.5h -1 .

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