Hydrocracking method for increasing yield of heavy naphtha

Abstract

The invention discloses a hydrocracking method for increasing the yield of heavy naphtha. In the method, a hydrogenation pretreatment reaction zone and a hydrocracking reaction zone are arranged, the hydrocracking reaction zone is provided with at least three hydrocracking catalyst bed layers, and the method comprises the following steps: (1) hydrocracking raw materials and hydrogen pass through the hydrogenation pretreatment reaction zone for hydrogenation pretreatment; (2) an effluent of the hydrogenation pretreatment reaction zone enters a hydrocracking reaction zone from the top for a hydrocracking reaction, and an effluent of the hydrocracking reaction zone is subjected to separation and fractionation to obtain light hydrocarbon, light naphtha, heavy naphtha and tail oil heavier than the heavy naphtha; the tail oil is introduced between hydrocracking catalyst bed layers as circulating oil, the circulating oil quantity is sequentially reduced from top to bottom, and the circulating oil quantity ratio between adjacent bed layers is more than 2: 1. According to the method, various conventional hydrocracking raw materials can be processed, and the yield of heavy naphtha is increased.

Description

Technical Field

[0001] The present invention relates to a hydrocracking process, in particular to a hydrocracking method for increasing the output of heavy naphtha. Background Art

[0002] The future of the oil refining and chemical industry will certainly face at least two challenges: first, the new requirements for the industry under the background of "dual carbon", reducing carbon emissions is a goal to be pursued; second, the pressure demand for energy transformation and upgrading, oil refining refineries need to transform into chemical refineries. Specifically, according to the forecast data of some research institutions, by 2035, the proportion of petroleum products in global energy consumption will be reduced to 28.50%, which was 33.28% in 2017, but the economic value of chemical products will show an upward trend, reaching 50% in 2035. Faced with such a development trend, it has become inevitable to produce more chemical raw materials.

[0003] In the critical period of energy transformation, hydrocracking process technology, as one of the key technologies for lightening heavy oil and changing product structure, needs to give full play to its regulator role. Making good use of the advantages of hydrocracking technology is the trump card for the transformation of oil refining to chemical industry. At the same time, due to the addition of hydrogen content, hydrocracking products have excellent quality and performance, which will inevitably 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.

[0004] Heavy naphtha is one of the core products of hydrocracking technology. It can be used as a raw material for catalytic reforming to produce aromatics. Therefore, the increase in the production of heavy naphtha represents the increase in the production of chemical raw materials to a certain extent. When using the hydrocracking process to produce more heavy naphtha, there are many influencing factors that need to be considered, including the characteristics of the raw materials, the performance of the catalyst, the optimization of the process, etc. The heavy naphtha produced under different conditions is very different, and can reach up to 70%. How to further improve the yield of heavy naphtha when such a high yield can be achieved is the difficulty in the research and the direction of efforts. In other words, the further improvement of the yield of heavy naphtha brings not only technological progress, but also an urgent demand in the market environment.

[0005] CN201711119101.0 discloses a hydrocracking method for improving the yield of heavy naphtha. The method comprises: the raw oil is mixed with hydrogen and then enters a hydrofining reactor, contacts with a hydrofining 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, a hydrocracking reaction is carried out, the generated oil is mixed with the circulating oil between different beds, the reaction is continued, the obtained generated oil enters a separation system, the obtained hydrogen is recycled, the obtained generated distillate oil enters a fractionation system, and gas, light naphtha, heavy naphtha, middle distillate oil, and hydrogenated tail oil are obtained, the hydrogenated tail oil is circulated to the inlet of the hydrocracking reactor, and the middle distillate oil is recycled to the inlet of the hydrocracking reactor. Return to the catalyst bed of the hydrocracking reactor, wherein the middle distillate oil is distilled into three fractions according to the distillation range, namely, middle distillate 3, middle distillate 2, and middle distillate 1, the distillation range of middle distillate 1 is 160-230°C, the distillation range of middle distillate 2 is 200-280°C, and the distillation range of middle distillate 3 is 270-350°C. The hydrocracking reactor is set to 4 beds, wherein middle distillate 3 is circulated between the first and second beds of the hydrocracking reactor, middle distillate 2 is circulated between the second and third beds of the hydrocracking reactor, and middle distillate 1 is circulated between the third and fourth beds of the hydrocracking reactor. This method is prone to excessive cracking in each hydrocracking catalyst bed, resulting in a low yield of heavy naphtha.

[0006] CN201610179274.0 discloses a hydrocracking method and reaction device for maximum production of heavy naphtha. The method mixes inferior high-nitrogen high-aromatic fraction oil, partially recycled hydrogenation pre-refined products with hydrogen, and enters a liquid phase hydrorefining reactor for reaction after heating, and partially circulates the hydrogenation pre-refined products, and the remaining part is mixed with hydrogen and enters a hydrocracking reactor; the hydrocracking products enter a fractionation tower for fractionation to obtain products mainly composed of heavy naphtha, and the unconverted fraction is recycled back to the hydrocracking reactor for further reaction; wherein the number of catalyst beds in the hydrocracking reactor is two or more, and the first catalyst bed that first contacts the cracking feed is filled with a noble metal-modified molecular sieve type and / or amorphous silicon-aluminum hydrocracking catalyst, and the other catalyst beds are filled with rare earth-modified molecular sieve type and / or amorphous silicon-aluminum non-noble metal hydrocracking catalyst. This method adopts a conventional single-stage full-cycle process. Although the yield of heavy naphtha can be improved to a certain extent by relying on the grading of the catalyst, from the perspective of the conventional process, there is still the disadvantage of excessive cracking, which easily leads to a low yield of heavy naphtha. Summary of the invention

[0007] In conventional hydrocracking processes, when heavy naphtha is generally produced in maximum quantities, the cracking activity of the hydrocracking catalyst used is relatively strong. In a single-stage process, the process is mostly to circulate the fraction heavier than heavy naphtha to the inlet of the hydrofining reactor or the inlet of the hydrocracking reactor for further cracking to increase the production of heavy naphtha, which is generally called a single-stage full-cycle hydrocracking process technology. The inventors of the present invention have found through research that in the process of producing more heavy naphtha, the fraction heavier than heavy naphtha is not circulated as a single stream, but is circulated in sections and at different flow rates to different positions of the hydrocracking section, which can optimize the structural composition of the oil products in the reaction atmosphere, effectively form a gradient molecular layout, inhibit excessive cracking in the reaction process, and achieve increased production of heavy naphtha, thereby completing the present invention.

[0008] In view of the shortcomings of the prior art, the present invention provides a hydrocracking method for increasing the production of heavy naphtha.

[0009] The method of the present invention can process various conventional hydrocracking raw materials and achieve increased production of heavy naphtha.

[0010] The present invention provides a hydrocracking method for increasing the production of heavy naphtha, wherein a hydrotreating pretreatment reaction zone and a hydrocracking reaction zone are provided, and at least three hydrocracking catalyst beds are provided in the hydrocracking reaction zone. The method comprises:

[0011] (1) The hydrocracking feedstock and hydrogen are passed through a hydropretreatment reaction zone for hydropretreatment. Preferably, the nitrogen content of the reaction effluent is controlled to be below 20 mg / kg, preferably below 15 mg / kg;

[0012] (2) The effluent from the hydrotreating reaction zone enters the hydrocracking reaction zone from the top for hydrocracking reaction. After separation and fractionation, the effluent from the hydrocracking reaction zone is separated to obtain light hydrocarbons, light naphtha, heavy naphtha and tail oil heavier than heavy naphtha. The tail oil is introduced as circulating oil between the hydrocracking catalyst beds. The amount of circulating oil decreases from top to bottom, and the ratio of circulating oil between adjacent beds is above 2:1, preferably 2:1 to 4:1, by mass. In the hydrocracking method, preferably, the total amount of circulating oil is weighted and circulated according to the above-mentioned ratio limit.

[0013] According to the present invention, in the hydrocracking method, tail oil is introduced as circulating oil between the hydrocracking catalyst beds, preferably at the top of the lower catalyst bed between two adjacent catalyst beds.

[0014] According to the present invention, in the hydrocracking method, the total amount of the circulating oil accounts for 20wt% to 55wt% of the total hydrocracking feed mass, preferably 22wt% to 53wt%.

[0015] According to the present invention, in the hydrocracking method, the hydrocracking feedstock can be a conventional hydrocracking feedstock, generally at least one of wax oil or diesel, preferably wax oil, the wax oil has a final distillation point of generally 450 to 550°C, preferably 480 to 540°C, and a density of generally 0.93 g / cm 3 (20°C) or less, preferably 0.92 g / cm 3 The content of nitrogen is generally below 0.25wt%, preferably below 0.20wt%, and the content of sulfur is generally below 5wt%, preferably below 4wt%. The wax oil can be vacuum wax oil (VGO), which can be 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.

[0016] According to the present invention, in the hydrocracking method, the hydrocracking method adopts a single-stage hydrocracking process, wherein the hydropretreatment reaction zone and the hydropretreatment catalyst loaded therein can be arranged according to conventional requirements, and there is no special requirement in the present invention.

[0017] According to the present invention, preferably, in the hydrocracking method, the hydropretreatment reaction zone may be provided with a plurality of hydropretreatment catalyst beds, preferably more than 2, and further 3 to 4. Each hydropretreatment catalyst bed may be separated by a cold hydrogen box or other facilities.

[0018] According to the present invention, in the hydrocracking method, the hydropretreatment reaction zone is filled with a corresponding hydropretreatment catalyst. The catalyst includes a carrier and an active metal; the 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 hydropretreatment catalyst, the content of the Group VIB metal in terms of oxide is 11% to 37%, preferably 15% to 32%, and the content of the Group VIII metal in terms of oxide is 0.3% to 7.5%, preferably 1% to 7%. The hydropretreatment catalyst can use 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, and can also be prepared according to actual needs and common sense in the field.

[0019] According to the present invention, in the hydrocracking method, the raw material is subjected to desulfurization, denitrogenation, aromatic saturation and other processes through a hydrogenation pretreatment process, the purpose of which is to provide a suitable feed for the hydrocracking reaction. Generally, the nitrogen content of the product is controlled to be below 20 mg / kg, preferably below 15 mg / kg. At this time, it can be determined that the other corresponding impurity removal purposes have been achieved simultaneously, and this logistics can enter the hydrocracking reaction zone for subsequent reactions.

[0020] According to the present invention, in the hydrocracking method, the operating conditions of the hydrogenation pretreatment reaction zone are: the average reaction temperature is 300°C to 440°C, the inlet hydrogen-oil volume ratio is 450:1 to 1000:1, the reaction pressure is 8.0MPa to 16.5MPa, and the liquid hourly volume space velocity is 0.3h -1 ~4.0h -1 The preferred operating conditions are: average reaction temperature of 310°C to 430°C, inlet hydrogen-oil volume ratio of 500:1 to 950:1, reaction pressure of 9.0MPa to 16.0MPa, liquid hourly volume space velocity of 0.5h -1 ~3.5h -1 The single-pass conversion rate of the hydrocracking reaction process is 45wt% to 80wt%.

[0021] According to the present invention, in the hydrocracking method, more than 3 hydrocracking catalyst beds are arranged in the hydrocracking reaction zone, preferably 4 to 6. The hydrocracking catalyst beds can be arranged at equal heights, and the beds can be divided by facilities such as cold hydrogen boxes. Among them, the top is the first hydrocracking catalyst bed, and the hydrocracking catalyst beds are arranged in sequence downward (i.e., from top to bottom, the first hydrocracking catalyst bed, the second hydrocracking catalyst bed, the third hydrocracking catalyst bed, etc.).

[0022] According to the present invention, in the hydrocracking method, heavy naphtha is the heaviest component of all products, with a final distillation point of 173-177°C and an initial distillation point of generally 63-67°C.

[0023] According to the present invention, in the hydrocracking method, the circulating oil is tail oil heavier than heavy naphtha, and the initial distillation point is 173-177°C.

[0024] According to the present invention, in the hydrocracking method, the hydrocracking catalyst loaded in the hydrocracking reaction zone is a hydrocracking catalyst for producing heavy naphtha, generally a light oil type hydrocracking catalyst. The catalyst includes a cracking component and a hydrogenation component, and may also contain components such as a binder. The cracking component preferably includes a molecular sieve, and may also include amorphous silica-alumina, and the molecular sieve includes but is not limited to a Y-type molecular sieve, such as a USY molecular sieve. The binder may be alumina and / or silicon oxide. The hydrogenation component is selected from one or more of the metals of Group VIB and Group VIII, preferably one or more of iron, chromium, molybdenum, tungsten, cobalt, and nickel. Based on the weight of the hydrocracking catalyst, the content of the hydrogenation component is 11wt% to 40wt% in terms of oxide, preferably 15wt% to 35wt%, and the content of the molecular sieve is 35wt% to 70wt%, preferably 40wt% to 70wt%. The hydrocracking catalyst can be selected from existing commercial hydrocracking catalysts, such as HC-185, HC-680 of UOP and FC-46, FC-52 developed by Dalian Petrochemical Research Institute, etc., or a hydrocracking catalyst that meets the requirements can be prepared as needed.

[0025] According to the present invention, in the hydrocracking method, the hydrocracking catalyst loaded in the hydrocracking reaction zone can be loaded with the above-mentioned hydrocracking catalyst for producing heavy naphtha in an equal proportion.

[0026] According to the present invention, in the hydrocracking method, the operating conditions of the hydrocracking reaction zone are: the average reaction temperature is 310°C to 445°C, the inlet hydrogen-oil volume ratio is 650:1 to 1400:1, the reaction pressure is 8.0MPa to 16.5MPa, and the liquid hourly volume space velocity is 0.3h -1 ~4.5h -1 Preferably, the average reaction temperature is 320°C to 440°C, the inlet hydrogen-oil volume ratio is 700:1 to 1350:1, the pressure is 9.0MPa to 16.0MPa, and the liquid hourly volume space velocity is 0.5h -1 ~4.0h -1 .

[0027] According to the present invention, in the hydrocracking method, the separation system performs gas-liquid separation to obtain a gas phase and a liquid phase, wherein hydrogen is separated from the gas phase and can be circulated back to the hydrogenation pretreatment reaction zone or the hydrocracking reaction zone as circulating hydrogen; the liquid phase enters the distillation system, and light hydrocarbons, light naphtha, heavy naphtha and tail oil are obtained by distillation. This part of the content and operation are well known to technicians in this field and do not need to be described here.

[0028] According to the present invention, in the hydrocracking method, the hydrogenation pretreatment reaction zone and the hydrocracking reaction zone may use protective agents and / or post-treatment agents in actual applications according to the characteristics of the raw materials.

[0029] The existing technologies for producing heavy naphtha by single-stage full-cycle hydrocracking mainly include:

[0030] (1) Conventional single-stage full-cycle hydrocracking technology is to recycle components heavier than the heavy naphtha fraction back to the inlet of the hydrotreating reactor or the hydrocracking reactor to increase the production of heavy naphtha. This method fails to control the secondary cracking reaction of heavy naphtha, resulting in a significant increase in the production of light hydrocarbons such as dry gas and liquefied gas and light naphtha, a decrease in the selectivity of heavy naphtha, and the heavy naphtha obtained usually has a low aromatic potential and poor quality.

[0031] (2) The method disclosed in CN201711119101.0 is based on the conventional single-stage full-cycle hydrocracking technology, and the components heavier than the heavy naphtha fraction are divided into an intermediate distillate oil and a tail oil fraction. The tail oil is circulated to the entrance of the hydrocracking reaction zone, and the intermediate distillate is divided into multiple fractions according to weight, and circulated from heavy to light between the catalyst beds corresponding to the top to the bottom. This is based on the mechanism of preferential cracking of heavy components (macromolecular) and the reaction characteristics of the graded hydrocracking catalyst and the weight of the circulating oil. A scientific circulating oil feed position is set. From the perspective of chemical reaction, the intermediate distillate can be obtained by shallow cracking to obtain a heavy naphtha fraction, so as to control the occurrence of secondary cracking reaction, thereby improving the selectivity of heavy naphtha. However, the inventors of the present invention have found that if the circulating oil is fed according to the shallow cracking of the intermediate distillate, the concentration of the reactants of the corresponding similar components in the corresponding hydrocracking catalyst bed will increase significantly, which will lead to an acceleration of the reaction rate at this time, and will also increase the occurrence of side reactions accordingly. It is possible that the tendency of multiple cracking will increase, resulting in an increase in non-target components such as gas, and the target product will inevitably decrease.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) The hydrocracking method of the present invention adopts a single-stage hydrocracking process, and the fraction heavier than heavy naphtha produced during the reaction is subjected to a staged directional circulation, and introduced between the catalyst beds in a step-by-step decreasing ratio from top to bottom according to the layout of the hydrocracking catalyst bed. Since the circulating oil is a mixed component, its composition is much wider than the components (referred to as similar components in the present invention) that are introduced into the catalyst bed for key cracking. The heavy components therein will inhibit the reaction of the similar components, and the light components as the products of the step-by-step reaction of the similar components will also inhibit the reaction of the similar components. The concentration is also lower than the concentration of the same component when a single component is circulated as in CN201711119101.0, and a step-by-step decreasing circulating oil volume is adopted. In this way, the present invention can achieve directional and precise control at the microscopic level according to the reaction order of different molecules, regulate the reaction concentration of each component, improve the adsorption efficiency of the heavy component, avoid excessive cracking of the target product, reduce the gasification rate of the reaction process, increase the liquid yield, and effectively control the conversion depth of the reaction raw materials, thereby achieving the purpose of the invention of improving the selectivity of heavy naphtha and increasing the production of heavy naphtha.

[0034] (2) The present invention introduces circulating oil between different beds in the hydrocracking zone. Through reasonable design, the amount of cold hydrogen used in the traditional bed cooling mode can be reduced to a certain extent, or even the cooling mode can be cancelled, effectively reducing the energy consumption of the circulating hydrogen compressor and saving the use of steam. In addition, the circulating oil does not need to be fractionated and cut according to the difference in fractions, but only needs to be circulated and pumped, which plays a certain role in energy saving and consumption reduction of the device, and is very consistent with the optimization direction of the current hydrocracking process.

[0035] (3) The hydrocracking method of the present invention can be powered by the existing circulating oil pump of the device and by making minor modifications to the bed cooling means. In principle, the purpose of maximizing the production of heavy naphtha can be achieved without adding any additional equipment. The method itself has the characteristics of small changes, low investment, quick results, and great advantages. It is in line with the development direction of energy conservation and consumption reduction, low-carbon development, oil conversion, and oil production in the field of refining and chemical industry under the current "dual carbon" background, and has significant value for application and promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the principle process flow of the present invention;

[0037] Description of main reference numerals:

[0038] 1-raw oil, 2-hydrogenation pretreatment reaction zone, 3-pretreatment reaction effluent, 4-hydrocracking reaction zone, 5-cracking reaction effluent, 6-separation system, 7-circulating hydrogen, 8-reactant flow after separation, 9-fractionation system, 10-light hydrocarbons, 11-light naphtha, 12-heavy naphtha, 13-circulating tail oil. DETAILED DESCRIPTION

[0039] Combine the following Figure 1 The process of the present invention is described in detail, and some conventional parts that are not described in the present invention are not fully mentioned, such as protective agents and post-treatment catalysts, and some necessary units but also conventional are also reasonably integrated in the figure, such as separation systems and distillation systems.

[0040] like Figure 1 As shown, the process flow of the present invention is described as follows:

[0041] After the raw oil 1 is mixed with the circulating hydrogen 7, it enters the hydrotreating reaction zone 2 filled with the hydrotreating catalyst as a reactant to carry out the raw material pretreatment reaction, and the effluent 3 enters the hydrocracking reaction zone 4 filled with a plurality of (taking 4 as an example) hydrocracking catalyst beds to carry out the hydrocracking reaction, and the number of beds is arranged according to the direction of the logistics, and the circulating tail oil 13 is introduced at the entrance of the second, third and fourth beds. The effluent 5 of the cracking reaction enters the subsequent separation system 6 for separation, and the circulating hydrogen 7 is obtained at the top, and the reaction stream 8 discharged from the bottom enters the subsequent fractionation system 9 for product fractionation and circulation process. In the fractionation system, light hydrocarbons 10, light naphtha 11, heavy naphtha 12 and circulating tail oil 13 are obtained from top to bottom in sequence, and the circulating tail oil 13 returns to the hydrocracking reaction zone 4 for reaction. The final target product of the present invention is heavy naphtha 12, thereby achieving its increased production.

[0042] The technical scheme and effect of the method of the present invention are described in detail below in conjunction with specific embodiments and comparative examples. In the process of describing the examples, if no special explanation is given, the percentages refer to the percentages by mass.

[0043] In the present invention, each embodiment adopts Figure 1 The process flow is shown in Table 1, the properties of the raw oil used are shown in Table 1, the main physical and chemical properties of the catalyst used are shown in Table 2, the process control conditions are shown in Table 3, and the implementation effects of each example are shown in Table 4.

[0044] Example 1

[0045] The hydrogenation pretreatment reaction zone and the hydrocracking reaction zone are respectively loaded with industrial catalysts FF-66 and FC-52.

[0046] Based on fresh raw materials, the liquid hourly volume space velocity in the hydrogenation pretreatment reaction zone is 1.0h -1 The reaction pressure is 15.5MPa, the average reaction temperature is 360℃, the inlet hydrogen-to-oil volume ratio is 850, and the nitrogen content of the oil generated by hydrogenation pretreatment is controlled to be 10mg / kg.

[0047] The oil produced after the raw material passes through the hydrogenation pretreatment reaction zone enters the hydrocracking reaction zone, in which 4 hydrocracking catalyst beds are set. The reaction conditions of the hydrocracking reaction zone are: the liquid hourly volume space velocity is 1.5h-1 according to the fresh raw material. -1 , the average reaction temperature is 368°C, the reaction pressure is 15.3MPa, and the inlet hydrogen-to-oil volume ratio is 1250. The single-pass conversion rate of the hydrocracking reaction process is 65wt%.

[0048] The reaction effluent is subsequently separated and fractionated to obtain light hydrocarbons, light naphtha, heavy naphtha and tail oil fractions, wherein the tail oil is returned to the top of the second, third and fourth beds of the hydrocracking reaction zone, and the ratio of the circulating oil amount of the tail oil returning to the top of the second, third and fourth beds of the hydrocracking reaction zone is 60:28:12. The total amount of circulating oil in this example accounts for 35wt% of the total feed mass of the hydrocracking.

[0049] In this example, the final boiling point of heavy naphtha is 175°C and the initial boiling point is 65°C. The initial boiling point of the cycle oil tail oil is 175°C.

[0050] Example 2

[0051] The hydrogenation pretreatment reaction zone and the hydrocracking reaction zone are respectively loaded with industrial catalysts FF-66 and FC-52.

[0052] Based on fresh raw materials, the liquid hourly volume space velocity in the hydrogenation pretreatment reaction zone is 1.0h -1 The reaction pressure is 15.5MPa, the average reaction temperature is 360℃, the inlet hydrogen-to-oil volume ratio is 850, and the nitrogen content of the oil generated by hydrogenation pretreatment is controlled to be 10mg / kg.

[0053] The oil produced after the raw material passes through the hydrogenation pretreatment reaction zone enters the hydrocracking reaction zone, in which 4 hydrocracking catalyst beds are set. The reaction conditions of the hydrocracking reaction zone are: the liquid hourly volume space velocity is 1.5h-1 according to the fresh raw material. -1 , the average reaction temperature is 368°C, the inlet reaction pressure is 15.3MPa, and the hydrogen-to-oil volume ratio is 1250. The single-pass conversion rate of the hydrocracking reaction process is 65wt%.

[0054] The reaction effluent is subjected to subsequent separation and fractionation operations to obtain light hydrocarbons, light naphtha, heavy naphtha and tail oil fractions, wherein the tail oil is returned to the top of the second, third and fourth beds of the hydrocracking reaction zone, and the ratio of the circulating oil amount of the tail oil returning to the top of the second, third and fourth beds of the hydrocracking reaction zone is 58:28:14. The total amount of circulating oil in this example accounts for 35wt% of the total feed mass of the hydrocracking.

[0055] In this example, the final boiling point of heavy naphtha is 175°C and the initial boiling point is 65°C. The initial boiling point of the cycle oil tail oil is 175°C.

[0056] Example 3

[0057] The hydrogenation pretreatment reaction zone and the hydrocracking reaction zone are respectively loaded with industrial catalysts FF-66 and FC-52.

[0058] Based on fresh raw materials, the liquid hourly volume space velocity in the hydrogenation pretreatment reaction zone is 1.0h -1 The reaction pressure is 15.5MPa, the average reaction temperature is 360℃, the inlet hydrogen-to-oil volume ratio is 850, and the nitrogen content of the oil generated by hydrogenation pretreatment is controlled to be 10mg / kg.

[0059] The generated oil obtained after the raw material passes through the hydrogenation pretreatment reaction zone enters the hydrocracking reaction zone, in which 5 hydrocracking catalyst beds are set. The reaction conditions of the hydrocracking reaction zone are: the liquid volume space velocity is 1.5h-1 according to the fresh raw material -1 , the average reaction temperature is 368°C, the inlet reaction pressure is 15.3MPa, and the hydrogen-to-oil volume ratio is 1250. The single-pass conversion rate of the hydrocracking reaction process is 65wt%.

[0060] The reaction effluent is subjected to subsequent separation and fractionation operations to obtain light hydrocarbons, light naphtha, heavy naphtha and tail oil fractions, wherein the tail oil is returned to the top of the second, third, fourth and fifth beds of the hydrocracking reaction zone, and the ratio of the circulating oil amount of the tail oil returning to the top of the second, third, fourth and fifth beds of the hydrocracking reaction zone is 54:27:13:6. The total amount of circulating oil in this example accounts for 35wt% of the total feed mass of the hydrocracking.

[0061] In this example, the final boiling point of heavy naphtha is 175°C and the initial boiling point is 65°C. The initial boiling point of the cycle oil tail oil is 175°C.

[0062] Example 4

[0063] The hydrogenation pretreatment reaction zone and the hydrocracking reaction zone are respectively loaded with industrial catalysts FF-66 and FC-52.

[0064] Based on fresh raw materials, the liquid hourly volume space velocity in the hydrogenation pretreatment reaction zone is 1.0h -1 The reaction pressure is 15.5MPa, the average reaction temperature is 359℃, the inlet hydrogen-to-oil volume ratio is 850, and the nitrogen content of the oil generated by hydrogenation pretreatment is controlled to be 13mg / kg.

[0065] The oil produced after the raw material passes through the hydrogenation pretreatment reaction zone enters the hydrocracking reaction zone, in which 4 hydrocracking catalyst beds are set. The reaction conditions of the hydrocracking reaction zone are: the liquid hourly volume space velocity is 1.5h-1 according to the fresh raw material. -1 , the average reaction temperature is 373°C, the inlet reaction pressure is 15.3MPa, and the hydrogen-to-oil volume ratio is 1250. The single-pass conversion rate of the hydrocracking reaction process is 75wt%.

[0066] The reaction effluent is subjected to subsequent separation and fractionation operations to obtain light hydrocarbons, light naphtha, heavy naphtha and tail oil fractions, wherein the tail oil is returned to the top of the second, third and fourth beds of the hydrocracking reaction zone, and the ratio of the circulating oil amount of the tail oil returning to the top of the second, third and fourth beds of the hydrocracking reaction zone is 60:28:12. The total amount of circulating oil in this example accounts for 25wt% of the total feed mass of the hydrocracking.

[0067] In this example, the final boiling point of heavy naphtha is 175°C and the initial boiling point is 65°C. The initial boiling point of the cycle oil tail oil is 175°C.

[0068] Comparative Example 1

[0069] According to the conventional single-stage full-circulation method, the feedstock oil in Table 1 is processed, and the hydrogenation pretreatment reaction zone and the hydrocracking reaction zone are respectively loaded with industrial catalysts FF-66 and FC-52.

[0070] Based on fresh raw materials, the liquid hourly volume space velocity in the hydrogenation pretreatment reaction zone is 1.0h -1 The reaction pressure is 15.5MPa, the average reaction temperature is 360℃, the inlet hydrogen-to-oil volume ratio is 850, and the nitrogen content of the oil generated by hydrogenation pretreatment is controlled to be 10mg / kg.

[0071] The oil produced after the raw material passes through the hydrogenation pretreatment reaction zone enters the hydrocracking reaction zone, in which 4 hydrocracking catalyst beds are set. The reaction conditions of the hydrocracking reaction zone are: the liquid hourly volume space velocity is 1.5h-1 according to the fresh raw material. -1 , the average reaction temperature is 368°C, the reaction pressure is 15.3MPa, and the hydrogen-to-oil volume ratio is 1250. The single-pass conversion rate of the hydrocracking reaction process is 65wt%.

[0072] The reaction effluent is subsequently separated and fractionated to obtain light hydrocarbons, light naphtha, heavy naphtha, and tail oil fractions, wherein the tail oil is returned to the top of the first bed of the hydrocracking reaction zone for hydrocracking reaction. The total amount of circulating oil in this example accounts for 35wt% of the total feed mass of hydrocracking.

[0073] In this example, the final boiling point of heavy naphtha is 175°C and the initial boiling point is 65°C. The initial boiling point of the cycle oil tail oil is 175°C.

[0074] Comparative Example 2

[0075] The hydrogenation pretreatment reaction zone and the hydrocracking reaction zone are respectively loaded with industrial catalysts FF-66 and FC-52.

[0076] Based on fresh raw materials, the liquid hourly volume space velocity in the hydrogenation pretreatment reaction zone is 1.0h -1 The reaction pressure is 15.5MPa, the average reaction temperature is 360℃, the inlet hydrogen-to-oil volume ratio is 850, and the nitrogen content of the oil generated by hydrogenation pretreatment is controlled to be 10mg / kg.

[0077] The oil produced after the raw material passes through the hydrogenation pretreatment reaction zone enters the hydrocracking reaction zone, in which 4 hydrocracking catalyst beds are set. The reaction conditions of the hydrocracking reaction zone are: the liquid hourly volume space velocity is 1.5h-1 according to the fresh raw material. -1 , the average reaction temperature is 368°C, the reaction pressure is 15.3MPa, and the hydrogen-to-oil volume ratio is 1250. The single-pass conversion rate of the hydrocracking reaction process is 65wt%.

[0078] The reaction effluent is subjected to subsequent separation and fractionation operations to obtain light hydrocarbons, light naphtha, heavy naphtha and tail oil fractions, wherein the tail oil is returned to the top of the second, third and fourth beds of the hydrocracking reaction zone, and the ratio of the circulating oil amount of the tail oil returning to the top of the second, third and fourth beds of the hydrocracking reaction zone is 12:28:60. The total amount of circulating oil in this example accounts for 35wt% of the total feed mass of the hydrocracking.

[0079] In this example, the final boiling point of heavy naphtha is 175°C and the initial boiling point is 65°C. The initial boiling point of the cycle oil tail oil is 175°C.

[0080] Comparative Example 3

[0081] According to CN201711119101.0, the feedstock oil in Table 1 was processed, and the hydrogenation pretreatment reaction zone and the hydrocracking reaction zone were respectively loaded with industrial catalysts FF-66 and FC-52.

[0082] Based on fresh raw materials, the liquid hourly volume space velocity in the hydrogenation pretreatment reaction zone is 1.0h -1 The reaction pressure is 15.5MPa, the average reaction temperature is 360℃, the inlet hydrogen-to-oil volume ratio is 850, and the nitrogen content of the oil generated by hydrogenation pretreatment is controlled to be 10mg / kg.

[0083] The oil produced after the raw material passes through the hydrogenation pretreatment reaction zone enters the hydrocracking reaction zone, in which 4 hydrocracking catalyst beds are set. The reaction conditions of the hydrocracking reaction zone are: the liquid hourly volume space velocity is 1.5h-1 according to the fresh raw material. -1, the average reaction temperature is 368°C, the reaction pressure is 15.3MPa, and the inlet hydrogen-to-oil volume ratio is 1250. The single-pass conversion rate of the hydrocracking reaction process is 65wt%.

[0084] The reaction effluent is subsequently separated and fractionated to obtain light hydrocarbons, light naphtha, heavy naphtha, middle distillate oil 1 (175-230°C), middle distillate oil 2 (230-280°C), middle distillate oil 3 (280-350°C) and tail oil fraction (>350°C), wherein the tail oil is returned to the top of the first bed layer of the hydrocracking reaction zone, the middle distillate oil 3 is returned to the top of the second bed layer of the hydrocracking reaction zone, the middle distillate oil 2 is returned to the top of the third bed layer of the hydrocracking reaction zone, and the middle distillate oil 1 is returned to the top of the fourth bed layer of the hydrocracking reaction zone.

[0085] Table 1 Properties of crude oil

[0086] Source of raw materials Vacuum wax oil <![CDATA[Density (20 °C) / g·cm -3 > 0.9168 Distillation range / ℃ 336～545 <![CDATA[Sulfur / mg·kg -1 > 17100 <![CDATA[Nitrogen / mg·kg -1 > 910

[0087] Table 2 Main physical and chemical properties of catalysts

[0088] 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

[0089] Table 3 Main operating conditions of each case

[0090]

[0091]

[0092] Table 4 Results of each case

[0093]

Claims

1. A hydrocracking method for increasing the production of heavy naphtha, wherein: A hydrotreating reaction zone and a hydrocracking reaction zone are provided, and at least three hydrocracking catalyst beds are provided in the hydrocracking reaction zone. The method comprises: (1) The hydrocracking feedstock and hydrogen pass through a hydrogenation pretreatment reaction zone for hydrogenation pretreatment; (2) The effluent from the hydrotreating reaction zone enters the hydrocracking reaction zone from the top for hydrocracking reaction. After separation and fractionation, the effluent from the hydrocracking reaction zone obtains light hydrocarbons, light naphtha, heavy naphtha, and tail oil heavier than heavy naphtha; The tail oil is introduced as circulating oil between the hydrocracking catalyst beds. The amount of circulating oil decreases from top to bottom, and the ratio of circulating oil between adjacent beds is above 2:1, measured by mass.

2. The method according to claim 1, characterized in that: The tail oil is introduced as circulating oil between each hydrocracking catalyst bed. The circulating oil amount decreases from top to bottom, and the circulating oil ratio between adjacent beds is 2:1 to 4:1, calculated by mass.

3. The method according to claim 1, characterized in that: The tail oil is introduced as circulating oil between the hydrocracking catalyst beds, preferably into the top of the lower catalyst bed between two adjacent catalyst beds.

4. The method according to any one of claims 1 to 3, characterized in that: The total amount of the circulating oil accounts for 20 wt% to 55 wt% of the total feed mass of the hydrocracking, preferably 22 wt% to 53 wt%.

5. The method according to claim 1, characterized in that: The hydrocracking feedstock is at least one of wax oil or diesel, preferably wax oil.

6. The method according to claim 1, characterized in that: The hydrotreating pretreatment reaction zone is provided with a plurality of hydrotreating pretreatment catalyst beds, preferably more than 2, and further 3 to 4; and / or, the hydropretreatment reaction zone is loaded with a corresponding hydropretreatment catalyst; Further preferably, the hydrogenation pretreatment catalyst comprises a carrier and an active metal; the active metal comprises a Group VIB metal and / or a Group VIII metal, the carrier is an inorganic refractory oxide, selected from one or more of alumina, amorphous silica-alumina, silica, titanium oxide, etc.; the Group VIB metal is preferably W and / or Mo, and the Group VIII metal is preferably Ni and / or Co; More preferably, based on the weight of the hydrogenation pretreatment catalyst, the content of the Group VIB metal as oxide is 11% to 37%, preferably 15% to 32%, and the content of the Group VIII metal as oxide is 0.3% to 7.5%, preferably 1% to 7%.

7. The method according to claim 1, characterized in that: The nitrogen content of the reaction effluent after hydrogenation pretreatment is controlled below 20 mg / kg, preferably below 15 mg / kg.

8. The method according to claim 1, characterized in that: In the hydrocracking method, the operating conditions of the hydrotreating pretreatment reaction zone are: average reaction temperature of 300°C to 440°C, inlet hydrogen-oil volume ratio of 450:1 to 1000:1, pressure of 8.0MPa to 16.5MPa, liquid hourly volume space velocity of 0.3h -1 ~4.0h -1 The preferred operating conditions are: average reaction temperature of 310°C to 430°C, inlet hydrogen-oil volume ratio of 500:1 to 950:1, pressure of 9.0MPa to 16.0MPa, liquid hourly volume space velocity of 0.5h -1 ~3.5h -1 .

9. The method according to claim 1, characterized in that: The hydrocracking reaction zone is provided with more than 3 hydrocracking catalyst beds, preferably 4 to 6; And / or, the hydrocracking catalyst loaded in the hydrocracking reaction zone includes a cracking component and a hydrogenation component; the cracking component preferably includes a molecular sieve; based on the weight of the catalyst, the content of the hydrogenation component is 11wt% to 40wt% in terms of oxide, preferably 15wt% to 35wt%, and the content of the molecular sieve is 35wt% to 70wt%, preferably 40wt% to 70wt%.

10. The method according to claim 1, characterized in that: In the hydrocracking method, the final distillation point of heavy naphtha is 173-177°C, and the initial distillation point is 63-67°C.

11. The method according to claim 1, characterized in that: In the hydrocracking method, the circulating oil is tail oil heavier than heavy naphtha, and has an initial distillation point of 173-177°C.

12. The method according to claim 1, characterized in that: In the hydrocracking method, the operating conditions of the hydrocracking reaction zone are: average reaction temperature of 310°C to 445°C, inlet hydrogen-oil volume ratio of 650:1 to 1400:1, pressure of 8.0MPa to 16.5MPa, liquid hourly volume space velocity of 0.3h -1 ~4.5h -1 .

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