A hydrocracking method for producing heavy naphtha

Abstract

The present invention discloses a hydrocracking method for producing heavy naphtha, comprising the following contents: (1) raw materials and hydrogen are mixed and introduced into a hydrocracking pretreatment reaction zone for desulfurization, denitrogenation and aromatic saturation reaction; (2) the reaction effluent of step (1) enters a first hydrocracking reaction zone for hydrocracking reaction; (3) the reaction effluent of step (2) is subjected to gas-liquid separation in a separator, and the hydrogen-rich gas obtained is used as circulating hydrogen, and the liquid phase enters a fractionation tower for fractionation to obtain gas, light naphtha, heavy naphtha and tail oil fractions; (4) the tail oil obtained in step (3) is mixed with hydrogen and introduced into a second hydrocracking reaction zone; (5) the reaction effluent of step (4) is returned to step (3) and mixed with the first hydrocracking reaction effluent, and then subjected to gas-liquid separation, and then enters a fractionation tower for separation to obtain gas, light naphtha, heavy naphtha and tail oil fractions. The method improves the yield of heavy naphtha while achieving full conversion of the raw materials.

Description

Technical Field

[0001] The present invention relates to a hydrocracking method for producing heavy naphtha, and in particular to a two-stage hydrocracking method for producing heavy naphtha in maximum quantity. Background Art

[0002] As one of the primary methods for converting heavy oil to lighter oil, hydrocracking technology offers advantages such as strong feedstock adaptability, wide product flexibility, high selectivity for target products, excellent product quality, and high added value. It not only allows the direct production of light, high-quality chemical raw materials, jet fuel, diesel, and other products from heavy, low-quality feedstock, but also meets the growing public awareness of environmental protection and the requirements of national environmental regulations, satisfying market demand for low-carbon, clean fuels. It is the most important clean production technology of the 21st century and the core of the integration of oil, chemical, and fiber production. As domestic crude oil quality deteriorates year by year, imports of inferior, heavy, high-sulfur crude oil have increased significantly. To ensure the "high-quality, high-yield, low-carbon, and stable" supply of finished fuel oil and chemical products to people's lives, hydrocracking technology will inevitably be more widely used.

[0003] CN201210408305.7 discloses a hydrocracking method for producing high-quality chemical feedstocks. The feedstock oil and hydrogen are sequentially passed through a hydrorefining and first cracking reaction zone, where the separated intermediate distillate oil enters a second cracking reaction zone for cracking. The first cracking reaction zone contains two cracking catalysts: Catalyst I in the upstream section and Catalyst II in the downstream section. Catalyst I contains 30% to 70% by weight of modified Y molecular sieve, while Catalyst II contains 15% to 50% by weight of modified Y molecular sieve. The modified Y molecular sieve content in Catalyst I is 10% to 30% higher than that in Catalyst II. This method exhibits low heavy naphtha selectivity.

[0004] CN201610236766.9 discloses a hydrogenation method for producing high-aromatic potential naphtha from aromatic-rich distillate oil. The method comprises: mixing the aromatic-rich distillate oil with hydrogen, sequentially passing it through a hydrogenation pretreatment reactor and a hydrocracking reactor for reaction. The reaction products are separated into gas and liquid by high- and low-pressure separators, and then entering a fractionating tower for separation. The resulting monocyclic aromatic fraction rich in tetralins at a temperature of 240-300°C enters a hydrogenation selective ring-opening reactor, and the fraction rich in dicyclic or higher aromatics at a temperature greater than 300°C is partially recycled and entered into the hydrogenation pretreatment reactor. Due to the influence of ammonia partial pressure, the cracking agent activity in this method cannot be fully utilized, and the naphtha yield is limited.

[0005] CN103059986A discloses a hydrocracking method for producing chemical raw materials. The raw oil is mixed with hydrogen and sequentially fed into a hydrotreating reactor and a first hydrocracking reactor for reaction. The first hydrocracking reactor is loaded with catalyst I. After the reactants are cooled and separated, the resulting 10% to 100% by weight diesel fraction (175 to 320°C) is fed into a second hydrocracking reactor for further reaction. The second hydrocracking reactor is loaded with catalyst II. Hydrocracking catalyst II is a low-metal loading hydrocracking catalyst, with a lower metal loading than that of hydrocracking catalyst I. This method has low heavy naphtha selectivity.

[0006] CN201210408343.2 discloses a two-stage hydrocracking method. The method comprises: (1) mixing low-quality feedstock oil with hydrogen and subjecting it to a hydrorefining reaction; (2) subjecting the hydrorefining effluent to gas-liquid separation to obtain gas and liquid; (3) subjecting the liquid to a hydrocracking reaction zone for a hydrocracking reaction, wherein the hydrocracking reaction zone comprises two hydrocracking catalysts, I and II, having different molecular sieve contents; and (4) separating and fractionating the hydrocracking effluent to obtain the desired product. This method results in a low heavy naphtha yield.

[0007] CN200410050741 discloses a two-stage hydrocracking method for increasing the production of high-quality middle distillates. A certain proportion of fresh crude oil is added to the second-stage feed to suppress the activity of the second-stage catalyst, improve the yield of middle distillates, and expand the processing capacity of the unit. Compared with existing technologies, the present method offers advantages such as high middle distillate yield, good catalyst activity stability, and a long operating cycle. To increase the production of middle distillates, both the first and second-stage hydrocracking reactors utilize hydrocracking catalysts with a low molecular sieve content. This method improves the yield of middle distillates, but also reduces the yield of heavy naphtha.

[0008] CN02144957.0 discloses a dual-cracking agent trans-hydrocracking process with cyclic cracking, which is characterized by adopting a process of first cracking and then refining. The unconverted oil is circulated to the second cracking stage and contacted with the second hydrocracking catalyst for cyclic cracking. The first stage of the two-stage hydrocracking uses a beta zeolite hydrocracking catalyst, and the second stage uses a Y zeolite hydrocracking catalyst. On the one hand, the process of the present invention fully utilizes the dual functions of the hydrocracking catalyst. In addition, by using different types of hydrocracking catalysts in combination, the process of the present invention has the advantages of high overall activity, high medium oil selectivity, good product quality, and low operating costs. The heavy naphtha yield of this method is relatively low.

[0009] CN200610008418.2 discloses a two-stage hydrocracking method that uses a two-stage hydrocracking process to treat low-quality catalytic fuel oil, particularly low-quality catalytic fuel oil obtained through a catalytic hydrogen transfer process. The catalytic fuel oil produced in this method has extremely poor properties, with a density of 0.90 g / ml or higher at 20°C, aromatics exceeding 60% by weight, and a cetane number less than 30. This method combines the low-quality catalytic fuel oil with a heavy cracking feedstock and hydrotreats it. The resulting oil is then separated and desulfurized to remove impurities such as sulfur and nitrogen before undergoing hydrocracking. This method results in limited chemical feedstock yields and significantly impacts the quality of the middle distillate product.

[0010] CN 201310523055.6 discloses a hydrocracking method. A high-nitrogen feedstock oil is mixed with a hydrogen-rich gas, heated, and then introduced into a first reaction zone, where hydrofining and hydrocracking reactions occur. The reactant stream is cooled, oil and gas separated, and fractionated to obtain light naphtha, heavy naphtha, and a tail oil fraction. The tail oil fraction is pressurized, mixed with recycled hydrogen, and introduced into a second reaction zone for a hydrocracking reaction. The first and second reaction zones of the present invention use different hydrocracking catalysts. This method has low heavy naphtha selectivity. Summary of the Invention

[0011] In view of the deficiencies of the prior art, the present invention provides a hydrocracking method for producing heavy naphtha, which achieves full conversion of the raw materials while increasing the yield of heavy naphtha and reducing the yield of by-products.

[0012] A hydrocracking method for producing heavy naphtha, comprising the following steps:

[0013] (1) The raw materials and hydrogen are mixed and enter the hydrocracking pretreatment reaction zone for desulfurization, denitrogenation and aromatic saturation reactions;

[0014] (2) The reaction effluent from step (1) enters the first hydrocracking reaction zone for hydrocracking reaction;

[0015] (3) The hydrogen-rich gas obtained after the reaction effluent of step (2) is separated into gas and liquid by a separator is used as circulating hydrogen, and the liquid phase enters a fractionation tower for fractionation to obtain gas, light naphtha, heavy naphtha and tail oil fractions;

[0016] (4) The tail oil obtained in step (3) is mixed with hydrogen and enters the second hydrocracking reaction zone;

[0017] (5) The reaction effluent from step (4) is returned to step (3) and mixed with the first hydrocracking reaction effluent, and then subjected to gas-liquid separation. The mixture then enters a fractionating tower for separation to obtain gas, light naphtha, heavy naphtha, and tail oil fractions.

[0018] In the method of the present invention, the raw material in step (1) is a vacuum gas oil raw material, generally vacuum gas oil (VGO); it can also generally include one or more of straight-run gas oil (AGO), coker gas oil (CGO), catalytic cracking heavy cycle oil (HCO), deasphalted oil (DAO), coal synthetic oil or coal tar.

[0019] In the method of the present invention, the reaction conditions in the hydrocracking pretreatment reaction zone of step (1) are generally as follows: reaction pressure of 5.0 to 35.0 MPa, preferably 6.0 to 19.0 MPa; average reaction temperature of 200 to 480°C, preferably 270 to 450°C; volume space velocity of 0.1 to 15.0 h-1, preferably 0.2 to 3.0 h-1; hydrogen to oil volume ratio of 100:1 to 2500:1, preferably 400:1 to 2000:1.

[0020] In the method of the present invention, the hydrocracking pretreatment reaction zone in step (1) is filled with a conventional hydrorefining catalyst in the art, wherein the hydrorefining catalyst comprises a carrier and a hydrogenation-active metal; wherein the carrier is an inorganic refractory oxide, generally selected from one or more of alumina, amorphous silica-alumina, silica or titania; and the hydrogenation-active metal comprises a Group VIB and / or Group VIII metal component, wherein Group VIB is selected from tungsten and / or molybdenum, and the content thereof is 10% to 35%, preferably 15% to 30%, calculated as oxide; and Group VIII is selected from nickel and / or cobalt, and the content thereof is 1% to 7%, preferably 1.5% to 6%, calculated as oxide. The carrier is an inorganic refractory oxide, generally selected from alumina, amorphous silica-alumina, silica, titania, and the like.

[0021] In the method of the present invention, the hydrocracking pretreatment reaction zone described in step (1) and the first hydrocracking reaction zone described in step (2) can be loaded in stages using one reactor, or can be loaded separately using two or more reactors.

[0022] In the method of the present invention, the hydrocracking catalyst loaded in the first hydrocracking reaction zone described in step (2) and the second hydrocracking reaction zone described in step (4) generally comprises a cracking component, a hydrogenation component, and a binder. For example, it can be any suitable hydrocracking catalyst, including those in the prior art. The cracking component generally comprises amorphous silica-alumina and / or molecular sieves, with Y-type or USY-type molecular sieves being common molecular sieves. The binder is generally alumina or silica. The hydrogenation component is a Group VI, Group VII, Group VIB, or Group VIII metal, metal oxide, or metal sulfide containing a Group VIB and / or Group VIII metal as the active metal component, more preferably one or more of iron, chromium, molybdenum, tungsten, cobalt, nickel, or their sulfides or oxides. Based on the weight of the hydrocracking catalyst, the hydrogenation component content is generally 5% to 40% by weight, and the cracking component content is 30% to 70% by weight, preferably 55% to 65% by weight. Specifically, an existing hydrocracking catalyst may be selected, or a specific hydrocracking catalyst may be prepared by oneself according to methods well known in the art as needed. Specifically, an existing hydrocracking catalyst may be selected, or a specific hydrocracking catalyst may be prepared by oneself according to methods well known in the art as needed.

[0023] In the method of the present invention, the operating conditions of the first hydrocracking reaction zone described in step (2) and the second hydrocracking reaction zone described in step (4) include: reaction pressure of 5.0 to 35.0 MPa, preferably 6.0 to 19.0 MPa; average reaction temperature of 200°C to 480°C, preferably 270°C to 450°C; volume space velocity of 0.1 to 15.0 h -1 , preferably 0.2 to 3.0 hours -1 ; The volume ratio of hydrogen to oil is 100:1 to 2500:1, preferably 400:1 to 2000:1.

[0024] Preferably, in certain specific embodiments, the hydrocracking catalyst loaded in the second hydrocracking reaction zone contains a VIB and / or VIII Group metal as an active metal component, and the catalyst contains 10% to 50 wt% of Y molecular sieve by weight, preferably 20% to 40 wt%; the mass content of Y molecular sieve in the hydrocracking catalyst loaded in the first hydrocracking reaction zone is 10% to 30 wt% higher than the Y molecular sieve content in the hydrocracking catalyst loaded in the second hydrocracking reaction zone.

[0025] Preferably, in certain specific embodiments, the hydrocracking catalyst loaded in the first hydrocracking reaction zone generally has a SiO2 / Al2O3 molar ratio of 5 to 30 and a relative crystallinity of 80 to 110%; the hydrocracking catalyst loaded in the second hydrocracking reaction zone has a SiO2 / Al2O3 molar ratio 10 to 20 higher and a relative crystallinity 10 to 30% higher than that of the hydrocracking catalyst loaded in the first hydrocracking reaction zone.

[0026] In the method of the present invention, the initial distillation point of the tail oil fraction in step (3) is generally 130-200°C, preferably 160-190°C.

[0027] Preferably, in certain specific embodiments, the reaction pressure of the first hydrocracking reaction zone is not lower than the reaction pressure of the second hydrocracking reaction zone. Preferably, the reaction pressure of the second hydrocracking reaction zone is 3-5 MPa lower than the reaction pressure of the first hydrocracking reaction zone; the average reaction temperature of the first hydrocracking reaction zone is 10-30°C higher than the average reaction temperature of the second hydrocracking reaction zone. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a principle flow diagram of the process method of the present invention.

[0029] The vacuum wax oil 1 is mixed with hydrogen 2 and enters the hydrotreatment reaction zone 3. The hydrogenation reaction effluent 4 enters the first hydrocracking reaction zone 5. The reaction effluent 6 enters the separator 7. The separated gas phase 8 enters the circulating hydrogen desulfurization tower 9 and is used as circulating hydrogen. The liquid phase 10 enters the fractionation tower 11 and is separated to obtain gas 12, light naphtha 13, heavy naphtha 14 and tail oil 15. The tail oil 15 enters the second hydrocracking reactor 16. The reaction effluent 17 of the second cracking reactor is mixed with the effluent 6 of the first hydrocracking reactor and enters the separator 7 and then enters the fractionation tower. DETAILED DESCRIPTION

[0030] The effects and benefits of the present invention are further illustrated below by way of examples. However, the following examples do not limit the method of the present invention. Unless otherwise specified, % in this application are percentages by mass.

[0031] use Figure 1 The process flow shown in the figure uses a catalyst with the brand FF-66 produced by Fushun Petrochemical Research Institute for hydrogenation pretreatment. The reaction conditions for hydrogenation pretreatment are as follows: reaction pressure 15.0 MPa; average reaction temperature 374°C; volume space velocity 1.0 h -1 The volume ratio of hydrogen to oil is 750:1. The hydrocracking catalyst selected is a Mo-Ni catalyst. The content of the hydrogenation component in terms of oxide is 30 wt%. Other main properties are shown in Table 1. The volume space velocity of the hydrocracking process is 1.0 h -1 The properties of the raw materials used are shown in Table 2.

[0032] Table 1

[0033]

[0034] Table 2

[0035]

[0036] Example 1

[0037] A two-stage full-cycle process flow was adopted. The properties of the raw materials are shown in Table 2. The first hydrocracking reactor and the second hydrocracking reactor were both loaded with Cat-1 catalyst.

[0038] Example 2

[0039] A two-stage full-cycle process flow was adopted. The properties of the raw materials are shown in Table 2. The first hydrocracking reactor was loaded with Cat-1 catalyst, and the second hydrocracking reactor was loaded with Cat-2 catalyst.

[0040] Example 3

[0041] A two-stage full-cycle process flow was adopted. The properties of the feedstock are shown in Table 2. The first hydrocracking reactor was loaded with Cat-1 catalyst, and the second hydrocracking reactor was loaded with Cat-3 catalyst.

[0042] Example 4

[0043] A two-stage full-cycle process flow was adopted. The properties of the raw materials are shown in Table 2. The first hydrocracking reactor was loaded with Cat-1 catalyst, and the second hydrocracking reactor was loaded with Cat-4 catalyst.

[0044] Example 5

[0045] A two-stage full-cycle process flow was adopted. The properties of the raw materials are shown in Table 2. The first hydrocracking reactor was loaded with Cat-1 catalyst, and the second hydrocracking reactor was loaded with Cat-2 catalyst.

[0046] Example 6

[0047] A two-stage full-cycle process flow was adopted. The properties of the raw materials are shown in Table 2. The first hydrocracking reactor was loaded with Cat-1 catalyst, and the second hydrocracking reactor was loaded with Cat-2 catalyst.

[0048] The hydrocracking process conditions and heavy naphtha yields of the above examples are shown in Table 3.

[0049] Table 3

[0050]

[0051] Table 3

[0052]

[0053] It can be seen from the above examples that the method of the present invention can effectively improve the yield of heavy naphtha through reasonable catalyst matching and optimized process conditions.

Claims

1. A hydrocracking process for producing heavy naphtha, characterized in that: The steps include: (1) The raw materials and hydrogen are mixed and enter the hydrocracking pretreatment reaction zone for desulfurization, denitrogenation and aromatic saturation reactions; (2) The reaction effluent from step (1) enters the first hydrocracking reaction zone for hydrocracking reaction; (3) The hydrogen-rich gas obtained after the reaction effluent of step (2) is separated into gas and liquid by a separator is used as circulating hydrogen, and the liquid phase enters a fractionation tower for fractionation to obtain gas, light naphtha, heavy naphtha and tail oil fractions; (4) The tail oil obtained in step (3) is mixed with hydrogen and enters the second hydrocracking reaction zone; (5) The reaction effluent from step (4) is returned to step (3) and mixed with the first hydrocracking reaction effluent, and then subjected to gas-liquid separation. The mixture is then fed into a fractionating tower for separation to obtain gas, light naphtha, heavy naphtha, and tail oil fractions. The mass content of the Y molecular sieve in the hydrocracking catalyst loaded in the first hydrocracking reaction zone is 10% to 30% higher than that in the hydrocracking catalyst loaded in the second hydrocracking reaction zone; The hydrocracking catalyst loaded in the second hydrocracking reaction zone has a SiO2 / Al2O3 molar ratio 10-20 higher than that of the hydrocracking catalyst loaded in the first hydrocracking reaction zone, and a relative crystallinity 10-30% higher; The reaction pressure of the second hydrocracking reaction zone is 3-5 MPa lower than that of the first hydrocracking reaction zone; the average reaction temperature of the first hydrocracking reaction zone is 10-30° C. higher than that of the second hydrocracking reaction zone.

2. The method according to claim 1, wherein: The raw material in step (1) is one or more of straight-run wax oil, coker wax oil, catalytic cracking heavy cycle oil, deasphalted oil, coal synthetic oil or coal tar.

3. The method according to claim 1, wherein: The reaction conditions of the hydrocracking pretreatment reaction zone in step (1) are as follows: reaction pressure 5.0-35.0 MPa; average reaction temperature 200-480°C; volume space velocity 0.1-15.0 h -1 ; The volume ratio of hydrogen to oil is 100:1~2500:

1.

4. The method according to claim 1, wherein: The catalyst loaded in the hydrocracking pretreatment reaction zone of step (1) comprises a carrier and a hydrogenation active metal; wherein the carrier is one or more selected from alumina, amorphous silica-alumina, silica or titania; and the hydrogenation active metal comprises a Group VIB and / or Group VIII metal component.

5. The method according to claim 1, wherein: The hydrocracking pretreatment reaction zone in step (1) and the first hydrocracking reaction zone in step (2) are loaded in stages using one reactor or are loaded separately using two or more reactors.

6. The method according to claim 1, wherein: The hydrocracking catalyst loaded in the first hydrocracking reaction zone described in step (2) and the second hydrocracking reaction zone described in step (4) includes a cracking component, a hydrogenation component and a binder.

7. The method according to claim 1, wherein: The operating conditions of the first hydrocracking reaction zone described in step (2) and the second hydrocracking reaction zone described in step (4) include: reaction pressure of 5.0 to 35.0 MPa; average reaction temperature of 200°C to 480°C; volume space velocity of 0.1 to 15.0 h -1 ; The volume ratio of hydrogen to oil is 100:1~2500:

1.

8. The method according to claim 1, wherein: The hydrocracking catalyst loaded in the second hydrocracking reaction zone has VIB and / or VIII group metals as active metal components, and contains 10% to 50% by weight of Y molecular sieve in the catalyst.

9. The method according to claim 1, wherein: The hydrocracking catalyst loaded in the first hydrocracking reaction zone has a SiO2 / Al2O3 molar ratio of 5 to 30 and a relative crystallinity of 80 to 110%.

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