A hydrocracking method for naphtha

Abstract

The present invention discloses a hydrocracking method for naphtha. The method includes: (1) in the presence of hydrogen, the naphtha raw material enters the hydrocracking reaction zone, and the n-alkanes in the naphtha raw material are selectively cracked to obtain a hydrocracking product; wherein, in the hydrocracking product, the mass content of C7 + n-alkanes is controlled below 5.0%; (2) the hydrocracking product enters the hydrotreating reaction zone for hydrotreating reaction; (3) the hydrotreated product enters the separation and fractionation system to obtain chemical raw materials. This method uses naphtha as the raw material, which can greatly improve the ethylene raw material yield and the quality of the reforming raw material.

Description

Technical Field

[0001] The present invention belongs to the field of hydrocarbon oil hydrocracking, and particularly relates to a hydrocracking method for naphtha. Background Art

[0002] With the increasingly tense resources, improving the utilization efficiency of petroleum resources has attracted more and more attention. The traditional petroleum processing route usually adopts the method of fraction cutting to cut the components in crude oil into different fractions to obtain products such as gasoline (naphtha), kerosene, diesel, wax oil and residue oil. Among them, naphtha is the most important raw material for downstream petrochemical industry, which can be used as the raw material for steam cracking to produce ethylene or as the raw material for catalytic reforming to produce aromatic products or high-octane gasoline. For a long time, there has been a problem of raw material competition between steam cracking units and catalytic reforming units in refining and chemical integration enterprises to varying degrees. How to maximize the value of limited naphtha resources is very important. As the main raw material for catalytic reforming units, naphtha has a high content of paraffins in its composition, and paraffins are difficult to undergo dehydrogenation cyclization reactions and are not beneficial raw material components for reforming units. Converting paraffins in naphtha into high-quality ethylene raw materials has become a beneficial technical path for refining and chemical enterprises to optimize product structures and improve economic benefits.

[0003] CN106221786A discloses a conversion method for naphtha. This method combines the catalytic cracking of naphtha with the steam cracking of light alkanes and the catalytic cracking of heavy alkanes and heavy olefins to produce light olefins, light aromatics and high-octane gasoline. This method significantly improves the yield of high-value products and reduces the yield of low-value products; at the same time, since most of the reactants are converted in the catalytic cracking at a relatively low temperature, the energy consumption can be reduced overall.

[0004] In the existing methods for producing chemical raw materials, there are defects such as low yield and poor product quality to varying degrees. Therefore, it is of great significance to develop a hydrocracking method suitable for producing high-quality chemical raw materials from hydrocarbon oil as the raw material. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a hydrocracking method for naphtha. This method uses naphtha as the raw material, greatly improves the quality of chemical products, especially converts long-chain paraffins into light paraffins, increases the yield of light hydrocarbons, enriches cyclic hydrocarbons in the heavy components, and improves the aromatic potential of heavy naphtha.

[0006] The present invention provides a hydrocracking method for naphtha, and the method includes:

[0007] (1) In the presence of hydrogen, the naphtha raw material enters the hydrocracking reaction zone, and selectively cracks the normal paraffins in the naphtha raw material to obtain a hydrocracking product; wherein, in the hydrocracking product, C7 +The mass content of n-alkanes is controlled below 5.0%;

[0008] (2) The hydrocracked product enters the hydrofining reaction zone for hydrofining reaction;

[0009] (3) The hydrofined product enters the separation and fractionation system to obtain chemical raw materials.

[0010] According to the present invention, in step (3), the chemical raw materials are ethylene raw materials and reforming raw materials.

[0011] According to the present invention, in step (3), the chemical raw materials mainly include ethane, propane, butane, light naphtha, and may also include heavy naphtha. Among them, heavy naphtha is used as a reforming raw material to produce BTX, and ethane, propane, butane, and light naphtha are used as ethylene raw materials to produce light olefins. For example, they are used as steam cracking raw materials to produce ethylene, and propane and butane can also be directly dehydrogenated to produce propylene and butene. Among them, light olefins refer to olefins with four or fewer carbon atoms, especially ethylene, propylene, and butadiene.

[0012] According to the present invention, in step (2), a hydrofining catalyst is loaded in the hydrofining reaction zone; the hydrofining catalyst can adopt a conventional hydrofining catalyst, which is mainly used for hydrodesulfurization, denitrification and other impurities. The hydrofining catalyst includes a carrier and a hydroactive metal. Among them, the carrier is an inorganic refractory oxide, generally selected from one or more of alumina, amorphous silica-alumina, silica, or titanium oxide, etc.; the hydroactive metal includes Group VIB and / or Group VIII metal components. In the hydrofining catalyst, Group VIB is preferably selected from tungsten and / or molybdenum, and its content in the catalyst is 5% - 30% by mass of the oxide, preferably 10% - 20%; Group VIII is preferably selected from nickel and / or cobalt, and its content in the catalyst is 1% - 6% by mass of the oxide, preferably 1.5% - 5%. The content of the carrier in the catalyst is 64% - 94% by mass of the oxide, preferably 75% - 88.5%.

[0013] According to the present invention, the reaction conditions of the hydrofining reaction in step (2) are as follows: the reaction pressure is 1.0 - 5.0 MPa, preferably 2.0 - 4.0 MPa.

[0014] According to the present invention, the reaction conditions of the hydrofining reaction in step (2) are as follows: the average reaction temperature is 150 - 400 °C, preferably 200 - 300 °C; the liquid hourly space velocity is 0.1 - 15.0 h -1 , preferably 1.0 - 5.0 h -1 ; the hydrogen-oil volume ratio is 100:1 - 2500:1, preferably 300:1 - 2000:1.

[0015] According to the present invention, preferably, the reaction temperature in the hydrofining reaction zone in step (2) is 50°C to 200°C lower than that in the hydrocracking reaction zone in step (1), preferably 80°C to 120°C lower.

[0016] According to the present invention, preferably, in the hydrocracking product in step (1), the mass content of C7 + normal paraffin is controlled at 1% to 5%.

[0017] According to the present invention, the naphtha feedstock in step (1) can be straight-run naphtha, coker naphtha, fluidized-bed residue hydrotreating naphtha, coal chemical naphtha and other naphtha fractions with a relatively high content of normal paraffin; the initial boiling point of the naphtha feedstock is 40°C to 80°C, preferably 50°C to 70°C; the final boiling point is 150°C to 200°C, preferably 160°C to 180°C.

[0018] According to the present invention, in the naphtha feedstock in step (1), the C7 + mass content of normal paraffin is 6% to 50%, preferably 10% to 40%.

[0019] According to the present invention, in the naphtha feedstock in step (1), the mass content of cyclic hydrocarbons is 30% to 80%, and the cyclic hydrocarbons are the sum of naphthenes and aromatics.

[0020] According to the present invention, in step (1), a hydrocracking catalyst is loaded in the hydrocracking reaction zone. The hydrocracking catalyst includes an active metal component and a carrier; the carrier includes a molecular sieve having selective cracking of normal paraffins. Preferably, the carrier includes one or more of ZSM-5 molecular sieve, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35 and ZSM-38 molecular sieves, more preferably ZSM-5 molecular sieve. The active metal component includes at least one of metals in Group VIB and Group VIII. The Group VIB metal is preferably molybdenum and / or tungsten, and the Group VIII metal is preferably cobalt and / or nickel.

[0021] According to the present invention, in step (1), the carrier of the hydrocracking catalyst may further include a binder. Preferably, the binder is alumina.

[0022] According to the present invention, in step (1), preferably, in the hydrocracking catalyst, based on the weight of the catalyst, the content of the Group VIB metal (calculated as the oxide) is 5.0% to 15.0%, the content of the Group VIII metal (calculated as the oxide) is 2.0% to 5.0%, and the content of the carrier is 80.0% to 93.0%.

[0023] According to the present invention, in step (1), preferably, in the carrier of the hydrocracking catalyst, based on the weight of the carrier, the content of the binder is 8% - 60%, and the content of the molecular sieve is 40% - 92%.

[0024] According to the present invention, in step (1), the specific surface area of the hydrocracking catalyst is 200 - 400 m 2 / g, and the pore volume is 0.25 - 0.45 mL / g.

[0025] According to the present invention, in step (1), the preparation method of the hydrocracking catalyst can be prepared according to the conventional methods in the art. The preparation method includes the preparation of the carrier and the loading of the active metal components. The process of preparing the carrier is as follows: The shape-selective cracking molecular sieve and the binder are mechanically mixed, formed, and then dried and calcined to make the catalyst carrier. The drying and calcination of the carrier can adopt conventional conditions. The conditions for drying are: drying at 100°C - 150°C for 1 - 12 hours. The conditions for calcination are: calcining at 450°C - 550°C for 2.5 - 6.0 hours.

[0026] According to the present invention, in step (1), in the preparation method of the hydrocracking catalyst, the method for loading the active metal components is a conventional method, such as the kneading method, the impregnation method, etc., and the impregnation method is preferred. The impregnation method can be the saturated impregnation method, the excess impregnation method or the complex impregnation method, that is, the catalyst carrier is impregnated with a solution containing the required active components, and then dried and calcined to obtain the first hydrocracking catalyst. The conditions for drying are: drying at 100°C - 150°C for 1 - 12 hours. The conditions for calcination are: calcining at 450°C - 550°C for 2.5 - 6.0 hours.

[0027] According to the present invention, in step (1), the reaction conditions for the hydrocracking reaction are as follows: the reaction pressure is 1.0 - 5.0 MPa, preferably 2.0 - 4.0 MPa.

[0028] According to the present invention, in step (1), the reaction conditions for the hydrocracking reaction are as follows: the average reaction temperature is 250 - 450°C, preferably 300 - 400°C; the liquid hourly space velocity is 0.1 - 15.0 h -1 , preferably 1.0 - 5.0 h -1 ; the hydrogen-oil volume ratio is 100:1 - 2500:1, preferably 400:1 - 2000:1.

[0029] Petroleum hydrocarbons have a complex composition, mainly including chain alkanes, cycloalkanes and aromatics, while high-quality ethylene raw materials are small molecular normal alkanes, and reforming raw materials are monocyclic cycloalkanes and aromatics. The inventors have found through research that hydrocarbon oil raw materials can be highly selectively generated by selective cracking of straight-chain alkanes and selective hydrocracking of long side chains on isomeric hydrocarbons or cyclic hydrocarbons to retain monocyclic cyclic hydrocarbons as much as possible, thereby achieving efficient enrichment of small molecular normal alkanes in ethylene raw materials, while retaining monocyclic cyclic hydrocarbons in heavy naphtha as much as possible to achieve efficient enrichment of high-quality reforming raw materials, so that the purpose of greatly improving the yield of chemical raw materials (i.e., ethylene raw materials and reforming raw materials) and the quality of ethylene raw materials and reforming raw materials can be achieved, thereby completing the present invention.

[0030] Compared with the prior art, the present invention has the following beneficial technical effects:

[0031] (1) In the method for hydrocracking of naphtha to produce chemical raw materials of the present invention, naphtha raw materials and hydrogen enter the hydrocracking reaction zone, mainly to selectively crack normal alkanes and isoalkanes and cycloalkanes containing long straight chains in the raw materials to produce small molecular normal alkanes, so that C7 + The content of normal alkanes is below 5%, so that a large amount of chain alkanes in the raw materials can be converted into gas and light naphtha components, which are enriched in the raw materials of the ethylene unit, while the monocyclic cyclic hydrocarbons are retained in the heavy naphtha fraction, which are enriched in the reforming raw materials; by controlling the refining reaction temperature to a certain extent, the bromine index in the heavy naphtha produced by hydrocracking can be effectively reduced to meet the requirements of catalytic reforming feed. Through simple fractionation, efficient separation of chain alkanes and cyclic hydrocarbons can be achieved, increasing the production of high-quality ethylene cracking feed while improving the quality of heavy naphtha as catalytic reforming feed.

[0032] (2) The heavy naphtha obtained by the method of the present invention has a high content of monocyclic cyclic hydrocarbons. When used as feed for a catalytic reforming unit, the cyclization and dehydrogenation units of the alkane in the catalytic reforming unit can be eliminated, thereby greatly reducing the investment and energy consumption of the catalytic reforming unit. At the same time, since the hydrocracking reaction follows the carbon ion reaction mechanism, the cyclic hydrocarbons above C9 can be selectively subjected to side chain breaking reaction, so that the C6-C8 cyclic hydrocarbons in the product have a high enrichment, and the BTX yield can be greatly increased after catalytic reforming and aromatics extraction.

[0033] (3) The present invention selectively converts the chain alkanes in the hydrocarbon oil into small molecule alkanes. This process consumes a certain amount of hydrogen. However, the hydrogen yield of light hydrocarbons as raw materials for ethylene plants is also high. The lower the carbon number, the higher the hydrogen yield. Therefore, most of the hydrogen consumed in the hydrogenation process can be recovered after passing through the ethylene plant. At the same time, light hydrocarbons as ethylene raw materials can greatly increase the yields of ethylene, propylene and butadiene, and extend the cleaning cycle of the ethylene plant, significantly improving the economic benefits of the plant. Description of the Drawings

[0034] Figure 1 is a schematic process flow diagram of the process method of the present invention;

[0035] Description of the main reference numerals:

[0036] 1 - Naphtha feedstock, 2 - Hydrogen, 3 - Hydrocracking reaction zone, 4 - Hydrocracking product, 5 - Hydrotreating reaction zone, 6 - Hydrotreating product, 7 - Separator, 8 - Hydrogen-rich gas in the gas-phase stream, 9 - Liquid-phase stream, 10 - Fractionating tower, 11 - Gas fraction, 12 - Light naphtha, 13 - Heavy naphtha. Detailed Embodiments

[0037] The functions and effects of the present invention will be further described below through examples, but the following examples do not limit the method of the present invention.

[0038] In the present invention, unless otherwise specified, % are all mass fractions.

[0039] The overall volume space velocity in the examples and comparative examples is the ratio of the fresh feed volume to the total volume of the catalyst.

[0040] The method of the present invention, as Figure 1 shown, includes: The naphtha feedstock 1 is mixed with hydrogen 2 and enters the hydrocracking reaction zone 3 for hydrocracking reaction. The hydrocracking product 4 enters the hydrotreating reaction zone 5 for hydrotreating reaction. The hydrotreating product 6 enters the separator 7. The separated hydrogen-rich gas 8 in the gas-phase stream is recycled. The liquid-phase stream 9 enters the fractionating tower 10, and gas fraction 11, light naphtha 12, and heavy naphtha 13 are fractionated.

[0041] In the present invention, the hydrocracking catalysts in each example are represented by Cat-L plus a number, such as Cat-L1, Cat-L2, Cat-L3, Cat-L4. The hydrocracking catalysts are prepared by the conventional active metal saturation impregnation method, and the physical and chemical properties of the obtained catalysts are shown in Table 1. The hydrotreating catalysts in each example are represented by Cat-J, and the physical and chemical properties of the catalysts are shown in Table 2. Among them, the properties of Beta zeolite are as follows: The SiO2 / Al2O3 molar ratio is 30, the specific surface area is 350 m 2 / g, and the pore volume is 0.32 cm 3 / g.

[0042] In the present invention, the feedstock oil in each example is heavy naphtha feedstock, and its main properties are shown in Table 3.

[0043] In the present invention, the ethylene feedstock in Table 4 refers to ethane, propane, butane, and light naphtha. It can be used to produce light olefins.

[0044] In the present invention, the bromine index of heavy naphtha refers to the number of milligrams of Br consumed per 100 grams of heavy naphtha, mgBr / 100g. The bromine index of heavy naphtha is determined by titration.

[0045] In the present invention, the distillation range of light naphtha is the liquid component with a boiling point less than 60°C, and the distillation range of heavy naphtha is 60 - 175°C.

[0046] In the present invention, the yield of ethylene feedstock refers to the mass ratio of ethane, propane, butane, and light naphtha in the hydrocracking product to the fresh hydrocracking feedstock, and the yield of heavy naphtha refers to the mass ratio of heavy naphtha in the hydrocracking product to the fresh hydrocracking feedstock.

[0047] Examples 1 - 4

[0048] The hydrocracking method described above adopts the following Figure 1 process, including:

[0049] (1) The feedstock oil is mixed with hydrogen and enters the hydrocracking reaction zone; the hydrocracking reaction zone is filled with hydrocracking catalyst; in step (1), the content of C7 + n - paraffin in the hydrocracking reaction effluent should be controlled.

[0050] (2) The hydrocracking reaction effluent obtained in step (1) enters the hydrotreating reaction zone, and the hydrotreating reaction zone is filled with hydrotreating catalyst; the hydrotreating reaction effluent enters the separation system and is separated into a gas - phase stream and a liquid - phase stream. The gas - phase stream is recycled, and the liquid - phase stream enters the fractionating tower to fractionate ethane, propane, butane, light naphtha, and heavy naphtha.

[0051] The process conditions and hydrocracking effects in each example are shown in Table 4.

[0052] Comparative Example 1

[0053] The difference from Example 1 is that the catalyst Cat - L5 is filled in the hydrocracking reaction zone.

[0054] The process conditions and hydrocracking effects in this example are shown in Table 4.

[0055] Comparative Example 2

[0056] The difference from Example 1 is that in step (1), the content of C7 + n - paraffin in the hydrocracking reaction effluent is 6%.

[0057] The process conditions and hydrocracking effects in this example are shown in Table 4.

[0058] Comparative Example 3

[0059] The difference from Example 1 is that in step (2), the reaction temperature in the hydrotreating reaction zone is 40°C lower than that in the hydrocracking reaction zone in step (1).

[0060] In this example, the process conditions and the hydrogenation effect are shown in Table 4.

[0061] Table 1 Physicochemical properties of the hydrocracking catalyst

[0062]

[0063] Table 2 Physicochemical properties of the hydrofining catalyst

[0064]

[0065]

[0066] Table 3 Main properties of the raw materials

[0067] Raw material oil name Heavy naphtha raw material <![CDATA[Density (20 °C) / kg·m -3 > 743.8 Distillation range / °C (ASTM D86) IBP / 10% 59 / 101 30％ / 50％ 119 / 132 70％ / 90％ 145 / 158 95% / EBP 163 / 173 <![CDATA[C7 + n-alkane, wt%]]> 16 Cyclic hydrocarbons, wt% 42 Nitrogen content, mg / kg 1.2

[0068] Table 4 Hydrogenation effect

[0069]

[0070]

[0071] Continued Table 4

[0072]

[0073] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A hydrocracking method for naphtha, the method comprising: (1) In the presence of hydrogen, the naphtha feedstock enters the hydrocracking reaction zone to selectively crack the normal paraffins in the naphtha feedstock, obtaining a hydrocracking product; wherein, in the hydrocracking product, the mass content of C7 + normal paraffins is controlled below 5.0%; (2) The hydrocracking product enters the hydrorefining reaction zone for hydrorefining reaction; (3) The hydrorefined product enters the separation and fractionation system to obtain chemical raw materials; In step (1), a hydrocracking catalyst is loaded in the hydrocracking reaction zone; the hydrocracking catalyst comprises an active metal component and a carrier; the carrier comprises one or more of ZSM-5 zeolite, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35 and ZSM-38 zeolites; In step (1), for the hydrocracking catalyst, based on the weight of the catalyst, the content of Group VIB metal in terms of oxide is 5.0% - 15.0%, the content of Group VIII metal in terms of oxide is 2.0% - 5.0%, and the content of the carrier is 80.0% - 93.0%; in the carrier of the hydrocracking catalyst, based on the weight of the carrier, the content of zeolite is 40% - 92%; In step (2), a hydrorefining catalyst is loaded in the hydrorefining reaction zone; the hydrorefining catalyst comprises a carrier and a hydroactive metal; the hydroactive metal comprises Group VIB and / or Group VIII metal components; in the hydrorefining catalyst, the content of Group VIB metal component in terms of oxide mass in the catalyst is 5% - 30%, and the content of Group VIII metal component in terms of oxide mass in the catalyst is 1% - 6%; The chemical raw materials include ethane, propane, butane, light naphtha, and heavy naphtha, wherein heavy naphtha is used as a reforming raw material to produce BTX; ethane, propane, butane, and light naphtha are used as ethylene raw materials to produce light olefins; In step (2), the reaction temperature in the hydrorefining reaction zone is 50°C - 200°C lower than that in the hydrocracking reaction zone in step (1).

2. The hydrocracking process according to claim 1, wherein In step (2), the reaction temperature in the hydrorefining reaction zone is 80°C - 120°C lower than that in the hydrocracking reaction zone in step (1).

3. The hydrocracking process according to claim 1, wherein The reaction conditions of the hydrofining reaction in step (2) are as follows: the average reaction temperature is 150~400°C; and / or, the liquid hourly space velocity is 0.1~15.0 h -1 ; and / or, the hydrogen-oil volume ratio is 100:1~2500:1; and / or, the reaction pressure is 1.0~5.0 MPa.

4. The hydrocracking process according to claim 3, characterized in that, The reaction conditions for the hydrofining reaction in step (2) are as follows: the average reaction temperature is 200~300°C; and / or, the liquid hourly space velocity is 1.0~5.0 h -1 ; and / or, the hydrogen-oil volume ratio is 300:1~2000:1; and / or, the reaction pressure is 2.0~4.0 MPa.

5. The hydrocracking process according to claim 1, characterized in that, In step (2), the carrier is an inorganic refractory oxide, selected from one or several of alumina, amorphous silica-alumina, silica, or titanium oxide.

6. The hydrocracking process according to claim 1, wherein In step (2), in the hydrorefining catalyst, the content of Group VIB metal in terms of oxide mass in the catalyst is 10% - 20%, and the content of Group VIII metal in terms of oxide mass in the catalyst is 1.5% - 5%.

7. The hydrocracking process according to claim 1 or 6, characterized in that, In step (2), in the hydrorefining catalyst, the Group VIB metal is selected from tungsten and / or molybdenum; the Group VIII metal is selected from nickel and / or cobalt.

8. The hydrocracking process according to claim 1, characterized in that, In the hydrocracking product described in step (1), the mass content of C7 + normal paraffin is controlled at 1% - 5%.

9. The hydrocracking process according to claim 1, characterized in that, The initial boiling point of the naphtha raw material in step (1) is 40°C - 80°C; the final boiling point is 150°C - 200°C.

10. The hydrocracking process according to claim 9, wherein, The initial boiling point of the naphtha raw material in step (1) is 50°C - 70°C; the final boiling point is 160°C - 180°C.

11. The hydrocracking method according to claim 1, characterized in that, In the naphtha feedstock described in step (1), the mass content of C7 + normal paraffins is 6% to 50%.

12. The hydrocracking process according to claim 11, characterized in that, In the naphtha raw material described in step (1), the mass content of C7 + normal paraffin is 10% to 40%.

13. The hydrocracking process according to claim 1 or 11, characterized in that, In the naphtha raw material in step (1), the mass content of cyclic hydrocarbons is 30% - 80%.

14. The hydrocracking process according to claim 1, characterized in that, In step (1), the reaction conditions for the hydrocracking reaction are as follows: the reaction pressure is 1.0 - 5.0 MPa.

15. The hydrocracking process according to claim 14, wherein, In step (1), the reaction conditions for the hydrocracking reaction are as follows: the reaction pressure is 2.0 - 4.0 MPa.

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

1.

17. The hydrocracking process according to claim 16, characterized in that, The reaction conditions of the hydrocracking reaction in step (1) are as follows: the average reaction temperature is 300~400°C; the liquid hourly space velocity is 1.0~5.0 h -1 ; the hydrogen-oil volume ratio is 400:1~2000:

1.

18. The hydrocracking process according to claim 1, characterized in that, In step (1), in the hydrocracking catalyst, the Group VIB metals are molybdenum and / or tungsten, and the Group VIII metals are cobalt and / or nickel.

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