A process for producing c3 / c4 products from light oils

Abstract

The present application relates to the field of raffinate oil utilization conversion, and discloses a method for producing C3 / C4 products from light oil, comprising: (1) introducing the light oil into a hydrocracking reaction zone filled with a hydrocracking catalyst under low-pressure hydrogen condition to perform a hydrocracking reaction, so as to obtain a hydrocracking product; the content of saturated hydrocarbon in the raffinate oil is 90wt%-100wt%; (2) separating the hydrocracking product. The method provided by the present application can produce liquefied gas rich in C3 and isomeric C4 from raffinate oil as raw material under low-pressure hydrogen condition.

Description

Technical Field

[0001] This invention relates to the field of light oil utilization and conversion technology, and specifically to a method for producing C3 / C4 products from light oil. Background Technology

[0002] Currently, the traditional oil refining industry faces the challenge of transitioning from large-scale and cleaner operations to "oil conversion" and energy conservation and carbon reduction. Because aromatic residue oil itself has a low octane rating and low demand for blended gasoline, a high-value utilization method for aromatic residue oil is urgently needed.

[0003] The best feedstock for chemical plants such as ethylene plants is low-carbon n-alkanes. Therefore, using low-sulfur and low-nitrogen raffinate as feedstock to produce propane and butane, while also producing a portion of light naphtha, which is mainly composed of low-carbon hydrocarbons, can provide high-quality feedstock for chemical plants and solve the problem of surplus low-value-added raffinate resources in refineries.

[0004] CN12409121A discloses a method for converting light naphtha into low-carbon olefins and aromatics. Light naphtha with a C5 and C6 alkane content of 99% undergoes isomerization separation. The isomerized components are fed into a hydrocracking unit and separated to obtain refinery dry gas, propane, n-butane, and isobutane. These components are then further converted into ethylene and propylene through steam cracking or propane dehydrogenation units. The hydrocracking unit conditions include a temperature of 330–360°C and a gauge pressure of 6–8 MPa. After separation in the hydrocracking unit, the proportions of refinery dry gas, propane, n-butane, and isobutane are 6%, 31%, 29%, and 34%, respectively.

[0005] WO2021236149A1 discloses a method for converting light naphtha fractions into high-value products through a two-stage reaction zone. The feedstock passes through a first reactor packed with a bifunctional catalyst, where a portion of the light naphtha is reformed into BTEX, and another portion is cracked into ethane, propane, and butane. The effluent from the first reactor is passed into a gas-liquid separation unit to produce liquid and gaseous products. After removing hydrogen and methane from the gaseous products, the gaseous products are passed through a second reactor under steam cracking conditions to convert the gas into low-carbon olefins.

[0006] CN13307717A discloses a method for producing propane through hydroconversion of light hydrocarbons. The method involves heating light hydrocarbon feedstock, hydrogen-rich gas, and recycled light hydrocarbons, followed by catalytic cracking under acidic catalyst conditions. The reaction products, after cooling and fractionation, yield dry gas, propane, and aromatic gasoline components, respectively. The feedstock used in this method has an alkane content greater than 50 wt% and a carbon number range of C4 to C13. The reaction temperature is 250–550 °C, the pressure is 0.01–5.0 MPa, and the mass hourly space velocity (HHSV) is 0.1–5.0 h⁻¹. -1The hydrogen-to-oil ratio is 30–800:1, and the catalyst is HZSM-5 molecular sieve.

[0007] Currently, technologies that primarily produce propane and butane often impose significant limitations on raw materials, such as the number of carbon atoms and the content of alkanes in the hydrocarbon composition. Furthermore, under relatively mild reaction conditions, the yields of propane and butane are often quite low. Summary of the Invention

[0008] The purpose of this invention is to provide a hydrocarbon oil conversion method that maximizes the yield of propane and isobutane using light oil as raw material.

[0009] To achieve the above objectives, the present invention provides a method for producing C3 / C4 products from light oil, the method comprising:

[0010] (1) Under low-pressure hydrogenation conditions, light oil is introduced into a hydrocracking reaction zone filled with a hydrocracking catalyst to carry out a hydrocracking reaction and obtain hydrocracking products; the content of saturated hydrocarbons in the light oil is 90wt% to 100wt%.

[0011] (2) The hydrocracking products are separated to obtain C3 / C4 products and light naphtha products with C5 or higher; the yield of liquefied gas in the C3 / C4 products is not less than 50 wt%.

[0012] The conditions for the hydrocracking reaction are controlled such that the conversion rate of the hydrocracking reaction zone is 42% to 88%; the conversion rate = (1 - mass percentage of C5 and above hydrocarbons in the light naphtha product * yield of the light naphtha product / mass percentage of C5 and above hydrocarbons in the light oil) * 100%.

[0013] Based on the total weight of the hydrocracking catalyst, the content of active metal elements in the hydrocracking catalyst, calculated as oxides, is 10wt% to 50wt%, with the remainder being the support; based on the total weight of the support, the support contains 45wt% to 80wt% of acidic components, wherein the acidic components are at least one of Y-type molecular sieves and their modified products.

[0014] The method provided by this invention can convert light oil feedstocks such as aromatic raffinate to produce C3 / C4 products.

[0015] The method provided by this invention can produce liquefied petroleum gas rich in C3 and isomer C4 from light oil under low-pressure hydrogen conditions.

[0016] The method provided by this invention enables the production of C3 and C4 products from raffinate under low-pressure hydrocracking conditions from low-nitrogen naphtha feedstock, maximizing the yield of propane and isobutane and providing high-quality feedstock for chemical plants. Attached Figure Description

[0017] Figure 1 This is a schematic flowchart of a preferred embodiment of the method for producing C3 / C4 products from light oil according to the present invention.

[0018] Explanation of reference numerals in the attached figures

[0019] Numbers 1, 3, 5, 7, 9, 11, 12, 14, 15, and 16 are all pipelines.

[0020] 2: Raw material oil pump

[0021] 4: Heating furnace

[0022] 6: Hydrocracking Reaction Zone

[0023] 8: High-pressure separator

[0024] 10: Gas purification unit

[0025] 13: Fractionation Unit Detailed Implementation

[0026] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0027] As previously stated, this invention provides a method for producing C3 / C4 products from light oil, the method comprising:

[0028] (1) Under low-pressure hydrogenation conditions, light oil is introduced into a hydrocracking reaction zone filled with a hydrocracking catalyst to carry out a hydrocracking reaction and obtain hydrocracking products; the content of saturated hydrocarbons in the light oil is 90wt% to 100wt%.

[0029] (2) The hydrocracking products are separated to obtain C3 / C4 products and light naphtha products with C5 or higher; the yield of liquefied gas in the C3 / C4 products is not less than 50 wt%.

[0030] The conditions for the hydrocracking reaction are controlled such that the conversion rate of the hydrocracking reaction zone is 42% to 88%; the conversion rate = (1 - mass percentage of C5 and above hydrocarbons in the light naphtha product * yield of the light naphtha product / mass percentage of C5 and above hydrocarbons in the light oil) * 100%.

[0031] Based on the total weight of the hydrocracking catalyst, the content of active metal elements in the hydrocracking catalyst, calculated as oxides, is 10wt% to 50wt%, with the remainder being the support; based on the total weight of the support, the support contains 45wt% to 80wt% of acidic components, wherein the acidic components are at least one of Y-type molecular sieves and their modified products.

[0032] In this invention, the yield of the light naphtha product with C5 or higher is equal to the total mass of the liquid product obtained after fractionation of the hydrocracking products / the mass of the light oil * 100%.

[0033] Preferably, the conditions of the hydrocracking reaction are controlled such that the conversion rate in the hydrocracking reaction zone is 60% to 88%, more preferably 62% to 88%.

[0034] Preferably, in the hydrocracking catalyst, the support contains 45 wt% to 60 wt%, more preferably 45 wt% to 55 wt%, and particularly preferably 45 wt% to 50 wt% of an acidic component, based on the total weight of the support.

[0035] The method of the present invention may further include preheating the light oil, either alone or together with hydrogen, before introducing the light oil into the hydrocracking reaction zone for hydrocracking; for example, preheating it in a heating furnace; and then introducing the preheated material into the hydrocracking reaction zone for the hydrocracking reaction. The present invention does not have particular requirements for the preheating temperature; it can be the temperature required for the hydrocracking reaction or slightly lower.

[0036] Preferably, in step (1), the light oil has a carbon number of C5 to C12, an alkanes content of 30 wt% to 100 wt%, a cycloalkanes content of 0 wt% to 70 wt%, and an aromatics content of 0 wt% to 10 wt%.

[0037] More preferably, the light oil has an alkane content of 45% to 90% by weight.

[0038] More preferably, the cycloalkanes content of the light oil is 10% to 50% by weight.

[0039] More preferably, the aromatic content of the light oil is 0.1% to 8% by weight.

[0040] Preferably, the light oil has a density of 0.68-0.75 g / cm³ at 20°C. 3 .

[0041] Preferably, the light oil is selected from one or more of the following: refinery light oil from an aromatics extraction unit, reforming residue oil, and DCC gasoline hydrotreating unit residue oil.

[0042] In a preferred embodiment, the light oil contains ≤20 μg / g nitrogen, ≤300 μg / g sulfur, and ≤0.2 μg / g arsenic.

[0043] Preferably, the pressure of the hydrocracking reaction is ≤8.0 MPa.

[0044] According to a preferred embodiment, the hydrocracking reaction is carried out at a temperature of 280–420°C, a pressure of 0.2–8.0 MPa, and a light oil volume hourly space velocity of 0.5–20.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is 100–2000.

[0045] In a preferred embodiment, the support for the hydrocracking catalyst further contains at least one heat-resistant inorganic oxide selected from silicon oxide and aluminum oxide.

[0046] Particularly preferably, the content of the heat-resistant inorganic oxide is 20wt% to 55wt% based on the total weight of the carrier.

[0047] In a preferred embodiment, the active metal element in the hydrocracking catalyst is selected from at least two of Group VIB and Group VIII metal elements.

[0048] According to a particularly preferred embodiment, in the hydrocracking catalyst, the active metal element includes at least one selected from Group VIB metal elements and at least one selected from Group VIII metal elements; based on the total weight of the hydrocracking catalyst, the content of the Group VIB metal element is 5 wt% to 35 wt% and the content of the Group VIII metal element is 1 wt% to 8 wt% in terms of oxides.

[0049] In a preferred embodiment, in step (1), a protective catalyst is also loaded upstream of the hydrocracking catalyst; based on the total volume of the catalyst in the hydrocracking reaction zone being 100%, the loading volume of the protective catalyst is 1% to 50%, and the loading volume of the hydrocracking catalyst is 50% to 99%.

[0050] Preferably, in step (1), the protective catalyst is selected from at least one of a hydrorefining catalyst, a hydrodearsenic removal catalyst, and a hydrodemetallization catalyst.

[0051] According to a particularly preferred embodiment, in step (1), the light oil has a nitrogen content >20 μg / g, or a sulfur content >300 μg / g, or an arsenic content >0.2 μg / g, or a mercury content >0.2 μg / g; and the protective catalyst is a hydrorefining catalyst and / or a hydrodemetallization catalyst.

[0052] In a preferred embodiment, in step (1), the light oil contains nitrogen content > 20 μg / g, sulfur content > 300 μg / g, arsenic content > 0.2 μg / g, or mercury content > 0.2 μg / g; the protective catalyst contains a protective agent carrier and a protective agent active metal component, wherein the protective agent carrier is alumina, and the protective agent active metal component contains at least one element selected from Group VIII metals and at least one element selected from Group VIB metals.

[0053] More preferably, in step (1), the light oil contains nitrogen > 20 μg / g, sulfur > 300 μg / g, arsenic > 0.2 μg / g, or mercury > 0.2 μg / g; and in the protective catalyst, based on the total weight of the protective agent, the content of the Group VIII metal element is 0.3 wt% to 5 wt% and the content of the Group VIB metal element is 1 wt% to 30 wt% (calculated as oxides).

[0054] According to a preferred embodiment, in step (1), the light oil has a nitrogen content >20 μg / g, or a sulfur content >300 μg / g, or an arsenic content >0.2 μg / g, or a mercury content >0.2 μg / g; and in the protective catalyst, the active metal component of the protective agent contains at least one of nickel and cobalt, and at least one of molybdenum and tungsten.

[0055] According to another preferred embodiment, in step (1), the arsenic content of the light oil is 1 μg / g to 30 μg / g, and the protective catalyst comprises a hydrodearsenic catalyst.

[0056] More preferably, the catalyst support for hydrodearsenic removal is alumina, and the active metal component contains at least one of nickel and cobalt, and at least one of molybdenum and tungsten. The total content of nickel and cobalt, calculated as oxides, is 0.1 wt% to 6 wt%, and the total content of molybdenum and tungsten is 1 wt% to 20 wt%.

[0057] According to another preferred embodiment, in step (1), the total metal content of the light oil is 0.1wt% to 2wt%, and the protective catalyst is a hydrodemetallization catalyst.

[0058] More preferably, the hydrodemetallization catalyst support is alumina, and the active metal component contains at least one of nickel and cobalt, and at least one of molybdenum and tungsten. The total content of nickel and cobalt, calculated as oxides, is 0.5 wt% to 3 wt%, and the total content of molybdenum and tungsten, calculated as oxides, is 1 wt% to 30 wt%. More preferably, the total content of nickel and cobalt, calculated as oxides, is 1 wt% to 3 wt%, and the total content of molybdenum and tungsten, calculated as oxides, is 1 wt% to 30 wt%.

[0059] The present invention does not have any particular requirements on the source of the aforementioned catalyst. It can be prepared by methods known in the art, or a commercially available catalyst with corresponding characteristics can be purchased. The present invention will not be described in detail here, and those skilled in the art should not understand it as a limitation of the present invention.

[0060] The present invention does not have any particular requirements for the specific method of separation described in step (2). Those skilled in the art can use separation methods known in the art, such as gas-liquid separation, fractionation, etc. The example section of the present invention provides a specific separation method by way of example, which should not be construed as a limitation on the scope of protection of the present invention.

[0061] The separation described in this invention can be performed in a separator (e.g., a high-pressure separator) for gas-liquid separation. The gaseous product obtained after gas-liquid separation can be purified and recycled back to the unit for the hydrocracking reaction. The liquid product obtained after gas-liquid separation is preferably subjected to further fractionation to obtain the C3 / C4 product and the light naphtha product.

[0062] The light naphtha product obtained by this invention can be mixed with feedstock as unconverted oil according to production needs, and then recycled to the reaction system for complete conversion, or it can be withdrawn from the device. This invention does not have any particular requirements in this regard.

[0063] The following combination Figure 1 The illustrated process flow diagram provides a preferred embodiment of a method for producing C3 / C4 products from light oil according to the present invention. Specifically, the method includes:

[0064] (1) Under low-pressure hydrogen conditions, light oil is introduced into the heating furnace 4 for preheating via pipeline 1, feedstock oil pump 2 and pipeline 3 in sequence, and hydrogen is introduced into the heating furnace 4 via pipeline 16 to obtain preheated material; the preheated material is introduced into the hydrocracking reaction zone 6, which is filled with hydrocracking catalyst in sequence, via pipeline 5 to carry out hydrocracking reaction to obtain hydrocracking products;

[0065] (2) The hydrocracking products are introduced into the high-pressure separator 8 via pipeline 7 for gas-liquid phase separation; the gas phase flowing out of the high-pressure separator 8 enters the gas purification unit 10 via pipeline 9, and the purified gas can be recycled back to the reaction system as circulating hydrogen via pipeline 11; the liquid phase flowing out of the high-pressure separator 8 enters the fractionation unit 13 via pipeline 12, and the propane-rich gas phase exits the device via pipeline 14; after fractionation by the fractionation unit, light naphtha containing C5 or higher components is drawn out from pipeline 15. This part of light naphtha can also be mixed with the feed oil from the pipeline as unconverted oil according to production needs, and then recycled to the reaction system for full conversion.

[0066] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, the raw materials used are all commercially available products.

[0067] Unless otherwise specified, the following examples all use Figure 1 The process flow shown is followed.

[0068] The properties of the light oils used are listed in Table 1; the catalysts used are listed in Table 2.

[0069] The catalysts used in the following examples were prepared using methods known in the art, such as those provided in CN112742440A or commercially available.

[0070] Table 1: Properties of Light Oils

[0071]

[0072] Table 2: Catalyst Information

[0073]

[0074] Example 1

[0075] use Figure 1 The process flow shown is as follows, and the process parameters involved, including the absence of a protective catalyst in the hydrocracking reaction zone, are listed in Table 3.

[0076] The distribution and properties of the obtained products are listed in Table 4.

[0077] Comparative Example 1

[0078] use Figure 1 The process flow shown is as follows, and the process parameters involved, including the absence of a protective catalyst in the hydrocracking reaction zone, are listed in Table 3.

[0079] The distribution and properties of the obtained products are listed in Table 4.

[0080] Example 2

[0081] use Figure 1 The process flow shown, the protective catalyst in the hydrocracking reaction zone, and the protective catalyst being located upstream of the hydrocracking catalyst, along with the relevant process parameters, are listed in Table 3.

[0082] The distribution and properties of the obtained products are listed in Table 4.

[0083] Comparative Example 2

[0084] use Figure 1 The process flow shown is as follows, and the process parameters involved, including the absence of a protective catalyst in the hydrocracking reaction zone, are listed in Table 3.

[0085] The distribution and properties of the obtained products are listed in Table 4.

[0086] Example 3

[0087] use Figure 1 The process flow shown, the protective catalyst in the hydrocracking reaction zone, and the protective catalyst being located upstream of the hydrocracking catalyst, along with the relevant process parameters, are listed in Table 3.

[0088] The distribution and properties of the obtained products are listed in Table 4.

[0089] Comparative Example 3

[0090] use Figure 1 The process flow shown, the protective catalyst in the hydrocracking reaction zone, and the protective catalyst being located upstream of the hydrocracking catalyst, along with the relevant process parameters, are listed in Table 3.

[0091] The distribution and properties of the obtained products are listed in Table 4.

[0092] Example 4

[0093] use Figure 1 The process flow shown is as follows, and the process parameters involved, including the absence of a protective catalyst in the hydrocracking reaction zone, are listed in Table 3.

[0094] The distribution and properties of the obtained products are listed in Table 4.

[0095] Comparative Example 4

[0096] use Figure 1 The process flow shown is as follows, and the process parameters involved, including the absence of a protective catalyst in the hydrocracking reaction zone, are listed in Table 3.

[0097] The distribution and properties of the obtained products are listed in Table 4.

[0098] Example 5

[0099] use Figure 1 The process flow shown is as follows. The types of feedstock oils in the hydrocracking reaction zone are different, as are the types of protective catalysts. The process parameters involved are listed in Table 3.

[0100] The distribution and properties of the obtained products are listed in Table 4.

[0101] Table 3

[0102]

[0103]

[0104] The percentage of catalyst loading volume in Table 3 is calculated based on the total catalyst loading volume of the hydrocracking reaction.

[0105] Table 3 (continued)

[0106]

[0107] The percentage of catalyst loading volume in Table 3 is calculated based on the total catalyst loading volume of the hydrocracking reaction.

[0108] Table 4

[0109]

[0110] The results above show that the method provided by this invention can convert naphtha feedstock into liquefied petroleum gas (LPG) products under milder conditions, with propane and isobutane yields being relatively close. In contrast, the method provided in the comparative example clearly requires higher temperatures and lower space velocities to convert feedstock into LPG.

[0111] Furthermore, the results above demonstrate that the hydrocracking technology of this invention has the excellent effect of producing more C3 / C4 liquefied gas.

[0112] Furthermore, the results of Example 5 also show that by using suitable hydrorefining or hydrodemetallizing agents to treat metal-containing feedstocks and meeting the feed requirements of the cracking section, high-quality cracking products can also be obtained, with high yields of C3 and C4 liquefied petroleum gas.

[0113] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for producing C3 / C4 products from light oil, characterized in that, The method includes: (1) Under low-pressure hydrogenation conditions, light oil is introduced into a hydrocracking reaction zone packed with a hydrocracking catalyst to carry out a hydrocracking reaction, thereby obtaining hydrocracking products; the content of saturated hydrocarbons in the light oil is 90wt%~100wt%; the number of carbon atoms in the light oil is C5~C12, the content of alkanes is 44.54wt%~90wt%, the content of cycloalkanes is 10wt%~50wt%, and the content of aromatics is 0.1wt%~8wt%; the sum of the contents of each component in the light oil is 100wt%; (2) The hydrocracking products are separated to obtain C3 / C4 products and light naphtha products with C5 or higher content; the yield of liquefied petroleum gas in the C3 / C4 products is not less than 50 wt%. The conditions for the hydrocracking reaction are controlled such that the conversion rate in the hydrocracking reaction zone is 42%~88%; the conversion rate = (1 - mass percentage of C5 and above hydrocarbons in the C5 and above light naphtha product * yield of the C5 and above light naphtha product / mass percentage of C5 and above hydrocarbons in the light oil) * 100%; The yield of the light naphtha product with C5 or higher is equal to the total mass of the liquid product obtained after fractionation of the hydrocracking products / the mass of the light oil * 100%. Based on the total weight of the hydrocracking catalyst, the content of active metal elements in the hydrocracking catalyst, calculated as oxides, is 10wt%~50wt%, with the remainder being the support; based on the total weight of the support, the support contains 45wt%~80wt% of acidic components, wherein the acidic components are at least one of Y-type molecular sieves and their modified products.

2. The method according to claim 1, wherein, The conditions of the hydrocracking reaction are controlled such that the conversion rate in the hydrocracking reaction zone is 60% to 88%.

3. The method according to claim 2, wherein, The conditions of the hydrocracking reaction are controlled such that the conversion rate in the hydrocracking reaction zone is 62% to 88%.

4. The method according to any one of claims 1-3, wherein, The light oil is selected from one or more of the following: refinery light oil from aromatics extraction units, reforming residue oil, and DCC gasoline hydrotreating unit residue oil.

5. The method according to any one of claims 1-3, wherein, The light oil contains nitrogen content ≤20μg / g, sulfur content ≤300μg / g, and arsenic content ≤0.2μg / g.

6. The method according to any one of claims 1-3, wherein, The pressure of the hydrocracking reaction is ≤8.0 MPa.

7. The method according to any one of claims 1-3, wherein, The hydrocracking reaction is carried out at a temperature of 280–420 °C, a pressure of 0.2–8.0 MPa, and a light oil volume hourly space velocity of 0.5–20.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is 100-2000.

8. The method according to any one of claims 1-3, wherein, The support for the hydrocracking catalyst also contains at least one heat-resistant inorganic oxide selected from silicon oxide and aluminum oxide.

9. The method according to claim 8, wherein, Based on the total weight of the carrier, the content of the heat-resistant inorganic oxide is 20wt%~55wt%.

10. The method according to any one of claims 1-3, wherein, In the hydrocracking catalyst, the active metal element is selected from at least two of Group VIB and Group VIII metal elements.

11. The method according to claim 10, wherein, In the hydrocracking catalyst, the active metal element includes at least one selected from Group VIB metal elements and at least one selected from Group VIII metal elements; based on the total weight of the hydrocracking catalyst, the content of the Group VIB metal element is 5wt% to 35wt% and the content of the Group VIII metal element is 1wt% to 8wt% in terms of oxides.

12. The method according to any one of claims 1-3, wherein, In step (1), a protective catalyst is also loaded upstream of the hydrocracking catalyst; based on the total volume of the catalyst in the hydrocracking reaction zone being 100%, the loading volume of the protective catalyst is 1% to 50%, and the loading volume of the hydrocracking catalyst is 50% to 99%.

13. The method according to claim 12, wherein, In step (1), the protective catalyst is selected from at least one of the following: hydrorefining catalyst, hydroarsenic removal catalyst, and hydrodemetallization catalyst.

14. The method according to claim 13, wherein, In step (1), the light oil contains nitrogen content >20 μg / g, sulfur content >300 μg / g, arsenic content >0.2 μg / g, or mercury content >0.2 μg / g; the protective catalyst is a hydrorefining catalyst and / or a hydrodemetallization catalyst.

15. The method according to claim 13, wherein, In step (1), the light oil contains nitrogen content >20 μg / g, sulfur content >300 μg / g, arsenic content >0.2 μg / g, or mercury content >0.2 μg / g; the protective catalyst contains a protective agent carrier and a protective agent active metal component, the protective agent carrier is alumina, and the protective agent active metal component contains at least one element selected from Group VIII metal elements and at least one element selected from Group VIB metal elements.

16. The method according to claim 15, wherein, In step (1), the light oil contains nitrogen content >20 μg / g, sulfur content >300 μg / g, arsenic content >0.2 μg / g, or mercury content >0.2 μg / g; in the protective catalyst, based on the total weight of the protective catalyst, the content of the Group VIII metal element is 0.3 wt% to 5 wt% and the content of the Group VIB metal element is 1 wt% to 30 wt% (calculated as oxides).

17. The method according to claim 15, wherein, In step (1), the light oil contains nitrogen content >20 μg / g or sulfur content >300 μg / g or arsenic content >0.2 μg / g or mercury content >0.2 μg / g; in the protective catalyst, the active metal component of the protective agent contains at least one of nickel and cobalt, and at least one of molybdenum and tungsten.

18. The method according to claim 13, wherein, In step (1), the light oil has an arsenic content of 1 μg / g to 30 μg / g, and the protective catalyst includes a hydrodearsenic catalyst.

19. The method according to claim 13, wherein, The catalyst support for the hydrodearsenic removal is alumina. The active metal component contains at least one of nickel and cobalt, and at least one of molybdenum and tungsten. The total content of nickel and cobalt, calculated as oxides, is 0.1 wt% to 6 wt%, and the total content of molybdenum and tungsten is 1 wt% to 20 wt%.

20. The method according to claim 13, wherein, In step (1), the total metal content of the light oil is 0.1wt%~2wt%, and the protective catalyst is a hydrodemetallization catalyst.

21. The method according to claim 20, wherein, The hydrogenation demetallization catalyst support is alumina, and the active metal component contains at least one of nickel and cobalt, and at least one of molybdenum and tungsten. The total content of nickel and cobalt, calculated as oxides, is 0.5wt% to 3wt%, and the total content of molybdenum and tungsten is 1wt% to 30wt%.

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