A process for producing an ethylene feedstock

Abstract

The application discloses a method for producing ethylene raw material. The method comprises the following steps: mixing hydrocracking light naphtha and hydrogen into a first hydroconversion reaction zone to react, and then the reaction effluent enters a separation system to obtain hydrogen-rich gas and a first hydroconversion product; the first hydroconversion product is separated to obtain ethane, propane, isobutane, isopentane and n-pentane; the isobutane is mixed with hydrogen into a second hydroconversion reaction zone, and the reaction effluent is separated to obtain n-butane; the second hydroconversion reaction zone is filled with a hydroconversion catalyst containing ZSM-35 molecular sieve; and the isopentane is recycled to the inlet of the first hydroconversion reaction zone. The first hydroconversion reaction zone is filled with a hydroconversion catalyst containing mordenite, and at least two catalyst beds are filled; and the active metal content of the hydroconversion catalyst decreases in turn along the flow direction. The method can effectively improve the proportion of normal alkanes in the product and improve the quality of the ethylene raw material.

Description

Technical Field

[0001] This invention belongs to the field of hydrocarbon oil hydroconversion, and specifically relates to a method for producing ethylene feedstock. Background Technology

[0002] Hydrocracking technology is characterized by strong adaptability to feedstocks, high flexibility in production operations and product solutions, and high product quality. It can directly convert various heavy and low-quality feedstocks into high-quality jet fuel, diesel, lubricating oil base materials, and chemical naphtha and tail oil steam cracking feedstocks for ethylene production, which are in high demand in the market. It has become one of the most important hydrocarbon oil deep processing technologies in modern oil refining and petrochemical industries. The ethylene industry is the core of the petrochemical industry.

[0003] CN115612524A discloses a method for increasing the concentration of n-chain alkanes in a light naphtha feed stream. The method includes separating the naphtha feed stream into a stream rich in n-chain alkanes and a stream rich in non-n-chain alkanes. An isomerization feed stream is obtained from the non-n-chain alkanes stream and isomerized on an isomerization catalyst to convert the non-n-chain alkanes into n-chain alkanes and generate an isomerized effluent. Optionally, the isomerized effluent can be separated into a propane stream and a C4 stream in a single column. + Hydrocarbon feedstock. C4 + The hydrocarbon feed stream can be recycled to the step of separating the naphtha feed stream.

[0004] CN116023214A discloses a method and system for producing n-alkanes. The method involves contacting isobutane feedstock with an isobutane conversion catalyst in an isobutane conversion unit to carry out an isobutane conversion reaction. The isobutane conversion catalyst has high catalytic activity, is chlorine-free, safe and non-toxic, and reduces corrosion and wear on equipment. The resulting reaction product containing n-alkanes is introduced into a membrane separation unit for membrane separation treatment. The membrane separation element, including a molecular sieve membrane, enables efficient separation of n-alkanes and isoalkanes. The separation efficiency is high and the method is simple and easy to implement.

[0005] The above methods can all convert small molecule isoalkanes into n-alkanes, but the energy required for the conversion of hydrocarbons with different molecular structures is different, and it is difficult to effectively guarantee the yield of the target product by using a single conversion process. Summary of the Invention

[0006] To address the problems existing in the prior art, the purpose of this invention is to provide a method for producing ethylene feedstock. This method uses hydrocracking light naphtha as feedstock and can effectively convert isoalkanes in hydrocracking light naphtha into n-alkanes, thereby improving the quality of ethylene feedstock.

[0007] This invention provides a method for producing ethylene feedstock, the method comprising:

[0008] (1) Hydrocracked light naphtha is mixed with hydrogen and enters the first hydroconversion reaction zone for hydroconversion reaction. The first hydroconversion reaction zone is filled with hydroconversion catalyst containing mordenite, and at least two catalyst beds are filled. The active metal content of the hydroconversion catalyst decreases sequentially along the flow direction.

[0009] (2) The reaction effluent from step (1) enters the separation system to separate hydrogen-rich gas and the first hydrogenation conversion product. The first hydrogenation conversion product enters the propane removal tower to separate ethane and propane, and the bottom effluent from the tower. The bottom effluent from the tower enters the fractionation tower to separate isobutane and the bottom effluent from the fractionation tower. The bottom effluent from the fractionation tower enters the isopentane removal tower to obtain isopentane and the bottom effluent from the isopentane removal tower, wherein the bottom effluent from the isopentane removal tower includes n-pentane and the above components.

[0010] (3) The isobutane obtained in step (2) is mixed with hydrogen and enters the second hydrogenation conversion reaction zone for hydrogenation conversion reaction. The second hydrogenation conversion product is separated to obtain n-butane. The second hydrogenation conversion reaction zone is filled with hydrogenation conversion catalyst containing ZSM-35 molecular sieve.

[0011] (4) The isopentane obtained in step (2) is recycled to the inlet of the first hydrogenation conversion reaction zone.

[0012] According to the present invention, the hydrogenation conversion products include a first hydrogenation conversion product and a second hydrogenation conversion product.

[0013] According to the present invention, a fixed-bed reactor is used for the hydrogenation conversion reaction.

[0014] According to the present invention, the hydrocracked light naphtha refers to the fraction obtained by separating hydrocarbon oil after undergoing a hydrocracking reaction process. The initial boiling point of the hydrocracked light naphtha is 10°C to 30°C, preferably 15°C to 25°C; the final boiling point is 50°C to 100°C, preferably 55°C to 70°C.

[0015] According to the present invention, the content of C5-C6 isoalkanes in the hydrocracked light naphtha is 60wt% to 90wt%, preferably 70wt% to 80wt%; C7 + The hydrocarbon content is 0–10 wt%, preferably 0.5 wt%–5 wt%; the C5–C6 n-alkanes content is 10 wt%–30 wt%, preferably 15 wt%–25 wt%; C4 - The hydrocarbon content is 0-10 wt%, preferably 2 wt%-5 wt%; the cyclic hydrocarbon content is 0-10 wt%, preferably 2 wt%-5 wt%; and the total weight of the hydrocracked light naphtha is 100 wt%.

[0016] According to the present invention, preferably, the first hydrogenation conversion reaction zone is packed with 2 to 3 catalyst beds. Further, along the flow direction, the ratio of the upstream catalyst loading volume to the downstream catalyst loading volume in two adjacent catalyst beds is 1:3 to 3:1, preferably 1:2 to 2:1.

[0017] According to the present invention, in the hydroconversion catalyst containing mordenite, the content of mordenite is 30wt% to 80wt%, preferably 40wt% to 70wt%, based on the weight of the catalyst.

[0018] According to the present invention, the hydroconversion catalyst containing mordenite further includes a binder, preferably alumina. Further, in the hydroconversion catalyst containing mordenite, the binder content (calculated as oxide) is 5 wt% to 65 wt%, preferably 10 wt% to 35 wt%, based on the weight of the catalyst.

[0019] According to the present invention, in the mordenite-containing hydroconversion catalyst, the active metal component is selected from one or more of Group VIB metals and Group VIII non-noble metals of the periodic table. The Group VIB metals are preferably selected from one or more of molybdenum and tungsten, and the Group VIII non-noble metals are preferably selected from one or more of cobalt and nickel. Further, in the mordenite-containing hydroconversion catalyst, based on the weight of the catalyst, the content of Group VIB metals (calculated as oxides) is 5 wt% to 30 wt%, preferably 10 wt% to 20 wt%; the content of Group VIII non-noble metals (calculated as oxides) is 0.5 wt% to 15 wt%, preferably 3 wt% to 10 wt%.

[0020] According to the present invention, the specific surface area of ​​the hydroconversion catalyst containing mordenite is 200-400 m². 2 / g, with a pore volume of 0.15~0.40mL / g.

[0021] According to the present invention, the preparation method of the mordenite-containing hydroconversion catalyst can be carried out according to conventional methods in the art. The preparation method includes the preparation of a support and the loading of an active metal component, wherein the support preparation process is as follows: mordenite and a binder are mechanically mixed, shaped, dried, and calcined to form a catalyst support. The drying and calcination of the support can be performed under conventional conditions. The drying conditions are: drying at 100℃~150℃ for 1~12 hours. The calcination conditions are: calcination at 450℃~550℃ for 2.5~6.0 hours.

[0022] According to the present invention, in the preparation method of the hydroconversion catalyst containing mordenite, the method of loading the active metal component is a conventional method, such as kneading, impregnation, etc., with impregnation being preferred. The impregnation method can be a saturated impregnation method, an excess impregnation method, or a complex impregnation method, that is, impregnating the catalyst support with a solution containing the desired active metal component, followed by drying and calcination to obtain the hydroconversion catalyst. The drying conditions are: drying at 100℃~150℃ for 1~12 hours. The calcination conditions are: calcination at 450℃~550℃ for 2.5~6.0 hours.

[0023] According to the present invention, in the first hydrogenation conversion reaction zone, in two adjacent catalyst beds, the active metal content in the downstream catalyst, calculated as oxides, is 1 to 25 percentage points lower than the active metal content in the upstream catalyst, calculated as oxides, preferably 5 to 15 percentage points lower.

[0024] According to the present invention, preferably, in the first hydrogenation conversion reaction zone, in two adjacent catalyst beds, the mass content of Group VIB metals as oxides in the downstream catalyst is 1 to 23 percentage points lower (preferably 3 to 15 percentage points lower) than the mass content of Group VIB metals as oxides in the upstream catalyst, and the mass content of Group VIII non-precious metals as oxides in the downstream catalyst is 0 to 4 percentage points lower than the mass content of Group VIII non-precious metals as oxides in the upstream catalyst.

[0025] According to the present invention, the hydroconversion catalyst containing ZSM-35 molecular sieve further includes a binder, which is preferably alumina. Further, in the hydroconversion catalyst containing ZSM-35 molecular sieve, the binder content (based on the weight of the catalyst) is 5 wt% to 65 wt%, preferably 10 wt% to 35 wt% (calculated as oxides).

[0026] According to the present invention, in the hydroconversion catalyst containing ZSM-35 molecular sieve, the active metal component is selected from one or more of Group VIB metals and Group VIII non-noble metals of the periodic table. The Group VIB metals are preferably selected from one or more of molybdenum and tungsten, and the Group VIII non-noble metals are preferably selected from one or more of cobalt and nickel. Further, in the hydroconversion catalyst containing ZSM-35 molecular sieve, based on the weight of the catalyst, the content of Group VIB metals (calculated as oxides) is 5 wt% to 30 wt%, preferably 10 wt% to 20 wt%; the content of Group VIII non-noble metals (calculated as oxides) is 0.5 wt% to 15 wt%, preferably 3 wt% to 10 wt%.

[0027] According to the present invention, the specific surface area of ​​the hydroconversion catalyst containing ZSM-35 molecular sieve is 200-400 m². 2 / g, with a pore volume of 0.20~0.40mL / g.

[0028] According to the present invention, the preparation method of the ZSM-35 molecular sieve-containing hydroconversion catalyst can be carried out according to conventional methods in the art. The preparation method includes the preparation of a support and the loading of an active metal component, wherein the support preparation process is as follows: ZSM-35 molecular sieve and a binder are mechanically mixed, shaped, and then dried and calcined to form a catalyst support. The drying and calcination of the support can be carried out under conventional conditions. The drying conditions are: drying at 100℃~150℃ for 1~12 hours. The calcination conditions are: calcination at 450℃~550℃ for 2.5~6.0 hours.

[0029] According to the present invention, in the preparation method of the hydroconversion catalyst containing ZSM-35 molecular sieve, the method for loading the active metal component is a conventional method, such as kneading, impregnation, etc., with impregnation being preferred. The impregnation method can be a saturated impregnation method, an excess impregnation method, or a complex impregnation method, that is, impregnating the catalyst support with a solution containing the desired active metal component, followed by drying and calcination to obtain the hydroconversion catalyst. The drying conditions are: drying at 100℃~150℃ for 1~12 hours. The calcination conditions are: calcination at 450℃~550℃ for 2.5~6.0 hours.

[0030] According to the present invention, the conditions for the first hydrogenation conversion reaction are as follows: reaction pressure is 0.5 MPa to 10.0 MPa, preferably 2.0 MPa to 5.0 MPa; reaction temperature is 250°C to 500°C, preferably 350°C to 450°C; and liquid hourly space velocity is 0.1 h⁻¹. -1 ~15.0h -1 0.5h is preferred -1 ~5.0h -1 The hydrogen-to-oil volume ratio is 10:1 to 2500:1, preferably 100:1 to 2000:1, and more preferably 100:1 to 1000:1. The second hydrogenation conversion reaction conditions are as follows: reaction pressure is 0.5 MPa to 10.0 MPa, preferably 2.0 MPa to 5.0 MPa; reaction temperature is 250℃ to 500℃, preferably 350℃ to 450℃; and liquid hourly space velocity is 0.1 h⁻¹. -1 ~15.0h -1 0.5h is preferred -1 ~5.0h -1 The hydrogen-to-oil volume ratio is 10:1 to 2500:1, preferably 100:1 to 2000:1, and even more preferably 100:1 to 1000:1. Furthermore, the conditions for the first hydrogenation reaction can be the same as or different from the conditions for the second hydrogenation reaction.

[0031] According to the present invention, in step (2), the hydrogen-rich gas obtained by separation can be used as recycled hydrogen.

[0032] According to the present invention, the ethane and propane, n-pentane and the above components obtained in step (2) and the n-butane obtained in step (3) are fed into a steam cracking ethylene production unit to obtain the main target products ethylene, propylene and butadiene, wherein the yield of the trienes is the mass percentage of the ethylene, propylene and butadiene yields relative to the feed amount. The operating conditions for the steam cracking ethylene production are: reaction temperature 860-890℃, reaction pressure 0.1-0.3MPa, and water-oil mass ratio 0.2-0.6.

[0033] Compared with the prior art, the present invention has the following beneficial technical effects:

[0034] (1) Hydrocracking light naphtha mainly contains C5 and C6 isoalkanes. The inventors have found that as the molecular weight increases, the difficulty of ortho-alkanization reactions gradually increases, with C6 components being more prone to cracking reactions. The reactivity of hydroconversion catalysts is mainly affected by hydrotreating performance, while the reaction process for isoalkanes is mainly influenced by acidic centers, i.e., molecular sieves. The inventors have found that mordenite zeolite with a high content of medium-strong acids tends to undergo ortho-alkanization reactions during hydroconversion, while ZSM-35 molecular sieves with a high content of strong acids tend to undergo cracking reactions, especially for the effective conversion of isobutane with a smaller molecular structure. For hydrocracking light naphtha, whose main components are C5 and C6 hydrocarbons, it is first converted using a mordenite zeolite molecular sieve. During the reaction, a certain amount of isobutane is generated. For this isoalkane with a smaller molecular structure, a ZSM-35 molecular sieve with an even smaller pore structure is then used for conversion, thereby increasing the reaction rate of the byproduct isobutane and fully utilizing the catalytic effects of the two molecular sieve catalysts. Further research by the inventors revealed that by first loading a hydroconversion catalyst bed with different active metal contents in the first hydroconversion reaction zone, with the active metal content gradually decreasing along the stream flow direction, the dehydrogenation performance of the catalysts can be matched to significantly increase the yield of n-alkane. Then, by loading a hydroconversion catalyst containing ZSM-35 molecular sieves in the second hydroconversion reaction zone, the reaction rate of isobutane can be increased, thereby further increasing the yield of n-alkane in the product.

[0035] (2) The hydrogenation conversion process of the present invention is simple, with low equipment investment and operating costs. The content of n-alkane in the hydrogenation conversion product reaches more than 90%, which can be directly used as a raw material for steam cracking to produce olefins, thereby improving the ethylene yield and total yield of trienes in the ethylene unit. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the process flow according to an embodiment of the present invention;

[0037] Explanation of key figure labels:

[0038] 1- Hydrocracking light naphtha, 2- Hydrogen, 3- First hydroconversion reaction zone, 4- Effluent from the first hydroconversion reaction zone, 5- Separation system, 6- Hydrogen-rich gas, 7- Liquid phase product (first hydroconversion product), 8- Propane removal tower, 9- Ethane and propane, 10- Bottom effluent from the propane removal tower, 11- Fractionation tower, 12- Isobutane, 13- Second hydroconversion reaction zone, 14- Effluent from the second hydroconversion reaction (second hydroconversion product), 15- n-Butane, 16- Bottom effluent from the fractionation tower, 17- Isopentane removal tower, 18- Bottom effluent from the isopentane removal tower (n-pentane and above components), 19- Isopentane. Detailed Implementation

[0039] The following examples further illustrate the function and effect of the present invention, but the following examples do not constitute a limitation on the method of the present invention.

[0040] Unless otherwise specified, all percentages in this invention refer to mass fractions.

[0041] The method of the present invention, such as Figure 1 As shown, the process includes: hydrocracking light naphtha 1 and hydrogen 2 are mixed and fed into the first hydroconversion reaction zone 3 for hydroconversion reaction; the effluent 4 from the first hydroconversion reaction enters the separation system 5; the separated hydrogen-rich gas 6 is recycled; the liquid product (first hydroconversion product) 7 enters the propane stripper 8, where ethane and propane 9 are separated; the bottom effluent 10 enters the fractionation column 11, where isobutane 12 and fractionation column bottom effluent 16 are separated; isobutane 12 is mixed with hydrogen 2 and fed into the second hydroconversion reaction zone 13; the second hydroconversion reaction effluent (second hydroconversion product) 14 enters the separation system 5; the separated n-butane 15 exits the unit; the fractionation column bottom effluent 16 enters the isopentane stripper 17 to obtain isopentane stripper bottom effluent 18; and isopentane 19 is recycled back to the first hydroconversion reaction zone. Ethane and propane 9, n-butane 15, and the bottom effluent of the deisopentane tower 18 are used as feedstocks for the steam cracking to ethylene production unit.

[0042] In this invention, the yield of n-alkane is calculated as (yield of n-alkane in the first hydrogenation conversion product + yield of n-alkane in the second hydrogenation conversion product) / fresh feed amount × 100%, by mass.

[0043] In this invention, the hydroconversion catalysts containing mordenite are designated as Cat-A followed by a number, such as Cat-A1, Cat-A2, Cat-A3, and Cat-A4. The hydroconversion catalysts containing ZSM-35 molecular sieves are designated as Cat-B followed by a number, such as Cat-B1, Cat-B2, Cat-B3, and Cat-B4. The hydroconversion catalysts were prepared using a conventional active metal saturated impregnation method, and the physicochemical properties of the obtained catalysts are shown in Tables 1-3.

[0044] The properties of the mordenite used in Cat-A are as follows: SiO2 / Al2O3 molar ratio is 20, and specific surface area is 450 m². 2 / g, pore volume 0.25cm 3 / g; The properties of ZSM-35 used in Cat-B are as follows: SiO2 / Al2O3 molar ratio is 15, specific surface area is 500m² / g; 2 / g, pore volume 0.22cm 3 / g; Cat-C uses Beta molecular sieves with a SiO2 / Al2O3 molar ratio of 30 and a specific surface area of ​​350m². 2 / g, pore volume is 0.30mL / g.

[0045] The main properties of the hydrocracked light naphtha used in each example of this invention are shown in Table 4.

[0046] In this invention, the n-alkanes in Tables 5-6 include ethane, propane, n-butane, n-pentane, and n-hexane.

[0047] Example 1

[0048] The conversion method of hydrocracking light naphtha adopts, for example... Figure 1 The process is shown below. The method specifically includes:

[0049] (1) Hydrocracked light naphtha is mixed with hydrogen and passed through the first hydroconversion reaction zone for hydroconversion reaction; the first hydroconversion reaction zone is sequentially filled with catalysts Cat-A2 and Cat-A3 along the flow direction;

[0050] (2) The effluent from the hydrogenation conversion reaction in step (1) enters the separation system. The hydrogen-rich gas obtained by separation is used as recycled hydrogen. The liquid product (the first hydrogenation conversion product) enters the propane removal tower, where ethane and propane are separated, as well as the bottom effluent. The bottom effluent enters the fractionation tower, where isobutane and the bottom effluent are separated. The bottom effluent from the fractionation tower enters the isopentane removal tower, where the bottom effluent from the isopentane removal tower and isopentane are obtained. The isopentane is recycled to the first hydrogenation conversion reaction zone.

[0051] (3) The isobutane obtained in step (2) is mixed with hydrogen and enters the second hydrogenation reaction zone. The second hydrogenation reaction zone is filled with catalyst Cat-B1. The effluent of the second hydrogenation reaction (the second hydrogenation product) is separated to obtain n-butane.

[0052] The process conditions and hydrogenation effect in this example are shown in Table 5.

[0053] Example 2

[0054] The conversion method of hydrocracking light naphtha adopts, for example... Figure 1 The process is shown below. The method specifically includes:

[0055] (1) Hydrocracked light naphtha is mixed with hydrogen and passed through the first hydroconversion reaction zone for hydroconversion reaction; the first hydroconversion reaction zone is sequentially filled with catalysts Cat-A1, Cat-A2 and Cat-A3 along the flow direction;

[0056] (2) The effluent from the hydrogenation conversion reaction in step (1) enters the separation system. The hydrogen-rich gas obtained by separation is used as recycled hydrogen. The liquid product (the first hydrogenation conversion product) enters the propane removal tower, where ethane and propane are separated, as well as the bottom effluent. The bottom effluent enters the fractionation tower, where isobutane and the bottom effluent are separated. The bottom effluent from the fractionation tower enters the isopentane removal tower, where the bottom effluent from the isopentane removal tower and isopentane are obtained. The isopentane is recycled to the first hydrogenation conversion reaction zone.

[0057] (3) The isobutane obtained in step (2) is mixed with hydrogen and enters the second hydrogenation reaction zone. The second hydrogenation reaction zone is filled with catalyst Cat-B2. The effluent of the second hydrogenation reaction (the second hydrogenation product) is separated to obtain n-butane.

[0058] The process conditions and hydrogenation effect in this example are shown in Table 5.

[0059] Example 3

[0060] The conversion method of hydrocracking light naphtha adopts, for example... Figure 1 The process is shown below. The method specifically includes:

[0061] (1) Hydrocracked light naphtha is mixed with hydrogen and passed through the first hydroconversion reaction zone for hydroconversion reaction; the first hydroconversion reaction zone is sequentially filled with catalysts Cat-A2, Cat-A3 and Cat-A4 along the flow direction;

[0062] (2) The effluent from the hydrogenation conversion reaction in step (1) enters the separation system. The hydrogen-rich gas obtained by separation is used as recycled hydrogen. The liquid product (the first hydrogenation conversion product) enters the propane removal tower, where ethane and propane are separated, as well as the bottom effluent. The bottom effluent enters the fractionation tower, where isobutane and the bottom effluent are separated. The bottom effluent from the fractionation tower enters the isopentane removal tower, where the bottom effluent from the isopentane removal tower and isopentane are obtained. The isopentane is recycled to the first hydrogenation conversion reaction zone.

[0063] (3) The isobutane obtained in step (2) is mixed with hydrogen and enters the second hydrogenation reaction zone. The second hydrogenation reaction zone is filled with catalyst Cat-B3. The effluent of the second hydrogenation reaction (the second hydrogenation product) is separated to obtain n-butane.

[0064] The process conditions and hydrogenation effect in this example are shown in Table 5.

[0065] Example 4

[0066] The conversion method of hydrocracking light naphtha adopts, for example... Figure 1 The process is shown below. The method specifically includes:

[0067] (1) Hydrocracked light naphtha is mixed with hydrogen and passed through the first hydroconversion reaction zone for hydroconversion reaction; the first hydroconversion reaction zone is sequentially filled with catalysts Cat-A1, Cat-A4 and Cat-A5 along the flow direction;

[0068] (2) The effluent from the hydrogenation conversion reaction in step (1) enters the separation system. The hydrogen-rich gas obtained by separation is used as recycled hydrogen. The liquid product (the first hydrogenation conversion product) enters the propane removal tower, where ethane and propane are separated, as well as the bottom effluent. The bottom effluent enters the fractionation tower, where isobutane and the bottom effluent are separated. The bottom effluent from the fractionation tower enters the isopentane removal tower, where the bottom effluent from the isopentane removal tower and isopentane are obtained. The isopentane is recycled to the first hydrogenation conversion reaction zone.

[0069] (3) The isobutane obtained in step (2) is mixed with hydrogen and enters the second hydrogenation reaction zone. The second hydrogenation reaction zone is filled with catalyst Cat-B4. The effluent of the second hydrogenation reaction (the second hydrogenation product) is separated to obtain n-butane.

[0070] The process conditions and hydrogenation effect in this example are shown in Table 5.

[0071] Example 5

[0072] The conversion method of hydrocracking light naphtha adopts, for example... Figure 1 The process is shown below. The method specifically includes:

[0073] (1) Hydrocracked light naphtha is mixed with hydrogen and passed through the first hydroconversion reaction zone for hydroconversion reaction; the first hydroconversion reaction zone is sequentially filled with catalysts Cat-A4, Cat-A6 and Cat-A3 along the flow direction;

[0074] (2) The effluent from the hydrogenation conversion reaction in step (1) enters the separation system. The hydrogen-rich gas obtained by separation is used as recycled hydrogen. The liquid product (the first hydrogenation conversion product) enters the propane removal tower, where ethane and propane are separated, as well as the bottom effluent. The bottom effluent enters the fractionation tower, where isobutane and the bottom effluent are separated. The bottom effluent from the fractionation tower enters the isopentane removal tower, where the bottom effluent from the isopentane removal tower and isopentane are obtained. The isopentane is recycled to the first hydrogenation conversion reaction zone.

[0075] (3) The isobutane obtained in step (2) is mixed with hydrogen and enters the second hydrogenation reaction zone. The second hydrogenation reaction zone is filled with catalyst Cat-B1. The effluent of the second hydrogenation reaction (the second hydrogenation product) is separated to obtain n-butane.

[0076] The process conditions and hydrogenation effect in this example are shown in Table 5.

[0077] Example 6

[0078] The conversion method of hydrocracking light naphtha adopts, for example... Figure 1 The process is shown below. The method specifically includes:

[0079] (1) Hydrocracked light naphtha is mixed with hydrogen and passed through the first hydroconversion reaction zone for hydroconversion reaction; the first hydroconversion reaction zone is sequentially filled with catalysts Cat-A4, Cat-A7 and Cat-A3 along the flow direction;

[0080] (2) The effluent from the hydrogenation conversion reaction in step (1) enters the separation system. The hydrogen-rich gas obtained by separation is used as recycled hydrogen. The liquid product (the first hydrogenation conversion product) enters the propane removal tower, where ethane and propane are separated, as well as the bottom effluent. The bottom effluent enters the fractionation tower, where isobutane and the bottom effluent are separated. The bottom effluent from the fractionation tower enters the isopentane removal tower, where the bottom effluent from the isopentane removal tower and isopentane are obtained. The isopentane is recycled to the first hydrogenation conversion reaction zone.

[0081] (3) The isobutane obtained in step (2) is mixed with hydrogen and enters the second hydrogenation reaction zone. The second hydrogenation reaction zone is filled with catalyst Cat-B5. The effluent of the second hydrogenation reaction (the second hydrogenation product) is separated to obtain n-butane.

[0082] The process conditions and hydrogenation effect in this example are shown in Table 5.

[0083] Comparative Example 1

[0084] The difference from Example 1 is that the first hydrogenation conversion reaction zone is filled with catalyst Cat-A5.

[0085] The process conditions and hydrogenation effect in this example are shown in Table 6.

[0086] Comparative Example 2

[0087] The difference from Example 1 is that the first hydrogenation conversion reaction zone is filled with catalyst Cat-C1.

[0088] The process conditions and hydrogenation effect in this example are shown in Table 6.

[0089] Comparative Example 3

[0090] The difference from Example 1 is that the first hydrogenation conversion reaction zone is sequentially filled with catalysts Cat-C1 / Cat-A4.

[0091] The process conditions and hydrogenation effect in this example are shown in Table 6.

[0092] Comparative Example 4

[0093] The difference from Example 1 is that the first hydrogenation conversion reaction zone is sequentially loaded with catalysts Cat-A4 / Cat-A2. The process conditions and hydrogenation effect in this example are shown in Table 6.

[0094] Table 1. Composition and physicochemical properties of hydroconversion catalysts

[0095] Catalyst number Cat-A1 Cat-A2 Cat-A3 Cat-A4 Cat-A5 Cat-A6 Cat-A7 Catalyst properties <![CDATA[Pore volume, cm 3 / g]]> 0.27 0.28 0.26 0.24 0.25 0.23 0.30 <![CDATA[Specific surface area, m 2 / g]]> 320 344 315 292 301 288 355 Catalyst composition Siliceous zeolite, wt% 50 50 50 50 50 45 60 Alumina, wt% 40 46 35 20 25 30 15 <![CDATA[MoO3,wt%]]> 7 3 10 25 20 20 20 NiO, wt% 3 1 5 5 5 5 5

[0096] Table 2 Composition and physicochemical properties of hydroconversion catalysts

[0097] Catalyst number Cat-C1 Catalyst properties <![CDATA[Pore volume, cm 3 / g]]> 0.30 <![CDATA[Specific surface area, m 2 / g]]> 350 Catalyst composition Beta, wt% 50 Alumina, wt% 20 <![CDATA[MoO3,wt%]]> 25 NiO, wt% 5

[0098] Table 3 Composition and physicochemical properties of hydroconversion catalysts

[0099] Catalyst number Cat-B1 Cat-B2 Cat-B3 Cat-B4 Cat-B5 Catalyst properties <![CDATA[Pore volume, cm 3 / g]]> 0.24 0.25 0.26 0.27 0.28 <![CDATA[Specific surface area, m 2 / g]]> 310 320 330 340 350 Catalyst composition ZSM-35, wt% 50 50 50 50 45 Alumina, wt% 15 15 15 25 20 <![CDATA[MoO3,wt%]]> 27 28 29 20 35 NiO, wt% 8 7 6 5 5

[0100] Table 4. Main Properties of Hydrocracked Light Naphtha

[0101] raw material Hydrocracking light naphtha <![CDATA[C4 isoparaffin content, wt%]]> 1 <![CDATA[Content of n-C4 paraffin, wt%]]> 2 <![CDATA[Content of C5-C6 normal paraffin, wt%]]> 16 <![CDATA[C5-C6 isoparaffin content, wt%]]> 78 <![CDATA[C7 + Hydrocarbon and cyclic hydrocarbon content, wt% 3 Initial boiling point, ℃ 24 Final boiling point, ℃ 64

[0102] Table 5. Process conditions and conversion results of each embodiment.

[0103]

[0104] Table 6. Process conditions and conversion results for each comparative example.

[0105]

[0106] 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 inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combining the 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 ethylene feedstock, the method comprising: (1) Hydrocracked light naphtha is mixed with hydrogen and enters the first hydroconversion reaction zone for hydroconversion reaction. The first hydroconversion reaction zone is filled with hydroconversion catalyst containing mordenite, and at least two catalyst beds are filled. The active metal content of the hydroconversion catalyst decreases sequentially along the flow direction. (2) The reaction effluent from step (1) enters the separation system to separate hydrogen-rich gas and the first hydrogenation conversion product. The first hydrogenation conversion product enters the propane removal tower to separate ethane and propane, and the bottom effluent from the tower. The bottom effluent from the tower enters the fractionation tower to separate isobutane and the bottom effluent from the fractionation tower. The bottom effluent from the fractionation tower enters the isopentane removal tower to obtain isopentane and the bottom effluent from the isopentane removal tower, wherein the bottom effluent from the isopentane removal tower includes n-pentane and the above components. (3) The isobutane obtained in step (2) is mixed with hydrogen and enters the second hydrogenation conversion reaction zone for hydrogenation conversion reaction. The second hydrogenation conversion product is separated to obtain n-butane. The second hydrogenation conversion reaction zone is filled with hydrogenation conversion catalyst containing ZSM-35 molecular sieve. (4) The isopentane obtained in step (2) is recycled to the inlet of the first hydrogenation conversion reaction zone.

2. The method according to claim 1, characterized in that, The initial boiling point of hydrocracked light naphtha is 10℃~30℃, preferably 15℃~25℃; the final boiling point is 50℃~100℃, preferably 55℃~70℃.

3. The method according to claim 1, characterized in that, In hydrocracking light naphtha, the content of C5-C6 isoalkanes is 60wt%–90wt%, preferably 70wt%–80wt%; C7 + The hydrocarbon content is 0–10 wt%, preferably 0.5 wt%–5 wt%; the C5–C6 n-alkanes content is 10 wt%–30 wt%, preferably 15 wt%–25 wt%; C4 - The hydrocarbon content is 0-10 wt%, preferably 2 wt%-5 wt%; the cyclic hydrocarbon content is 0-10 wt%, preferably 2 wt%-5 wt%; and the total weight of the hydrocracked light naphtha is 100 wt%.

4. The method according to claim 1, characterized in that, In the hydroconversion catalyst containing mordenite, the active metal is selected from one or more of Group VIB metals and Group VIII non-precious metals, the Group VIB metal is selected from one or more of molybdenum and tungsten, and the Group VIII non-precious metal is selected from one or more of cobalt and nickel. Preferably, the hydroconversion catalyst containing mordenite includes a binder, and the binder is preferably alumina.

5. The method according to claim 4, characterized in that, In the mordenite-containing hydroconversion catalyst, based on the weight of the mordenite-containing hydroconversion catalyst, the mordenite content is 30wt% to 80wt%, preferably 40wt% to 70wt%; the content of Group VIB metals as oxides is 5wt% to 30wt%, preferably 10wt% to 20wt%; the content of Group VIII non-precious metals as oxides is 0.5wt% to 15wt%, preferably 3wt% to 10wt%; and the content of binder as oxides is 5wt% to 65wt%, preferably 10wt% to 35wt%.

6. The method according to claim 1, characterized in that, In the hydroconversion catalyst containing ZSM-35 molecular sieve, the active metal is selected from one or more of Group VIB metals and Group VIII non-precious metals, the Group VIB metal is selected from one or more of molybdenum and tungsten, and the Group VIII non-precious metal is selected from one or more of cobalt and nickel. Preferably, the hydroconversion catalyst containing ZSM-35 molecular sieve includes a binder, and the binder is preferably alumina.

7. The method according to claim 6, characterized in that, In the hydroconversion catalyst containing ZSM-35 molecular sieve, based on the weight of the hydroconversion catalyst containing ZSM-35 molecular sieve, the content of ZSM-35 molecular sieve is 30wt% to 80wt%, preferably 40wt% to 70wt%; the content of Group VIB metals as oxides is 5wt% to 30wt%, preferably 10wt% to 20wt%; the content of Group VIII non-precious metals as oxides is 0.5wt% to 15wt%, preferably 3wt% to 10wt%; and the content of binder as oxides is 5wt% to 65wt%, preferably 10wt% to 35wt%.

8. The method according to claim 1, characterized in that, The first hydrogenation conversion reaction zone is packed with 2 to 3 catalyst beds; along the flow direction, the ratio of the upstream catalyst loading volume to the downstream catalyst loading volume in two adjacent catalyst beds is 1:3 to 3:1, preferably 1:2 to 2:

1.

9. The method according to claim 1, characterized in that, In the first hydrogenation conversion reaction zone, in two adjacent catalyst beds, the active metal content in the downstream catalyst, calculated as oxides, is 1 to 25 percentage points lower than the active metal content in the upstream catalyst, preferably 5 to 15 percentage points lower.

10. The method according to claim 1, characterized in that, The first hydrogenation conversion reaction conditions are as follows: reaction pressure is 0.5 MPa to 10.0 MPa, preferably 2.0 MPa to 5.0 MPa; reaction temperature is 250℃ to 500℃, preferably 350℃ to 450℃; liquid hourly space velocity is 0.1 h⁻¹. -1 ~15.0h -1 0.5h is preferred -1 ~5.0h -1 The hydrogen-to-oil volume ratio is 10:1 to 2500:1, preferably 100:1 to 2000:1, and even more preferably 100:1 to 1000:

1. Preferably, the conditions for the second hydrogenation conversion reaction are as follows: reaction pressure of 0.5 MPa to 10.0 MPa, preferably 2.0 MPa to 5.0 MPa; reaction temperature of 250°C to 500°C, preferably 350°C to 450°C; and liquid hourly space velocity of 0.1 h⁻¹. -1 ~15.0h -1 0.5h is preferred -1 ~5.0h -1 The hydrogen-to-oil volume ratio is 10:1 to 2500:1, preferably 100:1 to 2000:1, and even more preferably 100:1 to 1000:1.

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