A method for converting C5C6 hydrocarbons

Abstract

The application discloses a C5-C6 hydrocarbon conversion method. The method comprises the following steps: (1) C5-C6 hydrocarbon is separated by normal and iso separation, and the separated normal pentane and normal hexane are directly used as ethylene raw materials; (2) the separated iso-pentane and iso-hexane in step (1) are mixed with hydrogen and pass through a hydroconversion reaction zone, the hydroconversion reaction zone is filled with at least two hydroconversion catalyst beds, the active metal content of the hydroconversion catalysts decreases in turn along the flow direction, and the active metal content of the hydroconversion catalysts filled in the adjacent two catalyst beds differs by 1-25 percentage points in terms of oxides; and (3) the reaction effluent of step (2) enters a separation system, and the hydrogen-rich gas and the hydroconversion product are separated, the C2-C4 hydrocarbon in the hydroconversion product is directly used as ethylene raw materials, and the C5-C6 hydrocarbon is recycled to step (1) for continuous reaction. By adopting the method, the quality of the ethylene raw materials can be maximized, and the ethylene yield and the total triene yield of the ethylene device can be significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of hydrocarbon hydroconversion, specifically relating to a hydroconversion method for producing high-quality ethylene feedstock from C5C6 hydrocarbons. Background Technology

[0002] With the orderly advancement of oil conversion, hydrocracking units, serving as a crucial link between refining and chemical industries, have seen increasingly widespread application, leading to a year-on-year increase in the production of hydrocracking light naphtha. Hydrocracking light naphtha has a high content of isoalkanes and is typically used as a gasoline blending component. However, due to the influence of saturated vapor pressure, its blending volume is limited. Therefore, excess hydrocracking light naphtha is usually used as feedstock for steam cracking to produce ethylene. Steam cracking to produce ethylene is a thermal cracking reaction process, and its reaction follows the principle of free radical reactions. Isoalkanes are detrimental to the formation of the target product, ethylene. This results in low yields of both ethylene and trienes when hydrocracking light naphtha is used as ethylene feedstock, affecting the overall economic efficiency of the ethylene plant.

[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 converting C5C6 hydrocarbons. This method uses C5C6 hydrocarbons as raw materials and can effectively convert isoalkanes in C5C6 hydrocarbons into C2-C6 alkanes, thereby increasing the content of C2-C6 n-alkanes in the product and improving the quality of ethylene feedstock.

[0007] This invention provides a method for converting C5C6 hydrocarbons, the method comprising:

[0008] (1) C5C6 hydrocarbons are separated by isomerization, and the resulting n-pentane and n-hexane are used directly as ethylene feedstock;

[0009] (2) The isopentane and isohexane obtained in step (1) are mixed with hydrogen and passed through the hydroconversion reaction zone. The hydroconversion reaction zone is filled with at least two hydroconversion catalyst beds. The active metal content of the hydroconversion catalyst decreases sequentially along the flow direction. The active metal content of the hydroconversion catalyst in the adjacent catalyst beds differs by 1 to 25 percentage points in terms of oxides, preferably by 5 to 15 percentage points.

[0010] (3) The reaction effluent from step (2) enters the separation system to separate hydrogen-rich gas and hydrogenation conversion products. The C2-C4 hydrocarbons separated from the hydrogenation conversion products are used directly as ethylene feedstock, while the C5-C6 hydrocarbons are recycled to step (1).

[0011] According to the present invention, in step (1), the C5C6 hydrocarbon normal isomerization separation process includes:

[0012] (a) C5C6 hydrocarbons are fed into an isopentane removal column for distillation to obtain isopentane as the overhead effluent and I as the bottom effluent.

[0013] (b) The bottom effluent I obtained in step (a) is fed into a n-pentane removal column for distillation to obtain the top effluent n-pentane and the bottom effluent II, wherein the n-pentane is directly used as ethylene feedstock.

[0014] (c) The bottom effluent II obtained in step (b) is fed into the isohexane removal column for distillation to obtain the top effluent isohexane and the bottom effluent n-hexane, wherein the n-hexane is directly used as ethylene feedstock.

[0015] According to the present invention, a fixed-bed reactor is used for the hydrogenation conversion reaction.

[0016] According to the present invention, in step (a), the feed temperature of the deisopentane tower is 67-71°C, the top temperature is 59-62°C, and the bottom temperature is 98-103°C; the top pressure is 0.15-0.17 MPa, and the bottom pressure is 0.18-0.20 MPa.

[0017] According to the present invention, in step (b), the feed temperature of the n-pentane removal tower is 98-103°C, the top temperature is 66-75°C, and the bottom temperature is 102-105°C; the top pressure is 0.13-0.15 MPa, and the bottom pressure is 0.16-0.18 MPa.

[0018] According to the present invention, in step (c), the feed temperature of the isohexane removal tower is 102-105°C, the top temperature is 77-79°C, and the bottom temperature is 101-104°C; the top pressure is 0.07-0.08 MPa, and the bottom pressure is 0.10-0.12 MPa.

[0019] According to the present invention, the initial boiling point of the C5C6 hydrocarbon 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.

[0020] According to the present invention, the content of C5-C6 isoalkanes in the C5-C6 hydrocarbons is 40wt% to 60wt%, preferably 45wt% to 55wt%; C7 + The hydrocarbon content is 0–10 wt%, preferably 0.5 wt%–5 wt%; the C5–C6 n-alkanes content is 40 wt%–60 wt%, preferably 45 wt%–55 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 C5C6 hydrocarbons is 100 wt%.

[0021] According to the present invention, preferably, the hydroconversion reaction zone is packed with 2 to 3 hydroconversion 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.

[0022] According to the present invention, the hydroconversion catalyst comprises a molecular sieve, an active metal component, and a binder. The molecular sieve is preferably mordenite. Further, the mordenite has a SiO2 / Al2O3 molar ratio of 10–50 and a specific surface area of ​​300–600 m². 2 / g, with a pore volume of 0.15–0.35 mL / g. Further, in the hydroconversion catalyst, based on the weight of the catalyst, the content of the molecular sieve is 30 wt%–80 wt%, preferably 40 wt%–70 wt%.

[0023] According to the present invention, the binder is preferably alumina. Further, in the hydroconversion catalyst, 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.

[0024] According to the present invention, 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, based on the weight of the catalyst, the content of the Group VIB metals, calculated as oxides, is 5.0 wt% to 30.0 wt%, preferably 10 wt% to 20 wt%; the content of the Group VIII non-noble metals, calculated as oxides, is 0.5 wt% to 15 wt%, preferably 3 wt% to 10 wt%.

[0025] According to the present invention, along the flow direction, in the hydroconversion catalysts packed in two adjacent catalyst beds, the content of active metals in the downstream catalyst, calculated as oxides, is 1 to 25 percentage points lower than the content of active metals in the upstream catalyst, calculated as oxides, preferably 5 to 15 percentage points lower. Preferably, along the flow direction, in two adjacent catalyst beds, the mass content of Group VIB metals in the downstream catalyst, calculated as oxides, is 1 to 23 percentage points lower than the mass content of Group VIB metals in the upstream catalyst, preferably 3 to 15 percentage points lower, and the mass content of Group VIII non-precious metals in the downstream catalyst, calculated as oxides, is 0 to 4 percentage points lower than the mass content of Group VIII non-precious metals in the upstream catalyst, calculated as oxides.

[0026] According to the present invention, the specific surface area of ​​the hydroconversion catalyst is 200-400 m². 2 / g, with a pore volume of 0.15~0.35mL / g.

[0027] According to the present invention, the preparation method of the 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 preparation process of the support 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.

[0028] According to the present invention, in the preparation method of the hydroconversion catalyst, 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.

[0029] According to the present invention, the hydroconversion 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°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 even more preferably 100:1 to 1000:1.

[0030] According to the present invention, ethylene is produced by steam cracking, yielding the main target products ethylene, propylene, and butadiene. The triene yield is the sum of the yields of ethylene, propylene, and butadiene as a percentage by mass of the hydroconversion product feed. The operating conditions for the steam cracking to produce ethylene include: a reaction temperature of 860–890°C, a reaction pressure of 0.1–0.3 MPa, and a water-to-oil mass ratio of 0.2–0.6.

[0031] According to the present invention, in step (3), the hydrogenation reaction effluent enters the separation system, and the separated hydrogen-rich gas is used as recycled hydrogen.

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

[0033] (1) The reactivity of hydroconversion catalysts is mainly affected by hydrotreating performance, while the reaction process of isoalkanes is mainly affected by acid centers, i.e., molecular sieves. The inventors have discovered that mordenite with a high content of medium-strong acids tends to undergo normalization reactions during hydroconversion, enabling highly selective conversion of isoalkanes in hydrocracking light naphtha into C2-C6 normal alkanes. However, existing technologies generally use hydroconversion catalysts with the same metal content, resulting in low normal alkane yields. Further research by the inventors revealed that the method of this invention, by loading hydroconversion catalyst beds with different active metal contents, and with the active metal content gradually decreasing along the stream direction, can significantly improve normal alkane yield by matching the dehydrogenation performance of the catalysts.

[0034] (2) In this invention, C5C6 n-alkanes are separated from C5C6 hydrocarbons and used directly as ethylene feedstock. Then, C5C6 isoalkanes are hydrogenated to n-alkanes. Specifically, in this invention, pure C5C6 isoalkanes are used for hydrogenation and unconverted isoalkanes are recycled. Higher n-alkanes yield can be obtained from the hydrogenation products. At the same time, the active metal content in the hydrogenation catalyst gradually decreases along the flow direction, which can maximize the quality of the ethylene feedstock and significantly improve the ethylene yield and total terene yield of the ethylene plant. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the process flow according to an embodiment of the present invention;

[0036] Explanation of key figure labels:

[0037] 1-C5C6 hydrocarbons, 2-Isopentane removal tower, 3-Isopentane, 4-Isopentane removal tower bottom effluent, 5-N-pentane removal tower, 6-N-pentane, 7-N-pentane removal tower bottom effluent, 8-Isohexane removal tower, 9-Isohexane, 10-N-hexane, 11-Hydrogen, 12-Hydroconversion reaction zone, 13-Hydroconversion reaction effluent, 14-Separation system, 15-Hydrogen-rich gas, 16-Hydroconversion products, 17-Fracturing tower, 18-C2~C4 hydrocarbons, 19-Hydroconversion of C5C6 hydrocarbons. Detailed Implementation

[0038] 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.

[0039] Unless otherwise specified, all percentages in this invention refer to mass fractions.

[0040] The method of the present invention, such as Figure 1 As shown, the process includes: C5C6 hydrocarbon 1 enters the isopentane removal tower 2 to obtain isopentane 3 as the top effluent; bottom effluent 4 enters the n-pentane removal tower 5 to obtain n-pentane 6 as the top effluent; bottom effluent 7 enters the isohexane removal tower 8 to obtain isohexane 9 as the top effluent and n-hexane 10 as the bottom effluent; isopentane 3 and isohexane 9 are mixed with hydrogen 11 and enter the hydroconversion reaction zone 12 for hydroconversion reaction; hydroconversion reaction effluent 13 enters the separation system 14; the separated hydrogen-rich gas 15 is recycled; the hydroconversion product 16 enters the fractionation tower 17; the separated C2-C4 hydrocarbon 18 is directly used as ethylene feedstock; and the hydroconverted C5C6 hydrocarbon 19 is recycled to the isopentane removal tower 2.

[0041] In this invention, the hydroconversion catalysts in each example are designated as Cat-A followed by a number, such as Cat-A1, Cat-A2, Cat-A3, and Cat-A4. The hydroconversion catalysts were prepared using a conventional active metal saturation impregnation method, and the physicochemical properties of the obtained catalysts are shown in Table 1.

[0042] In this invention, the mordenite zeolite used in each example catalyst has a SiO2 / Al2O3 molar ratio of 20 and a specific surface area of ​​450 m². 2 / g, pore volume is 0.25mL / g; the Beta molecular sieve used in each catalyst example has a SiO2 / Al2O3 molar ratio of 30 and a specific surface area of ​​350m². 2 / g, pore volume is 0.30mL / g.

[0043] The main properties of the C5C6 hydrocarbons used in the various examples of this invention are shown in Table 3.

[0044] In this invention, the n-alkanes in Tables 3-4 include ethane, propane, n-butane, n-pentane, and n-hexane.

[0045] In this invention, the yield of n-alkanes = (yield of C2-C4 n-alkanes in the hydrogenation conversion products + n-pentane yield from the n-pentane removal tower + n-hexane yield from the isohexane removal tower) / fresh feed amount × 100%, by mass.

[0046] In this invention, the feed temperature of the isopentane removal tower is 69°C, the top temperature is 60°C, the bottom temperature is 100°C, the top pressure is 0.16 MPa, and the bottom pressure is 0.19 MPa; the feed temperature of the n-pentane removal tower is 100°C, the top temperature is 70°C, the bottom temperature is 103°C, the top pressure is 0.14 MPa, and the bottom pressure is 0.17 MPa; the feed temperature of the isohexane removal tower is 103°C, the top temperature is 78°C, the bottom temperature is 103°C, the top pressure is 0.07 MPa, and the bottom pressure is 0.11 MPa.

[0047] Example 1

[0048] The conversion methods for C5 and C6 hydrocarbons employ methods such as... Figure 1 The process is shown below. The method specifically includes:

[0049] (1) Isopentane and isohexane obtained by the normal isomerization of C5C6 hydrocarbons are mixed with hydrogen and passed through the hydrogenation conversion reaction zone for hydrogenation conversion reaction; the hydrogenation conversion reaction zone is sequentially filled with catalysts Cat-A2 and Cat-A3 along the flow direction; n-pentane and n-hexane obtained by the normal isomerization of C5C6 hydrocarbons are directly used as ethylene feedstock.

[0050] (2) The effluent from the hydrogenation conversion reaction in step (1) enters the separation system. The hydrogen-rich gas obtained from the separation is used as recycled hydrogen. The C2-C4 hydrocarbons obtained from the separation of the hydrogenation conversion products are used directly as ethylene feedstock. The C5-C6 hydrocarbons are recycled to the inlet of the deisopentane tower.

[0051] The process conditions and hydrogenation effect after cyclic operation in this example are shown in Table 4.

[0052] Example 2

[0053] The conversion methods for C5 and C6 hydrocarbons employ methods such as... Figure 1 The process is shown below. The method specifically includes:

[0054] (1) Isopentane and isohexane obtained by the normal isomerization of C5C6 hydrocarbons are mixed with hydrogen and passed through the hydrogenation conversion reaction zone for hydrogenation conversion reaction; the hydrogenation conversion reaction zone is sequentially filled with catalysts Cat-A1, Cat-A2 and Cat-A3 along the flow direction; n-pentane and n-hexane obtained by the normal isomerization of C5C6 hydrocarbons are directly used as ethylene feedstock.

[0055] (2) The effluent from the hydrogenation conversion reaction in step (1) enters the separation system. The hydrogen-rich gas obtained from the separation is used as recycled hydrogen. The C2-C4 hydrocarbons obtained from the separation of the hydrogenation conversion products are used directly as ethylene feedstock. The C5-C6 hydrocarbons are recycled to the inlet of the deisopentane tower.

[0056] The process conditions and hydrogenation effect after cyclic operation in this example are shown in Table 4.

[0057] Example 3

[0058] The conversion methods for C5 and C6 hydrocarbons employ methods such as... Figure 1 The process is shown below. The method specifically includes:

[0059] (1) Isopentane and isohexane obtained by the normal isomerization of C5C6 hydrocarbons are mixed with hydrogen and passed through the hydrogenation conversion reaction zone for hydrogenation conversion reaction; the hydrogenation conversion reaction zone is sequentially filled with catalysts Cat-A2, Cat-A3 and Cat-A4 along the flow direction; n-pentane and n-hexane obtained by the normal isomerization of C5C6 hydrocarbons are directly used as ethylene feedstock.

[0060] (2) The effluent from the hydrogenation conversion reaction in step (1) enters the separation system. The hydrogen-rich gas obtained from the separation is used as recycled hydrogen. The C2-C4 hydrocarbons obtained from the separation of the hydrogenation conversion products are used directly as ethylene feedstock. The C5-C6 hydrocarbons are recycled to the inlet of the deisopentane tower.

[0061] The process conditions and hydrogenation effect after cyclic operation in this example are shown in Table 4.

[0062] Example 4

[0063] The conversion methods for C5 and C6 hydrocarbons employ methods such as... Figure 1 The process is shown below. The method specifically includes:

[0064] (1) Isopentane and isohexane obtained by C5C6 hydrocarbons through normal isomerization are mixed with hydrogen and carried out in the hydrogenation conversion reaction zone; the hydrogenation conversion reaction zone is sequentially filled with catalysts Cat-A1, Cat-A4 and Cat-A5 along the flow direction; n-pentane and n-hexane obtained by C5C6 hydrocarbons through normal isomerization are directly used as ethylene feedstock.

[0065] (2) The effluent from the hydrogenation conversion reaction in step (1) enters the separation system. The hydrogen-rich gas obtained from the separation is used as recycled hydrogen. The C2-C4 hydrocarbons obtained from the separation of the hydrogenation conversion products are used directly as ethylene feedstock. The C5-C6 hydrocarbons are recycled to the inlet of the deisopentane tower.

[0066] The process conditions and hydrogenation effect after cyclic operation in this example are shown in Table 4.

[0067] Example 5

[0068] The conversion methods for C5 and C6 hydrocarbons employ methods such as... Figure 1 The process is shown below. The method specifically includes:

[0069] (1) Isopentane and isohexane obtained by the normal isomerization of C5C6 hydrocarbons are mixed with hydrogen and passed through the hydrogenation conversion reaction zone for hydrogenation conversion reaction; the hydrogenation conversion reaction zone is sequentially filled with catalysts Cat-A4, Cat-A6 and Cat-A3 along the flow direction; n-pentane and n-hexane obtained by the normal isomerization of C5C6 hydrocarbons are directly used as ethylene feedstock.

[0070] (2) The effluent from the hydrogenation conversion reaction in step (1) enters the separation system. The hydrogen-rich gas obtained from the separation is used as recycled hydrogen. The C2-C4 hydrocarbons obtained from the separation of the hydrogenation conversion products are used directly as ethylene feedstock. The C5-C6 hydrocarbons are recycled to the inlet of the deisopentane tower.

[0071] The process conditions and hydrogenation effect after cyclic operation in this example are shown in Table 4.

[0072] Example 6

[0073] The conversion methods for C5 and C6 hydrocarbons employ methods such as... Figure 1 The process is shown below. The method specifically includes:

[0074] (1) Isopentane and isohexane obtained by the normal isomerization of C5C6 hydrocarbons are mixed with hydrogen and passed through the hydrogenation conversion reaction zone for hydrogenation conversion reaction; the hydrogenation conversion reaction zone is sequentially filled with catalysts Cat-A4, Cat-A7 and Cat-A3 along the flow direction; n-pentane and n-hexane obtained by the normal isomerization of C5C6 hydrocarbons are directly used as ethylene feedstock.

[0075] (2) The effluent from the hydrogenation conversion reaction in step (1) enters the separation system. The hydrogen-rich gas obtained from the separation is used as recycled hydrogen. The C2-C4 hydrocarbons obtained from the separation of the hydrogenation conversion products are used directly as ethylene feedstock. The C5-C6 hydrocarbons are recycled to the inlet of the deisopentane tower.

[0076] The process conditions and hydrogenation effect after cyclic operation in this example are shown in Table 4.

[0077] Comparative Example 1

[0078] The difference from Example 1 is that the hydroconversion reaction zone is filled with a hydroconversion catalyst, Cat-A5.

[0079] The process conditions and hydrogenation effect after cyclic operation in this example are shown in Table 5.

[0080] Comparative Example 2

[0081] The difference from Example 1 is that the hydroconversion reaction zone is sequentially filled with hydroconversion catalysts Cat-B1 and Cat-A4.

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

[0083] Comparative Example 3

[0084] The difference from Example 1 is that the hydrogenation conversion reaction zone is sequentially filled with catalysts Cat-A4 and Cat-A2.

[0085] The process conditions and hydrogenation effect after cyclic operation in this example are shown in Table 5.

[0086] Comparative Example 4

[0087] The difference from Example 1 is that the hydrogenation conversion reaction zone is filled with catalyst Cat-B1.

[0088] The process conditions and hydrogenation effect after cyclic operation in this example are shown in Table 5.

[0089] Table 1. Composition and physicochemical properties of hydroconversion catalysts

[0090]

[0091]

[0092] Table 2 Composition and physicochemical properties of hydroconversion catalysts

[0093] Catalyst number Cat-B1 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

[0094] Table 3. Main Properties of C5C6 Hydrocarbons

[0095] raw material <![CDATA[C5C6 hydrocarbons]]> <![CDATA[C4 isoparaffin content, wt%]]> 1 <![CDATA[n-alkane content in C4, wt%]]> 2 <![CDATA[Content of C5-C6 normal paraffins, wt%]]> 53 <![CDATA[C5-C6 isoparaffin content, wt%]]> 43 <![CDATA[C7 + Hydrocarbon and cyclic hydrocarbon content, wt% 1 Initial boiling point, ℃ 23 Final boiling point, ℃ 65

[0096] Table 4. Process conditions and conversion results of each embodiment

[0097]

[0098] Table 4 continues with the process conditions and conversion results of each embodiment.

[0099] serial number Example 5 Example 6 Hydrogenation conversion reaction zone Catalyst loading sequence Cat-A4 / Cat-A6 / Cat-A3 Cat-A4 / Cat-A7 / Cat-A3 Volume ratio of each catalyst 1:1:1 1:1:1 Reaction temperature / ℃ 385 385 Reaction pressure / MPa 5.0 5.0 Hydrogen-to-oil volume ratio 500 500 <![CDATA[Liquid hourly space velocity / h - 1 > 1.0 1.0 n-Alkane yield, % 89 91

[0100] Table 5. Process conditions and conversion results for each comparative example.

[0101] serial number Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Hydrogenation conversion reaction zone Catalyst loading sequence Cat-A5 Cat-B1 / Cat-A4 Cat-A4 / Cat-A2 Cat-B1 Volume ratio of each catalyst - 1:1 1:1 - Reaction temperature / ℃ 385 385 385 385 Reaction pressure / MPa 5.0 5.0 5.0 5.0 Hydrogen-to-oil volume ratio 500 500 500 500 <![CDATA[Liquid hourly space velocity / h -1 > 1.0 1.0 1.0 1.0 n-Alkane yield, % 80 76 81 71

[0102] Application examples

[0103] The n-alkanes obtained in Examples 1, 2, and Comparative Example 2 of this invention (i.e., C2-C4 hydrocarbons separated from hydrogenation conversion products and n-pentane and n-hexane separated from isomerization) were respectively fed into a steam cracking unit for ethylene production, yielding the main target products ethylene, propylene, and butadiene. The operating conditions for the steam cracking to ethylene production were: reaction temperature 880°C, reaction pressure 0.2 MPa, and water-to-oil mass ratio 0.4. The reaction results are shown in Table 6.

[0104] Table 6

[0105] Example 1 Example 2 Comparative Example 2 Ethylene yield, wt% 38.1 39.7 34.2 Propylene yield, wt% 18.1 17.8 18.8 Butadiene yield, wt% 4.0 3.8 4.2

[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 converting C5C6 hydrocarbons, the method comprising: (1) C5C6 hydrocarbons are separated by isomerization, and the resulting n-pentane and n-hexane are used directly as ethylene feedstock; (2) The isopentane and isohexane obtained in step (1) are mixed with hydrogen and passed through the hydroconversion reaction zone. The hydroconversion reaction zone is filled with at least two hydroconversion catalyst beds. The active metal content of the hydroconversion catalyst decreases sequentially along the flow direction. The active metal content of the hydroconversion catalyst in the adjacent catalyst beds differs by 1 to 25 percentage points in terms of oxides, preferably by 5 to 15 percentage points. (3) The reaction effluent from step (2) enters the separation system to separate hydrogen-rich gas and hydrogenation conversion products. The C2-C4 hydrocarbons separated from the hydrogenation conversion products are used directly as ethylene feedstock, while the C5-C6 hydrocarbons are recycled to step (1).

2. The method according to claim 1, characterized in that: In step (1), the separation process of C5C6 hydrocarbon normal isomers includes: (a) C5C6 hydrocarbons are fed into an isopentane removal column for distillation to obtain isopentane as the overhead effluent and I as the bottom effluent. (b) The bottom effluent I obtained in step (a) is fed into a n-pentane removal column for distillation to obtain the top effluent n-pentane and the bottom effluent II, wherein the n-pentane is directly used as ethylene feedstock. (c) The bottom effluent II obtained in step (b) is fed into the isohexane removal column for distillation to obtain the top effluent isohexane and the bottom effluent n-hexane, wherein the n-hexane is directly used as ethylene feedstock.

3. The method according to claim 2, characterized in that: In step (a), the feed temperature of the isopentane removal tower is 67-71℃, the top temperature is 59-62℃, and the bottom temperature is 98-103℃; the top pressure is 0.15-0.17MPa, and the bottom pressure is 0.18-0.20MPa. And / or, in step (b), the feed temperature of the n-pentane removal column is 98-103℃, the top temperature is 66-75℃, and the bottom temperature is 102-105℃; the top pressure is 0.130-0.15MPa, and the bottom pressure is 0.160-0.18MPa. And / or, in step (c), the feed temperature of the isohexane removal column is 102-105℃, the top temperature is 77-79℃, and the bottom temperature is 101-104℃; the top pressure is 0.07-0.08MPa, and the bottom pressure is 0.10-0.12MPa.

4. The method according to claim 1, characterized in that: The initial boiling point of the C5C6 hydrocarbon is 10℃~30℃, preferably 15℃~25℃; the final boiling point is 50℃~100℃, preferably 55℃~70℃.

5. The method according to claim 1, characterized in that: The C5-C6 hydrocarbons contain 40 wt% to 60 wt% of C5-C6 isoalkanes, preferably 45 wt% to 55 wt%; C7 + The hydrocarbon content is 0–10 wt%, preferably 0.5 wt%–5 wt%; the C5–C6 n-alkanes content is 40 wt%–60 wt%, preferably 45 wt%–55 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 C5C6 hydrocarbons is 100 wt%.

6. The method according to claim 1, characterized in that: The hydroconversion reaction zone is filled with 2 to 3 hydroconversion catalyst beds; Preferably, 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, more preferably 1:2 to 2:

1.

7. The method according to claim 1, characterized in that: The hydroconversion catalyst comprises a molecular sieve, an active metal component, and a binder; Preferably, the molecular sieve is mordenite; the binder is alumina; and the active metal component is selected from one or more of Group VIB metals and Group VIII non-precious metals of the periodic table, wherein the Group VIB metals are preferably selected from one or more of molybdenum and tungsten, and the Group VIII non-precious metals are preferably selected from one or more of cobalt and nickel.

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

9. The method according to claim 1, 7 or 8, characterized in that: Along the flow direction, 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 than that in the upstream catalyst, preferably 3 to 15 percentage points lower, and the mass content of Group VIII non-precious metals as oxides in the downstream catalyst is 0 to 4 percentage points lower than that in the upstream catalyst.

10. The method according to claim 1, characterized in that: The specific surface area of ​​the hydroconversion catalyst is 200–400 m². 2 / g, with a pore volume of 0.15~0.35mL / g.

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

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