Method for hydro-converting light naphtha into low-carbon alkane

Abstract

The invention discloses a method for producing low-carbon alkane through hydro-conversion of light naphtha. The method comprises the following steps: (1) light naphtha and hydrogen are mixed and enter a hydro-conversion reaction zone for hydro-conversion reaction; the hydro-conversion reaction zone is sequentially filled with a first hydro-conversion catalyst and a second hydro-conversion catalyst in the material flowing direction, and the volume ratio of the first hydro-conversion catalyst to the second hydro-conversion catalyst is 1: 1-1: 10; and (2) separating a hydroconversion reaction effluent obtained in the step (1), and circulating a C4 + product obtained by separation to the hydroconversion reaction zone in the step (1) for continuous hydroconversion reaction to obtain ethane and propane. The light naphtha processed by the method can be efficiently converted into ethane and propane, and the proportion of byproduct methane is remarkably reduced.

Description

Technical Field

[0001] This invention relates to the field of comprehensive utilization of light naphtha, specifically to a method for the hydrogenation conversion of light naphtha rich in isoalkanes to produce low-carbon alkanes. Background Technology

[0002] Ethylene and propylene, as basic chemicals, have seen their equivalent consumption increase year by year. Currently, the production of low-carbon olefins in the petrochemical industry is mainly achieved through the cracking of light naphtha rich in alkanes. However, light naphtha generally contains more than 50% isoalkanes, especially hydrocracking light naphtha, where the isoalkanes ratio exceeds 70%. When used directly as feedstock for steam cracking, the cracking performance is poor and the yield of low-carbon olefins is low. Therefore, increasing the n-alkanes content of light naphtha or converting it into low-carbon alkanes can effectively improve the quality of feedstock for steam cracking to produce olefins, thereby increasing the yield of low-carbon olefins.

[0003] CN202011414743.5 discloses a method and system for increasing the production of low-carbon olefins, comprising the following steps: (1) sending light naphtha to a normal-isomeric separation unit to produce normal and non-normal components; (2) sending the non-normal components to a hydrocracking unit and separating them to obtain propane, n-butane, and isobutane; (3) processing the propane, n-butane, and isobutane respectively through different methods to obtain ethylene and propylene. This method can improve the utilization efficiency of naphtha and achieve rational resource allocation.

[0004] CN202110700670.4 discloses a method for ortho-configuration of light naphtha. This method involves mixing light naphtha feedstock with hydrogen and heating it before introducing it from the top of a reactor for ortho-configuration and gas-liquid separation. The separated gaseous product can be sent to a compressor for pressurization and recycling, while the separated liquid product is sent to a stabilization tower for further removal of light components to obtain ortho-configured light naphtha.

[0005] Currently, the main methods to improve light naphtha as a feedstock for steam cracking are through normal-isomeric separation or normalization reaction. However, normal-isomeric separation has high energy consumption and low equipment efficiency, while normalization reaction is limited by chemical equilibrium and has a low conversion rate. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for the hydrogenation conversion of light naphtha to produce low-carbon alkanes. This method processes light naphtha, resulting in a higher proportion of ethane and propane produced and a lower content of methane as a byproduct. This achieves efficient conversion of light naphtha, thereby increasing the yield of low-carbon olefins from steam cracking.

[0007] The first aspect of this invention provides a method for the hydroconversion of light naphtha to produce low-carbon alkanes, the method comprising:

[0008] (1) Light naphtha is mixed with hydrogen and enters the hydroconversion reaction zone for hydroconversion reaction; the hydroconversion reaction zone is sequentially filled with a first hydroconversion catalyst and a second hydroconversion catalyst along the material flow direction, wherein the volume ratio of the first hydroconversion catalyst and the second hydroconversion catalyst is 1:1 to 1:10, preferably 1:3 to 1:6.

[0009] (2) The effluent from the hydrogenation reaction obtained in step (1) is separated to obtain C4 + The product is recycled to the hydrogenation conversion reaction zone of step (1) to continue the hydrogenation conversion reaction, yielding ethane and propane.

[0010] In the method of this invention, the hydroconversion reaction zone is sequentially filled with a first hydroconversion catalyst and a second hydroconversion catalyst along the material flow direction. That is, the material first reacts with the first hydroconversion catalyst and then reacts with the second hydroconversion catalyst. The first and second hydroconversion catalysts can be graded and filled in one or more catalyst beds along the material flow direction.

[0011] In the method of this invention, the first hydroconversion catalyst comprises a mesoporous ten-membered ring molecular sieve supported on a Group VIII metal and macroporous alumina supported on both Group VIII and Group VIB metals. Further, the Group VIII and Group VIB metals exist in the catalyst in oxide form.

[0012] In the method of this invention, the second hydroconversion catalyst comprises a small-pore eight-membered ring molecular sieve supported on a Group VIII metal and a macroporous alumina supported on both Group VIII and Group VIB metals. Further, the Group VIII and Group VIB metals exist in the catalyst in oxide form.

[0013] In the method of the present invention, preferably, in the first hydroconversion catalyst, the mesoporous ten-membered ring molecular sieve loaded with a group VIII metal is loaded onto the mesoporous ten-membered ring molecular sieve using a solution containing a group VIII metal amine complex as an impregnation liquid.

[0014] In the method of the present invention, preferably, in the second hydrogenation conversion catalyst, the small-pore eight-membered ring molecular sieve loaded with a group VIII metal is loaded onto the small-pore eight-membered ring molecular sieve using a solution containing a group VIII metal amine complex as an impregnation liquid.

[0015] In the method of this invention, the light naphtha is selected from at least one of straight-run light naphtha or hydrocracked light naphtha. Further, the initial boiling point of the light naphtha is 15–30°C, and the final boiling point is 60–90°C; the mass content of C5-C6 isoalkanes in the light naphtha is 30%–100%, preferably 50%–90%.

[0016] In the method of this invention, the hydroconversion reaction conditions are as follows: reaction pressure is 1.0–8.0 MPa, reaction temperature is 300–500 °C, hydrogen-to-oil volume ratio is 50:1–2000:1, and liquid hourly space velocity is 0.2–10.0 h⁻¹. -1 Preferably, the reaction pressure is 2.0–6.0 MPa, the reaction temperature is 350–500 °C, the hydrogen-to-oil volume ratio is 100:1–1000:1, and the liquid hourly space velocity is 0.5–5.0 h⁻¹. -1 .

[0017] In the method of this invention, the mesoporous ten-membered ring molecular sieve in the first hydroconversion catalyst is selected from one or more of ZSM-5, ZSM-35, ZSM-22, and ZSM-23 molecular sieves, preferably ZSM-5 molecular sieve; the Group VIB metal is preferably molybdenum and / or tungsten, and the Group VIII metal is preferably cobalt and / or nickel. Further, in the first hydroconversion catalyst, M... x / M y The value is 1.20 to 3.00, preferably 1.50 to 2.50, and more preferably 2.00 to 2.40, wherein M x M represents the molar ratio of Group VIII metal atoms to Group VIB metal atoms in the bulk catalyst phase. y The molar ratio of Group VIII metal atoms to Group VIB metal atoms on the catalyst surface is given.

[0018] In the method of the present invention, the first hydrogenation conversion catalyst contains, based on the weight of the catalyst, 15% to 70% by mass of mesoporous ten-membered ring molecular sieve, 20% to 80% by mass of macroporous alumina, 1.0% to 6.0% by mass of Group VIII metals as oxides, and 4.0% to 24.0% by mass of Group VIB metals as oxides.

[0019] In the method of this invention, the specific surface area of ​​the first hydroconversion catalyst is 200–400 m². 2 / g, with a pore volume of 0.25~0.45mL / g.

[0020] The preparation method of the first hydrogenation conversion catalyst in the method of the present invention includes the following steps:

[0021] (1) A solution containing a group VIII metal amine complex was mixed with a mesoporous ten-membered ring molecular sieve, impregnated in a sealed environment, and then calcined to obtain a mesoporous ten-membered ring molecular sieve loaded with a group VIII metal.

[0022] (2) Macroporous alumina was impregnated with an aqueous solution containing Group VIB metals and Group VIII metals and then calcined to obtain macroporous alumina loaded with Group VIII metals and Group VIB metals.

[0023] (3) Mix the mesoporous ten-membered ring molecular sieve loaded with Group VIII metal and the macroporous alumina loaded with Group VIII metal and Group VIB metal, shape and calcine to obtain the first hydrogenation conversion catalyst.

[0024] Further, the preparation process of the solution containing the Group VIII metal amine complex in step (1) is as follows: dissolve the Group VIII metal salt in deionized water, stir evenly, and then add inorganic ammonium and / or organic amine dropwise to the solution until the pH value of the solution is 7-8. Further, the Group VIII metal in the Group VIII metal salt is preferably cobalt and / or nickel; the Group VIII metal salt is preferably a nitrate; the inorganic amine is selected from one or more of ammonia water (preferably, the mass concentration of ammonia water is 20%-30%) and ammonium chloride; the organic amine is selected from one or more of ethylamine, isopropylamine, and diethylamine. Further, the content of the Group VIII metal in the solution containing the Group VIII metal amine complex, calculated as oxide, is 1-15 g / 100 mL.

[0025] Further, the closed impregnation process in step (1) is as follows: the mesoporous ten-membered ring molecular sieve is mixed with a solution containing a group VIII metal amine complex, placed in a closed reaction vessel, and then heated to 100-120°C under autogenous pressure for stirring and impregnation for 2-4 hours at a stirring speed of 100-400 rpm. Further, the mesoporous ten-membered ring molecular sieve is in the hydrogen form and is selected from one or more of ZSM-5, ZSM-35, ZSM-22, and ZSM-23 molecular sieves, preferably ZSM-5 molecular sieve, wherein the pore volume of the ZSM-5 molecular sieve is 0.18-0.26 cm³. 3 / g, specific surface area of ​​300-450m² 2 / g, the silicon-aluminum molar ratio SiO2:Al2O3 is 20–100. Furthermore, the solid-liquid volume ratio of the mesoporous ten-membered ring molecular sieve and the solution containing a Group VIII metal amine complex is 1:2 to 1:5.

[0026] Further, after impregnation in step (1), the sieve is filtered and dried in a conventional manner, and then calcined to obtain a mesoporous ten-membered ring molecular sieve loaded with Group VIII metals. For example, the drying temperature is 100-150℃ and the drying time is 1-12h; the calcination temperature is 450-550℃ and the calcination time is 3-6h.

[0027] Further, in the aqueous solution containing Group VIB and Group VIII metals in step (2), the source of the Group VIB metal is one or more of tungsten salts (such as ammonium metatungstate) or molybdenum salts (such as ammonium molybdate), and the source of the Group VIII metal is one or more of nickel salts (such as nickel nitrate) or cobalt salts (such as cobalt nitrate). Further, in the aqueous solution containing Group VIB and Group VIII metals, the content of the Group VIB metal as oxide is 10–50 g / 100 mL, and the content of the Group VIII metal as oxide is 1–10 g / 100 mL.

[0028] Furthermore, the impregnation in step (2) is supersaturated impregnation, and the solid-liquid volume ratio of macroporous alumina to the aqueous solution containing Group VIB metals and Group VIII metals is 1:2 to 1:5.

[0029] Further, after impregnation in step (2), the alumina is filtered and dried in a conventional manner, and then calcined to obtain macroporous alumina loaded with Group VIII and Group VIB metals. For example, the drying temperature is 100-150°C and the drying time is 1-12 hours; the calcination temperature is 450-550°C and the calcination time is 3-6 hours.

[0030] Further, in step (3), the molding can be carried out using conventional methods in the art, such as extrusion molding. Molding aids can be added during the molding process, such as at least one of extrusion aids and pectinic acids, preferably pectinic acids; the extrusion aid can be guar gum powder; the pectinic acid can be at least one of citric acid, acetic acid, and nitric acid, preferably at least one of citric acid and nitric acid. Further, the amount of pectinic acid added is less than 2% of the sum of the mass of the mesoporous ten-membered ring molecular sieve loaded with Group VIII metals and the macroporous alumina loaded with Group VIII and Group VIB metals, and the amount of extrusion aid added is less than 3% of the sum of the mass of the mesoporous ten-membered ring molecular sieve loaded with Group VIII metals and the macroporous alumina loaded with Group VIII and Group VIB metals.

[0031] Furthermore, in step (3), after molding, the catalyst can be calcined after a conventional drying process to obtain the catalyst. The drying temperature is 100℃~150℃, and the drying time is 2~4h; the calcination temperature is 400℃~600℃, and the calcination time is 3~5h.

[0032] In the method of this invention, in the second hydroconversion catalyst, the small-pore eight-membered ring molecule is screened from one or more of SAPO-34, SSZ-13, SAPO-18, and SAPO-35 molecular sieves, preferably SAPO-34 molecular sieve; the Group VIB metal is preferably molybdenum and / or tungsten, and the Group VIII metal is preferably cobalt and / or nickel. In the second hydroconversion catalyst, M x / My The value is 1.20 to 3.00, preferably 1.50 to 2.50, and more preferably 2.00 to 2.40, wherein M x M represents the molar ratio of Group VIII metal atoms to Group VIB metal atoms in the bulk catalyst phase. y The molar ratio of Group VIII metal atoms to Group VIB metal atoms on the catalyst surface is given.

[0033] In the method of the present invention, the second hydrogenation conversion catalyst contains, based on the weight of the catalyst, 15% to 70% of the mass content of small-pore eight-membered ring molecular sieve, 20% to 80% of the mass content of macroporous alumina, 1.0% to 6.0% of the content of Group VIII metals as oxides, and 4.0% to 24.0% of the content of Group VIB metals as oxides.

[0034] In the method of this invention, the specific surface area of ​​the second hydroconversion catalyst is 250–450 m². 2 / g, with a pore volume of 0.30~0.50mL / g.

[0035] The preparation method of the second hydrogenation conversion catalyst in this invention includes the following steps:

[0036] (a) A solution containing a group VIII metal amine complex was mixed with a small-pore eight-membered ring molecular sieve, impregnated in a sealed environment, and then calcined to obtain a small-pore eight-membered ring molecular sieve loaded with a group VIII metal.

[0037] (b) Macroporous alumina was impregnated with an aqueous solution containing Group VIB metals and Group VIII metals and then calcined to obtain macroporous alumina loaded with Group VIII metals and Group VIB metals.

[0038] (c) A small-pore eight-membered ring molecular sieve loaded with Group VIII metals and a macroporous alumina loaded with Group VIII metals and Group VIB metals are mixed, shaped, and calcined to obtain a second hydrogenation conversion catalyst.

[0039] Further, the preparation process of the solution containing the Group VIII metal amine complex in step (a) is as follows: dissolve the Group VIII metal salt in deionized water, stir evenly, and then add an inorganic amine or an organic amine dropwise to the solution until the pH value of the solution is 7-8. Further, the Group VIII metal in the Group VIII metal salt is preferably cobalt and / or nickel; the Group VIII metal salt is preferably nickel nitrate or cobalt nitrate; the inorganic amine is selected from one or more of ammonia (preferably, the mass concentration of ammonia is 20%-30%) and ammonium chloride; the organic amine is selected from one or more of ethylamine, isopropylamine, and diethylamine. Further, the content of the Group VIII metal in the solution containing the Group VIII metal amine complex, calculated as oxide, is 1-15 g / 100 mL.

[0040] Further, step (a) the closed impregnation process is as follows: A small-pore octagonal ring molecular sieve is mixed with a solution containing a Group VIII metal amine complex, placed in a closed reaction vessel, and then heated to 100–120°C under autogenous pressure for stirring and impregnation for 2–4 hours at a stirring speed of 100–400 rpm. The small-pore octagonal ring molecular sieve is in the hydrogen form and is selected from one or more of SAPO-34, SSZ-13, SAPO-18, and SAPO-35 molecular sieves, preferably SAPO-34 molecular sieve, wherein the pore volume of the SAPO-34 molecular sieve is 0.22–0.32 cm³. 3 / g, specific surface area of ​​500-750m² 2 / g, the silicon-aluminum molar ratio SiO2:Al2O3 is 0.1 to 1.2. Furthermore, the solid-liquid volume ratio of the small-pore eight-membered ring molecular sieve and the solution containing a Group VIII metal amine complex is 1:2 to 1:5.

[0041] Further, after impregnation in step (a), the sieve is subjected to conventional filtration and drying, followed by calcination to obtain a small-pore eight-membered ring molecular sieve loaded with Group VIII metals. For example, the drying temperature is 100-150°C and the drying time is 1-12 hours; the calcination temperature is 450-550°C and the calcination time is 3-6 hours.

[0042] Further, in the aqueous solution containing Group VIB and Group VIII metals in step (b), the Group VIB metal source is one or more of tungsten salts (e.g., ammonium metatungstate) or molybdenum salts (e.g., ammonium molybdate), and the Group VIII metal source is one or more of nickel salts (e.g., nickel nitrate) or cobalt salts (e.g., cobalt nitrate). Further, in the aqueous solution containing Group VIB and Group VIII metals, the content of the Group VIB metal as oxide is 10–50 g / 100 mL, and the content of the Group VIII metal as oxide is 1–10 g / 100 mL.

[0043] Furthermore, the impregnation in step (b) is supersaturated impregnation, and the solid-liquid volume ratio of macroporous alumina to the aqueous solution containing Group VIB metals and Group VIII metals is 1:2 to 1:5.

[0044] Further, after impregnation in step (b), the alumina is filtered and dried in a conventional manner, and then calcined to obtain macroporous alumina loaded with Group VIII and Group VIB metals. For example, the drying temperature is 100-150°C and the drying time is 1-12 hours; the calcination temperature is 450-550°C and the calcination time is 3-6 hours.

[0045] Further, in step (c), the molding can be carried out using conventional methods in the art, such as extrusion molding. Molding aids can be added during the molding process, such as at least one of extrusion aids and pectinic acids, preferably pectinic acids; the extrusion aid can be guar gum powder, and the pectinic acid can be at least one of citric acid, acetic acid, and nitric acid, preferably at least one of citric acid and nitric acid. Further, the amount of pectinic acid added is less than 2% of the sum of the mass of the small-pore eight-membered ring molecular sieve loaded with Group VIII metals and the macroporous alumina loaded with Group VIII and Group VIB metals, and the amount of extrusion aid added is less than 3% of the sum of the mass of the small-pore eight-membered ring molecular sieve loaded with Group VIII metals and the macroporous alumina loaded with Group VIII and Group VIB metals.

[0046] Further, in step (c), after molding and conventional drying, the catalyst is calcined to obtain the catalyst. The drying temperature is 100℃~150℃, and the drying time is 2~4h; the calcination temperature is 400℃~600℃, and the calcination time is 3~5h.

[0047] In the method of this invention, the macroporous alumina in the first hydroconversion catalyst has the following properties: pore volume of 0.7–1.0 mL / g and specific surface area of ​​200–500 m² / g. 2 / g.

[0048] In the method of this invention, the macroporous alumina in the second hydroconversion catalyst has the following properties: pore volume of 0.7–1.0 mL / g and specific surface area of ​​200–500 m² / g. 2 / g.

[0049] In the method of the present invention, M in the first hydroconversion catalyst and the second hydroconversion catalyst x / M y The values ​​can be the same or different.

[0050] In the method of this invention, M in the catalyst x M was determined by X-ray fluorescence spectroscopy. y X-ray photoelectron spectroscopy was used for analysis.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] Compared to long-chain alkanes, the dehydrogenation process is more difficult in the hydrogenation conversion of C5 and C6 alkanes in light naphtha to C2 and C3 low-carbon alkanes. Since the dehydrogenation process is the controlling step of the overall reaction, improving the dehydrogenation capacity of the catalyst is beneficial to the conversion of light hydrocarbons.

[0053] The hydroconversion reaction zone of this invention employs a first hydroconversion catalyst (containing a mesoporous ten-membered ring molecular sieve catalyst) and a second hydroconversion catalyst (containing a small-pore eight-membered ring molecular sieve catalyst) arranged in an upper and lower cascade configuration. First, the high acid strength of the mesoporous ten-membered ring molecular sieve initiates the first-step cracking reaction of light naphtha. Then, the pore confinement effect of the small-pore eight-membered ring molecular sieve is used to improve the selectivity of low-carbon products, fully leveraging the catalytic effects of the two molecular sieve catalysts to achieve efficient hydroconversion of light naphtha into ethane and propane, significantly reducing the proportion of methane as a byproduct.

[0054] In the preparation process of the hydroconversion catalyst of this invention, the molecular sieve is first impregnated under self-generated pressure with a solution containing a Group VIII metal amine complex. The basic groups of the Group VIII metal amine complex selectively adsorb and bind to the acidic sites within the molecular sieve pores. This results in a more uniform dispersion of the Group VIII metal active particles with stronger dehydrogenation activity and significantly shortens the distance between the metal active sites and the acidic sites of the molecular sieve, thereby increasing the dehydrogenation rate of the reactants. After dehydrogenation, the olefin products rapidly generate carbocations under the influence of the acidic sites, promoting the cracking of light naphtha molecules. Then, the macroporous alumina is impregnated with a mixed aqueous solution containing Group VIB and Group VIII metals. This allows the bimetallic active sites with stronger hydrogenation activity to selectively adsorb in the macroporous alumina, enabling the small molecule olefins obtained from the cracking of light hydrocarbons to diffuse out of the molecular sieve pores and quickly become saturated, thus improving the catalytic activity.

[0055] In the method of this invention, a full-cycle process is adopted. The C2-C3 low-carbon alkane products generated from the conversion of light naphtha can be separated in the separation system, while the remaining C4... + The hydrocarbon products are recycled to the hydroconversion reaction zone for further cracking. The proportion of ethane and propane in the products reaches more than 94%, and the proportion of methane by-product can be reduced to below 6.0%, achieving maximum production of C2-C3 low-carbon alkane products. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the process flow of the embodiments and comparative examples of the present invention;

[0057] Explanation of key figure labels:

[0058] 1-Light naphtha, 2-Hydrogen, 3-Hydroconversion reaction zone, 4-First hydroconversion catalyst, 5-Second hydroconversion catalyst, 6-Hydroconversion product, 7-Separator, 8-Hydrogen-rich gas stream, 9-Liquid stream, 10-Fracturing tower, 11-Gaseous product, 12-C4 + product. Detailed Implementation

[0059] The following examples and comparative examples further illustrate the role and effect of the technical solution of the present invention, but the following examples do not constitute a limitation on the scope of protection of the present invention.

[0060] In this invention, the molar ratio of Group VIII metal atoms to Group VIB metal atoms in the bulk catalyst phase was obtained by X-ray fluorescence spectroscopy (XRF) analysis. A ZSX100e X-ray fluorescence spectrometer was used, with the spectral line being Kα, the crystal being LiF1, the target material being Rh, the detector being SC scintillation, the timing being 20s, and the optical path atmosphere being vacuum.

[0061] In this invention, the molar ratio of Group VIII metal atoms to Group VIB metal atoms on the catalyst surface was determined by X-ray photoelectron spectroscopy (XPS). The elemental composition and state of the catalyst surface (3 nm to 10 nm) were determined using a Thermofisher Multilab 2000 electron spectrometer. The excitation source was Mg Kα, and the cathode voltage and current were 13 kV and 20 mA, respectively. The electron binding energy was calibrated using C1s (284.6 eV).

[0062] In this invention, unless otherwise specified, all percentages (%) in the embodiments and comparative examples refer to mass fractions.

[0063] In this invention, the first hydrogenation conversion catalyst is represented by CAT-A plus a number, such as CAT-A-1, CAT-A-2, CAT-A-3, etc., and the second hydrogenation conversion catalyst is represented by CAT-B plus a number, such as CAT-B-1, CAT-B-2, CAT-B-3, etc.

[0064] The ZSM-5 used in the embodiments and comparative examples of this invention is a commercially available product with a pore volume of 0.22 cm³. 3 / g, specific surface area is 363m² 2 / g, the silicon-aluminum molar ratio SiO2∶Al2O3=55∶1; the SAPO-34 molecular sieve is a commercially available product with a pore volume of 0.28cm³. 3 / g, specific surface area is 607m² 2 / g, the silicon-to-aluminum molar ratio SiO2:Al2O3 = 0.4:1. The macroporous alumina is a commercially available product with a pore volume of 1.0 cm³. 3 / g, specific surface area is 400m² 2 / g.

[0065] In this invention, the calculation methods for the single-pass conversion rate and product yield of light naphtha are as follows:

[0066] Single-pass conversion rate = [1 - (loop C4)] + Hydrocarbon mass / (Cyclic C4) +Hydrocarbon mass + fresh raw material mass) × 100%;

[0067] C2+C3 yield = (sum of the masses of C2 and C3 in the product) / (sum of the masses of C1, C2 and C3 in the product) × 100%;

[0068] C1, C2, and C3 respectively name methane, ethane, and propane.

[0069] Example 1

[0070] (1) Dissolve 40g of nickel nitrate (NiO mass fraction of 25%) in deionized water, stir evenly, add ammonia water (mass concentration of 20%), adjust the pH of the solution to 7.0, and then make up to 1000mL to obtain a nickel amine complex solution with a nickel content (calculated as oxide) of 1.0g / 100mL. Mix 100g of ZSM-5 molecular sieve and 100g of SAPO-34 molecular sieve with 200mL of the above nickel amine complex solution, respectively, and put them into reaction vessels. After sealing, stir at 150rpm, heat to 100℃, keep at the temperature for 3h, then quench and cool, filter, dry at 120℃ for 6h, and calcine at 550℃ for 4h. The materials obtained are denoted as NA-1 and NB-1, respectively.

[0071] (2) Take 300g of macroporous alumina, soak it in 600ml of an aqueous solution with a nickel content (calculated as oxide) of 4.0g / 100mL and a tungsten content (calculated as oxide) of 10.0g / 100mL for 2h, filter it, dry it at 120℃ for 6h, and calcine it at 550℃ for 4h. The resulting material is denoted as NW-1.

[0072] (3) Take 100g NA-1 and 100g N-B-1 and mix them with 100g NW-1 respectively, and put them into a rolling mill for grinding. Add 80g dilute nitric acid solution (HNO3 mass fraction of 4%) to each, grind into paste, extrude into strips, dry the extruded strips at 120℃ for 6h, and then calcine at 550℃ for 4h to obtain catalysts CAT-A-1 and CAT-B-1 respectively. Their properties are shown in Table 1 and Table 2.

[0073] Example 2

[0074] (1) Dissolve 400g of nickel nitrate (NiO mass fraction of 25%) in deionized water, stir evenly, add isopropylamine, adjust the pH of the solution to 8.0, and then make up to 1000mL to obtain a nickel amine complex solution with a nickel content (calculated as oxide) of 10.0g / 100mL. Mix 100g of ZSM-5 molecular sieve and 100g of SAPO-34 molecular sieve with 200mL of the above nickel amine complex solution, respectively, and put them into reaction vessels. After sealing, stir at 300rpm, heat to 110℃, keep at the temperature for 3h, then quench and cool, filter, dry at 120℃ for 6h, and calcine at 550℃ for 4h. The materials obtained are denoted as NA-2 and NB-2, respectively.

[0075] (2) Take 300g of macroporous alumina, soak it in 600mL of an aqueous solution with a nickel content (calculated as oxide) of 4.0g / 100mL and a tungsten content (calculated as oxide) of 20.0g / 100mL for 2h, filter it, dry it at 120℃ for 6h, and calcine it at 550℃ for 4h. The resulting material is denoted as NW-2.

[0076] (3) Take 100g NA-2 and 100g N-B-2 and mix them with 80g NW-2 respectively, and put them into a rolling mill for grinding. Add 72g dilute nitric acid solution (HNO3 mass fraction of 4%) to each, grind into paste, extrude into strips, dry the extruded strips at 120℃ for 6h, and then calcine at 550℃ for 4h to obtain catalysts CAT-A-2 and CAT-B-2 respectively. Their properties are shown in Table 1 and Table 2.

[0077] Comparative Example 1

[0078] 100g of ZSM-5 molecular sieve and 100g of SAPO-34 molecular sieve were mixed with 100g of macroporous alumina, respectively. The mixtures were then impregnated for 4 hours in 400ml of an aqueous solution containing 5.0g / 100mL nickel (based on oxides) and 10.0g / 100mL tungsten (based on oxides). After filtration, drying at 120℃ for 6 hours, and calcination at 550℃ for 4 hours, DNW-A-1 and DNW-B-1 were obtained. DNW-A-1 and DNW-B-1 were then separately milled in a mill, and 80g of dilute nitric acid solution (4% HNO3 by mass) was added to each. The mixtures were then milled into pastes, extruded, dried at 120℃ for 6 hours, and then calcined at 550℃ for 4 hours to obtain comparative catalysts DCAT-A-1 and DCAT-B-1, respectively. Their properties are shown in Tables 1 and 2.

[0079] Comparative Example 2

[0080] (1) Dissolve 560g of nickel nitrate (NiO mass fraction of 25%) in deionized water, stir evenly, add isopropylamine, adjust the pH of the solution to 8.0, and then make up to 1000mL to obtain a nickel amine complex solution with a nickel content (calculated as oxide) of 14.0g / 100mL. Mix 100g of ZSM-5 molecular sieve and 100g of SAPO-34 molecular sieve with 200mL of the above nickel amine complex solution, respectively, and put them into reaction vessels. After sealing, stir at 300rpm, heat to 110℃, keep at the temperature for 3h, then quench and cool down. After filtration, drying at 120℃ for 6h and calcining at 550℃ for 4h, the materials obtained are recorded as DN-A-2 and DN-B-2, respectively.

[0081] (2) Take 300g of macroporous alumina, soak it in 600mL of an aqueous solution with a tungsten content (calculated as oxide) of 20.0g / 100mL for 2h, filter it, dry it at 120℃ for 6h, and calcine it at 550℃ for 4h. The resulting material is called DW-2.

[0082] (3) Take 100g of DN-A-2 and 100g of DN-B-2 and mix them with 80g of DW-2 respectively. Then put them into a rolling mill for grinding. Add 72g of dilute nitric acid solution (HNO3 mass fraction of 4%) to each, grind into paste, extrude into strips, dry the extruded strips at 120℃ for 6h, and then calcine at 550℃ for 4h to obtain comparative catalysts DCAT-A-2 and DCAT-B-2 respectively. Their properties are shown in Table 1 and Table 2.

[0083] Comparative Example 3

[0084] (1) Dissolve 40g of nickel nitrate (NiO mass fraction of 25%) in deionized water and make up to 1000mL to obtain a nickel salt aqueous solution with a nickel content (calculated as oxide) of 1.0g / 100mL. Mix 100g of ZSM-5 molecular sieve and 100g of SAPO-34 molecular sieve with 200mL of the above nickel salt solution respectively, put them into the reaction vessel, seal them and stir at 150rpm, heat to 100℃, keep the temperature for 3h, then quench and cool down, filter, dry at 120℃ for 6h, and calcine at 550℃ for 4h to obtain materials which are respectively denoted as DN-A-3 and DN-B-3;

[0085] (2) Take 300g of macroporous alumina and soak it in 600ml of an aqueous solution with a nickel content (calculated as oxide) of 4.0g / 100mL and a tungsten content (calculated as oxide) of 10.0g / 100mL for 2h. After filtration, drying at 120℃ for 6h and calcining at 550℃ for 4h, the second component is obtained, which is denoted as DNW-3.

[0086] (3) Take 100g of DN-A-3 and DN-B-3 and mix them with 100g of DNW-3 respectively. Then put them into a rolling mill for grinding. Add 80g of dilute nitric acid solution (HNO3 mass fraction of 4%) to each, grind into paste, extrude into strips, dry the extruded strips at 120℃ for 6h, and then calcine at 550℃ for 4h to obtain comparative catalysts DCAT-A-3 and DCAT-B-3 respectively. Their properties are shown in Table 1 and Table 2.

[0087] Example 3

[0088] (1) Dissolve 240g of cobalt nitrate (CoO mass fraction of 25%) in deionized water, stir evenly, add ammonia water (mass concentration of 20%), adjust the pH of the solution to 7.5, and then make up to 1000mL to obtain a cobalt amine complex solution with a cobalt content (calculated as oxide) of 8.0g / 100mL. Mix 100g of ZSM-5 molecular sieve and 100g of SAPO-34 molecular sieve with 200mL of the above cobalt amine complex solution, respectively, and put them into reaction vessels. After sealing, stir at 250rpm, heat to 120℃, keep at the temperature for 4h, then quench and cool, filter, dry at 120℃ for 6h, and calcine at 550℃ for 4h. The materials obtained are denoted as CA-3 and CB-3, respectively.

[0089] (2) Take 300g of macroporous alumina, soak it in 300mL of an aqueous solution with a cobalt content (calculated as oxide) of 6.0g / 100mL and a molybdenum content (calculated as oxide) of 30.0g / 100mL for 2h, filter it, dry it at 120℃ for 6h, and calcine it at 550℃ for 4h. The resulting material is CM-3.

[0090] (3) Take 100g CA-3 and 100g C-B-3 and mix them with 150g CM-3 respectively, and put them into a rolling mill for grinding. Add 100g dilute nitric acid solution (HNO3 mass fraction of 4%) to each, grind into paste, extrude into strips, dry the extruded strips at 120℃ for 6h, and then calcine at 550℃ for 4h to obtain catalysts CAT-A-3 and CAT-B-3 respectively. Their properties are shown in Table 1 and Table 2.

[0091] Example 4

[0092] (1) Dissolve 160g of nickel nitrate (NiO mass fraction of 25%) in deionized water, stir evenly, add isopropylamine, adjust the pH of the solution to 7.0, and then make up to 1000mL to obtain a nickel amine complex solution with a nickel content (calculated as oxide) of 7.0g / 100mL. Mix 100g of ZSM-5 molecular sieve and 100g of SAPO-34 molecular sieve with 200mL of the above nickel amine complex solution, respectively, and put them into reaction vessels. After sealing, stir at 300rpm and heat to 110℃, keep at the temperature for 4h, then quench and cool down. After filtration, drying at 120℃ for 6h and calcining at 550℃ for 4h, the materials obtained are denoted as NA-4 and NB-4, respectively.

[0093] (2) Take 300g of macroporous alumina, soak it in 600mL of an aqueous solution with a nickel content (calculated as oxide) of 7.0g / 100mL and a molybdenum content (calculated as oxide) of 40.0g / 100mL for 2h, filter it, dry it at 120℃ for 6h, and calcine it at 550℃ for 4h. The resulting material is denoted as NM-4.

[0094] (3) Take 100g NA-4 and 100g N-B-4 and mix them with 200g NM-4 respectively, and put them into a rolling mill for grinding. Add 120g dilute nitric acid solution (HNO3 mass fraction of 4%) to each, grind into paste, extrude into strips, dry the extruded strips at 120℃ for 6h, and then calcine at 550℃ for 4h to obtain CAT-A-4 and CAT-B-4 respectively. Their properties are shown in Table 1 and Table 2.

[0095] Example 5

[0096] (1) Dissolve 180g of cobalt nitrate (CoO mass fraction of 25%) in deionized water, stir evenly, add isopropylamine, adjust the pH of the solution to 8.0, and then make up to 1000mL to obtain a cobalt-amine complex solution with a cobalt content (calculated as oxide) of 6.0g / 100mL. Mix 100g of ZSM-5 molecular sieve and 100g of SAPO-34 molecular sieve with 200mL of the above cobalt-amine complex solution, respectively, and put them into reaction vessels. After sealing, stir at 350rpm and heat to 120℃, keep at the temperature for 4h, then quench and cool down. After filtration, drying at 120℃ for 6h and calcining at 550℃ for 4h, the materials obtained are denoted as CA-5 and CB-5, respectively.

[0097] (2) Take 300g of macroporous alumina, soak it in 600mL of an aqueous solution with a cobalt content (calculated as oxide) of 8.0g / 100mL and a tungsten content (calculated as oxide) of 40.0g / 100mL for 2h, filter it, dry it at 120℃ for 6h, and calcine it at 550℃ for 4h. The resulting material is called CW-5.

[0098] (3) Take 100g CA-5 and 100g C-B-5 and mix them with 60g CW-5 respectively. Then put them into a rolling mill for grinding. Add 64g dilute nitric acid solution (HNO3 mass fraction of 4%) to each, grind into paste, extrude into strips, dry the extruded strips at 120℃ for 6h, and then calcine at 550℃ for 4h to obtain catalysts CAT-A-5 and CAT-B-5 respectively. Their properties are shown in Table 1 and Table 2.

[0099] Example 6

[0100] (1) Dissolve 320g of nickel nitrate (NiO mass fraction of 25%) in deionized water, stir evenly, add ammonia water (mass fraction of 20%), adjust the pH of the solution to 7.0, and then make up to 1000mL to obtain a nickel amine complex solution with a nickel content (calculated as oxide) of 4.0g / 100mL. Mix 100g of ZSM-5 molecular sieve and 100g of SAPO-34 molecular sieve with 200mL of the above nickel amine complex solution, respectively, and put them into reaction vessels. After sealing, stir at 250rpm and heat to 120℃, keep at the temperature for 4h, then quench and cool down. After filtration, drying at 120℃ for 6h and calcining at 550℃ for 4h, the materials obtained are denoted as NA-6 and NB-6, respectively.

[0101] (2) Take 300g of macroporous alumina, soak it in 600ml of an aqueous solution with a nickel content (calculated as oxide) of 4.0g / 100mL and a tungsten content (calculated as oxide) of 30.0g / 100mL for 2h, filter it, dry it at 120℃ for 6h, and calcine it at 550℃ for 4h. The resulting material is called NW-6.

[0102] (3) Take 100g NA-6 and 100g N-B-6 and mix them with 40g NW-6 respectively. Then put them into a rolling mill for grinding. Add 56g dilute nitric acid solution (HNO3 mass fraction of 4%) to each, grind into paste, extrude into strips, dry the extruded strips at 120℃ for 6h, and then calcine at 550℃ for 4h to obtain catalysts CAT-A-6 and CAT-B-6 respectively. Their properties are shown in Table 1 and Table 2.

[0103] Table 1. Composition of the catalysts obtained in the examples and comparative examples.

[0104]

[0105]

[0106] Table 2. Properties of the catalysts obtained in the examples and comparative examples.

[0107]

[0108]

[0109] Example 7

[0110] The evaluation was conducted on a fixed-bed hydrogenation test apparatus under the following conditions: reaction pressure 4.0 MPa, hydrogen-to-oil volume ratio 500:1, and liquid hourly space velocity (LHSV) 1.0 h⁻¹. -1 The reaction temperature was 420℃. The feedstock oil underwent hydroconversion in the hydroconversion reaction zone. Catalysts CAT-A-1 and CAT-B-1 were loaded into the upper and lower parts (top feed) of the hydroconversion reaction zone of the reactor, respectively, with a loading volume ratio of 1:1. The properties of the feedstock oil used were evaluated as hydrocracking light naphtha, as shown in Table 3. The single-pass conversion rate and the yield of each product component are shown in Table 4.

[0111] Example 8

[0112] The evaluation was conducted on a fixed-bed hydrogenation test apparatus under the following conditions: reaction pressure 4.0 MPa, hydrogen-to-oil volume ratio 500:1, and liquid hourly space velocity (LHSV) 1.0 h⁻¹. -1 The reaction temperature was 420℃. The feedstock oil underwent hydroconversion in the hydroconversion reaction zone. Catalysts CAT-A-2 and CAT-B-2 were loaded into the upper and lower parts (top feed) of the hydroconversion reaction zone, respectively, at a volume ratio of 1:9. The properties of the feedstock oil used were evaluated as hydrocracking light naphtha, as shown in Table 3. The single-pass conversion rate and the yields of each product component are shown in Table 4.

[0113] Example 9

[0114] The evaluation was conducted on a fixed-bed hydrogenation test apparatus under the following conditions: reaction pressure 4.0 MPa, hydrogen-to-oil volume ratio 500:1, and liquid hourly space velocity (LHSV) 1.0 h⁻¹. -1 The reaction temperature was 420℃. The feedstock oil underwent hydroconversion in the hydroconversion reaction zone. Catalysts CAT-A-5 and CAT-B-5 were loaded into the upper and lower parts (top feed) of the hydroconversion reaction zone of the reactor, respectively, with a loading volume ratio of 1:4. The properties of the feedstock oil used were evaluated as hydrocracking light naphtha, as shown in Table 3. The single-pass conversion rate and the yield of each product component are shown in Table 4.

[0115] Example 10

[0116] The evaluation was conducted on a fixed-bed hydrogenation test apparatus under the following conditions: reaction pressure 4.0 MPa, hydrogen-to-oil volume ratio 500:1, and liquid hourly space velocity (LHSV) 1.0 h⁻¹. -1The reaction temperature was 420℃. The feedstock oil underwent hydroconversion in the hydroconversion reaction zone. Catalysts CAT-A-5 and CAT-B-5 were loaded into the upper and lower parts (top feed) of the hydroconversion reaction zone, respectively, at a volume ratio of 1:8. The properties of the feedstock oil used were evaluated as hydrocracking light naphtha, as shown in Table 3. The single-pass conversion rate and the yield of each product component are shown in Table 4.

[0117] Example 11

[0118] The evaluation was conducted on a fixed-bed hydrogenation test apparatus under the following conditions: reaction pressure 3.0 MPa, hydrogen-to-oil volume ratio 300:1, and liquid hourly space velocity (LHSV) 3.0 h⁻¹. -1 The reaction temperature was 420℃. The feedstock oil underwent hydroconversion in the hydroconversion reaction zone. Catalysts CAT-A-3 and CAT-B-3 were loaded into the upper and lower parts (top feed) of the hydroconversion reaction zone of the reactor, respectively, with a loading volume ratio of 1:6. The properties of the feedstock oil used were evaluated as hydrocracking light naphtha, as shown in Table 3. The single-pass conversion rate and the yield of each product component are shown in Table 4.

[0119] Example 12

[0120] The evaluation was conducted on a fixed-bed hydrogenation test apparatus under the following conditions: reaction pressure 4.0 MPa, hydrogen-to-oil volume ratio 800:1, and liquid hourly space velocity (LHSV) 5.0 h⁻¹. -1 The reaction temperature was 450℃. The feedstock oil underwent hydroconversion in the hydroconversion reaction zone. Catalysts CAT-A-4 and CAT-B-4 were loaded into the upper and lower parts (top feed) of the hydroconversion reaction zone of the reactor, respectively, with a loading volume ratio of 1:3. The properties of the feedstock oil used were evaluated as hydrocracking light naphtha, as shown in Table 3. The single-pass conversion rate and the yield of each product component are shown in Table 4.

[0121] Example 13

[0122] The evaluation was conducted on a fixed-bed hydrogenation test apparatus under the following conditions: reaction pressure 5.5 MPa, hydrogen-to-oil volume ratio 300:1, and liquid hourly space velocity (LHSV) 1.0 h⁻¹. -1 The reaction temperature was 480℃. The feedstock oil underwent hydroconversion in the hydroconversion reaction zone. Catalysts CAT-A-6 and CAT-B-6 were loaded into the upper and lower parts (top feed) of the hydroconversion reaction zone, respectively, at a volume ratio of 1:4. The properties of the feedstock oil used were evaluated as hydrocracking light naphtha, as shown in Table 3. The single-pass conversion rate and the yields of each product component are shown in Table 4.

[0123] Comparative Example 4

[0124] The evaluation was conducted on a fixed-bed hydrogenation test apparatus under the following conditions: reaction pressure 4.0 MPa, hydrogen-to-oil volume ratio 500:1, and liquid hourly space velocity (LHSV) 1.0 h⁻¹. -1 The reaction temperature was 420℃. The feedstock oil underwent hydroconversion in the hydroconversion reaction zone. Catalysts DCAT-A-1 and DCAT-B-1 were loaded into the upper and lower parts (top feed) of the hydroconversion reaction zone of the reactor, respectively, with a loading volume ratio of 1:1. The properties of the feedstock oil used were evaluated as hydrocracking light naphtha, as shown in Table 3. The single-pass conversion rate and the yield of each product component are shown in Table 5.

[0125] Comparative Example 5

[0126] The evaluation was conducted on a fixed-bed hydrogenation test apparatus under the following conditions: reaction pressure 4.0 MPa, hydrogen-to-oil volume ratio 500:1, and liquid hourly space velocity (LHSV) 1.0 h⁻¹. -1 The reaction temperature was 420℃. The feedstock oil underwent hydroconversion in the hydroconversion reaction zone. Catalysts DCAT-A-2 and DCAT-B-2 were loaded into the upper and lower parts (top feed) of the hydroconversion reaction zone, respectively, at a volume ratio of 1:9. The properties of the feedstock oil used were evaluated as hydrocracking light naphtha, as shown in Table 3. The single-pass conversion rate and the yields of each product component are shown in Table 5.

[0127] Comparative Example 6

[0128] The evaluation was conducted on a fixed-bed hydrogenation test apparatus under the following conditions: reaction pressure 4.0 MPa, hydrogen-to-oil volume ratio 500:1, and liquid hourly space velocity (LHSV) 1.0 h⁻¹. -1 The reaction temperature was 420℃. The feedstock oil underwent hydroconversion in the hydroconversion reaction zone. Catalysts DCAT-A-3 and DCAT-B-3 were loaded into the upper and lower parts (top feed) of the hydroconversion reaction zone, respectively, at a volume ratio of 1:1. The properties of the feedstock oil used were evaluated as hydrocracking light naphtha, as shown in Table 3. The single-pass conversion rate and the yields of each product component are shown in Table 5.

[0129] Comparative Example 7

[0130] The evaluation was conducted on a fixed-bed hydrogenation test apparatus under the following conditions: reaction pressure 4.0 MPa, hydrogen-to-oil volume ratio 500:1, and liquid hourly space velocity (LHSV) 1.0 h⁻¹. -1 The reaction temperature was 420℃. The feedstock oil underwent hydroconversion in the hydroconversion reaction zone, which was filled with CAT-A-1 catalyst. The properties of the feedstock oil used, hydrocracking light naphtha, are shown in Table 3, and the single-pass conversion rate and yields of each product component are shown in Table 5.

[0131] Comparative Example 8

[0132] The evaluation was conducted on a fixed-bed hydrogenation test apparatus under the following conditions: reaction pressure 4.0 MPa, hydrogen-to-oil volume ratio 500:1, and liquid hourly space velocity (LHSV) 1.0 h⁻¹. -1 The reaction temperature was 420℃. The feedstock oil underwent hydroconversion in the hydroconversion reaction zone, which was loaded with CAT-B-1 catalyst. The properties of the feedstock oil used, hydrocracking light naphtha, are shown in Table 3, and the single-pass conversion rate and yields of each product component are shown in Table 5.

[0133] Comparative Example 9

[0134] The evaluation was conducted on a fixed-bed hydrogenation test apparatus under the following conditions: reaction pressure 4.0 MPa, hydrogen-to-oil volume ratio 500:1, and liquid hourly space velocity (LHSV) 1.0 h⁻¹. -1 The reaction temperature was 420℃. The feedstock oil underwent hydroconversion in the hydroconversion reaction zone. Catalysts CAT-A-5 and CAT-B-5 were loaded into the upper and lower parts (top feed) of the hydroconversion reaction zone, respectively, at a volume ratio of 4:1. The properties of the feedstock oil used were evaluated as hydrocracking light naphtha, as shown in Table 3. The single-pass conversion rate and the yield of each product component are shown in Table 5.

[0135] Table 3 Composition of light naphtha feedstock

[0136] Hydrocarbon composition, % <![CDATA[i-C4 (isobutane)]]> 1.5 <![CDATA[n-C4 (n-butane)]]> 3.7 <![CDATA[i-C5 (isopentane)]]> 52.0 <![CDATA[n-C5 (n-pentane)]]> 12.4 <![CDATA[i-C6 (isopentane)]]> 28.8 <![CDATA[n-C6 (n-hexane)]]> 1.6 Initial boiling point, ℃ 24 Final boiling point, ℃ 63

[0137] Table 4 Evaluation results of the catalysts in the examples

[0138]

[0139] Table 5 Evaluation results of the comparative example catalysts

[0140] Test number Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 Comparative Example 9 One-way conversion rate, % 42.6 37.2 53.7 65.0 21.5 72.3 Product distribution, % <![CDATA[C1]]> 12.4 9.5 13.6 15.6 8.9 14.7 <![CDATA[C2]]> 25.5 28.7 23.8 21.3 37.6 22.5 <![CDATA[C3]]> 62.1 61.8 62.6 63.1 53.5 62.8 <![CDATA[Yield of C2 + C3, %]]> 87.6 90.5 86.4 84.4 91.1 85.3

[0141] 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 the hydrogenation conversion of light naphtha to produce low-carbon alkanes, the method comprising: (1) Light naphtha is mixed with hydrogen and enters the hydroconversion reaction zone for hydroconversion reaction; the hydroconversion reaction zone is sequentially filled with a first hydroconversion catalyst and a second hydroconversion catalyst along the material flow direction, wherein the volume ratio of the first hydroconversion catalyst and the second hydroconversion catalyst is 1:1 to 1:10, preferably 1:3 to 1:

6. (2) The effluent from the hydrogenation reaction obtained in step (1) is separated to obtain C4 + The product is recycled to the hydrogenation conversion reaction zone of step (1) to continue the hydrogenation conversion reaction, yielding ethane and propane.

2. The method according to claim 1, characterized in that: The first hydroconversion catalyst comprises a mesoporous ten-membered ring molecular sieve supported on a Group VIII metal and a macroporous alumina supported on a Group VIII metal and a Group VIB metal; the second hydroconversion catalyst comprises a microporous eight-membered ring molecular sieve supported on a Group VIII metal and a macroporous alumina supported on a Group VIII metal and a Group VIB metal.

3. The method according to claim 2, characterized in that: The mesoporous ten-membered ring molecular sieve loaded with Group VIII metals was loaded onto the mesoporous ten-membered ring molecular sieve using a solution containing a Group VIII metal amine complex as the impregnation solution. And / or, the small-pore eight-membered ring molecular sieve loaded with Group VIII metals is loaded onto the small-pore eight-membered ring molecular sieve using a solution containing a Group VIII metal amine complex as the impregnation solution.

4. The method according to claim 1, characterized in that: The light naphtha is selected from at least one of straight-run light naphtha or hydrocracked light naphtha. Preferably, the initial boiling point of the light naphtha is 15-30°C, and the final boiling point is 60-90°C; the mass content of C5-C6 isoalkanes in the light naphtha is 30%-100%, preferably 50%-90%.

5. The method according to claim 1, characterized in that: The hydroconversion reaction conditions are as follows: reaction pressure 1.0–8.0 MPa, reaction temperature 300–500 °C, hydrogen-to-oil volume ratio 50:1–2000:1, and liquid hourly space velocity 0.2–10.0 h⁻¹. -1 ; Preferably, the reaction pressure is 2.0–6.0 MPa, the reaction temperature is 350–500 °C, the hydrogen-to-oil volume ratio is 100:1–1000:1, and the liquid hourly space velocity is 0.5–5.0 h⁻¹. -1 .

6. The method according to claim 1, characterized in that: In the first hydroconversion catalyst, the mesoporous ten-membered ring molecular sieve is selected from one or more of ZSM-5, ZSM-35, ZSM-22, and ZSM-23 molecular sieves, preferably ZSM-5 molecular sieve; the Group VIB metal is preferably molybdenum and / or tungsten, and the Group VIII metal is preferably cobalt and / or nickel; And / or, in the second hydroconversion catalyst, the small-pore eight-membered ring molecule is screened from one or more of SAPO-34, SSZ-13, SAPO-18, and SAPO-35 molecular sieves, preferably SAPO-34 molecular sieve; the Group VIB metal is preferably molybdenum and / or tungsten, and the Group VIII metal is preferably cobalt and / or nickel.

7. The method according to claim 2, characterized in that: In the first hydroconversion catalyst, M x / M y The value is 1.20 to 3.00, preferably 1.50 to 2.50, where M x M represents the molar ratio of Group VIII metal atoms to Group VIB metal atoms in the bulk catalyst phase. y The molar ratio of Group VIII metal atoms to Group VIB metal atoms on the catalyst surface; And / or, in the second hydroconversion catalyst, M x / M y The value is 1.20 to 3.00, preferably 1.50 to 2.50, where M x M represents the molar ratio of Group VIII metal atoms to Group VIB metal atoms in the bulk catalyst phase. y The molar ratio of Group VIII metal atoms to Group VIB metal atoms on the catalyst surface is given.

8. The method according to claim 2, characterized in that: In the first hydroconversion catalyst, based on the weight of the catalyst, the mass content of mesoporous ten-membered ring molecular sieve is 15% to 70%, the mass content of macroporous alumina is 20% to 80%, the content of Group VIII metals as oxides is 1.0% to 6.0%, and the content of Group VIB metals as oxides is 4.0% to 24.0%.

9. The method according to claim 2, characterized in that: In the second hydroconversion catalyst, based on the weight of the catalyst, the mass content of small-pore eight-membered ring molecular sieve is 15% to 70%, the mass content of macroporous alumina is 20% to 80%, the content of Group VIII metals as oxides is 1.0% to 6.0%, and the content of Group VIB metals as oxides is 4.0% to 24.0%.

10. The method according to claim 1, characterized in that: The specific surface area of ​​the first hydroconversion catalyst is 200–400 m². 2 / g, with a pore volume of 0.25–0.45 mL / g; and / or, the specific surface area of ​​the second hydroconversion catalyst is 250–450 m² / g. 2 / g, with a pore volume of 0.30~0.50mL / g.

11. The method according to claim 1, characterized in that: In the first hydroconversion catalyst, the macroporous alumina has the following properties: pore volume of 0.7–1.0 mL / g and specific surface area of ​​200–500 m² / g. 2 / g; and / or, in the second hydroconversion catalyst, the macroporous alumina has the following properties: pore volume of 0.7–1.0 mL / g, specific surface area of ​​200–500 m² / g. 2 / g.

Images