Catalytic cracking of hydrocarbons to olefins

Abstract

This invention discloses a catalytic cracking catalyst for olefin production, its preparation method, and its application. The catalyst comprises a first active center and a second active center. The first active center is a zinc-modified ZSM-5 molecular sieve, and the second active center is a silver-modified β-molecular sieve. The preparation method includes the following steps: (1) preparing a zinc-modified ZSM-5 molecular sieve; (2) preparing a silver-modified β-molecular sieve; (3) thoroughly mixing the zinc-modified ZSM-5 molecular sieve obtained in step (1) and the silver-modified β-molecular sieve obtained in step (2), and further shaping to obtain the catalyst. The catalyst provided by this invention is suitable for the cracking reaction of C5-C10 n-alkanes and the cracking reaction of naphtha to produce low-carbon olefins, exhibiting high yield and selectivity of low-carbon olefins.

Description

Technical Field

[0001] This invention belongs to the field of petrochemical technology and relates to a catalytic material and its preparation method, particularly to a catalyst for cracking to produce low-carbon olefins (including but not limited to ethylene, propylene and butene) and its preparation method. Background Technology

[0002] Low-carbon olefins (ethylene, propylene, and butene) are important organic chemical raw materials, serving as a major source for the production of everyday chemicals such as rubber and plastics. They play a vital role in the petrochemical industry and in people's daily lives. In 2021, global demand for propylene and ethylene was 91 million tons and 210 million tons, respectively, with a propylene / ethylene ratio of 0.43. However, the production ratio of propylene to ethylene that year was only 0.35, indicating a significant supply-demand imbalance. It is predicted that future market demand for propylene will increase annually at a rate exceeding 6.5%, further exacerbating the supply-demand gap. Therefore, increasing the production of low-carbon olefins, especially propylene, to meet market demand has become a key research focus.

[0003] Currently, over 95% of the world's ethylene and over 60% of its propylene are produced through steam cracking. Naphtha steam cracking technology has a history of over 70 years and is quite mature. However, because hydrocarbon thermal cracking reactions follow a free radical reaction mechanism, this inherent characteristic cannot be changed, leading to many insurmountable shortcomings. These include high energy consumption, an unreasonable and difficult-to-adjust product distribution (low propylene / ethylene ratio, high proportion of low-value-added products), low feedstock utilization, and high carbon oxide emissions. Driven by the current trend of energy conservation and environmental protection, as well as market supply and demand imbalances, these shortcomings will severely limit the further promotion, application, and development of this technology.

[0004] Compared to steam cracking, naphtha catalytic cracking has the advantages of mild operating conditions, high selectivity of high value-added products, and adjustable propylene / ethylene ratio. It is considered a highly promising alternative to steam cracking and has attracted increasing attention from researchers.

[0005] USP3767567 discloses a catalyst for the cracking of naphtha to produce low-carbon olefins. The catalyst composition consists of any oxide (>20wt%) of CaO, BeO, or SrO and alumina as catalysts. Naphtha with a boiling point of 70-180℃ is used as feedstock, the reaction temperature is 650-900℃, and the water-to-oil ratio is 0.5-10. The CaO-Al2O3 type catalyst is the best. The highest yield of ethylene is 52.5%, and the yield of propylene is 16.3%.

[0006] US4705769 discloses a catalyst for butane cracking to produce low-carbon olefins. This catalyst uses manganese oxide or iron oxide as the active component, with the addition of rare earth element La and alkaline earth metal Mg. Isobutane is used as the feedstock, and the reaction temperature is 700°C. In a fixed-bed reactor, the butane conversion rate is 80%, and the selectivity for ethylene and propylene is 34% and 20%, respectively. The catalyst is also claimed to be suitable for naphtha and fluidized-bed reactors.

[0007] CN103785454A discloses a catalytic cracking catalyst and its preparation method. The catalyst, by weight percentage, comprises: (a) 15%–65% natural minerals; (b) 10%–30% oxides; and (c) 25%–75% phosphorus-containing, silicon-rich β-molecular sieves. The catalyst is suitable for use in naphtha catalytic cracking processes, exhibiting higher yields of low-carbon olefins.

[0008] CN102371172A discloses a catalyst for catalytic cracking to olefins, which comprises, by weight percentage: (1) 15%–60% kaolin; (2) 10%–30% at least one selected from silica or alumina; (3) 0.5%–15% at least one selected from phosphorus, rare earth, or alkaline earth metal oxides; and (4) 25%–70% ZSM-5 zeolite synthesized by a directing agent method with a grain size of 200–1000 nm. This catalyst, when used for naphtha catalytic cracking, can significantly improve the conversion rate of naphtha and the yields of ethylene and propylene.

[0009] CN101279285A discloses a catalyst for naphtha cracking to produce low-carbon olefins. The catalyst comprises at least one element or its oxide from Group IVB or Group VB of the periodic table supported on ZSM-5 / mordenite symbiotic molecular sieve, ZSM-5 / β-zeolite symbiotic molecular sieve, or ZSM-5 / Y-zeolite symbiotic molecular sieve for the catalytic cracking of naphtha to produce ethylene and propylene. In a fixed-bed reactor at a reaction temperature of 600-700℃, the total yield of ethylene and propylene from naphtha cracking can reach 54%.

[0010] CN1955255A discloses a petroleum hydrocarbon catalytic cracking catalyst and its application. The catalyst components include: (1) rare earth elements; (2) phosphorus or boron; (3) alkali metals, alkaline earth metals, and transition metals; and (4) a support. This catalyst is used to crack heavy hydrocarbons such as naphtha, diesel, and vacuum diesel to produce low-carbon olefins, and the feedstock does not require nitrogen dilution, which can increase the yield of ethylene, propylene, butene, and butadiene by more than 5%.

[0011] The above analysis shows that while existing technologies disclose some catalysts and their preparation methods, they still have some shortcomings to varying degrees, mainly high reaction temperatures, low olefin selectivity, and low propylene / ethylene ratios. Therefore, developing highly active and selective cracking catalysts is an urgent problem to be solved. To this end, this invention designs a high-performance catalyst for the cracking of alkane to low-carbon olefins based on the alkane cracking mechanism, significantly improving the catalyst's reaction performance. Summary of the Invention

[0012] To address the problems existing in existing cracking catalysts for producing low-carbon olefins, the main objective of this invention is to provide a cracking catalyst for producing olefins and its preparation method. The provided catalyst is based on the unimolecular reaction mechanism of alkane cracking and features a dual-active reaction center design: one active center in a larger molecular sieve channel promotes dehydrogenation and olefin formation, while the other active center in a smaller molecular sieve channel promotes the cracking reaction. The synergy of these two active centers significantly improves the catalyst activity and the selectivity for low-carbon olefins. The catalyst provided by this invention is suitable for the cracking of C5-C10 n-alkanes and the cracking of naphtha to produce low-carbon olefins, exhibiting high yields and selectivity of low-carbon olefins.

[0013] To achieve the objectives of this invention, the technical solution includes the following aspects:

[0014] I. A first aspect of the present invention provides a catalyst for catalytic cracking to olefins, the catalyst comprising a first active center and a second active center, wherein the first active center is a zinc-modified ZSM-5 molecular sieve; the second active center is a silver-modified β molecular sieve; based on the weight percentage of the catalyst, the ZnO content is 0.1%–5.0%, the Ag2O content is 0.1%–5.0%, the ZSM-5 molecular sieve content is 5%–80%, and the β molecular sieve content is 10%–94.8%; preferably, the content of each component is: ZnO content is 0.5%–3.0%, Ag2O content is 0.3%–2.0%, ZSM-5 molecular sieve content is 20%–60%, and β molecular sieve content is 35%–75%.

[0015] Furthermore, according to a specific embodiment of the present invention, the ZSM-5 molecular sieve is a hydrogen-type molecular sieve with a silicon-to-aluminum molar ratio of 50 to 1000 and a morphology of flake or columnar.

[0016] Furthermore, according to a specific embodiment of the present invention, the β molecular sieve is a hydrogen-type molecular sieve, and the silicon-aluminum molar ratio is 10 to 100.

[0017] II. This invention provides a method for preparing a catalyst for catalytic cracking to olefins, the method comprising the following steps:

[0018] (1) To prepare zinc-modified ZSM-5 molecular sieve, the zinc precursor was mixed with ZSM-5 molecular sieve, and then dried and calcined to obtain zinc-modified ZSM-5 molecular sieve.

[0019] (2) To prepare silver-modified β-zeolite, a silver precursor was mixed with β-zeolite, and then dried and calcined to obtain silver-modified β-zeolite.

[0020] (3) The zinc-modified ZSM-5 molecular sieve obtained in step (1) and the silver-modified β molecular sieve obtained in step (2) are thoroughly mixed and further shaped to obtain the catalyst.

[0021] Furthermore, according to a specific embodiment of the present invention, the zinc precursor is a soluble zinc-containing inorganic salt, specifically selected from one or a mixture of zinc nitrate, zinc chloride, and zinc sulfate, preferably zinc nitrate.

[0022] Furthermore, according to a specific embodiment of the present invention, the silver precursor is a soluble silver-containing inorganic salt compound, which may be selected from silver nitrate.

[0023] Furthermore, according to a specific embodiment of the present invention, the mixing in steps (1) and (2) can be carried out by at least one of kneading, impregnation, and spraying, preferably by kneading; specifically, further, the kneading in step (1) is to fully mix a calculated amount of zinc precursor, ZSM-5 molecular sieve and water into a slurry; the kneading in step (2) is to fully mix a calculated amount of silver precursor, β molecular sieve and water into a slurry.

[0024] Furthermore, according to a specific embodiment of the present invention, the drying and calcination operation conditions in steps (1) and (2) are the same or different, the drying temperature is 20℃~300℃, the drying time is 0.5 hours~24 hours; the calcination temperature is 300℃~700℃, and the calcination time is 0.5 hours~12 hours.

[0025] A third aspect of the present invention provides the application of the above-mentioned catalytic cracking catalyst for olefin production in the preparation of low-carbon olefins.

[0026] The fourth aspect of the present invention provides a method for catalytic cracking of alkane to produce low-carbon olefins, wherein the alkane feedstock enters a reactor and reacts with the above-mentioned catalytic cracking catalyst for producing olefins.

[0027] Furthermore, in the above-mentioned method for catalytic cracking of alkane to produce low-carbon olefins, the alkane feedstock is one or a mixture of several C5-C9 n-alkanes, preferably n-heptane and / or n-octane.

[0028] Furthermore, in the above-mentioned method for catalytic cracking of alkanes to produce low-carbon olefins, the catalyst for catalytic cracking to produce olefins generally needs to be crushed to obtain 20-40 mesh particles.

[0029] Furthermore, in the above-mentioned method for catalytic cracking of alkanes to produce low-carbon olefins, a fixed-bed reactor is used.

[0030] Furthermore, in the above method for catalytic cracking of alkanes to produce low-carbon olefins, the reaction conditions are as follows: reaction temperature of 450℃~850℃, and volume hourly space velocity of 0.1h. -1 ~5h -1 . Detailed Implementation

[0031] The present invention will be further illustrated by the following embodiments, but it should not be considered that the present invention is limited to the following embodiments.

[0032] Unless otherwise specified, all percentages in this document are by weight.

[0033] The catalyst of this invention is used in the catalytic cracking of n-heptane to produce low-carbon olefins. The specific reaction conditions are as follows: a fixed-bed reactor is used; the catalyst is crushed, and 20-40 mesh particles are used for evaluation; the catalyst loading is 5 mL; n-heptane is used as the feedstock; the temperature is 500℃-600℃; and the volume hourly space velocity is 0.1 h⁻¹. -1 ~5h -1 The reaction products were analyzed by an Agilent 7890 gas chromatograph with FID, and the results were compared after 2 hours. The relevant calculation methods are as follows:

[0034] n-Heptane conversion rate % = [n-Heptane concentration before reaction (v%) - n-Heptane concentration after reaction (v%)] / n-Heptane concentration before reaction (v%)

[0035] Low-carbon olefin selectivity % = [low-carbon olefin concentration after reaction (v%) - low-carbon olefin concentration before reaction (v%)] / [n-heptane concentration before reaction (v%) - n-heptane concentration after reaction (v%)]

[0036] Example 1

[0037] The ZSM-5 molecular sieve used in Example 1 has a silicon-to-aluminum molar ratio of 80 and a sheet-like morphology; the β molecular sieve used has a silicon-to-aluminum molar ratio of 22.

[0038] (1) Dissolve 4.6 g of zinc nitrate in 100 g of water to prepare a zinc nitrate solution. Then, mix the prepared zinc nitrate solution with 50 g of HZSM-5 molecular sieve (silicon-aluminum molar ratio 80, morphology flake) and slurry thoroughly. Dry at 120°C for 8 hours, calcine at 550°C for 4 hours, and pulverize to below 200 mesh to obtain zinc oxide modified ZSM-5 molecular sieve, numbered Z-1.

[0039] (2) Dissolve 0.8 g of silver nitrate in 100 g of water to prepare a silver nitrate solution. Then, mix the prepared silver nitrate solution with 47.5 g of Hβ molecular sieve (silicon-aluminum molar ratio 22) and slurry thoroughly. After drying at 110°C for 12 hours and calcining at 500°C for 6 hours, the mixture is pulverized to below 200 mesh to obtain a silver-modified β molecular sieve, numbered B-1.

[0040] (3) The zinc-modified ZSM-5 molecular sieve (Z-1) obtained in step (1) and the silver-modified β molecular sieve (B-1) obtained in step (2) are thoroughly mixed and pressed into tablets to obtain the binder-free dual active center pyrolysis catalyst of the present invention, numbered E-1.

[0041] The prepared catalyst E-1 was crushed, and 20-40 mesh particles were used for evaluation. The reactor was a fixed-bed reactor with a catalyst loading of 5 mL, using n-heptane as feedstock, at a temperature of 530 °C and a volume hourly space velocity (VHSV) of 2.0 h⁻¹. -1 The reaction products were analyzed by Agilent 7890 gas chromatograph with FID, and the results of the reaction over 2 hours were taken. The composition and catalyst preparation conditions are shown in Table 1, and the catalyst evaluation conditions and results are shown in Table 2.

[0042] Example 2

[0043] The preparation steps were the same as in Example 1, except for the catalyst composition, preparation conditions, and reaction conditions. The prepared catalyst was designated E-2, and its composition and preparation conditions are shown in Table 1. The catalyst evaluation conditions and results are shown in Table 2. The ZSM-5 molecular sieve used in Example 2 had a silica-alumina molar ratio of 80 and a plate-like morphology; the β-molecular sieve used had a silica-alumina molar ratio of 22.

[0044] Example 3

[0045] The preparation steps were the same as in Example 1, except for the catalyst composition, preparation conditions, and reaction conditions. The prepared catalyst was designated E-3, and its composition and preparation conditions are shown in Table 1. The catalyst evaluation conditions and results are shown in Table 2. The ZSM-5 molecular sieve used in Example 3 had a silica-alumina molar ratio of 80 and a plate-like morphology; the β-molecular sieve used had a silica-alumina molar ratio of 22.

[0046] Example 4

[0047] The preparation steps were the same as in Example 1, except for the catalyst composition, preparation conditions, and reaction conditions. The prepared catalyst was designated E-4, and its composition and preparation conditions are shown in Table 1. The catalyst evaluation conditions and results are shown in Table 2. The ZSM-5 molecular sieve used in Example 4 had a silica-alumina molar ratio of 120 and a columnar morphology, while the β-molecular sieve used had a silica-alumina molar ratio of 42.

[0048] Example 5

[0049] The preparation steps were the same as in Example 1, except for the catalyst composition, preparation conditions, and reaction conditions. The prepared catalyst was designated E-5, and its composition and preparation conditions are shown in Table 1. The catalyst evaluation conditions and results are shown in Table 2. The ZSM-5 molecular sieve used in Example 5 had a silica-alumina molar ratio of 120 and a columnar morphology, while the β-molecular sieve used had a silica-alumina molar ratio of 42.

[0050] Example 6

[0051] The preparation steps were the same as in Example 1, except for the molecular morphology, silicon-to-aluminum ratio, catalyst composition, preparation conditions, and reaction conditions. The prepared catalyst was designated E-6, and its composition and preparation conditions are shown in Table 1. The catalyst evaluation conditions and results are shown in Table 2. The ZSM-5 molecular sieve used in Example 6 had a silicon-to-aluminum molar ratio of 120 and a columnar morphology, while the β-molecular sieve used had a silicon-to-aluminum molar ratio of 42.

[0052] Example 7

[0053] The preparation steps were the same as in Example 1, except for the molecular morphology, silicon-to-aluminum ratio, catalyst composition, preparation conditions, and reaction conditions. The prepared catalyst was designated E-7, and its composition and preparation conditions are shown in Table 1. The catalyst evaluation conditions and results are shown in Table 2. In Example 7, the ZSM-5 molecular sieve used had a silicon-to-aluminum molar ratio of 120 and a columnar morphology, while the β-molecular sieve used had a silicon-to-aluminum molar ratio of 42.

[0054] Example 8

[0055] The preparation steps were the same as in Example 1, except for the molecular morphology, silicon-to-aluminum ratio, catalyst composition, preparation conditions, and reaction conditions. The prepared catalyst was designated E-8, and its composition and preparation conditions are shown in Table 1. The catalyst evaluation conditions and results are shown in Table 2. The ZSM-5 molecular sieve used in Example 8 had a silicon-to-aluminum molar ratio of 120 and a columnar morphology, while the β-molecular sieve used had a silicon-to-aluminum molar ratio of 42.

[0056] Example 9

[0057] The preparation steps were the same as in Example 1, except for the catalyst composition, preparation conditions, and reaction conditions. The prepared catalysts were numbered E-9, and their composition and preparation conditions are shown in Table 1. The catalyst evaluation conditions and results are shown in Table 2. The ZSM-5 molecular sieve used in Example 9 had a silica-alumina molar ratio of 500 and a plate-like morphology, while the β-molecular sieve used had a silica-alumina molar ratio of 31.

[0058] Comparative Example 1

[0059] 4.6 g of zinc nitrate and 0.8 g of silver nitrate were dissolved in 200 g of water to prepare a solution of zinc nitrate and silver nitrate. This mixture was then thoroughly slurried with 50 g of HZSM-5 molecular sieve (silicon-to-aluminum molar ratio 80, flake-like morphology) and 47.5 g of Hβ molecular sieve (silicon-to-aluminum molar ratio 22). The slurry was dried at 120 °C for 8 hours, calcined at 550 °C for 4 hours, pulverized to below 200 mesh, and pressed into tablets to obtain the comparative catalyst, designated C-1. Its composition and preparation conditions are shown in Table 1, and the catalyst evaluation conditions and results are shown in Table 2. The ZSM-5 molecular sieve used in Comparative Example 1 had a silicon-to-aluminum molar ratio of 80 and a flake-like morphology; the β molecular sieve used had a silicon-to-aluminum molar ratio of 22.

[0060] Comparative Example 2

[0061] The preparation steps were the same as in Comparative Example 1, except for the catalyst composition, preparation conditions, and reaction conditions. The comparative catalyst prepared was designated C-2, and its composition and preparation conditions are shown in Table 1. The catalyst evaluation conditions and results are shown in Table 2. The ZSM-5 molecular sieve used in Comparative Example 2 had a silica-to-alumina molar ratio of 120 and a columnar morphology, while the β-molecular sieve used had a silica-to-alumina molar ratio of 42.

[0062] Comparative Example 3

[0063] The preparation steps were the same as in Comparative Example 1, except for the molecular morphology, silicon-to-aluminum ratio, catalyst composition, preparation conditions, and reaction conditions. The comparative catalyst prepared was designated C-3, and its composition and preparation conditions are shown in Table 1. The catalyst evaluation conditions and results are shown in Table 2. The ZSM-5 molecular sieve used in Comparative Example 3 had a silicon-to-aluminum molar ratio of 120 and a columnar morphology, while the β-molecular sieve used had a silicon-to-aluminum molar ratio of 42.

[0064] Comparative Example 4

[0065] The preparation steps were the same as in Comparative Example 1, except for the molecular morphology, silicon-to-aluminum ratio, catalyst composition, preparation conditions, and reaction conditions. The comparative catalyst prepared was designated C-4, and its composition and preparation conditions are shown in Table 1. The catalyst evaluation conditions and results are shown in Table 2. The ZSM-5 molecular sieve used in Comparative Example 4 had a silicon-to-aluminum molar ratio of 120 and a columnar morphology, while the β-molecular sieve used had a silicon-to-aluminum molar ratio of 42.

[0066] Comparative Example 5

[0067] The preparation steps were the same as in Comparative Example 1, except for the molecular morphology, silicon-to-aluminum ratio, catalyst composition, preparation conditions, and reaction conditions. The comparative catalyst prepared was designated C-5, and its composition and preparation conditions are shown in Table 1. The catalyst evaluation conditions and results are shown in Table 2. The ZSM-5 molecular sieve used in Comparative Example 5 had a silicon-to-aluminum molar ratio of 120 and a columnar morphology, while the β-molecular sieve used had a silicon-to-aluminum molar ratio of 42.

[0068] Table 1 Catalyst composition and preparation conditions for each example (comparative example)

[0069]

[0070] Note: The ZSM-5 molecular sieves used in E-1 to E3 and C-1 have a silica-to-alumina molar ratio of 80, a plate-like morphology, and a β-silica-to-alumina molar ratio of 22; the ZSM-5 molecular sieves used in E-4 to E-5 and C-2 have a silica-to-alumina molar ratio of 120, a columnar morphology, and a β-silica-to-alumina molar ratio of 42; the ZSM-5 molecular sieves used in E-6 to E-7 and C-3 to C-5 have a silica-to-alumina molar ratio of 500, a plate-like morphology, and a β-silica-to-alumina molar ratio of 31. The unit is temperature * time (for example, 120 * 6 means drying at 120℃ for 6 hours). Temperature * Time

[0071] Table 2. Evaluation conditions and results of catalysts in each example (comparative example).

[0072]

[0073] As shown in Table 2, under the same process conditions, compared with the comparative catalyst, the catalyst of this invention significantly improved the conversion rate of n-heptane to low-carbon olefins by 11.8–30 percentage points, the selectivity of propylene by 8.71–22.54 percentage points, the selectivity of (ethylene + propylene) by 5.59–14.85 percentage points, and the ratio of propylene to ethylene by 0.45–1.95 in the reaction of n-heptane catalytic cracking to low-carbon olefins. The catalyst activity, the selectivity of low-carbon olefins, and the selectivity of propylene were all significantly higher than those of the comparative catalyst.

Claims

1. A catalyst for catalytic cracking to olefins, the catalyst comprising a first active center and a second active center, wherein, The first active center is a zinc-modified ZSM-5 molecular sieve; the second active center is a silver-modified β molecular sieve; based on the weight percentage of the catalyst, the ZnO content is 0.1%–5.0%, the Ag2O content is 0.1%–5.0%, the ZSM-5 molecular sieve content is 5%–80%, and the β molecular sieve content is 10%–94.8%.

2. The catalytic cracking catalyst for olefin production according to claim 1, characterized in that: Based on the weight percentage of the catalyst, the ZnO content is 0.5%–3.0%, the Ag2O content is 0.3%–2.0%, the ZSM-5 molecular sieve content is 20%–60%, and the β molecular sieve content is 35%–75%.

3. The catalytic cracking catalyst for olefin production according to claim 1, characterized in that: ZSM-5 molecular sieve is a hydrogen-type molecular sieve with a silicon-to-aluminum molar ratio of 50–1000.

4. The catalytic cracking catalyst for olefin production according to claim 1, characterized in that: β-zeolite is a hydrogen-type zeolite with a silicon-to-aluminum molar ratio of 10–100.

5. A method for preparing the catalytic cracking catalyst for olefin production according to any one of claims 1-4, the method comprising the following steps: (1) To prepare zinc-modified ZSM-5 molecular sieve, the zinc precursor was mixed with ZSM-5 molecular sieve, and then dried and calcined to obtain zinc-modified ZSM-5 molecular sieve. (2) To prepare silver-modified β-zeolite, a silver precursor was mixed with β-zeolite, and then dried and calcined to obtain silver-modified β-zeolite. (3) The zinc-modified ZSM-5 molecular sieve obtained in step (1) and the silver-modified β molecular sieve obtained in step (2) are thoroughly mixed and further shaped to obtain the catalyst.

6. The method for preparing the catalytic cracking catalyst for olefin production according to claim 5, characterized in that: The precursor of zinc is a soluble zinc-containing inorganic salt, which is selected from one or more of zinc nitrate, zinc chloride, and zinc sulfate.

7. The method for preparing the catalytic cracking catalyst for olefin production according to claim 6, characterized in that: The soluble zinc-containing inorganic salt is zinc nitrate.

8. The method for preparing the catalytic cracking catalyst for olefin production according to claim 5, characterized in that: The precursor of silver is a soluble silver-containing inorganic salt compound.

9. The method for preparing the catalytic cracking catalyst for olefin production according to claim 5 or 8, characterized in that: The precursor of silver is silver nitrate.

10. The method for preparing the catalytic cracking catalyst for olefin production according to claim 5, characterized in that: The mixing in steps (1) and (2) is performed by at least one of kneading, dipping, or spraying.

11. The method for preparing the catalytic cracking catalyst for olefin production according to claim 5, characterized in that: The mixing in steps (1) and (2) is done by kneading.

12. The method for preparing the catalytic cracking catalyst for olefin production according to claim 5, characterized in that: The drying and roasting conditions in steps (1) and (2) are the same or different. The drying temperature is 20℃~300℃ and the drying time is 0.5 hours~24 hours; the roasting temperature is 300℃~700℃ and the roasting time is 0.5 hours~12 hours.

13. The application of the catalytic cracking catalyst for olefin production according to any one of claims 1-4 or the catalytic cracking catalyst for olefin production obtained by the preparation method according to any one of claims 5-12 in the preparation of low-carbon olefins.

14. A method for catalytic cracking of alkanes to produce low-carbon olefins, wherein an alkane feedstock enters a reactor and reacts with a catalytic cracking catalyst for producing olefins, wherein the catalytic cracking catalyst for producing olefins is the catalytic cracking catalyst for producing olefins according to any one of claims 1-4 or the catalytic cracking catalyst for producing olefins obtained by the preparation method according to any one of claims 5-12.

15. The method for catalytic cracking of alkanes to produce low-carbon olefins according to claim 14, characterized in that: The alkane feedstock is one or a mixture of several C5-C9 n-alkanes.

16. The method for catalytic cracking of alkanes to produce low-carbon olefins according to claim 14, characterized in that: The alkane feedstock is n-heptane and / or n-octane.

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