Catalytic cracking catalyst, process for its preparation and use

Abstract

The application discloses a catalytic cracking catalyst and a preparation method and application thereof, and belongs to the technical field of catalytic materials. The catalytic cracking catalyst adopts intermittent hydrothermal treatment, and "dealuminization and rare earth supplement" of MFI type and FAU type molecular sieves are completed. The MFI and FAU type molecular sieves can occur dealuminization under high-temperature steam conditions. The removed aluminum ions are combined with phosphate ions in a rare earth phosphate modifier to generate new second binder aluminum phosphate, improve the strength of the catalyst, increase the specific surface area and medium-large pore channels of the catalyst, reduce the attrition index of the catalyst, promote the cracking reaction of macromolecular hydrocarbon compounds, and improve the selectivity of cracking products ethylene and propylene.

Description

Technical Field

[0001] This invention relates to the field of catalytic materials technology, and in particular to a catalytic cracking catalyst, its preparation method, and its application. Background Technology

[0002] Ethylene and propylene, as basic chemical raw materials, are facing increasing market demand. Their sources are primarily coal and oil. However, with the depletion of fossil fuels, refining enterprises are increasingly adopting heavier feedstock processes. Researchers have successively developed catalytic cracking technologies such as DCC, MCP, DCC-PLUS, and RTC, which can gradually upgrade refining feedstocks to include wax oil blended with some residual oil. Simultaneously, the transition from crude oil processing to energy fuel production to chemical feedstock production is an inevitable trend. Catalytic cracking, which yields high levels of low-carbon olefins and high-aromatic oils, has become a core technology for crude oil-to-chemicals feedstock production.

[0003] According to publicly available information, patents CN107971011B, CN112138710B, CN101722036B, CN102371171A, and CN114797962A provide a method for preparing a catalytic cracking catalyst. The core idea is to combine Y-type molecular sieves and shape-selective molecular sieves (ZSM-5) to achieve cracking and increased olefin production by utilizing the advantages of both. Patent CN113355126A uses Y-type molecular sieves, macroporous alumina, and P-ZSM-5 to prepare a mixed catalyst for the selective cracking of heavy and light components in crude oil. Patent CN113385223A uses Y-type molecular sieves and phosphorus / zirconium-modified ZSM-5 molecular sieves as active components to prepare a catalyst for catalytic cracking of crude oil to increase low-carbon olefin production. Patent CN114425417A discloses a core-shell structure catalyst with ZSM-5 molecular sieve as the core phase and β molecular sieve as the shell phase; Patent CN101491772A discloses a cracking catalyst with ZSM-5 and mordenite, β zeolite and Y-type zeolite as the active components.

[0004] However, in the aforementioned patents, the preparation process all uses a large amount of binder, resulting in the loss of active components. In some schemes, the molecular sieve needs to be modified beforehand, making the preparation process complex and resulting in products with poor strength. Furthermore, the prepared catalysts do not simultaneously possess abundant mesoporous to macroporous structures and highly efficient selectivity for low-carbon olefins and aromatics. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a catalytic cracking catalyst, its preparation method, and its application. The catalytic cracking catalyst is subjected to intermittent hydrothermal treatment to complete the "dealuminization and rare earth replenishment" of MFI and FAU type molecular sieves, producing a new second binder, aluminum phosphate, which improves the catalyst's strength, increases its specific surface area and meso-macro pore size, and reduces the catalyst's attrition index.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] This invention provides a method for preparing a catalytic cracking catalyst, comprising the following steps:

[0008] 1) Mix MFI type and FAU type molecular sieves, rare earth phosphate modifier, first binder and carrier in water to obtain mixed solution S1;

[0009] 2) The above mixed solution S1 is spray-formed and then subjected to a first calcination to obtain a microsphere-shaped catalyst precursor;

[0010] 3) The above catalyst precursor is subjected to intermittent hydrothermal treatment to obtain a catalytic cracking catalyst;

[0011] During the intermittent hydrothermal treatment process, aluminum ions in the molecular sieve are removed and combine with phosphate ions from the rare earth phosphate modifier to form a second binder, aluminum phosphate.

[0012] The production of the second binder increases the strength of the catalyst, reduces the need for the first binder, and lowers production costs.

[0013] The solid content in the above mixed solution S1 is preferably 25 wt% to 50 wt%; more preferably 30 wt% to 50 wt%; and even more preferably 40 wt% to 50 wt%.

[0014] In the above preparation method, step 2) involves slurrying the mixed solution S1, followed by spray molding and low-temperature calcination to obtain a firmly bonded microsphere catalyst precursor.

[0015] The microsphere catalyst precursor comprises MFI-type and FAU-type molecular sieves supported on rare earth metal oxides, a first binder, and a support. The microsphere particle size of the microsphere catalyst precursor conforms to the standard for catalytic cracking catalysts.

[0016] Preferably, the conditions for the intermittent hydrothermal treatment in step 3) of this invention are as follows:

[0017] The preferred mass hourly space velocity (MSV) for water vapor is 0.01–10 h⁻¹. -1 More preferably, 0.02–2h -1 .

[0018] The preferred hydrothermal treatment temperature is 400℃~800℃; more preferably 500℃~700℃.

[0019] The preferred hydrothermal treatment time is 0.1 to 1 hour.

[0020] The preferred roasting temperature is 400℃~800℃; more preferably 500℃~700℃.

[0021] The preferred roasting time is 0.1 to 1 hour.

[0022] The number of interruptions (pulses) is preferably 1 to 100 times; more preferably 1 to 10 times.

[0023] The aforementioned interruption time and number of interruptions refer to the cycle time and number of cycles of hydrothermal treatment and calcination as a single cycle.

[0024] This invention achieves "dealuminization and rare earth replenishment" through the above-mentioned intermittent (pulse) hydrothermal treatment, which allows the aluminum ions removed from the molecular sieve to combine with the phosphate ions in the modifier to generate the second binder, aluminum phosphate, thus preparing a catalytic cracking catalyst with high active component content, stronger adhesion, and low amount of the first binder.

[0025] Preferably, the MFI type molecular sieve of the present invention is ZSM-5 molecular sieve;

[0026] Preferably, the FAU-type molecular sieve is selected from the Y-type molecular sieve.

[0027] Preferably, the molar ratio of silicon dioxide to aluminum oxide in the ZSM-5 molecular sieve is (20-40):1; more preferably, it is (25-35):1.

[0028] Preferably, the sodium oxide content in the ZSM-5 molecular sieve is less than 0.1 wt%.

[0029] Preferably, the molar ratio of silicon dioxide to aluminum oxide in the Y-type molecular sieve is (3-7.5):1; more preferably (3.5-6.5):1.

[0030] Preferably, the sodium oxide content in the Y-type molecular sieve is less than 0.1 wt%.

[0031] Preferably, the temperature of the first roasting in step 2) of the present invention is 300℃~800℃; more preferably, it is 500℃~700℃.

[0032] Preferably, the first roasting time is 0.5 to 2 hours.

[0033] Preferably, the mass ratio of the total weight of the MFI and FAU type molecular sieves to the rare earth phosphate modifier is (10-40):(1-30); more preferably, it is (15-35):(3-25). In some specific embodiments of the present invention, the mass ratio of the total weight of the MFI and FAU type molecular sieves to the rare earth phosphate modifier is 38:6, 37:6, 39:4, or 36:6.

[0034] Preferably, the mass ratio of the total weight of the MFI and FAU type molecular sieves to the first binder is (10-40):(5-30); more preferably (20-40):(5-20); and even more preferably (30-40):(10-20). In some specific embodiments of the present invention, the mass ratio of the total weight of the MFI and FAU type molecular sieves to the first binder is 38:11, 37:14, 39:14, or 36:16.

[0035] Preferably, the mass ratio of the carrier to the total weight of the MFI and FAU molecular sieves is (20-60):(10-40); more preferably (40-60):(30-40). Even more preferably (40-50):(35-40). In some specific embodiments of the present invention, the mass ratio of the carrier to the total weight of the MFI and FAU molecular sieves is 45:38, 43:37, 43:39, or 42:36.

[0036] In the preparation method described in this invention, the molecular sieve is selected from MFI type molecular sieve and / or FAU type molecular sieve.

[0037] Preferably, the mass ratio of the MFI type molecular sieve to the FAU type molecular sieve is (0-100):(0-100), and neither of them can be 0 at the same time.

[0038] In some specific embodiments of the present invention, the molecular sieve is preferably an MFI type molecular sieve or a FAU type molecular sieve. The MFI type molecular sieve is selected from ZSM-5 molecular sieve, and the FAU type molecular sieve is selected from Y-type molecular sieve.

[0039] Preferably, the first adhesive is selected from one or more of aluminum sol, silica sol, water glass, acidified boehmite, and aluminum phosphate; more preferably, it is selected from one or more of aluminum sol, acidified boehmite, and aluminum phosphate; and even more preferably, it is selected from aluminum sol and / or aluminum phosphate.

[0040] The preferred mass ratio of the aluminum sol to the aluminum phosphate is (0-10):(3-20); more preferably (0-8):(3-15). In some specific embodiments of the present invention, the mass ratio of the aluminum sol to the aluminum phosphate is 8:3, 4:10, 0:14, or 4:12.

[0041] Preferably, the rare earth phosphate modifier is selected from lanthanum phosphate and / or cerium phosphate.

[0042] The preferred mass ratio of lanthanum phosphate to cerium phosphate is (0-10):(0-6). In some specific embodiments of the present invention, the mass ratio of lanthanum phosphate to cerium phosphate is 6:0, 2:4, 0:4, or 2:4.

[0043] Preferably, the carrier is selected from kaolin and / or montmorillonite; more preferably, it is kaolin.

[0044] The present invention also provides a catalytic cracking catalyst, which is prepared by the above-described method for preparing catalytic cracking catalysts.

[0045] Preferably, the meso-macro pore volume of the catalytic cracking catalyst is ≥0.17 mL / g.

[0046] The catalyst is prepared by intermittent (pulsed) hydrothermal treatment. It has a high specific surface area and abundant meso-macropore structure, which is conducive to the diffusion of macromolecular reactants and their products, thereby promoting catalytic cracking reaction.

[0047] In this invention, the content of key elements in the catalyst is obtained by normalizing the catalyst according to its oxides as follows:

[0048] Preferably, in the catalyst of the present invention, the content of each component includes:

[0049] Alumina: 10wt%~50wt%;

[0050] Silica: 40wt%~80wt%;

[0051] Phosphorus pentoxide: 2wt%~20wt%;

[0052] Rare earth metal oxides: 0–10 wt%;

[0053] Other: 0-2 wt%.

[0054] More preferably, the content of each component in the above catalyst includes:

[0055] Alumina: 15wt%~45wt%;

[0056] Silica: 45wt%~70wt%;

[0057] Phosphorus pentoxide: 2wt%~20wt%;

[0058] Rare earth metal oxides: 0–8 wt%;

[0059] Other: 0-2 wt%.

[0060] More preferably, the content of each component in the above catalyst includes:

[0061] Alumina: 20wt%~40wt%;

[0062] Silica: 45wt%~65wt%;

[0063] Phosphorus pentoxide: 2wt%~20wt%;

[0064] Rare earth metal oxides: 0–8 wt%;

[0065] Other: 0-2 wt%.

[0066] In the above catalyst component content, other components represent impurities introduced into the raw materials used to prepare the catalyst, such as iron, nickel, titanium, zirconium, chloride ions, sulfate ions, etc. in kaolin.

[0067] The present invention also provides the catalytic cracking catalyst prepared by the above preparation method or the application of the above catalytic cracking catalyst in the catalytic cracking reaction of feedstock oil.

[0068] The raw material oil includes C8 to C96 oils. 50 Aromatics, C8-C 50 Olefins, C8-C 50 Alkanes, C8-C 50 One or more of the cycloalkanes. The C8-C9 series... 50 Aromatic hydrocarbons are preferably C8-C9. 30 Aromatic hydrocarbons.

[0069] The C8~C 50 The preferred olefins are C8 to C9. 30 Olefins.

[0070] The C8~C 50 The alkanes are preferably C8 to C9. 30 Alkanes.

[0071] The C8~C 50 The cycloalkanes are preferably C8-C96. 30 Cycloalkanes.

[0072] The order of difficulty of the above catalytic cracking reactions is C8 to C8. 50 Olefins > C8~C 50 Alkanes > C8~C 50 Cycloalkanes > C8~C 50 Aromatic hydrocarbons.

[0073] The catalyst described in this invention is applied to the above-mentioned macromolecular hydrocarbons (C8-C9). 50 Aromatics, C8-C 50Olefins, C8-C 50 Alkanes or C8-C 50 In the catalytic cracking reaction of cycloalkanes, highly selective low-carbon olefins and aromatics are prepared.

[0074] In some specific embodiments of the present invention, the catalyst is used in a product containing C8 to C96. 30 n-Alkanes, C8-C 30 Isoalkanes, C8-C 30 Aromatics, C8-C 30 Olefins, C8-C 30 In the feedstock oil of cycloalkane, the total content of ethylene and propylene in the catalytic cracking reaction products is relatively high, ranging from 32.8% to 35.2%.

[0075] Compared with existing technologies, this invention provides a catalytic cracking catalyst, its preparation method, and its applications. The catalytic cracking catalyst of this invention employs intermittent hydrothermal treatment to complete the "dealuminization and rare earth replenishment" of MFI and FAU type molecular sieves. The MFI and FAU type molecular sieves of this invention can undergo dealuminization under high-temperature steam conditions. The removed aluminum ions combine with phosphate ions in the rare earth phosphate modifier to produce a new second binder, aluminum phosphate, which improves the catalyst's strength, increases its specific surface area and meso-macropore channels, reduces the catalyst's attrition index, promotes the cracking reaction of macromolecular hydrocarbons, and improves the selectivity of cracking products ethylene and propylene. Attached Figure Description

[0076] Figure 1 is a scanning electron microscope (SEM) image of the catalytic cracking catalyst prepared in Example 2. Figures 1-a & 1-b are SEM images of the catalytic cracking catalyst before intermittent (pulse) hydrothermal treatment. Figures 1-c & 1-d are SEM images of the catalytic cracking catalyst after intermittent (pulse) hydrothermal treatment. Detailed Implementation

[0077] To further illustrate the present invention, the catalytic cracking catalyst, its preparation method, and its application provided by the present invention are described in detail below with reference to embodiments.

[0078] In this embodiment of the invention, the molar ratio of silicon oxide to aluminum oxide in the ZSM-5 molecular sieve is selected as 28:1, and the sodium oxide content is 0.05wt%; the molar ratio of silicon oxide to aluminum oxide in the Y-type molecular sieve is 5.6:1, and the sodium oxide content is 0.1wt%.

[0079] Examples 1-4

[0080] Following conventional slurry preparation methods, the binder and carrier were dispersed in deionized water and rapidly stirred until homogeneous. Then, a modifier and two types of molecular sieves were added and stirred until homogeneous again. After grinding, a mixed slurry was obtained. The slurry composition is shown in Table 1. The slurry was spray-formed (spraying conditions: 1) drying tower inlet temperature 360–380℃; 2) drying tower outlet temperature 120–130℃; 3) drying evaporation rate: 1.2 kg / h; 4) feed rate: 3 kg / h) to obtain microspheres with a particle size of 20–150 micrometers. The microspheres were calcined at 600℃ for 1 hour to obtain a microsphere catalyst for catalytic cracking. The microsphere catalyst was subjected to intermittent (pulse-type) hydrothermal treatment in a tubular furnace under the following conditions: 1) space velocity: 0.1 h⁻¹. -1 2) Temperature: 560℃; 3) Processing time: 0.3h; 4) Calcination temperature: 650℃; 5) Calcination time: 0.5h; 6) Number of intermittent (pulse) cycles: 4. After intermittent (pulse) hydrothermal treatment, the catalytic cracking catalyst of the present invention is obtained.

[0081] Figure 1 shows a scanning electron microscope image of the catalytic cracking catalyst prepared in Example 2. Before intermittent (pulsed) hydrothermal treatment (Figure 1-a & b), the catalyst surface was smooth with no obvious pores. After intermittent (pulsed) hydrothermal treatment (Figure 1-c & d), obvious channels appeared on the surface of the catalyst microspheres, increasing the pore volume and specific surface area of ​​the catalyst (see Table 2), which is more conducive to the diffusion of macromolecules into the interior of the spheres.

[0082] Comparative Example 1

[0083] The method is the same as in Examples 1-4, except that no modifier is added.

[0084] Comparative Example 2

[0085] The method and detailed composition of the slurry were the same as those in Comparative Example 1. The difference was that intermittent (pulsed) hydrothermal treatment was not used. Instead, the microspheres were calcined at 650°C for 2 hours to prepare the catalyst.

[0086] Comparative Example 3

[0087] The method and detailed composition of the slurry were the same as in Example 1, except that intermittent (pulsed) hydrothermal treatment was not used. Instead, the microspheres were calcined at 650°C for 2 hours to prepare the catalyst.

[0088] Performance testing

[0089] The catalyst performance of the example was tested in a fixed fluidized bed apparatus under the following conditions: 1) Catalyst loading: 100 g; 2) Feed rate: 2.5 g / min; 3) Feed time: 10 min; 4) Steam dilution ratio: 1; 5) Reaction temperature: 650 °C; 6) Raw material properties (see Table 3). The test results are shown in Table 4.

[0090] Table 1. Detailed composition of slurries and catalyst particle size of Examples 1-4 and Comparative Examples 1-3 (based on dry weight).

[0091]

[0092] Table 2. Physical properties of Examples 1-4 and Comparative Examples 1-3 before and after intermittent (pulse-type) hydrothermal treatment.

[0093]

[0094]

[0095] In Comparative Example 1, without the addition of a modifier, the increase in the volume of meso-macro pores of the catalyst after intermittent (pulse) hydrothermal treatment was not significant. However, in Examples 1-4, not only did the volume of meso-macro pores increase significantly, but the wear index also decreased substantially. This indicates that the addition of the modifier produced a new binder, aluminum phosphate, and at the same time, new meso-macro pores were generated. As a result, the catalysts prepared in Examples 1-4 had higher strength and better catalytic effect.

[0096] Comparative Example 2, without the addition of a modifier and without intermittent (pulsed) hydrothermal treatment, showed almost no change in wear index, specific surface area (BET), and meso-macro pore volume compared to Comparative Example 1. This indicates that the present invention requires both a modifier and intermittent (pulsed) hydrothermal treatment to achieve its intended effects, namely, reducing the wear index, increasing the specific surface area, and increasing the meso-macro pore volume.

[0097] Comparative Example 3 had a modifier added, but no intermittent (pulsed) hydrothermal treatment was used. Compared with Example 1, it had a higher wear index, smaller specific surface area (BET), smaller medium-to-large pore volume, and worse overall physical properties.

[0098] Table 3 Physical properties of crude oil

[0099]

[0100]

[0101] The above-mentioned feedstock oils contain n-alkanes, isoalkanes, aromatics, alkenes, and cycloalkanes, all of which are C8 to C9. 30 Large molecular hydrocarbon compounds.

[0102] Table 4 Catalytic performance of the sample and contrast agent sample in the examples

[0103]

[0104] In summary, the results show that after intermittent (pulse-type) hydrothermal treatment, obvious large pores appear on the catalyst surface, which is beneficial for C8-C6 catalysts. 50 The diffusion of aromatic hydrocarbons, alkenes, alkanes or cycloalkanes reactants and their cracking products promotes the cracking reaction, thereby resulting in a high yield of dienes (i.e. ethylene and propylene) (35.2%).

[0105] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A process for the preparation of a catalytic cracking catalyst, characterized in that, The preparation method comprises the following steps: 1) mixing MFI type and FAU type molecular sieves, rare earth phosphate modifier, first binder and carrier in water to obtain a mixed solution S1; 2) spray forming the mixed solution S1 and then performing first calcination to obtain a microspherical catalyst precursor; 3) performing intermittent hydrothermal treatment on the catalyst precursor to obtain a catalytic cracking catalyst; During the intermittent hydrothermal treatment, aluminum ions in the molecular sieves are removed and combined with phosphate ions of the rare earth phosphate modifier to form a second binder aluminum phosphate; The conditions of the intermittent hydrothermal treatment in step 3) are as follows: water vapor mass space velocity of 0.01 to 10 h -1 ; The hydrothermal treatment temperature is 400-800 ℃; The hydrothermal treatment time is 0.1-1 h; The calcination temperature is 400-800 ℃; The calcination time is 0.1-1 h; The pulse number is 1-100.

2. The production method according to claim 1, characterized by, The MFI type molecular sieve is selected from ZSM-5 molecular sieves; The FAU type molecular sieve is selected from Y type molecular sieves.

3. The preparation method according to claim 2, characterized in that, The molar ratio of silicon oxide to aluminum oxide in the ZSM-5 molecular sieve is (20-40):1; The sodium oxide content in the ZSM-5 molecular sieve is less than 0.1 wt%.

4. The preparation method according to claim 2, characterized in that, The molar ratio of silicon oxide to aluminum oxide in the Y type molecular sieve is (3-7.5):1; The sodium oxide content in the Y type molecular sieve is less than 0.1 wt%.

5. The preparation method according to claim 1, characterized in that, The first calcination temperature in step 2) is 300-800 ℃; The first calcination time is 0.5-2 h.

6. The method of claim 1, wherein, The mass ratio of the total weight of the MFI type and FAU type molecular sieves to the rare earth phosphate modifier is (10-40):(1-30); The mass ratio of the total weight of the MFI type and FAU type molecular sieves to the first binder is (10-40):(5-30); The mass ratio of the total weight of the carrier to the MFI type and FAU type molecular sieves is (20-60):(10-40); The mass ratio of the MFI type molecular sieve to the FAU type molecular sieve is (0-100):(0-100), and both cannot be 0 at the same time.

7. The preparation method according to claim 1, characterized in that, The first binder is selected from one or more of aluminum sol, silicon sol, water glass, acidified pseudo-boehmite and aluminum phosphate salt; The rare earth phosphate modifier is selected from lanthanum phosphate and / or cerium phosphate; The carrier is selected from kaolin and / or montmorillonite.

8. A catalytic cracking catalyst characterized by, The catalytic cracking catalyst is prepared by the preparation method in any one of claims 1-7; The meso-macropore volume of the catalytic cracking catalyst is ≥0.17 mL / g.

9. Application of the catalytic cracking catalyst prepared by the preparation method in any one of claims 1-7 or the catalytic cracking catalyst in claim 8 in a catalytic cracking reaction of raw oil. The feed oil includes one or more of C8to C 50 aromatic hydrocarbons, C8to C 50 olefins, C8to C 50 alkanes, C8to C 50 naphthenes.

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