Catalyst composition, method of making, apparatus for making, and method of cracking light hydrocarbons

Abstract

The application provides a preparation method of a catalyst composition, comprising the following steps: uniformly mixing MFI molecular sieve, kaolin, a binder and an optional modifier to prepare microspheres; crystallizing the microspheres under the action of a template agent, and calcining to form the catalyst composition. The application also provides the catalyst composition, its use and a reaction device for preparing the catalyst composition. In the application, the MFI molecular sieve is mixed with the kaolin, the binder and the optional modifier to prepare the microspheres, and then the microspheres are crystallized and calcined under the action of the template agent, so that active phosphorus, aluminum and silicon elements in the microspheres are crystallized to form AEL structure molecular sieve, the number of ten-membered ring one-dimensional straight pore channels of the microsphere catalyst is expanded, and the diffusion of hydrocarbon molecules is more favorable. Meanwhile, the introduction of the AEL molecular sieve also adjusts the overall acidity of the microsphere catalyst, and when the microsphere catalyst is used for light hydrocarbon cracking reaction, the yield of ethylene and propylene can be greatly improved, and the yield of aromatic hydrocarbon is also considered.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to catalyst compositions, their preparation methods, preparation apparatus, and methods for cracking light hydrocarbons. Background Technology

[0002] Low-carbon olefins such as ethylene and propylene mainly originate from steam cracking, catalytic cracking and catalytic pyrolysis, methanol-to-olefins technology, and alkane dehydrogenation technology. Among these, catalytic pyrolysis has significant advantages such as deep cracking, high olefin yield, concurrent production of aromatics, low energy consumption (compared to steam cracking), and a wide range of feedstock sources, and is gradually being promoted and applied. When light oil (C5-C8 light hydrocarbons) is used as feedstock for catalytic pyrolysis, it can not only solve its instability problem, but also produce more high-value-added products such as ethylene, propylene, and high-aromatic oils.

[0003] Catalysts are a key focus of research in light hydrocarbon cracking. ZSM-5 molecular sieves, with their suitable pore structure, moderate acidity, and excellent hydrothermal stability, are widely used in chemical engineering fields such as catalytic cracking, catalytic pyrolysis, isomerization, aromatization, and alkylation. SAPO molecular sieves, composed of PO tetrahedra, Al-O tetrahedra, and a small amount of Si-O tetrahedra, exhibit excellent thermal and hydrothermal stability and moderate acidity. SAPO-11 molecular sieves, with their one-dimensional pore structure and abundant weak acidity, demonstrate excellent diffusion performance and cracking activity when used in catalytic reactions. Patent CN 202210089239.5 discloses a composite molecular sieve catalyst for light hydrocarbon cracking that produces more low-carbon olefins. This catalyst uses LTA-type molecular sieves and commercially available MFI-type molecular sieves, employing the synergistic effect of mechanical stirring and ultrasonic mixing to achieve thorough mixing of the molecular sieves, thereby fully utilizing the advantages of each type of molecular sieve's pore structure. Patent CN 201610681973.5 discloses an in-situ synthesis method for a hierarchical porous light hydrocarbon cracking catalyst. It uses mesoporous silica microspheres as a silicon source and synthesizes a hierarchical porous molecular sieve catalyst in the presence of additives such as promoters, templates, and modifiers. Patent CN200510134602.7 discloses a core-shell molecular sieve with a SAPO-11 molecular sieve as the core and a ZSM-5 molecular sieve as the shell. The prepared molecular sieve exhibits high ethylene and propylene yields when used for light hydrocarbon cracking. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a catalyst composition, its preparation method, preparation apparatus and a method for cracking light hydrocarbons. The catalyst composition provided in this application can significantly improve the yield of ethylene and propylene when used in light hydrocarbon cracking reactions, while also taking into account the yield of aromatics.

[0005] This invention provides a method for preparing a catalyst composition, comprising the following steps:

[0006] MFI molecular sieve, kaolin, binder and optional modifier are mixed evenly to prepare microspheres; at least one of the binder and modifier contains a P source;

[0007] The microspheres are crystallized under the action of a template agent and then calcined to form a catalyst composition.

[0008] This application mixes MFI molecular sieves with raw materials suitable for preparing AEL-structured molecular sieves, such as kaolin, binders, and optional modifiers, to form microspheres. These microspheres are then crystallized and calcined under the action of a template agent, causing the active phosphorus, aluminum, and silicon elements in the MFI-rich microspheres to crystallize and form AEL-structured molecular sieves. This expands the number of ten-membered ring one-dimensional straight pores in the microsphere catalyst, which is more conducive to the diffusion of hydrocarbon molecules. Simultaneously, the introduction of AEL molecular sieves modulates the overall acidity of the microsphere catalyst, significantly increasing the yield of ethylene and propylene in light hydrocarbon cracking reactions while also maintaining the yield of aromatics. Furthermore, the preparation method provided in this application involves no separation or washing operations, generates no wastewater, and achieves high catalyst product yields. The preparation process requires only one calcination, significantly reducing energy consumption.

[0009] This invention uses MFI molecular sieves, kaolin, binders, and optional modifiers as raw materials. The MFI molecular sieve is preferably ZSM-5 molecular sieve, and the silica-to-alumina ratio of the ZSM-5 molecular sieve is 20–60. In some specific implementations, the MFI molecular sieve is H-ZSM-5 molecular sieve, with a silica-to-alumina ratio of 20–40.

[0010] In some specific implementations, the binder includes, but is not limited to, one or more of aluminum sol, silica sol, water glass, acidified boehmite, and aluminum phosphate, preferably one or more of silica sol, aluminum sol, and aluminum phosphate, more preferably a mixture of silica sol and aluminum phosphate, with a mass ratio of silica sol to aluminum phosphate of 1-2:1-2.

[0011] In some specific implementations, the modifier is a rare earth salt (Re-X), including but not limited to one or more of lanthanum chloride, lanthanum nitrate, lanthanum phosphate, cerium chloride, cerium nitrate, and cerium phosphate, preferably one or more of lanthanum phosphate and cerium phosphate. When the modifier is lanthanum phosphate and cerium phosphate, the mass ratio of lanthanum phosphate to cerium phosphate is preferably 1 to 3:1.

[0012] In some specific implementations, the template agent is an organic amine, including but not limited to one or more of di-n-propylamine and diisopropylamine.

[0013] In some specific implementations, the mass ratio of MFI molecular sieve, kaolin, binder and optional modifier is 30-50:20-40:10-30:0-5, preferably 35-45:25-35:15-25:1-3.

[0014] In some specific implementations, at least one of the binder and modifier contains a P source to form an AEL-structured molecular sieve with aluminum and silicon sources in kaolin and other raw materials during crystallization.

[0015] This application first involves uniformly mixing MFI molecular sieves, kaolin, a binder, and optionally a modifier with water. Specifically, water, the modifier, and kaolin can be mixed uniformly first, then the binder is added, and finally the MFI molecular sieve is added. The mixing is preferably carried out under high-speed stirring conditions, with a stirring speed greater than 5 rpm. In some specific implementations, the solid content in the uniformly mixed solution is 20–50%, preferably 30–40%. After uniform mixing, the resulting solution is ball-milled until the slurry D50 is < 20 micrometers, and then the slurry is formed into microspheres. In some specific implementations, the slurry is formed into microspheres by spray molding. In some specific implementations, the microspheres are fluidized bed microspheres, i.e., fluidized bed spherical catalysts, with a diameter of 20–150 micrometers, and the particle size distribution meets the requirements of conventional catalytic cracking / pyrolysis.

[0016] After obtaining the microspheres, they are crystallized and calcined under the action of a template agent, causing the active phosphorus, aluminum, silicon, and other elements in the microspheres to crystallize and form AEL-structured molecular sieves, thereby obtaining a catalyst composition containing AEL-structured molecular sieves and MFI molecular sieves. In some specific implementations, the crystallization is carried out under closed conditions at a temperature of 160–200°C for 12–48 hours. Under closed conditions, heating causes the template agent to vaporize, and self-generated pressure drives the crystallization. In some specific implementations, the crystallization temperature is 170–190°C for 15–45 hours.

[0017] After crystallization, the obtained product is calcined. In some specific implementations, the calcination is carried out in an air atmosphere at a temperature of 550–750°C for 1–4 hours. In some specific implementations, the calcination temperature is 600–700°C for 2–3 hours.

[0018] After calcination, the catalyst composition is obtained. The catalyst composition obtained by this invention is a microsphere catalyst, comprising MFI molecular sieve and AEL molecular sieve, as well as kaolin, binder, and modifier. This catalyst expands the number of ten-membered ring one-dimensional straight pores in the microsphere catalyst, which is more conducive to the diffusion of hydrocarbon molecules. At the same time, the introduction of AEL molecular sieve also modulates the overall acidity of the microsphere catalyst, which can significantly improve the yield of ethylene and propylene when used in light hydrocarbon cracking reactions, while also taking into account the yield of aromatics. Experimental results show that the catalyst provided in this application, when used for light hydrocarbon cracking / cracking, achieves ethylene and propylene yields of over 35%.

[0019] The catalyst provided in this application can catalytically crack to obtain one or a mixture of C5-C8 alkanes, olefins, and aromatics. Based on this, this application provides a method for preparing light hydrocarbons, comprising the following steps: a feedstock oil is cracked / pyrolyzed under the action of a catalyst composition prepared by the method described above, or the catalyst composition described above, to obtain light hydrocarbons. This application does not impose special limitations on the cracking / pyrolysis conditions; process parameters well known to those skilled in the art are acceptable.

[0020] This application also provides a reactor for preparing the above-mentioned catalyst composition, including a sealable reaction chamber, wherein a heating device is provided outside the reaction chamber;

[0021] The reaction chamber is equipped with a sieve, which divides the reaction chamber into a microsphere filling area and a template agent filling area, with the microsphere filling area located above the template agent filling area.

[0022] This application sets a sieve inside the reaction chamber, dividing the reaction chamber into a microsphere filling area and a template agent filling area. The template agent is vaporized under the conditions of increasing temperature and pressure, and crystallizes by uniformly contacting the microspheres through the sieve to generate AEL structure molecular sieve.

[0023] Specifically, this application involves filling a template agent into a template agent-filled region, then filling the prepared microspheres into the microsphere-filled region, sealing the reactor, and heating to carry out the reaction. In some specific implementations, the amount of template agent used is sufficient, meaning that liquid template agent still exists in the template agent-filled region at the target reaction temperature and autogenous pressure.

[0024] This application mixes MFI molecular sieves with raw materials suitable for preparing AEL-structured molecular sieves, such as kaolin, binders, and optional modifiers, to form microspheres. These microspheres are then crystallized and calcined under the action of a template agent, causing the active phosphorus, aluminum, and silicon elements in the MFI-rich microspheres to crystallize and form AEL-structured molecular sieves. This expands the number of ten-membered ring one-dimensional straight pores in the microsphere catalyst, which is more conducive to the diffusion of hydrocarbon molecules. Simultaneously, the introduction of AEL molecular sieves modulates the overall acidity of the microsphere catalyst, significantly increasing the yield of ethylene and propylene in light hydrocarbon cracking reactions while also maintaining the yield of aromatics. Furthermore, the preparation method provided in this application eliminates separation and washing operations, generates no wastewater, and achieves high catalyst product yields. The preparation process requires only one calcination, significantly reducing energy consumption. Experimental results show that the catalyst provided in this application achieves ethylene and propylene yields of over 35% in light hydrocarbon cracking / cracking. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the reactor used in the embodiments of this application. Detailed Implementation

[0026] The following examples further illustrate the catalyst composition, its preparation method, and the method for cracking light hydrocarbons provided by the present invention.

[0027] In the following embodiments, the binder was prepared as follows: 62g of aluminum source (the mass ratio of boehmite and aluminum hydroxide was 1:1) was dispersed in 120g of deionized water, and 130g of phosphoric acid was slowly added under stirring conditions to form a slurry. After standing at room temperature (25°C) for 12 hours, aluminum phosphate sol was obtained.

[0028] Example 1

[0029] See Figure 1 , Figure 1 This is a schematic diagram of the reactor used in the embodiments of this application. 1 is a closed reaction chamber. A heating device 2 is installed outside the reaction chamber 1 to heat the reaction chamber and the materials inside. A screen 3 is installed inside the reaction chamber 1, dividing the reaction chamber into two parts: an upper part is a microsphere filling area 4 for placing microspheres; and a lower part is a template agent filling area 5 for placing template agent. A feed port 6 is provided at the top of the reaction chamber 1, and a discharge port 7 is provided at the bottom of the reaction chamber 1 and above the screen 2. A purging device 8 and a gas recovery device 9 are provided at the top of the reaction chamber 1.

[0030] Microspheres are filled into microsphere filling zone 4, and template agent is filled into template agent filling zone 5. The reactor is sealed, and the heating device is turned on to vaporize the template agent. The template agent is then mixed with the microspheres through a sieve to prepare the catalyst.

[0031] Examples 2-5

[0032] According to the formula shown in Table 1, deionized water, modifier, and kaolin are stirred evenly at a speed greater than 5 rpm. Then, binder solution and MFI molecular sieve are added, mixed evenly, and ball-milled until the slurry D90 < 20 μm.

[0033] The slurry was spray-molded to produce fluidized spherical catalysts with a particle size of 20–150 micrometers. The particle size distribution met the requirements of conventional catalytic cracking / pyrolysis, and were denoted as WQ-1 to WQ-4 respectively.

[0034] WQ-1 to WQ-4 were loaded into the reactor provided in Example 1. Following the preparation conditions described in Table 2, sufficient template agent was added to the bottom of the reactor (sufficient template agent is defined as the presence of a liquid phase at the bottom of the reactor under the target reaction temperature and autogenous pressure). The reactor was sealed and heated to 180°C, then held at autogenous pressure for 24 hours. After the reaction, the microspheres were calcined at 650°C for 2 hours to obtain the catalysts, designated as S-1 to S-4.

[0035] Table 1 Formulations of the catalysts prepared in Examples 1-4

[0036]

[0037] Table 2. Preparation conditions of catalysts in Examples 1-4

[0038]

[0039] Comparative Examples 1-2

[0040] Add deionized water, modifier, and kaolin sequentially to the slurry mixing tank according to the mixing direction shown in Table 3, stir at high speed until uniform, then add the prepared binder solution, and finally add MFI molecular sieve (silicon-to-aluminum ratio 25) and AEL molecular sieve (P2O5:Al2O3:SiO2=1:1:0.3), mix evenly, and ball mill until the slurry D90 < 20 microns;

[0041] The slurry was spray-molded and calcined at 650℃ for 2 hours to produce fluidized spherical catalysts with a particle size of 20-150 micrometers. The particle size distribution met the requirements of conventional catalytic cracking / pyrolysis, and were denoted as D-1 to D-2 respectively.

[0042] Comparative Example 3

[0043] The microspheres WQ-1 prepared in Example 2 were calcined at 650°C for 2 hours to obtain catalyst D-3.

[0044] Comparative Example 4

[0045] The microspheres WQ-4 prepared in Example 5 were calcined at 650°C for 2 hours to obtain catalyst D-4.

[0046] Table 3. Slurry composition of Comparative Examples 1-4 (based on dry weight)

[0047]

[0048] Performance testing: The catalyst performance of the example was tested in a fixed fluidized bed apparatus under the following conditions: 1) Catalyst loading: 200g; 2) Feed rate: 2.0g / min; 3) Feed time: 10min; 4) Steam dilution ratio: 1; 5) Reaction temperature: 650℃; 6) Raw material properties (see Table 4).

[0049] Table 4. Physical Properties of Raw Oil

[0050]

[0051] The results are shown in Table 5, which presents the physical properties and catalytic performance of the catalysts prepared in the examples and comparative examples of this application.

[0052] Table 5. Catalyst properties and catalytic performance

[0053]

[0054] As shown in Table 5, after the "recrystallization" process, molecular sieves with an AEL structure were introduced in Examples 2-5. Simultaneously, the specific surface area and pore volume were significantly improved compared to Comparative Examples 1-4. This indicates that the embodiments of the present invention have a significantly better effect on increasing specific surface area and pore volume than directly mixing two types of molecular sieves (Comparative Examples 1 and 2). Regarding catalytic performance, the highest diene yield in the embodiments was 35.78% (Example 4), and the lowest was 35.21% (Example 3). The highest diene yield in the comparative examples was 32.34%. The sample samples in the embodiments have a significant advantage in diene yield.

[0055] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing light hydrocarbons, comprising the following steps: The feedstock oil is cracked / pyrolyzed under the action of a catalyst composition to obtain light hydrocarbons; The catalyst composition is obtained by crystallizing and calcining microspheres prepared from MFI molecular sieve, kaolin, binder and modifier under the action of template agent to form AEL molecular sieve, and the catalyst composition contains AEL molecular sieve and MFI molecular sieve. The crystallization is carried out under sealed conditions at a temperature of 160~200℃ for 12~48h. Under sealed conditions, the template agent is vaporized by heating and crystallization is carried out by self-generated pressure. At least one of the binder and modifier contains a P source; The modifier is a rare earth salt; The template agent is selected from one or more of di-n-propylamine and diisopropylamine.

2. The preparation method according to claim 1, characterized in that, The MFI molecular sieve is a ZSM-5 molecular sieve, and the silica-alumina ratio of the ZSM-5 molecular sieve is 20~60; The binder is selected from one or more of aluminum sol, silica sol, water glass, acidified pseudoboehmite, and aluminum phosphate.

3. The preparation method according to claim 2, characterized in that, The rare earth salts are selected from one or more of lanthanum chloride, lanthanum nitrate, lanthanum phosphate, cerium chloride, cerium nitrate, and cerium phosphate.

4. The preparation method according to claim 2, characterized in that, The mass ratio of MFI molecular sieve, kaolin, binder and modifier is 30~50:20~40:10~30:0~5, wherein the amount of modifier is not 0.

5. The preparation method according to claim 2, characterized in that, The microspheres are fluidized microspheres with a diameter of 20-150 micrometers.

6. The preparation method according to claim 2, characterized in that, The calcination is carried out in an air atmosphere at a temperature of 550~750℃ for 1~4 hours.

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