Naphtha catalytic cracking agent material, preparation method and application

Abstract

The application discloses a naphtha catalytic cracking agent material, a preparation method and application, and belongs to the field of petroleum chemical catalytic materials. The method uses a thiourea micelle as a sacrificial template, constructs a core-shell precursor through a SiO2 shell, and then is cross-linked and loaded with ZSM-5 molecular sieves with a silicon-aluminum ratio of 20-25, so that a high-connection multi-level pore composite structure is formed after sintering. The application solves the pain points of traditional cracking agent, such as isolated pores, blocked mass transfer and easy carbon deposition and collapse, improves the mass transfer efficiency and the exposure amount of active sites through the multi-level pore structure, enhances the cross-linking of ZSM-5 molecular sieves through the outer SiO2, and enhances the structural stability through the inner SiO2 shell. The cracking agent is applied under the conditions of 600 DEG C, 0.2 MPa and a catalyst-oil ratio of 5:1, the initial conversion rate of naphtha is higher than 85%, the carbon deposition amount is low after 5 cycles, the preparation process is simple and controllable, and the application is suitable for industrial production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of petrochemical catalytic materials, and particularly relates to a naphtha catalytic cracking agent material, a preparation method and application. BACKGROUND

[0002] Light olefins (ethylene, propylene) are the core platform chemicals of modern petrochemical industry, and are widely used in the production of terminal products such as polyethylene, polypropylene and synthetic rubber. The naphtha catalytic cracking process has become the current mainstream production technology due to its strong adaptability to raw materials and high light olefin yield. The structure and catalytic performance of the catalytic cracking agent, as the core of the process, directly determine the product yield and raw material conversion rate.

[0003] The existing naphtha catalytic cracking agent mostly uses ZSM-5 molecular sieve as the active component, but there are significant technical bottlenecks: the pore structure of the traditional molecular sieve-based cracking agent is dense, the porosity is insufficient, and the pores are isolated and poorly connected, which leads to mass transfer resistance of naphtha macromolecules in the pore channel, easy carbon deposition and plugging, and reduces the catalytic efficiency and catalyst life. At the same time, the molecular sieve particles are prone to agglomeration, and the active sites are not exposed enough, which further limits the improvement of catalytic performance.

[0004] In order to improve the pore structure, the industry often uses organic polymers as pore-forming agents, but there are compatibility problems: the organic polymer (such as polyvinyl alcohol, polyethylene glycol) and the molecular sieve precursor solution (hydrophilic) have poor compatibility due to the difference in polarity, which easily causes the pore-forming agent to agglomerate, stratify or precipitate, and cannot be uniformly embedded in the precursor system. The final pore structure is chaotic and unstable, and the mechanical strength is insufficient, which easily causes pore collapse under the high temperature and high pressure conditions of catalytic reaction.

[0005] Therefore, it is necessary to develop a catalytic cracking agent with high pore connectivity, high active site exposure and excellent structural stability, which realizes the cooperation of pore forming and support through the design of core-shell structure, solves the problems of mass transfer limitation, agglomeration and structure collapse, and becomes the key to upgrading the naphtha catalytic cracking process. SUMMARY

[0006] In order to overcome the drawbacks of the prior art, the present application provides a naphtha catalytic cracking agent material, a preparation method and application. By constructing a thiourea micelle core and a SiO2 shell and a functionalized SiO2 structure, gasification pore forming, cross-linking and stability are realized, a high-connectivity, anti-collapse multi-level pore structure is realized, and the mass transfer efficiency, catalytic activity and structural stability are simultaneously improved.

[0007] To achieve the above purpose, the present application provides the following technical scheme:

[0008] A preparation method of a naphtha catalytic cracking agent material, comprising the following steps:

[0009] S1, thiourea micellar microspheres preparation: 0.8~1.5g thiourea is dissolved in 10~15mL deionized water, heated to 40~50℃ stirring dissolution, slowly drop 3~5mL sodium dodecyl sulfate aqueous solution (5% mass fraction), constant temperature stirring 60~90min, form uniform dispersion of thiourea micellar microspheres;

[0010] S2, precursor preparation: the thiourea micellar microspheres of step S1 are dispersed in 30~60mL anhydrous ethanol, ultrasonic dispersion 30~40min; first add 0.6~2mL tetraethyl orthosilicate, stirring 30min after drop 2~4mL ammonia water (25% mass fraction), reaction at 30~40℃ for 5~12h, form inner layer SiO2 shell; continue to add 0.5~1mL N-[3-(trimethoxysilyl)propyl]ethylenediamine (silicon source), heated to 45~55℃ reaction 5~12h, build outer layer functionalized SiO2, obtain precursor;

[0011] S3, active component loading and crosslinking: 30~45 mass parts ZSM-5 molecular sieve (silicon aluminum ratio = 20~25, molar ratio of SiO2 and Al2O3) is added to deionized water to form a dispersion (solid-liquid mass ratio 1:10~15), ultrasonic dispersion 30~40min; the core-shell structure precursor is slowly added to the ZSM-5 dispersion, stirring at 55~65℃, 400~600r / min for 1.5~2h, through the outer layer SiO2 and ZSM-5 surface hydroxyl crosslinking, realize the firm combination of active component and core-shell structure;

[0012] S4, sintering: the above mixed system is transferred to a ceramic crucible, first heated to 500~600℃ at a rate of 10℃ / min, and kept for 1~2h, so that the thiourea core is gasified and volatilized to form a hollow pore, and then ground into a powder after cooling to obtain a catalytic cracking agent.

[0013] According to the above method, a naphtha catalytic cracking agent material is obtained.

[0014] The application also provides the application of the above-mentioned naphtha catalytic cracking agent material in the catalytic cracking of naphtha to produce light olefins, and the specific application method is: the catalytic cracking agent and naphtha are added into a catalytic cracking reactor at a ratio of 5:1, and the catalytic cracking reaction is carried out at a reaction temperature of 600℃ and a reaction pressure of 0.2MPa, and then the products are collected and separated to obtain ethylene and propylene.

[0015] The application has the following beneficial effects

[0016] (1) By gasifying the thiourea micelles to form a "macropore-micropore" connected multi-level pore structure, the problem of isolated pores in traditional ZSM-5 is solved, and the mass transfer of naphtha molecules is accelerated; at the same time, the agglomeration of molecular sieve is inhibited, and the exposure amount of active sites is increased, and the initial conversion rate of the embodiment is more than 85%, which is significantly higher than that of the comparative example.

[0017] (2) The outer layer of SiO2 enhances the cross-linking of ZSM-5 molecular sieve, and the inner layer of SiO2 shell enhances the structural stability to avoid pore collapse under high temperature and high pressure; the high connectivity of the pore channels reduces the carbon deposition blockage, and the amount of carbon deposition is only 13.7% after 5 cycles.

[0018] (3) Thiourea has good compatibility with the precursor, the preparation steps are mature processes, the raw materials are easy to obtain, the parameters are controllable, no special equipment is needed, and the process is suitable for industrial production.

[0019] (4) The ZSM-5 crystal form in the catalytic cracking agent material is kept intact, and the conversion rate is increased by more than 20% compared with the ZSM-5 catalyst. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a transmission electron microscope photo of the catalytic cracking agent material prepared in Example 1;

[0021] Figure 2 is an XRD diffraction spectrum of the catalytic cracking agent material, SiO2 and ZSM-5 prepared in Example 1;

[0022] Figure 3 is a N2 adsorption-desorption isotherm of the catalytic cracking agent material prepared in Example 1 and Comparative Examples 1-4;

[0023] Figure 4 is a curve of the instantaneous conversion rate of the catalytic cracking agent material prepared in Example 1 and Comparative Examples 1-4 after application versus time.

[0024] Figure 5 is a thermogravimetric analysis curve of the catalytic cracking agent material prepared in Example 1 and Comparative Example 2 after 5 cycles. DETAILED DESCRIPTION

[0025] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below. The following content is only an example and description of the concept of the present application, and those skilled in the art can make various modifications or supplements to the described specific implementation cases or use similar ways instead, as long as they do not deviate from the concept of the present application, which shall belong to the protection scope of the present application.

[0026] The above preparation method of the present application will be described below through specific examples and comparative examples.

[0027] Example 1

[0028] S1. Thiourea micellar microspheres preparation: 0.8 g of thiourea was dissolved in 10 mL of deionized water, stirred to dissolve at 40℃, 3 mL of 5% sodium dodecyl sulfate aqueous solution was added dropwise, constant temperature stirring for 60 min, and thiourea micellar microspheres were obtained;

[0029] S2. Preparation of core-shell structure precursor: the micellar microspheres were dispersed in 30 mL of anhydrous ethanol and ultrasonicated for 30 min; 0.6 mL of tetraethyl orthosilicate was added, stirred for 30 min, and then 2 mL of ammonia water was added dropwise, and reacted at 30℃ for 5 h; 0.5 mL of N-[3-(trimethoxysilyl)propyl]ethylenediamine was added, and reacted at 45℃ for 5 h to obtain the core-shell structure precursor;

[0030] S3. Active component loading and crosslinking: 30 parts by mass of ZSM-5 molecular sieve was prepared into a dispersion (solid-liquid ratio 1:10) and ultrasonicated for 30 min; the core-shell structure precursor was added, and stirred at 55℃ and 400 r / min for 1.5 h;

[0031] S4, sintering: the above-mentioned mixed system was transferred to a ceramic crucible, first heated to 500℃ at a rate of 10℃ / min, and kept for 1 h to make the thiourea core gasify and volatilize, form hollow pores, and then ground into powder after cooling to obtain the catalytic cracking agent.

[0032] Example 2

[0033] S1. Thiourea micellar microspheres preparation: 1.2 g of thiourea was dissolved in 12 mL of deionized water, stirred to dissolve at 45℃, 4 mL of 5% sodium dodecyl sulfate aqueous solution was added dropwise, constant temperature stirring for 75 min, and thiourea micellar microspheres were obtained;

[0034] S2. Preparation of core-shell structure precursor: the micellar microspheres were dispersed in 45 mL of anhydrous ethanol and ultrasonicated for 35 min; 1.3 mL of tetraethyl orthosilicate was added, stirred for 30 min, and then 3 mL of ammonia water was added dropwise, and reacted at 35℃ for 8 h; 0.8 mL of N-[3-(trimethoxysilyl)propyl]ethylenediamine was added, and reacted at 50℃ for 8 h to obtain the core-shell structure precursor;

[0035] S3. Active component loading and crosslinking: 38 parts by mass of ZSM-5 molecular sieve was prepared into a dispersion (solid-liquid ratio 1:12) and ultrasonicated for 35 min; the core-shell structure precursor was added, and stirred at 60℃ and 500 r / min for 1.8 h;

[0036] S4, sintering: the above-mentioned mixed system was transferred to a ceramic crucible, first heated to 550℃ at a rate of 10℃ / min, and kept for 1.5 h to make the thiourea core gasify and volatilize, form hollow pores, and then ground into powder after cooling to obtain the catalytic cracking agent.

[0037] Example 3

[0038] S1. Thiourea micellar microspheres preparation: 1.5 g of thiourea was dissolved in 15 mL of deionized water, stirred to dissolve at 50°C, 5 mL of 5% sodium dodecyl sulfate aqueous solution was added dropwise, constant temperature stirring for 90 min, and thiourea micellar microspheres were obtained;

[0039] S2. Core-shell structure precursor preparation: the micellar microspheres were dispersed in 60 mL of anhydrous ethanol and ultrasonicated for 40 min; 2 mL of tetraethyl orthosilicate was added, stirred for 30 min, and then 4 mL of ammonia water was added dropwise, and reacted at 40°C for 12 h; 1 mL of N-[3-(trimethoxysilyl)propyl]ethylenediamine was added, and reacted at 55°C for 12 h to obtain a core-shell structure precursor;

[0040] S3. Active component loading and crosslinking: 45 parts by mass of ZSM-5 molecular sieve was taken to prepare a dispersion (solid-liquid ratio 1:15), and ultrasonicated for 40 min; the core-shell structure precursor was added, and stirred at 65°C and 600 r / min for 2 h;

[0041] S4, sintering: the above-mentioned mixed system was transferred to a ceramic crucible, first heated to 600°C at a rate of 10°C / min, and kept for 2 h to make the thiourea core gasify and volatilize, forming a hollow pore, and after cooling, the powder was ground to obtain a catalytic cracking agent.

[0042] Comparative Example 1

[0043] The difference from Example 1 is only that 12 mL of deionized water + 4 mL of 5% sodium dodecyl sulfate aqueous solution (without thiourea) is directly used in step S1, and the rest of the preparation steps (core-shell structure construction, loading, sintering) are consistent with Example 1.

[0044] Comparative Example 2

[0045] The difference from Example 1 is only that no tetraethyl orthosilicate is added in step S2 (only N-[3-(trimethoxysilyl)propyl]ethylenediamine is retained as a single silicon source), and the rest of the preparation steps (micelle preparation, loading, sintering) are consistent with Example 1.

[0046] Comparative Example 3

[0047] The difference from Example 1 is only that no N-[3-(trimethoxysilyl)propyl]ethylenediamine is added in step S2 (only tetraethyl orthosilicate is retained as a single silicon source), and the rest of the preparation steps (micelle preparation, loading, sintering) are consistent with Example 1.

[0048] Comparative Example 4

[0049] ZSM-5 molecular sieve is directly used.

[0050] The application method is: the catalytic cracking agent and naphtha are added into a catalytic cracking reactor at a ratio of 5:1, and the catalytic cracking reaction is carried out under the conditions of a reaction temperature of 600 DEG C and a reaction pressure of 0.2 MPa, and then the products are collected and separated to obtain ethylene and propylene.

[0051] Figure 1 Figure 1 is a transmission electron microscope photo of the catalytic cracking agent material prepared in Example 1; it can be visually observed that the catalytic cracking agent material has a large number of pore structures, the black area is the ZSM-5 active component aggregation area, and the bright hollow channel inside is the pore formed after the sulfur thiourea core is gasified.

[0052] Figure 2 Figure 2 is an XRD diffraction spectrum of the catalytic cracking agent material, SiO2 and ZSM-5 prepared in Example 1; in the XRD spectrum of the catalytic cracking agent, the characteristic diffraction peak of ZSM-5 appears, and the peak shape is sharp and the intensity is high. This shows that the ZSM-5 active component does not destroy the crystal form during the preparation process, and maintains the crystal structure required for catalysis. It is proved that the outer SiO2 and ZSM-5 form a stable composite structure through cross-linking, rather than physical mixing, which will cause the peak shape to be widened or the intensity to be attenuated.

[0053] Figure 3 Figure 3 is the N2 adsorption-desorption isotherm of the catalytic cracking agent material prepared in Example 1 and Comparative Examples 1-4; the isotherm of Example 1 is a typical IV isotherm, and there is a hysteresis loop, and the hysteresis loop area is much larger than that of Comparative Examples 1-4; the BET specific surface area and the pore volume are significantly higher than those of the comparative examples. The IV isotherm and the hysteresis loop are the characteristics of the multi-level pore material, which shows that the Example 1 forms a connected structure of "hollow macropore + ZSM-5 micropore", which solves the problem of isolated and poor connectivity of traditional ZSM-5 pores, and provides a "channel" for the mass transfer of naphtha molecules.

[0054] Figure 4 Figure 4 is the instantaneous conversion rate-time curve of the catalytic cracking agent material prepared in Example 1 and Comparative Examples 1-4 after application. The instantaneous conversion efficiency of Example 1 is obviously higher than that of Comparative Examples 1-4. Moreover, with the lapse of time, the conversion efficiency tends to be stable. This shows that the catalytic activity of the ZSM-5 active component is not covered by the double-layer SiO2 shell, and the active sites are fully exposed; the decay is slow: the multi-level connected pore structure accelerates the mass transfer of naphtha macromolecules, reduces the carbon deposition in the pore, and prolongs the effective action time of the active sites.

[0055] Figure 5is the thermogravimetric analysis curve of the catalytic cracking agent material prepared in Example 1 and Comparative Example 2 after 5 cycles. The mass loss rate of the thermogravimetric curve corresponds to the amount of carbon deposition, and the mass loss rate of Example 1 is 13.7%, while the mass loss rate in Comparative Example 2 is 33.1%, which indicates that the carbon deposition rate of Example 1 is lower. This is because Comparative Example 2 has no inner SiO2 shell, and only the outer functionalized SiO2 cannot stabilize the pore structure, and the pore collapses during recycling, leading to more severe carbon deposition blockage; the inner SiO2 shell of Example 1 forms a "rigid skeleton", which still maintains pore connectivity after 5 cycles, making it difficult for carbon deposition to adhere and block, proving its excellent structural stability and anti-collapse ability.

Claims

1. A method for preparing a naphtha catalytic cracking agent material, characterized in that, Includes the following steps: S1. Preparation of thiourea micelle microspheres: Thiourea is dissolved in deionized water, heated to 40~50℃ and stirred to dissolve, sodium dodecyl sulfate aqueous solution is slowly added dropwise, and stirred at a constant temperature for 60~90min to form uniformly dispersed thiourea micelle microspheres. S2. Precursor preparation: The thiourea micelle microspheres obtained in step S1 were dispersed in anhydrous ethanol and ultrasonically dispersed for 30-40 min; tetraethyl orthosilicate was added first, and after stirring for 30 min, ammonia was added dropwise, and the reaction was carried out at 30-40℃ for 5-12 h to form an inner SiO2 shell; N-[3-(trimethoxysilyl)propyl]ethylenediamine was added, and the temperature was raised to 45-55℃ for 5-12 h to construct an outer functionalized SiO2 shell, thus obtaining a core-shell structured precursor; S3. Loading and crosslinking of active components: ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 20-25 was added to deionized water to prepare a dispersion, which was ultrasonically dispersed for 30-40 min; the core-shell structure precursor obtained in step S2 was slowly added to the dispersion, and stirred at 55-65℃ and 400-600 r / min for 1.5-2 h, so that a strong bond was achieved by crosslinking the outer functionalized SiO2 with the hydroxyl groups on the ZSM-5 surface; S4. Sintering: Transfer the mixed system obtained in step S3 to a ceramic crucible, heat it to 500~600℃ at a rate of 10℃ / min, hold it at the temperature for 1~2h to allow the thiourea nuclei to vaporize and volatilize to form hollow pores, cool it and grind it into powder to obtain the catalytic cracking agent material.

2. The preparation method according to claim 1, characterized in that, In step S1, the amount of thiourea used is 0.8~1.5g, the amount of deionized water used is 10~15mL, and the mass fraction of sodium dodecyl sulfate aqueous solution is 5%, with a volume of 3~5mL.

3. The preparation method according to claim 1, characterized in that, In step S2, the amount of anhydrous ethanol used is 30-60 mL, the amount of tetraethyl orthosilicate used is 0.6-2 mL, the mass fraction of ammonia water is 25% and the amount used is 2-4 mL, and the amount of N-[3-(trimethoxysilyl)propyl]ethylenediamine used is 0.5-1 mL.

4. The preparation method according to claim 1, characterized in that, In step S3, the amount of ZSM-5 molecular sieve used is 30-45 parts by mass, and the solid-liquid mass ratio of the dispersion is 1:10-15.

5. A naphtha catalytic cracking agent material, characterized in that, It is prepared by any one of claims 1 to 4.

6. The application of the naphtha catalytic cracking agent material according to claim 5 in the catalytic cracking of naphtha to produce light olefins, characterized in that, The application method is as follows: the catalytic cracking agent and naphtha are added to the catalytic cracking reactor at a ratio of 5:1, and the catalytic cracking reaction is carried out at a reaction temperature of 600℃ and a reaction pressure of 0.2MPa. The products are collected and separated to obtain ethylene and propylene.

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