Magnetic recoverable low-green-coke heavy oil catalytic cracking catalyst capable of accurately passivating acid sites

Abstract

The invention relates to a magnetic recoverable low-green-coke heavy oil catalytic cracking catalyst with precise acid site passivation and a regeneration method thereof. The catalyst adopts a unique core-shell structure design: cobalt ferrite (CoFe2O4) is used as a magnetic core, and an aluminosilicate insulating layer is coated outside the magnetic core to form a core; the outer layer is an active catalytic layer containing a lanthanum-magnesium synergistically modified Y-type molecular sieve, and the outermost surface is modified with pH response type polymer gel. The preparation method comprises the steps of synthesis and insulation coating of the magnetic core, construction of the active layer and gel modification. According to the regeneration method, a magnetic fluidized bed technology is adopted, and low-temperature efficient regeneration is achieved in a weak oxidizing atmosphere containing trace ozone. The catalyst can be quickly recovered by magnetic separation (recovery rate gt: 95%) after reaction, excessive acid sites are intelligently passivated through pH response gel, and the coke yield is obviously reduced (can be reduced to 4.0% or below). The regeneration process is low in energy consumption, the service life of the catalyst is obviously prolonged, and an efficient, economic and environment-friendly heavy oil catalytic cracking solution is provided.

Description

Technical Field

[0001] This invention belongs to the field of petroleum refining catalyst technology, specifically relating to a magnetically recyclable and precisely passivated acid sites low-coke heavy oil catalytic cracking catalyst and its regeneration method. Background Technology

[0002] Catalytic cracking (FCC) is a core process in petroleum refining, but existing catalysts face challenges such as large amounts of waste after deactivation, high regeneration energy consumption, and imprecise control of coke production. Traditional regeneration technologies, such as high-temperature roasting and coking, easily damage the catalyst's crystal structure, leading to irreversible loss of activity. While magnetic separation technology offers a new approach to catalyst recovery, simple magnetic separation fails to address the precise control of active sites during the reaction process and the deep removal of coke deposits during regeneration.

[0003] The bottlenecks of existing technologies mainly include: 1. The contradiction between regeneration efficiency and structural damage: Traditional high-temperature regeneration, while removing carbon deposits, easily leads to molecular sieve dealuminization and structural collapse, resulting in severe activity loss; 2. Rigid acidity control: Conventional catalysts have fixed acid sites and cannot dynamically adjust in response to the reaction process, easily leading to an increase in coking rate due to excessive cracking in the later stages of the reaction; 3. Limited recovery and function: Existing magnetic recovery catalysts have limited functional design and lack synergistic optimization of the entire reaction-regeneration life cycle.

[0004] Therefore, developing a catalyst system that combines efficient recovery, intelligent reaction control, and mild regeneration is of great significance for promoting the green and low-carbon development of FCC technology. This invention aims to overcome the aforementioned technical bottlenecks by integrating magnetic composite materials, intelligent responsive polymers, and advanced regeneration processes. Summary of the Invention

[0005] I. Purpose of the Invention

[0006] The purpose of this invention is to overcome the technical bottlenecks of existing heavy oil catalytic cracking (FCC) catalysts when processing low-quality heavy oil, including high coke production rate, low diffusion efficiency of heavy oil macromolecules, difficulty in recovering deactivated catalysts, and high regeneration energy consumption. To achieve this goal, this invention provides a low-coke heavy oil catalytic cracking catalyst and its regeneration method, integrating magnetic recyclability, intelligent passivation of acid sites, and efficient low-temperature regeneration functions.

[0007] II. Technical Solution

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0009] A magnetically recoverable and precisely passivated acid site catalytic cracking catalyst for low-coke heavy oil, characterized in that the catalyst has a core-shell structure, comprising:

[0010] The magnetic core is composed of cobalt ferrite (CoFe2O4).

[0011] An insulating coating layer is uniformly coated around the magnetic core, and its material is amorphous aluminosilicate.

[0012] An active catalytic layer, supported outside the insulating coating layer, comprises a lanthanum-magnesium synergistically modified Y-type molecular sieve and a matrix;

[0013] A pH-responsive polymer gel layer is modified on the outermost layer of the active catalytic layer. The gel layer is an interpenetrating network structure formed by poly(N,N-dimethylaminoethyl methacrylate) and polyacrylic acid.

[0014] Preferably, the specific saturation magnetization of the magnetic core is 50-80 emu / g.

[0015] Preferably, the thickness of the insulating coating layer is 5-20 nm, and the SiO2 / Al2O3 molar ratio is 2-4:1.

[0016] Preferably, in the lanthanum-magnesium synergistic modified Y-type molecular sieve, the content of lanthanum oxide (La2O3) is 3%-8% and the content of magnesium oxide (MgO) is 1%-3% based on the dry weight of the molecular sieve, and the ratio of Brønsted acid to Lewis acid (B / L) is 1.5-2.5.

[0017] Preferably, the pH-responsive polymer gel layer has a volume swelling degree of over 200% when the pH value drops below 4.0.

[0018] A method for preparing the above-mentioned catalyst, characterized by comprising the following steps:

[0019] (1) Preparation of magnetic cores: CoFe2O4 magnetic microspheres were synthesized by coprecipitation method;

[0020] (2) Construction of insulating coating layer: Aluminosilicate insulating coating layer is formed on the surface of magnetic microspheres by sol-gel method;

[0021] (3) Loading of the active catalyst layer: The lanthanum-magnesium synergistically modified Y-type molecular sieve, matrix and binder are mixed and loaded onto the surface of the product obtained in step (2);

[0022] (4) Modification of the gel layer: A pH-responsive polymer gel layer is formed outside the active catalyst layer by vapor deposition or in-situ polymerization;

[0023] (5) Catalyst forming and calcination.

[0024] Preferably, the silicon source used in the sol-gel method in step (2) is tetraethyl orthosilicate, and the aluminum source is aluminum isopropoxide.

[0025] Preferably, the silanizing agent used in the vapor deposition in step (4) is trimethylchlorosilane, and the processing temperature is 300-450℃.

[0026] A method for catalytic cracking of heavy oil, characterized in that the above-mentioned catalyst is used.

[0027] Preferably, the deactivated catalyst after the reaction is separated by a magnetic separator, with a separation recovery rate of more than 95%.

[0028] Preferably, the regeneration of the deactivated catalyst is carried out in a magnetic fluidized bed, the regeneration atmosphere is a weak oxidizing gas containing 0.5% - 1.5% ozone by volume, and the regeneration temperature is 400 - 500 °C.

[0029] III. Beneficial Effects

[0030] Compared with the prior art, the catalyst and its preparation method provided by the present invention have the following significant advantages:

[0031] 1. Excellent low coke selectivity and high-value product yield

[0032] The gradient-pore carrier ensures efficient diffusion and pre-cracking of heavy oil macromolecules, physically reducing the probability of coking. Lanthanum-magnesium synergistically modified molecular sieves precisely optimize the ratio of Brønsted acid to Lewis acid (B / L = 1.5 - 2.5), chemically inhibiting excessive hydrogen transfer reactions that lead to coking. Meanwhile, the pH-responsive gel layer intelligently expands when the reaction becomes locally over-acidic, physically covering some strong acid sites and actively preventing a vicious coking cycle. This multi-level regulation, from diffusion and intrinsic acidity to dynamic response, collectively achieves a balance between low coking and high selectivity.

[0033] 2. Outstanding catalyst lifetime and regeneration efficiency

[0034] The tantalum-doped mesoporous cerium oxide coating not only provides shape-selective catalysis, but its unique oxygen vacancies can also efficiently catalyze the gasification of deposited coke precursors during the regeneration stage, achieving deep coke removal under mild conditions. Secondly, the synergistic design of the magnetic cobalt ferrite core (CoFe2O4) and the aluminosilicate insulating coating ensures that the catalyst can be rapidly and efficiently separated by an external magnetic field after deactivation (recovery rate > 95%), while effectively avoiding the adverse effects between the magnetic core and the active components, laying the foundation for the full life cycle management of the catalyst.

[0035] 3. Innovative renewable capabilities and low-energy operation

[0036] The accompanying magnetic fluidized bed regeneration process of this invention is a key innovation. This process achieves efficient and thorough removal of coke at a relatively low temperature (400-500℃) by introducing a weakly oxidizing atmosphere containing trace amounts of ozone (0.5%-1.5%). Compared to traditional regeneration technologies that require high-temperature coking above 600℃, this regeneration method can reduce energy consumption by more than 20% and significantly reduce the damage to the catalyst's molecular sieve structure during the regeneration process, thereby significantly extending the catalyst's overall lifespan. This low-energy, high-efficiency regeneration capability, combined with the catalyst's inherent magnetic recyclability, greatly reduces the operating costs of the equipment.

[0037] 4. Enhanced wear resistance and mechanical stability

[0038] After vapor-phase silanization treatment (e.g., using trimethylchlorosilane), a robust Si-O-Al bonded network is formed on the catalyst surface, resulting in an abrasion resistance strength ≥ 60 N / cm, a significant improvement compared to untreated or conventional catalysts (typically 50-55 N / cm). This enhanced mechanical strength ensures that the catalyst can withstand long-term, intense flow and impact in industrial fluidized bed devices, reducing catalyst loss and guaranteeing the stability and economy of the equipment operation.

[0039] 5. Significant environmental benefits

[0040] During the preparation process, an ionic liquid-organic acid mixed solution is used instead of traditional ammonium salts for molecular sieve modification, eliminating the generation of ammonia nitrogen wastewater at the source. In the reaction regeneration stage, the lower regeneration temperature and higher catalytic efficiency work together to help reduce the overall carbon emissions of the unit. Detailed Implementation

[0041] The following provides a detailed description of specific implementations of the present invention. It should be understood that the content described herein is illustrative and not restrictive of the invention.

[0042] Example 1: Preparation of catalyst C-1

[0043] Magnetic nucleus synthesis: Cobalt nitrate hexahydrate (Co(NO3)2·6H2O) and ferric nitrate nonahydrate (Fe(NO3)3·9H2O) were dissolved in deionized water at a Co:Fe molar ratio of 1:2 using a coprecipitation method. Ammonia was added dropwise to pH = 10 under vigorous stirring, and the mixture was aged at 60℃ for 1 hour. After washing and drying, the product was calcined at 700℃ for 3 hours to obtain CoFe2O4 magnetic microspheres, whose specific saturation magnetization was measured to be 65 emu / g.

[0044] Construction of the insulating coating layer: The above magnetic microspheres were dispersed in an ethanol-water mixed solvent, and tetraethyl orthosilicate (TEOS) and aluminum isopropoxide (Al(OiPr)3) were added, controlling the SiO2 / Al2O3 molar ratio to be 3. Hydrolysis and condensation were performed at 60 °C for 6 hours, followed by drying and calcination at 550 °C for 2 hours to form a uniform aluminosilicate insulating coating layer with a thickness of approximately 10 nm.

[0045] Active catalyst loading and gel modification: Commercially available ultrastable Y-type molecular sieve (USY) was subjected to ion exchange and calcination with lanthanum nitrate and magnesium nitrate solutions to obtain lanthanum-magnesium synergistically modified Y-type molecular sieve (La₂O₃ content 5.0%, MgO content 1.5%). 30 parts of this modified molecular sieve, 20 parts of kaolin, 40 parts of gradient-pore pseudoboehmite support, and 10 parts of alumina sol binder were mixed and slurried. The slurry was loaded onto the above-coated magnetic microspheres and spray-dried. At 400 °C, trimethylchlorosilane (TMCS) vapor was introduced for 1 hour for vapor deposition to form a pH-responsive gel layer.

[0046] Final calcination: Calcined at 550 °C for 2 hours to obtain catalyst product C-1.

[0047] Example 2: Comparative Evaluation of Catalyst Performance

[0048] The reaction was evaluated on a fixed-bed microreactor with vacuum residue (8.5% carbon residue) as the feedstock. The reaction conditions were 500°C and a catalyst-to-oil ratio of 6. The results are shown in the table below:

[0049] Performance indicators Catalyst C-1 of the present invention Comparative example (conventional REUSY catalyst) Heavy oil conversion rate (wt%) 87.5 80.2 Coke yield (wt%) 3.4 6.5 Gasoline yield (wt%) 46.1 41.0 Magnetic separation recovery rate (wt%) >96 not applicable

[0050] Example 3: Verification of Regeneration Effect

[0051] The deactivated catalyst C-1 was recovered using a high-gradient magnetic separator (recovery rate >96%) and then placed in a magnetic fluidized bed regeneration reactor. Regeneration was carried out at 450 °C under a nitrogen atmosphere containing 1.0% ozone for 2 hours. After regeneration, the carbon deposition on the catalyst decreased from 4.8% to 0.4%, and XRD characterization revealed that the molecular sieve crystallinity retention rate exceeded 90%, indicating that the regeneration process caused minimal damage to the catalyst structure.

[0052] In summary, this invention provides a comprehensive, efficient, economical, and green solution to the industry challenges of heavy oil catalytic cracking through the deep coupling of material innovation (core-shell structure, smart gel) and process innovation (magnetic recovery, low-temperature ozone regeneration).

Claims

1. A low coke forming heavy oil catalytic cracking catalyst with magnetic recyclability and accurate passivation of acid sites, characterized in that, The catalyst is a core-shell structure, comprising: a magnetic core, which is composed of cobalt ferrite (CoFe2O4); an insulating coating layer, which is uniformly coated on the outside of the magnetic core and is made of amorphous silico-aluminate; an active catalytic layer, which is loaded on the outside of the insulating coating layer and contains lanthanum-magnesium synergistically modified Y-type molecular sieve and a matrix; a pH-responsive polymer gel layer, which is modified on the outermost layer of the active catalytic layer and is an interpenetrating network structure formed by poly (N,N-dimethylaminoethyl methacrylate) and polyacrylic acid.

2. The catalyst according to claim 1, characterized in that, The specific saturation magnetization of the magnetic core is 50-80 emu / g; the thickness of the insulating coating layer is 5-20 nm, and the molar ratio of SiO2 / Al2O3 is 2-4:

1.

3. The catalyst of claim 1, wherein In the lanthanum-magnesium synergistically modified Y-type molecular sieve, the content of lanthanum oxide (La2O3) is 3%-8% and the content of magnesium oxide (MgO) is 1%-3% based on the dry weight of the molecular sieve, and the ratio of B acid to L acid (B / L) is 1.5-2.

5.

4. The catalyst of claim 1, wherein The volume swelling degree of the pH-responsive polymer gel layer can reach more than 200% when the pH value drops to below 4.

0.

5. A process for the preparation of the catalyst according to any one of claims 1 to 4, characterized in that, The method comprises the following steps: (1) Preparation of the magnetic core: CoFe2O4 magnetic microspheres are synthesized by co-precipitation method; (2) Construction of the insulating coating layer: a silico-aluminate insulating coating layer is formed on the surface of the magnetic microspheres by sol-gel method; (3) Loading of the active catalytic layer: the lanthanum-magnesium synergistically modified Y-type molecular sieve, the matrix, and the binder are mixed and then loaded on the surface of the product obtained in step (2); (4) Modification of the gel layer: a pH-responsive polymer gel layer is formed on the outside of the active catalytic layer by gas deposition or in-situ polymerization method; (5) Catalyst shaping and calcination: the product obtained in step (4) is spray dried and calcined to obtain the final catalyst.

6. The production method according to claim 5, wherein In step (2), the silicon source used in the sol-gel method is tetraethyl orthosilicate, and the aluminum source is aluminum isopropoxide; in step (4), the silanization agent used in the gas deposition is trimethylchlorosilane, and the treatment temperature is 300-450 ℃.

7. A heavy oil catalytic cracking process characterized by, The catalyst of any one of claims 1-4 is used.

8. The heavy oil catalytic cracking method according to claim 7, characterized by, The deactivated catalyst after the reaction is separated by a magnetic separation device, and the separation recovery rate is greater than 95%.

9. The heavy oil catalytic cracking method according to claim 7, characterized by, The regeneration of the deactivated catalyst is carried out in a magnetic fluidized bed, the regeneration atmosphere is a weak oxidizing gas containing 0.5%-1.5% by volume of ozone, and the regeneration temperature is 400-500 ℃.