Catalysts for the pyrolysis of chlorinated plastics, their preparation and application

Abstract

This invention discloses a catalyst for the pyrolysis of chlorinated plastics, with a specific surface area of ​​350–450 μm. 2 / g, pore volume 0.55~0.65mL / g. This invention also discloses its preparation and application. This invention prepares a catalyst for the cracking of chlorine-containing waste plastics by alkali treatment and ammonium salt modification of FCC waste catalyst, realizing waste utilization, improving resource utilization rate, and the process is simple and easy to industrialize.

Description

Technical Field

[0001] This invention relates to a catalyst for the pyrolysis of chlorinated plastics, its preparation, and its application. Background Technology

[0002] In recent years, the global volume of waste plastics has been continuously increasing, and pyrolysis of waste plastics into oil products is one of the most promising treatment methods. Due to the widespread use of polyvinyl chloride (PVC) plastics, waste PVC plastics inevitably mix into the raw materials used in waste plastic pyrolysis to produce oil products. During pyrolysis, chlorine-containing compounds are generated, which corrode equipment and produce harmful substances. Therefore, chlorine-containing waste plastics must undergo dechlorination treatment before pyrolysis. A common method is to add alkaline substances such as NaCO3, CaO, and Ca(OH)2 to the material, so that the HCl produced during pyrolysis immediately reacts with these substances to form chlorides, reducing the harmful effects of HCl. However, this method has limited effect on converting waste plastics into hydrocarbon components.

[0003] Fluidized catalytic cracking (FCC) is one of the most commonly used processes in refineries for processing heavy oil into lighter products. The catalyst used in FCC is the most widely used catalyst in refining processes, with my country consuming approximately 150,000 tons annually. During use, the activity of FCC catalysts gradually decreases, requiring regular and quantitative replenishment of fresh catalyst while simultaneously unloading deactivated spent catalyst. Spent catalyst has low activity and contains a certain amount of heavy metals; how to properly dispose of spent catalyst has always been a concern in the industry. Currently, most FCC spent catalyst is disposed of through landfill. The reactivation of a few spent catalysts mainly involves methods such as acid washing, carbonylation-chlorination, sulfidation-oxidation, and magnetic rotation, aiming to remove heavy metals and restore activity. However, these methods suffer from cumbersome processes and high reactivation costs. Summary of the Invention

[0004] In order to at least partially address the technical deficiencies in the prior art, the present invention provides a catalyst for the pyrolysis of chlorinated plastics and a method for preparing the same.

[0005] As one aspect of the present invention, a catalyst for the pyrolysis of chlorinated plastics with a specific surface area of ​​350–450 μm is disclosed. 2 / g, pore volume 0.55~0.65mL / g.

[0006] As another aspect of the present invention, a method for preparing the above-mentioned catalyst for the pyrolysis of chlorinated plastics is provided, comprising: (1) calcining industrial FCC waste catalyst at 500-900°C for 1-6 hours, preferably at 650-800°C for 1-3 hours; (2) mixing with alkaline solution and reacting at 80-100°C for 1-10 hours, preferably 1-3 hours, and adding ammonium salt to continue the reaction for 1-3 hours; (3) calcining at 450-600°C for 1-3 hours to obtain the catalyst for the pyrolysis of chlorinated plastics.

[0007] In step (2), the alkaline solution is a sodium hydroxide solution, and the amount added is 1% to 6% of the dry basis of the spent catalyst, preferably 2% to 4%.

[0008] In step (2), the ammonium salt is one of ammonium carbonate and ammonium bicarbonate or a mixture of both, and the amount added is 10% to 50% of the weight of the waste catalyst, preferably 10% to 30%.

[0009] As another aspect of the present invention, the application of the above-mentioned catalyst for the pyrolysis of chlorinated plastics is involved in the pyrolysis of chlorinated plastics, wherein the pyrolysis conditions are a pyrolysis temperature of 320-450°C, a pressure of 0.1-1.0 MPa, and a catalyst-to-waste plastic mass ratio of 2-15 wt%.

[0010] The chlorine-containing plastic is a mixture of waste polyvinyl chloride (58 wt% chlorine) and one or more of low-density polyethylene (0.910-0.925 relative molecular weight), high-density polyethylene (0.941-0.965 relative molecular weight), polypropylene, and polystyrene.

[0011] The beneficial effects of this invention are that it uses industrial FCC waste catalyst as raw material, and through alkali treatment and ammonium salt modification, it realizes catalyst channel reconstruction, surface aluminum rearrangement and composite metal oxide formation, thereby achieving efficient dechlorination and cracking, while realizing waste utilization and improving resource utilization rate.

[0012] This invention achieves efficient dechlorination and pyrolysis by using alkali treatment and ammonium salt modification to reconstruct catalyst channels, rearrange surface aluminum, and form composite metal oxides. At the same time, it enables the recycling of waste catalysts and improves resource utilization.

[0013] Chlorine-containing waste plastics must undergo dechlorination treatment before pyrolysis. A common method is to add alkaline substances such as NaCO3, CaO, and Ca(OH)2 to the material, causing the HCl produced during pyrolysis to react immediately with these substances to form chlorides, thus reducing the harmful effects of HCl. However, this method has limited effect on converting waste plastics into hydrocarbon components. This invention uses industrial FCC waste catalyst as raw material and, through alkali treatment and ammonium salt modification, achieves catalyst pore reconstruction, surface aluminum rearrangement, and the formation of composite metal oxides, resulting in highly efficient dechlorination and pyrolysis.

[0014] Currently, most spent FCC catalysts are disposed of through landfill. The reactivation of a few spent catalysts mainly involves methods such as acid washing, carbonylation-chlorination, sulfidation-oxidation, and magnetic rotation, aiming to remove heavy metals and restore activity. However, these methods are cumbersome and costly. This invention presents a catalyst for the pyrolysis of chlorine-containing waste plastics by alkali treatment and ammonium salt modification of spent FCC catalysts. This achieves waste utilization, improves resource utilization, and the process is simple and easily industrialized. Detailed Implementation

[0015] Source of raw materials or equipment: FCC spent catalyst (specific surface area 113.7 μm) 2 / g, pore volume is 0.127cm³ 3 The alkaline solution (NaOH 14w%) was sourced from Lanzhou Petrochemical Company, and the ammonium carbonate and ammonium bicarbonate were of analytical grade and produced by Sinopharm Group.

[0016] Evaluation and analysis methods: The surface area and pore volume of the catalyst were determined by low-temperature nitrogen adsorption-desorption method, and the chlorine content of the oil was determined by gas chromatography (for analytical methods, please refer to "Analytical Methods of Petrochemical Industry (RIPP Experimental Methods)", edited by Yang Cuiding et al., Science Press, 1990). The catalyst reaction performance was evaluated using a small fixed fluidized bed.

[0017] The inventors, referring to CN201910330159.2, prepared a silicon-aluminum material with a pore structure dominated by mesopores and macropores, which can be used as a catalyst support. However, in that patent, the purpose of contacting the spent catalyst with the alkaline mixture is to remove metals, and the mesopore structure of the silicon-aluminum material is caused by partial matrix dissolution, which is a cumbersome and complex process. In contrast, this invention first activates the catalyst by high-temperature calcination, and then performs low-temperature alkaline treatment to generate an alumina structure from the calcined and activated aluminum. The mesopore structure of the catalyst in this invention is composed of pores formed by the CO2 and NH3 gases generated during high-temperature calcination decomposition and the newly generated mesopore structure of alumina.

[0018] The catalyst prepared by the inventors according to CN200510095698.0 can only catalyze dechlorination and cannot crack plastic polymers, thus having a single function. This invention, through alkali treatment and ammonium salt modification of FCC waste catalyst, achieves microsphere pore reconstruction, surface aluminum rearrangement, and the formation of composite metal oxides; the catalyst of this invention simultaneously possesses dechlorination and cracking functions.

[0019] Referring to CN200810036703.4, the inventors found that the process involves a first-stage catalyst for dechlorination, followed by a second-stage catalyst for cracking, isomerization, and aromatization, resulting in a complex process flow. This invention, however, completes the dechlorination, cracking, and isomerization reactions in a single step.

[0020] The inventors prepared a dechlorination and cracking composite catalyst according to CN201810272820.4. The active components include copper oxide, iron oxide, and calcium oxide. It has micro-dechlorination, catalytic cracking, and heat-carrying functions, but its dechlorination capacity does not meet the inventors' expectations. The catalyst prepared by this invention from industrial FCC waste catalyst through alkali treatment and ammonium salt modification can efficiently dechlorinate and crack.

[0021] Example 1

[0022] 300g of industrial FCC waste catalyst was calcined at 700℃ for 2.5h, then mixed with 64g of alkaline solution and 536g of deionized water, reacted at 90℃ for 3h, followed by the addition of 90g of ammonium carbonate and a further reaction time of 1h. The mixture was then filtered, dried, and calcined at 500℃ for 1h to obtain catalyst C-1 prepared in this invention for the pyrolysis of chlorine-containing waste plastics, with a specific surface area of ​​441.9 μm. 2 / g, pore volume is 0.593cm³ 3 / g.

[0023] Using waste plastics as raw materials (polyvinyl chloride and polypropylene: 10% and 90%, respectively), under reaction conditions of 410℃, 0.35MPa, and catalyst: waste plastic = 5.5wt%, the dechlorination rate was 99.3% and the oil yield was 86.9%.

[0024] Example 2

[0025] 400g of industrial FCC waste catalyst was calcined at 900℃ for 1 hour, then mixed with 57g of alkaline solution and 743g of deionized water, and reacted at 80℃ for 10 hours. 160g of ammonium bicarbonate was then added, and the reaction continued for 3 hours. After filtration and drying, the mixture was calcined at 450℃ for 2 hours to obtain catalyst C-2 prepared in this invention for the pyrolysis of chlorine-containing waste plastics, with a specific surface area of ​​357.2 μm. 2 / g, pore volume is 0.603cm³ 3 / g.

[0026] Using waste plastics as raw materials (polyvinyl chloride, polypropylene, and low-density polyethylene: 15%, 60%, and 25%, respectively), under reaction conditions of 365℃, 0.1MPa, and catalyst: waste plastic = 9.0wt%, the dechlorination rate was 98.9% and the oil yield was 85.1%.

[0027] Example 3

[0028] 300g of industrial FCC waste catalyst was calcined at 500℃ for 6 hours, then mixed with 128g of alkaline solution and 472g of deionized water, and reacted at 100℃ for 1 hour. 150g of ammonium bicarbonate was then added, and the reaction continued for 2 hours. After filtration and drying, the mixture was calcined at 600℃ for 1 hour to obtain catalyst C-3 prepared in this invention for the pyrolysis of chlorine-containing waste plastics, with a specific surface area of ​​361.3 μm. 2 / g, pore volume is 0.582cm³ 3 / g.

[0029] Using waste plastics as raw materials (polyvinyl chloride, low-density polyethylene, and high-density polyethylene: 5%, 50%, and 45%, respectively), under reaction conditions of 405℃, 0.15MPa, and catalyst: waste plastic = 8wt%, the dechlorination rate was 99.7% and the oil yield was 86.1%.

[0030] Example 4

[0031] 335g of industrial FCC waste catalyst was calcined at 800℃ for 3 hours, then mixed with 96g of alkaline solution and 574g of deionized water, and reacted at 85℃ for 2 hours. Then, 34g of ammonium carbonate was added and the reaction continued for 1.5 hours. After filtration and drying, the mixture was calcined at 550℃ for 3 hours to obtain catalyst C-4 prepared in this invention for the pyrolysis of chlorine-containing waste plastics, with a specific surface area of ​​427.5 μm. 2 / g, pore volume is 0.559cm³ 3 / g.

[0032] Using waste plastics as raw materials (polyvinyl chloride, low-density polyethylene, high-density polyethylene, and polypropylene: 13%, 33%, 24%, and 30%, respectively), under reaction conditions of 375℃, 0.5MPa, and catalyst:polypropylene = 5wt%, the dechlorination rate was 98.3% and the oil yield was 85.1%.

[0033] Example 5

[0034] 270g of industrial FCC waste catalyst was calcined at 770℃ for 2.5h, then mixed with 19.5g of alkaline solution and 473g of deionized water, and reacted at 93℃ for 1.4h. Then, 135g of ammonium bicarbonate was added and the reaction continued for 2.2h. After filtration and drying, it was calcined at 510℃ for 1.5h to obtain the catalyst C-5 prepared in this invention for the pyrolysis of chlorine-containing waste plastics, with a specific surface area of ​​376.6 μm. 2 / g, pore volume is 0.587cm³ 3 / g.

[0035] Using waste plastics as raw materials (polyvinyl chloride, low-density polyethylene, polystyrene, and polypropylene: 7%, 20%, 23%, and 50%, respectively), under reaction conditions of 395℃, 0.5MPa, and catalyst:polypropylene = 4.5wt%, the dechlorination rate was 98.1% and the oil yield was 85.7%.

[0036] Example 6

[0037] 300g of industrial FCC waste catalyst was calcined at 600℃ for 5 hours, then mixed with 107g of alkaline solution and 303g of deionized water, reacted at 95℃ for 2 hours, followed by the addition of 45g of ammonium bicarbonate and a further reaction for 2 hours. The mixture was then filtered, dried, and calcined at 600℃ for 1 hour to obtain the catalyst C-6 prepared in this invention for the pyrolysis of chlorine-containing waste plastics, with a specific surface area of ​​390.1 μm. 2 / g, pore volume is 0.569cm³ 3 / g.

[0038] Using waste plastics as raw materials (polyvinyl chloride, low-density polyethylene, and polystyrene: 7%, 70%, and 23%, respectively), under reaction conditions of 395℃, 0.5MPa, and catalyst:polypropylene = 4.5wt%, the dechlorination rate was 99.0% and the oil yield was 86.2%.

[0039] Comparative Example 1

[0040] 300g of industrial FCC waste catalyst was calcined at 650℃ for 2.5h and then used as cracking catalyst D-1. Using waste plastics as raw materials (polyvinyl chloride and polypropylene: 10% and 90%, respectively), under reaction conditions of 410℃, 0.35MPa, and catalyst:waste plastic = 5.5wt%, the dechlorination rate was 83.2% and the oil yield was 83.9%.

[0041] Comparative Example 2

[0042] 400g of industrial FCC waste catalyst was calcined at 900℃ for 1 hour, then mixed with 57g of alkaline solution and 743g of deionized water, reacted at 80℃ for 9 hours, filtered and dried, and calcined at 450℃ for 2 hours to obtain catalyst D-2 for pyrolysis of chlorine-containing waste plastics prepared in this invention, with a specific surface area of ​​341.7 μm. 2 / g, pore volume is 0.306cm³ 3 / g.

[0043] Using waste plastics as raw materials (polyvinyl chloride, polypropylene, and low-density polyethylene: 15%, 60%, and 25%, respectively), under reaction conditions of 365℃, 0.1MPa, and catalyst: waste plastic = 9.0wt%, the dechlorination rate was 96.5% and the oil yield was 73.7%.

[0044] Comparative Example 3

[0045] 270g of industrial FCC waste catalyst was calcined at 770℃ for 2.5h, then mixed with 67.5g of ammonium bicarbonate and 473g of deionized water, reacted at 93℃ for 2.2h, filtered and dried, and calcined at 510℃ for 1.5h to obtain catalyst D-3 for the pyrolysis of chlorine-containing waste plastics prepared in this invention, with a specific surface area of ​​256.7 μm. 2 / g, pore volume is 0.273cm³ 3 / g.

[0046] Using waste plastics as raw materials (polyvinyl chloride, low-density polyethylene, polystyrene, and polypropylene: 7%, 20%, 23%, and 50%, respectively), under reaction conditions of 395℃, 0.5MPa, and catalyst:polypropylene = 4.5wt%, the dechlorination rate was 87.1% and the oil yield was 82.1%.

[0047] Comparative Example 4

[0048] Using calcium carbonate as a dechlorinating agent and waste plastics as raw materials (polyvinyl chloride, low-density polyethylene, high-density polyethylene, and polypropylene: 13%, 33%, 24%, and 30%, respectively), under reaction conditions of 375℃, 0.5MPa, and a dechlorinating agent:polypropylene ratio of 10wt%, the dechlorination rate was 98% and the oil yield was 69.3%.

[0049] Comparative Example 5

[0050] 270g of industrial FCC waste catalyst was calcined at 450℃ for 2.5h, then mixed with 19.5g of alkaline solution and 473g of deionized water, and reacted at 93℃ for 1.4h. Then, 135g of ammonium bicarbonate was added and the reaction continued for 2.2h. After filtration and drying, the mixture was calcined at 510℃ for 1.5h to obtain the catalyst C-5 prepared in this invention for the pyrolysis of chlorine-containing waste plastics, with a pore volume of 276.1 μm specific surface area. 2 / g, 0.496cm 3 / g.

[0051] Using waste plastics as raw materials (polyvinyl chloride, low-density polyethylene, polystyrene, polypropylene: 7%, 20%, 23%, 50%), under reaction conditions of 395℃, 0.5MPa, and catalyst:polypropylene = 4.5wt%, the dechlorination rate was 93.5% and the oil yield was 79.8%.

[0052] Comparative Example 6

[0053] 300g of industrial FCC waste catalyst was calcined at 920℃ for 5 hours, then mixed with 107g of alkaline solution and 303g of deionized water, and reacted at 95℃ for 2 hours. 45g of ammonium bicarbonate was then added and the reaction continued for another 2 hours. After filtration and drying, the mixture was calcined at 600℃ for 1 hour to obtain the catalyst C-6 prepared in this invention for the pyrolysis of chlorine-containing waste plastics, with a specific surface area of ​​336.9.1 μm. 2 / g, pore volume is 0.509cm³ 3 / g.

[0054] Using waste plastics as raw materials (polyvinyl chloride, low-density polyethylene, and polystyrene: 7%, 70%, and 23%, respectively), under reaction conditions of 395℃, 0.5MPa, and catalyst: polypropylene = 4.5wt%, the dechlorination rate was 95.1% and the oil yield was 82.1%.

[0055] Comparative Example 7

[0056] 300g of industrial FCC waste catalyst was calcined at 700℃ for 2.5h, then mixed with 17g of alkaline solution and 536g of deionized water, reacted at 90℃ for 3h, followed by the addition of 90g of ammonium carbonate and a further reaction time of 1h. The mixture was then filtered, dried, and calcined at 500℃ for 1h to obtain catalyst C-1 prepared in this invention for the pyrolysis of chlorine-containing waste plastics, with a specific surface area of ​​201.6m². 2 / g, pore volume is 0.365cm³ 3 / g.

[0057] Using waste plastics as raw materials (polyvinyl chloride and polypropylene: 10% and 90%, respectively), under reaction conditions of 410℃, 0.35MPa, and catalyst: waste plastic = 5.5wt%, the dechlorination rate was 86.3% and the oil yield was 78.1%.

[0058] As can be seen from the examples and comparative examples, the FCC waste catalyst, after alkali treatment and ammonium salt modification under suitable conditions, possesses a large specific surface area and pore volume. This catalyst exhibits excellent dechlorination and catalytic cracking effects in the pyrolysis process of chlorine-containing waste plastics, while simultaneously achieving high-value utilization of the FCC waste catalyst. The catalyst prepared by this method has advantages such as low cost, simple preparation process, and good catalytic effect, demonstrating certain practical value and application prospects.

Claims

1. A method for preparing a catalyst for the pyrolysis of chlorinated plastics, characterized in that, include: (1) calcining the industrial fluidized catalytic cracking waste catalyst at 500-900 DEG C for 1-6 hours; (2) mixing with lye, reacting at 80-100 DEG C for 1-10 hours, adding ammonium salt and continuing to react for 1-3 hours; (3) calcining at 450-600 DEG C for 1-3 hours, to obtain a catalyst for chloroplast cracking; the specific surface area of the catalyst for chloroplast cracking is 350 ~ 450 m 2 / g, and the pore volume is 0.55 ~ 0.65 mL / g; In step (2), the alkaline solution is a sodium hydroxide solution, and the amount added is 1% to 6% of the dry basis of the spent catalyst; the ammonium salt is one of ammonium carbonate and ammonium bicarbonate or a mixture of both, and the amount added is 10% to 50% of the weight of the spent catalyst. The chlorine-containing plastic is one or more of low-density polyethylene, high-density polyethylene, polypropylene, and polystyrene, mixed with waste polyvinyl chloride.

2. The method according to claim 1, characterized in that, In step (2), mix with alkaline solution and react at 80-100℃ for 1-3 hours.

3. The method according to claim 1, characterized in that, Step (1) Calcine the industrial fluidized catalytic cracking waste catalyst at 650-800℃ for 1-3 hours.

4. The method according to claim 1, characterized in that, In step (2), the amount of alkaline solution added is 2% to 4% of the dry basis of the waste catalyst.

5. The method according to claim 1, characterized in that, In step (2), the amount of ammonium salt added is 10% to 30% of the weight of the waste catalyst.

6. The catalyst prepared by any one of the methods described in claims 1-5.

7. The application of the catalyst according to claim 6 in the pyrolysis of chlorinated plastics, characterized in that, The pyrolysis conditions were: pyrolysis temperature 320–450℃, pressure 0.1–1.0 MPa, and catalyst to chlorinated plastic mass ratio 2–15 wt%. The chlorine-containing plastic is one or more of low-density polyethylene, high-density polyethylene, polypropylene, and polystyrene, mixed with waste polyvinyl chloride.