A catalyst for the pyrolysis of waste polystyrene, its preparation method and application

Abstract

This invention provides a catalyst for the pyrolysis of waste polystyrene, its preparation method, and its application, comprising the following steps: Step 1, grinding the waste FCC catalyst, then mixing it with sodium pyrophosphate and water, and then mixing it with ammonium carbonate; Step 2, mixing the mixture obtained in Step 1 with calcium chloride solution, drying, and forming microspheres; Step 3, calcining the microspheres to obtain the catalyst for the pyrolysis of waste polystyrene. The catalyst of this invention contains the waste FCC catalyst and metal oxides. The original pore structure of the waste FCC catalyst and the pore-bursting effect of CO2 give the catalyst a large pore size and pore volume, and the metal oxides are dispersed on the surface of the catalyst pores, improving the accessibility of the catalyst activity and enhancing the effective activity and selectivity of the catalyst.

Description

Technical Field

[0001] This invention relates to a catalyst for the pyrolysis of waste polystyrene, its preparation method, and its application. The catalyst of this invention is mainly used for the pyrolysis of waste polystyrene. Background Technology

[0002] Polymer chemicals have a short lifespan; for example, polystyrene used as packaging material has a short lifespan, resulting in a high waste rate. Because polymers are difficult to degrade, they easily cause environmental pollution.

[0003] CN1105351A discloses a method for producing light oil and gas from waste plastics through pyrolysis, desulfurization, and viscosity reduction in low-quality heavy oil. It uses zinc oxide, ferric oxide, and rare earth metal oxides as catalysts. The reactor employs an anchor-type stirrer and a liftable discharge device for the catalytic pyrolysis of waste polystyrene, achieving a styrene yield of 35-60%. However, traditional metal oxides, due to their small pore size, prevent larger polystyrene molecules from easily entering their inner surface, causing most to react on the outer surface. This not only affects their effective activity but also reduces the selectivity of the liquid product and styrene monomer. Therefore, the metal oxide catalyst in this invention has low effective activity, resulting in a styrene yield of less than 60%.

[0004] CN1220662A discloses a method using calcium oxide as a catalyst, mixing it with waste polystyrene, heating it to 150-250°C in a preheater, and then feeding it into a pyrolysis reactor for pyrolysis at 350-500°C and 0.005-0.02 MPa, achieving a styrene recovery rate of 70-85%. This invention requires preheating of both the waste polystyrene and the catalyst, and involves pyrolysis under certain pressure, resulting in a complex process and high production costs.

[0005] CN101891581A uses a mesoporous molecular sieve Mx / MCM-41 supported on alkali metals / or alkaline earth metals as a catalyst. The pyrolysis reaction is carried out at 300-450℃ under normal pressure, reduced pressure, or nitrogen purging conditions, achieving a liquid product yield of over 95% and a styrene content of over 80% in the liquid product. However, the synthesis of this mesoporous molecular sieve Mx / MCM-41 catalyst requires an organic template agent, making the process complex and costly.

[0006] CN1106371A uses a specially modified Y-type molecular sieve and high-purity, high-specific-surface-area alumina to prepare a waste polystyrene cracking catalyst. The cracking reaction is carried out at 320-390℃, with a styrene yield of 62-65%. The synthesis of the mesoporous molecular sieve Mx / MCM-41 catalyst of this invention also requires an organic template agent, making the process complex and costly.

[0007] Therefore, further research is needed in this field on catalysts for the cracking of waste polyethylene in order to reduce catalyst costs and improve catalyst activity. Summary of the Invention

[0008] The main objective of this invention is to provide a catalyst for the cracking of waste polystyrene, its preparation method and application, so as to overcome the defects of existing catalysts for the cracking of waste polystyrene, such as high cost and low activity.

[0009] To achieve the above objectives, the present invention provides a method for preparing a catalyst for the pyrolysis of waste polystyrene, comprising the following steps:

[0010] Step 1: Grind the FCC waste catalyst, then mix it with sodium pyrophosphate and water, and then mix it with ammonium carbonate;

[0011] Step 2: Mix the mixture obtained in Step 1 with calcium chloride solution, dry, and prepare microspheres;

[0012] Step 3: Calcining the microspheres to obtain a catalyst for the pyrolysis of waste polystyrene.

[0013] The method for preparing a catalyst for the cracking of waste polystyrene according to the present invention, wherein the particle size of the FCC waste catalyst after grinding is less than 10 μm.

[0014] The method for preparing a catalyst for the cracking of waste polystyrene according to the present invention, wherein the mass ratio of sodium pyrophosphate to the FCC waste catalyst is 0.01:1 to 0.1:1 on a dry basis; and the mass ratio of water to the FCC waste catalyst is 2:1 to 3:1.

[0015] The method for preparing a catalyst for the cracking of waste polystyrene according to the present invention, wherein the mass ratio of ammonium carbonate to the waste FCC catalyst is 0.17:1 to 0.26:1 on a dry basis.

[0016] The method for preparing a catalyst for the cracking of waste polystyrene according to the present invention, wherein the calcium chloride solution is based on the mass of calcium chloride, the FCC waste catalyst is based on the dry basis, and the mass ratio of the calcium chloride solution to the FCC waste catalyst is 0.1:1 to 0.3:1.

[0017] The method for preparing the catalyst for the cracking of waste polystyrene according to the present invention includes mixing the FCC waste catalyst with sodium pyrophosphate and deionized water, and then stirring for 1-2 hours.

[0018] The method for preparing the catalyst for the cracking of waste polystyrene according to the present invention includes mixing the mixture obtained in step 1 with a calcium chloride solution and stirring for 1-2 hours.

[0019] The method for preparing the catalyst for the pyrolysis of waste polystyrene according to the present invention includes the following steps: Step 2 is drying by spray drying; Step 3 is calcining the microspheres at a temperature of 830-900℃ for 1-3 hours.

[0020] To achieve the above objectives, the present invention also provides a catalyst for the pyrolysis of waste polystyrene obtained by the above preparation method.

[0021] The application of the catalyst described in this invention in the pyrolysis of waste plastics, wherein the pyrolysis conditions are: pyrolysis temperature of 330-380℃, pressure of atmospheric pressure, and mass ratio of catalyst to waste polystyrene of 2wt%-15wt%.

[0022] The beneficial effects of this invention are:

[0023] The catalyst of this invention contains FCC waste catalyst and metal oxides. The original pore structure of the FCC waste catalyst and the pore-bursting effect of CO2 give the catalyst a large pore size and pore volume. The metal oxides are dispersed on the surface of the catalyst pores, which improves the accessibility of the catalyst activity and enhances the effective activity and selectivity of the catalyst.

[0024] The catalyst of this invention uses FCC waste catalyst, which not only solves the problem of FCC waste catalyst treatment, but also realizes the reuse of FCC waste catalyst. Moreover, the process is simple and easy to industrialize. Attached Figure Description

[0025] Figure 1 This is a pore size distribution diagram of the waste polystyrene pyrolysis catalyst in Example 1. Detailed Implementation

[0026] The technical solution of the present invention will be described in detail below. The following embodiments are implemented under the premise of the technical solution of the present invention and a detailed implementation process is given. However, the protection scope of the present invention is not limited to the following embodiments. Structures or experimental methods that do not specify specific conditions in the following embodiments are generally performed under conventional conditions.

[0027] This invention provides a method for preparing a catalyst for the pyrolysis of waste polystyrene, comprising the following steps:

[0028] Step 1: Grind the FCC waste catalyst, then mix it with sodium pyrophosphate and water, and then mix it with ammonium carbonate;

[0029] Step 2: Mix the mixture obtained in Step 1 with calcium chloride solution, dry, and prepare microspheres;

[0030] Step 3: Calcining the microspheres to obtain a catalyst for the pyrolysis of waste polystyrene.

[0031] Currently, most FCC waste catalysts are disposed of by landfill. The few FCC waste catalyst regeneration and revival processes mainly include acid washing, carbonylation-chlorination, sulfidation-oxidation and magnetic rotation, etc., to remove heavy metals and restore the activity of FCC waste catalysts. However, these methods have problems such as complicated processes and high revival costs.

[0032] This invention prepares a catalyst with a specific structure by combining FCC waste catalyst with metal oxides. The original pore structure of the FCC waste catalyst and the pore-bursting effect of CO2 give it a large pore size and pore volume. The metal oxides are dispersed on the surface of the pores. Therefore, the catalyst prepared by this invention has good dispersibility for polyethylene macromolecules and good activity accessibility, thereby giving the catalyst high catalytic activity and selectivity.

[0033] This invention does not impose any particular limitation on FCC waste catalysts; any catalytic cracking catalyst discarded from the catalytic cracking process can be used. This invention also does not impose any particular limitation on the structure and elemental content of FCC waste catalysts.

[0034] In one embodiment, the present invention uses a ball mill to grind the spent FCC catalyst; in another embodiment, the spent FCC catalyst is ground to a particle size of less than 10 μm.

[0035] In one embodiment, the FCC waste catalyst of the present invention is mixed with sodium pyrophosphate and water, wherein the weight ratio of sodium pyrophosphate to the dry basis of the FCC waste catalyst is 0.01:1-0.1:1, preferably 0.02:1-0.05:1; and the mass ratio of water to the FCC waste catalyst is 2:1-3:1. After mixing the FCC waste catalyst, sodium pyrophosphate, and water, the mixture is stirred for, for example, 1-2 hours, and then mixed evenly with ammonium carbonate. In another embodiment, the weight ratio of ammonium carbonate to the dry basis of the FCC waste catalyst is 0.17:1-0.26:1.

[0036] Step 2 involves mixing the mixture obtained in Step 1 with a calcium chloride solution, drying it, and preparing microspheres.

[0037] The present invention does not impose a particular limitation on the concentration of the calcium chloride solution. In one embodiment, the mass content of calcium chloride in the calcium chloride solution is, for example, 35 wt%. The mass of the calcium chloride solution is based on calcium chloride, the mass of the FCC waste catalyst is based on the dry basis of the FCC waste catalyst, and the weight ratio of calcium chloride solution to FCC waste catalyst is 0.1:1-0.3:1, preferably 0.2:1-0.3:1.

[0038] In one embodiment, the mixture obtained in step 1 is mixed with calcium chloride solution and then stirred for, for example, 1-2 hours; in another embodiment, the drying method is spray drying to produce microspheres.

[0039] The microspheres are calcined to obtain a catalyst for the cracking of waste polystyrene. In one embodiment, the microspheres are calcined at 830-900°C for 1-3 hours.

[0040] In summary, sodium pyrophosphate plays a dispersing role in the preparation of the catalyst of this invention, so that the calcium carbonate generated by the reaction of ammonium carbonate and calcium chloride is evenly dispersed. During high-temperature calcination, calcium carbonate generates calcium oxide and carbon dioxide. The pore-bursting effect of the generated carbon dioxide gives the catalyst a larger pore size and pore volume. At the same time, calcium oxide, as an active component, is dispersed on the surface of the pores, which is beneficial to improving the effective activity of the catalyst.

[0041] The catalyst prepared by the method of this invention has a large pore size and pore volume, with metal oxides dispersed on the pore surface. This catalyst can be used to catalyze the pyrolysis of waste polystyrene plastics, under pyrolysis conditions such as a pyrolysis temperature of 330–380°C, atmospheric pressure, and a catalyst-to-waste polystyrene mass ratio of 2 wt%–15 wt%. This invention does not specifically limit the waste polystyrene plastics used; for example, it can include various discarded instrument housings, lampshades, optical and chemical instrument parts, transparent films, capacitor dielectric layers, etc.

[0042] The catalyst of this invention has excellent diffusion properties, which can improve its effective activity in the cracking reaction, thereby increasing the liquid yield and styrene yield.

[0043] The technical solution of the present invention will be further described in detail below through specific embodiments. The waste polystyrene used in the following embodiments and comparative examples is waste instrument housings, lamp covers, optical and chemical instrument parts, transparent films, capacitor dielectric layers, etc., and the polystyrene used in the embodiments and comparative examples is the same.

[0044] Source of raw materials or equipment: FCC spent catalyst (specific surface area 113.7 μm) 2 / g, pore volume is 0.127cm³ 3 Sodium pyrophosphate and ammonium carbonate were analytical grade and produced by Sinopharm Group; calcium chloride solution (35w%) was produced by Shandong Rongfeng Chemical Co., Ltd.

[0045] 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.

[0046] Example 1

[0047] 303g of pulverized FCC waste catalyst (dry basis) was mixed with 9.1g of sodium pyrophosphate and 636g of deionized water. After stirring for 1.2 hours, 63.6g of ammonium carbonate was added and mixed evenly. The above slurry was then mixed with 181.8g of calcium chloride solution and stirred for 2 hours. After spray drying, microspheres were prepared. The sprayed microspheres were calcined at 865℃ for 1.1 hours to obtain waste polystyrene cracking catalyst C-1.

[0048] Using waste polystyrene as raw material, under reaction conditions of 355℃ and catalyst C-1: waste polystyrene of 9wt%, the liquid yield was 96.7%, of which the styrene yield was 85.3%.

[0049] Figure 1 This is a pore size distribution diagram of the waste polystyrene pyrolysis catalyst from Example 1. Figure 1 As shown, the catalyst prepared in Example 1 of this invention has a good mesoporous structure and a dual-pore distribution. The two mesoporous distribution peaks are 3.8 nm and 11.7 nm, respectively, which can effectively promote the diffusion and mass transfer of polystyrene macromolecular raw materials and products.

[0050] Example 2

[0051] 356g of pulverized FCC waste catalyst (dry basis) was mixed with 14.2g of sodium pyrophosphate and 1060g of deionized water. After stirring for 1.9 hours, 89g of ammonium carbonate was added and mixed evenly. The slurry was then mixed with 86.4g of calcium chloride solution and stirred for 1.1 hours. After spray drying, microspheres were prepared. The sprayed microspheres were calcined at 890℃ for 1.5 hours to obtain waste polystyrene cracking catalyst C-2.

[0052] Using waste polystyrene as raw material, under reaction conditions of 330℃ and catalyst C-3: waste polystyrene ratio of 5 wt%, the liquid yield was 95.3%, of which the styrene yield was 86.6%.

[0053] Example 3

[0054] 432g of pulverized FCC waste catalyst (dry basis) was mixed with 8.7g of sodium pyrophosphate and 1080g of deionized water. After stirring for 1.5 hours, 73.5g of ammonium carbonate was added and mixed evenly. The above slurry was then mixed with 101.8g of calcium chloride solution and stirred for 1.5 hours. After spray drying, microspheres were prepared. The sprayed microspheres were calcined at 847℃ for 2.9 hours to obtain waste polystyrene cracking catalyst C-3.

[0055] Using waste polystyrene as raw material, under reaction conditions of 375℃ and catalyst C-3: waste polystyrene ratio of 3wt%, the liquid yield was 95.6%, of which the styrene yield was 85.7%.

[0056] Example 4

[0057] 369g of pulverized FCC waste catalyst (dry basis) was mixed with 18.4g of sodium pyrophosphate and 922g of deionized water. After stirring for 1.7 hours, 95.9g of ammonium carbonate was added and mixed evenly. The above slurry was then mixed with 110g of calcium chloride solution and stirred for 1.1 hours. After spray drying, microspheres were prepared. The sprayed microspheres were calcined at 835℃ for 2 hours to obtain waste polystyrene cracking catalyst C-4.

[0058] Using waste polystyrene as raw material, under reaction conditions of 335℃ and catalyst C-4: waste polystyrene ratio of 14wt%, the liquid yield was 96.7%, of which the styrene yield was 86.1%.

[0059] Example 5

[0060] 373g of pulverized FCC waste catalyst (dry basis) was mixed with 9.3g of sodium pyrophosphate and 821g of deionized water. After stirring for 1.1 hours, 84.8g of ammonium carbonate was added and mixed evenly. The above slurry was then mixed with 242g of calcium chloride solution and stirred for 1.5 hours. After spray drying, microspheres were prepared. The sprayed microspheres were calcined at 880℃ for 1.3 hours to obtain waste polystyrene cracking catalyst C-5.

[0061] Using waste polystyrene as raw material, under reaction conditions of 360℃ and catalyst C-5: waste polystyrene ratio of 8 wt%, the liquid yield was 96.1%, of which the styrene yield was 85.7%.

[0062] Example 6

[0063] 406g of pulverized FCC waste catalyst (dry basis) was mixed with 14.2g of sodium pyrophosphate and 1096g of deionized water. After stirring for 1.3 hours, 77.1g of ammonium carbonate was added and mixed evenly. The slurry was then mixed with 220g of calcium chloride solution and stirred for 1.7 hours. After spray drying, microspheres were prepared. The sprayed microspheres were calcined at 850℃ for 2.5 hours to obtain waste polystyrene cracking catalyst C-6.

[0064] Using waste polystyrene as raw material, under reaction conditions of 380℃ and catalyst C-6: waste polystyrene 2wt%, the liquid yield was 95.7%, of which the styrene yield was 85.1%.

[0065] Example 7

[0066] 467g of pulverized FCC waste catalyst (dry basis) was mixed with 21g of sodium pyrophosphate and 1120g of deionized water. After stirring for 1.7 hours, 93.4g of ammonium carbonate was added and mixed evenly. The above slurry was then mixed with 266g of calcium chloride solution and stirred for 1.1 hours. After spray drying, microspheres were prepared. The sprayed microspheres were calcined at 830℃ for 3 hours to obtain waste polystyrene cracking catalyst C-7.

[0067] Using waste polystyrene as raw material, under reaction conditions of 340℃ and catalyst C-6: waste polystyrene 6wt%, the liquid yield was 96.8%, of which the styrene yield was 86.9%.

[0068] Comparative Example 1

[0069] 9.1g sodium pyrophosphate and 636g deionized water were mixed and stirred for 1.2 hours. Then, 63.6g ammonium carbonate was added and mixed evenly. The slurry was then mixed with 181.8g calcium chloride solution and stirred for 2 hours. The mixture was then spray-dried to form microspheres. The spray-dried microspheres were calcined at 865℃ for 1.1 hours to obtain waste polystyrene cracking catalyst D-1.

[0070] Using waste polystyrene as raw material, under reaction conditions of 355℃ and catalyst D-1: waste polystyrene ratio of 9 wt%, the liquid yield was 86.7%, of which the styrene yield was 82.4%.

[0071] Comparative Example 2

[0072] FCC waste catalyst was roasted at 865℃ for 1.1 hours to obtain waste polystyrene cracking catalyst D-2.

[0073] Using waste polystyrene as raw material, under reaction conditions of 355℃ and catalyst D-2: waste polystyrene ratio of 9 wt%, the liquid yield was 79.8%, of which the styrene yield was 77.1%.

[0074] Comparative Example 3

[0075] Using waste polystyrene as raw material, under reaction conditions of 355℃ and a calcium oxide to waste polystyrene ratio of 9 wt%, the liquid yield was 85.3%, of which the styrene yield was 77.2%.

[0076] As can be seen from the above examples and comparative catalyst evaluation results, the catalyst prepared by the method of the present invention has the characteristics of good catalyst activity accessibility, high liquid yield and high styrene yield when used in the waste polystyrene pyrolysis process.

[0077] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A process for the preparation of a catalyst for the cracking of waste polystyrene, characterized in that, The preparation method comprises the following steps: Step 1, grinding the FCC waste catalyst, then mixing with sodium pyrophosphate and water, and then mixing with ammonium carbonate; Step 2, mixing the mixture obtained in step 1 with a calcium chloride solution, and drying to form microspheres; Step 3, calcining the microspheres at a temperature of 830-900℃ for 1-3 hours to obtain a catalyst for cracking waste polystyrene; The mass ratio of the ammonium carbonate to the FCC waste catalyst is 0.17:1-0.26:1; the mass ratio of the calcium chloride solution to the FCC waste catalyst is 0.1:1-0.3:

1.

2. The process for the preparation of catalyst for cracking of waste polystyrene according to claim 1, wherein, The particle size of the ground FCC waste catalyst is less than 10µm.

3. The process for the preparation of catalyst for cracking of waste polystyrene as claimed in claim 1 wherein, The mass ratio of the sodium pyrophosphate to the FCC waste catalyst is 0.01:1-0.1:1, and the mass ratio of the water to the FCC waste catalyst is 2:1-3:

1.

4. The process for the preparation of catalyst for cracking of waste polystyrene as claimed in claim 1 wherein, After mixing the FCC waste catalyst with the sodium pyrophosphate and the deionized water, stirring is performed for 1-2 hours.

5. The process for the preparation of catalyst for cracking of waste polystyrene as claimed in claim 1 wherein, After mixing the mixture obtained in step 1 with the calcium chloride solution, stirring is performed for 1-2 hours.

6. The process for the preparation of catalyst for cracking of waste polystyrene as claimed in claim 1 wherein, The drying method in step 2 is spray drying.

7. The catalyst for cracking waste polystyrene obtained by the preparation method in any one of claims 1-6.

8. Use of the catalyst according to claim 7 for cracking of waste plastics, characterized in that, The cracking conditions are: a cracking temperature of 330-380℃, a pressure of normal pressure, and a mass ratio of the catalyst to the waste polystyrene of 2 wt%-15 wt%.

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