An alkaline catalyst for catalytic cracking of waste plastics and its application

Abstract

The present invention discloses an alkaline catalyst for catalytic cracking of waste plastics and its application, belonging to the technical field of waste plastic recycling. The alkaline catalyst for catalytic cracking of waste plastics comprises plant ash, sodium carbonate, calcium hydroxide and magnesium oxide, and the mass contents of each component are as follows: the addition amount of plant ash is 50-80%, sodium carbonate is 5-30%, magnesium oxide is 2-10%, and calcium hydroxide is 10-20%. This alkaline catalyst is applied to the catalytic cracking of waste plastics. The alkaline catalyst for catalytic cracking of waste plastics is added to waste plastic particles and stirred evenly, and the reaction is carried out at 400-600 °C for 15-30 min in a high-temperature cracking furnace. The input weight ratio of the alkaline catalyst for catalytic cracking of waste plastics to waste plastic particles is 0.1-0.5:100. The present invention constructs a solid alkaline catalyst system through the combination of components with different alkalinities, reduces the reaction activation energy of waste plastic cracking, provides alkaline reaction sites, improves the selectivity of products, and cracks plastics into small-molecule gases, oil products and coke.

Description

Technical Field

[0001] The present invention relates to the technical field of waste plastic recycling, and particularly relates to an alkaline catalyst for catalytic cracking of waste plastics and its application. Background Art

[0002] Plastics are widely used in industry, agriculture and household life. At present, most plastic products cannot degrade by themselves and need to be treated to reduce the impact on the environment. Currently, the treatment of waste plastics mainly relies on incineration.

[0003] Recycling waste plastics using appropriate technologies is an urgent need for the current circular economy. Countries around the world are using administrative and legal means to promote the resource utilization of plastics.

[0004] The plastic heat treatment process is a relatively thorough plastic treatment technology, but its treatment temperature is high and the product distribution is not regulated. In order to further optimize the cracking process, in recent years, catalytic cracking of waste plastics has attracted people's attention. The core of catalytic cracking is the selection of the catalyst system. However, most catalysts still use conventional catalytic cracking catalysts in the oil refining industry, which have poor specificity and high prices, limiting their application. Summary of the Invention

[0005] The object of the present invention is to provide an alkaline catalyst for catalytic cracking of waste plastics and its application, which can reduce the reaction activation energy of waste plastic cracking, improve the selectivity of products, and crack plastics into small molecule gases, oils and cokes.

[0006] To achieve the above object, the present invention provides an alkaline catalyst for catalytic cracking of waste plastics. The alkaline catalyst for catalytic cracking of waste plastics includes plant ash, sodium carbonate, calcium hydroxide and magnesium oxide. The mass contents of each component are: plant ash is 50 - 80%, sodium carbonate is 5 - 30%, magnesium oxide is 2 - 10%, and calcium hydroxide is 10 - 20%.

[0007] Preferably, the potassium carbonate content in the plant ash is at least 10%.

[0008] Preferably, the particle size of the alkaline catalyst for catalytic cracking of waste plastics is 10 - 100 μm.

[0009] The present invention also provides the application of the above-mentioned alkaline catalyst for catalytic cracking of waste plastics. The alkaline catalyst for catalytic cracking of waste plastics is applied to the catalytic cracking of waste plastics, and the waste plastics include but are not limited to polyethylene, polypropylene, polyvinyl chloride and polystyrene.

[0010] Preferably, the alkaline catalyst for catalytic cracking of waste plastics is added to waste plastic particles and stirred evenly. Under normal pressure, in the range of 400 - 600 °C, it reacts in a high-temperature cracking furnace for 15 - 30 minutes.

[0011] Preferably, the input weight ratio of the alkaline catalyst for catalytic cracking of waste plastics to the waste plastic particles is 0.1-0.5:100.

[0012] Preferably, the waste plastic particles are crushed to less than 2 mm.

[0013] The alkaline catalyst reaction of the present invention complies with the carbon anion reaction mechanism. The alkaline catalyst first reacts with a carbon atom on the main chain to capture the hydrogen proton of the carbon to form a carbon anion and an alkaline metal ion. Then the main chain breaks and cracks into small molecular hydrocarbons. Then the carbon anion recaptures the hydrogen proton of the metal ion, and the metal ion is reduced to its original form to complete the reaction.

[0014] The invention discloses an alkaline catalyst for catalytic cracking of waste plastics and application thereof, which has the following beneficial effects:

[0015] 1. The catalyst of the present invention has a simple structure and low cost, reduces the activation energy of the reaction of waste plastic cracking, allows the reaction to proceed at a lower temperature, has a high resistance to carbon deposition, reduces the formation of coke, maintains the activity of the catalyst, is easy to recycle, reduces production costs, reduces dependence on new resources and environmental pollution problems in the waste treatment process, and complies with the concept of environmental protection and sustainable development;

[0016] 2. In the present invention, a solid alkaline catalyst system is constructed, wood ash and calcium hydroxide are used to promote the breakage and transformation of plastic molecules, and magnesium oxide has good thermal stability and chemical stability to provide alkaline sites. Sodium carbonate is used to adjust the pH value of the reaction system to optimize the catalytic effect, so that different alkaline components can be adjusted to each other, affecting the distribution and yield of cracking products, and obtaining higher cracking liquid and hydrocarbon yields.

[0017] The technical solution of the present invention is further described in detail below through embodiments. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is further illustrated by the following examples.

[0019] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0020] In addition, it should be understood that although this specification is described according to the implementation modes, not every implementation mode includes only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art. These other implementation modes are also covered within the protection scope of the present invention.

[0021] To achieve the above object, the present invention provides an alkaline catalyst for catalytic cracking of waste plastics, which includes plant ash, sodium carbonate, calcium hydroxide and magnesium oxide. The mass contents of each component are as follows: the addition amount of plant ash is 50 - 80%, sodium carbonate is 5 - 30%, magnesium oxide is 2 - 10%, and calcium hydroxide is 10 - 20%. The potassium carbonate content in the plant ash is at least 10%. The particle size of the alkaline catalyst for catalytic cracking of waste plastics is

[0022] The above alkaline catalyst for catalytic cracking of waste plastics is applied to the catalytic cracking of waste plastics, and the waste plastics include but are not limited to polyethylene, polypropylene, polyvinyl chloride, and polystyrene.

[0023] The specific steps are as follows: Add the alkaline catalyst for catalytic cracking of waste plastics into waste plastic particles with a size of less than 2 mm and stir evenly. The input weight ratio of the alkaline catalyst for catalytic cracking of waste plastics to the waste plastic particles is 0.1 - 0.5:100. React at 400 - 600 °C under the reaction pressure in a high-temperature cracking furnace for 15 - 30 minutes.

[0024] To further illustrate the present invention, the following describes the solution of the present invention in detail with reference to embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0025] Example 1

[0026] This example provides an alkaline catalyst for catalytic cracking of waste plastics. Among them, the weight ratio of plant ash, MgO, sodium carbonate and calcium hydroxide is 60:5:20:15. Put this catalyst into waste plastics with a size of 1 - 2 mm and stir evenly. The input weight ratio of the catalyst to the waste plastics is 0.3:100. React at 500 °C in a high-temperature cracking furnace for 15 minutes, and the reaction products are shown in Table 1 below.

[0027] Example 2

[0028] This example provides an alkaline catalyst for catalytic cracking of waste plastics. Among them, the weight ratio of plant ash, MgO, sodium carbonate and calcium hydroxide is 65:5:15:15. Put this catalyst into waste plastics with a size of 1 - 2 mm and stir evenly. The input weight ratio of the catalyst to the waste plastics is 0.3:100. React at 500 °C in a high-temperature cracking furnace for 20 minutes, and the reaction products are shown in Table 1 below.

[0029] Example 3

[0030] This embodiment provides an alkaline catalyst for catalytic cracking of waste plastics. Among them, the weight ratio of plant ash, MgO, sodium carbonate, and calcium hydroxide is 60:5:20:15. This catalyst is put into waste plastics with a size of 1-2 mm and stirred evenly. The input weight ratio of the catalyst to the waste plastics is 0.3:100, and it reacts at 400 °C in a high-temperature cracking furnace for 25 minutes. The reaction products are shown in Table 1 below.

[0031] Comparative Example 1

[0032] In this comparative example, the components and weight ratio of the catalyst are plant ash:magnesium oxide:sodium carbonate = 65:15:20. This catalyst is put into waste plastics with a size of 1-2 mm and stirred evenly. The input weight ratio of the catalyst to the waste plastics is 0.3:100, and it reacts at 500 °C in a high-temperature cracking furnace for 15 minutes. The reaction products are shown in Table 1 below.

[0033] Comparative Example 2

[0034] In this comparative example, the components and weight ratio of the provided catalyst are plant ash:sodium carbonate:calcium hydroxide = 65:20:15. This catalyst is put into waste plastics with a size of 1-2 mm and stirred evenly. The input weight ratio of the catalyst to the waste plastics is 0.3:100, and it reacts at 500 °C in a high-temperature cracking furnace for 20 minutes. The reaction products are shown in Table 1 below.

[0035] Comparative Example 3

[0036] In this comparative example, the components and weight ratio of the provided catalyst are plant ash:MgO:calcium hydroxide = 60:15:25. This catalyst is put into waste plastics with a size of 1-2 mm and stirred evenly. The input weight ratio of the catalyst to the waste plastics is 0.3:100, and it reacts at 400 °C in a high-temperature cracking furnace for 25 minutes. The reaction products are shown in Table 1 below.

[0037] Table 1 Reaction products of Examples 1-3 and Comparative Examples 1-3

[0038]

[0039] Through the comparison of the above data, in the component and ratio of this technical solution, when obtaining a lower solid ratio, the gas products are more concentrated in C3 - C4, and the liquid products are concentrated in C7-C8, optimizing the product ratio.

[0040] Therefore, the present invention adopts the above-mentioned alkaline catalyst for catalytic cracking of waste plastics and its application. The present invention constructs a solid alkaline catalyst system through the combination of components with different alkalinities, reduces the reaction activation energy of waste plastic cracking, provides alkaline reaction sites, has excellent stability, improves the selectivity of products, and cracks plastics into small molecule gases, oil products, and coke.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and such modifications or equivalent replacements do not cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. An alkaline catalyst for catalytic cracking of waste plastics, characterized in that, The basic catalyst for catalytic cracking of waste plastics is plant ash, sodium carbonate, calcium hydroxide and magnesium oxide, and the mass contents of each component are: plant ash is 50-80%, sodium carbonate is 5-30%, magnesium oxide is 2-10%, and calcium hydroxide is 10-20%; The potassium carbonate content in the plant ash is at least 10%.

2. The basic catalyst for catalytic cracking of waste plastics according to claim 1, characterized in that, The particle size of the basic catalyst for catalytic cracking of waste plastics is 10-100 μm.

3. Use of an alkaline catalyst for catalytic cracking of waste plastics as described in any one of claims 1-2, characterized in that, The basic catalyst for catalytic cracking of waste plastics is applied to catalytic cracking of waste plastics, and the waste plastics include polyethylene, polypropylene, polyvinyl chloride and polystyrene.

4. Use of an alkaline catalyst for catalytic cracking of waste plastics according to claim 3, characterized in that, The basic catalyst for catalytic cracking of waste plastics is added to waste plastic particles and stirred evenly. Under normal pressure, at 400-600 °C, the reaction is carried out in a high-temperature cracking furnace for 15-30 min.

5. Use of an alkaline catalyst for catalytic cracking of waste plastics according to claim 4, characterized in that, The input weight ratio of the basic catalyst for catalytic cracking of waste plastics to waste plastic particles is 0.1-0.5:

100.

6. The application of an alkaline catalyst for catalytic cracking of waste plastics according to claim 4, wherein, The waste plastic particles are crushed to less than 2 mm.

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