Basic catalyst for catalytic cracking of waste plastics and application of basic catalyst

Abstract

The invention discloses a basic catalyst for catalytic cracking of waste plastics and application of the basic catalyst, and belongs to the technical field of waste plastic recovery. The basic catalyst for waste plastic catalytic cracking comprises the following components in percentage by mass: 50 to 80 percent of plant ash, 5 to 30 percent of sodium carbonate, 2 to 10 percent of magnesium oxide and 10 to 20 percent of calcium hydroxide. The basic catalyst is applied to catalytic cracking of waste plastics, and the basic catalyst for catalytic cracking of the waste plastics is added into waste plastic particles, uniformly stirred and subjected to a reaction in a high-temperature cracking furnace at 400-600 DEG C for 15-30 min. The input weight ratio of the basic catalyst for catalytic cracking of the waste plastic to the waste plastic particles is (0.1-0.5): 100. According to the invention, a solid alkaline catalyst system is constructed by matching different alkaline components, so that the reaction activation energy of waste plastic cracking is reduced, alkaline reaction sites are provided, the selectivity of products is improved, and the plastic is cracked into small molecular gas, oil products and coke.

Description

Technical Field

[0001] The invention relates to the technical field of waste plastic recycling, in particular to an alkaline catalyst for catalytic cracking of waste plastic and application thereof. Background Art

[0002] Plastics are widely used in industry, agriculture and people's daily life. At present, most plastic products cannot be self-degraded and need to be treated to reduce the impact on the environment. Currently, incineration is still the main method of treating waste plastics.

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

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

[0005] The purpose of the present invention is to provide an alkaline catalyst for catalytic cracking of waste plastics and its application, so as to reduce the reaction activation energy of the cracking of waste plastics, improve the selectivity of the products, and crack the plastics into small molecule gases, oil products and coke.

[0006] To achieve the above-mentioned purpose, the present invention provides an alkaline catalyst for catalytic cracking of waste plastics, wherein the alkaline catalyst for catalytic cracking of waste plastics comprises wood ash, sodium carbonate, calcium hydroxide and magnesium oxide, and the mass content of each component is: wood 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 wood ash is at least 10%.

[0008] Preferably, the particle size of the alkaline catalyst for catalytic cracking of waste plastics is 10-100 μm The present invention also provides the use of the above-mentioned alkaline catalyst for catalytic cracking of waste plastics, wherein the alkaline catalyst for catalytic cracking of waste plastics is applied to catalytic cracking of waste plastics, and the waste plastics include but are not limited to polyethylene, polypropylene, polyvinyl chloride, and polystyrene.

[0009] Preferably, an alkaline catalyst for catalytic cracking of waste plastics is added to waste plastic particles and stirred evenly, and reacted in a high-temperature cracking furnace at 400-600° C. under normal pressure for 15-30 minutes.

[0010] 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.

[0011] Preferably, the waste plastic particles are crushed to less than 2 mm.

[0012] 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.

[0013] The invention discloses an alkaline catalyst for catalytic cracking of waste plastics and application thereof, which has the following beneficial effects: 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; 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.

[0014] The technical solution of the present invention is further described in detail below through embodiments. DETAILED DESCRIPTION

[0015] The technical solution of the present invention is further illustrated by the following examples.

[0016] 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.

[0017] 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.

[0018] To achieve the above object, the present invention provides an alkaline catalyst for catalytic cracking of waste plastics, comprising plant ash, sodium carbonate, calcium hydroxide and magnesium oxide, wherein the mass content of each component is: 50-80% of plant ash, 5-30% of sodium carbonate, 2-10% of magnesium oxide, and 10-20% of calcium hydroxide. 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 The alkaline catalyst for catalytic cracking of waste plastics is applied to catalytic cracking of waste plastics, and the waste plastics include but are not limited to polyethylene, polypropylene, polyvinyl chloride, and polystyrene.

[0019] The specific steps are: adding the alkaline catalyst for catalytic cracking of waste plastics to waste plastic particles with a size of less than 2 mm and stirring evenly, the weight ratio of the alkaline catalyst for catalytic cracking of waste plastics to the waste plastic particles is 0.1-0.5:100. Adding the reaction pressure in a high-temperature cracking furnace at 400-600°C for 15-30 minutes.

[0020] In order to further illustrate the present invention, the scheme of the present invention is described in detail below in conjunction with embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0021] Example 1 This embodiment provides an alkaline catalyst for catalytic cracking of waste plastics, wherein the weight ratio of plant ash, MgO, sodium carbonate and calcium hydroxide is 60:5:20:15. The catalyst is added to waste plastics with a size of 1-2 mm and stirred evenly, and the weight ratio of the catalyst to the waste plastics is 0.3:100. The reaction is carried out in a high-temperature cracking furnace at 500°C for 15 minutes, and the reaction products are shown in Table 1 below.

[0022] Example 2 This embodiment provides an alkaline catalyst for catalytic cracking of waste plastics, wherein the weight ratio of plant ash, MgO, sodium carbonate and calcium hydroxide is 65:5:15:15. The catalyst is added to waste plastics with a size of 1-2 mm and stirred evenly, the weight ratio of the catalyst to the waste plastics is 0.3:100, and the reaction is carried out at 500°C in a high-temperature cracking furnace for 20 minutes. The reaction products are shown in Table 1 below.

[0023] Example 3 This embodiment provides an alkaline catalyst for catalytic cracking of waste plastics, wherein the weight ratio of plant ash, MgO, sodium carbonate and calcium hydroxide is 60:5:20:15. The catalyst is added to waste plastics with a size of 1-2 mm and stirred evenly, the weight ratio of the catalyst to the waste plastics is 0.3:100, and the reaction is carried out at 400°C in a high-temperature cracking furnace for 25 minutes. The reaction products are shown in Table 1 below.

[0024] Comparative Example 1 The components and weight ratio of the catalyst in this comparative example are wood ash: magnesium oxide: sodium carbonate = 65:15:20. The catalyst is added to waste plastics with a size of 1-2 mm and stirred evenly. The weight ratio of the catalyst to the waste plastics is 0.3:100. The mixture is reacted at 500°C in a high-temperature cracking furnace for 15 minutes. The reaction products are shown in Table 1 below.

[0025] Comparative Example 2 The catalyst components and weight ratio provided in this comparative example are wood ash: sodium carbonate: calcium hydroxide = 65:20:15. The catalyst is added to waste plastics with a size of 1-2 mm and stirred evenly. The weight ratio of the catalyst to the waste plastics is 0.3:100. The mixture is reacted at 500°C in a high-temperature cracking furnace for 20 minutes. The reaction products are shown in Table 1 below.

[0026] Comparative Example 3 The catalyst components and weight ratio provided in this comparative example are plant ash: MgO: calcium hydroxide = 60: 15: 25. The catalyst is added to waste plastics with a size of 1-2 mm and stirred evenly. The weight ratio of the catalyst to the waste plastics is 0.3: 100. The reaction is carried out at 400° C. in a high-temperature cracking furnace for 25 minutes. The reaction products are shown in Table 1 below.

[0027] Table 1 Reaction products of Examples 1-3 and Comparative Examples 1-3

[0028] Through the comparison of the above data, the components and proportions in the technical solution can obtain a lower solid ratio, with the gas product being more concentrated on C3-C4 and the liquid product being concentrated on C7-C8, thereby optimizing the product ratio.

[0029] 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 by combining components of different alkalinity, reduces the reaction activation energy of waste plastic cracking, provides alkaline reaction sites, has excellent stability, improves the selectivity of the product, and cracks the plastic into small molecule gases, oil products and coke.

[0030] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

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

2. The alkaline catalyst for catalytic cracking of waste plastics according to claim 1, characterized in that: The potassium carbonate content in the wood ash is at least 10%.

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

4. An application of an alkaline catalyst for catalytic cracking of waste plastics as claimed in any one of claims 1 to 3, characterized in that: The alkaline 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.

5. The use of an alkaline catalyst for catalytic cracking of waste plastics according to claim 4, characterized in that: The alkaline catalyst for catalytic cracking of waste plastics is added to the waste plastic particles and stirred evenly, and reacted in a high-temperature cracking furnace at 400-600°C under normal pressure for 15-30 minutes.

6. The use of an alkaline catalyst for catalytic cracking of waste plastics according to claim 5, characterized in that: 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.

7. The use of an alkaline catalyst for catalytic cracking of waste plastics according to claim 5, characterized in that: Waste plastic particles are crushed to less than 2mm.

Images