Preparation method of high-selectivity catalyst for waste plastic degradation

Abstract

The invention discloses a preparation method of a high-selectivity catalyst for waste plastic degradation, and the preparation method comprises the following steps: mixing a template agent with deionized water, and dropwise adding tetraethoxysilane into the mixture to obtain gel; weighing an aluminum source and adding the aluminum source into the gel to obtain mixed gel; weighing a nickel source and citric acid, adding deionized water, performing ultrasonic dissolution, adding into the mixed gel, and putting into a stainless steel reaction kettle with polytetrafluoroethylene as a lining to obtain a reaction product; separating a reaction product, washing a filter cake to be neutral by using deionized water, collecting a product, and drying; the product is roasted and naturally cooled, and the high-selectivity catalyst for waste plastic degradation is obtained, the catalyst has high selectivity, the reaction temperature of the PE and PP depolymerization process can be remarkably reduced, the yield of gas-phase and liquid-phase products exceeds 90% or above, and low-cost and high-added-value recycling of waste plastic can be achieved.

Description

Technical Field

[0001] The invention relates to a method for preparing a catalyst, and more specifically, to a method for preparing a highly selective catalyst for degrading waste plastics, and belongs to the field of petrochemical industry. Background Art

[0002] In recent years, my country's plastic industry has developed rapidly and has become the world's largest plastic producer. my country's plastic production accounts for about 30% of the world's total production. With the sharp increase in the use of plastic products in daily life, the amount of waste plastic garbage has also increased rapidly. According to UN data, about 300 million tons of plastic end up in landfills every year. The non-degradability of plastics has also caused serious environmental pollution, especially plastic bags, mulch, plastic bottles, food packaging, etc., which seriously pollute water bodies, soil and ecosystems, and ultimately damage human health. However, due to the lack of efficient plastic recycling technology, 70% of plastic waste is finally disposed of by landfill and incineration. Landfilling will cause plastic waste leachate to pollute groundwater and release microplastics, and incineration will lead to the release of a large amount of greenhouse gases. With the continuous deepening of research on the environmental hazards of plastic waste, how to deal with plastic waste has attracted great attention from scholars, and the recycling of waste plastics has become an important topic of global concern.

[0003] At present, the most common methods for recycling plastics include mechanical methods and depolymerization methods. The mechanical recycling method is to melt the plastic and re-mold it, but the quality of the secondary molded plastic products will generally decrease. The depolymerization method of waste plastic recycling breaks the complex plastic macromolecular chain hydrocarbons into small molecules through thermal cracking or catalytic cracking. It is suitable for the recycling of polyolefin waste plastics to produce oil products and chemicals, and can replace some fossil raw materials, reduce fossil raw material consumption and process carbon emissions. Compared with thermal cracking, the catalyst used in catalytic cracking can reduce the activation energy of the reaction. The pyrolysis process that uses catalysts to regulate the reaction process and product distribution can achieve controllable breakage of polymer molecular chains, increase the yield of gas and liquid products, and ultimately reduce energy consumption and recycling costs. Highly selective catalysts are the key to the development of waste plastic depolymerization technology. Summary of the invention

[0004] In order to solve the problem of too low gas phase and liquid phase yields in the current waste plastic depolymerization process, the present invention provides a method for preparing a highly selective catalyst for the degradation of waste plastics with the technical characteristics of high selectivity, significantly improving the gas phase and liquid phase product yields in the depolymerization products of waste PE and PP, and realizing the direct production of chemicals by depolymerization of waste plastics.

[0005] In order to achieve the above object, the present invention is implemented by the following technical solutions:

[0006] The present invention provides a method for preparing a highly selective catalyst for the degradation of waste plastics, the preparation method comprising the following steps:

[0007] Step 1): a certain amount of template and a certain amount of deionized water are mixed, and then ethyl orthosilicate is added dropwise to the mixture, and stirred at room temperature for 4 to 6 hours to obtain a gel;

[0008] Step 2): weigh a certain amount of aluminum source and add it to the gel obtained in step 1) to obtain a mixed gel; then weigh a certain amount of nickel source and citric acid, add a certain amount of deionized water to ultrasonically dissolve for 30 to 60 minutes, then add it to the mixed gel, stir evenly, put it into a stainless steel reactor lined with polytetrafluoroethylene, react at 150 to 200° C. for 12 to 48 hours to obtain a reaction product;

[0009] Step 3): Separate the reaction product of step 2) by using a suction filtration device, wash the filter cake with deionized water until it is neutral, collect the product, and dry it at 90-130° C. for 4-8 hours;

[0010] Step 4): The product obtained in step 3) is heated to 500-600° C. in a muffle furnace at a rate of 1-5° C. / min and calcined for 4-8 hours, and then cooled naturally to obtain a highly selective catalyst for the degradation of waste plastics.

[0011] Preferably, the template in step 1) is one of tetrapropylammonium hydroxide and tetrapropylammonium bromide.

[0012] Preferably, in step 1), the molar ratio of tetraethyl orthosilicate, template and deionized water is 1:1.0-1.5:20-25.

[0013] Preferably, the aluminum source in step 2) is one of sodium aluminate and aluminum isopropoxide.

[0014] Preferably, the molar ratio of the aluminum source, the nickel source in step 2) and the tetraethyl orthosilicate in step 1) is 1:1.5-2.0:35-40.

[0015] Preferably, the molar ratio of the nickel source, citric acid and deionized water in step 2) is 1:1.5-2.0:500-600.

[0016] Beneficial effects: The process is simple, the preparation is efficient, the selectivity is high, and it is suitable for mass production. The catalyst can significantly reduce the reaction temperature of the PE and PP depolymerization process, and the yield of gas and liquid products exceeds 90%, which can achieve low-cost and high-value-added recycling of waste plastics and realize the direct production of chemicals by depolymerization of waste plastics. DETAILED DESCRIPTION

[0017] The present invention is further described below in conjunction with the specification, but the present invention is not limited to the following embodiments. The embodiments of the present application include embodiments formed by taking the left endpoint value of the range value in the technical scheme, embodiments formed by taking the right endpoint value, embodiments formed by taking the middle value, and embodiments formed by taking any value in the range value.

[0018] A specific embodiment of a method for preparing a highly selective catalyst for the degradation of waste plastics according to the present invention comprises the following steps:

[0019] Step 1): a certain amount of template agent and a certain amount of deionized water are mixed, and then tetraethyl orthosilicate is added dropwise to the mixture, and stirred at room temperature for 4 to 6 hours to obtain a gel; the template agent is one of tetrapropylammonium hydroxide and tetrapropylammonium bromide; the molar ratio of the tetraethyl orthosilicate, the template agent and the deionized water is 1:1.0-1.5:20-25;

[0020] Step 2): weigh a certain amount of aluminum source and add it to the gel obtained in step 1) to obtain a mixed gel; then weigh a certain amount of nickel source and citric acid, add a certain amount of deionized water to ultrasonically dissolve for 30 to 60 minutes, add it to the mixed gel, stir evenly, put it into a stainless steel reactor lined with polytetrafluoroethylene, react at 150 to 200° C. for 12 to 48 hours to obtain a reaction product; the aluminum source is one of sodium aluminate and aluminum isopropoxide; the molar ratio of the aluminum source, the nickel source and tetraethyl orthosilicate is 1:1.5 to 2.0:35 to 40; the molar ratio of the nickel source, the citric acid and deionized water is 1:1.5 to 2.0:500 to 600;

[0021] Step 3): Separate the reaction product of step 2) by using a suction filtration device, wash the filter cake with deionized water until it is neutral, collect the product, and dry it at 90-130° C. for 4-8 hours;

[0022] Step 4): The product obtained in step 3) is heated to 500-600° C. in a muffle furnace at a rate of 1-5° C. / min and calcined for 4-8 hours, and then cooled naturally to obtain a highly selective catalyst for the degradation of waste plastics.

[0023] The present invention is suitable for high-value-added recycling of waste plastics, and has a good promoting effect on reducing white pollution, practicing the concept of circular economy, and achieving the "dual carbon" goal.

[0024] Finally, it should be noted that the present invention is not limited to the above embodiments, and many variations are possible. All variations that can be directly derived or associated with the content disclosed by a person skilled in the art should be considered as within the protection scope of the present invention.

Claims

1. A method for preparing a highly selective catalyst for the degradation of waste plastics, characterized in that The preparation method comprises the following steps: Step 1): a certain amount of template and a certain amount of deionized water are mixed, and then ethyl orthosilicate is added dropwise to the mixture, and stirred at room temperature for 4 to 6 hours to obtain a gel; Step 2): weigh a certain amount of aluminum source and add it to the gel obtained in step 1) to obtain a mixed gel; then weigh a certain amount of nickel source and citric acid, add a certain amount of deionized water to ultrasonically dissolve for 30 to 60 minutes, then add it to the mixed gel, stir evenly, put it into a stainless steel reactor lined with polytetrafluoroethylene, react at 150 to 200° C. for 12 to 48 hours to obtain a reaction product; Step 3): Separate the reaction product of step 2) by using a suction filtration device, wash the filter cake with deionized water until it is neutral, collect the product, and dry it at 90-130° C. for 4-8 hours; Step 4): The product obtained in step 3) is heated to 500-600° C. in a muffle furnace at a rate of 1-5° C. / min and calcined for 4-8 hours, and then cooled naturally to obtain a highly selective catalyst for the degradation of waste plastics.

2. The method for preparing a highly selective catalyst for the degradation of waste plastics according to claim 1, characterized in that: The template agent in step 1) is one of tetrapropylammonium hydroxide and tetrapropylammonium bromide.

3. A method for preparing a highly selective catalyst for the degradation of waste plastics according to claim 1 or 2, characterized in that: The molar ratio of ethyl orthosilicate, template and deionized water in step 1) is 1:1.0-1.5:20-25.

4. The method for preparing a highly selective catalyst for the degradation of waste plastics according to claim 1, characterized in that: The aluminum source in step 2) is one of sodium aluminate and aluminum isopropoxide.

5. The method for preparing a highly selective catalyst for the degradation of waste plastics according to claim 3, characterized in that: The molar ratio of the aluminum source, the nickel source and the tetraethyl orthosilicate in step 2) is 1:1.5-2.0:35-40.

6. A method for preparing a highly selective catalyst for the degradation of waste plastics according to claim 1 or 5, characterized in that: The molar ratio of the nickel source, citric acid and deionized water in step 2) is 1:1.5-2.0:500-600.