Method for preparing dicarboxylic acid from plastic pyrolysis oil

Abstract

The invention relates to a method for preparing dicarboxylic acid from plastic pyrolysis oil. The method comprises the following steps: preheating and vaporizing plastic pyrolysis oil, a carboxylation auxiliary agent and oxidation carrier gas, introducing into a reactor, and reacting under the action of plasma to prepare dicarboxylic acid. The method has the following advantages that the application channel of waste plastic chemical recovery products is expanded, the obtained dicarboxylic acid is high in yield, the dicarboxylic acid can be used for synthesis of polyester after separation, and compared with a traditional plastic cracking oil preparation process, the method has higher product additional value. By introducing the carboxylation auxiliary agent and the oxidation carrier gas, the plastic is activated by the plasma, the introduction effect of a terminal carboxylic acid functional group is further enhanced, the synergistic effect of gaseous homogeneous oxidation in the plasma atmosphere is realized, the efficient activation of the plastic cracking light oil is promoted, and the reaction efficiency is improved.

Description

Technical Field

[0001] The invention relates to the field of waste plastic recycling, and in particular to a method for preparing dicarboxylic acid from plastic pyrolysis oil. Background Art

[0002] The world is seriously polluted by plastic waste. Recyclable and reusable plastics account for less than 9%, and most of them are discarded or treated as waste. There are two recycling technologies for waste plastics: chemical recycling and physical recycling. The number of physical recycling is limited, and the quality of recycled materials is poor. Chemical recycling realizes the utilization of plastics at the molecular level and is a better recycling method. At present, chemical recycling is mainly based on the process of thermal cracking to produce oil, which uses electric heating or pyrolysis furnace combustion heating to convert waste plastics into small molecule hydrocarbon products.

[0003] Invention patent CN 218932061 U discloses a plasma high-temperature cracking device for treating waste plastics. By changing the structure of the plasma reactor, the materials at different positions inside the cracking furnace body are heated more evenly, thereby increasing the cracking speed.

[0004] Invention patent CN 116286094 A discloses a method for low-temperature plasma-assisted co-conversion of waste plastics and methane, wherein a methane-containing reaction gas is passed into a low-temperature plasma reactor filled with waste plastics and a catalyst to obtain gaseous and liquid products with high added value;

[0005] Invention patent CN 114507542 B discloses a method and system for preparing light oil products from waste plastics. The obtained dechlorinated waste plastics are decontaminated in a waste plastic thermal dissolution and decontamination unit to obtain a decontaminated plastic-containing solution, which is further thermally cracked to obtain a light oil product.

[0006] The light oil products obtained from plastic chemical recycling are mainly used as naphtha cracking raw materials or catalytic cracking cracking raw materials in petroleum refining units. The utilization form is single and the overall benefits are low. Polyethylene plastic cracking light oil is mainly linear alkanes and olefins. Converting them into dicarboxylic acids can further expand the application channels of plastic chemical recycling products and increase their added value. However, it is difficult to directly achieve efficient oxidation by traditional high-temperature multiphase catalytic methods. Therefore, it is necessary to develop a method that can efficiently prepare dicarboxylic acids from plastic cracking oil. Summary of the invention

[0007] The present invention aims to solve the problem that the utilization channel of light oil recovered by plastic chemical recycling is single and the added value is low, and provides a method for preparing dicarboxylic acid from plastic pyrolysis oil. By optimizing plasma treatment technology, introducing carboxylation auxiliary agent and oxidizing carrier gas, the synergy of ionization and homogeneous oxidation in the plasma process is achieved.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0009] A method for preparing dicarboxylic acid from plastic pyrolysis oil comprises the following steps: preheating and vaporizing the plastic pyrolysis oil, a carboxylation aid and an oxidizing carrier gas, and then introducing them into a reactor to react under the action of plasma to prepare the dicarboxylic acid.

[0010] In the present invention, the plastic pyrolysis oil is a small molecule liquid oil obtained by pyrolysis of plastic (such as waste plastic) after heat treatment, and is mainly a mixture of low molecular hydrocarbons. For example, thermal pyrolysis light oil of mulch plastic, pyrolysis oil of plastic sorted by domestic garbage, pyrolysis oil of plastic disassembled by washing machines, and pyrolysis oil of factory defective polyolefin products. The plastic pyrolysis oil can be purchased from the market or obtained by pyrolysis. The present invention has no special requirements for its source. Plastic pyrolysis oil production is a prior art. Any feasible method in the field can be used to prepare pyrolysis oil by plastic pyrolysis reaction, such as the methods disclosed in patent CN114507542A and the document The Chemistry and Kinetics of Polyethylene Pyrolysis AProcess to Produce Fuels and Chemicals. The pyrolysis oil obtained by pyrolysis of plastic is suitable for the present invention.

[0011] The composition of the plastic pyrolysis oil is slightly different due to the influence of the type of pyrolysis raw material plastic, and mainly includes one or more components of C5-C20 alkanes (such as pentane, hexane, heptane, octane, nonane, decane, C10 and above alkanes, etc.), olefins (such as pentene, hexene, heptene, octene, nonene, decene, C10 and above terminal olefins and dienes), cycloalkanes (such as cyclohexane, cyclopentane, etc.), cycloolefins (such as methylcyclohexane, ethylcyclohexane, etc.), aromatic hydrocarbons (such as benzene, toluene, xylene, etc.), etc., preferably one or more components of C6-C10 straight-chain terminal olefins and straight-chain alkanes.

[0012] In a specific embodiment, the plastic pyrolysis oil is selected from at least one of polyethylene (PE) pyrolysis oil, polypropylene pyrolysis oil, polystyrene pyrolysis oil, etc., preferably polyethylene pyrolysis oil, such as pyrolysis oil obtained from high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), etc.

[0013] In a specific embodiment, the carboxylation auxiliary agent is a solution containing an organic iron compound; preferably, the mass concentration of the organic iron compound in the solution is 0.2-1%, such as 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, etc. or a range consisting of any two thereof, preferably 0.4-0.6%;

[0014] Preferably, the organic iron compound is selected from organic iron compounds with a boiling point of 50-350°C, for example, a boiling point of 50°C, 100°C, 150°C, 200°C, 250°C, 300°C, 350°C, etc. or a range consisting of any two thereof, preferably one or more of ferric acetate, ferric acrylate, ferric acetylacetonate, ferrocene, ferric citrate, etc., more preferably ferric acetate and / or ferric acetylacetonate;

[0015] Preferably, the solvent of the solution containing organic iron compounds is selected from one or more of ethanol, acetone, ether, etc., preferably ethanol.

[0016] In a specific embodiment, the oxidizing carrier gas is a mixture of an oxidizing component and argon; preferably, the volume fraction of the oxidizing component in the oxidizing carrier gas is 0.1-5%, such as 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc. or a range consisting of any two thereof, preferably 0.5-1%;

[0017] Preferably, the oxidizing component is selected from an inorganic oxidant or an organic oxidant; the inorganic oxidant is selected from one or more of ozone, oxygen, etc.; the organic oxidant is selected from one or more of hydrogen peroxide, tert-butyl hydroperoxide, ethylbenzene hydroperoxide, etc., preferably ozone and / or tert-butyl hydroperoxide. Among them, it is a non-gaseous substance at room temperature, and is calculated according to its volume fraction in the saturated gas phase at normal temperature and pressure. For example, tert-butyl hydroperoxide is a liquid substance at room temperature (25°C), and its saturated vapor pressure is 7.4 mmHg (about 1 kPa). It is calculated that the volume fraction of tert-butyl hydroperoxide in the saturated gas phase at normal temperature and pressure is about 1%.

[0018] In a specific embodiment, the feed volume ratio of the plastic pyrolysis oil, the oxidizing carrier gas, and the carboxylation auxiliary agent is 1-50:50-1000:1, for example (1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, etc. or a range consisting of any two of them): (50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, etc. or a range consisting of any two of them): 1, preferably 10-25:50-200:1, the feed volume ratio is the ratio of the feed volume per unit time (e.g., mL / min).

[0019] In a specific embodiment, the preheating vaporization temperature of the raw material plastic pyrolysis oil, carboxylation auxiliary agent, and oxidation carrier gas feeding is 300-500°C, for example, 300°C, 350°C, 400°C, 450°C, 500°C, etc. or a range composed of any two of them, preferably 350-400°C.

[0020] In a specific embodiment, the plasma is in the form of low-temperature dielectric barrier discharge plasma, and the reactor is preferably a low-temperature dielectric barrier plasma reactor.

[0021] In a specific embodiment, the plasma action has a voltage of 5000-40000V, for example, 5000V, 10000V, 15000V, 20000V, 25000V, 30000V, 35000V, 40000V, etc., or a range consisting of any two thereof; the AC frequency is 50-100kHz, for example, 50kHz, 60kHz, 70kHz, 80kHz, 90kHz, 100kHz, etc., or a range consisting of any two thereof, preferably 80-100kHz.

[0022] In a specific embodiment, the reaction temperature is 200-500°C, for example 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, etc., or a range consisting of any two thereof, preferably 300-400°C; the reaction time is 0.5-60min, for example 0.5min, 5min, 10min, 20min, 30min, 40min, 50min, 60min, etc., or a range consisting of any two thereof, preferably 2-25min.

[0023] In a specific embodiment, the reactor has a high-temperature gas phase as the outlet product, which is condensed to obtain a liquid phase product and a small amount of non-condensable gas, and the liquid phase product is collected; the main component of the liquid phase product is a dicarboxylic acid, including one or more of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, etc., with a total proportion of 31-64wt%, and the others are C4-C8 alcohols, C6-C10 monocarboxylic acids, C6-C10 aldehydes, carbon dioxide, carbon monoxide, etc. The liquid phase product obtained by the present invention can be obtained by conventional refining means such as distillation, crystallization, etc. to obtain a dicarboxylic acid product.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The application channels of waste plastic chemical recycling products are expanded. The obtained dicarboxylic acid has a high yield (up to 64% or more in some preferred examples) and can be used for polyester synthesis after separation. Compared with the traditional plastic cracking oil production process, it has a higher product added value.

[0026] (2) By regulating the plasma reaction conditions, an oxidizing atmosphere and a carboxylation aid are introduced simultaneously during the reaction process, so that the reaction is in a homogeneous state, achieving the synergy of plasma activation and carboxylic acid oxidation. The terminal carbon-hydrogen bonds of chain hydrocarbon substances (such as C6-C10 straight-chain hydrocarbons) in the plastic pyrolysis oil are ionized, and the generation of carboxyl groups is enhanced, thereby improving the reaction efficiency. DETAILED DESCRIPTION

[0027] The technical scheme of the present invention and its effects are further described below by specific examples. The following examples are only used to illustrate the content of the present invention and are not used to limit the protection scope of the present invention. Simple changes made to the present invention by applying the concept of the present invention are all within the scope of the protection claimed by the present invention.

[0028] The plastic pyrolysis oil raw material used in the embodiments and comparative examples was prepared by the following method:

[0029] Plastic pyrolysis oil was prepared by a pyrolysis reactor with a volume of 200 mL. 60 g of PE plastic particles (including different grades of HDPE, LLDPE, etc., PE molecular weight of 80000-200000 g / mol, PP molecular weight of 150000 g / mol) were weighed and loaded into the pyrolysis reactor. The experiment was carried out in a nitrogen atmosphere with a nitrogen flow rate of 50 mL / min, a pyrolysis temperature of 500 ° C, and a reaction time of about 1 h. The vapor produced by pyrolysis was condensed to obtain an oil product. The oil product was distilled under reduced pressure at 100 mbar to obtain cracking light oil, i.e., plastic pyrolysis oil, which mainly includes hexane, hexene, heptane, heptene, octane, octene, nonane, nonene, decane, decene, cyclohexane, benzene, toluene and other components.

[0030] Unless otherwise specified, other raw materials used in the examples or comparative examples can be obtained from commercial channels.

[0031] Low-temperature dielectric barrier plasma reactor: model WHDLZT-001, plasma voltage 2000V, power 5KW.

[0032] Yield: The yield is obtained by multiplying the conversion rate by the selectivity. The conversion rate is measured experimentally, and the mass proportion of the dicarboxylic acid in the product (i.e., the selectivity) is obtained by performing gas chromatography analysis on the obtained product.

[0033] The following is an introduction to the related methods used or possibly used in the embodiments or comparative examples of the present invention:

[0034] Example 1

[0035] HDPE plastic cracking oil, ozone / argon mixed gas (the volume fraction of ozone is 0.5%), and 0.4% ferric acetate ethanol solution with a feed volume ratio of 10:50:1 are preheated and vaporized at 350°C, and then enter a low-temperature dielectric barrier plasma reactor for reaction, with a plasma voltage of 15000V, an AC frequency of 80kHZ, a reaction temperature of 400°C, and a reaction time of 20min. After the reaction, the liquid phase product is condensed and collected and the composition is tested, wherein the dicarboxylic acid content is 40wt%, and the dicarboxylic acid yield is 39%.

[0036] Example 2

[0037] HDPE plastic cracking oil, tert-butyl hydroperoxide / argon mixed gas (the volume fraction of tert-butyl hydroperoxide is 1%), and an ethanol solution of ferric acetylacetonate with a mass concentration of 0.6% are preheated and vaporized at 400° C., and then enter a low-temperature dielectric barrier plasma reactor for reaction, wherein the plasma voltage is 25000 V, the AC frequency is 100 kHz, the reaction temperature is 400° C., the reaction time is 12 min, and after the reaction, the liquid phase product is condensed and collected and the composition is tested, wherein the dicarboxylic acid content is 31wt%, and the dicarboxylic acid yield is 30%.

[0038] Example 3

[0039] LLDPE plastic cracking oil, ozone / argon mixed gas (the volume fraction of ozone is 0.8%), and 0.5% ferric acetate ethanol solution with a feed volume ratio of 10:200:1 are preheated and vaporized at 350°C, and then enter a low-temperature dielectric barrier plasma reactor for reaction, with a plasma voltage of 20000V, an AC frequency of 80kHZ, a reaction temperature of 300°C, and a reaction time of 3min. After the reaction, the liquid phase product is condensed and collected and the composition is tested, wherein the dicarboxylic acid content is 57wt%, and the dicarboxylic acid yield is 54%.

[0040] Example 4

[0041] LLDPE plastic cracking oil, tert-butyl hydroperoxide / argon mixed gas (the volume fraction of tert-butyl hydroperoxide is 0.8%), and an ethanol solution of ferric acetylacetonate with a mass concentration of 0.4% are preheated and vaporized at 400° C., and then enter a low-temperature dielectric barrier plasma reactor for reaction, wherein the plasma voltage is 20000 V, the AC frequency is 100 kHz, the reaction temperature is 350° C., the reaction time is 3 min, and after the reaction, the liquid phase product is condensed and collected and the composition is tested, wherein the dicarboxylic acid content is 66wt%, and the dicarboxylic acid yield is 64%.

[0042] Example 5

[0043] LLDPE plastic cracking oil, ozone / argon mixed gas (the volume fraction of ozone is 0.8%), and 0.6% ferric acetate ethanol solution with a feed volume ratio of 20:50:1 are preheated and vaporized at 400°C, and then enter a low-temperature dielectric barrier plasma reactor for reaction, with a plasma voltage of 25000V, an AC frequency of 90kHZ, a reaction temperature of 300°C, and a reaction time of 12min. After the reaction, the liquid phase product is condensed and collected and the composition is tested, wherein the dicarboxylic acid content is 35wt%, and the dicarboxylic acid yield is 34%.

[0044] Example 6

[0045] HDPE plastic cracking oil, oxygen / argon mixed gas (oxygen volume fraction is 5%), and 1% iron acetate ethanol solution with a feed volume ratio of 25:100:1 are preheated and vaporized at 500°C, and then enter into a low-temperature dielectric barrier plasma reactor for reaction, with a plasma voltage of 40000V, an AC frequency of 50kHZ, a reaction temperature of 500°C, and a reaction time of 3min. After the reaction, the liquid phase product is condensed and collected and the composition is tested, wherein the dicarboxylic acid content is 40wt%, and the dicarboxylic acid yield is 38%.

[0046] Example 7

[0047] HDPE plastic cracking oil, oxygen / argon mixed gas (oxygen volume fraction is 0.1%), and 0.2% ferric acetate ethanol solution with a feed volume ratio of 15:150:1 are preheated and vaporized at 300°C, and then enter into a low-temperature dielectric barrier plasma reactor for reaction, with a plasma voltage of 5000V, an AC frequency of 100kHZ, a reaction temperature of 200°C, and a reaction time of 15min. After the reaction, the liquid phase product is condensed and collected and the composition is tested, wherein the dicarboxylic acid content is 32wt%, and the dicarboxylic acid yield is 30%.

[0048] Comparative Example 1

[0049] The method of Example 4 was used with reference to the method of Example 4, except that the plasma effect was not turned on, and other operating conditions and parameters remained unchanged. After the reaction, the liquid phase product was condensed and collected and the composition was tested, wherein the dicarboxylic acid content was 2 wt % and the dicarboxylic acid yield was 1.7%.

[0050] Comparative Example 2

[0051] The method of Example 4 was used with reference to the method of Example 4, except that the ethanol solution of ferric acetylacetonate was not added, and other operating conditions and parameters remained unchanged. After the reaction, the liquid product was condensed and collected and the composition was tested, wherein the dicarboxylic acid content was 4 wt % and the dicarboxylic acid yield was 3.2%.

[0052] Comparative Example 3

[0053] The method of Example 4 was used with reference to the method of Example 4, except that the carboxylation auxiliary agent was replaced by an ethanol solution of ferric chloride, and other operating conditions and parameters remained unchanged. After the reaction, the liquid product was condensed and collected and the composition was tested, wherein the dicarboxylic acid content was 3 wt % and the dicarboxylic acid yield was 2.3%.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing dicarboxylic acid from plastic pyrolysis oil, characterized in that the steps include: Plastic cracking oil, carboxylation auxiliary agent and oxidizing carrier gas are preheated and vaporized and then introduced into a reactor to react under the action of plasma to obtain dicarboxylic acid.

2. The method according to claim 1, characterized in that The plastic pyrolysis oil comprises one or more components of C5-C20 alkanes, olefins, cycloalkanes, cycloolefins, and aromatic hydrocarbons, preferably one or more components of C6-C10 linear terminal olefins and linear alkanes.

3. The method according to claim 1 or 2, characterized in that: The plastic pyrolysis oil is selected from at least one of polyethylene pyrolysis oil, polypropylene pyrolysis oil and polystyrene pyrolysis oil, preferably polyethylene pyrolysis oil.

4. The method according to any one of claims 1 to 3, characterized in that: The carboxylation auxiliary agent is a solution containing an organic iron compound; preferably, the mass concentration of the organic iron compound in the solution is 0.2-1%, preferably 0.4-0.6%; Preferably, the organic iron compound is selected from organic iron compounds with a boiling point of 50-350° C., preferably one or more of ferric acetate, ferric acrylate, ferric acetylacetonate, ferrocene, and ferric citrate, more preferably ferric acetate and / or ferric acetylacetonate; Preferably, the solvent of the solution containing organic iron compounds is selected from one or more of ethanol, acetone and ether, preferably ethanol.

5. The method according to any one of claims 1 to 4, characterized in that: The oxidizing carrier gas is a mixture of an oxidizing component and argon; preferably, the volume fraction of the oxidizing component in the oxidizing carrier gas is 0.1-5%, preferably 0.5-1%; Preferably, the oxidizing component is selected from an inorganic oxidant or an organic oxidant; the inorganic oxidant is selected from one or more of ozone and oxygen; the organic oxidant is selected from one or more of hydrogen peroxide, tert-butyl hydroperoxide, and ethylbenzene hydroperoxide, preferably ozone and / or tert-butyl hydroperoxide.

6. The method according to any one of claims 1 to 5, characterized in that: The feed volume ratio of the plastic pyrolysis oil, the oxidation carrier gas and the carboxylation auxiliary agent is 1-50:50-1000:1, preferably 10-25:50-200:

1.

7. The method according to any one of claims 1 to 7, characterized in that: The preheating vaporization temperature of the raw material plastic cracking oil, carboxylation auxiliary agent and oxidation carrier gas when feeding is 300-500°C, preferably 350-400°C.

8. The method according to any one of claims 1 to 7, characterized in that: The plasma is in the form of low-temperature dielectric barrier discharge plasma, and the reactor is preferably a low-temperature dielectric barrier plasma reactor.

9. The method according to any one of claims 1 to 8, characterized in that: The plasma action has a voltage of 5000-40000V and an AC frequency of 50-100kHz, preferably 80-100kHz.

10. The method according to any one of claims 1 to 9, characterized in that: The reaction temperature is 200-500°C, preferably 300-400°C; the reaction time is 0.5-60 min, preferably 2-25 min.