Method for preparing environment-friendly p-benzene PVC plasticizer from plastic solid waste

Abstract

The invention belongs to the field of high polymer material solid waste resource reutilization and treatment, and discloses a method for preparing an environment-friendly p-benzene PVC plasticizer from plastic solid waste, which comprises the following steps: catalytically converting polyolefin plastic solid waste into alpha olefin under mild conditions, and preparing 2-ethylhexanol by oxidation and carbonyl synthesis methods; decomposing the PET plastic solid wastewater into terephthalic acid; and finally, carrying out esterification reaction on the 2-ethylhexanol and terephthalic acid to prepare the environment-friendly p-benzene PVC plasticizer, namely di (2-ethylhexanol) terephthalate. The invention provides a controllable, green and efficient cracking-upgrading process which is a technology for converting a polyolefin plastic solid waste raw material into an environment-friendly p-benzene PVC (Polyvinyl Chloride) plasticizer. And the catalytic process for treating the plastic solid waste belongs to innovation in the field, and is beneficial to recycling of plastic solid waste resources.

Description

Technical Field

[0001] This invention belongs to the field of polymer material solid waste resource recycling and treatment, specifically a method for preparing environmentally friendly terephthalic acid-based PVC plasticizers from plastic solid waste. Specifically, it involves a mild treatment technology to degrade polyolefin solid waste into 2-ethylhexanol (2-EH) and hydrolyze polyethylene terephthalate (PET) into terephthalic acid (TPA), followed by the synthesis of the environmentally friendly plasticizer di(2-ethylhexanol) terephthalate (DOTP). This method particularly relates to the treatment of polyethylene and polyethylene terephthalate in daily life. Background Technology

[0002] By 2024, global plastic production is projected to reach 367 million tons. It is estimated that 50% of plastic products are discarded after a single use. Shopping bags, packaging bags, and containers, among other plastic products, have a lifespan of less than a month. The main types of plastics on the market include polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), and polyethylene terephthalate (PET), accounting for 74% of total plastic waste. Due to their biological and chemical inertness, these plastics have a long degradation period in the natural environment. Furthermore, the addition of antioxidants and stabilizers during production further prolongs this degradation period, causing serious environmental pollution. Therefore, finding an economically feasible method to improve the recycling of waste plastic bags and increase the added value of related products is crucial. Currently, the main methods for treating plastic solid waste include photocatalysis, catalytic pyrolysis, biodegradation, and hydrogenation catalysis.

[0003] Hydrogenation catalytic degradation of plastics can typically be carried out at lower temperatures and pressures, which helps save energy and improve degradation efficiency. For example, plastic resources can be converted into natural gas and liquid fuels through chemical hydrogenolysis, a method that is more efficient than traditional high-temperature pyrolysis. However, hydrogenation catalytic degradation of plastics requires the use of precious metals as catalytic sites, resulting in higher production costs and longer hydrogenolysis reaction times.

[0004] Biodegradable plastics can be broken down by microorganisms in the natural environment, eventually degrading into water and carbon dioxide, reducing environmental pollution. Furthermore, the raw materials are derived from renewable resources, reducing dependence on non-renewable resources such as petroleum. However, the biodegradation mechanism is still unclear, degradation efficiency is low, and costs are too high, all of which limit its widespread application in the market.

[0005] Photocatalytic degradation technology can utilize solar energy without requiring additional energy consumption, thus it is environmentally friendly and energy-efficient. Furthermore, this technology can be applied to a variety of plastic materials. However, the efficiency of photocatalytic degradation is greatly affected by environmental conditions; changes in environmental conditions can significantly impact the degradation effect. Compared to traditional plastic treatment methods, photocatalytic degradation technology is still in its developmental stage, with limited technological maturity and application scope.

[0006] Polyethylene terephthalate (PET) is a polyester material, and its chemical degradation is relatively easier compared to polyolefin plastic waste. The main methods include hydrolysis, alcoholysis, ammonolysis, and aminolysis, with hydrolysis being a commonly used method for chemically recycling PET plastic waste. This method can be further divided into neutral hydrolysis, alkaline hydrolysis, and acidic hydrolysis. Alkaline hydrolysis, due to its green and efficient characteristics, is becoming an increasingly important method in the chemical recycling of PET.

[0007] Polyvinyl chloride (PVC), a thermoplastic, is widely used due to its low production cost, ease of manufacturing, high chemical stability, and good mechanical properties, in applications such as cable insulation, pipes, construction, packaging, window profiles, and automotive interior materials. However, the dipoles in the PVC structure give it rigidity and brittleness, hindering chain migration. Therefore, processing flexible PVC products, such as cable insulation and automotive interior materials, requires plasticizers as additives to reduce the melt viscosity and glass transition temperature during PVC processing. Currently, plasticizers are mainly classified into: phthalates, aliphatic diesters, phosphate esters, polyol esters, and polyesters.

[0008] Traditional PVC plasticizers, phthalate plasticizers such as dioctyl phthalate (DOP), di(2-ethylhexyl) phthalate (DEHP), n-butyl phthalate (DBP), and diisononyl phthalate (DINP), are widely used due to their excellent plasticizing effect, low cost, good compatibility, low volatility, high water resistance, and low price. However, phthalates may cause abnormal reactions in the human immune system and may leach into soil and water sources during use and disposal, causing environmental pollution.

[0009] Aliphatic diester plasticizers perform well at low temperatures, significantly reducing the embrittlement temperature of materials and maintaining good flexibility even at low temperatures. They also exhibit high plasticizing efficiency, rapidly and effectively improving the processing properties of polymers and the performance of finished products. However, aliphatic diester plasticizers typically have poor compatibility. Furthermore, these plasticizers have poor durability and are prone to leaching from plastic products, leading to a decline in product performance.

[0010] Phosphate ester plasticizers have good compatibility with resins, can be well mixed with polymer materials, improve the processing performance of materials, and have good flame retardant properties, significantly improving the fire resistance of materials. However, most phosphate ester plasticizers have a certain degree of toxicity and are relatively expensive to produce.

[0011] To overcome the limitations of these plasticizers, especially phthalate plasticizers, the industry is adopting environmentally friendly plasticizers. Environmentally friendly plasticizers are new materials that replace traditional phthalates (such as DOP and DBP), characterized by low toxicity, biodegradability, or origin from renewable resources. These include citrate esters, vegetable oil-based plasticizers, bio-based plasticizers, and terephthalate plasticizers. This invention proposes a mild treatment technology to controllably degrade polyolefin plastic solid waste into 2-ethylhexanol (2-EH) and efficiently degrade polyethylene terephthalate (PET) into terephthalic acid (TPA). Finally, TPA and 2-EH are esterified to prepare the environmentally friendly PVC plasticizer di(2-ethylhexanol) terephthalate (DOTP). Summary of the Invention

[0012] This invention develops a waste plastic treatment technology that converts polyolefin plastic solid waste into environmentally friendly terephthalic acid-based PVC plasticizers. The invention utilizes zeolite molecular sieves with controlled morphology to enhance catalytic performance and improve the conversion rate of polyolefin solid waste to terminal olefins via catalytic cracking. Under mild conditions, polyethylene plastic solid waste is converted into α-olefins (e.g., 1-butene), and 2-ethylhexanol (2-EH) is prepared via oxidation and carbonyl synthesis. PET raw materials are hydrolyzed and cracked into terephthalic acid (TPA). Finally, TPA and 2-EH are esterified to produce the environmentally friendly PVC plasticizer di(2-ethylhexanol) terephthalate.

[0013] To achieve the above objectives, the present invention adopts the following technical solution:

[0014] In a first aspect, the present invention provides a method for preparing an environmentally friendly terephthalic acid-based PVC plasticizer from plastic solid waste, comprising:

[0015] S1. Polyolefin plastic solid waste is catalytically converted into α-olefin under mild conditions, and 2-ethylhexanol (2-EH) is prepared by oxidation and carbonyl synthesis.

[0016] S2. Decompose PET plastic solid waste into terephthalic acid (TPA).

[0017] S3. Finally, 2-EH and TPA are esterified to prepare an environmentally friendly terephthalic PVC plasticizer, namely di(2-ethylhexanol) terephthalate (DOTP).

[0018] Furthermore, the method described in step S1 for catalytically converting polyolefin plastic solid waste into α-olefins under mild conditions, and preparing 2-ethylhexanol (2-EH) via oxidation and carbonyl synthesis, includes:

[0019] A controlled pyrolysis reactor was employed, using zeolite molecular sieve catalyst. The catalyst was uniformly mixed with polyolefin solid waste raw material particles or fragments, and heated to a certain reaction temperature for a specific pyrolysis reaction time. A telescoping distillation unit was connected above the reactor, and condensers were connected to different layers of the distillation column to collect liquid α-olefins of different chain lengths.

[0020] In an oxidation-carbonyl synthesis reactor, the prepared α-olefin is oxidized with an oxidizing feed gas under the action of a ruthenium-based catalyst to produce n-butyraldehyde. n-Butyraldehyde undergoes a self-condensation reaction under the action of a Ni / La-Al₂O₃ catalyst, followed by hydrogenation. Finally, the reaction mixture is filtered to separate the catalyst, yielding the product 2-ethylhexanol.

[0021] Furthermore, the controllable pyrolysis reactor can be at least one or a combination of several of the following: a fixed-bed reactor, a fluidized-bed reactor, a batch-type total mixed reactor, and a continuous-flow total mixed reactor, and is equipped with a jacketed heating device. Preferably, the controllable pyrolysis reactor is a batch-type total mixed reactor.

[0022] Furthermore, the zeolite molecular sieve catalyst is selected from at least one of mordenite catalyst, beta zeolite catalyst, type A zeolite catalyst, and ZSM-5 zeolite catalyst. Preferably, the zeolite catalyst is ZSM-5 molecular sieve.

[0023] Furthermore, polyethylene plastic waste is used as raw material, with a controllable pyrolysis reaction temperature of 280-400℃, a reaction pressure of 0-0.15MPa, and a reaction time of 4-10h. Preferably, the plastic waste undergoes a catalytic pyrolysis reaction to generate 1-butene.

[0024] Furthermore, the oxidizing feed gas is selected from at least one of the following compositions: 10% O2, 20% Ar, 70% N2; 9% O2, 1% Ar, 90% N2; 1% O2, 9% Ar, 90% N2. Preferably, the oxidizing feed gas has a composition of 1% O2, 9% Ar, and 90% N2.

[0025] Furthermore, the ruthenium-based catalyst is selected from ruthenium trichloride, ruthenium tetrachloride, RuO4, and RuCl3-NaIO4 complex. Preferably, ruthenium tetrachloride is used as the catalyst.

[0026] Furthermore, 1-butene is used as a raw material and an oxidation reaction is carried out in the presence of ruthenium tetrachloride catalyst. The reaction temperature is 100-120℃, the reaction pressure is 0.5-2 MPa, and the reaction time is 0.5-2 h. Preferably, the product is n-butyraldehyde.

[0027] Furthermore, the temperature for the self-condensation reaction is 150-200℃, the reaction pressure is 0-2MPa, and the reaction time is 2-10h.

[0028] Furthermore, the hydrogenation reaction is carried out at a temperature of 150-200℃, a hydrogen pressure of 2-5 MPa, and a reaction time of 2-5 h.

[0029] Furthermore, in step S2, the method for hydrolyzing PET raw materials into terephthalic acid (TPA) involves cutting PET plastic waste into fragments of a certain size and cleaning them with deionized water. Subsequently, alkaline hydrolysis of PET is performed using a mixed solvent of water and ethylene glycol in a certain proportion, adding an alkaline solution of a certain concentration, and conducting the pyrolysis reaction at a certain temperature for a period of time. The solid product is then washed twice with ethanol, followed by washing with deionized water and drying to obtain terephthalate. The product is then adjusted to terephthalic acid using an acid solution of a certain concentration.

[0030] Furthermore, the PET plastic solid waste fragments of a certain size are squares with a side length of 1-10 mm. Preferably, the side length of the fragments is 2 mm.

[0031] Furthermore, the alkaline solution of a certain concentration is selected from at least one of sodium hydroxide, potassium hydroxide, and lithium hydroxide, and its concentration range is 0-35%. Preferably, the alkaline solution is a 30% sodium hydroxide solution.

[0032] Furthermore, the water-ethylene glycol mixed solvent in a certain proportion is selected from at least one of water / ethylene glycol (9:1), water / ethylene glycol (8:2), and water / ethylene glycol (7:3). Preferably, the solvent is water / ethylene glycol (8:2).

[0033] Furthermore, in the alkaline hydrolysis reaction of PET, the pyrolysis reaction temperature is 25-70℃, and the pyrolysis reaction time is 0.5-2.0h. Preferably, the pyrolysis reaction temperature is 65℃, and the pyrolysis reaction time is 1.0h.

[0034] Furthermore, the acid solution of a certain concentration is selected from at least one of sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, etc., and its concentration range is 0-2.0 mol·L⁻¹. -1 Preferably, the acidic solution is 1.0 mol·L⁻¹. -1 Hydrochloric acid solution.

[0035] Furthermore, the method described in step S3, which involves adding 2-EH and TPA in a certain proportion to an esterification reactor to prepare the environmentally friendly PVC plasticizer di(2-ethylhexyl) terephthalate, involves catalytically esterifying the 2-ethylhexanol prepared in step S1 and the terephthalic acid obtained in step S2 to finally obtain the environmentally friendly plasticizer, namely di(2-ethylhexanol) terephthalate (DOTP).

[0036] Furthermore, terephthalic acid and 2-ethylhexanol in a molar ratio of 1:(2-2.1) are added to the esterification reactor and heated while stirring.

[0037] Furthermore, the esterification reaction is carried out at a temperature of 170-210℃ for a reaction time of 7-13 hours.

[0038] Furthermore, a catalyst needs to be added during the reaction process. The catalyst is selected from at least one of tetrabutyl titanate and phosphotungstic acid intercalated Zn / Al type hydrotalcite hybrid catalysts. Preferably, the catalyst is tetrabutyl titanate.

[0039] Secondly, this invention provides an environmentally friendly PVC plasticizer, comprising the DOTP plasticizer obtained by the aforementioned method for preparing environmentally friendly terephthalic acid-based PVC plasticizers from plastic solid waste. Its beneficial innovation lies in solving environmental problems such as plastic pollution, turning waste into treasure, and simultaneously reducing the production cost of DOTP by 30-40%. This invention, through the substitution of petroleum raw materials with waste plastics, by-product value enhancement, and optimized reaction conditions, allows the new process to reduce the production cost of DOTP to 6000-8000 yuan / ton, a 30-40% reduction compared to the traditional route (9500-12500 yuan / ton).

[0040] Furthermore, the PVC plasticizer has the following formulation: 40-60 PHR of DOTP plasticizer, 100 PHR of PVC resin, 4.5 PHR of Ca / Zn stabilizer, and 10 PHR of calcium carbonate.

[0041] Furthermore, the method for using the aforementioned environmentally friendly PVC plasticizer to prepare PVC samples is as follows:

[0042] Ingredients: DOTP plasticizer (40-60 PHR), PVC resin (100 PHR), Ca / Zn stabilizer (4.5 PHR), calcium carbonate (10 PHR)

[0043] Sample preparation: The mixture prepared according to the formula is kneaded at 180℃ and 36rpm for 10-20 minutes, and then hot-pressed at 186℃ and 10MPa for 7-10 minutes to obtain soft PVC.

[0044] Compared with the prior art, the beneficial effects of the present invention are:

[0045] 1. This invention provides a controllable, green, and efficient pyrolysis-upgrading process to convert polyolefin plastic waste raw materials into environmentally friendly terephthalic acid-based PVC plasticizers, reducing the preparation cost of DOTP by 30-40%. Its catalytic process for treating plastic waste is an innovation in the field, facilitating the recycling of plastic waste resources.

[0046] 2. This invention utilizes the alkaline hydrolysis products of solid waste PET, combined with PE pyrolysis products, to produce environmentally friendly paraben-based PVC plasticizers. Compared with conventional treatment methods, this not only efficiently treats various types of waste plastics and saves more resources, but also chemically upgrades the hydrolysis and pyrolysis products into high-value-added products, providing technical support for solving white pollution, improving the recycling rate of plastics, and increasing the added value of their products.

[0047] 3. This invention responds to plastic management and recycling policies, is highly practical, and is easy to promote. Attached Figure Description

[0048] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. Exemplary embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0049] Figure 1 This is a technical roadmap for the preparation of 2-ethylhexanol from polyolefin solid waste.

[0050] Figure 2 This is a technical roadmap for the preparation of terephthalic acid by hydrolysis of polyethylene terephthalate from solid waste;

[0051] Figure 3 This is a technical roadmap for preparing di(2-ethylhexanol) terephthalate by esterification of 2-ethylhexanol and terephthalic acid. Detailed Implementation

[0052] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0053] This invention provides a method for preparing environmentally friendly terephthalic acid-based PVC plasticizers from plastic solid waste, comprising:

[0054] (i) A method for preparing 2-ethylhexanol from polyolefin solid waste using a catalytic process, including:

[0055] 1. The cracking process is carried out in a controlled-flow cracking reactor, which is a batch-type fully mixed reactor equipped with a jacketed heating device and a zeolite molecular sieve catalyst with controlled morphology. The catalyst is mixed uniformly with polyolefin solid waste raw material particles or fragments, heated to a certain reaction temperature, and the cracking reaction is carried out for a certain period of time. A telescopic distillation unit is connected above the reactor, and condensers are connected to different layers of the distillation column to collect liquid α-olefins of different chain lengths.

[0056] 2. In an oxidation-carbonyl synthesis reactor, the prepared α-olefin is oxidized with an oxidizing feed gas under the action of a ruthenium-based catalyst to produce n-butyraldehyde. n-Butyraldehyde undergoes a self-condensation reaction under the action of a Ni / La-Al₂O₃ catalyst, followed by hydrogenation. Finally, the reaction mixture is filtered to separate the catalyst, yielding the product 2-ethylhexanol.

[0057] In some embodiments, the zeolite molecules are selected from at least one of mordenite catalysts, beta zeolite catalysts, type A zeolite catalysts, and ZSM-5 zeolite catalysts. Preferably, the zeolite catalyst is a ZSM-5 molecular sieve.

[0058] In some embodiments, the oxidizing feed gas is selected from at least one of 10% O2, 20% Ar, 70% N2; 9% O2, 1% Ar, 90% N2; or 1% O2, 9% Ar, 90% N2. Preferably, 1% O2, 9% Ar, and 90% N2 are used as the feed gas.

[0059] In some embodiments, the ruthenium-based catalyst is selected from ruthenium trichloride, ruthenium tetrachloride, RuO4, and RuCl3-NaIO4 complex. Preferably, ruthenium tetrachloride is used as the catalyst.

[0060] In some embodiments, polyethylene solid waste is used as raw material, and the reaction is carried out at a temperature of 280-400°C, a pressure of 0-0.15 MPa, and a time of 4-10 h. Preferably, the plastic solid waste undergoes a catalytic cracking reaction to generate 1-butene.

[0061] In some embodiments, 1-butene is used as a raw material, and an oxidation reaction is carried out in the presence of ruthenium tetrachloride catalyst. The reaction temperature is 100-120°C, the reaction pressure is 0.5-2 MPa, and the reaction time is 0.5-2 h. Preferably, the product is n-butyraldehyde.

[0062] In some embodiments, n-butyraldehyde and Ni / La-Al2O3 catalyst are added to a high-pressure reactor to undergo a self-condensation reaction. Subsequently, the reaction mixture is directly hydrogenated, and finally the catalyst is separated by vacuum filtration to obtain the product 2-ethylhexanol.

[0063] (ii) Methods for the controlled degradation of PET to terephthalic acid via alkaline hydrolysis under mild conditions, including:

[0064] PET plastic waste was cut into fragments of a certain size and cleaned with deionized water. Then, PET underwent alkaline hydrolysis using a mixed solvent of water and ethylene glycol in a certain proportion, along with an alkaline solution of a certain concentration. After the pyrolysis reaction was carried out at a certain temperature for a period of time, the solid product was washed twice with ethanol, then washed again with deionized water and dried to obtain terephthalate. The product was then adjusted to terephthalic acid using an acid solution of a certain concentration.

[0065] In some embodiments, the mixed solvent is selected from at least one of water / ethylene glycol (9:1), water / ethylene glycol (8:2), and water / ethylene glycol (7:3). Preferably, the solvent is water / ethylene glycol (8:2).

[0066] In some embodiments, the alkaline solution of a certain concentration is selected from at least one of sodium hydroxide, potassium hydroxide, and lithium hydroxide, and its concentration range is 0-35%. Preferably, the alkaline solution is a 30% sodium hydroxide solution.

[0067] In some embodiments, the pyrolysis reaction temperature is 25-70°C, and the pyrolysis reaction time is 0.5-2.0 h. Preferably, the pyrolysis reaction temperature is 65°C, and the pyrolysis reaction time is 1.0 h.

[0068] In some implementation schemes, the acid solution of a certain concentration is selected from at least one of sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, etc., and its concentration range is 0-2.0 mol·L⁻¹. -1 Preferably, the acidic solution is 1.0 mol·L⁻¹. -1 Hydrochloric acid solution.

[0069] (III) The 2-ethylhexanol prepared in the first step and the terephthalic acid prepared in the second step are esterified to finally obtain an environmentally friendly plasticizer, namely di(2-ethylhexanol) terephthalate (DOTP).

[0070] In some embodiments, terephthalic acid and 2-ethylhexanol are added to an esterification reactor in a molar ratio of 1:(2-2.1) and heated while stirring.

[0071] In some embodiments, the esterification reaction is carried out at a temperature of 170-210°C for a reaction time of 7-13 hours.

[0072] In some embodiments, a catalyst is required during the reaction process. The catalyst is selected from at least one of tetrabutyl titanate and phosphotungstic acid intercalated Zn / Al type hydrotalcite hybrid catalysts. Preferably, the catalyst is tetrabutyl titanate.

[0073] Example 1:

[0074] This embodiment provides an environmentally friendly terephthalic acid-based PVC plasticizer prepared from plastic solid waste, the method comprising the following steps:

[0075] Step 1: Catalytic pyrolysis of polyethylene plastic solid waste - upgraded reaction

[0076] This step was carried out in a batch fully mixed reactor made of quartz tube (10 mm inner diameter, 270 mm length) equipped with a jacketed heating device for precise temperature control. 10 g of ZSM-5 catalyst was thoroughly mixed with 50 g of polyethylene powder, pressed into 50 mesh particles, and filled into the middle of the reaction tube, secured with quartz wool or quartz sand. The catalyst bed was heated to a reaction temperature of 300 °C ± 10 °C at a rate of 10 °C / min, and the catalytic reaction was carried out at atmospheric pressure for 6 hours. A telescopic distillation unit was connected to the top of the reactor, and liquid α-olefins of various chain lengths were collected through condensers at different tower layers, with a cracking yield of 82.6%.

[0077] Subsequently, 40g of 1-butene was used as a raw material, and an oxidizing gas (composed of 1% O2, 9% Ar, and 90% N2) was introduced at a flow rate of 600mL·h⁻¹ to carry out the oxidation reaction under the action of ruthenium tetrachloride catalyst. The reaction temperature was set at 110℃ and the pressure at 1MPa, and the reaction lasted for 1.5h, producing n-butyraldehyde with a conversion rate of 94%. 30g of n-butyraldehyde and 4.5g of Ni / La-Al₂O₃ catalyst were added to a high-pressure reactor, and a self-condensation reaction was carried out at 180℃ under normal pressure with stirring for 8h, followed by hydrogenation reaction at 4.0MPa hydrogen pressure and 180℃ for 4h. The catalyst was separated by vacuum filtration to obtain the target product 2-ethylhexanol, at which point the conversion rate of 1-butyraldehyde reached 95%. The technical route diagram of this step is shown below. Figure 1 As shown.

[0078] Step 2: Hydrolysis of PET plastic solid waste to prepare terephthalic acid

[0079] 40g of PET plastic waste was cut into fragments with sides approximately 2mm in length. After thorough washing with deionized water, a mixed solvent of water and ethylene glycol (volume ratio 8:2) was used, with 30% sodium hydroxide solution added as the reaction medium (volume ratio of mixed solvent to sodium hydroxide solution 1:9, total reagent volume to PET volume mass ratio 20:1). The hydrolysis reaction was carried out at 65℃ for 1 hour. The resulting solid product was washed twice with ethanol and then with deionized water, followed by drying to obtain terephthalate. Finally, acidification was performed using 1.0 mol·L⁻¹ hydrochloric acid solution (the amount of hydrochloric acid used was twice the molar amount of the theoretical yield of terephthalic acid) to convert the terephthalate to terephthalic acid. The hydrolysis conversion rate of the solid waste PET was 99.4%. The technical roadmap for this step is shown below. Figure 2 As shown.

[0080] Step 3: Preparation of di(2-ethylhexanol) terephthalate plasticizer

[0081] The terephthalic acid obtained in the second step and the 2-ethylhexanol synthesized in the first step were added to an esterification reactor containing a 1.0% tetrabutyl titanate catalyst at a molar ratio of 1:2 (e.g., 26 g of 2-ethylhexanol and 16.6 g of terephthalic acid). Under continuous stirring, the temperature was gradually increased to 190°C and maintained at this temperature for 10 h to finally synthesize di(2-ethylhexanol) terephthalate. The conversion rate was 95%, yielding 40.5 g of di(2-ethylhexanol) terephthalate plasticizer. The technical route diagram for this step is shown below. Figure 3 As shown, the preparation cost of DOTP decreased by 35%.

[0082] Step 4: Plasticizing and Modifying PVC Resin

[0083] Synthetic di(2-ethylhexanol) terephthalate (60 phr (parts per hundred rubber)) was used as a plasticizer, and added together with 100 phr of PVC resin and 4.5 phr of Ca / Zn stabilizer to a Banbury mixer. The mixture was initially Banbury mixerd at 85°C and 36 rpm for 10 minutes. Then, the temperature was raised to 100°C, 10 phr of calcium carbonate was added, and mixing continued while the temperature was raised to 120°C. After mixing, the mixture was discharged and cooled to below 40°C, at which point it was a free-flowing powder. The powder was then returned to the Banbury mixer and gelled at 180°C and 36 rpm for 10 minutes. Finally, it was hot-pressed at 186°C and 10 MPa for 7 minutes, successfully producing the plasticized PVC material. The plasticized PVC exhibited an elongation at break of 360% and a tear strength of 25 kN / m.

[0084] Example 2:

[0085] This embodiment provides an environmentally friendly terephthalic acid-based PVC plasticizer prepared from plastic solid waste, the method comprising the following steps:

[0086] Step 1: Catalytic cracking and oxidation reaction

[0087] This phase of the experiment was conducted in a batch-type fully mixed reactor. The reactor was made of quartz tube (6 mm inner diameter, 270 mm length) and equipped with a jacketed heating device for precise temperature control. 10 g of beta zeolite catalyst was thoroughly mixed with 50 g of polyethylene powder, pressed into 50-mesh particles, and filled into the middle of the reaction tube, secured with quartz wool and quartz sand. The catalyst bed was heated to a reaction temperature of 300 °C ± 10 °C at a rate of 10 °C / min, and the catalytic reaction was carried out at atmospheric pressure for 4 hours. A telescopic distillation unit was connected to the top of the reactor, and liquid α-olefins of various chain lengths were collected through condensers at different tower layers, with a cracking yield of 74.8%.

[0088] Subsequently, 40 g of 1-butene was used as a raw material, and an oxidizing feed gas (composed of 1% O2, 9% Ar, and 90% N2) was introduced at a flow rate of 600 mL·h⁻¹ to carry out the oxidation reaction under the action of RuCl₃-NaIO₄ composite catalyst. The reaction temperature was set at 110℃ and the pressure at 1 MPa, and the reaction was carried out for 1.5 h to produce n-butyraldehyde with a conversion rate of 86%. 30 g of n-butyraldehyde and 4.5 g of Ni / La-Al₂O₃ catalyst were added to a high-pressure reactor, and a self-condensation reaction was carried out at 180℃ under normal pressure for 8 h with stirring. Then, hydrogenation was carried out at 4.0 MPa hydrogen pressure and 180℃ for 4 h. The catalyst was separated by vacuum filtration to obtain the target product 2-ethylhexanol, at which point the conversion rate of 1-butene reached 75%.

[0089] Step 2: Hydrolysis treatment of PET plastic solid waste.

[0090] Step 3: Esterification reaction to prepare di(2-ethylhexanol) terephthalate, reducing the preparation cost of DOTP by 30%.

[0091] Step 4: Plasticization and modification of PVC resin.

[0092] The three parts—PET plastic solid waste hydrolysis treatment, esterification reaction to prepare di(2-ethylhexanol) terephthalate, and PVC resin plasticization modification—are the same as in Example 1.

[0093] Example 3:

[0094] This embodiment provides an environmentally friendly terephthalic acid-based PVC plasticizer prepared from plastic solid waste, the method comprising the following steps:

[0095] Step 1: Catalytic cracking and oxidation reaction.

[0096] Step 2: Hydrolysis treatment of PET plastic solid waste

[0097] 40g of PET plastic waste was cut into fragments with sides approximately 2mm in length. After thorough washing with deionized water, a water / ethylene glycol (volume ratio 7:3) mixed solvent was used, with 20% sodium hydroxide solution added as the reaction medium (volume ratio of mixed solvent to sodium hydroxide solution 1:9, total reagent volume to PET volume mass ratio 20:1). The hydrolysis reaction was carried out at 45℃ for 1 hour. The resulting solid product was washed twice with ethanol and then with deionized water, followed by drying to obtain terephthalate. Finally, acidification was performed for 0.5 hours with 1.0 mol·L⁻¹ hydrochloric acid solution (the amount of hydrochloric acid used was twice the theoretical molar amount of terephthalic acid) to convert the terephthalate into terephthalic acid. The conversion rate of solid waste PET was 84%.

[0098] Step 3: Esterification reaction to prepare di(2-ethylhexanol) terephthalate, reducing the preparation cost of DOTP by 40%.

[0099] Step 4: Plasticization and modification of PVC resin.

[0100] The three parts—catalytic cracking and oxidation reaction, esterification reaction to prepare di(2-ethylhexanol) terephthalate, and plasticizing modification of PVC resin—are the same as in Example 1.

[0101] Example 4:

[0102] This embodiment provides an environmentally friendly terephthalic acid-based PVC plasticizer prepared from plastic solid waste, the method comprising the following steps:

[0103] Step 1: Catalytic cracking and oxidation reaction.

[0104] Step 2: Hydrolysis treatment of PET plastic solid waste.

[0105] Step 3: Esterification reaction to prepare di(2-ethylhexanol) terephthalate

[0106] The terephthalic acid obtained in the second step and the 2-ethylhexanol synthesized in the first step were added to an esterification reactor containing a 1% phosphotungstic acid-intercalated Zn / Al type hydrotalcite hybrid catalyst at a molar ratio of 1:2.1. Under continuous stirring, the temperature was gradually increased to 190°C and maintained at this temperature for 10 hours to finally synthesize di(2-ethylhexanol) terephthalate. The conversion rate was 75%, and the preparation cost of DOTP decreased by 38%.

[0107] Step 4: Plasticization and modification of PVC resin.

[0108] The three parts—catalytic cracking and oxidation reaction, hydrolysis treatment of PET plastic solid waste, and plasticizing modification of PVC resin—are the same as in Example 1.

[0109] Example 5:

[0110] This embodiment provides an environmentally friendly terephthalic acid-based PVC plasticizer prepared from plastic solid waste, the method comprising the following steps:

[0111] Step 1: Catalytic cracking and oxidation reaction.

[0112] Step 2: Hydrolysis treatment of PET plastic solid waste.

[0113] Step 3: Esterification reaction to prepare di(2-ethylhexanol) terephthalate.

[0114] Step 4: Plasticizing and Modifying PVC Resin

[0115] Synthetic di(2-ethylhexanol) terephthalate (50 PHR) was used as a plasticizer, and added to a viscous mixer along with 100 PHR of PVC resin and 4.5 PHR of Ca / Zn stabilizer. The mixture was initially viscous at 85°C and 36 rpm for 20 minutes. Then, the temperature was raised to 100°C, 10 PHR of calcium carbonate was added, and mixing continued while the temperature was raised to 120°C. After mixing, the mixture was discharged and cooled to below 40°C, at which point it was a free-flowing powder. The powder was then returned to the mixer and gelled at 180°C and 36 rpm for 10 minutes. Finally, it was hot-pressed at 186°C and 10 MPa for 10 minutes, successfully producing softened PVC material. The plasticized PVC exhibited an elongation at break of 250% and a tear strength of 30 kN / m.

[0116] The three parts—catalytic cracking and oxidation reaction, hydrolysis treatment of PET plastic solid waste, and esterification reaction to prepare di(2-ethylhexanol) terephthalate—are the same as in Example 1.

[0117] The embodiments described above are merely illustrative of specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of protection of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing environmentally friendly terephthalic acid-based PVC plasticizers from plastic solid waste, characterized in that, include: 2-Ethylhexanol was prepared by catalytically converting polyolefin plastic solid waste into α-olefin under mild conditions and then synthesizing it via oxidation and carbonylation. PET plastic solid wastewater is decomposed and cracked into terephthalic acid; An environmentally friendly terephthalic acid-based PVC plasticizer, namely di(2-ethylhexanol) terephthalate, is prepared by esterification of 2-ethylhexanol and terephthalic acid.

2. The method for preparing environmentally friendly terephthalic acid-based PVC plasticizers from plastic solid waste according to claim 1, characterized in that, The method of catalytically converting polyolefin plastic solid waste into α-olefins under mild conditions is as follows: a controllable pyrolysis reactor is used to mix zeolite molecular sieve catalyst with polyolefin solid waste raw material particles or fragments evenly, and heat to a reaction temperature of 280-400℃ for pyrolysis reaction for 4-10 hours; a telescopic distillation device is connected above the reactor, and condensers are connected to different tower layers to collect liquid α-olefins with different chain lengths.

3. The method for preparing environmentally friendly terephthalic acid-based PVC plasticizers from plastic solid waste according to claim 2, characterized in that, The zeolite molecular sieve catalyst is selected from at least one of mordenite catalyst, beta zeolite catalyst, type A zeolite catalyst, and ZSM-5 zeolite catalyst.

4. The method for preparing environmentally friendly terephthalic acid-based PVC plasticizers from plastic solid waste according to claim 2, characterized in that, The method for preparing 2-ethylhexanol (2-EH) by oxidation and carbonyl synthesis is as follows: the prepared α-olefin is oxidized with the oxidizing feed gas in the presence of a ruthenium-based catalyst to generate n-butyraldehyde; n-butyraldehyde undergoes a self-condensation reaction in the presence of a Ni / La-Al2O3 catalyst, followed by a hydrogenation reaction; finally, the reaction mixture is filtered to separate the catalyst and obtain the product 2-ethylhexanol.

5. The method for preparing environmentally friendly terephthalic acid-based PVC plasticizers from plastic solid waste according to claim 4, characterized in that, The oxidizing feed gas is selected from at least one of the following compositions: 10% O2, 20% Ar, 70% N2; 9% O2, 1% Ar, 90% N2; 1% O2, 9% Ar, 90% N2.

6. The method for preparing environmentally friendly terephthalic acid-based PVC plasticizers from plastic solid waste according to claim 4, characterized in that, The ruthenium-based catalyst is selected from ruthenium trichloride, ruthenium tetrachloride, RuO4, and RuCl3-NaIO4 complex; The oxidation reaction was carried out under the action of ruthenium tetrachloride catalyst. The reaction temperature was 100-120℃, the reaction pressure was 0.5-2MPa, and the reaction time was 0.5-2h. The temperature for the self-condensation reaction is 150-200℃, the reaction pressure is 0-2MPa, and the reaction time is 2-10h. The hydrogenation reaction is carried out at a temperature of 150-200℃, a pressure of 2-5 MPa, and a time of 2-5 h.

7. The method for preparing environmentally friendly terephthalic acid-based PVC plasticizers from plastic solid waste according to claim 4, characterized in that, The method for hydrolyzing PET raw materials into terephthalic acid is as follows: PET plastic waste is cut into fragments and cleaned with deionized water; then, PET is subjected to alkaline hydrolysis using a mixed solvent of water and ethylene glycol, with an alkaline solution added. After the pyrolysis reaction is carried out at 25-70℃ for 0.5-2.0 hours, the solid product is washed twice with ethanol, then washed with deionized water and dried to obtain terephthalate. The product is then adjusted to terephthalic acid using an acid solution.

8. The method for preparing environmentally friendly terephthalic acid-based PVC plasticizers from plastic solid waste according to claim 7, characterized in that, The method for preparing environmentally friendly PVC plasticizer di(2-ethylhexyl) terephthalate from 2-ethylhexanol and terephthalic acid via esterification reaction specifically involves: adding terephthalic acid and 2-ethylhexanol at a molar ratio of 1:(2-2.1) into an esterification reactor containing a catalyst; gradually raising the temperature to 170-210°C under continuous stirring and maintaining this temperature for esterification reaction for 7-13 hours; wherein the catalyst is selected from at least one of tetrabutyl titanate and phosphotungstic acid intercalated Zn / Al type hydrotalcite hybrid catalysts.

9. An environmentally friendly PVC plasticizer, characterized in that: The invention includes di(2-ethylhexanol) terephthalate, abbreviated as DOTP plasticizer, prepared by a method for preparing environmentally friendly terephthalic PVC plasticizer from plastic solid waste according to any one of claims 1-8. This DOTP plasticizer solves the environmental problem of plastic pollution, turns waste into treasure, and reduces the preparation cost of DOTP by 30-40%.

10. The environmentally friendly PVC plasticizer according to claim 9, characterized in that, The PVC plasticizer has the following composition: 40-60 PHR of DOTP plasticizer, 100 PHR of PVC resin, 4.5 PHR of Ca / Zn stabilizer, and 10 PHR of calcium carbonate.

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