Composite catalyst, method for preparing ethylene glycol from domestic waste, and domestic waste treatment system

Abstract

The application provides a composite catalyst, a method for preparing ethylene glycol from domestic waste and a domestic waste treatment system, and relates to the technical field of waste treatment. The composite catalyst is formed by compounding Cu-ZnO-Al2O3 and HZSM-5 molecular sieve at a specific mass ratio of (3-5):1, so that a multifunctional catalytic system with synergistic effect is formed. The technical problem that the heterogeneous organic components in the domestic waste are difficult to be uniformly converted is solved, the high-selectivity synthesis of ethylene glycol is realized, and the resource utilization rate and process economy of the existing domestic waste are significantly improved. Meanwhile, the application also provides a method for preparing ethylene glycol from domestic waste. The method sets the pretreatment process of plastics, paper and kitchen waste organic matters, and introduces the above composite catalyst, so that the domestic waste which is originally low in value and is filled or incinerated is successfully converted into the high-value-added chemical raw material ethylene glycol, and the dependence of traditional ethylene glycol production on fossil resources is broken.

Description

Technical Field

[0001] This invention relates to the field of waste treatment technology, and in particular to a composite catalyst, a method for preparing ethylene glycol from municipal solid waste, and a municipal solid waste treatment system. Background Technology

[0002] Ethylene glycol is an important bulk chemical raw material, widely used in the production of polyester fibers, antifreeze, unsaturated polyester resins, and other products. Currently, industrially, ethylene glycol is mainly produced via either the petroleum route (such as ethylene oxidation to ethylene oxide followed by hydration) or the coal chemical route (coal-to-syngas followed by hydrogen esterification). These traditional preparation methods have the following drawbacks: First, they are highly dependent on raw materials; the petroleum route relies on non-renewable petroleum resources, while the coal chemical route consumes large quantities of high-quality coal, and both are significantly affected by raw material price fluctuations. Second, they cause severe environmental pollution; petroleum refining and coal-to-syngas processes generate large amounts of carbon dioxide, sulfur dioxide, and saline wastewater, which does not meet development requirements. Third, the processes are complex, typically requiring multiple reactions under harsh conditions, often necessitating high temperature and pressure environments, resulting in high equipment investment and energy consumption.

[0003] Meanwhile, the global annual production of municipal solid waste exceeds 2 billion tons, with my country producing over 300 million tons annually. Currently, the mainstream treatment methods remain landfill and incineration, which not only consume vast amounts of land resources but also release harmful substances such as methane and dioxins, causing secondary pollution. Although resource utilization technologies such as composting and incineration power generation exist, they generally suffer from low added value and insufficient utilization of organic components. How to achieve high-value transformation of organic components in municipal solid waste has become a key technical challenge that urgently needs to be overcome.

[0004] Although existing studies have attempted to prepare ethylene glycol from biomass raw materials (such as straw and sawdust), these raw materials suffer from high collection costs, unstable seasonal supply, and relatively simple composition, failing to reflect the complex composition and high impurity content of municipal solid waste. Given the heterogeneous, multi-component, and high-impurity characteristics of municipal solid waste, current technologies struggle to achieve efficient and targeted conversion into ethylene glycol, primarily facing the following key technological bottlenecks: First, the synergistic conversion between different organic components such as plastics, paper, and kitchen waste is difficult, lacking an effective pretreatment and reaction coupling mechanism; second, impurities such as heavy metals and chlorine in the raw materials can easily poison the catalyst, affecting its activity and lifespan; third, the reaction products have complex compositions, with ethylene glycol having similar boiling points to other polyols (such as 1,2-propanediol) and organic acids, making separation and purification difficult and hindering the acquisition of high-purity products.

[0005] Therefore, there is an urgent need to develop a new process that can use municipal solid waste as raw material to overcome problems such as complex composition, impurities, and low conversion efficiency, and achieve efficient, clean, and high-value conversion to ethylene glycol.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The primary objective of this invention is to provide a composite catalyst that effectively solves the technical challenge of the unified transformation of multi-source heterogeneous organic components in municipal solid waste, and also achieves highly selective synthesis of ethylene glycol.

[0008] The second objective of this invention is to provide a method for preparing ethylene glycol from municipal solid waste.

[0009] A third objective of this invention is to provide a municipal solid waste treatment system for implementing the above-described method for preparing ethylene glycol from municipal solid waste.

[0010] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: The present invention provides a composite catalyst, which is composed of Cu-ZnO-Al2O3 and HZSM-5 molecular sieve, wherein the mass ratio of Cu-ZnO-Al2O3 to HZSM-5 molecular sieve in the composite catalyst is (3~5):1.

[0011] Furthermore, based on oxides, the Cu-ZnO-Al2O3 comprises: CuO with a mass fraction of 30%~60%, ZnO with a mass fraction of 20%~40%, and Al2O3 with a mass fraction of 10%~30%.

[0012] The composite catalyst provided by this invention is used in the conversion of organic components in municipal solid waste into ethylene glycol, wherein: The household waste includes at least one of plastics, paper, and kitchen waste.

[0013] This invention provides a method for preparing ethylene glycol from municipal solid waste, comprising the following steps: (a) Pre-treat plastics, paper and kitchen waste separately in household waste to improve reactivity; (b) The pretreated plastic, paper and kitchen waste organic matter are mixed to form a slurry, and the above composite catalyst is added. The catalytic conversion reaction is carried out under hydrothermal conditions to obtain a reaction mixture. (c) The reaction mixture is subjected to gas-liquid separation to obtain a crude liquid product containing ethylene glycol; (d) The crude liquid product is subjected to filtration to remove slag, removal of impurity ions and multi-stage distillation purification in sequence to obtain ethylene glycol.

[0014] Furthermore, step (a) preprocessing includes: Alkaline surface modification treatment is applied to plastics; Paper is subjected to hydrolytic degradation treatment; Kitchen waste organic matter is dehydrated and bio-enzymatically hydrolyzed.

[0015] Furthermore, in step (b) of preparing the slurry, the mass ratio of plastic, paper and kitchen waste organic matter is (1~3):(2~4):(4~6).

[0016] And / or, the conditions for the catalytic conversion in step (b) include: a reaction temperature of 200~300℃, a pressure of 2~6MPa, and a reaction time of 3~8h.

[0017] Furthermore, in step (d), the removal of impurity ions is performed using an ion exchange resin column; the ion exchange resin column is obtained by connecting cation exchange resin and anion exchange resin in series. Preferably, the cation exchange resin is model 0017, the anion exchange resin is model D301, and the filling volume ratio of the cation exchange resin to the anion exchange resin is 1:1.

[0018] Furthermore, step (d) includes a three-stage series distillation column, wherein: The first distillation column operates at atmospheric pressure to remove moisture; The second distillation column operates under reduced pressure to separate 1,2-propanediol; The third distillation column operates under a higher vacuum to collect the ethylene glycol fraction.

[0019] The present invention provides a municipal solid waste treatment system for implementing the above-mentioned method for preparing ethylene glycol from municipal solid waste, comprising functional units connected in sequence: The grading pretreatment unit includes a twin-shaft crusher, a magnetic separator, an eddy current separator, an air-density separation device, a plastic preprocessor, a paper hydrolysis tank, a kitchen waste enzymatic hydrolysis tank, and a mixed pulping tank; The directional catalytic conversion unit includes a high-pressure reactor, a gas-liquid separator, and an H2 recovery device. The high-pressure reactor is equipped with a temperature control module, a pressure control system, and a stirring device. The refining and purification unit includes a filtration device, an ion exchange resin column, and first to third distillation columns, wherein the second and third distillation columns are equipped with a pressure reduction system; The control system uses a PLC controller to monitor the temperature, pressure, and flow parameters of each unit in real time and to achieve automated operation.

[0020] Furthermore, the high-pressure reactor is equipped with a catalyst fixed bed or a suspension stirring structure to accommodate the aforementioned composite catalyst.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: The composite catalyst provided by this invention is formed by combining Cu-ZnO-Al2O3 and HZSM-5 molecular sieve in a specific mass ratio of (3~5):1, creating a multifunctional catalytic system with synergistic effects. This not only solves the technical problem of the difficult unified conversion of multi-source heterogeneous organic components in municipal solid waste, but also achieves highly selective synthesis of ethylene glycol, significantly improving the resource utilization rate and process economy of existing municipal solid waste.

[0022] The present invention provides a method for preparing ethylene glycol from municipal solid waste. This method, through the pretreatment process of plastics, paper and kitchen waste, the introduction of the above-mentioned composite catalyst, and the construction of a closed-loop purification system, successfully transforms municipal solid waste that was originally intended for low-value landfill or incineration into high-value chemical raw material ethylene glycol. This method breaks through the dependence of traditional ethylene glycol production on fossil resources and has significant industrial application value and promotion prospects.

[0023] This invention relates to a municipal solid waste treatment system for implementing the aforementioned methods. The system scientifically configures its functional units and achieves sequential connection and parameter linkage, constructing a highly integrated process platform that combines sorting and conditioning, targeted conversion, tiered purification, and intelligent control. This system not only effectively solves key technical challenges such as the complex composition of municipal solid waste, low conversion efficiency, and difficulty in separating byproducts, but also achieves clean, automated, and resource-efficient operation throughout the entire process. Attached Figure Description

[0024] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 This is a process flow diagram for preparing ethylene glycol from municipal solid waste, as provided in Embodiment 1 of the present invention. Detailed Implementation

[0026] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] According to one aspect of the present invention, a composite catalyst is provided, the composite catalyst being composed of Cu-ZnO-Al2O3 and HZSM-5 molecular sieve, wherein the mass ratio of Cu-ZnO-Al2O3 to HZSM-5 molecular sieve in the composite catalyst is (3~5):1.

[0028] The composite catalyst provided by this invention is formed by combining Cu-ZnO-Al2O3 and HZSM-5 molecular sieve in a specific mass ratio of (3~5):1, creating a multifunctional catalytic system with synergistic effects. This not only solves the technical problem of the difficult unified conversion of multi-source heterogeneous organic components in municipal solid waste, but also achieves highly selective synthesis of ethylene glycol, significantly improving the resource utilization rate and process economy of existing municipal solid waste.

[0029] In a preferred embodiment of the present invention, the Cu-ZnO-Al2O3 comprises, based on oxides, 30% to 60% CuO, 20% to 40% ZnO, and 10% to 30% Al2O3 by mass.

[0030] According to one aspect of the present invention, the composite catalyst can be widely used in the conversion of organic components in municipal solid waste into ethylene glycol, wherein: The household waste includes at least one of plastics, paper, and kitchen waste.

[0031] According to one aspect of the present invention, a method for preparing ethylene glycol from municipal solid waste includes the following steps: (a) Pre-treat plastics, paper and kitchen waste separately in household waste to improve reactivity; (b) The pretreated plastic, paper and kitchen waste organic matter are mixed to form a slurry, and the above composite catalyst is added. The catalytic conversion reaction is carried out under hydrothermal conditions to obtain a reaction mixture. (c) The reaction mixture is subjected to gas-liquid separation to obtain a crude liquid product containing ethylene glycol; (d) The crude liquid product is subjected to filtration to remove slag, removal of impurity ions and multi-stage distillation purification in sequence to obtain ethylene glycol.

[0032] The present invention provides a method for preparing ethylene glycol from municipal solid waste. This method, through the pretreatment process of plastics, paper and kitchen waste, the introduction of a high-efficiency composite catalyst, and the construction of a closed-loop purification system, successfully transforms municipal solid waste that was originally intended for low-value landfill or incineration into high-value chemical raw material ethylene glycol. This method breaks through the dependence of traditional ethylene glycol production on fossil resources and has significant industrial application value and promotion prospects.

[0033] In a preferred embodiment of the present invention, step (a) pretreatment includes: alkaline surface modification treatment of plastic; hydrolytic degradation treatment of paper; and dehydration and enzymatic hydrolysis treatment of kitchen waste.

[0034] In one preferred embodiment, this application performs alkaline surface modification treatment on plastics to remove oil stains and aging layers from the plastic surface; performs hydrolytic degradation treatment on paper to initially degrade cellulose into oligosaccharides; and performs dehydration and bio-enzymatic hydrolysis treatment on kitchen waste to degrade components such as starch and fat.

[0035] It should be noted that the pretreatment method in this application addresses the differences in the physicochemical properties of the three major organic components in municipal solid waste. Based on the material characteristics, pretreatment methods are adopted, namely, through alkaline modification, hydrolytic degradation, and bio-enzymatic hydrolysis, which significantly improve the convertibility and reaction consistency of each component. This pretreatment process is not only a physical conditioning process but also a chemical preparation stage for constructing subsequent efficient synergistic catalytic conversion, playing an indispensable role in achieving the highly selective synthesis of ethylene glycol.

[0036] In a preferred embodiment of the present invention, in step (b) of preparing the slurry, the mass ratio of plastic, paper and kitchen waste organic matter is (1~3):(2~4):(4~6).

[0037] And / or, the conditions for the catalytic conversion in step (b) include: a reaction temperature of 200~300℃, a pressure of 2~6MPa, and a reaction time of 3~8h.

[0038] In a preferred embodiment, the catalytic conversion reaction mechanism is as follows: Under hydrothermal conditions, the alkaline-modified plastic component undergoes depolymerization to generate C2–C4 olefin intermediates; polysaccharides such as cellulose and starch in paper and kitchen waste organic matter undergo hydrolysis to generate monosaccharides such as glucose; these intermediates are further converted under the synergistic effect of a composite catalyst—HZSM-5 molecular sieve provides acidic sites, catalyzing the dehydration and reverse aldol condensation of monosaccharides into C2 / C3 oxygen-containing intermediates, and promoting olefin cracking and rearrangement; simultaneously, the highly dispersed Cu active centers in Cu-ZnO-Al2O3 catalyze the selective hydrogenation and C–O bond hydrogenolysis of key intermediates such as hydroxyacetaldehyde by in-situ hydrogen gas, directionally generating ethylene glycol. This process, by constructing an "olefin-sugar" multi-pathway carbon flow coupling network, achieves unified conversion of organic matter from different sources at the molecular scale, significantly improving the selectivity and yield of ethylene glycol, and solving the technical problem of the difficulty in the synergistic high-value utilization of multi-source heterogeneous components in municipal solid waste.

[0039] In a preferred embodiment of the present invention, the impurity ion removal in step (d) is performed using an ion exchange resin column; the ion exchange resin column is obtained by connecting a cation exchange resin and an anion exchange resin in series. Preferably, the cation exchange resin is model 0017, the anion exchange resin is model D301, and the filling volume ratio of the cation exchange resin to the anion exchange resin is 1:1.

[0040] As a preferred embodiment, the ion exchange resin column used in this application is obtained by connecting cation exchange resin and anion exchange resin in series, preferably configured (0017:D301 = 1:1). This not only solves the technical problem of the coexistence and mutual interference of multiple impurity ions in municipal solid waste conversion liquid, but also achieves efficient, deep and synergistic removal of Na+, Cl- and heavy metal ions.

[0041] In a preferred embodiment of the present invention, step (d) includes a three-stage series distillation column, wherein: The first distillation column operates at atmospheric pressure to remove moisture; The second distillation column operates under reduced pressure to separate 1,2-propanediol; The third distillation column operates under a higher vacuum to collect the ethylene glycol fraction.

[0042] As a preferred implementation, the above-mentioned three-stage series distillation column system, through the operation mode of gradually increasing vacuum from atmospheric pressure, achieves efficient, low-consumption, and safe separation of water, by-products, and target products in municipal solid waste conversion liquid. It not only significantly improves the recovery rate and purity of ethylene glycol, but also promotes the targeted resource utilization of by-products.

[0043] According to one aspect of the present invention, a municipal solid waste treatment system for implementing the above-described method includes functional units connected in sequence: The grading pretreatment unit includes a twin-shaft crusher, a magnetic separator, an eddy current separator, an air-density separation device, a plastic preprocessor, a paper hydrolysis tank, a kitchen waste enzymatic hydrolysis tank, and a mixed pulping tank; The directional catalytic conversion unit includes a high-pressure reactor, a gas-liquid separator, and an H2 recovery device. The high-pressure reactor is equipped with a temperature control module, a pressure control system, and a stirring device. The refining and purification unit includes a filtration device, an ion exchange resin column, and first to third distillation columns, wherein the second and third distillation columns are equipped with a pressure reduction system; The control system uses a PLC controller to monitor the temperature, pressure, and flow parameters of each unit in real time and to achieve automated operation.

[0044] This invention relates to a municipal solid waste treatment system for implementing the aforementioned methods. The system scientifically configures its functional units and achieves sequential connection and parameter linkage, constructing a highly integrated process platform that combines sorting and conditioning, targeted conversion, tiered purification, and intelligent control. This system not only effectively solves key technical challenges such as the complex composition of municipal solid waste, low conversion efficiency, and difficulty in separating byproducts, but also achieves clean, automated, and resource-efficient operation throughout the entire process.

[0045] In a preferred embodiment of the present invention, the high-pressure reactor is provided with a catalyst fixed bed or a suspension stirring structure for accommodating the above-mentioned composite catalyst.

[0046] The technical solution of the present invention will be further described below with reference to the embodiments.

[0047] Example 1 Figure 1 This is a process flow diagram for preparing ethylene glycol from municipal solid waste, as provided in this embodiment.

[0048] See Figure 1 A method for preparing ethylene glycol from municipal solid waste includes the following steps: (a) Graded pretreatment: 1. Take 1000 kg of typical municipal solid waste as raw material. Its composition by mass fraction is as follows: 20% plastic (mainly including polyethylene PE, polypropylene PP and polyethylene terephthalate PET), 30% paper, 40% kitchen waste organic matter, and 10% other (metal, sand, glass, etc.).

[0049] First, the household waste is fed into a twin-shaft crusher for crushing to control the particle size within the range of 5-8 mm. Then, metal (about 15 kg) is removed by magnetic separation and eddy current separation, and inorganic impurities (about 85 kg) are removed by air separation and density separation, resulting in a total of 900 kg of usable organic components.

[0050] 2. The three types of organic components were then subjected to targeted conditioning: Plastic component (200kg): Add 6% sodium hydroxide (NaOH) solution and stir at 90 °C for 45 min to remove surface oil and aging layer and improve subsequent depolymerization activity; Paper component (300 kg): Add deionized water at a solid-liquid ratio of 1:4 and hydrolyze at 65 °C for 40 min to initially degrade cellulose into oligosaccharides; Kitchen waste component (400kg): First, the moisture content is reduced to 45% by pressing and dehydration. Then, 2% of the total mass of compound enzyme preparation (cellulase, hemicellulase and lipase are compounded in a mass ratio of 3:2:1) is added. Enzymatic hydrolysis is carried out at 50℃ for 2.5h to achieve effective degradation of starch, protein and fat.

[0051] The above-prepared plastic, paper, and kitchen waste components were mixed in a mass ratio of 2:3:5. Deionized water was added to adjust the total slurry concentration to 25%. After stirring evenly, a total of 800 kg of mixed slurry was obtained and sent to the subsequent reaction system.

[0052] (II) Directed catalytic conversion The above-mentioned mixed slurry was transferred to a high-pressure reactor with a volume of 500 L, and a composite catalyst accounting for 4% of the slurry mass was added. The composite catalyst was composed of Cu-ZnO-Al2O3 and HZSM-5 molecular sieve in a mass ratio of 4:1.

[0053] Nitrogen (N2) was introduced into the reactor three times to replace the air, ensuring that the reaction system was in an inert atmosphere. Then the reactor was sealed and heated to 240°C, the reaction pressure was adjusted to 4 MPa, the stirring rate was controlled at 400 r / min, and the reaction was maintained under these conditions for 5 hours.

[0054] During the reaction, the plastic component undergoes depolymerization in an alkaline environment to generate olefin intermediates, while the carbohydrates in paper and kitchen waste hydrolyze to generate monosaccharide structures such as glucose. The above intermediates undergo hydrogenolysis under the synergistic effect of the composite catalyst, and are directionally converted into ethylene glycol and other polyols.

[0055] After the reaction is completed, the reaction mixture is introduced into a gas-liquid separator for phase separation to recover non-condensable gases (mainly including H2, CO2, etc.). The H2 can be purified and stored for reuse in the hydrogenation process, with a recovery rate of 80%. A total of 350 kg of crude liquid product containing ethylene glycol is obtained after separation.

[0056] It should be noted that the composite catalyst molding method described in this embodiment includes: 1. Mixing ratio: Weigh the Cu-ZnO-Al2O3 catalyst prepared above and the pretreated HZSM-5 molecular sieve at a mass ratio of 4:1, place them in a ball mill (agate balls, ball-to-material ratio 5:1), add a small amount of deionized water as a dispersant, and ball mill at room temperature for 2 hours to mix the two components evenly.

[0057] 2. Molding and drying: The mixed slurry is vacuum dried at 80℃ to constant weight and ground through an 80-mesh sieve; 5% by mass of graphite is added as a molding aid, and the mixture is pressed into tablets (3mm in diameter and 2mm in thickness) to avoid excessive pressure drop in the reaction bed due to excessively fine particles.

[0058] 3. Final activation: The shaped composite catalyst is placed in a muffle furnace and calcined at 300℃ for 2 hours to remove graphite additives and enhance particle strength; after cooling, it is sealed and stored. Before use, H2 (volume fraction 10%) is introduced in situ into the reaction system and reduced at 250℃ for 1 hour to ensure the activation of Cu active sites and obtain the composite catalyst.

[0059] (III) Refining and Purification The obtained crude liquid product was subjected to the following purification processes in sequence: 1. Solid-liquid separation: Unreacted solid residues and catalyst particles are removed by plate and frame filtration device; 2. Removal of impurity ions: The filtrate is passed through a series-connected ion exchange resin column system. This system consists of cation exchange resin (model 0017) and anion exchange resin (model D301) in a 1:1 volume ratio, effectively removing Na+ from the solution. + Cl - and Pb 2+ Cd 2+ Heavy metal ions; 3. Three-stage distillation separation: The distillation separation employs a three-stage series distillation column system, as detailed below: (a) First distillation column: atmospheric pressure operation, 35 trays, top temperature 100–105 °C, used to remove water and low-boiling-point organic compounds such as methanol and acetaldehyde, yielding about 5 kg of distillate; (b) Second distillation column: Reduced pressure operation, vacuum degree 0.092 MPa, number of trays 45, top temperature 122 ℃, 18 kg of 1,2-propanediol was separated; (c) Third distillation column: higher vacuum degree 0.096 MPa, 55 trays, top temperature 142 ℃, collect the 140–145℃ fraction to obtain ethylene glycol product.

[0060] Example 2 Except for step (ii) directional catalytic conversion, in which the composite catalyst is composed of "Cu-ZnO-Al2O3 and HZSM-5 molecular sieve in a mass ratio of 3:1", the rest of this embodiment is the same as in Example 1.

[0061] Example 3 Except for step (ii) directional catalytic conversion, in which the composite catalyst is composed of "Cu-ZnO-Al2O3 and HZSM-5 molecular sieve in a mass ratio of 5:1", the rest of this embodiment is the same as in Example 1.

[0062] Example 4 In this embodiment, except for step (ii) directional catalytic conversion, the catalytic conditions are as follows: Except for "nitrogen (N2) was introduced into the reactor to replace the air three times to ensure that the reaction system was in an inert atmosphere; then the system was sealed and heated to 200 °C, the reaction pressure was adjusted to 6 MPa, the stirring rate was controlled at 400 r / min, and the reaction was maintained under these conditions for 8 hours", the rest was the same as in Example 1.

[0063] Example 5 In this embodiment, except for step (ii) directional catalytic conversion, the catalytic conditions are as follows: Except for "nitrogen (N2) was introduced into the reactor to replace the air three times to ensure that the reaction system was in an inert atmosphere; then the system was sealed and heated to 300°C, the reaction pressure was adjusted to 2 MPa, the stirring rate was controlled at 400 r / min, and the reaction was maintained under these conditions for 3 hours", the rest was the same as in Example 1.

[0064] Comparative Example 1 Except for step (ii) directional catalytic conversion, in which the composite catalyst is composed of "Cu-ZnO-Al2O3 and HZSM-5 molecular sieve in a mass ratio of 1:1", the rest of this embodiment is the same as in Example 1.

[0065] Comparative Example 2 Except for step (ii) directional catalytic conversion, in which the composite catalyst is composed of "Cu-ZnO-Al2O3 and HZSM-5 molecular sieve in a mass ratio of 6:1", the rest of this embodiment is the same as in Example 1.

[0066] Comparative Example 3 Except for step (ii) directional catalytic conversion, in which the composite catalyst is replaced with Cu-ZnO-Al2O3, this embodiment is the same as in embodiment 1.

[0067] Comparative Example 4 Except for step (ii) directional catalytic conversion, in which the composite catalyst is replaced with HZSM-5 molecular sieve, this embodiment is the same as in embodiment 1.

[0068] Comparative Example 5 (excluding classification preprocessing steps) A method for preparing ethylene glycol from municipal solid waste includes the following steps: 1. Take 1000 kg of household waste with the same composition as in Example 1 as raw material (20% plastic, 30% paper, 40% kitchen waste organic matter, and 10% inorganic inert impurities). Put all the waste directly into a twin-shaft crusher and crush it to a particle size of 5–8 mm. Then, remove metal (about 15 kg) by magnetic separation and eddy current separation, and then remove inorganic impurities such as glass and ceramics (about 85 kg) by air separation and density separation, to obtain a total of 900 kg of mixed organic material.

[0069] Without any sorting or special conditioning, the mixture was directly mixed with deionized water to adjust the slurry concentration to 25%, and after stirring evenly, about 800 kg of mixed slurry was obtained. The mixed slurry was then sent to the subsequent reaction system.

[0070] 2. Directed catalytic conversion: Same as step (II) in Example 1; 3. Refining and purification: Same as step (iii) of Example 1.

[0071] Comparative Example 6 (excluding plastic components) A method for preparing ethylene glycol from municipal solid waste includes the following steps: (a) Graded pretreatment: 1. Take 1000 kg of simulated household waste as raw material, and adjust its composition as follows: 50% paper (300 kg), 60% kitchen waste organic matter (600 kg), and 10% other impurities (100 kg), without any plastic components (i.e., PE, PP, PET, etc. are removed or not added).

[0072] The above-mentioned waste is fed into a twin-shaft crusher and crushed to a particle size of 5-8 mm. Metal impurities (about 15 kg) are removed by magnetic separation and eddy current separation, and inorganic materials such as glass and sand (about 85 kg) are removed by air separation and density separation, resulting in a total of 900 kg of usable organic materials.

[0073] 2. The two types of organic components were then subjected to targeted conditioning: Paper component (300 kg): Add deionized water at a solid-liquid ratio of 1:4 and hydrolyze at 65 °C for 40 min to initially degrade cellulose into oligosaccharides; Kitchen waste component (600 kg): Press and dehydrate to a moisture content of about 45%, then add 2% of the total mass of compound enzyme preparation, and enzymatically hydrolyze at 50℃ for 2.5 h to achieve effective degradation of starch, protein and fat.

[0074] The prepared paper and kitchen waste components were mixed at a mass ratio of 1:2. Deionized water was added to adjust the total pulp concentration to 25%. After stirring evenly, a total of 800 kg of mixed pulp was obtained and sent to the subsequent reaction system.

[0075] (ii) Directed catalytic conversion: Same as Example 1; (III) Refining and purification: Same as in Example 1.

[0076] Comparative Example 7 (excluding paper components) A method for preparing ethylene glycol from municipal solid waste includes the following steps: (a) Graded pretreatment: 1. Take 1000 kg of simulated household waste as raw material, and adjust its composition as follows: 33.3% (333 kg) plastic, 56.7% (567 kg) kitchen waste organic matter, and 10% (100 kg) other impurities, without any paper or cellulose materials (i.e., newspapers, office paper, cardboard, etc. are all removed).

[0077] The above-mentioned waste is fed into a twin-shaft crusher and crushed to a particle size of 5–8 mm; metallic impurities (about 15 kg) are removed by magnetic separation and eddy current separation, and inorganic materials such as glass and sand (about 85 kg) are removed by air separation and density separation, resulting in a total of 900 kg of usable organic materials.

[0078] 2. The two types of organic components were then subjected to targeted conditioning: Plastic component (333 kg): Add 6% NaOH solution by mass, stir and react at 90 °C for 45 min to break the surface aging layer; Kitchen waste component (567 kg): Pressed and dehydrated to a moisture content of about 45%, then 2% of a compound enzyme preparation was added, and enzymatic hydrolysis was carried out at 50°C for 2.5 h to achieve partial degradation of starch and fat.

[0079] The prepared plastic and kitchen waste components are mixed in a ratio of 3:5. Deionized water is added to adjust the slurry concentration to 25%. After stirring evenly, about 800 kg of mixed slurry is obtained and sent to the subsequent reaction system.

[0080] (ii) Directed catalytic conversion: Same as Example 1; (III) Refining and purification: Same as in Example 1.

[0081] Comparative Example 8 (excluding organic components from kitchen waste) A method for preparing ethylene glycol from municipal solid waste includes the following steps: (a) Graded pretreatment: 1. Take 1000 kg of simulated household waste as raw material, and adjust its composition to: 33.3% (333 kg) plastic, 66.7% (667 kg) paper, and 10% (100 kg) inorganic inert impurities, without any kitchen waste organic matter (such as food scraps, fruit peels, grease, etc. are all removed).

[0082] The above-mentioned waste is fed into a twin-shaft crusher and crushed to a particle size of 5–8 mm; metallic impurities (about 15 kg) are removed by magnetic separation and eddy current separation, and inorganic materials such as glass and sand (about 85 kg) are removed by air separation and density separation, resulting in a total of 900 kg of usable organic materials.

[0083] 2. The two types of organic components were then subjected to targeted conditioning: Plastic component (333 kg): Add 6% NaOH solution by mass, stir and react at 90 °C for 45 min to break the surface aging layer; Paper component (667 kg): Deionized water was added at a solid-liquid ratio of 1:4, and hydrolyzed at 65 °C for 40 min to gradually degrade cellulose into oligosaccharides and glucose.

[0084] The prepared plastic and paper components were mixed in a ratio of 1:2, and deionized water was added to adjust the pulp concentration to 25%. After stirring evenly, approximately 795 kg of mixed pulp was obtained and sent to the subsequent reaction system.

[0085] (ii) Directed catalytic conversion: Same as Example 1; (III) Refining and purification: Same as in Example 1.

[0086] Experimental Example 1 To verify the effectiveness and superiority of the composite catalyst, the method for preparing ethylene glycol from municipal solid waste, and the treatment system provided by this invention, the products obtained in Examples 1-5 and Comparative Examples 1-8 were systematically tested and compared. The results are shown in Table 1.

[0087] Table 1:

[0088] Note: In the table above, "yield" refers to the amount of ethylene glycol that can be produced from each ton of municipal solid waste.

[0089] As shown in Table 1, the ethylene glycol products prepared in Examples 1-5 all have high purity and yield, which are much higher than those in the comparative examples.

[0090] Compared to the embodiments, Comparative Examples 1-4, by changing the catalyst composition, showed that when the mass ratio of Cu-ZnO-Al2O3 and HZSM-5 molecular sieves deviated from the range of (3-5):1 (e.g., 1:1 in Comparative Example 1 and 6:1 in Comparative Example 2), the ethylene glycol yield decreased to 65.1 kg / t and 63.4 kg / t, respectively, and the purity was also lower than 99.92% in Example 1. This indicates that excessive HZSM-5 leads to excessive cracking and generation of small molecule gases, while excessive Cu components inhibit the acid catalytic pathway. When Cu-ZnO-Al2O3 (Comparative Example 3) or HZSM-5 (Comparative Example 4) were used alone, the yield further decreased to 53.6 kg / t and 50.3 kg / t, respectively. This proves that a single catalyst cannot achieve unified and efficient conversion of multi-source organic matter, and a bifunctional synergistic system must be relied upon to drive the depolymerization and rearrangement reactions.

[0091] Compared to the embodiments, Comparative Examples 6-8 lacked plastic, paper, or kitchen waste organic matter, respectively. The results showed that the ethylene glycol yield was generally lower than 40 kg / t, significantly lower than Example 1 (92 kg / t). This indicates that in the ethylene glycol-directed catalytic process of this application, plastic provides olefinic carbon chain precursors, which can participate in the construction of C2 structural units under alkaline conditions; cellulose in paper hydrolyzes to produce glucose, which is the direct sugar source for ethylene glycol formation; kitchen waste organic matter is rich in active functional groups (such as hydroxyl and carboxyl groups), which helps to regulate the pH of the system and promote intermediate stability. Only when the above three components work together under the combined action of the composite catalyst to form an olefin-sugar-fatty acid synergistic conversion network can a truly efficient process be achieved; none of these components can be omitted.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite catalyst, characterized in that, The composite catalyst is composed of Cu-ZnO-Al2O3 and HZSM-5 molecular sieve. The mass ratio of Cu-ZnO-Al2O3 to HZSM-5 molecular sieve in the composite catalyst is (3~5):

1.

2. The composite catalyst according to claim 1, characterized in that, Based on oxides, the Cu-ZnO-Al2O3 comprises: CuO with a mass fraction of 30%~60%, ZnO with a mass fraction of 20%~40%, and Al2O3 with a mass fraction of 10%~30%.

3. The use of the composite catalyst as described in claim 1 or 2 in converting organic components in municipal solid waste into ethylene glycol, wherein: The household waste includes at least one of plastics, paper, and kitchen waste.

4. A method for preparing ethylene glycol from municipal solid waste, characterized in that, Includes the following steps: (a) Pre-treat plastics, paper and kitchen waste separately in household waste to improve reactivity; (b) The pretreated plastic, paper and kitchen waste are mixed to form a slurry, and the composite catalyst of claim 1 is added. The catalytic conversion reaction is carried out under hydrothermal conditions to obtain a reaction mixture. (c) The reaction mixture is subjected to gas-liquid separation to obtain a crude liquid product containing ethylene glycol; (d) The crude liquid product is subjected to filtration to remove slag, removal of impurity ions and multi-stage distillation purification in sequence to obtain ethylene glycol.

5. The method according to claim 4, characterized in that, The preprocessing in step (a) includes: Alkaline surface modification treatment is applied to plastics; Paper is subjected to hydrolytic degradation treatment; Kitchen waste organic matter is dehydrated and bio-enzymatically hydrolyzed.

6. The method according to claim 4, characterized in that, In step (b) of preparing the slurry, the mass ratio of plastic, paper and kitchen waste organic matter is (1~3):(2~4):(4~6); And / or, the conditions for the catalytic conversion in step (b) include: a reaction temperature of 200~300℃, a pressure of 2~6MPa, and a reaction time of 3~8h.

7. The method according to claim 4, characterized in that, In step (d), the removal of impurity ions is performed using an ion exchange resin column; the ion exchange resin column is obtained by connecting cation exchange resin and anion exchange resin in series. Preferably, the cation exchange resin is model 0017, the anion exchange resin is model D301, and the filling volume ratio of the cation exchange resin to the anion exchange resin is 1:

1.

8. The method according to claim 4, characterized in that, Step (d) includes a three-stage series distillation column, wherein: The first distillation column operates at atmospheric pressure to remove moisture; The second distillation column operates under reduced pressure to separate 1,2-propanediol; The third distillation column operates under a higher vacuum to collect the ethylene glycol fraction.

9. A municipal solid waste treatment system for implementing the method according to any one of claims 4 to 8, characterized in that, Includes functional units connected in sequence: The grading pretreatment unit includes a twin-shaft crusher, a magnetic separator, an eddy current separator, an air-density separation device, a plastic preprocessor, a paper hydrolysis tank, a kitchen waste enzymatic hydrolysis tank, and a mixed pulping tank; The directional catalytic conversion unit includes a high-pressure reactor, a gas-liquid separator, and an H2 recovery device. The high-pressure reactor is equipped with a temperature control module, a pressure control system, and a stirring device. The refining and purification unit includes a filtration device, an ion exchange resin column, and first to third distillation columns, wherein the second and third distillation columns are equipped with a pressure reduction system; The control system uses a PLC controller to monitor the temperature, pressure, and flow parameters of each unit in real time and to achieve automated operation.

10. A municipal solid waste treatment system according to claim 9, characterized in that, The high-pressure reactor is equipped with a catalyst fixed bed or a suspension stirring structure to accommodate composite catalysts.

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