Method for preparing acetic acid from water phase product of pulping and papermaking sludge pyrolysis and catalyst

Abstract

This application discloses a method and catalyst for preparing acetic acid from the aqueous phase products of pulp and paper sludge pyrolysis, belonging to the field of high-value utilization technology of biomass resources. The method includes two steps: pretreatment and catalytic wet oxidation. Using the aqueous phase products generated during the pyrolysis of pulp and paper sludge as raw materials, the products are first pretreated, and then subjected to catalytic wet oxidation under high temperature and high pressure conditions, using oxygen or oxygen-containing gas as an oxidant, in the presence of a supported metal catalyst. This selectively oxidizes the organic components in the pyrolysis aqueous phase products, yielding a product with acetic acid as the main component. This invention utilizes the selective oxidation effect of a supported metal catalyst to achieve the directional enrichment of acetic acid and the high-value utilization of the aqueous phase products from pulp and paper sludge pyrolysis. The acetic acid selection is high, and this technology can also be extended to the selective oxidation of other aqueous phase products generated from biomass pyrolysis / catalytic pyrolysis to produce high-value-added acetic acid, showing promising application prospects.

Description

Technical Field

[0001] This application relates to a method and catalyst for preparing acetic acid from the aqueous phase products of pulp and paper sludge pyrolysis, belonging to the technical field of pulp and paper waste treatment and resource recycling. Background Technology

[0002] The pulp and paper industry generates a large amount of sludge during wastewater treatment. Pulp and paper sludge has a high water content and complex composition. Traditional landfill disposal methods are land-consuming and pose a risk of secondary pollution, while incineration is energy-intensive and costly. Pyrolysis technology, as a sludge treatment method, can cause thermochemical decomposition of sludge under anaerobic or hypoxic conditions, producing combustible gas, pyrolysis oil / pyrolysis aqueous phase products, and solid carbon residue, thus achieving sludge volume reduction.

[0003] The pyrolysis aqueous phase products generated during the pyrolysis of pulp and paper sludge are typically complex mixed systems dominated by water. These systems contain various oxygen-containing organic compounds (such as acids, alcohols, aldehydes, ketones, and phenols), as well as nitrogen- and sulfur-containing compounds and small amounts of tar-like substances. They are characterized by high color, strong odor, and high chemical oxygen demand (COD), and some components are difficult to degrade using conventional biochemical methods. Direct discharge or discharge of these pyrolysis aqueous phase products after only simple treatment can easily pollute aquatic environments.

[0004] Wet oxidation (WAO) technology utilizes oxidants to oxidize and degrade organic matter under high temperature and pressure conditions. However, existing non-catalytic wet oxidation methods often require harsh reaction conditions (such as higher temperatures, pressures, and reaction times), and suffer from insufficient selectivity of target products when treating complex organic wastewater, making it difficult to achieve the targeted conversion of organic matter into high-value-added chemicals. Furthermore, if suspended solids and tar-like particles in the aqueous phase products of pulp and paper sludge pyrolysis are not effectively removed, they can interfere with catalyst activity, leading to a decrease in catalytic efficiency.

[0005] Therefore, it is necessary to develop a catalytic wet oxidation method specifically designed for the characteristics of aqueous products from pulp and paper sludge pyrolysis. This method would not only achieve the harmless treatment of aqueous products from pyrolysis but also selectively convert complex organic matter into high-value-added platform chemicals, thereby realizing the resource utilization of aqueous products from sludge pyrolysis. Summary of the Invention

[0006] The purpose of this application is to provide a method and catalyst for preparing acetic acid from the aqueous phase products of pulp and paper sludge pyrolysis, in order to solve the problems in the prior art where the aqueous phase products of pulp and paper sludge pyrolysis are complex in composition, difficult to biochemically degrade, and the non-catalytic wet oxidation method has harsh reaction conditions and insufficient selectivity of target products, making it difficult to achieve the directional conversion of complex organic matter into high value-added chemicals.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing acetic acid from the aqueous phase products of pulp and paper sludge pyrolysis, characterized by comprising the following steps: (1) Pretreatment: The aqueous phase products of pulp and paper sludge pyrolysis are treated by at least one of the following methods: air flotation, filtration, and centrifugation to remove suspended solids and tar-like particles from the aqueous phase products of pyrolysis. (2) Catalytic wet oxidation reaction: The pretreated pyrolysis aqueous phase product is introduced into the reaction system and a supported catalyst is added to carry out the catalytic wet oxidation reaction; The active component of the supported catalyst is at least one of Pt, Ru, Pd, Fe, and Co. The support for the supported catalyst is at least one of ZrO2, TiO2, CeO2, Al2O3, or clay. The loading of the active component is 0.1 to 10 wt%.

[0008] Optionally, in step (1), the pretreatment adopts a combination of air flotation and filtration, with an air flotation pressure of 0.3 to 0.8 MPa and a filter membrane with a pore size of 0.22 to 1 μm. Preferably, the pretreatment is performed by centrifugation, with a centrifugation speed of 3000-8000 r / min and a centrifugation time of 10-30 min.

[0009] Optionally, in step (2), when the active component is at least one of Pt, Ru, and Pd, the loading of the active component is not higher than 1 wt%. Preferably, when the active component is at least one of Fe and Co, the loading of the active component is not less than 1 wt%. Preferably, the carrier is a composite carrier, and the content of each component in the composite carrier is not less than 5 wt%.

[0010] Optionally, in step (2), the oxidant is air or oxygen, and the amount of oxygen introduced after conversion is 1.2 to 1.5 times the theoretical oxygen requirement for the reaction; Preferably, the reaction conditions are: temperature 200–280°C, reaction pressure 4–8 MPa, and reaction time 1–8 h.

[0011] According to another aspect of this application, a supported catalyst is provided for the catalytic wet oxidation of aqueous products from the pyrolysis of pulp and paper sludge to produce acetic acid. The active component of the catalyst is at least one of Pt, Ru, Pd, Fe, and Co. The catalyst support is at least one of ZrO2, TiO2, CeO2, Al2O3 or clay; The loading of the active ingredient is 0.1–10 wt%; Optionally, the active component is at least one of Pt, Ru, and Pd; Preferably, the active component is at least one of Fe and Co; Preferably, the carrier is a composite carrier, and the content of each component in the composite carrier is not less than 5 wt%.

[0012] According to another aspect of this application, an application of a supported catalyst in the preparation of acetic acid is provided, the application comprising: subjecting pretreated aqueous pyrolysis products of pulp and paper sludge to a catalytic wet oxidation reaction under the action of the catalyst, wherein the pretreatment is used to remove suspended solids and tar-like particles from the aqueous pyrolysis products, and the acetic acid purity of the product obtained by the reaction is not less than 60%; Optionally, the purity of acetic acid in the product is not less than 75%; Optionally, the acetic acid purity in the product is not less than 90%; the active component of the catalyst is Co or Pd, and the support is TiO2 or ZrO2.

[0013] Optionally, the application also includes using the prepared acetic acid product as an external carbon source in a denitrification bioreactor.

[0014] In this application, "aqueous phase products of pulp and paper sludge pyrolysis" refers to the aqueous phase products in the liquid phase products generated by the pyrolysis process of pulp and paper sludge and collected by condensation. It contains a high water content, various soluble or dispersible organic substances and a small amount of inorganic salts, and belongs to high-concentration organic waste liquid.

[0015] The beneficial effects that this application can produce include: 1) Synergistic effect of resource utilization and pollution reduction: Complex organic matter in the aqueous phase products of pulp and paper sludge pyrolysis can be selectively converted into small molecule organic acids and acetic acid can be enriched. The purity of acetic acid can reach more than 60%, and the highest can reach 93.7%, thus achieving simultaneous pollution reduction and resource utilization. 2) Significantly improved catalytic efficiency: Compared with non-catalytic wet oxidation methods, this invention can achieve acetic acid purity of 87.5% under milder conditions (such as 260℃, 6.5 MPa, 3 h), significantly reducing energy consumption and greatly improving selectivity; 3) Flexible catalyst system: It can use noble metal catalysts (Pt, Ru, Pd) to achieve high activity with low loading, or non-noble metal catalysts (Fe, Co) to achieve high cost performance, adapting to the needs of different application scenarios; 4) Simple process flow: Air or oxygen is used as the oxidant, without introducing additional organic solvents or complex reactants. The pretreatment steps effectively avoid catalyst deactivation. The process flow is short and easy to scale up. 5) Strong technology scalability: This method can also be extended to the selective oxidation of aqueous products from other biomass pyrolysis or catalytic pyrolysis to produce high-value-added acetic acid. Attached Figure Description

[0016] Figure 1 The purity of acetic acid produced from the aqueous phase products of pyrolysis of pulp and paper sludge by different catalysts in catalytic wet oxidation treatment. Detailed Implementation

[0017] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0018] Unless otherwise specified, the "purity of acetic acid" in this application is analyzed as follows: Total organic carbon (TOC) is determined using an organic carbon analyzer. The formula for calculating the purity of acetic acid is TOCacetic acid / TOCtotal × 100%, where TOCtotal includes organic acid components such as formic acid, acetic acid, propionic acid, butyric acid, lactic acid, and oxalic acid. TOCacetic acid corresponds to the total organic carbon value corresponding to the concentration of acetic acid. After the sample is filtered through a 0.45 μm filter membrane, the content of each organic acid is quantitatively analyzed using high-performance liquid chromatography (HPLC) or gas chromatography (GC), and the organic acid components determined by the chromatographic method used shall prevail.

[0019] Example 1 The pyrolysis aqueous phase product obtained by pyrolysis of pulp and paper sludge is used as raw material. It is first pretreated by a combination of air flotation and filtration. The air flotation pressure is 0.5 MPa, and the filtration uses a filter membrane with a pore size of 0.45 μm to remove suspended solids and tar-like particles from the pyrolysis aqueous phase product.

[0020] The pretreated aqueous pyrolysis product was added to the reaction system using a Pd / TiO2 supported catalyst with a Pd loading of 0.5 wt%. The reaction was carried out at a temperature of 260 ℃, a pressure of 6.5 MPa, and a time of 3 h, with air as the oxidant. The oxygen supply, calculated from the air, was 1.2 times the theoretical oxygen requirement.

[0021] The purity of acetic acid in the product obtained after the reaction was 87.5%.

[0022] Example 2 The difference from Example 1 is that the pyrolysis aqueous phase product was treated by centrifugation at a speed of 6000 r / min for 20 min, and the supernatant was collected for later use.

[0023] The pretreated aqueous pyrolysis product was introduced into a high-pressure reactor, and a supported catalyst Pd / ZrO2 was added, with Pd loading at 1 wt%. Oxygen was introduced at a reaction temperature of 270 ℃, a reaction pressure of 7.0 MPa, and a reaction time of 4 h, with the oxygen introduction rate being 1.3 times the theoretical oxygen requirement, to carry out a catalytic wet oxidation reaction.

[0024] After the reaction was completed, the sample was cooled and analyzed. Acetic acid was the main product in the reaction solution, with a purity of 90.8%.

[0025] Example 3 The difference from Example 1 is that the aqueous phase product of pulp and paper sludge pyrolysis is pretreated by centrifugation at a speed of 7000 r / min for 25 min.

[0026] The pretreated aqueous pyrolysis product and a Ru / Clay catalyst were added to the reaction system, with Ru loading at 0.9 wt%. A catalytic wet oxidation reaction was carried out using air as the oxidant at 240 °C, 5.8 MPa, and 3 h. The acetic acid content in the reaction solution was 86.8%.

[0027] Example 4 The difference from Example 1 is that the pyrolysis aqueous phase product is filtered by a filter membrane to remove suspended solids and tar-like particles, with a filter membrane pore size of 0.22 μm.

[0028] The pretreated aqueous pyrolysis product and Ru / CeO2 catalyst were added together into the reactor, with Ru loading at 0.8 wt%. The catalytic wet oxidation reaction was carried out under the conditions of reaction temperature 260 ℃, reaction pressure 6.5 MPa, and reaction time 5 h, with air as the oxidant. The oxygen supply was 1.4 times the theoretical oxygen requirement.

[0029] The purity of acetic acid in the resulting reaction solution was 82.7%.

[0030] Example 5 The difference from Example 1 is that the aqueous phase products of sludge pyrolysis are pretreated by first air flotation and then filtration; the air flotation pressure is 0.4 MPa, and then the filter membrane is used for filtration with a pore size of 1.0 μm.

[0031] A Pt / Al2O3 catalyst with a Pt loading of 0.3 wt% was added to the reaction system. The reaction was carried out at 230 °C and 5.0 MPa for 4 h, with oxygen introduced as an oxidant at a rate of 1.25 times the theoretical oxygen demand.

[0032] Post-reaction testing showed that the purity of acetic acid was 75.8%.

[0033] Example 6 The difference from Example 1 is that the aqueous phase products of pulp and paper sludge pyrolysis are pretreated by filtration, and the pore size of the filter membrane is 0.45 μm.

[0034] A Co / TiO2 catalyst with a Co loading of 5 wt% was added to the reaction system. Under the conditions of 280 °C, 8.0 MPa, and 2 h of reaction, oxygen was used as the oxidant, and the oxygen supply was 1.5 times the theoretical oxygen requirement.

[0035] The purity of the acetic acid produced in the reaction solution is 93.7%.

[0036] Example 7 The difference from Example 1 is that the aqueous phase product of pulp and paper sludge pyrolysis is pretreated by centrifugation at a speed of 5000 r / min for 15 min.

[0037] The treated pyrolysis aqueous phase product and Fe / ZrO2 catalyst were added to a reactor, with Fe loading at 3 wt%. A catalytic wet oxidation reaction was carried out using air as the oxidant under the conditions of a reaction temperature of 270 °C, a reaction pressure of 7.5 MPa, and a reaction time of 6 h.

[0038] The purity of acetic acid in the reaction product was 89.2%.

[0039] Example 8 The difference from Example 1 is that the aqueous phase product of pulp and paper sludge pyrolysis is pretreated by air flotation and centrifugation. The air flotation pressure is 0.4 MPa, the centrifugation speed is 4000 r / min, and the centrifugation time is 15 min. After treatment, a catalytic wet oxidation reaction is carried out.

[0040] A Pd / ZrO2–TiO2 composite catalyst was used, with ZrO2 and TiO2 having mass fractions of 50 wt% and 50 wt%, respectively, and Pd loading of 0.7 wt%. The reaction was carried out under the conditions of reaction temperature 245 ℃, reaction pressure 6.0 MPa, and reaction time 4 h, with air introduced.

[0041] The reaction results showed that the purity of acetic acid was 93.2%.

[0042] Example 9 The difference from Example 1 is that the aqueous phase products of pulp and paper sludge pyrolysis are pretreated by centrifugation at a speed of 6500 r / min for 25 min.

[0043] The pretreated aqueous pyrolysis product and a Pt-Ru / ZrO2 bimetallic catalyst were added to the reaction system, with Pt loading of 0.2 wt% and Ru loading of 0.3 wt%. A catalytic wet oxidation reaction was carried out using air as the oxidant under the conditions of a reaction temperature of 250℃, a reaction pressure of 6.0 MPa, and a reaction time of 4 h.

[0044] The acetic acid in the reaction solution has a purity of 85.3%.

[0045] Example 10 The difference from Example 1 is that the pyrolysis aqueous phase product is pretreated by filtration, and the filter membrane has a pore size of 0.45 μm.

[0046] A Fe-Co / TiO2 catalyst was added to the reaction system, with Fe loading of 1.5 wt% and Co loading of 2.0 wt%. Under the conditions of 265℃, 7.0 MPa, and 3 h of reaction, oxygen was used as the oxidant, and the oxygen supply rate was 1.3 times the theoretical oxygen demand.

[0047] The purity of acetic acid in the reaction product was 88.6%.

[0048] Example 11 The difference from Example 1 is that a combination of air flotation and filtration is used for pretreatment, with an air flotation pressure of 0.6 MPa and a filter membrane with a pore size of 0.45 μm for filtration.

[0049] The pretreated aqueous pyrolysis product was added to the reaction system using a Pd / Al2O3 supported catalyst with a Pd loading of 0.1 wt% (boundary value). Air was used as the oxidant under the conditions of a reaction temperature of 240℃, a reaction pressure of 5.5 MPa, and a reaction time of 5 h.

[0050] The purity of acetic acid in the product obtained after the reaction was 62.4%.

[0051] Example 12 The difference from Example 1 is that the pyrolysis aqueous phase product was pretreated by centrifugation at a speed of 7500 r / min for 20 min.

[0052] The pretreated aqueous pyrolysis product and a Co / CeO2 catalyst were added to the reaction system, with a Co loading of 10 wt% (boundary value). Oxygen was used as the oxidant under the conditions of 275 °C, 7.8 MPa, and 2 h of reaction.

[0053] The acetic acid in the reaction solution has a purity of 78.9%.

[0054] Comparative Example 1 The difference from Example 1 is that the aqueous phase products of pulp and paper sludge pyrolysis were not pretreated; instead, the aqueous phase products of the raw material pyrolysis were directly added to the reactor for catalytic wet oxidation. A Pd / TiO2 catalyst was used, with a Pd loading of 0.5 wt%, a reaction temperature of 260°C, a reaction pressure of 6.5 MPa, a reaction time of 3 h, and air as the oxidant.

[0055] During the reaction, it was found that the catalyst surface was rapidly covered by tar-like substances, the acetic acid purity in the reaction solution was only 38%, the catalyst activity decreased significantly, and the efficient conversion of the pyrolysis aqueous phase products could not be achieved.

[0056] Comparative Example 2 The difference from Example 1 is that a non-catalytic wet oxidation method was used to treat the pyrolysis aqueous phase product without adding any catalyst. After pretreatment by air flotation and filtration, the pyrolysis aqueous phase product was reacted with oxygen as the oxidant at a reaction temperature of 300°C and a reaction pressure of 10 MPa for 12 h.

[0057] The acetic acid purity in the reaction solution is only 27%, and most of the organic matter is over-oxidized into CO2 and H2O. The acetic acid selectivity is extremely low, and the reaction conditions are harsh and energy consumption is high.

[0058] Comparative Example 3 The difference from Example 6 is that the Co loading in the Co / TiO2 catalyst is 0.5 wt%, which is lower than the preferred loading limit (1 wt%) for non-precious metal catalysts in the method of this invention. After filtration pretreatment, the pyrolysis aqueous phase product was reacted at a temperature of 280°C, a pressure of 8.0 MPa, and a time of 2 h, with oxygen as the oxidant.

[0059] The purity of acetic acid in the reaction solution was 65%, which was significantly lower than 93.7% in Example 6. This indicates that when the loading of non-precious metal active components is less than 1 wt%, the catalyst activity is insufficient and cannot achieve highly selective conversion of organic matter in the pyrolysis aqueous phase products to acetic acid.

[0060] Comparative Example 4 The difference from Example 2 is that the Pd loading in the Pd / ZrO2 catalyst is 1.5 wt%, exceeding the upper limit of the preferred loading of noble metal catalysts (1 wt%) in the method of this invention. The pyrolysis aqueous phase product, after centrifugal pretreatment, is subjected to catalytic wet oxidation under the same reaction conditions.

[0061] The acetic acid in the reaction solution has a purity of 72.3%.

[0062] Comparative Example 5 The difference from Example 1 is that activated carbon was used as a support to prepare a Pd / activated carbon catalyst with a Pd loading of 0.5 wt%. The aqueous phase products from the pyrolysis were subjected to the same pretreatment and then carried out a catalytic wet oxidation reaction under the same reaction conditions.

[0063] The acetic acid in the reaction solution had a purity of only 58.2%.

[0064] Comparative Example 6 The difference from Example 1 is that the reaction temperature was adjusted to 180°C. All other conditions remained unchanged.

[0065] The acetic acid in the reaction solution had a purity of only 45.6%.

[0066] The process parameters and acetic acid purity test results of Examples 1 to 12 and Comparative Examples 1 to 6 are summarized in Table 1.

[0067] Table 1 Summary of process parameters and acetic acid purity for examples and comparative examples

[0068] As can be seen from Table 1, the acetic acid purity of Examples 1 to 12, using different catalyst systems, pretreatment methods and reaction conditions, all reached over 60%. Among them, the acetic acid purity of Examples 6 and 8 reached 93.7% and 93.2%, respectively, indicating that the method of the present invention can achieve highly selective conversion of aqueous products from the pyrolysis of pulp and paper sludge to prepare acetic acid.

[0069] Comparative Example 1, without pretreatment, resulted in a catalyst surface covered with tar-like substances, leading to decreased activity and an acetic acid purity of only 38%. This demonstrates the crucial role of pretreatment in removing suspended solids and tar-like particles and protecting catalyst activity. Comparative Example 2, employing a non-catalytic wet oxidation method, achieved an acetic acid purity of only 27%, requiring higher reaction temperatures (300°C), higher reaction pressures (10 MPa), and longer reaction times (12 h). This highlights the critical role of the catalyst in improving acetic acid selectivity and reducing the severity of reaction conditions. In Comparative Example 3, the Co loading was 0.5 wt%, lower than the preferred lower limit for non-precious metal catalyst loading (1 wt%) in this invention. The acetic acid purity was only 65%, significantly lower than the 93.7% in Example 6. This demonstrates that a non-precious metal active component loading of at least 1 wt% is necessary to ensure sufficient catalyst activity for high selective conversion. In Comparative Example 4, the Pd loading was 1.5 wt%, exceeding the preferred upper limit for precious metal catalyst loading (1 wt%) in this invention. The acetic acid purity decreased to 72.3%, indicating that excessively high precious metal loading leads to decreased selectivity. Comparative Example 5 used an activated carbon support, and the acetic acid purity was only 58.2%, lower than the baseline of 60%, demonstrating that the support type has a significant impact on catalytic performance. Comparative Example 6 reacted at 180℃, and the acetic acid purity was only 45.6%, demonstrating that the reaction temperature needs to be above 200℃ to ensure complete conversion.

[0070] Examples 11 and 12 verified the feasibility of the active component loading boundary values ​​(0.1 wt% and 10 wt%), respectively, with acetic acid purities of 62.4% and 78.9%, both meeting the basic requirement of ≥60%. Examples 9 and 10 verified the effectiveness of the bimetallic catalyst, further expanding the scope of application of the present invention.

[0071] This application utilizes a catalytic wet oxidation method under relatively mild reaction conditions (reaction temperature 200 to 280°C, reaction pressure 4 to 8 MPa, reaction time 1 to 8 h) to selectively convert complex organic matter in the aqueous phase products of pulp and paper sludge pyrolysis into acetic acid. The acetic acid purity can reach over 60%, achieving the synergistic treatment of waste reduction, harmlessness, and resource recovery. The process flow of this invention is simple, using air or oxygen as the oxidant, without introducing additional organic solvents or complex reactants, making it easy to scale up for industrial application. This technology can also be extended to the selective oxidation of aqueous phase products from other biomass pyrolysis or catalytic pyrolysis to prepare high-value-added organic acids.

[0072] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing acetic acid from the aqueous phase products of pulp and paper sludge pyrolysis, characterized in that, Includes the following steps: (1) Pretreatment: The aqueous phase products of pulp and paper sludge pyrolysis are treated by at least one of the following methods: air flotation, filtration, and centrifugation to remove suspended solids and tar-like particles from the aqueous phase products of pyrolysis. (2) Catalytic wet oxidation reaction: The pretreated pyrolysis aqueous phase product is introduced into the reaction system and a supported catalyst is added to carry out the catalytic wet oxidation reaction; The active component of the supported catalyst is at least one of Pt, Ru, Pd, Fe, and Co. The support for the supported catalyst is at least one of ZrO2, TiO2, CeO2, Al2O3, or clay. The loading of the active component is 0.1 to 10 wt%.

2. The method according to claim 1, characterized in that, In step (1), the pretreatment adopts a combination of air flotation and filtration, with an air flotation pressure of 0.3 to 0.8 MPa and a filter membrane with a pore size of 0.22 to 1 μm. Preferably, the pretreatment is performed by centrifugation, with a centrifugation speed of 3000-8000 r / min and a centrifugation time of 10-30 min.

3. The method according to claim 1, characterized in that, In step (2), when the active component is at least one of Pt, Ru, and Pd, the loading of the active component is not higher than 1 wt%. Preferably, when the active component is at least one of Fe and Co, the loading of the active component is not less than 1 wt%; Preferably, the carrier is a composite carrier, and the content of each component in the composite carrier is not less than 5 wt%.

4. The method according to claim 1, characterized in that, In step (2), the oxidant of the oxidation reaction is air or oxygen, and the amount of oxygen introduced after conversion is 1.2 to 1.5 times the theoretical oxygen requirement for the reaction; Preferably, the reaction conditions are: temperature 200–280°C, reaction pressure 4–8 MPa, and reaction time 1–8 h.

5. A supported catalyst for the catalytic wet oxidation of aqueous products from pulp and paper sludge pyrolysis to produce acetic acid, characterized in that, The active component of the catalyst is at least one of Pt, Ru, Pd, Fe, and Co. The catalyst support is at least one of ZrO2, TiO2, CeO2, Al2O3 or clay; The loading of the active component is 0.1 to 10 wt%.

6. The supported catalyst according to claim 5, characterized in that, The active component is at least one of Pt, Ru, and Pd; Preferably, the active component is at least one of Fe and Co; Preferably, the carrier is a composite carrier, and the content of each component in the composite carrier is not less than 5 wt%.

7. The use of the supported catalyst according to any one of claims 5 to 6 in the preparation of acetic acid, characterized in that, The application includes: catalytically wet-oxidizing the pretreated pulp and paper sludge pyrolysis aqueous phase product under the action of the catalyst, wherein the pretreatment is used to remove suspended solids and tar-like particles from the pyrolysis aqueous phase product, and the acetic acid purity of the product prepared by the reaction is not less than 60%.

8. The application according to claim 7, characterized in that, The purity of acetic acid in the product is not less than 75%.

9. The application according to claim 7, characterized in that, The purity of acetic acid in the product is not less than 90%; the active component of the catalyst is Co or Pd, and the support is TiO2 or ZrO2.

10. The application according to claim 7, characterized in that, The application also includes using the prepared acetic acid product as an external carbon source in a denitrification bioreactor.

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