Wet oxidation catalysts, their preparation methods and applications

Abstract

This invention relates to a wet oxidation catalyst, its preparation method, and its application. The catalyst comprises a support and a metal oxide active component, wherein the metal oxide comprises Mo, Fe, and Co, and the relative particle size ratio of the oxidized crystal phases of the catalyst (Co...) is... 0.7 Fe 0.3 The ratio of (MoO4) / MoO3 is greater than or equal to 3.50. When using the catalyst of this invention to treat organic wastewater, the COD removal rate is high.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment, specifically relating to a wet oxidation catalyst, its preparation method, and its application. Background Technology

[0002] The complex chemical reactions in chemical industrial production processes make the treatment of highly polluted wastewater a global challenge. Catalytic wet oxidation is an advanced environmental protection technology for treating high-concentration, highly toxic, and recalcitrant wastewater with high COD. The main principle of this technology is to utilize oxygen from the air under specific temperature (170-300℃) and pressure (2.0-10MPa) conditions in the presence of a catalyst to oxidize and degrade organic matter in wastewater, transforming it into smaller organic molecules or completely mineralizing it into harmless components such as CO2, H2O, N2, and SO2, thus achieving wastewater purification.

[0003] Based on the properties of the catalyst, catalytic wet oxidation technology is divided into homogeneous and heterogeneous catalytic wet oxidation. Early research mainly focused on homogeneous catalysts, but this method was gradually phased out because the catalyst dissolving in the waste would cause secondary pollution, requiring subsequent treatment. In recent years, heterogeneous catalysts have become a research hotspot. Heterogeneous catalysts are mainly divided into two categories: noble metals and metal oxides. Among them, composite metal catalysts mostly use TiO2, Al2O3, SiO2, ZrO2 or their composite oxides as supports, and the active components are mainly oxides of metal elements such as Mo, Bi, Fe, Cu, Co, Ni, and Mn.

[0004] The patent disclosure for catalytic wet oxidation technology is as follows: CN101844827B discloses a catalyst for degrading high concentrations of formaldehyde pollutants, which is composed of transition metal components (one of Cu, Ni, Fe, Mn, Co, Zn) and rare earth elements supported on AlO2, SiO2 or TiO2, and is prepared by impregnation method.

[0005] CN101219376B discloses a catalyst for wastewater treatment, which uses γ-Al2O3 as a support, Mn metal oxide, Sn metal oxide as the main active component, and Sb oxide as a promoter. CN101485987B belongs to the field of water treatment technology and environmental functional materials. This catalyst is prepared by a layered impregnation method using powdered zinc-aluminum hydrotalcite as a support, Fe as the active component, and Ce and Ti as promoters. Summary of the Invention

[0006] This invention addresses the problem of low chemical oxygen demand (COD) removal rate in the treatment of organic wastewater in existing technologies by providing a novel wet oxidation catalyst for treating organic wastewater. When using the catalyst to treat organic wastewater, it has the advantage of high COD removal rate.

[0007] Therefore, a first aspect of the present invention provides a wet oxidation catalyst, comprising a support and a metal oxide active component, wherein the metal component in the metal oxide comprises Mo, Fe and Co, wherein the relative particle size ratio of the oxidized crystal phase of the catalyst (Co) is [missing information]. 0.7 Fe 0.3 (MoO4) / MoO3 is greater than or equal to 3.5.

[0008] According to some embodiments of the catalyst described in this invention, the relative ratio of the particle size of the oxidized crystal phase of the catalyst (Co) 0.7 Fe 0.3 The ratio of (MoO4) / MoO3 is 3.50-10.00. In some embodiments, the relative particle size of the oxidized phase of the catalyst (Co) is... 0.7 Fe 0.3 The ratio of (MoO4) / MoO3 is 5.50-9.00.

[0009] In some embodiments, the XRD characteristic peak (2θ) of the catalyst appears around 25.8° and 26.5°, where 25.8° is (Co 0.7 Fe 0.3 The characteristic peaks of (MoO4) are observed, while the characteristic peak of MoO3 is observed at 26.5°. The average grain size of the oxidized state grains can be calculated using the Scherrer formula D = Kλ / βcosθ.

[0010] According to some embodiments of the catalyst of the present invention, the support is at least one of silica sol and alumina sol. According to some embodiments of the catalyst of the present invention, the support comprises 15.0-35.0 parts by weight, and the metal oxide comprises 65.0-85.0 parts by weight.

[0011] This invention also provides a method for preparing a wet oxidation catalyst, comprising: step S1, mixing a carrier sol with an active component salt solution to form a slurry, adding an organic chemical additive during the slurry forming process, wherein the organic chemical additive includes one or more of C1-C5 amide compounds, C1-C5 carboxylic acid compounds, and C1-C5 alcohol compounds; step S2, spray drying the slurry to obtain a powder; step S3, bonding the powder, water, and binder together, and obtaining the wet oxidation catalyst by extrusion, drying, and calcination.

[0012] According to some embodiments of the preparation method of the present invention, the organic chemical additive includes at least one of formamide, formic acid, propionic acid and glycerol.

[0013] According to some embodiments of the preparation method of the present invention, the active component in the active component salt includes Mo, Fe, and Co. According to some embodiments of the preparation method of the present invention, the active component is Mo, Fe, and Co.

[0014] According to some embodiments of the preparation method of the present invention, the amount of the organic chemical additive added is less than 3% of the total mass of the catalyst. In some embodiments, the amount of the organic additive added is 1-3% of the total mass of the catalyst.

[0015] According to some embodiments of the preparation method of the present invention, in step S1, the pulping temperature is 60-80℃ and the pulping time is 35-50min.

[0016] According to some embodiments of the preparation method of the present invention, the spray drying temperature in step S2 is 320-420℃ and the spray drying time is 40-60min.

[0017] According to some embodiments of the preparation method of the present invention, in step S3, the drying temperature is 100-120°C and the drying time is 10-16 hours.

[0018] According to some embodiments of the preparation method described in this invention, the calcination temperature is 400-600℃ and the calcination time is 2.5-4.5h.

[0019] According to some embodiments of the preparation method of the present invention, in step S3, the binder includes at least one of PEG, CMC, and methylcellulose.

[0020] According to some embodiments of the preparation method of the present invention, the amount of binder added is less than 5% of the total mass of the catalyst. In some embodiments, the amount of binder added is 1-5% of the total mass of the catalyst.

[0021] The present invention further provides a method for treating organic wastewater, wherein the organic wastewater is reacted with an oxidant in the presence of the catalyst of the present invention or the catalyst prepared by the preparation method described in the present invention.

[0022] According to some embodiments of the treatment method described in this invention, the COD content in the organic wastewater is 20,000-55,000 ppm.

[0023] In some embodiments of the processing method according to the present invention, the oxidant is oxygen or air.

[0024] According to some embodiments of the processing method of the present invention, the reaction temperature is 170-300°C and the reaction pressure is 2.0-10.0 MPa.

[0025] According to some embodiments of the present invention, the carrier is at least one of silicon oxide and aluminum oxide.

[0026] According to some embodiments of the present invention, the metal active group is selected from at least three of Mo, Fe, Co, Mn and Ni.

[0027] The second aspect of the present invention provides a method for preparing a wet oxidation catalyst, comprising the following steps: S1, mixing a support sol with an active component salt solution to form a slurry, wherein an organic chemical additive is added during the mixing and slurrying process, the organic chemical additive comprising one or more of C1-C5 amide compounds, C1-C5 carboxylic acid compounds, and C1-C5 alcohol compounds; S2, spray drying the slurry to obtain a powder; S3, bonding the powder, water, and a binder together, and obtaining the wet oxidation catalyst by extrusion, drying, and calcination.

[0028] According to some embodiments of the present invention, in step S1, the pulping temperature is 60-80°C and the pulping time is 35-50 min;

[0029] According to some embodiments of the present invention, in step S1, the organic chemical additive includes one of formamide, formic acid, propionic acid, and glycerol. According to some embodiments of the present invention, in step S1, the amount of the organic chemical additive added is less than 3% of the total mass of the catalyst.

[0030] According to some embodiments of the present invention, the spray drying temperature in step S2 is 320-420°C and the spray drying time is 40-60 min.

[0031] According to some embodiments of the present invention, in step S3, the binder includes at least one of PEG, CMC, and methylcellulose. According to some embodiments of the present invention, in step S3, the amount of binder added is less than 5% of the total mass of the catalyst.

[0032] According to some embodiments of the present invention, in step S3, the drying temperature is 100℃-120℃, and the drying time is 10-16h. According to some embodiments of the present invention, the calcination temperature is 400-600℃, and the calcination time is 2.5-4.5h.

[0033] Application of the catalyst according to the present invention or the catalyst prepared by the method according to the present invention in the treatment of industrial organic wastewater.

[0034] The third aspect of the present invention provides a method for treating organic wastewater, wherein the organic wastewater is reacted with an oxidant in the presence of a catalyst as described in the first aspect of the present invention or a catalyst prepared by the method described in the second aspect of the present invention to remove COD from the wastewater.

[0035] In some embodiments of the present invention, the COD content in the organic wastewater is 20,000-55,000 ppm.

[0036] The present invention does not explicitly limit the source of organic wastewater, such as pharmaceutical wastewater and food flavoring wastewater.

[0037] In some embodiments of the present invention, the oxidant is oxygen or air.

[0038] In other embodiments of the present invention, the reaction temperature is 170-280°C and the reaction pressure is 2.0-10.0 MPa.

[0039] This invention improves catalyst activity by adding organic chemical additives during catalyst slurry preparation, which can adjust the crystallinity of the active crystalline phase. Using the technical solution of this invention, industrial wastewater is mixed with oxygen and then passed through a wet oxidation reactor containing a catalyst. The catalyst comprises, by weight, 48 parts MoO3, 16 parts CoO, 6 parts Fe2O3, and 30 parts SiO2 support components. Under the conditions of a reaction temperature of 250°C, a pressure of 6.5 MPa, and an oxygen-to-wastewater volume ratio of 200, the wastewater mass hourly space velocity (MHV) is 0.8 h⁻¹. -1 After the reaction, the COD removal rate was 99.6%, achieving excellent results. Attached Figure Description

[0040] The invention will now be further described with reference to the accompanying drawings.

[0041] Figure 1 The X-ray diffraction patterns are those of the catalysts prepared in Example 1 and Comparative Example 1. Detailed Implementation

[0042] To make the present invention easier to understand, the present invention will be further described in detail below with reference to embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of application of the present invention. Unless otherwise specified, the raw materials or components used in the present invention can be obtained commercially or by conventional methods.

[0043] In the catalyst preparation method of this invention, changes in preparation conditions cause variations in the average particle size of the oxidized crystals of the metal active component on the catalyst surface (see attached figures in the specification). The XRD characteristic peaks (2θ) appear around 25.8° and 26.5°, with 25.8° being the peak value for Co. 0.7 Fe 0.3 The characteristic peaks of (MoO4) and 26.5° are characteristic peaks of MoO3. The average grain size of the oxidized state grains can be calculated using the Scherrer formula D=Kλ / βcosθ.

[0044] The Scherrer equation, D = Kλ / βcosθ, is the relationship between the average grain size and the half-maximum width of the diffraction peak, determined using an X-ray powder diffractometer. In the equation, D is the average size of the grain perpendicular to the crystal plane, K is the Scherrer constant, λ is the X-ray wavelength, β is the measured half-maximum width of the diffraction peak of the sample, and θ is the Bragg diffraction angle.

[0045] This invention uses XRD to determine the phase properties (structure) and the dispersion of the supported phase (metal). It employs a Broker ADVANCED 8 X-ray diffractometer with CuKa rays, Ni filter, a scanning speed of 4° / min, and a scanning range of 2θ = 10°-70°.

[0046] The evaluation method for the catalyst of this invention is as follows: 100g of catalyst was taken and loaded into a wet oxidation reactor (the reactor is a fixed-bed reactor with an inner diameter of 22mm and a reactor length of 700mm). Pharmaceutical wastewater (COD: 42000ppm) and food flavoring wastewater (COD: 25000ppm) were used as raw materials, mixed with oxygen, and then passed through the wet oxidation reactor containing the catalyst. The reaction temperature was 250℃, the pressure was 6.5MPa, the volume ratio of oxygen to industrial wastewater (coking wastewater and dyeing wastewater) was 200, and the mass hourly space velocity of the industrial wastewater was 0.8h. -1 The COD value of the reaction products was determined using a Hach analyzer.

[0047] Example 1

[0048] 1. Catalyst Preparation

[0049] A pulp was prepared by mixing 48 parts by weight of an ammonium molybdate solution containing MoO3, 16 parts by weight of a cobalt nitrate solution containing CoO, 6 parts by weight of an iron nitrate solution containing Fe2O3, and 30 parts by weight of silica sol. The pulping temperature was 75℃, and the pulping time was 60 min. 2 parts by weight of formamide were added during the pulping process. The pulp was then spray-dried (at 380℃ for 50 min) to obtain a powder.

[0050] The powder was mixed in a kneader, and 3 parts by weight of methylcellulose and 90 parts by weight of water were added. The mixture was stirred and kneaded for 30 minutes. The agglomerated material was dried at room temperature for 20 minutes, then extruded and sphericalized. The spherical material was first dried at room temperature for 60 minutes, and then dried in an oven at 105°C for 14 hours. Subsequently, it was calcined in a muffle furnace at 500°C for 3.5 hours to obtain shaped spherical catalysts with a diameter of 3 mm.

[0051] 2. Catalyst Evaluation

[0052] 100g of catalyst was loaded into a wet oxidation fixed-bed reactor for reaction. The reaction temperature was 250℃, the pressure was 6.5MPa, the oxygen to industrial wastewater volume ratio was 200, and the industrial wastewater mass hourly space velocity was 0.8h⁻¹. -1 The COD value of the reaction products was determined using a Hach analyzer. Industrial wastewater includes pharmaceutical wastewater (COD: 42,000 ppm) and food flavoring wastewater (COD: 25,000 ppm).

[0053] The composition of the active components of the catalyst is shown in Table 1, the catalyst preparation conditions are shown in Table 2, and the catalyst evaluation results are shown in Table 3.

[0054] Examples 2-6

[0055] Referring to Example 1, the differences from Example 1 are shown in Table 1. The catalyst preparation conditions are shown in Table 2, and the catalyst evaluation results are shown in Table 3.

[0056] Comparative Example 1

[0057] 1. Catalyst Preparation

[0058] A slurry containing 48 parts by weight of an ammonium molybdate solution of MoO3, 16 parts by weight of a cobalt nitrate solution of CoO, 6 parts by weight of an iron nitrate solution of Fe2O3, and 30 parts by weight of silica sol was prepared at a slurry temperature of 75°C for 60 minutes. The slurry was then spray-dried at 380°C for 50 minutes to obtain a powder.

[0059] The powder was mixed in a kneader, and 3 parts by weight of methylcellulose and 90 parts by weight of water were added. The mixture was stirred and kneaded for 30 minutes. The agglomerated material was dried at room temperature for 20 minutes, then extruded and sphericalized. The spherical material was first dried at room temperature for 60 minutes, and then dried in an oven at 105°C for 14 hours. Subsequently, it was calcined in a muffle furnace at 500°C for 3.5 hours to obtain shaped spherical catalysts with a diameter of 3 mm.

[0060] 2. Catalyst Evaluation

[0061] 100g of catalyst was loaded into a wet oxidation fixed-bed reactor for reaction. The reaction temperature was 250℃, the pressure was 6.5MPa, the oxygen to industrial wastewater volume ratio was 200, and the industrial wastewater mass hourly space velocity was 0.8h⁻¹. -1 The COD value of the reaction products was determined using a Hach analyzer. Industrial wastewater includes pharmaceutical wastewater (COD: 42,000 ppm) and food flavoring wastewater (COD: 25,000 ppm).

[0062] The composition of the active components of the catalyst is shown in Table 1, the catalyst preparation conditions are shown in Table 2, and the catalyst evaluation results are shown in Table 3.

[0063] Comparative Examples 2-7

[0064] Refer to Comparative Example 1; differences from Comparative Example 1 are shown in Table 1. Catalyst preparation conditions are shown in Table 2, and catalyst evaluation results are shown in Table 3.

[0065] Table 1

[0066]

[0067]

[0068] Table 2

[0069]

[0070] Table 3

[0071]

[0072]

[0073] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for preparing a wet oxidation catalyst, comprising: Step S1: Mix the carrier sol with the active component salt solution to form a slurry. During the slurry forming process, add an organic chemical additive. The organic chemical additive includes one or more of C1-C5 amide compounds, C1-C5 carboxylic acid compounds, and C1-C5 alcohol compounds. The active component salt contains Mo, Fe, and Co elements. Step S2: The slurry is spray-dried to obtain powder; Step S3: The powder, water and binder are bonded together, and the mixture is then extruded, dried and calcined to obtain the wet oxidation catalyst; The relative ratio of the particle size of the catalyst oxidized state crystal phase (Co) 0.7 Fe 0.3 (MoO4) / MoO3 is greater than or equal to 3.50:

1.

2. The preparation method according to claim 1, characterized in that: The organic chemical additive includes at least one of formamide, formic acid, propionic acid and glycerol, and / or the amount of the organic chemical additive added is less than 3% of the total mass of the catalyst.

3. The preparation method according to claim 1 or 2, characterized in that: In step S1, the pulping temperature is 60-80℃ and the pulping time is 35-50 min; and / or in step S2, the spray drying temperature is 320-420℃ and the spray drying time is 40-60 min.

4. The preparation method according to claim 1 or 2, characterized in that: In step S3, the drying temperature is 100-120℃ and the drying time is 10-16h; and / or the calcination temperature is 400-600℃ and the calcination time is 2.5-4.5h.

5. The preparation method according to claim 1 or 2, characterized in that: In step S3, the binder includes at least one of PEG, CMC, and methylcellulose, and / or the amount of the binder added is less than 5% of the total mass of the catalyst.

6. A wet oxidation catalyst, prepared by any one of the preparation methods of claims 1-5.

7. The catalyst according to claim 6, characterized in that: It includes a carrier and a metal oxide active component, wherein the metal component in the metal oxide is Mo, Fe and Co.

8. The catalyst according to claim 6, characterized in that, Relative ratio of oxidized crystal phase particle size of catalyst (Co) 0.7 Fe 0.3 The ratio of (MoO4) / MoO3 is 3.50-10.00:

1.

9. The catalyst according to claim 6, characterized in that, Relative ratio of oxidized crystal phase particle size of catalyst (Co) 0.7 Fe 0.3 The ratio of (MoO4) / MoO3 is 5.50-9.00:

1.

10. The catalyst according to claim 7, characterized in that, The carrier includes at least one of silicon oxide and aluminum oxide; the carrier is 15.0-35.0 parts by weight, and the metal oxide is 65.0-85.0 parts by weight.

11. A method for treating organic wastewater, wherein the organic wastewater is reacted with an oxidant in the presence of a catalyst as described in any one of claims 6-10; wherein the COD content of the organic wastewater is 20,000-55,000 ppm.

12. The processing method according to claim 11, characterized in that, The oxidant is oxygen or air; and / or the reaction temperature is 170-300°C, and the reaction pressure is 2.0-10.0 MPa.

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