A catalyst for catalytic ozonation and a preparation method and application thereof
By loading transition metal elements or their oxides onto the catalyst, the problem of reduced catalyst activity in the treatment of silicon-containing wastewater from coal chemical industry was solved, achieving efficient removal of organic matter and improved catalyst stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DALIAN INSTITUTE OF CHEMICAL PHYSICS CHINESE ACADEMY OF SCIENCES
- Filing Date
- 2022-06-23
- Publication Date
- 2026-06-05
AI Technical Summary
When treating silicon-containing wastewater from coal chemical industry, the high silicon content of existing catalysts leads to a decrease in catalyst activity and gradual inactivation. Traditional silicon removal methods cannot effectively reduce the content of colloidal and soluble silicon, affecting the normal operation of the water treatment process.
The catalyst is prepared by using a support loaded with a transition metal element or its oxide as a catalyst, and by steps such as impregnation, drying, calcination and reduction, with a loading of 1 to 12 wt%, in order to improve the anti-silicon performance and catalytic activity.
The catalyst exhibits high anti-silicon properties, which prolongs its stability, improves organic matter removal efficiency and ozone utilization, and reduces the loss of active components.
Smart Images
Figure SMS_1 
Figure HDA0003710839370000011 
Figure HDA0003710839370000012
Abstract
Description
Technical Field
[0001] This application relates to a catalyst for catalytic ozone oxidation, its preparation method, and its application, belonging to the fields of wastewater treatment technology and environmental functional materials. Background Technology
[0002] In the coal gasification process, a large amount of wastewater is generated during the cooling and washing of crude coal gas. This wastewater has a high concentration of organic matter, high suspended solids content, deep color, and poor biodegradability, making it one of the most difficult types of industrial wastewater to treat. Phenolic substances are considered one of the main pollutants in coal chemical wastewater, and traditional biological treatment methods cannot effectively remove phenols. Furthermore, silicon generated during the production process is introduced into the water system through contact water from the cooling of coal combustion slag, resulting in trace amounts of total silicon in the wastewater reaching up to 1000 mg / L. Common silicon removal methods include coagulation, reverse osmosis, ultrafiltration, electrocoagulation, and ion exchange, but none of these methods can effectively reduce the content of colloidal and soluble silicon (< 50 mg / L), thus affecting the normal operation of subsequent water treatment processes. Therefore, effective methods for removing m-cresol using silicon-resistant methods warrant further research.
[0003] In recent years, advanced oxidation processes (AOPs) have been widely used to treat organic pollutants, effectively improving the biodegradability of wastewater. Among these, heterogeneous catalytic ozone oxidation technology, under the action of a catalyst, converts ozone molecules into reactive oxygen species (ROS), such as hydroxyl radicals (·OH), superoxide radicals (O2·-), and singlet oxygen (1O2). These ROS can rapidly and indiscriminately mineralize organic matter into CO2 and H2O, used to treat emerging pollutants such as pesticides and herbicides, pharmaceuticals, phthalates, dyes, nitrobenzenes, and phenols. It is also used for the advanced treatment of coal gasification wastewater. However, prolonged passage of pollutants through the catalyst bed also affects the catalyst's lifespan. Studies have shown that residual silicon in a certain coal gasification wastewater, after prolonged passage through an ozone catalyst bed, caused silicate precipitation on the catalyst surface, with a silicon content as high as 17 wt.%, resulting in reduced catalyst activity and gradual deterioration. Research indicates that silicon is a common catalytic poison; when the silicon content exceeds 3 wt.%, its impact on the catalyst is non-renewable.
[0004] In summary, there is an urgent need for a catalyst that resists the removal of organic matter from silicon and can be used in ozone oxidation technology to treat silicon-containing wastewater from coal chemical industry. Summary of the Invention
[0005] This application provides a catalyst with advantages such as high silicon resistance, high organic matter removal efficiency, high ozone utilization, good catalyst stability, and low loss of active components.
[0006] According to one aspect of this application, a catalyst for catalytic ozone oxidation is provided, the catalyst comprising a support and an active component supported on the surface of the support;
[0007] The active component is selected from transition metal elemental substances or transition metal element oxides;
[0008] In the catalyst, the loading of the transition metal element is 1 to 12 wt%, based on the mass of the transition metal element;
[0009] The transition metal element is selected from at least one of Ag, Fe, Mn or Pt;
[0010] The carrier is selected from one of molecular sieves, pseudoboehmite, or metal oxides.
[0011] The metal oxide is selected from at least one of Al2O3, Co3O4, CeO2 or TiO2.
[0012] According to another aspect of this application, a method for preparing the above-mentioned catalyst is provided, comprising the following steps:
[0013] The surface of the support is impregnated with an equal volume of ethanol solution containing transition metal salts, and then stirred, ground, dried, calcined, granulated, and reduced to obtain the catalyst.
[0014] The transition metal salt is selected from the nitrates and / or sulfates of the transition metal element;
[0015] The ethanol solution containing the transition metal salt has a content of 0.5-20 wt% of the transition metal salt, a content of 0.5-4% of the ethanol, and the remainder is water.
[0016] The drying temperature is 50–100°C;
[0017] The drying time is 8 to 48 hours.
[0018] The roasting temperature is 350–550°C;
[0019] Optionally, the calcination temperature is 400–500°C;
[0020] The roasting time is 1 to 3 hours;
[0021] The roasting is air roasting in a muffle furnace.
[0022] The reduction temperature is 300–700°C;
[0023] Optionally, the reduction temperature is 400–600°C;
[0024] The reduction time is 0.5 to 2 hours;
[0025] The reducing atmosphere is a hydrogen-containing atmosphere; the hydrogen content in the hydrogen-containing atmosphere is 10-100 wt%.
[0026] The hydrogen-containing atmosphere also includes inactive gases;
[0027] The inactive gas is selected from at least one of nitrogen, helium, or argon;
[0028] The flow rate of the hydrogen-containing atmosphere is 5–20 mL / min;
[0029] Optionally, the flow rate of the hydrogen-containing atmosphere is 6–12 mL / min.
[0030] The stirring and grinding are described as follows: stirring until dry and grinding, stirring with magnetic force until dry, and grinding with an agate mortar to 60-100 mesh.
[0031] The granulation process involves compacting, crushing, and sieving the powder obtained after calcination.
[0032] The compaction conditions are 3-4 MPa for 20-60 seconds, followed by crushing and sieving through a 20-40 mesh sieve, with 20-40 mesh samples retained.
[0033] Specifically, it includes the following steps:
[0034] a) Dissolve the transition metal salt in an aqueous ethanol solution, gradually add the carrier to the transition metal ethanol salt solution, stir until dry, grind into powder, and obtain the precursor; the ethanol content in the ethanol solution is 0.5-4%.
[0035] b) The above-mentioned precursor is dried, calcined, granulated, and reduced to obtain the catalyst.
[0036] The precursor described in step a) is obtained by gradually adding the carrier to a salt solution formed by dissolving a transition metal salt in a certain amount of aqueous ethanol solution, stirring until dry, and then grinding.
[0037] The amount of water added to the resulting transition metal ethanol salt solution is equal to the saturated adsorption capacity of the carrier, and not less than the amount of water added to achieve the saturated solubility of the ethanol salt solution.
[0038] According to another aspect of this application, the application of the above-described catalyst in catalytic ozone oxidation is provided.
[0039] According to another aspect of this application, a method for treating wastewater by catalytic ozone oxidation is provided, wherein silicon-containing wastewater is passed into a reactor containing a catalyst and reacted in an atmosphere containing ozone.
[0040] The catalyst is selected from the catalysts described above or the catalysts prepared according to the preparation method described above.
[0041] The COD of the silicon-containing wastewater is 50–500 mg / L;
[0042] The silicon content in the silicon-containing wastewater is 50–100 mg / L;
[0043] The reaction temperature is 25–35°C;
[0044] The reaction pressure is 0.1 MPa to 0.3 MPa;
[0045] The pH of the silicon-containing wastewater is 5-10;
[0046] The ratio of ozone dosage to COD in the silicon-containing wastewater is O3 (mg / L):COD (mg / L) = 1.0–3.0;
[0047] In the ozone-containing atmosphere, the ozone concentration is 10–130 mg / L;
[0048] The volume hourly space velocity (VHSV) of the silicon-containing wastewater is 2–10 h⁻¹. -1 .
[0049] The silicon-containing wastewater comes from the coal chemical industry.
[0050] The beneficial effects that this application can produce include:
[0051] 1. The catalyst provided in this application has high initial activity in catalytic ozone oxidation technology, providing a new, reliable and easy-to-use catalyst for industrial applications.
[0052] 2. The catalyst provided in this application has high anti-silicon properties in catalytic ozone oxidation technology, which prevents silicon from poisoning the catalyst and prolongs the catalyst's stability. Attached Figure Description
[0053] Figure 1 From left to right, the graphs show a comparison of TOC removal rate, m-cresol conversion rate, and anti-silicone performance for Comparative Example 3, Comparative Example 2, Example 5, Example 6, and Example 2.
[0054] Figure 2 The images are XRD patterns of Examples 2 and 8. Detailed Implementation
[0055] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.
[0056] Unless otherwise specified, the raw materials and catalysts used in the embodiments of this application were all purchased commercially.
[0057] The analysis method in the embodiments of this application is as follows:
[0058] TOC (Total Organic Carbon) was determined using a TOC-VCPH / CPN analyzer manufactured by Shimadzu Corporation, Japan; pH was determined using a Leici PHS-3C precision pH meter; m-cresol content was determined using HPLC (High Performance Liquid Chromatography) with the chromatographic column kept at a constant temperature of 25°C; and the application of the prepared catalyst in catalytic ozone oxidation technology was evaluated using a fixed-bed batch reaction evaluation device.
[0059] The silicon content in solution was determined using the silicomolybdate blue spectrophotometric method, with ammonium molybdate sulfate as the colorimetric reagent, oxalic acid as the masking agent, and ferrous ammonium sulfate as the reducing agent. The determination conditions were: wavelength 815 nm, 5 cm cuvette, detection range 0–4 ppm. The silicon dioxide content was calculated using a standard curve based on the measured sample absorbance.
[0060] The wastewater containing 78 ppm m-cresol used in the experiment had the following characteristics: HPLC peak area 1062, TOC: 63.5 mg / L; silica concentration G = 87 ppm, absorbance after 20-fold dilution = 1.787; pH adjusted to 4.6. The reaction was conducted at ambient temperature and pressure, with an initial pH of 4.6, O3 (mg / L):COD (mg / L) ratio of 1.0–3.0, and a space velocity of 2–10 h⁻¹. -1 The reaction run time is 5 hours.
[0061] In the examples, all catalysts were ground into powder for evaluation.
[0062] Example 1
[0063] 1) Dissolve 0.0321g AgNO3 in 6mL of 2 wt% ethanol aqueous solution, and gradually add 2.0055g ZSM5(46) (SiO2 / Al2O3 molar ratio 46) molecular sieve support to the AgNO3 solution. Stir magnetically until dry, and grind to 60-100 mesh.
[0064] 2) Place in a drying oven and dry at 80℃ for 12 hours; then calcine in a muffle furnace at 450℃ for 2 hours.
[0065] 3) Hold the powder obtained after calcination at 3-4 MPa for 20-60 seconds, crush it, and sieve it through a 20-40 mesh sieve, retaining a 20-40 mesh sample;
[0066] 4) Finally, reduce at 500℃ for 1h under pure hydrogen conditions to obtain 1Ag / ZSM5(46)-H500. 1Ag represents the mass fraction of Ag loaded on the carrier ZSM5(46) is 1%, and H500 represents reduction at 500℃ under H2 conditions. The following examples are similar.
[0067] Example 2
[0068] 1) Dissolve 0.3154g AgNO3 in 6mL of 2wt% ethanol aqueous solution, gradually add 2.0024g β40 molecular sieve support to the AgNO3 solution, stir magnetically until dry, and grind to 60-100 mesh;
[0069] 2) Place in a drying oven and dry at 80℃ for 12 hours; then calcine in a muffle furnace at 450℃ for 2 hours.
[0070] 3) Hold the powder obtained after calcination at 3-4 MPa for 20-60 seconds, crush it, and sieve it through a 20-40 mesh sieve, retaining a 20-40 mesh sample;
[0071] 4) Finally, reduce with pure hydrogen at 400℃ for 1 hour to obtain 10Ag / β40-H400.
[0072] Figure 2 The image shows the XRD pattern of Example 2. It can be seen from the image that the Ag particles are relatively uniformly dispersed on the surface of the carrier.
[0073] Example 3
[0074] 1) Dissolve 0.0315g AgNO3 in 6mL of 2wt% ethanol aqueous solution, and gradually add 2.0072g β62.3 (SiO2 / Al2O3 molar ratio 62.3) support to the AgNO3 solution. Stir magnetically until dry, and grind to 60-100 mesh.
[0075] 2) Place in a drying oven and dry at 80℃ for 12 hours; then calcine in a muffle furnace at 450℃ for 2 hours.
[0076] 3) Hold the powder obtained after calcination at 3-4 MPa for 20-60 seconds, crush it, and sieve it through a 20-40 mesh sieve, retaining a 20-40 mesh sample;
[0077] 4) Finally, reduce with pure hydrogen at 500℃ for 1 h to obtain 1Ag / β62.3-H500.
[0078] Example 4
[0079] 1) Dissolve 0.3182g AgNO3 in 6mL of 2wt% ethanol aqueous solution, gradually add ALOOH support to the AgNO3 solution, stir magnetically until dry, and grind to 60-100 mesh;
[0080] 2) Place in a drying oven and dry at 80℃ for 12 hours; then calcine in a muffle furnace at 450℃ for 2 hours.
[0081] 3) Hold the powder obtained after calcination at 3-4 MPa for 20-60 seconds, crush it, and sieve it through a 20-40 mesh sieve, retaining a 20-40 mesh sample;
[0082] 4) Finally, reduce with pure hydrogen at 400℃ for 1 hour to obtain 10Ag / ALOOH-H400.
[0083] Example 5
[0084] 1) Dissolve 0.3182g AgNO3 in 6mL of 2wt% ethanol aqueous solution, gradually add β40 molecular sieve support to AgNO3 solution, stir magnetically until dry, and grind to 60-100 mesh;
[0085] 2) Place in a drying oven and dry at 80℃ for 12 hours; then calcine in a muffle furnace at 450℃ for 2 hours to obtain 10Ag / β40-unreduced.
[0086] Example 6
[0087] 1) Dissolve 0.3130g AgNO3 in 6mL of 2wt% ethanol aqueous solution, gradually add the β40 molecular sieve support to the AgNO3 solution, stir magnetically until dry, and grind to 60-100 mesh;
[0088] 2) Place in a drying oven and dry at 80℃ for 12 hours; then calcine in a muffle furnace at 450℃ for 2 hours.
[0089] 3) Hold the powder obtained after calcination at 3-4 MPa for 20-60 seconds, crush it, and sieve it through a 20-40 mesh sieve, retaining a 20-40 mesh sample;
[0090] 4) Finally, reduce at 400℃ for 1 h under 10% H2 / Ar conditions to obtain 10Ag / β40-H400 (10% H2).
[0091] Example 7
[0092] 1) Dissolve 0.3820g AgNO3 in 6mL of 2wt% ethanol aqueous solution, gradually add the β40 molecular sieve support to the AgNO3 solution, stir magnetically until dry, and grind to 60-100 mesh;
[0093] 2) Place in a drying oven and dry at 80℃ for 12 hours; then calcine in a muffle furnace at 450℃ for 2 hours.
[0094] 3) Hold the powder obtained after calcination at 3-4 MPa for 20-60 seconds, crush it, and sieve it through a 20-40 mesh sieve, retaining a 20-40 mesh sample;
[0095] 4) Finally, reduce at 400℃ for 1 h under 10% H2 / Ar conditions to obtain 12Ag / β40-H400 (10% H2).
[0096] Example 8
[0097] 1) Dissolve 0.0315g AgNO3 in 6mL of 2wt% ethanol aqueous solution, gradually add 2.0024g β40 molecular sieve support to the AgNO3 solution, stir magnetically until dry, and grind to 60-100 mesh;
[0098] 2) Place in a drying oven and dry at 80℃ for 12 hours; then calcine in a muffle furnace at 450℃ for 2 hours.
[0099] 3) Hold the powder obtained after calcination at 3-4 MPa for 20-60 seconds, crush it, and sieve it through a 20-40 mesh sieve, retaining a 20-40 mesh sample;
[0100] 4) Finally, reduce with pure hydrogen at 400℃ for 1 hour to obtain 1Ag / β40-H400.
[0101] Figure 2 The image shows the XRD pattern of Example 8. It can be seen from the image that the active component is loaded on the surface of the support in the form of Ag element.
[0102] Example 9
[0103] 1) Dissolve 0.0317g AgNO3 in 6mL of 2wt% ethanol aqueous solution, gradually add 1.9992g β40 molecular sieve support to the AgNO3 solution, stir magnetically until dry, and grind to 60-100 mesh;
[0104] 2) Place in a drying oven and dry at 80℃ for 12 hours; then calcine in a muffle furnace at 450℃ for 2 hours.
[0105] 3) Hold the powder obtained after calcination at 3-4 MPa for 20-60 seconds, crush it, and sieve it through a 20-40 mesh sieve, retaining a 20-40 mesh sample;
[0106] 4) Finally, reduce with pure hydrogen at 700℃ for 1 h to obtain 1Ag / β40-H700.
[0107] The catalysts prepared in Examples 1 to 9 were tested for catalytic ozone oxidation of wastewater. The test conditions and results are shown in Table 1. Experiments 10 to 12 show the results of comparative experiments with no catalyst and two industrial catalysts, respectively.
[0108] Table 1. Experimental results of catalytic ozone oxidation
[0109]
[0110] The experimental results show that silver-loaded MCM-41, Co3O4, CeO2, TiO2, and Al2O3... 3、ALOOH achieved a TOC removal rate of 10%–20% and a m-cresol removal rate of 60%–97% in the model wastewater. Co3O4, TiO2, and Al2O3 loaded with silver exhibited certain adsorption properties for silicon.
[0111] The comparison between the 6th and 7th groups of experiments showed that the catalyst with a 12% Ag loading had poorer silicon resistance than the catalyst with a 10% Ag loading, and the silicon absorption rate reached 49.25%.
[0112] The comparison of experiments in groups 2, 8, and 9 shows that Ag loaded on β40 molecular sieve has good activity and anti-silicone properties. Increasing the Ag loading slightly increases the TOC, and increasing the reduction temperature slightly increases the TOC, but has little effect on the adsorption of m-cresol and silicon.
[0113] Figure 1 From left to right, the graphs show a comparison of TOC removal rate, m-cresol conversion rate, and anti-silicone performance for Comparative Example 3, Comparative Example 2, Example 5, Example 6, and Example 2. The graphs show that the activity of industrial red spheres Fe / Al2O3 and KD-607-2 is not as high as that of 10Ag / β40-unreduced. H2 reduction can improve the anti-silicone properties of 10Ag / β40, and the concentration of reducing H2 can further improve the TOC removal rate.
[0114] 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 treating wastewater by catalytic ozone oxidation, characterized in that, Silicon-containing wastewater is passed into a reactor equipped with a catalyst and reacted in an ozone atmosphere; the wastewater originates from the coal chemical industry, with a silicon content of 50-100 mg / L and a COD of 50-500 mg / L. The catalyst is characterized in that it comprises a support and an active component loaded on the surface of the support; the active component is elemental Ag; the support is a β-molecular sieve; and the loading amount of Ag is 1~10 wt%.
2. The method according to claim 1, characterized in that, The preparation process of the catalyst includes the following steps: a) Dissolve AgNO3 in an aqueous ethanol solution with an ethanol content of 0.5~4wt% to form a transition metal salt solution; b) Gradually add the β-molecular sieve support to the solution, stir until dry and grind to obtain the precursor; c) The precursor is dried, calcined, granulated, and reduced to obtain the catalyst; wherein the reduction is carried out in a hydrogen-containing atmosphere at a reduction temperature of 400~600℃.
3. The method according to claim 2, characterized in that, The ethanol-water solution contains 2 wt% ethanol.
4. The method according to claim 2, characterized in that, The drying temperature is 50~100℃; The drying time is 8 to 48 hours.
5. The method according to claim 2, characterized in that, The roasting temperature is 350~550℃; The roasting time is 1 to 3 hours.
6. The method according to claim 2, characterized in that, The hydrogen content in the hydrogen-containing atmosphere is 10~100wt%; the gas flow rate is 5~20mL / min.
7. The method according to claim 1, characterized in that, The reaction temperature is 25~35℃, the pressure is 0.1~0.3MPa, and the ratio of ozone dosage to COD is 1.0~3.0, wherein both ozone dosage and COD are expressed in mass concentration mg / L.
8. The method according to claim 1, characterized in that, The volume hourly space velocity (VHSV) of the silicon-containing wastewater is 2-10 h⁻¹. -1 .