VOCs catalytic oxidation catalyst as well as preparation method and application thereof

Abstract

The invention relates to the field of catalyst preparation, and discloses a VOCs catalytic oxidation catalyst and a preparation method and application thereof. The catalyst comprises a regular-structure carrier and an active component coating distributed on the inner surface and / or the outer surface of the regular-structure carrier, wherein the active component coating comprises a matrix, an oxygen storage material and an active metal component; the active metal components comprise silver, titanium, tungsten and zinc; wherein on the basis of the volume of the regular-structure carrier, the content of the matrix is 35-110 g / L, and the content of the oxygen storage material is 2-20 g / L; in terms of elements, the content of silver is 0.2-2 g / L; in terms of oxide, the content of titanium is 0.2-4.4 g / L; in terms of oxide, the content of tungsten is 0.5-3g / L; the content of zinc is 1-3g / L in terms of oxide. The catalyst has high chlorine poisoning resistance and can realize efficient conversion of VOCs at low temperature.

Description

VOCs catalytic oxidation catalysts, their preparation methods and applications Technical Field

[0001] This invention relates to the field of catalyst preparation, specifically to a VOCs catalytic oxidation catalyst, its preparation method, and its application. Background Technology

[0002] Volatile organic compounds (VOCs) are a class of organic pollutants widely present in industrial production, energy consumption, and daily life. VOCs not only pose serious threats to the environment and human health, but also participate in the formation of ozone and secondary aerosols in the atmosphere, significantly impacting regional ozone pollution and PM2.5 pollution. Therefore, effectively controlling and treating VOC emissions has become a crucial research topic in the field of environmental protection.

[0003] Currently, the main methods for treating VOCs include adsorption, condensation, incineration, biodegradation, and catalytic oxidation. Among these, catalytic oxidation technology has become one of the most effective ways to control VOCs due to its high treatment efficiency, low energy consumption, and simple operation. VOCs catalytic oxidation catalysts typically use platinum and palladium as active components. These exhibit excellent removal activity for volatile organic compounds such as olefins, aromatics, and alkanes, completely converting them into harmless carbon dioxide and water. However, when treating chlorine-containing VOCs, chlorine easily deposits on the surface of Pt and Pd, leading to catalyst poisoning. Furthermore, platinum and palladium catalysts are expensive, resulting in high replacement costs after poisoning. How to efficiently convert chlorine-containing VOCs without poisoning the active sites remains a challenge in the field of environmental catalysis. Summary of the Invention

[0004] The purpose of this invention is to overcome the problem of poor resistance to chlorine poisoning in existing VOCs catalytic oxidation catalysts, and to provide a VOCs catalytic oxidation catalyst, its preparation method and application. This catalyst has high resistance to chlorine poisoning and can achieve efficient conversion of VOCs at low temperatures.

[0005] To achieve the above objectives, the first aspect of the present invention provides a VOCs catalytic oxidation catalyst, wherein the catalyst comprises a regular structure support and an active component coating distributed on the inner and / or outer surfaces of the regular structure support.

[0006] The active component coating comprises a matrix, an oxygen storage material, and an active metal component; the active metal component comprises silver, titanium, tungsten, and zinc.

[0007] Based on the volume of the regular structure carrier, the matrix content is 35-110 g / L, the oxygen storage material content is 2-20 g / L; in terms of elements, the silver content is 0.2-2 g / L; in terms of oxides, the titanium content is 0.2-4.4 g / L; in terms of oxides, the tungsten content is 0.5-3 g / L; and in terms of oxides, the zinc content is 1-3 g / L.

[0008] A second aspect of this invention provides a method for preparing a VOCs catalytic oxidation catalyst, wherein the method includes:

[0009] (1) Silver precursor, reducing agent and stabilizer are brought into first contact in the presence of solvent to prepare silver colloidal solution;

[0010] (2) The titanium precursor is brought into a second contact with the silver colloidal solution, and the pH of the material is adjusted to 3-7 to obtain a silver-titanium mixture.

[0011] (3) The tungsten precursor, zinc precursor, matrix source, oxygen storage material and silver-titanium mixture are brought into a third contact to obtain a catalyst slurry;

[0012] (4) The catalyst slurry is coated onto a regular structured support and then dried and calcined to make the inner and / or outer surfaces of the regular structured support have active component coatings.

[0013] Preferably, the molar ratio of titanium precursor to silver precursor, calculated by metal element, is 1-3:1, more preferably 1.2-2.5:1.

[0014] The third aspect of the present invention provides a catalyst prepared by the method described in the second aspect above.

[0015] The fourth aspect of the present invention provides the application of the catalyst described in the first aspect or the catalyst prepared by the method described in the second aspect in the catalytic oxidation of VOCs.

[0016] Through the above technical solution, this invention employs a structured support and an active component coating distributed on the inner and / or outer surfaces of the structured support, effectively preventing catalyst deactivation due to chlorine poisoning during catalysis, and achieving efficient VOC conversion of the catalyst under low-temperature conditions. By precisely controlling the content of each component in the active component coating, the catalyst further exhibits high resistance to chlorine poisoning and efficient VOC conversion under low-temperature conditions. The preparation method of this invention can produce a structured catalyst with the above characteristics; the preparation method is simple, possesses high resistance to chlorine poisoning, and can achieve efficient VOC conversion at low temperatures. Attached Figure Description

[0017] Figure 1 shows the Raman spectra of Ag-Ti catalyst (Example 1), Ag catalyst (Comparative Example 5), and Ti catalyst (titanium dioxide obtained by direct calcination of Ti precursor) after adsorption of pyridine. Detailed Implementation

[0018] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0019] Unless otherwise specified, all percentages, ratios, etc. mentioned in this invention are based on weight, unless being based on weight would not be in accordance with the common understanding of those skilled in the art.

[0020] In this invention, unless otherwise specified, the terms "first," "second," and "third" do not indicate a sequential order, nor do they limit the specific materials or steps; they are merely used to distinguish that these are not the same material or step. For example, in "first contact," "second contact," and "third contact," "first," "second," and "third" are simply used to indicate that these are not the same contact.

[0021] The first aspect of the present invention provides a VOCs catalytic oxidation catalyst, wherein the catalyst comprises a regular structure support and an active component coating distributed on the inner and / or outer surfaces of the regular structure support;

[0022] The active component coating comprises a matrix, an oxygen storage material, and an active metal component; the active metal component comprises silver, titanium, tungsten, and zinc.

[0023] Based on the volume of the regular structure carrier, the matrix content is 35-110 g / L, the oxygen storage material content is 2-20 g / L; in terms of elements, the silver content is 0.2-2 g / L; in terms of oxides, the titanium content is 0.2-4.4 g / L; in terms of oxides, the tungsten content is 0.5-3 g / L; and in terms of oxides, the zinc content is 1-3 g / L.

[0024] In this invention, the types and contents of each metal element are obtained through IPC testing, and the types and contents of other substances can be obtained through testing or by calculating the amount of material fed.

[0025] In this invention, VOCs have the conventional meaning in the art. Preferably, VOCs in this invention refer to organic compounds that have a high saturated vapor pressure, low boiling point, small molecular weight under standard conditions, and are easily volatile at room temperature.

[0026] The VOCs catalytic oxidation catalyst of the present invention employs a structured support and an active component coating distributed on the inner and / or outer surfaces of the structured support for synergistic effect. Through the careful design of the active component coating being uniformly distributed on the structured support, the catalyst has high catalytic activity, achieving efficient oxidation and decomposition of volatile organic compounds into harmless carbon dioxide and water. It has excellent catalytic performance and high resistance to chlorine poisoning, and can achieve efficient conversion of VOCs at low temperatures.

[0027] According to the present invention, preferably, based on the volume of the regular structure carrier, the total content of the active component coating is 40-130 g / L, for example, it can be 40, 50, 60, 70, 80, 90, 100, 110, 120, 130 g / L and any range between any two values, more preferably 60-100 g / L.

[0028] In this invention, the active component coating with the above-mentioned preferred content can improve the catalyst performance, enhance the resistance to chlorine poisoning, and more effectively treat chlorine-containing VOCs.

[0029] According to the present invention, preferably, based on the volume of the regular structure carrier, the content of the matrix is ​​50-88 g / L, the content of the oxygen storage material is 8-16 g / L; the content of silver is 0.5-1.5 g / L; the content of titanium is 1-3 g / L; the content of tungsten is 1-2 g / L; and the content of zinc is 1.5-2.5 g / L.

[0030] According to the present invention, preferably, at least a portion of the titanium oxide in the catalyst is coated on the surface of at least a portion of the silver element. "At least a portion of the titanium oxide is coated on the surface of at least a portion of the silver element" means that some silver surface sites are covered by titanium oxide.

[0031] The characteristic structure of the catalyst with titanium oxide coating on silver in this invention can be verified by pyridine Raman spectroscopy, as shown in Figure 1. Pyridine, as a probe molecule, has a strong adsorption capacity on the Ag surface but not on the Ti surface. The test results show that the adsorption capacity of Ag on pyridine weakens after adsorbing Ti, indicating that titanium oxide in the catalyst is coated on the surface of silver.

[0032] In this invention, by employing an active component coating, the catalyst acquires excellent catalytic performance and outstanding resistance to chlorine poisoning, thereby achieving efficient conversion of VOCs at low temperatures. In particular, when the content of each component is controlled within the aforementioned preferred range, the catalytic activity and resistance to chlorine poisoning of the catalyst are further enhanced, ensuring that it can still achieve efficient treatment and conversion of VOCs under low-temperature conditions, significantly improving the catalytic effect.

[0033] The present invention does not particularly limit the type of matrix. Preferably, the matrix can be an inorganic matrix material, more preferably at least one of alumina, silicon dioxide, zeolite, kaolin, diatomite and perlite, and even more preferably alumina and / or silicon dioxide, and even more preferably alumina.

[0034] In this invention, oxygen storage material refers to a material that can absorb, store and release oxygen during a catalytic reaction.

[0035] The present invention does not particularly limit the type of oxygen storage material, as long as it can provide active oxygen to the catalyst and maintain the high efficiency of the catalyst. Those skilled in the art can select according to actual needs. Preferably, the oxygen storage material is at least one of cerium-zirconium solid solution, cerium oxide, bismuth oxide and manganese oxide, more preferably bismuth oxide and / or cerium oxide.

[0036] In this invention, the term "regularly structured carrier" has its conventional meaning in the art. Preferably, the term "regularly structured carrier" in this invention refers to a monolithic porous material with a fixed geometric shape.

[0037] The present invention does not particularly limit the type of regular structure carrier, and can be any regular structure carrier commonly used in the art. Preferably, the regular structure carrier is an inorganic regular structure carrier material, more preferably at least one of cordierite, mullite, diamond, corundum, zirconium corundum, quartz, nepheline, feldspar, alumina and metal alloys, and even more preferably cordierite honeycomb regular structure carrier.

[0038] According to the present invention, preferably, the pore density of the cross section of the regular structure carrier is 10-300 pores / square inch, for example, it can be 10, 50, 100, 150, 200, 250, 300 pores / square inch and any range between any two values.

[0039] According to the present invention, preferably, the opening ratio of the cross surface of the regular structure carrier is 20-80%, more preferably 40-75%.

[0040] The holes can be regular or irregular in shape. The shapes of the holes can be the same or different. Each hole can be one of the following: square, equilateral triangle, regular hexagon, circle, and corrugated.

[0041] The structured carrier described in this invention can be used for coating active components in fixed-bed reactors. This structured carrier can be a monolithic structured carrier block with an internally formed hollow channel structure. Active components can be distributed on the inner and / or outer walls of the channels, and the channel space can serve as a fluid flow space. The structured carrier can also be a structured carrier with a honeycomb-shaped opening in its cross-section (referred to as a honeycomb structured carrier).

[0042] The present invention does not particularly limit the cross-sectional area of ​​each hole in the regular structure carrier. Those skilled in the art can select according to actual needs. According to a specific embodiment, preferably, the cross-sectional area of ​​each hole in the regular structure carrier can be 15,000 square millimeters.

[0043] A second aspect of this invention provides a method for preparing a VOCs catalytic oxidation catalyst, wherein the method includes:

[0044] (1) Silver precursor, reducing agent and stabilizer are brought into first contact in the presence of solvent to prepare silver colloidal solution;

[0045] (2) The titanium precursor is brought into a second contact with the silver colloidal solution, and the pH of the material is adjusted to 3-7 to obtain a silver-titanium mixture.

[0046] (3) The tungsten precursor, zinc precursor, matrix source, oxygen storage material and silver-titanium mixture are brought into a third contact to obtain a catalyst slurry;

[0047] (4) The catalyst slurry is coated onto a regular structured support and then dried and calcined to make the inner and / or outer surfaces of the regular structured support have active component coatings.

[0048] The present invention does not particularly limit the method of the first contact in step (1). Those skilled in the art can choose according to actual needs. The silver precursor, reducing agent, stabilizer and solvent can be added independently in any order, or the silver precursor, reducing agent and stabilizer can be provided independently in solution form before contacting with other components. Preferably, the silver precursor can be mixed with a portion of the solvent first, then the reducing agent and stabilizer can be mixed with the remaining portion of the solvent, and finally the silver precursor solution can be contacted with the mixed solution of reducing agent and stabilizer for the first time.

[0049] According to the present invention, preferably, the silver precursor is provided in the form of a silver precursor solution, wherein the silver content in the silver precursor solution is 1-15 mmol / L, for example, it can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 mmol / L and any range between any two values, more preferably 2-12 mmol / L.

[0050] The present invention does not particularly limit the type of silver precursor. Preferably, the silver precursor is a soluble salt of silver, more preferably silver nitrate and / or silver acetate, and even more preferably silver nitrate.

[0051] According to the present invention, preferably, the reducing agent in step (1) is provided in the form of a solution, and the concentration of the reducing agent is 1-15 mmol / L, for example, it can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 mmol / L and any range between any two values, more preferably 2-12 mmol / L.

[0052] The present invention does not particularly limit the type of reducing agent. Preferably, the reducing agent is at least one of ascorbic acid, borohydride and citrate, and more preferably ascorbic acid.

[0053] In this invention, preferably, the borohydride is sodium borohydride and / or potassium borohydride.

[0054] In this invention, preferably, the citrate is at least one of sodium citrate, potassium citrate, ferric citrate, magnesium citrate, and calcium citrate.

[0055] In this invention, the stabilizer coordinates with the surface of the silver particles through its lone pair electrons, preventing the silver particles from excessively aggregating and ensuring their stable existence in the colloidal solution.

[0056] According to the present invention, preferably, the stabilizer in step (1) is provided in the form of a solution. The present invention does not have a particular limitation on the concentration of the stabilizer, as long as it meets the requirements of the present invention. Those skilled in the art can select according to actual needs.

[0057] The present invention does not particularly limit the type of stabilizer. Preferably, the stabilizer is an organic amine, more preferably at least one of diethylamine, triethylamine and trimethylamine, and even more preferably triethylamine.

[0058] According to the present invention, preferably, the amount of reducing agent used is 0.2-2 mol compared to 1 mol of silver precursor, for example, it can be 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8, 2 mol and any range between any two values, more preferably 0.5-1.5 mol.

[0059] According to the present invention, preferably, the amount of stabilizer used is 1-100 mol compared to 1 mol of silver precursor, for example, it can be 1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 mol and any range between any two values, more preferably 10-60 mol.

[0060] The present invention does not particularly limit the type and amount of solvent mentioned in step (1), as long as it can fully disperse the components. It can be added alone or mixed with other raw materials. Those skilled in the art can choose according to actual needs. According to a specific embodiment of the present invention, water is preferred.

[0061] The present invention does not particularly limit the type of titanium precursor. Preferably, the titanium precursor is an organic carboxylic acid titanium salt, more preferably at least one of titanium citrate, titanium acetate, titanium oxalate, titanium tartrate and titanium malonate, and even more preferably titanium citrate.

[0062] According to the present invention, preferably, the molar ratio of titanium precursor to silver precursor, calculated as metal element, is 1-3:1, for example, it can be 1:1, 2:1, 3:1 and any range between any two values, more preferably 1.2-2.5:1.

[0063] The present invention does not particularly limit the form in which the titanium precursor is provided in step (2). Those skilled in the art can choose according to actual needs. Preferably, the titanium precursor is provided in the form of a solution of the titanium precursor.

[0064] The present invention does not particularly limit the type of solvent in the titanium precursor solution. It can be the same as or different from the solvent in step (1) above, as long as it can fully disperse the components.

[0065] In this invention, a pH adjuster is used to adjust the pH of the material. Preferably, the pH adjuster is an acidic adjuster, more preferably an inorganic acid, and even more preferably at least one of hydrochloric acid, nitric acid, and sulfuric acid.

[0066] The concentration of the inorganic acid can be selected within a wide range, as long as it meets the pH range required by the present invention. Those skilled in the art can select it according to actual needs.

[0067] According to the present invention, preferably, the amount of pH adjuster used is such that the pH of the material is in the range of 3-7, for example, it can be 3, 4, 5, 6, 7, or any range between any two values, preferably, the pH is 4-6.5. Under these preferred conditions, the catalytic performance of the catalyst is better.

[0068] It should be noted that in step (2), by adding an acidic regulator to adjust the reaction pH within the above range, at least some of the titanium oxide in the prepared catalyst can be coated on the surface of at least some of the silver elements. The reason for this may be that the acidic regulator reacts with amine compounds, which can disrupt the coordination between the amine and silver, allowing the amine to leave the surface of the silver, and titanium to have the opportunity to combine with the silver. If the pH value is too high, the amine cannot be protonated, that is, the coordination between the amine and silver cannot be disrupted. If the pH value is too low, the stability of the silver colloidal solution will be destroyed, forming a flocculent precipitate.

[0069] In this invention, step (2) is preferably carried out under stirring conditions. This invention does not particularly limit the stirring conditions, as long as they ensure thorough mixing of the materials.

[0070] The present invention does not particularly limit the type of tungsten precursor, and those skilled in the art can select it according to actual needs. Preferably, the tungsten precursor is at least one of tungsten oxide, sodium tungstate and ammonium tungstate, and more preferably tungsten oxide.

[0071] The present invention does not particularly limit the type of zinc precursor, and those skilled in the art can select it according to actual needs. Preferably, the zinc precursor is at least one of zinc oxide, zinc sulfate and zinc chloride, and more preferably zinc oxide.

[0072] According to the present invention, preferably, the matrix source in step (3) is a substance that can be transformed into a matrix under the calcination conditions in step (4). Those skilled in the art, knowing the types of matrices, know which matrix source to choose.

[0073] The range of types of matrix and oxygen storage material selected in the preparation method of this invention can be independently the same as the range described in the first aspect above, and will not be repeated here.

[0074] The present invention does not particularly limit the method of the third contact in step (3). Those skilled in the art can choose according to actual needs. Preferably, the tungsten precursor, zinc precursor, matrix source and oxygen storage material can be added independently in any order, or the tungsten precursor, zinc precursor, matrix source and oxygen storage material can be provided independently in solution form before contacting with other components. Preferably, the tungsten precursor, zinc precursor, matrix source and oxygen storage material can be mixed with solvent first and then contacted with silver-titanium mixture for the third contact.

[0075] The solvent in step (3) can be the same as or different from the solvent in step (1) above, as long as it can fully disperse the components.

[0076] In this invention, preferably, the solid content of the catalyst slurry is 5-35% by weight, for example, it can be 5, 10, 15, 20, 25, 30, 35% by weight or any range between any two values.

[0077] In this invention, solid content refers to the ratio of the mass of residual solids after the slurry is heated at high temperature to the total mass of the original slurry, which is obtained by thermogravimetric analysis.

[0078] The total content of the active component coating, the amount of each component, and the selection range of the regular structure carrier in the preparation method of this invention can each be independently the same as the range described in the first aspect above, and will not be repeated here.

[0079] The present invention does not particularly limit the third contact method described in step (3), as long as it is conducive to sufficient contact of the substances described in step (3), and those skilled in the art can make the selection according to actual needs.

[0080] According to a preferred embodiment of the present invention, the preparation method of the present invention further includes grinding and / or stirring the tungsten precursor, zinc precursor, matrix source and oxygen storage material described in step (3), preferably ball milling and / or stirring.

[0081] It should be noted that, in this invention, preferably, the tungsten precursor, zinc precursor, matrix source and oxygen storage material mentioned in step (3) are provided in the form of a solution. They can be ground first and then stirred, stirred first and then ground, ground only without stirring, or stirred only without grinding. Preferably, this invention adopts the method of grinding first and then stirring.

[0082] The present invention does not have any particular limitation on the ball milling conditions, as long as the average diameter of the material in step (3) is 3-8.5 μm. Preferably, the ball milling conditions include: ball milling time of 0.5-3 h and rotation speed of 200-500 rpm.

[0083] This invention does not impose any particular limitation on the ball milling equipment, as long as it can meet the above-mentioned ball milling conditions, it can be a planetary ball mill (such as the F-P400E planetary ball mill from Vorcas).

[0084] The present invention does not particularly limit the conditions of the third contact described in step (3). Preferably, the contact reaction conditions described in step (3) include: a reaction temperature of 10-35℃, more preferably 20-30℃; and a reaction time of 0.2-4h, more preferably 1-2h.

[0085] According to the present invention, preferably, in step (3), the average diameter of the particles in the catalyst slurry is less than 10 μm, and more preferably 3-8.5 μm.

[0086] The average particle diameter in the catalyst slurry was D50 as obtained by laser particle size distribution. Experimental instrument: Malvern Mastersizer 3000.

[0087] According to the present invention, preferably, in step (4), the catalyst slurry can be uniformly distributed on the surface of the structured carrier by spraying, coating or immersion, and then dried and calcined to obtain a structured carrier with an active component coating distributed on both the inner and outer surfaces. It should be noted that the catalyst slurry can be distributed onto the structured carrier by one or more processes.

[0088] According to the present invention, preferably, the drying conditions in step (4) include: a temperature of 100-140°C, for example, 100, 110, 120, 130, 140°C and any range between any two values, and a time of 2-15 hours.

[0089] The present invention does not particularly limit the roasting atmosphere, and those skilled in the art can choose according to actual needs. Preferably, the roasting in step (4) is carried out in the presence of ozone.

[0090] According to the present invention, preferably, the calcination conditions include: a calcination temperature of 150-250°C, for example, 150, 180, 200, 220, 250°C or any range between any two values, and a calcination time of 1-3 hours.

[0091] For example, the temperature can be increased to 150-250℃ at a rate of 3-15℃ / min and maintained for 1-3 hours. The ozone atmosphere is achieved through an ozone generator.

[0092] The present invention does not specifically limit the equipment of the ozone generator, but preferably, it can be the OZ-004 ozone generator of Qingdao Zhongke Sanyang Co., Ltd.

[0093] The inventors of this invention have discovered that ozone, when used in the calcination process of catalyst preparation, possesses strong oxidizing and low-temperature oxidation capabilities, effectively removing organic residues, optimizing the catalyst surface, and enhancing oxygen storage capacity and activity. Compared to traditional high-temperature calcination, ozone can achieve efficient oxidation at lower temperatures, reducing damage to the material structure and further improving the catalyst's performance in reactions such as VOCs oxidation.

[0094] The present invention does not particularly limit the first and second contact methods described in steps (1) and (2), as long as it is conducive to the independent and sufficient contact of the substances described in steps (1) and (2). Those skilled in the art can make the selection according to actual needs, for example, it can be stirring.

[0095] The present invention does not particularly limit the conditions of the first and second contacts described in steps (1) and (2). Preferably, the contact reaction conditions described in steps (1) and (2) independently include: a reaction temperature of 10-35°C, more preferably 20-30°C; and a reaction time of 0.1-1h, more preferably 0.2-0.8h.

[0096] A third aspect of the present invention provides a catalyst prepared by the method described in the second aspect above.

[0097] The fourth aspect of the present invention provides the application of the catalyst described in the first aspect or the catalyst prepared by the method described in the second aspect in the catalytic oxidation of VOCs.

[0098] This invention effectively prevents catalyst deactivation in chlorine environments by providing a structured support and an active component coating distributed on the inner and / or outer surfaces of the support, ensuring efficient VOC conversion at low temperatures. By precisely controlling the proportions of each component, the catalyst not only possesses strong resistance to chlorine poisoning but also improves the low-temperature conversion efficiency of VOCs. This invention not only features a simple preparation process but also produces a catalyst with excellent performance, capable of efficiently treating chlorine-containing VOCs, providing an efficient and economical solution for environmental protection.

[0099] The present invention will be described in detail below through embodiments. The following embodiments will further illustrate the present invention, but are not intended to limit the present invention.

[0100] In the following examples and comparative examples, the average particle diameter in the catalyst slurry was the D50 obtained by laser particle size distribution. Experimental apparatus: Malvern Mastersizer 3000.

[0101] In the following examples and comparative examples, the test methods for the types and contents of each metal element are as described above, and will not be repeated here. The types and contents of other substances can be obtained by testing or by calculating the amount of material fed.

[0102] In the following examples and comparative examples, the regularized structure carrier is a VOC-specific cordierite honeycomb regularized structure carrier purchased from Pingxiang Guanlin Environmental Protection Technology Co., Ltd. The regularized structure carrier has a pore density of 300 pores / square inch, a cross-sectional area of ​​1.5 square millimeters per pore, an opening rate of 70%, and a circular shape for the pores.

[0103] In the following examples and comparative examples, "fresh agent" refers to a catalyst that has not been used or has just been prepared. 99 This refers to the temperature at which the vinyl chloride conversion rate reaches 99%.

[0104] Example 1

[0105] (1) Preparation of noble metal colloidal solution: Prepare a 10 mmol / L silver nitrate solution and a mixed solution of 10 mmol / L ascorbic acid and 300 mmol / L triethylamine. The volume ratio of the noble metal solution to the mixed solution is 1:1. Under stirring conditions, the mixed solution is quickly added to the prepared noble metal solution and stirred continuously for 10 minutes to obtain the noble metal colloidal solution.

[0106] (2) Construction of noble metal-titanium interface by adsorbing titanium precursor salt: Prepare a 20 mmol / L titanium citrate solution. Under stirring conditions, add an appropriate amount of titanium citrate solution to the noble metal colloidal solution quickly, control the molar ratio of titanium to silver precursor to be 2:1, add an appropriate amount of nitric acid to adjust the pH to 6, stir for 10 minutes, and fully adsorb titanium salt by utilizing the electrical properties of the colloidal double layer to obtain a noble metal-titanium mixed solution.

[0107] (3) Catalyst slurry preparation and coating: Appropriate amounts of alumina, zinc oxide, bismuth oxide, and tungsten oxide powders were added to deionized water and thoroughly ground using a vibratory ball mill (Tianjin Shengyuan Equipment Co., Ltd., GZM-6). Specific grinding conditions were: ball milling time 2.5 h, rotation speed 1100 rpm, resulting in an average particle diameter of 5.2 μm in the ball-milled mixture. After stirring the ball-milled mixture for 1 hour, the above-mentioned precious metal-titanium mixed solution was added, and stirring continued for another hour to obtain the catalyst slurry. The solid content of the slurry was controlled. The amount was 15%, and then the catalyst slurry was uniformly coated on the surface of a 300-mesh regular structure support, so that the total coating amount of active components on each liter of cordierite honeycomb regular structure support was 88g. Among them, the amount of slurry relative to the volume of the regular structure support resulted in the following composition of each active component in the catalyst: matrix content 70g; silver content 1.0g (by element); titanium content 1.5g (by oxide); tungsten content 1.5g (by oxide); zinc content 2g (by oxide); and bismuth content 12g (by oxide).

[0108] (4) Post-treatment: The regular structure support coated with catalyst slurry was dried at 140°C for 2 hours, and then subjected to ozone calcination treatment. The temperature was increased to 180°C at a rate of 5°C / min and held for 2 hours to obtain VOCs catalytic oxidation catalyst.

[0109] Example 2

[0110] (1) Preparation of noble metal colloidal solution: Prepare 8 mmol / L silver nitrate solution and 8 mmol / L ascorbic acid and 250 mmol / L triethylamine mixed solution. The volume ratio of noble metal solution to mixed solution is 1:1. Under stirring conditions, the mixed solution is quickly added to the prepared noble metal solution and stirred continuously for 8 minutes to obtain noble metal colloidal solution.

[0111] (2) Construction of noble metal-titanium interface by adsorption of titanium precursor salt: Prepare 16 mmol / L titanium citrate solution. Under stirring conditions, add an appropriate amount of titanium citrate solution to the noble metal colloidal solution quickly, control the molar ratio of titanium to silver precursor to be 2:1, add an appropriate amount of nitric acid to adjust the pH to 4, stir for 10 minutes, and fully adsorb titanium salt by utilizing the electrical properties of the colloidal double layer to obtain a noble metal-titanium mixed solution.

[0112] (3) Catalyst slurry preparation and coating: Appropriate amounts of alumina, zinc oxide, bismuth oxide, and tungsten oxide powders were added to deionized water and thoroughly ground using a vibratory ball mill (Tianjin Shengyuan Equipment Co., Ltd., GZM-6). Specific grinding conditions were: ball milling time 2.5 h, rotation speed 1000 rpm, resulting in an average particle diameter of 6.1 μm in the ball-milled mixture. After stirring the ball-milled mixture for 1 hour, the above-mentioned precious metal-titanium mixed solution was added, and stirring continued for another hour to obtain the catalyst slurry. The solid content of the slurry was controlled. The amount was 15%, and then the catalyst slurry was uniformly coated on the surface of a 300-mesh structured support, so that the total coating amount of active components on each liter of ceramic structured support was 65g. Among them, the amount of slurry relative to the volume of the structured support resulted in the following composition of each active component in the catalyst: matrix content 50g; silver content 0.8g (by element); titanium content 1.2g (by oxide); tungsten content 1.3g (by oxide); zinc content 1.7g (by oxide); and bismuth content 10g (by oxide).

[0113] (4) Post-treatment: The regular structure support coated with catalyst slurry was dried at 120°C for 2 hours, and then subjected to ozone calcination treatment, with the temperature increased to 180°C at a rate of 4°C / min and held for 2 hours to obtain VOCs catalytic oxidation catalyst.

[0114] Example 3

[0115] The method is the same as in Example 1, except that the pH is adjusted to 7 in step (2).

[0116] A catalyst for the catalytic oxidation of VOCs was obtained.

[0117] Example 4

[0118] (1) Preparation of noble metal colloidal solution: Prepare a 10 mmol / L silver nitrate solution and a 10 mmol / L sodium borohydride and 100 mmol / L triethylamine mixed solution. The volume ratio of the noble metal solution to the mixed solution is 1:1. Under stirring conditions, the mixed solution is quickly added to the prepared noble metal solution and stirred continuously for 10 minutes to obtain the noble metal colloidal solution.

[0119] (2) Construction of noble metal-titanium interface by adsorbing titanium precursor salt: Prepare a 30 mmol / L titanium tartrate solution, and under stirring conditions, quickly add titanium citrate solution to noble metal colloidal solution, add an appropriate amount of nitric acid to adjust pH to 5, stir for 10 minutes, and fully adsorb titanium salt by utilizing the electrical properties of colloidal double layer to obtain noble metal-titanium mixed solution.

[0120] (3) Catalyst slurry preparation and coating: Appropriate amounts of alumina, zinc oxide, bismuth oxide, and tungsten oxide powders were added to deionized water and thoroughly ground using a vibratory ball mill (Tianjin Shengyuan Equipment Co., Ltd., GZM-6). Specific grinding conditions were: ball milling time 2.5 h, rotation speed 1100 rpm, resulting in an average particle diameter of 5.2 μm in the ball-milled mixture. After stirring the ball-milled mixture for 1 hour, the above-mentioned precious metal-titanium mixed solution was added, and stirring continued for another hour to obtain the catalyst slurry. The solid content of the slurry was controlled. The content is 15%. The catalyst slurry is then uniformly coated on the surface of a 300-mesh regular structure support, so that the total coating amount of active components on each liter of cordierite regular structure support is 100g. The amount of slurry used relative to the volume of the regular structure support results in the following composition of active components in the catalyst: matrix content 75g; silver content 1.5g (by element); titanium content 3g (by oxide); tungsten content 2g (by oxide); zinc content 2.5g (by oxide); and bismuth content 16g (by oxide).

[0121] (4) Post-treatment: The regular structure support coated with catalyst slurry was dried at 140°C for 2 hours, and then subjected to ozone calcination treatment. The temperature was increased to 180°C at a rate of 5°C / min and held for 2 hours to obtain VOCs catalytic oxidation catalyst.

[0122] Example 5

[0123] The method is the same as in Example 1, except that the silver content is 2g and the titanium content, calculated as oxides, is 2g.

[0124] A catalyst for the catalytic oxidation of VOCs was obtained.

[0125] Example 6

[0126] The other conditions are the same as in Example 1, except that the zinc content is 2g and the tungsten content is 0.5g.

[0127] A catalyst for the catalytic oxidation of VOCs was obtained.

[0128] Example 7

[0129] The method is the same as in Example 1, except that in step (4), an air atmosphere is used for roasting.

[0130] A catalyst for the catalytic oxidation of VOCs was obtained.

[0131] Comparative Example 1

[0132] The method is the same as in Example 1, except that zinc oxide is not added in step (3), while the other conditions are the same as in Example 1.

[0133] A catalyst for the catalytic oxidation of VOCs was obtained.

[0134] Comparative Example 2

[0135] The method is the same as in Example 1, except that tungsten oxide is not added in step (3), while the other conditions are the same as in Example 1.

[0136] A catalyst for the catalytic oxidation of VOCs was obtained.

[0137] Comparative Example 3

[0138] The method is the same as in Example 1, except that bismuth oxide is not added in step (3), and the other conditions are the same as in Example 1.

[0139] A catalyst for the catalytic oxidation of VOCs was obtained.

[0140] Comparative Example 4

[0141] The method is the same as in Example 1, except that in step (2), cerium oxide is used instead of titanium citrate, and the other conditions are the same as in Example 1.

[0142] A catalyst for the catalytic oxidation of VOCs was obtained.

[0143] Comparative Example 5

[0144] The method is the same as in Example 1, except that step (2) of adsorbing titanium precursor salt is not performed.

[0145] A titanium-free VOCs catalytic oxidation catalyst was obtained.

[0146] Test case

[0147] The performance of the VOCs catalytic oxidation catalysts obtained in the examples and comparative examples was evaluated using vinyl chloride as a model compound. The activity evaluation of the vinyl chloride catalytic oxidation reaction was performed on a micro fixed-bed reactor designed and manufactured by Tianjin Pengxiang Technology Co., Ltd., equipped with an MKS Multigas 2030 infrared detector. The reaction was carried out at atmospheric pressure, with an initial temperature of 150°C, and a programmed temperature increase at a rate of 3°C / min until the VOCs pollutants were completely converted. The inlet gas composition was 100 ppm vinyl chloride / 7 vol% O2 / N2, and the space velocity was 12000 h⁻¹. -1 T, freshener 99 The conversion temperatures are shown in Table 1.

[0148] Table 1. T values ​​for each catalyst sample 99

[0149] Number: Vinyl Chloride T 99 (°C) Example 1 185.4 Example 2 195.7 Example 3 218.1 Example 4 190.1 Example 5 214.4 Example 6 204.6 Example 7 215.8 Comparative Example 1 227.9 Comparative Example 2 238.2 Comparative Example 3 244.8 Comparative Example 4 221.7 Comparative Example 5 251.6 surface

[0150] As can be seen from the results in Table 1, the T of the VOCs catalytic material obtained using the catalyst provided by this invention is... 99 The conversion temperatures of the catalysts are all lower than those of the comparative example, which overcomes the problem of treating chlorine-containing VOCs in the existing technology. The VOCs catalytic oxidation catalyst prepared by this invention has high resistance to chlorine poisoning and significantly higher efficiency in degrading pollutants.

[0151] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A VOCs catalytic oxidation catalyst, characterized in that, The catalyst comprises a structured support and an active component coating distributed on the inner and / or outer surfaces of the structured support; wherein the active component coating comprises a matrix, an oxygen storage material, and an active metal component; the active metal component comprises silver, titanium, tungsten, and zinc; wherein, based on the volume of the structured support, the matrix content is 35-110 g / L, the oxygen storage material content is 2-20 g / L; the silver content is 0.2-2 g / L (elementally); the titanium content is 0.2-4.4 g / L (oxide-based); the tungsten content is 0.5-3 g / L (oxide-based); and the zinc content is 1-3 g / L (oxide-based).

2. The catalyst according to claim 1, wherein, Based on the volume of the well-structured carrier, the total content of the active component coating is 40-130 g / L, preferably 60-100 g / L; and / or, based on the volume of the well-structured carrier, the content of the matrix is ​​50-88 g / L, and the content of the oxygen storage material is 8-16 g / L; the silver content is 0.5-1.5 g / L; the titanium content is 1-3 g / L; the tungsten content is 1-2 g / L; the zinc content is 1.5-2.5 g / L; and / or, at least a portion of the titanium oxide in the catalyst is coated on the surface of at least a portion of the silver element.

3. The catalyst according to claim 1 or 2, wherein, The matrix is ​​at least one of alumina, silicon dioxide, zeolite, kaolin, diatomite, and perlite, preferably alumina and / or silicon dioxide, more preferably alumina; and / or, the oxygen storage material is selected from at least one of cerium-zirconium solid solution, cerium oxide, bismuth oxide, and manganese oxide, preferably bismuth oxide and / or cerium oxide; and / or, the regular structure carrier is at least one of cordierite, mullite, diamond, corundum, zirconium corundum, quartz, nepheline, feldspar, alumina, and metal alloys.

4. The catalyst according to any one of claims 1-3, wherein, The pore density of the regular structure carrier cross section is 10-300 pores / square inch, and the porosity is 20-80%.

5. A method for preparing a VOCs catalytic oxidation catalyst, characterized in that, The method includes: (1) in the presence of a solvent, a silver precursor, a reducing agent and a stabilizer are brought into first contact to prepare a silver colloidal solution; (2) a titanium precursor is brought into second contact with the silver colloidal solution and the pH of the material is adjusted to 3-7 to obtain a silver-titanium mixture; (3) a tungsten precursor, a zinc precursor, a matrix source, an oxygen storage material and the silver-titanium mixture are brought into third contact to obtain a catalyst slurry; (4) the catalyst slurry is coated onto a regular structured support and then dried and calcined to distribute an active component coating on the inner and / or outer surfaces of the regular structured support.

6. The preparation method according to claim 5, wherein, In step (1), the silver precursor is a soluble salt of silver, preferably silver nitrate and / or silver acetate, more preferably silver nitrate; and / or, the reducing agent is at least one of ascorbic acid, borohydride and citrate, preferably ascorbic acid; and / or, the stabilizer is an organic amine, preferably at least one of diethylamine, triethylamine and trimethylamine, more preferably triethylamine; preferably, the amount of the reducing agent is 0.2-2 mol compared to 1 mol of silver precursor, more preferably 0.5-1.5 mol; preferably, the amount of the stabilizer is 1-100 mol compared to 1 mol of silver precursor, more preferably 10-60 mol.

7. The preparation method according to claim 5 or 6, wherein, The titanium precursor is an organic carboxylic acid titanium salt, preferably at least one of titanium citrate, titanium acetate, titanium oxalate, titanium tartrate, and titanium malonate, more preferably titanium citrate; and / or, the molar ratio of the titanium precursor to the silver precursor, based on the metal element, is 1-3:1, preferably 1.2-2.5:1; and / or, the pH adjuster for adjusting the pH of the material is an acidic adjuster, preferably an inorganic acid, more preferably at least one of hydrochloric acid, nitric acid, and sulfuric acid.

8. The preparation method according to any one of claims 5-7, wherein, The tungsten precursor is at least one of tungsten oxide, sodium tungstate, and ammonium tungstate, preferably tungsten oxide; and / or, the zinc precursor is at least one of zinc oxide, zinc sulfate, and zinc chloride, preferably zinc oxide; and / or, the matrix source is a substance that can be converted into a matrix under the calcination conditions of step (4); And / or, the matrix is ​​at least one of alumina, silicon dioxide, zeolite, kaolin, diatomite and perlite, preferably alumina and / or silicon dioxide, more preferably alumina; and / or, the oxygen storage material is at least one of cerium-zirconium solid solution, cerium oxide, bismuth oxide and manganese oxide, preferably bismuth oxide and / or cerium oxide.

9. The preparation method according to any one of claims 5-8, wherein, The amount of catalyst slurry coating is such that, based on the volume of the regular structure carrier, the total content of the active component coating is 40-130 g / L, preferably 60-100 g / L.

10. The preparation method according to any one of claims 5-9, wherein, The amounts of each component are such that, based on the volume of the regularly structured carrier, the matrix content is 35-110 g / L, the oxygen storage material content is 2-20 g / L; the silver content is 0.2-2 g / L (elemental); the titanium content is 0.2-4.4 g / L (oxide); the tungsten content is 0.5-3 g / L (oxide); and the zinc content is 1-3 g / L (oxide). Preferably, based on the volume of the regularly structured carrier, the matrix content is 50-88 g / L, the oxygen storage material content is 8-16 g / L; the silver content is 0.5-1.5 g / L (elemental); the titanium content is 1-3 g / L (oxide); the tungsten content is 1-2 g / L (oxide); and the zinc content is 1.5-2.5 g / L (oxide).

11. The method according to any one of claims 5-10, wherein, The pore density of the cross-section of the regular structural carrier is 10-300 pores / square inch, and the porosity is 20-80%; preferably, the regular structural carrier is at least one of cordierite, mullite, diamond, corundum, zirconium corundum, quartz, nepheline, feldspar, alumina, and metal alloys.

12. The method according to any one of claims 5-11, wherein, In step (3), the average diameter of the particles in the catalyst slurry is less than 10 μm, preferably 3-8.5 μm.

13. The method according to any one of claims 5-12, wherein, The drying conditions include: a temperature of 100-140℃ and a time of 2-15h; and / or, the calcination in step (4) is carried out in the presence of ozone; and / or, the calcination conditions include: a calcination temperature of 150-250℃ and a time of 1-3h.

14. The catalyst prepared by the method according to any one of claims 5-13.

15. The use of the catalyst according to any one of claims 1-4 and 14 in the catalytic oxidation of VOCs.

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