Supported composite metal catalyst, and preparation method therefor and use thereof

Abstract

The present application provides a supported composite metal catalyst, and a preparation method therefor and a use thereof. The catalyst comprises an acidic oxide support, at least one noble metal, and at least one base metal. The acidic oxide support is strong acid acidified ZrO2, the noble metal is selected from Pt, Pd, Rh, Ru, or a combination thereof, and the base metal is selected from at least one of the following: Ni, Co, Mn, Ce, or Cu. A synthesis method for the catalyst comprises the steps of forming the acidic oxide support, forming a slurry by using raw materials of the noble and base metals and the acidic oxide support, spray drying, and heating treatment. The catalyst can be used to perform complete catalytic oxidative decomposition of volatile organic compounds under a suitable condition, or even at a high moisture level. The technology of the present invention has the advantages of a low use amount of noble metals, excellent low-temperature catalytic oxidation performance, good high-temperature stability, and easy industrial-scale production, and therefore, the volatile organic compounds in exhaust gas can be completely converted into harmless water and carbon dioxide at a relatively low reaction temperature, so that even under a high exhaust gas water vapor content, the catalyst still has extremely high stability.

Description

A supported composite metal catalyst and its preparation method and application Technical Field

[0001] The present application relates to the field of catalysis, and more specifically to a supported composite metal catalyst, a method for preparing the catalyst, and a method for catalytic combustion of volatile organic compounds in exhaust gas using the catalyst. Background Art

[0002] In recent years, with the implementation of green and sustainable development strategies, environmental protection has become an increasingly important issue. The government has tightened emission controls on industrial exhaust gases containing volatile organic compounds (VOCs). The treatment of volatile organic compounds (VOCs) in industrial exhaust gases has become an increasingly important consideration within the industry. Currently, industrial exhaust gas treatment methods include thermal combustion, catalytic combustion, physical adsorption, condensation recovery, and chemical treatment. Catalytic combustion technology is gaining increasing attention as a highly efficient purification technology. It uses catalysts to completely oxidize VOCs into CO2 and H2O. Catalytic combustion technology is increasingly widely used in the chemical industry. Its core technology is the catalyst, and the stability and low-temperature activity of the catalyst are crucial to the efficiency of the catalytic combustion system. To ensure the VOC removal efficiency of the catalytic combustion system for different VOC types and exhaust gas compositions, it is often necessary to develop catalysts with different active compositions. This significantly increases complexity and cost, creating significant obstacles to the industrialization and promotion of catalytic combustion technology. People are very eager to develop a catalyst that can be used to treat the different VOC compositions in the tail gas produced by various processes. In addition, some processes will produce tail gas with complex VOC composition, and people also hope to develop a new catalyst system that can be used to treat such tail gas.

[0003] For example, acrylic acid is an important chemical raw material, mainly used in the production of water-based coatings, water-based adhesives, super absorbent resins, etc. During the production process of acrylic acid, a large amount of tail gas containing VOCs such as propane, propylene and acrolein will be produced, and there is also a large amount of water vapor in the tail gas. When the catalytic combustion catalysts commonly used in the prior art are used to treat tail gas with high water vapor content, due to the influence of the high water vapor content, the catalyst performance will soon show a significant decline, resulting in irreversible deactivation of the catalyst. Therefore, the development of a low-temperature oxidation catalyst that still has excellent activity and stability under high water vapor content is an urgent problem to be solved. In order to solve the above problems, many attempts have been made in the prior art, such as further improving the catalyst composition formula or process conditions, but the results achieved are still extremely limited.

[0004] Summary of the Invention

[0005] In response to the above problems, the inventors of the present application conducted extensive and in-depth research and successfully developed a supported composite metal catalyst and a synthesis method thereof, thereby effectively solving a long-standing problem in the prior art that urgently needs to be solved.

[0006] The first aspect of the present application provides a supported composite metal catalyst, which comprises an acidic oxide support, at least one noble metal and at least one base metal, wherein the acidic oxide support is ZrO2 acidified with a strong acid, the noble metal is selected from Pt, Pd, Rh, Ru or a combination thereof, for example, one, two, three or four selected from Pt, Pd, Rh, Ru, and the base metal is selected from at least one of the following: Ni, Co, Mn, Ce, Cu, for example, one, two, three or four selected from Ni, Co, Mn, Ce, Cu; and

[0007] Based on the weight of the acidic oxide carrier, the content of the noble metal is 0.01-5.0% by weight, and the content of the base metal is 1.0-30.0% by weight.

[0008] The second aspect of the present application provides a method for synthesizing the supported composite metal catalyst of the present invention, the method comprising:

[0009] Step 1: providing ZrO2;

[0010] Step 2: treating ZrO2 with a strong acid to form the acidic oxide support;

[0011] Step 3: combining the solution containing the noble metal and the base metal with the acidic oxide support to form a slurry;

[0012] Step 4: spray drying the slurry to obtain a catalyst precursor; and

[0013] Step 5: heat-treating the catalyst precursor.

[0014] A third aspect of the present application provides a method for catalytically oxidizing and decomposing volatile organic compounds (VOCs), comprising reacting the VOCs with oxygen in the presence of a supported composite metal catalyst of the present invention to produce carbon dioxide and water. According to a preferred embodiment, the method does not produce products other than carbon dioxide and water. DETAILED DESCRIPTION

[0015] "Range" disclosed herein is in the form of a lower limit and an upper limit. It can be one or more lower limits, and one or more upper limits, respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower limit and upper limit define the boundaries of a particular range. All ranges that can be defined in this way are inclusive and combinable, i.e., any lower limit can be combined with any upper limit to form a range. For example, a range of 60-120 and 80-110 is listed for a particular parameter, and it is understood that a range of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​listed are 1 and 2, and if the maximum range values ​​listed are 3, 4, and 5, then the following ranges can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5.

[0016] In this application, unless otherwise specified, the numerical range "ab" is an abbreviation for any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is merely an abbreviation for these numerical combinations.

[0017] In this application, unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined with each other to form a new technical solution.

[0018] In this application, unless otherwise specified, all technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

[0019] In this application, unless otherwise specified, the term "comprising" as used herein may be open-ended or closed-ended. For example, "comprising" may mean that other components not listed may also be included, or only the listed components may be included.

[0020] The catalyst of the present application is a supported composite metal catalyst, wherein at least one noble metal and at least one base metal are supported on an acidic oxide support, preferably on the surface of the acidic oxide support.

[0021] According to one embodiment of the present application, the acidic oxide carrier is ZrO2 that is superacidified with a strong acid. The ZrO2 that is superacidified with a strong acid can be in the form of fine powder or small particles. It can have various particle sizes as needed, for example, its particle size range can be 10 nanometers to 1000 microns, for example, 20 nanometers to 500 microns, or 50 nanometers to 100 microns, or 80 nanometers to 50 microns, or 100 nanometers to 20 microns, or 150 nanometers to 10 microns, or 200 nanometers to 5 microns, or 250 nanometers to 2 microns, or 300 nanometers to 1 micron, or 400-800 nanometers, or 500-700 nanometers, or 550-600 nanometers, or its particle size can be within the numerical range obtained by combining any two of the above end values.

[0022] According to some embodiments of the present application, when describing the particle size of the carrier, catalyst or other components, the particle size can be measured by any suitable technique, such as microscopy, Fresnel method, sedimentation method, laser diffraction method, etc. For example, according to a specific embodiment of the present application, the powder particle size described in the present application is measured by laser diffraction method.

[0023] According to one embodiment of the present application, the precious metals and base metals supported on the acidic oxide support may be present in the final catalyst in their oxidized form rather than in their elemental form. For example, the precious metals Pd, Pt, Rh, and Ru may each be present in a valence state of +2, +3, +4, +5, or +6. For example, the precious metals in the catalyst may be present in one or more (e.g., one, two, three, or four) of the following forms: PdO, Pd2O3, PdO2, PtO, PtO2, RhO, Rh2O3, RhO2, RuO, Ru2O3, RuO2; for example, the precious metals in the catalyst may be present in one or more (e.g., one, two, three, or four) of the following forms: PdO, PtO2, Rh2O3, RuO2. According to another embodiment of the present application, the base metals Ni, Co, Mn, Ce, and Cu may each be in a +1, +2, +3, +4, +5, +6, or +7 valence state. For example, the base metals in the catalyst may be present in one or more (e.g., one, two, three, or four) of the following forms: NiO, Ni2O3, NiO2, CoO, Co2O3, Co3O4, MnO, Mn3O4, MnO2, Mn2O5, CeO, CeO2, Cu2O, and CuO. According to an exemplary embodiment, the base metal elements in the catalyst are selected from the group consisting of Ni, Co, Mn, Ce, Cu, a combination of Ni and Mn, and a combination of Ni and Co. When the base metal element used in the catalyst is a combination of Ni and Mn, the weight ratio of Ni to Mn (calculated as Ni element and Mn element) can be 1:10 to 10:1, for example, 1:8 to 8:1, or 1:6 to 6:1, or 1:5 to 5:1, or 1:3 to 3:1, or 1:2 to 2:1, or 1:2 to 1:1, or the element ratio can be within the numerical range obtained by combining any two of the above ratio values. When the base metal element used in the catalyst is a combination of Ni and Co, the weight ratio of Ni to Co (calculated as Ni element and Co element) can be 1:10 to 10:1, for example, 1:8 to 8:1, or 1:6 to 6:1, or 1:5 to 5:1, or 1:3 to 3:1, or 1:2 to 2:1, or 1:2 to 1:1, or the element ratio can be within the numerical range obtained by combining any two of the above ratio values.

[0024] According to one embodiment of the application, based on the weight of the acidic oxide carrier, the content of the noble metal is 0.01-5.0 weight %, such as 0.02-4.8 weight %, or 0.05-4.5 weight %, or 0.08-4.2 weight %, or 0.1-4.0 weight %, or 0.2-3.5 weight %, or 0.3-3.0 weight %, or 0.35-2.5 weight %, or 0.4-2.2 weight %, or 0.5-2.0 weight %, or 0.5-1.5 weight %, or 0.5-1.2 weight %, or 0.5-1.0 weight %, or 0.5-0.8 weight %, or 0.5-0.6 weight %, or can be within the numerical range obtained by combining any two of the above end values. It should be noted that the content of the noble metal is based on the weight of the noble metal element alone. When the catalyst comprises two or more noble metals, the total amount of these noble metals is within the above range.

[0025] According to one embodiment of the present application, based on the weight of the acidic oxide support, the content of the base metal is 1.0-30.0 weight %, for example 2.0-25.0 weight %, or 3.0-22.0 weight %, or 4.0-20.0 weight %, or 5.0-18.0 weight %, or 6.0-16.0 weight %, or 8.0-15.0 weight %, or 9.0-14.0 weight %, or 10.0-12.0 weight %, or can be within the numerical range obtained by combining any two of the above end values. It should be noted that the content of the base metal is based on the weight of the base metal element alone. When the catalyst contains two or more base metals, the total amount of these base metals is within the above range.

[0026] According to one embodiment of the present application, the catalyst of the present application does not contain other metal elements except the Zr element in the above-mentioned carrier, the noble metal elements and the base metal elements loaded on the carrier.

[0027] According to one embodiment of the present application, the supported composite metal catalyst of the present application can be synthesized by a method comprising the following steps:

[0028] Step 1: providing ZrO2;

[0029] Step 2: treating ZrO2 with a strong acid to form the acidic oxide support;

[0030] Step 3: combining the solution containing the noble metal and the base metal with the acidic oxide support to form a slurry;

[0031] Step 4: spray drying the slurry to obtain a catalyst precursor; and

[0032] Step 5: heat-treating the catalyst precursor.

[0033] According to one embodiment of the present application, in the above-mentioned step 1 of providing ZrO2 for preparing the carrier, ZrO2 can be purchased from various suitable commercial sources, or any thermally decomposable zirconium salt can be heat-treated to cause the thermally decomposable zirconium salt to thermally decompose and form the desired ZrO2. For zirconium dioxide purchased from commercial sources, the zirconium dioxide should have a particle size range as described above, and the purity of the zirconium dioxide can be chemically pure, analytically pure, etc., preferably analytically pure. In the case of preparing zirconium dioxide from a thermally decomposable zirconium salt, examples of thermally decomposable zirconium salts that can be used are selected from one or more of the following: zirconium carbonate, basic zirconium carbonate, zirconium nitrate, zirconium oxynitrate, ammonium zirconium carbonate, zirconium formate, zirconium acetate, zirconium propionate, zirconium isooctanoate, zirconium oxalate, zirconium citrate, zirconium methacrylate, zirconium n-butoxide, zirconium n-propoxide, and ammonium zirconate; the thermally decomposable zirconium salt is preferably zirconium carbonate.

[0034] According to one embodiment of the present application, the heat treatment temperature of the thermally decomposable zirconium salt can be carried out at 500-800°C, for example, the heat treatment temperature can be 550-750°C, or 580-720°C, or 600-700°C, or 600-750°C, or within the numerical range obtained by combining any two of the above end values. According to another embodiment of the present application, the heat treatment of the thermally decomposable zirconium salt at the above heat treatment temperature can last for 30 minutes to 24 hours, for example, 40 minutes to 20 hours, or 1-18 hours, or 1.5-16 hours, or 2-12 hours, or 3-8 hours, or 4-6 hours, or within the numerical range obtained by combining any two of the above end values.

[0035] According to some embodiments of the present application, all heat treatments mentioned in steps 1 to 5 can be carried out in any suitable heating equipment, for example, in a heating oven, a muffle furnace, a tube furnace, etc. Any of these heat treatments can be carried out in any suitable atmosphere, such as an air atmosphere, an oxidizing atmosphere (such as an oxygen atmosphere), an inert atmosphere (such as a nitrogen atmosphere, an argon atmosphere), a vacuum atmosphere, etc. According to one embodiment of the present application, all heat treatments mentioned in steps 1 to 5 can be carried out in an air atmosphere.

[0036] According to one embodiment of the present application, in step 2, the ZrO2 provided in step 1 is treated with a strong acid to form the acidic oxide support. According to another embodiment of the present application, the strong acid used in step 2 can be selected as needed, for example, the strong acid can be selected from one or more of the following: sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, formic acid, acetic acid, benzenesulfonic acid, etc., and preferably, an aqueous solution of the above strong acid is used for treatment. According to one embodiment of the present application, the concentration of the aqueous solution of the strong acid can be 0.1-10M, for example, 0.2-8M, or 0.4-6M, or 0.5-5M, or 0.6-4M, or 0.8-2M, or 0.9-1M, or the concentration of the strong acid aqueous solution can be within the numerical range obtained by combining any two of the above end values. According to one embodiment of the present application, the acid treatment may include immersing ZrO2 in a strong acid aqueous solution for a period of time under stirring conditions. For example, the immersion duration may be 10 minutes to 16 hours, such as 20 minutes to 10 hours, or 30 minutes to 8 hours, or 40 minutes to 6 hours, or 50 minutes to 4 hours, or 1-2 hours, or the immersion duration may be within the numerical range obtained by combining any two of the above end values.

[0037] According to one embodiment of the present application, after the above-mentioned acid treatment, the acid-treated ZrO2 powder / particles are filtered, dried and calcined to obtain an acidic oxide support that can be used to prepare the catalyst of the present application. The filtration can be carried out by any conventional filtration method, such as conventional filter funnel / filter paper filtration, Buchner funnel filtration, membrane vacuum filtration, etc. The drying step can be carried out at a temperature of 80-200°C for 1-24 hours, for example, the drying temperature can be 100-160°C, or 110-150°C, or 120-140°C, or within the numerical range obtained by combining any two of the above end values; the drying duration can be 2-22 hours, for example, 3-20 hours, or 4-18 hours, or 6-16 hours, or 8-14 hours, or 10-12 hours, or within the numerical range obtained by combining any two of the above end values. The calcination can be carried out at a temperature of 300-800°C for 1-24 hours, for example, the temperature used for calcination can be 350-750°C, or 400-700°C, or 450-650°C, or 500-600°C, or 500-550°C, or the calcination temperature can be within the numerical range obtained by combining any two of the above end values; the calcination duration can be 1-24 hours, for example, 1.5-22 hours, for example, 2-20 hours, or 2.5-18 hours, or 3-16 hours, or 3.5-14 hours, or 4-12 hours, or 4-8 hours, or 4-6 hours, or can be within the numerical range obtained by combining any two of the above end values.

[0038] After the acid treatment, filtration, drying, and calcination, the acidic oxide support is obtained. According to one embodiment, the obtained acidic oxide support contains, in addition to ZrO2, the residual portion of the strong acid introduced by the acid treatment after calcination, such as acid radicals, acid anhydrides, etc., collectively referred to herein as "acid residues." According to one embodiment of the present application, the content of the "acid residue" in the acidic oxide support can be 0.02-0.5 μmol / g ZrO2, that is, each gram of ZrO2 contains 0.05-0.5 μmol of the "acid residue", for example, the content of the acid residue can be 0.04-0.45 μmol / g ZrO2, or 0.05-0.4 μmol / g ZrO2, or 0.06-0.4 μmol / g ZrO2, or 0.08-0.4 μmol / g ZrO2, or 0.1-0.4 μmol / g ZrO2, or 0.15-0.35 μmol / g ZrO2, or 0.20-0.30 μmol / g ZrO2, or 0.22-0.25 μmol / g ZrO2, or the content of the acid residue in the acidic oxide support can be within the numerical range obtained by combining any two of the above end values.

[0039] According to a specific embodiment of the present application, the strong acid used is sulfuric acid, more specifically an aqueous solution of sulfuric acid. The acid residue in the catalyst obtained after treatment with sulfuric acid may include sulfate and / or sulfuric anhydride, which are collectively referred to as "SO4 2- ", its content in the acidic oxide carrier can be 0.02-0.5 μmol / g ZrO2, that is, each gram of ZrO2 contains 0.05-0.5 μmol of the "SO4 2- ”, such as “SO4 2- The content of " can be 0.04-0.45 μmol / g ZrO2, or 0.05-0.4 μmol / g ZrO2, or 0.06-0.4 μmol / g ZrO2, or 0.08-0.4 μmol / g ZrO2, or 0.1-0.4 μmol / g ZrO2, or 0.15-0.35 μmol / g ZrO2, or 0.20-0.30 μmol / g ZrO2, or 0.22-0.25 μmol / g ZrO2, or "SO4 2- The content of " can be within the numerical range obtained by combining any two of the above end values.

[0040] According to one embodiment of the present application, in step three, the solution containing the precious metal and the base metal is combined with the acidic oxide support to form a slurry. According to one embodiment of the present application, the slurry formation process may include stirring the solution and the acidic oxide support. Non-limiting examples of the stirring equipment include a magnetic stirrer, a paddle stirrer, and various dispersers.

[0041] According to one embodiment of the present application, the solution of the noble metal and the base metal may be an aqueous solution and may be prepared using water-soluble salts of the noble metal and the base metal, wherein the ions of the water-soluble salt of the base metal may include nitrate, sulfate, chloride (hydrochloride), acetate, formate, etc. The ions of the water-soluble salt of the noble metal include nitrate, chloro-noble metal acid or its salt, such as platinum nitrate, ruthenium nitrate, palladium nitrate, rhodium nitrate, chloroplatinic acid, chlororuthenic acid, chloropalladic acid, chlororhodic acid, ammonium chloroplatinate, ammonium chlororuthenate, ammonium chloropalladate, ammonium chlororhodate, etc.

[0042] The noble metal and the base metal can be prepared into an aqueous solution of the noble metal and an aqueous solution of the base metal, respectively, or can be mixed to prepare an aqueous solution containing both the noble metal and the base metal. According to one embodiment of the present application, whether the solutions are prepared separately or mixed together, the concentration of the noble metal in the aqueous solution is 0.05-5 mol / L, for example, 0.08-4.5 mol / L, or 0.1-4.2 mol / L, or 0.2-4.0 mol / L, or 0.4-3.5 mol / L, or 0.5-3.0 mol / L, or 0.8-2.5 mol / L, or 1.0-2.0 mol / L, or 1.2-1.5 mol / L, or within the numerical range obtained by combining any two of the above end values. According to one embodiment of the present application, regardless of whether the solutions are prepared separately or mixed together, the concentration of the base metal in the aqueous solution is 0.05-5 mol / L, for example, it can be 0.08-4.5 mol / L, or it can be 0.1-4.2 mol / L, or it can be 0.2-4.0 mol / L, or it can be 0.4-3.5 mol / L, or it can be 0.5-3.0 mol / L, or it can be 0.8-2.5 mol / L, or it can be 1.0-2.0 mol / L, or it can be 1.2-1.5 mol / L, or it can be within the numerical range obtained by combining any two of the above end values.

[0043] According to one embodiment of the present application, the ratio of the precious metal and base metal to the acidic oxide support in the slurry satisfies the ratio of each component in the final catalyst described above. The weight percentage of the solid component in the slurry can be calculated according to the following formula:

[0044] (Weight of precious metal salt + weight of base metal salt + weight of acidic oxide support) ÷ total weight of slurry × 100%

[0045] According to another embodiment of the present application, the weight percentage of the solid component in the slurry can be 5-50 weight%, for example, 6-48 weight%, or 8-45 weight%, or 10-42 weight%, or 12-40 weight%, or 15-35 weight%, or 18-32 weight%, or 20-30 weight%, or 22-28 weight%, or 24-26 weight%, or 25-26 weight%, or can be within the numerical range obtained by combining any two of the above end values.

[0046] According to one embodiment of the present application, the slurry prepared in step 3 is spray-dried to obtain a catalyst precursor. The spray drying can be performed using a spray dryer known in the art. In the spray dryer, the slurry prepared in step 3 is sprayed into a drying chamber in a mist form. Simultaneously, filtered and heated air is uniformly introduced into the drying chamber. The misted slurry droplets come into contact with the hot air in the drying chamber of the spray dryer, drying the droplets and obtaining a catalyst precursor in the form of fine particles. The particle size of the precursor can be 0.01-1000 μm, for example, 0.1-900 μm, or 0.5-850 μm, or 1-800 μm, or 5-750 μm, or 10-700 μm, or 20-650 μm, or 50-600 μm, or 70-550 μm, or 100-500 μm, or 150-450 μm, or 200-400 μm, or 250-350 μm, or 280-300 μm, or within the numerical range obtained by combining any two of the above end values. According to one embodiment of the present application, the air inlet temperature (i.e., the temperature of the hot air flowing into the drying chamber) during spray drying is 180-350°C, for example, 200-320°C, or 250-300°C, or 270-290°C, or within the numerical range obtained by combining any two of the above end values; the air outlet temperature (i.e., the temperature of the hot air leaving the drying chamber) is 80-120°C, for example, 90-100°C, or within the numerical range obtained by combining any two of the above end values.

[0047] According to one embodiment of the present application, in step five, the catalyst precursor prepared in step four is heat-treated to obtain the catalyst of the present application. The heat treatment can be carried out in any suitable heating equipment, for example, it can be carried out in a heating oven, a muffle furnace, a tube furnace and the like. The heat treatment can be carried out in any suitable atmosphere, such as an air atmosphere, an oxidizing atmosphere (such as an oxygen atmosphere), an inert atmosphere (such as a nitrogen atmosphere, an argon atmosphere), a vacuum atmosphere, etc. According to one embodiment of the present application, the heat treatment is carried out in an air atmosphere.

[0048] According to one embodiment of the present application, the heat treatment is carried out at a temperature of 400-600°C, for example, 450-580°C, or 480-560°C, or 500-550°C, or 550-580°C, or 520-540°C, or the temperature of the heat treatment can be within the numerical range obtained by combining any two of the above end values. The duration of the heat treatment can be 1-24 hours, for example, 2-20 hours, or 3-16 hours, or 4-12 hours, or 4-8 hours, or 4-6 hours, or the duration of the heat treatment can be within the numerical range obtained by combining any two of the above end values.

[0049] According to one embodiment of the present application, the supported composite metal catalyst of the present application is in the form of powder or fine particles. For example, the particle size of the catalyst can be 10 nanometers to 1000 microns, for example, 20 nanometers to 500 microns, or 50 nanometers to 100 microns, or 80 nanometers to 50 microns, or 100 nanometers to 20 microns, or 150 nanometers to 10 microns, or 200 nanometers to 5 microns, or 250 nanometers to 2 microns, or 300 nanometers to 1 micron, or 400-800 nanometers, or 500-700 nanometers, or 550-600 nanometers, or its particle size can be within the numerical range obtained by combining any two of the above end values.

[0050] According to one embodiment of the present application, the supported composite metal catalyst of the present invention can be used to catalytically oxidize and decompose various volatile organic compounds (VOCs) contained in tail gases generated by various industrial production, so that VOCs react with oxygen to generate carbon dioxide and water.

[0051] According to one embodiment of the present application, the VOC can include substances such as straight-chain or branched alkanes, olefins, aromatic hydrocarbons, alcohols, aldehydes, acids, esters, etc. Preferably, the VOC can include, for example, one to sixteen carbon atoms (i.e., C1-C16), for example, one to twelve carbon atoms, or one to eight carbon atoms, or one to six carbon atoms, or one to four carbon atoms, or one to three carbon atoms, and some other VOCs can also include oxygen atoms, such as one, two, three, four, five or six oxygen atoms can be included in each VOC molecule, and these oxygen atoms can exist in the form of hydroxyl, aldehyde, carboxyl, ester, etc. For example, the example of the hydrocarbon can include methane, ethane, propane, butane, ethylene, propylene, cyclohexane, benzene, toluene, formaldehyde, acetaldehyde, propionaldehyde, acrolein, acetic acid, propionic acid, acrylic acid, etc. According to one embodiment of the present application, the catalytic oxidation reaction does not generate products other than carbon dioxide and water.

[0052] According to another embodiment of the present application, the content of VOC in the tail gas treated using the catalyst of the present invention can be at least 0.1% by volume, based on the total volume of the tail gas, for example, the content of VOC in the tail gas can be 0.1-50% by volume, for example, 0.2-40% by volume, or 0.3-30% by volume, or 0.4-20% by volume, or 0.5-10% by volume, or 0.6-5% by volume, or 0.7-2% by volume, or 0.7-1% by volume, or within the numerical range obtained by combining any two of the above end values. According to another embodiment of the present application, the content of oxygen in the tail gas treated using the catalyst of the present invention can be 0-50% by volume, based on the total volume of the tail gas, for example, the content of oxygen in the tail gas can be 0.1-50% by volume, for example, 0.5-40% by volume, or 0.8-30% by volume, or 1-20% by volume, or 2-15% by volume, or 3-10% by volume, or 4-8% by volume, or 5-6% by volume, or within the numerical range obtained by combining any two of the above end values. According to one embodiment of the present application, when the amount of oxygen in the exhaust gas is insufficient to achieve complete oxidation of VOCs, an oxygen-containing gas, such as air or pure oxygen, can be added to the exhaust gas before the catalytic reaction as needed, so that the oxygen content in the gas undergoing catalytic oxidation is sufficient to completely oxidize all VOCs into CO2 and H2O.

[0053] According to another embodiment of the present application, the catalyst of the present application can be used to oxidatively decompose VOCs in exhaust gas with a high water vapor content, and can effectively avoid the negative impact of high-concentration water vapor on catalyst activity. However, when treating exhaust gas with such a high water vapor content, the catalyst of the prior art often undergoes significant catalyst deactivation after a limited period of time. According to one embodiment of the present application, the water vapor content in the exhaust gas treated using the catalyst of the present invention can be at least 0.5% by volume, based on the total volume of the exhaust gas, for example, the water vapor content in the exhaust gas can be 0.5-20% by volume, such as 0.8-18% by volume, or 1-15% by volume, or 1.5-12% by volume, or 2-10% by volume, or 3-8% by volume, or 4-7% by volume, or 5-6% by volume, or can be within the numerical range obtained by combining any two of the above end values.

[0054] According to one embodiment of the present application, the catalytic oxidative decomposition of VOCs is carried out in the presence of the catalyst of the present invention at a temperature of 180-600° C. For example, the catalytic oxidative decomposition of alkanes can achieve a VOC conversion rate of ≥95% within the temperature range of 180-600° C.

[0055] According to one embodiment of the present application, the catalytic oxidative decomposition of tail gas containing propane, propylene, and acrolein, and having a significant water vapor content (VOC), was investigated using the catalyst of the present application. According to one exemplary embodiment of the present application, the tail gas contained 0.1-5% by volume of propane, 0.1-5% by volume of propylene, 0.01-5% by volume of acrolein, 0.5-10% by volume of water vapor, 0.5-25% by volume of oxygen, and the balance of nitrogen, with the aforementioned volume percentages being based on the total volume of the tail gas. For example, in the exemplary tail gas, the content of propane may be 0.2-4.5% by volume, or 0.3-4% by volume, or 0.3-3.5% by volume, or 0.3-3% by volume, or 0.3-2.5% by volume, or 0.3-2% by volume, or 0.3-1.5% by volume, or 0.3-1.2% by volume, or 0.3-1% by volume, or 0.3-0.8% by volume, or 0.3-0.5% by volume, or within a numerical range obtained by combining any two of the above end values; the content of propylene may be The content of acrolein may be 0.2-4.5% by volume, or 0.3-4% by volume, or 0.3-3.5% by volume, or 0.3-3% by volume, or 0.3-2.5% by volume, or 0.3-2% by volume, or 0.3-1.5% by volume, or 0.3-1.2% by volume, or 0.3-1% by volume, or 0.3-0.8% by volume, or 0.3-0.5% by volume, or within a numerical range obtained by combining any two of the above end values; the content of acrolein may be 0.02-4.5% by volume, or 0. %, or 0.1-0.5 volume %, or within the range of any two of the above end values ​​combined; the water vapor content can be 0.6-9 volume %, or 0.7-8 volume %, or 1-7 % by volume, or 2-6% by volume, or 2.5-5.5% by volume, or 3-5% by volume, or 4-5% by volume, or within the range of values ​​obtained by combining any two of the above end values; the oxygen content may be 0.6-22% by volume, or 0.7-20% by volume, or 1-18% by volume, or 2-16% by volume, or 2.5-15% by volume, or 3-12% by volume, or 4-10% by volume, or 5-8% by volume, or within the range of values ​​obtained by combining any two of the above end values.

[0056] The tail gas containing propane, propylene and acrolein investigated in the embodiments of the present invention is a representative example of the tail gas generated in the industrial synthesis process of acrylic acid.

[0057] According to one embodiment of the present application, the lowest temperature at which the catalyst can achieve different conversion rates of VOCs (e.g., one, multiple, or all of the various VOCs described above) can be used to characterize the reactivity of the catalyst. The conversion rate of hydrocarbons can be calculated using the following formula:

[0058] VOC conversion rate (%) = [(VOC amount before reaction - VOC amount after reaction) / VOC amount before reaction] × 100%

[0059] According to one embodiment of the present application, the catalytic activity of a catalyst can be represented by T95 (referred to as the complete conversion temperature), at which the conversion rate of a VOC (e.g., one, two, or all three of propane, propylene, and acrolein) reaches 95%. The lower the temperature, the better the catalyst activity. According to one embodiment of the present application, when the conversion rate of a VOC (e.g., one, two, or all three of propane, propylene, and acrolein) reaches 95%, it is considered that the VOC has been completely converted, and therefore T95 is referred to as the complete conversion temperature.

[0060] According to one embodiment of the present application, the tail gas is passed through a reactor equipped with the catalyst of the present invention at a reaction temperature, so that VOC (e.g., propane, propylene, acrolein) reacts with oxygen under the catalytic action of the catalyst of the present invention, so that the VOC (e.g., propane, propylene, acrolein) is oxidized and decomposed to produce products CO2 and water, with substantially no other by-products, preferably no other by-products at all. The temperature of the VOC catalytic oxidation decomposition reaction is as described above, and may be 180-600°C. According to one embodiment of the present application, the propane in the tail gas can achieve a conversion rate of 95% at a temperature of 380-600°C, that is, complete conversion, for example, the above temperature may be 400-550°C, or 420-500°C, or 450-480°C, or may be within the numerical range obtained by combining any two of the above end values. According to one embodiment of the present application, the conversion rate of propylene in the tail gas can be achieved at a temperature of 180-300°C, that is, complete conversion. For example, the above temperature can be 189-290°C, or 190-250°C, or 200-265°C, or 210-250°C, or 220-230°C, or it can be within the numerical range obtained by combining any two of the above end values. According to one embodiment of the present application, the conversion rate of acrolein in the tail gas can be achieved at a temperature of 180-300°C, that is, complete conversion. For example, the above temperature can be 190-290°C, or 194-250°C, or 200-265°C, or 210-250°C, or 220-230°C, or it can be within the numerical range obtained by combining any two of the above end values.

[0061] As mentioned above, if necessary, the tail gas can be first mixed with pure oxygen or air to form a mixed gas, so that the mixed gas contains enough oxygen to completely oxidize and decompose the VOCs, and then the mixed gas is fed into the reactor.

[0062] The present application is described below in the form of specific examples for the purpose of providing a better understanding of the present application. It should be understood that these examples are merely illustrative and non-restrictive. The reagents used in the examples are all commercially available unless otherwise specified. The methods and conditions used in the examples are conventional methods and conditions unless otherwise specified.

[0063] Example

[0064] In the following examples, the catalyst of the present invention was synthesized and its catalytic activity was examined using artificially synthesized tail gas containing propane, propylene, and acrolein. However, it should be noted that the following examples are merely specific examples of this application and are not intended to limit the technical features of this application. Any simple variations, equivalent substitutions, or other modifications based on this application that solve essentially the same technical problems and achieve essentially the same technical effects are encompassed within the scope of this application.

[0065] The raw materials used in the following examples were all commercially purchased analytically pure samples and were used directly without further purification or treatment.

[0066] Example 1

[0067] In this Example 1, a catalyst supported with Pt and Ni was synthesized by the following steps.

[0068] Zirconium carbonate was placed in a muffle furnace and calcined at 600°C for 4 hours in an air atmosphere. After natural cooling, white powdery ZrO2 was obtained. 100 g of ZrO2 powder was added to 1000 ml of 1M sulfuric acid aqueous solution and stirred at room temperature for 1 hour using a paddle-type mechanical stirrer. The solid-liquid mixture was filtered with a Buchner funnel, and the solid was washed with a small amount of distilled water and dried again. The dried solid was placed in an oven and dried at 120°C for 12 hours in an air atmosphere. The dried solid was then placed in a muffle furnace and calcined at 500°C for 4 hours in an air atmosphere to obtain a carrier for the catalyst. The SO4 content in the carrier was measured by ICP-AES analyzer technology. 2- The content is 0.22μmol / g ZrO2.

[0069] 31.13 g of Ni(NO3)2 and 1.05 g of chloroplatinic acid were weighed and dissolved in 400 ml of distilled water. Then 100 g of the carrier prepared above was weighed and added to the aqueous solution containing nickel and platinum. Stirring was performed at room temperature for 1 hour to form a slurry. The slurry was transported to an Okawara OADB-8 spray dryer and dried by spray drying. The inlet air temperature in the spray dryer was 250°C and the outlet air temperature was 100°C. The dried precursor was placed in a muffle furnace and heat treated at 500°C for 4 hours in an air atmosphere. It was cooled naturally. The resulting catalyst contained zirconium dioxide (SO4) acidified with sulfuric acid. 2- / ZrO2) as a carrier, and 0.5 wt% of platinum and 10 wt% of nickel are also loaded on the carrier.

[0070] Example 2

[0071] In this example, the steps of Example 1 were repeated, except that 31.04 g of anhydrous Co(NO3)2 was used instead of the nickel nitrate of Example 1. The prepared catalyst comprised a zirconium dioxide support acidified with sulfuric acid and 0.5 wt% of Pt element and 10 wt% of Co element supported on the support.

[0072] Example 3

[0073] In this example, the steps of Example 1 were repeated, except that 32.57 g of Mn(NO3)2 was used instead of the nickel nitrate of Example 1. The prepared catalyst comprised a zirconium dioxide support acidified with sulfuric acid and 0.5 wt% of Pt element and 10 wt% of Mn element supported on the support.

[0074] Example 4

[0075] In this example, the procedure of Example 1 was repeated except that 32.57 g of Mn(NO3)2 and 15.56 g of Ni(NO3)2 were used. The resulting catalyst comprised a sulfuric acid-acidified zirconium dioxide support and 0.5 wt% of Pt, 5 wt% of Ni, and 10 wt% of Mn supported on the support.

[0076] Comparative Example 1

[0077] In this comparative example, the catalyst was synthesized by repeating the steps of Example 1, except that nickel nitrate was not added during the metal element loading. The resulting catalyst comprised a zirconium dioxide support acidified with sulfuric acid and 0.5 wt% Pt element loaded on the support.

[0078] Comparative Example 2

[0079] In this comparative example, the catalyst was synthesized by repeating the steps of Example 4, except that zirconium dioxide was used directly as a support without being treated with sulfuric acid. The resulting catalyst comprised the untreated zirconium dioxide support, and 0.5 wt% Pt, 5 wt% Ni, and 10 wt% Mn supported on the support.

[0080] Example 5: Catalyst Performance Characterization

[0081] In this example, the catalysts described in Examples 1-4 and Comparative Examples 1-2 were used to perform the catalytic oxidative decomposition of VOCs in exhaust gas. Specifically, propane, propylene, acrolein, water vapor, oxygen, and nitrogen were uniformly mixed to form a mixed gas containing 0.3% propane, 0.3% propylene, 0.1% acrolein, 5% water vapor, and 5% oxygen, with the remainder being nitrogen. This mixed gas served as simulated exhaust gas and was used to characterize the catalytic performance of the catalysts described herein.

[0082] A quartz tube with an inner diameter of 6 mm was used as a reactor. 100 mg of catalyst was loaded into the tube. The reaction section of the tube was inserted into a tubular furnace. After heating to the target reaction temperature, preheated simulated exhaust gas was introduced into the tube. The total space velocity of the mixed gas was 60,000 h / min. -1 The tail gas flowing out of the quartz tube was analyzed online using gas chromatography. For each catalyst, the T95 values ​​for propane, propylene, and acrolein were first measured on the fresh catalyst as described in this application specification. After the reaction was maintained at 550°C for 100 hours, the reactor temperature was lowered again and the T95 values ​​for propane, propylene, and acrolein on the catalyst after 100 hours of reaction were measured. The results are summarized in Table 1 below. Product types were also analyzed based on signal peaks in the gas chromatogram.

[0083] Table 1: T95 of various components measured in Examples 1-4 and Comparative Examples 1-2, where the unit of the value is °C

[0084] A comparison of Examples 1-4 and Comparative Examples 1-2 shows that the catalysts of Examples 1-4 exhibit excellent catalytic activity, enabling the decomposition of VOCs in exhaust gas at relatively low temperatures. Furthermore, under high water vapor conditions, the catalysts of the present invention can effectively maintain their catalytic activity after prolonged reaction, demonstrating their excellent stability. A comparison of Comparative Example 2 with Example 4 demonstrates that the present invention, by acidifying the zirconia support, can enhance the catalyst's catalytic oxidation ability for propane, propylene, and acrolein, particularly significantly improving the catalytic oxidation ability for propane. The acidic support facilitates the cleavage of carbon-hydrogen and carbon-carbon bonds, making it suitable for the complete oxidation of stable alkanes. The catalysts using the acidified support are also more stable than those using the unacidified support.

[0085] Furthermore, based on the signal peaks from gas chromatography, it can be determined that the products of the VOC catalytic oxidation reaction in Examples 1-4 of the present application are solely CO2 and water, with no other organic byproducts generated. In contrast, in Comparative Examples 1-2, small amounts of organic byproducts, CO and acetaldehyde, were observed, primarily as a result of incomplete oxidation of propylene.

[0086] The catalyst of this application has at least the following advantages:

[0087] The catalyst and preparation method of the present invention reduce the amount of precious metals used and can significantly reduce the catalyst cost. The prepared catalyst exhibits excellent catalytic activity and stability under conditions of high water vapor content and can thoroughly catalytically oxidize and decompose various VOC compounds contained in exhaust gas.

Claims

1. A supported composite metal catalyst, comprising an acidic oxide carrier, at least one noble metal and at least one base metal, wherein the acidic oxide carrier is ZrO2 acidified with a strong acid, the noble metal is selected from Pt, Pd, Rh, Ru or a combination thereof, and the base metal is selected from at least one of the following: Ni, Co, Mn, Ce, Cu; and Based on the weight of the acidic oxide carrier, the content of the noble metal is 0.01-5.0% by weight, and the content of the base metal is 1.0-30.0% by weight.

2. The supported composite metal catalyst according to claim 1, characterized in that The strong acid is sulfuric acid, and in the carrier, SO4 2- The content is 0.02-0.5 μmol / g ZrO2, preferably 0.1-0.4 μmol / g ZrO2.

3. The supported composite metal catalyst according to claim 1, characterized in that Based on the weight of the acidic oxide carrier, the content of the noble metal is 0.05-2.0% by weight, and the content of the base metal is 2.0-25.0% by weight.

4. A method for synthesizing a supported composite metal catalyst as claimed in any one of claims 1 to 3, the method comprising: Step 1: providing ZrO2; Step 2: treating ZrO2 with a strong acid to form the acidic oxide support; Step 3: combining the solution containing the noble metal and the base metal with the acidic oxide support to form a slurry; Step 4: spray drying the slurry to obtain a catalyst precursor; as well as Step five: heat-treating the catalyst precursor.

5. The method according to claim 4, characterized in that In the step 1, a thermally decomposable zirconium salt is heat-treated to provide ZrO2, wherein the thermally decomposable zirconium salt is selected from one or more of the following: zirconium carbonate, basic zirconium carbonate, zirconium nitrate, zirconium oxynitrate, ammonium zirconium carbonate, zirconium formate, zirconium acetate, zirconium propionate, zirconium isooctanoate, zirconium oxalate, zirconium citrate, zirconium methacrylate, zirconium n-methoxide, zirconium n-ethoxide, zirconium n-butoxide, zirconium n-propoxide, and ammonium zirconate; The heat treatment is performed at a temperature of 500-800° C., so that the thermally decomposable zirconium salt decomposes to form ZrO 2 .

6. The method according to claim 4, characterized in that In the step 2, the strong acid is sulfuric acid, the ZrO2 is soaked in sulfuric acid, and then dried and heat-treated to form the acidic oxide carrier.

7. The method according to claim 4, characterized in that In step 4, the inlet air temperature of the spray drying is 180-350°C, and the outlet air temperature is 80-120°C.

8. The method according to claim 4, characterized in that In the step five, the catalyst precursor is dried, and the dried precursor is calcined at a temperature of 300-800° C. for 1-24 hours.

9. A method for catalytically oxidizing and decomposing volatile organic compounds, the method comprising reacting the volatile organic compounds with oxygen to generate carbon dioxide and water in the presence of a supported composite metal catalyst as described in any one of claims 1 to 3.

10. The method according to claim 9, characterized in that The process does not generate products other than carbon dioxide and water; and the process can be carried out at a temperature of 180-600°C.

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