CN107694564B - Catalyst for decomposing formaldehyde and preparation method thereof - Google Patents
Catalyst for decomposing formaldehyde and preparation method thereof Download PDFInfo
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Abstract
The invention provides a catalyst for decomposing formaldehyde and a preparation method thereof. The catalyst for decomposing formaldehyde comprises active carbon as a carrier, platinum and palladium supported on the carrier as active components, and a hydrophobic component as a hydrophobic porous material layer coated on the surface of the catalyst, wherein the platinum is supported in an amount of 0.02-0.3 wt% and the palladium is supported in an amount of 0.02-0.3 wt%. The preparation method of the catalyst for decomposing formaldehyde is simple, and the prepared catalyst has the advantages of low cost, high moisture resistance, high adsorptivity, high activity and long service life, can be used for adsorbing and decomposing formaldehyde gas at room temperature, can be applied to an air purifier and an adsorption concentration tower, and can remarkably and rapidly reduce the formaldehyde concentration.
Description
Technical Field
The invention belongs to the technical field of catalysts, and relates to a catalyst for decomposing formaldehyde and a preparation method thereof.
Background
With the continuous improvement of the material culture level of people, the requirements of people on the air quality outdoors and indoors are higher and higher. A large amount of materials for interior decoration release harmful gases, including formaldehyde. Formaldehyde is widely sourced from indoor building materials, textile products, insufficient combustion, daily necessities and the like, can coagulate and denature with proteins in cells, can cause pathological changes of the respiratory system, the immune system, the central system, the nervous system and other skills of a human body, has the characteristics of long release period and great hazard, and has great significance in researching the decomposition of formaldehyde.
At present, the indoor formaldehyde decomposition technology comprises a natural traditional method, an adsorption method, an air negative ion technology method, a photocatalysis technology method and a catalytic oxidation technology method, wherein the adsorption method, the photocatalysis technology method and the catalytic oxidation technology method are mainly adopted. The adsorption method comprises physical adsorption and chemical adsorption, and mainly adopts active carbon, active alumina and the like as adsorbents. The following problems exist: the physical adsorption method has no selectivity, is easily influenced by the ambient atmosphere to be desorbed, is easy to cause secondary pollution, and needs to be replaced or regenerated periodically; the chemisorption method has poor adsorption effect on low-concentration formaldehyde. The photocatalysis technology method mainly uses modified nano TiO 2 The photocatalytic principle of (2) is used for decomposing formaldehyde, the catalytic oxidation technology mainly utilizes oxygen in air to decompose formaldehyde into carbon dioxide and water under the action of a catalyst,no external excitation light source is required and the product is clean.
CN102658115a discloses a cerium doped nano titanium dioxide/activated carbon fiber composite photocatalyst for air purification and a preparation method thereof, the method achieves the aim of improving the photocatalytic activity of nano titanium dioxide by doping rare earth cerium into nano titanium dioxide, but the method has the problems of needing an external excitation light source, low utilization efficiency of visible light, easy deactivation of the catalyst and the like.
The catalyst for catalytic oxidation technology mainly consists of noble metal and a porous matrix, and the porous matrix is generally active carbon, ceramic or covalent organic porous polymer with adsorption performance, etc.
CN102247842A discloses a high-efficiency catalyst for eliminating formaldehyde at room temperature, which can decompose formaldehyde with low concentration at normal temperature and normal humidity, and is mainly prepared by loading Pt with mass fraction of 0-5% on a catalyst coated with TiO 2 -SnO 2 The composite oxide is compounded in a cordierite honeycomb ceramic carrier of the composite oxide, the combination degree between the composite oxide and the honeycomb ceramic of the catalyst is weak, the composite oxide is easy to fall off, and the problems of serious powder falling, unstable activity and the like of the catalyst exist in long-term use.
CN101274281a discloses a catalyst for removing formaldehyde in air at room temperature and a preparation method thereof, cordierite honeycomb ceramics of Co-Ce-Sn porous composite oxide is used as a carrier, 0% -10% of Pt is loaded, formaldehyde can be oxidized and decomposed at normal temperature, but the problem of high cost exists.
CN105749974a discloses a formaldehyde degradation catalyst and a preparation method thereof, which is mainly compounded by 0.1-0.5% of nano gold and 0.1-0.5% of nano platinum in mass fraction loaded in a covalent organic porous polymer matrix COP-4, and the dispersity of active components on a porous carrier is improved, but the preparation process is complex and the electrical conductivity is poor.
CN105597682A discloses a method for preparing modified activated carbon for removing formaldehyde at normal temperature, which takes granular, columnar, spherical or honeycomb coconut shell activated carbon with high specific surface area as a carrier and CuCl 2 And FeCl 3 The mixed metal salt is used as a modifying component and is used for treating qiThe formaldehyde in the state has the characteristics of quick capture, high-efficiency adsorption, low cost, easy industrialization realization and the like, but has the problem of lower formaldehyde conversion rate.
In summary, the active carbon has the advantages of wide raw material sources, simple preparation process, low cost, environmental protection benefit and the like, but the existing carbon-supported catalyst has the defects of easy adsorption saturation, difficult regeneration and easy water poisoning, so the research on the hydrophobicity and the regeneration capability of the carbon-supported catalyst has practical significance.
Disclosure of Invention
Aiming at the defects of the prior art, one of the purposes of the invention is to provide a catalyst for decomposing formaldehyde, wherein the dispersity of noble metals platinum and palladium is high, and the catalyst has the advantages of superhydrophobicity, high adsorptivity, high activity, low cost, long service life, capability of decomposing formaldehyde at room temperature and realization of regeneration of an active carbon carrier.
To achieve the purpose, the invention adopts the following technical scheme:
the catalyst for decomposing formaldehyde comprises active carbon as a carrier, platinum and palladium supported on the carrier as active components, and a hydrophobic component as a hydrophobic porous material layer coated on the surface of the catalyst, wherein the platinum is supported in an amount of 0.02-0.3 wt% and the palladium is supported in an amount of 0.02-0.3 wt%.
According to the invention, platinum with the loading amount of 0.02-0.3 wt% and palladium with the loading amount of 0.02-0.3 wt% are firstly loaded in activated carbon subjected to vacuumization treatment, and then the activated carbon is subjected to hydrophobic treatment to obtain the carbon-supported catalyst with high moisture resistance and high adsorption performance. Wherein, the active carbon is a carrier, the noble metal platinum and palladium are active components, the hydrophobic porous material layer is a hydrophobic component, and the loading of the noble metal platinum and palladium is low, for example, the loading of the platinum can be 0.02wt%, 0.03wt%, 0.04wt%, 0.05wt%, 0.06wt%, 0.07wt%, 0.08wt%, 0.09wt%, 0.1wt%, 0.12wt%, 0.15wt%, 0.18wt%, 0.2wt%, 0.21wt%, 0.23wt%, 0.26wt%, 0.28wt% and 0.3wt%; the palladium loading may be 0.02wt%, 0.03wt%, 0.04wt%, 0.05wt%, 0.06wt%, 0.07wt%, 0.08wt%, 0.09wt%, 0.1wt%, 0.12wt%, 0.15wt%, 0.18wt%, 0.2wt%, 0.21wt%, 0.23wt%, 0.26wt%, 0.28wt%, 0.3wt%.
The second purpose of the invention is to provide a preparation method of the catalyst for decomposing formaldehyde, which comprises the following steps:
1) Preparation of activated carbon matrix: crushing, drying, carbonizing, activating, cleaning and drying the organic material rich in carbon to obtain the activated carbon with high specific surface area and high adsorptivity;
2) Preparation of carbon-supported catalyst: vacuumizing the activated carbon matrix obtained in the step 1), immersing the activated carbon matrix in a dimethylformamide solution containing a platinum precursor and a palladium precursor, adding a binder, extruding and molding, drying, and then introducing hydrogen for reduction treatment to obtain the carbon-supported catalyst;
3) Hydrophobing treatment of carbon-supported catalyst: and (3) uniformly mixing the carbon-supported catalyst obtained in the step (2) with the hydrophobic porous material in ethanol, and drying to obtain the catalyst for decomposing formaldehyde.
In the step 1), the organic material rich in carbon is one or a mixture of at least two of phosphor wood, fruit shell, coconut shell, walnut shell, jujube shell and apricot shell.
In the step 1), the crushing is carried out by adopting a ball mill, then drying, carbonizing the materials in a muffle furnace, removing hydrogen and oxygen in the raw materials, adding an activating agent for activation to make the raw materials porous, and finally carrying out acid washing and drying.
Preferably, in step 1), the carbonization is performed in a muffle furnace, the atmosphere of the carbonization is nitrogen, the temperature of the carbonization is 300-600 ℃, for example, the temperature of the carbonization is 300 ℃, 350 ℃, 400 ℃, 450 ℃, 500 ℃, 550 ℃, 600 ℃, and the time of the carbonization is 1-5 hours, for example, the time of the carbonization is 1 hour, 2 hours, 3 hours, 4 hours, 5 hours; further preferably, the carbonization temperature is 400-500 ℃, e.g. 400 ℃, 410 ℃, 420 ℃, 430 ℃, 440 ℃, 450 ℃, 460 ℃, 470 ℃, 480 ℃, 490 ℃, 500 ℃, and the carbonization time is 3-4 hours, e.g. 3.1 hours, 3.2 hours, 3.3 hours, 3.4 hours, 3.5 hours, 3.6 hours, 3.7 hours, 3.8 hours, 3.9 hours, 4 hours.
Preferably, in the step 1), chemical activation is adopted for the activation, the activated activator is potassium hydroxide, and the mass ratio of the activator to the activated carbon is 1 (3-7), for example, the mass ratio of the activator to the activated carbon is 1:3, 1:4, 1:5, 1:6 and 1:7; the activation temperature is 600-900 ℃, for example 600 ℃, 650 ℃, 700 ℃, 750 ℃, 800 ℃, 850 ℃, 900 ℃, and the activation time is 1-5 hours, for example 1 hour, 2 hours, 3 hours, 4 hours, 5 hours. In the activation treatment process, the activation temperature, activation time and impregnation ratio within the range of the invention are selected, so that on one hand, the number of open pores and reamers of raw material carbon can be ensured to be close to saturation; on the other hand, the collapse of the inner pore wall of the activated carbon caused by excessive alkali is avoided, so that the formed pore structure is damaged.
Preferably, the specific surface area of the activated carbon matrix obtained in step 1) is 1000-4000 m 3 Per gram, e.g. active carbon matrix with a specific surface area of 1000m 3 /g、1500m 3 /g、2000m 3 /g、2500m 3 /g、3000m 3 /g、3500m 3 /g、4000m 3 And/g, wherein the volume percent of micropores is 80-95%.
In step 2), the vacuum treatment aims to remove air remaining in the micropores of the activated carbon particles, so that the platinum-containing precursor and the palladium-containing precursor solution are more uniformly diffused into the internal micropores. The relative pressure difference of the vacuumizing treatment is-0.1 to 0MPa, for example, the relative pressure difference is-0.1 MPa, -0.09MPa, -0.08MPa, -0.07MPa, -0.06MPa, -0.05MPa, -0.04MPa, -0.03MPa, -0.02MPa, -0.01MPa, and more preferably-0.08 to-0.05 MPa; in the range of the relative pressure difference, the dispersity of the platinum-containing precursor and the palladium-containing precursor in the activated carbon micropores is better.
In the step 2), the platinum-containing precursor is one or a mixture of at least two of platinum nitrate, chloroplatinic acid, platinum acetylacetonate and hexahydroxyplatinate di (ammonium ethoxide); the mixture may be a mixture of two, for example, the platinum-containing precursor is a mixture of platinum nitrate, platinum chlorate, chloroplatinic acid, platinum acetylacetonate, and a mixture of platinum nitrate and hexahydroxy platinate di (ethanolammonium); the mixture may also be a mixture of three, for example, the mixture is a mixture of platinum nitrate, chloroplatinic acid, platinum acetylacetonate, platinum nitrate, platinum chlorate, bis (ethanolammonium) hexahydroxyplatinate, a mixture of chloroplatinic acid, platinum acetylacetonate and bis (ethanolammonium) hexahydroxyplatinate; the mixture may also be a mixture of four, for example, a mixture of platinum nitrate, chloroplatinic acid, platinum acetylacetonate, and bis (ethanolammonium) hexahydroxyplatinate.
The palladium-containing precursor is chloropalladac acid and/or palladium acetate;
the total weight of platinum and palladium in the dimethylformamide solution containing the platinum precursor and the palladium precursor accounts for 0.1-0.3% of the weight of the solution, for example, the total weight of platinum and palladium accounts for 0.1%, 0.15%, 0.2%, 0.25% and 0.3% of the weight of the solution, and the mass ratio of platinum and palladium in the solution is 1 (2-3), for example, the mass ratio of platinum and palladium in the solution is 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9 and 1:3.
In the step 2), the binder is one or a mixture of at least two of animal glue, synthetic resin and rubber; typical but non-limiting examples are mixtures of two binders, for example mixtures of animal glue, synthetic resin, mixtures of animal glue, rubber, mixtures of synthetic resin and rubber, and mixtures of three binders, for example mixtures of animal glue, synthetic resin and rubber.
Preferably, the binder is phenolic resin, and the mass ratio of the phenolic resin to the activated carbon is 1 (2-5), for example, the mass ratio of the phenolic resin to the activated carbon is 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5.
In the step 2), the hydrogen content in the reducing atmosphere of the reducing treatment is 5-15%, for example, the hydrogen content in the reducing atmosphere is 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, the temperature of the reducing treatment is 300-500 ℃, for example, the temperature of the reducing treatment is 300 ℃, 350 ℃, 400 ℃, 450 ℃, 500 ℃, and the time of the reducing treatment is 2-4 h, for example, the time of the reducing treatment is 2h, 2.5h, 3h, 3.5h, 4h.
In step 3), the hydrophobic porous material is one or a mixture of at least two of polytetrafluoroethylene, polyethylene, polystyrene, styrene-divinylbenzene, polymethyl methacrylate and polypropylene, and typical but non-limiting examples are a mixture of two materials, such as polytetrafluoroethylene, a mixture of polyethylene, polytetrafluoroethylene, a mixture of polystyrene, a mixture of polytetrafluoroethylene, styrene-divinylbenzene, a mixture of polytetrafluoroethylene, polymethyl methacrylate, a mixture of polytetrafluoroethylene and polypropylene; the mixture may also be a mixture of three materials, such as polytetrafluoroethylene, polyethylene, a mixture of polystyrene, polytetrafluoroethylene, polyethylene, a mixture of styrene-divinylbenzene, polytetrafluoroethylene, polyethylene, a mixture of polymethyl methacrylate, polytetrafluoroethylene, polyethylene, polypropylene, polytetrafluoroethylene, polystyrene, a mixture of styrene-divinylbenzene, polytetrafluoroethylene, polystyrene, a mixture of polymethyl methacrylate, polytetrafluoroethylene, polystyrene, polypropylene, polytetrafluoroethylene, a mixture of styrene-divinylbenzene, polymethyl methacrylate, polytetrafluoroethylene, a mixture of styrene-divinylbenzene, polypropylene, a mixture of polytetrafluoroethylene, polymethyl methacrylate, and polypropylene; the mixture may also be a mixture of four materials, such as polytetrafluoroethylene, polyethylene, polystyrene, a mixture of styrene-divinylbenzene, polytetrafluoroethylene, polyethylene, polystyrene, a mixture of polymethyl methacrylate, polytetrafluoroethylene, polyethylene, polystyrene, a mixture of polypropylene, polytetrafluoroethylene, polyethylene, styrene-divinylbenzene, a mixture of polymethyl methacrylate, polytetrafluoroethylene, polyethylene, a mixture of polymethyl methacrylate and polypropylene, polytetrafluoroethylene, styrene-divinylbenzene, a mixture of polymethyl methacrylate and polypropylene, a mixture of polyethylene, styrene-divinylbenzene, polymethyl methacrylate and polypropylene, a mixture of polystyrene, polymethyl methacrylate and polypropylene, a mixture of five materials, such as polytetrafluoroethylene, polyethylene, polystyrene, styrene-divinylbenzene, polymethyl methacrylate, a mixture of polytetrafluoroethylene, polyethylene, styrene-divinylbenzene, polymethyl methacrylate, a mixture of polystyrene, polystyrene-divinylbenzene, polystyrene-polymethyl methacrylate; the mixture may also be a mixture of six materials, for example a mixture of polytetrafluoroethylene, polyethylene, polystyrene, styrene-divinylbenzene, polymethyl methacrylate and polypropylene.
Because the hydrophobic porous material does not contain hydrophilic groups, the hydrophobic porous material is attached to the surface of the carbon-supported catalyst, so that the hydrophobicity of the catalyst is improved, and the probability of water poisoning of the catalyst is reduced. While it is desirable to prevent excessive hydrophobic porous materials from wrapping around the active sites of the carbon-supported catalyst, resulting in a decrease in catalyst activity. Within this mass ratio range, the hydrophobicity of the carbon-supported catalyst is greatly improved without affecting the activity thereof.
Preferably, in step 3), the hydrophobic porous material is polytetrafluoroethylene, the mass percentage of the carbon-supported catalyst to the polytetrafluoroethylene is (95-65%) (5-35%), for example, the mass percentage of the carbon-supported catalyst to the polytetrafluoroethylene is 95:5, 90:10, 85:15, 80:20, 75:25, 70:30, 65:35, the drying temperature is 60-90 ℃, the drying temperature is 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃.
The catalyst for decomposing formaldehyde can be applied to an air purifier and an adsorption concentration tower, and can remarkably and rapidly reduce the concentration of formaldehyde.
Compared with the prior art, the invention has the beneficial effects that:
(1) The catalyst for decomposing formaldehyde has high moisture resistance and high adsorptivity, the moisture resistance of the catalyst is obviously improved by carrying out hydrophobic treatment on the catalyst, the possibility of water poisoning of the catalyst is greatly reduced, the formaldehyde adsorption and decomposition amount is improved, the hydrophobic angle of the prepared catalyst is 150 degrees, the dispersity of metal platinum is up to 31 percent, the dispersity of metal palladium is up to 28 percent, the formaldehyde conversion rate is up to 99 percent, and the CO2 selectivity is up to 92 percent under the conditions of room temperature of 25 ℃ and humidity of 85 percent.
(2) The catalyst for decomposing formaldehyde can decompose formaldehyde gas at room temperature, so that the activated carbon saturated in adsorption is regenerated, and the original adsorption strength can be recovered after the catalyst is placed for 12 hours.
(3) In the preparation method of the catalyst for decomposing formaldehyde, when noble metals platinum and palladium are loaded, the dispersion degree of the platinum precursor and the palladium precursor in the active carbon micropores is higher by vacuumizing treatment, so that the overall catalytic capacity of the catalyst is improved, the dipping treatment time is obviously shortened, and the production efficiency of the catalyst is improved.
(4) The preparation method of the catalyst for decomposing formaldehyde has the advantages of simple preparation process, low content of noble metals such as platinum and palladium, and load capacity of only 0.02-0.3 wt% of the mass of the catalyst, thereby greatly reducing the cost.
Drawings
FIG. 1 is a schematic structural view of a catalyst for decomposing formaldehyde according to the present invention,
FIG. 2 is a scanning electron microscope image of the activated carbon of example 1 of the present invention without the hydrophobic porous material layer,
FIG. 3 is a scanning electron microscope image of a formaldehyde decomposing catalyst prepared in example 1 of the present invention.
The reference numerals are as follows:
1-activated carbon; a layer of 2-hydrophobic porous material; 3-microwells; 4-noble metal palladium; 5-noble metal platinum.
Detailed Description
The following is a description of the technical scheme of the present invention with reference to fig. 1, 2 and 3.
As shown in figure 1, the carrier of the catalyst is active carbon 1, the surface of the active carbon 1 is wrapped with a hydrophobic porous material layer 2, noble metal platinum 5 and noble metal palladium 4 are adsorbed on the surface of the active carbon 1 contacted with the hydrophobic porous material layer 2, and noble metal platinum 5 and noble metal palladium 4 are filled in micropores 3 of the active carbon 1.
Wherein the specific surface area of the activated carbon is 1000-4000 m 3 Per gram, e.g. the activated carbon has a specific surface area of 1000m 3 /g、1500m 3 /g、2000m 3 /g、2500m 3 /g、3000m 3 /g、3500m 3 /g、4000m 3 /g。
Preferably, the specific surface area of the activated carbon is 2000-3000 m 3 Per gram, e.g. the activated carbon has a specific surface area of 2000m 3 /g、2100m 3 /g、2200m 3 /g、2300m 3 /g、2400m 3 /g、2500m 3 /g、2600m 3 /g、2700m 3 /g、2800m 3 /g、2900m 3 /g、3000m 3 /g。
Wherein the activated carbon of the present invention has a micropore volume fraction of 80% to 95%, for example, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%.
Further, the activated carbon has a micropore volume fraction of 85% to 90%, such as 85%, 86%, 87%, 88%, 89%, 90%.
The filling rate of the micropores of the activated carbon is 40-70%, namely, the filling rate of the micropores of the activated carbon filled with noble metal is 40%, 45%, 50%, 55%, 60%, 65% and 70%.
The average inner diameter of the micropores of the activated carbon is 5 to 15 μm, for example, the average inner diameter of the micropores of the activated carbon is 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm.
Preferably, the thickness of the hydrophobic porous material layer is 1-5 mm, for example, the thickness of the hydrophobic porous material layer is 1mm, 2mm, 3mm, 4mm, 5mm.
More preferably, the pore size of the hydrophobic porous material layer is 1 to 10nm, for example, the pore size of the hydrophobic porous material layer is 1nm, 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm.
Further, the hydrophobic porous material layer of the present invention is a polytetrafluoroethylene layer.
The catalyst for decomposing formaldehyde comprises active carbon as a carrier, platinum and palladium as active components supported on the carrier, and a hydrophobic component which is a hydrophobic porous material layer coated on the surface of the catalyst, wherein the platinum loading is 0.02-0.3 wt% and the palladium loading is 0.02-0.3 wt%.
The catalyst for decomposing formaldehyde is prepared by the following steps:
1) Preparation of activated carbon matrix: crushing, drying, carbonizing, activating, cleaning and drying the organic material rich in carbon to obtain the activated carbon with high specific surface area and high adsorptivity;
2) Preparation of carbon-supported catalyst: vacuumizing the activated carbon matrix obtained in the step 1), immersing the activated carbon matrix in a dimethylformamide solution containing a platinum precursor and a palladium precursor, adding a binder, extruding and molding, drying, and then introducing hydrogen for reduction treatment to obtain the carbon-supported catalyst;
3) Hydrophobing treatment of carbon-supported catalyst: and (3) uniformly mixing the carbon-supported catalyst obtained in the step (2) with the hydrophobic porous material in ethanol, and drying to obtain the catalyst for decomposing formaldehyde.
Example 1
Step 1), collecting enough coconut shells, cleaning, crushing by using a ball mill, and drying to obtain a dry material;
step 2), carbonization: placing the dry material in a muffle furnace, and baking for 4 hours in a nitrogen atmosphere at 400 ℃;
step 3), activating: adding an activator KOH, wherein the mass ratio of KOH to C is 1:5, and activating for 3 hours at 700 ℃;
step 4), washing the generated activated carbon with acid, washing the activated carbon with water to remove impurities, and drying the activated carbon at 80 ℃;
and 5) weighing 100g of the coconut shell activated carbon generated in the previous step. At the relative pressure difference of-0.08 MPa and the operation temperature of 80 ℃, the active carbon is immersed in the dimethylformamide solution of chloroplatinic acid and chloropalladac acid, and phenolic resin is added as a binder. Wherein the weight percentage concentration of noble metal in the solution is 0.3%, the weight percentage concentration ratio of platinum and palladium in the solution is 1:2, and the mass ratio of phenolic resin to carbon is 1:3;
and 6) carrying out reduction treatment on the sample obtained in the last step for 3 hours at the operating temperature of 400 ℃ in a 10% hydrogen atmosphere to obtain the carbon-supported catalyst. The loading of Pt was 0.1wt% and the loading of Pd was 0.2wt% as measured by ICP-MS.
Step 7), mixing the sample obtained in the previous step with PTFE in ethanol in a mass percentage of 95%:5% of the catalyst was mixed at an operating temperature of 70 ℃.
And 8) physically characterizing the coconut shell activated carbon obtained in the step 5, tabletting, crushing and sieving the sample obtained in the step 7, and then taking the catalyst with 80-100 meshes for activity evaluation.
The scanned picture of the formaldehyde decomposing catalyst prepared in example 1 is shown in fig. 3, fig. 2 is a scanned picture of activated carbon without a hydrophobic porous material layer, and it can be seen from fig. 3 that the outer surface of activated carbon 1 is coated with a hydrophobic porous material layer 2. Experimental results show that the specific surface area of the coconut shell activated carbon is 2841m 3 And/g, the micropore volume is 90%. Under the conditions of room temperature of 25 ℃ and humidity of 85%, the final product catalyst has a hydrophobic angle of 150 ℃, the dispersity of metal platinum of 31%, the dispersity of metal palladium of 28%, the formaldehyde conversion of 99% and CO 2 The selectivity was 92% with partial CO formation and the deactivation parameter was 0.4%.
Example 2
Step 1) the procedure was as in example 1, and the carbon-supported catalyst was made into a honeycomb module having dimensions 105X 35X 10mm.
Step 2), 1m 3 In the glass sealing space, 1-2 drops of formaldehyde solution are dripped into the glass test tube, the electric heating is carried out until the formaldehyde solution is completely volatilized, the formaldehyde content in the sealing space is 1.8-2.8 ppm, and the environmental temperature is 26-28 ℃.
Step 3), two honeycomb modules are taken and placed in a glass sealed space, and the ventilation quantity is 5-10m 3 /min。
After 20-30 minutes, the formaldehyde concentration in the space is removed by 99 percent, and the concentration is reduced to below 0.1 ppm. The continuous test of steps 2 and 3 is repeated, the total content of the catalyst can be reduced to 0.1ppm within one week, and the catalyst can still be reduced to about 0.2ppm after 2-3 months of operation, namely, the conversion rate is kept to be 90%.
Example 3
The preparation process is the same as in example 1, 0.5kg of the obtained catalyst is applied to an air purifier, and the flow rate of a fan is 1000m 3 Formaldehyde clean air output ratio (CADR)>400 CCM is F4 grade, reaching the industry leading level.
The preparation method of the catalyst for decomposing formaldehyde is simple, and the prepared catalyst has the advantages of low cost, high moisture resistance, high adsorptivity, high activity and long service life, can be used for adsorbing and decomposing formaldehyde gas at room temperature, can be applied to an air purifier and an adsorption concentration tower, and can remarkably and rapidly reduce the formaldehyde concentration.
The detailed process equipment and process flow of the present invention are described by the above embodiments, but the present invention is not limited to, i.e., it does not mean that the present invention must be practiced depending on the detailed process equipment and process flow. It should be apparent to those skilled in the art that any modification of the present invention, equivalent substitution of raw materials for the product of the present invention, addition of auxiliary components, selection of specific modes, etc., falls within the scope of the present invention and the scope of disclosure.
Claims (5)
1. The preparation method of the catalyst for decomposing formaldehyde is characterized by comprising the following steps of:
1) Preparation of activated carbon matrix: crushing, drying, carbonizing, activating, cleaning and drying the organic material rich in carbon to obtain the activated carbon with high specific surface area and high adsorptivity;
2) Preparation of carbon-supported catalyst: vacuumizing the activated carbon matrix obtained in the step 1), immersing the activated carbon matrix in a dimethylformamide solution containing a platinum precursor and a palladium precursor, adding a binder, performing extrusion molding, drying, and then introducing hydrogen for reduction treatment to obtain an extruded carbon-supported catalyst;
3) Hydrophobing treatment of carbon-supported catalyst: uniformly mixing the extruded carbon-supported catalyst obtained in the step 2) with a hydrophobic porous material in ethanol, and drying to obtain a monolithic formaldehyde decomposing catalyst;
the catalyst prepared by the preparation method is characterized in that the carrier of the catalyst is activated carbon, the active components of the catalyst are platinum and palladium loaded on the carrier, the catalyst further comprises a hydrophobic component, the hydrophobic component is a hydrophobic porous material layer coated on the outer surface of the carbon-loaded catalyst after extrusion molding, wherein the loading amount of the platinum is 0.02-0.3 wt% and the loading amount of the palladium is 0.02-0.3 wt%;
in the step 1), the organic material rich in carbon is one or a mixture of at least two of phosphor wood, fruit shell, coconut shell, walnut shell, jujube shell and apricot shell; the carbonization is carried out in a muffle furnace, the atmosphere of the carbonization is nitrogen, the temperature of the carbonization is 300-600 ℃, and the time of the carbonization is 1-5 hours; the activation adopts chemical activation, the activating agent is potassium hydroxide, the mass ratio of the activating agent to the activated carbon is 1 (3-7), the activating temperature is 600-900 ℃, and the activating time is 1-5 h; the specific surface area of the activated carbon matrix obtained in the step 1) is 1000-4000 m 3 Per gram, the micropore volume percentage is 80-95%;
in the step 2), the platinum-containing precursor is one or a mixture of at least two of platinum nitrate, chloroplatinic acid, platinum acetylacetonate and hexahydroxyplatinate di (ammonium ethoxide); the palladium-containing precursor is chloropalladac acid and/or palladium acetate; the total weight of platinum and palladium in the dimethylformamide solution containing the platinum precursor and the palladium precursor accounts for 0.1-0.3 percent of the weight of the solution, and the mass ratio of platinum and palladium in the solution is 1 (2-3); the binder is phenolic resin, and the mass ratio of the phenolic resin to the activated carbon is 1 (2-5); the hydrogen content in the reducing atmosphere of the reducing treatment is 5-15%, the temperature of the reducing treatment is 300-500 ℃, and the time of the reducing treatment is 2-4 h;
in the step 3), the hydrophobic porous material is one or a mixture of at least two of polytetrafluoroethylene, polyethylene, polystyrene, styrene-divinylbenzene, polymethyl methacrylate and polypropylene; the mass percentage of the carbon-supported catalyst and the hydrophobic porous material is (95-65%) and (5-35%), and the drying temperature is 60-90 ℃.
2. The method according to claim 1, wherein in step 1), the pulverization is carried out by a ball mill.
3. The method according to claim 1, wherein in step 1), the carbonization temperature is 400 to 500 ℃ and the carbonization time is 3 to 4 hours.
4. The method according to claim 1, wherein in the step 2), the relative pressure difference of the vacuuming treatment is-0.1 to 0MPa.
5. The method according to claim 1, wherein in the step 2), the relative pressure difference of the vacuuming treatment is-0.08 to-0.05 MPa.
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| CN109395741A (en) * | 2018-11-22 | 2019-03-01 | 杭州艾驰凯环保科技有限公司 | A kind of catalyst and preparation method thereof of room temperature fast degradation formaldehyde in air |
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| CN114471541A (en) * | 2022-03-02 | 2022-05-13 | 中科鸿景(宁波)环保科技有限公司 | Indoor formaldehyde adsorption and catalysis spray and preparation method thereof |
| CN114618480A (en) * | 2022-04-08 | 2022-06-14 | 南京大学 | Composite catalyst and preparation method and application thereof |
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