CN113318719A

CN113318719A - Photocatalytic unit and application thereof

Info

Publication number: CN113318719A
Application number: CN202010130245.1A
Authority: CN
Inventors: 赵杰; 张皓
Original assignee: Guangdong Yuenengjing Environmental Protection Technology Co ltd
Current assignee: Guangdong Yuenengjing Environmental Protection Technology Co ltd
Priority date: 2020-02-28
Filing date: 2020-02-28
Publication date: 2021-08-31
Anticipated expiration: 2040-02-28
Also published as: CN113318719B

Abstract

The invention discloses a photocatalytic unit and application thereof. The photocatalytic unit comprises a photocatalyst and an ultraviolet light source device, wherein the photocatalyst comprises a honeycomb ceramic carrier, a modifier and an active component, the modifier and the active component are sequentially loaded on the honeycomb ceramic carrier, the modifier is alumina-titanium dioxide, and the active component is titanium dioxide. The photocatalytic unit is particularly suitable for carrying out photocatalytic reaction on gas to be purified containing organic matters, and has the characteristics of high catalytic activity and good stability.

Description

Photocatalytic unit and application thereof

Technical Field

The invention relates to a photocatalytic unit and application thereof, belonging to the field of photocatalytic materials.

Background

Semiconductor photocatalytic oxidation is a novel technology that can decompose organic substances into carbon dioxide and water through photocatalysis at normal temperature and normal pressure, and does not cause secondary pollution, and thus has attracted great attention from researchers in various countries in the world. Researches show that various organic pollutants in water and air can be effectively degraded by utilizing a semiconductor photocatalysis method, such as halogenated hydrocarbon, nitroaromatic, phenol, organic pigment, pesticide, surfactant and the like; cyanide, nitrite, thiocyanate and the like can also be converted into non-toxic or low-toxic compounds; can also be applied to the fields of antibiosis, deodorization, air purification, self-cleaning materials and the like. The semiconductor photocatalysts which have been studied so far mainly include metal oxides, sulfides and the like, among which titanium dioxide (TiO)₂) Has the characteristics of good chemical stability, safety, no toxicity, low cost and the like, and is widely researched and applied in the direction of photocatalytic oxidation.

The titanium dioxide photocatalyst is generally used in the form of powder, but this causes a suspension system in a fluid, thereby causing technical problems of difficulty in separation and difficulty in recovery, and thus limiting practical use. The titanium dioxide is fixed on the carrier, so that the defect of the suspension phase titanium dioxide photocatalyst can be overcome. Therefore, finding a suitable carrier and an efficient loading method to fix the catalyst and improve the photocatalytic efficiency of the catalyst are key points in realizing the industrialization of the titanium dioxide photocatalyst, and are hot spots in the research field of the photocatalytic technology in recent years.

At present, the technical problems of the supported photocatalyst are as follows: first, the use of non-catalytic materials such as binders can affect the amount of titanium dioxide on the surface during loading and sintering, thereby affecting catalytic activity; secondly, when titanium dioxide is loaded on a carrier such as ceramic, high-temperature roasting is generally adopted to increase the firmness of titanium dioxide loading, but titanium dioxide is easy to be sintered and generates a crystal phase with non-photocatalytic activity, so that the catalytic activity is influenced, and the problem that titanium dioxide is easy to run off even if the titanium dioxide is roasted at high temperature, so that the activity stability of the catalyst is influenced; thirdly, when the titanium dioxide is loaded on the carrier such as ceramic, the problem of uneven distribution is easy to occur, thereby further influencing the catalytic activity and stability of the carrier.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention provides a photocatalytic unit and application thereof. The catalytic unit is used for the photocatalytic reaction of gas to be purified containing organic matters and has the characteristics of high photocatalytic activity and good stability.

The present invention provides, in a first aspect, a photocatalytic unit comprising:

the photocatalyst comprises a honeycomb ceramic carrier, a modifier and an active component, wherein the modifier and the active component are sequentially loaded on the honeycomb ceramic carrier, the modifier is alumina-titanium dioxide, and the active component is titanium dioxide;

an ultraviolet light source device having a light emitting portion facing a photocatalyst.

In the photocatalyst, the honeycomb ceramic carrier has the water absorption (by volume) of 10-25%, the heat conductivity coefficient of 1.0-2.0W/(M.K), and the density (20 ℃) of 0.75-1.2 g/cm³。

In the photocatalyst of the present invention, the shape and size of the honeycomb ceramic carrier may be adjusted as needed, and may be, for example, a plate shape.

In the photocatalyst, the compressive strength of the honeycomb ceramic carrier is measured on the square column plate-shaped honeycomb ceramic with the size of 150mm multiplied by 10mm, the axial compressive strength is more than 35MPa, and the radial compressive strength is more than 9 MPa.

In the photocatalyst, the shape of the honeycomb through holes in the honeycomb ceramic carrier is not particularly limited, for example, the cross section can be in a conventional shape such as a triangle, a square, a hexagon and the like, and can also be in other regular shapes, the aperture of the honeycomb through holes is 1-6 mm, preferably 1-4 mm, the outer wall thickness is 0.6-2.9 mm, the inner wall thickness is 0.3-2.3 mm, and the area of the through holes on the cross section accounts for 50% -70%. The outer wall thickness refers to the distance between the axial outer surface of the honeycomb ceramic carrier and the outermost layer through hole, and the inner wall thickness refers to the distance between two adjacent through holes of the honeycomb ceramic carrier. Generally, the outer wall is thicker than the inner wall, which is beneficial for increasing the mechanical strength of the catalyst.

In the photocatalyst of the invention, the honeycomb ceramic carrier has the following pore distribution: the pore volume occupied by the pore channels with the pore diameter of 2-5 μm is more than 70% of the pore volume occupied by the pore channels with the pore diameter of less than 100 μm. The pore distribution is measured by mercury intrusion method.

In the photocatalyst, the content of titanium dioxide in the modifier is 10-23%.

In the photocatalyst, the weight of the catalyst is taken as a reference, the content of the honeycomb ceramic carrier is 72-96%, the content of the modifier is 1-10%, and the content of the active component is 3-18%. Preferably, based on the weight of the catalyst, the content of the honeycomb ceramic carrier is 77-93%, the content of the modifier is 2-8%, and the content of the active component is 5-15%.

In the photocatalyst, titanium dioxide crystal grains are dispersed on the surface of the catalyst in an embedded manner; the titanium dioxide crystal grains on the outer surface of the catalyst account for more than 70% of the titanium dioxide crystal grains with the grain size of 5-150 mu m, and further account for more than 70% of the titanium dioxide crystal grains with the grain size of 5-100 mu m.

In the photocatalyst of the present invention, the honeycomb ceramic may be cordierite honeycomb ceramic.

In the photocatalyst of the present invention, the titanium dioxide is mainly in the anatase form.

The preparation method of the photocatalyst comprises the following steps:

(1) spraying and soaking mixed slurry of titanium dioxide and alumina on a honeycomb ceramic carrier, and drying and roasting to obtain a modifier-loaded honeycomb ceramic carrier;

(2) preparing titanium sol;

(3) immersing the honeycomb ceramic carrier loaded with the modifier obtained in the step (1) into the titanium sol obtained in the step (2) for slurry coating, removing excessive slurry, drying,

(4) repeating the process of the step (3) for 0-5 times, preferably 1-4 times;

(5) and (4) carrying out heat treatment on the material obtained in the step (4) to obtain the photocatalyst.

In the method of the present invention, the honeycomb ceramic in step (1) may be cordierite honeycomb ceramic, and the preferred pore distribution properties are as follows: the pore volume occupied by the pore channels with the pore diameter of 2-5 microns accounts for more than 70% of the pore volume occupied by the pore channels with the pore diameter of less than 100 microns. The pore distribution was measured by mercury intrusion.

In the method of the invention, the mixed slurry of titanium dioxide and alumina in step (1) comprises nano titanium dioxide, pseudo-boehmite, an acidic peptizing agent and water, and preferably polyethylene glycol is added, wherein the weight ratio of the nano titanium dioxide to the pseudo-boehmite (calculated by alumina), the acidic peptizing agent to the water is 15: 2-4: 1-3: 12-25, wherein the addition amount of the polyethylene glycol accounts for 1-5% of the weight of the mixed slurry of the titanium dioxide and the alumina. The molecular weight of the polyethylene glycol is 200-4000. The particle size of the nano titanium oxide is less than 100nm, and preferably 10-100 nm. The acidic peptizing agent can adopt one or more of inorganic acid, such as nitric acid and hydrochloric acid. The pseudoboehmite is peptizable pseudoboehmite and can be prepared by a conventional neutralization method, an alcoholysis method and the like.

The preferable preparation method of the titanium dioxide and alumina mixed slurry in the step (1) is that the nano titanium dioxide is mixed with the polyethylene glycol, and then the mixture is mixed with the pseudo-boehmite, the acid peptizing agent and the water, so that at least part of the polyethylene glycol enters the nano titanium dioxide, more surfaces of the nano titanium dioxide are exposed outside the carrier in the subsequent treatment process, and an easily enriched area is formed, and the post-loaded titanium dioxide is more easily distributed around the nano titanium dioxide, thereby not only improving the dispersibility and the dispersion amount of the titanium dioxide on the surface of the carrier, but also better controlling the size of titanium dioxide grains, increasing the firmness of the titanium dioxide in the catalyst and further improving the activity and the stability of the catalyst.

In the method of the present invention, the spray soaking in step (1) is preferably an unsaturated spray soaking method, and the absorption rate is 50% to 90%, preferably 60% to 80%, based on the volume of saturated water absorption. The drying is carried out at 50-95 ℃ for 2-24 hours. The roasting is carried out at low temperature under oxygen-containing atmosphere, namely roasting for 2-8 hours at 200-300 ℃, then roasting for 1-6 hours at 400-750 ℃, preferably roasting for 2-8 hours at 200-300 ℃, and roasting for 1-5 hours at 400-700 ℃.

In the method of the present invention, the titanium sol prepared in step (2) may be prepared by the following method: dissolving the titanium dioxide precursor in an organic solvent, and uniformly mixing to obtain the titanium sol. The titanium dioxide precursor may be titanium (IV) acetylacetonate.

In the step (2) of the method, carboxymethyl cellulose is preferably added in the mixing process, and the molar ratio of the addition amount of the carboxymethyl cellulose to titanium atoms is 1-7: 100.

in step (2) of the method of the present invention, the organic solvent may be a lower alcohol, such as an alcohol having a carbon number of from 1 to 5, preferably one or more of methanol, ethanol, and propanol, and more preferably isopropanol. The molar concentration of titanium in the titanium sol is 0.5-4.0 mol/L.

In the method of the present invention, the slurry coating and the removal of excess slurry in the step (3) can be performed by a conventional method, for example, slurry coating by an immersion method, or excess slurry can be removed by atmospheric pressure immersion, preferably vacuum immersion, and extrusion by a roll pressing method.

In the method, the drying in the step (3) is carried out for 2-24 hours at the temperature of 50-95 ℃.

In the method of the present invention, the heat treatment conditions in step (5) are as follows: roasting in a steam and/or inert atmosphere in a segmented mode, namely roasting for 2-8 hours at 200-300 ℃, then roasting for 1-6 hours at 400-750 ℃, preferably roasting for 2-8 hours at 200-300 ℃, and roasting for 1-5 hours at 400-700 ℃. The inert atmosphere may be nitrogen.

In the method of the invention, the content of the modifier (calculated by alumina and titanium dioxide) introduced to the catalyst by the mixed slurry of titanium dioxide and alumina is 1-10% of the total weight of the catalyst, preferably 2-8%.

In the method of the invention, the content of the active component titanium dioxide introduced to the catalyst by titanium sol accounts for 3-18 percent of the total weight of the catalyst, and preferably 5-15 percent.

The photocatalyst adopts a photocatalyst plate, the ultraviolet light source device adopts an ultraviolet LED lamp plate, and one or two surfaces of the photocatalyst plate are provided with the ultraviolet LED lamp plates. Further, ultraviolet LED lamp plate sets up in the both sides of photocatalyst board symmetrically. The photocatalyst plate and the ultraviolet LED lamp panel are arranged in parallel.

In the ultraviolet light source device, the ultraviolet LED lamp panel comprises a substrate and a plurality of LED ultraviolet light-emitting particles arranged on the substrate, namely a Uv-LED point light source.

In the ultraviolet light source device, the LED ultraviolet light-emitting particles on the ultraviolet LED lamp panel can be arranged in an array form, the vent holes can be arranged between the adjacent arrays, or the vent holes are not arranged, namely, the non-porous entities are arranged between the adjacent arrays, and the arrangement is determined according to the use condition.

The substrate can be in a fence type, namely LED ultraviolet light-emitting particles which can be arranged in an array mode are arranged on the fence strips, and vent holes are formed among the fence strips. The ultraviolet LED lamp plate can set up the LED lamp simultaneously, also can both sides set up the LED lamp.

In the photocatalysis unit, N photocatalyst boards are arranged, ultraviolet LED lamp panels are arranged on two sides of each photocatalyst board and are arranged in parallel, wherein N is an integer larger than or equal to 1. The ultraviolet LED lamp panels arranged between the two adjacent photocatalyst boards are back to back and arranged on the two ultraviolet LED lamp panels of the single-sided LED lamp, and one ultraviolet LED lamp panel of the double-sided LED lamp can be selected.

The photocatalytic unit also comprises a fixing frame for fixing the photocatalyst plate and the ultraviolet LED lamp plate.

The second aspect of the present invention provides a photocatalytic method, which may adopt the photocatalytic unit provided in the first aspect, and the gas to be purified passes through the photocatalytic unit to undergo a photocatalytic reaction under the action of ultraviolet light and a catalyst, so as to obtain the purified gas.

In the photocatalysis method of the invention, the air inlet direction of the gas to be purified can be adjusted according to the requirement, and the air can be vertically fed, obliquely fed and the like.

In the photocatalysis method of the invention, N photocatalysis units can be adopted, and the N photocatalysis units can be arranged in parallel or in series. The plurality of photocatalytic units can be arranged in a flat plate shape or in a V shape. The arrangement modes of the N photocatalytic units can be the same or different.

In the photocatalysis method, the wavelength of ultraviolet light emitted by the ultraviolet LED lamp is 280-390 nm, which can be a single wavelength or a mixed wavelength, and is preferably a single wavelength, such as 365 nm.

In the photocatalysis method, the distance between the ultraviolet LED lamp panel and the photocatalyst plate is 0-10 cm. Further, the thickness is 0 to 5cm, preferably 0.5 to 3.5 cm. Further, the thickness of the photocatalyst plate can be 0.3-3.0 cm.

In the photocatalysis method, the radiation intensity on the photocatalyst plate is 0.01-500 mW/cm²Preferably 0.5-70 mW/cm²。

In the photocatalysis method of the invention, the gas to be purified is the gas containing volatile organic pollutants and/or sulfur and nitrogen-containing gas, such as indoor air, industrial gas and the like. The gas to be purified may also contain microorganisms, such as bacteria and the like.

The photocatalysis unit can remove various Volatile Organic Compounds (VOC) such as toluene, xylene, benzene, formaldehyde and homologues thereof, can also remove various gases containing sulfur and nitrogen such as sulfur dioxide, hydrogen sulfide, ammonia and the like, and can also play a role in sterilization and disinfection. The photocatalytic unit can be used for purifying indoor air, industrial polluted gas and haze pollutants, and has good photocatalytic degradation performance, stable catalyst performance and good application prospect.

The photocatalytic unit can be applied to the existing electric equipment, such as an air purifier, a refrigerator, an air conditioner and the like, can also be applied to pipelines with gas flowing, such as exhaust air, ventilation equipment, tail gas emission equipment, ventilation equipment and the like, can also be applied to transportation tools, such as automobiles, cruise ships, submarines, airplanes, subways, trains and the like, and can also be applied to furniture, office equipment or vehicle-mounted equipment, such as office desks, clamping seats, screens and the like, laboratory operation desks, ventilation cabinets, reagent cabinets and the like, hospital diagnosis and treatment desks, hospital purification isolation desks, isolation sickbeds, isolation chairs and the like, vehicle-mounted multifunctional purification armrest boxes and the like.

Compared with the prior art, the photocatalysis unit has the following advantages:

1. the photocatalyst unit of the invention adopts a specific photocatalyst which adopts a honeycomb ceramic carrier, and the alumina-titanium dioxide modifier and the active component are loaded on the honeycomb ceramic carrier in sequence, so that the catalyst of the invention not only has good adsorption performance and mechanical strength, but also has the advantages of difficult loss of titanium dioxide, higher photocatalytic reaction activity and stability.

2. For a unit number of titanium dioxide crystal grains, the smaller the crystal grains, the larger the specific surface area, the higher the catalytic activity, while the smaller the crystal grains, the less easy to load, and even if the load is carried, the leaching or the covering by the inactive component is liable to occur, thereby affecting the activity and stability of the catalyst.

The inventor finds that titanium dioxide crystal grains are distributed on the surface of the catalyst in an embedded mode in a proper micron-sized mode, titanium dioxide in a high-activity phase is formed, organic matters are decomposed under the ultraviolet light catalysis effect, and the catalyst has better activity.

3. In the preparation method of the photocatalyst used in the invention, honeycomb ceramics is adopted as a carrier, then an alumina-titanium dioxide modifier is loaded, the alumina-titanium dioxide modifier is baked at a low temperature, and then when titanium sol is subsequently utilized to load titanium dioxide, the low-temperature baking is adopted, so that the growth and aggregation of titanium dioxide grains are easily carried out on the basis of the titanium dioxide in the modifier, micron-sized grains with uniformly distributed and high-activity phases are formed, the micron-sized grains are embedded into the catalyst, the firmness of the titanium dioxide can be improved, and the stability of the photocatalyst is improved.

4. In the preparation method of the photocatalyst used in the invention, the heat treatment preferably adopts water vapor and/or inert gas sectional heat treatment, promotes the growth of proper titanium dioxide grains, improves the dispersion degree of the titanium dioxide grains on the surface of the carrier, improves the size of the non-embedded part of the titanium dioxide grains, increases the contact area of liquid or gas and the photocatalyst, and simultaneously enables the liquid or gas to rapidly pass through the photocatalyst, thereby improving the treatment efficiency.

Drawings

FIG. 1 is an external view of a photocatalyst A of the present invention;

FIG. 2 is an enlarged view of the photocatalyst A of the present invention;

FIG. 3 is an enlarged cross-sectional view of a photocatalyst according to the present invention; wherein, 1-titanium dioxide crystal grain, 2-photocatalyst;

fig. 4 is a schematic view of an ultraviolet LED lamp panel according to an embodiment of the present invention, wherein the lamp panel includes a 3-ultraviolet LED lamp panel, a 31-substrate, 32-LED ultraviolet light emitting particles, and 33-ventilation holes;

FIG. 5 is a schematic view of a photocatalytic unit according to an embodiment of the present invention; the LED light source comprises 4-a photocatalytic unit, 3-an ultraviolet LED lamp panel, 5-a photocatalyst plate and 6-a fixed frame;

FIG. 6 is a schematic view of a device for testing the performance of a photocatalytic unit of the catalyst of the present invention; wherein, 4-the photocatalytic unit, 7-the wind channel.

Detailed Description

The technical solution of the present invention is described in detail below with reference to the accompanying drawings and examples, but the examples do not limit the scope of the present invention. In the present invention, wt% is a mass fraction.

In the invention, the crystal form of titanium dioxide is measured by an XRD method, the instrument is a Rigaku D/max-2500X-ray diffractometer, a Cu target (0.15406nm) is adopted, graphite single crystal filtering is adopted, the operating tube voltage is 40kV, the tube current is 30mA, the scanning step length is 0.026 degrees, and the scanning range is 5-70 degrees.

In the invention, on the surface of the catalyst, the size and the crystal grain distribution of titanium dioxide crystal grains are measured by taking a picture by using an optical microscope and a come card fluorescence microscope/binocular 50-1000X.

The ultraviolet LED lamp panel and the photocatalytic unit in the present invention will be described in detail with reference to fig. 4 and 5.

As shown in fig. 4, the ultraviolet LED lamp panel 3 includes a substrate 31 and a plurality of ultraviolet LED light emitting particles 32 disposed on the substrate 31, and the substrate 31 is further provided with a vent 33. The shape of the lamp panel 3 may be square, and as an alternative embodiment, may also be square, circular, oval or other shapes. The shape of the vent hole 33 is rectangular. As an alternative embodiment, it may also be square, circular, oval or another shape. It should be understood that the shapes of the ultraviolet LED lamp panel 3 and the ventilation holes 33 can be determined by those skilled in the art according to the needs, the use place, the ventilation requirements, and the like, and the invention is not limited thereto. The ultraviolet LED luminescent particles 32 are arranged in an array on the substrate, with vents 33 between adjacent arrays. The substrate 31 is in a fence type, that is, the fence is provided with LED ultraviolet light emitting particles arranged in an array manner, and the ventilation holes 33 are formed between the fence. The number of the ultraviolet LED luminescent particles 32 can be adjusted according to the illumination intensity required by the photocatalyst.

As shown in fig. 5, the photocatalytic unit 4 includes an ultraviolet LED lamp panel 3, a photocatalyst panel 5, and a fixing frame 6. Wherein, two ultraviolet LED lamp panels 3 are respectively arranged on two sides of the photocatalyst plate 5 in parallel, and the photocatalyst plate 5 and the ultraviolet LED lamp panels 3 are fixed by adopting a fixing frame 6 to form a photocatalytic unit 4.

In the examples of the present invention and the comparative examples, the preparation process of the titanium sol was as follows: adding titanium (IV) acetylacetonate solid powder and carboxymethyl cellulose into isopropanol, and uniformly mixing to obtain a titanium sol with the titanium molar concentration of 3mol/L, wherein the molar ratio of the addition amount of the carboxymethyl cellulose to titanium atoms is 3: 100.

in the examples and comparative examples of the present invention, the cordierite honeycomb ceramic was a square plate of 150mm × 150mm × 10mm, the cross section of the honeycomb through-holes was square with a side length of about 2mm, the outer wall thickness was about 1mm, the inner wall thickness was about 0.5mm, the honeycomb through-holes were uniformly distributed, the area of the through-holes on the cross section was about 60%, the pore volume occupied by the cell channels with a pore diameter of 2 to 5 μ M was 75% of the pore volume occupied by the cell channels with a pore diameter of 100 μ M or less (the pore distribution was measured by mercury intrusion method), the water absorption (by volume) was 15%, the thermal conductivity was 1.5W/(M × K), and the density (20 ℃) was 1.05g/cm³The axial compressive strength is more than 35MPa, and the radial compressive strength is more than 9 MPa.

Example 1

Mixing nanometer titanium dioxide (particle diameter below 100nm, the same below) with polyethylene glycol (molecular weight 600), and mixing with pseudo-boehmite, nitric acid and water, wherein the weight ratio of the nanometer titanium dioxide to the pseudo-boehmite (calculated by alumina), the nitric acid to the water is 15: 3: 2: 15, mixing, wherein the adding amount of polyethylene glycol is 3 percent of the weight of the mixed slurry of titanium oxide and alumina, and obtaining the mixed slurry of titanium dioxide and alumina;

spraying and soaking mixed slurry of titanium dioxide and alumina on cordierite honeycomb ceramic, carrying out unsaturated spray soaking according to 70% of absorption rate, then drying for 4 hours at 65 ℃, roasting for 3 hours at 250 ℃, and roasting for 3 hours at 600 ℃ to obtain a honeycomb ceramic carrier A loaded with a modifier;

soaking the honeycomb ceramic carrier A loaded with the modifier into titanium sol for vacuum dipping and slurry hanging, removing excessive slurry, then drying for 4 hours at 65 ℃, and repeating the step for 1 time; then, in the presence of water vapor and nitrogen, the photocatalyst A is obtained by sectional roasting, namely roasting at 250 ℃ for 3 hours and then at 650 ℃ for 3 hours. In the catalyst A, the content of the modifier (calculated by alumina and titania) introduced onto the catalyst by the mixed slurry of titania and alumina was 3%, and the mass content of titania, which is an active component introduced onto the catalyst by a titanium sol, was 5.0%.

In the obtained catalyst A, the titanium dioxide is mainly anatase as measured by XRD.

Measuring the titanium dioxide crystal grains on the surface of the prepared catalyst by using a microscope, and obtaining the size of the titanium dioxide crystal grains by using a statistical method, wherein the representative catalyst surface is selected, and the statistical area is about 90000 mu m²The statistical total number of titanium dioxide grains exceeds 100. It was found that the particle size of 5 to 100 μm on the surface of the catalyst A was about 92%.

When the cross section of the catalyst is observed by a microscope, the titanium dioxide crystal grains 1 are partially embedded in the catalyst 2, and the non-embedded part is distributed on the outer surface of the catalyst 2, and the schematic diagram is shown in FIG. 3.

Example 2

Mixing nano titanium dioxide and polyethylene glycol (molecular weight is 600), and then mixing with pseudo-boehmite, nitric acid and water, wherein the weight ratio of the nano titanium dioxide to the pseudo-boehmite (calculated by alumina), the nitric acid to the water is 15: 3.5: 2: 18, adding 2.5 percent of polyethylene glycol by weight of the mixed slurry of titanium dioxide and alumina to obtain the mixed slurry of titanium dioxide and alumina;

spraying and soaking mixed slurry of titanium dioxide and alumina on cordierite honeycomb ceramic, carrying out unsaturated spray soaking according to 70% of absorption rate, then drying for 4 hours at 65 ℃, roasting for 2.5 hours at 260 ℃, and roasting for 3 hours at 650 ℃ to obtain a honeycomb ceramic carrier B loaded with a modifier;

soaking the honeycomb ceramic carrier B loaded with the modifier into titanium sol for vacuum dipping and slurry hanging, removing excessive slurry, drying for 4 hours at 65 ℃, and repeating the step for 1 time; then, in the presence of water vapor and nitrogen, the photocatalyst B is obtained by sectional roasting, namely roasting at 260 ℃ for 2.5 hours and then at 650 ℃ for 3 hours. In the catalyst B, the content of the modifier (calculated by alumina and titania) introduced onto the catalyst by the mixed slurry of titania and alumina was 2%, and the mass content of titania, which is an active component introduced onto the catalyst by a titanium sol, was 8.0%.

In the obtained catalyst B, it was determined by XRD that titanium dioxide was mainly composed of anatase.

Measuring the titanium dioxide crystal grains on the surface of the prepared catalyst by using a microscope, and obtaining the size of the titanium dioxide crystal grains by using a statistical method, wherein the representative catalyst surface is selected, and the statistical area is about 90000 mu m²The statistical total number of titanium dioxide grains exceeds 100. It was found that the particle size of 5 to 100 μm on the surface of the catalyst B accounted for about 90%.

Example 3

Mixing nano titanium dioxide and polyethylene glycol (molecular weight is 400), and then mixing with pseudo-boehmite, nitric acid and water, wherein the weight ratio of the nano titanium dioxide to the pseudo-boehmite (calculated by alumina), the nitric acid to the water is 15: 3.5: 2: 18, adding 2.5 percent of polyethylene glycol by weight of the mixed slurry of titanium dioxide and alumina to obtain the mixed slurry of titanium dioxide and alumina;

spraying and soaking mixed slurry of titanium dioxide and alumina on cordierite honeycomb ceramic, carrying out unsaturated spray soaking according to 70% of absorption rate, then drying for 4 hours at 65 ℃, roasting for 2.5 hours at 250 ℃, and roasting for 3 hours at 650 ℃ to obtain a modifier-loaded honeycomb ceramic carrier C;

soaking the honeycomb ceramic carrier C loaded with the modifier into titanium sol for vacuum dipping and slurry hanging, removing excessive slurry, then drying for 4 hours at 65 ℃, and repeating the step for 1 time; then, in the presence of water vapor and nitrogen, the photocatalyst C is obtained by sectional roasting, namely roasting at 250 ℃ for 2.5 hours and then at 650 ℃ for 3 hours. In the catalyst C, the content of the modifier (calculated by alumina and titania) introduced onto the catalyst by the mixed slurry of titania and alumina was 3%, and the mass content of the active component titania introduced onto the catalyst by the titanium sol was 10%.

In the obtained catalyst C, it was determined by XRD that titanium dioxide was mainly composed of anatase.

Measuring the titanium dioxide crystal grains on the surface of the prepared catalyst by using a microscope, and obtaining the size of the titanium dioxide crystal grains by using a statistical method, wherein the representative catalyst surface is selected, and the statistical area is about 90000 mu m²The statistical total number of titanium dioxide grains exceeds 100. It was found that the catalyst C had a particle size of 5 to 100 μm on the surface thereof of about 87%.

Example 4

This embodiment is basically the same as embodiment 1, except that: directly mixing nano titanium dioxide with pseudo-boehmite, nitric acid and water without adding polyethylene glycol, wherein the weight ratio of the nano titanium dioxide to the pseudo-boehmite (calculated by alumina), the nitric acid to the water is 15: 3: 2: 15 to obtain a mixed slurry of titanium dioxide and alumina.

This example gave a photocatalyst D. In the catalyst D, the content of the modifier (calculated by alumina and titania) introduced onto the catalyst by the mixed slurry of titania and alumina was 3%, and the mass content of titania, which is an active component introduced onto the catalyst by a titanium sol, was 5%.

In the obtained catalyst D, it was determined by XRD that titanium dioxide was mainly composed of anatase.

Measuring the titanium dioxide crystal grains on the surface of the prepared catalyst by using a microscope, and obtaining the size of the titanium dioxide crystal grains by using a statistical method, wherein the representative catalyst surface is selected, and the statistical area is about 90000 mu m²The statistical total number of titanium dioxide grains exceeds 100. It was found that the particle diameter of catalyst D was 5 to 100 μm on the surface and accounted for about 82%.

Example 5

This embodiment is basically the same as embodiment 1, except that: soaking the obtained modifier-loaded honeycomb ceramic carrier A into titanium sol for vacuum dipping and slurry hanging, removing excessive slurry, drying for 4 hours at 65 ℃, and repeating the step for 1 time; then in the presence of water vapor and nitrogen, single-stage roasting is adopted, namely roasting is carried out for 5 hours at 650 ℃, and the photocatalyst E is obtained. In the catalyst E, the content of the modifier (calculated by alumina and titania) introduced onto the catalyst by the mixed slurry of titania and alumina was 3%, and the content of titania, which is an active component introduced onto the catalyst by a titanium sol, was 5% by mass.

In the obtained catalyst E, it was determined by XRD that titanium dioxide was mainly composed of anatase.

Measuring the titanium dioxide crystal grains on the surface of the prepared catalyst by using a microscope, and obtaining the size of the titanium dioxide crystal grains by using a statistical method, wherein the representative catalyst surface is selected, and the statistical area is about 90000 mu m²The statistical total number of titanium dioxide grains exceeds 100. It was found that titanium dioxide grains having a particle size of 5 to 100 μm were present on the surface of the catalyst E in an amount of about 85%.

Comparative example 1

In this comparative example, a cordierite honeycomb ceramic was used as a carrier, and then a titania coating was supported to a supported film thickness of about 5 μm, to obtain catalyst DA.

Example 6

The test is to test the photocatalytic performance of the photocatalyst A, wherein the test conditions are as follows:

(1) testing raw materials: air with toluene, xylene, benzene, ammonia, formaldehyde, sulfur dioxide, and hydrogen sulfide as contaminants was used as the test feed.

(2) Testing equipment: as shown in FIG. 5, the photocatalyst A is taken out to be made into a photocatalytic unit, and then the photocatalytic unit is fixed in an air duct with a fan of a corresponding specification to form the testing equipment, as shown in FIG. 6. The parameters of the photocatalyst A and the LED lamp are set as follows:

the photocatalyst A is plate-shaped: the length is 15cm, the width is 15cm, and the thickness is 1 cm;

the ultraviolet LED lamp panel comprises a substrate and 48 LED ultraviolet light-emitting particles on the substrate, the LED ultraviolet light-emitting particles are evenly distributed on the substrate in an array mode, 8 LED ultraviolet light-emitting particles are distributed on each array, 6 LED ultraviolet light-emitting particles are distributed on each array, and the substrate is in a fence shape as shown in figure 4. The ultraviolet LED luminous particles face the photocatalyst A, the wavelength of light emitted by the ultraviolet LED luminous particles is 365nm ultraviolet light, the length of the substrate is 15cm, the width of the substrate is 15cm, the two ultraviolet LED lamp panels are placed on two sides of the photocatalyst A in parallel, the distance between the two ultraviolet LED lamp panels is 2cm, and the intensity of single-side ultraviolet light on the photocatalyst A reaches 10m W/cm 2;

the cross section of the air duct is square, and the photocatalyst unit is hermetically placed in the air duct;

(3) test method and test conditions: preparing a sample experiment chamber and a blank experiment chamber;

place the test equipment at 1m³And sealing the sample experiment chamber, and filling pollutants into the experiment chamber. Starting the test equipment and the LED lamp, wherein the feeding speed is 0.5L/min, the test temperature is 26 ℃, the normal pressure is realized, the test time is 1 hour, and the results are shown in Table 1;

the blank experiment chamber and the sample experiment chamber are operated differently by only starting the test equipment and not starting the LED lamp, and the results are shown in table 1;

(4) the detection method of benzene and benzene series is carried out according to GB/T11737-1989, and the detection method of formaldehyde is carried out according to GB/T18204.26-2000;

(5) the results of the catalyst sterilization test using a staphylococcus albus-containing gas as a raw material are shown in table 3.

Table 1 results of contaminant detection using catalyst a prepared in example 1

Examples 7 to 10

The detection method for contaminants purified and the detection method for sterilization were the same as in example 6 except that the catalyst samples were replaced with the catalysts B to E prepared in examples 2 to 5, respectively, and the results are shown in tables 2 and 3.

Comparative example 2

The detection method for contaminants purified and the detection method for sterilization were the same as in example 6 except that the catalyst sample was replaced with the catalyst DA prepared in comparative example 1, and the results are shown in tables 2 and 3.

Table 2 results of contaminant detection in the purification of catalyst prepared in examples 2 to 5 and comparative example 1

TABLE 3 results of the sterilization test using the catalysts prepared in examples and comparative examples

Catalyst numbering	Testing microorganisms	Treatment time, 0h	Treatment time, 1h	Removal Rate (%)
					Catalyst A	Staphylococcus albus	6.1×10⁴	52	99.91
Catalyst B	Staphylococcus albus	6.1×10⁴	61	99.90
					Catalyst C	Staphylococcus albus	6.1×10⁴	58	99.90
Catalyst D	Staphylococcus albus	6.1×10⁴	70	99.89
					Catalyst E	Staphylococcus albus	6.1×10⁴	70	99.89
Catalyst DA	Staphylococcus albus	6.1×10⁴	72	99.88

Example 11

This example is a catalyst stability test.

Putting the catalyst A into a container provided with ultrasonic waves, wherein the ultrasonic treatment conditions are as follows: the volume ratio of water to catalyst is 4: 1, the ultrasonic frequency is 30kHz, the power is 20W/L according to the volume of the solution, the temperature is 30 ℃, the treatment frequency is 5 times, the treatment time is 30min each time, then the catalyst A is used for the photocatalytic performance test, the test method is the same as the example 6, and the result shows that the removal rate of pollutants in each test is reduced, the reduction rate is less than 1 percent, and the removal rate of staphylococcus albus is 99.02 percent.

Examples 12 and 13

The stability of catalysts B and C was tested as in example 11, resulting in a reduction in the removal of each tested contaminant of less than 1% and a reduction in the removal of Staphylococcus albus of less than 1%.

Examples 14 and 15

The stability of catalysts D and E was tested as in example 11, resulting in a reduction in the removal of each contaminant tested, between 1% and 3%, and about 2% reduction in the removal of Staphylococcus albus.

Comparative example 3

The stability of catalyst DA was tested as in example 11, and as a result, the removal rate of each contaminant tested was reduced by more than 10%, and the removal rate of Staphylococcus albus was 86%.

Example 16

In the same manner as example 6, except that "two ultraviolet LED lamp panels in the test condition (2) were placed in parallel on both sides of the photocatalyst A plate at an interval of 2cm, and the intensity of single-sided ultraviolet light on the photocatalyst A reached 10m W/cm²"; the two ultraviolet LED lamp panels are arranged on two sides of the photocatalyst A plate in parallel, the distance is 5cm, and the single-side ultraviolet intensity on the photocatalyst A reaches 0.8m W/cm²", the results are shown in Table 4. Table 4 example 16 test results for decontamination of contaminants

Claims

1. A photocatalytic unit, comprising:

2. The photocatalytic unit of claim 1, wherein the honeycomb ceramic carrier has a water absorption of 10-25% by volume, a thermal conductivity of 1.0-2.0W/(M.K), and a density of 0.75-1.2 g/cm at 20 ℃³。

3. The photocatalytic unit of claim 1, wherein the diameter of the honeycomb through holes in the honeycomb ceramic carrier is 1-6 mm, preferably 1-4 mm, the outer wall thickness is 0.6-2.9 mm, the inner wall thickness is 0.3-2.3 mm, and the area of the through holes on the cross section is 50-70%.

4. The photocatalytic unit according to claim 1, wherein the honeycomb ceramic support has the following pore distribution: the pore volume occupied by the pore channels with the pore diameter of 2-5 mu m is more than 70% of the pore volume occupied by the pore channels with the pore diameter of less than 100 mu m.

5. A photocatalytic unit according to claim 1, characterized in that the modifier of the photocatalyst has a titanium dioxide content of 10-23%.

6. The photocatalytic unit according to claim 1, characterized in that the honeycomb ceramic is cordierite honeycomb ceramic.

7. A photocatalytic unit according to claim 1, characterized in that in the photocatalyst, titanium dioxide is mainly anatase.

8. A photocatalytic unit according to any one of claims 1-7, characterized in that, based on the weight of the catalyst, the honeycomb ceramic carrier is 72-96%, the modifier is 1-10%, and the active component is 3-18%; preferably, based on the weight of the catalyst, the content of the honeycomb ceramic carrier is 77-93%, the content of the modifier is 2-8%, and the content of the active component is 5-15%.

9. A photocatalytic unit according to any one of claims 1 to 8, characterized in that in the photocatalyst, titanium dioxide crystal grains are dispersed in an embedded manner on the surface of the catalyst; the titanium dioxide crystal grains on the outer surface of the catalyst account for more than 70% of the titanium dioxide crystal grains with the grain size of 5-150 mu m, and further account for more than 70% of the titanium dioxide crystal grains with the grain size of 5-100 mu m.

10. The photocatalytic unit of claim 1, wherein the photocatalyst is a photocatalyst plate, the ultraviolet light source device is an ultraviolet LED lamp panel, and one or two surfaces of the photocatalyst plate are provided with the ultraviolet LED lamp panels; further, the photocatalyst plate and the ultraviolet LED lamp panel are arranged in parallel.

11. The photocatalytic unit of claim 10, wherein in the uv light source device, the uv LED lamp panel comprises a substrate and a plurality of LED uv light emitting particles disposed on the substrate; further, the LED ultraviolet light-emitting particles on the ultraviolet LED lamp panel can be arranged in an array form, and ventilation holes are arranged or not arranged between adjacent arrays; furthermore, the substrate is in a fence type, namely LED ultraviolet light-emitting particles which are arranged in an array mode are arranged on the fence strips, and vent holes are formed among the fence strips.

12. The photocatalysis unit of claim 1, wherein, in the photocatalysis unit, N photocatalysis boards are arranged, ultraviolet LED lamp panels are arranged on two sides of each photocatalysis board, and the ultraviolet LED lamp panels and the photocatalysis boards are arranged in parallel, wherein N is an integer more than or equal to 1.

13. The photocatalysis unit of claim 1, further comprising a fixing frame for fixing the photocatalyst plate and the ultraviolet LED lamp plate.

14. A photocatalytic method characterized by: by using the photocatalytic unit as set forth in any one of claims 1-13, the gas to be purified is passed through the photocatalytic unit and is subjected to photocatalytic reaction under the action of ultraviolet light and a catalyst to obtain the purified gas.

15. A photocatalytic method according to claim 14, characterized in that the ultraviolet LED lamp emits ultraviolet light with a wavelength of 280-390 nm, preferably with a single wavelength, such as 365 nm; the distance between the ultraviolet LED lamp panel and the photocatalyst plate is 0-10 cm, further 0-5 cm, and preferably 0.5-3.5 cm; the radiation intensity on the photocatalyst plate is 0.01-500 mW/cm²Preferably 0.5-70 mW/cm²。

16. A photocatalytic method according to claim 14, characterized in that the gas to be purified contains a plurality of volatile organic compounds, preferably also microorganisms.

17. A photocatalytic method according to claim 14, characterized by being applied in electric appliances such as air purifiers, refrigerators or air conditioners.

18. A photocatalytic method according to claim 14 characterized by being applied in a duct with gas flow, such as exhaust, ventilation, exhaust gas discharge or ventilation.

19. A photocatalytic method according to claim 14 characterized by the application in transportation means such as cars, cruise ships, submarines, planes, subways or trains.

20. The photocatalytic method according to claim 14, characterized by being applied in furniture, office equipment or vehicle equipment, such as office desks, clamping seats or screens, such as laboratory tables, fume hoods or reagent cabinets, such as hospital tables, hospital bed purification isolation tables, isolation beds or isolation chairs, such as vehicle multifunctional purification arm boxes.