Micro plasma catalytic reactor

Abstract

A microplasma catalytic reactor for treating ambient air by decomposing VOC in the ambient air. The reactor comprises: a first electrode member comprising a conductive core and a dielectric coating; and a second electrode member disposed relative to the first electrode member so as to generate a plasma between the first and second electrode members upon application of a plasma generating voltage between the first and second electrode members such that, in use, VOC in ambient air in the reactor is decomposed to form a VOC decomposition product, and forming a plasma by-product. The dielectric coating further includes a catalyst that catalyzes the decomposition of one or more of: VOC; a VOC decomposition product; and a plasma by-product.

Description

Technical Field

[0001] The present invention relates to a microplasma catalytic reactor, air purification and a method for operating a microplasma catalytic reactor. Background Art

[0002] The negative impact of pollutants, such as VOCs, on human health in indoor environments is well known. Many indoor pollutants found in residential environments are organic chemicals and span a wide range of functional groups, sizes, and chemical potentials. These can be categorized as volatile organic compounds (VOCs) and volatile inorganic compounds (VICs). VOCs to which humans are commonly exposed in indoor environments include alcohols, aldehydes, aromatic compounds, ketones, alkanes, and alkenes.

[0003] Various technologies have been investigated for removing VOCs from air, such as adsorption, catalytic thermal oxidation, cold plasma, and photocatalysis.

[0004] It is known that VOCs are easily decomposed in the presence of plasma (ionized gas phase). However, plasma byproducts such as ozone (O3) and nitrogen oxides (NO x The formation of partially oxidized VOCs and other by-products is a major obstacle to the indoor adoption of this technology.

[0005] The World Health Organization's NO x The baseline values ​​are an annual average of 10 µg / m³ (5.3 ppb) and a 24-hour average of 25 µg / m³ (13.3 ppb). x Based on the toxicological profile of ozone, the European Commission Scientific Committee (ECSC) recommends an occupational exposure limit of 2 ppm (time-weighted average over 8 hours). OSHA recommends an immediate risk to life or health limit of 100 ppm and a permissible exposure limit of 25 ppm (time-weighted average over 8 hours). The World Health Organization's ozone baseline values ​​are 100 µg / m³ (51 ppb) for an 8-hour maximum daily exposure, 60 µg / m³ (31 ppb) for a daily maximum daily exposure, and 60 µg / m³ (31 ppb) for a daily time-weighted average daily exposure.

[0006] Microplasma dielectric barrier discharge (DBD) reactor is a reactor technology that generates plasma at low voltage (about 1 kV) and in a small discharge gap (<1 mm) with low free electron energy. The generation of high energy free electrons increases the possibility of generating various reactive species within the reactor, which then lead to NO x Therefore, when using plasma to treat VOC-containing gas streams, the microplasma DBD reactor has the advantages of reducing NO xHowever, the conversion of VOCs, the generation of O3, the generation of partially oxidized VOCs and NO x The generation of ions remains a problem for known microplasma DBD reactors.

[0007] The present invention has been devised based on the above considerations. Summary of the Invention

[0008] In a first aspect of the present disclosure, there is provided a microplasma catalytic reactor for treating ambient air by decomposing VOCs in the ambient air. The reactor comprises: a first electrode member comprising a conductive core and a dielectric coating; and a second electrode member disposed relative to the first electrode member so that, when a plasma generating voltage is applied between the first and second electrode members, a plasma is generated between the first and second electrode members such that, in use, VOCs in the ambient air in the reactor are decomposed to form VOC decomposition products and plasma byproducts. The dielectric coating further comprises a catalyst that catalyzes the decomposition of one or more of: VOCs; VOC decomposition products; and plasma byproducts. Advantageously, such a microplasma catalytic reactor is capable of effectively decomposing VOCs in ambient air while limiting the amount of plasma byproducts and partially oxidized VOCs released by the reactor.

[0009] The catalyst contained within the dielectric coating may include one or more of the following: a metal oxide, a mixed metal oxide, a noble metal, a noble metal-metal oxide composite, and a noble metal-mixed metal oxide composite. Advantageously, this allows the composition of the catalyst within the dielectric coating to be tailored to the amount and / or type of VOCs contained in the ambient air to be decomposed and / or the amount and / or type of plasma byproducts generated within the reactor.

[0010] The catalyst may comprise one or more of the following: Ag, Pt, Pd, Rh, Ni, Cu, Mo, Co, Mg, and Ti. Advantageously, the catalyst comprising one or more of the foregoing elements effectively catalyzes the decomposition of one or more of VOCs, VOC decomposition products, and plasma byproducts.

[0011] The first electrode and the second electrode can be arranged upstream and downstream of each other relative to the gas flow path through the reactor. Advantageously, a reactor having such a geometry is capable of generating a plasma that spans a range of residence times within the reactor, thereby catalyzing a range of compounds within the plasma.

[0012] The second electrode member of the first aspect may include a conductive core and a dielectric coating. Advantageously, the two electrodes having a conductive core and a dielectric coating structure reduce the likelihood of arcing between the electrode members and, therefore, the likelihood of forming significant amounts of plasma arc byproducts.

[0013] The dielectric coating of the second electrode member may further include a catalyst that catalyzes the decomposition of one or more of the following: VOCs; VOC decomposition products; and plasma byproducts. This advantageously provides a larger surface area of ​​catalyst to catalyze the decomposition of these compounds.

[0014] The dielectric coating of the first electrode member and / or the dielectric coating of the second electrode member may include a first catalyst and a second catalyst. Advantageously, the presence of two catalysts on the electrode members may allow each catalyst to more specifically catalyze the decomposition of a certain compound without unduly compromising the catalysis of other compounds within the reactor.

[0015] Alternatively, where both the first electrode member and the second electrode member include a dielectric coating comprising a catalyst, the dielectric coating of the first electrode member may include a first catalyst, and the dielectric coating of the second electrode member may include a second catalyst. The first catalyst may be different from the second catalyst. Advantageously, this may allow the catalytic efficiency of the reactor to be improved by adapting the catalyst on a given electrode to the compounds near that electrode during operation of the reactor.

[0016] Where the first and second electrode members are arranged upstream and downstream of one another with respect to the gas flow path through the reactor, the first catalyst can be applied only to the downstream electrode. Advantageously, such a configuration can allow for efficient use of the first catalyst because the catalyst is positioned in the direction in which reactive species generated in the plasma will travel through the reactor relative to the midpoint between the two electrode members.

[0017] The conductive core of each electrode member may comprise one or more of stainless steel, aluminum, brass, iron, or copper. Advantageously, the composition of the conductive core may be customized based on its desired conductivity, cost, weight, and ductility.

[0018] The dielectric coating of the electrode member can be porous or non-porous. For porous coatings, any catalyst included in the dielectric coating can be at least partially disposed on the inner surface of the pores of the dielectric coating. Advantageously, such a structure can provide increased surface area for catalysis of decomposition reactions occurring within the reactor.

[0019] Where the dielectric coating of the electrode member is porous and the catalyst is to be at least partially disposed on the interior surfaces of the pores of the dielectric coating, an impregnation technique (e.g., incipient wetness impregnation, wet impregnation) can be used to dispose the catalyst on the interior surfaces of the pores. Advantageously, incipient wetness impregnation is technically simple, low cost, and produces a limited amount of waste, while also ensuring that the catalyst is disposed within the pores of the substrate, meaning that the overall thickness and uniformity of the coating are not affected by catalyst deposition.

[0020] Porous dielectric coatings can exhibit inhomogeneities, manifested as numerous cracks and pores in the film that can extend inward and connect to the metal electrodes, potentially altering discharge characteristics and breakdown mechanisms. Impregnation of the dielectric film with a catalyst offers the added benefit of pore / crack sealing. In this way, the porosity of the coating can be controlled from relatively porous to non-porous, which is critical for maintaining the desired electrical, mechanical, and chemical properties.

[0021] The dielectric coating of the electrode component may include a metal oxide. The metal oxide may be one or more of MnO2, Al2O3, CeO2, SiO2, and TiO2. Alternatively, the dielectric coating of the electrode component may include activated carbon or zeolite. Advantageously, such materials have a high surface area and can also act as catalysts in the presence of plasma. A noble metal catalyst, one or more of Au, Ag, Tu, Rh, Pd, and Pt, may be impregnated in the metal oxide coating.

[0022] The reactor according to the first aspect of the present disclosure may include a plurality of first electrode members and a plurality of second electrode members, wherein each pair of adjacent first electrode members is interposed with a second electrode member, and each pair of adjacent second electrode members is interposed with a first electrode member. Advantageously, compared to a reactor having only a single first electrode member and a single second electrode member, such a reactor can process a larger volume of air while maintaining the reactor's conversion rate by increasing the residence time of the air within the reactor.

[0023] The reactor according to the first aspect of the present disclosure may further include a power supply connected to each first electrode member and / or each second electrode member. The power supply thus connected may be configured to deliver pulsed DC to each electrode member to which it is connected so as to generate plasma between the first electrode member and the second electrode member adjacent thereto. By providing pulsed DC to the electrode members connected to the power supply, energy consumption of the reactor can be reduced compared to using non-pulsed DC, and an additional control variable can be provided for controlling plasma discharge within the reactor.

[0024] The reactor according to the first aspect of the present disclosure may further include a third electrode member, the third electrode member being interposed between the first electrode member and the second electrode member. The third electrode member may combine one or more of the optional features of the first electrode member and / or the second electrode member described above.

[0025] The power supply can be configured such that the parameters of the pulsed DC that the power supply is configured to deliver to each electrode member to which it is connected can be adjusted independently of the other electrode members to which it is connected. Advantageously, this allows the plasma discharge between a pair of adjacent electrode members to be controlled independently of the plasma discharge between other pairs of adjacent electrode members.

[0026] The reactor can be configured such that the pulsed DC received by each electrode member connected to the power supply: generates an electric field strength between the electrode member and an adjacent electrode member having a voltage greater than or equal to [0.3 kV] and less than or equal to [1.9 kV]; has a pulse frequency greater than or equal to 0.5 kHz and less than or equal to 100 kHz; and has a pulse width greater than or equal to 0.6 μs and less than or equal to 50 μs. Advantageously, the reactor is configured to provide such pulsed DC to each electrode member connected to the power supply to promote efficient decomposition of VOCs in ambient air while limiting the amount of plasma byproducts and partially oxidized VOCs released by the reactor.

[0027] In a reactor comprising a power supply configured to deliver pulsed DC to each electrode member to which it is connected, the pulsed DC received by each electrode member may have a voltage greater than or equal to 0.3 kV. The pulsed DC received by each electrode member may have a voltage less than or equal to 1.9 kV. The pulsed DC received by each electrode member may have a voltage greater than or equal to 0.8 kV. The pulsed DC received by each electrode member may have a voltage less than or equal to 1.0 kV. The pulsed DC received by each electrode member may have a voltage greater than or equal to 0.88 kV. The pulsed DC received by each electrode member may have a voltage less than or equal to 0.92 kV. Providing pulsed DC having such voltages to each electrode member facilitates the generation of a plasma to catalyze the decomposition of VOCs while limiting the presence of plasma byproducts in the air exiting the reactor.

[0028] In a reactor comprising a power supply configured to deliver pulsed DC to each electrode member connected thereto, the pulsed DC received by each electrode member may have a current amplitude greater than or equal to 0.01 A. The pulsed DC received by each electrode member may have a current amplitude less than or equal to 8 A. The pulsed DC received by each electrode member may have a current amplitude greater than or equal to 0.2 A. The pulsed DC received by each electrode member may have a current amplitude greater than or equal to 0.3 A. The pulsed DC received by each electrode member may have a current amplitude greater than or equal to 0.4 A, and the pulsed DC received by each electrode member may have a current amplitude less than or equal to 0.5 A. Providing pulsed DC having such current amplitudes to each electrode member facilitates generating a plasma to catalyze the decomposition of VOCs while limiting the presence of plasma byproducts in the air exiting the reactor.

[0029] In a reactor comprising a power supply configured to deliver pulsed DC to each electrode member to which it is connected, the pulsed DC received by each electrode member may have a pulse width greater than or equal to 0.05 μs. The pulsed DC received by each electrode member may have a pulse width greater than or equal to 3 μs. The pulsed DC received by each electrode member may have a pulse width less than or equal to 10 μs. The pulsed DC received by each electrode member may have a pulse width less than or equal to 50 μs. The pulsed DC received by each electrode member may have a pulse width less than or equal to 15 μs. The pulsed DC received by each electrode member may have a pulse width less than or equal to 5 μs. Providing pulsed DC having such pulse widths to each electrode member facilitates the generation of a plasma to catalyze the decomposition of VOCs while limiting the presence of plasma byproducts in the air exiting the reactor.

[0030] In the reactor according to the first aspect of the present disclosure, each electrode member may be a perforated plate. Advantageously, configuring the electrode member as a perforated plate facilitates a large amount of contact between ambient air and the electrode member, thereby increasing the conversion of the reactor. In addition, the perforated plate structure is easy to manufacture and provides an electrode member with a high surface area to volume ratio, thereby reducing redundant material within the electrode member. The perforated plate may have an open area percentage greater than or equal to 10%. The perforated plate may have an open area percentage less than or equal to 35%. The perforated plate may have an open area percentage greater than or equal to 22%. The perforated plate may have an open area percentage less than or equal to 90%. The perforated plate may have an open area percentage greater than or equal to 24.5%. The perforated plate may have an open area percentage less than or equal to 25.5%. Advantageously, the open area percentage may be set so as to balance the pressure drop across the reactor with the surface area of ​​the electrode member available for catalysis and plasma generation.

[0031] In the case where the electrode members are plate-shaped and offset from one another in the axial direction of the plate-shaped electrode members, the first catalyst can be applied only to the surface of the electrode member adjacent to another electrode member within the electrode group. Advantageously, this positioning of the catalyst effectively utilizes the catalyst by positioning the catalyst near the center of the discharge zone where plasma is generated in the reactor.

[0032] In case the electrode members are perforated plates, those perforated plates may be curved and / or bent. Advantageously, perforated plates having curves and / or bends may facilitate different reactor geometries.

[0033] The reactor according to the first aspect of the present disclosure may further include a non-conductive separator positioned between adjacent electrode members. The non-conductive separator may extend around at least a portion of the circumference of the electrode member. Advantageously, the non-conductive separator may electrically isolate the electrode members from each other and from the rest of the reactor. The non-conductive separator may comprise PTFE or another electrically insulating polymer.

[0034] In the reactor according to the first aspect of the present invention in which each electrode member is a perforated plate, adjacent plate-shaped electrode members may be substantially parallel to each other and offset from each other by a distance of 1 mm or less between adjacent surfaces of adjacent electrode members. The offset distance between adjacent electrode members may be greater than or equal to 0.01 mm. The offset distance between adjacent electrode members may be less than or equal to 1 mm. The offset distance between adjacent electrode members may be less than or equal to 0.5 mm. The offset distance between adjacent electrode members may be less than or equal to 0.25 mm. The offset distance between adjacent electrode members may be less than or equal to 0.15 mm. The offset distance between adjacent electrode members may be greater than or equal to 0.05 mm. The offset distance between adjacent electrode members may be greater than or equal to 0.09 mm. The offset distance between adjacent electrode members may be less than or equal to 0.11 mm. The offset distance between adjacent electrode members may be greater than or equal to 0.20 mm. The offset distance between adjacent electrode members may be greater than or equal to 0.4 mm. Advantageously, providing such an offset distance between adjacent plate electrode members facilitates generating plasma having a voltage range of approximately 0.3 to 1.9 kV and having low electron energies, thereby resulting in the formation of fewer plasma byproducts than at higher voltages and electron energies.

[0035] In a second aspect of the present disclosure, an air purification device is provided, comprising an air inlet, an air outlet, and a microplasma catalytic reactor according to the first aspect of the present disclosure. In use, ambient air flows along an air path, which enters the device via the air inlet, passes through the reactor, and leaves the device via the air outlet.

[0036] The air purification device according to the second aspect may include a plurality of reactors according to the first aspect of the present disclosure positioned along the air path between the air inlet and the air outlet. Advantageously, including a plurality of microplasma catalytic reactors within the air purification device may allow the device to process a larger flow of air while achieving the same VOC decomposition performance.

[0037] In the case of multiple microplasma catalytic reactors within an air purification device, where multiple of these reactors receive pulsed DC from a power source, the parameters of the pulsed DC provided to a given reactor can be controlled independently of the pulsed DC provided to another such reactor. This facilitates controlling the plasma discharge within a given reactor independently of the plasma discharge within other reactors, allowing different microplasma catalytic reactors within the air purification device to be tailored to the decomposition of different compounds.

[0038] In the case of multiple microplasma catalytic reactors within the air purification device, those microplasma catalytic reactors can be placed in series along the air path between the air inlet and the air outlet. Advantageously, including multiple microplasma catalytic reactors in series within the air purification device can increase the residence time of ambient air in the microplasma catalytic reactors, thereby increasing the VOC conversion rate achieved by the air purification device.

[0039] The air cleaning device according to the second aspect may also include an adsorption unit, which is positioned between the reactor and the air outlet along the air path. The adsorption unit may be configured to be adsorbed on one or more of the VOC, VOC decomposition products, and plasma byproducts contained in the air flow leaving the reactor during use of the air cleaning device. Advantageously, including the adsorption unit downstream can reduce the concentration of the VOC, VOC decomposition products, and / or plasma byproducts contained in the air flow leaving the air cleaning device. In addition, the long-life plasma material that arrives at the adsorption unit from the reactor can decompose the VOC and the VOC decomposition products adsorbed on the adsorbent in the adsorption unit, thereby increasing the life of the adsorbent.

[0040] Where the air purification device comprises an adsorption unit or a catalytic unit, the air purification device may be configured to operate in a continuous store-and-discharge operation, wherein the air flows through the reactor once. Advantageously, this may increase the flow rate of ambient air that may be introduced into the device.

[0041] Alternatively, where the air purification device includes an adsorption unit and / or a catalytic unit, the air purification device can be configured to operate under a cyclic store-and-release operation, wherein the VOCs are first stored on the adsorbent / catalyst with the plasma off and then oxidized by the generated reactive species with the plasma on. Advantageously, this can increase the overall VOC conversion achieved, and the device can be more energy-efficient for removing very low concentrations of VOCs present in indoor air.

[0042] The air cleaning device according to the second aspect may further include a catalytic unit located between the reactor and the air outlet along the air path. The catalytic unit may be configured to catalyze the decomposition of one or more of the VOCs, VOC decomposition products, and plasma byproducts contained in the air flow leaving the reactor during use of the air cleaning device. Advantageously, including a catalytic unit downstream of the reactor may allow the VOC conversion rate achieved by the air cleaning device to be further increased over the VOC conversion rate achieved in the reactor. In addition, the long-life plasma species that arrive at the catalytic unit from the reactor may enhance the decomposition of the VOCs and VOC decomposition products on the catalyst surface in the catalytic unit, thereby further reducing the concentration of the VOCs and VOC decomposition products contained in the air flow leaving the air cleaning device. The catalytic unit may be operated at room temperature or a higher temperature, depending on the balance between the required energy consumption and conversion rate.

[0043] In a third aspect of the present disclosure, a method for treating ambient air using a microplasma catalytic reactor to reduce the concentration of VOCs in the air is provided. The reactor comprises: a first electrode member comprising a conductive core and a dielectric coating comprising a catalyst; and a second electrode member disposed relative to the first electrode member. The method comprises the following steps: passing an ambient gas stream containing VOCs through the reactor; applying a plasma generation voltage between the first electrode member and the second electrode member to generate a plasma in the VOC-containing gas stream, the plasma decomposing the VOCs contained in the gas stream and generating VOC decomposition products and plasma byproducts; and using a catalyst to catalyze the decomposition of one or more of the following: VOCs; VOC decomposition products; and plasma byproducts. Advantageously, this method of treating ambient air using a microplasma catalytic reactor can effectively decompose VOCs in the ambient air while limiting the amount of plasma byproducts and partially oxidized VOCs released by the reactor.

[0044] The anhydrous gaseous room temperature composition of the VOC-containing ambient gas stream entering the reactor may be: 21% by mass O2 and 78% by mass N2, with the remainder comprising VOCs, Ar, CO2 and also trace elements and molecules.

[0045] The present invention includes any combination of the described aspects and preferred features unless such a combination is expressly impermissible or explicitly avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Aspects, embodiments, and experiments related to the present disclosure will now be discussed with reference to the accompanying drawings, in which:

[0047] Figure 1 A microplasma catalytic reactor according to an embodiment of the first aspect of the present disclosure is shown, which has a first electrode member and a second electrode member;

[0048] Figure 2A A microplasma catalytic reactor according to an embodiment of the first aspect of the present disclosure is shown, which has a first electrode member, a second electrode member, and a third electrode member;

[0049] Figure 2B A microplasma catalytic reactor according to an embodiment of the first aspect of the present disclosure is shown, which has a plurality of first electrode members and a plurality of second electrode members;

[0050] Figure 3 Different controllable parameters of the pulsed DC supplied by the power supply to the electrode members of the microplasma catalytic reactor are shown on the voltage-time graph.

[0051] Figure 4 An air purification device is shown that includes a plurality of microplasma catalytic reactors positioned in series along an air path through the air purification device;

[0052] Figure 5 An air purification device including a HEPA filter, a microplasma catalytic reactor and a post-plasma adsorption unit is shown;

[0053] Figure 6A is a process flow chart of an air purification device according to an embodiment of the second aspect of the present disclosure, the air purification device comprising a microplasma catalytic reactor and a post-plasma adsorption unit;

[0054] Figure 6B is a process flow chart of an air purification device according to an embodiment of the second aspect of the present disclosure, the air purification device comprising a microplasma catalytic reactor and a post-plasma catalytic unit;

[0055] Figure 6C is a process flow chart of an air purification device according to an embodiment of the second aspect of the present disclosure, the air purification device comprising a HEPA filter, a microplasma catalytic reactor and a post-plasma catalytic unit;

[0056] Figure 6D is a process flow chart for an air purification device according to an embodiment of the second aspect of the present disclosure, the air purification device comprising a microplasma catalytic reactor, a post-plasma catalytic unit, and a post-plasma adsorption unit;

[0057] Figure 7 Contains chromatograms corresponding to the reactor feed and effluent streams of Comparative Example 1 in Table 3.

[0058] Figure 8 Contains chromatograms corresponding to the reactor feed and effluent streams of Example 2 in Table 3. DETAILED DESCRIPTION

[0059] Aspects, embodiments and experiments related to the present disclosure will now be discussed with reference to the accompanying drawings. Other aspects and embodiments will be apparent to those skilled in the art. All documents mentioned herein are incorporated herein by reference.

[0060] Figure 1 A schematic diagram of a microplasma catalytic reactor 1 according to an embodiment of the first aspect of the present disclosure is shown. The schematic diagram is a cross-sectional view of the catalytic reactor 100, which is substantially parallel to the air path through the reactor (defined by Figure 1 ). The reactor 1 has a first electrode member 110 and a second electrode member 120, which are separated by a discharge gap 140 between adjacent surfaces thereof. The first electrode member 110 includes a conductive core 111 and a dielectric coating 112. Figure 1 In the reactor 100, the second electrode member 120 further includes a corresponding conductive core 121 and a dielectric coating 122. For both electrode members 110, 120, the dielectric coatings 112, 122 of the electrode members 110, 120 completely coat the conductive cores 111, 112 of the electrode members 110, 120, such that no portion of the cores 111, 112 is exposed on the outer surfaces of the electrode members 110, 120. As described in more detail below, the dielectric coatings of the first electrode member 110 and the optional second electrode member 120 include one or more catalysts.

[0061] A power source 150 is connected to the conductive core 111 of the first electrode member 110, and the conductive core 121 of the second electrode member 120 is connected to ground 155. Current is supplied from the power source 150 to the first electrode member, providing a potential difference between the electrode members 110, 120 and generating an electric field across the discharge gap 140. Figure 3 The power supply 150 and the current supplied to the electrode members are discussed further. The potential difference applied between the electrode members 110, 120 and the strength of the resulting electric field in the discharge gap 140 can be made sufficiently large to generate a plasma in the discharge gap 140 and near the electrode members 110, 120 (i.e., near the surfaces of the electrode members 110, 120 not adjacent to the discharge gap 140), which together form the plasma discharge region of the reactor 100. The highly reactive species generated within the plasma are effective in decomposing VOCs contained in the ambient air within the reactor. However, the decomposition of VOCs in the plasma can result in the formation of partially oxidized VOCs (VOC decomposition products) and long-lived plasma byproducts such as O3 and NO. xBy providing a catalyst on the dielectric coatings 112, 122, the decomposition of one or more of the VOCs, VOC decomposition products, and plasma byproducts can be catalyzed in the vicinity of the plasma to reduce the concentration of these species in the gas stream exiting the reactor 100.

[0062] although Figure 1 The core 121 of the second electrode member 120 is connected to the ground 155, but other configurations are possible as long as a potential difference can be generated between the first electrode member 110 and the second electrode member 120 to generate plasma, for example, the cores 111, 121 of both the first electrode member 110 and the second electrode member 120 may also be connected to opposite terminals of the power supply 150, or the core 111 of the first electrode member 110 is connected to the ground 155 and the core 121 of the second electrode member 120 is connected to the power supply 150.

[0063] exist Figure 1 In the embodiment, the first electrode member 110 and the second electrode member 120 are both in the form of perforated plates, wherein the first electrode member 110 has a plurality of perforations 113 arranged in a regular array on its planar surface, and the second electrode member 120 also has a plurality of perforations 123 arranged in a regular array on its planar surface. Figure 1 In the case of the first electrode member 110, the through-hole 113 in the first electrode member 110 is aligned with the through-hole 123 in the second electrode member 120 across the discharge gap 140 separating the electrode members 110, 120. Figure 1 In the presence of airflow through the electrode members 110, 120 (as indicated by the thick arrows in the figure), the alignment of the through-holes 113, 123 of adjacent electrode members 110, 120 can reduce the pressure drop across the reactor 100. However, by misaligning the through-holes 113, 123 of adjacent electrode members 110, 120, the flow through the reactor 100 can be made more turbulent, and the residence time and mixing of air in the discharge gap 140 can be increased. When plasma is generated in the reactor 100 near the electrode members 110, 120, the increased residence time and mixing of air in the discharge gap 140 can increase the interaction of the plasma with the catalyst disposed on the dielectric coatings 112, 122, thereby increasing the VOC conversion rate achieved by the reactor 100. For similar reasons, it is desirable to control the reactor feed gas flow so that the air flow rate through the through-holes 113, 123 is uniform over the area of ​​the electrode members 110, 120, rather than the flow rate through the through-holes 113, 123 closer to the center of the electrode members 110, 120 being significantly greater than the flow rate through the through-holes 113, 123 closer to the edges of the electrode members 110, 120.

[0064] In such Figure 1In the reactor shown, the cores 111, 121 of the plate-shaped electrode members 110, 120 may have a thickness of approximately 1 mm, and the apertures may be spaced approximately 5 mm apart, with a 3 mm retaining diameter, thereby providing the cores 111, 112 with an open area of ​​approximately 32.7%. A dielectric coating 112, 122 is then uniformly applied to the cores 111, 121 and may have a thickness of approximately 200 μm, reducing the open area of ​​the resulting electrode members 110, 120 to approximately 24.6%. The width of the discharge gap 40 (i.e., the distance between adjacent surfaces of adjacent electrode members) is typically less than 1 mm, and preferably approximately 0.1 mm, to allow plasma formation at low voltage and low electron energy, thereby limiting the formation of plasma byproducts (discussed below with reference to the tests and examples in Tables 1-3).

[0065] The cores 111, 121 of the electrode members 110, 120 can be formed from any conductive material; however, preferably, the core comprises one or more of stainless steel, aluminum, brass, iron, or copper. These metals and metal alloys have high electrical conductivity and are readily available. Aluminum, copper, and brass are particularly advantageous in terms of light weight and high ductility compared to stainless steel and iron. Another factor in selecting the material for the cores 111, 121 is the proportion of the power supplied to the electrode members that is lost as heat energy. Of the materials listed above, stainless steel provides the highest process efficiency in terms of heat loss, while the efficiency of aluminum, brass, iron, and copper decreases gradually. The outer surface of the cores 111, 121 is ground before coating to increase surface uniformity and reduce plasma concentration areas and / or arc formation within the reactor 100.

[0066] The dielectric coatings 112, 122 applied to the cores 111, 121 of the electrode members 110, 120 can have a substrate formed from a metal oxide such as MnO2, Al2O3, CeO2, SiO2, and TiO2. Alternatives to metal oxides include activated carbon and zeolites. Advantageously, these metal oxide materials and alternative materials can be provided as a substrate having a high surface area, on which the catalytic material is disposed, and can also themselves act as a catalyst in the presence of the plasma. In the case where the dielectric coatings 112, 122 are porous, the catalyst can be disposed on the substrate, at least partially on the inner surfaces of the pores of the dielectric coating. In this way, the porosity of the coating can be controlled from relatively porous to non-porous by filling pores or cracks with the catalyst. The non-uniformity of the coating can be controlled, which can alter the discharge characteristics and breakdown mechanism and is crucial for maintaining electrical, mechanical, and chemical properties.

[0067] In the present microplasma catalytic reactor 100, at least the first electrode member 110 has a dielectric coating 112 that includes a catalyst that catalyzes the decomposition of one or more of: VOCs, VOC decomposition products; and plasma byproducts contained in the ambient air processed by the reactor 100. Figure 1 In the reactor 100 shown, only the first electrode member 110 includes a catalyst, and preferably the first electrode member 110 is located downstream of the second electrode member 120, as shown in FIG. Figure 1 In the case of FIG, because the catalyst is located downstream of the discharge gap 140, the plasma generated by the reactor 100 is concentrated in the discharge gap 140. This then means that the VOCs and plasma species are more likely to interact on the surface on which the catalyst is present, because this is the direction in which the VOCs and plasma species will travel through the reactor 100 after being generated.

[0068] The catalyst may comprise one or more of the following: a metal oxide, a mixed metal oxide, a noble metal, a noble metal-metal oxide composite, and a noble metal-mixed metal oxide composite. Such a catalyst may comprise one or more of Ag, Pt, Pd, Rh, Ni, Cu, Mo, Co, Mg, and Ti. An incipient wetness impregnation (IWI) technique is used to deposit the selected catalyst on the surface of the material forming the remainder of the dielectric coating 112, 122. The use of IWI technology means that the macroscale thickness and uniformity of the dielectric coating 112, 122 are not affected by the catalyst deposition.

[0069] While the reactor 100 may include only a single electrode component 110 having a dielectric coating 112 including a catalyst, typically several or all of the electrode components 110, 120 within the reactor 100 have a dielectric coating 112, 122, and each dielectric coating 112, 122 includes a catalyst. However, the catalyst included in the dielectric coating 112, 122 of each electrode component 110, 120 can differ between the electrode components 110, 120, such that different catalysts can be provided at different residence times within the reactor 100, i.e., the selection of the catalyst for each electrode component 110, 120 can be tailored to the species present in the plasma at the location of that electrode component 110, 120 in the reactor 100.

[0070] exist Figure 1 In the embodiment, both the first electrode member 110 and the second electrode member 120 include dielectric coatings 112, 122, as this can help reduce the likelihood of arcing between the electrodes and the formation of significant plasma byproducts and damage to the coatings caused by arcing.

[0071] Furthermore, the provision of the catalyst on the substrate of the dielectric coating 112 , 122 increases the capacitance of the electrode members 110 , 120 , allowing the reactor 100 to operate at lower current levels while still generating plasma, thereby reducing the energy consumption of the reactor 100 .

[0072] Figure 2A A schematic diagram of a microplasma catalytic reactor 200 according to an embodiment of the first aspect of the present disclosure is shown. The schematic diagram is a cross-sectional view of the catalytic reactor 200, which is substantially parallel to the air path through the reactor (defined by Figure 2A (shown by thick arrows in ). Figure 2A The reactor 200 can be considered as Figure 1 A modification of the reactor 100 shown in FIG. Figure 1 Many of the foregoing descriptions apply mutatis mutandis to Figure 2A .

[0073] However, Figure 2A The reactor 200 and Figure 1 The difference shown is that Figure 2A The reactor 200 further includes a third electrode member 230 disposed between the first electrode member 10 and the second electrode member 220. The electrode members 210, 220, 230 are spaced apart from each other so that a discharge gap 240 is provided between adjacent electrode members 210, 220, 230, as described with reference to FIG. Figure 1 The discussed Figure 2A The distance between the first electrode member 210 and the second electrode member 220 in the reactor 200 is larger to accommodate the third electrode member 230 therebetween, wherein the discharge gaps 240a, 240b provided between adjacent electrode members 210, 220, 230 are greater than the discharge gaps 240a, 240b provided between adjacent electrode members 210, 220, 230. Figure 1 The discharge gap 140 of the reactor 100 is within the same size range discussed above). Figure 2A The electrode members 210, 220, 230 of the reactor 200 have the same structure as previously described. Figure 1 The structures of the first electrode member 110 and / or the second electrode member 120 of the reactor 100 are substantially the same as those set forth in the description of the first electrode member 110 and / or the second electrode member 120 of the reactor 100. However, the catalyst included in the dielectric coating 212, 222, 232 of each electrode member 210, 220, 230 can differ between the electrode members 210, 220, 230, such that different catalysts can be provided at different residence times within the reactor 200, and such that the selection of catalyst for each electrode member 210, 220, 230 can be tailored to the species present in the plasma at the location of that electrode member 210, 220, 230 in the reactor 200.

[0074] Figure 2AThe reactor 200 and Figure 1 An additional difference between the reactors 100 in FIG. 1 is the connection of the power supply 250 to the electrode members 210, 220, 230. Figure 1 In the reactor 100 in FIG. 1 , the power supply 150 is connected only to the core 111 of the first electrode member 110, wherein the core 121 of the second electrode member 120 is connected to the ground 155. However, for Figure 2A The electric reactor 200 of the first electrode member 210 and the second electrode member 220 has cores 211 and 221 connected to the power supply 250, and the core 231 of the third electrode member 230 is connected to the ground 255. The power supplies 150 and 250 are connected at Figure 1 and 2A There is a difference between the two because the electrode members 210, 220, 230 of the reactor 200 need to be supplied with current in such a way that a potential difference is generated between a given electrode member and an electrode member adjacent to the given electrode member, so that plasma is then generated by the resulting electric field.

[0075] It is understandable that Figure 2A As shown, by inserting the third electrode member 230 between the first and second electrode members 210, 220, the distance in the direction of the air path in the reactor 200 in which the plasma is generated is increased. This increases the residence time of the air in the reactor 200 for a given flow rate of air entering the reactor 200, while still maintaining the potential difference between the discharge gap and the adjacent electrode members 210, 220, 230. This is beneficial for generating a plasma with minimal plasma byproducts. As a result, the conversion rate of VOCs and VOC decomposition products in the reactor 200 is increased because these compounds spend more time in the plasma and near the catalyst used to decompose them.

[0076] Figure 2A An additional feature of the reactor 200 shown in FIG is the presence of a non-conductive separator 260 located between the electrode members 210, 220, 230. The non-conductive separator extends circumferentially around the electrode members 210, 220, 230 to isolate adjacent electrode members 210, 220, 230 from each other and from any other conductive structures within the reactor 200 (e.g., the reactor housing). Typically, the separator 260 comprises PTFE. To provide adequate insulation, the separator 260 has a thickness greater than or equal to 25 μm. Typically, the separator thickness is less than or equal to 1000 μm.

[0077] Figure 2B A schematic diagram of a microplasma catalytic reactor 300 according to an embodiment of the first aspect of the present disclosure is shown. The schematic diagram is a cross-sectional view of the catalytic reactor 300, which is substantially parallel to the air path through the reactor (defined by Figure 2B (shown by thick arrows in ). Figure 2B The reactor 300 can be considered as Figure 1 A modification of the reactor 100 shown in FIG. Figure 1 Many of the foregoing descriptions apply mutatis mutandis to Figure 2B .

[0078] However, Figure 2B The reactor 300 and Figure 1 The reactor shown in FIG differs in that Figure 2B The reactor 300 includes a plurality of first electrode members 310 and a plurality of second electrode members 320. Specifically, Figure 2B The reactor 300 in FIG. 1 includes two first electrode members 310 a and 310 b and two second electrode members 320 a and 320 b. A pair of adjacent first electrode members 310 a-b is inserted by the second electrode member 320 b, and a pair of adjacent second electrode members 320 a-b is inserted by the first electrode member 310 a. The electrode members 310, 320 are spaced apart from each other so that Figure 1 The provision of a discharge gap 340 between adjacent electrode members is discussed (i.e., as discussed with respect to Figure 1 As discussed above with respect to the discharge gap 140 of the reactor 100, the discharge gaps 340a, 340b, and 340c provided between adjacent electrode members are within the same size range). The core 321 of both the second electrode members 320a, 320b is connected to the power supply 350, while the core 311 of both the first electrode members 310a, 310b is connected to the ground 355. It can be understood that by adding Figure 2B The number of first and second electrode members 310, 320 in the reactor 300 shown increases the Figure 2B The distance in the direction of the air path in which the plasma is generated within the reactor 300 is increased, so that for a given air flow rate, the residence time of the air within the reactor 300 is increased while still maintaining the potential difference between the discharge gap and the adjacent electrode members 310, 320, which is conducive to generating a plasma with minimal plasma byproducts. As a result, the conversion rate of VOCs and VOC decomposition products within the reactor 300 is increased because these compounds reside longer in the plasma and near the catalyst used to decompose them.

[0079] exist Figure 2B In the reactor 300, the catalyst included in the dielectric coating 312, 322 of each electrode component 310a-b, 320a-b can be different between the electrode components, so that different catalysts can be provided at different residence times within the reactor 300. That is, the catalyst selected for each electrode component 310a-b, 320a-b can be tailored to the species present in the plasma at the location of the electrode component in the reactor 300.

[0080] I understand. Figure 2A and 2B The reactor arrangement shown in can be expanded in a similar manner to further increase the residence time of the microplasma catalytic reactors 200, 300. For example, Figure 2B The reactor 300 shown in FIG3 may be scaled up so that there are three, four, or five first electrode members 310 and second electrode members 320, respectively, wherein each pair of adjacent first electrode members 310 is interposed with a second electrode member 320, and each pair of adjacent second electrode members 320 is interposed with a first electrode member 310.

[0081] As about Figure 1 As discussed in FIG2 , power supplies 150, 250, 350 are connected to Figure 1 One or more electrode components in the reactors 100, 200, and 300 of FIG. 2 are connected to supply current to the connected electrode components. This current generates a potential difference between adjacent electrode components, which in turn generates an electric field across the discharge gap between the adjacent electrode components. The potential difference applied between the electrode components and the electric field strength generated in the discharge gap can be sufficiently large to generate plasma within the discharge gap and near the electrode components (i.e., near the surfaces of the electrode components not adjacent to the discharge gap). These regions together constitute the plasma discharge region of the reactor. The energy of the free electrons within the plasma generated in the reactors 100, 200, and 300 affects the likelihood of plasma byproduct formation and also affects the conversion of VOCs contained within the plasma. Generally, higher free electron energy results in more plasma byproducts and a higher conversion rate of VOCs within the reactors 100, 200, and 300. Therefore, a balance must be struck between plasma byproduct formation and VOC conversion. The free electron energy within the plasma is strongly dependent on the electric field strength, and therefore on the potential difference between adjacent electrode components. The power supplies 150, 250, 350 are configured to provide pulsed DC to the electrode members to which they are connected; by providing pulsed DC to the electrode members connected to the power supplies, the energy consumption of the reactors 100, 200, 300 can be reduced compared to using non-pulsed DC, and an additional control variable for the electric field strength between adjacent electrode members is provided.

[0082] Figure 3An illustrative voltage-time diagram is provided, which contains the waveform of a pulsed DC supplied by a power supply to an electrode component of a microplasma catalytic reactor of the present disclosure. The pulsed DC waveform includes a pulse-on phase, during which the voltage of the power supply is non-zero, and a pulse-off phase, during which the voltage of the power supply is approximately zero. The pulsed DC waveform shown in FIG3 has three controllable parameters, which can be adjusted to vary the potential difference between adjacent electrode components in the reactor. First, the pulsed DC voltage amplitude 1 is adjustable, which refers to the amplitude of the waveform during the pulse-on phase. Second, the pulse width 2 is adjustable, which is the duration of the pulse-on phase. Third, the waveform period 3 is adjustable, which is the duration of a complete "pulse-on-pulse-off" cycle. Period 3 is the inverse of the pulsed DC frequency.

[0083] The effects of these pulsed DC parameters on the performance of the microplasma catalytic reactor will be further explained in conjunction with the data in Tables 1-3 of the examples.

[0084] In a second aspect of the present disclosure, the microplasma catalytic reactor is incorporated into an air purification device. This air purification device includes an air inlet and an air outlet. Ambient air containing VOCs can be supplied to the reactor through the air inlet, and air processed within the reactor can exit the air purification device through the air outlet. In other words, the air inlet, reactor, and air outlet are all arranged along an air path along which ambient air can flow.

[0085] Figure 4 1 shows an embodiment of such an air purification device 10. An air inlet 11 is provided at the bottom of the air purification device 10, and an air outlet 12 is provided at the top of the device 10, wherein three microplasma catalytic reactors 400a-c are inserted between the air inlet 11 and the air outlet 12 along the air path. The three reactors 400a-c of the device 10 are placed in series along the air path so that air leaving the first reactor 400a then enters the second reactor 400b and finally enters the third reactor 400c. Although the air purification device 10 may include a single reactor 400, by Figure 4By placing multiple reactors 400a-c in series along the air path, as in the apparatus 10 of FIGURE 1, for a given air flow rate through the apparatus 10, the residence time of the air within the air purification apparatus 10 can be increased, thereby increasing the conversion rate of VOCs and VOC decomposition products by the apparatus 10. This is because these compounds spend more time in the plasma and near the catalyst used to decompose them. From another perspective, increasing the number of reactors 400 in series along the air flow path can increase the air flow rate through the apparatus 10 without affecting the conversion rate of VOCs and VOC decomposition products. This is because the total residence time within each reactor 400a-c in the apparatus 10 can remain constant even with the increased air flow rate.

[0086] Figure 4 Each of the reactors 400a-c in the air purification device 10 includes a corresponding pair of electrode members 410a-c, 420a-c in the form of a perforated plate. Each of the reactors 400a-c is provided with a pulsed DC from a power supply so as to generate plasma near its electrode members 410a-c, 420a-c. The advantage of having multiple reactors 400a-c in the air purification device 10 is that the pulsed DC provided to a given reactor 400a-c can be controlled independently of the pulsed DC provided to other reactors 400a-c in the device 10. Therefore, the plasma generated in a given reactor 400a-c can be controlled independently of the plasma generated in other reactors 400a-c, and can be adjusted for the compounds present in the air flowing into the specific reactor 400a-c. Therefore, the performance of the air purification device 10 in terms of the concentration of VOCs, VOC decomposition products and plasma byproducts in the air leaving the device 10 via the air outlet 12 can be improved.

[0087] Figure 4 The air purification device 10 in the embodiment further includes an air moving unit 13 (eg, a compressor, a fan, a blower) to drive the air flow through the device 10 along the air path. Figure 4In the embodiment of the present invention, the air propulsion unit 13 is located downstream of the reactors 400a-c along the air path, so that air is drawn through the reactors 400a-c by the air propulsion unit 13. However, the air propulsion unit 13 can also be located upstream of the reactors 400a-c along the air path. The position of the air propulsion unit 13 relative to the reactors 400a-c affects the characteristics of the airflow through the reactors 400a-c: positioning the air propulsion unit 13 upstream of the reactors 400a-c results in more turbulent and higher-pressure airflow through the reactors 400a-c, while positioning the air propulsion unit 13 downstream of the reactors 400a-c provides more laminar and lower-pressure airflow through the reactors 400a-c. Although the air propulsion unit 13 is advantageous in driving airflow through the air purification device 10, the device 10 can also operate without the air propulsion unit 13, for example, if the device 10 is configured and / or positioned so that airflow through the device 10 occurs by natural convection.

[0088] Although Figure 4 The air purification device 10 in FIG. 1 includes three reactors 400a - c connected in series along the air path, but it is understood that the air purification device 10 may include only a single reactor 400 or may include multiple reactors 400 connected in parallel with each other.

[0089] Figure 5 An air purification device 20 is shown having a plurality of reactors 500a-b, wherein the reactors 500a-b have Figure 4 Alternative arrangement shown. Figure 5 In the embodiment, each reactor 500a-b is configured as a curved perforated plate arranged parallel to each other, wherein the air entering the device 20 flows through only one of the two reactors 500a-b. Figure 4 In the apparatus 10 of FIG. 1 , providing a plurality of reactors 500 a-b connected in parallel with one another allows the flow rate of air through the apparatus 20 to be increased without affecting the conversion of VOCs and VOC decomposition products by the apparatus 20 because the residence time within a given reactor 500 a-b can be maintained even when the air flow rate is increased because the increased volume of air can be divided among the increased number of reactors 500 connected in parallel with one another.

[0090] Figure 5 The air purification device 20 also includes a high efficiency particulate absorption (HEPA) filter 24 located upstream of the reactor 500a-b to remove particulate matter, such as pollen, dust, bacteria, and viruses, from the airflow entering the device 20 before the air enters the reactor 500a-b. It is desirable to remove such particulate matter so that it does not interfere with the performance of the reactor 500a-b by affecting plasma generation and / or clogging the reactor. Although Figure 5The apparatus 20 in the embodiment includes two HEPA filters 24, one HEPA filter 24 corresponding to each reactor 500a-b, but it is also possible to provide an apparatus 20 in which all air flows entering the reactor 500 flow through the same HEPA filter 4. In addition, the apparatus 20 includes an adsorption unit 25 located downstream of the reactor 500a-b relative to the air path through the apparatus 20. Depending on the operating conditions of the reactor 500a-b, the plasma generated within the reactor 500a-b may result in plasma byproducts (NO x , O3), especially when the free electron energy of the plasma is high. In addition, the decomposition of VOCs within the plasma generated by the reactors 500a-b can lead to the formation of harmful VOC decomposition products (partially oxidized VOCs). Therefore, in the event that such plasma by-products and VOC decomposition products are generated, a post-plasma adsorption unit can be used to adsorb these compounds from the air treated by the reactors 500a-b before the air leaves the air purification device 20 via the air outlet 22. Typically, the adsorption unit 25 within the air purification device 20 is a consumable unit because the adsorbent contained therein will reach its maximum load after a certain operating duration. However, in the present air purification device 20, the adsorbent of the adsorption unit 25 is able to be discharged by long-lived plasma species (e.g., , , , , , ) in situ regeneration (at least partially), these plasma species exist beyond the plasma discharge zone of reactors 500a-b. These long-lived plasma species enter the adsorption unit 25 within the airflow and decompose the compounds adsorbed on the adsorbent, wherein the resulting products are released from the adsorbent and exit the adsorption unit 25 and the air purification device 20 via the air outlet 22, thereby regenerating the adsorbent capacity. Compared to air purification devices 20 without a microplasma catalytic reactor 500 upstream of the adsorption unit 25, the adsorption unit 25 does not require frequent replacement.

[0091] exist Figure 5 In the embodiment of the present invention, the adsorption cells 25 are cylindrical, and therefore the perforated plates forming the electrode members of the reactors 500a-b are curved so that they correspond to the cylindrical surfaces of their adjacent adsorption cells 25. In order to form the electrode members having such a shape, it is desirable that the conductive core of the electrode members be formed of a ductile material such as aluminum, brass, or copper. The HEPA filter 24 of the device 20 is curved in a similar manner. By providing the air purification device 20 with a cylindrical form, air can be drawn into the device 20 from a wide range of directions.

[0092] Where the air purification device comprises an adsorption unit or a catalytic unit, the air purification device may be configured to operate in a continuous store-and-discharge operation, wherein the air flows through the reactor once. Advantageously, this may increase the flow rate of ambient air that may be introduced into the device.

[0093] Alternatively, where the air purification device comprises an adsorption unit or a catalytic unit, the air purification device can be configured to operate under a cyclic store-and-discharge operation, wherein a portion of the air leaving the reactor is recycled back into the reactor. Advantageously, this can increase the overall conversion of VOCs achieved by the device.

[0094] Figures 6A-6D Provided are process flow diagrams for several different configurations of air purification devices 30, 40, 50, 60 according to the present disclosure, wherein the air purification devices 30, 40, 50, 60 include at least one microplasma catalytic reactor 600, 700, 800, 900 and a plurality of different additional air treatment units (adsorption units 35, 65, catalytic units 46, 56, 66, HEPA filter 54, etc.). Figures 6A-6D In the flow chart, the air purification devices 30, 40, 50, 60 are provided with a test airflow, which is a humid, VOC-containing ambient airflow containing O2, N2, H2O, toluene and other trace elements and molecules. Figures 6A-6D The anhydrous gaseous composition of the VOC-containing ambient air stream from the reactors 30, 40, 50, 60 at room temperature is 21% by mass O, 78% by mass N, and 1 ppm toluene, with the remainder comprising Ar, CO, and other trace elements and molecules. In cases where the concentration of VOCs and / or plasma byproducts in the air exiting the final reactor 600, 700, 800, 900 along the air path through the apparatus 30, 40, 50, 60 remains high, it may be useful to incorporate an additional air treatment unit into the air purification apparatus including one or more microplasma catalytic reactors 600, 700, 800, 900. For example, the number of reactors 600, 700, 800, 900 and / or the number of electrode components within these reactors may be limited due to factors such as the pressure drop across the reactors 600, 700, 800, 900 and the space available in the air purification device 30, 40, 50, 60 for additional reactors 600, 700, 800, 900 and / or electrode components.

[0095] exist Figure 6A In the embodiment, the air purification device 30 includes a micro plasma catalytic reactor 600 and a post-plasma adsorption unit 35. The post-plasma adsorption unit 35 is arranged along the air path passing through the device 30 (by Figure 6AThe micro plasma catalytic reactor 600 is used to decompose the above-mentioned Figure 1-3 The reactor feed gas stream contains toluene molecules, wherein the reactor effluent gas stream contains toluene not decomposed by the reactor 30, partially oxidized VOCs produced by toluene decomposition, long-lived plasma species (such as O, O2 (A 1 Δ), OH, HO2) and plasma byproducts (such as O3, NO x The concentration of toluene, the concentration and identity of the VOC decomposition products, and the concentration of the plasma byproducts in the reactor effluent gas stream are functions of the operating conditions of the reactor 30 (as described above with respect to Figure 3 and the following about Tables 1-3 and Figure 7 and 8 discussed).

[0096] Then, Figure 6A The reactor outflow airflow enters the post-plasma adsorption unit 35. The adsorption unit 35 is arranged in the device 30 to adsorb toluene, toluene decomposition products and plasma by-products from the air treated by the reactor 30 before the air leaves the air purification device 30. Figure 5 As discussed, the adsorbent of the adsorption unit 35 located downstream of the micro plasma catalytic reactor 600 is able to pass long-lived plasma species (such as O, O2 (A 1 Δ), OH, HO2) (at least partially) regenerated in situ, the long-lived plasma species exist beyond the plasma discharge region of the reactor 600 and react with toluene, toluene decomposition products, and plasma byproducts adsorbed on the adsorbent of the adsorption unit 35. Thus, the microplasma catalytic reactor 600 and the post-plasma adsorption unit 35 work in synergy to provide a clean air stream in which the concentration of VOCs is reduced and ozone and nitrogen oxides meet the guidelines of the World Health Organization (WHO).

[0097] exist Figure 6B In the embodiment, the air purification device 40 includes a micro plasma catalytic reactor 700 and a post plasma catalytic unit 46, which is arranged along the air path passing through the device 40 (by Figure 6B The micro plasma catalytic reactor 700 is used to decompose the above-mentioned Figure 1-3 The reactor feed gas stream contains toluene molecules, wherein the reactor effluent gas stream contains toluene not decomposed by the reactor 700, partially oxidized VOCs produced by toluene decomposition, long-lived plasma species (such as O, O2 (A 1 Δ), OH, HO2) and plasma byproducts (such as O3, NO xThe concentration of toluene, the concentration and identity of toluene decomposition products, and the concentration of plasma byproducts in the reactor effluent gas stream are functions of the operating conditions of reactor 700 (as described above with respect to Figure 3 and below regarding Tables 1-3 and Figure 7 and 8 discussed).

[0098] Then, Figure 6B The reactor outflow gas stream enters the post-plasma catalytic unit 46. The catalytic unit 46 is disposed within the device 40 to catalyze the decomposition of one or more of toluene, toluene decomposition products, and plasma byproducts contained in the reactor outflow gas stream, so that the air leaving the catalytic unit 46 and ultimately leaving the air purification device 40 is a clean air stream with reduced VOC concentration and meets the WHO guideline standards for ozone and nitrogen oxides. Figure 6A The device 30 in the embodiment of the present invention, by positioning the catalytic unit 46 downstream of the micro plasma catalytic reactor 700, there are long-lived plasma species (such as O, O2 (A)) exceeding the plasma discharge region of the reactor 700. 1 Δ), OH, HO2) can reach the catalytic unit 46. In the presence of a catalyst in the catalytic unit 46, these long-lived plasma species can increase the conversion rate of toluene and other partially oxidized VOCs on the catalyst surface and decompose the plasma byproducts on the catalyst surface. The catalytic unit 46 can operate at room temperature or higher temperature, depending on the balance of energy consumption and conversion rate required. Therefore, the microplasma catalytic reactor 700 and the post-plasma catalytic unit 46 work together to provide a clean air stream with reduced VOC concentration and meet the WHO guideline standards for ozone and nitrogen oxides. The clean air stream then leaves Figure 6B The air purification device 40 is shown.

[0099] exist Figure 6C In the embodiment, the air purification device 50 includes a micro plasma catalytic reactor 800, a HEPA filter 54 positioned upstream of the reactor 800 along the air path through the device 50 (by Figure 6C The HEPA filter 54 is used to remove particulate matter, such as pollen, dust, bacteria, and viruses, from the air flow entering the device 50 before the air enters the reactor 800. This removal of particulate matter is desirable so that it does not interfere with the performance of the reactor 800 by affecting plasma generation and / or clogging the reactor 800. Thereafter, the micro plasma catalytic reactor 800 is operated as described above with respect to Figure 6A and 6B The above works. Then, Figure 6CThe outflow gas from the reactor enters the post-plasma catalytic unit 56, which is Figure 6B The rear plasma catalytic unit 46 functions in the same manner as described above.

[0100] exist Figure 6D In the embodiment, the air purification device 60 includes a micro plasma catalytic reactor 900, a post plasma catalytic unit 66 and a post plasma adsorption unit 65, wherein the post plasma catalytic unit 66 is positioned downstream of the reactor 900 along the air path through the device 60 (by Figure 6C ), the post-plasma adsorption unit 65 is positioned downstream of the catalytic unit 66 along the air path through the device 60. This configuration can allow the air purification device 60 to continue to provide satisfactory air purification even when the air flow rate through the device 60 is very large, or when maximizing the single-pass efficiency within the device 60 is sought, because three different units that can decompose and / or adsorb VOCs are provided within the device 60.

[0101] Despite Figure 6D The catalytic unit 66 and the adsorption unit 65 are shown as distinct units, but the catalytic and adsorption processes can also be combined within a single unit by doping the adsorbent contained within the adsorption unit 65 with a catalyst to accelerate the oxidation of adsorbed compounds, including VOCs, VOC decomposition products, and plasma byproducts.

[0102] Where the air purification device comprises an adsorption unit or a catalytic unit, the air purification device may be configured to operate in a continuous store-and-discharge operation, wherein the air flows through the reactor once. Advantageously, this may increase the flow rate of ambient air that may be introduced into the device.

[0103] Alternatively, where the air purification device comprises an adsorption unit or a catalytic unit, the air purification device can be configured to operate under a cyclic store-and-discharge operation, wherein a portion of the air leaving the reactor is recycled back into the reactor. Advantageously, this can increase the overall conversion of VOCs achieved by the device.

[0104] Example

[0105] Table 1 contains data from an experiment using a microplasma reactor supplied with pulsed DC to investigate the formation of plasma byproducts in the reactor. The reactor consisted of two perforated plate electrode members with a 200 μm thick alumina dielectric coating separated by a 100 μm discharge gap, with no catalyst within the dielectric coating. The electrode members had a diameter of 58.4 mm and a thickness of 1.4 mm. The perforations had a diameter of 2.6 mm and were arranged in a regular hexagonal array with a pitch of 5 mm, providing an open area of ​​24.6%. VOC-free, dry ambient air (relative humidity <1%) was supplied to the reactor at a flow rate of 5 L / min.

[0106] Tests 1-15 in Table 1 correspond to different pulsed DC parameters with voltage, frequency, and pulse width. The concentrations of ozone (O3), nitric oxide (NO), and nitrogen dioxide (NO2) (plasma byproducts) in the reactor effluent gas stream were measured, as well as the current amplitude and power consumption of the reactor. By using the relationship The power consumption is calculated by time-integrating the product of the voltage and current pulses over one cycle, where t is the cycle time, V(t) and I(t) are the applied voltage and current, respectively.

[0107] The tests in Table 1 can be roughly divided into three operating regions. There is a first region covering tests 1-9, in which the voltage of the DC power supply is in the range of 0.9-1.1 kV, and plasma is generated without forming plasma byproducts (i.e., no O3, NO, or NO2 is formed in the reactor). The second region covers tests 10 and 12, in which pulsed DC with a voltage of 1.2 kV and frequencies of 1 kHz and 50 kHz, respectively, is supplied, and O3 is formed but no NO2 is formed. x The third region covers tests 11 and 13-15 and results in the formation of O3 and NO in the plasma due to the high free electron energies generated by the pulsed DC parameters of tests 11 and 13-15. x , which more easily causes nitrogen dissociation and leads to NO x The existence of the second region indicates that it is possible to selectively form O radicals in the reactor while suppressing the formation of N radicals.

[0108] Table 2 contains experimental data from a microplasma reactor supplied with pulsed DC and a microplasma catalytic reactor supplied with pulsed DC to investigate plasma byproduct formation in the reactors. VOC-free, humidified ambient air (relative humidity ~50%) was supplied to the reactors at a flow rate of 5 L / min. The microplasma reactors used in Tests 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, and 44 were identical to those used in Tests 1-15 of Table 1. The microplasma catalytic reactors (used in Tests 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, and 43) were identical to those used in Tests 1-15 of Table 1, except that the dielectric coating also contained a MnO2 catalyst. The manganese oxide catalyst was incorporated into the alumina-coated electrodes of the microplasma catalytic reactors by an incipient wetness impregnation technique. The catalyst precursor, manganese(II) nitrate tetrahydrate, was dissolved in water in a volume equal to the pore volume of the alumina coating. The amount of precursor in the solution was based on the mass of the metal element (10 wt.% Mn) relative to the desired mass of Al2O3. Capillary action drew the precursor solution into the pores. The impregnated electrode was dried in an oven at 110°C for 30 minutes to remove water and then calcined at 450°C for 2 hours with a heating and cooling rate of 2°C / min. This calcination process converted the manganese nitrate precursor into manganese oxide.

[0109] Plasma discharges in humid ambient air have a strong tendency towards instability, so byproduct formation occurs more easily than in dry air under the same pulsed DC parameters. Considering first the microplasma reactor test results, it is obvious that under the same pulsed DC parameters, the humid air tests lead to much higher concentrations of O3, NO, and NO2 than the dry air tests in Table 1. In addition, for humid air, the first and second regions in Table 1 no longer exist within the voltage range studied in the tests in Table 2: O3 and NO2 x In contrast, in the case of dry air, the reactor only produced O3 and NO at voltages greater than or equal to 1.2 kV. x The explanation for the behavior observed with moist air is that the presence of water in the discharge gap modifies the formation of O3 and NO in the plasma. x In particular, it is expected that the plasma can act as a catalyst for the reaction of O3 and NO x The precursors for the formation of free radical species O and OH are O3 and NO in the air leaving the reactor. x Many of the tests in Table 2 using the microplasma catalytic reactor resulted in O3 concentrations in the reactor effluent gas stream exceeding the World Health Organization guideline for O3 exposure levels.

[0110] However, the tests in Table 2 using the microplasma catalytic reactor resulted in significantly lower concentrations of plasma byproducts than those using the microplasma reactor under the same or similar conditions. In tests 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, and 43, no O₃ was detected in the reactor effluent gas stream, even at voltages as high as 1 kV. Although NO and NO₂ were detected in the reactor effluent gas stream, their concentrations were consistently lower than those observed in microplasma reactors operating under the same or similar conditions, typically by an order of magnitude or more. The comparison of the tests in Table 2 using the microplasma reactor and the microplasma catalytic reactor suggests that when humid air is fed into the microplasma catalytic reactor, the MnO₂ catalyst within the dielectric layer catalyzes the decomposition of O₃, NO, and NO₂ formed within the plasma.

[0111] Table 3 contains data for an Example using a microplasma catalytic reactor according to the first aspect of the present disclosure to decompose toluene contained in a reactor feed gas stream, and data for a Comparative Example using a microplasma reactor to decompose toluene contained in a reactor feed gas stream. The microplasma catalytic reactor and microplasma reactor used in the Example and Comparative Example, respectively, are identical to those described above with respect to Tables 1 and 2. Humidified ambient air (relative humidity ~50%) containing 1 ppm of toluene was supplied to the reactor at a flow rate of 5 L / min. The electrode assembly was supplied with pulsed DC from a power supply, with the Example and Comparative Examples in Table 3 covering a range of pulsed DC parameters (voltage, frequency, pulse width).

[0112] In a low-energy plasma discharge, such as that generated in a microplasma reactor, toluene is oxidized to CO2 and water through a series of reactions with electrons and reactive radicals (O, H, OH, N2*). However, by supplying a catalyst within the plasma discharge, an alternative reaction mechanism for toluene oxidation is provided.

[0113] The comparative example in Table 3 shows that the microplasma catalytic reactor can achieve over 70% toluene decomposition and minimize the formation of O3, NO, and NO2 (<1 ppb) when operated under ambient conditions. Figure 8 Chromatograms of the reactor feed and effluent gas streams for Comparative Example 1 (0.9 kV, 25 kHz, 1 μs, 97.9% toluene conversion) are provided and demonstrate the presence of a range of partially oxidized VOC compounds in the effluent gas stream. The partially oxidized VOC compounds present include benzene, phenol, and o-xylene, which are roughly as toxic as the toluene contained in the reactor feed, as well as acetone and ethanol, which are less toxic. The formation of these partially oxidized VOCs, present at concentrations as high as 0.1 ppm, suggests that integrating an adsorption bed into the air purification device downstream of the microplasma reactor would be mandatory.

[0114] As shown in Table 3, the examples related to the microplasma catalytic reactor described in this disclosure demonstrate that this reactor achieves improved toluene conversion while reducing the generation of plasma byproducts. Because plasma processes are not selective, the presence of a catalyst can improve reaction selectivity by promoting specific reaction pathways. For example, the generation of O₃ in plasma does not directly react with toluene. However, under the action of the MnO₂ catalyst, ozone readily decomposes to produce oxygen free radicals with higher oxidative activity, which then react with toluene.

[0115] Furthermore, the energy consumption of the microplasma catalytic reactor is approximately an order of magnitude lower than that of the microplasma reactor. This reduction in power can be attributed to the increased capacitance of the electrode components when the dielectric-coated alumina substrate is impregnated with the catalyst (to 100 pF compared to 20 pF for the microplasma reactor) and the reduced activation energy of the reaction mechanism occurring in the presence of the catalyst. The examples in Table 3 indicate a wide operating window at 0.9 kV and 25 kHz pulsed DC, with pulse widths ranging from 0.6 μs to 30 μs.

[0116] Figure 8 also shows the chromatograms of the reactor feed and effluent streams from Example 1 (0.9 kV, 25 kHz, 1 μs, 99.8% toluene conversion). This chromatogram demonstrates that the concentrations (indicated by peak area) and species range of the partially oxidized VOCs present in the microplasma-catalyzed reactor effluent were much lower. Only benzene, ethanol, acetone, and phthalic anhydride were detected, all at very low concentrations (<0.01 ppm).

[0117] By comparing the examples in Table 3 with the comparative examples, it can be clearly seen that under the same operating conditions, the microplasma catalytic reactor described in the present disclosure can achieve higher conversion rates, less by-product generation (including plasma by-products and partially oxidized volatile organic compounds), and lower energy consumption compared to other microplasma catalytic reactors.

[0118]

[0119] Table 1

[0120]

[0121] Table 2

[0122]

[0123] Table 3

[0124] The features disclosed in the preceding description or in the following claims or in the accompanying drawings, expressed in their specific form or as a means for performing the disclosed function or as a method or process for obtaining the disclosed results, as the case may be, may be used alone or in any combination of these features to realize the invention in its various forms.

[0125] Although the present invention has been described in conjunction with the above exemplary embodiments, many equivalent modifications and variations will be apparent to those skilled in the art upon presentation of this disclosure. Therefore, the exemplary embodiments of the present invention set forth above are intended to be illustrative rather than restrictive. Various changes may be made to the described embodiments without departing from the spirit and scope of the present invention.

[0126] For the avoidance of any doubt, any theoretical explanations provided herein are provided to enhance the reader's understanding. The inventors do not wish to be bound by any of these theoretical explanations.

[0127] Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0128] Throughout this specification, including the claims that follow, unless the context requires otherwise, the words "comprise" and "include" and variations such as "comprises" and variations such as "comprises" will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0129] It must be noted that, as used in the specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from "about" one particular value and / or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when a value is expressed as an approximation by use of the antecedent "about," it is understood that the particular value forms another embodiment. The term "about" in relation to a numerical value is optional and means, for example, + / - 10%.

Claims

1. A microplasma catalytic reactor for treating ambient air by decomposing VOCs in the ambient air, the reactor comprising: a first electrode member comprising a conductive core and a dielectric coating; and a second electrode member disposed relative to the first electrode member to generate a plasma between the first and second electrode members when a plasma generating voltage is applied between the first and second electrode members such that, in use, VOCs in ambient air within the reactor are decomposed to form VOC decomposition products and plasma byproducts are formed; wherein the dielectric coating further comprises a catalyst that catalyzes the decomposition of one or more of: VOCs; VOC decomposition products; and Plasma byproducts.

2. The reactor according to claim 1, wherein The second electrode member includes a conductive core and a dielectric coating.

3. A reactor according to any one of the preceding claims, wherein: The dielectric coating is porous; and The catalyst is at least partially disposed on the interior surfaces of the pores of the dielectric coating.

4. A reactor according to any one of the preceding claims, wherein The dielectric coating comprises a metal oxide, optionally comprising one or more of MnO2, Al2O3, CeO2, SiO2 and TiO2.

5. A reactor according to any one of the preceding claims, wherein: The reactor includes a plurality of first electrode members and a plurality of second electrode members; Each pair of adjacent first electrode members is interposed with a second electrode member; and Each pair of adjacent second electrode members is interposed with a first electrode member.

6. A reactor according to any one of the preceding claims, wherein: The reactor further includes a power source connected to each first electrode member or each second electrode member; and The power supply is configured to deliver pulsed DC to each electrode member to which it is connected so as to generate a plasma between a first electrode member and an adjacent second electrode member.

7. The reactor according to claim 6, wherein The power supply is configured to deliver pulsed DC to each electrode member connected thereto, the pulsed DC received by each electrode member being: generating an electric field strength between the electrode member and an adjacent electrode member at an applied voltage greater than or equal to [0.3 kV] and less than or equal to [1.9 kV]; Having a pulse frequency greater than or equal to 0.5 kHz and less than or equal to 100 kHz; and The pulse width is greater than or equal to 0.05 μs and less than or equal to 50 μs.

8. A reactor according to any one of the preceding claims, wherein Each electrode member is a perforated plate.

9. The reactor according to claim 8, wherein Adjacent plate-like electrode members are substantially parallel to each other, and adjacent surfaces of the adjacent plate-like electrode members are offset from each other by a distance of 1 mm or less.

10. An air purification device comprising: Air inlet; Air outlet; and A reactor according to any one of the preceding claims; Wherein, in use, ambient air flows along an air path that enters the device via the air inlet, passes through the reactor, and exits the device via the air outlet.

11. The air purification device according to claim 10, comprising a plurality of reactors according to any one of claims 1 to 9 positioned along an air path between the air inlet and the air outlet. 12 . The air purification device of claim 11 , wherein the plurality of reactors are positioned in series along an air path between the air inlet and the air outlet.

13. The air purification device according to claim 12, wherein: The air purification device further includes an adsorption unit positioned along the air path between the reactor and the air outlet; and The adsorption unit is configured to adsorb one or more of the following contained in the air flow leaving the reactor during use of the air purification device: VOCs; VOC decomposition products; and Plasma byproducts.

14. The air purification device according to claim 12 or 13, wherein: The air purification device further includes a catalytic unit positioned along the air path between the reactor and the air outlet; and The catalytic unit is configured to catalyze the decomposition of one or more of the following contained in the gas stream exiting the reactor during use of the air purification device: VOCs; VOC decomposition products; and Plasma byproducts.

15. A method for treating ambient air to reduce the concentration of VOCs in the air using a microplasma catalytic reactor, the reactor comprising: a first electrode member comprising a conductive core and a dielectric coating comprising a catalyst; and a second electrode member disposed relative to the first electrode member; The method comprises the following steps: passing an ambient gas stream containing VOCs through the reactor; applying a plasma generating voltage between the first electrode member and the second electrode member to generate a plasma in the VOC-containing gas stream, the plasma decomposing the VOCs contained in the gas stream and generating VOC decomposition products and plasma byproducts; and The catalyst is used to catalyze the decomposition of one or more of: VOCs; VOC decomposition products; and Plasma byproducts.

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