NANO-CATALYST COMPOSITE FOR DECOMPOSING FORMALDEHYDE AT ROOM TEMPERATURE AND PREPARATION METHOD THEREOF

Abstract

Some embodiments of the disclosure provide a nano-catalyst composite for decomposing formaldehyde at room temperature and a preparation method. According to an embodiment, a nano-catalyst composite includes an alumina carrier of a nano dual-via structure. An inner part and a surface of the nano-alumina dual-via structure are loaded with a non-stoichiometric nano-metal manganese dioxide (MnO.sub.2-x) catalyst. According to another embodiment, a preparation method of a nano-catalyst composite for decomposing formaldehyde at room temperature includes the following steps. (1) Loading manganese dioxide onto the nano-alumina carrier by an electron beam thermal evaporation technology. (2) Conducting hydrogenation treatment on the manganese dioxide catalyst on the nano-alumina carrier under a condition of specific hydrogen pressure, specific temperature, and a specific hydrogenation time, to obtain the non-stoichiometric nano manganese dioxide (MnO.sub.2-x) catalyst.

Claims

1. A nano-catalyst composite for decomposing formaldehyde at room temperature, prepared by a method comprising the steps of: (1) loading manganese dioxide onto a nano-alumina carrier by an electron beam thermal evaporation technology; and (2) conducting a hydrogenation treatment on the manganese dioxide on the nano-alumina carrier under a condition of specific hydrogen pressure, specific temperature, and a specific hydrogenation time, to obtain a non-stoichiometric nano manganese dioxide (MnO.sub.2-x) catalyst; wherein: the nano-catalyst composite comprises an alumina carrier of a nano dual-via structure; and an inner part and a surface of the alumina carrier of the nano dual-via structure are loaded with a non-stoichiometric nano-metal manganese dioxide (MnO.sub.2-x) catalyst.

2. The nano-catalyst composite according to claim 1, wherein the formaldehyde is decomposed at room temperature by the non-stoichiometric nano-metal manganese dioxide (MnO.sub.2-x) catalyst of the nano-catalyst composite.

3. The nano-catalyst composite according to claim 2, wherein a non-stoichiometric ratio x of the nano manganese dioxide (MnO.sub.2-x) catalyst is between 0.05 and 0.2.

4. The nano-catalyst composite according to claim 1, further comprising a catalyst carrier, the catalyst carrier being an alumina of a nano dual-via structure.

5. The nano-catalyst composite according to claim 4, wherein a pore diameter of the alumina of a nano dual-via structure is between 80 nm and 350 nm.

6. The nano-catalyst composite according to claim 1, wherein a pore diameter of the alumina carrier of a nano dual-via structure is between 80 nm and 350 nm.

7. The nano-catalyst composite according to claim 1, wherein a non-stoichiometric ratio x of the nano manganese dioxide (MnO.sub.2-x) catalyst is between 0.05 and 0.2.

8. A preparation method of a nano-catalyst composite for decomposing formaldehyde at room temperature comprising the steps of: (1) loading manganese dioxide onto a nano-alumina carrier by an electron beam thermal evaporation technology; and (2) conducting a hydrogenation treatment on the manganese dioxide on the nano-alumina carrier under a condition of specific hydrogen pressure, specific temperature, and a specific hydrogenation time, to obtain a non-stoichiometric nano manganese dioxide (MnO.sub.2-x) catalyst.

9. The preparation method according to claim 8, wherein in the hydrogenation treatment condition, the specific hydrogen pressure is between 1.5 MPa and 2.5 MPa, the specific temperature is between 280 C. and 420 C., and the specific hydrogenation time is between 2 hours and 6 hours.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 is an SEM image of an alumina carrier of a nano dual-via structure and with a pore diameter of 100 nm.

[0020] FIG. 2 is an SEM image of nano manganese dioxide loaded on anodic aluminum oxide (AAO).

[0021] FIG. 3 shows a static-state detection apparatus for formaldehyde degradation.

[0022] FIGS. 4A through 4C show static-state formaldehyde degradation results.

DETAILED DESCRIPTION

[0023] The following describes some non-limiting exemplary embodiments of the disclosure with references to the accompanying FIGS. 1-4C.

Embodiment 1

[0024] A porous anodic aluminum oxide (AAO) alumina carrier of a dual-via structure and with a pore diameter of 100 nm is used. The via structure is shown in FIG. 1, and a diameter of a circular nano-alumina carrier is 50 mm and a thickness thereof is 120 m. A manganese dioxide target material is prepared by pressing manganese dioxide powder with purity of 99.99%. A nano-catalyst composite is prepared according to the following steps. (1) Manganese dioxide loading: loading a specific amount of manganese dioxide onto the AAO alumina carrier of a dual-via structure in a vacuum electron beam evaporation device by a suitable technology. FIG. 2 shows a morphology of nano manganese dioxide loaded onto the AAO. (2) Hydrogenation treatment: placing the dual-via alumina carrier loaded with the manganese dioxide in a high-pressure hydrogenation reactor, conducting vacuumizing first, heating to 320 C. at a heating rate of 5 C./min, introducing pure hydrogen gas until pressure reaches 1.5 MPa, conducting heat preservation for 4 hours, then naturally cooling to room temperature, and finally conducting depressurization to obtain a hydrogenated nano-catalyst composite. X-ray diffraction results show that a hydrogenated sample is still manganese dioxide of a typical orthorhombic phase, but a unit cell volume is reduced. It is determined through X-Ray diffraction results that x is 0.11 (MnO.sub.1.89).

[0025] An experiment of decomposing formaldehyde at room temperature is conducted in a static-state detection apparatus shown in FIG. 3. As shown in FIG. 3, 1 is formaldehyde detector, 2 is container cap, 3 is sampling head, 4 is glass container, 5 is photocatalyst, 6 is light source, 7 is gas injection port, and 8 is transformer. In an experiment of decomposing formaldehyde, a nano-catalyst composite 5 is placed to the bottom of a closed vessel 4, a specific amount of formaldehyde gas is injected from a gas injection port 7 by using a micro sampling needle, and a formaldehyde detector detects a concentration change of the formaldehyde in the vessel in real time by using a sampling head 3 and records data every five minutes.

[0026] Exemplary test results are shown in FIG. 4A. In this experiment group, the non-stoichiometric manganese dioxide is MnO.sub.1.89, and the hydrogenation treatment condition is 320 C./1.5 MPa/4 hours. As shown in FIG. 4A, after 100 minutes, a degradation rate of formaldehyde at the room temperature is 57.6%.

Embodiment 2

[0027] A preparation process of a catalyst composite for decomposing formaldehyde at room temperature is the same as that in Embodiment 1, but the hydrogenation condition of the dual-via alumina carrier loaded with the manganese dioxide is changed to the following: 350 C. hydrogenation temperature, 2.0 MPa hydrogen pressure, and 4 hours heat preservation. The x value measured by an X-ray diffraction experiment is 0.15 (MnO.sub.1.85). An experiment of decomposing formaldehyde at room temperature is conducted the same as that conducted in Embodiment 1.

[0028] Exemplary test results are shown in FIG. 4B. In this experiment group, the non-stoichiometric manganese dioxide is MnO.sub.1.85, and the hydrogenation treatment condition is 350 C./2 MPa/4 hours. As shown in FIG. 4B, after 100 minutes, a degradation rate of formaldehyde at the room temperature is 70%.

Embodiment 3

[0029] A preparation process of a catalyst composite for decomposing formaldehyde at room temperature is the same as that in Embodiment 1, but the hydrogenation condition of the dual-via alumina carrier loaded with the manganese dioxide is changed to the following: Hydrogenation temperature is 380 C., hydrogen pressure is 2.5 MPa, and heat preservation is conducted for 5 hours. x measured by an X-ray diffraction experiment is 0.18 (MnO.sub.1.82). An experiment of decomposing formaldehyde at room temperature is conducted the same as that conducted in Embodiment 1,

[0030] Exemplary test results are shown in FIG. 4C. In this experiment group, the non-stoichiometric manganese dioxide is MnO.sub.1.82, and the hydrogenation treatment condition is 380 C./2.5 MPa/4 hours. As shown in FIG. 4C, after 100 minutes, a degradation rate of formaldehyde at the room temperature is 54.5%.

[0031] Some embodiments of the disclosure may have one or more of the following effects. The disclosure may have characteristics such as high catalytic activity of decomposing formaldehyde at room temperature, adjustable concentration of active oxygen, good catalyst stability, simple preparation process, low costs, et cetera. The disclosure may be applied to the treatment of formaldehyde pollutants in air, especially the treatment of indoor formaldehyde pollutants and formaldehyde pollutants in a car. A nano-catalyst composite according to the disclosure may implement fast and efficient catalytic decomposition of formaldehyde in indoor air or formaldehyde in air in a car at room temperature. A non-stoichiometric nano-metal manganese dioxide (MnO.sub.2-x) according to the disclosure may have a large quantity of oxygen vacancy defects, and a large amount of active oxygen may be adsorbed onto the surface and a surface layer of the non-stoichiometric nano-metal manganese dioxide, which may improve catalytic activity of decomposing formaldehyde at the room temperature. A nano-alumina carrier of a dual-via structure according to the disclosure may have very high mechanical strength, heat resistance, and corrosion resistance, which may be convenient for the design of a formaldehyde catalytic degradation reactor.

[0032] Other embodiments of the disclosure may have one or more of the following effects. (1) An active oxygen concentration may be controllable. Different oxygen vacancy concentrations and ratios between lattice oxygen and surface oxygen may be obtained by adjusting an x value in the non-stoichiometric manganese dioxide (MnO.sub.2-x). (2) The catalyst composite may have stable performance and good consistency. The non-stoichiometric single-component manganese dioxide (MnO.sub.2-x) material may be used according to the disclosure, and the electron beam thermal evaporation technology may be used for loading and ensure catalyst stability consistency. (3) The structure may be simple. The used nano-alumina carrier of a dual-via structure may have very high mechanical strength, and integrated loading of the nano-manganese oxide (MnO.sub.2-x) may be used to implement a miniaturization of a formaldehyde catalytic degradation reactor. (4) The non-stoichiometric manganese dioxide (MnO.sub.2-x) catalyst may be used to decompose formaldehyde at room temperature without additional energy. Environmental pollution in a degradation process may be minimized.

[0033] The foregoing embodiments are merely used for description of the disclosure, and do not constitute any limitation on the disclosure. A person of ordinary skill in the related technical field can make various modifications and variations to the disclosure without departing from the spirit and scope of the disclosure Therefore, all equivalent technical solutions fall within the scope of the disclosure, and the protection scope of the disclosure shall not be limited by the claims.

[0034] Many different arrangements of the various components depicted, as well as components not shown, are possible without departing from the spirit and scope of the present disclosure. Embodiments of the present disclosure have been described with the intent to be illustrative rather than restrictive. Alternative embodiments will become apparent to those skilled in the art that do not depart from its scope. A skilled artisan may develop alternative means of implementing the aforementioned improvements without departing from the scope of the present disclosure.

[0035] It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations and are contemplated within the scope of the claims. Unless indicated otherwise, not all steps listed in the various figures need be carried out in the specific order described.