Nickel-based catalyst for low temperature co oxidation prepared using atomic layer deposition and application thereof

Abstract

The present invention relates to a nickel-based catalyst for oxidizing carbon monoxide, which is prepared by forming nickel oxide on the surface of a mesoporous support by one or more cycles of atomic layer deposition, and a use thereof. The nickel-based catalyst for oxidizing carbon monoxide according to the present invention is stable at high temperatures because the size of the nickel oxide particles can be restricted to nanometer scales even at high-temperature conditions. In addition, the nickel-based catalyst exhibits catalytic reactivity for oxidation of carbon monoxide even at room temperatures. Additionally, the catalytic activity, which has been deactivated after conducting the catalytic reaction, can be regenerated through annealing and increased gradually through repeated annealing.

Claims

1. A method for removing carbon monoxide, the method comprising: Preparing a nickel-based catalyst for forming nickel oxide on a surface of a mesoporous support by one or more cycles of atomic layer deposition; conducting oxidation of carbon monoxide using a nickel-based catalyst; and regenerating catalytic activity of the nickel-based catalyst by annealing the nickel based catalyst at 100 to 500 for 1 hour to 5 hours between cycles of the oxidation of carbon monoxide, wherein the regenerating comprises: increasing the catalytic activity of the nickel-based catalyst in proportion to a number of annealing, and removing a carbon deposited during the oxidation of carbon monoxide through the annealing, and wherein the nickel-oxide formed on the surface has a particle diameter between 0.5 nm and 15 nm, and the mesoporous support has a pore diameter between 1 nm and 15 nm, to prevent aggregation of the nickel-oxide above a threshold at high temperatures and maintain stability and catalytic activity without changing the physical shape of the mesoporous support.

2. The method for removing carbon monoxide according to claim 1, wherein the oxidation of carbon monoxide is conducted at 25 C. to 450 C.

3. The method for removing carbon monoxide according to claim 1, wherein the support is alumina, silica, zeolite, or a metal-organic framework.

4. The method for removing carbon monoxide according to claim 1, wherein the annealing is conducted in air.

5. The method of claim 1, wherein the atomic layer deposition is conducted by injecting a nickel precursor onto the mesoporous support at a pressure of between 100 mtorr and 300 mtorr and for an exposure time between 10 seconds and 60 seconds.

6. A method for preparing a gas having carbon monoxide removed or reduced from a mixture gas comprising carbon monoxide, the method comprising: preparing a nickel-based catalyst by forming nickel oxide on a surface of a mesoporous support by one or more cycles of atomic layer deposition; conducting oxidation of carbon monoxide of the mixture gas in the presence of a nickel-based catalyst, and regenerating catalytic activity of the nickel-based catalyst by annealing the nickel-based catalyst at 100 C. to 500 C. for 1 hour to 5 hours between cycles of the oxidation of carbon monoxide, wherein the regenerating comprises: increasing the catalytic activity of the nickel-based catalyst in proportion to a number of annealing, and wherein the nickel-oxide formed on the surface has a particle diameter between 0.5 nm and 15 nm, and the mesoporous support has a pore diameter between 1 nm and 15 nm, to prevent aggregation of the nickel-oxide above a threshold at high temperatures and maintain stability and catalytic activity without changing the physical shape of the mesoporous support.

7. The method for preparing a gas having carbon monoxide removed or reduced according to claim 6, wherein the oxidation of carbon monoxide is conducted at 25 C. to 450 C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 schematically describes an atomic layer desorption (ALD) process.

(2) FIG. 2 shows an exemplary apparatus for purifying an exhaust gas in which a catalyst according to the present invention can be included (source: http://www.preciousmetals.umicore.com/recyclables/SAC/CatalyticConverter/).

(3) FIG. 3 shows a result of analyzing the surface of a nickel oxide catalyst prepared in Example 1 by X-ray spectroscopy.

(4) FIG. 4 shows a transmission electron microscopic image of a nickel oxide catalyst prepared in Example 2 after annealing at 450 C. for 3 hours.

(5) FIG. 5 shows the carbon monoxide oxidation efficiency (%) of a nickel oxide catalyst prepared in Example 1 with reaction time analyzed by gas chromatography, when used for oxidation of carbon monoxide.

(6) FIG. 6 shows the carbon monoxide oxidation efficiency (%) of a nickel oxide catalyst prepared in Example 1 with reaction time analyzed by gas chromatography, when used for repeated oxidation of carbon monoxide. Annealing at 300 C. for 2 hours is included between adjacent cycles.

(7) FIG. 7 and FIG. 8 show nuclear spectra of Ni and C of a 2nd annealed catalyst after a first oxidation of carbon monoxide followed by annealing at 300 C. for 2 hours, and an 8th annealed catalyst after a seventh oxidation of carbon monoxide followed by annealing at 300 C. for 2 hours analyzed by X-ray spectroscopy, when a nickel oxide catalyst prepared in Example 1 has been used for repeated oxidation of carbon monoxide.

(8) FIG. 9 shows the carbon monoxide oxidation efficiency (%) of a nickel oxide catalyst prepared in Example 2 with reaction time analyzed by gas chromatography, when used for oxidation of carbon monoxide.

(9) FIG. 10 shows the carbon monoxide oxidation efficiency (%) of a nickel oxide catalyst prepared in Example 3 with reaction time analyzed by gas chromatography, when used for oxidation of carbon monoxide.

EXAMPLES

(10) Hereinafter, the present invention will be described in detail through examples. However, the following examples are for illustrative purposes only and it will be apparent to those of ordinary skill in the art that the scope of the present invention is not limited by the examples.

Example 1: Preparation of Nickel Oxide Catalyst Using Atomic Layer Deposition (ALD)

(11) A mesoporous alumina bead support was positioned in a reactor and the internal pressure of the reactor was maintained at a vacuum state of 10 mtorr or lower. The temperature inside the reactor was maintained at 250 C. and the temperature of a pipeline was maintained at 200 C.

(12) Ni(Cp).sub.2 vapor was injected into the reactor as a first precursor and a Ni(Cp).sub.2 single atomic layer was formed on the support surface by exposing for 30 seconds under a precursor vapor partial pressure of 200 mtorr. After purging the reactor by injecting nitrogen gas, the pressure inside the reactor was maintained at a vacuum state of 10 mtorr or lower by pumping using a pump. Then, oxygen gas was injected as a second precursor and a single atomic layer of nickel oxide was supported by exposing for 30 seconds under an oxygen gas partial pressure of 1 torr so that reaction occurred with the Ni(Cp).sub.2 deposited on the mesoporous alumina surface. For the next cycle, the reactor was purged by injecting nitrogen gas and then pumping.

(13) This procedure corresponds to one cycle. The thickness of the nickel oxide thin film supported on the support can be controlled by controlling the number of the cycles. A nickel oxide catalyst was prepared by conducting 50 cycles.

(14) FIG. 3 shows a result of analyzing the surface of the nickel oxide catalyst prepared in Example 1 by X-ray spectroscopy. The deposition of nickel oxide was confirmed by the newly observed Ni 2p peaks.

Experimental Example 1: Oxidation of Carbon Monoxide

(15) The mesoporous alumina bead catalyst on which nickel oxide is supported, which was prepared in Example 1, was annealed at 300 C. for 2 hours in the air and was positioned in a reactor. Then, air containing 1% carbon monoxide was flown at a rate of 10 mL/min as a reactant gas. While maintaining the temperature of the reactor at 30 C., 150 C., and 250 C., respectively, carbon monoxide oxidation efficiency was measured by gas chromatography.

(16) FIG. 5 shows a result of measuring the volume of carbon monoxide (vol %) consumed during the catalytic reaction by gas chromatography. As seen from FIG. 5, the nickel oxide catalyst prepared in Example 1 showed high catalytic reactivity for oxidation of carbon monoxide and stability at 250 C., and also showed high catalytic reactivity, even at the initial stage of reaction at 30 C. (90% carbon monoxide consumption).

Experimental Example 2: Oxidation of Carbon Monoxide after Repeated Annealing of Nickel Oxide Catalyst

(17) The mesoporous alumina bead catalyst on which nickel oxide is supported, which was prepared in Example 1, was positioned in a reactor. Then, air containing 1% carbon monoxide was flown at a rate of 10 ml/min as a reactant gas. While maintaining the temperature of the reactor at 30 C., reactants and products were monitored by gas chromatography. Annealing at 300 C. for 2 hours was included between 7 cycles of oxidation of carbon monoxide for 2 hours.

(18) As seen from FIG. 6, the reactivity of the nickel oxide catalyst for oxidation of carbon monoxide which had been decreased with reaction time was regenerated by annealing. In addition, the reactivity for oxidation of carbon monoxide increased gradually by repeated annealing. As the number of annealing increased, the initial reactivity of the nickel oxide catalyst for oxidation of carbon monoxide was increased.

(19) FIG. 7 and FIG. 8 show the spectra of a 2nd annealed catalyst after a first oxidation of carbon monoxide followed by annealing at 300 C. for 2 hours and an 8th annealed catalyst after a seventh oxidation of carbon monoxide followed by annealing at 300 C. for 2 hours analyzed by X-ray spectroscopy, when the nickel oxide catalyst was used for repeated oxidation of carbon monoxide. It can be seen that the intensity of the Ni 2p peaks was increased after repeated annealing, suggesting an increased proportion of nickel on the nickel oxide catalyst surface. Additionally, from the fact that the intensities of the C 1s peaks of the 2nd annealed catalyst and the 8th annealed catalyst are not significantly different, it can be seen that the carbon deposited during the oxidation of carbon monoxide was removed through the annealing (FIG. 8).

Example 2: Preparation of Nickel Oxide Catalyst Using Atomic Layer Deposition (ALD)

(20) A nickel oxide catalyst (40-cycled Ni/SiO.sub.2) was prepared in the same manner as in Example 1, except that SiO.sub.2 (Aldrich) was used as a support and 40 cycles of ALD were conducted.

(21) FIG. 4 shows a transmission electron microscopic image of the nickel oxide catalyst prepared in Example 2 after annealing at 450 C. for 3 hours. It can be seen that the particle diameter of nickel oxide deposited on the surface of pores is about 2 nm.

Experimental Example 3: Oxidation of Carbon Monoxide

(22) 1.1 g of the porous silica catalyst on which nickel oxide is supported, which was prepared in Example 2, was annealed at 450 C. for 3 hours in the air. Then, air containing 1% carbon monoxide was flown at a rate of 10 mL/min as a reactant gas. While maintaining the temperature of the reactor at 30 C., carbon monoxide consumption (vol %) was measured by gas chromatography. The result is shown in FIG. 9.

Example 3: Preparation of Nickel Oxide Catalyst Using Atomic Layer Deposition (ALD)

(23) A nickel oxide catalyst (5-cycled Ni/MIL-101(Cr)) was prepared in the same manner as in Example 1, except that MIL-101(Cr) was used as a support and 5 cycles of ALD was conducted under the condition described in Table 1.

(24) TABLE-US-00001 TABLE 1 5-cycled Ni/MIL-101(Cr) process Precursors Ni(Cp).sub.2 at 50 mTorr O.sub.2 at 1.2 Torr Precursors exposure time 300 s + 300 s 30 s + 270 s (Pulse + Exposure) (Pulse + Exposure) N.sub.2 purging time 30 s Pumping time 60 s/90 s Substrate temperature 150 C. Reactor base pressure <20 mTorr

Experimental Example 4: Oxidation of Carbon Monoxide

(25) 0.14 g of the MIL-101(Cr) catalyst on which nickel oxide is supported, which was prepared in Example 3, was annealed at 250 C. for 6 hours under an Ar atmosphere. Then, air containing 1% carbon monoxide and pure air were flown at a rate of 3 mL/min and 27 mL/min, respectively, as reactant gases. While maintaining the temperature of the reactor at 200 C., carbon monoxide consumption (vol %) was measured by gas chromatography. The result is shown in FIG. 10.