TWI542410B - A method for preparing nanometer copper-based catalyst - Google Patents

Description

Preparation method of nano copper base catalyst

The invention relates to a preparation method of a nano copper-based catalyst, in particular to a catalyst with high conversion rate synthesized by a solvothermal method (hydrothermal or alcoholic heat) at a low temperature reaction, in particular, it can be used for decomposing ammonia. Gas nano-copper based catalyst.

Ammonia is common in various industrial waste gases, causing odor and air pollution. The commonly used solution is decomposition, which decomposes ammonia into nitrogen (N ₂ ) and hydrogen (H ₂ ), but the production of hydrogen is safe. Concerns.

Another common solution is oxidative decomposition. A selective catalyst Pt/CuO/Al ₂ O ₃ can be used for the ammonia oxidation process, which produces nitrogen and water-based steam, although only By removing the water, the effect of detoxification and volume reduction can be achieved, but while nitrogen is generated, nitrogen will continue to oxidize to form nitric oxide (NO) or nitrogen dioxide (NO ₂ ), which will cause air pollution. Moreover, the catalyst Pt/CuO/Al ₂ O _{3 is formed} , which is costly and economically and economically incompatible with the demand.

All of the above methods are not in line with the needs of the solution. The commonly used treatment method is mostly catalyst, so if it can use the catalyst with safety, high selectivity, high conversion rate and low preparation cost, it has the most development potential.

Sobczyk et al. (Sobczyk, DP, Hensen, EJM, de Jong, AM, van Santen, RA, "Low-temperature Ammonia Oxidation over Pt/gamma-alumina: the Influence of the Alumina Support", Top. Catal., 23, 109 ( 2003)) and Gang et al. (Gang, L., Anderson, BG, van Grondelle, J., van Santen, RA, van Gennip, WJH, Niemantsverdriet, JW, Kooyman, PJ, Knoester, A., "Brongersma, HHAlumina -Supported Cu-Ag Catalysts for Ammonia Oxidation to Nitrogen at Low Temperature", J Catal, 206, 60 (2002).) Use of noble metals platinum (Pt), palladium (Pd), ruthenium (Ru), iridium (Ir) and silver (Ag) is a catalyst. Such catalysts have high activity and can carry out catalytic reactions at lower temperatures, but N ₂ selectivity is 80% poor, and nitrogen oxides (NOx) are often formed, which easily pollutes the environment and touches The high cost of preparation of the media is not economical.

The Republic of China Patent No. I237064 uses a carbon nanotube and is loaded with a metal catalyst. The catalyst contains precious metals and alloys, and must contain a precipitating agent and a reducing agent in the process, and the carbon nanotubes need to be at a reaction temperature of 400 during preparation. It is synthesized at ~600 °C, and finally the metal particles are deposited at 350~500 °C to remove the polymer and organic solvent. The preparation process is complicated, the energy consumption is also high, and it is economically inferior to the energy saving demand.

In addition, the Republic of China Patent No. I259782 uses activated carbon fiber, hearth or hearth powder as a porous support, and the support is made of copper metal or copper oxide as an active center, and the process is carried out by ion exchange method and calcination method. The catalyst is prepared, but it needs to be dried for more than 24 hours after the ion exchange method; the other calcination method is carried out by using an inert gas at a gas flow rate of 150 to 250 ml/min for more than 4 hours. The effect of ammonia decomposition can reach 90%, but the selectivity of N ₂₂ is 85%, and there are still doubts about the formation of nitrogen oxides. Therefore, the general practitioners cannot meet the needs of the user in actual use.

The main object of the present invention is to overcome the above problems encountered in the prior art and to provide a nano-copper base which has a high conversion rate and can be used for decomposing ammonia gas by a solvothermal method (hydrothermal or alcoholic heat) at a low temperature reaction. catalyst.

A secondary object of the present invention is to provide a method of depositing the nano copper on the surface of a porous oxide in the state of a supercritical fluid or a subcritical fluid.

Another object of the present invention is to provide a supercritical fluid or a subcritical fluid in combination with a solvothermal method (hydrothermal or alcoholic heat) to deposit nano-grade copper on an alumina support to increase the nano-copper A method for increasing the conversion rate of the nano copper-based catalyst to ammonia gas by uniformity and activity on the alumina support.

A further object of the present invention is to provide a method for specifically improving the conversion rate of the nano-copper-based catalyst to ammonia gas and reducing the reaction temperature of the nano-copper-based catalyst, thereby effectively reducing energy consumption. The method of achieving the goal of energy saving and carbon reduction.

In order to achieve the above object, the present invention provides a method for preparing a nano copper-based catalyst, which comprises providing an alumina support and a nano copper particle, wherein the nano copper particles are reacted by a supercritical fluid solvent. The nano copper particles are deposited on the alumina support to form a nano copper layer to obtain a nano copper based catalyst, wherein the supercritical fluid solvent may be water or n-butanol.

In a preferred embodiment, when the supercritical fluid solvent is water, the nano copper particles are deposited on the alumina support at a pressure of 250 bar (Bar) at a temperature of 350 to 400 ° C. on.

In a preferred embodiment, when the supercritical fluid solvent is n-butanol, the nano copper particles are deposited on the alumina support at a pressure of 100 bar and a temperature of 250 to 300 ° C. .

1‧‧•Nylon copper-based catalyst

10‧‧‧Alumina support

11‧‧‧Nano copper particles

12‧‧•Nylon copper layer

2‧‧‧catalytic decomposition device

20‧‧‧Open ammonia cylinder

21‧‧‧ argon cylinder

22‧‧‧Oxygen cylinder

23‧‧‧Mass flow meter

24‧‧‧ fixed bed reactor

25‧‧‧ ultraviolet light

(a) ‧ ‧ ammonia gas oxidation conversion rate of catalyst for supercritical water synthesis

(b) Ammonia gas oxidation conversion rate of ‧ ‧ critical catalysts for critical water synthesis

(c) ‧ ‧ ammonia gas oxidation conversion rate of catalyst for supercritical alcohol synthesis

(d) Ammonia gas oxidation conversion rate of the ‧ ‧ critical alcohol synthesis catalyst

Fig. 1 is a schematic view showing the preparation structure of the nano copper-based catalyst of the present invention.

Fig. 2 is a schematic view showing a catalyst decomposition apparatus for oxidizing ammonia gas of the present invention.

Fig. 3 is a SEM distribution image of the present invention using Cu Ka1 ray as a light source.

Figure 4 is an XRD pattern of various copper-based catalysts of the present invention.

Figure 5 is a copper 2PXPS pattern of a copper-based catalyst synthesized by the present invention using different methods.

Figure 6 is a schematic diagram showing the ammonia oxidation conversion rate of the catalyst obtained by the different preparation methods in the present invention.

Fig. 7 is a graph showing the results of the residence time required in the ammonia gas decomposition reaction of the present invention.

Please refer to FIG. 1 for a schematic diagram of the preparation structure of the nano copper-based catalyst of the present invention. As shown in the figure: the present invention is a preparation method of a nano copper-based catalyst, which uses a solvothermal method to prepare a copper-based catalyst using water or n-butanol as a solvent, and relies on the characteristics of hydrothermal or alcoholic heat. The nanoparticle is directly deposited on the substrate of the porous oxide. When prepared, it comprises providing an alumina support (Al ₂ O ₃ ) 10 and a nano copper particle 11 which is reacted in a supercritical fluid solvent (for example, water or n-butanol). The nano copper particles 11 are deposited on the alumina support 10 to form a nano copper layer 12, thereby obtaining a nano copper based catalyst 1. The nano copper-based catalyst is used for decomposing ammonia gas, and is deposited by using nano copper as an ammonia gas oxidation catalyst to enhance the reactivity thereof, thereby lowering the reaction temperature.

At least 1 to 3 percent of the surface of the alumina support 10 in the above-mentioned nano copper-based catalyst 1 is the nano copper layer 12.

In a preferred embodiment, the present invention synthesizes a copper-based catalyst by using a supercritical fluid method and a microwave method, and uses g-Al ₂ O ₃ as a catalyst carrier and copper nitrate as a catalyst for synthesizing a copper-based catalyst. The precursor, which deposits copper on g-Al ₂ O ₃ , compares the effects of subcritical, supercritical, and liquid deposition reactions, respectively.

In the hydrothermal and alcohol thermal system, the reaction is carried out with water and n-butanol as solvents respectively, wherein, in the hydrothermal reaction, the operating pressure is 250 bar (Bar), the reaction temperature is 400 ° C, 350 ° C; In the alcohol thermal reaction, the operating pressure is 100 bar, the reaction temperature is 300 ° C, 250 ° C; in the microwave system, with water as the solvent, n-butanol as a reducing agent, at a temperature of 100 ° C, 95 ° C reduction reaction.

Please refer to FIG. 2, which is a schematic diagram of a catalyst decomposition apparatus for oxidizing ammonia gas according to the present invention. As shown in the figure, when used, the present invention fills the catalyst synthesized in the fixed bed reactor 24, and uses ultraviolet light 25 as a light source to open the ammonia cylinder 20 and argon by using a catalyst decomposition device 2. The gas cylinder 21 and the oxygen cylinder 22 respectively adjust the flow rate of the ammonia gas (NH ₃ ) to be decomposed by argon gas (Ar) via the respective mass flow meters 23, and pass oxygen (O ₂ ) to the reaction temperature. Catalytic reaction, and finally detect the change of NH ₃ concentration, and then calculate the conversion rate of the synthesized catalyst.

Please refer to FIG. 3 to FIG. 5 for the SEM distribution image of Cu Ka1 ray as a light source, the XRD pattern of various copper-based catalysts of the present invention, and the different methods of the present invention. Copper 2PXPS map of copper-based catalyst. As shown in the figure, the present invention compares the structures of a copper-based catalyst by a supercritical fluid method and a microwave method, respectively, using an X-ray diffractometer (XRD) and an X-ray photoelectron spectrometer (XPS). The porous g-Al ₂ O ₃ is used as a catalyst carrier and copper nitrate is used as a precursor to deposit copper on g-Al ₂ O ₃ . Since g-Al ₂ O ₃ does not easily deposit metal, Figure 3 shows the results of the mapping of Cu Ka1 in a scanning electron microscope (SEM), where (a) is a subcritical water distribution image operating at 250 bar and 350 ° C; (b) is operated at 250 bar, 400 ° C. Supercritical water distribution image; and (c) is a microwave liquid distribution image operating at 100 bar. The distribution of copper in Fig. 3 shows that in the subcritical and liquid phase reactions, the metal material is not easily deposited in the pores due to the surface tension; relatively, in Fig. 3 (b), in the supercritical water. In the state, the deposited copper particles are more and evenly distributed. In addition, it can be seen from the XRD pattern shown in Fig. 4 that in addition to the supercritical water having a reaction temperature of 400 ° C, the copper formed by other alcohol heat and hydrothermal reaction contains copper oxide (CuO) and cuprous oxide. Three states (Cu ₂ O) and Cu.

In addition, it can be seen from the XPS spectrum shown in Fig. 5 that whether the copper-based catalyst is prepared by hydrothermal or mellow method, the amount of Cu deposited is higher when the temperature is higher, and from the fourth and fifth figures. It can also be seen that the copper obtained in the supercritical alcohol contains a lot of CuO in addition to a little Cu ^O , and the chemical structure obtained from the hydrothermal is very different.

Please refer to "Fig. 6 and Fig. 7" for the comparison of the ammonia oxidation conversion rate of the catalyst obtained by the different preparation methods of the present invention, and the result of the residence time required in the ammonia gas decomposition reaction of the present invention. schematic diagram. As shown in the figure: The present invention compares the catalyst obtained by the different preparation methods into the ammonia gas decomposition reaction in the apparatus of Fig. 2, and the catalytic ability analysis thereof is shown in Fig. 5, wherein (a) is supercritical water synthesis. The ammonia oxidation conversion rate of the catalyst; (b) the ammonia oxidation conversion rate of the catalyst for subcritical water synthesis; (c) the ammonia oxidation conversion rate of the catalyst for supercritical alcohol synthesis; and (d) Ammonia gas oxidation conversion rate of a catalyst for subcritical alcohol synthesis. The results show that the copper-based catalyst formed by microwave reaction decomposes ammonia gas at low temperature (200 ° C) less than 30%; in the alcohol thermal reaction, the supercritical alcohol obtains higher catalytic results, and the hydrothermal reaction results in Catalyst, whether at 150 ° C or 200 ° C, the catalytic effect is best, wherein the catalyst for supercritical water synthesis can be decomposed by 98.5% at 200 ° C, and the catalyst for supercritical alcohol synthesis is obtained at 200 ° C. The conversion rate can also reach over 90%.

In addition, the present invention also discusses the retention time required for the catalyst required for the catalyst synthesized by supercritical water in the reaction, as shown in Fig. 7, if more than 90% conversion is desired As a result, the fluid flow rate required to be used needs to be less than 0.6 cc/s.

The invention utilizes a solvothermal method for uniformly depositing nano copper particles on a porous alumina support, and uses water and n-butanol as solvents in the isostatic operation mode to analyze the supercritical fluid and the secondary The state of deposition under the condition of critical fluid, and its physical and chemical structure is analyzed by XRD, SEM, UV-vis and XPS, and ammonia gas decomposition is carried out in a fixed bed reactor at an operating pressure of 100 bar and a reaction temperature of 150-200. °C, using a fixed bed to test the catalytic decomposition ability, analyze the influence of different types of catalyst on ammonia decomposition, and then compare with the copper-based catalyst obtained by chemical reduction method; the experimental results show that the solvothermal method The nano copper particles obtained by the deposition are relatively uniform, and the conversion rate of 90-99% can be achieved at a low reaction temperature, indicating that the present invention successfully synthesized by a solvothermal method (hydrothermal and alcoholic) at a low temperature reaction. The copper-based catalyst makes it suitable for the decomposition of general ammonia gas, which can effectively reduce energy consumption and achieve the goal of energy saving and carbon reduction.

In summary, the present invention is a preparation method of a nano copper-based catalyst, which can effectively improve various disadvantages of the conventional use, is a solvothermal method for preparing a nano copper-based catalyst, and successfully applies a catalyst to ammonia gas. In the decomposition, high conversion rate can be obtained at low temperature, so that the production of the invention can be more advanced, more practical, and more in line with the requirements of the user. It has indeed met the requirements of the invention patent application, and the patent application is filed according to law.

However, the above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto; therefore, the simple equivalent changes and modifications made in accordance with the scope of the present invention and the contents of the invention are modified. All should remain within the scope of the invention patent.

1‧‧•Nylon copper-based catalyst

10‧‧‧Alumina support

11‧‧‧Nano copper particles

12‧‧•Nylon copper layer

Claims (1)

A method for preparing a nano copper-based catalyst provides an alumina support and a nano copper particle, wherein the nano copper particles are reacted in a supercritical fluid to cause the nano copper particles to be deposited on the alumina On the support, a nano copper-based catalyst is obtained, wherein the supercritical fluid solvent can be water or n-butanol, and when the supercritical fluid solvent is water, the nano copper particles are at a pressure of 250 bar. (Bar), deposited on the alumina support at a temperature of 350 to 400 ° C; when the supercritical fluid solvent is n-butanol, the nano copper particles are at a pressure of 100 Bar and a temperature of 250 to 300 Deposited on the alumina support under the conditions of °C.