Catalyst composition for removing high-concentration slip hydrogen

Abstract

The present invention relates to a catalyst composition for removing high-concentration slip hydrogen, having platinum and palladium noble metals supported on an alumina support. The noble metals of the catalyst composition of the present invention comprise platinum and palladium in a weight ratio of 1:1 to 9:1, and thus have, as synergistic effects of platinum and palladium, excellent oxidation performance in a high-concentration hydrogen atmosphere and can minimize the formation of nitrogen oxides, which are by-products.

Description

Catalyst composition for high-concentration slip hydrogen removal

[0001] The present invention relates to a catalyst composition for oxidizing and removing high-concentration slip hydrogen.

[0002] As the hydrogen industry ecosystem becomes more visible, interest in the hydrogen economy, which uses hydrogen as a primary energy source, is growing. As hydrogen use increases, the need for safe hydrogen use is also emerging. Explosions and flames can occur when hydrogen slips into the atmosphere at concentrations exceeding 4% on average. To prevent this risk, there is a growing demand for systems and catalysts that can remove hydrogen using a passive system that uses only a hydrogen oxidation catalyst, without the need for a separate power source like heat or electricity.

[0003] Korean Patent Publication No. 10-2013-0082272 discloses a method for manufacturing a Pt / TiO2 catalyst for hydrogen removal and a method for removing hydrogen using the same. Furthermore, Korean Patent Publication No. 10-2016-0073797 discloses a platinum-based catalyst capable of removing hydrogen at room temperature.

[0004] The present inventors focused on the problems when applying a ceramic honeycomb coated with a conventional Pt / TiO2 catalyst material for hydrogen removal to oxidize and remove high-concentration hydrogen at room temperature. As is known, Pt and a TiO2 support are evaluated as the best combination in terms of hydrogen oxidation capability. That is, when the noble metal Pt is supported on the TiO2 support, the dispersion of Pt is excellent (SMSI: Strong Metal Support Interaction effect), and the noble metal Pt is maintained in a metallic state that is favorable for oxidation reaction, so it is understood that the hydrogen oxidation performance is optimal. However, the present inventors unexpectedly found that the oxidation performance of the catalytic composition of the Pt / TiO2 combination rapidly decreases in a high-concentration H2 atmosphere. In particular, there is a need to improve the high-concentration hydrogen oxidation catalyst material in terms of the decrease in oxidation performance due to support modification and the byproduct nitrogen oxide (N2O).

[0005] The present invention relates to a catalyst composition for high-concentration slip hydrogen removal in which noble metals such as platinum and palladium are supported on an alumina support. Although not limited thereto, the noble metals of the catalyst composition according to the present invention include platinum and palladium in a weight ratio of 1:1 to 9:1,

[0006] It can be installed at the rear end of a hydrogen tank, or at the rear end of a fuel cell or other hydrogen-using device, and can oxidize and remove high-concentration hydrogen.

[0007] The catalyst composition for high-concentration slip hydrogen removal according to the present invention has excellent oxidation performance in a high-concentration hydrogen atmosphere due to the synergistic effect of platinum and palladium, and can minimize the formation of nitrogen oxide (N2O), a byproduct.

[0008] Figure 1 shows the initial (first oxidation cycle) hydrogen oxidation ability of a catalyst material impregnated with only Pt or only Pd as a noble metal on a support.

[0009] Figure 2 shows the oxidation reaction in the second and third oxidation cycles of Pt only or Pd only catalyst materials.

[0010] Figure 3 is an XRD showing the state of these precious metals in the initial (fresh) and deteriorated (used) states when Pt and Pd are impregnated into the support.

[0011] Figure 4 shows the oxidation capacity for 20% and 30% H2 for a catalyst composition in which platinum and palladium as precious metals are simultaneously impregnated into alumina.

[0012] In the present invention, high-concentration hydrogen refers to a hydrogen concentration of 4 vol% or more, which is hydrogen capable of spontaneous combustion. In the present invention, the terms "catalytic material" and "catalytic composition" are used interchangeably.

[0013] The present inventors propose a novel catalyst composition for preventing rapid deterioration of a Pt / TiO2 catalyst resulting from the oxidation reaction of high-concentration hydrogen and suppressing the production of nitrogen oxides (hereinafter, N2O), a by-product. The present invention relates to a catalyst composition for high-concentration slip hydrogen removal, in which noble metals platinum and palladium are supported on an alumina support in a specific weight ratio, and to a catalyst material for hydrogen oxidation that utilizes the synergistic effect according to the respective properties of platinum and palladium.

[0014] Although not limited to theory, various preliminary experiments conducted by the inventors of the present invention have shown that when an oxidation catalyst is exposed to a high concentration of H2, the exothermic temperature of the catalyst rises to over 700℃, and the TiO2, which is the support of the conventional oxidation catalyst, undergoes an irreversible phase change (anatase -> rutile), which appears to be the cause of the rapid performance decline of the conventional catalyst. In order to solve the problem of this support phase change, the inventors of the present invention applied a stable support, such as alumina, even when exposed to high temperatures, such as over 1000℃, as the support. In addition, in the case of the conventional oxidation catalyst in which only platinum is loaded on the support, it was confirmed that a large amount of N2O is generated when H2 is removed through the path of changing from N2 -> N2O because H2 is a strong reducing agent. The present inventors propose palladium together with platinum as a noble metal to minimize N2O formation, and the weight ratio of these noble metals is characterized by platinum:palladium = 1:1 to 9:1, preferably platinum:palladium = 4:1, which maximizes oxygen oxidation ability while minimizing N2O formation.

[0015] The present inventors believe that platinum and palladium produce a synergistic effect in the hydrogen oxidation reaction. From the perspective of N2O formation, a catalyst composition utilizing only palladium as a precious metal could be considered. However, in the case of a catalyst material impregnated solely with palladium, the initial hydrogen oxidation capacity is lower than expected because the palladium exists in the support in the form of palladium oxide rather than the metallic state, making it impractical. However, the catalyst material of the present invention, in which palladium is impregnated in a specific combination with platinum on the support, exhibits excellent initial oxidation capacity and minimizes N2O formation.

[0016] Table 1 shows the hydrogen oxidation rate and N2O formation rate by the catalyst materials of platinum or palladium impregnated on the support (10% H2conc.(%) w / air, 30℃). It was confirmed that N2O formation in the hydrogen oxidation reaction could be reduced when palladium was impregnated rather than when platinum was used. The present inventors unexpectedly found that the application of palladium, rather than platinum, was advantageous in minimizing N2O formation in the hydrogen oxidation reaction.

[0017] H2conv. (%)N2O generation (ppm)Pt only99.9599Pd only99.2173

[0018] First, the inventors of the present invention confirmed the possibility of applying palladium in addition to platinum in hydrogen oxidation catalysts. Figure 1 shows the initial hydrogen oxidation ability of a catalyst material impregnated with only platinum as a noble metal on a support and a catalyst material impregnated with only palladium as a noble metal on a support. The Pt only catalyst reacts immediately upon H2 input, but the Pd only catalyst does not react. This is thought to be because Pd exists in the PdO phase, as shown by the XRD of the Pd-impregnated catalyst (Figure 3). However, surprisingly, it was confirmed that the Pd only catalyst material also undergoes an oxidation reaction at room temperature after the initial (first oxidation cycle) H2 oxidation reaction, and in the subsequent oxidation reactions (second and third cycles). Figure 2 shows the oxidation reactions of the Pt only or Pd only catalyst material in the second and third cycles at room temperature.

[0019] Figure 3 shows XRD patterns showing the states of these precious metals in the initial (fresh) and deteriorated (used) states when Pt or Pd is impregnated into the support. According to this, unlike Pt, Pd exists in the PdO state in the initial catalyst material, making it difficult to trigger an oxidation reaction. However, through the second and third oxidation reaction cycles, the palladium oxidation state changes to a palladium metal state, making it suitable for a hydrogen oxidation reaction.

[0020] Through these preliminary experiments, the inventors of the present invention suggest that palladium can be employed as a precious metal in the hydrogen oxidation catalyst to minimize the formation of N2O as a by-product, but since palladium alone has limited activity, it is combined with platinum, and the weight ratio of these combinations is 1:1 to 9:1. Considering only the H2 oxidation ability, the performance of the Pt:Pd = 4:1 catalyst is the best, but considering the influence of N2O, the amount of N2O produced can be controlled by adjusting the Pt / Pd weight ratio up to 1:1. According to the present invention, it was confirmed that as the amount of Pd increases, the amount of N2O produced decreases, and the H2 oxidation performance does not decrease significantly.

[0021] Figure 4 shows the oxidation reaction for 20% and 30% H2 for a catalyst composition in which platinum and palladium as precious metals are simultaneously impregnated into alumina.

[0022] According to the present invention, a hydrogen oxidation catalyst composition for preventing high-concentration hydrogen slip of 4% or more has an optimal oxidation ability when platinum / palladium in a weight ratio of 4 / 1 is impregnated into an alumina support, and platinum / palladium in a weight ratio of 1:1 minimizes N2O formation.

[0023] Example

[0024] Similar to the method disclosed in Patent Publication No. 10-2013-0082272, a Pd precursor was first supported on an alumina support, then the Pt precursor was impregnated, dried, and heat-treated to complete Pt-Pd / Al2O3.

[0025] Experimental example

[0026] In order to evaluate the hydrogen removal ability of the Pt-Pd / Al2O3 catalyst according to the present invention, mixed gases containing moisture at a relative humidity of 100% (based on 25°C) and hydrogen at 20 and 30 volume%, respectively, were injected into a device containing catalyst powder, and the initial reaction temperature was maintained at 25°C, and the reaction was performed at a space velocity of 120,000 / hour. The composition of the exhausted gas was measured using gas chromatography, and the temperature change at the rear end of the catalyst due to the heat generated by the hydrogen oxidation reaction was measured (Fig. 4).

Claims

1. A catalyst composition for high-concentration slip hydrogen removal, wherein platinum and palladium noble metals are supported on an alumina support.

2. A catalyst composition characterized in that the weight ratio of platinum and palladium in paragraph 1 is 1:1 to 9:

1.

3. A catalyst composition in paragraph 1, wherein the concentration of the slip hydrogen is 4% or more.

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