Material for N2O decomposition

Abstract

The present invention relates to a material with a non-stoichiometric spinel-type crystal structure based on cobalt oxide doped with alkali elements, a manufacturing process for obtaining it by precipitation with controlled washing, and its specific use as a highly active catalyst in NO decomposition reactions. We therefore understand that the present invention is an invention in the field of green industry aimed at reducing NO emissions into the atmosphere.

Description

Technical Field

[0001] The present invention relates to a catalyst having a non-stoichiometric spinel-type crystal structure, a manufacturing process for obtaining it by precipitation with controlled washing, and its specific use in the N2O decomposition reaction. Therefore, we understand that the present invention is an invention in the field of green industries aimed at reducing N2O emissions.

Background Art

[0002] Nitrous oxide is a greenhouse gas with a potential 298 times higher than CO2, has a devastating effect on the ozone layer, and has a lifetime of 100 years in the troposphere. The industrial sector generates 5% of the total N2O emissions, and it is estimated that this is the sector that is likely to experience the largest increase in emissions in the very near future. Within the industrial sector, the production of nitric acid and adipic acid are the main sources of N2O emissions. Since the number of factories is limited, it may be easier to achieve emission reduction compared to other sectors with many diffuse sources such as biomass combustion and agriculture. Although many measures have already been established in many adipic acid factories, emission reduction in nitric acid factories is particularly difficult.

[0003] The most effective technology for removing nitrous oxide in nitric acid factories is the catalytic decomposition process carried out after the oxidation stage of ammonia (secondary treatment) or removal in the exhaust gas stream (tertiary treatment). There are several commercially available catalysts for secondary treatment, but they have drawbacks such as deactivation, low abrasion resistance, and sintering of the active phase due to high temperatures (750 °C to 940 °C) that they have to withstand.

[0004] Since tertiary treatment is carried out as exhaust gas treatment, it has the great advantage of not affecting the heart of the nitric acid factory. Since there are other components (O2, H2O, and optionally NO x ) in the exhaust gas that can significantly change the efficiency of the catalyst, the main technical challenge is to develop a catalyst system that is active at relatively low temperatures (250 °C to 500 °C) and operable under actual process conditions.

[0005] Catalysts that are considered to be active in the decomposition reaction of N2O at low temperatures include zeolites modified with various metals (Cr, Mn, Fe, Co, Ni, or Cu), noble metals (Rh, Ru, Pd) supported on ZnO, CeO2, Al2O3, TiO2, or ZrO2, hydrotalcite derivatives, spinels, and metal oxides. [M. Konsolakis, ACS Catal. 2015, 5, 6397 - 6421; J. Perez - Ramirez, Appl. Catal. B 44 (2003) 117 - 151]. Among these, the ones with the highest catalytic activity and the highest resistance to O2 and H2O are based on cobalt spinel. Yan et al [L. Yan, R. Ren, X. Wang, Q. Gao, D. Ji, J. Suo, Catal. Comm. 4 (2003) 505 - 509; L. Yan, R. Ren, X. Wang, D. Ji, J. Suo, Appl. Catal. B 45 (2003) 85 - 90]. The formula Zn x Co 1-x Co2O4 and M x Co 1-x Co2O4 (M = Ni, Mg) (the recorded T 50 (temperature required for 50% conversion of N2O) is 250 °C and 220 °C, respectively) are the published studies. The operating conditions used were 15000 hours -1 of GHSV (gas hourly space velocity), 1000 ppm N2O concentration, 10% O2, and 5% H2O. Similar results (T 50 = 260 °C) were obtained by Xu et al. [L. Xue, C. Zhang, H. He, Y. Teraoka, Appl. Catal. B 75 (2007) 167 - 174]. The CoCe 0.05 catalyst also operates at a space velocity of 15000 hours -1 , 1000 ppm N2O concentration, 10% O2, and 3% H2O.

[0006] The addition of an alkali element improves the catalytic activity of cobalt spinel Co3O4. [JP2007054714 (A)]. Stelmachowski et al. reported 50% conversion at 335 °C using cobalt spinel doped with K operating at 7000 h -1 , 1500 ppm N2O concentration, and 1% H2O. [P. Stelmachowski, G. Maniak, A. Kotarba, Z. Sojka, Catal. Comm. 10 (2009) 1062-1065]. Xue et al. reported 77% at 350 °C. [Li Xue, Changbin Zhang, Hong He, Yasutake Teraoka, Applied Catalysis B: Environmental, Volume 75, Issues 3-4, 2007, Pages 167-174]. In these studies, the presence of O2 and H2O is considered (even at concentrations higher than the actual concentrations), but the space velocities tested are much lower than those used industrially. Also, except for the case of the K-promoted Co3O4 catalyst, stability tests were not performed and the catalysts were evaluated for only 10 h. Other authors have also described the behavior of catalysts doped with other alkalis such as Cs, and the doping is carried out by the impregnation method. The addition of water to the feed, which is present under actual operating conditions, leads to a decrease in N2O conversion using these catalysts. [Pawel Stelmachowski, Gabriela Maniak, Andrzej Kotarba, Zbigniew Sojka, Catalysis Communications, Volume 10, Issue 7, 2009, Pages 1062-1065].

[0007] Therefore, there is a need to provide a catalyst that reports a conversion rate exceeding 90% at a temperature below 350 °C under actual conditions and to provide a catalyst that is stable under these conditions.

Summary of the Invention

[0008] The present invention relates to the formula Co3O 4-x / 2 A yRelates to a novel material, its manufacturing process, and its use as a catalyst in the decomposition reaction of N2O.

[0009] In a first aspect, the present invention has a non-stoichiometric spinel-type crystal structure of the general formula "Co3O 4-x / 2 A y ", where "X" has a value of 0.02 to 0.3, "A" is an alkali element, "y" has a value of 0.06 to 0.18, the A / Co ratio is 0.02 to 0.10, and the primary particle size corresponding to the crystallite size is 5 nm to 30 nm, characterizing the material.

[0010] In the present invention, "non-stoichiometric spinel" is understood to be a material having a cubic crystal structure of spinel-type cobalt oxide that has oxygen vacancies generated by the reduction from Co 3+ to Co 2+ due to the presence of an alkali element, and has the general formula Co3O 4-x / 2 A y and is partially reduced.

[0011] An advantage associated with such a catalyst is that the Co 2+ / Co 3+ ratio in the catalyst is 0.55 to 0.80, causing surface desorption of oxygen to occur at a temperature near 100 °C and lattice desorption of oxygen to occur at a temperature of 200 to 300 °C.

[0012] The material is preferably mesoporous. In the present invention, "mesoporous material" means a material having pores with a major pore size of 2 nm to 50 nm.

[0013] An advantage of the material being mesoporous is that, based on the ideal ratio of pore volume to specific surface area, the gas can easily reach the catalytically active centers. In a preferred embodiment, the material has a pore volume of 0.2 cm3 / g ~ 0.4 cm 3 / g of pore volume and 40 m 2 / g ~ 80 m 2 / g of BET specific surface area, and is a relatively high-bulk material, resulting in a high gas-solid contact surface area that is advantageous for catalytic activity.

[0014] In another preferred embodiment, the alkali element A is K, x is 0.182, and y is 0.09.

[0015] In another preferred embodiment, the alkali element A is Cs, x is 0.235, and y is 0.15.

[0016] Another aspect of the present invention is step (a) of dissolving a cobalt salt in water, step (b) of dissolving a salt or hydroxide of an alkali metal in water, step (c) of slowly adding the solution obtained in step (b) to the solution prepared in step (a) until a pH of 8 - 11 is reached, step (d) of filtering the solid obtained in step (c) and washing it with 5 ml - 75 ml of water per gram of cobalt salt added in step (a), step (e) of drying the solid obtained in step (d) at a temperature of 50°C - 200°C for 12 hours - 20 hours, step (f) of firing the solid obtained in step (e) in an air atmosphere at a temperature of 200°C - 700°C for at least 30 minutes, A process for obtaining a Co3O 4-x / 2 A y material having a non-stoichiometric spinel-type structure.

[0017] The washing in step (d) is carried out in a controlled manner and is very important because the content of A in the sample depends on it, which directly affects the reduction temperature from Co(III) to Co(II), and thus the resulting Co 2+ / Co 3+The ratio depends on the amount of water used in such control in relation to the initial Co salt content in the reaction, and a specific amount of alkali is introduced into the crystal lattice of the material of the present invention. Furthermore, this controlled washing avoids the additional step of adding alkali metal and simplifies the procedure of the present invention compared to the procedures described in the prior art.

[0018] According to the process described in the present invention, a non-stoichiometric cobalt spinel precipitate of cobalt oxide doped with an alkali metal is produced in such a way that close contact between Co and alkali ions occurs during the precipitation stage. The doping is a bulk-type doping, and the alkali element is distributed not only on the surface but also throughout.

[0019] This synthesis process directly affects the cobalt spinel formation process and produces a material having a primary particle size corresponding to the size of crystallites or crystal domains, as revealed by X-ray diffraction and scanning electron microscopy. The small primary particle size of cobalt spinel results in a highly exposed specific surface area, increases the ratio of active centers per gram of catalyst, and contributes to the improvement of catalytic efficiency.

[0020] Furthermore, the inclusion of alkali ions by this process causes a partial reduction of Co(III) ions to Co(II), thereby significantly changing the chemical-physical properties of the material. This changes the stoichiometry of the resulting spinel, reduces the proportion of oxygen in the lattice, thereby distorting the structure and obtaining catalytic properties clearly different from those of conventional spinels.

[0021] In another preferred embodiment of the process, the cobalt salt in step (a) is selected from cobalt nitrate hexahydrate, cobalt sulfate, cobalt chloride, and cobalt acetate.

[0022] In another preferred embodiment of the process, the alkali metal salt or hydroxide in step (b) is selected from alkali metal carbonates, alkali metal nitrates, alkali metal hydroxides and alkali metal acetates. In a more preferred embodiment, the alkali metal salt or hydroxide is an alkali metal carbonate.

[0023] In another preferred embodiment of the process, when the cobalt salt is cobalt nitrate hexahydrate and the alkali metal salt is an alkali metal carbonate, the washing in step (d) is carried out with water in an amount of 16 ml to 21 ml per 1 g of cobalt nitrate hexahydrate.

[0024] The third aspect of the present invention relates to the use of the above-described materials as a catalyst.

[0025] In a more preferred embodiment, it refers to the use of the material as a catalyst in the oxidation / decomposition of gases.

[0026] In an even more preferred embodiment, it refers to the use of the material as a catalyst for N2O decomposition.

[0027] The catalyst shows 98% conversion of N2O under actual operating conditions from 340 °C at a GHSV of 50330 h -1 .

[0028] The catalyst shows 98% conversion of N2O under actual operating conditions from 310 °C at a GHSV of 24000 h -1 .

[0029] Furthermore, it shows high stability in the presence of H2O and O2 for at least 65 hours without a decrease in the conversion of N2O and without a change in critical properties such as particle size or porosity.

[0030] Throughout the description and claims, the term "comprising" and its variations are not intended to exclude other technical features, additives, components or steps. Other objects, advantages and features of the present invention will become apparent to those skilled in the art, partly from the description and partly from the practice of the present invention. The following examples and drawings are provided for illustrative purposes and are not intended to limit the present invention.

Brief Description of the Drawings

[0031]

Figure 1

Figure 2

Figure 3

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Figure 6

Figure 7

Modes for Carrying Out the Invention

[0032] [Examples] In the following, the present invention will be described by the results of tests demonstrating the effectiveness of the products of the present invention conducted by the inventors.

[0033] [Example 1]

[0034] 14.84 grams of cobalt nitrate (Co(NO3)2·6H2O) was dissolved in 100 ml of water, and the solution was kept under stirring. 100 ml of a 15% w / w solution of potassium carbonate (K2CO3) was prepared, placed in a burette, and slowly added to the cobalt nitrate solution. The addition of potassium carbonate was continued until the pH reached 9. The solid was filtered off and washed with 250 ml of water at 15 °C. This was dried at 100 °C for 16 hours and calcined at 400 °C for 2 hours to obtain a catalyst of the formula Co3O 3.88 K 0.08 .

[0035] [Example 2]

[0036] A sample of the material obtained according to Example 1 was introduced into a tubular reactor, and an Ar gas stream with an N2O concentration of 1400 ppm was supplied at a ratio (gas flow rate: catalyst volume) GHSV = 50300 h -1 . When the gas inside the reactor was gradually heated, the N2O concentration at the reactor outlet gradually decreased, and the corresponding N2O conversion values were 73% at 260 °C, 95% at 280 °C, and 98% at temperatures above 310 °C.

[0037] A sample of this material was introduced into a tubular reactor, and an Ar gas stream with an N2O concentration of 1400 ppm and O2 = 3% v / v was supplied at a ratio (total gas flow rate: catalyst volume) GHSV = 50300 h -1 . When the gas inside the reactor was gradually heated, the N2O concentration at the reactor outlet gradually decreased, and the corresponding N2O conversion values were 17% at 250 °C, 88% at 300 °C, and 96% at temperatures above 350 °C.

[0038] A sample of this material was introduced into a tubular reactor, and an Ar gas stream with an N2O concentration of 1400 ppm and [H2O] = 0.5% v / v was supplied at a ratio (total gas flow rate: catalyst volume) GHSV = 50300 h -1 . When the gas inside the reactor was gradually heated, the N2O concentration at the reactor outlet gradually decreased, and the corresponding N2O conversion values were 25% at 250 °C, 75% at 280 °C, and 98% at temperatures above 340 °C.

[0039] A sample of the material obtained according to Example 1 was introduced into a tubular reactor, and a gas stream of Ar with an N2O concentration of 1400 ppm, [O2] = 3% v / v, and H2O = 0.5% v / v was supplied at a ratio (total gas flow rate: catalyst volume) GHSV = 50300 h−1. -1 When the gas inside the reactor was gradually heated, the N2O concentration at the reactor outlet gradually decreased, and the corresponding N2O conversion values were 17% at 260 °C, 42% at 275 °C, 73% at 290 °C, 94% at 315 °C, and 97% at temperatures above 350 °C.

[0040] A sample of the material obtained according to Example 1 was introduced into a tubular reactor, and a gas stream of Ar with an N2O concentration of 1400 ppm, [O2] = 3% v / v, and H2O = 0.5% v / v was supplied at a ratio (total gas flow rate: catalyst volume) GHSV = 50300 h−1. -1 When maintaining a reaction temperature of 360 °C, an initial N2O conversion value of 93% was obtained, and the conversion value slightly increased to 96% during the 65-hour reaction.

[0041] [Example 3]

[0042] 14.84 grams of cobalt nitrate (Co(NO3)2·6H2O) was dissolved in 100 ml of water, and the solution was kept under stirring. 100 ml of a 30% w / w solution of cesium carbonate (Cs2CO3) was prepared. This solution was poured into a burette. The cesium carbonate solution was slowly added and maintained until the pH reached 9. The total amount of cesium carbonate added was 57.5 ml. The solid was filtered off and washed with 220 ml of water at 15 °C. This was dried at 100 °C for 16 hours and calcined at 400 °C for 2 hours to obtain a material of the formula Co3O 3.88 Cs 0.15 .

[0043] [Example 4]

[0044] A sample of the material obtained according to Example 3 was introduced into a tubular reactor, and a gas stream of Ar with an N2O concentration of 1400 ppm, [O2] = 3% v / v, and H2O = 0.5% v / v was supplied at a ratio (total gas flow rate: catalyst volume) GHSV = 50300 h−1. -1When supplied and the gas inside the reactor is gradually heated, the N2O concentration at the reactor outlet gradually decreases, and the corresponding N2O conversion values were 50% at 280 °C, 80% at 300 °C, 93% at 320 °C, and 97% at temperatures above 340 °C.

[0045] [Example 5]

[0046] 59.36 grams of cobalt nitrate (Co(NO3)2·6H2O) was dissolved in 400 ml of water, and the solution was kept under stirring. 400 ml of a 30% w / w solution of cesium carbonate (Cs2CO3) was prepared. This solution was poured into a burette. The cesium carbonate solution was slowly added and maintained until the pH reached 9. The total amount of cesium carbonate added was 207 ml. The solid was filtered off and washed with 1160 ml of water at 15 °C. This was dried at 100 °C for 16 hours and calcined at 400 °C for 2 hours to obtain a material of the formula Co3O 3.88 Cs 0.06 to obtain a material of.

[0047] [Example 6]

[0048] A sample of the material obtained according to Example 5 was introduced into a tubular reactor, and an Ar gas stream with an N2O concentration of 1400 ppm, [O2] = 3% v / v, and H2O = 0.5% v / v was supplied at a ratio (total gas flow rate: catalyst volume) GHSV = 24000 h -1 When supplied and the gas inside the reactor is gradually heated, the N2O concentration at the reactor outlet gradually decreases, and the corresponding N2O conversion values were 47% at 250 °C, 88% at 280 °C, 95% at 300 °C, and 99% at temperatures above 320 °C.

[0049] [Example 7]

[0050] 14.84 grams of cobalt nitrate (Co(NO3)2·6H2O) was dissolved in 100 ml of water, and the solution was kept under stirring. 100 ml of a 15% w / w solution of potassium carbonate (K2CO3) was prepared, placed in a burette, and the potassium carbonate solution was slowly added to the cobalt nitrate solution, and the addition was continued until the pH reached 9. The total amount of potassium carbonate added was 54 ml. The solid was filtered off and washed with 400 ml of water at 15 °C. This was dried at 100 °C for 16 hours and calcined at 400 °C for 2 hours to obtain a K-free material of the formula Co3O4.

[0051] [Example 8]

[0052] A sample of the material obtained according to Example 7 was introduced into a tubular reactor, and an Ar gas stream with an N2O concentration of 1400 ppm was supplied at a ratio (gas flow rate: catalyst volume) GHSV = 50300 h-1. -1 When the gas inside the reactor was gradually heated, the N2O concentration at the reactor outlet gradually decreased, and the corresponding N2O conversion values were 9% at 280 °C, 20% at 320 °C, 34% at 360 °C, and 44% at 380 °C. A decrease in the N2O conversion value due to the absence of alkali elements was observed throughout the tested temperature range.

[0053] [Example 9]

[0054] The X-ray diffraction patterns (XRD) of the materials described in Examples 1 and 3 indicate that these materials have a cubic crystal structure close to the Co3O4 spinel described in Example 7 (JCPDS 00-042-1467) (Figure 1). The average crystallite size was calculated according to the Scherrer equation and was about 18 nm and 10 nm, respectively.

[0055] The scanning electron microscope images of these materials (Figure 2) showed that the average primary particle size of Example 1 was 10 - 20 nm and that of Example 3 was 8 - 15 nm.

[0056] These electron microscope images show the general surface appearance of the material formed by aggregates of primary particles. The primary particles have a size similar to the crystallite size obtained by XRD and have pores with diameters in the range of mesoporous materials determined by the N2 adsorption-desorption isotherm (2 - 50 nm) (Figure 3).

[0057] [Example 10]

[0058] Analysis by X-ray photoelectron spectroscopy (XPS) performed on samples of the materials described in Examples 1 and 7 shows that the Co2p level in the sample Co3O 3.88 K 0.08 (Example 1) is shifted to a lower binding energy, which is explained by an increase in the proportion of Co(II) (CoO) species stabilized by the electron-donating effect promoted by the presence of K + ions (Figure 4).

[0059] According to these results, the materials obtained according to the procedures described in the present invention are clearly different from those previously described with respect to their redox properties.

[0060] [Example 11]

[0061] The programmed temperature reduction experiments performed on the materials described in Examples 1 and 3 detected that the first reduction peak was shifted to a lower temperature compared to those reported in the prior art for conventional spinels (Co3O 3.88 K 0.08 and Co3O 3.88 Cs 0.15 at 246 °C and 262 °C, respectively) (Figure 5). From these results, Co 2+ / Co 3+When the ratio was calculated, a value higher than the stoichiometric value was obtained (0.7 vs. 0.5). This increase in the ratio of Co(II) to Co(III) in the spinel lattice results in the expression of a specific ratio of oxygen vacancies, thereby imparting special properties regarding the adsorption and activation of N2O molecules to the surface of the material. This changes the stoichiometry of the spinel and results in oxygen deficiency.

[0062] According to these results, the materials obtained according to the procedure described in the present invention are clearly different from those previously described with respect to their redox properties.

[0063] [Example 12]

[0064] O2 temperature programmed desorption (O2-TPD) experiments were carried out using the materials described in Examples 1, 3, and 7. The peak (P O2 -I) for surface oxygen appeared at 190 °C for the K-free material (Example 7), whereas it appeared at a temperature of about 100 °C for the materials with controlled washing (Examples 1 and 3) (Figure 6).

[0065] Furthermore, the peak (P O2 -II) for lattice oxygen shifted to lower temperatures (180 - 350 °C), whereas for the K-free spinel, this peak appeared after 300 °C.

[0066] Based on these results, it can be concluded that the materials covered by this patent are clearly different with respect to their O2 adsorption / desorption capacity.

[0067] The most accepted mechanism for the N2O decomposition reaction involves the adsorption of N2O on the active center [A], the release of N2, and the desorption of the O atom adsorbed on that center. A second N2O molecule adsorbs on this center and another N2 molecule is produced. The two adsorbed O atoms recombine to form molecular O2, which is the rate-limiting step of the reaction:

[0068] N2O (g) +[A]→N 2(g) +[O --A] [O - -A] + N2O (g) → N 2(g) + O 2(g) + [A]

[0069] The results of the obtained O2DTP indicate that the samples described in Examples 1 and 3 have the ability to perform the O2 desorption process (PO2-II) from lattice oxygen at a temperature (200 - 300 °C), which is significantly lower than the temperature (above 300 °C) required for the samples with the conventional spinel structure. This may be related to the decrease in the temperature required to carry out the N2O decomposition process under the conditions shown by these novel catalysts.

[0070] [Example 13]

[0071] Compare the data obtained from the catalyst obtained according to Example 1 of the present invention with the data described in the prior art document "D1": [Li Xue, Changbin Zhang, Hong He, Yasutake Teraoka, Applied Catalysis B: Environmental, Volume 75, Issues 3 - 4, 2007, Pages 167 - 174, figure 8]. For example, at 350 °C, it can be observed that the conversion rate obtained with this catalyst under the condition of the presence of wet O2 is about 77%, while the conversion rate obtained with the Co3O 3.88 K 0.08 material is 96%. To compare these results, the data was analyzed as a function of the space velocity (GHSV) when different experiments were carried out. Figure 7 shows the results of N2O conversion under the condition of the presence of wet O2 of the mentioned catalysts as a function of the space time or contact time. That is, the volume and flow rate of the catalyst used in each experiment are considered (T = V cat / F = 1 / GHSV). This comparison reveals that the catalytic activity of this material has been significantly improved compared with the prior art. Because the contact time required to achieve the same or higher conversion is shorter (the volume of the catalyst is less).

[0072] The following table shows the value of the reaction constant “K” at 350°C, calculated considering that the reaction proceeds according to first-order kinetics. This is the best quantitative representation of catalytic activity. 350℃ ”

[0073] [Table 1]

[0074] According to these data, the increase in reaction rate generated by the catalyst covered by this patent is orders of magnitude greater than that most well-described in the papers mentioned in this example.

[0075] On the other hand, the catalyst (D1) (Co3O4) described in this paper shows a binding energy of the Co2p3 / 2 component of 780.1 eV, similar to that of the K-free spinel described in Example 7 (Figure 3), and the desorption of lattice oxygen obtained by O2DTP occurs at 300°C or higher, similar to the K-free spinel described in Example 7 (Figure 5).

[0076] [Example 14]

[0077] Compare the materials obtained according to Example 1 and Example 3 of the present invention with the data shown in the prior art document “D2”: [Pawel Stelmachowski, Gabriela Maniak, Andrzej Kotarba, Zbigniew Sojka, Catalysis Communications, Volume 10, Issue 7, 2009, Pages 1062 - 1065, Figure 7]. From Figure 7 of “D2”, it can be seen that the Cs-doped catalyst achieves a conversion value of approximately 90% at 350°C under wet conditions (option b). Since the estimated conversion rate on this curve at this temperature is approximately 50%, the activity of the K-doped catalyst is significantly lower, while for the materials of Examples 1 and 5, the conversion rates are 96% and 98% respectively, and a significantly smaller amount of catalyst (shorter contact time) is used.

[0078] Furthermore, the following table shows the value of the reaction constant "K" at 350 °C, calculated considering that the reaction proceeds according to first-order kinetics 350℃ . 。 This is the best quantitative representation of the catalytic activity.

[0079]

Table 2

[0080] According to these data, the increase in the reaction rate generated by the materials covered by this patent is orders of magnitude greater than that most well-described in the papers mentioned in this example. Note that the present invention may include the following embodiments. <1> A non-stoichiometric spinel-type crystal structure of general formula Co 3 O 4-x / 2 A y having, X has a value of 0.02 to 0.3, A is an alkali element, y has a value of 0.06 to 0.18, the A / Co ratio is 0.02 to 0.10, Co 2+ / Co 3+ ratio is 0.55 to 0.80, the primary particle size corresponding to the crystallite size is 5 nm to 30 nm, a material characterized by this. <2> 40m 2 / g to 80 m 2 The material according to <1> above, having a BET specific surface area of / g. <3> The material according to <1> or <2> above, having a pore volume of 0.2 cm 3 / g to 0.4 cm 3 / g. <4> The material according to any one of <1> to <3> above, which is mesoporous. <5> The material according to any one of <1> to <4> above, wherein the alkali element A is K, x is 0.182, and y is 0.09. <6> The material according to any one of <1> to <4> above, wherein the alkali element A is Cs, x is 0.235, and y is 0.15. <7> Step (a) of dissolving a cobalt salt in water, Step (b) of dissolving a salt or hydroxide of an alkali metal in water, Step (c) of slowly adding the solution obtained in step (b) to the solution prepared in step (a) until a pH of 8 to 11 is reached, Step (d) of filtering the solid obtained in step (c) and washing it with 5 ml to 75 ml of water per gram of the cobalt salt added in step (a), Step (e) of drying the solid obtained in step (d) at a temperature of 50°C to 200°C for 12 hours to 20 hours, Step (f) of firing the solid obtained in step (e) in an air atmosphere at a temperature of 200°C to 700°C for at least 30 minutes, A process for obtaining the material according to <1> to <6> above, characterized by including this. <8> The process according to <7> above, wherein the cobalt salt in step (a) is selected from cobalt nitrate hexahydrate, cobalt sulfate, cobalt chloride, and cobalt acetate. <9> The process according to <7> or <8> above, wherein the salt or hydroxide of the alkali metal in step (b) is selected from alkali metal carbonates, alkali metal nitrates, alkali metal hydroxides, and alkali metal acetates. <10> The process according to <9>, wherein when the cobalt salt is cobalt nitrate hexahydrate and the alkali metal salt is an alkali metal carbonate, the washing in step (d) is carried out with water in an amount of 16 ml to 21 ml per 1 g of cobalt nitrate hexahydrate. <11> Use of the material according to any one of <1> to <6> as a catalyst. <12> Use of the material according to <11> as a catalyst in the oxidation / decomposition of a gas. <13> N 2 Use of the material according to <11> as a catalyst for the decomposition of O.

Claims

1. General formula Co ３ O ４－ｘ／２ A ｙ has a non-stoichiometric spinel-type crystal structure, x has a value of 0.02 to 0.3, A is an alkali element, y has a value of 0.06 to 0.18, The A / Co ratio is 0.02 to 0.10, Co ２＋ / Co ３＋ The ratio is 0.55 to 0.80, The primary particle size corresponding to the crystallite size is 5 nm to 30 nm, A catalyst for the N₂O decomposition reaction, characterized by the above.

2. 40 m ２ / g to 80 m ２ The catalyst for N2O decomposition reaction according to claim 1, having a BET specific surface area of / g to / g.

3. 0.2 cm ３ / g to 0.4 cm ３ The catalyst for N2O decomposition reaction according to claim 1 or claim 2, having a pore volume of / g to / g.

4. The catalyst for the N₂O decomposition reaction according to any one of Claims 1 to 3, which is mesoporous.

5. The catalyst for the N₂O decomposition reaction according to any one of Claims 1 to 4, wherein the alkali element A is K, x is 0.182, and y is 0.

09.

6. The catalyst for the N₂O decomposition reaction according to any one of Claims 1 to 4, wherein the alkali element A is Cs, x is 0.235, and y is 0.

15.

7. Step (a) of dissolving a cobalt salt in water; Step (b) of dissolving a salt or hydroxide of an alkali metal in water; Step (c) of slowly adding the solution obtained in step (b) to the solution prepared in step (a) until a pH of 8 to 11 is reached; Step (d) of filtering the solid obtained in step (c) and washing it with 5 ml to 75 ml of water per gram of the cobalt salt added in step (a); Step (e) of drying the solid obtained in step (d) at a temperature of 50°C to 200°C for 12 hours to 20 hours; Step (f) of firing the solid obtained in step (e) in an air atmosphere at a temperature of 200°C to 700°C for at least 30 minutes; A process for obtaining the catalyst for the N₂O decomposition reaction according to any one of Claims 1 to 6, characterized by including the above steps.

8. The process according to Claim 7, wherein the cobalt salt in step (a) is selected from cobalt nitrate hexahydrate, cobalt sulfate, cobalt chloride, and cobalt acetate.

9. The process according to Claim 7 or Claim 8, wherein the salt or hydroxide of the alkali metal in step (b) is selected from alkali metal carbonates, alkali metal nitrates, alkali metal hydroxides, and alkali metal acetates.

10. When the cobalt salt is cobalt nitrate hexahydrate and the salt of the alkali metal is an alkali metal carbonate, the washing in step (d) is performed with 16 ml to 21 ml of water per gram of cobalt nitrate hexahydrate. The process according to Claim 9.

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