JP2022187305A - Nitrous oxide purification system and nitrous oxide purification method using the same - Google Patents

Abstract

To provide a nitrous oxide purification system excellent in N2O decomposition performance in a steady state under a temperature of 100°C or lower.SOLUTION: A nitrous oxide purification system comprises; a reactor 2 with an N2O decomposition catalyst 1 decomposing nitrous oxide (N2O) under the existence of hydrogen (H2); a hydrogen supply portion 4 continuously supplying H2 into the reactor 2; and a temperature control unit controlling temperature in the reactor 2 in a range of 0-100°C. The N2O decomposition catalyst 1 contains rhodium (Rh) and platinum (Pt).SELECTED DRAWING: Figure 1

Description

The present invention relates to a nitrous oxide purification system and a nitrous oxide purification method using the same.

Nitrous oxide (N ₂ O) contained in flue gas emitted from combustion furnaces, automobiles, etc., and various industrial exhaust gases emitted from heating equipment, chemical plants, etc. is decomposed in the stratosphere to produce nitric oxide. Also, since it exhibits a high greenhouse effect, the development of an efficient decomposition removal method is desired, and various N ₂ O decomposition catalysts, decomposition apparatuses, and decomposition methods are being studied.

For example, E. V. Kondratenko et al., Applied Catalysis A: General, 2006, 298, 73-79, N ₂ O using platinum (Pt), rhodium (Rh), or Pt—Rh alloy At a high temperature of 750 ° C., the N ₂ O decomposition catalyst consisting only of Rh is the most excellent in N ₂ O decomposition performance, and the N ₂ O decomposition catalyst consisting only of Pt and Pt- It has been shown that N ₂ O decomposition catalysts made of Rh alloys are inferior in N ₂ O decomposition performance.

In addition, Japanese Patent Application Laid-Open No. 2014-237117 (Patent Document 1) describes at least one active metal selected from the group consisting of Rh, Pt, Cu, Co, Ni, Fe, Au and Ag, and Ce Specifically, the N ₂ O decomposition catalyst comprising a Rh-ceria composite oxide exhibits transient _{N 2 O} decomposition activity at a low temperature of 50°C. Are listed.

JP 2014-237117 A

E. V. Kondratenko et al., Applied Catalysis A: General, 2006, 298, 73-79.

However, an N ₂ O decomposition catalyst consisting of Rh alone and an N ₂ O decomposition catalyst consisting of a Rh-ceria composite oxide did not have high N ₂ O decomposition performance in a steady state at a low temperature of 100° C. or less.

The present invention has been made in view of the above problems of the prior art, and provides a nitrous oxide purification system excellent in N ₂ O decomposition performance in a steady state at a low temperature of 100 ° C. or less and a nitrous oxide purification system using the same. It is an object of the present invention to provide a nitrogen purification method.

The present inventors have made intensive studies to achieve the above object, and as a result, at a high temperature of 750°C, the N ₂ O decomposition performance in a steady state is inferior to that of an N ₂ O decomposition catalyst consisting only of Rh. The inventors have found that an N ₂ O decomposition catalyst containing Rh and Pt, which has been used in the past, has excellent N ₂ O decomposition performance in a steady state at a low temperature of 100° C. or less and in the presence of hydrogen, and completed the present invention. came to.

That is, the nitrous oxide purification system of the present invention includes a reactor equipped with an N ₂ O decomposition catalyst for decomposing nitrous oxide (N ₂ O) in the presence of hydrogen (H ₂ ), and H ₂ , and a temperature control device for controlling the temperature in the reactor within a range of 0 to 100° C., wherein the N ₂ O decomposition catalyst is It is characterized by containing rhodium (Rh) and platinum (Pt).

In the nitrous oxide purification system of the present invention, the molar ratio of Rh and Pt in the N ₂ O decomposition catalyst is preferably within the range of Rh:Pt=95:5 to 20:80.

Further, the nitrous oxide purifying method of the present invention is a method of purifying nitrous oxide (N ₂ O) using the nitrous oxide purifying system of the present invention, wherein the reactor contains a gas containing N ₂ O and continuously supplying hydrogen (H ₂ ) from the hydrogen supply unit to the reactor, and N ₂ O in the presence of H ₂ at a temperature within the range of ₀ to 100 ° C. This method is characterized by contacting with an O decomposition catalyst.

The reason why it is possible to decompose and remove N ₂ O at a high decomposition rate in a steady state at a low temperature of 100° C. or less according to the present invention is not necessarily clear, but the present inventors speculate as follows. do. That is, in the N ₂ O decomposition catalyst containing only Rh as an active site, Rh in an oxidized state due to the decomposition reaction of N ₂ O has a temperature of 100° C. or less even in the presence of hydrogen (H ₂ ). At low temperatures, it is difficult to reduce (metalate), and it is difficult to constantly maintain the high Rh N ₂ O decomposition activity, so it is presumed that the N ₂ O decomposition performance in the steady state is low. In addition, in the N ₂ O decomposition catalyst containing only Pt as an active site, Pt in an oxidized state due to the decomposition reaction of N ₂ O is easily reduced (metallized), but the N ₂ O decomposition activity of Pt is low. Therefore, it is presumed that the N ₂ O decomposition performance in the steady state is low.

On the other hand, in the N ₂ O decomposition catalyst used in the present invention, since Pt is combined with Rh, Rh in an oxidized state due to the decomposition reaction of N ₂ O is reduced to 100° C. or less by the catalytic action of Pt. is assumed to be reduced ₍ metalated) in the presence of H2 even at a low temperature of . As a result, since the high N ₂ O decomposition activity of Rh is constantly maintained, it is presumed that the N ₂ O decomposition performance in the steady state increases.

On the other hand, even with an N ₂ O decomposition catalyst in which Pt is combined with Rh, in the absence of H ₂ , Rh in an oxidized state due to the decomposition reaction of N ₂ O is reduced (metalated). It is assumed that the steady-state N ₂ O decomposition performance is low because it is difficult to constantly maintain the high N ₂ O decomposition activity of Rh.

According to the present invention, it becomes possible to decompose and remove N ₂ O at a low temperature of 100° C. or less and in a steady state with a high decomposition rate.

1 is a schematic diagram showing a preferred embodiment of a nitrous oxide purification system of the present invention; FIG. FIG. 3 is a schematic diagram showing another preferred embodiment of the nitrous oxide purification system of the present invention; 4 is a graph showing the decomposition rate of N ₂ O in decomposition experiments of nitrous oxide (N ₂ O) at 60° C. performed in Examples 1 to 4 and Comparative Examples 1 and 2. FIG. 4 is a graph showing the decomposition rate of N ₂ O in experiments on decomposition of nitrous oxide (N ₂ O) at 100° C. performed in Examples 1 to 4 and Comparative Example 1. FIG. 2 is a graph showing the decomposition rate of N ₂ O in decomposition experiments of nitrous oxide (N ₂ O) at 150° C. performed in Reference Examples 1 to 5. FIG. 2 is a graph showing the decomposition rate of N ₂ O in decomposition experiments of nitrous oxide (N ₂ O) at 200° C. performed in Reference Examples 1 to 5. FIG. FIG. 10 is a graph showing the decomposition rate of N ₂ O in nitrous oxide (N ₂ O) decomposition experiments at 300° C. performed in Comparative Examples 3 to 8. FIG. 1 is a graph showing the temperature dependence of the N ₂ O decomposition rate in a nitrous oxide (N ₂ O) decomposition experiment using an Rh:Pt=9:1 N ₂ O decomposition catalyst. 1 is a graph showing the temperature dependence of the N ₂ O decomposition rate in a nitrous oxide (N ₂ O) decomposition experiment using an Rh:Pt=7:3 N ₂ O decomposition catalyst. 1 is a graph showing the temperature dependence of the N ₂ O decomposition rate in a nitrous oxide (N ₂ O) decomposition experiment using an N ₂ O decomposition catalyst of Rh:Pt=5:5. 1 is a graph showing the temperature dependence of the N ₂ O decomposition rate in a nitrous oxide (N ₂ O) decomposition experiment using an N ₂ O decomposition catalyst of Rh:Pt=3:7. 1 is a graph showing the temperature dependence of the N ₂ O decomposition rate in a nitrous oxide (N ₂ O) decomposition experiment using an N ₂ O decomposition catalyst of Rh:Pt=10:0.

Preferred embodiments of the present invention will be described in detail below with reference to the drawings, but the present invention is not limited to the drawings. In the following description and drawings, the same or corresponding elements are denoted by the same reference numerals, and redundant description may be omitted.

[Nitrous oxide purification system]
First, the nitrous oxide purification system of the present invention will be described. The nitrous oxide purification system of the present invention includes a reactor equipped with a N ₂ O decomposition catalyst for decomposing nitrous oxide (N ₂ O) in the presence of hydrogen (H ₂ ), and supplying H ₂ to the reactor. A hydrogen supply unit for continuously supplying hydrogen, and a temperature control device for controlling the temperature in the reactor within the range of 0 to 100 ° C. The N ₂ O decomposition catalyst is rhodium ( Rh) and platinum (Pt).

FIG. 1 is a schematic diagram showing a preferred embodiment of the nitrous oxide purification system of the present invention. In the nitrous oxide purification system shown in FIG. 1, a reactor 2 equipped with an N ₂ O decomposition catalyst 1 is connected to an inlet gas passage 3 for supplying a gas A containing N ₂ O. A gas A containing N ₂ O is mixed with H ₂ , and a hydrogen supply unit 4 is provided in the gas flow path 3 so that a gas (incoming gas) B containing N ₂ O and H ₂ is supplied to the reactor 2 . is connected. Further, the reactor 2 is connected to an outlet gas flow path 5 for discharging a gas (outgoing gas) C from which N ₂ O has been purified, and a temperature sensor 6 is provided on the gas inlet side of the reactor 2. is installed, and this temperature sensor 6 is connected to a temperature control device (not shown).

Moreover, FIG. 2 is a schematic diagram showing another preferred embodiment of the nitrous oxide purification system of the present invention. In the nitrous oxide purifying system shown in FIG. 2, a reactor 2 equipped with an N ₂ O decomposition catalyst 1 is connected to an inlet gas flow path 3 for supplying a gas A containing N ₂ O, and a reaction H ₂ is mixed with gas A containing N ₂ O, and gas (incoming gas) B containing N ₂ O and H ₂ is supplied to the N ₂ O decomposition catalyst 1 on the gas inlet side of the vessel 2 . The hydrogen supply unit 4 is connected as shown. Further, the reactor 2 is connected to an outlet gas flow path 5 for discharging a gas (outgoing gas) C from which N ₂ O has been purified, and a temperature sensor 6 is provided on the gas inlet side of the reactor 2. is installed, and this temperature sensor 6 is connected to a temperature control device (not shown).

The N ₂ O decomposition catalyst 1 used in the present invention contains Rh and Pt. In the N ₂ O decomposition catalyst containing Rh and Pt, Rh in an oxidized state due to the decomposition reaction of N ₂ O is converted into H ₂ by the catalytic action of Pt even at a low temperature of 100° C. or less. In the presence of Rh, it is reduced (metalated), and the high N ₂ O decomposition activity of Rh is constantly maintained, so that it is possible to consistently exhibit high N ₂ O decomposition performance. On the other hand, in the N ₂ O decomposition catalyst that does not contain Pt, even in the presence of H ₂ , Rh in an oxidized state due to the decomposition reaction of N ₂ O is reduced (metal ), it becomes difficult to steadily obtain N ₂ O decomposition activity with high Rh, and the N ₂ O decomposition performance in a steady state is lowered. In addition, in the N ₂ O decomposition catalyst that does not contain Rh, the N ₂ O decomposition performance in the steady state is low because the N ₂ O decomposition activity of Pt is low.

In such an N ₂ O decomposition catalyst, the molar ratio of Rh and Pt is preferably Rh:Pt = 95:5 to 20:80, more preferably 90:10 to 30:70, more preferably 90:10 to 40: 60 is particularly preferred. If the ratio of _Rh exceeds the above upper limit, the ratio of Pt is relatively decreased, and sufficient catalytic action of _Pt cannot be obtained. Even in the presence, at a low temperature of 100 ° C. or less, it is difficult to reduce (metalate), and it becomes difficult to steadily obtain N ₂ O decomposition activity with high Rh, and the N ₂ O decomposition performance in the steady state is poor. tends to be lower. On the other hand, when the ratio of Rh is less than the above lower limit, high N ₂ O decomposition activity of Rh cannot be obtained, so the N ₂ O decomposition performance in a steady state tends to be low.

Moreover, in the N ₂ O decomposition catalyst, Rh and Pt are preferably supported on a carrier. Examples of such carriers include metal oxides such as alumina, zirconia, ceria, silica and titania. These metal oxides may be used singly or in combination of two or more. Moreover, among these metal oxides, ceria is preferable from the viewpoint of being excellent in oxygen absorption and release performance. Furthermore, it is preferable that the carrier composed of these metal oxides is porous.

Furthermore, the form of the N ₂ O decomposition catalyst 1 is not particularly limited, and for example, a known form such as a honeycomb-shaped monolith catalyst or a pellet-shaped pellet catalyst can be adopted. Also, the substrate used for the N ₂ O decomposition catalyst 1 having such a form is not particularly limited, and examples thereof include monolithic substrates, pellet-shaped substrates, plate-shaped substrates, and the like. Furthermore, the material of the substrate is not particularly limited, and examples thereof include ceramics such as cordierite, silicon carbide, and mullite; and metals such as stainless steel containing chromium, nickel, and aluminum.

Although the hydrogen supply unit 4 used in the present invention is not particularly limited, examples thereof include a hydrogen cylinder, a water electrolysis device, an electrochemical reactor for NOx purification, and the like.

The temperature control device used in the present invention measures the temperature in the reactor 2 using the temperature sensor 6, and adjusts the temperature in the reactor 2 within the range of 0 to 100 ° C. (preferably There is no particular limitation as long as it can be controlled within the range of 20 to 80 ° C.), for example, heating devices such as electric heating wire heaters such as mantle heaters, infrared furnaces, heater cores, heat pumps, heat exchangers, A cooling device such as a Peltier element cooler may be used.

[Nitrous oxide purification method]
Next, the nitrous oxide purification method of the present invention will be described using the nitrous oxide purification system shown in FIGS. 1 and 2 as an example. The method for purifying nitrous oxide (N ₂ O) using the nitrous oxide purification system shown in FIG. 1 is a preferred embodiment of the nitrous oxide purification method of the present invention, and the nitrous oxide purification system shown in FIG. A method of purifying nitrous oxide (N ₂ O) using a nitrous oxide purification system is another preferred embodiment of the nitrous oxide purification method of the present invention. Contents overlapping with the contents described in the preferred embodiment of the nitrous oxide purification system of the present invention will be omitted.

In the nitrous oxide purifying method of the present invention, the gas A containing N ₂ O is supplied to the reactor 2, and hydrogen (H ₂ ) is continuously supplied from the hydrogen supply unit 4 to the reactor 2. NO2 is decomposed to nitrogen _{( N2} ) by contacting N2O with N2O decomposition catalyst ₁ in the presence of H2 at a temperature in the range of 100< _{0 >} C.

In the nitrous oxide purification system shown in FIG. 1, in the inlet gas passage 3, the gas A containing N ₂ O is mixed with H ₂ from the hydrogen supply unit 4 to produce a gas containing N ₂ O and H ₂ ( Incoming gas) B is supplied to the reactor 2 . Further, in the nitrous oxide purification system shown in FIG. 2, the gas A containing N ₂ O is supplied to the reactor 2 from the inlet gas flow path 3, and H ₂ is supplied to the reactor 2 from the hydrogen supply unit 4. , N ₂ O and H ₂ are mixed at the gas inlet side in the reactor 2 and supplied to the N ₂ O decomposition catalyst 1 .

In the gas containing N ₂ O and H ₂ , the volume ratio of H ₂ to N ₂ O is preferably H ₂ /N ₂ O = 1 to 10, and H ₂ /N ₂ O = 1.2 to 5. more preferred. When the proportion of H ₂ is less than the lower limit, it is difficult to sufficiently reduce (metalate) Rh in an oxidized state due to the decomposition reaction of N ₂ O, and high N ₂ O decomposition activity of Rh can be constantly obtained. N ₂ O decomposition performance in a steady state tends to be low, and on the other hand, if the proportion of H ₂ exceeds the upper limit, the energy for H ₂ supply is wasted and the cost tends to be high. .

_The flow _rate of the gas to be _supplied is not particularly limited. flow rate/catalyst volume) is preferably in the range of 100 to 10000/min, more preferably in the range of 150 to 8000/min.

In the nitrous oxide purification method of the present invention, the temperature in the reactor 2 is controlled within the range of 0 to 100° C., and N _{2 O is converted to the N 2 O} decomposition catalyst 1 in the presence of H ₂ at this temperature. need to make contact. If the temperature in the reactor 2 is below the lower limit, the activity of the N ₂ O decomposition catalyst cannot be sufficiently obtained. On the other hand, if the temperature in the reactor 2 exceeds the upper limit, energy is required to raise the temperature in the reactor 2, resulting in an increase in cost.

Thus, by bringing N _{2 O into contact with the N 2 O} decomposition catalyst 1 in the presence of H ₂ at a predetermined temperature, N ₂ O is decomposed into N ₂ and N ₂ O is purified gas. (Out gas) is discharged from the out gas passage 5 . Then, due to this N ₂ O decomposition reaction, Rh constituting the _{N 2} O decomposition catalyst becomes oxidized. At low temperatures and in the presence of H ₂ , Pt catalytically reduces (metalates) the oxidized state of Rh. As a result, the high N ₂ O decomposition activity of Rh can be constantly maintained, and N ₂ O can be decomposed and removed at a high decomposition rate in a steady state.

The preferred embodiments of the nitrous oxide purification system and the nitrous oxide purification method of the present invention have been described above with reference to FIGS. It is not limited to the above embodiment.

EXAMPLES The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

(Preparation Example 1)
Add 3.27 g of rhodium nitrate aqueous solution (manufactured by Cataler Co., Ltd., Rh concentration: 2.75% by mass) and 0.41 g of platinum nitrate aqueous solution (manufactured by Cataler Co., Ltd., Rh concentration: 4.57% by mass) to 100 ml of ion-exchanged water. Further, 10 g of CeO ₂ powder (“Cerium oxide” manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.) was added and stirred, and the resulting mixture was evaporated to dryness at 150°C. The resulting dried product was calcined in air at 300° C. for 3 hours to obtain RhPt-supported CeO ₂ particles. After that, the RhPt-supported CeO ₂ particles were compacted, crushed, and RhPt-supported CeO ₂ particles having an average particle diameter of about 1 mm (amount of Rh supported: 0.9 parts by mass with respect to 100 parts by mass of CeO ₂ , Amount of Pt supported: 0.2 parts by mass with respect to 100 parts by mass of CeO ₂ , Rh:Pt (molar ratio) = 9:1).

(Preparation Example 2)
RhPt-supported CeO ₂ particles having an average particle size of about 1 mm (Rh supported amount: 0.7 parts by mass with respect to 100 parts by mass of CeO ₂ , amount of Pt supported: 0.6 parts by mass with respect to 100 parts by mass of CeO ₂ , Rh:Pt (molar ratio)=7:3).

(Preparation Example 3)
RhPt-supported CeO ₂ particles having an average particle size of about 1 mm (Rh supported amount: 0.5 parts by mass with respect to 100 parts by mass of CeO ₂ , amount of Pt supported: 0.95 parts by mass with respect to 100 parts by mass of CeO ₂ , Rh:Pt (molar ratio)=5:5).

(Preparation Example 4)
RhPt-supported CeO ₂ particles having an average particle size of about 1 mm (Rh supported amount: 0.3 parts by mass with respect to 100 parts by mass of CeO ₂ , amount of Pt supported: 1.3 parts by mass with respect to 100 parts by mass of CeO ₂ , Rh:Pt (molar ratio)=3:7).

(Comparative Preparation Example 1)
Rh-supported CeO ₂ particles having an average particle diameter of about 1 mm (Rh-supported amount: CeO ₂ 100 1 part by mass, Rh:Pt (molar ratio) = 10:0) was obtained.

(Comparative Preparation Example 2)
₂ Pt-supported CeO particles with an average particle size of about 1 mm (Pt supported amount: CeO ₂ 100 1.9 parts by mass, Rh:Pt (molar ratio) = 0:10) was obtained.

(Example 1)
A nitrous oxide (N ₂ O) decomposition experiment was conducted using the nitrous oxide purification system shown in FIG. That is, first, 1 g of RhPt-supported CeO ₂ particles (Rh:Pt=9:1) obtained in Preparation Example 1 was charged into a reactor 2 having an inner diameter of 12 mm (filling amount: about 1 ml). A hydrogen supply unit 4 (hydrogen cylinder) was connected to the gas flow path 3 .

Next, nitrogen gas was supplied from the inlet gas flow path 3 to the reactor 2 at a flow rate of 5 L/min and a temperature of 300° C. for 5 minutes to form a catalyst layer composed of RhPt-supported CeO ₂ particles (Rh:Pt=9:1). (N ₂ O decomposition catalyst 1) was pretreated.

After that, input gas B (N ₂ O (500 ppm) + H ₂ (3000 ppm) + H ₂ O (5%) + N ₂ (balance)) obtained by mixing H ₂ with gas A containing N ₂ O and moisture was introduced. The gas was supplied from the gas passage 3 to the reactor 2 under conditions of a flow rate of 5 L/min and a temperature of 60° C. or 100° C., and N ₂ O decomposition reaction was performed. The N ₂ O concentrations of the incoming gas B and the outgoing gas C to the N ₂ O decomposition catalyst 1 in a steady state were measured using a non-dispersive infrared gas analyzer (NDIR) to obtain the N ₂ O decomposition rate. Table 1 shows the results.

(Example 2)
Except that 1 g of the RhPt _- supported CeO2 particles (Rh:Pt=7:3) obtained in Preparation Example ₂ was used instead of the RhPt-supported CeO2 particles (Rh:Pt=9:1) obtained in Preparation Example 1. performs the N ₂ O decomposition reaction in the same manner as in Example 1, measures the N ₂ O concentration of the incoming gas B and the outgoing gas C to the N ₂ O decomposition catalyst 1 in a steady state, and calculates the N ₂ O decomposition rate. asked. Table 1 shows the results.

(Example 3)
Except for using 1 g of the RhPt-supported CeO ₂ particles (Rh:Pt=5:5) obtained in Preparation Example 3 instead of the RhPt-supported CeO ₂ particles (Rh:Pt=9:1) obtained in Preparation Example 1. performs the N ₂ O decomposition reaction in the same manner as in Example 1, measures the N ₂ O concentration of the incoming gas B and the outgoing gas C to the N ₂ O decomposition catalyst 1 in a steady state, and calculates the N ₂ O decomposition rate. asked. Table 1 shows the results.

(Example 4)
Except that 1 g of RhPt-supported CeO ₂ particles (Rh:Pt=3:7) obtained in Preparation Example 4 was used instead of the RhPt-supported CeO ₂ particles (Rh:Pt=9:1) obtained in Preparation Example 1. performs the N ₂ O decomposition reaction in the same manner as in Example 1, measures the N ₂ O concentration of the incoming gas B and the outgoing gas C to the N ₂ O decomposition catalyst 1 in a steady state, and calculates the N ₂ O decomposition rate. asked. Table 1 shows the results.

(Comparative example 1)
1 g of RhPt _- supported CeO2 particles (Rh:Pt=10:0) obtained in Comparative Preparation Example 1 was used instead of the RhPt _- supported CeO2 particles (Rh:Pt=9:1) obtained in Preparation Example 1. Except for this, the N ₂ O decomposition reaction was carried out in the same manner as in Example 1, and the N ₂ O concentrations of the incoming gas B and the outgoing gas C to the N ₂ O decomposition catalyst 1 in a steady state were measured, and the N ₂ O decomposition rate was determined. asked for Table 1 shows the results.

(Comparative example 2)
1 g of Pt-supported CeO ₂ particles (Rh:Pt=0:10) obtained in Comparative Preparation Example 2 was used instead of the RhPt-supported CeO ₂ particles (Rh:Pt=9:1) obtained in Preparation Example 1. The decomposition reaction of N ₂ O was performed in the same manner as in Example 1 except that the temperature was 60° C. only, and the N ₂ O concentrations of the incoming gas B and the outgoing gas C to the N ₂ O decomposition catalyst 1 in a steady state were measured. , the N ₂ O decomposition rate was obtained. Table 1 shows the results.

(Reference example 1)
Input gas B (N ₂ O (500 ppm) + H ₂ (3000 ppm) + H ₂ O (5%) + N ₂ (balance)), which is a mixture of H ₂ in gas A containing N ₂ O and moisture, is added to the input gas stream. N ₂ O decomposition reaction was carried out in the same manner as in Example 1, except that the flow rate was 5 L/min and the temperature was 150° C. or 200° C., and the N ₂ O decomposition catalyst 1 was obtained in a steady state. The N ₂ O concentrations of the incoming gas B and the outgoing gas C were measured to obtain the N ₂ O decomposition rate. Table 1 shows the results.

(Reference example 2)
Except that 1 g of the RhPt _- supported CeO2 particles (Rh:Pt=7:3) obtained in Preparation Example ₂ was used instead of the RhPt-supported CeO2 particles (Rh:Pt=9:1) obtained in Preparation Example 1. performs an N ₂ O decomposition reaction in the same manner as in Reference Example 1, measures the N ₂ O concentration of the incoming gas B and the outgoing gas C to the N ₂ O decomposition catalyst 1 in a steady state, and calculates the N ₂ O decomposition rate. asked. Table 1 shows the results.

(Reference example 3)
Except for using 1 g of the RhPt-supported CeO ₂ particles (Rh:Pt=5:5) obtained in Preparation Example 3 instead of the RhPt-supported CeO ₂ particles (Rh:Pt=9:1) obtained in Preparation Example 1. performs an N ₂ O decomposition reaction in the same manner as in Reference Example 1, measures the N ₂ O concentration of the incoming gas B and the outgoing gas C to the N ₂ O decomposition catalyst 1 in a steady state, and calculates the N ₂ O decomposition rate. asked. Table 1 shows the results.

(Reference example 4)
Except that 1 g of RhPt-supported CeO ₂ particles (Rh:Pt=3:7) obtained in Preparation Example 4 was used instead of the RhPt-supported CeO ₂ particles (Rh:Pt=9:1) obtained in Preparation Example 1. performs an N ₂ O decomposition reaction in the same manner as in Reference Example 1, measures the N ₂ O concentration of the incoming gas B and the outgoing gas C to the N ₂ O decomposition catalyst 1 in a steady state, and calculates the N ₂ O decomposition rate. asked. Table 1 shows the results.

(Reference example 5)
1 g of RhPt _- supported CeO2 particles (Rh:Pt=10:0) obtained in Comparative Preparation Example 1 was used instead of the RhPt _- supported CeO2 particles (Rh:Pt=9:1) obtained in Preparation Example 1. Except for this, the N ₂ O decomposition reaction was performed in the same manner as in Reference Example 1, and the N ₂ O concentrations of the incoming gas B and the outgoing gas C to the N ₂ O decomposition catalyst 1 in a steady state were measured, and the N ₂ O decomposition rate was determined. asked for Table 1 shows the results.

(Comparative Example 3)
Inlet gas B containing N ₂ O (N ₂ O (500 ppm) + H ₂ (0 ppm) + H ₂ O (0%) + N ₂ (remainder)) was fed from the inlet gas flow path 3 to the reactor 2 at a flow rate of 5 L/min. , _{N 2} O decomposition reaction was performed in the same manner as in Example ₁ except that the temperature was 300 ° C. was measured to obtain the N ₂ O decomposition rate. Table 1 shows the results.

(Comparative Example 4)
Except that 1 g of the RhPt _- supported CeO2 particles (Rh:Pt=7:3) obtained in Preparation Example ₂ was used instead of the RhPt-supported CeO2 particles (Rh:Pt=9:1) obtained in Preparation Example 1. performs an N ₂ O decomposition reaction in the same manner as in Comparative Example 3, measures the N ₂ O concentration of the incoming gas B and the outgoing gas C to the N ₂ O decomposition catalyst 1 in a steady state, and calculates the N ₂ O decomposition rate. asked. Table 1 shows the results.

(Comparative Example 5)
Except for using 1 g of the RhPt-supported CeO ₂ particles (Rh:Pt=5:5) obtained in Preparation Example 3 instead of the RhPt-supported CeO ₂ particles (Rh:Pt=9:1) obtained in Preparation Example 1. performs an N ₂ O decomposition reaction in the same manner as in Comparative Example 3, measures the N ₂ O concentration of the incoming gas B and the outgoing gas C to the N ₂ O decomposition catalyst 1 in a steady state, and calculates the N ₂ O decomposition rate. asked. Table 1 shows the results.

(Comparative Example 6)
Except that 1 g of RhPt-supported CeO ₂ particles (Rh:Pt=3:7) obtained in Preparation Example 4 was used instead of the RhPt-supported CeO ₂ particles (Rh:Pt=9:1) obtained in Preparation Example 1. performs an N ₂ O decomposition reaction in the same manner as in Comparative Example 3, measures the N ₂ O concentration of the incoming gas B and the outgoing gas C to the N ₂ O decomposition catalyst 1 in a steady state, and calculates the N ₂ O decomposition rate. asked. Table 1 shows the results.

(Comparative Example 7)
1 g of RhPt _- supported CeO2 particles (Rh:Pt=10:0) obtained in Comparative Preparation Example 1 was used instead of the RhPt _- supported CeO2 particles (Rh:Pt=9:1) obtained in Preparation Example 1. Except for this, the N ₂ O decomposition reaction was performed in the same manner as in Comparative Example 3, and the N ₂ O concentrations of the incoming gas B and the outgoing gas C to the N ₂ O decomposition catalyst 1 in a steady state were measured, and the N ₂ O decomposition rate was determined. asked for Table 1 shows the results.

(Comparative Example 8)
1 g of Pt-supported CeO ₂ particles (Rh:Pt=0:10) obtained in Comparative Preparation Example 2 was used instead of the RhPt-supported CeO ₂ particles (Rh:Pt=9:1) obtained in Preparation Example 1. _The decomposition reaction of _{N 2} O was performed in the same manner as in Comparative Example ₃ except that asked for Table 1 shows the results.

Based on the results shown in Table 1, a graph was created showing the N ₂ O decomposition rate of each N ₂ O decomposition catalyst for each decomposition temperature. The results are shown in FIGS. 3 to 7. FIG.

As shown in FIGS. 3-4, the N ₂ O purification system with the N ₂ O decomposition catalyst containing Rh and Pt, when operated at 60° C., produced N ₂ O decomposition containing only Rh. Compared to the N ₂ O purification system with a catalyst and the N ₂ O purification system with an N ₂ O decomposition catalyst containing only Pt, and operated at 100° C., N ₂ containing only Rh It has been found that steady-state N ₂ O decomposition rates are higher compared to N ₂ O purification systems with O decomposition catalysts.

On the other hand, as shown in FIGS. 5-6, when operated at 150° C. or 200° C., the N ₂ O purification system with the N ₂ O decomposition catalyst containing Rh and Pt and the _In any of the _N2O cleanup systems with N2O cracking catalysts containing , the steady state _N2O cracking rate was increased.

On the other hand, as shown in FIG. 7, when operated at 300° C. without supplying H ₂ , the N ₂ O purification system with the N ₂ O decomposition catalyst containing Rh and Pt, Rh In both the N ₂ O purification system with the N ₂ O decomposition catalyst containing only Pt and the N ₂ O purification system with the N ₂ O decomposition catalyst containing only Pt, the steady state N ₂ The O decomposition rate became low.

Further, based on the results shown in Table 1, a graph showing the N ₂ O decomposition rate at each decomposition temperature was created for each N ₂ O decomposition catalyst. The results are shown in FIGS. 8 to 12. FIG.

As shown in FIGS. 8-11, N ₂ O purification systems with N ₂ O decomposition catalysts containing Rh and Pt exhibit high steady-state It was found that the N ₂ O decomposition rate was maintained.

On the other hand, as shown in FIG. 12, the N ₂ O purification system with the N ₂ O decomposition catalyst containing only Rh, when operated at 150° C. or 200° C., showed a steady-state N ₂ O decomposition rate of However, it was found that operating at temperatures below 100° C. resulted in lower steady-state N ₂ O decomposition rates.

From the above results, the N ₂ O purification system equipped with the N ₂ O decomposition catalyst containing Rh and Pt exhibits excellent N ₂ O decomposition in a steady state even when operated at a low temperature of 100° C. or less. It was found to perform well.

As described above, according to the present invention, it is possible to decompose and remove N ₂ O at a low temperature of 100° C. or less and in a steady state with a high decomposition rate.

Therefore, the nitrous oxide purification system of the present invention can be used even when the temperature of combustion exhaust gases emitted from combustion furnaces, automobiles, etc., and various industrial exhaust gases emitted from heating devices, chemical plants, etc. reaches a temperature of 100 ° C. or less. is also useful as a system capable of purifying N ₂ O contained in these exhaust gases at a high decomposition rate without heating these exhaust gases.

1: N ₂ O decomposition catalyst 2: Reactor 3: Incoming gas flow path 4: Hydrogen supply unit 5: Outgoing gas flow path 6: Temperature sensor A: Gas containing N ₂ O B: Incoming gas (N ₂ O and hydrogen and gas)
C: outgassing (gas from which N ₂ O has been purified)

Claims (3)

a reactor comprising a _N2O decomposition catalyst for decomposing nitrous oxide ₍ N2O) in the presence of hydrogen ₍ H2);
a hydrogen supply for continuously supplying _H2 to the reactor;
a temperature control device for controlling the temperature in the reactor within a range of 0 to 100° C.;
and
A nitrous oxide purification system, wherein the N ₂ O decomposition catalyst contains rhodium (Rh) and platinum (Pt). 2. The nitrous oxide purification system according to claim 1, wherein the molar ratio of Rh and Pt in said N ₂ O decomposition catalyst is within the range of Rh:Pt=95:5 to 20:80. A method for purifying nitrous oxide (N ₂ O) using the nitrous oxide purification system according to claim 1 or 2,
A gas containing N ₂ O is supplied to the reactor, and hydrogen (H ₂ ) is continuously supplied from the hydrogen supply unit to the reactor, and H ₂ is added at a temperature within the range of 0 to 100 ° C. A method for purifying nitrous oxide, comprising bringing N 2 O into contact with the N _{2 O decomposition catalyst in the presence of said N 2 O} decomposition catalyst.

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