Method for synchronously coupling catalytic nitrogen oxide storage reduction by electric heat pulse cycle

Abstract

The application provides a method for synchronously coupling catalytic nitrogen oxide storage and reduction by electric heat pulse cycles, comprising the following steps: adding a conductive catalyst into a reaction device, inputting a lean combustion gas atmosphere into the reaction device in a lean combustion stage, and inputting a low-power electric pulse into the conductive catalyst, inputting a rich combustion gas atmosphere into the reaction device in a rich combustion stage, and inputting a high-power electric pulse into the conductive catalyst, and one lean combustion stage and one rich combustion stage constitute a cycle period. The application generates an electric heat effect by inputting an electric pulse into the conductive catalyst, and the conductive catalyst can instantaneously change the temperature of the conductive catalyst by flexibly responding to the electric power input. In the lean combustion stage, a low-power electric pulse is inputted, and in the rich combustion stage, a high-power electric pulse is inputted, so that the reaction temperature which instantaneously changes synchronously with the lean-rich combustion cycle is provided, and the defects that the single temperature of the traditional thermal catalysis cannot optimize the two processes of nitrogen oxide storage and reduction in the time dimension are overcome.

Description

TECHNICAL FIELD

[0001] The application relates to a nitrogen oxide (NOx) storage reduction technology field, in particular to a method for electric heating pulse period synchronization coupled catalytic nitrogen oxide storage reduction. x ) storage reduction technology field, in particular to a method for electric heating pulse period synchronization coupled catalytic nitrogen oxide storage reduction. BACKGROUND

[0002] Lean burn engines are considered as one of the power technologies for coping with the increasingly severe global energy crisis and preventing climate change due to their high fuel economy and low carbon emission advantages. NOx x storage-reduction (NOx x Storage and Reduction, NSR) is a relatively efficient NOx x purification technology suitable for lean burn engines. The NSR technology is divided into two processes, namely, lean phase catalyst storage of NOx x (absorption temperature interval is usually 80-160 DEG C), and desorption of NOx x in the rich phase is reduced to N2 (desorption temperature interval is usually 200-400 DEG C).

[0003] Typical NSR catalyst systems include noble metal type (Pt, Pd, etc.), perovskite type, and hydrotalcite type. At present, most of the research on NSR technology is focused on the optimization and development of NSR catalysts themselves to improve the catalytic activity of the catalysts in a wider temperature window, but it does not fundamentally solve the defects of traditional thermal catalytic NSR technology, that is, the adsorption of NOx x in the lean phase requires low temperature conditions (80-160 DEG C), and the desorption-reduction of NOx x in the rich phase requires high temperature conditions (200-400 DEG C), and traditional thermal catalysis cannot provide a reaction temperature that instantaneously changes synchronously with the lean-rich combustion cycle. SUMMARY

[0004] In view of the deficiencies of the prior art, the technical problem to be solved by the application is how to provide a reaction temperature that instantaneously changes synchronously with the lean-rich combustion cycle, so that the reaction temperatures in the lean and rich combustion stages are flexibly controllable.

[0005] To solve the above problems, the application provides a method for electric heating pulse period synchronization coupled catalytic nitrogen oxide storage reduction, which comprises the following steps: adding a conductive catalyst to a reaction device, introducing a lean combustion atmosphere into the reaction device in the lean combustion stage, and inputting a low-power electric pulse to the conductive catalyst, introducing a rich combustion atmosphere into the reaction device in the rich combustion stage, and inputting a high-power electric pulse to the conductive catalyst, and one lean combustion stage and one rich combustion stage constitute a cycle period.

[0006] The present application generates an electro-thermal effect by inputting an electric pulse to the conductive catalyst, utilizes the flexible response of the conductive catalyst to the input of electric power, and can instantaneously change the temperature of the conductive catalyst. In the lean combustion stage, a low-power electric pulse is inputted, and in the rich combustion stage, a high-power electric pulse is inputted. The present application provides a reaction temperature that instantaneously changes synchronously with the lean-rich combustion cycle, and overcomes the problem that the single temperature of the traditional thermal catalyst cannot optimize NO x storage and restoration of the two processes.

[0007] Further, in the lean combustion stage, the input electric power is 0.5-3.5 W, the input current is 0.05-1.5 A, or the input voltage is 5-20 V; in the rich combustion stage, the input electric power is 3.5-5 W, the input current is 1.5-5 A, or the input voltage is 10-60 V. The present application can instantaneously change the temperature of the conductive catalyst by periodically changing the current, voltage, or power in the lean-rich combustion input, without the need for an external heating source.

[0008] Further, the time of one lean combustion stage is 60-180 s, and the time of one rich combustion stage is 10-60 s. Controlling the alternating time of the lean combustion stage and the rich combustion stage can improve the NO x conversion rate and N2 selectivity.

[0009] Further, the lean combustion atmosphere is 500 ppm NO x , 5-10% O2, Ar or N2 as the balance gas; the rich combustion atmosphere is 1000-3000 ppm C3H6 or 1-5% H2 or 1-5% CO, Ar or N2 as the balance gas. Controlling the lean combustion atmosphere and the rich combustion atmosphere can improve the NO x conversion rate and N2 selectivity.

[0010] Further, the electric conductivity of the conductive catalyst is 10 -7 -10 5 S / m. The conductive catalyst can flexibly respond to the input of electric power, and instantaneously change the temperature of the conductive catalyst.

[0011] Further, the conductive catalyst comprises a conductive carrier, an alkaline storage component, and an active component.

[0012] Further, the loading amount of the alkaline storage component is 1-20 wt.%, and the loading amount of the active component is 0.5-3 wt.%. The conductive carrier provides the catalyst with conductive ability, the alkaline storage component can improve the NO x storage capacity of the catalyst, and the active component constitutes the redox center of the catalyst.

[0013] Further, the conductive carrier is selected from one or more of the following: tin antimony oxide, indium tin oxide, aluminum-doped zinc oxide, titanium nitride, zirconium nitride, tungsten bronze, La x N1-x MO3 perovskite, transition metal carbon / nitride.

[0014] Further, the basic storage component is barium oxide and / or potassium carbonate.

[0015] Further, the active component is a noble metal.

[0016] Compared with the prior art, the present application has the following beneficial effects:

[0017] (1) The present application adopts an electrothermal catalysis mode, the electrothermal effect generated by electrothermal catalysis responds quickly to power input, can change the temperature of the catalyst instantaneously, provides a reaction temperature that changes instantaneously synchronously with the lean-rich combustion cycle, and overcomes the problem that the single reaction temperature in the lean-rich combustion stage in the traditional thermal catalysis process cannot balance the storage and reduction processes.

[0018] (2) The present application overcomes the defects that the single temperature of the traditional thermal catalysis in the time dimension cannot optimize the storage and reduction processes of NO x , and the electrothermal pulse has better NO x conversion rate and N2 selectivity.

[0019] (3) The present application realizes temperature regulation by inputting periodic changes in the lean-rich combustion electro-pulse, and does not need an external heat source.

[0020] (4) The present application is used for the aftertreatment of the exhaust gas of a lean-burn engine, improves the activity of the catalyst, reduces the reaction energy consumption, and compared with the traditional thermal catalysis, the reaction energy consumption of the thermal catalysis is 15.8 times that of the electrothermal pulse mode under the same NO x conversion rate. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 FIG. 1 is a structural schematic diagram of a reaction device in an embodiment of the present application.

[0022] Figure 2 FIG. 2 is a cycle schematic diagram of lean-rich combustion atmosphere switching and pulse electric power switching in embodiment 1 of the present application.

[0023] BRIEF DESCRIPTION OF DRAWINGS:

[0024] 1 - reaction tube, 2 - conductive catalyst, 3 - power supply, 4 - electrode, 5 - filter core, 6 - heat preservation layer. DETAILED DESCRIPTION

[0025] In order to make the above objectives, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application are described in detail below with reference to the drawings. It should be noted that the following embodiments are only used to illustrate the implementation method and typical parameters of the present application, and are not used to limit the parameter range described in the present application, and any reasonable changes derived therefrom are still within the protection scope of the claims of the present application.

[0026] It should be noted that the endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The ranges and endpoints thereof, and the individual values thereof, are to be construed as being open-ended in the context of the descriptions. In the context of a number value range, the endpoints of each range, the endpoints of each range and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as being specifically disclosed herein.

[0027] The specific embodiments of the present application disclose a method for synchronously coupling catalytic nitrogen oxide storage and reduction by electric heat pulse cycle, which is used for exhaust aftertreatment of lean-burn engine, and the method comprises the following steps: a conductive catalyst is added into a reaction device, a lean-burn atmosphere is introduced into the reaction device in a lean-burn stage, and a low-power electric pulse is input to the conductive catalyst; a rich-burn atmosphere is introduced into the reaction device in a rich-burn stage, and a high-power electric pulse is input to the conductive catalyst, and one lean-burn stage and one rich-burn stage constitute a cycle. The input of the electric pulse to the conductive catalyst produces an electric heat effect, the low-power electric pulse is input in the lean-burn stage, the high-power electric pulse is input in the rich-burn stage, and a reaction temperature that instantaneously changes synchronously with the lean-rich burn cycle is provided, so that the defects of single temperature of traditional thermal catalysis in the time dimension cannot optimize NOx storage and reduction, the catalyst activity is further improved, and the reaction energy consumption is reduced. x

[0028] In specific embodiments, the electric pulse intensity can be adjusted by controlling the input electric power, current or voltage. In the lean-burn stage, the input electric power is 0.5-3.5 W, the current is 0.05-1.5 A or the voltage is 5-20 V, and the time is 60-180 s; in the rich-burn stage, the input electric power is 3.5-5 W, the current is 1.5-5 A or the voltage is 10-60 V, and the time is 10-60 s. By inputting the periodic electric pulse in the lean-rich burn cycle, the temperature of the conductive catalyst can be instantaneously changed.

[0029] In specific embodiments, the lean-burn atmosphere is 500 ppm NO x , 5-10% O2, Ar or N2 as balance gas; and the rich-burn atmosphere is 1000-3000 ppm C3H6 or 1-5% H2 or 1-5% CO, Ar or N2 as balance gas.

[0030] ​In specific embodiments, the conductive catalyst composition comprises three parts, (1) a conductive support: such as antimony tin oxide (ATO), indium tin oxide (ITO), aluminum-doped zinc oxide (AZO), titanium nitride (TiN), zirconium nitride (ZrN), tungsten bronze (M x WO3, M is Na, K or Cs, X ranges from 0.1 to 0.3), La x N 1-x MO3 perovskite (where N is one or several of K, Ce, Sr; M is one or several of Co, Ni), transition metal carbon / nitride (MXenes), etc.; (2) a basic storage component: BaO, K2CO3, etc. basic species, the basic storage component loading is 1-20 wt.%; (3) an active component: noble metals such as Pt, Pd or Au, the active component loading is 0.5-3 wt.%. The conductive catalyst has an electrical conductivity of 10 -7 -10 5 S / m, which can change the temperature instantaneously after power input.

[0031] The application will be described in detail below through specific embodiments.

[0032] The reaction device used in the following examples is shown in Figure 1 The reaction device includes a reaction tube 1, a power supply 3 and an electrode 4, the conductive catalyst 2 is filled in the reaction tube 1, the electrode 4 passes through the inside of the reaction tube 1, the two ends of the electrode 4 are electrically connected with the positive and negative electrodes of the power supply 3 respectively, and the two sides of the conductive catalyst 2 are provided with filter cores 5, and the outside of the reaction tube 1 is wrapped with a heat preservation layer 6. The reaction device has a gas inlet and a gas outlet, the directions of the gas inlet and the gas outlet are shown by arrows in the figure, and two electromagnetic four-way valves are arranged to control the lean combustion gas atmosphere and the rich combustion gas atmosphere to enter the reaction device.

[0033] Two control programs are designed in the following examples, program 1 controls the two electromagnetic four-way valves to realize the switching of the lean and rich combustion gas atmospheres, and program 2 is used to control the switching of the input electric pulse, the periods of program 1 and program 2 are the same, and the switching of the lean and rich combustion gas atmospheres and the switching of the pulse electric power are synchronously controlled.

[0034] Example 1

[0035] A Pt and K co-loaded ATO catalyst (150 mg, particle size 40-60 mesh, Pt loading 2 wt.%, K loading 3 wt.%) was placed in the reaction device and pre-treated for 30 min under an Ar atmosphere at 100 ml / min with an electric power of 0.5 W. After the temperature, current and voltage signals were stabilized, two programs were started to control the switching of lean and rich atmospheres and the switching of pulsed electric power. Program 1 controlled the switching of lean and rich atmospheres by two electromagnetic four-way valves, with a set time of 180 s for lean and 60 s for rich, for 20 cycles. Program 2 was used to control the switching of input electric power, i.e. 180 s of 0.5 W and 60 s of 4 W, for 20 cycles. Program 1 and program 2 were coupled synchronously, and the cycle mode of the switching of rich atmosphere and pulsed electric power is shown in Figure 2 . The atmosphere composition in the lean stage was 500 ppm NO x , 5% O2, Ar as the balance gas; the atmosphere composition in the rich stage was 1000 ppm C3H6, Ar as the balance gas. The total flow rate of the reaction gas was 100 ml / min.

[0036] The component gases NO x (NO and NO2), N2O, NH3, CO, CO2 flowing out of the reaction device were detected on-line by a MultiGas 2030 Fourier transform infrared spectrometer. After 20 cycles, the NO x conversion rate was calculated for the last 5 stable cycles, which was 23.19%, and the N2 selectivity was 82.35%.

[0037] Example 2

[0038] A Pt and K co-loaded ATO catalyst (150 mg, particle size 40-60 mesh, Pt loading 2 wt.%, K loading 3 wt.%) was placed in the reaction device and pre-treated for 30 min under an Ar atmosphere at 100 ml / min with an electric power of 0.5 W. After the temperature, current and voltage signals were stabilized, two programs were started to control the switching of lean and rich atmospheres and the switching of pulsed electric power. Program 1 controlled the switching of lean and rich atmospheres by two electromagnetic four-way valves, with a set time of 180 s for lean and 60 s for rich, for 20 cycles. Program 2 was used to control the switching of input electric power, i.e. 180 s of 0.5 W and 60 s of 4 W, for 20 cycles. Program 1 and program 2 were coupled synchronously, and the cycle mode of the switching of rich atmosphere and pulsed electric power is shown in x . The atmosphere composition in the lean stage was 500 ppm NO x , 5% O2, Ar as the balance gas; the atmosphere composition in the rich stage was 1000 ppm C3H6, Ar as the balance gas. The total flow rate of the reaction gas was 100 ml / min.

[0039] The component gases NOx NO and NO2, N2O, NH3, CO, and CO2 were detected online using a MultiGas2030 Fourier transform infrared spectrometer. After 20 cycles, the last 5 stable cycles were selected to calculate NO. x The conversion rate was 61.95%, and the N2 selectivity was 87.90%.

[0040] Example 3

[0041] 150 mg of Pt and K co-loaded ATO catalyst (Pt loading 2 wt.%, K loading 3 wt.%) with a particle size of 40-60 mesh was placed in a reaction apparatus and pretreated for 30 min under an Ar atmosphere with an applied electrical power of 0.5 W. After the temperature, current, and voltage signals stabilized, two programs were activated to synchronously control the switching between lean and rich fuel atmospheres and the pulsed electrical power. Program 1 controlled two solenoid four-way valves to switch between lean and rich fuel atmospheres, with set times of 180 s for lean fuel and 60 s for rich fuel, for 20 cycles. Program 2 controlled the switching of input electrical power, i.e., 3 W for 180 s and 4 W for 60 s, for 20 cycles. The atmosphere composition during the lean fuel stage was 500 ppm NO. x The atmosphere composition for the fuel-rich stage is 5% O2, with Ar as the equilibrium gas; the atmosphere composition for the fuel-rich stage is 1% H2, with Ar as the equilibrium gas. The total flow rate of the reacting gases is 100 ml / min.

[0042] The components of the gas flowing out of the reaction device, NO x NO and NO2, N2O, NH3, CO, and CO2 were detected online using a MultiGas2030 Fourier transform infrared spectrometer. After 20 cycles, the last 5 stable cycles were selected to calculate NO. x The conversion rate was 68.65%, and the N2 selectivity was 89.34%.

[0043] Example 4

[0044] A Pt and K co-supported ATO catalyst (150 mg, particle size 40-60 mesh, Pt loading 2 wt.%, K loading 3 wt.%) was placed in the reaction device and pre-treated for 30 min under an Ar atmosphere at 100 ml / min with an electric power of 0.5 W. After the temperature, current and voltage signals were stable, two programs were opened to control the switching of lean and rich atmospheres and the switching of pulsed electric power. Program 1 controlled two electromagnetic four-way valves to switch the lean and rich atmospheres, with a set time of 180 s for lean and 60 s for rich, for 20 cycles. Program 2 was used to control the switching of input electric power, i.e. 3 W for 180 s and 4 W for 60 s, for 20 cycles. The lean phase atmosphere consisted of 500 ppm NO x , 5% O2, Ar as the balance gas; the rich phase atmosphere consisted of 1% CO, Ar as the balance gas. The total flow rate of the reaction gas was 100 ml / min.

[0045] The component gases NO x (NO and NO2), N2O, NH3, CO, CO2 flowing out of the reaction device were detected online by a MultiGas 2030 Fourier transform infrared spectrometer. After 20 cycles, the NO x conversion rate was calculated to be 60.30%, and the N2 selectivity was 87.45%.

[0046] Comparative Example 1

[0047] A Pt and K co-supported ATO catalyst (150 mg, particle size 40-60 mesh, Pt loading 2 wt.%, K loading 3 wt.%) was placed in the reaction device and pre-treated for 30 min under an Ar atmosphere at 100 ml / min with an electric power of 0.5 W. After the temperature, current and voltage signals were stable, two programs were opened to control the switching of lean and rich atmospheres and the switching of pulsed electric power. Program 1 controlled two electromagnetic four-way valves to switch the lean and rich atmospheres, with a set time of 180 s for lean and 60 s for rich, for 20 cycles. Program 2 was used to control the switching of input constant electric power 4 W (temperature 300°C). The lean phase atmosphere consisted of 500 ppm NO x , 5% O2, Ar as the balance gas; the rich phase atmosphere consisted of 1000 ppm C3H6, Ar as the balance gas. The total flow rate of the reaction gas was 100 ml / min.

[0048] The component gases NO xNO (NO and NO2), N2O, NH3, CO, CO2 were detected on-line by MultiGas 2030 Fourier Transform Infrared Spectrometer. After 20 cycles, the last 5 stable cycles were selected to calculate NO x The conversion rate was 58.00%, and the N2 selectivity was 84.34%.

[0049] Comparative Example 2

[0050] 150 mg of Pt and K co-loaded ATO (Pt loading 2 wt.%, K loading 3 wt.%) with a particle size of 40-60 mesh was placed in the reaction device and pretreated at 90°C for 30 min in an Ar atmosphere of 100 ml / min. Subsequently, the reaction furnace was raised to 300°C, and after the temperature was stabilized, program 1 was started to control the switching of lean and rich gas atmosphere, and the time was set to be lean 180 s, rich 60 s, and the cycle was 20 cycles. The lean phase atmosphere composition was: 500 ppm NO x , 5% O2, Ar as the balance gas; the rich phase atmosphere composition was: 1000 ppm C3H6, Ar as the balance gas. The total flow rate of the reaction gas was 100 ml / min.

[0051] The effluent gas NO x (NO and NO2), N2O, NH3, CO, CO2 were detected on-line by MultiGas 2030 Fourier Transform Infrared Spectrometer. After 20 cycles, the last 5 stable cycles were selected to calculate NO x The conversion rate was 29.84%, and the N2 selectivity was 66.15%.

[0052] Although the present application is disclosed as above, the present application is not limited to this. Any person skilled in the art, without departing from the spirit and scope of the present application, can make various changes and modifications, therefore the protection scope of the present application should be limited by the scope defined by the claims.

Claims

1. A method for the synchronous coupling of electrically heated pulse periods to catalytic nitrogen oxide storage reduction, characterized in that, The method comprises the following steps: adding an electrically conductive catalyst into a reaction device, feeding a lean combustion atmosphere into the reaction device in a lean combustion stage, and inputting a low-power electric pulse to the electrically conductive catalyst; feeding a rich combustion atmosphere into the reaction device in a rich combustion stage, and inputting a high-power electric pulse to the electrically conductive catalyst; one lean combustion stage and one rich combustion stage constitute a cycle; in the lean combustion stage, the input electric power is 0.5-3.5 W, the input electric current is 0.05-1.5 A, or the input electric voltage is 5-20 V; in the rich combustion stage, the input electric power is 3.5-5 W, the input electric current is 1.5-5 A, or the input electric voltage is 10-60 V.

2. The method of electrically heated pulsed period synchronized coupled catalytic nitrogen oxides storage reduction of claim 1, wherein, The time of one lean combustion stage is 60-180 s, and the time of one rich combustion stage is 10-60 s.

3. The method of electrically heated pulsed periodic synchronized coupled catalysis nitrogen oxides storage reduction of claim 1 wherein, The lean combustion atmosphere is 500 ppm nitrogen oxide, 5-10% O2, Ar or N2 as the balance gas; the rich combustion atmosphere is 1000-3000 ppm C3H6 or 1-5% H2 or 1-5% CO, Ar or N2 as the balance gas.

4. The method of synchronously coupled catalytic nitrogen oxides storage reduction by electric heat pulse period according to any one of claims 1 to 3, characterized in that The electric conductivity of the electrically conductive catalyst is 10 -7 -10 5 S / m.

5. The method of electrically heated pulsed period synchronized coupled catalytic nitrogen oxides storage reduction of claim 4, wherein, The electrically conductive catalyst comprises an electrically conductive carrier, a basic storage component and an active component.

6. The method of electrically heated pulsed periodic synchronized coupled catalysis nitrogen oxides storage reduction of claim 5 wherein, The loading amount of the basic storage component is 1-20 wt.%, and the loading amount of the active component is 0.5-3 wt.%.

7. The method of electrically heated pulsed periodic synchronized coupled catalytic nitrogen oxides storage reduction of claim 6 wherein, The electrically conductive support is selected from one or several of the following: antimony tin oxide, indium tin oxide, aluminum-doped zinc oxide, titanium nitride, zirconium nitride, tungsten bronze, La x N 1-x MO3 perovskites, transition metal carbon / nitrides.

8. The method of electrically heated pulsed periodic synchronized coupled catalysis nitrogen oxides storage reduction of claim 6 wherein, The basic storage component is barium oxide and / or potassium carbonate.

9. The method of electrically heated pulsed periodic synchronized coupled catalysis nitrogen oxides storage reduction of claim 6 wherein, The active component is a noble metal.

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