Cr-In / H-SSZ-13 catalyst, preparation method thereof and application of Cr-In / H-SSZ-13 catalyst in CH4-SCR denitration

Abstract

The invention discloses a Cr-In / H-SSZ-13 catalyst, a preparation method of the Cr-In / H-SSZ-13 catalyst and application of the Cr-In / H-SSZ-13 catalyst in CH4-SCR denitration. The preparation method of the Cr-In / H-SSZ-13 catalyst comprises the following steps: preparing NH4-SSZ-13; the preparation method comprises the following steps: adding an In source, a Cr source and NH4-SSZ-13 into water, uniformly dispersing to obtain a mixed solution, the mass ratio of Cr to In of the Cr source and the In source is 1: (3-5), and the mass ratio of Cr in the Cr source to the NH4-SSZ-13 is 0.25%-2%; drying the mixed solution, grinding, roasting in a tubular furnace, and cooling to obtain a catalyst; in the roasting process, dry air is firstly introduced, then hydrogen and argon are introduced, then dry air is introduced, and the roasting temperature is 200-500 DEG C. By adopting the technical scheme provided by the invention, the highest NOx removal rate is 84.4%, the denitration performance of the catalyst is improved, and the preparation efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the field of catalyst technology, and in particular to a Cr-In / H-SSZ-13 catalyst, a preparation method thereof, and application thereof in CH4-SCR denitration. Background Art

[0002] Nitrogen oxides (NO x ) is a major atmospheric pollutant that has caused great harm to the natural environment and human health. CH4, as a reducing agent, is widely available and has no secondary pollution, making CH4-SCR a highly promising denitrification technology. SSZ-13 molecular sieve has shown broad application prospects in catalytic fields such as CO2 alcohol production and NOx removal due to its unique pore structure and excellent hydrothermal stability. It is currently considered to be one of the most important catalyst supports in the application of SCR technology. SSZ-13 molecular sieve has an excellent pore structure and high specific surface area. The Cr-In / H-SSZ-13 catalyst prepared with it as a support has good denitrification activity and hydrothermal stability in the field of CH4-SCR denitrification, but its complex preparation process seriously restricts its large-scale application. Summary of the Invention

[0003] In response to the above technical problems, the present invention discloses a Cr-In / H-SSZ-13 catalyst and a preparation method thereof, as well as application thereof in CH4-SCR denitrification, which has better denitrification performance and higher preparation efficiency.

[0004] To this end, the technical solution adopted in the present invention is:

[0005] The preparation method of Cr-In / H-SSZ-13 catalyst comprises the following steps:

[0006] Step S1, preparing NH4-SSZ-13;

[0007] Step S2: Add an In source, a Cr source, and NH4-SSZ-13 to water and disperse them evenly to obtain a mixed solution, wherein the mass ratio of Cr:In of the Cr source and the In source is 1:3-5, and the mass of Cr in the Cr source accounts for 0.25%-2% of the mass of NH4-SSZ-13; dry the mixed solution and grind it, then place it in a tubular furnace for roasting, and cool it to obtain a Cr-In / H-SSZ-13 catalyst; during the roasting process, first introduce dry air for 50-70 minutes, then introduce hydrogen and argon gas for 50-70 minutes, and then introduce dry air for 50-70 minutes, and the roasting temperature is 200-500°C.

[0008] This technical solution adopts the order of "oxidation + reduction + oxidation" to introduce the atmosphere, and the dynamic atmosphere control of oxidation and reduction can promote the InO +The formation of active sites improves the denitrification performance of the catalyst. The prepared Cr-In / H-SSZ-13 catalyst has better denitrification performance and shorter preparation time.

[0009] As a further improvement of the present invention, in step S1, the NH4-SSZ-13 is prepared by adding Na-SSZ-13 to a 0.05-0.4M (NH4)2SO4 solution, uniformly dispersing the Na-SSZ-13, stirring and reacting at 60-85°C for 3-5 hours, centrifuging, washing, and drying to obtain NH4-SSZ-13. Furthermore, the solution is washed with deionized water multiple times until the pH is 6-7.

[0010] Furthermore, the solid-liquid ratio of Na-SSZ-13 to (NH4)2SO4 solution is 1:50.

[0011] As a further improvement of the present invention, the mass proportion of In in the In source is 1% to 3%, and further, the mass proportion of In in the In source is 2%.

[0012] As a further improvement of the present invention, in step S2, ultrasonic dispersion is used for uniform dispersion, and the ultrasonic time is 4 to 6 minutes.

[0013] As a further improvement of the present invention, in step S2, oven drying is adopted.

[0014] As a further improvement of the present invention, in step S2, the mass ratio of Cr:In of the Cr source and the In source is 1:4 to 5. Further, in step S2, the mass ratio of Cr:In of the Cr source and the In source is 1:4.

[0015] As a further improvement of the present invention, in step S2, the mass ratio of Cr in the Cr source to the mass ratio of NH4-SSZ-13 is 0.25% to 1%. Furthermore, in step S2, the mass ratio of Cr in the Cr source to the mass ratio of NH4-SSZ-13 is 0.5%.

[0016] As a further improvement of the present invention, the In source is In(NO3)3·xH2O, and the Cr source is Cr(NO3)3·9H2O.

[0017] As a further improvement of the present invention, in step S2, the calcination temperature is 200-300°C. Further, in step S2, the calcination temperature is 300°C.

[0018] The invention discloses a Cr-In / H-SSZ-13 catalyst, which is prepared by adopting the preparation method of the Cr-In / H-SSZ-13 catalyst.

[0019] The present invention discloses the application of the Cr-In / H-SSZ-13 catalyst described above for CH4-SCR denitration.

[0020] The invention discloses a catalyst ceramic filter tube, which comprises a ceramic filter tube. The ceramic filter tube is loaded with the above-mentioned Cr-In / H-SSZ-13 catalyst.

[0021] The present invention discloses a method for preparing the catalyst ceramic filter tube as described above, comprising the following steps:

[0022] Step S10, breaking the ceramic filter tube, acid-washing to remove impurities, washing with water and drying, and calcining at 350-450° C. for 1-3 hours to obtain a pretreated ceramic filter tube;

[0023] Step S20: loading the Cr-In / H-SSZ-13 catalyst onto the pretreated ceramic filter tube by an impregnation method, drying, and calcining at 350° C. to 450° C. for 2 to 4 hours to obtain a catalytic ceramic filter tube.

[0024] As a further improvement of the present invention, in step S10, the ceramic filter tube is broken into small pieces of 10 to 20 mesh.

[0025] As a further improvement of the present invention, in step S10, 0.1M nitric acid solution is used for pickling, and ultrasonic treatment is performed for 25 to 35 minutes to remove impurities.

[0026] As a further improvement of the present invention, in step S10, the product is repeatedly washed with deionized water and then placed in an oven at 95-105°C for drying. Furthermore, the oven temperature is 100°C.

[0027] As a further improvement of the present invention, in step S10 and step S20, the calcination temperature is 300° C. and the calcination time is 3 hours.

[0028] As a further improvement of the present invention, in step S20, the Cr-In / H-SSZ-13 catalyst is loaded onto the pretreated ceramic filter tube by the impregnation method, including: placing the Cr-In / H-SSZ-13 catalyst, deionized water, and a binder, polyethylene glycol 400 (PEG 400), (solid-to-liquid ratio of 1:5) in a beaker and stirring continuously for 0.5 hours until the mixture is uniformly mixed; immersing the pretreated ceramic filter tube in the slurry, and ultrasonically treating it at 35-45°C for 5 minutes to ensure uniform adhesion of the catalyst, thereby completing the impregnation. Furthermore, the mass ratio of the Cr-In / H-SSZ-13 catalyst, deionized water, and the binder, polyethylene glycol 400 (PEG 400), is 1:2:3.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The technical solution of the present invention adopts NH4-SSZ-13 as the source of SSZ-13, simplifies the preparation steps, shortens the catalyst preparation time by 48 hours, improves the preparation efficiency, and introduces the atmosphere in the order of "oxidation + reduction + oxidation". The dynamic atmosphere control of oxidation and reduction can promote the InO in the catalyst In species. + The formation of active sites improves the denitrification performance of the catalyst. The prepared Cr-In / H-SSZ-13 catalyst has a high denitrification rate under the reaction conditions of 500ppmNO, 800ppmCH4, 8%O2, 5% water vapor, 40000h -1 When the highest NO x The removal rate was 84.4%, showing the best denitrification performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The denitration performance test results of the catalysts of Example 1 and Comparative Example 1 of the present invention are shown in FIG. 1 , wherein (a) is NO x (b) is the conversion rate, (c) is the CH4 selectivity.

[0032] Figure 2 1 is the PXRD pattern of the catalysts of Example 1 of the present invention and Comparative Example 1.

[0033] Figure 3 These are SEM images of the catalysts of Example 1 and Comparative Example 1 of the present invention; wherein, (a) to (c) are SEM images of the catalyst of Example 1 at different positions, and (d) to (f) are SEM images of the catalyst of Comparative Example 1 at different positions.

[0034] Figure 4 1 and 2 are element distribution diagrams of the catalysts of Example 1 and Comparative Example 1 of the present invention; wherein (a) is the catalyst of Example 1, and (b) is the catalyst of Comparative Example 1.

[0035] Figure 5 These are the pore structure analysis results of the catalysts of Example 1 and Comparative Example 11 of the present invention; wherein, (a) is the N2 adsorption-desorption isotherm curve, and (b) is the DFT adsorption pore distribution diagram.

[0036] Figure 6 The CH4-SCR denitration activity results of Cr-In / H-SSZ-13 catalysts prepared in different calcination atmospheres in Example 1 of the present invention and Comparative Examples 2-7 are shown; wherein (a) is NO x (b) is the conversion rate, (c) is the CH4 selectivity.

[0037] Figure 7 The CH4-SCR denitrification activity results of Cr-In / H-SSZ-13 catalysts prepared at different calcination temperatures in the embodiment of the present invention; wherein (a) is NOx (b) is the conversion rate, (c) is the CH4 selectivity.

[0038] Figure 8 The CH4-SCR denitrification activity results of Cr-In / H-SSZ-13 catalysts prepared with different metal loading ratios in the embodiment of the present invention are shown in FIG. 1 ; wherein (a) is NO x (b) is the conversion rate, (c) is the CH4 selectivity.

[0039] Figure 9 is the CH4-SCR denitration activity result of Cr-In / H-SSZ-13 catalyst prepared with different loaded metal contents in the embodiment of the present invention; wherein, (a) is NO x (b) is the conversion rate, (c) is the CH4 selectivity.

[0040] Figure 10 The results of CH4-SCR denitrification activity of the catalyst of Example 1 of the present invention under different SO2 concentrations are shown; wherein (a) is NO x (b) is the conversion rate, (c) is the CH4 selectivity.

[0041] Figure 11 The results of CH4-SCR denitrification activity of the catalyst of Example 1 of the present invention under different water vapor concentrations are shown; wherein (a) is NO x (b) is the conversion rate, (c) is the CH4 selectivity.

[0042] Figure 12 The results of CH4-SCR denitrification activity under the combined influence of SO2 and water vapor on the catalyst of Example 1 of the present invention are shown in FIG. 1 ; wherein (a) is NO x (b) is the conversion rate, (c) is the CH4 selectivity.

[0043] Figure 13 The CH4-SCR denitration activity of the Cr-In / H-SSZ-13 catalyst under 12 h operation of the catalyst of Example 1 of the present invention. DETAILED DESCRIPTION

[0044] The preferred embodiments of the present invention are described in further detail below.

[0045] Example 1

[0046] The Cr-In / H-SSZ-13 catalyst was prepared by the following steps:

[0047] Step S1, preparing NH4-SSZ-13;

[0048] Weigh 1g of Na-SSZ-13 into a beaker, add 0.1M (NH4)2SO4 solution at a solid-liquid ratio of 1:50 (g / mL), ultrasonically disperse the solid, place it in a heated magnetic stirrer and stir at 80°C for 4h. After the end, use a centrifuge to recover the solid; repeat the exchange three times, then wash it with deionized water several times until the pH is 6-7, and then place it in an oven to dry to obtain NH4-SSZ-13.

[0049] Step S2, In(NO3)3·xH2O, Cr(NO3)3·9H2O and NH4-SSZ-13 are added to water, and dispersed uniformly by ultrasonication for 5 minutes to obtain a mixed solution, wherein the mass ratio of Cr:In of the Cr source and the In source is 1:4, and the mass of Cr in the Cr source accounts for 0.5% of the mass of NH4-SSZ-13; the mixed solution is placed in an oven for drying and then ground, and then placed in a tube furnace for roasting, and cooled to obtain a Cr-In / H-SSZ-13 catalyst (also known as Cr-In / H-SSZ-13-NH4 + catalyst); during the calcination process, dry air was first introduced for 1 hour, then hydrogen and argon gas was introduced for 1 hour, and then dry air was introduced for 1 hour. The calcination temperature was 300°C.

[0050] Comparative Example 1

[0051] Based on Example 1, the difference of this comparative example is that the H-SSZ-13 molecular sieve prepared in step S1 is used, and the H-SSZ-13 molecular sieve is used in step S2 for preparation, comprising the following steps:

[0052] Comparative Example:

[0053] Preparation of H-SSZ-13: Weigh 1g of Na-SSZ-13 into a beaker, add an appropriate concentration of (NH4)2SO4 solution at a ratio of 1:50, ultrasonically disperse the solid, place it in a heated magnetic stirrer and stir at 80°C for 4 hours, repeat three times; after the end, use a centrifuge to recover the solid, then wash it with deionized water several times until the pH is 6-7, and then place it in an oven to dry to obtain NH4-SSZ-13; then place it in a muffle furnace and calcine it at 500°C to obtain H-SSZ-13.

[0054] Catalyst preparation: In(NO3)3·xH2O, Cr(NO3)3·9H2O, and H-SSZ-13 were added to water and stirred for 24 hours to disperse uniformly. The resulting mixture was then rotary evaporated to remove moisture and dried in an oven. The mass ratio of Cr:In between the Cr and In sources was 1:4, and the mass of Cr in the Cr source accounted for 0.5% of the mass of H-SSZ-13. The mixture was oven-dried, ground, and then calcined in a tube furnace. The mixture was cooled to obtain the Cr-In / H-SSZ-13 catalyst (also known as Cr-In / H-SSZ-13-H catalyst). Dry air was introduced for 1 hour, followed by hydrogen and argon gas for 1 hour, and then dry air for 1 hour. The calcination temperature was 500°C.

[0055] The Cr-In / H-SSZ-13-H catalyst was obtained.

[0056] The performance of the catalysts obtained in Example 1 and Comparative Example 1 was compared, and the CH4-SCR denitrification performance of the catalysts was evaluated using a fixed bed reactor. The reaction conditions were: initial NO concentration of 500 ppm, CH4 concentration of 800 ppm, O2 content of 8%, water vapor content of 5%, and space velocity of 40,000 h -1 , the reaction temperature range is 400~650℃. Figure 1 shown.

[0057] pass Figure 1 The comparison shows that the Cr-In / H-SSZ-13 catalyst prepared with H-SSZ-13 can only reach the highest NO at 600℃. x The removal rate was 43.0%, and the catalyst prepared with NH4-SSZ-13 reached the highest NO removal rate at 550℃. x Removal rate: 84.4%. Cr-In / H-SSZ-13-NH4 + The overall CH4 conversion rate of the catalyst is higher than that of the Cr-In / H-SSZ-13-H catalyst, and the higher CH4 conversion rate corresponds to higher NO x Removal rate: Cr-In / H-SSZ-13-NH4 + The CH4 selectivity of the catalyst gradually increases in the temperature range of 450-500℃, reaching a peak of 39.7% at 500℃. The CH4 selectivity gradually decreases in the temperature range above 500℃, which is related to the strengthening of the side reaction of direct catalytic oxidation of CH4. The CH4 selectivity of the Cr-In / H-SSZ-13-H catalyst is at a low value in the temperature range of 450-550℃, corresponding to its low NO x In the temperature range above 550℃, the CH4 selectivity first increases and then decreases, with the highest value being 14.3%, which is consistent with the NO xThe removal rate changes are similar to those of , and the subsequent decline is also due to the enhancement of the direct oxidation side reaction of CH4.

[0058] From the above comparison, it can be seen that compared with Cr-In / H-SSZ-13-H catalyst, Cr-In / H-SSZ-13-NH4 + This type of catalyst not only simplifies the preparation process (omitting the muffle furnace calcination step), but also has higher denitrification rate, CH4 conversion rate and selectivity, a lower temperature corresponding to the highest denitrification rate, and a wider temperature window.

[0059] The catalysts obtained in Example 1 and Comparative Example 1 were characterized, and the PXRD spectra were as follows: Figure 2 As shown, it can be seen that the addition of Cr and In ions makes the structure of the original molecular sieve well preserved, and no obvious peaks of Cr and In species are found, which may be due to the low loading amount and high dispersion of Cr and In metals.

[0060] The catalysts obtained in Example 1 and Comparative Example 1 were characterized by SEM-EDS Mapping to characterize their morphology and analyze their components. Figure 3 and Figure 4 As shown. Both catalysts are uniform ~ 500nm cubic crystals with regular structure. Figure 4 Analysis shows that the Al, Si, O, Cr, and In elements of the two catalysts are evenly distributed, and the Cr and In metals are highly dispersed on the surface of the cubic crystals.

[0061] The pore structure of the catalyst was characterized by N2 adsorption-desorption method at 77K. The N2 adsorption-desorption isotherm and DFT pore distribution diagram are shown in Figure 2. Figure 5 The pore structure parameters of the two catalysts are shown in Table 1. Figure 5 It can be seen that the adsorption amount of NH4-SSZ-13 molecular sieve increases rapidly in the low pressure area and then tends to be flat, which is consistent with the characteristics of type I isotherm. The pore size is mainly concentrated in 0.4-0.8nm, indicating that the material is dominated by micropores. In the medium and high pressure areas, there is an inconspicuous closed hysteresis loop. Figure 5 (b) No obvious mesopores were found, but the value was 10 -5 The adsorption capacity of Cr-In / H-SSZ-13-NH4+ and Cr-In / H-SSZ-13-H catalysts is higher than that of NH4-SSZ-13, indicating that the specific surface area is larger. Figure 5 (b) It can be seen that the micropore diameters of the two catalysts are more concentrated around 0.39 nm than that of NH4-SSZ-13, but their micropore volumes are larger (as shown in Table 1), indicating that the NH4 +It will block the pores and reduce the pore volume. + There is still a small amount of NH4 in the pores of the + This further illustrates that high temperature roasting can decompose NH4 in molecular sieves + , a deamination reaction occurs.

[0062] Table 1 Pore structure parameters of catalysts

[0063]

[0064] Comparative Examples 2 to 7

[0065] On the basis of Example 1, the difference of this embodiment lies in the different atmospheres introduced during the calcination in step S2; Comparative Examples 2 to 7 are respectively static calcination (i.e., calcination in a tubular furnace without introducing gas), introduction of dry air (abbreviated as O2), introduction of hydrogen-argon gas (abbreviated as H2), introduction of dry air first and then hydrogen-argon gas (abbreviated as O2+H2), introduction of hydrogen-argon gas first and then dry air (abbreviated as H2+O2), introduction of argon gas first and then hydrogen-argon gas and then dry air (abbreviated as Ar+H2+O2). The experiment uses a fixed bed reactor to evaluate the CH4-SCR denitrification performance of the catalyst. The reaction conditions are: NO concentration 500ppm, CH4 concentration 800ppm, O2 content 8%, water vapor content 5%, space velocity 40,000h -1 , the reaction temperature range is 400~650℃. Figure 6 shown.

[0066] Figure 6 (a), (b), and (c) are NO emissions of Cr-In / H-SSZ-13 zeolite catalysts prepared under different calcination atmospheres. x Removal rate, CH4 conversion rate, CH4 selectivity. Under all calcination atmospheres, NO x The removal rate peaks all appeared at 500-600℃, indicating that this temperature range is the active temperature window of the Cr-In / H-SSZ-13 catalyst. However, different calcination atmospheres have different effects on the CH4-SCR activity of the prepared catalysts. The Cr-In / H-SSZ-13 catalyst calcined in the atmosphere combination of "O2+H2+O2" has a maximum denitrification rate of 84.4% at 550℃, and the NO x The removal rate is the highest, the active temperature window is the widest, and the CH4 conversion rate is the highest, indicating that the catalyst calcined under this atmosphere has the highest catalytic activity.

[0067] Example 2

[0068] Based on Example 1, the difference of this example is that the calcination temperature in step S2 is 200°C.

[0069] Example 3

[0070] Based on Example 1, the difference of this example is that the calcination temperature in step S2 is 400°C.

[0071] Example 4

[0072] Based on Example 1, the difference of this example is that the calcination temperature in step S2 is 500°C.

[0073] The catalysts obtained at different calcination temperatures were used as a control sample in step S2 to evaluate their CH4-SCR denitrification performance in a fixed-bed reactor. The reaction conditions were: NO concentration 500ppm, CH4 concentration 800ppm, O2 content 8%, water vapor content 5%, and a space velocity of 40,000h-1. -1 , the reaction temperature range is 400~650℃. Figure 7 As shown in Figure 2, it can be seen that the uncalcined Cr-In / H-SSZ-13 catalyst lacks deamination reaction and has a low specific surface area, so NO x The highest NO removal rate was obtained for the catalysts calcined at 200℃, 400℃ and 500℃. x The removal rates were 76.1%, 79.5% and 73.6% respectively. x The removal rate is the highest, with a peak value of 84.4%, and the corresponding temperature is the lowest. Figure 7 Figures 7(b) and 7(c) show the CH4 conversion and selectivity of the Cr-In / H-SSZ-13 zeolite catalysts prepared at different calcination temperatures. The CH4 conversion of the catalyst calcined at 300°C is highest in the 400-650°C temperature range, and its CH4 selectivity reaches its highest value at 500°C.

[0074] Example 5

[0075] Based on Example 1, the difference of this example is that the mass ratio of Cr to In in step S2 is 1:3, and the mass of Cr in the Cr source accounts for 0.5% of the mass of NH4-SSZ-13.

[0076] Example 6

[0077] Based on Example 1, the difference of this example is that the mass ratio of Cr to In in step S2 is 1:5, and the mass of Cr in the Cr source accounts for 0.5% of the mass of NH4-SSZ-13.

[0078] The CH4-SCR denitrification performance of the catalysts was evaluated in a fixed bed reactor for Examples 1, 5, and 6. The reaction conditions were: NO concentration 500 ppm, CH4 concentration 800 ppm, O2 content 8%, water vapor content 5%, and space velocity 40,000 h-1. -1 , the reaction temperature range is 400-650℃. The experimental results are as follows Figure 8 shown.

[0079] Depend on Figure 8 It can be seen that the NO x The removal rates gradually increased from 400 to 550 °C and reached a peak of 84.4% and 79.3% at 550 °C, respectively. The active temperature windows of CH4-SCR reaction were relatively close. x The removal rate reached a maximum of 60.9% at 575℃, and the temperature window was relatively narrow. The catalyst with a Cr:In ratio of 1:4 had the best denitrification performance. As the In content increased, the CH4 conversion rate of the catalyst increased. This may be because when Cr:In=1:3, the In content was relatively insufficient, resulting in the activation of methane InO + When Cr:In=1:5, the In content is relatively increased, which may form more inactive phase In2O3, which is not conducive to the CH4-SCR reaction and thus leads to a decrease in CH4 selectivity. When Cr:In=1:4, the bimetallic active sites and The acid sites reach the optimal ratio, and this synergistic effect significantly improves the reaction efficiency and catalyst activity.

[0080] Example 7 to Example 9

[0081] On the basis of Example 1, while keeping the Cr:In ratio at 1:4 unchanged, the loading amounts of Cr and In were changed to 0.25% Cr-1% In, 1% Cr-4% In, and 2% Cr-8% In, respectively (x% Cr-y% In means that the mass fraction of Cr metal in the catalyst is x%, and the mass fraction of In metal in the catalyst is y%).

[0082] The catalysts of Examples 1 and 7-9 were used to evaluate their CH4-SCR denitrification performance in a fixed-bed reactor. The reaction conditions were: NO concentration 500 ppm, CH4 concentration 800 ppm, O2 content 8%, water vapor content 5%, and a space velocity of 40,000 h-1. -1 , the reaction temperature range is 400-650℃. The experimental results are as follows Figure 9 shown.

[0083] The experimental results show that the metal loading has an important influence on the catalytic activity window and NO x The maximum removal rate of NO was significantly affected when the metal loading increased from 0.5% Cr-2% In to 2% Cr-8% In. x The removal rate gradually decreases and the active temperature window gradually narrows. This may be because as the metal loading increases, the metal dispersion in the molecular sieve gradually deteriorates, making it more likely to agglomerate and form larger oxide particles, reducing the specific surface area of ​​the catalyst and thus affecting the catalytic activity of the catalyst. x The removal rate is lower than that of the catalyst (0.5% Cr-2% In), and the highest NO removal rate is at 575℃. x The removal rate is 74.2%, and the temperature window moves to the high temperature zone. This is because the amount of metal salt is low, resulting in After the acidic site exchange, the number of metal active sites is insufficient, making NO x The activation reaction of NO and CH4 was weakened. The catalyst with 0.5% Cr-2% In loading was the strongest among the four catalysts. x The removal rate is the highest, and the denitrification rate can reach 84.4% at 550℃, and the active temperature window is the widest, indicating that the moderate metal loading has better dispersion, and the metal active sites are closely connected with the adjacent The acid sites form the best ratio, which makes the denitrification activity of the catalyst the highest.

[0084] like Figure 9 (b) It can be seen that as the metal loading increases, the CH4 conversion rate increases, but the rate of increase is obviously slowing down. This is because as the metal loading increases, the oxide particles formed gradually increase in size, which is not conducive to the CH4-SCR reaction. At the same time, as the metal loading increases, the exchanged The acid sites increase, thus weakening The adsorption of reaction gases by acidic sites and the polarization of CH bonds further reduce the CH4 conversion rate. Figure 9 (c) CH selectivity of Cr-In / H-SSZ-13 catalysts prepared with different metal loadings. The results show that the catalyst with a 0.5% Cr-2% In loading exhibits the highest CH selectivity, reaching a maximum of 39.7% at 500°C. Under these conditions, the catalyst exhibits high metal dispersion and an optimal ratio of metal active sites to B acidic sites.

[0085] Example 10

[0086] The catalyst prepared in Example 1 was subjected to a sulfur water effect experiment.

[0087] Sulfur impact experiment: A fixed bed reactor was used to evaluate the CH4-SCR denitrification performance of the catalyst. The reaction conditions were: NO concentration 500ppm, CH4 concentration 800ppm, O2 content 8%, and space velocity 40,000h-1. -1 The reaction temperature range is 400-650℃, and the SO2 concentration is set to 0ppm, 25ppm, 50ppm, and 100ppm. Figure 10 As shown. It can be seen that the introduction of SO2 significantly inhibits the NO x Removal efficiency. When no SO2 is added to the reaction gas, the catalyst removes NO at 500℃. x The removal rate can reach 95.9% and remain relatively stable in the temperature range of 500-550℃. After adding SO2 into the reaction gas, the highest NO x The removal rate gradually decreased. When the SO2 concentration was 100ppm, the catalyst was x The removal rate is 80.8%. This may be because as the SO2 concentration increases, the competitive adsorption of SO2 on the active sites of the catalyst gradually increases, resulting in an enhanced inhibitory effect on NO adsorption and activation; at the same time, SO2 may be oxidized by the active sites to generate sulfate, thereby reacting with Cr 3+ Combined with the formation of stable sulfate, resulting in a decrease in catalyst activity. However, when the SO2 concentration was 100ppm, the highest NO x The removal rate can still reach more than 80%, indicating that it has a certain tolerance to SO2. Figure 10 (b) and (c) are the CH4 conversion and selectivity of Cr-In / H-SSZ-13 catalyst under different SO2 concentrations. When the SO2 concentration is ≤50ppm, the CH4 conversion rate remains basically unchanged, while NO x The removal rate and CH4 selectivity decreased. This may be because SO2 has a greater impact on the competitive adsorption of NO than CH4; and at this time, the CH4 concentration is significantly higher than the SO2 concentration, and the CH4 molecule shows a clear competitive advantage in the competitive adsorption process. When the SO2 concentration increases to 100ppm, the competitive adsorption of SO2 is enhanced, resulting in NO x And the CH4 conversion rate decreases and the CH4 selectivity is low.

[0088] Water vapor effect experiment: A fixed bed reactor was used to evaluate the CH4-SCR denitrification performance of the catalyst. The reaction conditions were: NO concentration 500ppm, CH4 concentration 800ppm, O2 content 8%, and space velocity 40,000h-1. -1 The reaction temperature range is 400~650℃, and the water vapor concentration is set as 0%, 5%, 10%, and 15%. Figure 11As shown. It can be seen that the introduction of water vapor significantly inhibits the denitrification efficiency of the catalyst, and the catalytic activity of the catalyst gradually decreases with the increase of water vapor concentration, and the CH4-SCR temperature window continues to move towards the high temperature zone. This may be related to the active component InO + When it encounters water vapor, it forms In(OH) 3-x The higher the water vapor content, the easier it is to form In(OH) 3-x , so that InO + Less, reducing the CH4-SCR catalytic activity of the catalyst.

[0089] SO2 and water vapor combined interference experiment: 50ppm SO2 and 5% water vapor were introduced. A fixed bed reactor was used to evaluate the CH4-SCR denitrification performance of the catalyst. The reaction conditions were: NO concentration 500ppm, CH4 concentration 800ppm, O2 content 8%, space velocity 40000h -1 , SO2 concentration is 50ppm, water vapor content is 5%, and the reaction temperature range is 400~650℃. Figure 12 As shown. Compared with the case where only 50ppm SO2 and only 5% water vapor are added, when SO2 and water vapor exist at the same time, the NO x The removal rate dropped significantly, with the highest being only 44.4%.

[0090] It can be seen that the catalyst of Example 1 exhibits excellent catalytic performance in the presence of SO2 alone and water vapor alone. Under the reaction conditions of 50ppm SO2 and 5% H2O, the highest NO x The removal rates were 87.7% and 84.4%, respectively, compared with the highest NO removal rate of the catalyst without SO2 and H2O. x The removal rate (98.0%) only decreased by 10.3% and 13.6%, respectively, indicating that the catalyst has good resistance to sulfur or water. When sulfur and water affect together, the two have a synergistic effect on the inhibition of the catalyst. At this time, the highest NO x The removal rate was 44.4%.

[0091] Example 11

[0092] The stability test of the catalyst prepared in Example 1 was carried out. Whether the molecular sieve catalyst can maintain high activity for a long time under high temperature hydrothermal conditions is the key to judging the life of the catalyst. x Under the condition of a reaction temperature of 550℃, which corresponds to the removal rate, a 12-hour continuous CH4-SCR reaction test was conducted on the Cr-In / H-SSZ-13 catalyst to investigate its long-term denitrification performance stability. Figure 13 As shown.x The removal rate showed a two-stage attenuation characteristic with the operation time. During the 0-8h operation period, NO x The removal rate slowly decreased at an average rate of 0.8% per hour, indicating that the catalyst was gradually deactivated during long-term operation. During the 8-12h operation period, the NO x The removal rate decreased more slowly and fluctuated, eventually falling to 70.0%. Compared with the initial 84.4% denitrification rate, after 12 hours of long-term operation, the NO x The removal rate only decreased by 14.4%, indicating that the Cr-In / H-SSZ-13 catalyst has good hydrothermal stability.

[0093] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A method for preparing a Cr-In / H-SSZ-13 catalyst, characterized in that: The steps include: Step S1, preparing NH4-SSZ-13; Step S2: Add an In source, a Cr source, and NH4-SSZ-13 to water and disperse them evenly to obtain a mixed solution, wherein the mass ratio of Cr:In of the Cr source and the In source is 1:3-5, and the mass of Cr in the Cr source accounts for 0.25%-2% of the mass of NH4-SSZ-13; dry the mixed solution and grind it, then place it in a tubular furnace for roasting, and cool it to obtain a Cr-In / H-SSZ-13 catalyst; during the roasting process, first introduce dry air for 50-70 minutes, then introduce hydrogen and argon gas for 50-70 minutes, and then introduce dry air for 50-70 minutes, and the roasting temperature is 200-500°C.

2. The method for preparing the Cr-In / H-SSZ-13 catalyst according to claim 1, wherein: In step S1, the NH4-SSZ-13 is prepared by the following steps: adding Na-SSZ-13 to a 0.05-0.4M (NH4)2SO4 solution, dispersing it evenly, stirring and reacting it at 60-85°C for 15-60 minutes, centrifuging, washing, and drying to obtain NH4-SSZ-13.

3. The preparation method of the Cr-In / H-SSZ-13 catalyst according to claim 1, characterized in that: In step S2, ultrasonic dispersion is performed for 4 to 6 minutes, and oven drying is performed.

4. The method for preparing the Cr-In / H-SSZ-13 catalyst according to claim 1, wherein: In step S2, the mass ratio of Cr:In of the Cr source and the In source is 1:4-5; the mass ratio of Cr in the Cr source to the mass ratio of NH4-SSZ-13 is 0.25%-1%.

5. The method for preparing the Cr-In / H-SSZ-13 catalyst according to claim 4, characterized in that: In step S2, the mass ratio of Cr in the Cr source to the mass ratio of NH4-SSZ-13 is 0.5%.

6. The method for preparing the Cr-In / H-SSZ-13 catalyst according to claim 1, characterized in that: In step S2, the calcination temperature is 200-300°C.

7. Cr-In / H-SSZ-13 catalyst, characterized by: The catalyst is prepared by the preparation method of the Cr-In / H-SSZ-13 catalyst according to any one of claims 1 to 6.

8. Use of the Cr-In / H-SSZ-13 catalyst in CH4-SCR denitration according to claim 7, characterized in that: Used for CH4-SCR denitrification.

9. A catalyst ceramic filter tube, characterized in that: The method comprises a ceramic filter tube on which the Cr-In / H-SSZ-13 catalyst as claimed in claim 7 is loaded.

10. The method for preparing a catalyst ceramic filter tube according to claim 9, wherein: The steps include: The ceramic filter tube is broken, acid-washed to remove impurities, washed with water and dried, and calcined at 350°C to 450°C for 1-3 hours to obtain a pretreated ceramic filter tube; The Cr-In / H-SSZ-13 catalyst is loaded on a pretreated ceramic filter tube by an impregnation method, dried, and calcined at 350-450° C. for 2-4 hours to obtain a catalytic ceramic filter tube.

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