Low-temperature denitration catalyst and preparation method thereof

Abstract

The application belongs to the technical field of denitration catalysts, and particularly relates to a low-temperature denitration catalyst and a preparation method thereof. The catalyst comprises Mg(NO3)2.6H2O, Cu(NO3)2.3H2O, citric acid and ammonia water. The prepared catalyst has a certain denitration effect at low temperature (<200 DEG C), and the denitration efficiency exceeds 80% when the temperature is higher than 200 DEG C, thereby meeting the existing emission standard of flue gas denitration. The doping of metal Cu enables the catalyst to have good sulfur resistance, and the denitration can be maintained in a relatively stable state for about 2h.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of denitration catalysts, and particularly relates to a low-temperature denitration catalyst and a preparation method thereof. BACKGROUND

[0002] The control of nitrogen oxide emissions in the non-power field faces extremely severe challenges. The generally accepted method for flue gas denitration is the selective catalytic reduction (SCR) method. However, the SCR system is located downstream of the bag-type dust removal device and the flue gas desulfurization device, resulting in a relatively low flue gas temperature. For example, the flue gas emission temperature of some industrial boiler (kiln) equipment (for example, industrial boilers, steel smelting sintering furnaces, magnesium product kilns, cement furnaces, cracking equipment of coking and petrochemical systems, etc.) in the non-power industry is usually lower than 300℃ after the dust removal and desulfurization system. However, the working temperature window of the SCR denitration catalyst widely used in the power industry currently ranges from 300 to 400℃, which is relatively narrow and high in temperature, and is not conducive to direct use in the control of nitrogen oxide emissions in small and medium kilns in the non-power industry, etc.

[0003] The SCR method denitration catalyst widely used in the field of nitrogen oxide emission reduction is mainly a vanadium-titanium series catalyst. However, the main component of this type of catalyst is vanadium pentoxide (V2O5), which has a certain toxicity and can easily cause secondary pollution to the environment if not properly treated. The catalyst has a relatively low activity at low temperatures and cannot exist stably. In addition, H2O and SO2 present in the flue gas can cause the catalyst to be seriously deactivated.

[0004] In view of the current environmental problems, especially the emission of NO x , an efficient low-temperature denitration catalyst is needed. SUMMARY

[0005] In view of the problems existing in the prior art, the present application provides a low-temperature denitration catalyst and a preparation method thereof. The catalyst has a certain denitration effect at low temperatures (<200℃), and the denitration efficiency exceeds 80% when the temperature exceeds 200℃, meeting the current emission standards for flue gas denitration. The doping of metal Cu enables the catalyst to have good sulfur resistance, and the denitration can still be maintained in a relatively stable state for about 2h.

[0006] To achieve the above-mentioned purpose, the present application provides a low-temperature denitration catalyst in the first aspect, which comprises: Mg(NO3)2·6H2O, Cu(NO3)2·3H2O, citric acid, and ammonia.

[0007] Further, the mass ratio of Mg(NO3)2·6H2O to Cu(NO3)2·3H2O is 9:1 to 7:3.

[0008] Further, the mass of the citric acid is equal to the sum of the masses of the Mg(NO3)2·6H2O and Cu(NO3)2·3H2O.

[0009] Further, the ratio of the volume of the ammonia water to the total volume of the solutions of the Mg(NO3)2·6H2O, Cu(NO3)2·3H2O and citric acid is (0.8-1.5):40.

[0010] The second aspect of the present application provides a preparation method of a low-temperature denitration catalyst, specifically comprising the following steps:

[0011] Step 1, a certain mass of Mg(NO3)2·6H2O and Cu(NO3)2·3H2O are weighed and dissolved in a certain volume of deionized water, respectively, to prepare solutions with a mass concentration of 1 mol / L, and fully stirred to be uniform; meanwhile, a citric acid with a mass equal to the sum of the masses of the Mg(NO3)2·6H2O and Cu(NO3)2·3H2O is weighed and dissolved in deionized water to prepare a solution with a mass concentration of 1 mol / L, and stirred to be uniform; the three are mixed to obtain a mixed solution.

[0012] Step 2, ammonia water is added dropwise to the mixed solution of step 1, and after fully stirring, it is placed in a magnetic stirrer for stirring, the heating temperature is controlled at 80℃, and the stirring is performed for about 2h; until the mixed solution presents a transparent gel, the heating is stopped to obtain a sample; and the sample is placed in an electric heating air constant temperature drying oven for constant temperature drying for 2h, until the sample presents a blue bread shape, the drying is stopped, and a dry gel is obtained.

[0013] Step 3, the dry gel is crushed and loaded into a crucible, and then heated in a mixing furnace to obtain a Cu-doped magnesium-based catalyst sample.

[0014] Step 4, the prepared Cu-doped magnesium-based catalyst sample, hydroxypropyl methyl cellulose and water are mixed uniformly to a soft state that can be formed; then a strip-shaped sample is extruded using an extruder, and is placed at room temperature for 12h; then the formed strip-shaped sample is placed in an oven and dried at a temperature of 120℃ for 2h; after drying, the sample is cut into fine strips with a length of 3-5mm to obtain a final product, a low-temperature denitration catalyst.

[0015] Further, in step 3, the heating conditions of the mixing furnace are as follows: the temperature rising condition is to heat from room temperature to 450-600℃ at a temperature rising rate of 6 ℃·min -1 -1, and the temperature is kept for 1h.

[0016] Further, in step 4, the Cu-doped magnesium-based catalyst sample, hydroxypropyl methyl cellulose and water are mixed uniformly at a mass ratio of 75:(1-3):(100-140).

[0017] The catalyst is used for low-temperature flue gas denitration, and results show that the denitration efficiency is above 50% at 200 DEG C, and the denitration efficiency is above 80% when the temperature is above 200 DEG C.

[0018] Compared with the prior art, the application has the following beneficial effects.

[0019] 1. China is the largest magnesium resource country in the world, and has rich magnesium reserves. The magnesium product is used for denitration, which is cheap and has great economic benefits, and ecological benefits are also considered.

[0020] 2. When the mass ratio of Mg(NO3)2.6H2O and Cu(NO3)2.3H2O is 7:3, the catalyst has a certain denitration effect at low temperature (<200 DEG C), and the denitration efficiency is above 80% when the temperature is above 200 DEG C, which meets the existing flue gas denitration emission standard.

[0021] 3. The doping of metal Cu makes the catalyst have good sulfur resistance effect, and the denitration can be maintained in a relatively stable state for about 2h. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The figure is a flue gas denitration removal efficiency curve of the catalyst of examples 1-3.

[0023] Figure 2 The figure is an N2 isothermal adsorption-desorption curve of the catalyst of example 1.

[0024] Figure 3 The figure is a pore volume distribution graph of the catalyst of example 1.

[0025] Figure 4 The figure is a SEM graph of the catalyst of example 1.

[0026] Figure 5 The figure is an XRD graph of the catalyst of example 1.

[0027] Figure 6 The figure is an infrared spectrum graph of the catalyst of example 1. DETAILED DESCRIPTION

[0028] The endpoints of the ranges and any values claimed in this disclosure are not to be understood as being limited to the exact numerical values recited. The ranges should be interpreted as including values near the recited ranges and values within the recited ranges. For values having an endpoint range, combinations of any of the endpoint values, or individual endpoint values, with combinations of adjacent point values or ranges, can be taken to produce new ranges that are within the scope of the disclosure.

[0029] A low-temperature denitration catalyst, the catalyst comprising: Mg(NO3)2.6H2O, Cu(NO3)2.3H2O, citric acid, ammonia water.

[0030] Further, the mass ratio of the Mg(NO3)2·6H2O and Cu(NO3)2·3H2O is 9:1~7:3.

[0031] Further, the mass of the citric acid is equal to the sum of the mass of the Mg(NO3)2·6H2O and Cu(NO3)2·3H2O.

[0032] Further, the volume ratio of the ammonia water to the total volume of the Mg(NO3)2·6H2O, Cu(NO3)2·3H2O and citric acid is (0.8-1.5):40.

[0033] The second aspect of the present application provides a preparation method of a low-temperature denitration catalyst, specifically comprising the following steps:

[0034] Step 1, a certain mass of Mg(NO3)2·6H2O and Cu(NO3)2·3H2O is respectively dissolved in a certain volume of deionized water to prepare a solution with a mass concentration of 1 mol / L, and fully stirred; meanwhile, a citric acid with a mass equal to the sum of the mass of the Mg(NO3)2·6H2O and Cu(NO3)2·3H2O is dissolved in deionized water to prepare a solution with a mass concentration of 1 mol / L, and fully stirred; the three are mixed to obtain a mixed solution.

[0035] Step 2, ammonia water is added dropwise to the mixed solution of step 1, and after fully stirring, it is placed in a magnetic stirrer for stirring, the heating temperature is controlled at 80℃, and the stirring is performed for about 2h; until the mixed solution presents a transparent gel, the heating is stopped to obtain a sample; and the sample is placed in an electric heating air constant temperature drying oven for constant temperature drying for 2h, until the sample presents a blue bread shape, the drying is stopped, and a dry gel is obtained.

[0036] Step 3, the dry gel is crushed and loaded into a crucible, and then heated in a mixing furnace to obtain a Cu-doped magnesium-based catalyst sample.

[0037] Step 4, the prepared Cu-doped magnesium-based catalyst sample, hydroxypropyl methyl cellulose and water are mixed uniformly until a soft state that can be formed; then a strip-shaped sample is extruded using an extruder, and is placed at room temperature for 12h; then the formed strip-shaped sample is placed in an oven for drying at a temperature of 120℃ for 2h, after drying, it is cut into fine strips with a length of 3-5mm to obtain a final product, a low-temperature denitration catalyst.

[0038] Further, in step 3, the heating conditions of the mixing furnace are as follows: the temperature rising condition is to heat from room temperature to 450~600℃ at a temperature rising rate of 6 ℃·min -1 , and the temperature is kept for 1h.

[0039] Further, in step 4, the Cu-doped magnesium-based catalyst sample, hydroxypropyl methyl cellulose, and water are mixed uniformly at a mass ratio of 75: (1-3): (100-140).

[0040] Example 1.

[0041] A certain amount of 4.6154 g of Mg(NO3)2·6H2O and 0.4832 g of Cu(NO3)2·3H2O were dissolved in 20 mL of deionized water, respectively, and stirred uniformly; at the same time, 4.2028 g of citric acid was dissolved in 20 mL of deionized water and stirred uniformly; the three were mixed to obtain a mixed solution. 1 mL of ammonia water was added dropwise to the mixed solution, which was stirred in a magnetic stirrer after being fully stirred, and the heating temperature was controlled at 80°C, and stirred for about 2 h; until the mixed solution became transparent gel, the heating was stopped to obtain a sample; and the sample was placed in an electric heating air constant temperature drying oven for constant temperature drying for 2 h, until the sample became blue bread, the drying was stopped, and a dry gel was obtained. The dry gel was crushed and loaded into a crucible, and then heated in a mixed furnace, with a temperature rising rate of 6 ℃·min -1 -1 of the sample was obtained. The prepared Cu-doped magnesium-based catalyst sample 0.75 g, hydroxypropyl methyl cellulose 0.02 g, and water 1.2 mL were mixed uniformly to a soft state that could be formed; then a strip-shaped sample was extruded using an extruder, and was placed at room temperature for 12 h; then the formed strip-shaped sample was placed in an oven and dried at a temperature of 120°C for 2 h, and after drying, it was cut into fine strips of 3-5 mm.

[0042] Example 2.

[0043] A certain amount of 4.1026 g of Mg(NO3)2·6H2O and 0.9664 g of Cu(NO3)2·3H2O were dissolved in 20 mL of deionized water, respectively, and stirred uniformly; at the same time, 4.2028 g of citric acid was dissolved in 20 mL of deionized water and stirred uniformly; the three were mixed to obtain a mixed solution. 0.8 mL of ammonia water was added dropwise to the mixed solution, which was stirred in a magnetic stirrer after being fully stirred, and the heating temperature was controlled at 80°C, and stirred for about 2 h; until the mixed solution became transparent gel, the heating was stopped to obtain a sample; and the sample was placed in an electric heating air constant temperature drying oven for constant temperature drying for 2 h, until the sample became blue bread, the drying was stopped, and a dry gel was obtained. The dry gel was crushed and loaded into a crucible, and then heated in a mixed furnace, with a temperature rising rate of 6 ℃·min -1The Cu-doped magnesium-based catalyst sample was obtained by heating at a temperature increasing rate of 6 ℃·min-1 from room temperature to 600 ℃ and keeping the temperature for 1 h. The prepared Cu-doped magnesium-based catalyst sample 1.5 g, hydroxypropyl methyl cellulose 0.03 g and water 2.3 mL were mixed uniformly to a soft state that could be formed; then a strip sample was extruded using an extruder, placed at room temperature for 12 h, and then the formed strip sample was placed in an oven and dried at a temperature of 120 ℃ for 2 h, and after drying, it was cut into fine strips of 3-5 mm.

[0044] Example 3.

[0045] A certain 3.5897 g of Mg(NO3)2·6H2O and 1.4496 g of Cu(NO3)2·3H2O were weighed and dissolved in 20 mL of deionized water, respectively, and stirred uniformly; at the same time, 4.2028 g of citric acid was weighed and dissolved in 20 mL of deionized water and stirred uniformly; the three were mixed to obtain a mixed solution. 1 mL of ammonia water was added dropwise to the mixed solution, and after stirring, it was placed in a magnetic stirrer and stirred, with the heating temperature controlled at 80 ℃, and stirred for about 2 h; until the mixed solution became transparent and gel-like, the heating was stopped to obtain a sample; and the sample was placed in an electric heating air constant temperature drying oven and dried at constant temperature for 2 h, until the sample became blue bread-shaped, the drying was stopped, and a dry gel was obtained. The dry gel was crushed and loaded into a crucible, and then heated in a mixed furnace, with the temperature increasing condition being heating at a temperature increasing rate of 6 ℃·min-1 from room temperature to 600 ℃, and keeping the temperature for 1 h, to obtain a Cu-doped magnesium-based catalyst sample. -1 The Cu-doped magnesium-based catalyst sample was obtained by heating at a temperature increasing rate of 6 ℃·min-1 from room temperature to 600 ℃ and keeping the temperature for 1 h. The prepared Cu-doped magnesium-based catalyst sample 0.75 g, hydroxypropyl methyl cellulose 0.02 g and water 1.3 mL were mixed uniformly to a soft state that could be formed; then a strip sample was extruded using an extruder, placed at room temperature for 12 h, and then the formed strip sample was placed in an oven and dried at a temperature of 120 ℃ for 2 h, and after drying, it was cut into fine strips of 3-5 mm.

[0046] The catalysts of Examples 1-3 were applied to flue gas denitration, wherein the flue gas temperature range was 100-300 ℃, the total gas flow rate was 600 mL / min, 0.24 mL / min NO, 0.26 mL / min NH3, 30 mL / min O2, N2 was the balance gas, and the space velocity was 9000 h-1. -1 1.8 g of the catalyst was placed in a fixed device to perform flue gas denitration experiment to verify the removal efficiency, and the results are shown in Figure 1 When the molar ratio of Mg(NO3)2·6H2O and Cu(NO3)2·3H2O was 7:3, the catalyst had the best catalytic effect, had a certain denitration effect at low temperature (<200 ℃), and the denitration efficiency was more than 80% when the temperature was more than 200 ℃, which met the existing flue gas denitration emission standard.

[0047] The catalyst prepared in Example 1 was characterized and analyzed.

[0048] (1) BET analysis

[0049] Specific surface area analysis of the catalysts calcined at 450℃ and 500℃ revealed that the catalyst calcined at 500℃ had a higher specific surface area of ​​81.767 m²·g. -1 As temperature increases, a larger specific surface area leads to better catalytic performance; the pore size distribution is mainly concentrated in the 2-29 nm range, with a high proportion of mesopores; for example... Figures 2-3 As shown.

[0050] (2) SEM analysis

[0051] The shaped catalyst sample is blocky with numerous petal-like flakes on its surface, which explains its large specific surface area; for example... Figure 4 As shown.

[0052] (3) XRD analysis

[0053] XRD analysis results showed that the crystal phase structure of the catalyst sample was mainly Mg(OH)2 and MgO, while Cu was in an amorphous state or in a highly dispersed state; Figure 5 As shown.

[0054] (4) FTIR analysis

[0055] Infrared spectroscopy analysis was performed on the catalyst before and after catalyst activity testing. The figure shows that the catalyst sample at 1450 cm⁻¹... -1 and 419.67 cm -1 The Mg-O bond stretching vibration exists at 3699.46 cm⁻¹. -1 The value at this point represents the antisymmetric stretching vibration of the basic -OH group on the catalyst surface, consistent with the XRD results. The characteristic peaks of the catalyst did not change significantly after the catalytic reaction with simulated flue gas, indicating that the catalytic reaction did not significantly affect the functional groups of the catalyst; Figure 6 As shown.

Claims

1. A low-temperature de-NOx catalyst, characterized by, The catalyst raw material comprises: Mg(NO3)2.6H2O, Cu(NO3)2.3H2O, citric acid, ammonia water; The preparation method of the low-temperature denitration catalyst specifically comprises the following steps: Step 1, a certain mass of Mg(NO3)2.6H2O and Cu(NO3)2.3H2O are respectively dissolved in a certain volume of deionized water to prepare a solution with a substance concentration of 1 mol / L, and fully stirred and mixed; meanwhile, citric acid with a substance concentration equal to the sum of the substance concentrations of Mg(NO3)2.6H2O and Cu(NO3)2.3H2O is dissolved in deionized water to prepare a solution with a substance concentration of 1 mol / L, and fully stirred and mixed; the three are mixed to obtain a mixed solution; Step 2, ammonia water is added dropwise into the mixed solution of step 1, and after fully stirring, the mixed solution is placed in a magnetic stirrer and stirred, the heating temperature is controlled to be 80 DEG C, and the stirring is performed for about 2 hours; until the mixed solution presents a transparent gel, the heating is stopped to obtain a sample; and the sample is placed in an electric heating air constant temperature drying oven, and is dried at constant temperature for 2 hours, until the sample presents a blue bread shape, the drying is stopped, and a dry gel is obtained; Step 3, the dry gel is crushed and loaded into a crucible, and then is heated in a mixing furnace to obtain a Cu-doped magnesium-based catalyst sample; Step 4, the prepared Cu-doped magnesium-based catalyst sample, hydroxypropyl methyl cellulose and water are mixed uniformly until a soft state that can be formed; then a strip-shaped sample is extruded by using an extruder, and is placed at room temperature for 12 hours; and then the formed strip-shaped sample is placed in an oven and is dried at a temperature of 120 DEG C for 2 hours, after drying, the sample is cut into fine strips with a length of 3-5 mm to obtain a final product, i.e., a low-temperature denitration catalyst.

2. The low-temperature de-NOx catalyst according to claim 1, characterized by, The mass ratio of Mg(NO3)2.6H2O to Cu(NO3)2.3H2O is 9:1-7:

3.

3. The low-temperature de-NOx catalyst according to claim 1, characterized by, The substance concentration of the citric acid is equal to the sum of the substance concentrations of Mg(NO3)2.6H2O and Cu(NO3)2.3H2O.

4. The low-temperature de-NOx catalyst according to claim 1, characterized by, The volume ratio of the ammonia water to the total volume of the solutions of Mg(NO3)2.6H2O, Cu(NO3)2.3H2O and citric acid is (0.8-1.5):

40.

5. The low-temperature de-NOx catalyst according to claim 1, wherein In step 3, the heating conditions of the mixing furnace are as follows: the temperature rising condition is to heat from room temperature to 450-600℃ at a temperature rising rate of 6℃·min -1 for 1h.

6. The low-temperature de-NOx catalyst according to claim 1, wherein In step 4, the Cu-doped magnesium-based catalyst sample, hydroxypropyl methyl cellulose and water are mixed uniformly according to a mass ratio of 75:(1-3):(100-140).

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