Catalysts for NOx reduction and sulfur resistance

Abstract

The present invention belongs to the technical field of functional organic macromolecule composite catalysts and involves the preparation of a nitrogen-doped lattice macromolecule composite loaded with an efficient denitrification and sulfur resistance catalyst, firstly using the method of adding metal salts to make a large amount of Ce.sup.3+, Ce.sup.4+, Sn.sup.3+ and Sn.sup.4+ ions accumulate around the cyanuric acid molecule. Afterwards, 2,4,6-triaminopyrimidine and cytosine were added to graft with the cyanuric acid to produce the N-doped macromolecule in the first stage. After that, potassium permanganate was used as the oxidizing agent, and redox reaction occurred on the surface of N-doped macromolecules, so that the manganese cerium tin catalyst was grown in situ on the surface of N-doped macromolecules, and finally calcined at once to cross-link the N-doped macromolecules to generate catalyst composites. The catalysts described in this invention have higher efficient NOx reduction and sulfur resistance performance.

Claims

1. A method for preparing a catalyst for NOx reduction and sulfur resistance, characterized in that, a modified nitrogen-doped grid macromolecule as the catalyst carrier, the ternary Mn—Ce—SnOx catalyst in-situ growth on the surface of the nitrogen-doped grid macromolecule, wherein the method comprising the steps of: Step 1: adding cerium acetate Ce(Ac).sub.3 to the configured solution of cyanuric acid CA solution and stirring for 1 hour at room temperature until Ce(Ac).sub.3 is completely dissolved; at this time, Ce.sup.3+ is seized to the CA surface through a dehydration condensation reaction; Step 2: weighing tin tetrachloride SnCl.sub.4, adding it to the step 1 solution, and continuing to stir at room temperature for 1 hour until SnCl.sub.4 is completely dissolved; at this time, the CA surface is filled with the products of the reaction between Sn.sup.4+ and Ce.sup.3+; Step 3: accurately weighing 0.075 g of 2,4,6-triaminopyrimidine TAP and adding it to the solution obtained in step 2, then adding 0.025 g of cytosine C and react at room temperature for 1 h, then adding KMnO.sub.4 solution, continue the reaction at room temperature for 1 h, transferring the reaction solution to a surface dish after the reaction is finished, after which it is dried in an oven; Step 4: calcining of the dried sample from step 3 in a high-temperature tube furnace to obtain the final latticed organic-like macromolecular-based catalyst composites labeled as Mn—Ce—SnO.sub.x/TAP-CA-C.

2. The method for preparing a catalyst for NOx reduction and sulfur resistance according to claim 1, wherein the CA solution in step 1 was prepared by accurately weighing 0.1 g of CA sample of cyanuric acid, dissolving it in 50 mL of N,N-dimethylformamide solvent, placing it in a sonicator for 30 min.

3. The method for preparing a catalyst for NOx reduction and sulfur resistance according to claim 1, wherein the molar ratio of CA to Ce(Ac).sub.3 in step 1 was any one of 1:0.1, 1:0.2, 1:0.3 and 1:0.4.

4. The method for preparing a catalyst for NOx reduction and sulfur resistance according to claim 1, wherein the molar ratio of CA to Ce(Ac).sub.3 in step 1 was 1:0.3.

5. The method for preparing a catalyst for NOx reduction and sulfur resistance according to claim 1, wherein the molar ratio of SnCl.sub.4 to Ce(Ac).sub.3 in step 2 is 1:1.

6. The method for preparing a catalyst for NOx reduction and sulfur resistance according to claim 1, wherein the molar ratio of Ce(Ac).sub.3 to KMnO.sub.4 is 1:1.

7. The method for preparing a catalyst for NOx reduction and sulfur resistance according to claim 1, wherein the oven temperature as described in step 3 is 102° C.

8. The method for preparing a catalyst for NOx reduction and sulfur resistance according to claim 1, wherein the calcination described in step 4 is specifically calcined at 550° C. for 2 h.

9. A catalyst for NOx reduction and sulfur resistance prepared by the method of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 shows a diagram of the homemade tubular SCR reactor setup for catalyst activity testing.

[0026] In the figure, 1 is the vapor source; 2 is the pressure reducing valve; 3 is the mass flow meter; 4 is the mixer; 5 is the air preheater; 6 is the catalytic bed; 7 is the composite material; 8 is the flue gas analyzer.

[0027] FIG. 2 shows the scanning electron micrograph of the sample at the molar ratio of CA to Ce(Ac).sub.3 of 1:0.3.

[0028] FIG. 3 shows the catalytic stability analysis.

DETAILED DESCRIPTION OF EMBODIMENTS

[0029] The present invention will be further described below in combination with the drawings and specific embodiments, but the protection scope of the present invention is not limited this.

Example 1

[0030] A sample of 0.1 g of cyanuric acid (abbreviated as CA) was weighed, dissolved in 50 mL of N,N-dimethylformamide solvent, placed in a sonicator for 30 min, and prepared as CA solution. Then weigh 0.024 g of cerium acetate (abbreviated as Ce(Ac).sub.3) and add it to the configured above solution, and stir for 1 hour at room temperature until Ce(Ac).sub.3 is completely dissolved. After complete dissolution, weigh 0.027 g of tin tetrachloride (SnCl.sub.4), add to the above solution and continue to stir at room temperature for 1 hour until SnCl.sub.4 is completely dissolved.

[0031] After complete dissolution, weigh 0.075 g of 2,4,6-triaminopyrimidine (TAP) into the above solution, then add 0.025 g of cytosine (C) and react for 1 h at room temperature.

[0032] Then 0.012 g of KMnO.sub.4 was dissolved in 30 mL of N,N-dimethylformamide, sonicated for 10 min and added to the above reaction solution, and the reaction was continued at room temperature for 1 h.

[0033] After the reaction, the reaction solution was transferred to a surface dish, followed by drying in an oven at 102° C. The dried sample was placed in a high temperature tube furnace and calcined at 550° C. for 2 h to obtain the final catalyst to be tested.

[0034] The mass of cerium acetate was calculated as follows: 0.1+129×0.1×317=0.024 g; the mass of tin chloride was calculated as follows: 0.024+317×350.6=0.027 g; the concentration of potassium permanganate was calculated as follows: 0.024+317×158=0.012 g.

[0035] The NOx reduction and sulfur resistance performance of the obtained catalysts were evaluated in a homemade tubular SCR reactor with NO and NH.sub.3 volume fraction of 0.05%, O.sub.2 volume fraction of 5% and the rest as N.sub.2, gas flow rate of 700 mL.Math.min.sup.−1. When the temperature was set to 140° C., the NOx reduction ratio was 57% measured by the UK KM940 flue gas analyzer; when the temperature was set to 160° C., the NOx reduction ratio was 71%; when the temperature was set to 180° C., the ratio of NOx reduction and sulfur resistance was 82%; the final NOx reduction ratio was basically stabilized at 58% when SO.sub.2 was introduced at 180° C. for 30 min interval test.

Example 2

[0036] A sample of 0.1 g of cyanuric acid (abbreviated as CA) was weighed, dissolved in 50 mL of N,N-dimethylformamide solvent, placed in a sonicator for 30 min, and prepared as CA solution. Then weigh 0.048 g of cerium acetate (abbreviated as Ce(Ac).sub.3) and add it to the configured above solution, and stir for 1 hour at room temperature until Ce(Ac).sub.3 is completely dissolved. After complete dissolution, weigh 0.054 g of tin tetrachloride (SnCl.sub.4), add to the above solution and continue to stir at room temperature for 1 hour until SnCl.sub.4 is completely dissolved.

[0037] After complete dissolution, weigh 0.075 g of 2,4,6-triaminopyrimidine (TAP) into the above solution, then add 0.025 g of cytosine (C) and react for 1 h at room temperature.

[0038] Then 0.024 g of KMnO.sub.4 was dissolved in 30 mL of N,N-dimethylformamide, sonicated for 10 min and added to the above reaction solution, and the reaction was continued at room temperature for 1 h.

[0039] After the reaction, the reaction solution was transferred to a surface dish, followed by drying in an oven at 102° C. The dried sample was placed in a high temperature tube furnace and calcined at 550° C. for 2 h to obtain the final catalyst to be tested.

[0040] The mass of cerium acetate was calculated as follows: 0.1+129×0.2×317=0.048 g; the mass of tin chloride was calculated as follows: 0.048+317×350.6=0.054 g; the concentration of potassium permanganate was calculated as follows: 0.048+317×158=0.024 g.

[0041] The NOx reduction and sulfur resistance performance of the obtained catalysts were evaluated in a homemade tubular SCR reactor with NO and NH.sub.1 volume fraction of 0.05%, O.sub.2 volume fraction of 5% and the rest as N.sub.2, gas flow rate of 700 mL.Math.min.sup.−1. When the temperature was set to 140° C., the NOx reduction ratio was 61% measured by the UK KM940 flue gas analyzer; when the temperature was set to 160° C., the NOx reduction ratio was 75%; when the temperature was set to 180° C., the ratio of NOx reduction and sulfur resistance was 86%; the final NOx reduction ratio was basically stabilized at 60% when SO.sub.2 was introduced at 180° C. for 30 min interval test.

Example 3

[0042] A sample of 0.1 g of cyanuric acid (abbreviated as CA) was weighed, dissolved in 50 mL of N,N-dimethylformamide solvent, placed in a sonicator for 30 min, and prepared as CA solution. Then weigh 0.072 g of cerium acetate (abbreviated as Ce(Ac).sub.3) and add it to the configured above solution, and stir for 1 hour at room temperature until Ce(Ac).sub.3 is completely dissolved. After complete dissolution, weigh 0.081 g of tin tetrachloride (SnCl.sub.4), add to the above solution and continue to stir at room temperature for 1 hour until SnCl.sub.4 is completely dissolved.

[0043] After complete dissolution, weigh 0.075 g of 2,4,6-triaminopyrimidine (TAP) into the above solution, then add 0.025 g of cytosine (C) and react for 1 h at room temperature.

[0044] Then 0.036 g of KMnO.sub.4 was dissolved in 30 mL of N,N-dimethylformamide, sonicated for 10 min and added to the above reaction solution, and the reaction was continued at room temperature for 1 h.

[0045] After the reaction, the reaction solution was transferred to a surface dish, followed by drying in an oven at 102° C. The dried sample was placed in a high temperature tube furnace and calcined at 550° C. for 2 h to obtain the final catalyst to be tested.

[0046] The mass of cerium acetate was calculated as follows: 0.1+129×0.3×317=0.072 g; the mass of tin chloride was calculated as follows: 0.072+317×350.6=0.081 g; the concentration of potassium permanganate was calculated as follows: 0.072+317×158=0.036 g.

[0047] The NOx reduction and sulfur resistance performance of the obtained catalysts were evaluated in a homemade tubular SCR reactor with NO and NH.sub.3 volume fraction of 0.05%, O.sub.2 volume fraction of 5% and the rest as N.sub.2, gas flow rate of 700 ml.Math.min.sup.−1. When the temperature was set to 140° C., the NOx reduction ratio was 63% measured by the UK KM940 flue gas analyzer; when the temperature was set to 160° C., the NOx reduction ratio was 78%; when the temperature was set to 180° C., the ratio of NOx reduction and sulfur resistance was 91%; the final NOx reduction ratio was basically stabilized at 69% when SO.sub.2 was introduced at 180° C. for 30 min interval test.

Example 4

[0048] A sample of 0.1 g of cyanuric acid (abbreviated as CA) was weighed, dissolved in 50 mL of N,N-dimethylformamide solvent, placed in a sonicator for 30 min, and prepared as CA solution. Then weigh 0.096 g of cerium acetate (abbreviated as Ce(Ac).sub.3) and add it to the configured above solution, and stir for 1 hour at room temperature until Ce(Ac).sub.3 is completely dissolved. After complete dissolution, weigh 0.108 g of tin tetrachloride (SnCl.sub.4), add to the above solution and continue to stir at room temperature for 1 hour until SnCl.sub.4 is completely dissolved.

[0049] After complete dissolution, weigh 0.075 g of 2,4,6-triaminopyrimidine (TAP) into the above solution, then add 0.025 g of cytosine (C) and react for 1 h at room temperature.

[0050] Then 0.048 g of KMnO.sub.4 was dissolved in 30 mL of N,N-dimethylformamide, sonicated for 10 min and added to the above reaction solution, and the reaction was continued at room temperature for 1 h.

[0051] After the reaction, the reaction solution was transferred to a surface dish, followed by drying in an oven at 102° C. The dried sample was placed in a high temperature tube furnace and calcined at 550° C. for 2 h to obtain the final catalyst to be tested.

[0052] The mass of cerium acetate was calculated as follows: 0.1+129×0.4×317=0.096 g; the mass of tin chloride was calculated as follows: 0.096+317×350.6=0.108 g; the concentration of potassium permanganate was calculated as follows: 0.096+317×158=0.048 g.

[0053] The NOx reduction and sulfur resistance performance of the obtained catalysts were evaluated in a homemade tubular SCR reactor with NO and NH.sub.3 volume fraction of 0.05%, O.sub.2 volume fraction of 5% and the rest as N.sub.2, gas flow rate of 700 mL.Math.min.sup.−1. When the temperature was set to 140° C., the NOx reduction ratio was 59% measured by the UK KM940 flue gas analyzer: when the temperature was set to 160° C., the NOx reduction ratio was 71%; when the temperature was set to 180° C., the ratio of NOx reduction and sulfur resistance was 88%; the final NOx reduction ratio was basically stabilized at 61% when SO.sub.2 was introduced at 180° C. for 30 min interval test.

[0054] Activity evaluation: The reactor in the homemade tubular SCR reactor was externally electrically heated, and thermocouples were placed next to the catalyst bed of the reactor tube to measure the temperature, and the flow of the experimental setup is shown in FIG. 1. The flue gas composition was simulated with a steel cylinder, including NO, O.sub.2, N.sub.2, NH.sub.3 as reducing gases. NO and NH.sub.3 were 0.04-0.06% by volume, O.sub.2 was 4-6% by volume, the rest was N.sub.2, and the gas flow rate was 700 mL.Math.min.sup.−1, the temperature was controlled between 120 The gas flow rate is 700 mL.Math.min.sup.−1, the temperature is controlled at 120-200° C., and the gas flow rate and composition are regulated and controlled by the mass flow meter. The gas analysis was carried out by KM940 flue gas analyzer from UK. To ensure the stability and accuracy of the data, each working condition was stabilized for at least 30 min.

TABLE-US-00001 TABLE 1 Effect of various factors on catalyst NOx reduction sulfur resistance rate (reaction temperature of 180° C.). Experimental conditions Example 1 Example 2 Example 3 Example 4 The molar 1:0.1 1:0.2 1:0.3 1:0.4 ratio of CA to Ce(Ac).sub.3 The NOx 82% 86% 91% 88% reduction ratio The NOx 58% 60% 69% 61% reduction ratio when SO.sub.2 was introduced at 180° C. for 30 min interval test

[0055] From the data in Table 1, it can be seen that at 180° C., with the increasing mass ratio, the NOx reduction ratio along with the trend of increasing and then decreasing, and the maximum value appeared at the molar ratio of 1:0.3, and the NOx reduction sulfur resistance performance also reached the maximum value.

[0056] As can be seen from FIG. 3, the NOx reduction effect of the catalyst did not decrease significantly with the increase of catalytic reaction time, and it was stable at about 90%, indicating that the catalyst has good catalytic stability.