Preparation method of anti-poisoning SCR denitration catalyst

Abstract

The invention discloses a preparation method of an anti-poisoning SCR (Selective Catalytic Reduction) denitration catalyst, which is used for solving the technical problem that the alkali and sulfide poisoning resistance of the SCR denitration catalyst in the prior art needs to be further improved. The method comprises the following steps: mixing and stirring titanium dioxide, pretreated red mud, composite vanadium-iron particles, acidic zirconium sulfate, calcium fluoride, sodium silicate, acrylamide, N, N '-methylene bisacrylamide and deionized water, raising the temperature of a reaction system to 70-80 DEG C, dropwise adding an initiator solution into the reaction system, carrying out heat preservation reaction for 2-3 hours, stirring until the system is gelatinized, and defoaming; vanadium-iron coprecipitation particles are modified by germanium and manganese and then are matched with the pretreated red mud, titanium dioxide and acidic zirconium sulfate, so that the denitration efficiency and denitration activity of the denitration catalyst are effectively improved, and the alkali and sulfide poisoning resistance of the denitration catalyst is also improved.

Description

Technical Field

[0001] The present invention relates to the technical field of denitration catalytic materials, and particularly relates to a preparation method of an anti-poisoning SCR denitration catalyst. Background Art

[0002] Nitrogen oxides are one of the main air pollutants causing acid rain, photochemical smog, and ozone layer depletion, and cause serious harm to human health and the ecological environment. At present, the main principle of the selective catalytic reduction (SCR) nitrogen oxide technology using NH3 as a reducing agent is to selectively reduce NOx to N2 under the action of a denitration catalyst. Due to its high-efficiency and reliable denitration performance, it has been widely applied in industrial fields such as coal-fired power plants.

[0003] The SCR denitration catalyst is the core part of the SCR technology. However, in practical applications, the catalyst is in flue gas containing components such as fly ash, SOx, alkali metals (K, Na, etc.), Hg, and As for a long time, and these components are extremely likely to cause the catalyst to be poisoned and inactivated. Catalyst poisoning will not only reduce the denitration efficiency, but also shorten the service life of the catalyst and increase the operation cost.

[0004] At present, the widely used denitration catalysts are honeycomb commercial V2O5-WO3 / TiO2-based catalysts or V2O5-MoO3 / TiO2-based catalysts. Although these catalysts have high denitration activity, in flue gas containing toxic components such as sulfides and alkali metals, their denitration efficiency will rapidly decrease, the activity will become poor, and the service life will be shortened.

[0005] In view of the technical defects in this regard, a solution is proposed. Summary of the Invention

[0006] The purpose of the present invention is to provide a preparation method of an anti-poisoning SCR denitration catalyst, which is used to solve the technical problem that the performance of the existing SCR denitration catalyst in resisting alkali and sulfide poisoning needs to be further improved.

[0007] The purpose of the present invention can be achieved by the following technical solutions: A preparation method of an anti-poisoning SCR denitration catalyst includes the following steps:

[0008] S1. Mix titanium dioxide, pretreated red mud, composite vanadium-iron particles, acidic zirconium sulfate, calcium fluoride, sodium silicate, acrylamide, N,N'-methylenebisacrylamide, and deionized water and stir. Raise the temperature of the reaction system to 70-80 °C, dropwise add an initiator solution to the reaction system, keep the temperature for reaction for 2-3 h, stir until the system gels, and defoam to obtain a mixed gel;

[0009] S2. Pour the mixed gel into a mold at a temperature of 80 - 90 °C, react and gel for 60 - 80 min, and after demolding, perform programmed drying to obtain a denitration catalyst green body;

[0010] S3. High-temperature calcine the denitration catalyst green body to obtain a denitration catalyst.

[0011] The synthesis reaction mechanism of the denitration catalyst is as follows:

[0012] During the preparation process, acrylamide and N,N'-methylenebisacrylamide are used as monomers and crosslinking agents respectively, and under the action of the initiator potassium persulfate, a free radical polymerization reaction occurs. At the same time, the silicic acid colloid generated by the hydrolysis of sodium silicate will also interact with the polymer formed by acrylamide to form a gel-like substance. Titanium dioxide, pretreated red mud, composite vanadium-iron particles, acidic zirconium sulfate, calcium fluoride are used as inorganic particles and are uniformly dispersed in the gel. As the polymerization reaction proceeds, the polymer chains continuously grow and intertwine to form a three-dimensional network structure. At the same time, the crosslinking effect of the silicic acid colloid also promotes the formation of the gel. When the intertwining of the polymer chains and the silicic acid colloid reaches a certain degree, the system undergoes gelation to form a stable mixed gel. After the mixed gel gels in the mold, it is dried to remove the moisture in the gel. During the calcination process, the organic matter in the catalyst green body undergoes pyrolysis and combustion, generating gases and escaping, leaving a porous structure. Calcium fluoride acts as a sintering aid to promote the growth of crystal grains and the stability of crystal phases in the catalyst. At high temperatures, calcium fluoride interacts with other components in the catalyst to form a solid solution, which helps the growth of crystal grains and the clarification of grain boundaries, and improves the thermal stability and chemical stability of the catalyst.

[0013] Further, in step S1, the dosage ratios of titanium dioxide, pretreated red mud, composite vanadium-iron particles, acidic zirconium sulfate, calcium fluoride, sodium silicate, acrylamide, N,N'-methylenebisacrylamide, deionized water and the initiator solution are 2 g:7 g:3 g:5 g:1 g:15 g:5 g:1 g:90 mL:10 mL, and the initiator solution is composed of potassium persulfate and deionized water in a ratio of 1 g:50 mL; in step S2, the programmed drying includes: after demolding, place the material in a drying oven at a temperature of 60 - 70 °C, dry for 20 h, and the drying oven is heated to 90 - 95 °C at a heating rate of 2 °C / min and keep warm and dry for 24 h to obtain the catalyst green body; in step S3, the high-temperature calcination temperature is 700 - 760 °C and the calcination time is 3 - 5 h.

[0014] Further, the preparation method of titanium dioxide is as follows: Add hydrofluoric acid to tetrabutyl titanate. After the reaction system is sealed, the temperature of the reaction system is raised to 160 - 180 °C, keep warm and react for 20 - 22 h, perform post-treatment and calcination to obtain titanium dioxide.

[0015] The synthesis reaction mechanism of titanium dioxide is as follows:

[0016] During the reaction process, tetrabutyl titanate is used as the titanium source, and hydrofluoric acid is used as the catalyst to accelerate the hydrolysis of tetrabutyl titanate. Polycondensation reactions occur between the hydrolyzed titanium hydroxy compounds to form a titanium oxide precursor with a titanium oxide chain or network structure. After high-temperature treatment, while removing fluorine, the titanium oxide precursor undergoes a phase change, and at the same time, the internal structure of the crystal is also optimized to form a more stable and ordered arrangement, resulting in the preparation of titanium dioxide nanoparticles with a high specific surface area.

[0017] Furthermore, the dosage ratio of tetrabutyl titanate to hydrofluoric acid is 10 g:3 mL, the concentration of hydrofluoric acid is 40%, and the post-treatment includes: after the reaction is completed, the temperature of the reaction system is reduced to room temperature, suction filtration is carried out, the filter cake is washed with deionized water until neutral and then dried by suction, the filter cake is transferred to an oven at a temperature of 80 - 90 °C and dried to a constant weight, ground, passed through a 100-mesh sieve, the calcination temperature is 580 - 620 °C, the calcination time is 90 - 120 min, and the calcination atmosphere is air.

[0018] Furthermore, the preparation method of the composite vanadium-iron particles is as follows: mix the vanadium-iron coprecipitated particles and deionized water and stir, raise the temperature of the reaction system to 60 - 70 °C, add a germanium-manganese mixed solution dropwise to the reaction system, then add ammonia water to the reaction system to adjust the system pH = 11 - 12, carry out heat preservation treatment for 2 - 3 h, followed by post-treatment and calcination to obtain the composite vanadium-iron particles.

[0019] The synthesis reaction mechanism of the composite vanadium-iron particles is as follows:

[0020] During the reaction process, germanium acetate and manganese acetate are used as the metal sources, and the vanadium-iron coprecipitated particles are used as the basic materials for the reaction. After mixing them by stirring, the system pH is adjusted to alkaline with ammonia water to promote the precipitation of germanium ions and manganese ions in the form of hydroxides, and at the same time, they are tightly combined with the vanadium-iron coprecipitated particles to form a composite precipitate. In addition, the addition of ammonia water may also promote the hydroxylation of the particle surface and enhance the interaction between particles. After high-temperature treatment, germanium ions and manganese ions interact with the vanadium and iron elements in the vanadium-iron coprecipitated particles to form stable composite vanadium-iron particles.

[0021] Furthermore, the dosage ratio of the vanadium-iron coprecipitation particles, deionized water and the germanium-manganese mixed solution is 10 g: 100 mL: 20 mL. The germanium-manganese mixed solution is composed of germanium acetate, manganese acetate and deionized water in a ratio of 1 g: 5 g: 20 mL. The post-treatment includes: after the reaction is completed, the temperature of the reaction system is reduced to room temperature, followed by suction filtration. The filter cake is washed 3 times with deionized water and then dried by suction. The filter cake is transferred to an oven at 80-90 °C and dried to a constant weight, ground, passed through an 80-mesh sieve, and calcined to obtain composite vanadium-iron particles. The calcination temperature is 480-500 °C, the calcination time is 4-6 h, and the calcination atmosphere is air.

[0022] Furthermore, the preparation method of the vanadium-iron coprecipitation particles is as follows: The ammonium metavanadate solution is dropped into the ferric nitrate solution, and the mixture is stirred at room temperature until dissolved. Then, 10-15 wt% ammonia water is added to the reaction system, and the temperature of the reaction system is raised to 85-95 °C. After holding the temperature for 8-9 h, post-treatment and calcination are carried out to obtain the vanadium-iron coprecipitation particles.

[0023] The synthesis reaction mechanism of the vanadium-iron coprecipitation particles is as follows:

[0024] During the reaction, in the mixed acid solution composed of ferric nitrate nonahydrate and ammonium metavanadate, as ammonia water is added, the pH value of the reaction system gradually increases. Iron ions and vanadium ions begin to combine with hydroxide ions to form precipitates of iron hydroxide and vanadium hydroxide. Through high-temperature heat preservation and stirring, the complete formation of the precipitate and the growth of crystals are promoted to form precipitates of vanadium and iron hydroxides at a certain temperature. Then, through high-temperature calcination, the hydroxide ions in the hydroxide may lose hydrogen atoms at high temperature to form oxygen ions, which combine with metal ions to form oxides, optimizing the structure of the particles. Thus, the precipitates of vanadium and iron hydroxides are transformed into oxides of vanadium and iron, and the vanadium-iron coprecipitation particles are prepared.

[0025] Furthermore, the volume ratio of the ammonium metavanadate solution, ferric nitrate solution and ammonia water is 0.8-1.2: 4-5: 1.8-2.2. The ammonium metavanadate solution is composed of ammonium metavanadate and 6 wt% acetic acid aqueous solution in a ratio of 1 g: 20 mL. The ferric nitrate solution is composed of ferric nitrate nonahydrate and deionized water in a ratio of 1 g: 15 mL. The mass fraction of the ammonia water is 10-15%. The post-treatment includes: after the reaction is completed, the temperature of the reaction system is reduced to room temperature, followed by suction filtration. The filter cake is washed with deionized water until neutral and then dried by suction. The filter cake is transferred to an oven at 80-90 °C and dried to a constant weight, ground, passed through an 80-mesh sieve, and calcined to obtain the vanadium-iron coprecipitation particles. The calcination temperature is 460-480 °C, the calcination time is 3-5 h, and the calcination atmosphere is air.

[0026] Further, the preparation method of the pretreated red mud is as follows: Mix red mud and nitric acid and stir. Raise the temperature of the reaction system to 70 - 80°C, keep it warm for 2 - 3 h, add dilute ammonia water to the reaction system, adjust the pH of the system to 9 - 10, keep it warm for 80 - 100 min, perform post-treatment, and calcine to obtain the pretreated red mud.

[0027] The synthesis reaction mechanism of the pretreated red mud is as follows:

[0028] During the reaction process, the red mud is treated with heat preservation and stirring by nitric acid to promote the dissolution of alkaline harmful substances such as sodium and calcium in the red mud. Then, by adjusting the pH of the system, effective components such as iron, silicon, and titanium are retained. After high-temperature calcination, the hydroxides in the solid substances of the alkali precipitation are further converted into oxides, and at the same time, residual moisture and organic substances are removed to prepare the pretreated red mud.

[0029] Further, the dosage ratio of the red mud to the nitric acid is 1 g:4 mL, the concentration of the nitric acid is 6 - 8 mol / L, the concentration of the dilute ammonia water is 2 - 3 mol / L. The post-treatment includes: after the reaction is completed, lower the temperature of the reaction system to room temperature, perform suction filtration, wash the filter cake with deionized water until it is neutral and then drain it. Transfer the filter cake to a drying oven at a temperature of 85 - 95°C and dry it to a constant weight, then calcine to obtain the pretreated red mud. The calcination temperature is 550 - 580°C, the calcination time is 5 - 6 h, and the calcination atmosphere is air.

[0030] The present invention has the following beneficial effects:

[0031] 1. For the anti-poisoning SCR denitration catalyst of the present invention, vanadium-iron coprecipitated particles are formed by vanadium and iron elements. Vanadium usually has high denitration activity, while iron can inhibit its loss and maintain the activity of the catalyst by forming chemical bonds or physical adsorption with these active components. Iron has an unfilled d electron shell, enabling it to form chemisorption with sulfur oxides or alkali metal ions, adsorbing sulfur oxides or alkali metal ions on the catalyst surface to prevent them from further diffusing into the catalyst interior or occupying more active sites. Moreover, iron is a variable-valence metal element with redox properties. After the catalyst is poisoned, it can adapt to different reaction conditions by adjusting its redox performance, reducing the impact of poisons on the catalyst performance, enhancing the stability and anti-poisoning performance of the catalyst. Modifying the catalytically active manganese element with vanadium-iron coprecipitated particles further enhances the overall catalytic activity of the catalyst, thereby improving the denitration efficiency. Moreover, manganese has a strong adsorption capacity for sulfur oxides or alkali metal ions, and its cooperation with iron further improves the anti-poisoning performance of the catalyst. Germanium can promote the transfer of electrons in the catalytic reaction. As a "bridge" for electron transfer, it accelerates the electron transfer step in the catalytic reaction, thereby improving the denitration efficiency.

[0032] 2. The anti-poisoning SCR denitration catalyst of the present invention promotes the dissolution and separation of substances such as sodium and calcium in red mud by treating the red mud, thereby providing more active sites for effective components such as iron, silicon, and titanium, improving the denitration activity. By treating the red mud, substances such as sodium and calcium are removed to avoid their reaction with the active sites of the catalyst in an alkaline environment, preventing catalyst poisoning. Titanium dioxide itself has certain antioxidant and chemical stability. While being able to resist the oxidation reaction of SO2 on the catalyst surface, it is not prone to react with alkaline substances. Therefore, in an alkaline environment, titanium dioxide can maintain its catalytic activity, thus improving the anti-alkali poisoning performance.

[0033] 3. The anti-poisoning SCR denitration catalyst of the present invention, acidic zirconium sulfate is a compound with high chemical stability. A stable ionic bond is formed between zirconium ions and sulfate ions in its molecular structure, making the whole molecule have high stability. By adding acidic zirconium sulfate to the denitration catalyst, more acidic sites are provided for the denitration catalyst, which is beneficial to the adsorption and activation of nitrogen oxides, thereby increasing the reaction rate of nitrogen oxides with reducing agents (such as NH3), and then improving the denitration efficiency and denitration activity. Acidic zirconium sulfate can occupy the active center of SO2 oxidation on the surface of the denitration catalyst, thus inhibiting the oxidation reaction of SO2, effectively reducing the SO2 / SO3 conversion rate, and improving the overall performance of the catalyst. Acidic zirconium sulfate with strong acidity can neutralize some alkaline sites on the surface of the denitration catalyst, making the acid-base balance on the surface of the denitration catalyst more balanced, and then reducing the negative impact of alkaline substances on the catalyst, thereby improving the anti-alkali poisoning performance of the catalyst. Detailed implementation mode

[0034] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0035] Example 1

[0036] This example provides a preparation method for an anti-poisoning SCR denitration catalyst and an alkali-poisoning denitration catalyst, including the following steps:

[0037] S1. Prepare vanadium-iron coprecipitation particles

[0038] Mix ammonium metavanadate and 6wt% acetic acid aqueous solution at a ratio of 1g:20mL, stir until the system dissolves to obtain an ammonium vanadate solution for standby;

[0039] Mix ferric nitrate nonahydrate and deionized water at a ratio of 1 g:15 mL, stir until the system dissolves to obtain a ferric nitrate solution for standby.

[0040] Weigh: Add 4 L of the ferric nitrate solution to a reaction kettle and stir. Dropwise add 0.8 L of ammonium metavanadate solution to the reaction kettle, stir at room temperature until the system dissolves, add 1.8 L of 10 wt% ammonia water to the reaction kettle, raise the temperature of the reaction kettle to 85 °C, keep the temperature for reaction for 8 h, lower the temperature of the reaction kettle to room temperature, carry out suction filtration, wash the filter cake with deionized water until neutral and then drain it, transfer the filter cake to a drying oven at 80 °C, dry to constant weight, grind, sieve through an 80-mesh sieve to obtain metal powder, place the metal powder in a muffle furnace at 460 °C, keep the temperature for 3 h, let the muffle furnace cool down to room temperature, and discharge to obtain vanadium-iron coprecipitated particles.

[0041] S2. Preparation of composite vanadium-iron particles

[0042] Mix germanium acetate, manganese acetate and deionized water at a ratio of 1 g:5 g:20 mL, stir until the system dissolves to obtain a germanium-manganese mixed solution for standby.

[0043] Weigh: Add 200 g of vanadium-iron coprecipitated particles and 2 L of deionized water to a reaction kettle and stir, raise the temperature of the reaction kettle to 60 °C, dropwise add 400 mL of the germanium-manganese mixed solution to the reaction kettle, after dropping, stir for 30 min, add ammonia water to the reaction kettle to adjust the pH of the system to 11, carry out heat preservation treatment for 2 h, lower the temperature of the reaction kettle to room temperature, carry out suction filtration, wash the filter cake with deionized water 3 times and then drain it, transfer the filter cake to a drying oven at 80 °C, dry to constant weight, grind, sieve through an 80-mesh sieve to obtain a solid, place the solid in a muffle furnace at 480 °C, roast for 4 h, let the muffle furnace cool down to room temperature naturally to obtain composite vanadium-iron particles.

[0044] S3. Preparation of titanium dioxide

[0045] Weigh: Add 500 g of tetrabutyl titanate to a three-necked flask with a polytetrafluoroethylene inner liner and stir. Add 150 mL of 40 wt% hydrofluoric acid to the three-necked flask. After closing the three-necked flask, raise the temperature of the three-necked flask to 160 °C, keep the temperature for reaction for 20 h, lower the temperature of the three-necked flask to room temperature, carry out suction filtration, wash the filter cake with deionized water until neutral and then drain it, transfer the filter cake to a drying oven at 80 °C, dry to constant weight, grind, sieve through a 100-mesh sieve to obtain nanoparticles, transfer the nanoparticles to a muffle furnace at 580 °C, keep the temperature for roasting for 90 min, lower the temperature of the muffle furnace to room temperature to obtain titanium dioxide.

[0046] S4. Preparation of pretreated red mud

[0047] Weigh: Add 500 g of red mud and 2 L of 6 mol / L nitric acid into the reaction kettle and stir. Raise the temperature of the reaction kettle to 70 °C, keep stirring for 2 h. Add 2 mol / L ammonia water into the reaction kettle to adjust the pH of the system to 9, keep stirring for 80 min. Lower the temperature of the reaction kettle to room temperature, filter by suction. Wash the filter cake with deionized water until neutral and then drain it by suction. Transfer the filter cake to a drying oven at 85 °C and dry until constant weight. Transfer the solid to a muffle furnace at 550 °C, keep roasting for 5 h. Lower the temperature of the muffle furnace to room temperature and discharge to obtain pretreated red mud.

[0048] S5. Preparation of composite gel

[0049] Mix potassium persulfate and deionized water at a ratio of 1 g:50 mL evenly to obtain an initiator solution for standby;

[0050] Weigh: Add 100 g of titanium dioxide, 350 g of pretreated red mud, 150 g of composite vanadium-iron particles, 250 g of acidic zirconium sulfate, 50 g of calcium fluoride, 750 g of sodium silicate, 250 g of acrylamide, 20 g of N,N′-methylenebisacrylamide and 4.5 L of deionized water into the reaction kettle and stir. Raise the temperature of the reaction kettle to 70 °C. Dropwise add 500 mL of the initiator solution into the reaction system. After dropping, keep reacting for 2 h and stir until the system gels. Lower the temperature of the reaction kettle to room temperature. Draw a negative pressure of -0.1 MPa in the reaction kettle to defoam and obtain a mixed gel.

[0051] S6. Preparation of denitration catalyst

[0052] Pour the mixed gel into a mold at 80 °C and let it gel for 60 min. After demolding, place the material in a drying oven at 60 °C and dry for 20 h. The drying oven is heated to 90 °C at a heating rate of 2 °C / min and keep drying for 24 h to obtain a catalyst blank;

[0053] Place the denitration catalyst blank in a muffle furnace. The muffle furnace is heated to 700 °C at a heating rate of 3 °C / min, keep roasting for 3 h, and naturally cool to room temperature and discharge to obtain a denitration catalyst.

[0054] S7. Preparation of alkali-poisoned denitration catalyst

[0055] Mix the denitration catalyst and 0.5 wt% sodium carbonate solution at a ratio of 1 g:1 mL, disperse ultrasonically for 2 h. Take out the catalyst from the solution, place it in a drying oven at 100 °C and dry for 3 h. Then transfer it to a muffle furnace at 380 °C and roast for 4 h to obtain an alkali-poisoned denitration catalyst.

[0056] Example 2

[0057] This example provides a preparation method of an anti-poisoning SCR denitration catalyst and an alkali-poisoned denitration catalyst, including the following steps:

[0058] S1. Preparation of vanadium-iron coprecipitated particles

[0059] Mix ammonium metavanadate and 6 wt% acetic acid aqueous solution at a ratio of 1 g:20 mL, stir until the system dissolves to obtain ammonium vanadate solution for standby;

[0060] Mix ferric nitrate nonahydrate and deionized water at a ratio of 1 g:15 mL, stir until the system dissolves to obtain ferric nitrate solution for standby;

[0061] Weigh: Add 4.5 L of ferric nitrate solution to the reaction kettle and stir. Dropwise add 1.0 L of ammonium vanadate solution to the reaction kettle, stir at room temperature until the system dissolves. Add 2.0 L of 13 wt% ammonia water to the reaction kettle, raise the temperature of the reaction kettle to 90 °C, keep the temperature for reaction for 8.5 h, lower the temperature of the reaction kettle to room temperature, carry out suction filtration, wash the filter cake with deionized water until neutral and then drain it. Transfer the filter cake to a drying oven at 85 °C, dry to constant weight, grind, pass through an 80-mesh sieve to obtain metal powder. Place the metal powder in a muffle furnace at 470 °C, keep the temperature for 4 h, let the muffle furnace cool down to room temperature, and discharge to obtain vanadium-iron coprecipitated particles.

[0062] S2. Preparation of composite vanadium-iron particles

[0063] Mix germanium acetate, manganese acetate and deionized water at a ratio of 1 g:5 g:20 mL, stir until the system dissolves to obtain germanium-manganese mixed solution for standby;

[0064] Weigh: Add 200 g of vanadium-iron coprecipitated particles and 2 L of deionized water to the reaction kettle and stir. Raise the temperature of the reaction kettle to 65 °C. Dropwise add 400 mL of germanium-manganese mixed solution to the reaction kettle. After dropping, stir for 40 min. Add ammonia water to the reaction kettle to adjust the pH of the system to 11.5, carry out heat preservation treatment for 2.5 h, lower the temperature of the reaction kettle to room temperature, carry out suction filtration, wash the filter cake with deionized water 3 times and then drain it. Transfer the filter cake to a drying oven at 85 °C, dry to constant weight, grind, pass through an 80-mesh sieve to obtain a solid. Place the solid in a muffle furnace at 490 °C, roast for 5 h, and let the muffle furnace cool down to room temperature naturally to obtain composite vanadium-iron particles.

[0065] S3. Preparation of titanium dioxide

[0066] Weigh: 500 g of tetrabutyl titanate was added to a three-necked flask with a PTFE liner and stirred. 150 mL of 40 wt% hydrofluoric acid was added to the three-necked flask. After the three-necked flask was sealed, the temperature of the three-necked flask was raised to 170 °C, and the reaction was carried out under insulation for 21 h. Then the temperature of the three-necked flask was lowered to room temperature. The mixture was filtered by suction, and the filter cake was washed with deionized water until neutral and then dried by suction. The filter cake was transferred to a drying oven at 85 °C and dried to a constant weight. Then it was ground and passed through a 100-mesh sieve to obtain nanoparticles. The nanoparticles were transferred to a muffle furnace at 600 °C and calcined under insulation for 105 min. After the temperature of the muffle furnace was lowered to room temperature, titanium dioxide was obtained.

[0067] S4. Preparation of pretreated red mud

[0068] Weigh: 500 g of red mud and 2 L of 7 mol / L nitric acid were added to a reaction kettle and stirred. The temperature of the reaction kettle was raised to 75 °C, and the mixture was stirred under insulation for 2.5 h. Then 2.5 mol / L ammonia water was added to the reaction kettle to adjust the pH of the system to 9.5, and the mixture was stirred under insulation for 90 min. After the temperature of the reaction kettle was lowered to room temperature, the mixture was filtered by suction. The filter cake was washed with deionized water until neutral and then dried by suction. The filter cake was transferred to a drying oven at 90 °C and dried to a constant weight. The solid was transferred to a muffle furnace at 565 °C and calcined under insulation for 5.5 h. After the temperature of the muffle furnace was lowered to room temperature, the product was discharged to obtain pretreated red mud.

[0069] S5. Preparation of composite gel

[0070] Potassium persulfate and deionized water were mixed evenly at a ratio of 1 g:50 mL to obtain an initiator solution for standby.

[0071] Weigh: 100 g of titanium dioxide, 350 g of pretreated red mud, 150 g of composite vanadium-iron particles, 250 g of acidic zirconium sulfate, 50 g of calcium fluoride, 750 g of sodium silicate, 250 g of acrylamide, 20 g of N,N′-methylenebisacrylamide and 4.5 L of deionized water were added to a reaction kettle and stirred. The temperature of the reaction kettle was raised to 75 °C, and 500 mL of the initiator solution was added dropwise to the reaction system. After the addition was completed, the reaction was carried out under insulation for 2.5 h and stirred until the system was gelled. Then the temperature of the reaction kettle was lowered to room temperature, and the reaction kettle was evacuated to -0.1 MPa to remove bubbles to obtain a mixed gel.

[0072] S6. Preparation of denitration catalyst

[0073] The mixed gel was poured into a mold at 85 °C, and the reaction was gelled for 70 min. After demolding, the material was placed in a drying oven at 65 °C and dried for 20 h. Then the drying oven was heated at a heating rate of 2 °C / min to 93 °C and dried under insulation for 24 h to obtain a catalyst blank.

[0074] Place the denitration catalyst blank in a muffle furnace. The muffle furnace is heated to 730 °C at a heating rate of 4 °C / min, kept at a constant temperature for roasting for 4 h, naturally cooled to room temperature, and the product is taken out to obtain the denitration catalyst.

[0075] S7. Preparation of alkali-poisoned denitration catalyst

[0076] Mix the denitration catalyst and 0.5 wt% sodium carbonate solution at a ratio of 1 g:1 mL, ultrasonically disperse for 2 h, take out the catalyst from the solution, place it in a drying oven at 100 °C for drying for 3 h, and then transfer it to a muffle furnace at 380 °C for roasting for 4 h to obtain the alkali-poisoned denitration catalyst.

[0077] Example 3

[0078] This example provides a method for preparing an anti-poisoning SCR denitration catalyst and an alkali-poisoned denitration catalyst, including the following steps:

[0079] S1. Preparation of vanadium-iron coprecipitation particles

[0080] Mix ammonium metavanadate and 6 wt% aqueous acetic acid solution at a ratio of 1 g:20 mL, stir until the system dissolves to obtain an ammonium vanadate solution for standby;

[0081] Mix ferric nitrate nonahydrate and deionized water at a ratio of 1 g:15 mL, stir until the system dissolves to obtain a ferric nitrate solution for standby;

[0082] Weigh: Add 5 L of the ferric nitrate solution to a reaction kettle and stir. Dropwise add 1.2 L of the ammonium vanadate solution to the reaction kettle, stir at room temperature until the system dissolves, add 2.2 L of 15 wt% ammonia water to the reaction kettle, raise the temperature of the reaction kettle to 95 °C, keep the temperature for reaction for 9 h, lower the temperature of the reaction kettle to room temperature, perform suction filtration, wash the filter cake with deionized water until neutral and then drain it, transfer the filter cake to a drying oven at 90 °C, dry to constant weight, grind, pass through an 80-mesh sieve to obtain metal powder, place the metal powder in a muffle furnace at 480 °C, keep the temperature for 5 h, cool the muffle furnace to room temperature, and take out the product to obtain vanadium-iron coprecipitation particles.

[0083] S2. Preparation of composite vanadium-iron particles

[0084] Mix germanium acetate, manganese acetate and deionized water at a ratio of 1 g:5 g:20 mL, stir until the system dissolves to obtain a germanium-manganese mixed solution for standby;

[0085] Weigh: 200 g of vanadium-iron coprecipitated particles and 2 L of deionized water are added to a reaction kettle and stirred. The temperature of the reaction kettle is raised to 70 °C. 400 mL of germanium-manganese mixed solution is added dropwise to the reaction kettle. After the addition is complete, stir for 50 min. Ammonia water is added to the reaction kettle to adjust the pH of the system to 12, and keep warm for 3 h. The temperature of the reaction kettle is lowered to room temperature, and then filtered by suction. The filter cake is washed 3 times with deionized water and then dried by suction. The filter cake is transferred to a drying oven at 90 °C and dried to constant weight, ground, and passed through an 80-mesh sieve to obtain a solid. The solid is placed in a muffle furnace at 500 °C and calcined for 6 h. The muffle furnace is allowed to cool naturally to room temperature to obtain composite vanadium-iron particles.

[0086] S3. Preparation of titanium dioxide

[0087] Weigh: 500 g of tetrabutyl titanate is added to a three-necked flask with a polytetrafluoroethylene inner liner and stirred. 150 mL of 40 wt% hydrofluoric acid is added to the three-necked flask. After the three-necked flask is sealed, the temperature of the three-necked flask is raised to 180 °C and kept warm for reaction for 22 h. The temperature of the three-necked flask is lowered to room temperature, and then filtered by suction. The filter cake is washed with deionized water until neutral and then dried by suction. The filter cake is transferred to a drying oven at 90 °C and dried to constant weight, ground, and passed through a 100-mesh sieve to obtain nanoparticles. The nanoparticles are transferred to a muffle furnace at 620 °C and kept warm for calcination for 120 min. The temperature of the muffle furnace is lowered to room temperature to obtain titanium dioxide.

[0088] S4. Preparation of pretreated red mud

[0089] Weigh: 500 g of red mud and 2 L of 8 mol / L nitric acid are added to a reaction kettle and stirred. The temperature of the reaction kettle is raised to 80 °C and kept warm and stirred for 3 h. 3 mol / L ammonia water is added to the reaction kettle to adjust the pH of the system to 10, and keep warm and stir for 100 min. The temperature of the reaction kettle is lowered to room temperature, and then filtered by suction. The filter cake is washed with deionized water until neutral and then dried by suction. The filter cake is transferred to a drying oven at 95 °C and dried to constant weight. The solid is transferred to a muffle furnace at 580 °C and kept warm for calcination for 6 h. The temperature of the muffle furnace is lowered to room temperature and discharged to obtain pretreated red mud.

[0090] S5. Preparation of composite gel

[0091] Potassium persulfate and deionized water are mixed evenly at a ratio of 1 g:50 mL to obtain an initiator solution for standby;

[0092] Weigh: 100 g of titanium dioxide, 350 g of pretreated red mud, 150 g of composite vanadium-iron particles, 250 g of acidic zirconium sulfate, 50 g of calcium fluoride, 750 g of sodium silicate, 250 g of acrylamide, 20 g of N,N′-methylenebisacrylamide and 4.5 L of deionized water, add them to a reaction kettle and stir. Raise the temperature of the reaction kettle to 80 °C, dropwise add 500 mL of initiator solution to the reaction system. After the dropping is completed, keep the temperature for reaction for 3 h, stir until the system gels, lower the temperature of the reaction kettle to room temperature, evacuate the reaction kettle to -0.1 MPa for defoaming to obtain a mixed gel.

[0093] S6. Prepare a denitration catalyst

[0094] Pour the mixed gel into a mold at 90 °C, react and gel for 80 min. After demolding, place the material in a drying oven at 70 °C and dry for 20 h. The drying oven is heated to 95 °C at a heating rate of 2 °C / min and kept for drying for 24 h to obtain a catalyst green body;

[0095] Place the denitration catalyst green body in a muffle furnace, heat the muffle furnace to 760 °C at a heating rate of 5 °C / min, keep the temperature for roasting for 5 h, naturally cool to room temperature, and discharge to obtain a denitration catalyst.

[0096] S7. Prepare an alkali-poisoned denitration catalyst

[0097] Mix the denitration catalyst and 0.5 wt% sodium carbonate solution at a ratio of 1 g:1 mL, ultrasonically disperse for 2 h, take out the catalyst from the solution, place it in a drying oven at 100 °C and dry for 3 h, then transfer it to a muffle furnace at 380 °C and roast for 4 h to obtain an alkali-poisoned denitration catalyst.

[0098] Comparative Example 1

[0099] The difference between this comparative example and Example 3 is that step S2 is cancelled, and the vanadium-iron coprecipitation particles in step S1 are used to replace the composite vanadium-iron particles in step S5.

[0100] Comparative Example 2

[0101] The difference between this comparative example and Example 3 is that step S4 is cancelled, and the red mud in step S4 is used to replace the pretreated red mud in step S5.

[0102] Comparative Example 3

[0103] The difference between this comparative example and Example 3 is that in step S5, acidic zirconium sulfate is not added.

[0104] Performance test:

[0105] Referring to the standard GB / T 31587-2015 "Honeycomb Flue Gas Denitration Catalyst", the denitration efficiency, SO2 / SO3 conversion rate and denitration activity of the denitration catalysts and alkali-poisoned denitration catalyst samples prepared in Examples 1-3 and Comparative Examples 1-3 were measured at 380 °C. The specific test results are shown in Table 1 below.

[0106] Table 1 - Performance Detection Data Table of Samples

[0107]

[0108]

[0109] Data Analysis:

[0110] By comparing and analyzing the data in Table 1 above, the denitration efficiency of the anti-poisoning SCR denitration catalyst prepared in the present invention reaches 91.4%, the SO2 / SO3 conversion rate is reduced to 0.22%, and the denitration activity reaches 42 m / h. After simulating alkali poisoning, the denitration efficiency of the sample reaches 90.7%, the retention rate reaches 99.23%, the SO2 / SO3 conversion rate is 0.25%, the growth rate is 12%, and the denitration activity reaches 40 m / h, with a decay rate of 4.76%. All the test results are better than those of the comparative examples. Therefore, in the present invention, the vanadium-iron coprecipitated particles are modified by germanium and manganese and then cooperate with pretreated red mud, titanium dioxide, and acidic zirconium sulfate, which not only effectively improves the denitration efficiency and denitration activity of the denitration catalyst, but also improves the performance of the denitration catalyst against alkali and sulfide poisoning.

[0111] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only the specific embodiments. Obviously, many modifications and changes can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principle and practical application of the present invention, so that those skilled in the art can understand and utilize the present invention well. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A method for preparing a poisoning-resistant SCR denitration catalyst, characterized in that: The following steps are involved: S1. Mix titanium dioxide, pretreated red mud, composite vanadium-iron particles, acidic zirconium sulfate, calcium fluoride, sodium silicate, acrylamide, N,N′-methylenebisacrylamide and deionized water, raise the temperature of the reaction system to 70-80° C., dropwise add the initiator solution into the reaction system, keep the temperature for 2-3 hours, stir until the system is gelled, degas, and obtain a mixed gel; S2, pouring the mixed gel into a mold at a temperature of 80-90°C, reacting and gelling for 60-80 minutes, and drying after demoulding to obtain a denitration catalyst body; S3, calcining the denitration catalyst blank at high temperature to obtain a denitration catalyst.

2. The method for preparing a poisoning-resistant SCR denitration catalyst according to claim 1, characterized in that: In step S1, the amount ratio of titanium dioxide, pretreated red mud, composite vanadium-iron particles, acidic zirconium sulfate, calcium fluoride, sodium silicate, acrylamide, N,N′-methylenebisacrylamide, deionized water and initiator solution is 2g:7g:3g:5g:1g:15g:5g:1g:90mL:10mL, and the initiator solution is composed of potassium persulfate and deionized water at a ratio of 1g:50mL; in step S2, the programmed drying comprises: after demolding, placing the material in a drying oven at a temperature of 60-70°C, drying for 20h, heating the drying oven to 90-95°C at a heating rate of 2°C / min, and drying at this temperature for 24h to obtain a catalyst blank; in step S3, the high-temperature calcination temperature is 700-760°C, and the calcination time is 3-5h.

3. The method for preparing a poisoning-resistant SCR denitration catalyst according to claim 1, characterized in that: The preparation method of titanium dioxide is as follows: hydrofluoric acid is added to n-butyl titanate, the reaction system is sealed, the temperature of the reaction system is increased to 160-180° C., the reaction is kept warm for 20-22 hours, post-processed, and calcined to obtain titanium dioxide.

4. The method for preparing a poisoning-resistant SCR denitration catalyst according to claim 3, characterized in that: The dosage ratio of n-butyl titanate to hydrofluoric acid is 10 g:3 mL, the concentration of hydrofluoric acid is 40%, the calcination temperature is 580-620° C., the calcination time is 90-120 min, and the calcination atmosphere is air.

5. The method for preparing a poisoning-resistant SCR denitration catalyst according to claim 1, characterized in that: The preparation method of composite vanadium-iron particles is as follows: vanadium-iron co-precipitated particles and deionized water are mixed and stirred, the temperature of the reaction system is increased to 60-70°C, a germanium-manganese mixed solution is added dropwise to the reaction system, and then ammonia water is added to the reaction system, the pH of the system is adjusted to 11-12, the reaction is heat-treated for 2-3 hours, post-treated, and calcined to obtain composite vanadium-iron particles.

6. The method for preparing a poisoning-resistant SCR denitration catalyst according to claim 5, characterized in that: The dosage ratio of the vanadium-iron co-precipitated particles, deionized water and germanium-manganese mixed solution is 10g:100mL:20mL, the germanium-manganese mixed solution is composed of germanium acetate, manganese acetate and deionized water in the ratio of 1g:5g:20mL, the roasting temperature is 480-500°C, the roasting time is 4-6, and the roasting atmosphere is air.

7. The method for preparing a poisoning-resistant SCR denitration catalyst according to claim 5, characterized in that: The preparation method of vanadium-iron co-precipitated particles is as follows: adding ammonium vanadate solution dropwise into ferric nitrate solution, stirring at room temperature until the system is dissolved, adding ammonia water to the reaction system, raising the temperature of the reaction system to 85-95°C, keeping the reaction warm for 8-9h, post-treating, and calcining to obtain vanadium-iron co-precipitated particles.

8. The method for preparing a poisoning-resistant SCR denitration catalyst according to claim 7, characterized in that: The volume ratio of the ammonium vanadate solution, the ferric nitrate solution and the ammonia water is 0.8-1.2:4-5:1.8-2.2, the ammonium vanadate solution is composed of ammonium metavanadate and a 6wt% acetic acid aqueous solution at a ratio of 1g:20mL, the ferric nitrate solution is composed of ferric nitrate nonahydrate and deionized water at a ratio of 1g:15mL, the mass fraction of the ammonia water is 10-15%, the roasting temperature is 460-480°C, the roasting time is 3-5h, and the roasting atmosphere is air.

9. The method for preparing a poisoning-resistant SCR denitration catalyst according to claim 1, characterized in that: The preparation method of pretreated red mud is as follows: red mud and nitric acid are mixed and stirred, the temperature of the reaction system is increased to 70-80°C, and the reaction system is kept warm for 2-3 hours, dilute ammonia water is added to the reaction system, the pH of the system is adjusted to 9-10, the reaction system is kept warm for 80-100 minutes, post-treated, and roasted to obtain pretreated red mud.

10. The method for preparing a poisoning-resistant SCR denitration catalyst according to claim 9, characterized in that: The dosage ratio of the red mud and nitric acid is 1g:4mL, the concentration of the nitric acid is 6-8mol / L, the concentration of the dilute ammonia water is 2-3mol / L, the roasting temperature is 550-580°C, the roasting time is 5-6h, and the roasting atmosphere is air.

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