Application of a hydrated deep eutectic solvent in arsenic removal from spent SCR catalysts

Abstract

The invention discloses an application of a hydrated low eutectic solvent in arsenic removal from waste SCR catalysts, which comprises adding arsenic-poisoned waste SCR catalysts into the hydrated low eutectic solvent for leaching, filtering, washing and drying to obtain a detoxification catalyst; the hydrated low eutectic solvent is an aqueous solution of a hydrogen bond acceptor and a hydrogen bond donor, and the water content is 20-99%; the hydrogen bond acceptor is choline chloride; the hydrogen bond donor includes acids and / or amines; and the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:(2-10). The hydrated low eutectic solvent has an obvious effect of removing arsenic from arsenic-poisoned waste SCR catalysts, has low energy consumption, is simple to operate, has low operating costs, and is in line with the development trend of green and environmental protection.

Description

Technical Field

[0001] The invention relates to application of a hydrated low eutectic solvent in removing arsenic from a waste SCR catalyst, belonging to the technical field of solid waste resource utilization. Background Art

[0002] In recent years, with the rapid development of the new energy industry, people's demand for electricity has been growing. The main source of electricity in my country is thermal power generation. At present, the mainstream denitrification method in coal-fired power plants is selective catalytic reduction (SCR). SCR is an efficient, mature and reliable technology. The catalyst has high activity and good sulfur resistance, which can effectively reduce the emission of nitrogen oxides. The catalyst is a key part in the SCR system, accounting for 30% to 50% of the total cost. On average, the service life of the SCR catalyst is 3-5 years. Although the used SCR catalyst contains a variety of valuable metals such as V, W, and Ti, it is considered to be a hazardous waste due to toxic elements such as As, Hg, and Pb. Therefore, if it is not properly disposed of, it will cause huge pollution to the environment and is a huge waste of resources. Arsenic poisoning is the main reason for the deactivation of SCR catalysts. The raw coal used in coal-fired power plants contains a relatively high arsenic content, which causes the As element to deposit a large amount of As2O3 and As2O5 on the surface of the catalyst and the internal channels of the catalyst, which will prevent NO x Reacts with the active sites on the catalyst. Therefore, the recycling and regeneration of As-rich spent SCR catalysts is of great significance.

[0003] The traditional methods for regenerating As-rich waste SCR catalysts are mainly acid washing to remove arsenic, alkaline washing to remove arsenic, and acid-base gradual leaching to remove arsenic. However, the traditional methods inevitably use strong acids or strong bases, which not only cause corrosion of instruments and equipment, but also make the regeneration waste liquid difficult to handle. Therefore, it is of great significance to find a green and efficient arsenic removal solvent. Summary of the invention

[0004] The purpose of the present invention is to provide an application of a hydrated deep eutectic solvent in the removal of arsenic from waste SCR catalysts. The hydrated deep eutectic solvent has obvious arsenic removal effect on arsenic-poisoned SCR catalysts, low energy consumption, simple operation, low operating cost, and is in line with the development trend of green and environmental protection.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] An application of a hydrated low eutectic solvent in the removal of arsenic from an SCR catalyst comprises adding arsenic-poisoned waste SCR catalyst into the hydrated low eutectic solvent for leaching, and then filtering, washing and drying to obtain a detoxified catalyst;

[0007] The hydrated low eutectic solvent is an aqueous solution of a hydrogen bond acceptor and a hydrogen bond donor, and the water content is 20-99%;

[0008] The hydrogen bond acceptor is choline chloride;

[0009] The hydrogen bond donors include acids and / or amines;

[0010] And the molar ratio of hydrogen bond acceptor to hydrogen bond donor is 1:(2-10).

[0011] Preferably, the acid is any one of oxalic acid dihydrate, boric acid, and citric acid;

[0012] The amine is any one of ethanolamine, diethanolamine, ethylenediamine and urea.

[0013] Preferably, the amine is ethanolamine, and the molar ratio of choline chloride to ethanolamine is 1:(6-10);

[0014] The water content of the hydrated low eutectic solvent is 20-97%.

[0015] Preferably, the leaching conditions are: liquid-to-solid ratio 1-15 mL / g, 20-100° C., 1-24 h;

[0016] The drying conditions are: 70-100° C., 1-5 h.

[0017] Preferably, the preparation method of the hydrated low eutectic solvent is to mix choline chloride and ethanolamine and then add water.

[0018] Preferably, the mixing and stirring conditions are: 70-90°C, 200-1000rpm, 1-5h.

[0019] Preferably, after obtaining the detoxified catalyst, a catalyst regeneration step is also performed. The specific regeneration step is: immersing the detoxified catalyst in an oxalic acid solution containing ammonium metavanadate, and then filtering, drying and calcining to obtain a regenerated catalyst.

[0020] Preferably, the content of ammonium metavanadate in the oxalic acid is 0.1-1 wt.%.

[0021] Preferably, the impregnation conditions are: liquid-to-solid ratio (4-28):1 (mass ratio, mass units are the same), 70-100° C., 5-15 h.

[0022] Preferably, the drying conditions are: 100-150°C, 5-10h;

[0023] The calcination conditions are: 250-350°C, 2-5h.

[0024] The beneficial effects of the present invention are:

[0025] Removing arsenic from arsenic-poisoned waste SCR catalysts by hydrating low eutectic solvents can avoid corrosion of instruments and equipment by strong acids and alkalis, reduce production costs and environmental pressures, comply with the development trend of green and environmental protection, and have low energy consumption, simple operation, and low running costs, and can be applied in practice.

[0026] The arsenic removal rate of this application can reach more than 98%, and the crystal structure of the SCR catalyst matrix anatase (TiO2) after regeneration is not affected by the leaching process. After impregnation with active components, the activity of the regenerated SCR catalyst is close to the level of fresh catalyst, and the NO conversion rate at 300°C is 93.2%. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The catalyst deactivation mechanism and the detoxification and regeneration flow chart provided by the present invention;

[0028] Figure 2 Synthesize Fourier transform infrared spectra for deep eutectic solvents;

[0029] Figure 3 (a) Effect of different hydrogen bond donors and acceptors on leaching efficiency (90℃, 10:1 mL·g -1 , 2h, molar ratio 1:2); (b) Effect of different molar ratios of choline chloride-ethanolamine on leaching efficiency (90℃, 10:1mL·g -1 , 2h); (c) Effect of different water contents of DES on leaching efficiency (90℃, 10:1 mL·g -1 , 2h); (d) Effect of leaching temperature on leaching efficiency (90℃, 10:1mL·g-1, 2h);

[0030] Figure 4 The diagram is the mechanism of arsenic removal by bidentate chelation coordination;

[0031] Figure 5 (a) Absorbance test of DES with different water contents in OMe dye probe molecules; (b) Absorbance test of DES with different water contents in OH dye probe molecules; (c) Π*, β and pH values ​​of DES with different water contents;

[0032] Figure 6 (a) isothermal adsorption diagram of the catalyst before and after arsenic removal; (b) XRD diffraction diagram of the catalyst before and after arsenic removal; (c, d) Raman scattering spectra of the catalyst before and after arsenic removal;

[0033] Figure 7 The scanning electron microscope images of the SCR catalyst before (a) and after (b) arsenic removal and the EDS energy spectrum images of the SCR catalyst before (c) and after (d) arsenic removal;

[0034] Figure 8(a) XPS full spectrum of the catalyst before and after arsenic removal; (b) XPS spectrum of the catalyst As3d before and after arsenic removal; (c) XPS spectrum of the catalyst O1s before arsenic removal; (d) XPS spectrum of the catalyst O1s after arsenic removal;

[0035] Fig. 9 NO conversion rate of SCR catalyst before arsenic removal, SCR catalyst after arsenic removal, and regenerated SCR catalyst (conditions: 100 mg catalyst, 250 ppm NO, 250 ppm NH3, 5 vol.% O2, 5 vol.% H2O, balance gas is N2, total flow rate is 100 mL / min);

[0036] Fig.10 This is a magnified picture of the experimental SCR catalyst. DETAILED DESCRIPTION

[0037] Selective catalytic reduction (SCR) is the mainstream denitrification method in coal-fired power plants. x Converted into N2 and H2O, but due to poisoning by arsenic and alkali metals during use, a large amount of waste SCR catalysts are produced every year. Arsenic is very harmful to the catalyst and has attracted widespread attention due to its difficulty in removal. The present invention has developed a green and efficient hydrated alkaline eutectic process to deeply remove arsenic from waste SCR catalysts. The results show that the optimal arsenic removal rate can reach more than 98%, and the crystal structure of the catalyst matrix anatase (TiO2) is not affected by the leaching process. After impregnation with active components, the activity of the regenerated SCR catalyst is close to that of the fresh catalyst, and the NO conversion rate is 93.2% at 300°C. Figure 1 The invention discloses a catalyst deactivation mechanism and a detoxification and regeneration process.

[0038] The present invention is specifically described below.

[0039] Material

[0040] Used SCR catalyst (Benxi), crushed, washed with running water to remove dust and then dried. All chemicals used in the work are of analytical grade. High-purity water is used in all experiments.

[0041] method

[0042] First, choline chloride is used as HBA and ethanolamine is used as HBD. Choline chloride and ethanolamine are mixed in a molar ratio of 1:9, placed on a constant temperature magnetic stirrer, the temperature is set to 80°C, the speed is 300rpm, and the reaction is stirred for about 1.5 hours to obtain a uniform, clear and transparent liquid, which is the DES solvent; then water is added to form a hydrated DES solvent as a solution for direct leaching of the waste SCR catalyst.

[0043] like Figure 2 As shown, by using Fourier transform infrared spectroscopy to determine the shift of hydroxyl groups after the synthesis of DES solvent, it can be proved that the synthesis of the low eutectic solvent was successful.

[0044] The leaching conditions were: spent SCR catalyst fragments, hydrated DES solvent, liquid-to-solid (L / S) ratio of 10 (mL / g), temperature 90°C, and time 2 h. Each experiment was repeated three times and the average extraction was reported to minimize any errors.

[0045] The regeneration conditions are as follows: after leaching, the waste SCR catalyst is filtered, washed with deionized water, and then dried at 80°C for 12 hours to obtain a detoxified catalyst. Then, 0.2wt.% ammonium metavanadate (NH4VO3) is dissolved in an oxalic acid aqueous solution and stirred for 5 hours at a stirring condition of 500rpm and a temperature of 50°C. Then, the detoxified catalyst is added and immersed at 80°C for 8 hours (liquid-solid ratio (4-28): 1 (mass ratio, same mass unit)). After filtering, it is dried at 110°C for 8 hours, and then air calcined in a 300°C tubular furnace for 3 hours to obtain a regenerated catalyst.

[0046] Characterization of spent SCR catalyst

[0047] It can be seen from Table 1 that the main elements in the fresh SCR catalyst and the spent SCR catalyst are Ti, W, and V.

[0048] Compared with the fresh SCR catalyst, the V of the spent SCR catalyst decreased by 25wt.%, and the contents of As, Ca, Na and K also increased significantly. It is worth noting that As increased from 0% to 1.78%, and Ca, Na and K also accumulated significantly in the spent SCR catalyst, and their concentrations increased by about 2 times and 3 times compared with the fresh SCR catalyst, respectively. Obviously, the spent SCR catalyst cannot be directly used as a new SCR catalyst carrier due to the poisoning of As and alkali metals.

[0049] Table 1 Main chemical components of spent SCR catalyst, fresh SCR catalyst and SCR catalyst after arsenic removal

[0050]

[0051] Effect of leaching process on arsenic removal rate

[0052] Figure 3 The middle ad area and Table 2 respectively give the effects of different leaching parameters on arsenic leaching efficiency.

[0053] Table 2 Arsenic removal rate of different deep eutectic solvent systems

[0054] Deep eutectic solvent system Molar Ratio Arsenic removal rate Choline chloride: boric acid 1:2 1.5％ Choline chloride: urea 1:2 1.8％ Choline chloride: oxalic acid dihydrate 1:2 7.5％ Choline chloride: ethylenediamine 1:2 9.7％ Choline chloride: diethanolamine 1:2 9.8％ Choline chloride: ethanolamine 1:2 11.3％ Choline chloride: ethanolamine 1:3 13.7％ Choline chloride: ethanolamine 1:6 14.1％ Choline chloride: ethanolamine 1:9 19.5％

[0055] Combining Table 2 and Figure 3It can be seen from the middle a area that the arsenic removal rate of choline chloride: urea (ChCl:Urea) is only 1.8%, because urea is a neutral substance, and the formed DES is difficult to react with arsenic oxide, resulting in an arsenic removal rate that is not as good as that of acidic or alkaline DES. The arsenic removal rate of choline chloride: dihydrated oxalic acid (ChCl:OA) is higher than that of choline chloride:urea, because arsenic oxide is an amphoteric oxide and easily reacts with acidic solvents; when HBD is boric acid (BA), the arsenic removal rate is low, because choline chloride:boric acid is too viscous and the mass transfer between it and the catalyst is too poor. When HBD is dihydrated oxalic acid, the arsenic removal rate can also reach 7.5%, which may be because dihydrated oxalic acid contains water, forming a three-component DES and a more complex hydrogen bond network. Choline chloride:ethanolamine and choline chloride:diethanolamine are both alkaline, and their arsenic removal effects are greatly improved compared to urea, boric acid and oxalic acid dihydrate. However, the effect of ethanolamine is much better than that of diethanolamine, so ethanolamine-choline chloride was selected for subsequent experimental research.

[0056] from Figure 3 It can be seen from the middle b area that DES with different hydrogen bond donor-acceptor molar ratios also affects the arsenic removal efficiency. With the increase of the molar ratio of ethanolamine, the arsenic leaching efficiency is significantly improved. The leaching effect of choline chloride:ethanolamine at a molar ratio of 1:9 is much better than that at molar ratios of 1:3 and 1:6. Therefore, DES with a molar ratio of choline chloride:ethanolamine of 1:9 was used for subsequent research.

[0057] from Figure 3 It can be seen from the middle c area and Table 3 that in the selected optimal DES, the addition of water has a significant effect on the arsenic leaching efficiency. After adding water, the arsenic removal rate first increases with the increase of water content and then remains stable. When the water content exceeds 90%, the arsenic removal rate begins to decrease. This is because the excessive water content destroys the structure of DES. The arsenic removal rate when the water content is 85% to 95% is higher than 90%, but the increase in water content will reduce the cost, so when removing arsenic from the waste SCR catalyst, the 90% water content is the best.

[0058] Table 3 Arsenic removal effect of choline chloride-ethanolamine deep eutectic solvents with different water contents

[0059] Moisture content Arsenic removal rate 20％ 40.0％ 40％ 55.9％ 60％ 80.1％ 80％ 86.9％ 85％ 92.3％ 90％ 98.2％ 95％ 95.3％ 97％ 83.3％

[0060] from Figure 3It can be seen from the middle d area that temperature is an important factor affecting the arsenic removal rate. When the temperature rises from 20°C to 90°C, the arsenic removal rate gradually increases. The reason is that the molecular thermal motion speed becomes more intense as the temperature rises, causing the viscosity of DES to decrease and the fluidity to increase. Therefore, the arsenic removal rate will continue to increase with the increase in temperature. After the temperature exceeds 90°C, the high temperature will destroy the structure of DES, causing the DES structure to change, and the effective ingredients will volatilize (close to the boiling point of water, water evaporates too much), which will then lead to a decrease in the arsenic removal rate. This data was obtained through multiple sets of parallel experiments, and the arsenic removal effect at 90°C is the best.

[0061] Leaching mechanism

[0062] The hydrated low eutectic solvent is mainly composed of three components: water, choline chloride and ethanolamine. The addition of water in the synthesized DES solvent reduces the viscosity of the reaction medium, enhances mass transfer, and improves the arsenic removal efficiency. In addition, water molecules solvate the hydrophilic part of the catalyst, increase the solubility of arsenic oxide, and water also reacts with As2O3 and As2O5 in the catalyst. The reaction formula is as follows:

[0063] As2O3+3H2O=2H3AsO3

[0064] As2O5+3H2O=2H3AsO4

[0065] After adding water, ethanolamine will hydrolyze when it meets water, and choline chloride will hydrolyze when it meets water. At the same time, the Cl- in choline chloride may accelerate the hydrolysis of ethanolamine. The reaction formula is as follows:

[0066]

[0067] The hydroxide ions ionized from ethanolamine react with As2O3 and As2O5 in the catalyst to generate arsenate ions and arsenite ions. The reaction formula is as follows:

[0068] As2O3+6OH - →2AsO3 3- +3H2O

[0069] As2O5+6OH - →2AsO4 3- +3H2O

[0070] The arsenate and arsenite generated by the reaction may react with water again, and the reaction formula is as follows:

[0071]

[0072]

[0073] The arsenic acid and arsenous acid generated above may react with ethanolamine, and the reaction formula is as follows:

[0074] C2H7NO+H3AsO3→Arsenite

[0075] C2H7NO+H3AsO4→Arsenate

[0076] The nitrogen atoms in choline chloride will undergo electrostatic potential penetration with water, making it easier to introduce water into the low eutectic solvent and promote the formation of a hydrated low eutectic solvent. At the same time, choline chloride will ionize into chloride ions when it encounters water. The chloride ions may react with As2O3 and As2O5 in the catalyst. The reaction formula is as follows:

[0077] As2O3+6Cl - →2AsCl3+3O2

[0078] As2O5+10Cl - →2AsCl3+5O2

[0079] like Figure 4 As shown, the hydrated low eutectic solvent forms a bidentate ligand, and the NH- ions in the bidentate ligand directly attack the inactivated active site to form a five-membered ring complex, remove the As-OH group, re-expose the V-OH on the catalyst, and restore the activity of the catalyst.

[0080] Solvent property analysis

[0081] Kamlet-Taft solvatochromic parameters are a common research method to describe the microscopic physical and chemical properties of solvents, mainly including hydrogen bond acidity (α), hydrogen bond basicity (β), and hydrogen bond polarity (Π*). Since DES solvents are alkaline, the main tests and calculations are for hydrogen bond basicity and hydrogen bond polarity. The test method is to select one or more compounds with spectral activity and strong dependence on solvent as probe molecules. The interaction relationship of solvents is predicted based on the difference in the electronic transition energy of the probe molecules in different solvents.

[0082] In this experiment, 4-nitroanisole (OMe) and 4-nitrophenol (OH) were selected as probes to test the hydrogen bond polarity (Π*) and hydrogen bond basicity (β) of DES at different water contents. The calculation formula is as follows:

[0083] Π*=0.427×(34.12-VOMe)

[0084] β=0.346×(35.04-VOH)-0.57Π*

[0085] Where V = 1 / (λ×10-4) and λ is the wavelength corresponding to the absorption of the dye.

[0086] Figure 5 The absorbance test of DES in OMe dye and OH dye probe molecules shows that the absorption peaks of DES with different water contents are concentrated at 350-500nm. According to the above formula, the β value of 90% water content is less than the β value of 60% water content, less than the β value of 20% water content, and less than the β value of pure DES; the Π* value of 90% water content is less than the Π* value of 60% water content, less than the Π* value of 20% water content, and less than the Π* value of pure DES. Through the pH value test, the pH value of pure DES is 13.531, the pH value of 20% water content is 12.935, the pH value of 60% water content is 12.356, and the pH value of 90% water content is 11.688. The higher the water content, the lower the pH value, which is also consistent with the calculation.

[0087] Structural analysis of SCR catalyst after arsenic removal

[0088] Figure 6 The structural characteristics of the spent SCR catalyst and the detoxified SCR catalyst were studied by N2 adsorption and desorption method in the middle a region. After calculation, the specific surface areas of the spent SCR catalyst and the detoxified SCR catalyst were 44.146 m 2 / g and 50.15m 2 / g, indicating that the hydrated DES system process effectively reduced the pore blockage of the catalyst. Figure 6 Region a in the middle also shows that the spent SCR catalyst and the detoxified SCR catalyst exhibit IV adsorption / desorption isotherms and H1-type hysteresis loops.

[0089] Figure 6 Region b in the middle is the XRD spectra of the phase change of the SCR catalyst before and after arsenic removal. The main crystal phase of the two catalysts is anatase TiO2, but the crystal phases of As, V, and W are not detected. This is because their content is low, they are in an amorphous state, and are highly dispersed on the carrier TiO2. The main crystal phase of the detoxification catalyst is still anatase TiO2, indicating that the hydrated DES system does not cause damage to the crystal structure of TiO2 after leaching the waste SCR catalyst.

[0090] The difference between the spent catalyst and the detoxified catalyst was determined by Raman scattering spectroscopy. Figure 6 As shown in the middle cd region, the Raman spectra of the spent SCR catalyst and the detoxified SCR catalyst are 147, 197, 395, 515, and 638 cm -1 , indicating that the Raman spectrum did not change after being treated with the hydrated DES system. These results also indicate that the main crystalline phase of the catalyst after leaching is still anatase TiO2, which is consistent with the conclusion obtained by XRD.

[0091] Figure 7Scanning electron microscopy shows that the surface of the waste SCR catalyst has some raised patterns in the middle a area, but the surface is still relatively smooth. After arsenic removal, the raised areas are reduced and many concave areas appear ( Figure 7 The reason is that the pores on the surface of the spent SCR catalyst are filled and covered by arsenic oxides in the flue gas, and the hydrated DES system can effectively remove impurities (arsenic oxides) on the surface of the spent SCR catalyst. Figure 7 After the middle c area) Figure 7 Surface element analysis of area (d) in the middle showed that the As content decreased from 8wt.% to 0.3wt.%.

[0092] The XPS full spectra of the catalyst before and after arsenic removal and the XPS spectra of As3d are shown in Figure 2. Figure 8 As shown in the ab region, the binding energies of 44.38 eV and 45.12 eV are respectively attributed to As 3+ and As 5+ , in addition 3+ The area ratio is 67%, indicating that the arsenic in the spent SCR catalyst is mainly As 3+ However, some As2O3 reacts with O2 on the adsorption surface to generate As2O5. 3+ Gradually oxidized to As 5+ , As 5+ The proportion of As is about 33%, so the catalyst pores are generated 5+ The absence of peaks after arsenic removal indicates that arsenic is almost completely removed.

[0093] The presence of sufficient oxygen-containing groups is the key to ensure the oxidation of As(III), such as Figure 8 As shown in the middle cd region, the peaks of the O spectrum at 529 and 530.1 / 530.2 eV are attributed to lattice oxygen (Olat) and surface adsorbed oxygen (Osurf). O mainly exists in the Olat state, indicating that the SCR catalyst can provide sufficient Lewis acid sites for the formation of As2O5, and As2O3 on the surface of the SCR catalyst is oxidized to As2O5. After arsenic removal, the content of surface adsorbed oxygen decreased by 37.7%. Combined with the XPS spectrum of arsenic, the reason for the decrease in surface adsorbed oxygen is that arsenic oxides are basically completely removed, As 5+ The proportion is about 33%, and the surface adsorbed oxygen has decreased by 37.7%, indicating that the oxygen of As2O5 comes from the surface adsorbed oxygen, and arsenic is basically completely removed.

[0094] The NO removal rates of the SCR catalyst before arsenic removal, the SCR catalyst after arsenic removal, and the regenerated SCR catalyst are shown in Figure 2. Fig. 9As shown in the figure, the catalytic activity of the SCR catalyst increases rapidly in the low temperature range (100℃~200℃), shows excellent performance at about 250℃~300℃, and slightly decreases in the higher temperature range. Compared with the regenerated SCR catalyst, the maximum NO conversion efficiency of the spent SCR catalyst before arsenic removal at 250℃ is only 68%, and the maximum NO conversion efficiency of the regenerated SCR catalyst at 250℃ is 92%, indicating that the spent SCR catalyst has basically lost its SCR catalytic performance. After leaching with a hydrated low eutectic solvent, the catalytic activity of the SCR catalyst after arsenic removal is only slightly lower than that of the regenerated SCR catalyst, indicating that the hydrated low eutectic solvent has a good arsenic removal effect on the spent SCR catalyst and less loss of active sites. In addition, the components of the hydrated low eutectic solvent are very cheap and easy to obtain, and the impregnation conditions are simple, easy to operate and environmentally compatible.

[0095] In summary, the present invention provides a green and economical hydrated DES system to detoxify and regenerate spent SCR catalysts. The optimal leaching conditions are: choline chloride-ethanolamine molar ratio of 1:9, water content of the hydrated DES system of 90%, temperature of 90°C, time of 2h, and the leaching rate of As is greater than 98%.

[0096] At the same time, in subsequent experiments, a 3*3SCR catalyst with a length of 10 cm ( Fig.10 ) was scaled up and XRF characterization proved that the As leaching rate was greater than 90%, as shown in Table 4, indicating that this experiment has practical significance.

[0097] Table 4 XRF characterization data of catalysts in the amplified experiment

[0098]

[0099] In the arsenic removal process of the hydrated DES system, the structure of the SCR catalyst is not destroyed and is still anatase TiO2. After the recovered detoxification catalyst is impregnated with fresh active compounds, the NO conversion efficiency is significantly improved, and the NO conversion rate reaches 93.2% at 300°C. In addition, the reagent of the present invention is low in price, providing a new process idea for efficient arsenic removal and comprehensive utilization of waste catalysts.

[0100] The above is only a preferred implementation of the patent of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the patent of the present invention. These improvements and modifications should also be regarded as the scope of protection of the patent of the present invention.

Claims

1. Application of a hydrated deep eutectic solvent in the removal of arsenic from waste SCR catalysts, characterized in that: The method is to add the arsenic-poisoned waste SCR catalyst into a hydrated low eutectic solvent for leaching, and then filter, wash and dry to obtain a detoxified catalyst; The hydrated low eutectic solvent is an aqueous solution of a hydrogen bond acceptor and a hydrogen bond donor, and the water content is 20-99%; The hydrogen bond acceptor is choline chloride; The hydrogen bond donor includes amines, and the amines are any one of ethanolamine, diethanolamine and ethylenediamine; And the molar ratio of hydrogen bond acceptor to hydrogen bond donor is 1:(2-10).

2. The use according to claim 1, characterized in that: The amine is ethanolamine, and the molar ratio of choline chloride to ethanolamine is 1:(6-10); The water content of the hydrated low eutectic solvent is 20-97%.

3. The use according to claim 2, characterized in that: The leaching conditions are: liquid-to-solid ratio 1-15 mL / g, 20-100° C., 1-24 h; The drying conditions are: 70-100° C., 1-5 h.

4. The use according to claim 2, characterized in that: The preparation method of the hydrated low eutectic solvent is to mix choline chloride and ethanolamine, stir and eutectic, and then add water.

5. The use according to claim 4, characterized in that: The mixing and stirring conditions are: 70-90°C, 200-1000rpm, 1-5h.

6. The use according to claim 1, characterized in that: After obtaining the detoxified catalyst, a catalyst regeneration step is also carried out. The specific regeneration step is: the detoxified catalyst is added into an oxalic acid solution containing ammonium metavanadate for immersion, and then filtered, dried, and calcined to obtain a regenerated catalyst.

7. The use according to claim 6, characterized in that: The content of ammonium metavanadate in the oxalic acid is 0.1-1wt.%.

8. The use according to claim 6, characterized in that: The impregnation conditions are: liquid-solid ratio (4-28):1, mass ratio, mass unit is the same; 70-100° C., 5-15h.

9. The use according to claim 6, characterized in that: The drying conditions are: 100-150°C, 5-10h; The calcination conditions are: 250-350°C, 2-5h.

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