Catalyst for simultaneously removing nitrogen oxides and chlorine-containing volatile organic compounds and preparation method thereof

Abstract

The invention relates to a catalyst for simultaneously removing nitrogen oxides and chlorine-containing volatile organic compounds and a preparation method thereof, which comprises the following steps: taking oxides of Co and Ce as active components, mixing metal salt solutions of Co and Ce according to a certain ratio to generate a white precipitate, stirring, aging, centrifugally collecting the precipitate, and washing; and uniformly dispersing the white precipitate in an ethanol solution under an ultrasonic-assisted condition, adding water and a titanium source, aging, centrifugally collecting the precipitate, drying and roasting to obtain the catalyst. The catalyst has excellent nitrogen oxide and chlorine-containing volatile organic compound oxidation performance under medium and low temperature conditions, and can realize efficient removal of nitrogen oxide and chlorine-containing volatile organic compounds at the same time.

Description

Technical Field

[0001] The invention relates to a denitration catalyst, in particular to a catalyst for simultaneously removing nitrogen oxides and chlorine-containing volatile organic matter and a preparation method thereof. Background Art

[0002] Nitrogen oxides (NO x ) and chlorinated volatile organic compounds (Cl-VOCs) coexist in many industrial flue gases. They are the main precursors of photochemical smog and particulate matter. Cl-VOCs have great harm to the ecological environment and human health. Their high toxicity can cause photochemical smog, atmospheric ozone layer destruction, cancer and deformity of the body. Nitrogen oxides (NO x ) as an important precursor, easily undergoes photochemical reactions with active species such as hydroxyl radicals (HOX) in the atmosphere to generate a large amount of secondary pollutants such as O3, secondary fine particulate matter and organic aerosols, resulting in the continuous enhancement of the oxidizing nature of my country's atmospheric environment. The regional complex pollution caused by it is extremely difficult to deal with, and its control is imminent.

[0003] Therefore, many countries have enacted strict environmental policies to manage Cl-VOCs and NO x An ultra-low emission policy has also been formulated, and the NOx emission concentration in the sintering flue gas of the steel industry is limited to 50mg / m 3 .

[0004] Therefore, NO x The removal of NOx and Cl-VOCs has attracted great attention, and the use of catalytic technology can effectively degrade NOx and Cl-VOCs. Selective catalytic reduction of nitrogen oxides with NH3 (NH3-SCR) has been proven to be an effective post-combustion technology to minimize nitrogen oxide emissions from stationary pollution sources. Regarding the removal of Cl-VOCs, catalytic oxidation is believed to be the most effective method for the removal of Cl-VOCs.

[0005] Therefore, developing a catalyst that can simultaneously remove nitrogen oxides and chlorinated volatile organic compounds from industrial waste gas is of great environmental significance. Summary of the invention

[0006] The first purpose of the present application is to simultaneously remove the catalyst of nitrogen oxides and chlorinated volatile organic compounds in industrial waste gas, and to improve the conversion rate of nitrogen oxides and chlorinated volatile organic compounds, and the corresponding selectivity of nitrogen and carbon dioxide is also significantly improved.

[0007] The second purpose of the present application is that the catalyst can simultaneously remove nitrogen oxides and chlorine-containing volatile organic compounds in industrial waste gas in a water-containing and sulfur-containing environment.

[0008] To achieve the above-mentioned purpose of the invention, the present application provides a catalyst, including oxides of Co and Ce and TiO2, wherein at least a portion of the outer surface of the oxides of Co and Ce is covered by TiO2.

[0009] In the catalyst, the molar ratio of Ce element to Co element is (0.5-2):(0.1-1).

[0010] The catalyst of the present application can improve the conversion rate of nitrogen oxides and chlorine-containing volatile organic compounds by controlling the ratio of Ce and Co and covering TiO2 on at least part of the outer surface of the oxides of Co and Ce. The corresponding selectivity of nitrogen and carbon dioxide is also significantly improved. At the same time, it also has the effects of resistance to water and sulfur.

[0011] The preparation method of the catalyst of the present application comprises:

[0012] 1) mixing a soluble salt containing a Ce element, a soluble salt containing a Co element and polyvinyl pyrrolidone, allowing the mixture to stand to obtain a first precipitate, and drying the precipitate to obtain a solid powder;

[0013] 2) After the solid powder is dispersed in the solution, it is mixed with a titanium-containing substance, and a second precipitate is generated after standing. The second precipitate is dried and calcined to obtain a catalyst.

[0014] The catalyst prepared by the above method has a partial area on the surface of the cerium-cobalt composite metal oxide coated with TiO2. This specific structural form of the catalyst enables the catalyst to simultaneously remove nitrogen oxides and chlorine-containing volatile organic compounds in industrial waste gas in a water-containing and sulfur-containing environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The figure is a graph showing the conversion rate of chlorine-containing volatile organic compounds of the catalysts obtained in Examples 1-3 of the present invention and Comparative Examples 1 and 2.

[0016] Figure 2 Graph showing the selectivity of CO2 for the catalysts obtained in Examples 1-3 of the present invention and Comparative Examples 1 and 2.

[0017] Figure 3 It is a graph showing the nitrogen oxide conversion rate of the catalysts obtained in Examples 1-3 of the present invention and Comparative Examples 1 and 2.

[0018] Figure 4 It is a graph showing the N2 selectivity of the catalysts obtained in Examples 1-3 of the present invention and Comparative Examples 1 and 2.

[0019] Figure 5 This is a scanning electron microscope image of the catalyst Ce3[Co(CN)6]2-nH2O@TiO2 obtained in Example 1 of the present invention.

[0020] Figure 6 This is a water resistance curve of the catalyst prepared in the present invention.

[0021] Figure 7 This is a stability curve diagram of the catalyst prepared in the present invention. DETAILED DESCRIPTION

[0022] The catalyst for simultaneously removing nitrogen oxides and volatile chlorine-containing substances of the present invention is further described in detail below. The protection scope of the present application is not limited, and its protection scope is defined by the claims. Certain disclosed specific details provide a comprehensive understanding of each disclosed embodiment. However, those skilled in the relevant art know that the embodiment can be implemented without using one or more of these specific details and using other materials, etc.

[0023] Unless the context requires otherwise, in the specification and claims, the terms "include" and "comprising" should be construed as having an open-ended, inclusive meaning, that is, "including, but not limited to".

[0024] The "embodiment", "one embodiment", "another embodiment" or "certain embodiments" mentioned in the specification means that the specific features, structures or characteristics described in connection with the embodiment are included in at least one embodiment. Therefore, "embodiment", "one embodiment", "another embodiment" or "certain embodiments" do not necessarily all refer to the same embodiment. Moreover, specific features, structures or characteristics may be combined in any manner in one or more embodiments. Each feature disclosed in the specification may be replaced by any alternative feature that can provide the same, equal or similar purpose. Therefore, unless otherwise specified, the disclosed features are only general examples of equal or similar features.

[0025] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples without specifying specific conditions are usually performed under normal conditions or according to the conditions recommended by the manufacturer. Unless otherwise stated, all percentages, ratios, proportions, or parts are by weight.

[0026] The term "nitrogen oxides" refers to compounds composed of only two elements, nitrogen and oxygen, and includes a variety of compounds, such as nitrous oxide (N2O), nitric oxide (NO), nitrogen dioxide (NO2), nitrogen trioxide (N2O3), nitrogen tetroxide (N2O4) and nitrogen pentoxide (N2O5).

[0027] The "chlorinated volatile organic compounds" (Cl-VOCs) in this application can be mainly divided into aliphatic chlorides and aromatic chlorides. Aliphatic chlorides can be mainly used as raw materials for organochlorine products, organic solvents, degreasing agents, etc. Aromatic chlorides are usually used as solvents, pesticides and synthetic intermediates for many organic compounds.

[0028] Unless otherwise defined, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to those described herein can be applied to the methods of the present invention. The preferred implementation methods and materials described herein are for demonstration purposes only.

[0029] Generally, most catalysts have serious poisoning and deactivation problems during the oxidation of Cl-VOCs at low temperatures, especially poisoning caused by chlorine deposition. The accumulated chlorine not only causes the pores of the catalyst to be blocked, but also occupies the active sites, reducing the redox performance of the catalyst. The catalyst provided in the present application has good tolerance to chlorine and can simultaneously remove nitrogen oxides and chlorine-containing volatile organic compounds from industrial waste gas.

[0030] On the one hand, the catalyst of the present application comprises oxides of Co and Ce and TiO2, wherein at least a portion of the outer surface of the oxides of Co and Ce is covered by TiO2.

[0031] From the appearance of the catalyst, the overall structure is a hexagonal bipyramid. That is, the TiO2 covering the surface of the cerium-cobalt composite metal oxide wraps its surface discontinuously, similar to a tortoise shell structure.

[0032] In certain embodiments, in the catalyst, the molar ratio of Ce element to Co element is (0.5-2):(0.1-1).

[0033] Preferably, the molar ratio of Ce element to Co element is (1.5-3):1.

[0034] In the catalyst, the main valence states of Ce are +4 and +3, and the main valence states of Co are +3 and +2. The content of oxygen in the catalyst is determined to satisfy the valence balance according to the content and valence state of the metal elements in the catalyst.

[0035] In the catalyst, the content of TiO2 is greater than 0 and less than or equal to 5wt.%.

[0036] Preferably, in the catalyst, the content of TiO2 is 1wt.%-4wt.%.

[0037] TiO2 partially covers the surface of the cerium-cobalt composite metal oxide. Due to the introduction of titanium dioxide, the acid sites are enhanced, the conversion rate of chlorinated volatile organic compounds (such as o-dichlorobenzene) and the NH3-SCR activity are balanced, and the NH3-SCR temperature window is matched with the conversion temperature of chlorinated volatile organic compounds (such as o-dichlorobenzene). TiO2 also has excellent heat resistance and corrosion resistance. The addition of Ti distorts the crystal structure, thereby increasing the acidity and oxygen mobility at high temperatures, and can prevent the exchange of Cl with basic lattice oxygen and hydroxyl groups, thereby improving the chlorine resistance of the catalyst.

[0038] The titanium dioxide of the catalyst covers part of the outer surface of the cerium-cobalt alloy oxide, which can greatly reduce the content of Ti without sacrificing activity, and can significantly reduce costs. Compared with the carrier catalyst (Ce / Co loaded on TiO2), the catalytic efficiency is high, the service life is long, and it can be used continuously for more than one hundred hours. When the catalyst removes oxides and chlorinated volatile organic compounds at the same time, there are few dechlorination by-products. Through the interface effect between titanium dioxide and cerium-cobalt alloy oxide, bifunctional selective reaction can be better achieved. In addition, the preparation method of the present application is efficient and low in cost.

[0039] The catalyst of the present application removes chlorine-containing volatile organic matter by catalytically oxidizing the chlorine-containing volatile organic matter into target products of carbon dioxide and chlorine or hydrogen chloride.

[0040] On the other hand, the preparation method of the above catalyst comprises:

[0041] 1) mixing a soluble salt containing a Ce element, a soluble salt containing a Co element, and polyvinyl pyrrolidone or a citrate, and allowing the mixture to stand to obtain a first precipitate, and drying the precipitate to obtain a solid powder;

[0042] 2) After the solid powder is dispersed in the solution, it is mixed with a titanium-containing substance, and a second precipitate is generated after standing. The second precipitate is dried and calcined to obtain a catalyst.

[0043] The preparation method of the catalyst of the present application is to first prepare a cerium-cobalt composite metal oxide, disperse it into a solution, and then mix it with a titanium-containing substance to introduce the titanium element into the surface of the cerium-cobalt composite metal oxide; after subsequent drying and calcination, a Ce-Co@TiO2 catalyst is obtained.

[0044] Polyvinyl pyrrolidone (PVP) is divided into four grades according to its average molecular weight, which is usually expressed by K value. Different K values ​​represent the corresponding PVP average molecular weight range. Preferably, the polyvinyl pyrrolidone of the present application is K-30. The corresponding number average molecular weight is about 44000-54000.

[0045] In certain embodiments, in step (1), the mass ratio of the amount of cobalt element to polyvinyl pyrrolidone is (0.35-1.4): 1 mmol / g.

[0046] Preferably, in step (1), the mass ratio of the amount of cobalt element to polyvinyl pyrrolidone is (0.35-0.5): 1 mmol / g.

[0047] In step (1), the mass ratio of the amount of cobalt element to citrate (such as sodium citrate) is (0.35-1.4): 1 mmol / g.

[0048] In step (1), the mass ratio of the amount of cobalt element to citrate (such as sodium citrate) is (0.35-0.5): 1mmol / g. In the process of preparing the catalyst, sodium citrate or polyvinyl pyrrolidone is added to the cobalt-containing solution, which mainly plays a precipitation buffering role, can increase the size of the catalyst (for example, the catalyst size is 2μm-4μm), and improve the oxidation performance of the catalyst.

[0049] In step (1), a soluble salt containing the Co element and polyvinyl pyrrolidone are dissolved in an aqueous solvent, and then fully mixed with an alcohol solution of a soluble salt containing the Ce element, and allowed to stand to obtain a first precipitate.

[0050] During the preparation process, a solid with a hexagonal bipyramid structure can be prepared by controlling the mixing order of the soluble salt of the Ce element, the soluble salt of the Co element and polyvinyl pyrrolidone. If the soluble salt of the Ce element, the soluble salt of the Co element and polyvinyl pyrrolidone are mixed at the same time, a complexing effect will occur and the hexagonal bipyramid structure cannot be obtained.

[0051] The usage of the soluble salt containing the Co element and the soluble salt containing the Ce element conforms to the proportion of each substance of the above-mentioned catalyst.

[0052] In certain embodiments, the obtained first precipitate is washed with alcohol water and then dried at a temperature ranging from 60 to 105°C.

[0053] In certain embodiments, in step (2), the solid powder of step (1) is first dispersed in anhydrous ethanol to form a suspension, and then water is added to the suspension.

[0054] Preferably, under ultrasonic conditions, the solid powder of step (1) is first dispersed in anhydrous ethanol to form a suspension.

[0055] In step (2), the mass ratio of solid powder to tetrabutyl titanate is (0.02-2):1.

[0056] Preferably, the mass ratio of solid powder to tetrabutyl titanate is (0.14-0.2):1.

[0057] In certain embodiments, the calcination temperature of the second precipitate is controlled at 400-550°C.

[0058] The calcination time is controlled between 2.5 hours and 4 hours.

[0059] The heating rate during the calcination process is controlled at 1-2°C / min.

[0060] By controlling the heating rate during roasting, the complete hexagonal bipyramidal structure can be maintained, and the organic embryo can be decomposed to form sufficient oxides, thereby achieving better catalytic denitrification and dechlorination effects.

[0061] The drying temperature of the second precipitate is 80-105°C.

[0062] The soluble salt containing Co element can be K3[Co(CN)6]; the soluble salt containing Ce element can be Ce(NO3)3.

[0063] A preferred embodiment of the method for preparing the catalyst comprises:

[0064] S1: Dissolve Ce(NO3)3·6H2O in anhydrous ethanol; add polyvinyl pyrrolidone (PVP, K-30) to K3[Co(CN)6] deionized water and stir to mix;

[0065] Then, Ce(NO3)3·6H2O ethanol solution was dropped into the mixed solution with K3[Co(CN)6] water and stirred vigorously;

[0066] S2: The mixed solution obtained in S1 is placed for 24-48 hours, the first precipitate is collected by centrifugation, and washed twice with anhydrous ethanol / water;

[0067] After drying at 60-105 °C overnight, white Ce3[Co(CN)6]2-nH2O powder was obtained;

[0068] S3: The Ce3[Co(CN)6]2-nH2O nanocubes prepared in S2 are dispersed in anhydrous ethanol and ultrasonically treated to form a turbid solution.

[0069] S4: adding deionized water to the turbid solution prepared in S3; dropping tetrabutyl titanate (TBOT) dissolved in ethanol into the turbid solution; after aging, collecting the second precipitate by a centrifuge;

[0070] S5: The second precipitate prepared in S4 was washed three times with ethanol and then dried at 80-105°C for 12-24 hours; the obtained off-white powder was Ce3[Co(CN)6]2-nH2O@TiO2;

[0071] S6: After calcining for 24 hours at a rate of 1°C / min to 400-550°C, Ce3[Co(CN)6]2-nH2O@TiO2 was obtained.

[0072] The metal salt of cerium is any one of cerous chloride, cerous nitrate, ammonium cerous nitrate or cerous sulfate, or a mixture of two or more thereof.

[0073] The titanium source is any one of titanyl sulfate, titanium sulfate, and tetrabutyl titanate, or a mixture of two or more thereof.

[0074] On the other hand, the above catalyst is used to simultaneously remove nitrogen oxides and chlorine-containing volatile organic compounds in industrial waste gas, and the operating temperature is controlled at 250-300°C.

[0075] Under the above conditions, the conversion rate of nitrogen oxides is above 80%, the selectivity of nitrogen is above 80%, the conversion rate of Cl-VOCs is above 70%, and the selectivity of carbon dioxide is above 60%. It can effectively solve the problems of denitrification and removal of chlorinated volatile organic compounds at the same time.

[0076] The catalyst and method for simultaneously removing nitrogen oxides and chlorine-containing volatile organic compounds of the present invention are further described below with reference to specific examples.

[0077] Example 1

[0078] The molar ratio of active components Ce and Co is 0.7:0.4, and the weight of TBOT is 0.7 g.

[0079] The preparation method of the catalyst comprises the following steps:

[0080] S1: Dissolve 0.7 mmol Ce(NO3)3·6H2O in 150 mL of anhydrous ethanol under stirring. At the same time, add 0.4 mmol K3[Co(CN)6] and 1 g of polyvinyl pyrrolidone (PVP, K-30) to 100 mL of deionized water and stir for 30 minutes. Then, drop the Ce(NO3)3·6H2O alcohol solution into the mixed solution of K3[Co(CN)6] and deionized water and stir vigorously for 20 minutes.

[0081] S2: The mixed solution obtained in S1 was placed at ambient temperature for 24 hours, the white precipitate was collected by centrifugation, and washed twice with anhydrous ethanol / water. After drying at 60°C overnight, white Ce3[Co(CN)6]2-nH2O powder was obtained.

[0082] S3: 0.1 g of the hexagonal bipyramidal structure of Ce3[Co(CN)6]2-nH2O of S2 was dispersed in 20 mL of anhydrous ethanol and treated with ultrasound for 30 min to form a turbid solution.

[0083] S4: 3 mL of deionized water was added to the turbid solution prepared in S3, and after stirring for 30 minutes, 0.7 g of tetrabutyl titanate (TBOT) dissolved in 10 ml of ethanol was dropped into the mixed solution. After aging for 2 hours, the precipitate was collected by centrifuge.

[0084] S5: The precipitate prepared in S4 was washed three times with ethanol and then dried at 80 °C for 12 h. The obtained off-white powder is Ce3[Co(CN)6]2-nH2O@TiO2.

[0085] S6: After calcining at 400°C at a rate of 1°C / min for 3 hours, Ce3[Co(CN)6]2-nH2O@TiO2 was obtained, which was named CeCoOx-P@TiO2.

[0086] Example 2

[0087] The catalyst for simultaneously removing nitrogen oxides and chlorine-containing volatile organic compounds in this embodiment is prepared by referring to the preparation method of Example 1, except that steps S3-S5 are not performed, and the powder of S2 is directly calcined. The catalyst does not contain TiO2. It is named CeCoOx-P.

[0088] Example 3

[0089] The catalyst for simultaneously removing nitrogen oxides and chlorine-containing volatile organic compounds in this embodiment is prepared by referring to the preparation method of Example 1, except that PVP is not added in step S1. The obtained catalyst is named CeCoOx@TiO2.

[0090] Comparative Example 1

[0091] The catalyst for simultaneously removing nitrogen oxides and chlorine-containing volatile organic compounds in this comparative example is prepared by referring to the method of Example 1, except that the weight of tetrabutyl titanate is 0 g and the amount of PVP added is 0 g. The obtained catalyst is named CeCoOx.

[0092] Comparative Example 2

[0093] This comparative example provides a catalyst for simultaneously removing nitrogen oxides and chlorine-containing volatile organic compounds, wherein the catalyst uses oxides of Co and Ce as active components. The molar ratio of the active components Ce and Co is 0.7:0.4, the weight of TiO2 is 1g, and the amount of PVP added is 0g. Specific preparation method:

[0094] 1) Weigh 0.7 g TiO2, 0.303 g Ce(NO3)3·6H2O, and 0.116 g Co(NO3)2·6H2O, dissolve them in 100 mL deionized water, and stir to obtain solution A;

[0095] 2) Then, 100 mL of dilute ammonia solution was dropped into the solution under stirring and aged for 48 hours, and the resulting suspension was filtered at room temperature, and then the residue was washed;

[0096] 3) Dry at 80°C for 12 hours, heat to 400°C at a rate of 1°C / min and calcine for 3 hours to obtain a solid powder, which is named CeCoO x / TiO2.

[0097] Experimental Example 1

[0098] This experimental example tests the catalytic performance of the catalysts prepared in Examples 1-3 and Comparative Examples 1 and 2.

[0099] Test conditions: Flue gas composition: [NO] = [NH3] = 300ppm, [Cl-VOCs] = 100ppm (Cl-VOCs is o-dichlorobenzene), [O2] = 16%, N2 as balance gas, total flue gas flow rate of 200mL / min, reaction space velocity of 30000h -1 The test process was carried out in a fixed bed reactor, the reaction temperature range was 100℃-400℃, and the reaction stayed at each temperature for 1 hour until the reaction equilibrium. The test results are as follows Figure 1-4 , Figure 5 The following are scanning electron microscope images of the catalysts obtained in Examples 1-5.

[0100] Depend on Figure 1 and Figure 2 It can be seen that the catalyst of the present invention has excellent low-temperature NH3-SCR and Cl-VOCs oxidation performance, achieving a nitrogen oxide removal rate of more than 65% in the temperature range of 175-350°C, and a chlorine-containing volatile organic matter removal rate of more than 50% in the temperature range of 200-400°C. In particular, between 250-300°C, the removal rates of chlorine organic matter and nitrogen oxides can reach more than 80% at the same time, the selectivity of CO2 is greater than 60%, and the selectivity of N2 is greater than 80%.

[0101] Experimental Example 2

[0102] This experimental example tests the catalytic performance of the catalysts prepared in Examples 1 and 2 and Comparative Example 2.

[0103] Test conditions: Flue gas composition: [NO] = [NH3] = 300ppm, [Cl-VOCs] = 100ppm (Cl-VOCs is o-dichlorobenzene), [O2] = 16%, N2 as balance gas, total flue gas flow rate of 200mL / min, reaction space velocity of 30000h -1 To investigate the water resistance of the catalyst, water vapor with a volume fraction of 5% was introduced. The test process was carried out in a fixed bed reactor at a reaction temperature of 300°C. The test results are shown in Figure 6 shown.

[0104] Figure 6 In the figure, curves 2, 4, and 6 respectively represent the removal rates of nitrogen oxides of the catalysts prepared in Example 1, Example 2, and Comparative Example 2, and curves 1, 3, and 5 respectively represent the removal rates of o-dichlorobenzene of the catalysts prepared in Example 1, Example 2, and Comparative Example 2.

[0105] As shown in the figure, in a water-containing atmosphere, the dechlorination effect of the catalyst of Example 1 is almost unaffected, and the removal rate of nitrogen oxides is reduced by about 8.4%. The dechlorination effect and nitrogen oxide removal rate of the catalyst of Comparative Example 2 are both reduced, especially, the removal rate of nitrogen oxides is significantly reduced, and after the water is removed, the removal rate of nitrogen oxides is also reduced. The dechlorination effect of the catalyst of Example 2 is almost unaffected, and the removal rate of nitrogen oxides is reduced by about 15.6%. Therefore, the catalyst prepared by the present invention has water resistance.

[0106] Experimental Example 3

[0107] This experimental example tests the long-term catalytic performance of the catalysts prepared in Examples 1 and 2 and Comparative Example 2.

[0108] Test conditions: Flue gas composition: [NO] = [NH3] = 300ppm, [Cl-VOCs] = 100ppm (Cl-VOCs is o-dichlorobenzene), [O2] = 16%, N2 as balance gas, total flue gas flow rate of 200mL / min, reaction space velocity of 30000h -1 The test process was carried out in a fixed bed reactor at a reaction temperature of 300°C and the stability of the catalyst was tested for 60 hours. Figure 7 shown.

[0109] Figure 7 In the figure, curves 2, 4, and 6 respectively represent the removal rates of nitrogen oxides of the catalysts prepared in Example 1, Example 2, and Comparative Example 2, and curves 1, 3, and 5 respectively represent the removal rates of o-dichlorobenzene of the catalysts prepared in Example 1, Example 2, and Comparative Example 2.

[0110] As shown in the figure, within 60 hours, the dechlorination effect of the catalyst of Example 1 has basically no significant change, and the removal rate of nitrogen oxides has slightly decreased, and is basically above 80%. The dechlorination effect and nitrogen oxide removal rate of the catalyst of Comparative Example 2 have both significantly decreased. The dechlorination effect of the catalyst of Example 2 has no significant change, but the removal rate of nitrogen oxides is very low. Therefore, the catalyst prepared by the present invention has high stability and can be used for a long time.

[0111] In all the drawings, o-DCB on the coordinate axis represents ortho-dichlorobenzene.

Claims

1. A catalyst for removing nitrogen oxides and chlorine-containing volatile organic compounds, comprising oxides of Co and Ce and TiO2, wherein: At least part of the outer surface of the Co and Ce oxides is covered by TiO2; Preferably, in the catalyst, the molar ratio of Ce element to Co element is (0.5-2): (0.1-1); More preferably, the molar ratio of Ce element to Co element is (1.5-3):

1.

2. The catalyst according to claim 1, characterized in that The overall appearance of the catalyst shows a hexagonal bipyramidal structure; Preferably, in the catalyst, the content of TiO2 is greater than 0 and less than or equal to 5 wt.%. Preferably, in the catalyst, the content of TiO2 is 1wt.%-4wt.%.

3. A method for preparing the catalyst according to claim 1, comprising: 1) mixing a soluble salt containing a Co element and polyvinyl pyrrolidone or a citrate, and then mixing with a soluble salt containing a Ce element, and allowing to stand to obtain a first precipitate, and drying the precipitate to obtain a solid powder; 2) After the solid powder is dispersed in the solution, it is mixed with a titanium-containing substance, and a second precipitate is generated after standing. The second precipitate is dried and calcined to obtain a catalyst.

4. The preparation method according to claim 3, characterized in that: In step (1), in step (1), the mass ratio of the amount of cobalt element to polyvinyl pyrrolidone is (0.35-1.4): 1 mmol / g; preferably, the mass ratio of the amount of cobalt element to polyvinyl pyrrolidone is (0.35-0.5): 1 mmol / g; In step (1), the mass ratio of the amount of cobalt element to citrate is (0.35-1.4):1 mmol / g; preferably, the mass ratio of the amount of cobalt element to citrate is (0.35-0.5):1 mmol / g.

5. The preparation method according to claim 3, characterized in that: In step (1), a soluble salt containing the Co element and polyvinyl pyrrolidone or citrate are dissolved in an aqueous solvent, and then fully mixed with an alcohol solution of a soluble salt containing the Ce element, and allowed to stand to obtain a first precipitate.

6. The preparation method according to claim 3, characterized in that: After the obtained first precipitate is washed with alcohol water, it is dried at a temperature ranging from 60 to 105° C.; The drying temperature of the second precipitate is 80-105°C.

7. The preparation method according to claim 3, characterized in that: In step (2), the solid powder of step (1) is first dispersed in anhydrous ethanol to form a suspension, and then water is added to the suspension; Preferably, under ultrasonic conditions, the solid powder of step (1) is first dispersed in anhydrous ethanol to form a suspension.

8. The preparation method according to claim 3, characterized in that: In step (2), the mass ratio of solid powder to tetrabutyl titanate is (0.02-2):

1. Preferably, the mass ratio of solid powder to tetrabutyl titanate is (0.14-0.2):

1.

9. The preparation method according to claim 3, characterized in that: The calcination temperature of the second precipitate is controlled at 400-550°C; Preferably, the calcination time is controlled at 2.5 hours to 4 hours; More preferably, the heating rate during the calcination process is controlled at 1-2°C / min.

10. Use of the catalyst according to claim 1 for simultaneously removing nitrogen oxides and chlorine-containing volatile organic compounds from industrial waste gas, wherein the operating temperature is controlled at 250-300°C.

Images