SCR catalyst and preparation method thereof

Abstract

The invention discloses an SCR catalyst and a preparation method thereof, and relates to the technical field of flue gas purification, the SCR catalyst comprises a titanium dioxide carrier and transition metal oxides loaded on the titanium dioxide carrier, the transition metal oxides comprise a first transition metal oxide and a second transition metal oxide, the first transition metal oxide comprises vanadium oxide and tungsten oxide, and the second transition metal oxide comprises at least one of manganese oxide, iron oxide, molybdenum oxide and cerium oxide. The SCR catalyst provided by the invention can keep activity at a low temperature of 150 DEG C of tail gas, and has good denitration performance and durability in a high-temperature and high-water sulfur-containing environment; the denitration efficiency reaches 55% or above after the catalyst is exposed for 2 h under the conditions that the volume ratio of water vapor is 18% or below, the concentration of sulfur dioxide is 400 ppm or below and the temperature is 150 DEG C.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas purification, and in particular to an SCR catalyst and a preparation method thereof. Background Art

[0002] Nitrogen oxides (NO x ) is one of the main air pollutants. A large amount of nitrogen oxides accumulated in the air for a long time will cause environmental problems such as photochemical pollution, haze, acid rain and greenhouse effect, which are extremely harmful to human health and environmental safety. With the increasingly stringent emission standards for air pollutants, the requirement of "ultra-low emission" has made NO x Emission reduction work faces new challenges. At present, the ultra-low emission transformation of my country's power industry is nearing completion, while ultra-low emission in non-power industries is still in its early stages. The share of pollution emissions from non-power industries such as metallurgy continues to increase, which means that flue gas treatment in non-power industries will become the main battlefield for air pollution control in the next few years.

[0003] Selective catalytic reduction (SCR) technology is the most effective denitrification technology at present, and its core is the catalyst. Although traditional SCR catalysts have been widely used in flue gas denitrification in the power industry, this catalyst is a medium-high temperature catalyst with a reaction temperature of 300-400°C, which is difficult to apply to the low-temperature flue gas denitrification needs of non-power industries. In addition, traditional SCR catalysts are easily deactivated by SO2 and water poisoning under low temperature conditions, which has become a major problem for denitrification in non-power industries such as waste incineration, sintering, metallurgy, and cement. Summary of the invention

[0004] The main purpose of the present invention is to provide an SCR catalyst and a preparation method thereof, aiming to solve the problem that the existing SCR catalyst is easily deactivated due to sulfur dioxide and water poisoning under low temperature conditions.

[0005] To achieve the above-mentioned object, the present invention provides an SCR catalyst, which includes a titanium dioxide carrier and a transition metal oxide loaded on the titanium dioxide carrier, wherein the transition metal oxide includes a first transition metal oxide and a second transition metal oxide, wherein the first transition metal oxide includes vanadium oxide and tungsten oxide, and the second transition metal oxide includes at least one of manganese oxide, iron oxide, molybdenum oxide and cerium oxide.

[0006] In one embodiment, in the SCR catalyst, the mass ratio of the titanium dioxide support to the transition metal oxide is 100:(2-15); and / or,

[0007] In the transition metal oxide, the ratio of the sum of the amount of tungsten oxide and the second transition metal oxide to the amount of vanadium oxide is (1-2):1; and / or,

[0008] The second transition metal oxide includes at least one of manganese dioxide, iron oxide, molybdenum oxide and cerium oxide.

[0009] The present invention also provides a method for preparing the SCR catalyst as described above, comprising the following steps:

[0010] S10, mixing titanium dioxide, a first transition metal oxide source, and a second transition metal oxide source with water to obtain a mixed solution;

[0011] S20, subjecting the mixed solution to a hydrothermal reaction and drying to obtain a precursor;

[0012] S30, calcining the precursor to obtain an SCR catalyst.

[0013] In one embodiment, in step S10, the first transition metal oxide source includes a vanadium salt and a tungsten salt, wherein:

[0014] The vanadium salt comprises at least one of ammonium metavanadate and sodium metavanadate; and / or,

[0015] The tungsten salt includes at least one of ammonium tungstate and sodium tungstate.

[0016] In one embodiment, in step S10, the second transition metal oxide source includes at least one of manganese nitrate, manganese sulfate, manganese acetate, ferric nitrate, ferric sulfate, ferric acetate, ammonium metamolybdate, sodium molybdate, cerium chloride, cerium oxalate and cerium nitrate.

[0017] In one embodiment, the step S10 includes:

[0018] Titanium dioxide, a first transition metal oxide source and a second transition metal oxide source are mixed with water, and an acid additive is added to obtain a mixed solution.

[0019] In one embodiment, in step S10:

[0020] The pH value of the mixed solution is 1 to 2; and / or,

[0021] The acid additive includes at least one of hydrochloric acid and oxalic acid.

[0022] In one embodiment, in step S20:

[0023] The temperature of the hydrothermal reaction is 160°C to 200°C; and / or,

[0024] The hydrothermal reaction time is 12h to 24h; and / or,

[0025] The drying temperature is 60°C to 120°C; and / or,

[0026] The drying time is 12h to 24h.

[0027] In one embodiment, in step S30:

[0028] The calcination temperature is 300°C to 550°C; and / or,

[0029] The calcination time is 2h to 8h.

[0030] In one embodiment, the step S10 includes:

[0031] S101, mixing titanium dioxide and water to obtain solution A;

[0032] S102, mixing a first transition metal oxide source with water to obtain a solution B;

[0033] S103, mixing a second transition metal oxide source with water to obtain a solution C;

[0034] S104, adding solution B and solution C to solution A in sequence and mixing them to obtain a mixed solution.

[0035] In the technical solution provided by the present invention, vanadium oxide and tungsten oxide are loaded on a titanium dioxide carrier, and the second transition metal oxide including at least one of manganese oxide, iron oxide, molybdenum oxide and cerium oxide is loaded. By jointly loading the above transition metal oxides, the obtained SCR catalyst can maintain activity at a low temperature of 150°C at the tail gas temperature, and has good denitration performance and durability in a high temperature, high water and sulfur-containing environment; when the volume ratio of water vapor is within 18%, the sulfur dioxide concentration is within 400ppm, and the denitration efficiency reaches more than 55% after exposure for 2 hours at 150°C. Therefore, the SCR catalyst provided by the present invention can meet the low-temperature flue gas denitration needs of the non-electric industry, and the reaction temperature is 150-230°C, with the effect of low-temperature sulfur resistance and water resistance. DETAILED DESCRIPTION

[0036] To make the purpose, technical scheme and advantages of the embodiment of the present invention clearer, the technical scheme in the embodiment of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiment, it is carried out according to the normal conditions or the conditions recommended by the manufacturer. If the reagents or instruments used do not specify the manufacturer, they are all conventional products that can be purchased commercially. In addition, the meaning of "and / or" appearing in the full text includes three parallel schemes, taking "A and / or B" as an example, including scheme A, or scheme B, or schemes that A and B meet at the same time. In addition, the technical schemes between the various embodiments can be combined with each other, but must be based on the ability of ordinary technicians in the field to achieve. When the combination of technical solutions is contradictory or cannot be achieved, it should be considered that the combination of such technical solutions does not exist, and is not within the scope of protection required by the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present invention.

[0037] Nitrogen oxides (NO x ) is one of the main air pollutants. A large amount of nitrogen oxides accumulated in the air for a long time will cause environmental problems such as photochemical pollution, haze, acid rain and greenhouse effect, which are extremely harmful to human health and environmental safety. With the increasingly stringent emission standards for air pollutants, the requirement of "ultra-low emission" has made NO x Emission reduction work faces new challenges. At present, the ultra-low emission transformation of my country's power industry is nearing completion, while ultra-low emission in non-power industries is still in its early stages. The share of pollution emissions from non-power industries such as metallurgy continues to increase, which means that flue gas treatment in non-power industries will become the main battlefield for air pollution control in the next few years.

[0038] Selective catalytic reduction (SCR) technology is the most effective denitrification technology at present, and its core is the catalyst. Although traditional SCR catalysts have been widely used in flue gas denitrification in the power industry, this catalyst is a medium-high temperature catalyst with a reaction temperature of 300-400°C, which is difficult to apply to the low-temperature flue gas denitrification needs of non-power industries. In addition, traditional SCR catalysts are easily deactivated by SO2 and water poisoning under low temperature conditions, which has become a major problem for denitrification in non-power industries such as waste incineration, sintering, metallurgy, and cement.

[0039] In view of this, the present invention proposes a low-temperature sulfur-resistant and water-resistant SCR catalyst, aiming to solve the problem that the existing SCR catalyst is easily deactivated due to sulfur dioxide and water poisoning under low-temperature conditions.

[0040] The SCR catalyst provided by the present invention includes a titanium dioxide carrier and a transition metal oxide loaded on the titanium dioxide carrier, wherein the transition metal oxide includes a first transition metal oxide and a second transition metal oxide, wherein the first transition metal oxide includes vanadium oxide and tungsten oxide, and the second transition metal oxide includes at least one of manganese oxide, iron oxide, molybdenum oxide and cerium oxide.

[0041] In the technical solution provided by the present invention, the first transition metal oxide vanadium oxide and tungsten oxide are loaded on the titanium dioxide carrier, and at least one of manganese oxide, iron oxide, molybdenum oxide and cerium oxide is loaded. By loading the above transition metal oxides, the obtained SCR catalyst can maintain activity at a low temperature of 150°C at the tail gas temperature, and has good denitration performance and durability in a high temperature, high water and sulfur-containing environment; when the volume ratio of water vapor is within 18%, the sulfur dioxide concentration is within 400ppm, and the denitration efficiency reaches more than 55% after exposure for 2 hours at 150°C. Therefore, the SCR catalyst provided by the present invention can meet the low-temperature flue gas denitration needs of the non-electric industry, and the reaction temperature is 150-230°C, with the effect of low-temperature sulfur resistance and water resistance.

[0042] It should be noted that the selective catalytic reduction (SCR) denitration catalyst refers to a catalyst that catalyzes the reaction of nitrogen oxides and ammonia to generate nitrogen and water. The SCR catalyst provided in the present application loads the above-mentioned transition metal oxide in a titanium dioxide carrier, and the transition metal oxide is mainly deposited in the pores of the titanium dioxide carrier, and a small portion of the transition metal oxide may be deposited on the surface of the titanium dioxide carrier, so that in the selective catalytic reduction (SCR) denitration process, ammonia and nitrogen oxide molecules can be effectively adsorbed, making them more likely to react on the surface of the SCR catalyst. The SCR catalyst has a high degree of selectivity for ammonia and nitrogen oxide molecules, and can ensure that the reaction is mainly carried out in the direction of generating nitrogen and water, while avoiding the occurrence of other side reactions.

[0043] Furthermore, in the SCR catalyst, the mass ratio of the titanium dioxide carrier to the transition metal oxide is 100:(2-15), specifically, the mass ratio of the titanium dioxide carrier to the transition metal oxide can be 100:2, 100:6, 100:10, 100:12, 100:15, etc. As the loading amount of the transition metal oxide on the titanium dioxide carrier increases, the activity of the catalyst will first increase and then decrease. Within a certain range, the increase in loading allows more active sites to be exposed to the reaction system, thereby improving the catalytic efficiency; however, when the loading amount is too high, the number of effective active sites may be reduced, and the catalytic activity will be reduced. Therefore, the mass ratio of the titanium dioxide carrier to the transition metal oxide can improve the catalytic activity of the SCR catalyst within the above range.

[0044] In the transition metal oxide, the ratio of the sum of the amounts of tungsten oxide and the second transition metal oxide to the amount of vanadium oxide is (1-2):1. It should be noted that in the transition metal oxide, the amount of vanadium oxide is n1, the amount of tungsten oxide is n2, and the amount of the second transition metal oxide is n3, (n1): (n2+n3) is 1: (1-2), specifically, (n1): (n2+n3) can be 1:1, 1:1.5, 1:2, etc. The ratio of the sum of the amounts of tungsten oxide and the second transition metal oxide to the amount of vanadium oxide is within the above range, which can make the obtained SCR catalyst have better catalytic activity in a low temperature, high sulfur and high water environment. Preferably, when the ratio of the sum of the amounts of tungsten oxide and the second transition metal oxide to the amount of vanadium oxide is 1:1, the obtained SCR catalyst can have better catalytic activity in a low temperature, high sulfur and high water environment.

[0045] The second transition metal oxide includes at least one of manganese dioxide (MnO2), iron oxide (Fe2O3), molybdenum oxide (MoO3) and cerium oxide (CeO2). By loading vanadium oxide and tungsten oxide on the titanium dioxide carrier, and loading at least one of manganese dioxide, iron oxide, molybdenum oxide and cerium oxide, the denitration performance and durability of the SCR catalyst in a high-temperature, high-water and sulfur-containing environment can be better improved.

[0046] The present invention also provides a method for preparing the SCR catalyst as described above, the method for preparing the SCR catalyst comprising the following steps:

[0047] S10, mixing titanium dioxide, a first transition metal oxide source, and a second transition metal oxide source with water to obtain a mixed solution;

[0048] S20, subjecting the mixed solution to a hydrothermal reaction and drying to obtain a precursor;

[0049] S30, calcining the precursor to obtain an SCR catalyst.

[0050] Furthermore, in the step S10, titanium dioxide and water may be mixed, the first transition metal oxide source and water may be mixed, and the second transition metal oxide source and water may be mixed to obtain three solutions respectively, and then the three solutions may be mixed. That is, the step S10 includes:

[0051] S101, mixing titanium dioxide and water to obtain solution A;

[0052] S102, mixing a first transition metal oxide source with water to obtain a solution B;

[0053] S103, mixing a second transition metal oxide source with water to obtain a solution C;

[0054] S104, adding solution B and solution C to solution A in sequence and mixing them to obtain a mixed solution.

[0055] By adopting the above mixing method, each transition metal oxide source can be fully dispersed in water, so that in the obtained SCR catalyst, each transition metal oxide can be evenly loaded in the titanium dioxide carrier, thereby improving the catalytic activity of the SCR catalyst.

[0056] Further, the first transition metal oxide source includes a vanadium salt and a tungsten salt, wherein the vanadium salt includes at least one of ammonium metavanadate and sodium metavanadate, and using at least one of ammonium metavanadate and sodium metavanadate as the vanadium salt has the effects of easy availability and stability of the raw materials, controllable preparation process, and excellent product performance. The tungsten salt includes at least one of ammonium tungstate and sodium tungstate. Using at least one of ammonium tungstate and sodium tungstate as the tungsten salt has the effects of easy availability and stability of the raw materials, and excellent product performance.

[0057] Further, in step S10, the second transition metal oxide source includes at least one of manganese nitrate, manganese sulfate, manganese acetate, ferric nitrate, ferric sulfate, ferric acetate, ammonium metamolybdate, sodium molybdate, cerium chloride, cerium oxalate and cerium nitrate. It should be noted that in the specific preparation process, the material of the second transition metal oxide source can be selected as needed. When vanadium, tungsten and iron are loaded in the titanium dioxide carrier, the second transition metal oxide source can be selected from at least one of iron nitrate, iron sulfate and iron acetate; when vanadium, tungsten and manganese are loaded in the titanium dioxide carrier, the second transition metal oxide source can be selected from at least one of manganese nitrate, manganese sulfate and manganese acetate; when vanadium, tungsten and molybdenum are loaded in the titanium dioxide carrier, the second transition metal oxide source can be selected from at least one of ammonium metamolybdate and sodium molybdate; when vanadium, tungsten and cerium are loaded in the titanium dioxide carrier, the second transition metal oxide source can be selected from at least one of cerium chloride, cerium oxalate and cerium nitrate; when vanadium, tungsten, cerium and iron are loaded in the titanium dioxide carrier, the second transition metal oxide source can be selected from at least one of cerium chloride, cerium oxalate and cerium nitrate and at least one of iron nitrate, iron sulfate and iron acetate, etc. The use of the above-mentioned second transition metal oxide source can better load the required transition metal oxide in the titanium dioxide carrier.

[0058] It should be noted that when ammonium metavanadate and ammonium tungstate are used as the first transition metal oxide source and ferric nitrate is used as the second transition metal oxide source, the mass ratio of titanium dioxide, ammonium metavanadate, ammonium tungstate and ferric nitrate is 60-80:12-20:12-20:6-10, so that the obtained SCR catalyst meets the above loading conditions. The above is only an example and is not intended to limit the technical solution of the present application. When the second transition metal oxide source is selected from other substances, other mass ratios can also be used, as long as the obtained SCR catalyst meets the above loading conditions.

[0059] Further, the step S10 comprises: mixing titanium dioxide, a first transition metal oxide source and a second transition metal oxide source with water, and adding an acid additive to obtain a mixed solution. By adding an acid catalyst, the pH of the mixed solution can be adjusted so that each substance in the mixed solution can be fully dissolved, which can not only reduce the loss of raw materials, but also make the transition metal oxide more evenly loaded on the titanium dioxide carrier.

[0060] Furthermore, in step S10: the pH value of the mixed solution is 1 to 2; such a setting can make all substances in the mixed solution fully dissolved. Among them, the mass ratio of the acid additive to the titanium dioxide is 1: (50 to 200), and the acid additive can also be first dissolved in water and then added to the reaction system to obtain a mixture with a specific pH value. Specifically, the mass ratio of the acid additive to the titanium dioxide can be 1: 50, 1: 100, 1: 150, 1: 200, etc., as long as the various substances in the mixed solution can be fully dissolved during the addition process and the pH of the mixed solution is 1 to 2. The acid additive includes at least one of hydrochloric acid and oxalic acid. Using at least one of hydrochloric acid and oxalic acid is not only economical and easy to obtain, but also can better dissolve the various substances in the mixed solution. The above conditions can be set separately or simultaneously. When set simultaneously, the effect is better.

[0061] Furthermore, the mixture can be subjected to ultrasonic vibration before the hydrothermal reaction to promote uniform mixing. Wherein, the temperature of the hydrothermal reaction is 160°C to 200°C; the time of the hydrothermal reaction is 12h to 24h. Specifically, the temperature of the hydrothermal reaction can be 160°C, 170°C, 180°C, 190°C, 200°C, etc., and the time of the hydrothermal reaction can be 12h, 16h, 18h, 20h, 24h, etc. The hydrothermal reaction time is too short or the temperature is too low, which will lead to too low loading of the transition metal oxide, thereby resulting in low activity of the SCR catalyst; the hydrothermal reaction time is too long or the temperature is too high, which will lead to too large particle size, thereby affecting the activity of the SCR catalyst. When the temperature of the hydrothermal reaction is 160°C to 200°C and the time of the hydrothermal reaction is 12h to 24h, the obtained SCR catalyst can not only have a higher loading, but also have a suitable particle size, so that the particle size is less than 2 microns, thereby being able to improve the activity of the SCR catalyst from multiple angles.

[0062] Furthermore, the mixed solution after the hydrothermal reaction can be centrifugally washed with water before drying until the pH is neutral. Wherein, the drying temperature is 60°C to 120°C; the drying time is 12h to 24h. Specifically, the drying temperature can be 60°C, 80°C, 100°C, 120°C, etc., and the drying time can be 12h, 16h, 18h, 20h, 24h, etc. Within the above drying temperature and time range, a uniform drying effect can be achieved, and the temperature will not be too high, causing the surface of the SCR catalyst particles to dry quickly while the inside is moist, nor will the temperature be too low, causing the drying process to be too slow.

[0063] In step S30, the precursor needs to be calcined to obtain an SCR catalyst. The calcination temperature is 300°C to 550°C, and the calcination time is 2h to 8h. Specifically, the calcination temperature can be 300°C, 400°C, 500°C, 550°C, etc., and the calcination time can be 2h, 4h, 6h, 8h, 24h, etc. If the calcination temperature is too low, the crystallinity of the catalyst will deteriorate, thereby affecting its stability and durability, and may also lead to a low impurity removal rate in the catalyst, thereby reducing the catalytic efficiency of the catalyst; if the calcination temperature is too high, the internal pore structure of the catalyst will be destroyed, thereby reducing the adsorption and catalytic performance of the catalyst. Therefore, when the calcination temperature is 300°C to 550°C and the calcination time is 2h to 8h, the obtained SCR catalyst can have a good pore structure and crystallinity.

[0064] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to explain the present invention, and are not used to limit the present invention.

[0065] Example 1

[0066] Provided is an SCR catalyst, comprising a titanium dioxide carrier, and a transition metal oxide supported on the titanium dioxide carrier, wherein the transition metal oxide comprises vanadium pentoxide, tungsten oxide (WO3) and iron oxide (Fe2O3), wherein the mass ratio of the titanium dioxide carrier to the transition metal oxide is 100:8, and the amount ratio of the vanadium pentoxide, tungsten oxide (WO3) and iron oxide (Fe2O3) is 1:0.5:0.5.

[0067] Example 2

[0068] Provided is an SCR catalyst, comprising a titanium dioxide carrier, and a transition metal oxide supported on the titanium dioxide carrier, wherein the transition metal oxide comprises vanadium pentoxide, tungsten oxide (WO3) and manganese dioxide (MnO2), wherein the mass ratio of the titanium dioxide carrier to the transition metal oxide is 100:8, and the molar ratio of the vanadium pentoxide, tungsten oxide (WO3) and manganese dioxide (MnO2) is 1:0.5:0.5.

[0069] Example 3

[0070] Provided is an SCR catalyst, comprising a titanium dioxide carrier, and a transition metal oxide supported on the titanium dioxide carrier, wherein the transition metal oxide comprises vanadium pentoxide, tungsten oxide (WO3) and molybdenum oxide (MoO3), wherein the mass ratio of the titanium dioxide carrier to the transition metal oxide is 100:8, and the amount ratio of the vanadium pentoxide, tungsten oxide (WO3) and molybdenum oxide is 1:0.5:0.5.

[0071] Example 4

[0072] Provided is an SCR catalyst, comprising a titanium dioxide carrier, and a transition metal oxide supported on the titanium dioxide carrier, wherein the transition metal oxide comprises vanadium pentoxide, tungsten oxide (WO3) and cerium oxide (CeO2), wherein the mass ratio of the titanium dioxide carrier to the transition metal oxide is 100:8, and the amount ratio of the vanadium pentoxide, tungsten oxide (WO3) and cerium oxide is 1:0.5:0.5.

[0073] Example 5

[0074] Provided is an SCR catalyst, comprising a titanium dioxide carrier, and a transition metal oxide supported on the titanium dioxide carrier, wherein the transition metal oxide comprises vanadium pentoxide, tungsten oxide (WO3), iron oxide (Fe2O3) and cerium oxide (CeO2), wherein the mass ratio of the titanium dioxide carrier to the transition metal oxide is 100:8, and the amount ratio of the vanadium pentoxide, tungsten oxide (WO3), iron oxide (Fe2O3) and cerium oxide (CeO2) is 1:0.5:0.3:0.2.

[0075] Example 6

[0076] A method for preparing the SCR catalyst in Example 1 is provided, comprising the following steps:

[0077] S101, mixing 10 g of titanium dioxide with 50 ml of water to obtain solution A;

[0078] S102, 1.14 g of ammonium metavanadate, 0.22 g of ammonium tungstate and 30 ml of water were mixed to obtain solution B;

[0079] S103, mixing 1.01 g of ferric nitrate nonahydrate with water to obtain a solution C;

[0080] S104, adding solution B and solution C to solution A successively, mixing, stirring evenly, adding 10 g of hydrochloric acid and 5 g of oxalic acid, stirring for 30 min, and obtaining a mixed solution with a pH of 1;

[0081] S20, subjecting the mixed solution to ultrasonic vibration for 2 h, hydrothermal reaction at 180° C. for 12 h, centrifugation and water washing until the pH value is 7, and drying at 100° C. for 12 h to obtain a precursor;

[0082] S30, calcining the precursor at 300° C. for 4 hours to obtain an SCR catalyst.

[0083] Example 7

[0084] A method for preparing the SCR catalyst in Example 2 is provided, wherein the other steps are the same as those in Example 6 except that step S103 is changed to "mix 0.58 g of manganese nitrate tetrahydrate with water to obtain solution C".

[0085] Example 8

[0086] A method for preparing the SCR catalyst in Example 3 is provided, wherein the other steps are the same as those in Example 6 except that step S103 is changed to "mix 0.4 g of ammonium metamolybdate tetrahydrate with water to obtain solution C".

[0087] Example 9

[0088] A method for preparing the SCR catalyst in Example 4 is provided, wherein the other steps are the same as those in Example 6 except that step S103 is changed to "mix 0.38 g of cerium nitrate with water to obtain solution C".

[0089] Example 10

[0090] A method for preparing the SCR catalyst in Example 5 is provided, wherein the other steps are the same as those in Example 6 except that step S103 is changed to "mix 0.15 g of cerium nitrate, 0.61 g of ferric nitrate nonahydrate with water to obtain solution C".

[0091] Embodiment 11

[0092] A method for preparing an SCR catalyst is provided, comprising the following steps:

[0093] S101, mixing 10 g of titanium dioxide with 50 ml of water to obtain solution A;

[0094] S102, 1.14 g of ammonium metavanadate, 0.44 g of ammonium tungstate and 30 ml of water were mixed to obtain solution B;

[0095] S103, mixing 2.01 g of ferric nitrate nonahydrate with water to obtain a solution C;

[0096] S104, adding solution B and solution C to solution A successively, mixing, stirring evenly, adding 10 g of hydrochloric acid and 5 g of oxalic acid, stirring for 30 min, and obtaining a mixed solution with a pH of 1;

[0097] S20, subjecting the mixed solution to ultrasonic vibration for 2 h, hydrothermal reaction at 200° C. for 14 h, centrifugation and water washing until the pH value is 7, and drying at 120° C. for 12 h to obtain a precursor;

[0098] S30, calcining the precursor at 320° C. for 8 hours to obtain an SCR catalyst.

[0099] Example 12

[0100] A method for preparing an SCR catalyst is provided, comprising the following steps:

[0101] S101, mixing 10 g of titanium dioxide with 50 ml of water to obtain solution A;

[0102] S102, 1.14 g of ammonium metavanadate, 0.33 g of ammonium tungstate and 30 ml of water were mixed to obtain solution B;

[0103] S103, mixing 1.5 g of ferric nitrate nonahydrate with water to obtain a solution C;

[0104] S104, adding solution B and solution C to solution A successively, mixing, stirring evenly, adding 10 g of hydrochloric acid and 5 g of oxalic acid, stirring for 30 min, and obtaining a mixed solution with a pH of 1;

[0105] S20, subjecting the mixed solution to ultrasonic vibration for 2 h, hydrothermal reaction at 160° C. for 24 h, centrifugation and water washing until the pH value is 7, and drying at 60° C. for 24 h to obtain a precursor;

[0106] S30, calcining the precursor at 550° C. for 2 hours to obtain an SCR catalyst.

[0107] Comparative Example 1

[0108] A method for preparing an SCR catalyst is provided, wherein step S103 is deleted and step S104 is changed to "S104, solution B is added to solution A, mixed, and stirred evenly, and then 10 g of hydrochloric acid and 5 g of oxalic acid are added, and stirred for 30 min to obtain a mixed solution with a pH of 1", and other steps are the same as those in Example 6.

[0109] Performance Testing

[0110] The SCR activity test was carried out using the SCR catalysts prepared in Examples 6 to 12 and Comparative Example 1. The raw gas components were NOx (400 ppm), NH3 (400 ppm), O2 (18 vol.%), SO2 (400 ppm), N2 as the balance gas, the total gas flow rate was 500 mL / min, the catalyst dosage was 1 g, and the reaction space velocity was 160000 h -1 , reaction temperature 150°C. The denitration efficiency of the catalyst was tested at 150°C for 5.5h, and the results are shown in Table 1.

[0111] Table 1 Denitration efficiency of SCR catalysts prepared in Examples 6 to 12 and Comparative Example 1

[0112]

[0113]

[0114] It can be seen from Table 1 that the denitration efficiency of the SCR catalysts provided in Examples 6 to 12 reaches more than 55% at 150°C, and the denitration efficiency of the SCR catalyst provided in Comparative Example 1 is only 29.6% at 150°C. Therefore, the SCR catalyst provided in the present application has good denitration performance in a low temperature environment with sulfur dioxide and water.

[0115] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. An SCR catalyst, characterized in that: The SCR catalyst includes a titanium dioxide carrier and a transition metal oxide supported on the titanium dioxide carrier, wherein the transition metal oxide includes a first transition metal oxide and a second transition metal oxide, wherein the first transition metal oxide includes vanadium oxide and tungsten oxide, and the second transition metal oxide includes at least one of manganese oxide, iron oxide, molybdenum oxide and cerium oxide.

2. The SCR catalyst according to claim 1, characterized in that In the SCR catalyst, the mass ratio of the titanium dioxide carrier to the transition metal oxide is 100:(2-15); and / or, In the transition metal oxide, the ratio of the sum of the amount of tungsten oxide and the second transition metal oxide to the amount of vanadium oxide is (1-2):1; and / or, The second transition metal oxide includes at least one of manganese dioxide, iron oxide, molybdenum oxide and cerium oxide.

3. A method for preparing an SCR catalyst as claimed in claim 1 or 2, characterized in that: The following steps are involved: S10, mixing titanium dioxide, a first transition metal oxide source, and a second transition metal oxide source with water to obtain a mixed solution; S20, subjecting the mixed solution to a hydrothermal reaction and drying to obtain a precursor; S30, calcining the precursor to obtain an SCR catalyst.

4. The method for preparing the SCR catalyst according to claim 3, characterized in that: In step S10, the first transition metal oxide source includes a vanadium salt and a tungsten salt, wherein: The vanadium salt comprises at least one of ammonium metavanadate and sodium metavanadate; and / or, The tungsten salt includes at least one of ammonium tungstate and sodium tungstate.

5. The method for preparing the SCR catalyst according to claim 3, characterized in that: In the step S10, the second transition metal oxide source includes at least one of manganese nitrate, manganese sulfate, manganese acetate, ferric nitrate, ferric sulfate, ferric acetate, ammonium metamolybdate, sodium molybdate, cerium chloride, cerium oxalate and cerium nitrate.

6. The method for preparing the SCR catalyst according to claim 3, characterized in that: The step S10 comprises: Titanium dioxide, a first transition metal oxide source and a second transition metal oxide source are mixed with water, and an acid additive is added to obtain a mixed solution.

7. The method for preparing the SCR catalyst according to claim 3, characterized in that: In step S10: The pH value of the mixed solution is 1 to 2; and / or, The acid additive includes at least one of hydrochloric acid and oxalic acid.

8. The method for preparing the SCR catalyst according to claim 3, characterized in that: In step S20: The temperature of the hydrothermal reaction is 160°C to 200°C; and / or, The hydrothermal reaction time is 12h to 24h; and / or, The drying temperature is 60°C to 120°C; and / or, The drying time is 12h to 24h.

9. The method for preparing the SCR catalyst according to claim 3, characterized in that: In step S30: The calcination temperature is 300°C to 550°C; and / or, The calcination time is 2h to 8h.

10. The method for preparing the SCR catalyst according to claim 3, characterized in that: The step S10 comprises: S101, mixing titanium dioxide and water to obtain solution A; S102, mixing a first transition metal oxide source with water to obtain a solution B; S103, mixing a second transition metal oxide source with water to obtain a solution C; S104, adding solution B and solution C to solution A in sequence and mixing them to obtain a mixed solution.

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