Flue gas and tail gas purification catalyst, method and application

Abstract

The invention discloses a flue gas and tail gas purification catalyst, a method and application. A method for preparing a flue gas and tail gas purification catalyst through low-temperature and low-power microwave calcination comprises the following steps that a catalyst blank formed by raw materials comprising a carrier and active ingredients is put into a microwave reaction furnace, microwave calcination is started under the conditions that the power of the microwave reaction furnace is set to be 30-200 W, the final temperature is 110-200 DEG C, and the calcination time is 180-500 min, and the catalyst blank is cooled to the room temperature to obtain the flue gas and tail gas purification catalyst. And stopping microwave calcination after the set calcination time reaches the set final temperature to obtain the flue gas and tail gas purification catalyst. According to the invention, the flue gas and tail gas purification catalyst can be prepared by microwave calcination at lower temperature and lower power.

Description

Technical Field

[0001] The present invention relates to a flue gas and tail gas purification catalyst, a method and an application thereof, and in particular to a method for preparing a flue gas and tail gas purification catalyst by low-temperature and low-power microwave calcination, a flue gas and tail gas purification catalyst and an application thereof. Background Art

[0002] Flue gas purification is to reduce or adsorb the nitrogen oxides that have been generated in the tail flue gas, thereby reducing NOx emissions. Flue gas denitrification can be carried out by catalytic reduction, that is, catalytic reduction using a flue gas purification catalyst.

[0003] Microwave heating has the characteristics of fast heating speed, small heat loss and convenient operation. Microwave heating generates heat by using the energy consumed by the electromagnetic field of the dielectric material itself. Microwave heating is a "cold heat source". When it is generated and contacts an object, it is not a stream of hot air, but electromagnetic energy. It has a series of unique advantages that traditional heating does not have. Usually, in order to speed up the heating speed, the temperature must be increased, but it is easy to cause the outside to burn and the inside to not heat up. Microwave heating generates heat based on the dielectric loss of the material itself. Except for very large objects, it can generally achieve uniform heating inside and outside.

[0004] CN111821997A discloses a method for preparing a demercuration and denitration catalyst, comprising: 1) adding Ce(NO3)3·6H2O to deionized water, adding an appropriate amount of oxalic acid; then adding 5(NH4)2O·12WO3·5H2O and Cu(NO3)2 to prepare an impregnation solution; then adding TiO2 to prepare a mixed solution; and microwave treatment; 2) stirring, drying, roasting, and cooling the mixed solution after microwave treatment. Although this method uses microwave heating, it is used to treat the mixed solution, and it still needs to be dried and roasted in a muffle furnace. Moreover, the power of its microwave treatment is relatively high (600-800W).

[0005] CN109046370A discloses a preparation process of a natural gas distributed energy flue gas denitration catalyst, comprising: 1) using a high-energy ball milling method to grind activated alumina, a zeolite molecular sieve containing transition metal oxides, and an iron-nickel-chromium composite oxide into a composite powder, and then adding silica sol, mannitol gum, silicon oxide fine powder, water-soluble phenolic resin and deionized water, and mixing to obtain a plastic mud; 2) filtering impurities from the plastic mud obtained in step 1), kneading mud, and aging; 3) extruding the mud obtained in step 2) to obtain a honeycomb wet blank; 4) microwave drying the honeycomb wet blank obtained in step 3) for 6 to 8 minutes, and then steam drying for 4 to 6 days to obtain a shaped blank; 5) roasting the shaped blank obtained in step 4) at 550 to 650°C to obtain an energy flue gas denitration catalyst. In this preparation process, the wet blank is dried by microwave, steam dried, and then roasted at high temperature.

[0006] CN103464194A discloses a low-temperature flue gas denitrification SCR integral honeycomb catalyst and a preparation method thereof, with TiO2 and molecular sieve as carriers, MnO2 and Fe2O3 as main active ingredients, and a combination of one or more of ZrO2, NiO, WO3, CoO and CeO2 as auxiliary active ingredients; (1) the precursors of the carrier, the main active ingredient and the auxiliary active ingredient are prepared with additives in proportion and dry mixed; (2) a plastic wet mass is kneaded; (3) the plastic wet mass is successively extruded through large and small sieve plates or transferred to a vacuum mud kneading machine for mixing to obtain a dense and uniform degassed mud segment; (4) the degassed mud segment is extruded to obtain an integral honeycomb catalyst blank; (5) the blank is dried and then subjected to microwave treatment; and then calcined after microwave treatment. In the preparation method, microwave treatment is first used, and then microwave calcined at a relatively high power of 300 to 700 W. The number of microwave treatments is relatively large, and the calcination power is still relatively high. Summary of the invention

[0007] In view of this, one object of the present invention is to provide a method for preparing a flue gas purification catalyst by low-temperature and low-power microwave calcination, which method can obtain a flue gas purification catalyst with good performance by only one low-temperature and low-power microwave treatment, and the catalyst has a large specific surface area and high axial compressive strength. Another object of the present invention is to provide a flue gas purification catalyst prepared according to the method as described above. Another object of the present invention is to provide an application of the flue gas purification catalyst obtained as above in flue gas denitrification.

[0008] The present invention adopts the following technical solutions to achieve the above-mentioned purpose.

[0009] In one aspect, the present invention provides a method for preparing a flue gas purification catalyst by low-temperature and low-power microwave calcination, comprising the following steps:

[0010] A catalyst body formed by raw materials including a carrier and an active ingredient is placed in a microwave reactor, and microwave calcination is started when the power of the microwave reactor is set to 30-200 W, the terminal temperature is set to 110-200° C., and the calcination time is set to 180-500 min. The microwave calcination is stopped after the set calcination time reaches the set terminal temperature to obtain a flue gas exhaust purification catalyst.

[0011] According to the method of the present invention, preferably, the active ingredient is selected from salts or oxides of metal elements; the metal element is selected from at least one of tungsten, molybdenum, zirconium, vanadium, manganese, platinum, palladium, rhodium, cerium, lanthanum, praseodymium, neodymium and yttrium.

[0012] According to the method of the present invention, preferably, the carrier is selected from at least one of titanium dioxide, aluminum oxide, zirconium dioxide, titanium zirconium powder, layered graphite and diatomaceous earth.

[0013] According to the method of the present invention, preferably, the mass ratio of the carrier to the active component is (60-95):(0.1-15).

[0014] According to the method described in the present invention, preferably, the raw materials for forming the catalyst body also include a molding aid, a pore-forming agent and a binder; the mass of the molding aid is 1 to 15 wt% of the mass of the carrier; the mass of the pore-forming agent is 0.5 to 3 wt% of the mass of the carrier; the mass of the binder is 0.4 to 2.1 wt% of the mass of the carrier.

[0015] According to the method of the present invention, preferably, the catalyst body is prepared by the following steps:

[0016] (1) Providing a solution containing an active ingredient;

[0017] (2) kneading raw materials including a carrier and a solution containing an active ingredient to obtain a kneaded slurry;

[0018] (3) filtering the mixed clay material, vacuum kneading it, sealing it, and aging it; extruding the aged clay material into a shape to obtain a catalyst body.

[0019] According to the method of the present invention, preferably, the power of the microwave reaction furnace is set to 80-200W.

[0020] According to the method of the present invention, preferably, the terminal temperature of the microwave reaction furnace is set to 150-200° C.; and the calcination time is set to 300-500 min.

[0021] On the other hand, the present invention also provides a flue gas and exhaust gas purification catalyst, which is prepared according to the method for preparing the flue gas and exhaust gas purification catalyst by low-temperature and low-power microwave calcination as described above.

[0022] In another aspect, the present invention further provides an application of the flue gas exhaust purification catalyst as described above in flue gas exhaust denitrification.

[0023] The present invention can realize the preparation of flue gas and tail gas purification catalyst by microwave calcination at low temperature and low power, the temperature can be lower than 200°C, the power can be lower than 200W, and energy saving and consumption reduction are obvious. The present invention realizes automatic adjustment by setting the power, end temperature and calcination time of the microwave reactor at the same time, which is conducive to automatic control. In addition, the present invention is simple to operate, has good repeatability, and the quality of the obtained product is stable. In addition, compared with the electric kiln equipment used in actual production, the temperature and time are greatly reduced, and low carbon can be achieved. DETAILED DESCRIPTION

[0024] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0025] Microwave heating mainly achieves calcination results through electric field strength and dielectric properties of materials. During the calcination process, electric field parameters are not directly affected by temperature, but dielectric properties of materials will change greatly with temperature, thus affecting the entire calcination process. At low temperatures, dielectric loss changes little with temperature. When the temperature reaches a certain critical temperature, the local conductivity of the material increases due to crystal softening and amorphous tendency. Dielectric loss increases exponentially with rising temperature, which is beneficial to calcination. However, if dielectric loss increases too much with rising temperature, thermal runaway will occur, which should be noted and avoided during microwave calcination. It is not a conventional choice to use microwave reaction conditions for different materials to obtain better performance of the flue gas purification catalyst.

[0026] The present invention provides a method for preparing a flue gas purification catalyst by low-temperature and low-power microwave calcination, which comprises the following steps: a microwave calcination step. Optionally, it also comprises a catalyst blank preparation step. The method is described in detail below.

[0027] <Catalyst body preparation steps>

[0028] In the present invention, the catalyst body is formed from raw materials including a carrier and an active component. The catalyst body described in the present invention is not particularly limited.

[0029] In the present invention, the active ingredient is selected from a salt or oxide of a metal element, preferably a salt of a metal element. For example, it may be a nitrate, a carbonate, a sulfate, a chloride, or an acid ammonium salt. The metal element may be selected from at least one of tungsten, molybdenum, zirconium, vanadium, manganese, platinum, palladium, rhodium, cerium, lanthanum, praseodymium, neodymium, and yttrium. Preferably, the metal element is selected from one or more of tungsten, molybdenum, zirconium, vanadium, manganese, platinum, palladium, rhodium, cerium, lanthanum, praseodymium, neodymium, and yttrium. More preferably, the metal element is selected from a plurality of tungsten, molybdenum, vanadium, cerium, and lanthanum.

[0030] According to a specific embodiment of the present invention, the metal elements in the active component only include tungsten, molybdenum, vanadium and cerium.

[0031] In the present invention, the carrier can be selected from one of titanium dioxide, aluminum oxide, zirconium dioxide, titanium zirconium powder, layered graphite and diatomaceous earth. Preferably, the carrier is selected from one of titanium dioxide, aluminum oxide and titanium zirconium powder. In some embodiments, the carrier is titanium dioxide. In other embodiments, the carrier is titanium zirconium powder. According to a specific embodiment of the present invention, the carrier is a powder.

[0032] In the present invention, the mass ratio of the carrier to the active ingredient may be (60-95):(0.1-15), preferably (60-95):(0.5-10), and more preferably (60-95):(0.6-7). This is conducive to forming a flue gas purification catalyst with better performance.

[0033] In the present invention, the raw materials for forming the catalyst body may also include a molding aid, a pore former and a binder, and may also include other required aids. The molding aid, the pore former and the binder may be those known in the art. In certain embodiments, the molding aid may be selected from at least one of glass fiber and pulp fiber. The pore former may be selected from one of polyethylene oxide, carboxymethyl cellulose and ethyl cellulose. The binder may be selected from one of carboxymethyl cellulose, nano silica sol, aluminum hydroxide sol, polyethylene glycol and starch. The mass of the molding aid may be 1 to 15 wt % of the mass of the carrier, preferably 2 to 13 wt %, and more preferably 5 to 10 wt %. The mass of the pore former may be 0.5 to 3 wt % of the mass of the carrier, preferably 1.0 to 2.5 wt %, and more preferably 1.2 to 2.0 wt %. The mass of the binder may be 0.4 to 2.1 wt % of the mass of the carrier, preferably 0.5 to 1.6 wt %, and more preferably 0.6 to 1.3 wt %.

[0034] In the present invention, the preparation method of the catalyst body is not particularly limited, and the catalyst body can be obtained by mixing raw materials including a carrier and an active ingredient, kneading, degassing or aging, and then extruding and molding.

[0035] According to one embodiment of the present invention, the catalyst body can be prepared by the following steps: (1) providing a solution containing an active ingredient; (2) mixing raw materials including a carrier and a solution containing an active ingredient to obtain a mixed mud; (3) filtering the mixed mud, vacuum kneading, sealing, and aging; extruding the aged mud to obtain a catalyst body. Wherein, stirring is performed during mixing, and mixing can be performed at room temperature. The pH value of the mixed mud is controlled to be 7 to 8. In the present invention, ammonia water can be used to adjust the pH value of the mud. The solution containing the active ingredient is an aqueous solution containing the active ingredient. When the solution of the active ingredient is prepared, it can be heated to 60 to 100°C, preferably 60 to 90°C. The moisture content of the mixed mud is controlled to be 28 to 29%. In the present invention, drying can be performed after extrusion molding to obtain a catalyst body after drying. The drying temperature can be 20 to 70°C.

[0036] According to a specific embodiment of the present invention, the catalyst body of the present invention can be prepared according to the Chinese patent application with application number CN201911021202.3 (the invention name is rare earth-based low vanadium medium and low temperature flue gas denitration catalyst and its preparation method), and the content of preparing the catalyst body is introduced here in full. Specifically including: (1) preparation of active solution; heating pure water to 70-90°C, adding cerium precursor cerium nitrate or cerium carbonate, stirring, dissolving, adding tungsten precursor ammonium paratungstate or ammonium metatungstate, molybdenum precursor ammonium heptamolybdate, stirring, so that it fully reacts, recorded as active component solution A; adding pure water and interface agent to the reactor, when the temperature reaches 60-70°C, adding ammonium metavanadate to the reactor, stirring the mixed solution in the container, heating to about 90-100°C, keeping the temperature unchanged, and stirring continuously for 30-40 minutes until it is completely dissolved, recorded as active component solution B ; (2) Mixing the clay; weigh the carrier, release agent, Ba(OH)2, and pure water, add them to the mixer, and mix at high speed; weigh the carrier again, add it, slowly add the active component solution A, add ammonia water, and mix; add the molding aid, interface agent, and active component solution B, and mix; add the adhesive and pore-forming agent, and mix at high speed; add the adhesive and pore-forming agent again, and mix at low speed to control the moisture content of the clay to 28-29%; (3) After filtering and vacuum kneading, seal the mixed clay and age it; extrude the aged clay into a catalyst blank through a strong extruder. Among them, the release agent is stearic acid; the molding aid is glass fiber and / or wood pulp; the interface agent is monoethanolamine; the adhesive is carboxymethyl cellulose; and the pore-forming agent is polyethylene oxide. In the present invention, active component and active ingredient have the same meaning.

[0037] <Microwave Calcination Step>

[0038] The catalyst body (the catalyst body as described above, formed by raw materials including carriers and active ingredients) is placed in a microwave reactor, microwave calcination is started when the power of the microwave reactor is set to 30-200W, the terminal temperature is 110-200°C, and the calcination time is 180-500min, and the microwave calcination is stopped after the set calcination time reaches the set terminal temperature, to obtain a flue gas exhaust purification catalyst. In this way, while obtaining a flue gas exhaust purification catalyst with better performance, the power and temperature of microwave calcination can be reduced, which can save energy and reduce consumption. In the prior art, some methods use microwave hydrothermal synthesis, then dry the catalyst body, and then roast it in a muffle furnace at high temperature; some methods use drying treatment of the catalyst body, and then calcination at high temperature in a mesh belt kiln; some methods use a drying oven to dry the catalyst body, and then microwave roasting at a higher power. These existing methods have high energy consumption, and some methods have the problem of easily causing cracks in the catalyst.

[0039] In the present invention, the power of the microwave reactor is set to 30-200W, preferably 60-200W, and more preferably 80-200W. For example, it can be 50W, 60W, 80W, 90W, 100W, 120W, 130W, 150W, 170W, 180W, 190W, 200W. The end temperature is set to 110-200°C, preferably 115-200°C, and more preferably 120-200°C. For example, it can be 110°C, 115°C, 120°C, 130°C, 150°C, 170°C, 180°C, 190°C, and 200°C. The calcination time is set to 180-500min, preferably 200-500min, and more preferably 260-500min. For example, it can be 200min, 250min, 280min, 300min, 320min, 350min, 380min, 400min, 420min, 450min, 480min, 500min. The present invention has found through a large number of studies and experiments that a flue gas exhaust purification catalyst with a large specific surface area and high axial compressive strength can be obtained under such conditions, and the microwave power and terminal temperature can be significantly reduced. The present invention sets the power, terminal temperature and duration, which is also conducive to automatic control.

[0040] By setting the power, end temperature and duration of the microwave reactor, the microwave reactor automatically controls the heating rate so that the microwave reactor reaches the set end temperature within the set duration. After reaching the set end temperature, the microwave calcination is stopped, and then the product is naturally cooled to room temperature. The product is taken out of the microwave reactor to test the specific surface area and axial compressive strength of the product. The present invention can obtain a flue gas exhaust purification catalyst with a surface free of cracks and a uniform color and a honeycomb or mesh-shaped interior. The specific surface area of ​​the flue gas exhaust purification catalyst obtained by the present invention can reach 60m 2 / g or more, preferably 65m 2 / g or more, more preferably 70m 2 The axial compressive strength can reach 3 MPa or more, preferably 3.5 MPa or more, and more preferably 4 MPa or more.

[0041] The flue gas exhaust purification catalyst obtained by the present invention can be applied to flue gas exhaust denitration. Due to the large specific surface area, it is beneficial to improve the denitration efficiency. Due to the high axial compressive strength, it is beneficial to repeated activation and utilization.

[0042] The test methods used in the following examples are described as follows:

[0043] Specific surface area: tested according to the method of GB / T 31587-2015.

[0044] Axial compressive strength: tested in accordance with GB / T 31587-2015 method.

[0045] In the following examples, the microwave reactor used is from Hunan Zhongsheng Thermal Energy Technology Co., Ltd.

[0046] Preparation Example 1

[0047] The catalyst body was prepared according to Example 2 of CN201911021202.3, as follows:

[0048] Weigh 25.25 kg of cerium nitrate, add 100.0 L of water to dissolve, heat to 85°C, add 25.28 kg of ammonium metatungstate and 24.38 kg of ammonium molybdate, stir to fully react, and record it as active ingredient solution A; take 40.0 L of pure water, add 2 kg of monoethanolamine, weigh 3.16 kg of ammonium metavanadate and add it to the mixed solution, heat, stir to fully dissolve it, and record it as active ingredient solution B.

[0049] In the first mixing, 433 kg of titanium zirconium powder containing 1.5% ZrO2, 6.5 kg of stearic acid, 7.00 kg of lactic acid, and 1.95 kg of barium hydroxide were weighed and added to the mixer, and 150 L of pure water were added, and the mixture was mixed at high speed for 30 min. In the second mixing, 150 kg of titanium zirconium powder containing 1.5% ZrO2 was weighed and added to the mixer, and the active ingredient solution A was slowly added, and 15 kg of ammonia water was added, and the mixture was stirred at high speed for 40 min. In the third mixing, 4.5 kg of pulp fiber as a molding aid was added. g, 39kg of glass fiber, slowly add active ingredient solution B, and stir at high speed for 30min; for the fourth mixing, add 4.5kg of polyethylene oxide and 2.14kg of carboxymethyl cellulose, and stir at high speed for 10min; for the fifth mixing, add 4.5kg of polyethylene oxide and 2.14kg of carboxymethyl cellulose, and stir at high speed for 30min; adjust the pH to 7-8 with ammonia water, control the moisture content at 28.0%, and seal the raw materials after filtration and vacuum kneading, and let them age for 48h.

[0050] The aged raw materials are extruded and formed by a strong extruder, and then dried after packaging, with the drying environment temperature being 20-60°C and the humidity being 80-20%, gradually changing from low temperature and high humidity to high temperature and low humidity, and the drying time being 10 days to obtain a catalyst body.

[0051] Example 1

[0052] The catalyst body obtained in Preparation Example 1 after drying was placed in a microwave reactor, and microwave calcination was started when the power of the microwave reactor was set to 120W, the end temperature was set to 200°C, and the calcination time was set to 420min. The microwave calcination was stopped after the temperature was raised to 200°C at the set time of 420min. After the calcination reaction was completed, it was naturally cooled to room temperature to obtain a finished flue gas exhaust purification catalyst.

[0053] After analysis and testing, the specific surface area of ​​the obtained flue gas exhaust purification catalyst is 73.92m 2 / g, and the axial compressive strength is 3.12MPa.

[0054] Example 1 was repeated three times, and the specific surface areas of the obtained flue gas purification catalysts were 73.92 m 2 / g, 73.91m 2 / g, 73.94m 2 / g, and the axial compressive strengths are 3.12MPa, 3.12MPa, and 3.14MPa, respectively. It can be seen that the method of the present invention has good repeatability and the quality of the obtained product is stable.

[0055] Comparative Example 1

[0056] The microwave calcination was started when the power of the microwave reactor was set to 300W, the terminal temperature was set to 180°C, and the calcination time was set to 420min. The microwave calcination was stopped after the set calcination time reached the set terminal temperature, and the flue gas exhaust purification catalyst under this condition was obtained. The other operating conditions were the same as those in Example 1. The obtained catalyst had two large cracks, and the appearance was judged to be a substandard product, and no analysis and detection was required at this time.

[0057] In the prior art CN109046370A (named Natural Gas Distributed Energy Flue Gas Denitrification Catalyst and Preparation Process thereof), microwaves play a role in the drying process, but microwaves are not mentioned in the calcination process. From a technical point of view, it is impossible to calcine the catalyst at 550-650℃ in the form of microwaves, and there are phenomena of cracking and burning, and it is impossible to obtain qualified products.

[0058] Comparative Example 2

[0059] The only difference from Example 1 is that the terminal calcination temperature of the microwave reaction furnace is set to 90° C. After analysis and testing, the axial compressive strength of the obtained flue gas exhaust purification catalyst is 1.34 MPa, which does not reach the qualified target value of 2.5 MPa and is a substandard product.

[0060] The present invention is not limited to the above-mentioned embodiments. Without departing from the essential content of the present invention, any deformation, improvement and substitution that can be conceived by those skilled in the art shall fall within the scope of the present invention.

Claims

1. A method for preparing a flue gas purification catalyst by low-temperature and low-power microwave calcination, characterized in that: The steps include: A catalyst body formed by raw materials including a carrier and an active ingredient is placed in a microwave reactor, and microwave calcination is started when the power of the microwave reactor is set to 30-200 W, the terminal temperature is set to 110-200° C., and the calcination time is set to 180-500 min. The microwave calcination is stopped after the set calcination time reaches the set terminal temperature to obtain a flue gas exhaust purification catalyst.

2. The method according to claim 1, characterized in that The active ingredient is selected from salts or oxides of metal elements; the metal element is selected from at least one of tungsten, molybdenum, zirconium, vanadium, manganese, platinum, palladium, rhodium, cerium, lanthanum, praseodymium, neodymium and yttrium.

3. The method according to claim 1, characterized in that: The carrier is selected from at least one of titanium dioxide, aluminum oxide, zirconium dioxide, titanium zirconium powder, layered graphite and diatomaceous earth.

4. The method according to claim 1, characterized in that: The mass ratio of the carrier to the active component is (60-95):(0.1-15).

5. The method according to claim 1, characterized in that The raw materials for forming the catalyst body also include a molding aid, a pore former and a binder; the mass of the molding aid is 1 to 15 wt% of the mass of the carrier; the mass of the pore former is 0.5 to 3 wt% of the mass of the carrier; the mass of the binder is 0.4 to 2.1 wt% of the mass of the carrier.

6. The method according to claim 1, characterized in that The catalyst body is prepared by the following steps: (1) Providing a solution containing an active ingredient; (2) kneading raw materials including a carrier and a solution containing an active ingredient to obtain a kneaded slurry; (3) filtering the mixed clay material, vacuum kneading it, sealing it, and aging it; extruding the aged clay material into a shape to obtain a catalyst body.

7. The method according to claim 1, characterized in that The power of the microwave reactor is set to 80-200W.

8. The method according to claim 1, characterized in that The end temperature of the microwave reaction furnace is set to 150-200° C.; the calcination time is set to 300-500 min.

9. A flue gas purification catalyst, characterized in that: The catalyst is prepared according to the method for preparing a flue gas and tail gas purification catalyst by low-temperature and low-power microwave calcination as described in any one of claims 1 to 8.

10. Use of the flue gas purification catalyst according to claim 9 in flue gas denitrification.