CN104941630B - Low-temperature high-activity flue gas denitration catalyst and preparation thereof - Google Patents
Low-temperature high-activity flue gas denitration catalyst and preparation thereof Download PDFInfo
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Abstract
The invention relates to a rare earth-containing flue gas denitration catalyst and preparation thereof, wherein the catalyst takes a carbon-based material as a carrier and is loaded with active Al2O3Any one or more metal active components of Mn, Cu and Fe, and any one or two rare earth active components of Ce and La; wherein, the content of the carbon-based carrier is 35-65%, and the Al is2O3The loading content of the metal active component is 2-5% by the content of the aluminum element, the loading content of the metal active component is 13-26% by the content of the metal element, and the loading content of the rare earth active component is 20-39% by the content of the rare earth element. The catalyst is obtained by activating a carbon-based material by using dilute nitric acid, then coating alumina sol, loading a metal active component and a rare earth active component, and finally drying and calcining in an inert atmosphere. The catalyst is high in flue gas denitration catalytic efficiency at low temperature (90-120 ℃) and not prone to poisoning failure. The production cost is low, the production process is simple, and the method is particularly suitable for large-smoke-amount emission enterprises of thermal power plants, iron and steel plants, sintering plants and the like.
Description
Technical Field
The invention relates to a catalyst in the field of environmental protection, which is mainly used in the field of flue gas denitration, and particularly relates to a low-temperature efficient denitration catalyst and a preparation method thereof.
Background
With the rapid development of Chinese economy, the consumption of coal energy is increased day by day, and sulfur oxides and nitrogen oxides generated in the combustion process of coal are one of main pollution sources causing air pollution, so that the efficient and reasonable control of discharged flue gas becomes an important strategy for modern development at present.
Flue Gas Desulfurization (FGD), limestone/gypsum method is suitable for wide range of coal, stable operation, good operation elasticity, easy access of desulfurizer, and becomes the flue gas desulfurization process with the widest application and the most mature technology in the world at present.
The flue gas denitration is to remove NOXReduction to N2The process mainly comprises the following steps: selective catalytic reduction, non-selective catalytic reduction, acid absorption, alkali absorption, adsorption, plasma activation, and the like. Researchers at home and abroad also develop the microbial treatment of NOXThe method of (1). Among the various processes, Selective Catalytic Reduction (SCR) is the most effective process route for flue gas denitration at present.
The selective catalytic reduction technology is to utilize a reducing agent NH under the action of a catalyst3(liquid ammonia, ammonia water, urea, etc.) and NO in flue gasXReaction, NO in the flue gasXReduction to nitrogen and water. However, the catalyst needs a reactor arranged between the outlet of a boiler economizer and the inlet of an air preheater, the reaction temperature of the commercial catalyst in the current market is higher, generally between 320 and 400 ℃, the denitration efficiency is high, the system is safe and stable, and NO is removedxThe plant must precede dust removal and desulfurization, which results in SO in the flue gasxAnd dust aggravate the poisoning and clogging of the catalyst, reducing the catalytic activity.
The SCR technology research in China is late, and the flue gas denitration market is almost monopolized by foreign technologies. Therefore, it is important to develop a catalyst that can efficiently exhibit denitration performance at low temperature. Low temperature high efficiency removal of NOxThe device can be directly placed on dust removal and SO removalxAfter the device is installed. Currently, the removal of NO from low-temperature flue gasxThe research on the catalyst is not few,mainly MnOx/Al2O3、CuO/AC、Fe2O3/AC、Al2O3A catalyst such as a supported metal halogen compound and activated coke. Among them, the research on the use of activated coke as a catalyst has been put to industrial use in Germany and Japan, but denitration is mainly carried out under the condition of lower than 80 ℃ by virtue of self-adsorption property. For most of boilers with the outlet temperature of 100-280 ℃, the catalytic activity of the active coke is very low, and the applicable space velocity is small (400 h)-1) The operation cost is high.
The prior flue gas denitration catalyst mainly comprises CuO/Al2O3、V2O5/TiO2、V2O5and/AC, etc. CuO as an active component supported on Al2O3In addition, the simultaneous removal of sulfur dioxide and nitrogen oxide in flue gas has been studied extensively to remove SO in flue gas simultaneously2And NOX. The adsorption temperature of the catalyst is 600-750 ℃, the desulfurization and denitrification rate can reach more than 90%, solid and liquid secondary pollution is not generated, thiamine byproducts can be generated, and the catalyst can be recycled. However, after a long run, CuO/Al2O3Surface acidification by alumina leads to SO2The removal capacity of (2) is reduced, the temperature required during application is higher, the device needs to be heated continuously, and the process cost is higher. In addition V2O5/TiO2、V2O5Research on denitration catalysts such as/AC has also been attracting attention. V prepared by taking cordierite honeycomb ceramic as carrier2O5/TiO2/cordierite catalyst, TiO used2Crystal form transformation is easy to occur in the preparation process, so that the yield is reduced, the denitration efficiency is reduced, and meanwhile, alkali metal in the flue gas is easy to poison and inactivate the catalyst under the denitration condition.
The active semicoke is taken as an ideal carrier of a low-temperature dry flue gas denitration catalyst, and V is impregnated by adopting an isometric impregnation method as described in CN1475305A2O5Loading the semi-coke on a forming semi-coke, and filling a catalyst in a fixed bed reactor, wherein the denitration temperature is 150-250 ℃, and the airspeed is 500-5000 h-1。V2O5The denitration efficiency of the/AC catalyst is obviously reduced under the influence of desulfurization products in flue gas, and the catalyst is not suitable for industrial application. Therefore, it is imperative to research a low-temperature, high-efficiency and sulfur poisoning-resistant denitration catalyst.
Disclosure of Invention
The defects of the low-temperature high-efficiency denitration catalyst in the prior art mainly comprise the following 2 aspects:
a) the denitration activity is low;
b) the operating temperature is higher.
In order to solve the technical problems, the invention develops a method for efficiently removing NO at low temperaturexThe catalyst of (1). High denitration efficiency, difficult poisoning failure and simple process. Specifically, the present invention provides the following technical solutions.
A rare earth-containing flue gas denitration catalyst is characterized in that a carbon-based material is used as a carrier and Al is loaded on the carrier2O3One or more metal active components selected from Mn, Cu and Fe, and a rare earth active component selected from any one or both of Ce and La. Wherein the mass content of each component is as follows: the content of the carbon-based carrier is 35-65%, preferably 40-60%, and the Al is2O3The loading content of the metal active component is 2-5%, preferably 3-4% in terms of the content of the aluminum element, the loading content of the metal active component is 13-26%, preferably 21-25% in terms of the content of the metal element, and the loading content of the rare earth active component is 20-39%, preferably 30-39% in terms of the content of the rare earth element.
Preferably, for the catalyst, wherein the carbon-based material is activated semicoke.
Preferably, for the catalyst, the activated carbocoal pore density is 100-300 pores/inch2The specific surface area is 100-500m2/g。
In addition, the present invention provides a method for preparing the catalyst described in any one of the above, comprising the steps of:
a) ultrasonically activating the formed carbon-based material by using 10% -25% nitric acid, ultrasonically dipping at room temperature, and drying;
b)Al2O3loading of sol: based on the step a), carrying out ultrasonic loading on Al by using an excess impregnation method after semicoke activation2O3Sol, drying, calcining and fixing;
c) loading of metal active components: preparing one or more metal compounds in metal Mn/Cu/Fe to be loaded into a metal compound solution, adjusting the pH value to 4-6, soaking the active semicoke into the solution at room temperature in an excessive ultrasonic manner on the basis of the step b), performing suction filtration, drying at constant temperature and calcining;
d) loading of rare earth active components: loading the rare earth active component on the basis of the step c), preparing the rare earth active component into an aqueous solution in advance, and performing ultrasonic excessive dipping loading and drying;
e) calcining the sample obtained in the step d) in an inert atmosphere by using N as inert gas2Or He, the calcination temperature is 350-500 ℃.
Preferably, for the preparation method, wherein, in step b), Al is used2O3The sol solution has a concentration of Al2O31-5% of the mass.
Preferably, for the preparation method, wherein, in the step c), the metal active ingredient is used in the form of an aqueous solution of a metal compound, the solution contains 5% to 10% of the metal active ingredient based on the metal active ingredient.
Preferably, for the preparation process, wherein, in step d), the rare earth active ingredient used is in the form of an aqueous solution of a rare earth compound, the solution contains from 0.5% to 2%, preferably from 1.0 to 1.5% of an aqueous solution of the metal active ingredient, calculated as metal active ingredient.
Preferably, for the preparation method, in the step b), the ultrasonic loading time is 2-3h, the drying is at 110 ℃, and the calcination temperature is 350-450 ℃.
Preferably, in the preparation method, in the step c), the condition pH value of the aqueous solution of the metal in the mixed solution is adjusted by citric acid.
Preferably, in the preparation method, the step d) further comprises adding 1, 4-phthalic acid, which is an acidic ligand, to the rare earth element in advance in a ratio of 1: uniformly mixing the components in a molar ratio of 1.0-2.0, preferably 1:1.0-1.5, and carrying out ultrasonic loading.
Preferably, for the preparation method, wherein, in the step e), the calcination time is 2-4 h.
Preferably, in the preparation method, in the step c), the metal compound solution is in the form of manganese nitrate/copper nitrate or ferric nitrate aqueous solution; in the step d), the rare earth active component is selected from cerium nitrate or cerium oxide, or lanthanum nitrate or lanthanum oxide.
Preferably, for the preparation method, wherein, in the step c), the forging is performed at a temperature of 350-500 ℃.
In addition, the invention also provides the application of the catalyst in flue gas denitration, or denitration and desulfurization at the same time.
Preferably, for the application, the denitration is carried out at 90-120 ℃.
Preferably, for said applications, said denitrification rate is greater than 90%.
That is, the catalyst of the present invention is obtained by activating a carbon-based material with dilute nitric acid, then coating an alumina sol, loading a metal active component and a rare earth active component, and finally drying and calcining under an inert atmosphere. The catalyst is high in flue gas denitration catalytic efficiency at low temperature (90-120 ℃) and not prone to poisoning failure. The production cost is low, the production process is simple, and the method is particularly suitable for large-smoke-amount emission enterprises of thermal power plants, iron and steel plants, sintering plants and the like.
Specifically, the denitration catalyst prepared by the method of the present invention has the following advantages:
1. high denitration activity
The traditional commercial flue gas denitration reaction temperature is generally between 180 ℃ and 400 ℃, the denitration efficiency is obviously reduced when the temperature is lower than 180 ℃, the use temperature of the denitration catalyst is 90-120 ℃, and the denitration efficiency can reach more than 93% in the temperature range. The catalyst has high selectivity, and the treated tail gas can be directly exhausted.
2. Low denitration reaction temperature
The traditional commercial flue gas denitration reaction temperature is generally between 320 ℃ and 400 ℃, the use temperature of the denitration catalyst is 90 ℃ to 120 ℃, and NO is in the temperature rangexThe removal rate can reach more than 93 percent, and NO is removed at the temperature of less than 150 DEG CxThe removal rate remained almost unchanged.
3. Simple process
The traditional flue gas denitration reactor needs to be arranged between the outlet of a boiler economizer and the inlet of an air preheater, and the denitration catalyst can be directly used for heating after traditional flue gas desulfurization. No secondary pollutants such as waste water, solid wastes, dust and the like are generated.
Drawings
FIG. 1 is a schematic view showing an outline of a process for producing a denitration catalyst according to the present invention;
fig. 2 is a flow chart of preparation of a denitration catalyst according to a preferred embodiment of the present invention.
Detailed Description
The denitration catalyst is mainly prepared by the process shown in figure 1, namely, semi-coke is activated firstly, and then Al is coated2O3Then coating active components on the surface of the substrate, and drying and calcining the substrate.
To solve the above technical problems, preferred embodiments of the present invention are specifically as follows:
(1) the utility model provides a high-efficient flue gas denitration catalyst of low temperature that contains tombarthite which characterized in that: using carbon-based material as catalyst carrier and loading Al2O3One or more of metals Mn, Cu and Fe are used as active components, one or more of rare earth Ce and La are additionally added as active component auxiliaries, and the mass content of each component is as follows: wherein the carbon-based material is 35-65%, preferably 40-60%, and the Al2O3The loading content of the metal active component is 2-5%, preferably 3-4% in terms of the content of the aluminum element, the loading content of the metal active component is 13-26%, preferably 21-25% in terms of the content of the metal element, and the loading content of the rare earth active component is 20-39%, preferably 30-39% in terms of the content of the rare earth element.
Wherein the active components are loaded by respectively adding Al2O3The sol solution, the metal active component solution and the rare earth active component solution are loaded on a carbon-based carrier to prepare the catalyst carrier.
Among them, for the carbon-based carrier in the present invention, all kinds of semi-cokes conventionally formed from coal mines in the art, such as semi-cokes formed from lignite or anthracite, can be used in the present invention.
Preferably, the mass concentration (mass fraction) of the prepared solution when loaded on the carrier and the content of the used carbon-based carrier are as follows:
the content of the carbon-based carrier is 85-90%;
5% -10% of metal active component;
0.5-2% of rare earth active component auxiliary agent;
Al2O3the content of the solution is 1-5%.
(2) Preferred material characteristics of the catalyst described in the above (1) are as follows:
a) the carbon-based material mainly uses active semicoke, and the specific surface area is 100-500m2/g；
b) The metal salt is soluble manganese nitrate;
c) the rare earth active auxiliary agent is cerium nitrate and lanthanum nitrate;
(3) the preferred catalysts according to (1) and (2) are specifically prepared by the steps shown in figure 1, and figure 1 is a brief description of the preparation method of the denitration catalyst, which comprises the steps of semi-coke activation, alumina solution coating, active component loading and drying and calcining; the details are as follows:
a) ultrasonically activating the formed semicoke by using 10-25% nitric acid, ultrasonically dipping for 2-4h at room temperature, and then drying for 1.5-3h at constant temperature of 110 ℃;
b) on the basis of the step a), the activated semicoke is subjected to excessive impregnation to load Al2O3Sol, supported Al2O3The mass fraction of the sol solution is 1-5%, preferably 1.5-5%, most preferably 1.5-2.5%, and the sol solution is dried and calcined (preferably calcined) at 110 deg.C after ultrasonic loading for 2-3hThe burning temperature is 350-;
c) the compound of the metal Mn is prepared into a certain mass fraction (the solution concentration is 5-10 percent, preferably 7-10 percent in terms of Mn element; also possible with Cu or Fe compound solutions) Mn/H2O mixed solution, citric acid to adjust the pH value to 4-6, ultrasonic excess impregnation is carried out at room temperature on the basis of the step b), drying is carried out at the constant temperature of 110 ℃, and then calcination (preferably the calcination temperature is 350-500 ℃) is carried out for 1.5-3 h;
d) loading the rare earth active component on the basis of the step c). The rare earth is rare earth nitrate, the rare earth nitrate is prepared into an aqueous solution with the mass fraction of 0.5-2%, preferably 0.5-1.5%, and the aqueous solution is subjected to ultrasonic excessive dipping loading and drying;
e) optionally, during step d), it is also preferable to add an acidic ligand, 1, 4-phthalic acid, previously mixed with the rare earth active ingredient in a ratio of 1: uniformly mixing the raw materials in a ratio of 1.0-2.0, preferably 1: 1.0-1.5;
f) calcining the sample obtained in the step d) for 2-4h in an inert atmosphere, wherein the inert gas is N2Or He, the calcination temperature is 350-500 ℃.
g) The obtained catalyst is subjected to flue gas denitration activity detection at the temperature of 90-120 ℃, and NO isXThe removal rate is more than 90 percent.
How the catalyst of the present invention is prepared will be described below by way of specific examples, and as shown in FIG. 2, a flow chart of a method for preparing the denitration catalyst of examples 1 to 4 of the present invention; the following examples are specifically detailed:
example 1:
a commercial semicoke was mechanically formed (from the manufacturer: DeRunTeku Equipment Co., Ltd., Yulin, Shanxi, the same applies to the following examples, which contained, by mass, 17.96% of moisture, 20.12% of ash, 29.19% of volatile matter, 50.69% of fixed carbon, 1.20% of total sulfur) at a pore density of 100 to 300 pores/inch2. Soaking the semi-coke carrier in 20% dilute nitric acid for 2 hr, ultrasonic (SB-25-12 DT, 20-80KHz, Ningbo Xinzhi Biotechnology Co., Ltd.) at room temperature for 2 hr, and drying at constant temperature of 110 deg.C for 2 hr; on the basis, the activated semicoke is subjected to excessive impregnation to load Al2O3Sol is prepared by mixing Al with mass fraction of 1%2O3Carrying out ultrasonic loading on the solution for 2h, then drying at 110 ℃ and calcining for 3h for fixation at 400 ℃; preparing a soluble Mn salt into an aqueous solution with the mass fraction of 5 percent (calculated by the manganese content), wherein the soluble Mn salt is manganese nitrate. Ultrasonically dipping the manganese nitrate solution at 30 ℃ for 2h, then drying at constant temperature of 110 ℃ for 2h and calcining at 450 ℃ for 3 h; preparing soluble cerium salt into 2% aqueous solution by mass fraction, wherein the soluble Ce salt is Ce (NO)3)3·6H2Adjusting the pH value to 4 by using citric acid, carrying out ultrasonic excessive impregnation loading for 2h, drying at 110 ℃ for 2h, and calcining at 450 ℃ for 3 h; calcining in N2And (4) in an atmosphere.
The loading amounts of the Al element, the metal Mn element and the rare earth Ce element on the carrier are respectively 2.10%, 21.3% and 32.5% as determined by an X-ray spectrometer EDS (signal processing line). The NOx removal performance of the catalyst is tested in a catalyst evaluation test system built in a laboratory to obtain NOxThe conversion was 91%.
Example 2:
mechanically forming the commercial semicoke with the hole density of 100-300 holes/inch2Activating with 10% dilute nitric acid, ultrasonically soaking at room temperature for 4h, and drying at constant temperature of 110 deg.C for 2 h; on the basis, the activated semicoke is subjected to excessive impregnation to load Al2O3Sol, Al used2O3The mass fraction is 1.5%, after ultrasonic loading for 2h, drying for 2h at 110 ℃, and calcining for 2h for fixation at 400 ℃; the soluble manganese nitrate is prepared into an aqueous solution with the mass fraction of 7% in terms of manganese content, ultrasonic impregnation is carried out for 3 hours at the room temperature of 30 ℃ on the basis, drying is carried out for 2 hours at the constant temperature of 110 ℃, and calcination is carried out for 3 hours at the temperature of 450 ℃; adding Ce (NO)3)3·6H2O and the used acidic ligand 1, 4-phthalic acid are mixed uniformly in a molar ratio of 1:1.5 in advance to prepare the mixture containing Ce (NO)3)3The water solution with the mass fraction of 2 percent, the pH value of citric acid is adjusted to be 6, the water solution is soaked and loaded for 2 hours by ultrasonic excess, dried for 3 hours at the temperature of 110 ℃ and calcined for 2 hours at the temperature of 450 ℃; calcining in N2The preparation is carried out in an atmosphere;
the load amounts of the Al element, the metal Mn element and the rare earth Ce element on the carrier are determined by EDS, and the load amounts of the Al element, the metal Mn element and the rare earth Ce element are respectively 3.05%, 17.6% and 38.4%. The NOx removal performance of the catalyst is tested in a catalyst evaluation test system built in a laboratory to obtain NOxThe conversion was 93%.
Example 3:
mechanically forming the commercial semi-coke with the pore density of 100-2Taking 25% dilute nitric acid to excessively dip the semi-coke for activation, performing ultrasonic dipping activation for 3 hours at room temperature, and then drying for 2 hours at constant temperature of 110 ℃; the activated semicoke is carried out excessive impregnation loading Al2O3Sol, Al used2O3The mass fraction is 2%, after ultrasonic loading for 2h, drying for 3h at 110 ℃, and calcining for 3h at 450 ℃ for fixation; immersing the carrier into a soluble manganese nitrate solution, wherein the solution is a pre-prepared water solution with the mass fraction of 8 percent in terms of manganese content, carrying out ultrasonic impregnation for 2h at the room temperature of 30 ℃ on the basis, drying for 3h at the constant temperature of 110 ℃, and calcining for 3h for fixation at the temperature of 350 ℃; ce (NO) will be preceded3)3·6H2O and the used acidic ligand 1, 4-phthalic acid are uniformly mixed according to the molar ratio of 1:2.0 to prepare the mixture containing Ce (NO)3)3The water solution with the mass fraction of 1.5 percent, and the pH value is adjusted to 5 by citric acid; carrying out ultrasonic excessive impregnation loading for 2h, drying at 110 ℃ for 3h and calcining at 500 ℃ for 2 h; calcining in N2Under the atmosphere;
the load amounts of the Al element, the metal Mn element and the rare earth Ce element on the carrier are determined by EDS, and the load amounts of the Al element, the metal Mn element and the rare earth Ce element are respectively 3.7%, 23.6% and 26.9%. The NOx removal performance of the catalyst is tested in a catalyst evaluation test system built in a laboratory to obtain NOxThe conversion was 92%.
Example 4:
mechanically forming the commercial semi-coke to obtain the semi-coke with the pore density of 100-2The carrier is prepared by taking 15% dilute nitric acid to excessively impregnate semicoke for activation, ultrasonically impregnating and activating for 3h at room temperature, and then drying for 2h at constant temperature of 110 ℃; activated semicoke is processedQuantitative immersion loading of Al2O3Sol, Al used2O32.5 percent by mass, carrying out ultrasonic loading for 2 hours, drying at 110 ℃, calcining at 350 ℃ for 3 hours, and fixing; the carrier is immersed in a soluble manganese nitrate solution, wherein the solution is a pre-prepared aqueous solution with the mass fraction of 9 percent of manganese content. Performing ultrasonic impregnation for 3h at room temperature of 30 ℃ on the basis, drying for 3h at constant temperature of 110 ℃, and calcining for 2h for fixation at 350 ℃; ce (NO) is preliminarily formed3)3·6H2O and the acidic ligand 1, 4-benzenedicarboxylic acid used are as follows: 1.0 mol ratio, and is prepared into a mixture containing Ce (NO)3)3The water solution with the mass fraction of 1.5 percent, and the pH value is adjusted to be 4 by citric acid; carrying out ultrasonic excessive impregnation loading for 2h, drying at 110 ℃ for 3h and calcining at 350 ℃ for 2 h; the resulting vector is in N2Calcining in an inert gas atmosphere;
the load amounts of the Al element, the metal Mn element and the rare earth Ce element on the carrier are determined by EDS, and the load amounts of the Al element, the metal Mn element and the rare earth Ce element are respectively 4.26%, 24.8% and 37.9%. The NOx removal performance of the catalyst is tested in a catalyst evaluation test system built in a laboratory to obtain NOxThe conversion was 95%.
Example 5:
mechanically forming the commercial semicoke with the hole density of 100-300 holes/inch2Activating with 15% dilute nitric acid, ultrasonically soaking at room temperature for 3h, and drying at constant temperature of 110 deg.C for 2 h; on the basis, the activated semicoke is subjected to excessive impregnation to load Al2O3Sol, Al used2O33 percent of the weight percentage, drying for 2 hours at 110 ℃ after ultrasonic loading for 2 hours, and calcining for 2 hours for fixation at 400 ℃; the soluble copper salt is an aqueous solution with the mass fraction of 5%, and the soluble copper salt with the mass fraction of 5% is copper nitrate and is calculated by the copper content. Performing ultrasonic impregnation for 3h at room temperature of 30 ℃ on the basis, drying for 2h at constant temperature of 110 ℃, and calcining for 3h at 500 ℃; adding Ce (NO)3)3·6H2O and the used acidic ligand 1, 4-phthalic acid are mixed uniformly in a molar ratio of 1:1.5 in advance to prepare the mixture containing Ce (NO)3)3The water solution with the mass fraction of 1.0 percent and the pH value adjusted to 5 by citric acidCarrying out ultrasonic excessive dipping and loading for 2h, drying at 110 ℃ for 3h and calcining at 450 ℃ for 3 h; calcining in N2Under the atmosphere;
the load amounts of the Al element, the metal Cu element and the rare earth Ce element on the carrier are determined by an X-ray energy spectrometer EDS, and the load amounts of the Al element, the metal Cu element and the rare earth Ce element are respectively 4.52%, 24.8% and 30.0%. The NOx removal performance of the catalyst is tested in a catalyst evaluation test system built in a laboratory to obtain NOxThe conversion was 91%.
Example 6:
mechanically forming the commercial semicoke with the hole density of 100-300 holes/inch2Activating with 20% dilute nitric acid, ultrasonically soaking at room temperature for 4h, and drying at constant temperature of 110 deg.C for 2 h; on the basis, the activated semicoke is subjected to excessive impregnation to load Al2O3Sol, Al used2O3The mass fraction is 5%, after ultrasonic loading for 2h, drying for 2h under the condition of 110 ℃, and calcining for 2h for fixation under the condition of 350 ℃; preparing soluble ferric nitrate into an aqueous solution with the mass fraction of 5% in terms of iron content, carrying out ultrasonic impregnation for 3 hours at room temperature and 30 ℃ on the basis, drying for 2 hours at constant temperature of 110 ℃, and calcining for 3 hours at 450 ℃; adding Ce (NO)3)3·6H2O and the used acidic ligand 1, 4-phthalic acid are mixed uniformly in a molar ratio of 1:1.5 in advance to prepare the mixture containing Ce (NO)3)3The water solution with the mass fraction of 0.5 percent, the pH value is adjusted to be 6 by citric acid, the water solution is soaked and loaded for 2 hours by ultrasonic excess, dried for 3 hours at the temperature of 110 ℃ and calcined for 2 hours at the temperature of 450 ℃; calcining in N2Under the atmosphere;
the load amounts of the Al element, the metal Fe element and the rare earth Ce element on the carrier are determined by an X-ray energy spectrometer EDS, and the load amounts of the Al element, the metal Fe element and the rare earth Ce element are 5.23%, 14.8% and 27.2% respectively. The NOx removal performance of the catalyst is tested in a catalyst evaluation test system built in a laboratory to obtain NOxThe conversion was 90%.
Comparative example
Substantially the same as example 1 except that the active ingredient Al was omitted2O3The prepared catalyst is used for denitration evaluation, and the denitration rate of the prepared catalyst reachesTo 83%.
The performance evaluation method comprises the following steps:
the catalysts prepared in examples 1 to 4 above were subjected to evaluation of denitration performance in accordance with the following procedures:
putting the catalyst prepared in the process into a fixed bed reactor, heating to 90 ℃, starting aeration, taking 10 ℃ as a temperature step, and measuring NO of the catalyst within the range of 90-150 DEG CxAnd (4) removing performance. Wherein the simulated smoke under normal pressure comprises the following components: 850ppm/min NOx; 950ppm/min NH3；30ml/min O2；N2968ml/min，N2Is the balance gas. When in test, the airspeed is 10000h-1(ii) a Test duration 72h, NOxThe removal rate was > 90% (91%, 93%, 92%, 95%, 91% and 90% for the catalysts of examples 1-6, respectively), and none of the catalysts prepared in examples 1-6 was deactivated.
The simulated gas passes through the gas mixing chamber before being introduced into the fixed bed reactor, is fully mixed and preheated to 90 ℃ (the temperature is the same as that of the reaction system).
Said catalyst NOxThe removal rate is calculated, and NO in the inlet flue gas is respectively measured by a testo350 flue gas analyzerxContent and NO in outlet flue gasxContent of, in the final product Process, converted NOxAmount of (i) i.e. NOxRemoval rate (conversion rate calculated as a change in the content of NO, which is a main component contained in nitrogen oxides).
The catalysts of examples 1-4 were not deactivated, meaning that the activity of the catalyst remained unchanged after 72h of the test.
NO Using the catalysts of examples 1-4 evaluated as abovexThe activity of the conventional commercial vanadium tungsten titanium catalyst was evaluated under the same conditions and apparatus for removal rate, and the results were as follows:
1. the catalyst has high denitration activity
The traditional commercial flue gas denitration reaction temperature is generally 180-400 ℃ (the model of the traditional commercial tungsten titanium catalyst (anatase titanium dioxide) is PC-200, the selling manufacturer is Shanghai Pengbo titanium dioxide Co., Ltd.), the denitration efficiency is obviously reduced when the temperature is lower than 180 ℃, the use temperature of the denitration catalyst is 90-120 ℃, and the denitration efficiency can reach more than 93% in the temperature range. The catalyst has high selectivity, and the treated tail gas can be directly exhausted.
2. The denitration reaction temperature of the catalyst is low
The traditional commercial flue gas denitration reaction temperature is generally between 320 and 400 ℃ (the model of the traditional commercial vanadium-titanium catalyst is TX100, and sold by Shanghai Sabo chemical industry), the use temperature of the denitration catalyst is between 90 and 120 ℃, and NO is generated in the temperature rangexThe highest removal rate can reach more than 93 percent, and NO is generated under the condition that the temperature is lower than 150 DEG CxThe removal rate remained almost unchanged.
3. Simple process
The traditional flue gas denitration reactor needs to be arranged between the outlet of a boiler economizer and the inlet of an air preheater, and the denitration catalyst can be directly used for heating after traditional flue gas desulfurization. No secondary pollutants such as waste water, solid wastes, dust and the like are generated.
Claims (19)
1. A rare earth-containing flue gas denitration catalyst is characterized in that a carbon-based material is used as a carrier and Al is loaded on the carrier2O3The composite material comprises one or more metal active components selected from Mn, Cu and Fe and a rare earth active component selected from any one or two of Ce and La, wherein the mass content of each component is as follows: 40-60% of carbon-based carrier, and Al2O3The catalyst comprises 3-4% of aluminum element, 21-25% of metal active component and 30-39% of rare earth active component, wherein the total mass content of the components of the catalyst is 100%; the carbon-based material is activated semicoke; the catalyst is prepared by a method comprising the following steps:
a) ultrasonically activating the formed carbon-based material by using 10% -25% nitric acid, ultrasonically dipping at room temperature, and drying;
b) Al2O3loading of sol: based on the step a), carrying out ultrasonic loading on Al by using an excess impregnation method after semicoke activation2O3Sol, drying, calcining and fixing;
c) loading of metal active components: preparing one or more metal compounds in metal Mn/Cu/Fe to be loaded into a metal compound solution, adjusting the pH value to 4-6, soaking the active semicoke into the solution at room temperature in an excessive ultrasonic manner on the basis of the step b), performing suction filtration, drying at constant temperature and calcining;
d) loading of rare earth active components: loading the rare earth active component on the basis of the step c), preparing the rare earth active component into an aqueous solution in advance, and performing ultrasonic excessive dipping loading and drying;
e) calcining the sample obtained in the step d) in an inert atmosphere by using N as inert gas2Or He, the calcination temperature is 350-500 ℃.
2. The catalyst as claimed in claim 1, wherein the activated carbocoal pore density is 100-2The specific surface area is 100-500m2/g。
3. The catalyst according to claim 1 or 2, wherein in step b) Al is used2O3The sol solution has a concentration of Al2O31-5% of the mass.
4. The catalyst according to claim 3, wherein in step c) the metal active component is used in the form of an aqueous solution of a metal compound, which solution contains 5% to 10% metal active component based on the metal active component.
5. The catalyst according to claim 4, wherein in step c) the solution contains 7-10% metal active component based on metal active component.
6. The catalyst as claimed in claim 4, wherein in step d), the rare earth active component is used in the form of an aqueous solution of a rare earth compound, the solution being 0.5% to 2% of the rare earth active component based on the rare earth active component.
7. The catalyst according to claim 4, wherein in step d) the rare earth active component is used in the form of an aqueous solution of a rare earth compound, the solution being an aqueous solution containing 1.0-1.5% of the rare earth active component, calculated on the rare earth active component.
8. The catalyst as claimed in claim 6, wherein in the step b), the ultrasonic loading time is 2-3h, the drying is at 110 ℃, and the calcination temperature is 350-450 ℃.
9. The catalyst as claimed in claim 7, wherein in the step b), the ultrasonic loading time is 2-3h, the drying is at 110 ℃, and the calcination temperature is 350-450 ℃.
10. The catalyst according to claim 8, wherein in step c) the pH is adjusted by citric acid.
11. The catalyst according to claim 9, wherein in step c) the pH is adjusted by citric acid.
12. The catalyst according to claim 10, wherein step d) further comprises adding 1, 4-phthalic acid, an acidic ligand, which has been previously mixed with rare earth elements in a ratio of 1: uniformly mixing the components in a molar ratio of 1.0-2.0, and carrying out ultrasonic loading.
13. The catalyst according to claim 11, wherein the step d) further comprises adding 1, 4-phthalic acid as an acidic ligand, uniformly mixing the acidic ligand with the rare earth element in a molar ratio of 1:1.0-1.5 in advance, and carrying the mixture by ultrasonic.
14. The catalyst according to claim 12, wherein in step e) the calcination is carried out for a time of 2-4 h.
15. The catalyst according to claim 14, wherein in step c), the metal compound solution is in the form of manganese/copper nitrate or ferric nitrate aqueous solution; in the step d), the rare earth active component is selected from cerium nitrate or cerium oxide, or lanthanum nitrate or lanthanum oxide.
16. The catalyst according to claim 15, wherein in step c) the calcination is carried out at a temperature of 350 ℃ and 500 ℃.
17. Use of a catalyst as claimed in any one of claims 1 to 16 for denitration, or simultaneous denitration and desulfurization of flue gas.
18. The use according to claim 17, wherein the denitration is carried out at 90-120 ℃.
19. The use according to claim 18, wherein the denitrification rate is greater than 90%.
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| CN105854874B (en) * | 2016-05-12 | 2018-09-11 | 石河子大学 | Denitrating catalyst and preparation method thereof and the application in denitrating flue gas |
| CN106345488A (en) * | 2016-11-07 | 2017-01-25 | 北京石油化工学院 | Copper-manganese-cerium composite oxide FCC regenerated flue gas combustion-supporting denitration auxiliary agent and preparation method thereof |
| CN106582606B (en) * | 2016-12-28 | 2022-02-08 | 湖北思搏盈环保科技有限公司 | Non-vanadium low-temperature denitration catalyst and preparation method thereof |
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| CN110479299B (en) * | 2019-09-06 | 2021-09-28 | 山东科技大学 | Low-temperature flue gas denitration catalyst and preparation method thereof |
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