CN110354892B - Preparation method of oxide modified MCM-48 molecular sieve and application thereof in denitration and demercuration - Google Patents
Preparation method of oxide modified MCM-48 molecular sieve and application thereof in denitration and demercuration Download PDFInfo
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- B01D53/34—Chemical or biological purification of waste gases
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- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
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- B01J29/00—Catalysts comprising molecular sieves
- B01J29/03—Catalysts comprising molecular sieves not having base-exchange properties
- B01J29/0308—Mesoporous materials not having base exchange properties, e.g. Si-MCM-41
- B01J29/0341—Mesoporous materials not having base exchange properties, e.g. Si-MCM-41 containing arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
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- B01J29/00—Catalysts comprising molecular sieves
- B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
- B01J29/041—Mesoporous materials having base exchange properties, e.g. Si/Al-MCM-41
- B01J29/045—Mesoporous materials having base exchange properties, e.g. Si/Al-MCM-41 containing arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
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- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/08—Heat treatment
- B01J37/10—Heat treatment in the presence of water, e.g. steam
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- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/34—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation
- B01J37/341—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation making use of electric or magnetic fields, wave energy or particle radiation
- B01J37/343—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation making use of electric or magnetic fields, wave energy or particle radiation of ultrasonic wave energy
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- B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
- B01J2229/10—After treatment, characterised by the effect to be obtained
- B01J2229/18—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself
Abstract
The invention discloses a preparation method of an oxide modified MCM-48 molecular sieve and application thereof in denitration and demercuration, and relates to the technical field of molecular sieves. Firstly, pretreating an MCM-48 molecular sieve without removing a template agent; then, taking manganese oxide as an active substance and N oxide as an auxiliary agent to synthesize a MnN mixed solution; adding the mixture into a molecular sieve for dipping treatment and drying; calcining the dried molecular sieve in air; finally obtaining the oxide modified MCM-48 molecular sieve. The oxide modified MCM-48 molecular sieve prepared by the method is used for carrying out NOx and Hg in a simulated flue gas atmosphere0The experiment proves that the denitration and demercuration efficiency test has good demercuration performance in a low-temperature range and high-efficiency removal of NOx.
Description
Technical Field
The invention relates to the technical field of molecular sieves, in particular to a preparation method of a molecular sieve for denitration and cooperative demercuration.
Background
The MCM-48 molecular sieve is a three-dimensional helicoid pore channel structure with uniform pore diameter about 2.6nm and two sets of mutually independent pore channels, has good long-range periodicity and structural characteristics of stable framework, and has good hydrothermal stability and thermal stability, so that the MCM-48 molecular sieve is particularly suitable for high-temperature process and is likely to be developed into an excellent industrial catalyst. The catalyst has very attractive application prospects in the aspects of selective catalysis, macromolecular adsorption separation and the like, and can be used as an adsorbent and a catalytic material to be applied in industry. And because of the large aperture, the heavy metal ions which have large ionic radius and are difficult to be absorbed by the microporous molecular sieve, such as Hg and the like, can be well absorbed from the wastewater. Therefore, the method is hopeful to load macromolecular metal, so as to prepare a novel catalytic material. The MCM-48 molecular sieve has become one of the most important molecular sieve adsorption catalytic materials at present due to a plurality of unique characteristics in the aspects of chemical composition, crystal structure, physicochemical properties and the like.
NOx and the heavy metal Hg, as two typical pollutants in coal combustion flue gas, pose serious hazards to the environment and human health. The emission of NOx into the atmosphere can generate photochemical smog, acid rain and acid mist, damage the ozone layer and have toxic effect on human and animals. Mercury released by coal combustion, mainly as elemental mercury (Hg)0) In addition to their morphological forms, also mercury (Hg) in its combined state+And Hg2+) And mercury in particulate form. Wherein Hg2+Has high water solubility, and the mercury in the particle state can be captured by a dust remover, so the mercury is easy to remove. And Hg in the smoke0The removal is not easy, the pollution is high, and the harm to the environment and human is more. The mercury has the characteristics of high toxicity, easy volatilization and biological enrichment, and is the most harmful element in the human environment, thereby threatening the health of human beings. Although the research of individual denitration and demercuration units of coal-fired flue gas is relatively mature at present; however, in practical engineering application, if each pollutant is provided with an independent removal facility, the system is not only complicated, but alsoAnd the investment and the operation cost are greatly increased, so that the existing denitration facilities can be utilized to expand the mercury pollutant removal function, and the denitration and demercuration integrated multi-pollutant cooperative control is realized.
Currently, Selective Catalytic Reduction (SCR) is considered one of the most effective NOx reduction methods. Typical commercial SCR catalyst V2O5-WO3/TiO2Has higher denitration efficiency and Hg at the high temperature (300-0A certain influence of removal. However, high temperatures not only lead to high energy consumption, but also to decomposition of the mercury compounds formed. Furthermore, the Air Pollution Control Device (APCD) alone is used only in power plants for the removal of NO or Hg0And the like, which results in large investment and high operation cost. Recently, research focuses on the integration of high-temperature SCR denitration and demercuration, and mainly aims at the denitration catalyst which is commercially applied at present to examine the denitration catalyst for the elemental Hg0The efficiency of the removal is synergistic, and the research related to the low-temperature denitration and mercury removal is relatively less.
The research related to the low-temperature denitration and demercuration catalyst in the prior art mainly comprises the following steps:
application number 201210221067.9 discloses a composite catalyst for simultaneous denitration and demercuration and a preparation method thereof, the catalyst comprises an active component and a carrier, the active component is CeO2And ZrO2Wherein the molar ratio of Ce to Zr is 1: 0.1-1, and the carrier is one or more of honeycomb ceramics, molecular sieves, ceramic plates, activated carbon fibers, silica gel carriers, diatomite, metal alloys and filter bags. The content of the active component of the catalyst is 5-30% by mass of the carrier. The additive is one or any combination of more than two of oxides of W, Cu, Fe, Ti and Ni; based on the mass of the carrier, the content of the auxiliary agent is 0-15%. The results of the detection of the smoke show that: when the reaction temperature is 300 ℃, the denitration rate is 95.6 percent, and the oxidation rate of the gaseous elementary substance mercury is 92.1 percent.
However, the above prior art also has the following drawbacks:
based on dust and SO in the high-temperature denitration process2And the like have serious influence on the activity and selectivity of the catalyst, and researchers propose a low-temperature SCR denitration arrangement mode in which a denitration reactor is arranged behind a dust remover or even a desulfurization unit. SO in flue gas after desulfurizing tower2The concentration is less than 50mg/Nm3The dust concentration after dust removal is lower than 20mg/Nm3The poisoning effect on the catalyst is reduced and the dust deposition and abrasion of the catalyst are reduced. But medium and small-sized fuel oil and gas boiler for environmental protection product determination technical requirements
(HBC31-2004) stipulates that the smoke temperature of hot water boiler should be less than 180 deg.C, and the temperature of steam boiler and domestic boiler should be less than 200 deg.C. When the reaction temperature of the catalyst is 300 ℃, the denitration and demercuration efficiency is as high as more than 90%, an additional heating device is needed, and the needed investment and operation cost are high.
Application number 201610857931.2 discloses a preparation method of a low-temperature efficient sulfur-resistant water-resistant synergetic denitration and demercuration catalyst, which comprises the steps of directionally modifying the surface of a catalyst carrier, optimally loading a plurality of metal salts by an isometric impregnation method, calcining, and pyrolyzing to obtain the efficient low-temperature denitration and demercuration catalyst; the preparation method comprises the following steps: firstly, commercial gamma-Al is used2O3Carrying out directional modification on the surface groups of the carrier to obtain a carrier of the catalytic sample; then soaking the carrier in a metal salt solution with a certain mass concentration, and drying at a low temperature after soaking for a certain time; and finally, carrying out high-temperature calcination pyrolysis on the dried sample to obtain the catalyst. NOx and Hg at 240 ℃ when the support is placed in 0.5M hydrochloric acid and sodium hydroxide solution, respectively0The conversion of (A) was 98% and 92%, respectively, but SO was fed separately2When it is time, catalyst poisoning cannot be recovered.
The defects of the prior art are as follows:
the catalyst is resistant to SO alone2Poor poisoning effect, SO2Recovery after poisoning is impossible; the preparation needs strong acid and strong alkali, the pH value needs to be adjusted during the filtration and washing, and the operation is complicated.
Because the reaction temperature windows of low-temperature denitration and high-temperature denitration are different, the flue gas composition is also greatly different, and the low-temperature (100-The mechanism of response lacks systematic and in-depth knowledge. Research and development of the product with high efficiency, good low-temperature activity and SO resistance2The poisoned novel catalyst and the influence rule and reason of the composition of impurity gas and dust in the flue gas on the denitration and demercuration performance of the catalyst need further research.
Disclosure of Invention
The invention aims to provide a preparation method of an oxide modified MCM-48 molecular sieve and application thereof in denitration and mercury removal, and the oxide modified MCM-48 molecular sieve prepared by the method is used for removing Hg0Has good removal effect, and the MnN/MCM-48 molecular sieve can well convert NOx into N within the low temperature range (100 ℃ and 280 ℃)2And better denitration efficiency is achieved.
One of the tasks of the invention is to provide a preparation method of an oxide modified MCM-48 molecular sieve, which adopts the following technical scheme:
a preparation method of an oxide modified MCM-48 molecular sieve sequentially comprises the following steps:
a. pretreating the MCM-48 molecular sieve without the template agent;
b. synthesizing a MnN mixed solution by taking a manganese oxide as an active substance and an N oxide as an auxiliary agent; the N is La, Co or Ce;
c. fully and uniformly mixing the MCM-48 molecular sieve pretreated in the step a with the MnN mixed solution in the step b to prepare a mixed solution with a molar ratio of 2:1, wherein the mixed solution is represented as Mn2N/MCM-48 solution;
d. for the Mn2Stirring the N/MCM-48 solution, and then drying the solution in an oven at the temperature of 60-80 ℃;
e. and d, sequentially roasting the solid obtained after drying in the step d, naturally cooling to room temperature, and transferring to a vacuum drying oven to obtain the catalyst.
As a preferred embodiment of the present invention, the pretreatment step of step a comprises:
a1dissolving the MCM-48 molecular sieve in ethanol, refluxing for 10-14h at the temperature of 60-80 ℃, washing and drying, and repeating twice;
a2step a is carried out1Dissolving the treated MCM-48 molecular sieve in normal hexane for ultrasonic treatment;
a3dropwise adding a certain amount of 3-aminopropyltriethoxysilane, and carrying out ultrasonic treatment for a period of time;
a4step a is carried out3Transferring the MCM-48 molecular sieve subjected to ultrasonic treatment into a water bath kettle for condensation and reflux;
a5finally filtering, washing and drying.
As another preferred embodiment of the present invention, in the step b, the specific steps of synthesizing the MnN mixed solution are as follows:
b1weighing a certain amount of manganese-based material, and preparing the manganese-based material into 150mL of Mn (NO) with the concentration of 0.2mol/L3)2A solution;
b2weighing a certain amount of lanthanum-based material, and preparing 50mL of 0.1mol/L La (NO)3)2A solution;
b3weighing a certain amount of cobalt-based material, and preparing the cobalt-based material into 50mL of 0.1mol/L Co (NO)3)2A solution;
b4weighing a certain amount of cerium-based material, and preparing the cerium-based material into 50mL of 0.1mol/L Ce (NO)3)2A solution;
adding said Mn (NO)3)2Solution with La (NO)3)2Solution, Co (NO)3)2Solution or Ce (NO)3)2Mixing the solutions to obtain the final product.
And in the step d, stirring for 10-14h, and drying for 22-26 h.
Further, in the step e, the solid obtained after the drying in the step d is placed in a muffle furnace to be roasted for 1-4h at the temperature of 450-500 ℃.
Further, N is La. After the MCM-48 molecular sieve is subjected to demoulding plate and then is pretreated by amino, manganese and lanthanum are loaded by an impregnation method (the molar ratio is 2: 1), and the denitration and demercuration efficiency is good.
Further, step a1In the step a, the mass volume ratio of the MCM-48 molecular sieve to the ethanol is 1:20g/mL2Ultrasonic treatment for 10-20min, step a3And performing medium ultrasonic treatment for 20-40min.
Further, step a4The temperature of the water bath is 60-80 ℃, and the condensing reflux time is 10-14 h.
The invention also aims to provide the application of the MCM-48 molecular sieve prepared by the preparation method of the oxide modified MCM-48 molecular sieve in denitration and demercuration.
In the application, the denitration and demercuration temperature is set to be 100-240 ℃, and when the temperature is 100-240 ℃, the denitration and demercuration rate of the MCM-48 molecular sieve is more than 90%.
The preparation method of the oxide modified MCM-48 molecular sieve has the main reaction principle that:
firstly, in the step of pretreating an MCM-48 molecular sieve without removing a template agent, refluxing the MCM-48 molecular sieve without removing the template agent in ethanol in water bath at 60-80 ℃ for about 12h, repeating twice, washing and drying to remove the template agent of the molecular sieve without damaging hydroxyl on the surface of the molecular sieve, and then carrying out activation modification on the inner surface and the outer surface of the molecular sieve to introduce amino; then, uniformly dispersing active substances onto the MCM-48 molecular sieve, specifically uniformly dispersing manganese, lanthanum, cobalt and cerium onto the MCM-48 molecular sieve, and specifically comprising the following steps: firstly, a solution containing manganese and lanthanum (cobalt and cerium) is prepared according to the molar ratio of Mn: la (Co, Ce) is mixed evenly 2:1, then molecular sieve is added, and the mixture is stirred for about 12 hours at room temperature, so as to prevent active substances from clustering on the molecular sieve, and the mixed solution is directly put into a drying oven at about 80 ℃ for drying, so as to ensure that the active substances are dispersed on the molecular sieve without waste; and finally, converting the active substances loaded on the molecular sieve into oxides, specifically, putting the solid dried in the step d into a muffle furnace at about 450-500 ℃ for calcining for about 2h, so that the manganese, the lanthanum, the cobalt and the cerium are converted into the corresponding oxides.
Compared with the prior art, the invention has the beneficial technical effects that:
the oxide modified MCM-48 molecular sieve prepared by the invention shows unique characteristics in physical and chemical aspects, and has good mercury removal performance while removing NOx at high efficiency (75-100%) in a low temperature range (100 ℃ C.). sub.300 ℃.
The mesoporous material has the characteristics of large aperture, large specific surface area and large pore volume, and the existence of abundant silicon hydroxyl groups which are on the inner and outer surfaces of the pore channel and on the silicon hydroxyl groups provides good active points for surface modification of the mesoporous material; the metal oxide is used as an active component, the metal source is wide, the price is low, and the method for converting the metal oxide into the oxide is simple. The method is simple, has low requirements on equipment and can be used for industrial production.
The beneficial technical effects of the invention can be further embodied from the following examples, which study the influence of different metals loaded on the MCM-48 molecular sieve on the removal efficiency of NOx and mercury, and the study shows that when the modified MCM-48 molecular sieve is manganese and lanthanum oxide, and the molar ratio of manganese to lanthanum is 2:1, the denitration and demercuration rate of the oxide modified MCM-48 molecular sieve is more than 95%.
Drawings
The invention is further described below with reference to the accompanying drawings:
FIG. 1 shows MnO as a raw material in example 1 of the present invention2And finally preparing the obtained MnLa0.5XRD diffractogram of/MCM-48 catalyst;
FIG. 2 shows MnLa of example 1 of the present invention0.5A denitration and demercuration efficiency chart of the/MCM-48 catalyst at different temperatures.
Detailed Description
The invention provides a preparation method of an oxide modified MCM-48 molecular sieve and application thereof in denitration and mercury removal, and the invention is described in detail below by combining specific examples in order to make the advantages and technical scheme of the invention clearer and more clear.
The raw materials required by the invention can be purchased from commercial sources.
The method for evaluating the activity of the catalyst of the present invention is as follows:
the detection method comprises the following steps: a detection system of a fixed bed reactor, a flue gas analyzer and a mercury detector is adopted.
And (3) adsorbent activity detection:
the prepared oxide modified MCM-48 molecular sieve is 4cm3The catalyst is placed in a tubular furnace of a fixed bed reactor, and a mass flow meter is adopted to carry out N of an air inlet2,NO,NH3,O2The SCR equipment is well adjusted, and a flue gas analyzer is adopted to measure the concentration of NO in the flue gas; the water bath temperature of the mercury generator is controlled at 30 ℃, and the mercury vapor concentration is measured by a mercury detector.
The evaluation method comprises the following steps: denitration efficiency can be obtained through the change of the concentration of NO in the flue gas before and after denitration. The calculation method is as shown in formula (1):
the denitration efficiency is obtained through the change of the concentration of NO in the front flue gas and the concentration of NO in the rear flue gas. The calculation method is as follows:
example 1:
firstly, dissolving an MCM-48 molecular sieve in ethanol for refluxing, washing and drying, repeating twice, dissolving the MCM-48 molecular sieve in n-hexane for ultrasonic dispersion, dropwise adding 3-Aminopropyltriethoxysilane (APTES) and continuing ultrasonic treatment for 30 min; and finally, transferring the treated MCM-48 molecular sieve into a water bath, refluxing for 12h, filtering, washing and drying for subsequent experiments.
Secondly, preprocessing the manganese-based material and the lanthanum-based material: 2.5g of 50% Mn (NO) are weighed out3)2Preparing a solution, namely preparing 50mL of the solution in a beaker; 1.02g La (NO) was weighed3)2·6H2O, preparing 50mL of solution in a beaker; the two solutions were added and mixed well to obtain MnLa0.5A solution;
step three, weighing 5g of the processed MCM-48 molecular sieve, and adding Mn2Fully and uniformly mixing the La solution in a beaker;
fourthly, placing the mixed solution into a magnetic stirrer, stirring at a constant speed for 12 hours at room temperature, and then placing the mixed solution into an oven at 80 ℃ for drying for 24 hours;
fifthly, placing the dried solid in a muffle furnace for roasting at the temperature of 450 ℃ for 5h, naturally cooling the roasted solid in the muffle furnace to room temperature, grinding the solid to about 80-100 meshes, transferring the ground solid to a vacuum drying oven, and obtaining Mn2La/MCM-48 catalyst.
Mn prepared in this example2The La/MCM-48 catalyst is used for carrying out denitration and demercuration experiments, the denitration efficiency is about 99% at the temperature of 140 ℃ and 240 ℃, and the demercuration efficiency is about 96% according to the experiment results, which is shown in figure 2. MCM-48 molecular sieve and Mn finally prepared2The diffraction pattern of the La/MCM-48 catalyst is shown in figure 1. By comparing the two curves, Mn is found2The small diffraction peaks appearing on La/MCM-48 are those of manganese oxide and lanthanum oxide.
Example 2:
the difference from the embodiment 1 is that,
the mixed solution in the second step is Mn2And (3) a Co solution.
Selecting 0.1 percent of simulated flue gas NO and NH30.12% of oxygen, O2The content is 5 percent, and the rest is N2The balance gas is made, and at the same time, a certain concentration of Hg is obtained in the mercury permeation tube by changing the temperature of the water bath0Steam, Hg0The flow rate of the carrier gas is 90mL/min, the total gas flow is 667mL/min, and the space velocity is 10000h-1And carrying out denitration and demercuration experiments in the temperature range of 100-260 ℃. The experiment result shows that the denitration efficiency is about 95% at the temperature of 160-240 ℃, and the demercuration efficiency is about 94%.
Example 3:
the difference from the embodiment 1 is that,
the mixed solution in the second step is Mn2And (3) a Ce solution.
Selecting 0.1 percent of simulated flue gas NO and NH30.12% of oxygen, O2The content is 5 percent, and the rest is N2The balance gas is made, and at the same time, a certain concentration of Hg is obtained in the mercury permeation tube by changing the temperature of the water bath0Steam, Hg0The flow rate of the carrier gas is 90mL/min, the total gas flow is 667mL/min, and the space velocity is 10000h-1And carrying out denitration and demercuration experiments in the temperature range of 100-260 ℃. Experiment ofAs a result, the denitration efficiency is about 95% at the temperature of 160 ℃ and 240 ℃, and the demercuration efficiency is about 92%.
From the above examples 1-3, it can be seen that the temperature range for denitration and demercuration of the present invention is preferably controlled to 160-240 ℃, wherein the efficiency of denitration and demercuration of the manganese lanthanum oxide modified MCM-48 catalyst is the best, and the temperature window is wider.
The difference of the space velocity also has influence on the denitration and demercuration efficiency,
the invention researches the influence of the prepared manganese-lanthanum oxide modified MCM-48 catalyst on the denitration and demercuration performance.
Example 4:
the difference from the embodiment 1 is that: the molar ratio of the supported manganese to the lanthanum is 2: 1.
Selecting 0.1 percent of simulated flue gas NO and NH30.12% of oxygen, O2The content is 5 percent, and the rest is N2The balance gas is made, and at the same time, a certain concentration of Hg is obtained in the mercury permeation tube by changing the temperature of the water bath0Steam, Hg0The flow rate of the carrier gas is 150mL/min, the total gas flow is 1000mL/min, and the space velocity is 30000h-1And carrying out a denitration and demercuration experiment, wherein the experiment result shows that the denitration efficiency is about 100% at the temperature of 120-240 ℃, and the demercuration efficiency is about 98%.
Example 5:
the difference from the example 1 is that the molar ratio of the supported manganese to the lanthanum is 2: 1.
Selecting 0.1 percent of simulated flue gas NO and NH30.12% of oxygen, O2The content is 5 percent, and the rest is N2The balance gas is made, and at the same time, a certain concentration of Hg is obtained in the mercury permeation tube by changing the temperature of the water bath0Steam, Hg0The flow rate of the carrier gas is 225mL/min, the total gas flow is 1500mL/min, and the space velocity is 45000h-1And carrying out denitration and demercuration experiments in the temperature range of 100-260 ℃. The experimental result shows that the denitration efficiency is about 100% at the temperature of 140 ℃ and 240 ℃, and the demercuration efficiency is about 99%.
From the above examples 1, 4 and 5, it can be seen that the catalyst of the present invention has certain influence on denitration and demercuration due to different space velocities, and the higher the space velocity is, the better the efficiency is.
The addition of sulfur dioxide also has an effect on denitration and demercuration.
The invention researches the influence of the prepared manganese-lanthanum oxide modified MCM-48 catalyst on the denitration and demercuration performance.
Example 6:
the difference from the example 1 is that the molar ratio of the supported manganese to the lanthanum is 2: 1.
Selecting 0.1 percent of simulated flue gas NO and NH30.12% of oxygen, O2The content is 5 percent, and the rest is N2The balance gas is made, and at the same time, a certain concentration of Hg is obtained in the mercury permeation tube by changing the temperature of the water bath0Steam, Hg0The flow rate of the carrier gas is 90mL/min, the total gas flow is 667mL/min, and the space velocity is 10000h-1The experiment is carried out for a period of time and then 500ppm SO is introduced2And stopping introducing SO after the experiment is carried out for about 30h2And carrying out denitration and demercuration experiments at the temperature of 140 ℃. The experimental result is that SO is introduced2The post-denitration efficiency is about 89%, and the demercuration efficiency is about 88%; stopping the supply of SO2After 1h, the denitration efficiency is 95%, and the demercuration efficiency is 93%.
From example 1 and example 6, it can be seen that when the molar ratio of the supported manganese to lanthanum is 2:1 and the temperature is controlled at 140 ℃, the MnLa prepared by the invention0.5the/MCM-48 catalyst has good sulfur resistance.
Comparative example 1:
the difference from the embodiment 1 is that:
the second step comprises the following specific steps: pretreating the manganese-based and lanthanum-based materials: 2.5g of 50% Mn (NO) are weighed out3)2Preparing a solution, namely preparing 50mL of the solution in a beaker; 2.04g La (NO) was weighed3)2·6H2O, preparing 50mL of solution in a beaker; fully and uniformly mixing the two solutions to obtain a MnLa solution;
finally, preparing the MnLa/MCM-48 catalyst with the manganese-lanthanum molar ratio of 1: 1.
The MnLa/MCM-48 catalyst with the Mn-La molar ratio of 1:1 prepared by the comparative example is subjected to denitration and demercuration experiments, and simulated flue gas NO content of 0.1 percent and NH are selected30.12% of oxygen, O2The content is 5 percent, and the rest is N2To carry out the balanceGas, and at the same time, by changing the temperature of the water bath, certain concentration of Hg is obtained in the mercury permeation tube0Steam, Hg0The flow rate of the carrier gas is 90mL/min, the total gas flow is 667mL/min, and the space velocity is 10000h-1And carrying out denitration and demercuration experiments in the temperature range of 100-260 ℃. The experiment result shows that the denitration efficiency is 95 percent at the temperature of 140 ℃ and 240 ℃ and the demercuration efficiency is 92 percent.
Comparative example 2:
the difference from the embodiment 1 is that:
the second step comprises the following specific steps: pretreating the manganese-based and lanthanum-based materials: 2.5g of 50% Mn (NO) are weighed out3)2Preparing a solution, namely preparing 50mL of the solution in a beaker; 2.04g La (NO) was weighed3)2·6H2O, preparing 50mL of solution in a beaker; the two solutions were mixed well to obtain Mn0.5La solution;
finally, Mn with the manganese-lanthanum molar ratio of 1:2 is obtained by preparation0.5La/MCM-48 catalyst.
MnLa with a Mn-La molar ratio of 1:2 prepared for this comparative example2the/MCM-48 catalyst is used for carrying out denitration and demercuration experiments, and simulated flue gas NO content is 0.1 percent and NH is selected30.12% of oxygen, O2The content is 5 percent, and the rest is N2The balance gas is made, and at the same time, a certain concentration of Hg is obtained in the mercury permeation tube by changing the temperature of the water bath0Steam, Hg0The flow rate of the carrier gas is 90mL/min, the total gas flow is 667mL/min, and the space velocity is 10000h-1And carrying out denitration and demercuration experiments in the temperature range of 100-260 ℃. The experiment result shows that the denitration efficiency is 95 percent at the temperature of 140 ℃ and 240 ℃ and the demercuration efficiency is 91 percent.
Comparative example 3:
the difference from the embodiment 1 is that:
the second step comprises the following specific steps: pretreating the manganese-based and lanthanum-based materials: 2.5g of 50% Mn (NO) are weighed out3)2Preparing a solution, namely preparing 50mL of the solution in a beaker; 2.04g La (NO) was weighed3)2·6H2O, preparing 50mL of solution in a beaker; the two solutions were mixed well to obtain Mn0.5La solution;
finally preparing MnLa with the manganese-lanthanum molar ratio of 1:33/MCM-48 catalyst.
MnLa with a Mn-La molar ratio of 1:3 prepared for this comparative example3the/MCM-48 catalyst is used for carrying out denitration and demercuration experiments, and simulated flue gas NO content is 0.1 percent and NH is selected30.12% of oxygen, O2The content is 5 percent, and the rest is N2The balance gas is made, and at the same time, a certain concentration of Hg is obtained in the mercury permeation tube by changing the temperature of the water bath0Steam, Hg0The flow rate of the carrier gas is 90mL/min, the total gas flow is 667mL/min, and the space velocity is 10000h-1And carrying out denitration and demercuration experiments in the temperature range of 100-260 ℃. The experiment result shows that the denitration efficiency is 94 percent at the temperature of 140 ℃ and 240 ℃, and the demercuration efficiency is about 91 percent.
The parts which are not described in the invention can be realized by taking the prior art as reference.
It is intended that any equivalents, or obvious variations, which may be made by those skilled in the art in light of the teachings herein, be within the scope of the present invention.
Claims (5)
1. A preparation method of an oxide modified MCM-48 molecular sieve for denitration and cooperative demercuration is characterized by sequentially comprising the following steps:
a. pretreating the MCM-48 molecular sieve without the template agent;
b. manganese oxide is used as an active substance, N oxide is used as an auxiliary agent, and a mixed solution with a molar ratio of 2:1 is prepared, wherein Mn is expressed as Mn2N, wherein N is La;
c. b, mixing the MCM-48 molecular sieve pretreated in the step a with the Mn in the step b2The N mixed solution was thoroughly and uniformly mixed and represented as Mn2N/MCM-48 solution;
d. for the Mn2Stirring the N/MCM-48 solution, and then drying the solution in an oven at the temperature of 60-80 ℃;
e. d, sequentially roasting and naturally cooling the solid obtained after drying in the step d to room temperature, and transferring the solid to a vacuum drying oven to obtain the catalyst;
the pretreatment step of the step a comprises the following steps:
a1dissolving the MCM-48 molecular sieve without the template agent in ethanol, refluxing for 10-14h at the temperature of 60-80 ℃, washing and drying, and repeating twice;
a2step a is carried out1Dissolving the treated MCM-48 molecular sieve in normal hexane for ultrasonic treatment;
a3dropwise adding a certain amount of 3-aminopropyltriethoxysilane, and carrying out ultrasonic treatment for a period of time;
a4step a is carried out3Transferring the MCM-48 molecular sieve subjected to ultrasonic treatment into a water bath kettle for condensation and reflux;
a5finally filtering, washing and drying;
the denitration and demercuration temperature of the oxide modified MCM-48 molecular sieve is set to be 100-260 ℃.
2. The preparation method of the oxide modified MCM-48 molecular sieve for denitration and cooperative demercuration as claimed in claim 1, wherein the method comprises the following steps: in the step d, stirring for 10-14h, and drying for 22-26 h.
3. The preparation method of the oxide modified MCM-48 molecular sieve for denitration and cooperative demercuration as claimed in claim 1, wherein the method comprises the following steps: in the step e, the solid obtained after the drying in the step d is placed in a muffle furnace to be roasted for 1-4h at the temperature of 450-500 ℃.
4. The method for preparing the oxide modified MCM-48 molecular sieve for denitration and cooperative demercuration as claimed in claim 1, wherein step a is carried out1In the step a, the mass volume ratio of the MCM-48 molecular sieve to the ethanol is 1:20g/mL2Ultrasonic treatment for 10-20min, step a3And performing medium ultrasonic treatment for 20-40min.
5. The preparation method of the oxide modified MCM-48 molecular sieve for denitration and cooperative demercuration as claimed in claim 1, wherein the method comprises the following steps: step a4The temperature of the water bath is 60-80 ℃, and the condensing reflux time is 10-14 h.
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| Characterization of Pt-impregnated MCM-41 and MCM-48 and their catalytic performances in selective catalytic reduction for NOx;Jea-Hun Jang et al.;《Applied Catalysis A: General》;20150412;第286卷;摘要、第36页左栏第1段 * |
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