CN114471696B - HC-SCR denitration forming catalyst and preparation method thereof - Google Patents

HC-SCR denitration forming catalyst and preparation method thereof Download PDF

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CN114471696B
CN114471696B CN202011168010.8A CN202011168010A CN114471696B CN 114471696 B CN114471696 B CN 114471696B CN 202011168010 A CN202011168010 A CN 202011168010A CN 114471696 B CN114471696 B CN 114471696B
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catalyst
molecular sieve
sapo
drying
denitration
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CN114471696A (en
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王宽岭
王学海
刘忠生
汪鹏
刘淑鹤
李勇
张新军
孟凡立
于维国
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Sinopec Dalian Petrochemical Research Institute Co ltd
China Petroleum and Chemical Corp
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Sinopec Dalian Research Institute of Petroleum and Petrochemicals
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/82—Phosphates
    • B01J29/84—Aluminophosphates containing other elements, e.g. metals, boron
    • B01J29/85—Silicoaluminophosphates [SAPO compounds]
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
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    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • 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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    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0201—Impregnation
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/03—Precipitation; Co-precipitation
    • B01J37/036—Precipitation; Co-precipitation to form a gel or a cogel
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    • 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
    • B01J2229/186—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself not in framework positions

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Abstract

The application relates to an HC-SCR denitration forming catalyst and a preparation method thereof, and the specific steps are as follows: (1) Mixing a magnesium source solution and a titanium source solution, adding a dispersing agent, adjusting the pH to 2-4 to obtain white gel, drying, crystallizing, washing and filtering to obtain a product; (2) Preparing a mixed solution from the product of the step (1), citric acid and water, adding a silicon aluminum phosphate molecular sieve into the mixed solution for soaking, and drying and roasting to prepare a composite carrier; (3) loading active components to obtain catalyst powder; (4) preparing the denitration molded catalyst. The catalyst provided by the application is prepared by the method of the application. The prepared catalyst can ensure NO to NO under the condition of low oxygen 2 Oxidation is avoided, hydrocarbon is prevented from being oxidized, and HC-SCR denitration effect is improved.

Description

HC-SCR denitration forming catalyst and preparation method thereof
Technical Field
The application belongs to the field of denitration catalysts, and particularly relates to an HC-SCR denitration forming catalyst and a preparation method thereof.
Background
The national control of nitrogen oxide emissions is becoming more and more stringent. At present, the most effective control measure for the fixed source NOx is NH 3 Selective catalytic reduction technique (NH) for reducing agents 3 SCR), wherein the catalyst is the core of the technology. At present, V is used for large-scale application 2 O 5 -TiO 2 A series of medium-high temperature SCR denitration catalysts. The method has NH 3 Easy corrosion to equipment, difficult storage and transportation, easy secondary pollution and other problems, especially V 2 O 5 Is a highly toxic substance, and can have certain influence on human body and environment.
As NH 3 Alternative technologies to SCR, SCR denitration technologies with hydrocarbons as reducing agent (HC-SCR) are becoming a hotspot of research. The reducing agent can be one or more of a series of hydrocarbon compounds such as methane, ethane, ethylene, ethanol, propane, propylene and the like. The total denitration reaction equation is shown as a formula (1). The hydrocarbon is used as the reducing agent, so that the ammonia escape problem can be avoided, and meanwhile, the reducing agent is low in cost and has wider market prospect.
NO+HC+O 2 →N 2 +CO 2 +H 2 O （1）
At present, one important cause affecting the denitration efficiency of HC-SCR technology is the negative effect of oxygen in flue gas on NOx reduction reaction. For most HC-SCR reactions, the reaction mechanism is relatively well-recognized: firstly, NO in the flue gas is oxidized into NO by oxygen 2 Is simultaneously adsorbed to the catalyst surface (R1) and activated. In the process, oxygen in the flue gas is favorable for oxidation and adsorption, and the adsorption capacity of NO is increased. Then, NO adsorbed to the catalyst surface 2 Is reduced by hydrocarbon to generate N 2 ，CO 2 And H 2 O (R2). At the same time, the hydrocarbon as a reducing agent can also be replaced by O in the flue gas 2 Oxidation to CO 2 And H 2 O (R3) is greatly reducedIn a ratio of reducing agent effective for reducing NOx.
NO+ O 2 →NO 2 (R1)
NO 2 +HC+O 2 →N 2 +CO 2 +H 2 O (R2)
HC+O 2 →CO 2 +H 2 O (R3)
CN103920392a relates to a process for flue gas denitration by lean-rich oxygen alternative reaction, wherein boiler flue gas with higher oxygen content flows through HC-SCR catalyst layer of fluidized bed to oxidize and adsorb nitrogen oxides; the flue gas after adsorbing the nitrogen oxides is collected; flowing a reducing agent gas with lower oxygen content through the HC-SCR catalyst layer after adsorbing nitrogen oxides; repeating steps (1) and (2) to alternately flow the boiler flue gas and the reductant gas through the HC-SCR catalyst layer. The application needs to utilize lean-rich oxygen alternating reaction, firstly oxygen in oxygen-rich flue gas is utilized to promote NO to be fully adsorbed and oxidized, and then the inhibition of excessive oxygen concentration on the reduction process is avoided in the oxygen-lean process. This is because the catalyst cannot effectively perform oxidation under low oxygen conditions, and thus oxygen-enriched flue gas needs to be used to promote oxidation.
CN106807440A discloses a high-efficient CH under oxygen-enriched conditions 4 SCR denitration catalyst, preparation method and application thereof, and efficient CH under oxygen-enriched condition 4 The active ingredient of the SCR denitration catalyst is indium, and the indium is supported on an H-Beta molecular sieve. Said CH 4 The SCR denitration catalyst needs to exert catalytic activity under oxygen-rich conditions, and thus has poor denitration activity under low oxygen conditions.
The negative effect of oxygen on the denitration efficiency is derived from the competing reaction of oxygen and NO with respect to HC, but at the same time, oxygen in the flue gas is a necessary factor for the NO to be oxidized and adsorbed on the surface of the catalyst. Oxygen plays a dual role in the NO reaction process, both positive (adsorption promotion) and negative (reduction inhibition). So in order to ensure that NO in the flue gas is oxidized into NO by oxygen 2 To ensure that the oxidation and adsorption processes proceed, the catalyst generally needs to perform the oxidation under oxygen-rich conditions and under oxygen-lean conditionsAnd plays a role of reduction. However, the higher the concentration of oxygen, the more hydrocarbon is oxidized, which is not effectively utilized for reducing NOx, and the overall denitration efficiency is lowered. Therefore, the oxidation performance of the catalyst to NO under the condition of low oxygen is improved, and the oxidation of NO to NO can be ensured 2 Meanwhile, the oxidation of the reducing agent HC can be inhibited, and the catalyst has important significance in promoting the HC-SCR reaction performance.
Disclosure of Invention
Aiming at the defects of the prior art, the application provides an HC-SCR denitration forming catalyst and a preparation method thereof. The catalyst provided by the application can ensure that NO is converted into NO under the condition of low oxygen 2 Avoiding the oxidation of hydrocarbon and improving the HC-SCR denitration effect.
The application provides a preparation method of an HC-SCR denitration forming catalyst, which comprises the following steps:
(1) Mixing a magnesium source solution and a titanium source solution, adding a dispersing agent, adjusting the pH to 2-4 to obtain white gel, drying, crystallizing, washing and filtering to obtain a product;
(2) Preparing a mixed solution from the product of the step (1), citric acid and water, adding a silicon aluminum phosphate molecular sieve into the mixed solution for soaking, and drying and roasting to prepare a composite carrier;
(3) Impregnating the composite carrier into impregnating solution containing active component precursors, and drying and roasting after the impregnation is finished to obtain catalyst powder;
(4) The catalyst powder is made into denitration molding catalyst.
In the application, the magnesium source in the step (1) is at least one of magnesium chloride, magnesium carbonate, magnesium sulfate and the like, and the concentration of the magnesium source solution is 5-20g/L.
In the application, the titanium source in the step (1) is at least one of titanium sulfate, tetrabutyl titanate, titanium tetrachloride and the like, and the concentration of the titanium source solution is 50-600g/L.
In the application, the magnesium source and the titanium source in the step (1) are mixed according to the mass ratio of 1:10-1:50.
In the present application, the dispersant in the step (1) may be at least one of urea, citric acid, and the like. The mass ratio of the dispersing agent to the titanium source is 1:10-1:50.
In the present application, the step (1) of adjusting the pH may employ at least one of inorganic acids, specifically at least one of hydrochloric acid, nitric acid, sulfuric acid, etc.
In the application, the white gel in the step (1) is dried for 10 to 20 hours at the temperature of 100 to 120 ℃; crystallizing at 300-500 deg.c for 6-12 hr. Washing and filtering in a conventional manner to obtain the product.
In the application, in the mixed solution in the step (2), the content of the product in the step (1) is 300-2000 g/L, and the content of the citric acid is 10-100 g/L.
In the application, the silicoaluminophosphate molecular sieve in the step (2) is self-made or commercially available, preferably an SAPO-type silicoaluminophosphate molecular sieve, and the SAPO-type silicoaluminophosphate molecular sieve can be at least one of SAPO-17, SAPO-18, SAPO-26, SAPO-33, SAPO-34, SAPO-35, SAPO-39, SAPO-42, SAPO-43, SAPO-44, SAPO-47 and the like, preferably an SAPO-35 molecular sieve.
Further, the rare earth modified silicoaluminophosphate molecular sieve is adopted, and preferably, the rare earth metal is at least one of cerium, samarium, niobium and the like. The modification process comprises the following steps: dispersing the silicon aluminum phosphate molecular sieve in water to form a dispersion liquid, wherein the mass ratio of the silicon aluminum phosphate molecular sieve to the water is 1:10-200; preparing rare earth nitrate solution from required amount of rare earth nitrate and water, wherein the mass ratio of the rare earth nitrate to the water is 1:50-200; adding rare earth nitrate solution into the dispersion liquid dropwise, stirring for 0.5-2 h, ageing for 1-5 h, centrifuging and washing, drying for 0.5-3 h at 80-120 ℃, and then placing in a muffle furnace for treatment for 1-5 h at 300-500 ℃ to obtain the rare earth modified silicon aluminum phosphate molecular sieve.
In the application, the soaking method of the silicoaluminophosphate molecular sieve in the step (2) in the mixed solution can adopt methods such as equal volume soaking and the like. The mass ratio of the silicon aluminum phosphate molecular sieve to the mixed solution is 1:10-1:50, and the soaking time is 10-100 min.
In the application, the drying temperature in the step (2) is 80-120 ℃ and the drying time is 1-12 h. The roasting temperature is 300-600 ℃, and the roasting time is 1-6 h.
In the application, the active components in the step (3) are Ru and Sn, the content of the active component precursor in the impregnating solution is 0.3-1 mol/L, wherein the mol ratio of Ru to Sn is 1:1-1:3, and the impregnating is carried out for 5-50 min. Furthermore, the impregnating solution also comprises an auxiliary component which is at least one of Cu, co, mo and the like, the addition amount is that the content of an auxiliary component precursor in the impregnating solution is 0.1-0.5 mol/L, and the use of the auxiliary component is helpful for preventing the reducing agent from being excessively oxidized. The precursors of the active component, the adjuvant component are generally selected from their soluble salts.
In the application, the drying temperature in the step (3) is 20-120 ℃ and the drying time is 3-10 h. The roasting temperature is 300-600 ℃, and the roasting time is 1-10 hours.
In the application, the step (4) is to knead, age, extrude, dry and bake the catalyst powder to obtain the shaped catalyst. The formed catalyst adopts the following formula, and the mass parts of the formed catalyst are 75-90 parts of denitration catalyst powder, 2-6 parts of glass fiber, 0.1-2 parts of wood pulp, 0.1-2 parts of polyacrylamide, 0.1-2 parts of carboxymethyl cellulose, 5-10 parts of ammonia water and 10-40 parts of deionized water. Wherein the diameter of the glass fiber is 10+/-1.5 mu m, the length is 5+/-1.5 mu m, and the drying weight loss (drying to constant weight at 105 ℃) is less than or equal to 10 percent. The wood pulp is softwood pulp and hardwood pulp. The polyacrylamide is anionic polyacrylamide, and the molecular weight is 700-900 ten thousand. The viscosity of the 1% aqueous solution of the carboxymethyl cellulose is 100-300 mPa.s, and the drying weight loss (drying to constant weight at 105 ℃) is less than or equal to 20%.
In the present application, the kneading, aging, extruding, drying, calcining and the like described in the step (4) are all conventional operations in the art. The aging time is generally 12 to 48 hours. The drying temperature is 20-80 ℃ and the drying time is 1-7 days; the roasting temperature is 300-600 ℃, and the roasting time is 3-20 hours.
The HC-SCR denitration catalyst is prepared by adopting the method. The prepared denitration molded catalyst comprises the following components: based on the total mass of the catalystThe content of the silicon aluminum phosphate molecular sieve is 5 to 20 percent, and the TiO is the same as that of the silicon aluminum phosphate molecular sieve 2 60-85% of magnesium oxide, 2-10% of active component, 0.5-10% of oxide and 1-10% of auxiliary agent. The active components are Ru and Sn, and the auxiliary component is at least one of Cu, co, mo and the like.
The application of the HC-SCR denitration catalyst provided by the application carries out catalytic denitration reaction under the condition of low oxygen in the presence of NOx, HC reducing agent and the denitration catalyst, and the denitration rate can reach more than 95%.
In the application of the application, the low oxygen condition means that the volume concentration of oxygen is less than 2%, preferably 0.5% -2%.
In the application of the application, the NOx is NO 2 And mixtures thereof.
In the application of the application, the HC reducing agent can be at least one hydrocarbon such as methane, ethane, ethylene, ethanol, propane, propylene and the like, and is preferably C 2 H 4 、C 3 H 6 At least one of them.
In the application of the application, the catalytic denitration reaction conditions are as follows: the temperature is less than 600 ℃, preferably 300-500 ℃.
Compared with the prior art, the application has the following advantages:
(1) Typically, HC-SCR denitration reactions are performed stepwise under different oxygen conditions, which are otherwise affected by the oxygen concentration, resulting in a decrease in denitration rate. The inventor of the application researches, taking efficient oxidation and adsorption of NO under the condition of low oxygen as starting points, the prepared catalyst can ensure the efficient oxidation of NO under the condition of low oxygen, avoid the oxidation of HC reducing agent, improve the utilization rate of the reducing agent and improve the denitration effect.
(2) The magnesium source and the titanium source are adopted to prepare a mixed solution, pH regulation and crystallization are carried out, and then the silicon aluminum phosphate molecular sieve is added into the mixed solution for impregnation to prepare the composite carrier, so that the NO oxidation and the NO2 adsorption are promoted under the condition of low oxygen, and the denitration effect is improved.
(3) The denitration catalyst prepared by adopting the rare earth modified composite carrier disclosed by the application is beneficial to balancing the oxidation-reduction cycle performance of the catalyst, reduces the oxidation side reaction of the HC reducer, and further improves the utilization rate of the reducer.
Detailed Description
The method and effect of the present application will be described in detail with reference to the following specific examples, which are given as detailed embodiments and specific operation procedures on the premise of the technical solution of the present application, but the scope of protection of the present application is not limited to the following examples.
The experimental methods in the following examples, unless otherwise specified, are all conventional in the art. The experimental materials used in the examples described below, unless otherwise specified, were purchased from conventional biochemical reagent stores.
The glass fiber used in the embodiment of the application has the diameter of 10+/-1.5 mu m and the length of 5+/-1.5 mu m, and the drying weight loss (drying to constant weight at 105 ℃) is less than or equal to 10 percent. The wood pulp is softwood pulp or hardwood pulp. The polyacrylamide is anionic polyacrylamide, and the molecular weight is 800 ten thousand. The viscosity of the 1% aqueous solution of the carboxymethyl cellulose is 200 mPa.s, and the drying weight loss (drying at 105 ℃) is less than or equal to 20%.
Example 1
(1) Preparing 10g of magnesium chloride and 1L of water into a solution; mixing 200g of titanium sulfate and 1L of water to obtain a solution, stirring, adding 10g of urea while stirring, and regulating the pH to 3 by adopting hydrochloric acid to obtain white gel, and stopping stirring; drying at 110 ℃ for 16h, crystallizing at 400 ℃ for 10h, washing and filtering to obtain the product.
(2) 500g of the product of step (1), 20g of citric acid and 1L of water were prepared into a mixed solution. 60g of SAPO-35 molecular sieve is added into the mixed solution for soaking, the mixture is taken out after 20min of soaking, and is dried at 100 ℃ for 2h and baked at 400 ℃ for 3h, thus obtaining the composite carrier.
(3) The composite carrier was immersed in an immersion liquid containing 0.1mol/L ruthenium chloride, 0.3mol/L tin chloride and 0.3mol/L copper nitrate for 10min. And taking out, drying at 80 ℃ for 6 hours, and roasting at 450 ℃ for 10 hours to obtain the catalyst powder.
(4) Mixing 80 parts of catalyst powder with 6 parts of glass fiber, 0.1 part of wood pulp, 0.5 part of polyacrylamide, 2 parts of carboxymethyl cellulose, 8 parts of ammonia water and 20 parts of deionized water, kneading, aging for 24 hours, extruding and other procedures to prepare a honeycomb body, drying the honeycomb body for 3 days at 70 ℃, and roasting at 500 ℃ for 10 hours to prepare the denitration molding catalyst.
In the catalyst, based on the total mass of the catalyst, tiO 2 71.8 percent of the content, 11.4 percent of the silicon aluminum phosphate molecular sieve, 4.9 percent of the magnesium oxide and RuO 2 Content 1.8%, snO 2 The content of CuO is 5.3 percent and the content of CuO is 1.5 percent.
Example 2
(1) Taking 5g of magnesium chloride and 1L of water to prepare a solution; preparing 100g of titanium sulfate and 1L of water into a solution, uniformly mixing, stirring, adding 6g of citric acid, adjusting the pH to 2 by adopting sulfuric acid, and obtaining white gel to stop stirring; drying the gel at 100 ℃ for 18 hours, crystallizing at 350 ℃ for 12 hours, washing and filtering to obtain the product.
(2) 400g of the product of step (1), 15g of citric acid and 1L of water were prepared into a mixed solution. Adding 40g of SAPO-35 molecular sieve into the mixed solution for soaking, taking out after 15min of soaking, drying at 90 ℃ for 3h, and roasting at 350 ℃ for 5h to prepare the composite carrier.
(3) The composite carrier was immersed in an immersion liquid containing 0.2mol/L ruthenium chloride, 0.5mol/L tin chloride and 0.4mol/L cobalt nitrate for 10min. And taking out, drying at 70 ℃ for 4 hours, and roasting at 550 ℃ for 8 hours to obtain the catalyst powder.
(4) Mixing 80 parts of catalyst powder with 6 parts of glass fiber, 0.1 part of wood pulp, 0.5 part of polyacrylamide, 2 parts of carboxymethyl cellulose, 8 parts of ammonia water and 20 parts of deionized water, kneading, aging for 24 hours, extruding and other procedures to prepare a honeycomb body, and drying the honeycomb body at 60 ℃ for 4 days. And (3) drying, and roasting at 500 ℃ for 10 hours to obtain the denitration molded catalyst.
In the catalyst, based on the total mass of the catalyst, tiO 2 68.6 percent of silicon aluminum phosphate molecular sieve, 10.3 percent of magnesium oxide, 5.4 percent of RuO 2 Content of 2.1% SnO 2 5.6% and 1.1% CoO.
Example 3
(1) Preparing 20g of magnesium chloride and 1L of water into a solution; preparing 300g of titanium sulfate and 1L of water into a solution, uniformly mixing, stirring, adding 8g of citric acid, adjusting the pH to 2 by adopting nitric acid, and obtaining white gel, and stopping stirring; drying gel at 120deg.C for 10 hr, crystallizing at 450deg.C for 8 hr, washing, and filtering to obtain the final product.
(2) 600g of the product of step (1), 15g of citric acid and 1L of water were prepared into a mixed solution. 80g of SAPO-35 molecular sieve is added into the mixed solution for soaking, the mixture is taken out after 15min of soaking, and the mixture is dried at 120 ℃ for 1h and baked at 450 ℃ for 2h, thus obtaining the composite carrier.
(3) The composite carrier was immersed in an immersion liquid containing 0.1mol/L ruthenium chloride, 0.2mol/L tin chloride and 0.2mol/L ammonium molybdate for 10min. And taking out, drying at 60 ℃ for 5 hours, and roasting at 450 ℃ for 10 hours to obtain the catalyst powder.
(4) Mixing 80 parts of catalyst powder with 6 parts of glass fiber, 0.1 part of wood pulp, 0.5 part of polyacrylamide, 2 parts of carboxymethyl cellulose, 8 parts of ammonia water and 20 parts of deionized water, kneading, aging for 24 hours, extruding and other procedures to prepare a honeycomb body, and drying the honeycomb body at 80 ℃ for 2 days. And (3) drying, and roasting at 500 ℃ for 10 hours to obtain the denitration molded catalyst.
In the catalyst, based on the total mass of the catalyst, tiO 2 74.2 percent of silicon aluminum phosphate molecular sieve, 11.1 percent of magnesium oxide, 5.2 percent of RuO 2 Content of 1.5%, snO 2 Content 3.5%, moO 3 The content is 1.6%.
Example 4
The preparation process and operating conditions were the same as in example 1, except that: the silicoaluminophosphate molecular sieve adopts a SAPO-37 molecular sieve. In the catalyst, based on the total mass of the catalyst, tiO 2 72.1 percent of the content, 10.8 percent of the silicon aluminum phosphate molecular sieve, 4.3 percent of the magnesium oxide and RuO 2 Content 1.9%, snO 2 The content of CuO is 5.1 percent and the content of CuO is 1.6 percent.
Example 5
The preparation process and operating conditions were the same as in example 1, except that: the silicoaluminophosphate molecular sieve adopts a SAPO-17 molecular sieve. In the catalyst, based on the total mass of the catalyst, tiO 2 71.5 percent of the content, 11.3 percent of the silicon aluminum phosphate molecular sieve, 5.2 percent of the content of magnesium oxide and RuO 2 Content of 2.0%, snO 2 4.6% of CuO and 1.7%.
Example 6
The preparation process and operating conditions were the same as in example 1, except that: the silicoaluminophosphate molecular sieve adopts a SAPO-47 molecular sieve. In the catalyst, based on the total mass of the catalyst, tiO 2 72.2 percent of silicon aluminum phosphate molecular sieve, 10.6 percent of magnesium oxide, 5.7 percent of RuO 2 Content 1.8%, snO 2 4.7% of CuO and 1.4%.
Example 7
The preparation process and operating conditions were the same as in example 1, except that: the silicon aluminum phosphate molecular sieve adopts niobium nitrate modified silicon aluminum phosphate molecular sieve, and the specific method comprises the following steps: dispersing the SAPO-35 molecular sieve in water to form a dispersion liquid, wherein the mass ratio of the SAPO-35 molecular sieve to the water is 1:50; and dissolving the niobium nitrate with water according to the required amount to prepare a solution, wherein the mass ratio of the niobium nitrate to the water is 1:100. Adding the niobium nitrate solution into the SAPO-35 molecular sieve dispersion liquid dropwise, stirring for 1h, standing and aging for 3h, centrifuging the obtained mixed liquid, washing with water for more than 3 times, drying at 110 ℃ for 2h, and then placing in a muffle furnace for 3h at 400 ℃ to obtain the niobium nitrate modified SAPO-35 molecular sieve.
In the catalyst, based on the total mass of the catalyst, tiO 2 70.8 percent of metal modified silicon aluminum phosphate molecular sieve with 12.1 percent of niobium oxide with 2.6 percent of MgO with 4.2 percent of RuO 2 Content 1.6%, snO 2 The content of CuO is 4.8 percent and the content of CuO is 1.4 percent.
Example 8
The preparation process and operating conditions were the same as in example 7, except that: cerium nitrate is adopted to replace niobium nitrate to modify the SAPO-35 molecular sieve. In the catalyst, based on the total mass of the catalyst, tiO 2 71.4%, 12.9% (cerium oxide 2.4%), 5.3% magnesium oxide and RuO 2 2.6% of SnO 2 4.3% of CuO and 1.6%.
Example 9
The preparation process and operating conditions were the same as in example 7, except that: the samarium nitrate is adopted to replace niobium nitrate to modify the silicon aluminum phosphate molecular sieve. In the catalyst, based on the total mass of the catalyst, tiO 2 71.3 percent and 11.9 percent of metal modified silicoaluminophosphate molecular sieve(wherein the content of samarium oxide is 2.5%), the content of magnesium oxide is 4.6%, and RuO 2 Content 2.7%, snO 2 4.7% of CuO and 1.5%.
Example 10
The preparation process and operating conditions were the same as in example 1, except that: titanium sulfate was replaced with an equimolar amount of tetra-n-butyl titanate and magnesium chloride was replaced with an equimolar amount of magnesium carbonate. In the catalyst, based on the total mass of the catalyst, tiO 2 70.7 percent of silicon aluminum phosphate molecular sieve, 11.1 percent of MgO, 5.2 percent of RuO 2 Content of 1.5%, snO 2 The content of CuO is 4.8 percent and the content of CuO is 1.4 percent.
Example 11
The preparation process and operating conditions were the same as in example 1, except that: titanium sulfate was replaced with an equimolar amount of titanium tetrachloride and magnesium chloride was replaced with an equimolar amount of magnesium sulfate. In the catalyst, based on the total mass of the catalyst, tiO 2 72.5 percent of silicon aluminum phosphate molecular sieve, 9.8 percent of MgO, 6.1 percent of RuO 2 Content 1.8%, snO 2 The content is 4.2%. The CuO content was 1.5%.
Example 12
The preparation process and operating conditions were the same as in example 1, except that no auxiliary component was included. In the catalyst, based on the total mass of the catalyst, tiO 2 72.5 percent of silicon aluminum phosphate molecular sieve, 12.1 percent of MgO, 5.2 percent of RuO 2 Content of 2.0%, snO 2 The content is 5.4%.
Comparative example 1
The preparation process and operating conditions were the same as in example 1, except that: and (2) adopting ZSM-5 molecular sieve to replace SAPO-35 molecular sieve.
Comparative example 2
The preparation process and operating conditions were the same as in example 1, except that: and (3) adding no SAPO-35 molecular sieve in the step (2).
Comparative example 3
The preparation process and operating conditions were the same as in example 1, except that: step (1) does not add a magnesium source.
Comparative example 4
The preparation process and operating conditions were the same as in example 1, except that: step (1) does not add a titanium source.
Comparative example 5
The preparation process and operating conditions were the same as in example 1, except that: and (3) the active metal component in the step (1) adopts Sn, and Ru is not added.
Comparative example 6
The preparation process and operating conditions were the same as in example 1, except that: the active metal component in the step (1) adopts Ru, and Sn is not added.
Test example 1
The method for testing the NO oxidizing property and the denitration activity of the catalyst comprises the following steps:
the experimental device consists of a gas distribution system, a flow control (mass flowmeter), a gas mixer, a gas preheater, a catalytic reactor and a flue gas analysis system. The monolithic honeycomb catalyst (150×150×1000× 1000 mm) was cut into small test pieces (45×45×50 mm) and the small test pieces were then placed in a fixed tubular reactor. Total flow rate of mixed gas 304L/h, O 2 Concentration is 1.0%, airspeed is 3000h -1 HC reductant concentration and NO concentration were 100ppm, HC/NO=1, H 2 O steam: 5% (volume ratio), and the reaction temperature is controlled between 300 and 500 ℃. Each gas flow is controlled by a mass flow meter. The gas is mixed by a gas mixer before entering the reactor and then preheated by a preheater. NO and NO at the inlet and outlet 2 The concentration was determined by a flue gas analyzer. The catalytic activity of the catalyst is reflected by the denitration activity of NO, which is calculated by the following formula:
NO oxidation rate= [ C NO2(out) /C NO(in) ]×100%
Denitration Activity= [ (C) 0 -C)/C 0 ]×100%
Wherein C is 0 The initial concentration of NO, and the concentration of NO in the treated gas.
The NO oxidation performance and denitration performance selectivities of the catalysts prepared in the different examples and comparative examples are shown in table 1.
TABLE 1
Test example 2
Other procedures and operating conditions were the same as in test example 1 except that different HC reducing agents were used, the reaction temperature was 400℃and the results are shown in Table 2.
TABLE 2
Test example 2
Other procedures and operating conditions were the same as in test example 1 except that the oxygen concentration in the flue gas was adjusted to 3%, the reaction temperature was 400℃and the results are shown in Table 3.
TABLE 3 Table 3

Claims (17)

1. The preparation method of the HC-SCR denitration forming catalyst is characterized by comprising the following steps of:
(1) Mixing a magnesium source solution and a titanium source solution, adding a dispersing agent, adjusting the pH to 2-4 to obtain white gel, drying, crystallizing, washing and filtering to obtain a product; the magnesium source and the titanium source are mixed according to the mass ratio of 1:10-1:50; the dispersing agent is at least one of urea and citric acid; the mass ratio of the dispersing agent to the titanium source is 1:10-1:50;
(2) Preparing a mixed solution from the product of the step (1), citric acid and water, adding a silicon aluminum phosphate molecular sieve into the mixed solution for soaking, and drying and roasting to prepare a composite carrier; in the mixed solution, the content of the product in the step (1) is 300-2000 g/L, and the content of the citric acid is 10-100 g/L; the silicon aluminum phosphate molecular sieve is at least one of SAPO-17, SAPO-18, SAPO-26, SAPO-33, SAPO-34, SAPO-35, SAPO-39, SAPO-42, SAPO-43, SAPO-44 and SAPO-47; the mass ratio of the silicon aluminum phosphate molecular sieve to the mixed solution is 1:10-1:50, and the soaking time is 10-100 min;
(3) Dipping the composite carrier into dipping liquid containing active component precursor, wherein the active components are Ru and Sn; drying and roasting after the impregnation is completed to obtain catalyst powder; the content of the active component precursor in the impregnating solution is 0.3-1 mol/L, wherein the mol ratio of Ru to Sn is 1:1-1:3;
(4) The catalyst powder is made into denitration molding catalyst.
2. The method according to claim 1, characterized in that: the magnesium source in the step (1) is at least one of magnesium chloride, magnesium carbonate and magnesium sulfate, and the concentration of the magnesium source solution is 5-20g/L.
3. The method according to claim 1, characterized in that: the titanium source in the step (1) is at least one of titanium sulfate, tetrabutyl titanate and titanium tetrachloride, and the concentration of the titanium source solution is 50-600g/L.
4. The method according to claim 1, characterized in that: the pH is adjusted by inorganic acid; drying the white gel at 100-120deg.C for 10-20 hr; crystallizing at 300-500 deg.c for 6-12 hr.
5. The method according to claim 1, characterized in that: the silicoaluminophosphate molecular sieve in the step (2) is a SAPO-35 molecular sieve.
6. The method according to claim 1 or 5, characterized in that: the silicon aluminum phosphate molecular sieve in the step (2) adopts a rare earth modified silicon aluminum phosphate molecular sieve, and the rare earth metal is at least one of cerium, samarium and niobium.
7. The method according to claim 6, wherein: the modification process comprises the following steps: dispersing the silicon aluminum phosphate molecular sieve in water to form a dispersion liquid, wherein the mass ratio of the silicon aluminum phosphate molecular sieve to the water is 1:10-200; preparing rare earth nitrate solution from required amount of rare earth nitrate and water, wherein the mass ratio of the rare earth nitrate to the water is 1:50-200; adding rare earth nitrate solution into the dispersion liquid dropwise, stirring for 0.5-2 h, ageing for 1-5 h, centrifuging and washing, drying for 0.5-3 h at 80-120 ℃, and then placing in a muffle furnace for treatment for 1-5 h at 300-500 ℃ to obtain the rare earth modified silicon aluminum phosphate molecular sieve.
8. The method according to claim 1, characterized in that: the drying temperature in the step (2) is 80-120 ℃ and the drying time is 1-12 h; the roasting temperature is 300-600 ℃, and the roasting time is 1-6 h.
9. The method according to claim 1, characterized in that: the impregnating solution in the step (3) also comprises an auxiliary agent component which is at least one of Cu, co and Mo; the addition amount is that the content of the precursor of the auxiliary agent component in the impregnating solution is 0.1-0.5 mol/L.
10. The method according to claim 1, characterized in that: the drying temperature in the step (3) is 20-120 ℃ and the drying time is 3-10 h; the roasting temperature is 300-600 ℃, and the roasting time is 1-10 hours.
11. The method according to claim 1, characterized in that: step (4) kneading, aging, extruding, drying and roasting the catalyst powder to prepare a molded catalyst; the formed catalyst adopts the following formula, and the mass parts of the catalyst comprise 75-90 parts of denitration catalyst powder, 2-6 parts of glass fiber, 0.1-2 parts of wood pulp, 0.1-2 parts of polyacrylamide, 0.1-2 parts of carboxymethyl cellulose, 5-10 parts of ammonia water and 10-40 parts of deionized water.
12. A HC-SCR denitration catalyst prepared by the method of any one of claims 1 to 11.
13. Use of the catalyst according to claim 12, characterized in that: under the condition of low oxygen, the catalytic denitration reaction is carried out in the presence of NOx, HC reducing agent and denitration forming catalyst, and the denitration rate is more than 95%.
14. The use according to claim 13, characterized in that: the low oxygen condition means that the volume concentration of oxygen is less than 2.5%.
15. The use according to claim 14, characterized in that: the low oxygen condition refers to the volume concentration of oxygen being 0.5% -2%.
16. The use according to claim 13, characterized in that: the HC reducing agent is at least one of methane, ethane, ethylene, ethanol, propane and propylene.
17. The use according to claim 16, characterized in that: the HC reducing agent is C 2 H 4 、C 3 H 6 At least one of them.
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