photo-Fenton desulfurization and denitrification catalyst and preparation method thereof
阅读说明：本技术 一种光-Fenton脱硫脱硝催化剂及其制备方法 (photo-Fenton desulfurization and denitrification catalyst and preparation method thereof ) 是由 李春虎 张程真 李浩智 郑锐 冯丽娟 王亮 王文泰 于 2019-10-30 设计创作，主要内容包括：本发明公开了一种光-Fenton脱硫脱硝催化剂及其制备方法。所述的光-Fenton脱硫脱硝催化剂,包括催化剂载体、通过粘结剂负载在催化剂载体上的光-Fenton活性组分,所述光-Fenton活性组分包括管状锰掺杂石墨相氮化碳、负载于管状锰掺杂石墨相氮化碳上的钼酸铁；其重量组分如下：催化剂载体70-85份,粘结剂10-30份,管状锰掺杂石墨相氮化碳0.5-2.0份,钼酸铁0.5-2.0份。所构建的管状Mn-g-C<Sub>3</Sub>N<Sub>4</Sub>/Fe<Sub>2</Sub>(MoO<Sub>4</Sub>)<Sub>3</Sub>具备光催化、臭氧催化、Fenton催化三种功能,不同催化体系之间能够相互依赖,相互促进,增加反应活性自由基含量,提高了真空紫外光催化协同H<Sub>2</Sub>O<Sub>2</Sub>氧化吸收体系的脱硫脱硝效率。本发明可广泛应用于各类烟气净化处理,实现SO<Sub>2</Sub>和NOx的超低排放,且具有成本低廉、合成简单、绿色环保等特点。(The invention discloses a photo-Fenton desulfurization and denitrification catalyst and a preparation method thereof. The photo-Fenton desulfurization and denitrification catalyst comprises a catalyst carrier and a photo-Fenton active component loaded on the catalyst carrier through a binder, wherein the photo-Fenton active component comprises tubular manganese-doped graphite-phase carbon nitride and iron molybdate loaded on the tubular manganese-doped graphite-phase carbon nitride; the weight components are as follows: 70-85 parts of catalyst carrier, 10-30 parts of binder and tubular manganese doping0.5-2.0 parts of graphite phase carbon nitride and 0.5-2.0 parts of iron molybdate. The constructed tubular Mn-g-C 3 N 4 /Fe 2 (MoO 4 ) 3 The catalyst has three functions of photocatalysis, ozone catalysis and Fenton catalysis, different catalytic systems can be interdependent and mutually promoted, the content of reactive free radicals is increased, and the cooperation of vacuum ultraviolet light catalysis and H is improved 2 O 2 And the desulfurization and denitrification efficiency of the oxidation absorption system. The invention can be widely applied to the purification treatment of various flue gases to realize SO 2 And the ultra-low emission of NOx, and has the characteristics of low cost, simple synthesis, environmental protection and the like.)
1. The photo-Fenton desulfurization and denitrification catalyst is characterized by comprising a catalyst carrier and a photo-Fenton active component loaded on the catalyst carrier through a binder, wherein the photo-Fenton active component comprises tubular manganese-doped graphite-phase carbon nitride and iron molybdate loaded on the tubular manganese-doped graphite-phase carbon nitride; the weight components are as follows: 70-85 parts of catalyst carrier, 10-30 parts of binder, 0.5-2.0 parts of tubular manganese-doped graphite-phase carbon nitride and 0.5-2.0 parts of iron molybdate.
2. The photo-Fenton desulfurization and denitrification catalyst according to claim 1, wherein the catalyst carrier is γ -Al 2O 3One or more of ZSM-5 molecular sieve, activated carbon fiber felt and ceramic.
3. The photo-Fenton desulfurization and denitrification catalyst according to claim 1, wherein the tubular manganese-doped graphite-phase carbon nitride is synthesized by a template-free method.
4. The photo-Fenton catalyst for desulfurization and denitration according to claim 1, wherein the iron molybdate is synthesized by a hydrothermal method by using ferric nitrate or ferric chloride as an iron source and ammonium molybdate or sodium molybdate as a molybdenum salt.
5. A method for preparing the photo-Fenton desulfurization and denitrification catalyst according to claim 1, which is characterized by comprising the following steps:
(1) washing and drying the catalyst carrier for later use;
(2) dissolving melamine or urea in organic solvent, heating and stirring to dissolve melamine or urea, cooling the solution, adding a certain amount of dilute nitric acid and manganese salt, washing and drying the generated precipitate, and finally roasting in a muffle furnace to obtain tubular Mn-g-C 3N 4；
(3) Ferric nitrate or ferric chloride is used as ferric salt, ammonium molybdate or sodium molybdate is used as molybdenum salt, and alkali liquor is used for adjusting the pH value to generate an iron molybdate precursor;
(4) tubular Mn-g-C obtained in the step (2) 3N 4Adding the mixture into mixed solution of iron molybdate precursors, and preparing tubular Mn-g-C by one-step solvothermal reaction 3N 4/ Fe 2(MoO 4) 3A photo-Fenton active component;
(5) and (3) preparing a binder solution, adding the photo-Fenton active component obtained in the step (4) into the binder solution, stirring for 2 hours, then adding the carrier washed and dried in the step (1), ultrasonically dipping, and drying for 12 hours to obtain the photo-Fenton desulfurization and denitrification catalyst.
6. The method according to claim 5, wherein the organic solvent in the step (2) is ethylene glycol or ethanol.
7. The method according to claim 5, wherein the manganese salt in the step (2) is one of manganese acetate, manganese nitrate and manganese chloride.
8. The preparation method according to claim 5, wherein the muffle furnace roasting temperature in the step (2) is 350-550 ℃, and the temperature rise rate is 5-10 ℃/min.
9. The method according to claim 5, wherein the iron salt: the molar ratio of the molybdenum salt is 1: 1.5.
10. The preparation method of claim 5, wherein the one-step solvothermal method in the step (4) is to place the reactants in a polytetrafluoroethylene-lined hydrothermal kettle, the heating temperature is 140 ℃ to 180 ℃, and the reaction time is 12 to 24 hours.
Technical Field
The invention relates to a photocatalyst and a preparation method thereof, in particular to a vacuum ultraviolet light catalysis and H synergistic photocatalyst 2O 2A photo-Fenton catalyst for oxidation absorption desulfurization and denitrification and a preparation method thereof belong to the field of flue gas purification.
Background
SO discharged by industrial boiler coal 2And NOx are the main causes of acid rain and photochemical smog, seriously threatening the ecological environment and human health. In 2016, the ministry of environment, the national development and improvement committee and the national energy agency jointly issue a working scheme for comprehensively implementing ultralow emission and energy-saving modification of coal-fired power plants, the task of ultralow emission modification completed in 2020 years before the original plan of the eastern region is totally completed in 2017, the strive of the middle region is basically completed in 2018 years, and the strive of the western region is completed in 2020 years. The ultra-low emission standard is smoke dust and SO 2And NOx emission concentrations not exceeding 10, 35, 50mg/m 3。
At present, the denitration is mainly performed by a wet desulfurization (WFGD) combined Selective Catalytic Reduction (SCR) method or a non-selective catalytic reduction (SNCR) method in China, the combined method can realize high pollutant removal rate, and the series desulfurization and denitration system has the problems of complex system, large occupied area, high investment and operation cost and the like.
Although the wet desulphurization is widely accepted in the market, the problems are still outstanding: firstly, the water consumption is high; secondly, the by-product gypsum has high water content, certain viscosity and low commercial value, and is usually discarded for landfill treatment; thirdly, the problems of corrosion and scaling blockage are serious.
The SCR denitration device is usually arranged behind the dust remover and in front of the desulfurization tower, however, the flue gas in the interval contains higher fly ash and SO 2And easily causes the blockage, poisoning and inactivation of the SCR catalyst. As the temperature interval required by the SCR catalyst does not exist in some small and medium-sized thermal power plants, the SCR method denitration is difficult to be applied to the small and medium-sized power plants.
Photocatalytic technology using O 2And H 2Production of superoxide radical (. O) on catalyst surface by O 2 -) And active free radicals such as hydroxyl free radical (. OH) to remove SO from flue gas 2And NOx to SO 3And NO 2And then the flue gas is purified by absorption of the eluent. H 2O 2Is an economic and environment-friendly oxidant, has the oxidation potential of +1.78 eV, and can generate hydroxyl free radicals (OH) with higher activity in the presence of a catalyst or ultraviolet rays SO as to rapidly react SO 2And NOx to SO 4 2-And NO 3 -. Photocatalytic coupling H 2O 2The oxidation absorption desulfurization and denitrification has great industrial development prospect. The Lichunhu et al have been engaged in research in this field, and have applied for a plurality of Chinese invention patents, such as "an integrated device and process for selective photocatalytic desulfurization and denitrification of flue gas" (CN 109046017A) and "a method and device for simultaneous photocatalytic oxidation and desulfurization and denitrification of flue gas" (CN 106621799A).
g-C 3N 4The material is a non-metal organic semiconductor material, has a layered structure similar to graphite, relatively stable physical and chemical properties, simple preparation and cheap raw materials; however, they also have disadvantages such as a small specific surface area and a high electron-hole recombination rate. Heterogeneous Fenton-like catalyst Fe 2(MoO 4) 3The catalyst has the advantages of multiple active sites, low zero charge, solid acid property, wide pH application range and the like, but the catalyst has lower catalytic efficiency when being used alone.
Disclosure of Invention
The invention aims to provide a photo-Fenton desulfurization and denitrification catalyst which is large in specific surface area, high in efficiency of photocatalytic Fenton synergy, high in ozone catalysis, and high in desulfurization and denitrification efficiency, and a preparation method thereof.
The invention uses gamma-Al 2O 3ZSM-5 molecular sieve, activated carbon fiber felt or ceramic as catalyst carrier, and synthesizing tubular Mn-g-C by template-free method 3N 4Further preparing tubular Mn-g-C by a one-step solvothermal method 3N 4/ Fe 2(MoO 4) 3And finally, loading the active component on a catalyst carrier through a binder. The synthesized multifunctional Mn-g-C 3N 4/ Fe 2(MoO 4) 3photo-Fenton desulfurization and denitrification catalyst for g-C 3N 4Performing morphology regulation and ion doping, and simultaneously constructing Mn-g-C 3N 4/ Fe 2(MoO 4) 3The composite photo-Fenton catalyst improves the photocatalytic efficiency and increases H 2O 2And O 3The utilization rate of the catalyst can not only generate a photo-promoted Fenton reaction to reduce the recombination of electrons and holes, but also catalyze O 3Thus greatly improving the photocatalytic synergy H 2O 2And (3) desulfurization and denitrification performance of oxidation absorption.
The photo-Fenton desulfurization and denitrification catalyst is characterized by comprising a catalyst carrier and a photo-Fenton active component loaded on the catalyst carrier through a binder, wherein the photo-Fenton active component comprises tubular manganese-doped graphite-phase carbon nitride and iron molybdate (Fe) loaded on the tubular manganese-doped graphite-phase carbon nitride 2(MoO 4) 3) (ii) a The weight components are as follows: 70-85 parts of catalyst carrier, 10-30 parts of binder and tubular manganese-doped graphite-phase carbon nitride (Mn-g-C) 3N 4) 0.5-2.0 parts of iron molybdate (Fe) 2(MoO 4) 3) 0.5 to 2.0 portions.
The catalyst carrier is gamma-Al 2O 3One or more of ZSM-5 molecular sieve, activated carbon fiber felt, ceramics (such as honeycomb ceramics and foamed ceramics) and the like.
The tubular manganese-doped graphite-phase carbon nitride (Mn-g-C) 3N 4) Tong (Chinese character of 'tong')Synthesized by a template-free method.
The iron molybdate (Fe) 2(MoO 4) 3) Ferric nitrate or ferric chloride is used as an iron source, ammonium molybdate or sodium molybdate is used as molybdenum salt, and the catalyst is synthesized by a hydrothermal method.
The binder is one or more of sodium carboxymethylcellulose, epoxy resin and sodium silicate, and an active component is loaded by an ultrasonic impregnation method.
A preparation method of a photo-Fenton desulfurization and denitrification catalyst comprises the following steps:
(1) washing and drying the catalyst carrier for later use;
(2) dissolving melamine or urea in organic solvent, heating and stirring to dissolve melamine or urea, cooling the solution, adding a certain amount of dilute nitric acid and manganese salt, washing and drying the generated precipitate, and finally roasting in a muffle furnace to obtain tubular Mn-g-C 3N 4；
(3) Ferric nitrate or ferric chloride is used as ferric salt, ammonium molybdate or sodium molybdate is used as molybdenum salt, and alkali liquor is used for adjusting the pH value to generate an iron molybdate precursor;
(4) tubular Mn-g-C obtained in the step (2) 3N 4Adding the mixture into mixed solution of iron molybdate precursors, and preparing tubular Mn-g-C by one-step solvothermal reaction 3N 4/ Fe 2(MoO 4) 3A photo-Fenton active component;
(5) and (3) preparing a binder solution, adding the photo-Fenton active component obtained in the step (4) into the binder solution, stirring for 2 hours, then adding the carrier washed and dried in the step (1), ultrasonically dipping, and drying for 12 hours to obtain the photo-Fenton desulfurization and denitrification catalyst.
The organic solvent in the step (2) is ethylene glycol or ethanol.
The manganese salt in the step (2) is one of manganese salts such as manganese acetate, manganese nitrate, manganese chloride and the like.
The concentration of the dilute nitric acid in the step (2) is 0.1-0.2 mol/L.
In the step (2), the roasting temperature of the muffle furnace is 350-550 ℃, and the heating rate is 5-10 ℃/min.
In the step (3), iron salt: the molar ratio of the molybdenum salt is 1: 1.5.
And (4) adjusting the pH of the alkali liquor in the step (3) to be ammonia water or sodium hydroxide solution.
The one-step solvothermal method in the step (4) is to place the reaction mixture in a hydrothermal kettle with a polytetrafluoroethylene lining, wherein the heating temperature is 140-180 ℃, and the reaction time is 12-24 hours.
The drying temperature in the step (6) is 30-120 ℃.
The photo-Fenton desulfurization and denitrification catalyst is used for VUV/H 2O 2The main chemical reactions involved in oxidation desulfurization and denitrification are as follows:
free radical generation and SO photolysis under vacuum ultraviolet radiation 2And NO reaction process:
tubular Mn-g-C 3N 4/ Fe 2(MoO 4) 3The process of generating free radicals on the surface of the photo-Fenton catalyst comprises the following steps:
(Vo represents an oxygen vacancy)
H 2O 2、O 3And free radical oxidation of SO 2The reaction process of (1):
H 2O 2、O 3and free radical oxidation of NO:
compared with the prior art, the invention has the following advantages:
1. synthesizing tubular Mn-g-C by template-free method 3N 4The method is simple and environment-friendly, and can effectively improve the g-C 3N 4The specific surface area of (a) increases the surface active sites.
2. For g-C 3N 4Mn ion doping can effectively separate photoproduction electrons and holes and catalyze O generated by a VUV system 3Avoidance of O 3Discharge to the atmosphere causes secondary pollution.
3. One-step solvothermal method for mixing iron molybdate precursor with tubular Mn-g-C 3N 4The catalyst is converted into the photo-Fenton catalytic active component, and the steps are simple.
4. Constructed Mn-g-C 3N 4/ Fe 2(MoO 4) 3The composite system can effectively promote the transfer of photon-generated carriers and realize the Fe on the surface of the photo-Fenton catalyst 2+And Fe 3+And Fe is circulated and made 2+And H 2O 2A photo-promoted Fenton reaction occurs in the photo-catalytic system.
The invention can be widely applied to the purification treatment of various flue gases to realize SO 2And the ultra-low emission of NOx, and the invention has the characteristics of low cost, simple synthesis, environmental protection and the like.
Drawings
FIG. 1 is a tubular g-C prepared in example 1 3N 4Topography at 45 times magnification.
Fig. 2 is a morphology diagram of the photo-Fenton catalyst prepared in example 1.
FIG. 3 shows tubular Mn-g-C prepared in example 1 3N 4/Fe 2(MoO 4) 3XRD spectrum of photo-Fenton catalyst.
FIG. 4 shows tubular Mn-g-C prepared in example 1 3N 4/Fe 2(MoO 4) 3TEM images of photo-Fenton catalyst.
FIG. 5 shows photo-Fenton catalysts prepared in example 1 in different H 2O 2Desulfurization and denitrification performance under concentration.
FIG. 6 shows a tubular Mn-g-C 3N 4/Fe 2(MoO 4) 3A photo-Fenton effect mechanism diagram of the photo-Fenton catalyst.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings by way of specific embodiments.