阅读说明：本技术 用于催化燃烧脱除烟气氯苯的scr催化剂改性方法及催化剂 (SCR catalyst modification method for removing flue gas chlorobenzene by catalytic combustion and catalyst ) 是由 何川 孔凡海 王丽朋 张发捷 李乐田 吴国勋 卞子君 李昂 于 2021-07-28 设计创作，主要内容包括：本发明涉及一种用于催化燃烧脱除烟气氯苯的SCR催化剂改性方法及催化剂,方法包括：S1、准备钒钛系催化剂,将该催化剂研磨,得到钒钛系催化剂粉末；S2、准备改性前驱体,将该前驱体加入水溶液中得到改性前驱体溶液,改性前驱体包括锰、铬、铜、锆、铌、钼元素中的一种或多种；S3、将钒钛系催化剂粉末加入步改性前驱体溶液中形成混合液；S4、将步骤S3中混合液进行烘干、煅烧,得到改性催化剂,该催化剂的活性组分为锰、铬、铜、锆、铌、钼的氧化物中的一种或多种。本发明对钒钛系催化剂改性,在保证NOx脱除性能的同时强化其对氯苯的催化燃烧性能,进而实现工业炉烟气NOx和氯苯的协同处理,可大幅削减工业炉烟气处理成本。(The invention relates to a method for modifying an SCR (selective catalytic reduction) catalyst for removing chlorobenzene in flue gas by catalytic combustion and the catalyst, wherein the method comprises the following steps: s1, preparing a vanadium-titanium catalyst, and grinding the catalyst to obtain vanadium-titanium catalyst powder; s2, preparing a modified precursor, and adding the precursor into an aqueous solution to obtain a modified precursor solution, wherein the modified precursor comprises one or more of manganese, chromium, copper, zirconium, niobium and molybdenum; s3, adding vanadium-titanium catalyst powder into the modified precursor solution to form a mixed solution; s4, drying and calcining the mixed solution in the step S3 to obtain the modified catalyst, wherein the active component of the modified catalyst is one or more of oxides of manganese, chromium, copper, zirconium, niobium and molybdenum. The vanadium-titanium catalyst is modified, the catalytic combustion performance of the vanadium-titanium catalyst to chlorobenzene is enhanced while the NOx removal performance is ensured, the synergistic treatment of the NOx and the chlorobenzene in the industrial furnace flue gas is further realized, and the treatment cost of the industrial furnace flue gas can be greatly reduced.)

1. A method for modifying an SCR catalyst for removing chlorobenzene in flue gas by catalytic combustion is characterized by comprising the following steps: the method comprises the following steps:

s1, preparing a vanadium-titanium catalyst, and grinding the catalyst to obtain vanadium-titanium catalyst powder;

s2, preparing a modified precursor, and adding the precursor into an aqueous solution to obtain a modified precursor solution, wherein the modified precursor comprises one or more of manganese, chromium, copper, zirconium, niobium and molybdenum;

s3, adding the vanadium-titanium catalyst powder obtained in the step S1 into the modified precursor solution obtained in the step S2 to form a mixed solution;

s4, drying and calcining the mixed solution in the step S3 to obtain the modified catalyst, wherein the active component of the modified catalyst is one or more of oxides of manganese, chromium, copper, zirconium, niobium and molybdenum.

2. The SCR catalyst modification method for catalytic combustion removal of flue gas chlorobenzene according to claim 1, characterized in that: the modified precursor is selected from one or more of ammonium orthomolybdate, ammonium paramolybdate, ammonium dimolybdate, ammonium tetramolybdate, molybdenum nitrate, molybdenum sulfate, manganese nitrate, chromium nitrate, copper nitrate, zirconium nitrate and niobium oxalate.

3. The SCR catalyst modification method for catalytic combustion removal of flue gas chlorobenzene according to claim 2, characterized in that: in step S4, the mass of the oxide in the modified catalyst accounts for 2 to 6% of the mass of the modified catalyst.

4. The SCR catalyst modification method for catalytic combustion removal of flue gas chlorobenzene according to claim 1, characterized in that: the mass ratio of the modified precursor in the step S2 to the vanadium-titanium catalyst in the step S1 is 3: 20-3: 5.

5. the SCR catalyst modification method for catalytic combustion removal of flue gas chlorobenzene according to claim 1, characterized in that: in step S1, the mesh number of the vanadium-titanium based catalyst powder is not more than 200 mesh.

6. The SCR catalyst modification method for catalytic combustion removal of flue gas chlorobenzene according to claim 1, characterized in that: in step S3, the vanadium-titanium based catalyst powder in step S1 is added to the modified precursor solution in step S2, and then stirred at 40 to 50 ℃ to form a viscous mixture.

7. The SCR catalyst modification method for catalytic combustion removal of flue gas chlorobenzene according to claim 6, characterized in that: heating by magnetic stirring forms a viscous mixture.

8. The SCR catalyst modification method for catalytic combustion removal of flue gas chlorobenzene according to claim 1 or 6, characterized in that: in step S4, the drying and calcining steps are as follows: drying the mixed solution at 80-150 ℃ for 10-15h, and calcining at 400-600 ℃ for 3-6 h.

9. A modified catalyst prepared by the SCR catalyst modification method for catalytic combustion removal of flue gas chlorobenzene according to any one of claims 1 to 8, characterized in that: the active component of the modified catalyst is one or more of oxides of manganese, chromium, copper, zirconium, niobium and molybdenum.

10. Use of a modified catalyst according to claim 9 for catalytic combustion removal of flue gas chlorobenzene, characterized in that: the catalyst is used as a catalyst for removing the chlorobenzene in the flue gas at the reaction temperature of 200-400 ℃.

Technical Field

The invention belongs to the field of SCR denitration catalyst modification, and particularly relates to an SCR catalyst modification method and a catalyst for removing flue gas chlorobenzene by catalytic combustion.

Background

Because the raw materials or fuels of non-electric boilers such as steel, garbage incineration, chemical industry and the like have diversity and complexity, the flue gas discharged by partial industrial furnaces often contains a large amount of nitrogen oxides (NOx) and chlorinated volatile organic compounds. For high-concentration NOx flue gas, Selective Catalytic Reduction (SCR) is the most effective method, wherein a vanadium-based catalyst has excellent denitration capability in a medium-temperature section (300-400 ℃), and the SCR catalyst widely used at present is mainly V₂O₅-WO₃/TiO₂Catalyst (vanadium tungsten titanium catalyst).

The catalytic combustion method is an effective method for treating low-density organic pollutants in flue gas, can be used for removing chlorobenzene in the flue gas, reduces reaction energy barrier through a catalyst, leads volatile organic compounds and oxygen to be more easily subjected to degradation reaction on the surface of a solid catalyst, and generates CO₂And H₂And O, achieving the purpose of harmlessness. However, in the catalytic combustion process of the chlorine-containing volatile organic compounds, the reaction process is complex, and intermediate toxic and side effects are generatedThe products are of various kinds. At high temperature, chlorine-containing reaction intermediates are easy to interact to form highly toxic polychlorinated compounds, and simultaneously, generated chlorine species react with the surface of the catalyst to cause irreversible poisoning of active components of the catalyst.

For such an industrial boiler, if a tail NOx treatment facility and a chlorobenzene treatment facility are separately constructed, there are problems of large floor space, high investment and high running costs. Taking both practicability and economy into consideration, the currently generally accepted treatment mode is to use the same catalyst to cooperatively treat NOx and chlorobenzene in the flue gas. At present, the research on the catalyst for the denitration and the chlorobenzene removal of the waste gas of the industrial furnace is less. The denitration mainly adopts an SCR method and uses V₂O₅-WO₃/TiO₂A catalyst. The chlorobenzene and other volatile organic compounds are mainly removed by a catalyst combustion method.

Chinese patent CN201910806321.3 discloses a VOCs catalytic combustion catalyst, a preparation method and application thereof, TiO modified by sulfuric acid₂ CeO₂The composite oxide is used as a carrier, a catalyst taking noble metal ruthenium oxide and/or transition metal vanadium oxide as active components is loaded, and SiO is finally wrapped₂Shell, core-shell type VOCs catalytic combustion catalyst is formed.

Chinese patent CN202011140987.9 discloses a catalyst for waste gas purification and a preparation method thereof, namely samarium (Sm) and erbium (Er) co-doped CuFe₂O₄As an active component, CeO₂The catalyst is used as a carrier to prepare the catalyst with excellent catalytic combustion performance of VOCs.

Chinese patent CN202110251025.9 discloses a highly stable catalyst for low-temperature catalytic combustion of chlorine-containing volatile organic compounds and a preparation method thereof, the method adopts transition metal elements niobium, cerium and chromium as catalytic components, and the oxidation-reduction capability and electronic structure of the catalyst are adjusted by processes of coprecipitation, hydrothermal treatment, atmosphere heat treatment and the like, and the prepared composite metal catalyst has the advantages that due to the change of the electronic structure, the catalytic property of the active component is correspondingly changed, and the catalyst has stronger tolerance to chlorine species in the reaction process, and has excellent degradation effect on industrial chlorobenzene.

The above patents generally focus only on catalytic combustion performance of volatile organic compounds such as chlorobenzene, and do not take synergistic consideration of NOx and chlorobenzene removal. In addition, the methods disclosed in the above patents generally have high cost and are economically disadvantageous in the case of industrialization.

Disclosure of Invention

The invention aims to provide an SCR catalyst modification method and a catalyst for catalytic combustion removal of flue gas chlorobenzene, which can coordinate NOx removal and chlorobenzene removal and greatly reduce the treatment cost of industrial furnace flue gas.

In order to achieve the purpose, the invention adopts a technical scheme that:

an SCR catalyst modification method for removing chlorobenzene in flue gas by catalytic combustion comprises the following steps:

s1, preparing a vanadium-titanium catalyst, and grinding the catalyst to obtain vanadium-titanium catalyst powder, preferably a vanadium-tungsten-titanium catalyst;

s2, preparing a modified precursor, and adding the precursor into an aqueous solution to obtain a modified precursor solution, wherein the modified precursor comprises one or more of manganese, chromium, copper, zirconium, niobium and molybdenum;

s3, adding the vanadium-titanium catalyst powder obtained in the step S1 into the modified precursor solution obtained in the step S2 to form a mixed solution;

s4, drying and calcining the mixed solution in the step S3 to obtain the modified catalyst, wherein the active component of the modified catalyst is one or more of oxides of manganese, chromium, copper, zirconium, niobium and molybdenum, and more preferably, the active component in the modified precursor is only molybdenum element.

Preferably, the modification precursor is selected from one or more of ammonium orthomolybdate, ammonium paramolybdate, ammonium dimolybdate, ammonium tetramolybdate, molybdenum nitrate, molybdenum sulfate, manganese nitrate, chromium nitrate, copper nitrate, zirconium nitrate and niobium oxalate.

Further preferably, in step S4, the mass of the oxide in the modified catalyst accounts for 2 to 6% of the mass of the modified catalyst.

Preferably, the mass ratio of the modified precursor in step S2 to the vanadium-titanium based catalyst in step S1 is 3: 20-3: 5, preferably, 200g of the vanadium-titanium based catalyst is used in the step S1, and 37 to 104g of the modification precursor is used in the step S2.

Preferably, in step S1, the mesh number of the vanadium-titanium based catalyst powder is not more than 200 meshes, so that the vanadium-titanium based catalyst powder is easily dissolved in the modified precursor solution in step S2.

Preferably, in step S3, the vanadium-titanium based catalyst powder in step S1 is added to the modified precursor solution in step S2, and then stirred at 40 to 50 ℃ to form a viscous mixture.

Preferably, a viscous mixed solution is formed by magnetic stirring and heating, and the stirring effect is good.

Preferably, in step S4, the drying and calcining steps are as follows: drying the viscous mixed solution at 80-150 ℃ for 10-15h, and calcining at 400-600 ℃ for 3-6h, wherein the drying temperature is more preferably 90 ℃, and the drying time is more preferably 12 h; the calcination temperature is more preferably 500 ℃, and the calcination time is more preferably 4 hours; the calcined catalyst has higher mechanical strength and better wear resistance.

The invention adopts another technical scheme that:

the modified catalyst is prepared by an SCR catalyst modification method for removing chlorobenzene in flue gas through catalytic combustion, the active component of the modified catalyst is one or more of oxides of manganese, chromium, copper, zirconium, niobium and molybdenum, and further preferably, the active component in the modified precursor only comprises molybdenum.

The invention adopts another technical scheme that:

the application of the modified catalyst for catalytic combustion removal of flue gas chlorobenzene is that the catalyst is used as a catalyst for removal of flue gas chlorobenzene at a reaction temperature of 200-400 ℃, preferably at a reaction temperature of 210-300 ℃.

Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages: the method modifies the conventional vanadium-titanium catalyst, strengthens the catalytic combustion performance of the catalyst to chlorobenzene while ensuring the NOx removal performance, further realizes the cooperative treatment of the NOx and the chlorobenzene in the industrial furnace flue gas, can greatly reduce the treatment cost of the industrial furnace flue gas, and has wide application prospect.

Detailed Description

The invention will be further described with reference to the examples shown below.

An SCR catalyst modification method for removing chlorobenzene in flue gas by catalytic combustion comprises the following steps:

s1, preparing a vanadium-titanium catalyst, and grinding the catalyst to obtain vanadium-titanium catalyst powder, wherein the mesh number of the vanadium-titanium catalyst powder is less than or equal to 200 meshes, so that the vanadium-titanium catalyst powder is conveniently dissolved in the modified precursor solution in the step S2, and the vanadium-titanium catalyst is preferably a vanadium-tungsten-titanium catalyst;

s2, preparing a modified precursor, and adding the precursor into an aqueous solution to obtain a modified precursor solution, wherein the modified precursor comprises one or more of manganese, chromium, copper, zirconium, niobium and molybdenum; the modified precursor is selected from one or more of ammonium orthomolybdate, ammonium paramolybdate, ammonium dimolybdate, ammonium tetramolybdate, molybdenum nitrate, molybdenum sulfate, manganese nitrate, chromium nitrate, copper nitrate, zirconium nitrate and niobium oxalate, and is prepared from ammonium molybdate [ (NH)₄)₆Mo₇O₂₄·4H₂O]Is optimal;

the mass ratio of the modified precursor in the step S2 to the vanadium-titanium catalyst in the step S1 is 3: 20-3: for example, 200g of the vanadium-titanium based catalyst in step S1 and 37 to 104g of the modification precursor in step S2 are used.

S3, adding the vanadium-titanium catalyst powder obtained in the step S1 into the modified precursor solution obtained in the step S2 to form a mixed solution; preferably, the catalyst powder and the modified precursor solution are stirred at 40-50 ℃ to form a viscous mixed solution, and preferably, the viscous mixed solution is formed by magnetic stirring and heating, is fully dissolved and has a good stirring effect.

S4, drying and calcining the mixed solution obtained in the step S3 to obtain the modified catalyst, wherein the active component of the modified catalyst is one or more oxides of manganese, chromium, copper, zirconium, niobium and molybdenum, and the mass of the oxide in the modified catalyst accounts for 2-6% of the mass of the modified catalyst. Further preferably, the active component in the modified precursor only includes molybdenum element.

Preferably, the drying and calcining steps are as follows: drying the viscous mixed solution at 80-150 ℃ for 10-15h, and calcining at 400-600 ℃ for 3-6h, wherein the drying temperature is more preferably 90 ℃, and the drying time is more preferably 12 h; the calcination temperature is more preferably 500 ℃, and the calcination time is more preferably 4 hours; the calcined catalyst has higher mechanical strength and better wear resistance.

Example one

S1 taking a typical V₂O₅-WO₃/TiO₂Crushing and grinding the catalyst, and sieving the crushed and ground catalyst by a 200-mesh sieve to obtain catalyst powder;

s2, adding 300ml deionized water into 1L beaker, adding 37g ammonium molybdate [ (NH) while continuously stirring₄)₆Mo₇O₂₄·4H₂O]Forming a modified precursor solution;

s3, adding 200g of vanadium, tungsten and titanium catalyst powder obtained in the step S1 into the modified precursor solution obtained in the step S2, continuously stirring at 45 ℃ until water is volatilized to form viscous slurry, removing magnetons, and stopping stirring;

s4, placing the beaker filled with the viscous slurry into a 90 ℃ oven for drying for 12h, transferring the dried modified catalyst into a crucible, placing the crucible into a muffle furnace for calcining for 4h at 500 ℃, and obtaining the reinforced modified catalyst S1 which can be used for removing NOx in a synergistic manner and removing chlorobenzene by catalytic combustion.

Example two

The second embodiment is different from the first embodiment in that: the quality of ammonium molybdate varies.

S1 taking a typical V₂O₅-WO₃/TiO₂Crushing and grinding the catalyst, and sieving the crushed and ground catalyst by a 200-mesh sieve to obtain catalyst powder;

s2, adding 300ml deionized water into a 1L beaker, and adding 76g ammonium molybdate [ (NH) into the beaker while continuously stirring₄)₆Mo₇O₂₄·4H₂O]Forming a modified precursor solution;

s3, adding 200g of vanadium, tungsten and titanium catalyst powder obtained in the step S1 into the modified precursor solution obtained in the step S2, continuously stirring at 45 ℃ until water is volatilized to form viscous slurry, removing magnetons, and stopping stirring;

s4, placing the beaker filled with the viscous slurry into a 90 ℃ oven for drying for 12h, transferring the dried modified catalyst into a crucible, placing the crucible into a muffle furnace for calcining for 4h at 500 ℃, and obtaining the reinforced modified catalyst S1 which can be used for removing NOx in a synergistic manner and removing chlorobenzene by catalytic combustion.

EXAMPLE III

The third embodiment is different from the first embodiment in that: the quality of ammonium molybdate varies.

S1 taking a typical V₂O₅-WO₃/TiO₂Crushing and grinding the catalyst, and sieving the crushed and ground catalyst by a 200-mesh sieve to obtain catalyst powder;

s2, adding 300ml deionized water into a 1L beaker, and adding 104g ammonium molybdate [ (NH) while continuously stirring₄)₆Mo₇O₂₄·4H₂O]Forming a modified precursor solution;

s3, adding 200g of vanadium, tungsten and titanium catalyst powder obtained in the step S1 into the modified precursor solution obtained in the step S2, continuously stirring at 45 ℃ until water is volatilized to form viscous slurry, removing magnetons, and stopping stirring;

s4, placing the beaker filled with the viscous slurry into a 90 ℃ oven for drying for 12h, transferring the dried modified catalyst into a crucible, placing the crucible into a muffle furnace for calcining for 4h at 500 ℃, and obtaining the reinforced modified catalyst S1 which can be used for removing NOx in a synergistic manner and removing chlorobenzene by catalytic combustion.

Comparative example

200g of typical V is selected₂O₅-WO₃/TiO₂Catalyst, i.e. conventional vanadium tungsten titanium catalyst.

Testing and analysis

Test 1

Comparative examples and the main components of the catalysts S1, S2 and S3 for the enhancement modification in examples 1 to 3 were measured by an X-ray fluorescence spectrometer, and the main components of the four samples are shown in Table 1.

TABLE 1 Main Components (%)% of the conventional vanadium-tungsten-titanium catalyst in the comparative example, and the strengthening modified catalysts S1, S2 and S3 in examples 1 to 3

Composition (I)	Comparative example	S1	S2	S3
					TiO2	90.32	87.95	86.61	86.12
WO3	5.43	5.57	5.27	4.83
					V2O5	1.2	1.13	1.09	0.93
MoO3	-	2.31	4.52	5.93
					SiO2	2.45	2.55	2.44	2.16

As can be seen from Table 1, in examples 1 to 3, all of the catalysts S1, S2 and S3 had MoO as an active component₃The reinforced modification method of the invention is proved to effectively load the active substance on the vanadium-tungsten-titanium catalyst.

Test 2

And (3) evaluating the performance of the SCR denitration catalyst strengthening modification method for removing the chlorobenzene in the flue gas by catalytic combustion.

Respectively crushing and grinding four samples of the conventional vanadium-tungsten-titanium catalyst in the comparative example and the enhanced modified catalysts S1, S2 and S3 in the examples 1 to 3 to 40-60 meshes, sieving, taking 2ml of the respectively prepared granular samples, and then carrying out a performance test of coordinated denitration and dechlorination on a self-made fixed bed reactor, wherein the conventional vanadium-tungsten-titanium catalyst in the comparative example and the enhanced modified catalysts S1, S2 and S3 in the examples 1 to 3 correspond to one reactor, and the simulated flue gas type, the simulated flue gas quality and the tested flue gas temperature in each reactor are the same.

The simulated smoke consists of 500ppm NO and 500ppm NH₃、100ppm SO₂、7％O₂、10％H₂O, 100ppm chlorobenzene and the balance N₂The flow is controlled by a mass flowmeter. And all components of the flue gas enter the self-made fixed bed reactor through the mixer. The reactor is made of a quartz tube with the diameter of 8mm, and the outside of the reactor is heat-tracing and heat-preserving by a heat tracing band. And placing a test sample in a constant-temperature section of the reactor, and testing the temperature of flue gas to be 200-400 ℃. And the flue gas at the outlet of the reactor is treated by an activated carbon tail gas treatment system and then is discharged.

And after the temperature of the flue gas reaches each testing temperature point and the system is stabilized for 0.5h, testing the concentration of NO and chlorobenzene in the flue gas at the inlet and the outlet of the reactor.

The denitration efficiency of the sample is calculated by formula (1).

η＝(NO_in-NO_out)/NO_in×100 (1)

In the formula: eta is the denitration efficiency of the sample; NO_inIs the concentration of the reactor inlet flue gas NO; NO_outIs the concentration of the flue gas NO at the outlet of the reactor.

The sample chlorobenzene removal efficiency was calculated by formula (2).

E＝(CB_in-CB_out)/CB_in×100 (1)

In the formula: e is the chlorobenzene removal efficiency of the sample; CB (CB)_inThe concentration of chlorobenzene in the inlet flue gas of the reactor; CB (CB)_outIs the concentration of chlorobenzene in the outlet flue gas of the reactor.

The conventional vanadium-tungsten-titanium catalyst in the comparative example and the enhanced modified catalysts S1, S2 and S3 in examples 1 to 3 were subjected to denitration and dechlorination tests, and the results are shown in Table 2.

TABLE 2 test results of denitration efficiency and chlorobenzene removal efficiency (%)

As can be seen from table 2, for the denitration efficiency at the same temperature, the denitration efficiency of the enhanced modified catalysts S1, S2 and S3 in examples 1 to 3 is significantly higher than that of the conventional vanadium tungsten titanium catalyst in the comparative example; aiming at the chlorobenzene removal efficiency at the same temperature, the chlorobenzene removal efficiency of the enhanced modified catalysts S1, S2 and S3 in the examples 1-3 is obviously higher than that of the conventional vanadium tungsten titanium catalyst in the comparative example; and can know that: at the same temperature, the denitration efficiency and chlorobenzene removal efficiency of the enhanced modified catalyst S2 in example 2 are higher than those of the enhanced modified catalysts S1 and S3 in examples 1 and 3, respectively. In addition, the strengthening and modifying catalysts S1, S2 and S3 can be used at the temperature of 200-400 ℃; the catalyst has good denitration efficiency and chlorobenzene removal efficiency at the temperature of 200-300 ℃, the denitration efficiency and chlorobenzene removal efficiency of the catalyst at 210 ℃ are higher than 200 ℃, and the catalyst is preferably used at the reaction temperature of 210-300 ℃.

The SCR catalyst modification method for removing the chlorobenzene in the flue gas by catalytic combustion provided by the invention leads the conventional V₂O₅-WO₃/TiO₂The catalyst greatly widens the low-temperature denitration activity, and simultaneously greatly improves the catalytic combustion effect of the catalyst on chlorobenzene at each temperature point.

The modification method effectively realizes the functional reinforcement of the conventional SCR catalyst, and ensures V₂O₅-WO₃/TiO₂The denitration performance of the SCR catalyst is excellent in chlorobenzene catalytic combustion performance, so that the aim of coordinated denitration and chlorobenzene removal of the non-electric industrial furnace is fulfilled, the flue gas treatment cost of the industrial furnace can be greatly reduced, and the application prospect is wide.

The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.