阅读说明：本技术 一种适用于低温含硫烟气的脱硝催化剂及其制备方法 (Denitration catalyst suitable for low-temperature sulfur-containing flue gas and preparation method thereof ) 是由 杨治 于 2019-04-23 设计创作，主要内容包括：本发明公开了一种适用于低温含硫烟气的脱硝催化剂及其制备方法,催化剂以五氧化二钒为活性组分,以活性炭为载体,以硫酸氢铝为抗硫剂,该催化剂具有优良的低温催化活性及低的二氧化硫氧化率。(The invention discloses a denitration catalyst suitable for low-temperature sulfur-containing flue gas and a preparation method thereof.)

1. The denitration catalyst suitable for low-temperature sulfur-containing flue gas is characterized in that vanadium pentoxide is used as an active component, activated carbon is used as a carrier, and aluminum bisulfate is used as a sulfur-resisting agent, and the denitration catalyst comprises the following components in percentage by mass: 0.1-5.0% of vanadium pentoxide, 1-20% of aluminum bisulfate and 75-98.9% of activated carbon.

2. The denitration catalyst suitable for low-temperature sulfur-containing flue gas as claimed in claim 1, wherein one or more of ammonium metavanadate, vanadyl sulfate and vanadyl oxalate is a raw material of vanadium pentoxide, which is converted into vanadium pentoxide during preparation or use.

3. The denitration catalyst suitable for low-temperature sulfur-containing flue gas as claimed in claim 1, wherein aluminum bisulfate is used as a sulfur-resistant agent, the source of aluminum bisulfate in the catalyst can be selected from aluminum persulfate, aluminum sulfate, aluminum nitrate, aluminum chloride, aluminum acetate and aluminum oxide, and the aluminum compound which is not the source of aluminum bisulfate can be converted into aluminum bisulfate during preparation or use.

4. The denitration catalyst according to claim 1, wherein the form of the activated carbon is selected from the group consisting of powdered activated carbon, granular activated carbon, honeycomb activated carbon, fibrous activated carbon fiber, and gauze activated carbon cloth.

5. The preparation method of the denitration catalyst suitable for low-temperature sulfur-containing flue gas, which is implemented according to claim 1, is characterized in that the denitration catalyst suitable for low-temperature sulfur-containing flue gas is prepared by one of (1) an impregnation method, (2) a spraying method and (3) an extrusion method.

6. The method according to claim 5, wherein the vanadium salt and the aluminum salt described in claim 2 or claim 3 are supported on the activated carbon support described in claim 4 by an impregnation method to obtain the denitration catalyst suitable for low-temperature sulfur-containing flue gas, the weight percentage of aluminum bisulfate in the catalyst is 1 to 20%, the weight percentage of other aluminum salts is calculated by aluminum bisulfate, the weight percentage of vanadium salt is calculated by vanadium pentoxide is 0.1 to 5%, and the impregnation method is a preferred preparation method, and comprises the following steps:

step one, dissolving vanadium salt and aluminum salt with calculated mass in water, soaking activated carbon for 5 minutes in equal volume,

step two, draining the catalyst at room temperature for 15 minutes,

step three, placing the drained catalyst in an oven for drying at the temperature of 120 ℃ for 5 hours,

and step four, roasting the dried catalyst for 3 hours at 400 ℃ in a nitrogen atmosphere.

7. The method according to claim 5, wherein the vanadium salt and the aluminum salt according to claims 2 and 3 are supported on the activated carbon carrier according to claim 4 by a spraying method to obtain the denitration catalyst suitable for low-temperature sulfur-containing flue gas, the weight percentage of aluminum bisulfate in the catalyst is 1-20%, the weight percentage of other aluminum salts is calculated by aluminum bisulfate, the weight percentage of vanadium salt is calculated by vanadium pentoxide is 0.1-5%, and the spraying method is a suboptimal preparation method, comprising the following steps:

dissolving vanadium salt and aluminum salt with calculated mass in water, atomizing the salt solution by using spraying equipment, uniformly spraying the atomized salt solution on active carbon,

step two, the catalyst is drained at room temperature, the draining time is 15 minutes,

step three, placing the drained catalyst in an oven for drying at the temperature of 120 ℃ for 5 hours,

and step four, roasting the dried catalyst for 3 hours at 400 ℃ in a nitrogen atmosphere.

8. The method for preparing the denitration catalyst suitable for the low-temperature sulfur-containing flue gas as claimed in claim 5, wherein the method for preparing the denitration catalyst suitable for the low-temperature sulfur-containing flue gas by an extrusion method comprises the following steps:

step one, preparing pug: mixing aluminum salt, vanadium salt and powdered activated carbon according to the formula ratio, adding water 0.9 times of the weight of the mixture and clay 0.2 times of the weight of the mixture, mixing the mixture in a mixing mill for 2 hours to obtain pug,

step two, forming a catalyst: and (2) preparing the pug into a honeycomb catalyst blank by an extruder, or a plate catalyst blank, or extruding and coating the pug on a steel wire mesh plate to prepare a plate catalyst blank containing a supporter, drying the prepared catalyst blank at 60 ℃ for 20 hours, drying at 120 ℃ for 5 hours, and roasting the dried catalyst at 400 ℃ for 3 hours in a nitrogen atmosphere.

Technical Field

The invention relates to a denitration catalyst suitable for low-temperature sulfur-containing flue gas and a preparation method thereof, belonging to the technical field of nitrogen oxide control in environmental protection.

Background

Nitrogen oxides NOx are important atmospheric pollutants, and are one of the main pollutants causing disasters such as acid rain, photochemical fog, greenhouse effect and the like, and adverse effects of nitrogen oxides on the environment are seriously concerned by human beings. The combustion process using coal, biomass and garbage as fuel is the main source of nitrogen oxides, so the emission control of the flue gas generated by the combustion of the fuel is increasingly strengthened. NH (NH)₃Selective Catalytic Reduction (SCR) is widely used in the aforementioned flue gas treatment process because of its excellent reaction selectivity and activity. At present, NH₃The selective catalytic reduction technology mainly uses a vanadium tungsten titanium catalyst to realize the reduction of the emission of nitrogen oxides. The using temperature of the vanadium-tungsten-titanium catalyst is 300-400 ℃, and the vanadium-tungsten-titanium catalyst has good stability of resisting sulfur and water poisoning, so the catalyst is usually arranged in a high-temperature flue gas environment.

However, in the actual combustion process, the flue gas temperature of many emission scenarios is below 300 degrees celsius, for example: (1) when a power plant runs at low load, the smoke temperature is usually lower than 300 ℃, the activity of the catalyst is poor, 2, the smoke temperature of non-electric power industries (steel, nonferrous materials, building materials, glass, cement and the like) is lower and is usually lower than 250 ℃, and 3, a small boiler (1-5 tons/hour) is adopted, and the smoke temperature is usually lower than 200 ℃.

The research shows that the manganese and copper oxides are NH under low temperature condition₃The flue gas treated by the denitration catalyst in the practical application process may contain tens to thousands of ppm of sulfur dioxide, and the sulfur dioxide and the water vapor in the flue gas can react with manganese and copper oxides to generate corresponding sulfates. Sulfate of manganese and copper to NH at the temperature lower than 200 DEG C₃SCR reactions have little catalytic activity. Wangbaodong et al (environmental chemistry, 2018, volume 37, page 782) summarize the research work of sulfur resistance and water resistance of low-temperature SCR denitration catalysts. The existing work shows that the addition of cerium oxide into the catalyst can well improve the water-resistant and sulfur-resistant performance of the catalyst, sulfur dioxide preferentially reacts with cerium oxide under the reaction condition to generate cerium sulfate, and the cerium sulfate can inhibit the adsorption of the sulfur dioxide on the catalyst, thereby protecting the active substance manganese oxide. The final activity of the catalyst cannot be clearly controlled due to the difference in test time and temperature among researchers in the literature, but it is certain that the catalyst activity gradually decreases as the test time increases. The water and sulfur resistance of the catalyst can be greatly improved by adding the ferric salt into the manganese catalyst, but the sulfur dioxide oxidation rate is not mentioned.

Liu Zheng Yu (chemical industry, 2008, 59 vol., 1894) summarized V₂O₅Research on the application of the carbon-based material in flue gas desulfurization and denitrification is advanced. V₂O₅When the temperature of the carbon-based material is lower than 200 ℃, the catalyst has excellent denitration catalytic reaction activity even if water vapor and sulfur dioxide exist. To increase V₂O₅Desulfurization activity of carbon-based materials, researchers have promoted the oxidation of sulfur dioxide on catalysts by post-treatment to increase oxygen-containing functional groups on the carbon material. But due to V₂O₅Reaction of the sulfuric acid adsorbed by the carbon-based material with ammonia gas to form ammonium bisulfate, resulting in V₂O₅CarbonThe denitration activity of the base material is reduced along with the time, and the denitration activity of the catalyst can be recovered after the ammonium bisulfate is decomposed.

From the above description, it can be seen that the demand for developing a denitration catalyst with excellent sulfur resistance and steam poisoning resistance at low temperature is urgent, but the existing copper and manganese oxide catalyst systems cannot meet the actual demand. V₂O₅The good desulfurization and denitrification performance of the carbon-based material shows that the improvement of the material can inhibit the adsorption of sulfur dioxide on the surface of the catalyst, and the development of the denitrification catalyst with excellent sulfur resistance and steam poisoning resistance at low temperature is very possible.

Note: flue gas treated by the denitration catalyst in the practical application process may contain tens to thousands of ppm of sulfur dioxide. In order to reduce the corrosion of sulfuric acid generated by sulfur dioxide oxidation to downstream pipelines and equipment, the oxidation rate of sulfur dioxide of the catalyst by the national standard of vanadium denitration catalyst (see the national standard of the people's republic of China, honeycomb type flue gas denitration catalyst GB/T31587 and 2015 inner surface 7) is limited to be not more than 1%, and in order to achieve the standard, a catalyst manufacturer has strict internal limits on metal impurities of the catalyst, especially iron elements and alkali metal elements. However, most of the current patent applications or research reports do not disclose sulfur dioxide oxidation rate data of the relevant catalyst.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a denitration catalyst suitable for low-temperature sulfur-containing flue gas and a preparation method thereof, wherein the catalyst has excellent catalytic activity at 130-260 ℃, and the oxidation rate of sulfur dioxide is not more than 2%.

The existing research (journal of chemical industry, 2008, volume 59, 1894) shows that V₂O₅V for carbon-based materials at temperatures below 200 ℃ even in the presence of water vapor and sulfur dioxide₂O₅The carbon-based material also has excellent denitration catalytic reaction activity, but as the catalyst testing time is prolonged, due to V₂O₅Ammonium sulfate V is generated on the surface of carbon-based material₂O₅Carbon-based material loses denitration catalytic activity and inactivated V₂O₅C carbon-based material subjected to appropriate regeneration treatment, V₂O₅The carbon-based material can recover the denitration catalytic reaction activity. At V₂O₅In a carbon-based material, V₂O₅Is an active species for denitration catalytic reaction, and the carbon material is a carrier and is SO₂Oxidation to SO₃The catalyst of (1). Such as V₂O₅When the carbon-based material is applied to denitration catalytic reaction activity, the carrier pair SO must be inhibited₂Catalytic oxidation to SO₃The reactivity of (a). The following measures can generally be taken to suppress SO₂Catalytic oxidation to SO₃Reaction (1) of (1) increasing acidity of the catalyst surface and suppressing SO₂Adsorption, (2) masking or eliminating SO₂Catalytic oxidation to SO₃The reactive center of (1).

The inventor's earlier application (chinese patent, application No. 201510704002.3) shows that after aluminum sulfate is added to a vanadium-tungsten-titanium catalyst, the catalyst has good alkali metal poisoning resistance, and at the same time, the sulfur dioxide oxidation rate of the catalyst is even slightly reduced, and the denitration activity is slightly increased. The above results suggest that the aluminum sulfate salt can increase the acidity of the catalyst surface to suppress the adsorption of sulfur dioxide and promote NH₃Adsorption on the catalyst surface results in NH₃The SCR reaction proceeds faster. For better inhibition of sulfur dioxide adsorption, the inventor adopts aluminum bisulfate with stronger acidity to V₂O₅Surface modification is carried out on the carbon-based material to inhibit sulfur dioxide adsorption and block SO on the surface of the carbon-based material₂Catalytic oxidation to SO₃The reactive center of (1). The inventor has not seen a report of the related inventive idea in the published reports.

Since aluminium bisulfate has acidic and non-oxidizing properties, it can: (1) promoting ammonia gas adsorption, thereby keeping and even increasing the activity of the catalyst, (2) inhibiting sulfur dioxide adsorption, maintaining low sulfur dioxide oxidation rate, and (3) stabilizing vanadium pentoxide active centers. By passing at V₂O₅Preparation of aluminum bisulfate suitable for low temperature content by adding aluminum bisulfate to carbon-based materialDenitration catalyst for sulfur flue gas, active component V₂O₅Catalytic NH₃SCR reaction with carbon material as support for increasing V₂O₅The activity of the catalyst is improved by the dispersion degree, and the aluminum bisulfate is used as a sulfur resisting agent to inhibit the adsorption of sulfur dioxide on the catalyst and mask the active center of the oxidation reaction of the sulfur dioxide on the carbon material carrier, so that the deposition of ammonium bisulfate on the catalyst is inhibited, and the catalytic activity of the catalyst is kept. Because the aluminum bisulfate is an ionic compound, the aluminum bisulfate can stably exist at the use temperature (lower than 250 ℃), and the sulfuric acid has certain volatility and the phenomenon of slow decomposition occurs.

The invention adopts the following technical scheme: a denitration catalyst suitable for low-temperature sulfur-containing flue gas takes vanadium pentoxide as an active component, takes active carbon as a carrier and takes aluminum bisulfate as a sulfur-resisting agent, and comprises the following components in percentage by mass: 0.1-5.0% of vanadium pentoxide, 1-20% of aluminum bisulfate and 75-98.9% of activated carbon. The catalyst can be prepared by one of (1) an impregnation method, (2) a spraying method and (3) an extrusion method, and the impregnation method and the secondary selection spraying method are preferred.

Since aluminum bisulfate is not readily available, aluminum sulfate and sulfuric acid can be dissolved in water in a molar ratio of 1:3 to obtain an aluminum bisulfate solution.

The source of aluminium bisulfate can also be aluminium persulfate, aluminium sulfate, aluminium nitrate, aluminium chloride, aluminium acetate, aluminium oxide. The aluminum compound derived from a source other than aluminum bisulfate can be converted to aluminum bisulfate during the preparation or use of the catalyst by the following process:

in the process (1), the aluminum persulfate reacts with water in the preparation process to generate oxygen and aluminum bisulfate,

in the process (2), sulfur dioxide adsorbed on the catalyst in the flue gas reacts with oxygen and water to generate sulfuric acid,

in the process (3), the aluminum sulfate reacts with the sulfuric acid generated in the process (2) to generate aluminum bisulfate,

in the process (4), the aluminum nitrate is heated and decomposed to generate aluminum oxide, the aluminum oxide reacts with the sulfuric acid generated in the process (2) to generate aluminum bisulfate,

the process (5) is that the aluminum chloride is hydrolyzed to generate aluminum hydroxide, the aluminum hydroxide is decomposed to generate aluminum oxide, the aluminum oxide reacts with the sulfuric acid generated in the process (2) to generate aluminum bisulfate,

the process (6) is that the aluminum acetate is decomposed to generate aluminum oxide, the aluminum oxide reacts with the sulfuric acid generated in the process (2) to generate aluminum bisulfate,

and (7) reacting the alumina with the sulfuric acid generated in the step (2) to generate aluminum bisulfate.

The active component vanadium pentoxide comes from: (1) vanadyl oxalate with CAS number 15500-04-6; (2) ammonium metavanadate, CAS number 7803-55-6; (3) vanadyl sulfate, CAS number 27774-13-6, by decomposition and oxidation under catalyst preparation conditions.

Since vanadyl oxalate is not readily available, oxalic acid can be mixed with ammonium metavanadate in a molar ratio of 2: 1, dispersing in water, stirring and heating until bubbles are generated in the solution, and finally, when the bubbles are not generated any more, obtaining the vanadyl oxalate solution, wherein the solution is dark blue.

The form of the catalyst carrier activated carbon may be powdered activated carbon, granular activated carbon, honeycomb activated carbon, fibrous activated carbon fiber, gauze activated carbon cloth, depending on the actual use requirements of the catalyst.

The denitration catalyst suitable for low-temperature sulfur-containing flue gas is prepared by an impregnation method, and comprises the following steps: (1) dissolving vanadium salt and aluminum salt with calculated mass in water, soaking activated carbon for 5 minutes in equal volume, (2) draining the catalyst at room temperature for 15 minutes, (3) placing the drained catalyst in an oven for drying at 120 ℃ for 5 hours, and (4) roasting the dried catalyst for 3 hours at 400 ℃ under a nitrogen atmosphere. The weight percentage of the aluminum bisulfate in the catalyst is 1-20%, the weight percentage of the vanadium pentoxide is 0.1-5% calculated by the aluminum bisulfate as other aluminum salts, and the dipping method is a preferred preparation method.

The denitration catalyst suitable for low-temperature sulfur-containing flue gas is prepared by a spraying method, and comprises the following steps: (1) dissolving vanadium salt and aluminum salt with calculated mass in water, atomizing the salt solution by using a spraying device, and uniformly spraying the salt solution on active carbon, (2) draining the catalyst at room temperature for 15 minutes, (3) placing the drained catalyst in an oven for drying at 120 ℃ for 5 hours, and (4) roasting the dried catalyst for 3 hours at 400 ℃ under a nitrogen atmosphere. The weight percentage of the aluminum bisulfate in the catalyst is 1-20%, the weight percentage of the vanadium pentoxide is 0.1-5% calculated by the weight percentage of other aluminum salts converted into the aluminum bisulfate, and the spraying method is a suboptimal and preferred preparation method.

The method for preparing the denitration catalyst suitable for the low-temperature sulfur-containing flue gas by an extrusion method comprises the following steps: (1) the preparation of pug, aluminum salt, vanadium salt, powder activated carbon of formulation amount are mixed, add water of weight 0.9 times of this mixture, clay of weight 0.2 times, mix the above-mentioned mixture in the mixer for 2 hours and get pug, (2) the shaping of catalyst, make the above-mentioned pug into the blank of honeycomb catalyst through the extruder, or the blank of plate catalyst, or extrude and apply on the wire mesh board to make the blank of plate catalyst containing supporter, the blank of catalyst made is oven dried for 20 hours at 60 duC, oven dry for 5 hours at 120 duC, roast catalyst for 3 hours under the atmosphere of nitrogen of 400 duC. The weight percentage of the aluminum bisulfate in the catalyst is 1-20%, the weight percentage of the vanadium pentoxide is 0.1-5% calculated by the aluminum bisulfate as other aluminum salts, and the clay does not participate in the calculation of the weight percentage of each component of the catalyst. The catalyst with high content of vanadium pentoxide and aluminum bisulfate is suitable for being manufactured by an extrusion method.

Detailed Description

It is stated that the actual conditions of use of the catalyst are not limited by the test strip, and the flue gas conditions in the examples are only as close as possible to the actual flue gas conditions so as to reflect as much as possible the catalytic performance of the catalyst under the actual conditions of use.

The invention will be further illustrated with reference to specific examples, without however restricting the scope of the invention thereto.

The calculation method of the concentration of the impregnation liquid used by the equal-volume impregnation method is referred to as 'an integral denitration catalyst suitable for the flue gas with high content of alkali metal elements and a preparation method thereof' (Chinese patent, application No. 201510704002.3).

Unless otherwise specified, the test conditions for catalyst activity were: space velocity of 10000h^-13% oxygen, 310ppm NO, NH in the reaction gas₃310ppm，SO₂600ppm，H₂O10% and nitrogen balance gas.