CN111939959B

CN111939959B - Nitrogen-sulfur co-doped graphene composite material loaded with ternary efficient denitration sulfur-resistant catalyst and preparation method thereof

Info

Publication number: CN111939959B
Application number: CN202010831948.7A
Authority: CN
Inventors: 郑玉婴; 郑伟杰
Original assignee: Fuzhou University
Current assignee: Fuzhou University
Priority date: 2020-08-18
Filing date: 2020-08-18
Publication date: 2021-11-30
Anticipated expiration: 2040-08-18
Also published as: NL2028037B1; CN111939959A; NL2028037A

Abstract

The invention discloses a nitrogen-sulfur co-doped graphene composite material (marked as Mn-Ce-SnOx/rGO-N,S) supporting a ternary high-efficiency denitration and sulfur-resistant catalyst and a preparation method thereof. After in-situ growth of an efficient denitration and anti-sulfur ternary catalyst on heterographene oxide, nitrogen-sulfur co-doping is performed and graphene oxide is reduced to obtain a nitrogen-sulfur co-doped graphene catalyst composite material. Due to the in-situ growth method, the three-way catalyst is uniformly and firmly loaded on the surface of nitrogen-sulfur co-doped graphene; the overall synthesis of the present invention is carried out in a low temperature environment, the reaction synthesis method and operation are very simple, and the reaction is fast. , there is no specific requirement for the reaction vessel, and the synthetic material does not pollute the environment, the synthesized catalyst and the nitrogen-sulfur co-doped graphene are firmly bonded, the service life is long, and the out-of-stock rate is high.

Description

Nitrogen-sulfur co-doped graphene composite material loaded with ternary efficient denitration sulfur-resistant catalyst and preparation method thereof

Technical Field

The invention belongs to the technical field of functional doped graphene composite catalysts, and particularly relates to a nitrogen and sulfur co-doped graphene composite material loaded with a ternary efficient denitration sulfur-resistant catalyst and a preparation method thereof.

Background

With the rapid development of the Chinese industrialization process, a lot of unavoidable pollution is generated, wherein the atmospheric pollution is the most serious and most concerned problem in a plurality of pollution, and the generation of the atmospheric pollution causes the life, health, work, nature and the like of people to be damaged more badly. At present, air pollution sources can be divided into fixed pollution sources and mobile pollution sources, pollutants of the pollution sources are mainly generated due to coal combustion, the pollution sources comprise PM2.5, PM10, sulfur dioxide, nitrogen oxide, nitrogen dioxide and the like, and the gases can cause harm to the environment such as haze, acid rain, photochemical smog, greenhouse effect and the like.

It is known that, because of the large power demand brought by the construction of infrastructure and the development of manufacturing industry which are greatly promoted in China, and the power demand needs to provide energy by the combustion of coal, the usage amount of coal resources in China is huge. Since 2011, in order to control the serious air pollution problem caused by the combustion of coal, environmental protection departments in China issue emission standards of atmospheric pollutants for thermal power plants (GBl3223-2011) in combination with the national quality supervision and quarantine bureau, aiming at controlling the emission of the atmospheric pollutants and the structure of the thermal power industry and promoting the healthy and sustainable development of the thermal power industry. Although emissions are still much higher than in many developed countries and other industries. But since the stipulation, the coal consumption proportion of China is obviously reduced, and the consumption proportion of the substituted crude oil, natural gas and the nuclear energy of wind power, water and electricity is increased. However, according to the energy consumption proportion in 2017 in China, the consumption of coal resources is still high, and the consumption proportion reaches about 60%. Among coal-fired equipment, the discharge amount of nitrogen oxides discharged by boilers of power plants is the most serious, and accounts for over 36.1 percent of the total discharge amount of the whole country, and the discharge amount of smoke dust accounts for over 40 percent. It is predicted that coal will still be the main source of energy supply in the next few years, and the requirements for pollution control by coal will become more and more strict in the future.

Graphene is a new two-dimensional carbon nano material, and carbon atoms are sp in a plane²However, the band gap between the valence band and the conduction band of graphene is zero, which limits the application of graphene in nanoelectronics, and the band gap can be opened to enable graphene to be an n-type or p-type material by doping the graphene with heteroatoms (such as nitrogen, boron, fluorine, sulfur and the like), so that the electronic structure and other inherent properties of the graphene can be adjusted, and the application of the graphene in various fields can be effectively improved or expanded. At present, doped graphene has been widely studied in a supercapacitor, but no mature technology exists for improving the denitration and sulfur resistance performance of the doped graphene as a catalyst carrier.

The commercial vanadium-titanium system catalyst has high activation temperature (>300 deg.c) and is difficult to apply at the end of a flue gas treatment system and is expensive to install and operate. Therefore, low temperature SCR technology, which is economical and suitable for end treatment, has been a focus of attention by researchers. Unsupported MnO_x-CeO₂The catalyst has the highest activity of the medium-low temperature SCR reported at present, and NO is generated at the temperature of 120 DEG C_xCan be almost completely converted into N₂However, no suitable technique has been provided for successful in-situ growth of the graphene on the nitrogen and sulfur co-doped graphene.

Disclosure of Invention

The invention aims to provide a nitrogen and sulfur co-doped graphene composite material (marked as Mn-Ce-SnO) loaded with a ternary efficient denitration sulfur-resistant catalyst_xThe preparation method comprises the steps of growing an efficient denitration and sulfur-resistant ternary catalyst on self-made nitrogen-doped graphene oxide in situ, carrying out nitrogen-sulfur co-doping, and reducing the graphene oxide to prepare the nitrogen-sulfur co-doped graphene catalyst composite material. Due to the in-situ growth method, the three-way catalyst is uniformly and firmly loaded on the surface of the nitrogen and sulfur co-doped graphene.

The method comprises the steps of taking self-made nitrogen-doped graphene oxide as a catalyst carrier, firmly loading the catalyst by adopting an in-situ growth method, carrying out nitrogen-sulfur co-doping, and simultaneously reducing the graphene oxide to prepare efficient Mn-Ce-SnO_x/rGO_-N,SA composite material of a denitration sulfur-resistant catalyst.

The technical scheme adopted by the invention is as follows:

the self-made nitrogen-doped graphene oxide can be prepared by the following method:

(1) 1g of graphite was added to a 150mL beaker, and 40mL of concentrated sulfuric acid (abbreviated as H) was added₂SO₄) And placing the mixture in a water bath kettle for stirring at room temperature until the mixture is fully dissolved. Then accurately weighing 5g of potassium permanganate (KMnO for short)₄) 0.2g of KMnO is added every 10min₄。

（2）KMnO₄After all the materials are added, the temperature of the water is raised to 50 ℃, the mixture is stirred and reacted for 2 hours, then 0.5g of Cyanuric Acid (CA) is added to be fully dissolved, the reaction is continued for 2 hours, and 80mL of deionized water is added.

(3) Placing the reaction solution added with deionized water in a water bath kettle at 90 deg.C, stirring for 10min, and dropwise adding H₂O₂Until no bubble is present. And finally, adding 20mL of hydrochloric acid, repeatedly centrifuging the obtained product to be neutral, and transferring the product to a freeze dryer for freeze drying for later use. The final product obtained was named GO_-N。

More specifically, the nitrogen and sulfur co-doped graphene composite material loaded with the ternary efficient denitration sulfur-resistant catalyst can be prepared by the following method:

(1) accurately weigh 0.1g of GO_-NDissolving the sample in 50mL of deionized water to prepare GO_-NAnd (5) carrying out ultrasonic dispersion on the solution for 10 min. 0.06g of sodium dodecyl sulfate (SDS for short) was added to the above solution, and sonication was continued for 10 min.

(2) Adding a certain mass of cerium acetate (Ce (Ac) for short)₃) Adding into the prepared solution, adding a stirrer, and stirring at room temperature for 1 hour until the solution is Ce (Ac)₃Completely dissolving; at this time, Ce³⁺Grafted to the GO-N surface through a dehydration condensation reaction; weighing a certain mass of stannic chloride (SnCl)₄) Adding into the above solution, and stirring at room temperature for 1 hr until SnCl₄Completely dissolving; at this time, the GO-N surface is filled with Sn⁴⁺And Ce³⁺The product of the reaction.

(3) KMnO with certain concentration₄Adding the solution into the step (2). Continuously reacting for 1h at room temperature, and weighing thiourea (CH for short) with certain mass after the reaction is finished₄N₂S) adding the mixture into a reaction solution, stirring the mixture until the mixture reacts for 4 hours, after the reaction is finished, centrifugally washing the obtained suspension for a plurality of times, and carrying out vacuum freeze drying to obtain the final nitrogen and sulfur co-doped graphene catalyst composite material marked as Mn-Ce-SnO_x/rGO_-N,S。

Further, the mass ratio of GO-N to Ce (Ac)3 in the step (2) is 1:1-1: 2.5; the molar ratio of Ce (Ac)3 to SnCl4 is 1: 1; the molar ratio of Ce (Ac)3 to KMnO4 is 1: 2; the mass ratio of Ce (Ac)3 to CH4N2S is 1: 1.

The invention has the beneficial effects that:

firstly, cyanuric acid is used for grafting graphene oxide, so that the surface of the graphene oxide obtains more N functional groups and defects. Due to the existence of the oxygen-containing functional groups and defects, the cerium-containing cerium acetate can react with each other to react with Ce³⁺The nitrogen-doped graphene oxide is firmly bonded on the surface of the nitrogen-doped graphene oxide. In addition, the tin chloride can be well added on the surface of the nitrogen-doped graphene oxide and Ce³⁺Carrying out oxidation-reduction reaction to ensure that a large amount of Ce is accumulated on the surface of the nitrogen-doped graphene oxide³⁺，Ce⁴⁺，Sn³⁺And Sn⁴⁺Ions. And finally, performing oxidation-reduction reaction on the surface of the nitrogen-doped graphene oxide by using potassium permanganate as an oxidant to enable the manganese-cerium-tin catalyst to grow on the surface of the nitrogen-doped graphene oxide in situ, and finally preparing the nitrogen-sulfur co-doped graphene composite material loaded with the catalyst with the efficient denitration and sulfur-resistance functions by utilizing the reduction characteristic of thiourea.

The method has the advantages that:

1. the unitary high-efficiency denitration catalyst mainly based on Mn is easy to be SO₂Can be poisoned to generate MnSO₄Therefore, the catalyst is denatured and inactivated, so that the denitration rate is greatly reduced, and even the denitration and sulfur resistance performance is almost lost. The presence of nitrogen and sulfur as hetero atoms and cerium and tin as rare earth metal makes it have better performanceAnd (4) sulfur resistance.

2. Due to the addition of cyanuric acid and thiourea, the self-made nitrogen and sulfur co-doped graphene in-situ growth catalyst has a higher specific surface, surface defects and more nitrogen and sulfur elements, and the factors have great contribution to the denitration and sulfur resistance reaction. Therefore, compared with a pure graphene catalyst product, the catalyst has higher denitration and sulfur resistance.

3. The addition of the sodium dodecyl sulfate improves the dispersibility of the high-performance catalyst on the surface of the graphene, so that the high-performance catalyst is not agglomerated on the surface of the graphene, a porous graphene catalyst composite material is obtained, and the denitration and sulfur resistance of the graphene catalyst composite material is greatly improved.

4. The whole synthesis is carried out in a low-temperature environment, the reaction synthesis method and the operation are simple, the reaction is quick, no specific requirements are required on a reaction container, the environment is not polluted by synthetic substances, the synthesized catalyst and the nitrogen-sulfur co-doped graphene are firmly combined, the service life is long, and the denitration rate is high.

Drawings

FIG. 1 is a diagram of a self-made tubular SCR reactor device in a catalyst activity test;

in the figure, 1 is a steam source; 2 is a pressure reducing valve; 3 is a mass flow meter; 4 is a mixer; 5 is an air preheater; 6 is a catalyst bed; 7 is a composite material; 8 is a flue gas analyzer;

FIG. 2 is GO_-NAnd Ce (Ac)₃The mass ratio is 1: 3, scanning electron microscope images of the composite material;

FIG. 3 is GO of the present invention_-NAnd Ce (Ac)₃The mass ratio is 1: 3 catalytic stability analysis diagram of the composite material.

Detailed Description

Example 1

Accurately weighing 0.1g of the self-made nitrogen-doped graphene oxide sample, dissolving the sample in 50mL of deionized water, performing ultrasonic treatment for 10min, adding 0.06g of sodium dodecyl sulfate (SDS for short), performing ultrasonic dissolution, and then dissolving 0.1g of cerium acetate (Ce (Ac for short)₃) Adding into the prepared solution, adding a stirrer, and stirring at room temperature for 1 hour until the Ce (Ac)₃And completely dissolving. Then weighing0.111g of tin tetrachloride (SnCl)₄) Adding into the above solution, and stirring at room temperature for 1 hr until SnCl₄And completely dissolving. Then accurately weigh 0.100g KMnO₄Dissolved in 50mL of deionized water, and added to the reaction solution. The reaction was continued at room temperature for 1 hour, and after the reaction was completed, 0.1g of thiourea (abbreviated as CH) was weighed₄N₂S) adding the mixture into the reaction solution, stirring the mixture until the mixture reacts for 4 hours, after the reaction is finished, centrifugally washing the obtained suspension for a plurality of times, and carrying out vacuum freeze drying to obtain the final composite material to be tested. The mass of tin chloride is calculated as follows: 0.1 ÷ 317 × 350.6=0.111g, the concentration of potassium permanganate is calculated as follows: 0.1 ÷ 317 × 2 × 158= 0.100.

The denitration and sulfur resistance of the composite material is evaluated in a self-made tubular SCR reactor. NO and NH₃Volume fractions of 0.05% and O₂The volume fraction is 5 percent, and the rest is N₂The gas flow rate is 700 mL/min^-1The temperature is set to be 140 ℃, and the denitration rate is 63.2 percent by using a British KM940 flue gas analyzer; the temperature is set to be 160 ℃, the denitration rate is 75.1 percent, the temperature is set to be 180 ℃, and the denitration sulfur-resistant rate is 89.8 percent; introducing SO at 180 DEG C₂The test is carried out at intervals of 30min, and finally the out-of-stock rate is basically stabilized at 61.2 percent.

Example 2

Accurately weighing 0.1g of the self-made nitrogen-doped graphene oxide sample, dissolving the sample in 50mL of deionized water, performing ultrasonic treatment for 10min, adding 0.06g of sodium dodecyl sulfate (SDS for short), performing ultrasonic dissolution, and then dissolving 0.15g of cerium acetate (Ce (Ac for short)₃) Adding into the prepared solution, adding a stirrer, and stirring at room temperature for 1 hour until the Ce (Ac)₃And completely dissolving. 0.165g of tin tetrachloride (SnCl) is then weighed out₄) Adding into the above solution, and stirring at room temperature for 1 hr until SnCl₄And completely dissolving. Then accurately weigh 0.149g KMnO₄Dissolved in 50mL of deionized water, and added to the reaction solution. The reaction was continued at room temperature for 1 hour, and after the reaction was completed, 0.15g of thiourea (abbreviated as CH) was weighed₄N₂S) adding the suspension into the reaction solution, stirring the mixture until the reaction solution reacts for 4 hours, centrifugally washing the obtained suspension for a plurality of times after the reaction is finished, freeze-drying the suspension in vacuum,and obtaining the final composite material to be tested. The mass of tin chloride is calculated as follows: 0.15 ÷ 317 × 350.6=0.165g, the concentration of potassium permanganate is calculated as follows: 0.15 ÷ 317 × 2 × 158= 0.149.

The denitration and sulfur resistance of the composite material is evaluated in a self-made tubular SCR reactor. NO and NH₃Volume fractions of 0.05% and O₂The volume fraction is 5 percent, and the rest is N₂The gas flow rate is 700 mL/min^-1The temperature is set to be 140 ℃, and the denitration rate is 71.8 percent by using a British KM940 flue gas analyzer; the temperature is set to be 160 ℃, the denitration rate is 82.2 percent, the temperature is set to be 180 ℃, and the denitration sulfur-resistant rate is 93.9 percent; introducing SO at 180 DEG C₂The test is carried out at intervals of 30min, and finally the final denitration rate is basically stabilized at 69.8 percent.

Example 3

Accurately weighing 0.1g of the self-made nitrogen-doped graphene oxide sample, dissolving the sample in 50mL of deionized water, performing ultrasonic treatment for 10min, adding 0.06g of sodium dodecyl sulfate (SDS for short), performing ultrasonic dissolution, and then dissolving 0.15g of cerium acetate (Ce (Ac for short)₃) Adding into the prepared solution, adding a stirrer, and stirring at room temperature for 1 hour until the Ce (Ac)₃And completely dissolving. 0.221g of tin tetrachloride (SnCl) is then weighed out₄) Adding into the above solution, and stirring at room temperature for 1 hr until SnCl₄And completely dissolving. Then accurately weigh 0.199gKMnO₄Dissolved in 50mL of deionized water, and added to the reaction solution. The reaction was continued at room temperature for 1 hour, and after the reaction was completed, 0.2g of thiourea (abbreviated as CH) was weighed₄N₂S) adding the mixture into the reaction solution, stirring the mixture until the mixture reacts for 4 hours, after the reaction is finished, centrifugally washing the obtained suspension for a plurality of times, and carrying out vacuum freeze drying to obtain the final composite material to be tested. The mass of tin chloride is calculated as follows: 0.2 ÷ 317 × 350.6=0.221g, the concentration of potassium permanganate is calculated as follows: 0.2 ÷ 317 × 2 × 158= 0.199.

The denitration and sulfur resistance of the composite material is evaluated in a self-made tubular SCR reactor. NO and NH₃Volume fractions of 0.05% and O₂The volume fraction is 5 percent, and the rest is N₂The gas flow rate is 700 mL/min^-1The temperature is set to 140 ℃, and the gas content is measured by British KM940The denitration rate measured by an analyzer is 70.1%; the temperature is set to be 160 ℃, the denitration rate is 83.3 percent, the temperature is set to be 180 ℃, and the denitration sulfur-resistant rate is 100 percent; introducing SO at 180 DEG C₂The test is carried out at intervals of 30min, and finally the out-of-stock rate is basically stabilized at 70.9 percent.

Example 4

Accurately weighing 0.1g of the self-made N-doped graphene oxide sample, dissolving the sample in 50mL of deionized water, performing ultrasonic treatment for 10min, adding 0.06g of sodium dodecyl sulfate (SDS for short), performing ultrasonic dissolution, and then dissolving 0.25g of cerium acetate (Ce (Ac for short)₃) Adding into the prepared solution, adding a stirrer, and stirring at room temperature for 1 hour until the Ce (Ac)₃And completely dissolving. 0.276g of tin tetrachloride (SnCl) is then weighed out₄) Adding into the above solution, and stirring at room temperature for 1 hr until SnCl₄And completely dissolving. Then accurately weigh 0.249gKMnO₄Dissolved in 50mL of deionized water, and added to the reaction solution. The reaction was continued at room temperature for 1 hour, and after the reaction was completed, 0.25g of thiourea (abbreviated as CH) was weighed₄N₂S) adding the mixture into the reaction solution, stirring the mixture until the mixture reacts for 4 hours, after the reaction is finished, centrifugally washing the obtained suspension for a plurality of times, and carrying out vacuum freeze drying to obtain the final composite material to be tested. The mass of tin chloride is calculated as follows: 0.25 ÷ 317 × 350.6=0.276g, the concentration of potassium permanganate is calculated as follows: 0.25 ÷ 317 × 2 × 158= 0.249.

The denitration and sulfur resistance of the composite material is evaluated in a self-made tubular SCR reactor. NO and NH₃Volume fractions of 0.05% and O₂The volume fraction is 5 percent, and the rest is N₂The gas flow rate is 700 mL/min^-1The temperature is set to be 140 ℃, and the denitration rate is 61.1 percent by using a British KM940 flue gas analyzer; the temperature is set to be 160 ℃, the denitration rate is 78.8 percent, the temperature is set to be 180 ℃, and the denitration sulfur-resistant rate is 88.4 percent; introducing SO at 180 DEG C₂The test is carried out at intervals of 30min, and finally the out-of-stock rate is basically stabilized at 70.4 percent.

Activity evaluation: the catalyst was evaluated in a self-made tubular SCR reactor. The reactor is electrically heated externally, a thermocouple is arranged beside a catalyst bed layer of the reaction tube to measure the temperature, and the flow of the experimental device is shown in figure 1. Flue gas group simulated by steel gas cylinderThe flue gas contains NO and O₂、N₂、NH₃To reduce gas, NO and NH₃Volume fraction of 0.04-0.06%, O₂The volume fraction is 4-6%, and the rest is N₂The gas flow rate is 700 mL/min^-1The temperature is controlled between 120 ℃ and 200 ℃, and the gas flow and the gas composition are regulated and controlled by a mass flow meter. Gas analysis adopts a British KM940 smoke gas analyzer, and each working condition is stable for at least 30min in order to ensure the stability and accuracy of data.

Table 1 influence of various factors on the denitration sulfur resistance of the composite material (reaction temperature is 180 ℃):

as can be seen from the data in Table 1, at 180 ℃, the denitration sulfur resistance rate tends to increase and decrease with the increase of the mass ratio, and the maximum value appears at the mass ratio of 1: 2.5. And the sulfur resistance reaches the maximum.

The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the claims of the present invention should be covered by the present invention.

Claims

1. The utility model provides a load nitrogen sulphur codope graphite alkene combined material of high-efficient denitration anti-sulfur catalyst of ternary which characterized in that: the composite material takes modified nitrogen and sulfur co-doped graphene as a catalyst carrier and takes ternary Mn-Ce-SnO_xThe catalyst grows on the surface of the nitrogen and sulfur co-doped graphene in situ;

the nitrogen and sulfur co-doped graphene is prepared by a self-improved Hummers method to prepare graphene oxide serving as a reaction precursor, and the reaction precursor is obtained by the following method:

(1) adding 1g of graphite into a 150mL beaker, adding 40mL of concentrated sulfuric acid, placing the beaker in a water bath kettle, stirring the beaker at room temperature until the graphite is fully dissolved, accurately weighing 5g of potassium permanganate, and adding 0.2g of KMnO every 10min₄；

（2）KMnO₄All areAfter the addition is finished, heating the water to 50 ℃, stirring and reacting for 2h, then adding 0.5g of cyanuric acid for full dissolution, continuing to react for 2h, and then adding 80mL of deionized water;

(3) placing the reaction solution added with deionized water in a water bath kettle at 90 deg.C, stirring for 10min, and dropwise adding H₂O₂Until no bubble exists, adding 20mL hydrochloric acid, repeatedly centrifuging the obtained product to neutrality, transferring to a freeze dryer for freeze drying, and naming the finally obtained product as GO_-N；

The preparation method of the nitrogen and sulfur co-doped graphene composite material loaded with the ternary efficient denitration sulfur-resistant catalyst comprises the following steps:

(1) weigh 0.1g of GO_-NDissolved in 50mL of deionized water to prepare GO_-NCarrying out ultrasonic dispersion on the solution for 10min, adding 0.06g of sodium dodecyl sulfate into the solution, and continuing ultrasonic treatment for 10 min;

(2) addition of Ce (Ac)₃Adding into the solution of the step (1), stirring for 1 hour at room temperature until the solution is Ce (Ac)₃The mixture is completely dissolved and dissolved in the solvent,

(3) SnCl₄Adding the solution obtained in the step (2), and continuing stirring at room temperature for 1 hour till SnCl₄The mixture is completely dissolved and dissolved in the solvent,

(4) mixing KMnO₄Adding the solution into the solution obtained in the step (3), continuing to react for 1h at room temperature, and adding CH after the reaction is finished₄N₂S, stirring to react for 4 hours, after the reaction is finished, centrifugally washing the obtained suspension, and carrying out vacuum freeze drying to obtain the nitrogen and sulfur co-doped graphene composite material loaded with the ternary efficient denitration sulfur-resistant catalyst; the Ce (Ac)₃And CH₄N₂The mass ratio of S is 1: 1.

2. The nitrogen and sulfur co-doped graphene composite material loaded with the ternary high-efficiency denitration sulfur-resistant catalyst according to claim 1 is characterized in that: GO in step (2)_-NAnd Ce (Ac)₃The mass ratio of (A) to (B) is 1:1-1: 2.5.

3. The loaded ternary high efficiency reactor of claim 1The nitrogen and sulfur co-doped graphene composite material of the nitro-sulfur-resistant catalyst is characterized in that: the Ce (Ac)₃With SnCl₄Is 1: 1.

4. The nitrogen and sulfur co-doped graphene composite material loaded with the ternary high-efficiency denitration sulfur-resistant catalyst according to claim 1 is characterized in that: the Ce (Ac)₃With KMnO of step (4)₄In a molar ratio of 1:2.