NL2028037B1

NL2028037B1 - Nitrogen-sulfur co-doped graphene composite loaded with ternary high-efficiency denitrification anti-sulfur catalyst and its preparation method

Info

Publication number: NL2028037B1
Application number: NL2028037A
Authority: NL
Inventors: Zheng Yuying; Zheng Weijie
Original assignee: Univ Fu Zhou
Priority date: 2020-08-18
Filing date: 2021-04-22
Publication date: 2022-09-08
Also published as: NL2028037A; CN111939959A; CN111939959B

Abstract

The present invention discloses a nitrogen-sulfur co-doped graphene composite (labeled Mn-Ce-SnOx/rGO-N,S) loaded with a ternary high-efficiency denitrification 5 and anti-sulfur catalyst and its preparation method, in which a high-efficiency denitrification and anti-sulfur ternary catalyst is grown in situ on home-made nitrogen-doped graphene oxide and then nitrogen-sulfur co-doping is performed while reducing graphene oxide to produce a nitrogen-sulfur co-doped graphene catalyst composite . Due to the in situ growth method, the ternary catalysts are uniformly and 10 firmly loaded on the surface of nitrogen and 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 simple, and the reaction is fast, there is no specific requirement for the reaction vessel, and the synthesized material does not pollute the environment, the synthesized catalyst and nitrogen and sulfur co-doped 15 graphene are firmly bonded, the service life is long, and the denitration The synthesized catalysts are strongly bonded with nitrogen and sulfur co-doped graphene, with long service life and high decommissioning rate.

Description

1 001758P-NL NITROGEN-SULFUR CO-DOPED GRAPHENE COMPOSITE LOADED WITH TERNARY HIGH-EFFICIENCY DENITRIFICATION ANTI-SULFUR CATALYST AND

ITS PREPARATION METHOD Technical Field The present 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 ternary high-efficiency denitrification anti-sulfur catalyst and its preparation method.

Background Technology With the rapid development of industrialization in China, many unavoidable pollutions have been generated, among which air pollution is the most serious and the most concerned problem among many pollutions. At present, air pollution sources can be divided into fixed sources and mobile sources of pollution, the pollutants are mainly due to coal combustion, including PM2.5, PM10, sulfur dioxide, nitrogen oxides and nitrogen dioxide, these gases can cause haze, acid rain, photochemical smog and the greenhouse effect on the environment and other hazards.

Itis well known that China's coal resources are used in huge amounts due to the large amount of electricity demand brought by the construction of infrastructure and the development of manufacturing industries, which all rely on the burning of coal to provide energy. Since 2011, China's environmental protection department, in order to control the serious air pollution caused by the burning of coal, together with the General Administration of Quality Supervision and Quarantine, promulgated the “Emission Standards for Air Pollutants from Thermal Power Plants (GBI3223-2011)", with the aim of controlling the emissions of air pollutants and the structure of the thermal power generation industry, and promoting the healthy and sustainable development of the thermal power generation industry. Although its emissions are still much higher compared to many developed countries and other industries. However, since the promulgation of the regulations, there has been a significant decline in the

2 001758P-NL proportion of coal consumption in China, with an increase in the proportion of crude oil, natural gas, and wind and hydropower nuclear energy consumption instead. However, from the proportion of energy consumption in China in 2017 can be seen, the consumption of coal resources is still high, the proportion of consumption reached about 60%. Among the coal-fired equipment, especially the boilers of power plants emit the most serious emissions of nitrogen oxides, accounting for more than 36.1% of the total national emissions, and soot emissions account for more than 40%. It can be predicted that in the next few years, coal will continue to be the main source of energy supply, so the requirements for pollution control caused by coal burning will become more and more stringent in the future.

Graphene is an emerging two-dimensional carbon nanomaterial, in-plane carbon atoms are hybridized with sp? electron orbitals to form a honeycomb lattice structure with a thickness of only 0.34 nm, which has excellent optoelectronic properties.

However, the band gap between the valence and conduction bands of graphene is zero, which limits its application in nanoelectronics. By doping graphene with heteroatoms (e.g., nitrogen, boron, fluorine, and sulfur), the band gap can be opened to make it an n-type or p-type material, and its electronic structure and other intrinsic properties can be adjusted to effectively improve or expand its applications in various fields. Currently, doped graphene has been extensively studied in supercapacitors, but there is no mature technology to use it as a catalyst carrier to enhance its denitrification and sulfur resistance performance.

The commercialized vanadium-titanium system catalysts with high starting temperature (>300°C) are difficult to apply at the end of the flue gas treatment system and have high installation and operation costs. Therefore, low-temperature SCR technology, which is economical and suitable for end-of-pipe treatment, has become a hot topic of interest for researchers. The carrier-free MnO,-CeO2 catalyst is the most active low-temperature SCR of this kind reported so far, and NOx can be almost completely converted to Nz at a temperature of 120°C. However, there is no suitable

3 001758P-NL technology to successfully grow it in situ on nitrogen-sulfur co-doped graphene. Content of the Invention The purpose of the present invention is to provide a nitrogen-sulfur co-doped graphene composite (labeled Mn-Ce-SnO,/rGO-N,S) loaded with a ternary high-efficiency denitrification and anti-sulfur catalyst and its preparation method, which is based on the in situ growth of a high-efficiency denitrification and anti-sulfur ternary catalyst on home-made nitrogen-doped graphene oxide, followed by nitrogen-sulfur co-doping and simultaneous reduction of graphene oxide to produce a nitrogen-sulfur co-doped graphene catalyst composites. Due to the in situ growth method, the ternary catalysts were uniformly and firmly loaded on the nitrogen-sulfur co-doped graphene surface. The homemade nitrogen-doped graphene oxide was used as the catalyst carrier, and after the catalyst was firmly loaded by the in situ growth method, the nitrogen-sulfur co-doping was carried out with simultaneous reduction of graphene oxide to prepare the highly efficient Mn-Ce-SnOx/rGO-N,S denitrification and anti-sulfur catalyst composites.

The technical solutions used in the present invention are: Said home-made nitrogen-doped graphene oxide can be prepared by the following methods: (1) Add 1g of graphite to a 150mL beaker, add 40mL of concentrated sulfuric acid (abbreviated as H2SO4}, and place it in a water bath at room temperature and stir until itis fully dissolved. Then accurately weigh 5g of potassium permanganate (abbreviated as KMnO4) and add 0.2g of KMnO4 every 10min. (2) After all the KMnOa, is added, raise the water temperature to 50°C and stir the reaction for 2h. After that, add 0.59 of cyanuric acid (abbreviated as CA) to fully dissolve and continue the reaction for 2h and then add 80mL of deionized water.

(3) Place the reaction solution with deionized water in a 90°C water bath and stir for

4 001758P-NL 10min, then add H202 drop by drop until there is no bubble. Finally add 20mL hydrochloric acid, centrifuge the obtained product repeatedly to neutral, transfer to lyophilizer for freeze-drying. The final product obtained was named as GO.n.

More specifically, the nitrogen and sulfur co-doped graphene composites loaded with ternary high-efficiency denitrification anti-sulfur catalyst described in the present invention can be prepared as follows: (1) Accurately weigh 0.1g of GO-N sample, dissolve it in 50mL of deionized water, prepare GO-N solution, and ultrasonically disperse it for 10min. Add 0.06g of dodecyl sulfate (SDS for short) to the above solution and continue to ultrasonicate for 10min. (2) Add a certain mass of cerium acetate (referred to as Ce(Ac)s) to the above solution, and put it into the stirrer, and stir for 1 hour at room temperature until Ce(Ac)s is completely dissolved; at this time, Ce? is grafted to the surface of GO-N through dehydration condensation reaction; then weigh a certain mass of tin tetrachloride (SnCls), add it to the above solution, and continue to stir for 1 hour at room temperature until SnCls is completely dissolved Then add a certain mass of tin tetrachloride (SnCls) to the above solution and continue to stir at room temperature for 1 hour until the SnCls is completely dissolved; at this time, the GO-N surface is filled with the products of the reaction between Sn* and Ce®.

(3) Configure a certain concentration of KMnOas solution and add it to step (2). Continue the reaction at room temperature for 1h, and after the reaction is finished, weigh a certain mass of sulfur urea (abbreviated as CHsN2S) and add it to the reaction solution, stir until the reaction is finished for 4h, and after the reaction is finished, wash the obtained suspension by centrifugation several times and freeze-dry it under vacuum to obtain the final nitrogen-sulfur co-doped graphene catalyst composite, labeled as Mn-Ce-SnOy/rGO-N,S.

Further, the mass ratio of GO-N to Ce(Ac)s in step (2) is 1:1-1:2.5; the molar ratio of said Ce(Ac)a to SnCls is 1:1; the molar ratio of said Ce(Ac)s to KMnOas is 1:2; the mass ratio of said Ce(Ac)s to CHsN2S is 1:1.

001758P-NL Beneficial effects of the present invention: Firstly, grafting of graphene oxide by using melamine to obtain more N-functional groups and defects on its surface. Due to the presence of these oxygen-containing 5 functional groups and defects, it is able to react with cerium acetate with each other to firmly bind Ce%* on the surface of nitrogen-doped graphene oxide. In addition, the addition of tin chloride is well able to carry out redox reactions with Ce?* on the surface of nitrogen-doped graphene oxide, causing the accumulation of a large amount of Ce3*, Ce**, Sn3* and Sn** ions on the surface of nitrogen-doped graphene oxide. Finally, potassium permanganate was used as the oxidizing agent to carry out the redox reaction on the surface of nitrogen-doped graphene oxide, so that the manganese cerium tin catalyst was grown in situ on the surface of nitrogen-doped graphene oxide, and then the reduction property of sulfur urea was used to finally prepare nitrogen-sulfur co-doped graphene composites loaded with highly efficient denitrification and anti-sulfur functional catalysts.

The advantages of this method are:

1. Mono-efficient denitrification Mn-based catalysts are easily poisoned by SO; will generate MnSO4, which leads to the denaturation and deactivation of the catalyst, resulting in a significant decrease in the rate of denitrification, and even almost lose denitrification anti-sulfur performance, this method in the nitrogen-sulfur co-doped graphene surface in situ growth of rare earth elements Ce, Sn. the presence of heteroatomic nitrogen sulfur and rare earth metal cerium tin makes it have better anti-sulfur performance.

2. Due to the addition of melamine and sulfur urea, the homemade nitrogen-sulfur co-doped graphene in-situ grown catalyst has higher specific surface, surface defects and more nitrogen-sulfur elements, and these factors have greatly facilitated the denitrification anti-sulfur reaction. Therefore, it has higher denitrification anti-sulfur performance than simple graphene catalyst products.

6 001758P-NL

3. The addition of sodium dodecyl! sulfate improves the dispersion of the high performance catalyst on the graphene surface, so that it does not agglomerate on the surface and obtains a porous graphene catalyst composite, which greatly enhances its denitrification and anti-sulfur ability.

4. The overall synthesis is carried out in a low temperature environment, the reaction synthesis method and operation are simple, and its reaction is fast, there is no specific requirement for the reaction vessel, and the synthesized material is not polluting to the environment, the synthesized catalyst and nitrogen-sulfur co-doped graphene are firmly bonded, the service life is long, and the de-sulfurization rate is high. Description of the accompanying figures FIG. 1 shows a diagram of a homemade tubular SCR reactor setup for catalyst activity testing; in the figure, 1 is a vapor 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 catalytic bed; 7 is a composite material; 8 is a flue gas analyzer. FIG. 2 is a scanning electron micrograph of the composite material with a 1:3 mass ratio of GO.n to Ce(Ac)a. FIG. 3 shows the catalytic stability analysis of the composite material with GO.n to Ce{Ac)3 mass ratio 1:3 of the present invention.

Specific embodiments Example 1 Accurately weigh 0.1g of the above sample of homemade nitrogen-doped graphene oxide, dissolve it in 50mL of deionized water, add 0.06g of sodium dodecyl sulfate (abbreviated as SDS) after 10min of sonication, and then add 0.1g of cerium acetate

7 001758P-NL (abbreviated as Ce(Ac)s) to the configured above solution, put it into a stirrer, and stir it for 1 hour at room temperature until Ce{Ac)3 is completely dissolved. Next, weigh

0.111g of tin tetrachloride (SnCl4), add it to the above solution and continue to stir at room temperature for another 1 hour until SnCl4 is completely dissolved. After that, accurately weigh 0.100g of KMnO4 dissolved in 50mL of deionized water and then add it to the above reaction solution. Continue the reaction at room temperature for 1h. After the reaction is finished, weigh 0.1g sulfur urea (abbreviated as CH«N>S) and add it to the reaction solution and stir until the reaction is finished for 4h. After the reaction is finished, the suspension obtained is washed several times by centrifugation and then vacuum freeze-dried to obtain the final composite material to be tested. The mass of tin chloride was calculated as follows: 0.1+317x350.6=0.111¢; the concentration of potassium permanganate was calculated as follows:

0.1+317x2x158=0. 100.

The denitrification and anti-sulfur performance of the composites was evaluated in a homemade tubular SCR reactor. the volume fractions of NO and NH: were both

0.05 %, the volume fraction of O2 was 5 %, and the rest was Ng, the gas flow rate was 700mL-min’*, the temperature was set to 140°C, and the denitrification rate was

63.2% measured by KM940 flue gas analyzer from UK; the temperature was set to 160°C, and the denitrification rate was 75.1%, the temperature was set to 180°C, the denitrification anti-sulfur rate was 89.8%; the final denitrification rate was basically stable at 61.2% when SO2 was passed into the test at 180°C for 30min interval. Example 2 Accurately weigh 0.1g of the above sample of homemade nitrogen-doped graphene oxide, dissolve in 50mL of deionized water, sonicate for 10min and then add 0.06g of sodium dodecyl sulfate (abbreviated as SDS), sonicate to dissolve and then add

0.15g of cerium acetate (abbreviated as Ce(Ac)3) to the configured above solution, put into stirrer and stir for 1 hour at room temperature until Ce(Ac)s is completely dissolved. Next, weigh 0.165 g of tin tetrachloride (SnCls), add it to the above solution,

8 001758P-NL continue to stir again at room temperature for 1 hour until SnCls is completely dissolved. After that, accurately weigh 0.149g of KMnOa dissolved in 50mL of deionized water and then add it to the above reaction solution. Continue the reaction at room temperature for 1h, and after the reaction is finished weigh 0.15¢g sulfur urea (abbreviated as CH4N2S) and add it to the reaction solution, stirring until the reaction is finished for 4h. After the reaction is finished, the suspension obtained is washed several times by centrifugation and then vacuum freeze-dried to obtain the final composite material to be tested. The mass of tin chloride was calculated as follows:

0.15+317x350.6=0.165g; the concentration of potassium permanganate was calculated as follows: 0.15+31/x2x158=0.149. The denitrification and anti-sulfur performance of the composites was evaluated in a homemade tubular SCR reactor. the volume fractions of NO and NH: were both

0.05 %, the volume fraction of O2 was 5 %, and the rest was Ny, the gas flow rate was 700mL-min-1, the temperature was set to 140°C, and the denitrification rate was

71.8% measured by KM940 flue gas analyzer from UK; the temperature was set to 160°C, and the denitrification rate was 82.2%, the temperature was set to 180°C, the denitrification anti-sulfur rate was 93.9%; the final denitrification rate was basically stable at 69.8% when SO. was passed into the test at 180°C for 30min interval.

Example 3 Accurately weigh 0.1g of the above sample of homemade nitrogen-doped graphene oxide, dissolve in 50mL of deionized water, sonicate for 10min and then add 0.06g of sodium dodecyl sulfate (abbreviated as SDS), sonicate to dissolve and then add

0.15g of cerium acetate (abbreviated as Ce(Ac)3) to the configured above solution, put into stirrer and stir for 1 hour at room temperature until Ce(Ac)s is completely dissolved. Next, weigh 0.221 g of tin tetrachloride (SnCls), add it to the above solution, and continue to stir at room temperature for another 1 hour until SnCls is completely dissolved. After that, accurately weigh 0.199g of KMnOa dissolved in 50mL of deionized water and then add it to the above reaction solution. Continue the reaction

9 001758P-NL at room temperature for 1h. After the reaction is finished, weigh 0.29 of sulfur urea {abbreviated as CH4N2S) and add it to the reaction solution and stir until the reaction is finished for 4 h. After the reaction is finished, the suspension obtained is washed several times by centrifugation and then vacuum freeze-dried to obtain the final composite material to be tested. The mass of tin chloride was calculated as follows:

0.2+317x350.6=0.221g; the concentration of potassium permanganate is calculated as follows: 0.2+317x2x158=0.199.

The denitrification and anti-sulfur performance of the composites was evaluated in a homemade tubular SCR reactor. the volume fraction of NO and NH: were both 0.05%, the volume fraction of O2 was 5%, and the rest was Nz, the gas flow rate was 700 mL-min-1, the temperature was set to 140°C, and the denitrification rate was 70.1 % measured by KM940 UK flue gas analyzer; the temperature was set to 160°C, and the denitrification rate was 83.3%, the temperature was set to 180°C, the denitrification anti-sulfur rate was 100%; the final denitrification rate was basically stable at 70.9% when SO: was passed into the test at 180°C with an interval of 30min. Example 4 Accurately weigh 0.1g of the above sample of homemade N-doped graphene oxide, dissolve in 50mL of deionized water, sonicate for 10min and then add 0.06g of sodium dodecyl sulfate (abbreviated as SDS), sonicate to dissolve and then add 0.259 of cerium acetate (abbreviated as Ce(Ac)3) to the configured above solution, put into stirrer and stir for 1 hour at room temperature until Ce(Ac)s is completely dissolved. Next, weigh 0.276 g of tin tetrachloride (SnCl4), add it to the above solution and continue to stir at room temperature for another 1 hour until SnCl4 is completely dissolved. After that, accurately weigh 0.249g of KMnQ4 dissolved in 50mL of deionized water and then add it to the above reaction solution. Continue the reaction at room temperature for 1h. After the reaction is finished, weigh 0.259 of sulfur urea {abbreviated as CH4N2S) and add it to the reaction solution and stir until the reaction is finished for 4 h. After the reaction is finished, the suspension obtained is washed

10 001758P-NL several times by centrifugation and then vacuum freeze-dried to obtain the final composite material to be tested. The mass of tin chloride was calculated as follows:

0.25+317x350.6=0.276g; the concentration of potassium permanganate is calculated as follows: 0.25+317x2x158=0.249.

The denitrification and anti-sulfur performance of the composites was evaluated in a homemade tubular SCR reactor. the volume fraction of NO and NH: were both 0.05 %, the volume fraction of O2 was 5 %, and the rest was Nz, the gas flow rate was 700 mL-min-1, the temperature was set to 140°C, and the denitrification rate was 61.1 % measured by KM940 UK flue gas analyzer; the temperature was set to 160°C, and the denitrification rate was 78.8%, the denitrification anti-sulfur rate was 88.4% when the temperature was set to 180°C; the final denitrification rate was basically stable at

70.4% when SO was passed through at 180°C for 30min interval test.

Activity evaluation: The catalyst was evaluated in a homemade tubular SCR reactor. The reactor was externally heated electrically and thermocouples were placed next to the catalyst bed of the reactor tube to measure the temperature, the flow of the experimental setup is shown in Figure 1. The flue gas composition was simulated with a steel cylinder, including NO, O2, N2 and NH3 as reducing gases, with NO and NH3 at 0.04-0.06% by volume, O2 at 4-6% by volume and N2 at the rest. -The gas flow rate and composition were adjusted and controlled by mass flow meter. In order to ensure the stability and accuracy of the data, each working condition was stabilized for at least 30 min.

Table 1 Effect of various factors on the anti-sulfur rate of denitrification of composite materials (reaction temperature is 180°C):

11 001758P-NL passing S2attec | | | |] From the data in Table 1, it can be seen that at 180°C, with the increasing mass ratio, the denitrification anti-sulfur rate along with a trend of first increasing and then decreasing, with a maximum value occurring at a mass ratio of 1:2.5 out.

And to the anti-sulfur performance also reached the maximum.

The above-mentioned is only a better implementation of the invention, all the equal changes and modifications made in accordance with the scope of the patent application of the invention, should be covered by the invention.

Claims

12 001758P-NL Patent Claims

1. A nitrogen-sulfur-co-doped graphene composite loaded with a ternary high-efficiency denitrification antisulfur catalyst, characterized in that this composite is a novel modified nitrogen-sulfur-co-doped graphene (abbreviated as rGO.n,s) as a catalyst support, and the Mn-Ce-SnO 3 ternary catalyst is grown in situ on the surface of the nitrogen-sulfur co-doped graphene, which has both high denitrification rate and anti-sulfur effect.

2. The nitrogen-sulfur co-doped graphene composite loaded with a ternary high-efficiency denitrification and antisulfur catalyst as claimed in theorem 1, characterized in that: that nitrogen-sulfur co-doped graphene has been prepared as a reaction precursor by means of a self-modified Hummers method for the preparation of graphene oxide, obtaining that reaction precursor as follows: (1) 1g of graphite was added to a 150ml beaker containing 40m! concentrated sulfuric acid (called H250O4}, which was placed in a water bath at room temperature and stirred until completely dissolved. Then accurately weigh 5g of potassium permanganate (called KMnO4) and add 0.2g of KMnO4 every 10 minutes; (2) After all KMnOa has been added, raise the temperature of the water to 50°C and stir the reaction for 2 hours, then add 0.5g of cyanuric acid (abbreviated to CA) to dissolve it completely and continue the reaction for 2 more hours before adding 80 ml of deionized water; (3) Place the reaction solution with added deionized water in a water bath at 90°C and stir for 10 minutes, add H202 dropwise until no more air bubbles.Finally, 20 ml hydrochloric acid is added, and the obtained product is centrifuged repeatedly until neutral, transferred to a freeze-drying apparatus for freeze-drying and set aside, the final obtained product is called GO.n.

13 001758P-EN

3. A method for preparing a nitrogen-sulfur co-doped graphene composite loaded with a ternary high-efficiency denitrification anti-sulfur catalyst as claimed in statement 2, characterized in that it comprises the following steps: (1) weighing 0.1g GO .n, dissolve in 50 mL of deionized water, prepare a GO.n solution, disperse ultrasonic for 10 min, add 0.069 dodecyl sulfate nano to the solution and sonicate for 10 min; (2) Add Ce(Ac)s to the solution of step (1) and stir at room temperature for 1 hour until Ce(Ac)s is completely dissolved; (3) add SnCl to the solution of step (2) and stir at room temperature for another 1 hour until SnCl4 is completely dissolved; and (4) adding a KMnO4 solution to the solution of step (3) and continuing the reaction at room temperature for 1 hour. After the reaction, CH4N2S is added and stirred until the reaction is completed for 4 hours.

After the reaction is completed, the resulting slurry is washed by centrifugation and freeze-dried under vacuum to obtain a nitrogen-sulfur co-doped graphene composite loaded with a ternary high-efficiency denitrification-sulfur-fighting catalyst.

The preparation method according to claim 3, provided that the mass ratio between GO.n and Ce(Ac)s in step (2) is 1:1-1:2.5.

5. The method of preparation according to claim 3, characterized in that : said molar ratio of Ce(Ac) 3 to SnCl 3 is 1:1.

6. The method of preparation according to claim 3, characterized in that : said molar ratio of Ce(Ac)s to KMnOa is 1:2.

7. The method of preparation according to claim 3, characterized in that : said Ce(Ac): has a mass ratio of 1:1 with CH 4 N: 2 S.