CN107934931B - Modified graphite phase carbon nitride and preparation method and application thereof - Google Patents

Modified graphite phase carbon nitride and preparation method and application thereof Download PDF

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CN107934931B
CN107934931B CN201711137247.8A CN201711137247A CN107934931B CN 107934931 B CN107934931 B CN 107934931B CN 201711137247 A CN201711137247 A CN 201711137247A CN 107934931 B CN107934931 B CN 107934931B
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carbon nitride
phase carbon
modified graphite
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CN107934931A (en
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江莉龙
沈丽娟
雷淦昌
曹彦宁
王心晨
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Fuzhou University
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Abstract

The invention belongs to the technical field of material preparation and environmental catalysis, and particularly relates to modified graphite-phase carbon nitride and a preparation method and application thereof, wherein the modified graphite-phase carbon nitride is prepared from urea and tetrabromobisphenol A through copolymerization, wherein the bromine content in the modified graphite-phase carbon nitride is 0.1-0.5 wt%, and the modified graphite-phase carbon nitride has a nano-layered structure. The modified graphite-phase carbon nitride provided by the invention is applied to desulfurization reaction in H2In S selective reaction, the material shows good catalytic activity and selectivity, and simultaneously has certain activity on COS catalytic hydrolysis.

Description

Modified graphite phase carbon nitride and preparation method and application thereof
Technical Field
The invention belongs to the technical field of material preparation and environmental catalysis, and particularly relates to modified graphite-phase carbon nitride and a preparation method and application thereof.
Background
In the chemical production process of petroleum, natural gas, coal and the like as raw materials, sulfur-containing gases such as hydrogen sulfide, carbonyl sulfide and the like are generally generated. Not only can pollute the ecological environment, but also can harm the human health. At present, H is removed2The most common technique for S is the Claus sulfur recovery process, which can remove both H and sulfur2S can realize the resource utilization of the sulfur element. However, due to the thermodynamic limitations of the Claus reaction, the Claus tail gas still contains 3-5% H2S cannot be converted to elemental sulphur and, in addition, the process requires the use of H2S is subjected to enrichment and desorption, the process route is long, and the equipment investment is large. With the stricter and stricter environmental regulations, the development of H with lower operation energy consumption is urgently needed2The S removal efficiency is higher, and the sulfur resource can be realized.
In the developed method, H2Method for selective oxidation of S to elemental sulfurThe attention of people is widely paid. The reaction is not limited by thermodynamic equilibrium, the process is simple, and the device construction and operation costs are low. And the reaction is exothermic, and the energy consumption is low. The characteristics show that the selective oxidation of H2S into elemental sulfur has good application prospect, and the practical application of the process focuses on the development of efficient catalysts.
H of current development2The S selective oxidation catalyst mainly comprises a molecular sieve, a carbon material, a SiC carrier system, a metal oxide and the like. The above materials still have disadvantages. For example, molecular sieves and carbon materials have large specific surface area and rich pore channels, so that the catalytic performance of the molecular sieves and the carbon materials is good in the initial stage, but the stability of the molecular sieve activity is poor, the carbon materials are easy to decompose, and CS can be generated2And COS species, adversely affecting the apparatus and reaction, etc. The SiC catalyst system has fast heat transfer and good thermal stability, but the granular SiC carrier is easy to inactivate; metal oxides such as Al2O3、TiO2、Fe2O3、V2O5Etc., which have catalytic active sites themselves and have a better conversion in H2The S selective oxidation reaction is widely applied. However, the above metal oxides require high reaction temperature and high volatility in use, and Al is also contained2O3Has poor activity stability, TiO2Easy sulfation, Fe2O3Low sulfur selectivity, V2O5The problems of high self toxicity and the like limit the metal oxide catalyst in H2S selective catalytic oxidation reaction. In addition, in actual industrial production, complicated exhaust gas containing carbonyl sulfide and other components is also contained, and the above catalyst cannot effectively remove carbonyl sulfide gas. Therefore, in addition to the modification of the original catalyst, a catalyst which can be modified in H has been developed2The S selective oxidation shows better catalytic activity and selectivity, and simultaneously can be used as a catalyst with certain activity for COS catalytic hydrolysis reaction, which has important significance for treating actual industrial gas with complex components.
The graphite phase carbon nitride contains Lewis alkali function, Bronsted alkali function and nitrogen-containing polar group, and has unique and controllable electronic property and mesoporousSize effect on some small molecules such as CO2、H2S、COS、O2Has certain adsorption effect. The characteristics show that the catalyst has great application potential in the field of catalysis. However, the application of the single-phase graphite-phase carbon nitride catalyst in the field of desulfurization catalysis is limited due to the high electron-hole recombination rate, low specific surface area, low electron transmission efficiency and easy agglomeration morphology of the single-phase graphite-phase carbon nitride catalyst, and the single-phase graphite-phase carbon nitride catalyst has the defects of complex preparation method or high raw material cost, and cannot meet the industrial requirements. So far, the use of tetrabromobisphenol A as a copolymer for preparing graphite phase carbon nitride by using cheap urea as a precursor of the graphite phase carbon nitride and the application of the graphite phase carbon nitride in desulfurization has not been reported.
Disclosure of Invention
Therefore, the technical problem to be solved by the invention is to overcome the defects of complicated preparation process of graphite-phase carbon nitride, expensive raw materials, low specific surface area and pore volume and high content of carbon nitride in H2The S selective oxidation reaction has the defects of poor catalytic activity and stability, no activity on COS catalytic hydrolysis and the like, thereby providing a preparation method of copolymerization modified graphite-phase carbon nitride and application thereof.
In order to solve the technical problems, the invention adopts the following technical scheme:
a modified graphite phase carbon nitride has a nano-layered structure, wherein the molar ratio of carbon to nitrogen atoms is 0.65-0.72, the content of bromine is 0.1-0.5 wt%, and C-Br response peaks in aromatic rings are present when the binding energy is 70.0 and 70.9eV as detected by X-ray photoelectron spectroscopy.
Further, the specific surface area of the modified graphite phase carbon nitride is 60-106 square meters per gram, and the pore volume is 0.233-0.395m3(ii)/g, the pore diameter is 20.0-24.7 nm.
A preparation method of the modified graphite phase carbon nitride comprises the following steps:
(1) dissolving urea and tetrabromobisphenol A in water, evaporating to dryness, and grinding to obtain mixed powder;
(2) heating the mixed powder to 500-600 ℃ in an inert atmosphere, keeping the temperature for 1-3h, and cooling to room temperature.
Further, the mass ratio of the urea to the tetrabromobisphenol A is 100: 0.15-0.75.
Further, in the step (2), the temperature was raised to 550 ℃ and maintained for 2 hours.
Further, the particle size of the mixed powder in the step (1) is 250-300 meshes.
Further, the evaporation temperature is 60-90 ℃.
Further, the temperature rise rate in the step (2) is 2-5 ℃/min.
An application of the modified graphite-phase carbon nitride in a desulfurization catalyst.
Further, the modified graphite-phase carbon nitride is used as a hydrogen sulfide selective oxidation catalyst and a carbonyl sulfide catalytic hydrolysis catalyst.
The technical scheme of the invention has the following advantages:
1. the modified graphite-phase carbon nitride provided by the invention has high specific surface area and pore volume, effectively accelerates the mass transfer diffusion process and increases the reactive sites. At the same time, the introduction of bromine element and aromatic benzene ring can effectively regulate and control the surface property and pi conjugated system of material to make it implement reaction on H2S、COS、O2The adsorption and activation of small molecules are obviously improved.
2. The preparation method of the modified graphite phase carbon nitride provided by the invention introduces a means of copolymerization of urea and tetrabromobisphenol A into the preparation of the graphite phase carbon nitride for the first time, and has the advantages that the prepared carbon nitride does not contain metal, is nontoxic, has good chemical stability, low raw material price, simple synthesis process and easy realization of industrial production.
3. The modified graphite phase carbon nitride provided by the invention is applied to desulfurization reaction, and experiments prove that in H2In S selective reaction, the material shows good catalytic activity and selectivity, and the performance is better than that of nitrogen-doped graphitized carbon and Fe2O3Good; meanwhile, the catalyst has certain activity on catalytic hydrolysis of COS.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is an XRD pattern of graphite phase carbon nitride obtained in comparative example 1 and examples 1 to 4 of the present invention;
FIG. 2 is an FTIR spectrum of graphite phase carbon nitride prepared in comparative example 1, examples 1-4 of the present invention;
FIG. 3 is a DRS map of graphite phase carbon nitride obtained in comparative example 1 and examples 1-4 of the present invention;
FIG. 4 is an SEM/TEM image of graphite phase carbon nitride obtained in comparative example 1 and example 4 according to the present invention;
FIG. 5 is an XPS spectrum of Br3d in graphite-phase carbon nitride obtained in comparative example 1;
FIG. 6 is an XPS spectrum of Br3d in graphite-phase carbon nitride obtained in example 4;
FIG. 7 is an XPS spectrum of Br3d in CNU-KBr (physical doping);
FIG. 8 shows the results of comparative examples 1 and 4 of the present invention13A C-NMR spectrum;
FIG. 9 shows the results of the present invention in comparative example 1 and examples 1 to 4, wherein the graphite phase carbon nitride is in H2H in S selective catalytic oxidation2S conversion rate curve diagram;
FIG. 10 shows the results of the present invention in comparative example 1 and examples 1 to 4, wherein the graphite phase carbon nitride is in H2H in S selective catalytic oxidation2S, a selectivity curve graph;
FIG. 11 shows the results of the present invention in comparative example 1 and examples 1 to 4, wherein the graphite phase carbon nitride is in H2S is a yield curve diagram of sulfur simple substance in selective catalytic oxidation reaction;
FIG. 12 is a graph of graphite phase carbonitride particles in H prepared in example 4 of the present invention2An activity stability curve diagram at 210 ℃ in the S selective catalytic oxidation reaction;
FIG. 13 shows graphite phase carbonitride particles in H prepared in example 4 of the present invention2S is a sulfur elemental yield curve diagram at 210 ℃ in the selective catalytic oxidation reaction;
FIG. 14 is a graph showing the conversion rate of graphite-phase carbonitride in COS-catalyzed hydrolysis reaction according to the present invention in comparative example 1, example 2, and example 4;
FIG. 15 shows XRD patterns of graphite-phase carbon nitride obtained in example 4 of the present invention before and after catalytic reaction.
Detailed Description
Example 1
10g of urea and 15mg of tetrabromobisphenol A are dissolved in 100mL of water and evaporated to dryness with stirring at 60 ℃. Grinding the sample after evaporation to dryness into powder with the granularity of 250 meshes, placing the powder in a heating device, heating to 600 ℃ at the heating rate of 5 ℃/min in the nitrogen atmosphere, and carrying out thermal polymerization for 2 h. Naturally cooling to room temperature, collecting the synthesized sample to obtain graphite-phase carbon nitride with nano-layered structure, named CNU-Br0.015。
Example 2
10g of urea and 25mg of tetrabromobisphenol A are dissolved in 100mL of water and evaporated to dryness with stirring at 90 ℃. Grinding the sample after evaporation to dryness into powder with the granularity of 300 meshes, placing the powder in a heating device, heating to 500 ℃ at the heating rate of 5 ℃/min in the nitrogen atmosphere, and carrying out thermal polymerization for 2 h. Naturally cooling to room temperature, collecting the synthesized sample to obtain graphite-phase carbon nitride with nano-layered structure, named CNU-Br0.025。
Example 3
10g of urea and 50mg of tetrabromobisphenol A are dissolved in 100mL of water and evaporated to dryness with stirring at 80 ℃. Grinding the sample after evaporation to dryness into powder with the granularity of 250 meshes, placing the powder in a heating device, heating to 550 ℃ at the heating rate of 5 ℃/min under the nitrogen atmosphere, and carrying out thermal polymerization for 2 h. Naturally cooling to room temperature, collecting the synthesized sample to obtain graphite-phase carbon nitride with nano-layered structure, named CNU-Br0.05。
Example 4
10g of urea and 75mg of tetrabromobisphenol A are dissolved in 100mL of water and evaporated to dryness with stirring at 80 ℃. Grinding the sample after evaporation to dryness into powder with the granularity of 250 meshes, placing the powder in a heating device, heating to 550 ℃ at the heating rate of 5 ℃/min under the nitrogen atmosphere, and carrying out thermal polymerization for 2 h. After the mixture is naturally cooled to the room temperature,collecting the synthesized sample to obtain graphite-phase carbon nitride with nano-layered structure, which is named CNU-Br0.075。
Comparative example 1
10g of urea was ground into powder having a particle size of 250 mesh, placed in a heating apparatus, heated to 550 ℃ at a heating rate of 5 ℃/min under a nitrogen atmosphere, and subjected to thermal polymerization for 2 hours. And naturally cooling to room temperature, and collecting the synthesized sample to obtain the graphite-phase carbon nitride with the nano-layered structure, which is named as CNU.
Comparative example 2
10g of graphitized carbon is treated with 50% HNO3Oxidized at room temperature for 5h and then washed 5 times with deionized water to remove excess acid. 10g of the oxidised sample was dispersed in the suspension (6.67g in 34mL of ethanol) and stirred at room temperature for 5h, evaporated to dryness at 80 ℃ and dried in an oven at 120 ℃ for 12h, placed in a heating apparatus and heated to 450 ℃ at a rate of 10 ℃/min under nitrogen and held for 30 min. And naturally cooling to room temperature to obtain the nitrogen-doped graphitized carbon which is named as N-GC.
And (3) characterization and analysis:
1. instrumentation and equipment
X-ray powder diffraction (XRD): the XRD pattern of the catalyst was determined by X-ray diffraction of Bruker D8 Advance model, with a copper target (Cu K alpha, lambda 0.154nm) X-ray tube, Ni filter, operating voltage 45kV, current 40mA, and scanning range 2 theta 10-60 deg.
Fourier red spectroscopy (FTIR): the Fourier transform Infrared Spectroscopy (FTIR) of the catalyst was characterized on a Nicolet model 6700 infrared spectrometer. And (3) testing conditions are as follows: a blank KBr sheet is taken as a background, a sample and KBr are mixed and ground according to the mass ratio of 1:200, and tabletting, sample preparation and testing are carried out. Test range: the number of scanning times is 32, and the resolution is 4cm-1The scanning range is 4000-400 cm-1。
Ultraviolet-visible diffuse reflectance (UV-Vis DRS) the diffuse reflectance spectrum of a sample was determined by a Varian Cary 500Scan type UV-Vis-NIR spectrophotometer fitted with a small integrating sphere, using a BaSO4For reference, the scan range was 200 and 800 nm. Converting the diffuse reflectivity measured by the experiment into light absorption by using a Kubelka-Munk methodAnd obtaining the ultraviolet-visible diffuse reflectance spectrum.
Field emission Scanning Electron Microscope (SEM): the catalyst was observed by Scanning Electron Microscopy (SEM) on a S-4800 field emission Scanning Electron Microscope (SEM) of Hitachi, Japan. And (3) testing conditions are as follows: the scanning acceleration voltage is 5-10 kV, the resolution is 1.0nm, and the magnification is 20-800,000X.
Determination of specific surface area and pore size distribution (Low temperature N)2Physical adsorption): the specific surface area and pore size distribution of the catalyst were determined analytically by other adsorption pore size measuring instruments of model ASAP2020 (Micrometrics, usa). Vacuum degree P/P in sample chamber0And measuring by a liquid nitrogen static adsorption method within the range of 0-1. Before testing, the catalyst is degassed under vacuum degree at 453K for 4h, then the adsorption-desorption isotherm is determined according to a static method, the specific surface area is calculated by a multipoint Barrett-Emmett-Teller (BET) method, and the pore volume and the pore size distribution are calculated by a Barrett-Joyner-Halanda (BJH) model.
Elemental analysis: the chemical composition of the catalyst (C, N, S, B, F, Cl) was measured on a Vario Micro type Elemental Analyzer (EA) and the detector was a high sensitivity, high accuracy TCD detector.
X-ray photoelectron spectroscopy (XPS): the chemical composition elements and the valence state of the catalyst are measured by an ESCALB250 type X-ray photoelectron spectrometer (XPS), an excitation light source is Al target Kalpha rays, the energy is 20eV, and the power is 200W. Background subtraction using Sherry function, fitting of curves with Gauss-LorentZ function, C1sBinding energy (binding energy)284.6eV is used as a reference value.
13C-NMR solid nuclear magnetic resonance spectrum (13C-NMR): 13C solid NMR13C solid-state NMR) was tested on a Bruker AVANCE model III 500M nuclear magnetic resonance spectrometer. And (3) testing conditions are as follows: cp/mas, contact 8ms, masfreq 10kHz, decoupling spine 164 and delay 3 s.
2. Analysis results
As shown in fig. 1, XRD patterns of the graphite-phase carbon nitride prepared in comparative example 1 and examples 1 to 4 of the present invention are shown. As can be seen from the figure, the CNU-Br series samples have two obvious diffraction peaks near 12.7 degrees and 27.5 degrees, which are respectively assigned to in-plane repeating unit (100) and interlayer accumulation (002) crystal face diffraction in a carbon nitride structure. From the XRD pattern, it was observed that as the amount of tetrabromobisphenol A increased, the diffraction angles of the (100) crystal plane and the (002) crystal plane decreased, and the diffraction angle of the (002) crystal plane shifted from 27.7 to 27.2. This indicates that the degree of order is destroyed and the lamella is correspondingly thinned in the CNU-Br series samples with the increase of the amount of tetrabromobisphenol A.
As shown in FIG. 2, the FT-IR spectra of the graphite-phase carbon nitride prepared in comparative example 1 and examples 1 to 4 of the present invention are shown. As can be seen from the figure, the chemical bond characteristic absorption of the CNU-Br series samples is consistent with that of the conventional CN phase, indicating that the chemical structure of the graphite phase carbon nitride is not destroyed by the copolymerization modification of tetrabromobisphenol A. For example 3000--1、1200-1600cm-1And 800cm-1Are respectively assigned to NH2NH stretching vibration, aromatic carbon nitrogen heterocycle (heptazine ring, C)6N7) C-N, C ═ N stretching vibration and heptazine ring breathing vibration modes. Compared with CNU, the introduction of bromine and aromatic ring reduces the orderliness of chemical structure to a certain extent, leads to broadening of characteristic peak, and simultaneously 3000-3500cm-1The diffraction peak is reduced, which is mainly attributed to the replacement of the hydrogen on the-NH at the terminal with an aromatic ring.
FIG. 3 is a DRS map of the graphite phase carbon nitride prepared in comparative example 1 and examples 1-4 of the present invention. As can be seen from the figure, with the increase of the content of tetrabromobisphenol A, the absorption band is red-shifted, and the characteristic absorption peaks at 265nm and 360nm are obviously enhanced, wherein 265nm is assigned to a B band generated by pi → pi transition of aromatic benzene ring, and 360nm is an R band generated by n → pi transition. This indicates that the introduction of aromatic benzene rings effectively extends the delocalization of the pi-conjugated system.
FIG. 4 shows SEM/TEM images of the graphite-phase carbon nitride prepared in comparative example 1 and example 5 according to the present invention. As can be seen from fig. (a), the unmodified CNUs are morphologies resulting from the stacking of denser lamellae. FIGS. (B) to (D) show the modified catalysts of example 5. As can be seen, the surface is composed of thin sheets and there are many irregular small holes. The method proves that the copolymerization of urea and tetrabromobisphenol A changes the traditional thermal polymerization process of carbon nitride to a certain extent and can effectively optimize the surface appearance and the nano structure of the catalyst.
As shown in Table 1, the physical and chemical properties of the graphite-phase carbon nitride prepared in comparative example 1 and examples 1 to 4 according to the present invention were determined. As can be seen from Table 1, the C/N molar ratio of the catalyst after copolymerization modification gradually increased, and when the tetrabromobisphenol A content was 75mg, the C/N molar ratio was 0.72, which was caused by the introduction of the aromatic carbon ring. And the specific surface area and the pore volume of the tetrabromobisphenol A are increased along with the increase of the content of the tetrabromobisphenol A, which is favorable for the mass transfer process of the catalytic reaction and the increase of the reactive sites.
TABLE 1 physicochemical Properties of graphite-phase carbon nitride prepared according to the invention
As shown in fig. 5 to 7, XPS spectra of the graphite-phase carbon nitride prepared in comparative example 1 and example 4 and the KBr-supported CNU according to the present invention are shown. As can be seen from the figure, no Br response was found for the CNU samples. It can be observed from FIG. 6 that there are response peaks at binding energies of 70.0, 70.9eV, which are mainly attributed to the Br state in C-Br in the aromatic ring; from the comparison of FIG. 7, it can be seen that the binding energy of Br loaded alone is only in response to 68.75eV, which is mainly attributed to the physically adsorbed Br-. The above results show that Br-doped aromatic copolymerized carbon nitride is successfully prepared in the present patent, and the following table shows the bromine content detection data of the graphite-phase carbon nitride prepared in the present invention.
Table 2 bromine content detection of graphite-phase carbon nitride prepared according to the present invention
Sample CNU CNU-Br0.015 CNU-Br0.025 CNU-Br0.05 CNU-Br0.075
Br(wt％) 0 0.096 0.151 0.333 0.486
As shown in FIG. 8, the method for preparing graphite phase carbon nitride according to the present invention is that of comparative example 1 and example 413C-NMR spectrum. CNU and CNU-Br0.075Two distinct nuclear magnetic resonance peaks appear at 157ppm and 165ppm, which are mainly assigned to the chemical shifts of c (i) and c (e) in the heptazine ring building block, consistent with conventional graphite phase carbon nitride. CNU-Br after tetrabromobisphenol A copolymerization modification0.075A large peak package exists in the chemical shift of 120-129 ppm, and is mainly caused by aromatic benzene ring molecules which are grafted on the surface of carbon nitride and participate in pi conjugation. Illustrating the successful incorporation of our aromatic rings into the carbon nitride compositional structure.
Selective catalytic oxidation of H2And (S) performance test:
catalysts prepared in each of examples and comparative examples were used for H2The test conditions of the selective catalytic oxidation activity of S are as follows: the loading of catalyst is 0.2g, the reaction temp. is 90-240 deg.C, and the raw material gas is three-component gas (5000 ppmH)2S，2500ppmO2，N2Equilibrium gas), the inner diameter of the reaction tube is 5mm, and the space velocity (WHSV) of the raw material gas is 3000mL g-1·h-1The raw material gas flow rate is 10 mL/min-1. Of catalystsActivity with H2S conversion, sulfur selectivity, and percent sulfur yield.
The catalysts prepared in each example and comparative example were applied to H2In the S selective catalytic oxidation reaction, the activity calculation formula is as follows:
FIGS. 9 and 10 show the graphite-phase carbonitride prepared in comparative example 1 and examples 1 to 4 according to the present invention in H2And (3) a catalytic activity curve diagram of the S selective catalytic oxidation reaction. As shown in FIG. 9, H increased with the tetrabromobisphenol A content2The conversion of S is correspondingly increased. But at 90 ℃ CNU-Br0.025Slightly higher than CNU-Br0.05. When tetrabromobisphenol A content is 75mg, its H2The S conversion rate reaches more than 94.6 percent at 90-240 ℃. As can be seen from FIG. 10, the sulfur selectivity of the CNU-Br series of catalysts was reduced at 240 ℃ indicating that the series of catalysts had good sulfur selectivity. As shown in FIG. 11, the carbon nitrides after the copolymerization modification were all better than those of the unmodified CNU, and CNU-Br0.075The sulfur yield of the catalyst is more than 94.6 percent in each temperature interval.
FIG. 12 and FIG. 13 show the graphite phase carbon nitride in H prepared in example 4 of the present invention2And (3) an activity stability curve diagram at 210 ℃ in the S selective catalytic oxidation reaction. As can be seen from fig. 12 and 13, the sulfur yield was 100% in the first 3 hours; running for 73H, H2The S conversion rate is 100%; within 100h, the sulfur yield is over 93 percent; within 180h, the sulfur yield is over 88 percent; within 200h, the sulfur yield is over 85 percent. And the sulfur selectivity is over 95 percent in the whole reaction time.
As shown in Table 2, the graphite phase carbon nitride prepared in example 4And nitrogen-doped graphitized carbon prepared in comparative example 1 and comparative example 2 and commercial Fe2O3Compared with the prior art, the catalyst has high conversion rate and selectivity within the temperature range of 90-240 ℃, and the sulfur yield is over 94 percent.
Table 3 catalysts prepared according to example 4 of the invention and comparative example 1 and commercial Fe2O3Catalytic activity of
And (3) testing the catalytic hydrolysis performance of COS:
the test conditions for the activity of the graphite phase nitrogen carbide prepared in the comparative example 1, the example 2 and the example 4 for the catalytic hydrolysis of COS were as follows: the loading of catalyst is 0.2g, the reaction temp is 30-150 deg.C, the temp of steam in reactant is 40 deg.C, and the concentration of raw material gas is 112.2mg/m3COS/N2The inner diameter of the reaction tube is 5mm, and the space velocity (WHSV) of the raw material gas is 6000mL g-1·h-1The flow rate of the raw material gas is 20 mL/min-1. The activity of the catalyst is expressed as a percentage of COS conversion.
Fig. 14 is a graph showing activity curves of the graphite-phase carbon nitride prepared in comparative example 1, example 2, and example 4 according to the present invention in COS catalytic hydrolysis. As shown in fig. 13, the catalyst modified by copolymerization showed better catalytic activity. When the reaction temperature was 150 ℃, the hydrolysis conversion of COS in example 4 reached 50% or more, which was improved by about 35% as compared with unmodified comparative example 1.
Fig. 15 is an XRD pattern before and after the reaction of the graphite phase carbonitride catalyst prepared in example 4 of the present invention. From the map, CNU-Br0.075The diffraction peaks of the (100) and (002) crystal faces of the samples are basically not changed before and after the reaction, and no new diffraction peak is generated, which indicates that the chemical stability of the catalyst is better.
The catalytic activity of the CNU-Br series catalyst is correspondingly improved along with the increase of the content of tetrabromobisphenol A. The reason is that the bromine doping and the introduction of aromatic benzene ring can improve the carbon nitride to H2S、COS、O2Adsorption and activation. At the same time, copolymerization modificationThe morphology and the structure of the catalyst are optimized, more active sites such as nitrogen-containing polar groups and the like are exposed, and the performance of the catalyst is effectively improved.
In conclusion, the bromine-doped graphite-phase carbon nitride catalyst with the nano-layered structure prepared by the invention can selectively oxidize H2The S reaction has good low-temperature activity and high catalytic stability, and simultaneously shows certain activity in the COS catalytic hydrolysis reaction, thereby having great application value in the actual industrial production.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.

Claims (9)

1. A modified graphite phase carbon nitride is characterized in that the modified graphite phase carbon nitride has a nano-layered structure, wherein the molar ratio of carbon to nitrogen atoms is 0.65-0.72, the bromine content is 0.1-0.5 wt%, and an X-ray photoelectron spectroscopy detection shows that when the binding energy is 70.0 and 70.9eV, a C-Br response peak in an aromatic ring exists.
2. The modified graphite phase carbon nitride of claim 1, wherein the modified graphite phase carbon nitride has a specific surface area of from 60 to 106 square meters per gram and a pore volume of from 0.233 to 0.395m3(ii)/g, the pore diameter is 20.0-24.7 nm.
3. A method for producing the modified graphite-phase carbon nitride according to claim 1 or 2, characterized by comprising the steps of:
(1) dissolving urea and tetrabromobisphenol A in water, evaporating to dryness, and grinding to obtain mixed powder;
(2) heating the mixed powder to 500-600 ℃ in an inert atmosphere, keeping the temperature for 1-3h, and cooling to room temperature to obtain the modified graphite-phase carbon nitride;
wherein the mass ratio of the urea to the tetrabromobisphenol A is 100: 0.15-0.75.
4. The method for producing a modified graphite-phase carbon nitride according to claim 3, wherein the temperature in the step (2) is raised to 550 ℃ for 2 hours.
5. The method as claimed in claim 3, wherein the particle size of the mixed powder in step (1) is 250-300 mesh.
6. The method for producing modified graphite-phase carbon nitride according to claim 3, wherein the evaporation temperature is 60 to 90 ℃.
7. The method for producing a modified graphite-phase carbon nitride according to claim 3, wherein the temperature increase rate in the step (2) is 2 to 5 ℃/min.
8. Use of the modified graphite-phase carbon nitride of any one of claims 1 to 7 in a desulfurization catalyst.
9. Use according to claim 8, wherein the modified graphitic carbon nitride is used as a hydrogen sulfide selective oxidation catalyst and a carbonyl sulfide catalytic hydrolysis catalyst.
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