A magnesium-based sulfur high-value catalyst, a preparation method and application thereof

Abstract

The application discloses a magnesium-based sulfur high-value catalyst and a preparation method and application thereof, and belongs to the technical field of material preparation and environmental catalysis. The magnesium-based sulfur high-value catalyst is prepared by using a nano-flower cluster-shaped nitrogen-carbon polymer as a carrier and Mg in a single-atom Mg-N X chemical bond form and is dispersed on the carrier. The magnesium-based high-value catalyst has high specific surface area and pore volume, and Mg-N X atoms are bonded on the nitrogen-carbon carrier by chemical coordination, so that the electronic structure and surface properties of the catalyst can be regulated and optimized. In the reactions of H2S nucleophilic addition of aryl nitrile compounds to form thio-benzamide products and H2S reduction of aryl nitro compounds to form aniline products, the magnesium-based high-value catalyst has high catalytic activity and product selectivity. The application can realize efficient removal of an H2S source and high-value utilization of H2S, and has better performance than traditional catalysts such as MgO, h-BN and g-C3N4 and is not prone to sulfur poisoning, so that the magnesium-based high-value catalyst can be recycled, has wide applicability to organic substrates and has great industrial application prospect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of material preparation and environmental catalysis, and particularly relates to a magnesium-based sulfur high-value catalyst, a preparation method and application thereof. BACKGROUND

[0002] Hydrogen sulfide (H2S) is a highly toxic gas associated with the exploitation and utilization of oil, coal and natural gas. For example, in the production process using coal as raw material, about 2 g / Nm 3 of sulfides (H2S, COS, etc.) are contained, and the total amount of sulfur to be treated (calculated as SO2) is as high as ~23 million tons per year. Their presence not only corrodes pipelines and chemical production equipment, and makes downstream catalysts poisoned and inactivated, but also seriously pollutes the environment and endangers human health. Among them, COS generates H2S and CO2 through hydrolysis reaction (COS + H2O → CO2 + H2S). At the same time, the generated H2S is removed with the H2S associated with the raw gas by using efficient treatment process. The current mature technology for H2S treatment is the Claus process. However, this process can only catalytically convert H2S into sulfur and sulfuric acid with low added value, while the H element contained is converted into H2O and discharged as waste water, which not only pollutes the environment, but also loses a large amount of valuable hydrogen resources. Therefore, it is urgent to develop new technologies and new materials for atomic economic utilization of H2S and high-value utilization of H2S.

[0003] In principle, if H2S is used as the raw material of H and S at the same time, a new chemical reaction system and a new type of high-efficiency catalyst are constructed, H2S is directly used as a "hydrogen donor" and a "sulfur donor" to synthesize high-value sulfur-containing chemicals, and the source removal and high-value utilization of H2S are simultaneously realized. The key lies in constructing a new practical chemical reaction system and designing a new type of high-efficiency catalyst.

[0004] Arylthioamides and their derivatives are important organic compounds, which have wide application prospects in fine chemical industry, biological medicine, polymer materials and other fields. At present, the commonly used method for synthesizing arylthioamides is to use aromatic nitrile or amide and sulfurizing reagents such as carbon disulfide, hexamethyldisilthiane, etc. to carry out the reaction of sulfur replacing oxygen. However, the atom utilization rate of this technology is low, and toxic waste gas, waste water and foul-smelling thio by-products are easily produced in the reaction process. Another method is to use H2S and aromatic nitrile to carry out nucleophilic addition reaction to synthesize thioamide compounds. This reaction not only realizes the green conversion of H2S, but also utilizes the "hydrogen resource" in H2S molecule, and each atom in H2S molecule is utilized atom-economically, and "near zero waste discharge" is realized. However, the deficiency of this technology is that the amine assistant used is difficult to separate from the product, and only thioamide compounds of free amine can be synthesized, and the reaction efficiency and yield are low due to the aggregation of the product and the increase of by-products during the reaction, which hinders its practical application. Therefore, a new process for efficiently synthesizing arylthioamides from H2S and aromatic nitrile-based compounds is designed and developed, and a new type of efficient catalyst system is designed to realize the efficient conversion of H2S to arylthioamide compounds under mild conditions.

[0005] At present, there is no report on related catalysts for the synthesis of thioamides by H2S nucleophilic addition to aromatic nitriles. The catalysts for H2S catalytic reaction mainly use Fe, Co, Cu, Ni, Zn and other transition metals as active sites. Although they have certain activity, there are still some deficiencies: (1) the sulfur atom in H2S is easy to poison the active centers of these transition metals, which makes the desorption energy barrier of sulfur intermediates on the active sites always remain high, and it is difficult to desorb and dissociate from the catalyst, resulting in low efficiency; (2) the strong oxidizing property of conventional transition metal oxides easily promotes the formation of sulfate in the reaction system, resulting in the deposition of salt on the surface of the catalyst and the deactivation of the catalyst. Therefore, another key is to design and prepare a new type of efficient catalyst that promotes the reaction.

[0006] Based on the above research, a new reaction for preparing arylthioamide products from H2S nucleophilic addition to aromatic nitrile-based compounds is designed, and a high-performance catalyst system is designed to develop a new method for efficient catalytic conversion of H2S at the source, which provides a theoretical basis and technical source for efficient removal and high-value utilization of H2S.

[0007] In recent years, nitrogen-carbon polymer materials composed of nitrogen and carbon elements through covalent bonds have attracted extensive attention in the field of catalysis. Notably, the N element in the skeleton of such materials endows them with special electronic and chemical properties: (1) Due to the difference in the radii of carbon and nitrogen atoms, the introduction of N easily causes a certain degree of lattice distortion and increases defect sites, which is beneficial to promoting the adsorption and activation of reactant molecules; (2) The electronegativity of nitrogen atoms (3.04) is greater than that of carbon atoms (2.55), and the enrichment of electrons to nitrogen atoms can induce changes in the electronic structure and surface polarity of the material. More importantly, the nitrogen atoms in the nitrogen-carbon polymer can act as anchoring points for metal atoms, and electron transfer can occur between the metal atoms and the nitrogen atoms to form a strongly coupled M-N x center. The embedded nanometer metal can have strong metal-support interactions with the carbon-nitrogen support, which is beneficial to improving the dispersion and stability of the metal active sites, and improving the electronic environment and spatial structure of the metal active sites. We noticed that s-block metal magnesium materials have been studied in selective catalytic conversion of sulfide reactions, such as COS hydrolysis desulfurization, hydrogenation desulfurization, and H2S selective oxidation reactions. However, due to the fact that traditional catalysts mainly load s-block metals on oxide supports through impregnation, the weak binding force between the central metal atoms and the support makes the active sites prone to agglomeration or loss during the reaction process, which is not an ideal solution for direct application in H2S catalytic removal reactions. Based on this, the present invention creatively develops a green and simple method for preparing Mg-doped carbon nitride catalysts, and applies them to the source removal and high-value reaction of H2S. We use one or more of melamine, urea, dicyanamide, thiourea, and monocyamine, and one or more of cyanuric acid and trithiocyanic acid to self-assemble into flower-shaped nitrogen-carbon polymer precursors and unit point metal space isolators, and use magnesium compounds (such as magnesium chloride, magnesium carbonate, ethylenediaminetetraacetic acid magnesium, magnesium citrate, magnesium lactate, and glycine) as metal Mg atom precursors to achieve high dispersion of Mg atoms anchored on the carbon-nitrogen polymer support. The present invention provides a reference for the simple and green preparation of Mg-based catalysts, and has far-reaching research significance. At the same time, the prepared Mg-based nitrogen-carbon polymer catalyst can efficiently remove H2S and realize the high-value application of H2S, further expanding the application field of magnesium-based and polymer nitrogen-carbon materials. SUMMARY

[0008] The present invention aims to provide a magnesium-based sulfur high-value catalyst and its preparation method and application. The catalyst solves the problems of H2S poisoning and carbon poisoning desulfurization in the desulfurization reaction process in the prior art, and can simultaneously realize the catalytic conversion of H2S to arylthioamide and arylamino compounds with high added value under mild conditions.

[0009] To achieve the above-mentioned purpose, the present invention adopts the following technical solutions:

[0010] A magnesium-based sulfur high-value catalyst, its preparation method and application, characterized in that the catalyst is composed of a flower cluster-shaped graphite phase carbon nitride as a carrier and an active s-region metal Mg dispersed on the carrier in an atomic level; the preparation method comprises the following steps:

[0011] (1) Take a nitrogen-containing and thiocyanic acid-containing precursor, and dissolve it in a corresponding solvent, ultrasonic dissolution and dispersion;

[0012] (2) Take a magnesium source, and dissolve it in a corresponding solvent, ultrasonic to complete dissolution;

[0013] (3) Mix the two solutions of steps (1) and (2), stir for a certain time, then centrifuge, and then dry and grind;

[0014] (4) Transfer the white powder obtained in step (3) to a tube furnace, and after calcination under corresponding calcination gas, obtain a nano flower cluster-shaped magnesium-doped nitrogen carbon material, i.e. a magnesium-based sulfur high-value catalyst.

[0015] Further, the nitrogen-containing precursor of step (1) is one or more of melamine, urea, dimelamine, thiourea, and monocyamine, and the thiocyanic acid-containing precursor is one or more of tricyanic acid and trithiocyanic acid, and the molar ratio of the nitrogen-containing precursor to the thiocyanic acid-containing precursor is 1:1-1.5.

[0016] Further, the magnesium source is one or more of magnesium chloride, magnesium carbonate, magnesium sulfate, ethylenediaminetetraacetic acid magnesium salt, magnesium hydroxide, magnesium citrate, magnesium lactate, magnesium malate, magnesium taurate, magnesium L-threonic acid, and glycine magnesium, and the mass ratio of the magnesium source to the nitrogen-containing precursor is 1:20-40.

[0017] Further, the solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, triethanolamine, diethylamine, deionized water, isopropylamine, ethanol, methanol, and ethylene glycol, and the amount of solvent added is 40-80 mL.

[0018] Further, the drying temperature in step (3) is 60-120 ℃, and the stirring time is 1-4 h.

[0019] Further, the drying in step (3) is at 60-120 ℃ for 4-12 h.

[0020] Further, the calcination temperature in step (4) is 400-600 ℃, and the time is 1-4 h.

[0021] Further, the heating rate of the calcination in step (4) is 1-5 ℃ / min.

[0022] Further, the roasting in step (4) is one of nitrogen, air, ammonia, argon and helium.

[0023] Further, the doping amount of Mg in the catalyst is 1-5 wt.%, and the single-atom activity is Mg-N X , wherein 2<X<6.

[0024] Further, the specific surface area of the catalyst is 80-160 m 2 / g.

[0025] Further, the application conditions of the H2S nucleophilic addition to aryl nitrile group and the reduction of aryl nitro group to aniline are as follows: the gas flow rate of raw material gas is 10-30 mL / min, the reaction temperature is 30-110 DEG C, the reaction pressure is normal pressure to 2.0 MPa, the heating rate is 2.5 DEG C / min, the H2S concentration in the raw material gas is 500-50000 ppm, and the aryl nitrile group substrate and / or aryl nitro group content in the system is 0.1-10 mmol.

[0026] The beneficial effects of the present application are as follows:

[0027] (1) The process for preparing aryl thioamide and aryl nitro group by using H2S provided by the present application innovatively uses H2S as "hydrogen donor" and "sulfur donor", simultaneously realizes the source removal of H2S and the high-value utilization of H2S, and the process route is simple and green.

[0028] (2) The nano-flower cluster Mg-based sulfur high-value catalyst provided by the present application has large specific surface area and pore volume, which is beneficial to accelerate the mass transfer and diffusion process and increase the exposure of active sites. At the same time, the coordination bond formed by Mg and N can effectively improve the geometric structure and electronic structure of Mg center and the surface chemical properties of nitrogen-carbon carrier, which can enhance the adsorption and activation of reactants on one hand, and is beneficial to the desorption of sulfur-containing products on the active site on the other hand.

[0029] (3) The nano-flower cluster Mg-based sulfur high-value catalyst provided by the present application uses EDTA-Mg as metal ion precursor, and has nano-cluster polymer carbon nitride as metal atom anchoring carrier, which has the advantages that the obtained carrier has rich defect sites and N active sites, Mg atoms are stably anchored on the carbon-nitrogen carrier through Mg-N chemical bond, Mg atoms are in a highly dispersed form and are not easy to agglomerate, and the chemical stability is good. In addition, the raw material price is low, the synthesis process is simple, and the industrial production is easy to realize.

[0030] (4) The nano-flower cluster Mg-based sulfur high-value catalyst provided by the application has good catalytic activity, experiments prove that the catalyst has excellent catalytic activity and product selectivity in the H2S nucleophilic addition aryl nitrile compound to prepare thio benzamide compound and H2S reduction aryl nitro compound to prepare aniline compound, and can be recycled, and the performance is better than that of traditional desulfurizers such as g-C3N4, h-BN, nitrogen-doped carbon, MgO, CuO, TiO2, CeO2, ZrO2, CoO, NiO, SnO2, MnO2, MoS2, ZnO, Fe2O3 and Si / Al molecular sieve. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 Pristine CN and Mg-N / CN prepared in examples 1-4 of the application X X-ray powder diffraction spectrum of Mg-N / CN;

[0032] Figure 2 Pristine CN and Mg-N / CN prepared in examples 1-4 of the application X CNMR spectrum of Mg-N / CN; 13

[0033] Figure 3 Pristine CN and Mg-N / CN prepared in examples 1-4 of the application X TEM, TEM Mapping and HAADF-STEM images of Mg-N / CN;

[0034] Figure 4 N2 physical adsorption-desorption curve of pristine CN and Mg-N / CN prepared in examples 1-4 of the application X

[0035] Figure 5 Pore size distribution graph of pristine CN and Mg-N / CN prepared in examples 1-4 of the application X

[0036] Figure 6 Pristine CN and Mg-N / CN prepared in examples 1-4 of the application X Aniline yield of Mg-N / CN in the reaction of catalyzing H2S to convert nitroaromatic hydrocarbon at 24 h

[0037] Figure 7 Activity graph of 4Mg-N / CN prepared in example 3 of the application in the reaction of catalyzing H2S to convert nitroaromatic hydrocarbon to prepare aniline in five cycles of regeneration test

[0038] Figure 8 Pristine CN and Mg-N / CN prepared in examples 1-4 of the application X ​​​Mg-N / CN in the conversion of aryl nitrile compounds to thio-benzamide in the presence of H2S after 4 h;

[0039] Figure 9 Figure of the activity of 4Mg-N / CN prepared for Example 3 in the conversion of aryl nitrile compounds to thio-benzamide in the presence of H2S in five regeneration tests. DETAILED DESCRIPTION

[0040] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be described in detail below with reference to examples and drawings, and the examples described are further illustrations of the present application rather than limitations on the content of the present application.

[0041] Example 1

[0042] 2.0 g of melamine (A) and 2.04 g of cyanuric acid (B) were added to 40 mL of dimethyl sulfoxide, respectively, and were uniformly dispersed by ultrasonic. After mixing and stirring the above-mentioned A and B solutions for 30 minutes, white solids were obtained by centrifugation at 5000 rpm / min for 5 minutes, and then were transferred to an oven at 80 °C for drying for 10 h. Subsequently, the dried sample was ground and transferred to a tube furnace, and was heated to 500 °C at a heating rate of 2 °C / min under a nitrogen atmosphere and was kept at this temperature for 4 h. After natural cooling to room temperature, the synthesized sample was collected to obtain a nitrogen-carbon polymer catalyst with nanoflower cluster structure, which was named as pristine CN.

[0043] Example 2

[0044] A method for synthesizing a nanoflower-shaped monatomic magnesium-doped carbon nitride polymer material: 2.0 g of melamine (A) and 2.04 g of cyanuric acid (B) were added to 40 mL of dimethyl sulfoxide, respectively, and were uniformly dispersed by ultrasonic. Then, 0.0715 g (2 mmol) of EDTA-Mg was added to the cyanuric acid solution. After mixing and stirring the above-mentioned A and B solutions for 30 minutes, white solids were obtained by centrifugation at 5000 rpm / min for 5 minutes, and then were transferred to an oven at 80 °C for drying for 10 h. Subsequently, the dried sample was ground and transferred to a tube furnace, and was heated to 500 °C at a heating rate of 2 °C / min under a nitrogen atmosphere and was kept at this temperature for 4 h. After natural cooling to room temperature, the synthesized sample was collected to obtain a Mg-doped carbon nitride polymer catalyst with nanoflower cluster structure, which was named as 2Mg-N / CN.

[0045] Example 3

[0046] A method for synthesizing a nanoflower-shaped monatomic magnesium-doped carbon nitride polymer material: 2.0 g of melamine (A) and 2.04 g of cyanuric acid (B) were added to 40 mL of dimethyl sulfoxide, respectively, and ultrasonically dispersed. Then, 0.143 g (4 mmol) of EDTA-Mg was added to the cyanuric acid solution. After mixing and stirring the above-mentioned A and B solutions for 30 minutes, white solids were obtained by centrifugation at 5000 rpm / min for 5 minutes, and then transferred to an oven at 80°C for drying for 10 hours. Subsequently, the dried sample was ground and transferred into a tube furnace, and heated to 500°C at a heating rate of 2°C / min under a nitrogen atmosphere and kept at this temperature for 4 hours. After natural cooling to room temperature, the synthesized sample was collected to obtain a Mg-doped carbon nitride polymer catalyst with a nanoflower cluster structure, which was named 4Mg-N / CN.

[0047] Example 4

[0048] A method for synthesizing a nanoflower-shaped monatomic magnesium-doped carbon nitride polymer material: 2.0 g of melamine (A) and 2.04 g of cyanuric acid (B) were added to 40 mL of dimethyl sulfoxide, respectively, and ultrasonically dispersed. Then, 0.143 g (4 mmol) of EDTA-Mg was added to the cyanuric acid solution. After mixing and stirring the above-mentioned A and B solutions for 30 minutes, white solids were obtained by centrifugation at 5000 rpm / min for 5 minutes, and then transferred to an oven at 80°C for drying for 10 hours. Subsequently, the dried sample was ground and transferred into a tube furnace, and heated to 500°C at a heating rate of 2°C / min under a nitrogen atmosphere and kept at this temperature for 4 hours. After natural cooling to room temperature, the synthesized sample was collected to obtain a Mg-doped carbon nitride polymer catalyst with a nanoflower cluster structure, which was named 4Mg-N / CN.

[0049] Characterization analysis:

[0050] 1. Instrumentation

[0051] X-ray powder diffraction (XRD): The XRD pattern of the catalyst was measured by a Bruker D8 Advance X-ray diffractometer with a copper target (Cu Ka, λ = 0.154 nm) X-ray tube, a Ni filter, a working voltage of 45 kV, and a current of 40 mA, and a scanning range of 2θ = 10-60°.

[0052] 13 C-NMR solid-state nuclear magnetic resonance 13 C-NMR): 13C solid-state nuclear magnetic resonance 13C solid-state NMR) were tested on a Bruker AVANCE III 500 M nuclear magnetic resonance spectrometer. Test conditions: cp / mas, contact 8 ms, mas freq 10 kHz, decoupling spina 164 and delay 3 s.

[0053] The morphology and particle size distribution of the sample were observed by a transmission electron microscope of Philips, Netherlands. Before testing, the sample was ultrasonically dispersed in an ethanol solution, and after 20 min, the sample was dropped on a carbon film-loaded copper mesh, and after natural drying, analysis was performed.

[0054] The distribution state of metal atoms in the sample was observed by a Titan Cubed Themis G2300 condenser spherical aberration correction transmission electron microscope. Before testing, the sample was first dispersed in an ethanol solution and ultrasonically, and then dropped on a fresh surface of a mica sheet, and after natural drying, analysis was performed in the instrument.

[0055] Determination of specific surface area and pore size distribution (low-temperature N2 physical adsorption): The specific surface area and pore size distribution of the catalyst were analyzed and determined by an (American Micrometrics Company) ASAP2020 other adsorption pore size analyzer. In the sample chamber, the vacuum degree P / P0 was in the range of 0-1, and the determination was performed by a liquid nitrogen static adsorption method. Before testing, the catalyst was first placed in a vacuum degree at a temperature of 453K for 4h, and then the adsorption-desorption isotherm was determined according to the static method, and the specific surface area was calculated by the multi-point Barrett-Emmett-Teller (BET) method, and the pore volume and pore size distribution were calculated by the Barrett-Joyner-Halanda (BJH) model.

[0056] Figure 1 The pristine CN and Mg-N / CN prepared for Examples 1-4 of the present application X The X-ray powder diffraction spectrum of Mg-N / CN; two diffraction peaks near 13.1° and 27.4° were detected, which were attributed to the (100) and (002) crystal planes of g-C3N4, and no diffraction peak of Mg nanoparticles was detected. In addition, with the increase of the amount of Mg doping, the diffraction peak intensity also correspondingly weakened, which may be related to the exfoliation of the layered material. The analysis results show that Mg basically does not destroy the main structure of g-C3N4.

[0057] Figure 2 The pristine CN and Mg-N / CN prepared for Examples 1 and 3 of the present application X The X-ray powder diffraction spectrum of Mg-N / CN 13CNMR spectrum; as shown in the figure, there are two carbon NMR peaks at 156 ppm and 164 ppm, which correspond to the C in the heptaazine ring structure, respectively. (i) and C (e) The chemical shift indicates that the main structure of g-C3N4 remains a heptaazine ring unit after the introduction of Mg atoms.

[0058] Figure 3 The images show TEM, TEM mapping, and HAADF-STEM images of the 4Mg-N / CN sample prepared in Example 3 of this invention. The images reveal that the 4Mg-N / CN exhibits a nanofloral morphology, with C, N, and Mg elements uniformly distributed on the catalyst support. HAADF-STEM was used to characterize the dispersion form and state of FeMg atoms on the surface of the 4Mg-N / CN sample. Figure 3 As shown in d, in the HAADF-STEM image of 4Mg-N / CN, monodisperse bright spots are uniformly distributed on the sample surface, and no Mg atom agglomeration was found. Therefore, it can be considered that Mg atoms are uniformly dispersed on the catalyst surface.

[0059] Figure 4 and Figure 5 pristine CN and pristine prepared in Examples 1-4 of this invention, respectively. X N2 physical adsorption-desorption curves and pore size distribution of Mg-N / CN; as shown in the figure, X The adsorption-desorption curves of Mg-N / CN are typical IV adsorption curves, indicating that... X Mesoporous structures exist in Mg-N / CN. In addition, the material exhibits distinct peaks in pore size values ​​at ~3.9 nm and 20-90 nm, indicating the presence of numerous mesopores (2-50 nm) and macropores (>50 nm). X The lamellar and porous structure of Mg-N / CN endows the material with a large specific surface area and pore volume. This special surface structure facilitates the contact of reactants and the rapid desorption of products, effectively optimizing the reaction kinetics on the catalyst surface and thus improving the efficiency of H2S selective catalytic conversion to aniline and thiobenzamide.

[0060] H2S reduction of aromatic nitro groups to aniline reaction test: pristine CN prepared in Examples 1-4 and X The Mg-N / CN mixture was ground and then used for the activity test. The test conditions were as follows: catalyst dosage was 40 mg, feed gas consisted of 5% H2S and equilibrium nitrogen, aromatic nitrate substrate concentration was 10 mmol, and feed gas flow rate was 20 mL / min. -1, the reaction time was 24 h, and the reaction temperature was 80 ℃. The catalysts prepared in each example were applied to the reaction of reducing aryl nitro to aniline by H2S, and gas-liquid chromatography was used for quantitative analysis.

[0061] Figure 6 The pristine CN and Mg-N / CN prepared in examples 1-4 of the application X The catalytic activity curve of Mg-N / CN material in the conversion of nitrobenzene to aniline by H2S at 80 ℃ and normal pressure. The conversion rate and selectivity of 4Mg-N / CN prepared in example 3 of the application reached 35.2% and 76.0%, respectively, while the conversion rate and selectivity of examples 2 and 4 at normal pressure and 80 ℃ were 33.0% and 64.3%, 30.1% and 58.6%, respectively. It is worth noting that, X The conversion rate and selectivity of Mg-N / CN are better than those of unmodified CN (the conversion rate and selectivity are 25.6% and 58.3%, respectively). In addition, the catalytic activity and selectivity of the 4Mg-N / CN catalyst synthesized in example 3 of the application are good, and after five cycles of regeneration test, the catalytic activity and aniline selectivity do not decrease significantly (the conversion rate and selectivity of the fifth cycle are 34.6% and 74.3%, respectively). Figure 7 ), and are better than those of g-C3N4, h-BN, nitrogen-doped carbon, MgO, CuO, TiO2, CeO2, ZrO2, CoO, NiO, SnO2, MnO2, MoS2, ZnO, Fe2O3 and Si / Al molecular sieve and other materials (Table 1). More importantly, xMg-N / CN can be applied to the catalytic conversion of different aryl nitro substrates, and shows good H2S removal rate and amine preparation activity, and has wide substrate applicability (Table 2).

[0062] Table 1 Statistical table of H2S reduction of aryl nitro to aniline activity of examples 1-3 of the application and g-C3N4, h-BN, nitrogen-doped carbon, MgO, CuO, TiO2, CeO2, ZrO2, CoO, NiO, SnO2, MnO2, MoS2, ZnO, Fe2O3 and Si / Al molecular sieve

[0063]

[0064]

[0065] H2S nucleophilic addition of aryl nitrile to thiobenzamide: The pristine CN and Mg-N / CN prepared in examples 1-4 were applied to the activity test after being ground. The test conditions are as follows: the catalyst dosage is 40 mg, the raw gas is composed of 5% H2S and balance nitrogen, the concentration of aryl nitro substrate is 1 mmol, and the raw gas flow rate is 20 mL·min X H2S nucleophilic addition of aryl nitrile to thiobenzamide: The pristine CN and Mg-N / CN prepared in examples 1-4 were applied to the activity test after being ground. The test conditions are as follows: the catalyst dosage is 40 mg, the raw gas is composed of 5% H2S and balance nitrogen, the concentration of aryl nitro substrate is 1 mmol, and the raw gas flow rate is 20 mL·min -1The reaction time was 4 h, and the reaction temperature was 60 °C. The catalysts prepared in each example were applied to the reaction of H2S nucleophilic addition to thiobenzamide with an aromatic nitrile group, and quantitative analysis was performed by gas-liquid chromatography.

[0066] Figure 8 pristine CN and prepared in Examples 1-4 of this invention X The catalytic activity curve of Mg-N / CN material for the nucleophilic addition of H2S to thiobenzamide at 60 °C and atmospheric pressure is shown. The conversion and selectivity of the xMg-N / CN prepared in Example 2 of this invention remained above 90%, significantly better than the pristine CN synthesized in Example 1 (conversion and selectivity were 45.1% and 50.1%, respectively). Correspondingly, the 4Mg-N / CN catalyst synthesized in Example 3 of this invention exhibited good catalytic activity and product selectivity, and was recyclable. After five rounds of regeneration tests, neither the conversion nor the thiobenzamide selectivity showed a significant decrease. Figure 9 The product yield remains above 91%, outperforming materials such as g-C3N4, h-BN, nitrogen-doped carbon, MgO, CuO, TiO2, CeO2, ZrO2, CoO, NiO, SnO2, MnO2, MoS2, ZnO, Fe2O3, and Si / Al molecular sieves (Table 3). Furthermore, xMg-N / CN can also be applied to the catalytic activation of various aromatic nitrile substrates, exhibiting good catalytic activity and selectivity, demonstrating broad substrate applicability (Table 4).

[0067] Table 3. Statistical table of the H2S nucleophilic addition activity of the molecular sieves in Examples 1-3 of the present invention and g-C3N4, h-BN, nitrogen-doped carbon, MgO, CuO, TiO2, CeO2, ZrO2, CoO, NiO, SnO2, MnO2, MoS2, ZnO, Fe2O3 and Si / Al to produce thiobenzamides.

[0068]

[0069]

[0070] In summary, the single-atom Mg-based sulfur high-value catalyst with nanofloral cluster structure prepared by this invention can not only efficiently catalyze H2S into high-value derivatives such as aniline and thiobenzamide under mild conditions, but also deeply remove H2S, and has great application prospects in industrial production.

[0071] The above detailed description of the specific embodiments of the present application has been given to understand the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. The application of a magnesium-based sulfur-enhancing catalyst in the H2S nucleophilic addition reaction of aromatic nitrile groups to produce thioaromatic amides or the H2S reduction of aromatic nitro groups to aniline, characterized in that: The preparation method of the magnesium-based sulfur enhancement catalyst includes the following steps: (1) Dissolve the nitrogen-containing precursor and the cyanate-containing precursor in a solvent, and then sonicate to dissolve and disperse them evenly; (2) Dissolve the magnesium source in a solvent and sonicate until completely dissolved; (3) Mix the solutions from steps (1) and (2), stir, centrifuge, dry, grind, and calcine to obtain the magnesium-based sulfur high-value catalyst; the prepared magnesium-based sulfur high-value catalyst uses flower-like graphitic carbon nitride as a support, and metallic Mg is dispersed in it in atomic form.

2. The application according to claim 1, characterized in that: The nitrogen-containing precursor is at least one of melamine, urea, dimelamine, thiourea, and monocyanamide; the cyanic acid precursor is at least one of cyanuric acid and trithiocyanic acid; the molar ratio of the nitrogen-containing precursor to the cyanic acid precursor is 1:1 to 1.

5.

3. The application according to claim 1, characterized in that: The magnesium source is at least one of magnesium chloride, magnesium sulfate, magnesium ethylenediaminetetraacetate, magnesium citrate, magnesium lactate, magnesium malate, magnesium taurate, magnesium L-threonate, and magnesium glycine; the mass ratio of the magnesium source to the nitrogen-containing precursor is 1:20~40.

4. The application according to claim 1, characterized in that: The solvent is at least one selected from N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, triethanolamine, diethylamine, deionized water, isopropylamine, ethanol, methanol, and ethylene glycol.

5. The application according to claim 1, characterized in that: In step (3), the stirring time is 1-4 h; the drying temperature is 60-120℃ and the time is 4-12 h; the calcination temperature is 400-600℃ and the time is 1-4 h, the heating rate is 1-5℃ / min, and the calcination atmosphere is one of nitrogen, air, ammonia, argon, and helium.

6. The application according to claim 1, characterized in that: The catalyst has a Mg doping concentration of 1-5 wt.%, with single-atom active sites being Mg-N. X Where 2 < X < 6; the specific surface area of ​​the catalyst is 80-160 m². 2 / g.

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