An ultra-high sulfur capacity two-dimensional carbon nanosheet-based room-temperature oxidative desulfurization catalyst and its preparation method and application

Abstract

The present invention relates to an ultra-high sulfur capacity two-dimensional carbon nanosheet-based room temperature oxidative desulfurization catalyst, its preparation method, and application. The desulfurization catalyst comprises porous carbon nanosheets and sodium carbonate dispersed on the porous carbon nanosheets. The mass ratio of the porous carbon nanosheets to the sodium carbonate is (60-70):(30-40). The preparation method comprises the following steps: calcining calcium gluconate hydrate in an inert atmosphere, pickling, and washing with water to obtain a two-dimensional porous carbon sheet; mixing the two-dimensional porous carbon sheet with a sodium carbonate solution, stirring, and ultrasonically impregnating to obtain a mixed slurry; rapidly freezing the mixed slurry, and then vacuum freeze-drying to obtain an ultra-high sulfur capacity two-dimensional carbon nanosheet-based room temperature oxidative desulfurization catalyst. The catalyst is used for H2S oxidation reaction. Compared with the prior art, the present invention has the advantages of being able to effectively activate oxygen and significantly improve the sulfur penetration capacity of H2S oxidation at room temperature.

Description

Technical Field

[0001] The present invention relates to the field of desulfurization catalysts, and in particular to an ultra-high sulfur capacity two-dimensional carbon nanosheet-based room-temperature oxidation desulfurization catalyst, a preparation method thereof, and applications thereof. Background Art

[0002] Hydrogen sulfide (H2S) is a toxic gas with a rotten egg odor at low concentrations and a dulling effect at high concentrations. It is widely present in industrial processes such as petroleum refining and natural gas extraction, as well as in sewers. In industrial processes, H2S not only corrodes equipment but also poisons catalysts. Leaked H2S can cause human poisoning and, further oxidized, produce acid rain. Therefore, research on H2S removal processes is of great significance. Currently, carbon-based catalysts, due to their rich pore structure, controllable surface chemistry, and excellent electrochemical performance, are widely used for the precise removal of low-concentration H2S at room temperature.

[0003] CN105617986 B discloses a method for preparing a composite activated carbon hydrogen sulfide remover. The catalyst is composed of rice husk activated carbon and copper oxide, with phosphoric acid as an activator, attapulgite clay as a binder, and copper nitrate and copper carbonate as copper sources. The catalyst is extruded and molded. This method integrates the preparation and modification of the activated carbon. The addition of copper salt increases the speed of the sulfidation reaction, which helps improve the removal rate.

[0004] CN 108014835 A discloses an alkaline mesoporous carbon catalyst for room-temperature oxidation of hydrogen sulfide. The catalyst is characterized by using phenol-aldehyde as a carbon precursor and silica sol as a hard template. The catalyst is obtained through sol-gel, drying, carbonization, etching, and loading of an alkaline substance. The catalyst comprises 100 grams of an organic precursor, 100-200 grams of an inorganic template, and 100-200 grams of an alkaline substance. The catalyst synchronizes etching and loading, reducing the preparation cycle and exhibiting high penetration and saturation capacities. Conventional porous carbon desulfurization catalysts are often limited in pore distribution, and insufficient sulfur storage capacity often inhibits subsequent reactions. Summary of the Invention

[0005] The purpose of the present invention is to overcome at least one of the defects of the above-mentioned prior art and to provide an ultra-high sulfur capacity two-dimensional carbon nanosheet-based room temperature oxidative desulfurization catalyst that can effectively activate oxygen and significantly improve the room temperature oxidation penetration sulfur capacity of H2S, as well as its preparation method and application.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] The inventors learned that the mechanism of carbon-based catalytic hydrogen sulfide is mainly a gas-liquid-solid three-phase reaction mechanism: water molecules in the gas phase form a water film of a certain thickness on the surface of the carbon material, H2S and O2 diffuse from the gas phase to the surface and pores, H2S is adsorbed and dissociated into HS around the alkaline sites. - , O2 is activated on the carbon wall to form O2 ·- , HS - with O2 ·- The reaction rapidly forms elemental sulfur, which then flows into larger pores along with the water film. Molecular oxygen is one of nature's most economical oxidants, but its structure determines its chemical stability. Carbon catalysts, however, can activate molecular oxygen into active oxygen at room temperature, demonstrating high activity.

[0008] Previous studies have shown that the micropores of carbon materials are the sites for hydrogen sulfide adsorption and reaction, while the mesopores are the storage sites for the product sulfur. The ultimate sulfur capacity of carbon materials is determined by the available storage space. In practice, the disappearance and coverage of alkaline sites and micropores make it difficult to sustain the catalytic reaction.

[0009] The inventors believe that thin, two-dimensional carbon sheets not only possess a large specific surface area and a rich porous structure, but also possess sulfur storage spaces between the sheets, demonstrating high catalytic activity for hydrogen sulfide at room temperature. Compared to three-dimensional materials, two-dimensional materials have a larger dimension in one direction, exposing a higher contact area and forming a certain amount of intralayer voids, which provides a higher site for product deposition. The present invention uses two-dimensional materials as a carrier for alkaline sodium carbonate, significantly improving hydrogen sulfide removal. The specific scheme is as follows:

[0010] A two-dimensional carbon nanosheet-based room-temperature oxidative desulfurization catalyst with ultra-high sulfur capacity comprises porous carbon nanosheets and sodium carbonate dispersed on the porous carbon nanosheets.

[0011] Furthermore, the mass ratio of the porous carbon nanosheets to sodium carbonate is (60-70):(30-40).

[0012] Furthermore, the porous carbon nanosheets present a porous self-supporting sheet structure with a specific surface area of about 820m 2 / g, pore volume is about 1.6cm 3 / g, thickness is 20-30nm; sodium carbonate is well dispersed on the carbon sheet.

[0013] A method for preparing the ultra-high sulfur capacity two-dimensional carbon nanosheet-based room temperature oxidative desulfurization catalyst as described above comprises the following steps:

[0014] Calcium gluconate hydrate is calcined, pickled, and washed with water in an inert atmosphere to obtain a two-dimensional porous carbon sheet. Calcium gluconate is a substance that can foam at 180°C, has a volume about 20 times that of the precursor, and has an extremely low density.

[0015] The two-dimensional porous carbon sheet is mixed with a sodium carbonate solution, stirred, and ultrasonically impregnated to obtain a mixed slurry;

[0016] The mixed slurry is rapidly frozen and then freeze-dried under vacuum to produce an ultra-high sulfur capacity, two-dimensional carbon nanosheet-based room-temperature oxidative desulfurization catalyst. Rapid freezing maintains the original dispersion in the solution, while vacuum freeze-drying facilitates the formation of a three-dimensional network structure within the carbon sheets, reducing the thickness of the accumulated carbon sheets.

[0017] Furthermore, the terminal temperature of the calcination is 650-750° C., the heating rate is 2.5-3.5° C. / min, and the constant temperature time at the terminal temperature is 160-200 min.

[0018] Furthermore, the acid washing uses 4-6 wt% dilute hydrochloric acid, and the water washing makes the pH of the entire system = 7. The mass of the hydrochloric acid solution can be calculated based on 1.5-2 times the required hydrogen chloride molecules.

[0019] Furthermore, in the mixed slurry, the mass ratio of sodium carbonate to the porous carbon sheet is (3-4):(6-7).

[0020] Furthermore, the specific process of rapid freezing is: the mixed slurry is loaded into a container and then placed in dry ice or liquid nitrogen for rapid freezing.

[0021] An application of the above-mentioned ultra-high sulfur capacity two-dimensional carbon nanosheet-based room temperature oxidative desulfurization catalyst, wherein the catalyst is used for H2S oxidation reaction, and the reaction specifically comprises the following steps:

[0022] The quartz tube containing the catalyst was fixed in the reactor, and humidified high-purity nitrogen was introduced to remove the air in the system;

[0023] A mixture of H2S, O2 and N2 is introduced to carry out H2S oxidation reaction;

[0024] The concentration of hydrogen sulfide at the reaction outlet was monitored using a gas chromatography PFD detector, and adsorption breakthrough was defined when the hydrogen sulfide concentration was 5% of the inlet concentration.

[0025] Furthermore, the temperature during the oxidation reaction is 20-30°C.

[0026] Furthermore, the concentration of the mixed gas is H2S (0.01 vol.%), O2 (0.1 vol.%), and N2 (balance).

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] (1) Compared with traditional porous carbon materials, two-dimensional carbon nanosheets have larger sulfur storage space;

[0029] (2) The two-dimensional carbon nanosheets of the present invention are about 20 nm thick, which can expose more carbon active sites and improve oxygen activation ability;

[0030] (3) The desulfurization performance of the present invention far exceeds that of porous carbon materials, reaching a penetration sulfur capacity of 10.7 g H2S / g cat. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a SEM image of the carbon sheet of Example 1;

[0032] Figure 2 is an AFM image of the carbon sheet of Example 1;

[0033] Figure 3 1 is the adsorption-desorption curve and pore size distribution curve of the carbon sheet of Example 1. DETAILED DESCRIPTION

[0034] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0035] A room-temperature oxidative desulfurization catalyst based on two-dimensional carbon nanosheets with ultra-high sulfur capacity, its preparation method, and application are disclosed. The desulfurization catalyst is made by impregnating activated two-dimensional porous carbon sheets with sodium carbonate. The mass fraction of the carbon sheets in the catalyst is 60-70%, and the mass fraction of sodium carbonate is 30-40%. The carbon sheets exhibit a porous, self-supporting sheet structure with a specific surface area of 820 m 2 / g, pore volume 1.6cm 3 / g; sodium carbonate is well dispersed on the carbon sheet.

[0036] The preparation method comprises the following steps:

[0037] (1) Calcium gluconate hydrate was placed in a quartz ark and calcined at 700 °C for 3 h in a nitrogen atmosphere;

[0038] (2) The obtained product was washed with an appropriate amount of low-concentration hydrochloric acid solution (mass fraction 5%) to remove surface calcium and expose pores to obtain a two-dimensional porous carbon sheet, and then washed with an appropriate amount of water until the pH value was 7;

[0039] (3) Mix the carbon sheet with an appropriate amount of sodium carbonate solution, stir, and ultrasonically immerse for 3 hours;

[0040] (4) The mixed slurry is loaded into a container and quickly frozen in dry ice or liquid nitrogen, and finally placed in a vacuum freeze drying box for 24 hours to obtain a hydrogen sulfide degradation catalyst.

[0041] The catalyst is used for H2S oxidation reaction, which specifically includes the following steps:

[0042] (1) First, fix the quartz tube containing the catalyst in the reactor, then introduce humidified high-purity nitrogen gas with a humidity of 80% to remove the air in the system;

[0043] (2) Then, a mixed gas of H2S, O2, and N2 is introduced, and the temperature of the circulating cooling water is adjusted to 20-30°C to carry out the H2S oxidation reaction; the concentrations of H2S, O2, and N2 are H2S (0.01 vol.%), O2 (0.1 vol.%), and N2 (balance).

[0044] (3) The concentration of hydrogen sulfide at the reaction outlet was monitored using a gas chromatography PFD detector. Adsorption breakthrough was defined when the hydrogen sulfide concentration was 5% of the inlet concentration.

[0045] Example 1

[0046] An ultra-high sulfur capacity two-dimensional carbon nanosheet-based room temperature oxidative desulfurization catalyst and its preparation method and application, the preparation method comprising the following steps:

[0047] (1) Calcium gluconate hydrate was placed in a quartz ark, placed in a tube furnace, heated to 700°C at a rate of 3°C / min, kept constant for 180 min, cooled naturally to room temperature, and taken out to obtain a carbon sheet;

[0048] (2) Add 5.00 g of carbon sheet and 12 g of dilute hydrochloric acid into 100 ml of deionized water, stir for 12 h, and filter and wash with a large amount of deionized water to obtain porous carbon nanosheets, such as Figure 1-3 ;

[0049] Figure 1 This is the microscopic morphology of the carbon flakes. The carbon flakes appear as curled and wrinkled flakes with edges. Figure 2 Atomic force microscopy of a carbon sheet. The carbon sheet shows a thickness of about 13 nm. Figure 3 The adsorption-desorption curve and pore size distribution curve of the carbon sheet are shown in Figure 2. The carbon sheet exhibits a rich microporous and mesoporous structure.

[0050] (3) Weigh 0.4 g of sodium carbonate and place it in 40 ml of deionized water, stirring to dissolve. Take 0.6 g of porous carbon sheet and place it in the solution. After stirring and ultrasonicating for 3 hours, place it in dry ice and quickly freeze it. Then place it in a freeze drying box for 48 hours to obtain 40% Na2CO3 / C.

[0051] Catalytic performance testing: 0.1g of catalyst was first placed in a quartz tube (1cm outer diameter, 0.1cm wall thickness). The tube was then connected to the reaction gas line and humidified high-purity nitrogen was introduced to expel air from the system. A mixture of H2S, O2, and N2 was then introduced. The circulating cooling water temperature was adjusted between 20-30°C, and the H2S oxidation reaction was carried out. Initially, the H2S conversion rate was nearly 100%, and the breakthrough sulfur capacity reached 10.7g H2S / g cat.

[0052] Sodium carbonate is used as an alkaline activator. On the one hand, sodium carbonate is a weak base that can maintain the alkaline environment on the surface of the carbon sheet for a long time. Strong bases can easily form sodium sulfide with hydrogen sulfide, and negative divalent sulfur ions are difficult to be oxidized by air. On the other hand, sodium carbonate can modify the carbon matrix without chemical treatment, and the process is simple and convenient.

[0053] Example 2

[0054] An ultra-high sulfur capacity two-dimensional carbon nanosheet-based room temperature oxidative desulfurization catalyst and its preparation method and application, the preparation method comprising the following steps:

[0055] (1) Calcium gluconate hydrate was placed in a quartz ark, placed in a tube furnace, heated to 700°C at a rate of 3°C / min, kept constant for 180 min, cooled naturally to room temperature, and taken out to obtain a carbon sheet;

[0056] (2) Add 5.00 g of carbon sheet and 12 g of dilute hydrochloric acid to 100 ml of deionized water, stir for 12 h, and filter and wash with a large amount of deionized water to obtain porous carbon nanosheets;

[0057] (3) Weigh 0.3 g of sodium carbonate and place it in 40 ml of deionized water, stirring to dissolve. Take 0.7 g of porous carbon sheet and place it in the solution. After stirring and ultrasonicating for 3 hours, place it in dry ice and quickly freeze it. Then place it in a freeze drying box for 48 hours to obtain 30% Na2CO3 / C.

[0058] Catalytic performance testing: 0.1g of catalyst was first placed in a quartz tube (1cm outer diameter, 0.1cm wall thickness). The tube was then connected to the reaction gas line and humidified high-purity nitrogen was introduced to expel air from the system. A mixture of H2S, O2, and N2 was then introduced. The circulating cooling water temperature was adjusted to 20-30°C, and the H2S oxidation reaction was carried out. In the early stages, the H2S conversion rate was nearly 100%, and the breakthrough sulfur capacity reached 9.5g H2S / g cat.

[0059] Comparative Example 1

[0060] A desulfurization catalyst and its preparation method and application, the preparation method comprising the following steps:

[0061] (1) Calcium gluconate hydrate was placed in a quartz ark, placed in a tube furnace, heated to 700°C at a rate of 3°C / min, kept constant for 180 min, cooled naturally to room temperature, and taken out to obtain a carbon sheet;

[0062] (2) Add 5.00 g of carbon sheet and 12 g of dilute hydrochloric acid to 100 ml of deionized water, stir for 12 h, and filter and wash with a large amount of deionized water to obtain porous carbon nanosheets;

[0063] (3) Weigh 0.4 g of sodium carbonate and place it in 40 ml of deionized water, stir and dissolve it, take 0.6 g of porous carbon sheet and place it in the solution, stir and sonicate for 3 h, then place it in a low-temperature refrigerator to freeze, and then place it in a freeze-drying box for 48 h.

[0064] Catalytic performance testing: 0.1g of catalyst was first placed in a quartz tube (1cm outer diameter, 0.1cm wall thickness). The tube was then connected to the reaction gas line and humidified high-purity nitrogen was introduced to expel air from the system. A mixture of H2S, O2, and N2 was then introduced. The circulating cooling water temperature was adjusted to 20-30°C, and the H2S oxidation reaction was carried out. In the early stages, the H2S conversion rate was nearly 100%, and the breakthrough sulfur capacity reached 9.0g H2S / g cat.

[0065] Compared with Example 1, the difference is that the carbon sheet slurry is frozen in a low-temperature refrigerator. Due to the slow freezing, the carbon sheet slurry forms aggregates in the upper layer of water due to its low density during the freezing process, which inhibits the dispersion of the carbon sheet to a certain extent.

[0066] Comparative Example 2

[0067] A desulfurization catalyst and its preparation method and application, the preparation method comprising the following steps:

[0068] (1) Calcium gluconate hydrate was placed in a quartz ark, placed in a tube furnace, heated to 700°C at a rate of 3°C / min, kept constant for 180 min, cooled naturally to room temperature, and taken out to obtain a carbon sheet;

[0069] (2) Add 5.00 g of carbon sheet and 12 g of dilute hydrochloric acid to 100 ml of deionized water, stir for 12 h, and filter and wash with a large amount of deionized water to obtain porous carbon nanosheets;

[0070] (3) Weigh 0.4 g of sodium carbonate and place it in 40 ml of deionized water, stirring to dissolve. Take 0.6 g of porous carbon sheet and place it in the solution. After stirring and ultrasonicating for 3 h, place it in dry ice and quickly freeze it. Then place it in a forced air drying oven for 48 h.

[0071] Catalytic performance testing: 0.1g of catalyst was first placed in a quartz tube (1cm outer diameter, 0.1cm wall thickness). The tube was then connected to the reaction gas line and humidified high-purity nitrogen was introduced to expel air from the system. A mixture of H2S, O2, and N2 was then introduced. The circulating cooling water temperature was adjusted to 20-30°C, and the H2S oxidation reaction was carried out. In the early stages, the H2S conversion rate was nearly 100%, and the breakthrough sulfur capacity reached 4.8g H2S / g cat.

[0072] Compared with Example 1, the carbon sheet slurry is dried in a forced air drying oven. As the water evaporates, sodium carbonate crystals quickly precipitate, making it difficult to ensure nanoscale dispersion of sodium carbonate on the carbon sheet. At the same time, the drying process easily leads to accumulation of carbon sheets.

[0073] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

Claims

1. An ultra-high sulfur capacity two-dimensional carbon nanosheet-based room temperature oxidative desulfurization catalyst, characterized in that: The desulfurization catalyst comprises porous carbon nanosheets and sodium carbonate dispersed on the porous carbon nanosheets; The mass ratio of the porous carbon nanosheets to sodium carbonate is (60-70): (30-40); The method for preparing the ultra-high sulfur capacity two-dimensional carbon nanosheet-based room temperature oxidative desulfurization catalyst comprises the following steps: Calcium gluconate hydrate is calcined in an inert atmosphere, acid-washed, and washed with water to obtain a two-dimensional porous carbon sheet; The two-dimensional porous carbon sheet is mixed with a sodium carbonate solution, stirred, and ultrasonically impregnated to obtain a mixed slurry; The mixed slurry is rapidly frozen and then vacuum-freeze-dried to obtain an ultra-high sulfur capacity two-dimensional carbon nanosheet-based room-temperature oxidative desulfurization catalyst; The acid washing adopts 4-6wt% dilute hydrochloric acid, and the pH of the whole system is adjusted to 7 during water washing; The specific process of rapid freezing is: the mixed slurry is loaded into a container and then placed in dry ice or liquid nitrogen for rapid freezing.

2. The ultra-high sulfur capacity two-dimensional carbon nanosheet-based room temperature oxidative desulfurization catalyst according to claim 1, characterized in that: The terminal temperature of the calcination is 650-750° C., the heating rate is 2.5-3.5° C. / min, and the constant temperature time at the terminal temperature is 160-200 min.

3. The ultra-high sulfur capacity two-dimensional carbon nanosheet-based room temperature oxidative desulfurization catalyst according to claim 1, characterized in that: In the mixed slurry, the mass ratio of sodium carbonate to two-dimensional porous carbon sheets is (3-4): (6-7).

4. An application of the ultra-high sulfur capacity two-dimensional carbon nanosheet-based room temperature oxidative desulfurization catalyst according to claim 1, characterized in that: The catalyst is used for H2S oxidation reaction, which specifically includes the following steps: The quartz tube containing the catalyst was fixed in the reactor, and humidified high-purity nitrogen was introduced to remove the air in the system; A mixture of H2S, O2 and N2 is introduced to carry out H2S oxidation reaction; The concentration of hydrogen sulfide at the reaction outlet was monitored using a gas chromatography PFD detector, and adsorption breakthrough was defined when the hydrogen sulfide concentration was 5% of the inlet concentration.

5. The use of an ultra-high sulfur capacity two-dimensional carbon nanosheet-based room temperature oxidative desulfurization catalyst according to claim 4, characterized in that: The temperature during the oxidation reaction is 20-30°C.

6. The use of an ultra-high sulfur capacity two-dimensional carbon nanosheet-based room temperature oxidative desulfurization catalyst according to claim 4, characterized in that: The concentration of the mixed gas is H2S 0.01vol.%, O2 0.1vol.%, and N2 as a balance.

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