A porous adsorbing material prepared from an aldehyde sugar compound and application thereof

Abstract

The application discloses a method for preparing porous carbon material from aldosic compounds, the porous carbon material and application. The preparation method comprises the following steps: pyrolyzing a certain mass of aldosic compounds under the atmosphere of inert gas such as nitrogen or argon at a certain temperature rising rate to reach a specified temperature, and then naturally cooling to obtain uniform porous carbon material. The porous carbon material can be used as an adsorption separation material of methane and nitrogen, and is used for separating methane and nitrogen. Compared with the traditional organic precursor adding activator pyrolysis to obtain the porous carbon and the limitation that the pore diameter of the porous carbon is difficult to control, the prepared porous carbon of the application can be directly pyrolyzed to prepare the porous carbon without adding the activator, and the pore diameter and pore volume can be accurately controlled by controlling the pyrolysis temperature and the temperature rising rate, and the process is simple, the method is reliable, and the cost is low.

Description

Technical Field

[0001] This invention belongs to the field of new materials industry, and in particular relates to a porous adsorbent material prepared from aldose compounds and its application in the separation and purification of unconventional natural gas. Background Technology

[0002] Natural gas (primarily methane, CH4) is a relatively clean primary low-carbon energy source because it produces only carbon dioxide and water when burned, and its development and application have been vigorously promoted in recent years. Coalbed methane, a byproduct of coal mining, is mainly composed of methane. During actual mining, air (nitrogen) is mixed in, causing concentration fluctuations. High-concentration methane can be directly integrated into the natural gas pipeline network, while low-concentration methane, due to its low calorific value, is generally not directly usable and must be vented, increasing the greenhouse effect. Therefore, separating and enriching methane from the methane-nitrogen mixture is of great significance for effectively supplementing natural gas and reducing greenhouse gas emissions.

[0003] Porous carbon materials, as the most commonly used porous adsorbents, possess characteristics such as high specific surface area, strong stability, and industrial production capability, and are widely used in adsorption and separation fields such as water treatment, gas adsorption, and air purification. The most common method for preparing porous carbon involves impregnating or grinding an organic precursor and an activator, followed by high-temperature activation in a tube furnace under an inert atmosphere. The pore size is created by the chemical reaction between the activator and the carbon at high temperature. For example, Chinese patent CN118183733A involves pre-carbonizing the carbon precursor, then mixing it with an activator and performing high-temperature activation, followed by acid washing to obtain the porous carbon material. This process is not only cumbersome but also consumes a lot of energy and generates waste acid and metal waste liquid. Other porous carbon materials use sacrificial templates as a method for preparing microporous carbon, which significantly increases the cost of using porous carbon and imposes many limitations on the materials used as templates. While some methods do not require activators, they still require multi-step processing, such as pre-hydrothermal reactions or chemical modification using strong acids and bases. Summary of the Invention

[0004] In view of the aforementioned traditional methods for preparing porous carbon, this invention proposes a one-step method for preparing porous carbon materials using aldose compounds as carbon precursors, ingeniously utilizing the chemical structural characteristics of these compounds. The method for directly preparing porous carbon from carbon precursors with aldose structural characteristics proposed in this invention is simple and easy to prepare, providing a new approach for the synthesis of porous carbon materials and the screening of carbon precursors.

[0005] This invention is achieved through the following technical solution:

[0006] A method for preparing porous carbon materials using aldose compounds involves using aldose compounds as carbon precursors, heating them to 800–900°C at a heating rate of 2–10°C / min under an inert atmosphere, holding them at that temperature for 0.5–3 hours, and then cooling them to room temperature to obtain porous carbon materials.

[0007] Preferably, the aldose compound is an oxygen-containing heterocyclic compound containing an acetal or hemiacetal structure.

[0008] More preferably, the oxygen-containing heterocyclic compound is any one of glucose, sucrose, fructose, L-arabinose, D-ribose, cyclodextrin, starch, cellulose, propionaldehyde, butyraldehyde, pentaldehyde, hexaldehyde, furfural, cyclocaprolactone, cyclic ethers, furans and furan derivatives, and pyrans and pyran derivatives.

[0009] More preferably, the furan derivative is either methyl-β-D-furanoside or β-D-fructose-furanoside.

[0010] In the above method, the inert atmosphere is any one of nitrogen, argon, or helium; the programmed heating rate is preferably 5℃ / min, the temperature is raised to 900℃, and the holding time is 2h.

[0011] The porous carbon material prepared by the above method is characterized in that the porous carbon material has a uniform micropore distribution with a pore size distribution concentrated in the range of 0.5 nm to 0.8 nm.

[0012] The porous carbon material prepared by the above method exhibits an equilibrium adsorption capacity of 6.22-32.77 cm⁻¹ for methane at room temperature and pressure. 3 / g, the equilibrium adsorption capacity for nitrogen is 1.74-10.9cm³. 3 / g, IAST (CH4 / N2) The selectivity ranges from 5.5 to 7.96.

[0013] Based on the adsorption properties of the porous carbon materials described above, they can be applied to the field of methane and nitrogen adsorption separation technology. For example, they can be used for the separation and purification of unconventional natural gas, and are particularly suitable for extracting methane or removing nitrogen contained therein from low-concentration coalbed methane, low-saturation natural gas, or shale gas.

[0014] This invention, through in-depth research into the chemical structural characteristics of carbon precursors in the preparation of porous carbon materials in existing technologies, and based on a thorough understanding of the pore-forming mechanism in the preparation process of porous carbon, selects aldose compounds as carbon precursors and cleverly utilizes the inherent chemical structural characteristics of these compounds to propose a one-step method for preparing porous carbon materials using aldose compounds as carbon precursors. When using aldose compounds as carbon precursors, during high-temperature treatment, the -COC- groups in the aldose compound structure exhibit poor thermal stability, breaking their chemical bonds at relatively low temperatures and decomposing to produce CO2, CO, and H2O gases. The escape of these primary gases plays a certain role in pore formation. In particular, by adjusting the heating rate and controlling the final treatment temperature and time, the aldose compounds can maintain a certain overall carbon skeleton structure while generating microporous structures through the breaking of -COC- and -OH groups, thereby preparing porous carbon materials. Using aldose compounds as carbon precursors to prepare porous carbon can achieve zero addition of activators, which greatly reduces the preparation cost of porous carbon and simplifies the preparation process.

[0015] Therefore, compared with the prior art, the present invention has the following beneficial technical effects:

[0016] (1) Based on the characteristics of the chemical structure, carbon precursors with -COC- structure can be selected to directly prepare porous carbon without physical or chemical activation, which greatly simplifies the preparation process.

[0017] (2) Compounds with the chemical structural features described in this invention are common and abundant in nature, such as starch, sucrose, fructose and cellulose, which greatly reduces the preparation cost of porous carbon.

[0018] (3) Compounds with the chemical structural features described in this invention generally contain only three elements: carbon, hydrogen, and oxygen. They have a simple composition and rely on CO. x The release of the substance achieves the effect of pore formation without the need for post-treatment or pre-treatment with acid or other reagents. It does not release volatile components that are harmful to the environment and humans, and the preparation process is relatively green and safe. Attached Figure Description

[0019] Figure 1 BET diagram and pore size distribution of porous carbon materials prepared from cellulose.

[0020] Figure 2 A diagram showing the adsorption and separation of methane and nitrogen in porous carbon materials prepared from cellulose.

[0021] Figure 3 BET diagram and pore size distribution of porous carbon materials prepared from β-cyclodextrin.

[0022] Figure 4 Methane nitrogen adsorption separation diagram of porous carbon material prepared from β-cyclodextrin.

[0023] Figure 5 Selectivity diagram of two-component separation of porous carbon materials prepared from β-cyclodextrin.

[0024] Figure 6 Methane nitrogen adsorption diagram of porous carbon material prepared from L-arabinose.

[0025] Figure 7 Methane nitrogen adsorption diagram of porous carbon material prepared for methyl-β-D-furan riboside.

[0026] Figure 8 BET diagram of porous carbon prepared using sodium gluconate as a carbon precursor. Detailed Implementation

[0027] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the invention.

[0028]

Example 1

[0029] 2g of cellulose powder was placed in a tube furnace under a nitrogen atmosphere. The heating program of the furnace was set to increase the temperature from room temperature to 900℃ at a rate of 2℃ / min. The temperature was then maintained at 900℃ for 1.5h to obtain cellulose-based porous carbon (Cell-900). Figure 1 BET diagram and pore size distribution of porous carbon materials prepared from cellulose. Figure 2 Methane-nitrogen adsorption separation diagram of porous carbon materials prepared from cellulose. Figure 1 It can be seen that the porous carbon material exhibits a typical Type I adsorption isotherm curve. In the low-pressure region, the N2 equilibrium adsorption capacity increases sharply. After the micropores are filled, adsorption almost ceases with increasing pressure, indicating that the porous carbon material contains only micropores. Pore size analysis of the nitrogen adsorption-desorption isotherm (BET) of the cellulose-based porous carbon using a DFT model revealed only micropores with a diameter of 0.718 nm. This suggests that the microporous structure of the cellulose-based porous carbon is formed by the volatilization of oxygen as small gaseous molecules such as carbon dioxide, carbon monoxide, and water. This microporous environment is conducive to the adsorption and separation of methane and nitrogen. Figure 2 It can be seen that at 298 K, the equilibrium adsorption capacity of cellulose-based porous carbon for methane is 31.75 cm⁻¹. 3 / g, the equilibrium adsorption capacity of nitrogen is 10.45cm³. 3 / g; combination Figure 1 , Figure 2 It can be seen that the cellulose-based porous carbon prepared by direct carbonization of cellulose has a uniform pore size and can effectively adsorb and separate methane and nitrogen.

[0030]

Example 2

[0031] 1g of β-cyclodextrin (β-CD) was placed in a tube furnace under a nitrogen atmosphere. The heating program of the furnace was set to increase the temperature from room temperature to 900℃ at a rate of 5℃ / min, and the temperature was held at 900℃ for 1h to obtain porous carbon material (βCD-900). Figure 3 The 77 K nitrogen adsorption-desorption isotherm of the carbon material prepared from β-cyclodextrin is a typical Type I adsorption isotherm. The equilibrium adsorption capacity increases sharply in the low-pressure region, and after the micropores are fully filled, adsorption almost ceases with increasing pressure, indicating that the porous carbon material contains only micropores. DFT analysis of the nitrogen adsorption-desorption isotherm (BET) of the β-cyclodextrin-based porous carbon revealed the presence of only micropores with a diameter of 0.559 nm. This microporous environment is highly favorable for the adsorption and separation of methane nitrogen. Figure 4 The equilibrium adsorption capacity for methane is observed to be 32.77 cm⁻¹. 3 / g, the equilibrium adsorption capacity of nitrogen is 10.9 cm⁻¹. 3 / g. To evaluate the effect of βCD-900 on the separation of methane and nitrogen. Figure 5 IAST was calculated using the Dual-Site-Langmuir Freundlich model. (CH4 / N2) Based on the selectivity, the methane-nitrogen selectivity was calculated to be 5.55. Combined with... Figure 3 and Figure 4 It can be seen that the porous carbon prepared by direct carbonization of β-cyclodextrin has a uniform pore size and can effectively adsorb and separate methane and nitrogen.

[0032]

Example 3

[0033] 1g of L-arabinose was placed in a tube furnace under a nitrogen atmosphere. The heating program of the furnace was set to increase the temperature from room temperature to 900℃ at a rate of 5℃ / min, and then held at 900℃ for 1 hour to obtain porous carbon material. Figure 6 It can be seen that the equilibrium adsorption capacity of directly carbonized L-arabinose-based porous carbon for methane is 19.2 cm⁻¹ at 298 K. 3 The equilibrium adsorption capacity of nitrogen is 7.9 cm³ / g. 3 / g.

[0034]

Example 4

[0035] 1 g of methyl-β-D-furanoside was placed in a tube furnace under a nitrogen atmosphere. The furnace temperature program was set to increase from room temperature to 900°C at a rate of 5°C / min, and then held at 900°C for 1 hour to obtain porous carbon material. This material was then used for methane-nitrogen adsorption and separation tests. Figure 7 As shown, the equilibrium adsorption capacity for methane at 298 K is 24 cm⁻¹. 3 The equilibrium adsorption capacity of nitrogen is 8.4 cm³ / g.3 / g.

[0036]

Example 5

[0037] 1g of sodium gluconate was placed in a tube furnace under a nitrogen atmosphere. The furnace was heated from room temperature to 900℃ at a rate of 5℃ / min, and held at 900℃ for 1 hour to obtain porous carbon material. Figure 8 As shown, BET testing revealed that the prepared carbon material has a very small specific surface area and a very low equilibrium adsorption capacity for nitrogen in the low-pressure region, exhibiting a non-microporous structure. This explains the necessity of the oxygen-containing heterocycle of the aldose group.

[0038] Although the present invention has been described in detail above with general descriptions, specific embodiments, and experiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing porous adsorbent materials from aldose compounds, characterized in that, Using aldose compounds as carbon precursors, the temperature was increased to 900 °C at a rate of 5 °C / min under an inert atmosphere, held for 0.5–2 h, and then cooled to room temperature to obtain a porous carbon material with a uniform micropore distribution and a pore size distribution concentrated in the range of 0.5 nm–0.8 nm. The equilibrium adsorption capacity of the porous carbon material for methane at room temperature and pressure was 6.22–32.77 cm⁻¹. 3 / g, the equilibrium adsorption capacity for nitrogen is 1.74-10.9cm³. 3 / g, IAST (CH4 / N2) The selectivity ranges from 5.5 to 7.

96.

2. The method according to claim 1, characterized in that, The aldose compounds are oxygen-containing heterocyclic compounds containing acetal or hemiacetal structures.

3. The method according to claim 2, characterized in that, The oxygen-containing heterocyclic compound is one of glucose, sucrose, fructose, L-arabinose, D-ribose, cyclodextrin, starch, cellulose, propionaldehyde, butyraldehyde, pentaldehyde, hexaldehyde, furfural, cyclocaprolactone, cyclic ethers, furans and furan derivatives, and pyrans and pyran derivatives.

4. The method for preparing porous adsorbent materials from aldose compounds according to claim 3, characterized in that, The furan derivatives mentioned are either methyl-β-D-furanoside or β-D-fructofuranose.

5. The method for preparing porous adsorbent materials from aldose compounds according to claim 1, characterized in that, The inert atmosphere is any one of nitrogen, argon, or helium.

6. A porous adsorbent material prepared by any one of claims 1 to 5 is applied to the adsorption and separation of methane nitrogen.

7. A porous adsorbent material prepared by any one of claims 1 to 5 is applied to the separation and purification of unconventional natural gas.

8. The application according to claim 7, characterized in that, The unconventional natural gas mentioned is any one of low-enriched coalbed methane, low-saturation natural gas, or shale gas.

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