A method for the preparation of a carbon molecular sieve adsorbent for methane-nitrogen separation

Abstract

The application discloses a preparation method of a carbon molecular sieve adsorbent for methane-nitrogen separation. The method comprises the following steps: 1) grinding graphite powder and placing the same in a metal salt solution, drying after sufficient stirring to obtain modified graphite; 2) placing phenolic resin powder in a metal salt solution, drying after sufficient stirring to obtain modified resin; 3) mixing the modified graphite and the modified resin, adding tar into the mixture, kneading and then extruding into a strip shape; 4) sufficiently drying the formed material, then transferring the material into a gas atmosphere calcination furnace, and calcining the material under an inert gas atmosphere for a certain time; and 5) performing programmed temperature heating on the obtained material under an inert gas atmosphere, introducing a carbon source, and depositing pyrolytic carbon on the surface of the material by a gas phase deposition method to obtain a carbon molecular sieve adsorption material. The carbon molecular sieve material is used as an adsorbent by adopting a pressure swing adsorption technology, has high adsorption capacity for nitrogen and high methane-nitrogen selectivity in methane-nitrogen separation application, and has a good industrial application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of adsorbent material preparation and application, and particularly relates to a preparation method of a carbon molecular sieve adsorbent for separating methane and nitrogen. BACKGROUND

[0002] Methane is an important chemical raw material and a high-efficiency clean energy, but it is also a greenhouse gas. Efficient utilization of methane in resources such as coalbed methane, landfill gas and oilfield gas can effectively reduce the emission of greenhouse gases and improve the current situation of poor oil and gas in China. To efficiently utilize methane in these resources, the prerequisite is to concentrate low-quality methane.

[0003] The key to methane concentration lies in the separation of methane and nitrogen. Due to the similar physicochemical properties of methane and nitrogen, the removal of N2 is the most challenging. Carbon molecular sieves are widely used in the fields of CO2 capture and separation, air separation, and methane concentration due to their uniform pore size distribution, developed pore structure, high chemical stability and thermal stability.

[0004] At present, research on the separation of methane and nitrogen by using carbon molecular sieves as adsorbents has made certain progress. CN106345410B discloses a preparation method of a carbon adsorbent, which uses pitch and starch carbon source as raw materials, and is subjected to carbonization and high-temperature treatment in a carbon dioxide atmosphere to obtain a carbon adsorbent with high methane adsorption capacity, but the methane / nitrogen equilibrium separation is low. Yang et al. developed a carbon molecular sieve adsorbent prepared by modifying coal with an organic reagent, which has a saturated adsorption capacity of 6.76 mmol / g for methane and 5.56 mmol / g for nitrogen, and also exhibits a low separation factor for methane and nitrogen (Yang Z Y, Wang D H, Meng Z Y, et al. adsorption separation of CH4 / N2 on modified coal-based carbon molecular sieve [J]. Separation and purification technology, 2019, (218): 130-137.). At present, carbon-based adsorbent materials generally have low gas adsorption capacity and relatively low separation factor in the field of methane / nitrogen separation. Therefore, developing an adsorbent with high adsorption capacity, high selectivity and easy regeneration is the key to further improving the separation effect of methane and nitrogen and concentrating methane. SUMMARY

[0005] In order to solve the problem of low-quality methane recovery, it is necessary to further improve the adsorption capacity of the adsorbent to N2 and the separation selectivity of methane and nitrogen, and the application provides a preparation method of a carbon molecular sieve adsorbent for methane and nitrogen separation. In the method, modified graphite is used as one of the main raw materials, and through steps such as loading modification and carbon deposition, a new carbon molecular sieve adsorption material with high nitrogen adsorption capacity and high methane and nitrogen selectivity is successfully synthesized. The problems of low methane purity and low yield in the large-scale recovery and utilization of coal bed gas or biogas are solved, and the method has good industrial application prospect.

[0006] In order to achieve the above application purposes, the specific technical solutions of the application are as follows:

[0007] A preparation method of a carbon molecular sieve adsorbent for methane and nitrogen separation, comprising the following steps:

[0008] (1) grinding graphite powder and placing it in a metal salt solution, fully stirring, and then drying to obtain modified graphite; (2) placing phenolic resin powder in a metal salt solution, fully stirring, and then drying to obtain modified resin;

[0009] (3) mixing the modified graphite obtained in step (1) and the modified resin obtained in step (2), adding tar, kneading and mixing, and then extruding into strips;

[0010] (4) fully drying the formed material, and then transferring it into a gas atmosphere calcination furnace for calcination under an inert gas atmosphere for a certain time;

[0011] (5) continuing to heat the material obtained in step (4) under an inert gas atmosphere to a certain temperature, introducing a carbon source, and performing pyrolytic carbon deposition on the surface of the material by gas phase deposition to obtain a carbon molecular sieve adsorption material.

[0012] As a better embodiment in the application, the graphite used in step (1) is artificial graphite or natural graphite; the graphite powder is ground into micron-level powder, which is more conducive to the full mixing with the modified resin, and the pore size distribution after carbonization and deposition is more uniform.

[0013] As a better embodiment in the application, the metal salt used in steps (1) and (2) is a transition metal nitrate or a transition metal sulfate; wherein the transition metal is any one of Cu, Fe, Cr, Ni, Zn and Co; the concentration of the metal salt solution is 0.1-1.0 mol / L (specifically, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, etc.).

[0014] As a preferred embodiment in the present application, the mass ratio of the modified graphite and the modified resin in step (3) is 0.5:1-1:1, more preferably 0.5:1.

[0015] As a preferred embodiment in the present application, the amount of the tar added in step (3) is 5-10% of the mass sum of the modified graphite and the modified resin (specifically 5%, 6%, 7%, 8%, 9%, 10%, etc.), more preferably 10%.

[0016] As a preferred embodiment in the present application, the calcination temperature in step (4) is 600-800°C (specifically 600°C, 650°C, 700°C, 750°C, 800°C, etc.), and the calcination time is 4-8h (specifically 4h, 5h, 6h, 7h, 8h, etc.).

[0017] As a preferred embodiment in the present application, the inert atmosphere in step (4) is nitrogen or nitrogen, more preferably nitrogen.

[0018] As a preferred embodiment in the present application, the carbon source in step (5) is any one of benzene, methane and cyclohexane; the amount of the carbon source added is 0.5-5g / 50g of the mixed material, more preferably 1g / 50g of the mixed material; and the inert atmosphere is nitrogen or helium, more preferably nitrogen.

[0019] As a preferred embodiment in the present application, the temperature rising program rate in step (5) is 5-20°C / min (specifically 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, 11°C / min, 12°C / min, 13°C / min, 14°C / min, 15°C / min, 16°C / min, 17°C / min, 18°C / min, 19°C / min, 20°C / min, etc.), more preferably 10°C / min; and the temperature for cracking and depositing carbon is 600-900°C (specifically 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, etc.), and the time is 30-200min (specifically 30min, 50min, 70min, 90min, 110min, 130min, 150min, 170min, 190min, 200min, etc.).

[0020] The carbon molecular sieve adsorbent for methane-nitrogen separation prepared by any one of the above methods or step combinations is used for the separation of methane and nitrogen.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] (1) The new carbon molecular sieve adsorption material prepared by the present application has greater porosity and specific surface area than the carbon molecular sieve prepared by the traditional method, and significantly improves the gas adsorption capacity.

[0023] (2) In the present application, transition metal salt is impregnated on the graphite, and then the volatilized components overflow the graphite layer to expand the interlayer distance, and form metal oxides inside and outside the layer. In the subsequent carbon deposition process, carbon cracking and deposition are more likely to occur on the surface of the metal oxides, further modifying the pore structure of the graphite layer structure. By adjusting the deposition time and deposition temperature, a carbon molecular sieve adsorbent with excellent separation effect for specific gas components such as methane and nitrogen is prepared.

[0024] (3) In the present application, one of the main raw materials, phenolic resin, is modified by impregnating transition metal salt. In the carbonization process, the gas decomposed from the metal salt increases the porosity of the material, and in combination with the expanded layer structure of the graphite, a more abundant pore structure is created for the precursor material of the carbon molecular sieve.

[0025] (4) The preparation process of the carbon molecular sieve adsorbent prepared by the present application is based on the current industrial production conditions, and is a process technology that can be quickly applied in industrial production. DETAILED DESCRIPTION

[0026] The present application will be further described in detail by specific examples to better understand the technical solutions and purposes of the present application. The specific embodiments described herein are only used to explain the present application and do not limit the content involved in the present application.

[0027] The static adsorption data (methane adsorption capacity and separation coefficient of methane and nitrogen) involved in the embodiments of the present application are obtained by using a manual adsorption instrument EA-III to preliminarily evaluate and screen the separation performance of the adsorbent for methane and nitrogen mixed gas. Under the conditions of normal pressure and a certain temperature, the adsorption volume of the adsorbent for single component helium, methane and nitrogen within 3 min is tested, so as to respectively calculate the adsorption amount of the adsorbent for methane and nitrogen, and obtain the dynamic separation coefficient of the corresponding methane and nitrogen mixed gas, which are respectively shown in formula (1) and formula (2).

[0028]

[0029]

[0030] In the formula, q i and q j are the adsorption amounts of gas components i and j, mL / g; V i is the adsorption volume of gas component i, mL; and V HeVabs is the adsorption volume, mL; K value corresponds to the equilibrium coefficient at the test temperature; m is the mass of the test sample, g; S ads S is the separation coefficient of the mixed gas; p i , p j P is the adsorption pressure, MPa.

[0031] The product gas methane purity and yield data involved in the embodiments of the present application are determined by single-tower pressure swing adsorption experiments. The specific method is as follows: pressurize with methane gas (100%), pressurization time 5 s, pressurize to an adsorption pressure of 0.3 MPa, control the adsorption time for 60 s, stop adsorption, release to 0.2 MPa, release for 15 s, then release to normal pressure, release for 30 s, vacuum pump to a vacuum degree of -0.08 MPa, evacuate for 90 s, and regenerate the adsorbent. After the single-tower adsorption process reaches a steady state, the corresponding purified gas, release gas, backflow gas, and evacuation desorption gas are collected and measured. Gas chromatography is used to analyze the component content of the collected gas.

[0032] In the single-tower pressure swing adsorption desorption experiment, the raw material gas is composed of 75% methane and 25% nitrogen by volume, and the product gas is composed of purified gas and release gas. The CH4 concentration and recovery rate of the product gas are shown in formula (3) and formula (4).

[0033]

[0034]

[0035] In the formula, C is the methane concentration of the product gas, %; η is the methane recovery rate of the product gas, %; C0 is the methane concentration of the raw material gas, %; V0 is the raw material gas volume when pressurized, mL; C1 is the methane concentration of the purified gas, %; V1 is the purified gas volume, mL; C2 is the methane concentration of the release gas, %; V2 is the release gas volume, mL; V3 is the backflow gas volume, mL; V4 is the evacuation desorption gas volume, mL; C5 is the methane concentration of the pressurized gas, %; and V5 is the methane volume of the pressurized gas, mL.

[0036] Example 1

[0037] A preparation method of a carbon molecular sieve adsorbent for methane-nitrogen separation, and the specific preparation process is as follows:

[0038] (1) 50 g of graphite is added to 100 mL of 0.2 mol / L iron nitrate solution, stirred thoroughly for 30 min, and then placed in a 120°C oven for drying for 12 h until the liquid is completely dried, to obtain modified graphite.

[0039] (2) 50 g of phenolic resin was added into 100 mL of 0.2 mol / L ferric nitrate solution, stirred thoroughly for 30 min, and then placed in an oven at 120°C for drying for 12 h until the liquid was completely dried to obtain a modified resin.

[0040] (3) The two modified materials obtained above were mechanically mixed, 10 g of tar was added and mixed thoroughly, and then extruded into a strip.

[0041] (4) The molded mixed material was placed in a gas atmosphere calcination furnace for carbonization, heated to 300°C at a heating rate of 10°C / min under N2 protection, kept for 4 h, then heated to 800°C at a heating rate of 15°C / min, kept for 6 h, and then taken out after cooling to obtain a carbon molecular sieve precursor material.

[0042] (5) The carbonized carbon molecular sieve precursor material was placed in a rotating tube furnace, 250 mL / min of N2 gas flow was continuously introduced, the temperature was increased to 700°C at a heating rate of 10°C / min, then 100 mL / min of N2 gas flow was used to continuously introduce benzene vapor, the benzene vapor was stopped after 40 min, heating was stopped, the consumed benzene mass was calculated by the mass difference method to be 1.8 g, and the carbon molecular sieve adsorption material was obtained after the temperature naturally decreased to room temperature.

[0043] The static adsorption device was used to test the adsorption capacity of nitrogen and the separation coefficient of methane and nitrogen mixed gas, and the results are shown in Table 1.

[0044] The single-tower pressure swing adsorption device was used to test the adsorption separation effect of the mixed gas with a volume fraction of 75% methane and 25% nitrogen, and the results are shown in Table 2.

[0045] Example 2

[0046] A preparation method of a carbon molecular sieve adsorbent for methane-nitrogen separation, and the specific preparation process is as follows:

[0047] (1) 50 g of graphite was added into 100 mL of 0.1 mol / L nickel nitrate solution, stirred thoroughly for 30 min, and then placed in an oven at 120°C for drying for 12 h until the liquid was completely dried.

[0048] (2) 50 g of phenolic resin was added into 100 mL of 0.1 mol / L nickel nitrate solution, stirred thoroughly for 30 min, and then placed in an oven at 120°C for drying for 12 h until the liquid was completely dried.

[0049] (3) The two modified materials above were mechanically mixed, 10 g of tar was added and mixed thoroughly, and then extruded into a strip.

[0050] (4) Put the shaped mixed material into the atmosphere calcination furnace, and heat to 300℃ at a heating rate of 10℃ / min under N2 protection, keep for 4h, then heat to 800℃ at a heating rate of 15℃ / min, keep for 6h, and then take out after cooling.

[0051] (5) Put the carbonized carbon molecular sieve precursor material into a rotating tube furnace, continuously input 250mL / min of N2 flow, heat to 700℃ at a heating rate of 10℃ / min, then continuously input appropriate amount of benzene vapor with 100mL / min of N2 flow, stop the input of benzene vapor and heating after 40min, calculate the consumed benzene mass of 1.8g by mass difference method, and take out the new carbon molecular sieve adsorption material after the temperature naturally decreases to room temperature, numbered as Example 2.

[0052] Use a static adsorption device to test the adsorption capacity of nitrogen and the separation coefficient of methane and nitrogen mixed gas, and the results are shown in Table 1.

[0053] Use a single-tower pressure swing adsorption device to test the adsorption separation effect of 75% methane and 25% nitrogen mixed gas, and the results are shown in Table 2.

[0054] Example 3

[0055] A preparation method of a carbon molecular sieve adsorbent for methane-nitrogen separation, the specific preparation process is as follows:

[0056] (1) Add 50g of graphite to 100mL of 0.5mol / L zinc sulfate solution, stir thoroughly for 30min, and then place in a 120℃ oven to dry for 12h until the liquid is completely dried.

[0057] (2) Add 50g of phenolic resin to 100mL of 0.5mol / L zinc sulfate solution, stir thoroughly for 30min, and then place in a 120℃ oven to dry for 12h until the liquid is completely dried.

[0058] (3) Mechanically mix the above two modified materials, add 10g of tar and mix thoroughly, and extrude into strips.

[0059] (4) Put the shaped mixed material into the atmosphere calcination furnace, and heat to 300℃ at a heating rate of 10℃ / min under N2 protection, keep for 4h, then heat to 800℃ at a heating rate of 15℃ / min, keep for 6h, and then take out after cooling.

[0060] (5) Put the carbonized carbon molecular sieve precursor material into a rotating tube furnace, continuously pass in 250 mL / min of N2 flow, increase the temperature to 700℃ at a rate of 10℃ / min, then continuously bring in an appropriate amount of benzene vapor with 100 mL / min of N2 flow, stop passing in benzene vapor and stop heating after 40 min, calculate the consumed benzene mass 1.8 g by the mass difference method, and take out the carbon molecular sieve adsorption material after the temperature naturally decreases to room temperature, numbered as Example 3.

[0061] The static adsorption device is used to test the adsorption capacity of nitrogen and the separation coefficient of methane and nitrogen mixed gas, and the results are shown in Table 1.

[0062] The single-tower pressure swing adsorption device is used to test the adsorption separation effect of 75% methane and 25% nitrogen mixed gas, and the results are shown in Table 2.

[0063] Example 4

[0064] A preparation method of a carbon molecular sieve adsorbent for methane-nitrogen separation, the specific preparation process is as follows:

[0065] (1) Put 50g of graphite into 100mL of 0.5mol / L manganese nitrate solution, stir thoroughly for 30min, then place in a 120℃ oven and dry for 12h until the liquid is completely dried.

[0066] (2) Put 50g of phenolic resin into 100mL of 0.5mol / L manganese nitrate solution, stir thoroughly for 30min, then place in a 120℃ oven and dry for 12h until the liquid is completely dried.

[0067] (3) Mechanically mix the above two modified materials, add 10g of tar and mix thoroughly, and extrude into strips.

[0068] (4) Put the formed mixed material into a gas-fired calcining furnace, under the condition of N2 protective gas, increase the temperature to 300℃ at a rate of 10℃ / min, keep for 4h, then increase the temperature to 800℃ at a rate of 15℃ / min, keep for 6h, and then take out after cooling.

[0069] (5) Put the carbonized carbon molecular sieve precursor material into a rotating tube furnace, continuously pass in 250 mL / min of N2 flow, increase the temperature to 700℃ at a rate of 10℃ / min, then continuously bring in an appropriate amount of benzene vapor with 100 mL / min of N2 flow, stop passing in benzene vapor and stop heating after 40 min, calculate the consumed benzene mass 1.8 g by the mass difference method, and take out the carbon molecular sieve adsorption material after the temperature naturally decreases to room temperature, numbered as Example 3.

[0070] The static adsorption device was used to test the adsorption capacity of nitrogen and the separation coefficient of nitrogen and methane mixed gas, and the results are shown in Table 1.

[0071] The single-tower pressure swing adsorption device was used to test the adsorption separation effect of the mixture of 75% methane and 25% nitrogen, and the results are shown in Table 2.

[0072] Comparative Example 1

[0073] A common method for preparing carbon molecular sieve adsorption material is as follows:

[0074] (1) 100 g of phenolic resin was dried in an oven at 120°C for 12 h, 10 g of tar was added and mixed thoroughly, and then extruded into strips.

[0075] (2) The formed mixed material was placed in a gas atmosphere calcination furnace, and heated to 300°C at a heating rate of 10°C / min under N2 protection, kept for 4 h, then heated to 800°C at a heating rate of 15°C / min, kept for 6 h, and then cooled and taken out.

[0076] (3) The carbonized carbon molecular sieve precursor material was placed in a rotary tube furnace, and a N2 gas flow of 250 mL / min was continuously introduced, the temperature was raised to 700°C at a heating rate of 10°C / min, then an appropriate amount of benzene vapor was continuously introduced with a N2 gas flow of 100 mL / min, after 40 min, the benzene vapor was stopped and the heating was stopped, the consumed benzene mass was calculated by mass difference method to be 1.8 g, after the temperature naturally decreased to room temperature, the carbon molecular sieve adsorption material was taken out, and was numbered as Comparative Example 1.

[0077] The static adsorption device was used to test the adsorption capacity of nitrogen and the separation coefficient of nitrogen and methane mixed gas, and the results are shown in Table 1.

[0078] The single-tower pressure swing adsorption device was used to test the adsorption separation effect of the mixture of 75% methane and 25% nitrogen, and the results are shown in Table 2.

[0079] Comparative Example 2

[0080] A method for preparing carbon molecular sieve adsorption material is as follows:

[0081] (1) 50 g of phenolic resin and 50 g of graphite were mechanically mixed, placed in an oven at 120°C for 12 h, then 10 g of tar was added and mixed thoroughly, and then extruded into strips.

[0082] (2) Put the shaped mixed material into the atmosphere calcination furnace, and heat to 300°C at a temperature increasing rate of 10°C / min under the protection of N2, keep for 4h, then heat to 800°C at a temperature increasing rate of 15°C / min, keep for 6h, and then take out after cooling.

[0083] (3) Put the carbonized carbon molecular sieve precursor material into a rotating tube furnace, continuously input 250mL / min of N2 flow, heat to 700°C at a temperature increasing rate of 10°C / min, then continuously input appropriate amount of benzene vapor with 100mL / min of N2 flow, stop the input of benzene vapor and heating after 40min, calculate the consumed benzene mass of 1.8g by mass difference method, and take out the carbon molecular sieve adsorbent after the temperature naturally decreases to room temperature, numbered Comparative Example 2.

[0084] The static adsorption device is used to test the adsorption capacity of nitrogen and the separation coefficient of methane and nitrogen mixed gas, and the results are shown in Table 1.

[0085] The single-tower pressure swing adsorption device is used to test the adsorption separation effect of 75% methane and 25% nitrogen mixed gas, and the results are shown in Table 2.

[0086] Comparative Example 3

[0087] A preparation method of a carbon molecular sieve adsorbent for methane-nitrogen separation, the specific preparation process is as follows:

[0088] (1) Put 50g of graphite into a 120°C oven and dry for 12h, and dry for use.

[0089] (2) Put 50g of phenolic resin into 100mL of 0.5mol / L iron nitrate solution, stir for 30min, then put it into a 120°C oven and dry for 12h until the liquid is completely dried.

[0090] (3) Mechanically mix the above two modified materials, add 10g of tar and mix well, and extrude into strips.

[0091] (4) Put the shaped mixed material into the atmosphere calcination furnace, and heat to 300°C at a temperature increasing rate of 10°C / min under the protection of N2, keep for 4h, then heat to 800°C at a temperature increasing rate of 15°C / min, keep for 6h, and then take out after cooling.

[0092] (5) The carbonized carbon molecular sieve precursor material was placed in a rotating tube furnace, 250 mL / min of N2gas was continuously introduced, the temperature was raised to 700°C at a rate of 10°C / min, then an appropriate amount of benzene vapor was continuously introduced with 100 mL / min of N2gas, after 40 min, the introduction of benzene vapor was stopped and heating was stopped, the mass of consumed benzene was calculated by the mass difference method to be 1.8 g, after the temperature naturally decreased to room temperature, the carbon molecular sieve adsorbent material was taken out, numbered as Example 3.

[0093] The static adsorption device was used to test the adsorption capacity of nitrogen and the separation coefficient of methane and nitrogen mixed gas, and the results are shown in Table 1.

[0094] The single-tower pressure swing adsorption device was used to test the adsorption separation effect of the adsorbent on the mixture of 75% by volume of methane and 25% of nitrogen, and the results are shown in Table 2.

[0095] Table 1 Static adsorption test results of adsorbent in Examples and Comparative Examples on methane and nitrogen (3 min)

[0096]

[0097] Table 2 Single-tower pressure swing adsorption test results of adsorbent in Examples and Comparative Examples on the mixture of 75% by volume of methane and 25% of nitrogen

[0098]

[0099] From Table 1 and Table 2, it can be seen that the static adsorption data (nitrogen adsorption capacity and nitrogen and methane separation coefficient) and single column pressure swing adsorption data (product gas methane purity and yield) of the carbon molecular sieve prepared by the conventional method are lower than those of the new adsorption material, while the separation and adsorption performance of the new adsorption material prepared by the modified graphite and phenolic resin as raw materials in the examples is effectively improved (the product gas methane purity can reach about 95%, and the product gas methane yield can reach about 75%-80%). Compared with Examples 1-3 and Comparative Example 2, the carbon molecular sieve prepared by the modified graphite and resin as raw materials has more excellent separation effect than the material prepared directly by the graphite and resin as raw materials. Compared with other examples, the adsorbent material prepared by using manganese salt as a modifier in Example 4 has a significantly decreased separation and adsorption effect compared with iron salt, nickel salt and zinc salt, and the separation effect is close to that of the unmodified adsorbent (Comparative Example 2). In Comparative Example 3, the adsorbent material is prepared by modifying only the resin with ferric nitrate and without modifying the graphite. It can be found that the nitrogen adsorption capacity and separation coefficient are significantly lower than those of Example 1, and slightly better than those of Comparative Examples 1 and 2. In the case where the graphite is not loaded with active components, the interlayer spacing does not experience the expansion effect during the decomposition of the active components in the carbonization process, and the relative loading amount and dispersion degree of the transition metal are lower than those of Comparative Example 1, which finally affects the separation effect.

[0100] By adjusting the conditions of the carbon deposition process, the pore size can be accurately adjusted in theory, and the separation of gas molecules with similar properties can be realized. However, in actual test results, the carbon molecular sieve prepared by the traditional method often has low porosity and specific surface area, which is reflected in the separation of methane and nitrogen. The adsorption capacity of nitrogen and the separation coefficient of nitrogen and methane are usually low, making it difficult to improve the purity and yield of the product gas. Therefore, by introducing graphite with large voids into the raw materials, loading transition metal salts to increase the interlayer spacing of the graphite during calcination, and using the presence of transition metal oxides to optimize the carbon deposition reaction, the porosity of the carbon molecular sieve material is increased, thereby improving the performance of the adsorbent in separating and concentrating methane.

[0101] The above examples only express the specific embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as a limitation on the protection scope of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the technical concept of the present application, a number of modifications and improvements can be made, which are within the protection scope of the present application.

[0102] This Background section is intended to provide a general overview of the context of the application, the work of the current named inventors, to the extent the work is associated with the present application, and the work of others in the field of the application to the extent the work is associated with the present application, and to the extent the work described in this section is associated with the present application, neither expressly nor impliedly, is admitted to be prior art to the present application.

Claims

1. A method for the preparation of a carbon molecular sieve adsorbent for methane-nitrogen separation, characterized in that The method comprises the following steps: (1) grinding graphite powder and placing it in a metal salt solution, stirring thoroughly, and then drying to obtain modified graphite; (2) placing phenolic resin powder in a metal salt solution, stirring thoroughly, and then drying to obtain modified resin; (3) mixing the modified graphite obtained in step (1) and the modified resin obtained in step (2), adding tar, kneading and mixing, and then extruding into a strip; (4) fully drying the formed material, and then transferring it into an atmosphere calcination furnace, and calcining under an inert atmosphere for a certain time; (5) continuing to heat the material obtained in step (4) under an inert atmosphere at a programmed temperature, introducing a carbon source, and depositing pyrolytic carbon on the surface of the material by gas phase deposition to obtain a carbon molecular sieve adsorbent material; The metal salt used in steps (1) and (2) is a transition metal nitrate or a transition metal sulfate; the transition metal is any one of Fe, Ni, and Zn.

2. The method of claim 1 for the preparation of carbon molecular sieve adsorbents for methane / nitrogen separation, characterized in that, The graphite used in step (1) is artificial graphite or natural graphite.

3. The method of making a carbon molecular sieve adsorbent for methane nitrogen separation of claim 1, wherein, The concentration of the metal salt solution is 0.1-1.0 mol / L.

4. The method of claim 1 for the preparation of carbon molecular sieve adsorbents for methane / nitrogen separation, characterized in that, The mass ratio of the modified graphite to the modified resin in step (3) is 0.5:1-1:

1.

5. The method of claim 1 for the preparation of carbon molecular sieve adsorbents for methane / nitrogen separation, characterized in that, The amount of tar added in step (3) is 5-10% of the total mass of the modified graphite and the modified resin.

6. The method of making a carbon molecular sieve adsorbent for methane nitrogen separation of claim 1, wherein, The calcination temperature in step (4) is 600-800℃, and the calcination time is 4-8 h.

7. The method of claim 1 for the preparation of carbon molecular sieve adsorbents for methane / nitrogen separation, characterized by, The inert atmosphere in step (4) is nitrogen or helium.

8. The method of claim 1 for the preparation of carbon molecular sieve adsorbents for methane / nitrogen separation, characterized by, The carbon source in step (5) is any one of benzene, methane, and cyclohexane; the amount of the carbon source added is 0.5-5 g per 50 g of the mixed material; and the inert atmosphere is nitrogen or helium.

9. The method of claim 1 for the preparation of carbon molecular sieve adsorbents for methane / nitrogen separation, characterized in that, The programmed temperature rate in step (5) is 5-20℃ / min; the temperature for depositing pyrolytic carbon is 600-900℃, and the time is 30-200 min.

10. Use of a carbon molecular sieve adsorbent for methane / nitrogen separation produced according to any one of claims 1 to 9, characterized in that, The adsorbent is used for separating methane and nitrogen.

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