CN113019318B - Preparation method and application of carbon molecular sieve for separating olefin and alkane - Google Patents

Preparation method and application of carbon molecular sieve for separating olefin and alkane Download PDF

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CN113019318B
CN113019318B CN202110217538.8A CN202110217538A CN113019318B CN 113019318 B CN113019318 B CN 113019318B CN 202110217538 A CN202110217538 A CN 202110217538A CN 113019318 B CN113019318 B CN 113019318B
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starch
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alkane
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CN113019318A (en
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李忠
杜胜君
肖静
夏启斌
周欣
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South China University of Technology SCUT
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    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/20—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising free carbon; comprising carbon obtained by carbonising processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
    • B01J20/28054—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J20/28078—Pore diameter
    • B01J20/2808—Pore diameter being less than 2 nm, i.e. micropores or nanopores
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    • C01B32/00—Carbon; Compounds thereof
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    • C07C7/12—Purification; Separation; Use of additives by adsorption, i.e. purification or separation of hydrocarbons with the aid of solids, e.g. with ion-exchangers
    • C07C7/13—Purification; Separation; Use of additives by adsorption, i.e. purification or separation of hydrocarbons with the aid of solids, e.g. with ion-exchangers by molecular-sieve technique
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    • C01P2004/03—Particle morphology depicted by an image obtained by SEM

Abstract

The invention discloses a preparation method and application of a carbon molecular sieve for separating olefin and alkane. The method comprises the following steps: adding a starch carbon precursor into a distilled water solvent to prepare a starch water solution, uniformly stirring and dispersing, and then carrying out medium-pressure medium-temperature hydrothermal controllable polymerization and dehydration carbonization reaction in a reaction kettle to obtain homogeneous carbon microspheres; and (3) washing and drying the obtained carbon microspheres, placing the carbon microspheres in an inert atmosphere at the temperature of 700-1000 ℃ for controlled high-temperature defunctionalization treatment, and controlling carbon layer rearrangement and heteroatom pyrolysis reaction to obtain the carbon molecular sieve material with uniform and adjustable ultramicropore channels. The invention takes cheap, nontoxic and harmless starch biomass as a carbon source, forms carbon microspheres through a direct hydrothermal polymerization carbonization process, can control the defect content and graphitization degree of the microspheres by adjusting the reactant concentration, and obtains the carbon molecular sieve through pyrolysis at a corresponding calcination temperature, thereby realizing the aperture at the sub-angstrom level precision
Figure DDA0002954444640000011
Fine adjustment within the range.

Description

Preparation method and application of carbon molecular sieve for separating olefin and alkane
Technical Field
The invention relates to the field of olefin and alkane adsorption separation materials, in particular to a carbon molecular sieve material which has the advantages of low cost, stable structure, uniform and adjustable pore size distribution and optimal screening separation characteristics on olefin and alkane.
Background
Propylene and ethylene are among the two largest organic chemicals and the basic petrochemical products produced in the world. Since the olefin product often contains unreacted alkane, and the corresponding alkane (C)2H4/C2H6，C3H6/C3H8) Has similar physical and chemical properties, so that the separation and purification of the compound face great challenges. For more than 70 years, the separation is still carried out by using an energy-intensive high-pressure low-temperature rectifying tower in industry, and the energy consumption accounts for 10-15% of the global energy consumption. The adsorption separation is considered to be the most potential technology for replacing high-pressure low-temperature rectification, and the high-efficiency separation of olefin and alkane under the normal temperature condition can be realized.
Adsorptive separation is based primarily on three mechanisms: thermodynamic equilibrium separation, kinetic separation and molecular sieving mechanisms, wherein the separation efficiency of the separation mechanism based on molecular sieving is the highest. Materials reported in recent years to be useful for screening Ethylene Ethane include primarily Ag modified Molecular sieves (Aguado S, et al. Absolute Molecular sieves with Silver Zeolite A [ J. for Ethylene/Ethane Mixtures]Journal of the American Chemical Society,2012,134(36):14635.) and a metal-organic framework material [ Ca (C)4O4)(H2O)](Rui-Biao,Lin,Libo,et al.Molecular sieving of ethylene from ethane using a rigid metal-organic framework.[J]Nature materials, 2018; 17(12):1128-1133), the materials reported to be capable of screening propylene propane have only several ultramicropore metal-organic framework materials, such as: y-abtc (Hao W, et al. Tailor-Made Micropole Metal-Organic Frameworks for the Full Separation of Propane from Propane Through selected Size. J ]Advanced materials, 2018; 30(49):1805088) and NbOFFIVE-1-Ni (Cadiau, et al. A. metallic-based template for separating propylene from propylene [ J ]]Science,2016,353(6295): 137). They have the following disadvantages: MOFs has high cost and poor hydrothermal stability, and is difficult to be really applied to industrial production; the Ag modified molecular sieve as a microporous material is limited by pore volume and adsorbsThe amount is usually not high, and strong acid sites and metal sites in the material can form strong pi bond effect with carbon-carbon double bonds in olefin, so that the regeneration energy consumption is high, carbon deposition is easy, and the service life is short.
The porous carbon material has a developed pore structure, excellent stability, higher adsorption capacity and lower cost, and is an adsorbent widely applied. However, the material has wider pore size distribution, so that the selectivity is low, and the material is difficult to be applied to high-selectivity adsorption separation of gas mixtures. Therefore, attempts have been made mainly to produce carbon molecular sieves having narrow micropores by using a chemical vapor deposition method. For example, patent (CN103349973A) uses CO2Activating a carbon material by using CO mixed gas to prepare pores, and then repeatedly introducing dimethylbenzene to perform vapor deposition to modify pore channels so as to reduce the pore diameter and narrow the pore diameter distribution of the carbon material; the patent (CN107324307A) uses a mixture of methane and nitrogen containing a low concentration of methane for channel deposition at low temperatures to further modify and reduce the channel size. The developed carbon molecular sieves are mainly used for nitrogen making machines, and dynamic separation is realized by utilizing different adsorption and diffusion rates of nitrogen and oxygen in pore channels. However, the material still has a wide pore size distribution in the micropore range, and does not have the real 'molecular sieving' performance. There has not been any report that carbon molecular sieve materials can be used for the sieving separation of olefin and alkane.
Therefore, the invention discloses a preparation method of a carbon molecular sieve for separating olefin and alkane and application of the carbon molecular sieve in screening separation of olefin and alkane. The former method of chemical vapor deposition modification is difficult to modify porous carbon to obtain a carbon molecular sieve in a real sense, and the difficulty is substantially the defect of irregular carbon material and discrete pore size distribution, so that the modification method after application cannot perform precise and effective regulation and control on pore channels with various sizes. In general, defect-rich and sp-rich3Carbon precursors of carbon often generate wide pore size distribution, such as commonly used porous carbon like coconut shells, coal, pitch, etc., and the carbon has many defects and uncontrollable and discrete pore size distribution, so that people are difficult to apply a post-modification method to realize accurate control of full pores. Thus, the preparation has real meaningThe carbon molecular sieve which can realize the sieving separation of similar molecules has high difficulty and is very challenging. The invention develops a new method, changes the thought, provides a method for controlling the carbon precursor to have a more homogeneous structure and a certain graphitization degree, and controls the generation of screening holes by matching with a matched and controllable reaction process for removing surface functional groups, thereby developing a novel carbon molecular sieve capable of screening and separating propylene-propane analogues and ethylene-ethane analogues. Meanwhile, the developed carbon molecular sieve does not contain metal ions on the surface, so that carbon deposition in the application process can be reduced or avoided to a great extent, and the material has enough service life.
Disclosure of Invention
Aiming at the problems of high defect content, difficult fine adjustment and wide pore size distribution of the prior carbon molecular sieve carbon precursor, the invention innovatively provides a preparation method and application of a carbon molecular sieve material with sieving characteristic for olefin and alkane separation.
The purpose of the invention is realized by the following technical scheme.
A process for preparing the carbon molecular sieve used to separate olefin from alkane includes regulating the graphitization degree and sp of carbon precursor3And finally preparing the novel carbon molecular sieve capable of screening and separating propylene, propane, ethylene and ethane by matching the hybridization degree and a pore-forming process adaptive to the structure of the carbon precursor.
The method comprises the following steps:
(1) regulating and controlling the structure of the carbon precursor, namely adding the starch carbon precursor into a distilled water solvent according to a solid-liquid ratio in a certain range, preparing a starch water solution with a certain concentration, uniformly stirring and dispersing, and then carrying out medium-pressure medium-temperature hydrothermal controllable polymerization and dehydration carbonization reaction in a reaction kettle to obtain homogeneous carbon microspheres with a certain degree of polymerization and graphitization; in the step, the hydrothermal polymerization can be changed by configuring different solid-liquid ratios and regulating and controlling the starch concentration and the corresponding hydrothermal reaction environment Degree of polymerization, thereby regulating and controlling the graphitization degree and sp of the carbon precursor3Obtaining a carbon precursor with a specific structure and a regular structure through hybridization;
(2) and (2) forming and regulating and controlling the sieving holes, namely washing and drying the carbonaceous microspheres obtained in the step (1), and then placing the carbonaceous microspheres in an inert atmosphere at a certain matching temperature (700-.
Preferably, in step (1), the starch carbon precursor is soluble starch.
Preferably, in step (1), the starch precursor is one or more of corn starch, wheat starch and sweet potato starch.
Preferably, in the step (1), the weight ratio of the starch carbon precursor to the distilled water is 1: 1-1: 10.
Preferably, in step (1), the concentration of the aqueous starch solution is 0.05-1g/mL, and the concentration of the aqueous starch solution is preferably 0.1-1 g/mL.
Preferably, in the step (1), the hydrothermal polymerization carbonization temperature is 180-;
preferably, in the step (1), the time for the hydrothermal polymerization and the moderate-temperature carbonization reaction is 8 to 20 hours, and preferably 10 to 20 hours.
Preferably, in the step (1), the prepared homogeneous carbon microsphere has Raman spectrum I D/IGThe ratio of (A) to (B) is 0.85-0.95.
Preferably, in step (2), the inert atmosphere is argon or nitrogen.
Preferably, in the step (2), the inert atmosphere is a mixed gas of argon and nitrogen in any mixing ratio.
Preferably, in step (2), the heating rate of the high temperature defunctionalization reaction is 2-10 ℃/min.
Preferably, in the step (2), the temperature of the high-temperature calcination is 700-.
Preferably, in the step (2), the high-temperature calcination time is 0.5-6h, preferably 1-3 h.
Preferably, in the step (2), the carbon molecular sieve with the sieving and separating performance on olefin and alkane is obtained after high-temperature roasting.
An ultra-microporous carbon molecular sieve material prepared by the above method, wherein the ultra-microporous carbon molecular sieve only adsorbs olefin, and does not adsorb alkane; the pore size of the ultra-microporous carbon molecular sieve is uniform and is between the kinetic diameters of olefin and alkane.
In the present invention, the test material is used for CO at 273K2Then analyzing the obtained isotherm by using an NLDFT model to obtain the ultramicropore pore diameter of the material, and finally drawing a pore diameter distribution diagram of the material in the range of less than 1nm, wherein as shown in figure 3, the pore diameter of the material is uniform and concentrated in the ultramicropore range of 0.48nm between propylene (0.47nm) and propane (0.47nm) <0.51nm) is used as an adsorbent excellent in the separation of propylene and propane by sieving. .
The adsorption isotherm of the carbon molecular sieve material of the invention on ethylene and ethane is tested under 298K, and the material shows the characteristics of only adsorbing ethylene and completely excluding ethane, thereby proving that the aperture size is between the kinetic diameters of ethylene and ethane. Under the conditions of 298K and 1bar, the adsorption quantity of the ethylene is up to 2.14 mmol/g. It was demonstrated that it can extract high purity ethylene from the C2 bi-component, achieving the most efficient ethylene ethane separation performance (as shown in fig. 2 in particular).
The carbon molecular sieve material disclosed by the invention is tested on the adsorption isotherm of propylene and propane under 298K, and the test result shows that the carbon molecular sieve material has the characteristic of only adsorbing propylene and not adsorbing propane. The uniformity of the ultramicropore diameter is further proved, and the pore diameter is between the kinetic diameters of propylene and propane. In addition, the adsorption amount of the material to propylene under the conditions of 298K and 1bar is as high as 2.54mmol/g, which is the highest value of the current propylene propane screening material. The test results further prove that the carbon molecular sieve material provided by the invention can extract high-purity propylene from the C3 bi-component, and achieves the highest propylene-propane separation selectivity (shown in a specific figure 4).
By analyzing the Raman spectrum of the carbonaceous microspheres before controlled pyrolysis (FIG. 5)And analyzing from the graph, and finally adjusting the graphitization degree of the carbonaceous microspheres by changing the concentration of the starch, thereby controlling the pore diameter range of the carbonaceous microspheres after high-temperature annealing. And it is ID/IGThe ratios of (A) to (B) are all less than 1, which proves that the defect content is low.
In addition, the carbon molecular sieve for separating olefin and alkane, which is a product of the invention, shows a uniform spherical shape after being tested, and can still maintain the regular shape of the carbon microsphere after being roasted at high temperature. The material has uniform pore diameter, is concentrated in the ultramicropore range of 0.48nm and is between the kinetic diameters of propylene (0.47nm) and propane (less than 0.51nm), and further proves that the carbon molecular sieve for separating olefin and alkane can be used as an excellent adsorbent for screening and separating propylene and propane.
Based on the structural characteristics, the ultramicropore carbon molecular sieve material is applied to olefin and alkane adsorption separation.
Based on the technical scheme, the invention is different from the traditional preparation method of the carbon material, and provides a novel establishment concept for preparing the uniform molecular sieve by synergistic regulation. The method comprises the steps of taking low-price, nontoxic and harmless starch biomass as a carbon source, forming carbonaceous microspheres through a direct hydrothermal polymerization carbonization process, controlling the defect content and the graphitization degree of the microspheres by adjusting the concentration of reactants, matching corresponding calcination temperature, pyrolyzing to obtain corresponding carbon molecular sieves, and realizing the pore diameter in a sub-angstrom level precision
Figure BDA0002954444620000051
Fine adjustment within the range.
Compared with the prior art, the invention has the following advantages:
(1) the carbon molecular sieve with screening and separating functions on olefin and alkane prepared by the invention has the functions of really screening and separating propane, propylene and ethane, ethylene and the like;
(2) the carbon source is from renewable resources, is cheap, easy to obtain and can be sustained; the controllable carbon precursor has a homogeneous structure and a certain graphitization degree, and is matched with a matched and controllable reaction process for removing surface functional groups, so that the generation of screening holes is controlled, the process operation is simple, and the large-scale industrial production is facilitated;
(3) the developed carbon molecular sieve does not contain metal ions on the surface, so that carbon deposition in the application process can be reduced or avoided to a great extent, and the material has enough service life.
(4) The invention can realize the aperture of the carbon molecular sieve with the sub-angstrom-scale precision
Figure BDA0002954444620000052
Fine adjustment within the range.
Drawings
FIG. 1 is a scanning electron micrograph of a carbon molecular sieve material prepared in example 1.
Figure 2 adsorption isotherm (298K) of ethylene ethane for the carbon molecular sieve material prepared in example 2.
Figure 3 pore size distribution diagram of the carbon molecular sieve material prepared in example 3.
FIG. 4 adsorption isotherm (298K) of the carbon molecular sieve material prepared in example 3 for propene propane.
FIG. 5 is a Raman spectrum of carbonaceous microspheres prepared in examples 3 to 6 before pyrolysis.
Detailed Description
The present invention will be described in further detail with reference to specific examples, but the embodiments of the present invention are not limited thereto, and the process parameters not specifically mentioned may be performed with reference to conventional techniques.
In the following description, technical solutions are set forth in conjunction with specific figures in order to provide a thorough understanding of the present invention. This application is capable of embodiments in many different forms than those described herein and it is intended that all such modifications that would occur to one skilled in the art are deemed to be within the scope of the invention.
The following steps are adopted in this example.
(1) Regulating and controlling the structure of carbon precursor, adding starch carbon precursor into distilled water solvent according to a certain range of solid-to-liquid ratio to prepare starch aqueous solution with a certain concentration, stirringUniformly stirring and dispersing, and then carrying out medium-pressure medium-temperature hydrothermal controllable polymerization and dehydration carbonization reaction in a reaction kettle to obtain homogeneous carbon microspheres with certain polymerization degree and graphitization degree; in the step, the concentration of starch and the corresponding hydrothermal reaction environment are regulated and controlled by configuring different solid-liquid ratios, and the hydrothermal polymerization degree can be changed, so that the graphitization degree and sp of the carbon precursor are regulated and controlled 3Obtaining a carbon precursor with a specific structure and a regular structure through hybridization;
(2) and (2) forming and regulating and controlling the screening holes, namely washing and drying the carbonaceous microspheres obtained in the step (1), and then placing the carbonaceous microspheres in an inert atmosphere at a certain matching temperature to perform controlled high-temperature defunctionalization hole making to obtain the carbon molecular sieve material with uniform and adjustable ultramicropore channels.
Example 1
(1) 3g of wheat starch and 30mL of distilled water are mixed to prepare a mixed solution with the concentration of 0.03g/mL, and the mixed solution is stirred for 30min to be uniformly dispersed. Then transferring the mixture into a reaction kettle for hydrothermal polymerization carbonization, reacting for 10h at a constant temperature of 200 ℃ and a pressure of 1.55MPa to obtain the compound ID/IGA carbon microsphere value of 0.94.
(2) The carbon microspheres were washed thoroughly with deionized water. Drying the solid, placing in a high-temperature tube furnace, heating to 900 ℃ at a heating rate of 5 ℃/min in nitrogen atmosphere, carbonizing and pyrolyzing for 1h, and cooling to obtain a product 1#A carbon molecular sieve material.
Example 2
(1) Mixing 6g of corn starch and 6mL of distilled water to prepare a starch water solution with the concentration of 1g/mL, and stirring for 30min at normal temperature to uniformly disperse the starch water solution. Then transferring the mixture into a reaction kettle for hydrothermal polymerization reaction at the constant temperature of 190 ℃ and the pressure of 1.24MPa for 14h to obtain the compound I D/IGA carbon microsphere value of 0.87.
(2) The carbon microspheres were washed thoroughly with deionized water. Drying the solid, placing in a high-temperature tube furnace, heating to 1000 ℃ at a heating rate of 5 ℃/min in nitrogen atmosphere, carbonizing and pyrolyzing for 2h, and cooling to obtain a product 2#A carbon molecular sieve material.
Example 3
(1) Mixing 6g of corn starch and 6mL of distilled water to prepare a mixed solution with the concentration of 1g/mL, and stirring for 30min at normal temperature to uniformly disperse the mixed solution. Then transferring the mixture into a reaction kettle for hydrothermal polymerization reaction at the constant temperature of 190 ℃ and the pressure of 1.24MPa for 14h to obtain the compound ID/IGA carbon microsphere value of 0.87.
(2) The carbon microspheres were washed thoroughly with deionized water. Drying the solid, placing in a high-temperature tube furnace, heating to 800 ℃ at a heating rate of 5 ℃/min in nitrogen atmosphere, carbonizing and pyrolyzing for 2h, and cooling to obtain a product 3#And (3) a carbon molecular sieve material.
Example 4
(1) Mixing 6g corn starch and 30mL distilled water to obtain a mixture with a concentration of 0.5g/mL, and stirring for 30min to disperse the mixture uniformly. Then transferring the mixture into a reaction kettle for hydrothermal polymerization carbonization, reacting for 14h at the constant temperature of 190 ℃ and the pressure of 1.24MPa to obtain the compound I D/IGA carbon microsphere value of 0.89.
(2) The carbon microspheres were washed thoroughly with deionized water. Drying the solid, placing in a high-temperature tube furnace, heating to 800 ℃ at a heating rate of 5 ℃/min in nitrogen atmosphere, carbonizing and pyrolyzing for 2h, and cooling to obtain a product 4#A carbon molecular sieve material.
Example 5
(1) 6g of corn starch and 60mL of distilled water are mixed to prepare a mixed solution with the concentration of 0.1g/mL, and the mixed solution is stirred for 30min to be uniformly dispersed. Then transferring the mixture into a reaction kettle for hydrothermal polymerization carbonization, reacting for 20h at the constant temperature of 180 ℃ and the pressure of 1.24MPa to obtain the compound ID/IGA carbon microsphere value of 0.94.
(2) The carbon microspheres were washed thoroughly with deionized water. Drying the solid, placing in a high-temperature tube furnace, heating to 700 deg.C at a heating rate of 5 deg.C/min under nitrogen atmosphere, carbonizing, pyrolyzing for 2h, and cooling to obtain product 5#A carbon molecular sieve material.
Example 6
(1) 3g of corn starch and 60mL of distilled water are mixed to prepare a mixed solution with the concentration of 0.05g/mL, and the mixed solution is stirred for 30min to be uniformly dispersed. Then transferring the mixture into a reaction kettle for hydrothermal polymerization carbonization, reacting for 14h at the constant temperature of 190 ℃ and the pressure of 1.24MPa to obtain the compound I D/IGCarbon microspheres with a value of 0.95.
(2) The carbon microspheres were washed thoroughly with deionized water. Drying the solid, placing in a high-temperature tube furnace, heating to 800 ℃ at a heating rate of 5 ℃/min in nitrogen atmosphere, carbonizing and pyrolyzing for 2h, and cooling to obtain a product of 6#And (3) a carbon molecular sieve material.
The products obtained in the above examples were subjected to the relevant tests, and the results thereof are shown below.
According to the method, a Hitachi SU8220 scanning electron microscope is adopted to characterize the surface morphology of the carbon molecular sieve prepared by the embodiment of the invention, so that the microstructure of the material can be further understood. Fig. 1 is a scanning electron microscope image of the carbon molecular sieve material obtained in example 1, and it can be seen from the image that the material exhibits a uniform spherical morphology, and the regular morphology of the carbon microsphere can be maintained after the high-temperature calcination.
The adsorption separation performance of the carbon molecular sieve material prepared in the example of the present invention was characterized by ASAP2020, manufactured by U.S. Micro corporation. The carbon molecular sieve material of the invention is tested on the static adsorption isotherm under 298K by using a volume method.
Fig. 2 is an adsorption isotherm of the carbon molecular sieve material prepared in example 2 for ethylene ethane at 298K, and from analysis in the figure, the material shows the characteristics of only adsorbing ethylene and completely excluding ethane, and the pore size is proved to be between the kinetic diameters of ethylene and ethane. Under the conditions of 298K and 1bar, the adsorption quantity of the ethylene is up to 2.14 mmol/g. It is proved that the ethylene with high purity can be extracted from the C2 bi-component, and the most efficient ethylene and ethane separation performance is realized.
The present application uses carbon dioxide as a molecular probe to characterize the pore size of the carbon molecular sieve materials in the examples of the invention. Specifically, the material was tested for CO at 273K2And (3) analyzing the obtained isotherm by using an NLDFT model to obtain the ultramicropore diameter of the material, and finally drawing to obtain a pore diameter distribution diagram of the material in the range of less than 1 nm.
Figure 3 is a pore size distribution diagram of the carbon molecular sieve material prepared in example 3, and from the pore size distribution diagram, the pore size of the material is uniform and concentrated in the ultramicropore range of 0.48nm, which is between the kinetic diameters of propylene (0.47nm) and propane (<0.51nm), and the test result shows that the product can be used as an excellent adsorbent for propylene-propane screening separation.
Fig. 4 is an adsorption isotherm of the carbon molecular sieve material prepared in example 3 for propylene propane at 298K, and from the result chart, the carbon molecular sieve material shows the characteristics of only adsorbing propylene and not adsorbing propane, further demonstrating the uniformity of the ultramicropore diameter and being between the kinetic diameters of propylene and propane. And the adsorption amount of the material to propylene under the conditions of 298K and 1bar is as high as 2.54mmol/g, which is the highest value of the existing propylene propane screening material. The results further prove that the carbon molecular sieve material can extract high-purity propylene from the C3 bi-component, and achieves the highest propylene-propane separation selectivity.
The application adopts a LabRAMAramis full-automatic Raman spectrometer to carry out structural characterization on the carbon microspheres before the carbon molecular sieve is roasted at high temperature in the embodiment of the invention, wherein the structural characterization is carried out at 1603cm-1G band of (2) is sp2The plane vibration of carbon atoms is 1343cm-1The D band of (a) is a defect raman characteristic peak representing the amorphous structure of the material. I.C. AD/IGThe ratio of (a) can be used to analyze the degree of graphitization. I isD/IGThe higher the content of defects, the higher the degree of graphitization. Fig. 5 is a raman spectrum of the carbonaceous microspheres of examples 3-6 of the present invention before controlled pyrolysis, which was analyzed from the graph, and the graphitization degree of the carbonaceous microspheres can be finally adjusted by changing the concentration of starch, thereby controlling the pore size range after high temperature annealing. And it is ID/IGThe ratios of (A) to (B) are all less than 1, which proves that the defect content is low.
It should be understood that the above detailed description of the embodiments of the present invention with reference to the preferred embodiments is illustrative and not restrictive, and it should not be considered that the detailed description of the embodiments of the present invention is limited thereto, and it should be understood that those skilled in the art to which the present invention pertains that modifications may be made to the embodiments described in the embodiments or that equivalents may be substituted for some of the features thereof without departing from the spirit of the present invention and the scope of the patent protection is defined by the claims to be filed with the present invention.
The above examples of the present invention are merely examples for clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims (7)

1. A method for preparing a carbon molecular sieve for separating olefin and alkane, which is characterized by comprising the following steps:
(1) regulating and controlling the structure of the carbon precursor, namely adding the starch carbon precursor into a distilled water solvent to prepare a starch water solution, stirring and dispersing uniformly, and then carrying out medium-pressure and medium-temperature hydrothermal controllable polymerization and dehydration carbonization reaction in a reaction kettle to obtain homogeneous carbon microspheres with certain polymerization degree and graphitization degree;
(2) forming and regulating the screening holes, namely washing and drying the homogeneous carbon microspheres obtained in the step (1), placing the homogeneous carbon microspheres in an inert atmosphere at the temperature of 700-1000 ℃ for controlled high-temperature defunctionalization treatment, and obtaining the carbon molecular sieve material with uniform and adjustable ultramicropore channels by controlling carbon layer rearrangement and heteroatom pyrolysis reaction;
In the step (1), the weight ratio of the starch carbon precursor to distilled water is 1: 1-1: 20, and the concentration of a starch water solution is 0.05-1 g/mL;
in the step (1), the temperature of the medium-pressure medium-temperature hydrothermal controllable polymerization and dehydration carbonization reaction is 180 DEGAt the temperature of 210 ℃ to 1 MPa to 4 MPa; the time of the medium-pressure medium-temperature hydrothermal controllable polymerization and dehydration carbonization reaction is 8-20 h; raman spectrum I of prepared homogeneous carbon microsphereD/IGThe ratio of (A) to (B) is 0.85-0.95;
in the step (2), the heating rate of the high-temperature defunctionalization treatment reaction is 2-10 ℃/min, the reaction temperature is 700-1000 ℃, and the reaction time is 0.5-6 h.
2. The method according to claim 1, wherein in step (1), the starch carbon precursor is soluble starch.
3. The method according to claim 1, wherein in step (1), the starch-carbon precursor is one or more of corn starch, wheat starch, sweet potato starch, and mung bean starch.
4. The method of claim 1, wherein in step (2), the inert atmosphere is argon or nitrogen.
5. The method according to claim 1, wherein in the step (2), the inert atmosphere is a mixed gas of argon gas and nitrogen gas in any mixing ratio.
6. The carbon molecular sieve for separating olefin and alkane prepared by the method of any one of claims 1 to 5, wherein the carbon molecular sieve with ultramicropore channels only adsorbs olefin and does not adsorb alkane; the carbon molecular sieve of the ultramicropore pore channel has uniform pore size and is between the kinetic diameters of olefin and alkane.
7. The use of the carbon molecular sieve of claim 6 in olefin alkane adsorption separation.
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