CN113351163B - Microporous carbon adsorbent for separating C6 alkane isomer and C8 xylene isomer, and preparation method and application thereof - Google Patents

Microporous carbon adsorbent for separating C6 alkane isomer and C8 xylene isomer, and preparation method and application thereof Download PDF

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CN113351163B
CN113351163B CN202110745079.0A CN202110745079A CN113351163B CN 113351163 B CN113351163 B CN 113351163B CN 202110745079 A CN202110745079 A CN 202110745079A CN 113351163 B CN113351163 B CN 113351163B
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coke
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肖静
杜胜君
黄佳武
廖能
黄保林
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South China University of Technology SCUT
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    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
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Abstract

The invention discloses a microporous carbon adsorbent for separating C6 alkane isomer and C8 xylene isomer, and a preparation method and application thereof. The method comprises the following steps: adding a catalyst into deionized water to prepare an aqueous solution with the pH value of 2.5-7, then adding hexatomic ring monosaccharide, and uniformly stirring and mixing to obtain a reaction solution, wherein the mass ratio of the hexatomic ring monosaccharide to the aqueous solution is 5-15: 100; carrying out hydrothermal reaction on the obtained reaction solution at the temperature of 180-210 ℃, naturally cooling after the reaction is finished, carrying out suction filtration to retain a solid product, and then washing and drying to obtain glycosyl hydrated coke; and (3) carrying out programmed heating on the obtained hydrated coke to 800-1000 ℃ under the protection of inert gas in a high-temperature furnace for carrying out pyrolysis carbonization reaction, and carrying out programmed cooling to room temperature to obtain the narrow-micropore carbon adsorbent, wherein the pore diameter of the narrow-micropore carbon adsorbent is 4.8-6.8 angstrom. The carbon adsorbent prepared by the invention can separate C6 alkane isomer and C8 xylene isomer.

Description

Microporous carbon adsorbent for separating C6 alkane isomer and C8 xylene isomer, and preparation method and application thereof
Technical Field
The invention relates to the technical field of angstrom-level carbon molecular sieve chemistry, in particular to a microporous carbon adsorbent for separating C6 alkane isomers and C8 xylene isomers, and a preparation method and application thereof.
Background
The separation of alkane isomers based on different degrees of branching represents a key but challenging process in the petrochemical industry. In the refinery process, light naphtha fractions (mainly including linear C6 alkanes) are catalytically isomerized to linear (n-HeX), mono-branched (3-MP) and di-branched (2, 2-DMB) isomers. Isomers with higher degrees of branching generally have higher octane numbers (RON). For example, RON of 3-MP (75) and 2,2-DMB (94) is much higher than that of n-hexane (25), the linear isomer thereof. Thus, in order to produce gasoline with high RON, alkane isomers with low RON need to be removed from the mixture and recycled back to the catalytic reactor. The C8 xylene isomer is a key feedstock for the production of many important chemicals and polymers, with worldwide annual production rates exceeding 4000 million tons. Among these isomers, p-xylene (p-X) is an indispensable monomer for the mass production of polyethylene terephthalate. By 2022, the global p-X market revenue is expected to reach 669 billion dollars. However, the C8 xylene isomers have the same molecular formula and conventional distillation methods are not suitable for separating the lower boiling components (p-X411.53K, o-xylene o-X417.59K). Therefore, the separation of the C8 xylene isomer is very challenging.
The adsorption separation method is an effective method for separating the C6 alkane isomer and the C8 xylene isomer, has the advantages of being capable of operating at normal temperature and pressure and the like, and the adsorbent is the key point of the adsorption separation. Currently, faujasite plays a dominant role in the industry. However, such conventional adsorbents have low separation selectivity and require complex simulated moving bed technology. And the desorption regeneration for the zeolite adsorbent requires a large amount of energy consumption. In order to save energy and reduce costs, efforts are being made to find potential new separation materials.
The adsorbents reported to date for the separation of C6 alkanes and C8 xylene isomers are mainly zeolitic molecular sieves and metal organic framework Materials (MOFs). Wang et al reported that calcium-based microporous metal-organic frameworks Ca (H) using only a single adsorbent 2 tcpb) (tcpb = 1,2,4, 5-tetrakis (4-carboxyphenyl) -benzene), unique molecular sieving capabilities for C6 alkane isomers are exhibited, which allow for different separations to be achieved by temperature changes. Specifically, n-HeX and 3MP can be completely separated at 120 ℃, and can be separated at 60 DEG CIsolate 3MP and 2,2-DMB alkane isomers. Wherein the structural flexibility of the material backbone and the structural variation of guest molecules play a crucial role in the temperature-controlled molecular sieve performance [ Wang H, Dong X, Veasco E, et al. One-of-a-king: a microporous metal-organic framework available for the optimal separation of threads, mono-and di-branched alkyl isomers of vitamin temperature-and adsorbed-dependent molecular sieve spacing [ J]. Energy & Environmental Science, 2018, 11(5):1226-1231.]. In addition, in 2020 Yu et Al reported Al-bttotb (H) as an aluminum-based MOF material 3 btotb = 4,4', 4 "- (benzene-1, 3, 5-triyltris (oxy)) tribenzoic acid) with a pore size of 0.56 nm, which is just between the kinetic diameters of 3MP (0.55 nm) and 2,2-DMB molecules (0.62 nm) of C6 alkanes. Single-component and multi-component adsorption experiments show that the material only adsorbs n-HeX and 3MP, but completely excludes 2,2-DMB isomer, and can realize high-selectivity screening separation. The adsorption isotherm measurement results showed that the adsorption amounts of n-HeX and 3MP molecules reached 151 and 94 mg/g respectively at room temperature and pressure [ Splitting monomer and bridged alkali reagents by a Robust Aluminum-Based Metal-Organic Framework materials with Optimal Pore Dimensions [ J]. Journal of the American Chemical Society, 2020, 142(15):6925-6929]. In 2020, Cui et al used NbOF with a rotating anionic site 5 2- The metal organic framework material NbOFFIVE-bpy-Ni is used for separating xylene isomers. ZU-61 with guest-responsive nanospace/sites can adapt to the shape of a particular isomer by geometric deformation or rotation of fluorine atoms in the anion sites, allowing ZU-61 to interact through multiple C-H.F. ZU-61 showed both a high meta-xylene absorption capacity (3.4 mmol/g) and a high meta-xylene/para-xylene separation selectivity (2.9). Fixed bed permeation experiments show that paraxylene is eluted first in high purity (. gtoreq.99.9%) and then is m-xylene and o-xylene.
Although these MOFs materials have excellent separation selectivity, they are limited by framework stability and high production cost, and are difficult to be directly used industrially. Molecular sieves, a class of structurally stable and uniform pore size materials, have been used in commercial production and applications, which also exhibit potential advantages for the separation of C6 and C8 isomers. For example, David et al used 5A molecular sieve to separate C6 alkane isomers, and the pore size (0.50 nm) of the C6 alkane isomers is between the kinetic diameters of n-HeX (0.43 nm) and 3MP (0.55 nm), so that the C6 alkane isomers can be separated by sieving, fixed bed permeation experiments further prove that the sieving performance is realized, n-HeX permeates from the bed at the beginning, and 3MP permeates after nearly 8 minutes, so that the C6 alkane isomers have a better dynamic separation effect. The use of molecular sieves still has certain limitations, such as low adsorption capacity and high desorption energy consumption.
Carbon adsorbents are widely accepted as adsorbents which are low in cost, stable in structure and capable of being produced and used in large scale, but currently researched and produced carbon adsorbents cannot be put into a separation system of C6 alkane isomers and C8 xylene isomers, and due to the fact that the carbon adsorbents face wide pore size distribution and poor specific recognition capability of each isomer, low separation selectivity is caused, and the purity of a final gas product cannot meet the industrial target requirement.
Disclosure of Invention
In view of the above, in order to overcome the defects in the existing applications, the invention provides a carbon adsorbent for sieving and separating C6 alkane isomers and C8 xylene isomers, and the carbon adsorbent has narrow pore size distribution, can realize the highest selectivity of sieving and separating, has low production cost and excellent regeneration performance, and can be produced and used in industrial scale.
In a first aspect, the present application provides a method of preparing a carbon adsorbent for separating a C6 alkane isomer and a C8 xylene isomer, comprising the steps of:
(1) preparation of reaction solution: adding a catalyst into deionized water to prepare an aqueous solution with the pH value of 2.5-7, then adding hexatomic ring monosaccharide, and uniformly stirring and mixing to obtain a reaction solution, wherein the mass ratio of the hexatomic ring monosaccharide to the aqueous solution is 5-15: 100;
(2) synthesis of glycosyl hydrated coke: carrying out hydrothermal reaction on the reaction liquid obtained in the step (1) at the temperature of 180-210 ℃, naturally cooling after the reaction is finished, carrying out suction filtration to retain a solid product, and then washing and drying to obtain glycosyl hydrated coke;
(3) and (3) preparing holes by reduction pyrolysis: and (3) carrying out programmed heating on the glycosyl hydrated coke obtained in the step (2) to 800-1000 ℃ under the protection of inert gas in a high-temperature furnace for carrying out pyrolysis carbonization reaction, and carrying out programmed cooling to room temperature to obtain the narrow microporous carbon adsorbent, wherein the pore diameter of the narrow microporous carbon adsorbent is 4.8-6.8 angstrom.
Preferably, the mass ratio of the six-membered cyclic sugar to the aqueous solution is 8-12: 100. More preferably, the mass ratio of the six-membered cyclic sugar to the aqueous solution is 10: 100.
Preferably, in the step (1), the six-membered ring monomer is at least one of glucose, fructose, galactose and mannose.
Preferably, in the step (1), the catalyst is at least one of hydrochloric acid, phosphoric acid and sulfuric acid. Preferably, in step (1), the pH is 3 to 7.
Preferably, in the step (2), the temperature of the hydrothermal reaction is 180-200 ℃, and the reaction time is 12-18 h.
Preferably, in the step (3), the inert gas is at least one of argon, nitrogen and helium.
Preferably, in the step (3), the temperature-rising rate of the programmed temperature rise is 5-15 ℃/min, the reaction time is 1-3h, and the temperature-reducing rate of the programmed temperature reduction is 5-15 ℃/min. Preferably, in the step (3), the temperature-increasing rate of the programmed temperature increase is 5 ℃/min, the reaction time is 1-3h, and the temperature-decreasing rate of the programmed temperature decrease is 5 ℃/min.
In a second aspect, the present application provides a microporous carbon adsorbent having a narrow pore size distribution prepared by the preparation method of any one of the above.
In a third aspect, the present application provides the use of a microporous carbon adsorbent having a narrow pore size distribution for separating a C6 alkane isomer and a C8 xylene isomer.
Preferably, the C6 alkane isomers include n-hexane, 3-methylpentane and 2, 2-dimethylbutane, and the pore size of the narrow pore carbon adsorbent is in the range of from 5.0 angstroms to 5.5 angstroms.
Preferably, the C8 xylene isomers include para-xylene and ortho-xylene; the pore size of the narrow microporous carbon adsorbent is between 5.8 and 6.8 angstroms.
The beneficial effect of this application: the application provides a carbon adsorbent for screening and separating C6 alkane isomers and C8 xylene isomers, the screening and separating performance of the carbon material is rarely reported, the carbon adsorbent takes low-cost hexatomic ring monomer sugar as a raw material, the pH value of a hydrothermal reaction solution is adjusted by a small amount of acid catalyst, so that the hydrothermal reaction is catalyzed to different degrees, and the high-selectivity adsorbent with the screening and separating performance on the C6 alkane isomers and the C8 xylene isomers is prepared by combining optimized regulation and control of temperature. Meanwhile, the material has the industrial requirements of good stability, low cost, good regeneration performance and the like, and is a high-performance adsorbent with great potential and industrial large-scale application.
Compared with the prior art, the invention has the following advantages:
the adsorption material with the sieving and separating performance for the C6 alkane isomer and the C8 xylene isomer, which is prepared by the method, has the advantages of stable structure and low cost compared with MOFs materials. Compared with the molecular sieve, the method has the characteristics of low regeneration energy consumption and good adsorption capacity; compared with the carbon material in conventional industrial application, the carbon material has the advantage of high separation and selection performance, so that the narrow microporous carbon adsorbent has very good industrial application prospect.
Drawings
FIG. 1N of narrow pore carbon adsorbent prepared in example 1 2 Adsorption and desorption isotherms (77K) and pore size distribution.
FIG. 2 CO pairing of the narrow microporous carbon adsorption material prepared in example 2 2 Adsorption and desorption isotherms (273K).
FIG. 3 shows the adsorption isotherm (298K) of the C8 xylene isomer on the narrow microporous carbon adsorbent material prepared in example 1.
Fig. 4 shows adsorption and desorption isotherms (298K) of the alkane isomer of C6 on the narrow microporous carbon adsorbent material prepared in example 2.
Detailed Description
The invention is further described with reference to the following figures and detailed description.
Example 1
(1) 100ml of neutral deionized water was added to 10g of glucose and mixed well. And then transferring the reaction solution to a closed environment of a reaction kettle, carrying out hydrothermal reaction for 14 h at 190 ℃, and fully cleaning the obtained solid hydrated coke with deionized water.
(2) Drying the hydrated coke, placing the dried hydrated coke in a porcelain boat, and then placing the porcelain boat in a high-temperature furnace to be subjected to N 2 And (2) performing reduction pyrolysis reaction for 2h after raising the temperature to 800 ℃ at a heating rate of 5 ℃/min under atmosphere protection, then cooling to room temperature at a cooling rate of 5 ℃/min to obtain a carbon adsorbent with a microporous pore diameter distribution of 5.8-6.8A (over 70%) in the invention, recording as a sample No. 1, and finally performing a steam adsorption test of a C8 aromatic hydrocarbon isomer.
Example 2
(1) Add 8.33. mu.L concentrated HCl into 100ml deionized water to prepare an aqueous solution with pH 3, then add 10g glucose and mix well. And then transferring the reaction solution to a closed environment of a reaction kettle, carrying out hydrothermal reaction for 14 h at 190 ℃, and fully cleaning the obtained solid hydrated coke with deionized water.
(2) Drying the hydrated coke, placing the dried hydrated coke in a porcelain boat, and then placing the porcelain boat in a high-temperature furnace to be subjected to N 2 Performing reduction pyrolysis reaction for 2h after raising the temperature to 800 ℃ at the temperature rise speed of 5 ℃/min under the atmosphere protection, then lowering the temperature to room temperature at the temperature drop speed of 5 ℃/min to obtain a carbon adsorbent with a micropore diameter of 5.0A-5.5A (over 75%) in the invention, recording as a sample 2#, and finally performing a steam adsorption test of C6 alkane isomers.
The invention uses the American ASAP2460 analyzer in combination with a density functional theory model (DFT) to characterize the pore size distribution of the carbon adsorbent. FIG. 1 shows the material prepared in example 1 at 77K (liquid nitrogen temperature) for N 2 The curve of the adsorption and desorption isotherm shows a typical I-type isotherm model, and a hysteresis loop does not exist, which proves thatIt has a rich and relatively uniform microporous structure. The pore size distribution further demonstrates that its microporous structure is predominantly distributed in a range of 5.8 a-6.8 a (over 70%).
The invention adopts the American ASAP2020 analyzer to determine the CO content of the material under 273K 2 The adsorption and desorption isotherm is combined with four standards of specific surface area calculation, so as to obtain the specific surface area of the carbon adsorbent prepared by the invention in the micropore range. FIG. 2 shows the CO pairing of the material prepared in example 2 2 The calculated micropore specific surface area is 451.7 m 2 /g。
The invention adopts Beijing Bestard instrument company to determine the steam adsorption isotherm of the material on the C8 xylene isomer.
Figure 3 is a gas phase adsorption isotherm of the carbon adsorbent of example 1 for the two isomers of C8 xylene at 298K. The isotherm results show that the carbon adsorbent of example 1 can exhibit adsorption of only para-xylene (p-X) and not ortho-xylene (o-X). The amount of adsorption to p-X may reach 71.3 mg/g at normal temperature (where 1mg/g refers to adsorption of 1mg target per gram of carbon adsorbent), while the amount of adsorption to o-X is only 14.7 mg/g, and this sieving separation effect is due to the adsorbent having a pore size having a primary distribution within the range of 5.8 a-6.8 a, just between the kinetic diameters of p-X5.8 a and o-X6.8 a, such that the highest sieving separation selectivity may be achieved.
The invention adopts an ASAP2020 analyzer to determine the vapor adsorption isotherm of a material on a C6 alkane isomer. Fig. 4 is a gas phase adsorption isotherm of the three isomers of C6 alkane with the carbon adsorbent of example 2 at 298K. The results show that the material achieved an adsorption capacity of 91.3 mg/g for a linear molecule with a kinetic diameter of 4.3 a (n-hexane: n-HeX) and a steep linear trend in the low pressure region, demonstrating a microporous adsorption effect in carbon adsorbents, due to a pore size distribution predominantly in the range of 5.0 a-5.5 a (over 75%). The material has a repulsive effect on larger size mono-branched (3-methylpentane: 3-MP, kinetic diameter: 5.5A) and di-branched molecules (2, 2-dimethylbutane: 2,2-DMB, kinetic diameter: 6.2A), with adsorption amounts of 17.9 mg/g and 16.1 mg/g, and more importantly, the material has almost no adsorption effect on two branched guest molecules in the low pressure region, thus demonstrating a molecular sieving effect due to narrow micropores.
Example 3
(1) 0.054 mul of concentrated sulfuric acid is added into 100ml of deionized water to prepare an aqueous solution with pH value of 5, and then 10g of glucose is added and mixed well. And then transferring the reaction liquid to a closed environment of a reaction kettle, carrying out hydrothermal reaction for 12 hours at 200 ℃, and fully cleaning the obtained solid hydrated coke with deionized water.
(2) Drying the hydrated coke, placing the dried hydrated coke in a porcelain boat, and then placing the porcelain boat in a high-temperature furnace to be subjected to N 2 Performing reduction pyrolysis reaction for 2h after the temperature is increased to 900 ℃ at the temperature rising speed of 5 ℃/min, then cooling to room temperature at the temperature lowering speed of 5 ℃/min to obtain a carbon adsorbent with a micropore diameter of 5.0-5.5 (more than 60%) in the invention, which is recorded as a sample 3#, and finally performing a steam adsorption test of a C6 alkane isomer, wherein the carbon adsorbent can have a good adsorption effect on a straight chain molecule (n-hexane: n-HeX, kinetic diameter: 4.3A), can adsorb a double branched chain molecule (2, 2-dimethylbutane: 2,2-DMB, kinetic diameter: 5.5A) with a poor adsorption on a single branched chain molecule (3-methylpentane: 3-MP, kinetic diameter: 6.2A), has an adsorption amount on n-HeX of 82.7 mg/g, and an adsorption amount on 3-MP of 28.7 mg/g, the adsorption amount to 2,2-DMB was 24.2 mg/g.
Example 4
(1) 100ml of neutral deionized water was added with 8g of glucose and mixed well. And then transferring the reaction liquid to a closed environment of a reaction kettle, carrying out hydrothermal reaction for 14 h at 190 ℃, and fully cleaning the obtained solid hydrated coke with deionized water.
(2) Drying the hydrated coke, placing the dried hydrated coke in a porcelain boat, and then placing the porcelain boat in a high-temperature furnace to be subjected to N 2 Performing atmosphere protection, heating to 800 ℃ at a heating rate of 5 ℃/min, performing reduction pyrolysis reaction for 2h, cooling to room temperature at a cooling rate of 5 ℃/min to obtain a carbon adsorbent with a microporous pore diameter distribution of 6.0-7.0A (over 65%), marking as a sample No. 4, and performing C8 aromatic hydrocarbon isomerThe amount of adsorbed p-o-xylene (o-X) was 30.1 mg/g and the amount of adsorbed p-xylene (p-X) was 79.6 mg/g, as measured by vapor adsorption.
Example 5
(1) Add 8.33. mu.L concentrated HCl into 100ml deionized water to prepare an aqueous solution with pH 3, then add 8g glucose and mix well. And then transferring the reaction liquid to a closed environment of a reaction kettle, carrying out hydrothermal reaction for 14 h at 190 ℃, and fully cleaning the obtained solid hydrated coke with deionized water.
(2) Drying the hydrated coke, placing the dried hydrated coke in a porcelain boat, and then placing the porcelain boat in a high-temperature furnace to be subjected to N 2 And (2) performing reduction pyrolysis reaction for 2h after raising the temperature to 800 ℃ at a temperature raising speed of 5 ℃/min under atmosphere protection, then reducing the temperature to room temperature at a temperature reducing speed of 5 ℃/min to obtain a carbon adsorbent with a micropore diameter of 5.0-5.8A (over 60 percent), recording as a sample No. 5, and finally performing a steam adsorption test of C6 alkane isomers, wherein the adsorption quantity to n-HeX is 91.6 mg/g, the adsorption quantity to 3-MP is 31.1 mg/g, and the adsorption quantity to 2,2-DMB is 28.5 mg/g.
Example 6
(1) 100ml of neutral deionized water is added with 10g of fructose and fully and uniformly mixed. And then transferring the reaction liquid to a closed environment of a reaction kettle, carrying out hydrothermal reaction for 14 h at 190 ℃, and fully cleaning the obtained solid hydrated coke with deionized water.
(2) Drying the hydrated coke, placing the dried hydrated coke in a porcelain boat, and then placing the porcelain boat in a high-temperature furnace to be subjected to N 2 And (2) performing reduction pyrolysis reaction for 2h after raising the temperature to 800 ℃ at a heating rate of 5 ℃/min under the atmosphere protection, then reducing the temperature to room temperature at a cooling rate of 5 ℃/min to obtain a carbon adsorbent with a microporous pore diameter distribution of 5.6-6.8A (over 65%), marking as a sample No. 6, and finally performing a steam adsorption test of C8 aromatic hydrocarbon isomers, wherein the adsorption quantity of p-o-xylene (o-X) is 19.2 mg/g, and the adsorption quantity of p-xylene (p-X) is 73.6 mg/g.
Example 7
(1) Adding 8.33 μ L concentrated hydrochloric acid into 100ml deionized water to prepare a water solution with pH value of 3, then adding 10g galactose and mixing well. And then transferring the reaction solution to a closed environment of a reaction kettle, carrying out hydrothermal reaction for 14 h at 190 ℃, and fully cleaning the obtained solid hydrated coke with deionized water.
(2) Drying the hydrated coke, placing the dried hydrated coke in a porcelain boat, and then placing the porcelain boat in a high-temperature furnace to be subjected to N 2 And (2) performing reduction pyrolysis reaction for 2h after raising the temperature to 800 ℃ at a temperature raising speed of 5 ℃/min under atmosphere protection, then reducing the temperature to room temperature at a temperature reducing speed of 5 ℃/min to obtain a carbon adsorbent with a micropore diameter of 5.0-5.5 angstrom (more than 70%), marking as a sample No. 7, and finally performing a steam adsorption test of C6 alkane isomers, wherein the adsorption quantity to n-HeX is 90.8 mg/g, the adsorption quantity to 3-MP is 18.2 mg/g, and the adsorption quantity to 2,2-DMB is 16.9 mg/g.
In order to illustrate the superiority of the present application, the present application also makes the following comparative examples.
Comparative example 1
In comparison with example 1, the pH was 2. (1) 54 mu L of concentrated sulfuric acid is added into 100ml of deionized water to prepare an aqueous solution with the pH value of 2, and then 10g of glucose is added and mixed well. And then transferring the reaction liquid to a closed environment of a reaction kettle, carrying out hydrothermal reaction for 14 h at 190 ℃, and fully cleaning the obtained solid hydrated coke with deionized water.
(2) Drying the hydrated coke, placing the dried hydrated coke in a porcelain boat, and then placing the porcelain boat in a high-temperature furnace to be subjected to N 2 And (2) performing reduction pyrolysis reaction for 2h after raising the temperature to 800 ℃ at a heating rate of 5 ℃/min under atmosphere protection, then cooling to room temperature at a cooling rate of 5 ℃/min to obtain a carbon adsorbent with a microporous pore diameter distribution of 4.8-5.0A (over 60%) in the invention, recording as a sample No. 8, and finally performing a steam adsorption test of a C8 aromatic hydrocarbon isomer. The adsorbed amount of p-o-xylene (o-X) was 2.9 mg/g and the adsorbed amount of p-xylene (p-X) was 16.4 mg/g, indicating that the separation of C8 alkane isomers was not as effective as in example 1.
Comparative example 2
In comparison with example 1, the pH was 9. (1) 0.04 mg NaOH is added into 100ml deionized water to prepare an aqueous solution with pH value of 9, and then 10g glucose is added and mixed well. And then transferring the reaction liquid to a closed environment of a reaction kettle, carrying out hydrothermal reaction for 14 h at 190 ℃, and fully cleaning the obtained solid hydrated coke with deionized water.
(2) Drying the hydrated coke, placing the dried hydrated coke in a porcelain boat, and then placing the porcelain boat in a high-temperature furnace to be subjected to N 2 And (3) performing reduction pyrolysis reaction for 2h after raising the temperature to 800 ℃ at a temperature rise speed of 5 ℃/min under atmosphere protection, then lowering the temperature to room temperature at a temperature drop speed of 5 ℃/min to obtain a carbon adsorbent with a micropore diameter distribution of 6.5A-7.2 (over 50%) in the invention, marking as a sample 9#, and finally performing a steam adsorption test of a C8 aromatic hydrocarbon isomer. The adsorbed amount of p-o-xylene (o-X) was 43.1 mg/g and the adsorbed amount of p-xylene (p-X) was 74.4 mg/g, indicating that the separation of C8 alkane isomers was not as effective as in example 1.
Comparative example 3
The amount of glucose used was reduced compared to example 1. (1) 100ml of neutral deionized water was added with 2g of glucose and mixed well. And then transferring the reaction solution to a closed environment of a reaction kettle, carrying out hydrothermal reaction for 14 h at 190 ℃, and fully cleaning the obtained solid hydrated coke with deionized water.
(2) Drying the hydrated coke, placing the dried hydrated coke in a porcelain boat, and then placing the porcelain boat in a high-temperature furnace to be subjected to N 2 The reduction pyrolysis reaction is carried out for 2h after the temperature is raised to 800 ℃ at the temperature raising speed of 5 ℃/min under the protection of atmosphere, then the temperature is lowered to room temperature at the temperature lowering speed of 5 ℃/min, so that the carbon adsorbent with the micropore diameter distribution of 6.5-7.5A (more than 40%) in the invention is obtained and is marked as a sample No. 10, and finally the steam adsorption test of C8 aromatic hydrocarbon isomers is carried out, wherein the adsorption quantity of o-xylene (o-X) is 52.9 mg/g, and the adsorption quantity of p-xylene (p-X) is 73.4 mg/g, which shows that the separation effect of the C8 alkane isomer is not as good as that of example 1.
Comparative example 4
The amount of glucose used was larger than that used in example 1. (1) To 100ml of neutral deionized water, 18g of glucose was added and mixed well. And then transferring the reaction solution to a closed environment of a reaction kettle, carrying out hydrothermal reaction for 14 h at 190 ℃, and fully cleaning the obtained solid hydrated coke with deionized water.
(2) Drying the hydrated coke, placing the dried hydrated coke in a porcelain boat, and then placing the porcelain boat in a high-temperature furnace to be subjected to N 2 The method comprises the steps of performing reduction pyrolysis reaction for 2h after raising the temperature to 800 ℃ at a temperature raising speed of 5 ℃/min under the protection of an atmosphere, then reducing the temperature to room temperature at a temperature reducing speed of 5 ℃/min to obtain a carbon adsorbent with a microporous pore diameter distribution of 5.2-6.0A (over 45%), marking as a sample No. 11, and finally performing a steam adsorption test on C8 aromatic hydrocarbon isomers, wherein the adsorption amount of p-o-xylene (o-X) is 10.7 mg/g, and the adsorption amount of p-xylene (p-X) is 23.4 mg/g, which indicates that the separation effect on C8 alkane isomers is inferior to that of example 1.
Comparative example 5
The temperature of the reduction pyrolysis reaction in step (2) was 700 c, compared to example 1. (1) 100ml of neutral deionized water was added with 10g of glucose and mixed well. And then transferring the reaction solution to a closed environment of a reaction kettle, carrying out hydrothermal reaction for 14 h at 190 ℃, and fully cleaning the obtained solid hydrated coke with deionized water.
(2) Drying the hydrated coke, placing the dried hydrated coke in a porcelain boat, and then placing the porcelain boat in a high-temperature furnace to be subjected to N 2 And (2) performing reduction pyrolysis reaction for 2h after raising the temperature to 700 ℃ at a temperature raising speed of 5 ℃/min under atmosphere protection, then reducing the temperature to room temperature at a temperature reducing speed of 5 ℃/min to obtain a carbon adsorbent with a microporous pore diameter distribution of 6.5-7.5A (over 40%), which is recorded as a sample No. 12, and finally performing a steam adsorption test on a C8 aromatic hydrocarbon isomer, wherein the adsorption amount of p-o-xylene (o-X) is 49.3 mg/g and the adsorption amount of p-xylene (p-X) is 67.7 mg/g, which indicates that the separation effect on a C8 alkane isomer is not as good as that in example 1.
Comparative example 6
The amount of glucose used was reduced compared to example 2. (1) Add 8.33. mu.L concentrated HCl to 100ml deionized water to prepare an aqueous solution with pH 3, then add 2g glucose and mix well. And then transferring the reaction liquid to a closed environment of a reaction kettle, carrying out hydrothermal reaction for 14 h at 190 ℃, and fully cleaning the obtained solid hydrated coke with deionized water.
(2) The hydrated coke is dried and then placed in a porcelain boat, thenThen put into a high-temperature furnace to be subjected to N 2 The carbon adsorbent with the micropore diameter of 5.3-6.0A (over 42%) is obtained by performing reduction pyrolysis reaction for 2h after being heated to 800 ℃ at the heating rate of 5 ℃/min under the protection of atmosphere, then the temperature is reduced to room temperature at the cooling rate of 5 ℃/min, the carbon adsorbent is recorded as a sample No. 13, and finally the steam adsorption test of C6 alkane isomers is performed, wherein the adsorption amount to n-HeX is 77.5 mg/g, the adsorption amount to 3-MP is 46.7 mg/g, and the adsorption amount to 2,2-DMB is 36.6 mg/g, which shows that the separation effect to C6 alkane isomers is not as good as that of example 2.
Comparative example 7
The amount of glucose used was larger than that in example 2. (1) Add 8.33. mu.L concentrated HCl to 100ml deionized water to prepare an aqueous solution with pH 3, then add 18g glucose and mix well. And then transferring the reaction solution to a closed environment of a reaction kettle, carrying out hydrothermal reaction for 14 h at 190 ℃, and fully cleaning the obtained solid hydrated coke with deionized water.
(2) Drying the hydrated coke, placing the dried hydrated coke in a porcelain boat, and then placing the porcelain boat in a high-temperature furnace to be subjected to N 2 The carbon adsorbent with the micropore diameter of 4.6-5.0A (over 50%) is obtained by performing reduction pyrolysis reaction for 2h after being heated to 800 ℃ at the heating rate of 5 ℃/min under the protection of atmosphere, then the temperature is reduced to room temperature at the cooling rate of 5 ℃/min, the carbon adsorbent is recorded as a sample No. 14, and finally the steam adsorption test of C6 alkane isomers is performed, wherein the adsorption capacity to n-HeX is 42.4 mg/g, the adsorption capacity to 3-MP is 25.3 mg/g, and the adsorption capacity to 2,2-DMB is 22.4 mg/g, which indicates that the separation effect to C6 alkane isomers is not as good as that of example 2.
Comparative example 8
The temperature of the reductive pyrolysis reaction in step (2) was 700 deg.c, compared to example 2. (1) Add 8.33. mu.L concentrated HCl into 100ml deionized water to prepare an aqueous solution with pH 3, then add 10g glucose and mix well. And then transferring the reaction liquid to a closed environment of a reaction kettle, carrying out hydrothermal reaction for 14 h at 190 ℃, and fully cleaning the obtained solid hydrated coke with deionized water.
(2) Drying the hydrated coke, placing the dried hydrated coke in a porcelain boat, and then placing the porcelain boatIn a high temperature furnace, N 2 The reduction pyrolysis reaction is carried out for 2h after the temperature is raised to 700 ℃ at the temperature raising speed of 5 ℃/min under the protection of atmosphere, then the temperature is lowered to room temperature at the temperature lowering speed of 5 ℃/min, so that the carbon adsorbent with the micropore diameter of 5.2-6.0A (more than 45%) in the invention is obtained and is marked as a sample No. 15, and finally the steam adsorption test of C6 alkane isomer is carried out, wherein the adsorption quantity to n-HeX is 80.9 mg/g, the adsorption quantity to 3-MP is 43.5 mg/g, and the adsorption quantity to 2,2-DMB is 36.1 mg/g, which shows that the separation effect to C6 alkane isomer is not as good as that of example 2.
Comparative example 9
The temperature of the reductive pyrolysis reaction in step (2) was 1100 deg.c, compared to example 2. (1) Add 8.33. mu.L concentrated HCl into 100ml deionized water to prepare an aqueous solution with pH 3, then add 10g glucose and mix well. And then transferring the reaction liquid to a closed environment of a reaction kettle, carrying out hydrothermal reaction for 14 h at 190 ℃, and fully cleaning the obtained solid hydrated coke with deionized water.
(2) Drying the hydrated coke, placing the dried hydrated coke in a porcelain boat, and then placing the porcelain boat in a high-temperature furnace to be subjected to N 2 The reduction pyrolysis reaction is carried out for 2h after the temperature is raised to 1100 ℃ at the temperature raising speed of 5 ℃/min under the protection of atmosphere, then the temperature is lowered to room temperature at the temperature lowering speed of 5 ℃/min, so that a carbon adsorbent with the micropore diameter of 4.0-4.5A (more than 75%) in the invention is obtained and is marked as a sample No. 16, and finally the steam adsorption test of C6 alkane isomers is carried out, wherein the adsorption quantity to n-HeX is 16.1 mg/g, the adsorption quantity to 3-MP is 14.4 mg/g, and the adsorption quantity to 2,2-DMB is 13.5 mg/g, which shows that the separation effect to C6 alkane isomers is not as good as that of example 2.

Claims (2)

1. A method for preparing a microporous carbon adsorbent for separating C6 alkane isomers, comprising the steps of: (1) preparation of reaction solution: adding a catalyst into deionized water to prepare an aqueous solution with the pH value of 3-5, then adding six-membered ring monosaccharide, and uniformly stirring and mixing to obtain a reaction solution, wherein the mass ratio of the six-membered ring monosaccharide to the aqueous solution is (5-15): 100;
(2) synthesis of carbohydrate-based hydrated coke: carrying out hydrothermal reaction on the reaction liquid obtained in the step (1) at the temperature of 180-210 ℃, naturally cooling after the reaction is finished, carrying out suction filtration to retain a solid product, and then washing and drying to obtain glycosyl hydrated coke;
(3) and (3) reducing and pyrolyzing to prepare holes: carrying out programmed heating on the glycosyl hydrated coke obtained in the step (2) to 800-1000 ℃ under the protection of inert gas in a high-temperature furnace for pyrolysis carbonization reaction, and carrying out programmed cooling to room temperature to obtain a microporous carbon adsorbent, wherein the pore diameter of the microporous carbon adsorbent is 5.0-5.5 angstroms, and the C6 alkane isomers comprise n-hexane, 3-methylpentane and 2, 2-dimethylbutane; the microporous carbon adsorbent is used for separating n-hexane, 3-methylpentane and 2, 2-dimethylbutane;
in the step (1), the six-membered ring monosaccharide is more than one of glucose, fructose, galactose and mannose;
in the step (1), the catalyst is more than one of hydrochloric acid, phosphoric acid and sulfuric acid;
in the step (2), the hydrothermal reaction time is 12-18 h;
in the step (3), the inert gas is more than one of argon, nitrogen and helium;
in the step (3), the temperature rise rate of the programmed temperature rise is 5-15 ℃/min, the time of the pyrolysis carbonization reaction is 1-3h, and the temperature drop rate of the programmed temperature drop is 5-15 ℃/min.
2. A method of preparing a microporous carbon adsorbent for separating C8 xylene isomers, comprising the steps of: (1) preparing a reaction solution: adding six-membered ring monosaccharide into neutral deionized water, and uniformly stirring and mixing to obtain a reaction solution, wherein the mass ratio of the six-membered ring monosaccharide to the deionized water is (5-15) to 100;
(2) synthesis of carbohydrate-based hydrated coke: carrying out hydrothermal reaction on the reaction liquid obtained in the step (1) at the temperature of 180-210 ℃, naturally cooling after the reaction is finished, carrying out suction filtration to retain a solid product, and then washing and drying to obtain glycosyl hydrated coke;
(3) and (3) preparing holes by reduction pyrolysis: carrying out programmed heating on the glycosyl hydrated coke obtained in the step (2) to 800-1000 ℃ under the protection of inert gas in a high-temperature furnace for pyrolysis carbonization reaction, and carrying out programmed cooling to room temperature to obtain a microporous carbon adsorbent, wherein the pore diameter of the microporous carbon adsorbent is 5.8-6.8 angstrom, the C8 xylene isomers comprise p-xylene and o-xylene, and the microporous carbon adsorbent is used for separating p-xylene and o-xylene;
in the step (1), the six-membered ring monosaccharide is more than one of glucose, fructose, galactose and mannose;
in the step (2), the hydrothermal reaction time is 12-18 h;
in the step (3), the inert gas is more than one of argon, nitrogen and helium;
in the step (3), the temperature rise rate of the programmed temperature rise is 5-15 ℃/min, the time of the pyrolysis carbonization reaction is 1-3h, and the temperature drop rate of the programmed temperature drop is 5-15 ℃/min.
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