CN113461513B - Porous cobalt formate material, preparation method and application thereof, and separation method of alkane isomer mixture - Google Patents
Porous cobalt formate material, preparation method and application thereof, and separation method of alkane isomer mixture Download PDFInfo
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Abstract
The invention discloses a porous cobalt formate material, a preparation method and application thereof, and a separation method of alkane isomer mixture. Wherein the porous cobalt formate material comprises Co5The structural units are connected into a three-dimensional network structure by taking formate as a bridging ligand, and the structure comprises a diameter of about
The one-dimensional pore passage; the porous cobalt formate material is a crystal, and cobalt ions are polyhedrons and are bonded by oxygen atoms and carbon atoms. The porous cobalt formate material has good stability, and can improve the octane number of the isomerized oil component and improve the utilization efficiency of the ethylene raw material and the reforming raw material when the alkane isomer mixture is separated. The single-branched chain and double-branched chain C6 isomer can be well separated, and the complete screening of the single-branched chain and double-branched chain alkane is realized.
Description
Technical Field
The invention relates to the technical field of chemical separation, in particular to a porous cobalt formate material, a preparation method and application thereof, a separation method of alkane isomers and a separation method of naphtha.
Background
Currently, the chemical separation in industry mainly adopts a thermal driving separation technology (such as distillation), the energy consumption related to the chemical separation process accounts for about 50% of the industrial energy consumption and 10-15% of the total world energy consumption, and the process releases a large amount of carbon dioxide and other harmful gases, thereby having serious influence on the environment. Therefore, the development of an energy-saving and environment-friendly alternative technology is urgent, so that the energy consumption required in the chemical separation process in the chemical industry is reduced, the release of harmful gases is reduced, and the pollution to the environment is reduced. The high octane gasoline has excellent anti-knock performance and is an important energy substance in the current society. The alkane isomer is one of the main components in the gasoline composition, and the separation of the alkane (mainly C5 and C6) isomer is an important process indispensable for preparing high-octane gasoline in the petrochemical industry. In the petroleum refining process, C5 and C6 alkane isomers with different branching degrees are generated by catalytic isomerization reaction and are separated, a low-octane branched isomer (such as n-hexane, the octane number is 30) returns to a catalytic isomerization reactor for circulation, and a higher-octane branched isomer (such as 2, 2-dimethylbutane, the octane number is 92) can be used as a gasoline raw material. At present, the alkane isomers are generally separated by a distillation technology in industry, but because the boiling points of the alkane isomers are very close, the distillation separation process is complex, the energy consumption is huge, and the capital investment is high. In order to reduce the energy consumption required for separation and reduce the cost, a more efficient, energy-saving and environment-friendly separation technology needs to be developed urgently, and in recent years, a great deal of research is carried out in the process of separating alkane isomers with different branch degrees by an adsorption separation technology taking a solid porous material as an adsorbent and further improving the octane number of gasoline components in many countries, and the research is proved to be feasible.
The core of the adsorption separation technology lies in finding an ideal adsorbent material. At present, partial petrochemical plants adopt 5A molecular sieves to separate C5 and C6 alkane isomers, which are beneficial to replacing the traditional distillation separation process and achieve positive effects. The 5A molecular sieve has a diameter of about
The one-dimensional pore canal solid adsorbent has the pore canal diameter between the kinetic diameters of C5 and C6 straight-chain alkane and branched-chain alkane, and the relatively rigid structural characteristic of the molecular sieve, so that the 5A molecular sieve can only adsorb C5 and C6 straight-chain alkane isomers, but not all branched isomers, and therefore, the C5 and C6 branched-chain alkane isomers can be separated through molecular sieving. However, in order to further improve the average octane number of the isomers, the industry needs to recycle the single-branched paraffin to the isomerization reactor for further treatment, but the 5A molecular sieve cannot screen the single-branched and double-branched components of C5 and C6, so that the single-branched paraffin and the double-branched paraffin cannot be separated, and the octane number of the isomerized oil cannot be further improved, so that the practical value of the isomerized oil is improved. Therefore, in order to improve the performance of the adsorption separation unit and to make the adsorption separation technology widely applicable, it is highly desirable to develop a novel adsorbent material capable of efficiently separating alkane isomers.
If the application range is set to be wider, the separation of C5 and C6 isomers and the increase of the octane number of an isomerized oil component are only one purpose of naphtha separation. Naphtha separation is performed to provide an ethylene feed and a reformate feed. The traditional naphtha separation scheme is light-heavy cut by rectification technology, i.e. separating the component with more carbon atoms (C3-C6), which is the ethylene feedstock, from the component with less carbon atoms (C7-C11), which is the reforming feedstock. This rough separation method of light and heavy cuts fails to partition the resource allocation according to the characteristics of the different compositions in the naphtha. Firstly, the ethylene raw material contains partial cyclane and aromatic hydrocarbon, which affects the quality yield of triene and is easy to coke; the distillate oil above C7 contains a large amount of normal paraffin and is a high-quality ethylene raw material. Secondly, the reforming raw material contains part of normal alkane, which affects the reforming operation and the liquid quality yield. The optimized naphtha separation solution is to separate the linear and branched components and naphthenes and aromatics by utilizing 5A molecular sieve based adsorption separation. The efficiency of the separation method is remarkably improved compared with the traditional separation method. Based on the separation strategy, the UOP develops a simulated moving bed technology MaxEne technology based on a 5A molecular sieve, and a 120-million-ton/year industrial device is built in a winnowing petrochemical process. Under the same cracking conditions, such as COT (total olefin content) 85 ℃, the ethylene yield is increased from 24-25% of that of straight-run naphtha raw material to 37-38% of that of absorption naphtha raw material, and the cracking performance is obviously improved. However, this technique has several drawbacks, which have led to the failure of MaxEne technology to be popularized in large scale since 2013 production of global first-set devices: first, the fraction of normal paraffins in the naphtha is limited and the ethylene yield enhancement effect is diluted. Second, the MaxEne device did not significantly improve reforming, with only a 1.32% increase in simulation results. Thirdly, the pore volume of the 5A molecular sieve is only 0.24ml/g, the adsorption is easy to saturate, and frequent adsorption and desorption are needed. The desorption link of the simulated moving bed has high energy consumption and complex valve switching operation. Under the background, a novel solution for naphtha separation is proposed, namely, normal-single-branched paraffin in naphtha is separated from other components by using an adsorption separation technology, and then a larger high-quality ethylene raw material and a high-octane gasoline additive component are provided.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the porous cobalt formate material and the preparation method thereof are provided, and the problems of low separation efficiency of alkane isomers, high energy consumption and the like in the existing separation method are solved.
The invention aims to solve another technical problem that: provides a separation method of alkane isomers and a separation method of naphtha, and solves the problems of low separation efficiency of alkane isomers, high energy consumption and the like in the existing separation method.
In order to solve the technical problems, the invention adopts the following technical scheme:
the invention has the beneficial effects that:
the porous cobalt formate material prepared by the invention has better stability, and can improve the octane number of an isomerized oil component and improve the utilization efficiency of an ethylene raw material and a reforming raw material when an alkane isomer mixture is separated. The method has the advantages of obvious advantages in C6 isomer separation and naphtha separation, can better separate single-branched chain and double-branched chain C6 isomers, realizes the complete screening of single-branched chain and double-branched chain alkane, has better separation effect than a molecular sieve and a standard rod material ZSM-5 and Al-btttotb in MOF, and obtains naphtha with higher octane number and larger adsorption capacity.
The above features, and other features, objects, and advantages of the present invention will be described in connection with various embodiments of the present invention and the accompanying drawings. However, the disclosed illustrative embodiments are merely examples and are not intended to limit the scope of the invention.
Drawings
FIG. 1 shows Co contained in a porous cobalt formate material Co-fa according to an embodiment of the present invention5Structure of the structural unit.
FIG. 2 is a schematic diagram of the crystal structure of cobalt formate in the embodiment of the present invention.
Fig. 3 is an XRD pattern of variously treated Co-fa of examples of the present invention.
FIG. 4 is a thermogravimetric analysis of Co-fa synthesized in the examples of the present invention.
Fig. 5 is an adsorption and desorption isotherm of N2 at 77K for a porous cobalt formate material according to an embodiment of the present invention.
FIG. 6 is a multicomponent chromatography column breakthrough measurement of a separation embodiment of the invention; wherein FIG. 6(a) is a single component vapor sorption isotherm of hexane isomers in the separation examples of the present invention; FIG. 6(b) is a three component breakthrough curve for n-hexane, 3-methylpentane, 2-dimethylbutane in separation examples of the present invention.
FIG. 7 is a separation apparatus for separating naphtha in accordance with an embodiment of the present invention.
Detailed Description
The description of certain embodiments presented with reference to the figures and described below is not intended to limit the invention to these embodiments, but rather to provide any person skilled in the art to make and use the invention.
The embodiment of the invention provides a porous cobalt formate material Co-fa and a preparation method thereof, and also provides a separation method of alkane mono/double branched chain isomers such as C5, C6 and the like by using the porous cobalt formate material Co-fa, and a separation method of naphtha. The separation method of the invention improves the octane number of the isomerized oil component and improves the utilization efficiency of the ethylene raw material and the reforming raw material, namely, compared with the raw material, the main product separated by the invention has greatly reduced linear chain and single branch chain compounds, and enriched multi-branch chain and aromatic hydrocarbon; wherein, straight chain paraffin and single branch paraffin are high-quality ethylene raw materials and are used for the process for producing ethylene, and multi-branch paraffin and aromatic hydrocarbon are high-quality reforming raw materials and are used for the process for producing aromatic hydrocarbon. The porous cobalt formate material Co-fa prepared by the invention has better stability, shows remarkable advantages in C6 isomer separation and naphtha separation, and can better separate single-branched and double-branched alkanes such as C6 isomer. Adsorption experiments show that the cobalt formate porous Co-fa material only adsorbs straight-chain and single-branch paraffin, does not adsorb double-branch chain, and realizes complete screening of the single-branch and double-branch chain paraffin. The porous cobalt formate material Co-fa prepared by the invention is used for separating a plurality of components of the whole naphtha 180 from the MOF material in the prior art, and experimental results show that the material has better separation effect than the molecular sieve and the standard rod materials ZSM-5 and Al-btttotb in the MOF, and the obtained naphtha has higher octane value and larger adsorption capacity. Compared with the raw material, the main product separated out has greatly reduced linear chain and single branched chain compounds and enriched multi-branched chain and aromatic hydrocarbon. Refer specifically to the following table.
In the embodiment of the synthesis method of cobalt formate material Co-fa of the invention:
200-300 g cobalt nitrate hexahydrate and 20-100 ml formic acid are stirred and mixed evenly in a glass bottle containing 200-1000 ml DMF (N, N-dimethylformamide), placed in an oven at 80-150 ℃ for 10-50 hours, naturally cooled and filtered to obtain the product (the yield is about 80% calculated by cobalt nitrate). The scale of preparation can be enlarged or reduced in equal proportion.
In a specific example, a method for synthesizing Co-fa on a 1g scale: 2.0g of Co (NO)3)2·6H2O and 1.0mL formic acid were dissolved in 10mL DMF in a 20mL glass vial and the mixture was sonicated until a clear solution was obtained. The solution was placed in an oven maintained at 100 ℃ for 24 hours. After the reaction system was naturally cooled to room temperature, the formed pink powder was collected by filtration and dried in the air (yield: 78%).
Another specific example of a cobalt formate material Co-fa synthesis process: 200 g of cobalt nitrate hexahydrate and 50ml of formic acid are stirred and mixed uniformly in a 500 ml glass bottle containing 300 ml of DMF (N, N-dimethylformamide), placed in an oven at 100 ℃ for 24 hours, naturally cooled and filtered to obtain about 100g of a product.
The cobalt formate material has the molecular formula as follows: co3(HCOO)6Abbreviated as Co-fa, and the three-dimensional structure diagram thereof is shown in fig. 1-2. The compound structure comprises Co5Building blocks connected in a three-dimensional network by formate as a bridging ligand, based on Co2+ and formate (HCOO-), having a three-dimensional (3D) framework comprising a diameter of about
Just between the molecular size of the mono-branched and di-branched alkanes. The cobalt formate material has a crystal structure, and cobalt ions are polyhedral and are bonded by oxygen atoms and carbon atoms.
Embodiments of the invention also relate to the use of the obtained porous cobalt formate material as an adsorbent for the separation of mixtures of alkane isomers.
Embodiments of the invention further relate to the use of the obtained porous cobalt formate material as an adsorbent for the separation of naphtha.
Embodiments of the invention relate to a method for separating a mixture of alkane isomers, comprising the steps of:
the porous cobalt formate material prepared in the embodiment is used as an adsorbent, and is heated for a preset time to be activated;
adding the activated cobalt formate material into an adsorption column, wherein the bottom of the adsorption column is filled with glass wool;
introducing the alkane isomer mixture into an adsorption column for adsorption separation treatment;
the products of the adsorptive separation were collected drop by drop into a collection tube.
Preferably, the porous cobalt formate material is pressurized and sieved to 20-40 mesh particles as the adsorbent.
Wherein, the separation method is used for separating the alkane isomer mixture into the C5 and/or C6 isomer mixture, and the separation result refers to figure 6. Preferably, the separation method is a naphtha separation method.
In the above step, the heating for a predetermined time is activated by: heating the porous cobalt formate material at 100-280 ℃ for a preset time under vacuum or inert gas atmosphere for pretreatment; preferably 120-; preferably for 4 hours or more. In a specific example, the adsorbent is pressurized and sieved to 20-40 mesh granules, then activated at 150 ℃ overnight, and then loaded into an adsorption column.
The octane number of the product obtained by separation is 85.69; for each treatment of 18g of naphtha separated, the components of the naphtha product having an octane number greater than 83 were separated to be 3.26 g.
After the cobalt formate material Co-fa is synthesized, the obtained product, namely the porous cobalt formate material, is heated for a preset time at 100-280 ℃ in vacuum or in an inert gas atmosphere for pretreatment; the porous cobalt formate material obtained after cooling was used as an adsorbent. In a specific example, the pretreatment method after the synthesis of the cobalt formate material Co-fa and before the adsorption and separation experiment is heating at 150 ℃ for 4 hours or more in vacuum or in an inert gas atmosphere (nitrogen, helium, etc.).
The cobalt formate material Co-fa of the invention can realize synthesis in different scales, and is particularly suitable for enlarging preparation scale. The material was characterized by powder X-ray diffraction (PXRD) and thermogravimetric analysis (TGA), see fig. 3-5. Wherein the powder X-ray diffraction PXRD pattern of FIG. 3 is with Cu Ka radiation
Recorded on Bruker D8 Advance, data were collected at room temperature 2 θ ═ 5-40 °. The thermogravimetric analysis of fig. 4 was performed on a TGA550(TA Instruments) analyzer, heating approximately 5mg of the sample from room temperature to 600 ℃ at a ramp rate of 10 ℃/min for each run. The adsorption and desorption isotherms of fig. 5 were used to measure nitrogen adsorption at 77K on a Micromeritics 3Flex analyzer and gas phase adsorption experiments on a Quantachrome Vstar analyzer.
With particular reference to fig. 3, XRD (specifically powder X-ray diffraction PXRD) results for the cobalt formate material of the present invention show that: after the expanded preparation, the production scale of the product is expanded from 1g to 100g, the sample still keeps better quality and crystal form, and after the sample is heated and kept for one week at 150 ℃ after adsorption experiment and high-temperature treatment and is placed for 1 week under high humidity, namely 90% RH humidity, the crystal form of the sample is kept intact, and the better water and heat stability of the material is verified.
Referring to fig. 4 in particular, the thermogravimetric analysis of the synthesized cobalt formate material Co-fa of the present invention shows that: the Co-fa sample is best stable in the range of 120-180 ℃ after the solvent is removed, and can be stabilized to about 280 ℃.
FIG. 5 shows the N of the cobalt formate material Co-fa of the present invention at 77K2The specific surface area of the cobalt formate material Co-fa of the invention was calculated to be 365m by measuring the porosity of Co-fa by nitrogen adsorption at 77K on an adsorption and desorption isotherm (this adsorption experiment was tested on a Mac 3Flex adsorber)2/g。
Multicomponent chromatography column breakthrough measurement: column breakthrough measurements were performed at 30 ℃ using a laboratory scale fixed bed reactor. In the experiment, 0.3g of MOF material was packed into a quartz column (5.8 mm. times.150 mm internal diameter) and the voids were filled with silane treated glass wool. The adsorbent was purged with a stream of nitrogen (1 mL/min). The MOF powder was activated at 150 ℃ overnight, then the nitrogen flow was turned off while another dry nitrogen flow was bubbled into the mixture of hexane isomers at a rate of 1mL/min according to the following volumes (the determined volumes were tested repeatedly and calculated by GC: experiments were performed without any sample and the gas phase ratio was optimized to an equimolar mixture): 5.84mL of nHEX, 4.12mL of 3MP and 2.57mL of a ternary mixture of nHEX/3MP/22DMB for 22DMB (the partial pressure per component is 49 torr). The effluent of the column was monitored using an online GC equipped with an HP-PONA column and FID.
Referring to fig. 6, fig. 6(a) is a single component vapor adsorption isotherm of Co-fa versus alkane isomer for the cobalt formate material of the present invention, and fig. 6(b) is a multicomponent breakthrough curve of Co-fa versus alkane isomer for the cobalt formate material of the present invention. Single component adsorption experiments of alkane isomers were performed on a Quantachrome Vstar volumetric vapor adsorption analyzer. The cobalt formate material Co-fa of the present invention adsorbs similar amounts (1.5-1.7mmol/g) of linear and mono-branched paraffins, but completely excludes the di-branched isomer (FIG. 6 (a)). Thus, the cobalt formate material Co-fa of the present invention is a rigid framework capable of separating mono-and di-branched alkanes by selective molecular sieving. The adsorption behavior of Co-fa is strongly related to its pore size. As shown in fig. 6(b), further experimental validation by multicomponent column breakthrough measurement of nHEX, 3MP and 22DMB equimolar ternary mixtures, 22DMB eluted from the column in the first minute without any retention, confirming that the Co-fa material as an adsorbent did not substantially adsorb any di-branched alkanes. In contrast, 3MP and nHEX remained in the column until 36 and 51 minutes, which is consistent with their full adsorption by the adsorbent Co-fa material. Experimental results demonstrate that Co-fa materials as adsorbents are able to completely separate straight/mono-branched paraffins from their di-branched isomers by selective molecular repulsion.
The alkane isomers are the major component of naphtha, so naphtha is often used as a model mixture to evaluate the separation capacity of the adsorbent (hexane isomers are used in most cases). In order to understand the separation ability of Co-fa more deeply, the present invention was validated in a naphtha separation experiment using Co-fa as an adsorbent, and the performance thereof was compared with those of ZSM-5 and Al-bttotb (representative zeolites and MOF adsorbents for alkane separation). In the experiment for separating naphtha according to the present invention, the separation apparatus shown in FIG. 7 was used. The naphtha used in the experiment was from a medium petroleum refinery and contained C5-C12 alkanes. Naphthenes and aromatics in naphtha, see table 1 below for details of composition:
TABLE 1 detailed hydrocarbon composition analysis of naphtha
Naphtha separation test: the naphtha separation experiment was carried out using a 50ml adsorption column, i.e., a glass tube (inner diameter 15 mm. times.480 mm). The bottom of the glass tube was filled with glass wool and the Co-fa material prepared in the above example of the invention was deposited as an adsorbent on top of the glass wool. The adsorbent was first pressurized and sieved to 20-40 mesh granules, then activated at 150 ℃ overnight. Each adsorbent, 18g, was charged into a respective glass tube, and then naphtha was pumped thereinto through a sealed tube. The adsorbed products were collected drop-wise into chromatography vials (collection tubes), respectively, and then diluted with 2, 2-dimethylbutane, analyzed by the PONA analysis software by GC (Agilent 7890B) and the weights were recorded. The composition of the naphtha feed was analyzed directly by GC and PONA software. The composition of the product was determined by deleting the 2, 2-dimethylbutane peak in the GC and then analyzed using PONA software.
For the naphthenic and aromatic hydrocarbon details, see table 1 above, the initial RON value with RON is 69.41, the number of peaks is detected at 185, and the total area is detected at 99.819%; octane number MON: 63.9; a density of 0.7382; the carbon to hydrogen ratio was 5.89.
Referring to FIG. 7, an experimental set-up for naphtha separation is shown. The column was packed with a Co-fa column (18.0g), and a naphtha mixture was added to the column. The eluted product was collected in a receiver tube and subjected to GC analysis. The first drop of eluted product had a RON of 85.69, met and exceeded the industry standard for refined hexane blends (RON 83) and the experimental feed was a true naphtha mixture with 185 components (see table 1). The RON of the eluted product was maintained above 83 until a total of 3.26g of product was collected, indicating that Co-fa has the ability to effectively purify naphtha RON. A parallel experiment was performed on ZSM-5 and Al-bttotb under the same conditions. The RON values of the first drop of eluted product were 84.23 and 84.10, respectively, lower than Co-fa for ZSM-5 and Al-bttotb, respectively, with the same amount of adsorbent, see Table 2 below. More importantly, the yield of RON >83 is significantly lower for ZSM-5 and Al-btttotb than for Co-fa. The results show that the adsorption efficiency of Co-fa in naphtha separation is superior to that of ZSM-5 and Al-bttotb, mainly due to the better pore structure of Co-fa. The results of the naphtha separation experiment using cobalt formate material were compared to ZSM-5 and Al-bttotb as follows:
TABLE 2 comparison of results for ZSM-5, Al-bttotb and Co-fa separated naphthas
The experimental results in the above table show that: compared with the marker post materials ZSM-5 and Al-bttotb, the cobalt formate material provided by the invention has higher treatment efficiency and better separation effect in a full naphtha separation experiment. The octane number of the naphtha obtained by separation was 85.69, which is higher than the other two materials (84.23 and 84.10, respectively). The throughput of this material (ensuring a naphtha octane number higher than 83) was 3.26 grams, much higher than the other two materials (0.94 grams and 2.08 grams, respectively). The experimental result shows that the material has better naphtha separation effect.
The results of experiments on the separation of naphtha by cobalt formate material Co-fa of the invention prove that the alkane isomer is separated by Co-fa. The material adsorbs only linear and monobranched paraffins, completely excludes the dibranched isomers, and is effective in separating naphtha for RON purification. The cobalt formate material Co-fa is easy to synthesize, good in stability and low in cost, and has a special value for industrial separation of naphtha.
In other embodiments, the porous cobalt formate material prepared in the above embodiments is used as an adsorbent for separating the alkane isomer mixture, comprising the steps of:
heating the prepared porous cobalt formate material for a preset time to activate;
adding the activated cobalt formate material into an adsorption column, wherein the bottom of the adsorption column is filled with glass wool;
introducing the alkane isomer mixture into an adsorption column for adsorption separation treatment;
the products of the adsorptive separation were collected drop by drop into a collection tube.
Wherein the alkane isomer mixture used for separation is a C5 and/or C6 isomer mixture.
With the separation apparatus shown in fig. 7, the bottom of the glass tube of the adsorption column was filled with glass wool, and the Co-fa material prepared in the above example of the present invention was deposited as an adsorbent on top of the glass wool. The adsorbent was first pressurized and sieved to 20-40 mesh granules, then activated at 150 ℃ overnight. The alkane isomer mixture was then pumped through a sealed tube. The adsorbed products were collected drop-wise into chromatography vials (collection tubes), respectively, and then diluted with 2, 2-dimethylbutane, analyzed by the PONA analysis software by GC (Agilent 7890B) and the weights were recorded.
When the mixture of alkane isomers is the mixture of hexane isomers, double-branched chains are not adsorbed, and the complete screening of single-branched chain and double-branched chain alkane is realized.
The adsorption temperature is 0-200 deg.C, and the total pressure of the mixed gas is 0-5 bar.
The desorption temperature is 100-200 ℃, and the total pressure of the mixed gas is 0.05-1 bar.
In some embodiments, the mixture of hexane isomers, wherein the mixture of 2-5 components of a straight chain (n-hexane), a single chain (2-methylpentane, 3-methylpentane) double chain (2, 2-dimethylbutane, 2, 3-dimethylbutane) containing hexane isomers, can be in liquid phase or in vapor phase. The liquid phase form of the catalyst can contain one or more impurity components such as n-pentane, isopentane, water and the like; the gaseous phase may contain one or more of the contaminant gases n-pentane, isopentane, oxygen, nitrogen, helium, carbon dioxide, water vapor, methane, etc. The mass ratio of the hexane isomer component to the impurity component is 70-90% of the hexane isomer component, and the impurity component is 0-30%.
In one particular separation example: about 0.5g of a cobalt formate sample was packed in a quartz column having a length of 15cm and an inner diameter of 4mm, and the sample was activated at 150 ℃ for 4 hours under a nitrogen atmosphere. A stream of 1ml/min nitrogen was then passed through a bubbling gas containing nHEX, 3MP, 22DMB, with an equimolar ratio of the three-component vapors being carried by the nitrogen into the adsorption column and the gas component at the outlet being detected by on-line GC. The results are shown in FIG. 6 b. The results show that the material can effectively separate the C6 alkane isomers with different degrees of branching.
The above embodiments of the present invention, wherein:
1) single component vapor adsorption and multicomponent column breakthrough measurements showed that Co-fa selectively repels molecules and completely separates single and di-branched alkanes; the separation ability of Co-fa was further evaluated by naphtha separation tests, which showed that Co-fa separation efficiency was higher and better than the reference zeolites ZSM-5 and Al-bttotb; furthermore, the density of Co-fa is lower than that of both adsorbents, which means that its separation efficiency by volume may be higher; this is also an important parameter for industrial implementation;
2) the Co-fa has excellent thermal stability and moisture stability, and can meet the requirement of industrial separation of naphtha;
3) in the experiment, hectogram-scale Co-fa can be synthesized through one reaction, and the method for synthesizing Co-fa is easy to expand;
4) co-fa was synthesized from Co (II) salts, formic acid and DMF, without the use of elaborate organic linkers or the addition of expensive templates or modifiers, making it one of the most readily available, least expensive MOF adsorbent materials.
The present invention is described with reference to the accompanying drawings, which are incorporated in and constitute a part of this specification. Other embodiments may be utilized and derived therefrom, such that structural and logical substitutions and changes may be made without departing from the scope of this disclosure. These embodiments of the inventive subject matter may be referred to, individually or collectively, by the term "invention" merely for convenience and without intending to voluntarily limit the scope of this application to any single invention or inventive concept if more than one is disclosed. Thus, although specific embodiments have been disclosed herein, any arrangement calculated to achieve the same purpose may be substituted for the specific embodiments shown. This description is intended to cover any and all adaptations or variations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described, will be apparent to those of skill in the art upon reviewing the above description.
Claims (4)
1. A process for separating a mixture of alkane isomers, comprising:
heating for a preset time by using a porous cobalt formate material as an adsorbent to activate;
adding the activated cobalt formate material into an adsorption column, wherein the bottom of the adsorption column is filled with glass wool;
introducing the alkane isomer mixture into an adsorption column for adsorption separation treatment;
collecting the products of the adsorption separation into a collecting pipe drop by drop;
wherein the porous cobalt formate material comprises Co5The structural units of (a) are connected into a three-dimensional network structure by taking formate as a bridging ligand, and the structure comprises a one-dimensional pore channel with the diameter of about 5.5A; the porous cobalt formate material is a crystal, and cobalt ions are polyhedrons and are bonded by oxygen atoms and carbon atoms;
the porous cobalt formate material is used as an adsorbent, only straight-chain and single-branch paraffin is adsorbed, and double-branch paraffin is not adsorbed, so that complete screening of the single-branch and double-branch paraffin is realized;
the alkane isomer mixture is a C6 isomer mixture; or the alkane isomer mixture is naphtha;
the formula for synthesizing the porous cobalt formate material is as follows:
2.0 g Co(NO3)2•6H2o: 1.0ml of formic acid: 10ml of DMF; alternatively, the first and second liquid crystal display panels may be,
200 grams of cobalt nitrate hexahydrate: 50ml of formic acid: 300 ml of DMF;
the preparation method of the porous cobalt formate material comprises the following steps:
2.0 g Co(NO3)2•6H2dissolving O and 1.0ml of formic acid in 10ml of DMF, and uniformly mixing to obtain a clear solution; heating the solution at 100 ℃ for 24 hours; cooling to room temperature, collecting the generated pink powder by filtration, and drying to obtain a 1 g-scale product, namely the porous cobalt formate material; the using amount proportion of reactants is enlarged or reduced in equal proportion according to the preparation scale;
or, the preparation method of the porous cobalt formate material comprises the following steps:
uniformly mixing reactants according to the formula proportion of 200 g of cobalt nitrate hexahydrate, 50ml of formic acid and 300 ml of DMF to obtain a clear solution; heating the solution at 100 ℃ for 24 hours; cooling and filtering to obtain about 100g of a product porous cobalt formate material; the amount of reactants is scaled up or down according to the scale of preparation.
2. The separation method according to claim 1,
the porous cobalt formate material keeps a crystal form and has stability below 280 ℃;
the specific surface area of the cobalt formate material is 365m2/g；
The porous cobalt formate material is used as an adsorbent for separating naphtha, and the octane number of a naphtha product obtained by separation is more than 83.
3. The separation method according to claim 1,
the cobalt formate material is used as an adsorbent for naphtha separation:
for each treatment of 18g of naphtha separated, the components of the naphtha product having an octane number greater than 83 were separated to be 3.26 g.
4. The separation process according to any one of claims 1 to 3,
the heating for the preset time is activated as follows: heating the porous cobalt formate material at 100-280 ℃ for a preset time under vacuum or inert gas atmosphere for pretreatment;
the porous cobalt formate material was pressurized and sieved to 20-40 mesh particles prior to activation.
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