CN115304778B - Porous coordination polymer, preparation method and application in ethylene separation - Google Patents
Porous coordination polymer, preparation method and application in ethylene separation Download PDFInfo
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Abstract
The invention provides a porous coordination polymer and a preparation method thereofAnd its use in ethylene separation, the present invention uses a post-synthesis process of a boiling alkaline solution to convert crystals to produce crystals (i.e., NTU-67) having traps and flow channels of acetylene (C) 2 H 2 ) And carbon dioxide (CO) 2 ) The isopolar molecules provide efficient shape and size dependent sieving pathways, while the traps contained in adjacent channels facilitate efficient molecular capture. The trefoil array of nanospaces enables the crystals to be grown from C 2 H 2 /CO 2 /C 2 H 4 C is separated from the mixture with high separation efficiency 2 H 4 . In addition, the material has excellent chemical and aqueous solution stability characteristics.
Description
Technical Field
The invention provides a porous coordination polymer, a preparation method and application in ethylene separation, belonging to the technical field of coordination polymers and gas separation.
Background
Ethylene (C) 2 H 4 ) Is typically a light hydrocarbon and is also related to oxidative coupling of methane for C 2 H 4 And (5) reporting the production. However, in addition to generating C 2 H 4 In addition, acetylene (C) is formed 2 H 2 ) And carbon dioxide (CO) 2 ) And the like. Thus, two kinds of impurities C are selectively removed 2 H 2 And CO 2 For the slave C 2 H 2 /CO 2 /C 2 H 4 Recovery of Polymer grade C from ternary mixtures 2 H 4 Is of great importance because of C 2 H 2 Will be at C 2 H 4 Poisoning the catalyst during polymerization, and CO 2 The quality of Polyethylene (PE) is reduced. Current industrial separation technologies mainly employ multi-step purification processes involving CO 2 Chemisorption of (with huge waste liquid) and C 2 H 2 The catalytic hydrogenation of (involving the use of noble metal catalysts at high pressure/temperature) is energy intensive.
Physical adsorption provides a potential solution for high-efficiency and energy-saving separation. It is noteworthy that although binary mixtures (including C) can be achieved by using adsorbents under ambient conditions 2 H 2 /C 2 H 4 And C 2 H 2 /CO 2 Mixture) but from containing CO 2 And C 2 H 2 Purification of ternary mixture of (C) 2 H 4 It remains a great challenge because of the lack of ability to selectively capture CO 2 And C 2 H 2 To exclude C 2 H 4 The physical adsorbent of (1). One possible solution is to package two or more physical adsorbents using a synergistic adsorbent separation technology (SSST). However, it was sought to exclude C from ternary mixtures using a single adsorbent 2 H 4 Is considered to be optimal. Furthermore, it is also worth noting the practical problem of determining the order and weight ratio of the arrangement of the corresponding adsorbents for SSST.
Porous Coordination Polymers (PCPs) are novel crystalline materials assembled from organic ligands and inorganic nodes, have controllable nanopore chemistry, and can be used in gas separation applications. Generally, in the sieving mechanism, the emphasis is on using rigid PCP with narrow pore size to achieve gas size differential separation, with smaller size molecules adsorbed and larger size molecules excluded. However, in such a suitable porous system, the adsorption equilibrium is confounded by competing host-guest interactions of two or more impurities, especially in the series of one-dimensional channels. PCP with skeletal kinetics is considered another platform for multi-component separations because the corresponding response allows the material to distinguish minor differences within the multi-component but requires precise control of external conditions (e.g., specific temperature, pressure, and gas ratio) and once open, further co-adsorption may occur. Kinetic-related molecular diffusion to achieve gas separation by creating localized motion sites in the crystal has also been proposed. However, when the number of components in the gas mixture is increased to three or more, the desired separation objective is often not achieved.
Disclosure of Invention
The invention aims to solve the problem that the prior art lacks the C 2 H 4 、CO 2 And C 2 H 2 Ternary mixture purification C of 2 H 4 Has succeeded in producing a novel crystal (NTU-67) containing a molecular trap and a flow channel and capable of removing CO from the crystal 2 And C 2 H 2 In the ternary mixture of (A) and (B) 2 H 4 Even in the presence of moisture, the separation can be achieved at high temperatures and wide gas ratios. Flow channels with optimized window aperture can dynamically distinguish linear CO 2 Or C 2 H 2 Molecule and butterfly C 2 H 4 The molecule, while a trap in the other channel can effectively trap the linear molecule. In addition, the crystal has excellent stability under hot acid and alkali conditions.
A porous coordination polymer having the molecular formula [ Cu (L1) ] 2 SiF 6 ]xSolvent; wherein Solvent refers to the bound Solvent molecules, x is the number of bound Solvent molecules, and L1 is 1,4-bis (imidazol-1-yl) benzene; in the porous coordination polymer structure, each ligand and SiF 6 2- Respectively with Cu 2+ Connection of each Cu 2+ From two SiFs 6 2- Two F atoms of the ion are bridged with four imidazole N atoms of four ligands; and in the coordination polymer framework, triangular channels A with coplanarity and triangular channels B with a zigzag shape are contained.
The triangular passage A is provided with
The size of the space; the narrowest aperture of the triangular passage B
The preparation method of the porous coordination polymer comprises the following steps:
and 2, washing the product, and activating to obtain the porous coordination polymer.
The alkali solution is an aqueous solution with a pH value of 11-13.
The pH value of the alkaline solvent is adjusted by NaOH or KOH.
The dosage ratio of NTU-65 crystal to alkali solution in the step 1 is 50-120mg.
The temperature of the treatment process in the step 1 is 353-393K, and the time is 5-10d.
The activation process is to place the sample in ethanol for solvent exchange, heat treat and heat treat under vacuum condition to obtain activated crystal.
The time for solvent exchange with ethanol is 1-5 days; the temperature of the heating treatment is 50-70 ℃, and the time is 1-20h; the heat treatment temperature under vacuum condition is 100-150 deg.C, and the treatment time is 10-30h.
The porous coordination polymer is used in the preparation of the polymer 2 H 2 /CO 2 /C 2 H 4 Separation of C from ternary mixed gas 2 H 4 The use of (1).
In the application, the method also comprises the following steps: passing the mixed gas through a porous coordination polymer to form C 2 H 4 Compared with C 2 H 2 And CO 2 C to be preferentially passed and released 2 H 4 And (4) collecting.
In the mixed gas, C 2 H 2 /CO 2 /C 2 H 4 0.1-5:1-20:65-95; the separation process temperature is 273-373K.
Advantageous effects
The invention successfully prepares a novel crystal (NTU-67) containing a three-leaf trap and a flow channel and can obtain a crystal containing CO 2 And C 2 H 2 In ternary mixture of (A) and (B) 2 H 4 In which molecular traps and tortuous channels in the molecular structure can trap linear gas molecules CO 2 And C 2 H 2 Simultaneously make C 2 H 4 Therefore, the method has better separation efficiency.
Drawings
FIG. 1 is a schematic diagram of a trap and a channel crystal, which shows the dynamic sieving and molecular trap related to the shape and size of the porous coordination polymer in the patent, and can realize high-efficiency purification of C in ternary mixture 2 H 4 。
Fig. 2 is a photograph of the crystal before and after activation.
FIG. 3 is a block diagram of NTU-67, wherein (a) asymmetric unit; (b) ligand attachment; (c) SiF 6 2- Connecting; (d) Cu 2+ Connecting; (e) Involving SiF 6 2- A peripheral hydrogen bond; (f) NTU-67 along the a-axis and (g) c-axis, with a pitch of
The helical chain of (1).
FIG. 4 is a crystalline three-dimensional framework structure in which Cu 2+ Self-connecting square grid sheet formed between cation and organic linker by SiF 6 2- The ions are further connected.
FIG. 5 is the structure of NTU-67: (a-B) a schematic of the route by which NTU-67 synthesizes NTU-67 from NTU-65 and a stacking diagram of the NTU-67 framework, in which there are two triangular channels A and B; (c) Cross-sectional view of a Connolly surface in a structure in which molecular traps and nanochannels are connected in a trefoil array. Radius of the probe is
(d) View of the interior space in channel a. The open area is composed of three SiFs 6 2- Molecular traps for ions. The elliptical region is almost separated by three imidazole rings at both ends; (e-f) slice views of corresponding locations in channel a; (h) view of the interior space in channel B; (i-j) slice views of the corresponding locations in channel B.
FIG. 6 shows the structural differences between NTU-65 (a, c) and NTU-67 (b, d).
FIG. 7 is a simplified network of NTU-65 (a) and NTU-67 (b). The topology of NTU-67 is mmo, which is different from that of NTU-65 (pcu).
FIG. 8 is a PXRD for NTU-67 synthesis and activation samples.
FIG. 9 shows the LeBali analysis of PXRD of NTU-67 after synthesis
FIG. 10 is NTU-67 in CO 2 /C 2 H 4 Structural view under atmosphere: (a) Along the c-axis
(b) Along the a-axis>
FIG. 11 is NTU-67 vs. CO at 298K 2 、C 2 H 2 And C 2 H 4 Adsorption kinetics curve of (a).
FIG. 12 is a graph of NTU-67 vs CO at 298K 2 、C 2 H 2 And C 2 H 4 Adsorption kinetics curve of (1). The values of their single gas adsorption isotherms were measured at 50kPa and the single point adsorption equilibrium between pressure and time changes was recorded. The slope is obtained from a linear fit of the kinetic curve. The equilibration time was 7200s.
FIG. 13 is a graph of SIFSIX-2-Cu-i vs CO at 298K 2 、C 2 H 2 And C 2 H 4 Adsorption kinetics curve of (a).
FIG. 14 is a sequential control purge test: (a) NTU-67@ C 2 H 2 -CO 2 Purge with helium only; (b) NTU-67@ C 2 H 2 -CO 2 From helium and C 2 H 4 Purging; (c) NTU-67@ C 2 H 4 Purge with helium only; (d) NTU-67@ C 2 H 4 From helium and C 2 H 2 /CO 2 And (5) mixing and purging. The sample weight of NTU-67 after activation was 0.6532g. C 2 H 2 /CO 2 (1/1,v/v) and C 2 H 4 The gas flow rate of (2) and 1mL/min, respectively, whereas the gas flow rate of helium is 5mL/min and the pressure is 1.1bar.
FIG. 15 shows the results of the isolation test, binary mixture C of (a) NTU-67 (1.2049 g) 2 H 2 /C 2 H 4 (1/99, v/v) results; (b) CO of NTU-67 2 /C 2 H 4 Binary mixture (50/50, v/v) results; (C-e) ternary mixture of NTU-67 (C) 2 H 2 /CO 2 /C 2 H 4 1/9/90, v/v/v) results; (f-i) are SIFSIX-1-Cu (0.8745 g), activated carbon (0.9798 g), zeolite 5A (1.738 g) and SIFSIX-2-Cu-i (0.5210 g) ternary mixtures (C) 2 H 2 /CO 2 /C 2 H 4 1/9/90, v/v/v). All ofIn the experiment, the pressure is 1bar, the gas velocity is 5mL/min, the temperature is 298K, the change temperature in d is 343K, and the change velocity in f is 2mL/min.
FIG. 16 shows the result of NTU-65 (0.9154 g) at 298K vs C 2 H 2 /CO 2 /C 2 H 4 (1/9/90, v/v/v). The pressure was 1bar and the gas flow rate was 5mL min-1.
FIG. 17 shows the result of NTU-67 (1.2049 g) at 298K vs C 2 H 2 /CO 2 /C 2 H 4 (0.96/4.04/95.00, v/v/v). The pressure is 1bar, the gas flow rate is 5mL/min -1 。
FIG. 18 is a SIFIX-1-Cu single gas adsorption isotherm.
Fig. 19 is a UTSA-200a single gas adsorption isotherm.
Fig. 20 is a UTSA-300a single gas adsorption isotherm.
Figure 21 is an activated carbon single gas adsorption isotherm.
Figure 22 is a 5A molecular sieve single gas adsorption isotherm.
FIG. 23 is a SIFIX-2-Cu-i single gas adsorption isotherm.
FIG. 24 is a SIFSIX-17-Ni single gas adsorption isotherm.
Detailed Description
Synthesis of NTU-67
The NTU-65 crystal used in this patent can be referred to the literature (Tuning Gate-Opening of a Flexible Metal-Organic Framework for Ternar Gas sizing Separation [ J)]The preparation process of Angewandte Chemie,2020, 59 (22756-22762)). The method comprises the following steps: 1mL of a DMF solution containing L1 (1,4-bis (imidazol-1-yl) benzene) (0.11 g, 0.50 mmol) was slowly added to 0.5mL of a solution containing CuSiF 6 ·6H 2 O (4 mg, 0.014mmol) in water, the intermediate layer is DMF/MeOH/H 2 Crystals of NTU-65 were obtained after one week of O (3/3/0.5, 1.5 mL) reaction.
The synthesis steps of NTU-67 are as follows: the fully activated NTU-65 crystals (100 mg) were soaked in an aqueous alkaline solution (8 mL, adjusted with NaOH) in a glass vial (20 mL) and then heated for one week. After cooling, the mixture is washed with ethanol/water (volume ratio 1/1) to obtain purple massive crystals.
Activation of crystals: the activation method of solvent exchange NTU-67 crystal is to soak the synthetic sample in absolute ethanol for 3 days to remove the non-volatile solvent, and to exchange the sample with fresh ethanol every 8 hours. Fully activated samples were obtained by heating the solvent exchanged sample at 60 ℃ for 6h, followed by heating at 120 ℃ under high vacuum for 20 h.
Prior to gas adsorption testing, the initial NTU-67 sample was tightly packed in a stainless steel column (
L =12 cm). The sample column was then activated for 12h under vacuum at 393K and then purged with a helium gas stream to remove impurities, requiring the activation process to be repeated before each experiment.
Elemental analysis characterization
The activated NTU-67[ 2 ], [ C ] 24 H 20 CuF 6 N 8 Si]Elemental analysis of (2): calculated C,46.04; h,3.22; n,17.90; experimental value C, 46.23; h,3.07; n,18.06 percent.
Characterization of crystal morphology
The photographs of the crystals before and after activation are shown in FIG. 2. The crystal of NTU-65 in the alkaline aqueous solution at 100 ℃ is converted into a crystal of polyhedron shape (NTU-67). This is mainly to consider that the crystal transformation in aqueous solution may tune the nanopore according to the size of the water template. Crystal transformation in aqueous alkaline solutions may also reduce the energy state of the resulting backbone, allowing the assembly of chemically stable structures. Direct synthesis of NTU-67 by adjusting conditions and other solvent-triggered crystal transformations has also been attempted, but none of these attempts have been successful.
Crystal analysis
The fully activated NTU-67 crystals were packed in glass tubes and pressed at 298K and 1bar with C, respectively 2 H 2 、C 2 H 4 、 CO 2 And CO 2 /C 2 H 4 (2, 8,v/v) and the tube was then sealed with hot candle under the corresponding atmosphere. Single crystal X-ray diffraction characterization was performed on a Bruker Smart Apex CCD diffractometer at 298K. KnotThe structure was solved by a direct method, for synthesized NTU-67, using PLATON/SQUEEZE (A.L. Spek, PLATON, A Multipurpose crystalline Tool (untrecht University, 2001); b) P.Vanderplus, A.L. Spek, acta crystalline. Sec.A. A1990,46, 194.) to calculate the diffraction contribution of the solvent molecules, resulting in a set of solventless diffraction intensities, and then using the resulting data to obtain a refined structure.
Crystal analysis showed that NTU-67 crystallized in the R32 space group, where the asymmetric unit included half of the Cu 2+ Cationic, half-size SiF6 2- An anion and an L1 ligand having the same formula as NTU-65 ([ Cu (L1)) 2 SiF 6 ]X solvent) (table 1). In NTU-67, each ligand and SiF6 2- The anions being bound by two Cu atoms, each Cu 2+ The cation is formed by two SiF6 2- Two F atoms of the ion are bridged with four Imidazole (IM) N atoms of four ligands. SiF 6 2- Two F atoms in ion para position are connected with two adjacent Cu 2+ Octahedral coordination of the ions creates inorganic helical chains along the c-axis. Therefore, in Cu 2+ The self-associating square lattice sheets formed between the cations and the organic linkers are further connected by the chains to create a three-dimensional (3D) framework (fig. 4). Further topological analysis showed that NTU-67 was double-linking the ligand to SiF6 2- After ions are contained in 6 times of connected Cu nodes, a mmo network is formed, and a group of new porous isomers are formed with NTU-65 (pcu structure) (a-b regions of figure 5 and figures 6 and 7). FIG. 6 shows the structural differences between NTU-65 (a, c) and NTU-67 (b, d): siF 6 2- Two F atoms in ortho position coordinate to Cu ion in NTU-65, while SiF 6 2- Two of F in para position - The atom coordinates to the Cu ion in NTU-67. The deformation angles of imidazole and benzene ring in NTU-65 were 12.27 ° and 15.06 °, respectively, and the two values in NTU-67 were reduced to 5.42 ° and 4.11 °, respectively. In this new frame structure there are triangular channels (a and B) common to both faces. The narrowest hole is
Channel B of can be regarded as CO 2 /C 2 H 4 And C 2 H 2 /C 2 H 4 The separated diffusion promotes kinetically selective nanochannels. From three SiF6 in channel A 2- Anion and six IMs modulated->
Limited space, which can be considered as a molecular trap for preferential adsorption. In addition, the arrangement of molecular traps and nanochannels is trilobal and interconnected (fig. 5). The structure and phase purity of the synthesized and activated NTU-67 was confirmed by powder X-ray diffraction (PXRD) analysis and roebel analysis (FIGS. 8-9).
TABLE 1 NTU-67, and Crystal and Structure data after gas Loading
Crystal structure in gas mixture
To investigate the competitive binding of gases, the exposure to CO was analyzed 2 /C 2 H 4 Crystal structure of NTU-67 under (2/8,v/v, 1bar, 298K) atmosphere. Indistinguishable C by X-ray diffraction measurements 2 H 2 /C 2 H 4 A mixture of (a). A CO interacting with the F atom is found in the molecular trap of channel A 2 Molecule, and a unique one-dimensional (1D) CO is found in channel B 2 And C 2 H 4 Array (fig. 10). This observation indicates that CO is present even at relatively low partial pressures 2 And is also more readily adsorbed by molecular traps. In addition, the one-dimensional (1D) molecular array confirmed that channel B provided an efficient flow channel. This is a rare observation of competitive binding of gases by crystallographic studies at the molecular level.
NTU-67 to CO 2 、C 2 H 2 And C 2 H 4 Study of adsorption Process
To verify the synergy of the nanospace, the adsorption kinetics of each gas of NTU-67 at 298K was evaluated (fig. 11-13). Pressure change indicates CO 2 Has an adsorption rate much higher than that of C 2 H 4 。
CO 2 /C 2 H 4 Has a kinetic selectivity of 5.26,C 2 H 2 /C 2 H 4 The kinetic selectivity of (a) was 3.86. For comparison, the adsorption kinetics of the gas in SIFSIX-2-Cu-i, which had the same SiF6, were also collected 2– Ions and square window apertures. CO in SIFSIX-2-Cu-i 2 /C 2 H 4 (3.50) and C 2 H 2 /C 2 H 4 The kinetic selectivity of (2.49) was lower than that of NTU-67. The advantages of NTU-67 can be achieved by enhancing CO 2 And C 2 H 2 Diffusion and trefoil array of molecular capture to rationalize. As described above, nanochannels allow CO 2 And C 2 H 2 Flow along channel B is smooth and molecular traps provide effective trapping sites for it, resulting in current dynamic sieving in NTU-67. In contrast, since the adsorption sites and flow paths in SIFSIX-2-Cu-i exist in the same 1D channel, the adsorbed molecules occupy limited space in the 1D channel, making subsequent molecules difficult to pass through.
Based on different trap-object interactions and size effects, the effect of molecular traps under dynamic conditions was explored. A sequential controlled air-blowing test was performed on NTU-67. At 298K, C saturated in adsorption 2 H 2 /CO 2 Mixture (NTU-67 @ C) 2 H 2 -CO 2 ) Swept by a helium gas stream to remove loosely adsorbed components. After heating the system to 393K, C was detected 2 H 2 And CO 2 Release (area a of fig. 14). Changing helium scavenging to C 2 H 4 After that, C in the bed 2 H 2 And CO 2 Negligible (area b of fig. 14). A helium purge was further performed until no more gas was detected. C is detected during the final heating phase 2 H 2 And CO 2 But not detectC 2 H 4 Thus confirming the comparison with C 2 H 4 C can be preferentially captured by a molecular trap in NTU-67 2 H 2 And CO 2 In a similar manner to that of. In fact, NTU-67@ C 2 H 4 In which only a small amount of C is adsorbed 2 H 4 This may also be by C 2 H 2 /CO 2 The mixture was replaced (region c-d of FIG. 14).
Separation test of binary raw material gas
The separation ability of NTU-67 to a gas mixture was evaluated. Using C 2 H 2 /C 2 H 4 Feed gas of mixture (5 mL/min,1/99, v/v), polymer grade C 2 H 4 (>99.95%) eluted at 8.1 minutes, and C 2 H 2 Captured before the critical point of 41.4 minutes (region a of fig. 15). When the gas feed becomes CO 2 /C 2 H 4 When the gas mixture was mixed (5 mL/min,50/50, v/v) (region b in FIG. 15), pure C was also detected first 2 H 4 And CO 2 Is absorbed. CO 2 2 Has a retention time of 37.4 minutes, confirmed from CO 2 /C 2 H 4 Selective CO capture in mixtures 2 Excellent ability of the resin.
C 2 H 2 /CO 2 /C 2 H 4 Ternary raw material gas separation test
The proportion of the tertiary gas is adjusted by adjusting the gas flow from two tanks, one being C 2 H 2 /C 2 H 4 (1/99) and the other comprising pure CO 2 . The total gas flow rate of the ternary mixture was 5mL/min. When CO is present 2 The gas flow rate of (a) is 0.2 mL/min, and C 2 H 2 /C 2 H 4 At a gas flow rate of 4.8mL/min, we obtained a ternary C ratio of 95.00/0.96/4.04 2 H 4 /C 2 H 2 /CO 2 And (3) mixing. When CO is present 2 The gas flow rate of (2) is 1.75mL/min, and C 2 H 2 /C 2 H 4 At a gas flow rate of 3.25mL/min, a ternary mixture in the ratio of 65.00/0.65/34.34 was obtained.
Filling a sample in a stainless steel column, sending ternary mixed gas, detecting the flowing gas by adopting gas chromatography, and evaluating the separation characteristics of the three gases.
With C 2 H 2 /CO 2 /C 2 H 4 The ternary feed gas (5 ml/min,1/9/90, v/v/v,1 bar) was subjected to separation experiments, which is a common industrial mixture for oxidative coupling of methane. Likewise, NTU-67 simultaneously selectively captures C 2 H 2 And CO 2 And C is generated at the column outlet within 27.0min at 298K 2 H 4 (>99.95%) (c of fig. 15). C 2 H 2 、CO 2 And C 2 H 4 The staged release of (A) indicated that NTU-67 could well separate each component. Depending on the sample weight and gas flow rate, 1g NTU-67 can yield 121.5mL (STP) of pure C from the ternary mixture 2 H 4 . Notably, recovered C 2 H 4 The separation performance at 263K was about 5 times higher than NTU-65 (25.4 mL (STP)/g) due to the lack of para-CO 2 The selective opening mechanism of (1), NTU-65, has no separation ability at 298K (FIG. 16). In sharp contrast, NTU-67 showed promise in purifying C from these ternary mixtures even at elevated temperatures (343 and 363K) 2 H 4 (d of FIG. 15).
Industrially, the gas ratio of the ternary mixture is always different, and therefore, by adjusting the CO 2 Percent (typically from 4% to 35%) and retention C 2 H 2 /C 2 H 4 The ratio 1/99 was explored to change the separation performance of the mixture. It can be seen that by using two boundary mixtures, namely C 2 H 4 /C 2 H 2 /CO 2 Mixtures (95.00/0.96/4.04 and 65.00/0.65/34.34, v/v/v), high purity C can be collected from the outlet of the NTU-67 bed 2 H 4 (e of FIG. 15 and FIG. 17). NTU-67 is effective at capturing a lower percentage of CO 2 . When CO is present 2 When the content is increased to 34.34 percent, CO 2 And C 2 H 2 Both gases are released almost simultaneously. With C 2 H 4 The release efficiency of NTU-67 was kept at 48.8mL (STP)/g.
To determine NTU-67 vs C 2 H 4 Unique ability of purification, separation studies were performed on a set of benchmark PCPs (SIFIX-1-Cu, SIFIX-2-Cu-i, UTSA-200UTSA-300 and SIFIX-17-Ni, activated carbon and 5A zeolite (FIGS. 18-24) 2 H 2 、CO 2 And C 2 H 4 Type I adsorption isotherm of (1), C in UTSA-300a 2 H 2 Except for type IV adsorption isotherms. C of three PCPs UTSA-200a, UTSA-300a and SIFIX-1-Cu 2 H 2 Relatively high absorption, but its CO 2 And C 2 H 4 The adsorption behavior is very similar. Except that activated carbon is paired with C 2 H 2 And C 2 H 4 Very close to absorption of CO, slightly higher than 2 . In contrast, with C 2 H 2 And CO 2 In contrast, the 5A zeolite exhibited a relatively high C in the low pressure zone 2 H 4 Absorb, but C 2 H 4 The adsorption amount of (A) gradually decreases with the increase of the pressure, resulting in CO 2 And C 2 H 2 Two intersections of isotherms. Furthermore, SIFSIX-2-Cu-i and SIFSIX-17-Ni showed the ratio C 2 H 4 Higher C 2 H 2 And CO 2 And (4) absorbing. These adsorption isotherms reflect the opportunity for SIFSIX-2-Cu-i and SIFSIX-17-Ni to recover pure C 2 H 4 . Further studies showed that all three gases flowed out of the activated carbon almost simultaneously, while the SIFSIX-1-Cu packed sample bed retained C 2 H 2 The time of (a) is almost 40 minutes. The separation time of the 5A zeolite is negligible. Furthermore, in SIFSIX-2-Cu-i sample bed, C 2 H 4 、CO 2 And C 2 H 2 Detected at 12.7, 24.2 and 276.6min, respectively. Similar results were also observed in SIFSIX-17-Ni (f-i region of FIG. 15 and FIGS. 22-24). This means that the polymer grade C in SIFSIX-2-Cu-i and SISIX-17-Ni 2 H 4 (>99.95%) could harvest in 11.5 minutes and 12.1 minutes, which is much shorter than NTU-67 (27.0 minutes). Considering a single gas isotherm and a stronger host-C 2 H 2 By interaction, we can reasonably infer SIFX-2-Cu-i andthe ability to separate SIFIX-17-Ni is based on thermodynamics, which makes them free of C 2 H 2 In a binary mixture of 2 H 4 Rather than from C 2 H 2 /CO 2 /C 2 H 4 In the ternary mixture of (2) to separate C 2 H 4 。
Claims (9)
1. A porous coordination polymer having the molecular formula [ Cu (L1) ] 2 SiF 6 ]·xA Solvent; wherein Solvent refers to the bound Solvent molecules, x is the number of bound Solvent molecules, and L1 is 1,4-bis (imidazol-1-yl) benzene; characterized in that each ligand and SiF in the porous coordination polymer structure 6 2- Is through Cu 2+ Connection of each Cu 2+ From two SiF6 2- Two F atoms of the ion are bridged with four imidazole N atoms of four ligands; and in the coordination polymer framework, triangular channels A with coplanarity and triangular channels B with zigzag shape are contained;
the triangular channel A has 4.2' 7.4A 3 The size of the space; and the narrowest pore diameter of the triangular channel B is 3.4 ANG.
2. The method of preparing a porous coordination polymer according to claim 1, comprising the steps of:
step 1, obtaining NTU-65 crystals, and treating the crystals in an alkali solution;
and 2, washing the product obtained in the step 1, and activating to obtain the porous coordination polymer.
3. The method of claim 2, wherein the alkali solution is an aqueous solution having a pH of 11 to 13.
4. The method of claim 3, wherein the pH of the alkali solution is adjusted by NaOH or KOH.
5. The method for preparing porous coordination polymer according to claim 2, characterized in that the dosage ratio of NTU-65 crystal to alkaline solution in step 1 is 50-120mg:5-20mL.
6. The method of claim 2, wherein the step 1 is carried out at a temperature of 353-393K and for a time of 5-10d.
7. The method for preparing the porous coordination polymer according to claim 2, wherein the activation is to place the sample in ethanol for solvent exchange, heat-treat the sample, and then heat-treat the sample under vacuum conditions to obtain activated crystals; the time for solvent exchange in ethanol is 1-5d; the temperature of the heating treatment is 50-70 ℃, and the time is 1-20h; the temperature of the heat treatment under the vacuum condition is 100-150 ℃, and the treatment time is 10-30h.
8. The porous coordination polymer of claim 1 in the reaction from C 2 H 2 /CO 2 /C 2 H 4 Separation of C from ternary mixed gas 2 H 4 The use of (1).
9. The use according to claim 8, further comprising the steps of: passing the ternary gas mixture through a porous coordination polymer to form C 2 H 4 Compared with C 2 H 2 And CO 2 C to be preferentially passed and released 2 H 4 Collecting; in the mixed gas, C 2 H 2 /CO 2 /C 2 H 4 0.1-5:1-20:65-95 parts; the separation process temperature is 273-373K.
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| WO2013112792A1 (en) * | 2012-01-25 | 2013-08-01 | Dow Corning Corporation | Metal silicon framework composition useful for gas separations |
| CN107022087A (en) * | 2017-03-08 | 2017-08-08 | 南京工业大学 | A kind of high hole permeability coordination polymer, preparation method, using and its film preparation method |
| CN114849649A (en) * | 2022-05-05 | 2022-08-05 | 浙江师范大学 | Ion hybrid porous material with zsd topological structure and preparation method and application thereof |
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| CN107022087A (en) * | 2017-03-08 | 2017-08-08 | 南京工业大学 | A kind of high hole permeability coordination polymer, preparation method, using and its film preparation method |
| CN114849649A (en) * | 2022-05-05 | 2022-08-05 | 浙江师范大学 | Ion hybrid porous material with zsd topological structure and preparation method and application thereof |
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