CN114768873A

CN114768873A - Application of Fe-based metal organic framework material as combustion catalyst

Info

Publication number: CN114768873A
Application number: CN202210391462.5A
Authority: CN
Inventors: 李明静; 武文杰; 谢钢
Original assignee: Northwest University
Current assignee: Northwest University
Priority date: 2022-04-15
Filing date: 2022-04-15
Publication date: 2022-07-22

Abstract

The invention discloses a Fe-based metal organic framework material MIL-101(Fe) -R% of the Fe-based metal organic framework material is MIL-101(Fe) -R%, which is prepared by FeCl₃·6H₂O, terephthalic acid and 2-amino terephthalic acid are synthesized in N, N' -dimethylformamide solvent, whereinRIs the mol ratio of the 2-amino terephthalic acid ligand to the total ligand,R0% to 48%. The invention can control part of heat-sensitive ligand NH by accurately controlling pyrolysis temperature₂-BDC removal to obtain HP-MIL-101(Fe) material with controllable concentration of nano active iron oxide, and Fe₂O₃Uniformly dispersed in MOFs pore canal and can be used as promotionA combustion catalyst in which the propellant component is thermally decomposed.

Description

Application of Fe-based metal organic framework material as combustion catalyst

Technical Field

The invention relates to an application of Fe-based metal organic framework material as a combustion catalyst in a solid propellant, belonging to the technical field of combustion catalysis.

Background

Solid propellants are widely used in the rocket launch and aerospace fields, and are one of the most important sources of propulsion energy. With the rapid development of aerospace technology and the increasingly fierce competition of various countries, higher requirements are put forward on the performance of the solid propellant. The development of composite solid propellants with high energy characteristics, long range and high viability has become a mainstream research direction. The composite solid propellant mainly comprises functional components such as fuel, oxidant and the like. Ammonium Perchlorate (AP) and hexogen (RDX) are the most widely used energy-containing components in current composite solid propellants. One common method for improving their combustion efficiency and performance is to add a combustion catalyst.

The combustion catalyst has the characteristics of widening the combustion speed range of the solid propellant, reducing the pressure index and the like, and is widely researched, wherein the nanometer combustion catalyst is an important research direction in the field of combustion catalysis due to the unique small-size effect. The nanometer material can realize defect engineering regulation and control through various ways such as size, doping and the like, and obviously enhance the catalytic activity of the nanometer material. Researches show that the iron oxide, the iron oxide-based composite material and the ferrocenyl compound have certain promotion effect on AP thermal decomposition, and particularly, the nano iron oxide catalyst shows good catalytic activity. Thomas et al found nano Fe₂O₃The burning rate of the solid propellant can be improved by about 60 percent. Hagihara et al use different size alpha-Fe₂O₃Andβ-Fe₂O₃the AP/HTPB is catalyzed and the smaller the particle size of the combustion catalyst, the higher the combustion rate of the propellant. Although the nano iron oxide provides reference for realizing high-efficiency catalysis of the combustion catalyst, the problem that the catalytic efficiency is limited by the concentration of the nano iron oxide is still faced, and the key for improving the catalytic performance of the combustion catalyst is how to improve the catalytic activity to the maximum extent.

Disclosure of Invention

The invention aims to provide a Fe-based metal organic framework material MIL-101(Fe) -R% use as combustion catalyst.

The invention is realized as follows:

the Fe-based metal organic framework material is used as a combustion catalyst in a solid propellant, and the Fe-based metal organic framework material is MIL-101(Fe) -R% by FeCl₃·6H₂O, terephthalic acid and 2-amino terephthalic acid are synthesized in N, N' -dimethylformamide solvent, whereinR2-amino terephthalic acid ligand accounts for the total ligand (terephthalic acid)Acid and 2-aminoterephthalic acid), R from 0% to 48%, preferably from 28% to 48%, most preferably 38%.

The Fe-based metal organic framework material MIL-101(Fe) -RThe percentage is obtained by heat treatment for 5 to 60 minutes at 200 to 320 ℃ in an air atmosphere, preferably at 260 to 300 ℃ for 20 to 40 minutes.

MIL-101(Fe) is a metal organic framework, a member of the iron-containing MOF material, CAS:1189182-67-9, formula: c₂₄H₁₂ClFe₃O₁₃Molecular weight: 711.33.

the heat treatment of metal organic frameworks is becoming increasingly popular as a post-treatment process and has resulted in a variety of MOFs derived oxide materials. However, the extreme pyrolysis conditions (typically above 500 ℃) that are widely used not only destroy the highly ordered porous structure, but also eliminate most of the intrinsic properties of MOFs. In order to realize the high-efficiency catalytic combustion of the solid propellant, the invention selects aromatic carboxylic acid ligand 2-amino terephthalic acid (NH) with different thermal stabilities₂-BDC) and terephthalic acid (H)₂BDC) to synthesize a series of mixed ligands MIL-101(Fe) -NH₂-R% (R= 0, 9, 19, 28, 38, 48) catalytic material, and different NH was systematically investigated₂The effect of the introduction of the amount of BDC ligand on the thermal decomposition performance of AP and RDX. By selective pyrolysis of thermosensitive ligand NH in MIL-101(Fe) -38%₂BDC to obtain the HP-MIL-101(Fe) -one with controllable concentration of nano iron oxide and iron active siteX (X= 320, 300, 280, 260 and 200 ℃) combustion catalyst.

Due to Fe₂O₃With combustion catalytic activity, the invention can control part of heat-sensitive ligand NH by precisely controlling pyrolysis temperature (200-320 ℃), and can reduce the temperature of the catalyst₂BDC removal to obtain HP-MIL-101(Fe) material with controllable concentration of nano active iron oxide, and Fe₂O₃Uniformly dispersed in the MOFs pore canal. DSC thermal analysis is adopted to test the catalytic effect of the catalyst material with controllable ferric oxide concentration and adjustable iron active sites on AP and RDX thermal decomposition performance, and the mixed ligand MIL-101(Fe) -NH is verified₂-R% effect of the material on AP and RDX combustion catalysis before and after heat treatment. Oxidation prepared by the inventionThe catalytic effect of the HP-MIL-101(Fe) combustion catalyst with controllable iron concentration and iron active sites on AP and RDX is better than that of the raw material MIL-101(Fe) -NH₂-RPercent, wherein, the material with HP-MIL-101(Fe) -280 ℃ has the best catalytic performance, and can be used as a combustion catalyst for promoting the thermal decomposition of the propellant component.

Drawings

FIG. 1 MIL-101(Fe) -NH₂-R% (R= 0, 9, 19, 28, 38, 48) SEM picture;

FIG. 2MIL-101(Fe) -NH₂-38% (a) TEM images, (b) elemental distribution plots;

FIG. 3 MIL-101(Fe) -NH₂-R% (R= 0, 9, 19, 28, 38, 48): (a) (b) a PXRD pattern;

FIG. 4MIL-101(Fe) -NH₂-R% (R= 0, 9, 19, 28, 38, 48) thermogravimetric analysis plot;

FIG. 5 MIL-101(Fe) -NH₂-R% (R= 0, 9, 19, 28, 38, 48) DSC-TGA plot;

FIG. 6HP-MIL-101(Fe) -X (XPXRD patterns of = 320, 300, 280, 260 and 200 ℃);

FIG. 7(a) MIL-101(Fe) -NH₂-R% (R= 0, 9, 19, 28, 38, 48) at a heating rate of 10 ℃ · min^-1DSC curve of catalytic AP thermal decomposition, (b) MIL-101(Fe) -NH₂-38% catalytic AP thermal decomposition DSC profile at different ramp rates;

FIG. 8 (a) HP-MIL (Fe) -101-X (X= 320, 300, 280, 260 and 200 ℃) at a heating rate of 10 ℃. min^-1Lower catalytic AP thermal decomposition DSC curve; (b) HP-MIL (Fe) -101-280 ℃ and AP thermal decomposition DSC curve is catalyzed at different heating rates;

FIG. 9(a) MIL-101(Fe) -NH₂-R% (R= 0, 9, 19, 28, 38, 48) at a heating rate of 10 ℃ · min^-1Lower catalytic RDX thermal decomposition DSC curve; (b) MIL-101(Fe) -NH₂-38% catalytic RDX thermal decomposition DSC curve at different ramp rates;

FIG. 10(a) HP-MIL (Fe) -101-X (X= 320, 300, 280, 260 and 200 ℃) at a heating rate of 10 ℃ · min^-1Lower catalytic RDX thermal decomposition DSC profile; (b) HP-MIL (Fe) -101-280 ℃ for catalyzing RDX at different heating ratesThermal decomposition DSC curve.

Detailed Description

Example 1 Mixed ligand MIL-101(Fe) -NH₂-R% preparation of the materials

Synthesis of MIL-101(Fe) -NH series₂-R% (R= 0, 9, 19, 28, 38, 48) mixed ligand material, whereinRIs the ratio of 2-aminoterephthalic acid ligand to total ligand (terephthalic acid and 2-aminoterephthalic acid). The specific experimental scheme is as follows: separately weighing FeCl₃·6H₂O (324 mg), terephthalic acid (H)₂BDC, 100, 90, 80, 70, 60 mg) and 2-aminoterephthalic acid (NH)₂-BDC, 0, 10, 20, 30, 40, 50 mg) was dissolved in N, N dimethylformamide (DMF, 7.5 mL), after 15 minutes of sonication, the above mixed solution was transferred to a reaction vessel, and then the reaction was heated in an oven at 125 ℃ for 12 hours, after cooling to room temperature, washed three times with DMF and ethanol, respectively, and the product obtained by centrifugation was dried overnight at 70 ℃.

Example 2 preparation of HP-MIL-101(Fe) Material

The resulting dark brown powder MIL-101(Fe) -NH was mixed based on the mixed ligand MIL-101(Fe) -38% material synthesized in example 1₂Putting 38% of raw material into a muffle furnace, heating for 30 min at different temperatures (320, 300, 280, 260 and 200 ℃) to obtain HP-MIL-101(Fe) -X (X= 320, 300, 280, 260 and 200 ℃), and the like. After cooling to room temperature, the mixture was placed in a vacuum drying oven and activated at 100 ℃ for 6 hours. Finally, after cooling to room temperature, the obtained solid powder was transferred to a 6 ml centrifuge tube and stored under sealed and dry conditions.

Example 3 Mixed ligand MIL-101(Fe) -NH₂-R% material structure and morphology analysis

（1）MIL-101-NH₂-R% material morphology analysis

The microscopic morphology of the material was first characterized by Scanning Electron Microscopy (SEM). One-pot method for synthesizing different NH₂-H₂MIL-101(Fe) -NH at BDC ratio₂-R% (R= 0, 9, 19, 28, 38, 48) material as shown in fig. 1. MIL-101(Fe) -NH₂The-0% exhibited a typical octahedral morphology with a uniform distribution. With NH₂Increase in the proportion of BDC ligand, MIL-101(Fe) -NH₂-R% (R= 9, 19, 28, 38, 48) morphology similar to MIL-88B, exhibiting spindle morphology with average size length of 1 μm and diameter around 500 nm. However, when the doping ratio is too high, the ligand MIL-101(Fe) -NH is mixed₂A strong competitive reaction may occur in 48%, each forming a mono-ligand MOF, with maldistribution.

To further confirm that the synthesized sample successfully introduced NH₂-H₂BDC, Transmission Electron Microscope (TEM) topographical characterization of the samples was performed. From MIL-101(Fe) -NH₂The obvious observation in the-38% element distribution diagram (figure 2) that the crystal mainly contains Fe, N, O, C and other elements, and N, Fe elements are uniformly distributed on the surface of the crystal, which indicates that ligand 2-amino terephthalic acid successfully replaces part of terephthalic acid to be introduced into MIL-101(Fe) and forms double ligand MIL-101(Fe) -NH with amino₂-R% of the material, and the Fe element is uniformly loaded on the material, which also achieves one of the original purposes of the MOF material, namely, the reduction of the agglomeration of metal particles.

（2）MIL-101-NH₂-R% Material Crystal analysis

To verify the successful synthesis of MIL-101(Fe) -NH₂-R% (R= 0, 9, 19, 28, 38, 48) crystal, which was subjected to X-ray diffraction testing (PXRD) and compared to corresponding PXRD simulation data. As shown in FIG. 3(a), MIL-101(Fe) -NH was found₂The characteristic peak of PXRD and MIL-101(Fe) simulation diagram of the-0% material is consistent, which indicates that MIL-101(Fe) -NH is successfully synthesized₂-0% crystalline material. NH as shown in FIG. 3(b)₂The introduction of-BDC may affect MIL-101(Fe) -NH₂-R% (R= 9, 19, 28, 38, 48) preferential growth of crystal structure while MIL-101(Fe) -NH₂-R% another important change is a slight shift of the (202) crystal planes to higher angles, which is consistent with a reduced interplanar spacing. This is because of NH₂Introduction of BDC causes a slight right shift of the characteristic peak, which may result from incorporation of MOF with a diameter smaller than thatA C atom diameter N atom. Thus, it confirmed NH₂-BDC successfully incorporated into MIL-101(Fe) structures. Of note are MIL-101(Fe) -NH₂PXRD at-48% shows a reduced characteristic peak intensity due to the addition of NH₂Too high a BDC ratio.

（3）MIL-101-NH₂-R% material thermogravimetric analysis

Thermal stability is very important for catalysis of solid propellant components, for MIL-101(Fe) -NH₂-R% (R= 0, 9, 19, 28, 38, 48) thermogravimetric analysis (TGA) to assess its thermal stability as shown in figure 4. Approximately 10mg of sample was weighed and heated from room temperature to 700 ℃ on a TGA Q500 thermogravimetric analyzer (at 100 mL. min)⁻¹At an air flow rate of 10 ℃ per minute⁻¹Heating at a temperature increase rate of (1). Application of TGA and DSC to MIL-101(Fe) -NH under air atmosphere₂-R%(R= 0, 9, 19, 28, 38, 48) material test, the obtained thermogravimetric curve is shown in fig. 4, and the stability of 0% -48% is reduced sequentially along with the increase of the proportion, which is consistent with the previous characterization means results of SEM, TEM, FT-IR, fluorescence and the like, and the expected amino functionalized double ligand MIL-101(Fe) -NH is proved₂-R% has been successfully achieved. In order to study the influence of ligands with different proportions on the structural stability of MOFs, the ligand ratio was simultaneously applied to MIL-101(Fe) -NH₂-R% (R= 0, 9, 19, 28, 38, 48) DSC-TGA of material (fig. 5) one detailed analysis was performed as MIL-101(Fe) -NH₂-38% for example. As shown in FIG. 5(e), the complex MIL-101(Fe) -NH ₂38% underwent three successive weight loss phases. First, starting from 50 ℃ to finishing at 160 ℃, the weight loss rate is 9.05 percent, corresponding to the removal of water molecules, DMF and impurities; starting from 160 ℃ the linking group thermosensitive ligand NH₂BDC starts to decompose until all 326 ℃ is removed, corresponding to the first sharp exothermic peak appearing at 330 ℃ on the DSC curve; starting from 330 ℃ H₂The BDC ligand starts to decompose and the body frame starts to collapse until 463 ℃ (corresponding to the DSC second sharp exothermic peak) and finally 27.34% by mass of refractory iron oxide clusters remain. Thus, DSC-TGA shows that the thermosensitive ligand NH is varied with different ratios₂Introduction of BDC, DSC gradual transition from 1 exothermic peak to 2 exothermic peaks, confirming the heat-sensitive ligand NH₂The introduction of BDC has a certain influence on its structural stability.

Example 4 HP-MIL-101 Material Crystal form analysis

To study the structural changes of MOF after heat treatment at 200-320 ℃, MIL-101(Fe) -NH was followed by PXRD technique₂-evolution of crystallinity before and after heat treatment of 38% material. As shown in FIG. 6, the crystallinity of the sample at middle temperature of 200-280 ℃ is retained after the heat treatment, but the crystallinity is reduced when the sample is heat treated at high temperature of 300-320 ℃, and a slightly wider PXRD peak is observed, which is probably a part of the heat-sensitive ligand NH₂Removal of BDC, defects appear inside the material, forming a frame with mesopores.

Example 5 Mixed ligand MIL-101(Fe) -NH₂-R% Material on AP catalytic Performance

As shown in fig. 7(a), pure AP thermal decomposition is divided into three stages: a crystal form transformation phase at 245.6 ℃, a low temperature decomposition phase at 333 ℃, and a high temperature decomposition phase occurring at 433 ℃. Adding MIL-101(Fe) -NH₂-R% (R= 0, 9, 19, 28, 38, 48) post-catalyst, with NH₂-H₂Increase in the proportion of BDC ligand, AP/MIL-101(Fe) -NH₂-RThe% complex had both the low temperature decomposition peak and the high temperature decomposition peak advanced. The reason for this is NH₂The introduction of BDC ligand provides more active sites for Fe atom to form coordination bond with Fe-O, so that NH₂The introduction of BDC ligands has a promoting effect on AP catalysis in a certain range. Wherein, MIL-101(Fe) -NH₂The 38% catalyst allowed the peak of exothermic AP decomposition to advance the most (318 ℃ C.), with the greatest exotherm (2303J g)^-1) Therefore, the catalyst has excellent catalytic performance. In addition, MIL-101(Fe) -NH was also tested₂38% catalyst at different ramp rates (2, 5, 10 and 15 ℃ C. min.)^-1) Next, the effect on AP catalysis (fig. 7 (b)), it can be seen that the thermal decomposition temperature of AP increases as the temperature increase rate increases.

Example 6HP-MIL-101(Fe) Material on AP catalytic Performance Studies

Use of HP-MIL (Fe) -101-X (XCatalyst = 320, 300, 280, 260 and 200 ℃) to study the effect on the AP combustion process. As shown in FIG. 8, the HP-MIL-101(Fe) -320 ℃ and HP-MIL-101-300 ℃ materials catalyze AP, so that the low-temperature decomposition peak is advanced to 320 ℃ and 312 ℃, the high-temperature decomposition peak is advanced to 332 ℃ and 328 ℃, and the heat release is 1909J g^-1And 2477J. g^-1Has better promoting effect. When the catalyst calcined at the medium temperature (280 ℃, 260 ℃ and 200 ℃) catalyzes AP, the combination of low-temperature and high-temperature decomposition peaks can be seen as one peak, the peak is advanced to 316 ℃, 315 ℃ and 312 ℃, and the heat release reaches 2969 J.g^-1、2477 J·g^-1And 1909J g^-1And the HP-MIL-101(Fe) -280 ℃ has the best catalytic effect. The intrinsic defects are introduced into the HP-MIL-101(Fe) framework, so that active sites are increased, the surface charge transfer capacity of a system is changed, and the catalytic behavior of the reaction is optimized. At the same time, the catalytic efficiency is shown to be influenced by Fe with the increase of temperature₂O₃Limitation of concentration increase. In conclusion, the low-temperature and high-temperature decomposition process of AP has appropriate concentration of nano Fe₂O₃And HP-MIL-101(Fe) defect materials with controllable active sites can play a better synergistic role.

Example 7 Mixed ligand MIL-101(Fe) -NH₂-R% material catalytic Effect on RDX Combustion Process

To further determine MIL-101-NH₂-R% material, the thermal decomposition catalytic activity of which on RDX was evaluated by Differential Scanning Calorimetry (DSC) testing. The decomposition peak of RDX can be well observed in DSC curve, and for the combustion decomposition of pure RDX, a sharp endothermic peak is provided at about 205 ℃, a wider exothermic peak is provided at about 250 ℃, and the exothermic quantity is 961 J.g^-1(FIG. 9). As shown in FIG. 9(a), MIL-101-NH₂-R% (R= 0, 9, 19, 28, 38, 48) catalyst and RDX after mixing, the endothermic peak of pure RDX is not changed, the exothermic peak temperature is obviously improved, and the influence on the exothermic amount is relatively large. It was found that at the same temperature increase rate of 10 ℃ min^-1Lower, different NH₂-H₂M of BDC ratioIL-101-NH₂-R% material and RDX composite, typical exothermic peak occurs obvious left shift, this is attributed to the sublimation and melting process of RDX, from which NH is presumed₂The introduction of BDC ligand has a catalytic effect on the combustion of RDX. Wherein MIL-101-NH₂The peak temperature is advanced to 245 ℃ by 38 percent of material, and the heat release reaches 1294J g^-1. Furthermore, MIL-101-NH₂Catalyzing RDX by 38 percent of material at different heating rates, wherein the heating rate is 2 ℃ min^-1The catalyst has the best catalytic performance, and the thermal decomposition temperature is advanced to 225 ℃, but the heat release is obviously reduced.

Example 8 catalytic Effect of HP-MIL-101(Fe) Material on the RDX Combustion Process

RDX/HP-MIL (Fe) -101-XAnd (3) catalyzing the thermal decomposition of the composite material. As shown in FIG. 10(a), at the same heating rate of 10 ℃ C. min^-1Then, the HP-MIL-101-280 ℃ material has the best catalytic effect on RDX, so that the peak temperature is advanced to 243 ℃, and the heat release reaches 1302 J.g^-1. Meanwhile, under different heating rates, the mixture is mixed with RDX at the rate of 2 ℃ min^-1At this time, the decomposition peak was advanced to 224 ℃. These catalyst materials may decompose with the release of heat before the melting point of RDX, allowing RDX to decompose earlier by lowering its melting point. Generally, the decomposition mechanism is changed by the nanoscale additives, resulting in a difference in the exotherm. The above results indicate that the HP-MIL-101-280 ℃ catalytic activity is optimal, consistent with the above analysis of the catalytic decomposition performance of AP.

Claims

The application of Fe-based metal organic framework material as a combustion catalyst in a solid propellant, wherein the Fe-based metal organic framework material is MIL-101(Fe) -R%, which is prepared by FeCl₃·6H₂O, terephthalic acid and 2-amino terephthalic acid are synthesized in N, N' -dimethylformamide solvent, whereinRIs the mol ratio of the 2-amino terephthalic acid ligand to the total ligand,R0% to 48%.
2. Use according to claim 1, characterized in thatIn thatRIs 28% -48%.
3. Use according to claim 2, characterized in thatRThe content was found to be 38%.
4. The use according to claim 1, wherein the Fe-based metal-organic framework material is MIL-101(Fe) -RThe percentage is obtained by heat treatment at 200-320 ℃ in air atmosphere.
5. The use according to claim 4, characterized in that the Fe-based metal-organic framework material is MIL-101(Fe) -RThe percentage is obtained by heat treatment at 260-300 ℃ in air atmosphere.
6. The use according to claim 4, wherein the heat treatment time is 5 to 60 minutes.
7. The use according to claim 6, wherein the heat treatment time is 20 to 40 minutes.