Burning Rate Catalysts Research Articles

Research progress of EMOFs-based burning rate catalysts for solid propellants.

Energetic Metal Organic Frameworks (EMOFs) have been a hotspot of research on solid propellants in recent years. In this paper, research on the application of EMOFs-based burning rate catalysts in solid propellants was reviewed and the development trend of these catalysts was explored. The catalysts analyzed included monometallic organic frameworks-based energetic burning rate catalysts, bimetallic multifunctional energetic burning rate catalysts, carbon-supported EMOFs burning rate catalysts, and catalysts that can be used in conjunction with EMOFs. The review suggest that monometallic organic frameworks-based burning rate catalysts have relatively simple catalytic effects, and adding metal salts can improve their catalytic effect. Bimetallic multifunctional energetic burning rate catalysts have excellent catalytic performance and the potential for broad application. The investigation of carbon-supported EMOFs burning rate catalysts is still at a preliminary stage, but their preparation and application have become a research focus in the burning rate catalyst field. The application of catalysts that can be compounded with EMOFs should be promoted. Finally, environmental protection, high energy and low sensitivity, nanometerization, multifunctional compounding and solvent-free are proposed as key directions of future research. This study aims to provide a reference for the application of energetic organic burning rate catalysts in solid propellants.

Enhanced anti-migration performance of carbon nanotubes confined ferrocenyl compounds and their synergistic catalytic activity on the thermal decomposition of ammonium perchlorate

To retard high-migration issues of the commercialized ferrocene-based burning rate catalysts (BRCs), six commercial ferrocenyl derivatives (FcR), including catocene, N, N-dimethylaminomethyl ferrocene, n-butylferrocene, tert-butylferrocene, n-octylferrocene and ferrocene, were filled into carbon nanotubes (CNTs) by ultrasonication. The CNTs incorporated ferrocene nanocomposites (FcR@CNTs) were characterized by TEM, SEM, BET, XPS, FTIR, Raman and XRD techniques, which indicated that the ferrocenes are successfully filled into the CNTs. The anti-migration and anti-volatility tests unveiled that the FcR@CNTs exhibit neglectable migration tendency after four weeks of aging at 50 °C and low volatility when tested at 70 °C for 24 h. The combustion catalytic results displayed that the FcR@CNTs nanocomposites play a vital role in promoting the thermal decomposition of ammonium perchlorate (AP), with the best one lowering the peak temperature of high-temperature decomposition stage (HTD) of AP by 114.2 °C and increasing its released heat by 160%. And it was found that the smaller the diameter of a CNT is, the lower the peak temperature of AP and the higher the released heat of AP. In addition, the decomposition mechanism of AP catalyzed by FcR@CNTs(L1) was studied by thermal decomposition kinetics, in-situ solid FTIR and TG-FTIR-MS methods. The results revealed that the nanocomposites can absorb more generated NH3 and HClO4 gases during AP decomposition with formation of superoxide anions (O2−), accelerating the oxidation of N2O to NO, and promoting the AP decomposition at lower temperature. Thus, a possible decomposition mechanism of AP catalyzed by FcR@CNTs is proposed.

2D metal-organic frameworks endow ammonium perchlorate with enhanced thermal effect

To investigate the effect of different structures of MOF on the catalytic performance of ammonium perchlorate (AP) thermal decomposition. By adding 2-methylimidazole (2-MI) as an inhibitor during the synthesis of MOF-5, a two-dimensional (2D) MOF material was prepared and characterized by SEM, EDS, XRD, FT-IR and other means. The prepared two-dimensional material was added to the AP raw material to investigate its effect on the AP thermal decomposition process. After DSC and TG test, it was found that the addition of this kind of 2D MOF material can completely eliminate the low-temperature decomposition peak of the AP-based composite and advance the high temperature decomposition peak to 296.5 °C, and the apparent heat of decomposition increase to 905.6 J/g, which has a better catalytic effect than the bulk MOF-5. In addition, through the combustion test, it was found that 2D MOF, as a burning rate catalyst, can effectively enhance the burning rate of AP based solid propellant.

Bimetallic ruthenium compound derived from 6,12-dihydroindeno[1,2-b]fluorene ligand as burning rate catalyst for solid rocket motor propellant

We reported the synthesis of a novel bimetallic compound with the formula [(Cp*Ru)2-IF] derived from 6,12-dihydroindeno[1,2-b]fluorene ligand (IFH2). This compound was characterized by 1H and 13C NMR, elemental analysis, FT-IR, and UV-vis.The bimetallic compound was tested as a burning rate catalyst on the thermal decomposition of ammonium perchlorate. It was assessed by differential scanning calorimetry technique (DSC) analysis to understand its catalytic behavior further. [(Cp*Ru)2-IF] shows a decrease in the decomposition temperature of AP to 381°C, increasing the energy release to 1271 J•g−1. In addition, this compound leads to the lowest activation energy (20.7 kJ•mol−1), suggesting a suitable and competitive alternative to be used as a modifier for composite solid propellants.

Synthesis, Anti‐migration and Catalytic Effect of Ferrocene Azine Derivatives on the Thermal Decomposition of Ammonia Perchlorate

AbstractFerrocene burning rate catalyst (BRC) is a common catalyst to promote the combustion of composite solid propellant because of its high catalytic performance, but this kind of catalyst has the disadvantage of easy migration. Ammonia perchlorate (AP) is the main oxidant of composite solid propellant, and its thermal degradation behavior has an important impact on the combustion of propellant. New mononuclear and polynuclear ferroceneazine BRCs were synthesized, and their structures were characterized by UV‐Vis, NMR, HRMS and IR spectra. The catalytic effects of these ferrocenylazines on the thermal degradation of AP were studied by DSC and TG. The results confirmed that the catalytic performance of azine without bisferrocenylpropane was inferior to that of Catocene (Cat), while the catalytic performance of azine with bisferrocenylpropane was equivalent to that of Cat. Anti‐migration studies showed that both mononuclear ferroceneazines and Cat showed mobility, while polynuclear ferroceneazines did not migrate after long‐term storage. Therefore, polynuclear ferroceneazine is a new kind of high‐efficiency and non‐migration BRC with application prospects.

Effect of fast-burning compound ACP and catalyst on the combustion performance of Al/Mg-based fuel-rich HTPB propellants

In order to solve the problem of weak injection of fuel-rich propellant and to enhance its burning rate, the combustion behaviors of Al/Mg-based fuel-rich HTPB propellants with 40wt% metal content were studied with and without the addition of fast burning compound hydrated tetra-(4-amino-1, 2, 4-triazole) copper perchlorate (ACP) and burning rate catalyst Pb5. The results show that the burning rates of the Al/Mg-based fuel-rich HTPB propellants with the addition of fast burning compound and catalyst increase significantly, and the pressure exponents decrease. With the increase of pressure, the fluctuation of burning interface of the propellants increases and the flame height decreases. Compared with the Mg-based propellants of high burning rate, the agglomeration of condensed combustion products of the Al-based propellants is much more serious; the combustion extent of aluminum in the Al-based propellants is obviously lower than that of magnesium in the Mg-based propellants. These results are very meaningful for the design of fuel-rich HTPB propellants with high performance.

Bimetallic Ruthenium Compound Derived from 6,12-Dihydroindeno[1,2-B]Fluorene Ligand as Burning Rate Catalyst for Solid Rocket Motor Propellant

Bimetallic Ruthenium Compound Derived from 6,12-Dihydroindeno[1,2-B]Fluorene Ligand as Burning Rate Catalyst for Solid Rocket Motor Propellant

Anti‐migration of Nitrogen‐rich N‐Heterocyclic Ferrocenes and Their Combustion Catalytic Properties in the Thermal Decomposition of Energetic Oxidizers

AbstractTo retard high migration tendency of alkylferrocene‐based burning rate catalysts and ameliorate their combustion catalytic activity, twenty new nitrogen‐rich N‐heterocyclic ferrocenyl compounds 1–20 were synthesized by click reaction and characterized by NMR, UV‐Vis, FT‐IR, ESI‐MS, etc. Six compounds were structurally confirmed by single crystal X‐ray diffraction additionally. TG studies showed that the new ferrocenyl compounds are highly thermal stable. Cyclic voltammetry results implied that some new ferrocenyl compounds exhibit reversible electrochemical behavior, which are favorable for their combustion catalytic performance in the composite solid propellants. The anti‐migration tests confirmed that the new ferrocenyl compounds exhibit neglectable migration trends after four‐week aging on comparison with ferrocene and catocene. The catalytic combustion tests of AP, RDX and HMX over the compounds 1–20 indicated that these N‐heterocyclic ferrocenes are all highly active for improving thermal degradation of AP and RDX and more active than the aniline‐derived counterparts prepared by click reaction.

Preparation of ferrocene-based phenylethylamino compounds and their properties as burning rate catalysts

Ferrocene (Fc)-based compounds as common burning rate catalysts (BRCs) are often used in composite solid propellants, such as catocene (Cat). To solve the migration problem of common Fc-based compounds, six novel ferrocene (Fc)-based phenylethylamino BRCs were designed and synthesized. Their structures as well as catalytic performance for ammonium perchlorate (AP) decomposition were studied by UV–Vis, FT-IR, 1H NMR, 19F NMR, ESI-MS, EA, CV and TG, respectively. The test results indicated that these Fc-based phenylethylamino BRCs had good catalytic activity for thermal decomposition of AP and better anti-migration ability than Cat and Fc in simulated AP-based propellant. Among these compounds, Fc-2 showed the best catalytic activity for thermal decomposition of AP and Fc-6 showed the best anti-migration ability. This study demonstrates that Fc-based phenylethylamino compounds are promising BRCs for AP-based propellant.

Ferrocene-modified dendrimers as support of copper nanoparticles: evaluation of the catalytic activity for the decomposition of ammonium perchlorate

Ferrocene (Fc)-based systems are frequently used as burning rate catalysts in the decomposition of ammonium perchlorate (AP)-based propellants. However, small Fc derivatives migrate to the surface of the propellant resulting in undesirable changes in the designed burning parameters and unstable combustion. To retard the migration and to increase the combustion rate of AP, fourth-generation polyamidoamine (PAMAM) dendrimers modified with Fc (PAMAM generation 4 [G4]-Fc) were synthetized and used as support for the obtention of copper nanoparticles (CuNPs). PAMAM G4 produced smaller nanoparticles (1–2 nm) with lower aggregation than PAMAM G4-Fc (12–14 nm). X-ray photoelectron spectroscopy (XPS) characterization confirmed the superior stabilizing and protecting effect against oxidation of CuNPs by PAMAM G4 in comparison to PAMAM G4-Fc, whereas molecular dynamics simulations have shown less flexibility and lower presence of stabilizing sites for nanoparticles in PAMAM G4-Fc. Antimigration tests confirmed the negligible migration of PAMAM G4-Fc compared with Fc, whereas PAMAM G4-Fc|CuNP affected the high-temperature decomposition of AP positively, decreasing the decomposition temperature in 87 °C owing to a synergistic effect between CuNPs and Fc. PAMAM G4-Fc can act both as an effective antimigration system of Fc and as a stabilizing framework of metal nanoparticles with application as catalysts of AP.

A Green Approach for Photometric Determination of Copper β-Resorcylate in Double Base Solid Propellants

This paper describes the applicability of micellar media instead of extraction steps with toxic solvents for direct determination of copper beta-resorcylate as burning rate catalyst in double base propellant (DB propellant). The method is based on a simple and safe sample preparation of DB propellant, and then complex formation of copper ion with Diethyldithiocarbamate (DDTC) in the presence of sodium dodecyl sulfate (SDS) as a micellar media. Under optimal conditions, at λmax= 445 nm, the calibration graph was linear in the range of 0.25-4.5 µg mL-1 for copper with detection limits 0.125 µg mL-1. The validity of the method was evaluated by means of the data statistical analysis. For this purpose, the method was applied to the determination of copper beta-resorcylate in DB propellant and the results were statistically compared based on t- and F-tests with those obtained by the by ICP-AES. There was no significant difference between the mean values and the precisions of the two methods at the 95% confidence level. The results showed that the proposed method offers an accuracy and reliable approach for the determination of copper β-resorcylate in DB propellant, and can be suggested as a routine method in military quality control laboratories.

Catalytic effect of [trans-Cu(μ-OH)(μ-dmpz)]6 on the thermal decomposition of ammonium perchlorate

Spatial race under low oxygen conditions requires solid mild propellants to be used. Therefore, we study the catalytic effect of the previously reported [trans-Cu(μ-OH)(μ-dmpz)]6 complex on the thermal decomposition of ammonium perchlorate by a differential scanning calorimetry (DSC) technique. The copper compound causes a decrease of ammonium perchlorate’s decomposition temperature to 372.5 °C, consequently increasing the heat release by 576 J·g−1, when used in a 5 wt% as burning rate (BR) catalyst. It must be remarked that, the [trans-Cu(μ-OH)(μ-dmpz)]6 complex presents a superior performance as BR catalyst when compared to nano-metallic oxides. This Cu(II) compound modifies the decomposition mechanism of ammonium perchlorate, providing the necessary O2 to accelerate the overall burning process paving the way to the study of copper pyrazolate complexes as BR catalysts.

Synthesis of poly(2-(methacryloyloxy) ethyl ferrocene carboxylate-co-glycidyl methacrylic acid)s and their anti-migration and burning rate catalytic properties

Ferrocene (Fc)-based polymers have promising application in burning rate catalysts (BRCs) for solid composite propellants, and some of them have already been practically used. However, they have some drawbacks such as high migration during a long-time storage. Copolymers of poly(2-(methacryloyloxy) ethyl ferrocene carboxylate-co-glycidyl methacrylic acid)s (P(FHEMA-co-GMA)s) were synthesized to overcome the migration problem of Fc-based BRCs as well as to boost the burning rate (BR) of ammonium perchlorate (AP)-based propellants. The structures of the obtained P(FHEMA-co-GMA)s were confirmed by proton nuclear magnetic resonance (1H NMR) and Fourier transform infrared (FT-IR) spectroscopy. Cyclic voltammetry (CV) method was used to study their electrochemical behavior, and the P(FHEMA-co-GMA)s showed redox behavior for the existence of the Fc units. Because of the formation of integrated network structures, the P(FHEMA-co-GMA)s have good anti-migration performances. The BR catalytic property of P(FHEMA-co-GMA)s were investigated by thermogravimetry (TG) and differential thermogravimetry (DTG). They showed competent catalytic effects on the thermal decomposition of AP.

Heterobimetallic Catalysts for the Thermal Decomposition of Ammonium Perchlorate: Efficient Burning Rate Catalysts for Solid Rocket Motors and Missiles

We show the synthesis and characterization of four heterobimetallic compounds derived from s-indacene of general formula [{(CO)3Mn}-s-Ic-{MCp*}]q with M = Fe, Co, Ni, and Ru; q = 0, 1+. The complexes reported here were characterized by 1H and 13C NMR, elemental analysis and FT-IR. Additionally, the X-ray crystal structure of [(CO)3Mn-s-Ic-FeCp*] (1) and Mössbauer spectra are reported. The heterobimetallic compounds exhibit higher quasireversible redox potentials compared with ferrocene and catocene under the same reaction conditions. The complexes were tested as catalysts on the thermal decomposition of ammonium perchlorate examined by a differential scanning calorimetry technique to study their catalytic behavior. Compound (1) causes a decrease of ammonium perchlorate's decomposition temperature to 315 °C, consequently increasing the heat release by 138 J·g-1. Conversely, [{(CO)3Mn}-s-Ic'-{CoCp*}] (2) presents a higher heat release (2462 J·g-1), comparable to catocene.

Synthesis and Anti-migration Studies of Ferrocene-Based Amides as Burning Rate Catalysts

To overcome the migration problems of burning rate catalysts (BRCs), ferrocene-based amide compounds (AM-Fcs) were synthesized. The successful synthesis of AM-Fcs were confirmed by proton nuclear magnetic resonance, and Fourier transform infrared spectroscopy. The electrochemistry behaviors of AM-Fcs were examined by cyclic voltammetry (CV). The CV experimental results indicated that these AM-Fcs showed good electrochemical performances, which were contributable to their burning rate (BR) catalytic activity in composite solid propellants. The anti-migration test of AM-Fcs verified significantly slower migration than ferrocene and the most commonly used BRCs catocene. Thermal stability and BR catalytic impact of AM-Fcs on the thermal decomposition of ammonium perchlorate (AP) were studied by thermogravimetry and differential thermogravimetry. These AM-Fcs revealed good catalytic behaviors on the thermal degradation of AP.

Unanticipated ionic ferrocenyl compounds based on 5,5′-bis(1-hydroxytetrazole). Molecular structures, anti-migration and burning rate catalytic performances

Twenty-one ionic ferrocenyl ammonium (1–17) and 1,2,4-triazolium (18–21) compounds derived from 5,5′-bis(1-hydroxytetrazole) were synthesized and characterized by NMR, FT-IR, UV − Vis and elemental analysis, aiming at improving anti-migration ability of neutral ferrocene-based burning rate catalysts and reducing sensitivity of the ionic ferrocenyl compounds containing picrate anions. Six new compounds were additionally characterized by single-crystal X-ray diffraction. The characterization results showed that, by ion-exchange reactions, 1–10, 12, 15 and 17 are the anticipated compounds in their molecular structures, compounds 11, 13 and 16 were formed by C-N bond cleavage of the dinuclear ferrocenyl cation units and 18–21 were obtained by protonation of the divalent 5,5′-bis(1-hydroxytetrazolate) anion at one oxygen atom. Thermal gravimetry and anti-migration test indicated that the new compounds are highly thermally stable and show low volatility and low migration tendency. Cyclic voltammetry studies suggested that most of the novel salts are irreversible redox systems. The sensitivity tests towards impact revealed that compounds 1–17 are insensitive compounds. The catalytic tests implied that all compounds exhibit great effects on the thermal degradation of ammonium perchlorate and 1,3,5-trinitro-1,3,5-triazacyclohexane. Compounds 13–15 can be used as potential alternatives to catocene in the composite solid propellants.

Anti‐migration and Combustion Catalytic Performances of Ferrocenyl Compounds of Anilines and Alkylamines Synthesized by Click Reaction

To enhance anti‐migratory performance and combustion catalytic activities of neutral ferrocene‐based burning rate catalysts (BRCs), nine ferrocenyl 1,2,3‐triazolyl compounds of anilines and aliphatic amines (Fc‐ATAZs, 1–9) were synthesized by click reaction and characterized by NMR, UV/Vis, FT‐IR, and MS. TG and DSC studies confirmed that the Fc‐ATAZs are highly thermal stable. Cyclic voltammetry results implied that 1 and 6 are reversible redox systems. The anti‐migration and anti‐volatility tests showed that the Fc‐ATAZs are low‐migratory and low‐volatile compounds.Combustion catalytic activity results of the Fc‐ATAZs revealed that they are highly active for promoting thermal disintegration of AP, RDX and HMX. Compounds 3, 2 and 8 can increase released heats of AP, RDX and HMX, respectively, by 132 %, 112 % and 36 %, respectively, being the highest in each case. Most of them are more active than the reported analogs derived from phenols and benzoic acids. They, except 9, are more active than catocene and can be used as potential BRCs in composite solid propellants.

Synthesis of Ferrocene‐based Esters as Burning Rate Catalysts and their Anti‐migration Study

Ferrocene‐based (Fc‐based) burning rate catalysts (BRCs) play an essential role in the solid rocket propellants. However, the migration problem during curing and storage limits their applications. To retard the migration problems of Fc‐based BRCs and to increase the burning rate (BR) of AP‐based propellants, Fc‐based esters compounds (Es‐Fcs) were synthesized. The synthesized Es‐Fcs were characterized by X‐ray diffraction, proton nuclear magnetic resonance (1H NMR),13C NMR and Fourier transform infrared (FT‐IR) spectroscopy. The electrochemical behaviors of Es‐Fcs were investigated by cyclic voltammetry (CV). The BR catalytic activity of Es‐Fcs on thermal decomposition of AP were examined by thermogravimetry (TG). Thermal analysis results showed that these Es‐Fcs had good BR catalytic effects on thermal decomposition of AP. It was found that the anti‐migration performance of Es‐Fcs were better than catocene and Fc.

Ferrocene-containing cross-conjugated polymers synthesized by palladium-catalyzed cross-coupling polymerization

We have exploited an extremely efficient and versatile route to prepare ferrocene-containing cross-conjugated polymers (oligomers) in the main-chain. Using a variety of 1,1′-disubstituted ferrocenyl ketone-derived N-tosylhydrazones, reaction with aryl halides under palladium-catalysis gave 14 poly(ferrocenylene-vinylidene) cross-conjugated polymers (oligomers) in 50–80% yield. It was noteworthy that all the polymeric products were well soluble in common organic solvents, endowing them with high solution processability. Pendant double bonds of these cross-conjugated polymers (oligomers) were suitable towards further processing with high reactivity. The optical properties of the polymers (oligomers) were examined. The electrochemical properties of polymers (oligomers) were investigated by cyclic voltammetry (CV) and suggested a quasi-reversible process. Moreover, these cross-conjugated polymers (oligomers) proved thermally stable and demonstrated promising potential as low-migration burning rate catalysts.

Synthesis of poly(2-(methacryloyloxy) ethyl ferrocene carboxylate-co-methacrylic acid)s and their anti-migration and burning rate catalytic properties

A series of copolymers of poly(2-(methacryloyloxy) ethyl ferrocene carboxylate-co-methacrylic acid)s (P(FHEMA-co-MAA)s) were synthesized as burning rate catalysts (BRCs). Their structures were verified using proton nuclear magnetic resonance (1H NMR) and Fourier transforms infrared (FT-IR) spectroscopy. The electrochemical behavior of P(FHEMA-co-MAA)s was investigated by cyclic voltammetry (CV). The CV results indicated that P(FHEMA-co-MAA)s showed redox behavior. Anti-migration test proved that P(FHEMA-co-MAA)s possesses better anti-migration properties than ferrocene (Fc) and 2, 2-bis (ethylferrocenyl) propane (Catocene). The burning rate (BR) catalytic effect of P(FHEMA-co-MAA)s on thermal decomposition of AP was examined through thermogravimetry (TG) and differential thermogravimetry (DTG). P(FHEMA-co-MAA)s were found to have high catalytic effects in accelerating thermal decomposition of ammonium perchlorate (AP).