Rapid ignition of “green” bipropellants enlisting hypergolic copper (II) promoter-in-fuel

ACS Appl. Mater. Interfaces

et al. 2022

Exploring novel hypergolic fuels for modern space propulsion is highly desired. However, the analysis and understanding of the structure and hypergolic performance at the molecular level are still insufficient. To understand the factors that dictate hypergolicity, we conducted a comparative study on a series of metal–organic frameworks (MOFs) characterized by the same topology but with varied ligand structures. The ignition delay (ID) time trend was found to be imidazole < triazole < tetrazole, and the rapid ID time was 8 ms. By combining experimental studies and density functional theory (DFT) calculations, we found that propargyl and cyanoborohydride groups that functioned as dual hypergolic triggers contributed to the hypergolicity, and a distinct electronic structure was detrimental to ID time. The structure–performance relationships presented herein can potentially provide some fundamental insights into the field of developing high-performance hypergolic fuels.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Programming a Metal–Organic Framework toward Excellent Hypergolicity

Zhang

Xing

ACS Appl. Mater. Interfaces

et al. 2022

“…12−15 The promoter-in-fuel approach is one of the promising solutions to facilitate the hypergolic ignitions of ionic liquid− HTP bipropellants. Transition metal-containing promoters have the ability to catalyze the decomposition of HTP releasing a large amount of heat and highly reactive oxygen species, 16−20 iodocuprate-containing ionic liquids/salts, 22,23 closo-icosahedral periodoborane salts, 24 and energetic copper(II) complexes, 25,26 have been reported. These studies demonstrate that the addition of promoters to ionic liquid fuels is capable of initiating hypergolic ignition reactions of some boroncontaining ionic liquids with tetrahydroborate (BH 4 − ) anions or cyanoborohydride (BH 3 CN − ) anions and HTP.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Transition metal-containing promoters have the ability to catalyze the decomposition of HTP releasing a large amount of heat and highly reactive oxygen species, − which results in spontaneous autoignition of the promoter–fuel–oxidizer mixture. In recent years, some pioneering promoters, such as ferrocenyl iodocuprates, iodocuprate-containing ionic liquids/salts, , closo-icosahedral periodoborane salts, and energetic copper(II) complexes, , have been reported. These studies demonstrate that the addition of promoters to ionic liquid fuels is capable of initiating hypergolic ignition reactions of some boron-containing ionic liquids with tetrahydroborate (BH 4 – ) anions or cyanoborohydride (BH 3 CN – ) anions and HTP.…”

Section: Introductionmentioning

confidence: 99%

Designing Difunctional Promoters for Hypergolic Ignitions of Green Bipropellants Combining Ionic Liquids with H₂O₂

Jin

et al. 2022

Ind. Eng. Chem. Res.

The emergence of tetrahydroborate (BH 4 − )/ cyanoborohydride (BH 3 CN − ) anion-based ionic liquid fuels in combination with high test peroxide (>90%H 2 O 2 , HTP) oxidizers has accelerated the greening of bipropellants. However, most BH 4 − and BH 3 CN − anion-based ionic liquids are sensitive to water, making it difficult to store them. Here, novel difunctional promoters are designed for hypergolic ignition of BH 4 − / BH 3 CN − anion-free ionic liquids with 90%H 2 O 2 . The transition metal in anions of promoters is expected to catalyze the exothermic decomposition of H 2 O 2 , and the substituted borohydride in cations of promoters acts as the ignition source. These novel difunctional promoters show good solubility in commercially available 1-allyl-3-methylimidazolium dicyanamide and 1-butyl-3methylimidazolium dicyanamide ionic liquid fuels, and the composite fuels exhibit high density, acceptable viscosity, and high thermostability. The addition of difunctional promoters ensures the smooth hypergolic ignition of BH 4 − /BH 3 CN − anion-free ionic liquid fuels with a minimum ignition delay time of 34.0 ms, and no apparent microexplosion and secondary combustion are observed during the ignition process. With the increase in the amount of the promoter, density specific impulses of the composite fuels improve gradually. This work provides a platform strategy for designing promoters by synergy of cations and anions and makes efforts to seek green bipropellants.

“…Another approach to promote hypergolic reactions between HILs and HTP is the use of catalysts. − Generally, these catalysts can be divided into two categories based on their catalytic ignition mechanisms. One group is called energetic catalysts, which include strongly reducing agents, for example, borohydride and metal hydrides .…”

Section: Introductionmentioning

confidence: 99%

Hunting for Energetic Complexes as Hypergolic Promoters for Green Propellants Using Hydrogen Peroxide as Oxidizer

Zhao

et al. 2021

Inorg. Chem.

The development of hypergolic materials has aroused great interest due to their important applications in aerospace technology. In this work, six new energetic complexes were prepared and comprehensively characterized. All energetic complexes had isostructural characteristics, which made them ideal candidates for studying their structure−performance relationships. These energetic complexes had good thermal stabilities and excellent specific impulses. The vacuum-specific impulses were in the range 264.0−271.9 s, which was greater than most reported solid hypergolic materials. Moreover, the hypergolic performance of these compounds was examined by using 100% HNO 3 as the oxidizer, and their catalytic performance in the hypergolic reaction of typical energetic ionic liquids and 90% H 2 O 2 was comprehensively studied. All compounds displayed excellent hypergolic performance with the shortest ignition delay time of 4 ms. The examined copper-containing energetic complexes displayed excellent catalytic activities for the hypergolic reaction between energetic ionic liquids and 90% H 2 O 2 . The shortest ignition delay time of the examined hypergolic reactions was 31 ms. The suitable physicochemical properties, excellent energetic properties, and high catalytic activity of the hypergolic reactions have demonstrated the great potential of these energetic complexes as promoters for the development of green hypergolic bipropellants.