3 research outputs found
Designing Difunctional Promoters for Hypergolic Ignitions of Green Bipropellants Combining Ionic Liquids with H<sub>2</sub>O<sub>2</sub>
The
emergence of tetrahydroborate (BH4–)/cyanoborohydride
(BH3CN–) anion-based
ionic liquid fuels in combination with high test peroxide (>90%H2O2, HTP) oxidizers has accelerated the greening
of bipropellants. However, most BH4– and
BH3CN– anion-based ionic liquids are
sensitive to water, making it difficult to store them. Here, novel
difunctional promoters are designed for hypergolic ignition of BH4–/BH3CN– anion-free
ionic liquids with 90%H2O2. The transition metal
in anions of promoters is expected to catalyze the exothermic decomposition
of H2O2, 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-3-methylimidazolium 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 BH4–/BH3CN– 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
Fabrication of Swellable Organic–Inorganic Hybrid Polymers for CO<sub>2</sub>‑Assisted Hydration of Propylene Epoxide
Swelling is a very common phenomenon in organic substances.
However,
the swelling behaviors of inorganic substances had rarely been reported.
In this study, a new type of swellable organic–inorganic hybrid
polymer (PIL@CHT) was designed and successfully synthesized through
free-radical copolymerization of polymerizable phosphonium ionic liquid
monomer and vinyl-functionalized hydrotalcite (CHT). The swelling
behaviors of PIL@CHT in various solvents with a wide range of Hansen
solubility parameters (δT) were investigated, and
PIL@CHT exhibited excellent swellable capacity in the solvents with
δT > 24.4 MPa1/2. The swollen state
of
the hybrid PIL@CHT in water presented a network structure with a diameter
of approximately 8–12 μm, and CHT particles were well
dispersed to the channel of PIL. PIL@CHT was applied to catalyze the
CO2-assisted hydration of propylene oxide (PO), in which
a cascade reaction including the cycloaddition of CO2 and
PO and the subsequent hydrolysis of propylene carbonate (PC) occurred.
PIL@CHT, combining the active sites of PIL and CHT, synergistically
catalyzed this cascade reaction and achieved a high yield (93.0%)
and selectivity (98.2%) of 1,2-propanediol (1,2-MPG) under a low H2O/PO ratio of 1.5/1. Moreover, the catalyst could be recycled
seven times without any significant loss of catalytic activities and
had good substrate generality
Swelling Poly(ionic liquid)s: Synthesis and Application as Quasi-Homogeneous Catalysts in the Reaction of Ethylene Carbonate with Aniline
Homogeneous
catalysts generally show higher catalytic activities,
while heterogeneous catalysts are more easily separated from products.
To combine the advantages of heterogeneous and homogeneous catalysts
has been of great interest for many years. Here, we report a kind
of facilely prepared cross-linked polyÂ(ionic liquid)Âs (PILs) with
swelling property to increase catalytic activities of heterogeneous
catalysts. The swelling ability of PILs was greatly affected by cross-linking
density and chain length of substituents on imidazolium, and the unique
swelling property prompted the nonporous PILs to contact with substrates
sufficiently, enhancing their catalytic activities similar to homogeneous
ionic liquid monomers