Catalytic Effects of Zeolite Socony Mobil-5 (ZSM-5) on the Oxidation of Acoustically Levitated exo-Tetrahydrodicyclopentadiene (JP-10) Droplets

Abstract

Jet propulsion 10 (JP-10) droplets with and without aluminum nanoparticles in conjunction with HZSM-5 zeolite and surfactants were ultrasonically levitated, and their oxidation processes were explored to identify how the oxidation process of JP-10 is catalytically affected by the HZSM-5 zeolites and how the surfactant and Al NPs in the system impacted the key experimental parameters of the ignition such as ignition delay time, burn rate, and the maximum temperatures. Singly levitated droplets were ignited using a carbon dioxide laser under an oxygen−argon atmosphere. Pure JP-10 droplets and JP-10 droplets with silicon dioxide of an identical size distribution as the zeolite HZSM-5 did not ignite in strong contrast to HZSM-5-doped droplets. Acidic sites were found to be critical in the ignition of the JP-10. With the addition of the surfactant, the characteristic features of the JP-10 ignition were improved, so the ignition delay time of the zeolite-JP-10 samples were decreased by 2−3 ms and the burn rates were increased by 1.3 to 1.6 × 10 5 K s −1 . The addition of Al NPs increased the maximum temperatures during the combustion of the systems by 300−400 K. Intermediates and end products of the JP-10 oxidation over HZSM-5 were characterized by UV−vis emission and Fourier-transform infrared transmission spectroscopies, revealing key reactive intermediates (OH, CH, C 2 , O 2 , and HCO) along with the H 2 O molecules in highly excited rovibrational states. Overall, this work revealed that acetic sites in HZSM-5 are critical in the catalytic ignition of JP-10 droplets with the addition of the surfactant and Al NPs, enhancing the oxidation process of JP-10 over HZSM-5 zeolites.

Combined Spectroscopic and Computational Investigation on the Oxidation of exo-Tetrahydrodicyclopentadiene (JP-10; C10H16) Doped with Titanium–Aluminum–Boron Reactive Metal Nanopowder

“…Similar to the FTIR transmission spectra obtained for the oxidation of Al NP-doped JP-10, − the FTIR data collected after the combustion of the droplet revealed the gaseous products of the oxidation to be solely carbon dioxide (CO 2 ) and water (H 2 O). These cover the asymmetric stretching mode [ν as (H 2 O)] (3756 cm –1 ) along with the bending mode [δ­(OH)] (1600 cm –1 ) of water.…”

“…Fourth, the emission spectra reveal the presence of rovibrationally excited metal monoxides, namely, aluminum monoxide (AlO), boron monoxide (BO), and titanium monoxide (TiO) via five, nine, and five emissions, respectively. The emissions of aluminum monoxide, which were also detected in the oxidation of JP-10 droplets doped with Al NPs, − originate from the Δν = 2, 1, and 0 transitions of AlO (A 2 Σ + –X 2 Σ + ), where Δν denotes the change in the vibrational quantum number ν . Titanium monoxide produces a series of broad emissions, the largest of which have maxima at around 595, 623, 675, 713, and 777 nm.…”

“…First, recall that under the same experimental conditions, pure JP-10 droplets did not ignite. − Monitored via the high-speed optical camera, the carbon dioxide laser led to the evaporation of the droplet prior to the autoignition temperature of JP-10 of 509 K. The addition of RMNPs could have increased the boiling point of JP-10. However, JP-10 droplets doped with silicon dioxide (SiO 2 ), titanium dioxide (TiO 2 ), aluminum oxide (Al 2 O 3 ), and copper (II) oxide (CuO) nanoparticles of comparable size to the Ti–Al–B RMNPs did not ignite either. ,, Consequently, the RMNPs must have played an active role in the ignition of JP-10.…”

“…However, JP-10 droplets doped with silicon dioxide (SiO 2 ), titanium dioxide (TiO 2 ), aluminum oxide (Al 2 O 3 ), and copper (II) oxide (CuO) nanoparticles of comparable size to the Ti−Al−B RMNPs did not ignite either. 65,66,68 Consequently, the RMNPs must have played an active role in the ignition of JP-10. Second, the UV−vis emission spectra revealed the presence of gas-phase aluminum (Al) and titanium (Ti) atoms.…”

“…We also explore the effects of adding 1 wt % surfactant (Span80) to the JP-10-RMNP droplet (system b) on the oxidation process including, for example, ignition delay and maximum flame temperature. JP-10 droplets doped with 2 wt % aluminum (Al) (system c) and 2 wt % aluminum (Al) along with 1 wt % surfactant (Span80) (system d) serve as the baseline systems to determine the improvements in the combustion compared to the more traditional single-metal additive Al and investigate the effects of the sorbitan monooleate. − These experiments are complemented by the electronic structure calculations exploring the initial steps on the formation of JP-10-based hydrocarbon radicals accessed through hydrogen abstraction pathways by molecular oxygen (O 2 , X 3 Σ – g ), atomic oxygen [O­( 3 P j )], and oxides [BO­(X 2 Σ + ); AlO­(X 2 Σ + ); TiO­(X 3 Δ); and BO 2 (X 2 Σ g + )] formed during the oxidation of the RMNPs to gauge the effect of Ti–Al–B-based RMNPs on the oxidation of JP-10.…”