A vacuum ultraviolet photoionization study on the thermal decomposition of ammonium perchlorate

The ionic liquids upon perchlorate to promote the C-C/C-O bonds cleavage in alkali lignin under photothermal synergism

Transforming lignin into aromatic monomers is critically attractive to develop green and sustainable energy supplies. However, the usage of the additional catalysts like metal or base/acid is commonly limited by the caused repolymerized and environmental issues. The key step is to mediate electron transfer in lignin to trigger lignin C-C/C-O bonds cleavage without the catalysts mentioned above. Here, we report that the ionic liquids [BMim][ClO4] was found to trigger lignin electron transfer to cleave the C-C/C-O bonds for aromatic monomers without any additional catalyst. The proton transfer from [BMim]+ to [ClO4]- could polarize the anion and decrease its structure stability, upon which the active hydroxyl radical generated and induced lignin C-C/C-O bonds fragmentation via free radical-mediated routes with the assistance of photothermal synergism. About 4.4 wt% yields of aromatic monomers, mainly composed of vanillin and acetosyringone, are afforded in [BMim][ClO4] under UV-light irradiation in the air at 80 °C. This work opens the way to produce value-added aromatic monomers from lignin using an eco-friendly, energy-efficient, and simple route that may contribute to the sustainable utilization of renewable natural resources.

Mechanism of Interaction between Ammonium Perchlorate and Aluminum

There is an interactive effect between ammonium perchlorate (AP) and aluminum (Al) powder during the combustion process of composite solid propellants, but the mechanism of this effect is still lacking. Using quantum chemical methods, we investigated this mechanism from a molecular perspective. The interaction process between Al and AP was analyzed by comparing the chemical bond changes between the atoms during the reaction process of the Al/AP system and the AP unimolecular thermal decomposition system. The results show that Al atoms alter the reaction mechanism of AP thermal decomposition, significantly decreasing the activation energy of AP decomposition at high temperature but increasing that at low temperature. Meanwhile, the temperature-dependent rate constant of each basic reaction was calculated by transition state theory. The rate constants increase with temperature. Under high temperature and pressure, Al can increase the high-temperature decomposition rate of AP by up to 1-3 orders of magnitude.

Thermal decomposition of ammonium perchlorate-based molecular perovskite from TG-DSC-FTIR-MS and ab initio molecular dynamics

(H₂dabco)[NH₄(ClO₄)₃] (DAP, dabco = 1,4-diazabicyclo[2.2.2]octane) is a recently synthesized ammonium perchlorate-based molecular perovskite energetic material. The high-symmetry perovskite configuration assembles the oxidant ClO₄⁻ and fuel H₂dabco²⁺ into a compact cubic crystal, realizing a high energy-releasing efficiency. In this study, the thermal decomposition of DAP has been investigated by thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) coupled with Fourier transform infrared (FTIR) spectroscopy and mass spectroscopy (MS). The TG-DSC profiles show that DAP has an intense one-stage heat release process with a weight loss of 94.7%. The evolved gas products are identified as H₂O, CO₂, CO, HCl, HCN, NH₃, HNCO by FTIR spectrum, in which the infrared characteristic peak at 2283 and 2250 cm⁻¹ is clarified not from N₂O and assigned to HNCO. The principal products are H₂O and CO₂ together with significant amounts of HCl, HCN, NH₃ in MS, while few nitrogen oxides and O₂ are detected. The experimental results show that organic components have been the prominent media for the degradation of ClO₄⁻. To refine the mechanism observed in experiment, ab initio molecular dynamics simulations are carried out to reveal the atomistic reaction mechanisms. The decomposition of DAP starts with proton transfer from NH₄⁺ and H₂dabco²⁺ to ClO₄⁻. The deprotonated carbon skeleton is preferable to NH₃ in capturing O atoms, realizing a faster consumption of O atoms. Amounts of H atoms enter the environment being active free radicals, realizing an efficient autocatalytic chain propagation of degradation of ClO₄⁻. The atomistic thermal decomposition reaction mechanism of DAP uncovers the role of organic components in promoting the degradation of ClO₄⁻, which will help improve the synthesis strategy of molecular perovskite energetic materials with improved performance.

Organic components realize a more efficient autocatalytic chain propagation for degradation of ClO₄⁻ in the thermal decomposition process of DAP.

Interpol review of detection and characterization of explosives and explosives residues 2016-2019

This review paper covers the forensic-relevant literature for the analysis and detection of explosives and explosives residues from 2016-2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/Resources/Documents#Publications.

Porous Cr2O3 bead with a 3D continuous pore architecture: synthesis and its catalytic performance for decomposition of ammonium perchlorate

Mesoporous/macroporous Cr₂O₃ beads with 3D continuous pore structure exhibit improved thermal decomposition of ammonium perchlorate compared with Cr₂O₃ crystals.

Enabling liquid vapor analysis using synchrotron VUV single photon ionization mass spectrometry with a microfluidic interface

Vacuum ultraviolet (VUV) single photon ionization mass spectrometry (SPI-MS) is a vacuum-based technique typically used for the analysis of gas phase and solid samples, but not for liquids due to the challenge in introducing volatile liquids in a vacuum. Here we present the first demonstration of in situ liquid analysis by integrating the System for Analysis at the Liquid Vacuum Interface (SALVI) microfluidic reactor into VUV SPI-MS. Four representative volatile organic compound (VOC) solutions were used to illustrate the feasibility of liquid analysis. Our results show the accurate mass identification of the VOC molecules and the reliable determination of appearance energy that is consistent with ionization energy for gaseous species in the literature as reported. This work validates that the vacuum-compatible SALVI microfluidic interface can be utilized at the synchrotron beamline and enable the in situ study of gas-phase molecules evaporating off the surface of a liquid, which holds importance in the study of condensed matter chemistry.