Chemical and Physical Ionic Liquids in CO2 Capture System Using Membrane Vacuum Regeneration.

Carbon Capture Utilization and Storage technologies are essential mitigation options to reach net-zero CO2 emissions. However, this challenge requires the development of sustainable and economic separation technologies. This work presents a novel CO2 capture technology strategy based on non-dispersive CO2 absorption and membrane vacuum regeneration (MVR) technology, and employs two imidazolium ionic liquids (ILs), [emim][Ac] and [emim][MS], with different behavior to absorb CO2. Continuous absorption-desorption experiments were carried out using polypropylene hollow fiber membrane contactors. The results show the highest desorption behavior in the case of [emim][Ac], with a MVR performance efficiency of 92% at 313 K and vacuum pressure of 0.04 bar. On the other hand, the IL [emim][MS] reached an efficiency of 83% under the same conditions. The MVR technology could increase the overall CO2 capture performance by up to 61% for [emim][Ac] and 21% for [emim][MS], which represents an increase of 26% and 9%, respectively. Moreover, adding 30%vol. demonstrates that the process was only favorable by using the physical IL. The results presented here indicate the interest in membrane vacuum regeneration technology based on chemical ILs, but further techno-economic evaluation is needed to ensure the competitiveness of this novel CO2 desorption approach for large-scale application.

CO2 Desorption Performance from Imidazolium Ionic Liquids by Membrane Vacuum Regeneration Technology.

In this work, the membrane vacuum regeneration (MVR) process was considered as a promising technology for solvent regeneration in post-combustion CO2 capture and utilization (CCU) since high purity CO2 is needed for a technical valorization approach. First, a desorption test by MVR using polypropylene hollow fiber membrane contactor (PP-HFMC) was carried out in order to evaluate the behavior of physical and physico-chemical absorbents in terms of CO2 solubility and regeneration efficiency. The ionic liquid 1-ethyl-3-methylimidazolium acetate, [emim][Ac], was presented as a suitable alternative to conventional amine-based absorbents. Then, a rigorous two-dimensional mathematical model of the MVR process in a HFMC was developed based on a pseudo-steady-state to understand the influence of the solvent regeneration process in the absorption-desorption process. CO2 absorption-desorption experiments in PP-HFMC at different operating conditions for desorption, varying vacuum pressure and temperature, were used for model validation. Results showed that MVR efficiency increased from 3% at room temperature and 500 mbar to 95% at 310K and 40 mbar vacuum. Moreover, model deviation studies were carried out using sensitivity analysis of Henry's constant and pre-exponential factor of chemical interaction, thus as to contribute to the knowledge in further works.

Potassium Poly(Heptazine Imide): Transition Metal-Free Solid-State Triplet Sensitizer in Cascade Energy Transfer and [3+2]-cycloadditions.

Polymeric carbon nitride materials have been used in numerous light-to-energy conversion applications ranging from photocatalysis to optoelectronics. For a new application and modelling, we first refined the crystal structure of potassium poly(heptazine imide) (K-PHI)-a benchmark carbon nitride material in photocatalysis-by means of X-ray powder diffraction and transmission electron microscopy. Using the crystal structure of K-PHI, periodic DFT calculations were performed to calculate the density-of-states (DOS) and localize intra band states (IBS). IBS were found to be responsible for the enhanced K-PHI absorption in the near IR region, to serve as electron traps, and to be useful in energy transfer reactions. Once excited with visible light, carbon nitrides, in addition to the direct recombination, can also undergo singlet-triplet intersystem crossing. We utilized the K-PHI centered triplet excited states to trigger a cascade of energy transfer reactions and, in turn, to sensitize, for example, singlet oxygen (1 O2 ) as a starting point to synthesis up to 25 different N-rich heterocycles.

Acting Role of Background Gas in the Emission Response of Laser-Induced Plasmas of Energetic Nitro Compounds.

This study focuses on the analysis of the optical emission response obtained by laser-induced breakdown spectroscopy from energetic nitro compounds in condensed phase sampled in atmospheres of variable composition. The influence of different background gases was evaluated from the characteristic emissions of the excited species coexisting in the plasma plume and conclusions concerning the main pathways involved in the generation of such emission species were extracted. Different reactive (O2, N2, H2) and inert (Ar, He) gases were tested to establish the comparative emission features of organic compounds.

Pressure effects in laser-induced plasmas of trinitrotoluene and pyrene by laser-induced breakdown spectroscopy (LIBS).

The influence of the ambient atmosphere on the dynamics of plasma expansion, besides the interaction between excited plasma and gas molecules, has been studied for specific organic aromatic compounds. To analyze the influence of air on the formation pathways of atomic and molecular species inside the plasma plume, the spectral emissions in laser-induced breakdown spectroscopy (LIBS) of 2,4,6-trinitrotoluene (TNT) and pyrene were compared at different pressure environments, from high vacuum to atmospheric pressure. Pelletized samples of the compounds were introduced in a vacuum chamber for excitation with the fourth harmonic output of an Nd : YAG laser (266 nm). The optical emission signal was collected with an optical fiber connected to a spectrograph fitted with a intensified charge-coupled device detector. Results from LIBS spectra indicate that changes in pressure level affect the kinetics of the characteristic excited species and their spatial distribution inside the plasma plume.

Condensed-phase laser ionization time-of-flight mass spectrometry of highly energetic nitro-aromatic compounds.

RATIONALE: Analysis of explosive compounds represents an interesting field of work due to the obvious social relevance of these compounds. Direct laser ionization allows the analysis of these high internal energy compounds without sampling or preparation procedures. We have studied nitro-aromatic compounds to understand their mass spectra when directly ionized in the condensed phase, different from the gas-phase studies commonly conducted. METHODS: Direct condensed-phase laser ionization time-of-flight mass spectrometry of high energy density materials has been performed using a 5 ns width quadrupled Nd:YAG laser. No matrix assistance was used. Fine control of the laser energy allowed the study of the fragmentation processes from values close to the ionization threshold to ones where atomic-only mass spectra were recorded. RESULTS: The influence of the variation of extraction conditions on the recorded mass spectra was investigated. For low extraction width pulses, ions with low m/z values were mainly observed, whereas, at higher widths, higher mass fragment ions were also detected while the total ion current was maintained. Therefore, the mass spectra can be modulated to obtain mass spectra containing molecular or atomic information. The onset of ion generation for the different fragment ions was also studied, yielding information that can help to understand the processes involved in the fragmentation pathways of the molecule and in the dissociation mechanisms. Two sampling procedures allowed the prospective use of LIMS as a screening technique for nitro-aromatic-based highly energetic explosives. CONCLUSIONS: Direct analysis of explosive compounds has been performed by laser ionization. A large dependence of the resultant spectra on the laser energy was observed that might be useful for studies of fragmentation pathways. For forensic applications, two sampling procedures might allow the use of LIMS as a screening technique.

Secondary ion mass spectrometry of powdered explosive compounds for forensic evidence analysis.

RATIONALE: Residual quantities of explosives deposited on, or absorbed in, nearby surfaces can be of forensic value in post-blast analysis. As secondary ion mass spectrometry (SIMS) may be a suitable analytical approach for the screening of such residues, its performance was evaluated. METHODS: The analyses were carried out in a SIMS instrument fitted with a quadrupole analyzer. The sample was sputtered at a 45º incidence angle with a 100 µm primary Ar(+) beam (3 keV, 500 nA). Surface sample compensation was performed with low-energy electrons (500 eV, 0.75 mA). RESULTS: TNT, RDX, PETN and cloratite were deposited in powdered form on double-sided tape and introduced into the mass spectrometer, without further handling, for SIMS analysis. The analysis conditions including compensation were optimized. A mixture of energetic compounds commonly used for explosive preparation was also analyzed, proving the potential of SIMS in forensic analysis. CONCLUSIONS: This study demonstrated the possibility of detecting explosives by SIMS making use of a simple sampling procedure consisting of sticking the sample in powdered form (compatible with the collection performed in forensic post-blast analysis) onto double-sided tape without handling or preparation.

Storm sewers as larval habitats for Aedes aegypti and Culex spp. in a neighborhood of Merida, Mexico.

We report the collection of Aedes aegypti, Culex quinquefasciatus, Cx. interrogator, Cx. thriambus, Cx. coronator, and Cx. salinarius larvae from storm sewers within an endemic area for dengue transmission in Merida, Mexico, during the rainy season of 2011. This is the first record of the dengue vector Ae. aegypti breeding in storm sewers in the southeast of Mexico.